the economic aspects of geology c. k. leith university of wisconsin [illustration] new york henry holt and company copyright, by henry holt and company _august, _ printed in the u. s. a. contents page chapter i. introduction survey of field economic applications of the several branches of geology and of other sciences mineralogy and petrology stratigraphy and paleontology structural geology physiography rock alterations or metamorphism application of other sciences treatment of the subject in this volume chapter ii. the common elements, minerals, and rocks of the earth and their origins relative abundance of the principal elements of the lithosphere relative abundance of the principal minerals of the lithosphere relative abundance of the principal rocks of the lithosphere water (hydrosphere) soils and clays comparison of lists of most abundant rocks and minerals with commercial rocks and minerals the origin of common rocks and minerals igneous processes igneous after-effects weathering of igneous rocks and veins sedimentary processes weathering of sedimentary rocks consolidation, cementation, and other sub-surface alterations of rocks cementation dynamic and contact metamorphism the metamorphic cycle as an aid in studying mineral deposits chapter iii. some salient features of the geology and classification of mineral deposits various methods of classification names mineral deposits as magmatic segregations in igneous rocks mineral deposits within and adjacent to igneous rocks, which were formed immediately after the cooling and crystallization of the magmas through the agency of hot magmatic solutions evidence of igneous source possible influence of meteoric waters in deposition of ores of this class zonal arrangement of minerals related to igneous rocks the relation of contact metamorphism to ore bodies of the foregoing class secondary concentration in place of the foregoing classes of mineral deposits through the agency of surface solutions residual mineral deposits formed by the weathering of igneous rocks in place mineral deposits formed directly as placers and sediments mechanically deposited minerals chemically and organically deposited minerals sedimentary mineral deposits which have required further concentration to make them commercially available anamorphism of mineral deposits conclusion chapter iv. mineral resources--some general quantitative considerations world annual production of minerals in short tons world annual production of minerals in terms of value significance of geographic distribution of mineral production the increasing rate of production capital value of world mineral reserves political and commercial control of mineral resources reserves of mineral resources chapter v. water as a mineral resource general geologic relations distribution of underground water movement of underground water wells and springs composition of underground waters relation of geology to underground water supply surface water supplies underground and surface waters in relation to excavation and construction chapter vi. the common rocks and soils as mineral resources economic features of the common rocks granite basalt and related types limestone, marl, chalk marble sand, sandstone, quartzite (and quartz) "sand and gravel" clay, shale, slate the feldspars hydraulic cement (including portland, natural, and puzzolan cements) geologic features of the common rocks building stone crushed stone stone for metallurgical purposes clay limitations of geologic field in commercial investigation of common rocks soils as a mineral resource origin of soils composition of soils and plant growth use of geology in soil study chapter vii. the fertilizer group of minerals general comments nitrates economic features geologic features phosphates economic features geologic features pyrite economic features geologic features sulphur economic features geologic features potash economic features geologic features chapter viii. the energy resources--coal, oil, gas (and asphalt) coal economic features world production and trade production in the united states coke classification of coals geologic features petroleum economic features production and reserves methods of estimating reserves classes of oils conservation of oil geologic features organic theory of origin effect of differential pressures and folding on oil genesis and migration inorganic theory of origin oil exploration oil shales natural gas economic features geologic features asphalt and bitumen economic features geologic features chapter ix. minerals used in the production of iron and steel (the ferro-alloy group) general features iron ores economic features technical and commercial factors determining use of iron ore materials geographic distribution of iron ore production world reserves and future production of iron ore geologic features sedimentary iron ores iron ores associated with igneous rocks iron ores due to weathering of igneous rocks iron ores due to weathering of sulphide ores manganese ores economic features geologic features chrome (or chromite) ores economic features geologic features nickel ores economic features geologic features tungsten (wolfram) ores economic features geologic features molybdenum ores economic features geologic features vanadium ores economic features geologic features zirconium ores economic features geologic features titanium ores economic features geologic features magnesite economic features geologic features fluorspar economic features geologic features silica economic features geologic features chapter x. copper, lead and zinc minerals copper ores economic features geologic features copper deposits associated with igneous flows copper veins in igneous rocks "porphyry coppers" copper in limestone near igneous contacts copper deposits in schists sedimentary copper deposits general comments lead ores economic features geologic features zinc ores economic features geologic features chapter xi. gold, silver, and platinum minerals gold ores economic features geologic features silver ores economic features geologic features platinum ores economic features geologic features chapter xii. miscellaneous metallic minerals aluminum ores economic features geologic features antimony ores economic features geologic features arsenic ores economic features geologic features bismuth ores economic features geologic features cadmium ores economic features geologic features cobalt ores economic features geologic features mercury (quicksilver) ores economic features geologic features tin ores economic features geologic features uranium and radium ores economic features geologic features chapter xiii. miscellaneous non-metallic minerals natural abrasives economic features geologic features asbestos economic features geologic features barite (barytes) economic features geologic features borax economic features geologic features bromine economic features geologic features fuller's earth economic features geologic features graphite (plumbago) economic features geologic features gypsum economic features geologic features mica economic features geologic features monazite (thorium and cerium ores) economic features geologic features precious stones economic features geologic features salt economic features geologic features talc and soapstone economic features geologic features chapter xiv. exploration and development the general relations of the geologist to exploration and development partly explored versus virgin territories the use of all available information co�peration in exploration economic factors in exploration geologic factors in exploration mineral provinces and epochs classification of mineral lands outcrops of mineral deposits some illustrative cases topography and climate as aids in searching for mineral outcrops size and depth of ore bodies as determined from outcrops the use of placers in tracing mineral outcrops the use of magnetic surveys in tracing mineral ledges the use of electrical conductivity and other qualities of rocks in exploration the use of structure and metamorphism in exploration drilling in exploration quantitative aspects of geologic exploration origin of mineral deposits as a factor in exploration lake superior iron ore exploration as an illustration development and exploitation of mineral deposits chapter xv. valuation and taxation of mineral resources popular conception of mineral valuation valuation and taxation of mines intrinsic and extrinsic factors in valuation values of mineral deposits not often established by market transfers the ad valorem method of valuation other methods of mineral valuation and taxation general comments on taxation of mineral resources chapter xvi. laws relating to mineral resources i. laws relating to ownership and control of mineral resources on alienated lands on the public domain nationalization of mineral resources effect of ownership laws on exploration use of geology in relation to ownership laws ii. laws relating to extraction of mineral resources iii. laws relating to distribution and transportation of mineral resources iv. other relations of geology to law chapter xvii. conservation of mineral resources the problem differences between private and public efforts in conservation the interest rate as a guide in conservation anti-conservational effects of war conservation of coal measures introduced or proposed to conserve coal (a) mining and preparation of coal progress in above methods (b) improvement of labor and living conditions at the mines (c) introduction or modification of laws to regulate or to remove certain restrictions on the coal industry (d) distribution and transportation of coal (e) utilization of coal (f) substitutes for coal as a source of power division of responsibility between government and private interests in the conservation of coal conservation of minerals other than coal chapter xviii. international aspects of mineral resources world movement of minerals movement of minerals under pre-war conditions of international trade changes during the war post-war condition of the mineral trade tendencies toward international co�peration and possibility of international control of minerals methods of international coöperation conservation in its international relations exploration in its international relations valuation in its international relations relative position of the united states in regard to supplies of minerals the coal and iron situation of western europe under the terms of the peace conclusion literature chapter xix. geology and war geology behind the front geology at the front effect of the war on the science of economic geology chapter xx. geology and engineering construction foundations surface waters tunnels slides subsidence railway building road building geology in engineering courses chapter xxi. the training, opportunities and ethics of the economic geologist pure versus applied science course of study suggested field work specialization in studies a degree of economic geology the opportunities of the economic geologist ethics of the economic geologist illustrations figure page . graphic representation of volume change in weathering of a georgia granite . commercial (financial) control of the mineral resources of the world . political (territorial) control of the mineral resources of the world . the fertilizer situation in the united states . diagram showing the chemical composition and heat efficiency of the several ranks of coal . origin and development of coal . chart showing the present tendency of the united states in respect to its unmined reserve of petroleum . the annual output of the principal oil fields of the united states for the last twenty years . curve showing the usual decline in oil field production after the period of maximum output is reached . chart showing the relative values of the principal petroleum products manufactured in the united states from to . alteration of lake superior iron formation to iron ore by the leaching of silica . representing in terms of weight the mineralogical changes in the katamorphism of serpentine rocks to iron ore, eastern cuba . diagram showing gradation from syenite to bauxite in terms of volume chapter i introduction survey of field in adapting ourselves to physical environment it has been necessary to learn something about the earth. mainly within the last century has this knowledge been organized into the science of geology, and only within the last few decades have the complex and increasing demands of modern civilization required the applications of geology to practical uses, resulting in the development of the science generally known as _economic geology_. this science is not sharply marked off from the science of geology proper; almost any phase of geology may at some time or some place take on its economic aspect. the usefulness of economic geology was first recognized in relation to mineral resources,--and particularly in relation to metallic resources, their discovery and development,--but the science has been found to have much wider practical application. the practice of the economic geologist in recent years has taken on many new phases. the geologist is called upon to study the geologic features of mineral deposits, their occurrence, structure, and origin. the basic information thus acquired is useful in estimating reserves and life of mineral deposits. this leads naturally to considerations of valuation. because valuation plays such a large part in any tax program, the geologist is being used by tax boards of the federal and state governments. both in the formulation of laws relating to mineral resources, and in the litigation growing out of the infraction of these laws, the economic geologist plays a part. one cannot go very far with the study of mineral resources without consideration of the question of conservation. geologists are called on not only for broad surveys of the mineral reserves, but for the formulation of general principles of conservation and their application to specific mines and minerals. the geologist's familiarity with the distribution and nature of mineral resources has given him a part in coping with broad questions of international use of natural resources. war conditions made it necessary to use new sources of supply, new channels of distribution, and new methods of utilization. the economic geologist came into touch with questions of international trade, tariffs, and shipping. but economic geology is not solely confined to mineral resources. in relation to engineering enterprises of the greatest variety--canals, aqueducts, tunnels, dams, building excavations, foundations, etc.--geology now figures largely, both in war and in peace. the nature, amount, and distribution of underground water supplies are so involved with geologic considerations that a considerable number of geologists give up their time wholly to this phase of the subject. it might seem from this list of activities that geology is spreading too far into the fields of engineering and commerce, but there are equally rapid extensions of other fields of knowledge toward geology. the organization of these intermediate fields is required both in the interest of science and in the interest of better adaptation of the race to its environment. the geologist is required to do his part in these new fields, but not to abandon his traditional field. it is proposed in this volume to discuss the economic aspects of geology without exhaustive discussion of the principles of geology which are involved. practically the whole range of geologic science has some sort of economic application, and it would be futile to attempt in one volume even a survey of the science of geology as a whole. our purpose is rather to indicate and illustrate, in some perspective, the general nature of the application of geology to practical affairs. in professional preparation for the practice of economic geology there is no easy short-cut. students sometimes think that a smattering of geological principles, combined with a little business and economic information, may be sufficient. analysis of professional successes should make it clear that economic geologists are most effective and in most demand, not primarily because of business aptitude, though this helps, but because of their proficiency in the science of geology itself. in short, to enter successfully the field of economic geology one should first become a scientist, if only in a limited field. the traditional conception of the geologist as a musty and stooped individual, with a bag, hammer, and magnifying glass, collecting specimens to deposit in a dusty museum, will doubtless survive as a caricature, but will hardly serve to identify the economic geologist in his present-day work. in writing this book, it is hoped in some measure to convey an impression of the breadth and variety in this field. few other sciences offer so wide a range of opportunity, from the purely scientific to the practical and commercial, coupled with travel, exploration, and even adventure. economic applications of the several branches of geology and of other sciences there is no phase of geology which at some time or place does not have its economic application. many references to these applications are made in other chapters. it is proposed here to indicate briefly some of the phases of geologic science which are most necessary to the practice of economic geology. the student in his preparation cannot afford to eliminate any of them on the ground that they are merely "scientific" or "academic" or "theoretical." mineralogy and petrology mineralogy, the study of minerals, and petrology, the study of rocks (aggregations of minerals), are of course elementary requisites in preparation. there must be familiarity with the principal minerals and rocks, and especially with the methods and processes of their identification, with their nature, and with their origin. this involves a study of their crystallography, chemical composition, physical qualities, and optical properties as studied with the microscope. in recent years the microscopical study of polished and etched surfaces of ores has proved a valuable tool. stratigraphy and paleontology stratigraphy and paleontology are concerned with the sedimentary and life history of the earth. the determination of the ages of the earth's strata and of the conditions of their deposition is required in the practice of economic geology. for example, a detailed knowledge of the succession of rocks and their ages, as determined by fossils and other stratigraphic evidence, is vital to the interpretation of conditions in an oil or coal field, and to the successful exploration and development of its deposits. the success of certain paleontologists and stratigraphic specialists in oil exploration is an evidence of this situation. certain iron ores, phosphates, salts, potash, and other minerals, as well as many of the common rocks used for economic purposes, are found in sedimentary deposits, and require for their successful exploration and development the application of stratigraphic and paleontologic knowledge. closely related to stratigraphy (as well as to physiography, see pp. - ) is the study of sedimentation,--_i. e._, the study of the physical, chemical, climatic, and topographic conditions of the deposition of sediments. this is coming to play an increasingly large part in geologic work, and is essential to the interpretation of many mineral deposits, particularly those in which stratigraphic and physiographic questions are involved. still another aspect of the problem of stratigraphy and sedimentation is covered by the study of _paleogeography_, or the areal distribution of the faunas and sediments of geologic periods caused by the alternating submergence and emergence of land areas. in the search for the treasures of sedimentary deposits, a knowledge of ancient geographies and of ancient faunas makes it possible to eliminate certain regions from consideration. from a study of the faunas of eastern kansas and missouri, and of those along the eastern part of the rocky mountains, it has been inferred that a ridge must have extended across eastern kansas during early pennsylvanian time,--a conclusion which is of considerable economic importance in relation to oil exploration. structural geology structural geology is the study of the physical forms and relations of rocks which result mainly from deformation by earth forces. if rocks remained in their original forms the structural problem would be a comparatively easy one, but usually they do not. often they are faulted and folded and mashed to such an extent that it is difficult to go behind the superposed structural features to the original conditions in order to work out the geologic history. not only is structural study necessary for the interpretation of geologic history, but it is often more directly applicable to economic problems,--as when, for instance, ore deposits have been formed in the cracks and joints of rocks, and the ore deposits themselves have been faulted and folded. water resources are often located in the cracks and other openings of rocks, and are limited in their distribution and flow because of the complex attitude of deformed rocks. oil and gas deposits often bear a well-defined relation to structural features, the working out of which is almost essential to their discovery. it is not desirable to stop with the merely descriptive aspects of structural geology, as is so often done; for much light can be thrown on the economic applications of this subject by consideration of the underlying principles of mechanics,--involving the relations of earth stresses to rock structures. the mere field mapping and description of faults and joints is useful, but in some cases it is necessary to go a step further and to ascertain the mechanical conditions of their origin in order to interpret them clearly. if, for illustration, there are successive groups of mineralized veins in a mining camp, the later ones cutting the earlier ones, these might be treated as separate structural units. but if it can be shown that the several sets of veins have formed from a single movement, that there is no sharp genetic separation between the different sets and that they are a part of a single system, this interpretation throws new light on exploration and development, and even on questions of ownership and extralateral rights (chapter xvi). physiography physiography is a phase of geology which investigates the surface features of the earth. it has to do not only with the description and classification of surface forms, present and past (physical geography or geomorphology), but with the processes and history of their development. the subject is closely related to geography, climatology, sedimentation, and hydrology. as one of the latest phases of geology to be organized and taught, its economic applications have been comparatively recent and are not yet widely recognized. because of this fact its economic applications may be summarized at somewhat greater length than those of the other branches of geology above mentioned, which are to be more or less taken for granted. the central feature of physiography is the so-called erosion cycle or topographic cycle. erosion, acting through the agencies of wind, water, and ice, is constantly at work on the earth's surface; the eroded materials are in large part carried off by streams, ultimately to be deposited in the ocean near the continental margins. the final result is the reduction of the land surface to an approximate plain, called a _peneplain_, somewhere near sea level. geological history shows that such peneplains are often elevated again with reference to sea level, by earth forces or by subsidence of the sea, when erosion again begins its work,--first cutting narrow, steep gulches and valleys, and leaving broad intervening uplands, in which condition the erosion surface is described as that of _topographic youth_; then forming wider and more extensive valleys, leaving only points and ridges of the original peneplains, in which stage the surface is said to represent _topographic maturity_; then rounding off and reducing the elevations, leaving few or none of the original points on the peneplain, widening the valleys still further and tending to reduce the whole country to a nearly flat surface, resulting in the condition of _topographic old age_. the final stage is again the peneplain. this cycle of events is called the _erosion cycle_ or _topographic cycle_. uplift may begin again before the surface is reduced to base level; in fact, there is a constant oscillation and contest between erosion and relative uplift of the land surface. the action of the erosion cycle on rocks of differing resistance to erosion and of diverse structure gives rise to the great variety of surface forms. the physiographer sees these forms, not as heterogeneous units, but as parts of a definite system and as stages in an orderly series of events. he is able to see into the topographic conditions beyond the range of immediate and direct observation. he is able to determine what these forms were in the past and to predict their condition in the future. he is able to read from the topography the underground structure which has determined that topography. a given structure may in different stages of topographic development give quite diverse topographic forms. in such a case it is important to realize that the diversity is only superficial. on the other hand, a slight local divergence from the usual topographic forms in a given region may reflect a similar local divergence in the underground structure. thus it is that an appreciation of the physiographic details may suggest important variations in the underground structure which would otherwise pass undiscovered. many mineral deposits owe their origin or enrichment to weathering and other related processes which are preliminary to erosion. these processes vary in intensity, distribution, and depth, with the stage of erosion, or in relation to the phase of the erosion cycle. they vary with the climatic conditions which obtain on the erosion surface. mineral deposits are therefore often closely related to the topographic features, present and past, in kind, shape, and distribution. a few illustrative cases follow. many of the great copper deposits of the western united states owe their values to a secondary enrichment through the agency of waters working down from the surface. when this fact of secondary enrichment was discovered, it was naturally assumed that the process was related to the present erosion surface and to present climatic and hydrologic conditions. certain inferences were drawn, therefore, as to depth and distribution of the enriched ores. this conception, however, proved to be too narrow; for evidences were found in many cases that the copper deposits had been concentrated in previous erosion cycles, and therefore in relation to erosion surfaces, now partly buried, different from the present surface. the importance of this knowledge from an exploring and development standpoint is clear. it has made it possible to find and follow rich ores, far from the present erosion surface, which would otherwise have been disclosed solely by chance. studies of this kind in the copper camps are yet so recent that much remains to be learned. the economic geologist advising exploration and development in copper ores who does not in the future take physiographic factors into account is likely to go wrong in essential ways, as he has done in some cases in the past. not only is it necessary to relate the secondary enrichment of copper deposits to the erosion surface, present or past, but by a study of the conditions it must be ascertained how closely erosion has followed after the processes of enrichment. in some cases erosion has followed so slowly as to leave large zones of secondary enrichment. in other cases erosion has followed up so closely after the processes of secondary enrichment as to remove from the surface important parts of the secondarily enriched deposits. the iron ores of the lake superior region are the result of the action of waters from the surface on so-called iron formations or jaspers. here again it was at first supposed that the enrichment was related to the present erosion surface; but upon further studies the fact was disclosed that the concentration of the ores took place in the period between the deposition of keweenawan and cambrian rocks, and thus a new light was thrown on the possibilities as to depth and distribution of the ores. the old pre-cambrian surface, with reference to which the concentration took place, can be followed with some precision beneath the present surface. this makes it possible to forecast a quite different depth and distribution of the ores from that which might be inferred from present surface conditions. present surface conditions, of low relief, considerable humidity, and with the water table usually not more than feet from the surface, do not promise ore deposits at great depth. the erosion which formed the old pre-cambrian surface, however, started on a country of great relief and semi-arid climate, conditions which favored deep penetration of the surface waters which concentrated the ores. the iron ores of eastern cuba are formed by the weathering of a serpentine rock on an elevated plateau of low relief, where the sluggish streams are unable rapidly to carry off the products of weathering. where streams have cut into this plateau and where the plateau breaks down with sharp slopes to the ocean, erosion has removed the products of weathering, and therefore the iron ore. an important element, then, in iron ore exploration in this country is the location of regions of slight erosion in the serpentine area. one of the largest discoveries was made purely on a topographic basis. it was inferred merely from a study of topography that a certain large unexplored area ought to carry iron ore. subsequent work in the thick and almost impenetrable jungle disclosed it. bauxite deposits in several parts of the world require somewhat similar conditions of concentration, and a study of the physiographic features is an important factor in their location and interpretation. a physiographic problem of another sort is the determination of the conditions surrounding the origin of sedimentary ores. certain mineral deposits, like the "clinton" iron ores, the copper ores in the "red beds" of southwestern united states and in the mansfield slates of germany, many salt deposits, and almost the entire group of placer deposits of gold, tin, and other metals, are the result of sedimentation, from waters which derived their materials from the erosion of the land surface. it is sometimes possible from the study of these deposits to discover the position and configuration of the shore line, the depth of water, and the probable continuity and extent of the deposits. similar questions are met in the study of coal and oil. this general problem is one of the phases of geology which is now receiving a large amount of attention, not only from the standpoint of ore deposition, but from a broader geologic standpoint. in spite of the fact that sedimentary processes of great variety can be observed in operation today, it is yet extremely difficult to infer from a given sedimentary deposit the precise conditions which determined its deposition and limited its distribution. for instance, sedimentary iron formations furnish a large part of the world's iron ore. the surface distribution, the structure, the features of secondary enrichment, are all pretty well understood; likewise the general conditions of sedimentation are reasonably clear,--but the close interpretation of these conditions, to enable us to predict the extent of one of these deposits, or to explain its presence in one place and absence in another, is in an early and sketchy stage. an understanding of the principles and methods of physiography is also vital to an intelligent application of geology to water resources, to soils, to dam and reservoir construction, and to a great variety of engineering undertakings, but as these subjects involve the application of many other phases of geology, they are considered in separate chapters. (chapters v, vi, and xx.) rock alterations or metamorphism this is one of the newer special phases of geology which for a long time was regarded as the plaything of the petrographer or student of rocks. with the systematic development of the subject, however, it was found that the extremely numerous and complex alterations of rocks and minerals may be definitely grouped, and that they are controlled by broad principles. it became apparent also that these principles apply both to the economic and non-economic minerals and rocks,--in other words, that the segregation of economic minerals is a mere incident in pervasive cycles of the alterations which affect all rocks. metamorphic geology, therefore, for some geologists becomes a convenient approach to the subject of economic geology. it has the great advantage that it tends to keep all minerals and all processes of ore deposition in proper perspective with relation to rocks and rock processes in general. it is not argued that this is the only approach or that it is the best for all purposes. a brief account of this phase of geology is given in chapter ii. application of other sciences geology is sometimes defined as the application of other sciences to the earth. considered broadly, there is no phase of science which is not involved in economic geology. in other chapters in this book many references are made to applications of engineering, mathematics, physics, chemistry, metallurgy, biology, and economics. at different times and places the requirements for earth materials are quite different. in the stone age there was little use for metals; in later ages the use of metals broadened. the multiplicity of demands of modern civilization, the increasing knowledge of processes of metallurgy, chemistry and physics, better transportation, better organization of commercial life, and many other factors, tend to bring new earth materials into use,--and, therefore, into the field of economic geology. a comparatively few years ago alumina, one of the most common and abundant substances of the earth's crust, was in no general demand except for very limited use as an ornament. little attention was paid to it by economic geologists as a commercial product; now, however, aluminum is in great demand, and the raw materials which produce it have become the subjects of intensive study by economic geologists. in short, economic geology includes the consideration of man in reaction to his physical environment. there are some earth materials and some conditions of the earth environment which do not yet come within the field of economic geology. but so large a proportion of them do, that the "complete economic geologist" should indeed be almost omniscient. when one considers what an insignificantly small portion of this field can be covered by any individual, it is apparent that the title of economic geologist implies no mastery of the entire field. there is yet no crowding. treatment of the subject in this volume in scope and manner of treatment this volume follows somewhat the writer's presentation of the subject in university teaching. the purpose is to explain the nature of the economic demands for the science of geology, and to discuss something of the philosophy of the finding and use of raw materials. somewhat generalized statistics are used as a means of gaining perspective. no effort has been made for detailed accuracy or for completeness. so far as possible the quantitative features are expressed in general proportions, and where specific figures are given they are meant to indicate only such general proportions. the thought has been not to be so specific that the figures would soon be out of date. all standard statistical sources have been drawn on, but the principal sources have been the results of the various special investigations called out by the war, in which the writer had a part. on the geologic side many sources have been drawn on outside of the writer's own experience. for the most part, no specific references or acknowledgments are made, on the ground that the book aims to present the general features which are now the more or less common knowledge of economic geologists. to make the references really adequate for exhaustive study would not only burden the text, but would require a specificity of treatment which it has been hoped to avoid. the illustrative cases chosen for discussion are often taken from the writer's field of experience. this field has been principally the lake superior region, but has included also the principal mineral deposits of north america, cuba, and limited areas in south america and europe. thus the lake superior iron and copper region might seem to be brought forward more than is warranted by its scientific or economic importance. for this, the writer offers no apology. an author's perspective is largely determined by his background of training and experience, and a frank recognition of this fact may aid in determining the weight to be given to his conclusions. it might even add to scientific efficiency if each writer were to confine his discussion almost solely to matters within his own range of observation and study. the writer's indebtedness for information derived from the printed page and for personal discussion and advice is of wide range. he would express his warm appreciation of the friendly spirit of coöperation and advice with which this effort has been aided--a spirit which he likes to think is particularly characteristic of the profession of economic geology. in particular he would acknowledge the efficient aid of mr. julian d. conover in preparation and revision of the manuscript. chapter ii the common elements, minerals, and rocks of the earth and their origins a list of the solid substances of the earth making up the so-called lithosphere (or rock sphere) in order of their abundance, does not at all correspond to a list made in order of commercial importance. some of the most valuable substances constitute such a small proportion of the total mass of the lithosphere that they hardly figure at all in a table of the common substances. relative abundance of the principal elements of the lithosphere when reduced to the simplest terms of elements the outer ten miles of the lithosphere consists of:[ ] percentage of principal elements in the lithosphere oxygen . silicon . aluminum . iron . calcium . magnesium . sodium . potassium . ----- . the remainder of the elements exist in quantities of less than per cent. none of these principal elements occur separately in nature and none of them are mined as elements for economic purposes. relative abundance of the principal minerals of the lithosphere minerals exceptionally consist of single elements, but ordinarily are combinations of two or more elements; for instance, quartz consists of a chemical combination of silicon and oxygen. the proportions of the common minerals in the outer ten miles of the lithosphere are in round numbers as follows: percentage of common minerals in lithosphere feldspar quartz augite, hornblende, and olivine mica magnetite titanite and ilmenite kaolin, limonite, hematite, dolomite, calcite, chlorite, etc. --- in making up this table it is assumed that the rocks to a depth of ten miles are about per cent of igneous type, that is, crystallized from molten magma, and about per cent of sedimentary type, that is, formed from the weathering and erosion of igneous rocks or preëxisting sediments, and deposited in beds or layers, either by water or by air (see pp. - ). more reliable figures for the relative abundance of the minerals are available for each of the two classes of rocks, igneous and sedimentary. the igneous rocks contain minerals in about the following proportions: percentage of common minerals in igneous rocks feldspar quartz augite, hornblende, olivine, etc. mica magnetite titanite and ilmenite --- the sedimentary rocks contain minerals in about the following proportions: percentage of common minerals in sedimentary rocks quartz feldspar white mica kaolin (clay) dolomite chlorite calcite limonite gypsum, carbon, rutile, apatite, magnetite, etc. --- the sedimentary rocks comprise three main divisions: ( ) the muds and clays, with their altered equivalents, shale, slate, etc.; ( ) the sands, with their altered equivalents, sandstone, quartzite, quartz-schist, etc.; ( ) the marls, limestones, and dolomites, with their altered equivalents, marble, talc-schist, etc. for brevity these groups are referred to respectively as shale, sandstone, and limestone. the proportions of minerals in each of these groups of rocks are as follows: percentage of common minerals in shale, sandstone, and limestone -----------+----------+-----------+----------- | average | average | average | shale | sandstone | limestone -----------+----------+-----------+----------- quartz | . | . | . kaolin | . | . | . white mica | . | | chlorite | . | . | limonite | . | . | dolomite | . | . | . [ ] calcite | | . | . gypsum | . | . | . feldspar | . | . | . magnetite | | . | rutile | . | . | . ilmenite | | . | apatite | . | . | . carbon | . | | -----------+----------+-----------+----------- total | . | . | . -----------+----------+-----------+----------- : includes small amount of feco_{ }. in comparing the mineral composition of igneous and sedimentary rocks, it will be noted that the most abundant single mineral of the igneous rocks, and the most abundant mineral of the lithosphere as a whole, is _feldspar_; that next in order is _quartz_; and that third comes a group of dark green minerals typified by augite and hornblende, commonly called _ferro-magnesian silicates_ because they consist of iron and magnesia, with other bases, in combination with silica. the sedimentary rocks, which are ultimately derived from the destruction of the igneous rocks, contrast with the igneous rocks mainly in their smaller proportions of feldspars and ferro-magnesian minerals, their higher proportions of quartz and white mica (sericite or muscovite), and their content of kaolin, dolomite, calcite, chlorite, limonite, etc., which are nearly absent from the unaltered igneous rocks. evidently the development of sediments from igneous rocks has involved the destruction of much of the feldspars and ferro-magnesian silicates, and the building from the elements of these destroyed minerals of more quartz, white mica, clay, dolomite, calcite, chlorite and limonite. the composition of the minerals of the sedimentary rocks is such as to indicate that the constituents of the air and water have been added in important amounts to accomplish this change of mineral character. for instance, carbon dioxide of the atmosphere has been added to lime and magnesia of the igneous rocks to make calcite and dolomite, water has been added to some of the alumina and silica of the igneous rocks to make kaolin or clay, and both oxygen and water have been added to the iron of the igneous rocks to make limonite. relative abundance of the principal rocks of the lithosphere just as elements combine chemically to form minerals, so do minerals combine mechanically, either loosely or compactly, to form rocks. for instance, quartz is a mineral. an aggregation of quartz particles forms sand or sandstone or quartzite. most rocks contain more than one kind of mineral. sedimentary rocks occupy considerable areas of the earth's surface, but they are relatively superficial. it has been estimated that if spread evenly and continuously over the earth, which they are not, they would constitute a shell scarcely a half mile thick.[ ] igneous rocks are relatively more abundant deep below the surface. if the sediments be assumed to be limited to a volume equivalent to a half-mile shell, and the remainder of the rocks be assumed to be igneous, it is evident that to a depth of ten miles per cent of the rocks are igneous. our actual observation is confined to a shallow superficial zone in which sediments make up at least half of all the rocks. igneous rocks can be divided for convenience into two main types: ( ) granite and allied rocks, containing a good deal of silica and therefore _acid_ in a chemical sense, and ( ) basalt and allied types, containing less silica and more lime, magnesia, iron, soda and potassa, and therefore _basic_ in a chemical sense. the former are light-colored gray and pink rocks while the latter are dark-colored green and gray rocks. granite and basalt as technically defined are very common igneous rocks,--so common that the names are sometimes used to classify igneous rocks in general into two great groups, the granitic and the basaltic. it has been estimated that about per cent of the igneous rocks are of the granitic group and per cent of the basaltic group. sedimentary rocks, as already indicated, consist principally of three groups, which for convenience are named shale, sandstone, and limestone. if we approximate the average composition of each group and the average composition of the igneous rocks from which they are ultimately derived, it can be calculated that sedimentary rocks must form in the proportions of per cent shale, per cent sandstone, and per cent limestone. only this combination of the three sediments will yield an average composition comparable with that of the parent igneous rocks. as actually observed in the field the sandstones and limestones are in relatively higher percentage than is here indicated, suggesting that part of the shales may have been deposited in deep seas where they cannot be observed, and that part may have been so changed or metamorphosed that they are no longer recognized as shales. soils and clays weathered and disintegrated rocks at the surface form soils and clays. no estimate is made of abundance, but obviously the total volume of these products is small as compared with the major classes of earth materials above noted, and in large part they may be included with these major classes. water (hydrosphere) it has been estimated that all the water of the earth, including the ocean, surface waters, and underground waters, constitutes about per cent of the volume of the earth to a depth of miles.[ ] comparison of lists of most abundant rocks and minerals with commercial rocks and minerals of the common rocks and minerals figuring as the more abundant materials of the earth's crust, only a few are prominently represented in the tables of mineral resources. of these water and soils stand first. others are the common igneous and sedimentary rocks used for building and road materials. missing from the lists of the most abundant minerals and rocks, are the greater part of the commercially important mineral resources--including such as coal, oil, gas, iron ore, copper, gold, and silver,--implying that these mineral products, notwithstanding their great absolute bulk and commercial importance, occur in relatively insignificant amounts as compared with the common rock minerals of the earth. the origin of common rocks and minerals the common rocks and minerals develop in a general sequence, starting with igneous processes, and passing through stages of weathering, erosion, sedimentary processes, and alterations beneath the surface. the commercial minerals are incidental developments under the same processes. igneous processes the earliest known rocks are largely igneous. sedimentary rocks are formed from the breaking down of igneous rocks, and the origin of rocks therefore starts with the formation of igneous rocks. igneous rocks are formed by the cooling of molten rock material. the ultimate source of this molten material does not here concern us. it may come from deep within the earth or from comparatively few miles down. it may include preëxisting rock of any kind which has been locally fused within the earth. wherever and however formed, its tendency is to travel upward toward the surface. it may stop far below the surface and cool slowly, forming coarsely crystallized rocks of the granite and gabbro types. igneous rocks so formed are called _plutonic_ intrusive rocks. or the molten mass may come well toward the surface and crystallize more rapidly into rocks of less coarse, and often porphyritic, textures. such intrusive rocks are porphyries, diabases, etc. or the molten mass may actually overflow at the surface or be thrown out from volcanoes with explosive force. it then cools quickly and forms finely crystalline rocks of the rhyolite and basalt types. these are called effusives or extrusives, or lavas or volcanics, to distinguish them from intrusives formed below the surface. the intrusive masses may take various forms, called stocks, batholiths, laccoliths, sills, sheets and dikes, definitions and illustrations of which are given in any geological textbook. the effusives or volcanics at the surface take the form of sheets, flows, tuffs, agglomerates, etc. some of the igneous rocks are themselves "mineral" products, as for instance building stones and road materials. certain basic intrusive igneous rocks contain titaniferous magnetites or iron ores as original constituents. others carry diamonds as original constituents. certain special varieties of igneous rocks, known as pegmatites, carry coarsely crystallized mica and feldspar of commercial value, as well as a considerable variety of precious gems and other commercial minerals. pegmatites are closely related to igneous after-effects, discussed under the next heading. as a whole, the mineral products formed directly in igneous rocks constitute a much less important class than mineral products formed in other ways, as described below. =igneous after-effects.= the later stages in the formation of igneous rocks are frequently accompanied by the expulsion of hot waters and gases which carry with them mineral substances. these become deposited in openings in adjacent rocks, or replace them, or are deposited in previously hardened portions of the parent igneous mass itself. they form "contact-metamorphic" and certain vein deposits. pegmatites, referred to above, are in a broad sense in this class of "igneous after-effects," in that they are late developments in igneous intrusions and often grade into veins clearly formed by aqueous or gaseous solutions. among the valuable minerals of the igneous after-effect class are ores of gold, silver, copper, iron, antimony, mercury, zinc, lead, and others. while mineral products of much value have this origin, most of them have needed enrichment by weathering to give them the value they now have. weathering of igneous rocks and veins no sooner do igneous rocks appear at or near the earth's surface, either by extrusion or as a result of removal by erosion of the overlying cover, than they are attacked vigorously by the gases and waters of the atmosphere and hydrosphere as well as by various organisms,--with maximum effect at the surface, but with notable effects extending as far down as these agents penetrate. the effectiveness of these agents is also governed by the climatic and topographic conditions. under conditions of extreme cold or extreme aridity, weathering takes the form mainly of mechanical disintegration, and chemical change is less conspicuous. under ordinary conditions, however, processes of chemical decomposition are very apparent. the result is definitely known. the rocks become softened, loose, and incoherent. voids and openings appear. the volume tends to increase, if all end products are taken into account. the original minerals, largely feldspar, ferro-magnesian minerals, and quartz, become changed to clay, mixed with quartz or sand, calcite or dolomite, and iron oxide, together with residual particles of the original feldspars and ferro-magnesian minerals which have only partly decomposed. in terms of elements or chemical composition, water, oxygen, and carbon dioxide, all common constituents of the atmosphere and hydrosphere, have been added; and certain substances such as soda, potassa, lime, magnesia, and silica have in part been carried away by circulating waters, to be redeposited elsewhere as sediments, vein fillings, and cements. figure illustrates the actual mineral and volume changes in the weathering of a granite--one of the most common rocks. the minerals anorthite, albite, and orthoclase named in this figure are all feldspars; sylvite and halite are chlorides of potash and soda. the weathering processes tend to destroy the original minerals, textures, and chemical composition. they are collectively known as _katamorphic_ alterations, meaning destructive changes. the zone in which these changes are at a maximum is called the _zone of weathering_. this general zone is principally above the surface or level of the ground-waters, but for some rocks it extends well below this level. in some regions the ground-water level may be nearly at the surface, and in others, especially where arid, it may be two thousand or more feet down. disintegrated weathered rocks form a blanket of variable thickness, which is sometimes spoken of as the residual mantle, or "mantle rock." [illustration: fig. . graphic representation of volume change in weathering of a georgia granite.] mineral products formed by weathering from common igneous rocks include soils, clay, bauxite, and certain iron, chromite, and nickel ores. again the commercial importance of this group is not large, as compared with products formed in other ways described below. the same weathering processes described above for igneous rocks cause considerable changes of economic significance in deposits formed as igneous after-effects. in some cases they result in removing the less valuable minerals, thus concentrating the more valuable ones, as well as in softening the rock and making it easier to work; and in other cases they tend to remove the valuable constituents, which may then be redeposited directly below or may be carried completely out of the vicinity. the _oxide zones_ of many ore bodies are formed by these processes. sedimentary processes sedimentary rocks are formed by the removal and deposition of the weathered products of a land surface. air, water, and ice, moving under the influence of gravity and other forces, all aid in this transfer. the broken or altered rock materials may be merely moved down slopes a little way and redeposited on the surface, forming one type of _terrestrial_ or _subaërial deposits_, or they may be transferred and sorted by streams. when deposited in streams or near their mouths, they are known as _river_, _alluvial_, or _delta deposits_. when carried to lakes and deposited they form _lake deposits_. ultimately the greater part of them are likely to be carried to the ocean and deposited as _marine sediments_. part of the weathered substances are carried mechanically as clay and sand, which go to make up the _shale_ and _sandstone_ sediments. part are carried in solution, as for example lime carbonate and magnesium carbonate, which go to make up _limestone_ and _dolomite_. some of the dissolved substances are never redeposited, but remain in solution as salts in the sea, the most abundant of which is sodium chloride. some of the dissolved substances of weathering, such as calcite, quartz, and iron oxide, are carried down and deposited in openings of the rocks, where they act as cements. the sediments as a whole consist of three main types,--_shales_ (kaolin, quartz, etc.), _sandstones_ (quartz, feldspar, etc.), and _limestones_ or _dolomites_ (carbonates of lime and magnesia). of these, the shale group is by far the most abundant. there are of course many sediments with composition intermediate between these types. there are also sediments made up of large undecomposed fragments of the original rocks, cemented to form _conglomerates_, or made up of small fragments of the original rocks cemented to form _arkoses_ and _graywackes_. these, however, may be regarded as simply stages in the alteration, which in repeated cycles of weathering must ultimately result in producing the three main groups,--shales, sandstones, and limestones. mineral products formed by sedimentary processes include sandstones, limestones, and shales, used as building stone and road materials; certain sedimentary deposits of iron, like the clinton ores of the southeastern united states and the brazilian ores; important phosphate deposits; most deposits of salt, gypsum, potash, nitrates, etc.; comparatively few and unimportant copper deposits; and important placer deposits of gold, tin, and other metals, and precious stones. with the aid of organic agencies, sedimentary processes also account for the primary deposition of coal and oil. weathering of sedimentary rocks after sedimentary rocks are formed, and in many cases covered by later sediments, they may be brought again by earth movements and erosion to the surface, where they in turn are weathered. the weathering of sedimentary rocks proceeds along lines already indicated for the igneous rocks. residual mantles of impure clay and sand are commonly formed. the mineral composition of sedimentary rocks being different from that of igneous rocks to start with, the resulting products are in slightly different proportions; but the changes are the same in kind and tend merely to carry the general process of alteration farther in the same direction,--that is, toward the production of a few substances like clay, quartz, iron oxide, and calcite, which are transported and redeposited to form clay, sand, and limestone. cycles of this kind may be repeated indefinitely. by weathering of sedimentary rocks are produced some soils, certain commercial clays, iron ores, lead and zinc ores, and other valuable mineral products. consolidation, cementation, and other subsurface alterations of rocks. =cementation.= no sooner are residual weathered mantles formed or sedimentary rocks deposited, whether under air or water, than processes of consolidation begin. settling, infiltration of cementing materials, and new growths, or recrystallization, of the original minerals of the rock all play a part in the process. the mud or clay becomes a shale, the sand becomes sandstone or quartzite, the marl becomes limestone or marble. all the minute openings between the grains, as well as larger openings such as fissures and joints, may thus be filled. at the same time the cementing materials may replace some of the original minerals of the rock, the new minerals either preserving or destroying the original textures. this process is sometimes called _metasomatic replacement_. igneous rocks as a rule are compact, and hence are not so much subject to the processes of cementation as sedimentary rocks; but certain of the more porous phases of the surface lavas, as well as any joints in igneous rocks, may become cemented. all of these changes may be grouped under the general term _cementation_. a special phase of consolidation and cementation is produced near intrusive igneous rocks through the action of the heat and pressure and the expelled substances of the igneous rock. this is called _contact metamorphism_ or _thermal metamorphism_. the processes are even more effective when acting in connection with the more intense metamorphism described under the next heading. by cementation some of the common rocks, especially the sediments, become sufficiently compact and strong to be useful as commercial products, such as building stones and road materials. more important as mineral products are the cementing materials themselves. these are commonly quartz, calcite, or iron oxide, of no especial value, but locally they include commercially valuable minerals containing gold, copper, silver, lead, zinc, and many other mineral products. it is a matter of simple and direct observation, about which there is no controversy, that many minerals are deposited as cements in the openings in rocks or replacing rocks. as to the source of the solutions bringing in these minerals, on the other hand, there has been much disagreement. in general, the common cementing materials such as quartz and calcite, as well as some of the commercial minerals, are clearly formed as by-products of weathering, and are transported and redeposited by the waters penetrating downward from the surface. the so-called _secondary enrichment_ of many valuable veins is merely one of the special phases of cementation from a superficial source. in other cases it is believed that deep circulation of ordinary ground-waters may pick up dispersed mineral substances through a considerable zone, and redeposit them in concentrated form in veins and other trunk channels. for still other cementing materials, it is suspected that the ultimate source is in igneous intrusions; in fact, deposits of this general character show all gradations from those clearly formed by surface waters, independently of igneous activity, to those of a contact-metamorphic nature and others belonging under the head of "igneous after-effects." hypothesis and inference play a considerable part in arriving at any conclusion as to the source of cementing materials,--with the result that there is often wide latitude for difference of opinion and of emphasis on the relative importance of the different sources of ore minerals. =dynamic and contact metamorphism.= beneath the surface rocks are not only cemented, but may be deformed or mashed by dynamic movements caused by great earth stresses; the rocks may undergo rock flowage. the result is often a remarkable transformation of the character of the rocks, making it difficult to recognize their original nature. also, igneous intrusions may crowd and mash the adjacent rocks, at the same time changing them by heat and contributions of new materials. this process may be called _contact metamorphism_, but in so far as it results in mashing of the rocks it is closely allied to _dynamic metamorphism_. the former term is also applied to less profound changes in connection with igneous intrusions, which result merely in cementation without mashing. dynamic and contact metamorphism may in some cases produce rocks identical in appearance with those produced by ordinary processes of cementation and recrystallization without movement. for instance, it is difficult to tell how much movement there has been in the production of a marble, because both kinds of processes seem to produce much the same result. commonly, however, the effect of dynamic metamorphism is to produce a parallel arrangement of mineral particles and to segregate the mineral particles of like kind into bands, giving a _foliated_ or _schistose_ or _gneissic_ structure, and the rocks then become known as slates, schists, or gneisses. commonly they possess a capacity to part along parallel surfaces, called _cleavage_. the development of the schistose or gneissic structure is accompanied by the recrystallization of the rock materials, producing new minerals of a platy or columnar type adapted to this parallel arrangement. even the composition of the rock may be substantially changed, though this is perhaps not the most common case. whereas by weathering the rock is loosened up and disintegrated, substances like carbon dioxide, oxygen, and water are abundantly added, and light minerals of simple composition tend to develop,--by dynamic metamorphism on the other hand, carbon dioxide, oxygen, and water are usually expelled, the minerals are combined to make heavier and more complex minerals, pore space is eliminated, and altogether the rock becomes much more dense and crystalline. while segregation of materials is characteristic of the surficial products of weathering, the opposite tendency, of mixing and aggregation, is the rule under dynamic metamorphism, notwithstanding the minor segregation above noted. dynamic metamorphism is for the most part unfavorable to the development of mineral products. ore bodies brought into a zone where these processes are active may be profoundly modified, but not ordinarily enriched. one of the exceptions to this general rule is the development of the cleavage of a slate, which enables it to be readily split and thereby gives it value. contact metamorphism, on the other hand, may develop valuable mineral deposits (see pp. , - ). the metamorphic cycle as an aid in studying mineral deposits all of the chemical, mineralogical, and textural changes in rocks above described may be collectively referred to as _metamorphism_. the phase of metamorphism dealing with surficial weathering, similar changes below the surface, and the formation of sediments, is called _katamorphism_ or destructive change. the phase of metamorphism dealing with the constructive changes in rocks, due to cementation, dynamic movements, and igneous influences, is called _anamorphism_. some geologists confine the term metamorphism to the changes involved in contact and dynamic metamorphism, and call the resulting products _metamorphic rocks_. the zone in which katamorphism is most active, usually near the surface, is called the _zone of katamorphism_. the deeper zone in which anamorphism is preponderant is called the _zone of anamorphism_. there are no definite limits of depth to these zones. a given rock may be undergoing katamorphism while rocks on either side at the same depth are suffering anamorphism. by katamorphism rocks break down to produce the surficial rocks, and by anamorphism the surficial rocks are again consolidated and altered to produce highly crystalline rocks, which are not dissimilar in many of their characteristics to the igneous rocks from which all rocks trace their ultimate origin. in other words, anamorphism tends toward the reproduction of igneous rocks, though it seldom fully accomplishes this result. these two main groups of changes together constitute the _metamorphic cycle_. some rocks go through all phases of the cycle, but others may pass directly from one phase to an advanced phase without going through the intermediate stages. for instance, an igneous rock may become a schist without going through the intermediate stage of sedimentation. rocks are not permanent in their condition, but at practically all times and places are undergoing some kind of metamorphism which tends to adapt them to their environment. the conception of rocks as representing phases or stages in a progressive series of changes called the metamorphic cycle aids greatly in correlating and holding in mind many details of rock nature and origin, and brings into some sort of perspective the conditions which have produced rocks. a schistose sediment comes to be regarded as an end product of a long series of alterations, beginning with igneous rocks and passing through the stages of weathering, sedimentation, cementation, etc., each of which stages has been responsible for certain mineralogical, chemical, and textural features now characterizing the rock. the alternation of constructive and destructive changes of the metamorphic cycle, and the repetitions of the cycle itself, periodically work over the earth materials into new forms. usually the cycles are not complete, in the sense that they seldom bring the rock back to exactly the same condition from which it started. more sediments are formed than are changed to schists and gneisses, and more schists and gneisses are formed than are changed back to igneous rocks. salts in the ocean continuously accumulate. the net result of the metamorphic cycle, is, therefore, the accumulation of materials of the same kinds. incidental to these accumulations is the segregation of commercial mineral products. the metamorphic cycle becomes a logical and convenient geologic basis for correlating, interpreting, and classifying mineral products. because of the great variety of materials and conditions represented in mineral deposits, prodigious efforts are required to remember them as independent entities; but as incidents or stages in the well-known progress of the metamorphic cycle, their essential characteristics may be easily remembered and kept in some perspective. ores of certain metals, such as iron, occur in almost every phase of the metamorphic cycle,--as igneous after-effects, as weathered products, as sediments, and as schists. the ores of each of these several phases have group characteristics which serve to distinguish them in important particulars from ores belonging to other phases of the cycle. having established the position of any particular ore in the metamorphic cycle, a number of safe inferences are possible as to mineralogical composition, shape, extent, and other conditions, knowledge of which is necessary for an estimate of commercial possibilities. footnotes: [ ] clarke, f. w., data of geochemistry: _bull. , u. s. geol. survey_, , p. . [ ] clarke, f. w., data of geochemistry: _bull. , u. s. geol. survey_, , p. . [ ] clarke, f. w., data of geochemistry: _bull. , u. s. geol. survey_, , pp. - . chapter iii some salient features of the geology and classification of mineral deposits various methods of classification mineral products may be classified according to use, commercial importance, geographic distribution, form and structure, mineralogical and chemical composition, or origin. each of these classifications is useful for some purposes. the geologist usually prefers a classification based on origin or genesis. in the following chapters on mineral resources, however, such a classification is not the primary one, because of the desire to emphasize economic features. the mineral commodities are treated as units and by group uses. some mineral commodities have so many different kinds of origin in different regions that to distribute them among several genetic groups in description would make it impossible to preserve the unity necessary for consideration of the economic features. while in the descriptive chapters many references are made to origin, it may be difficult for the reader to assemble them in perspective; for this reason we summarize at the outset some of the salient features of origin of mineral deposits and of their geologic classification. to the layman the reason for emphasis on origin is often not clear. the "practical" man frequently regards this phase of the subject as merely incidental to the immediate economic questions--a playground for harmless theorists. the answer of the economic geologist is that in no other way than by a knowledge of origin is it possible to arrive at an understanding of conditions which so well enables one to answer many practical questions. in the exploration for mineral deposits, it is obvious that an understanding of the kinds of geologic conditions and processes under which a given type of deposit is known to develop results in the elimination of much unpromising territory, and the concentration of work on favorable localities. in forming any estimate of mineral deposits beyond the ground immediately opened up,--for instance, in estimating depth, form, change in values, mineralogical character, or interruptions due to faulting,--it is difficult to form any intelligent conception of the probabilities unless the history of the deposit is understood. if, for instance, the ore is known to be formed by hot waters, associated with the cooling of igneous rocks, different conditions are to be expected below the zone of observation than if the ore is formed by surface waters. if the ore body is formed as a single episode under simple geologic conditions, the interpretation of the possibilities in the situation may be quite different from the interpretation applied where the history has been more complex. if the surface conditions suggest possibilities of secondary enrichment of the ores, the interpretation of the conditions underground will be different from those applied where there is no evidence of such enrichment. where a mineral deposit is completely opened up in three dimensions, it is often possible to work out economic questions of tonnage, grade, shape, and values, without the aid of geology. also, where conditions are comparatively simple and uniform throughout a district, the local knowledge of other mines may be a sufficient basis for answering these questions for any new property developed. empirical methods may suffice. however, it is seldom that the conditions are so simple that some geological inference is not necessary. even where problems are settled without calling in the geologist, geological inferences are required in the interpretation of, and projection from, the known facts. it is often the case that the practical man has in his mind a rather elaborate assortment of geologic hypotheses, based on his individual experience, which make the so-called theories of the geologist seem conservative in comparison. the geologist comes to the particular problem with a background of established geologic principles and observations, and his first thought is to ascertain all the local conditions which will aid in deciphering the complete history of the mineral deposit. there is no fact bearing on the history, however remote from practical questions, which may not be potentially valuable. with this digression to explain the geologist's emphasis on origin of mineral products, we may return to a consideration of a few of the principles of rock and mineral genesis which have been found to be significant in the study of mineral products. in the preceding chapters it has been indicated that mineral deposits are mere incidents in the mass of common rocks; that they are made by the same processes which make common rocks, that none of the processes affecting mineral deposits are unique for these minerals, and that most common rocks are on occasion themselves used as mineral resources. these facts are emphasized in order to make it clear that the study of mineral deposits cannot be dissociated from the study of rocks, and that the study of the latter is essential to bring mineral deposits into their proper perspective. absorption in the details of a mineral deposit makes it easy for the investigator to forget or minimize these relations. nevertheless, in the study of mineral deposits, and especially deposits of the metallic minerals, certain geologic features stand out conspicuously against the common background indicated above. our discussion of these features will follow the order of rock genesis indicated in the description of the metamorphic cycle. names any classification of mineral deposits on the basis of origin is more or less arbitrary. the sharp lines implied by the use of class names do not exist in nature. mineral deposits are so complex and so interrelated in origin, that a classification according to genesis indicates only the essential and central class features; it does not sharply define the limits of the classes. it is practically impossible for any geologist to present a classification which will be accepted without qualification by other geologists, although there may be agreement on essential features. difficulties in reaching agreement are increased by the inheritance from the past of names, definitions, and classifications which do not exactly fit present conceptions based on fuller information,--but which, nevertheless, have become so firmly established in the literature that it is difficult to avoid their use. in the progress of investigation many new names are coined to fit more precisely the particular situation in hand, but only in fortunate cases do these new names stand up against the traditional currency and authority of old names. the geologist is often in despair in his attempt to express his ideas clearly and precisely, and at the same time to use terms which will be understandable by his readers and will not arouse needless controversy. as illustrative of the above remarks reference may be made to a few terms commonly used in economic geology, such as _primary_, _secondary_, _syngenetic_, _epigenetic_, _supergene_, _hypogene_, _protore_, etc. the most commonly used of these terms are _primary_ and _secondary_. it is almost impossible to define them in a way which will cover all the conceptions for which they have been used, and yet in their context they have been very useful in conveying essential ideas. an ore formed by direct processes of sedimentation has sometimes been called primary, whereas an ore formed by later enrichment of these sediments has been called secondary. an ore formed directly by igneous processes has been called primary, while an ore formed by enrichment of such primary ore by later processes has been called secondary. it is clear, however, that these terms are merely relative, with application to a specific sequence, and that they do not fix the absolute position of the ore in a sequence applying to all ores. for instance, ores deposited directly as sediments or placers may be derived from the erosion of preëxisting ore bodies,--in which case it may sometimes be convenient to refer to the sedimentary ores or placers as secondary and the earlier ores as primary. or a sulphide deposit originating through igneous agencies may undergo two or three successive enrichments, each successive one secondary to the preceding, but primary to the one following. in spite of these obvious difficulties, the terms primary and secondary may be entirely intelligible as indicating relative order of development under a given set of conditions. the term _syngenetic_ has been used for mineral deposits formed by processes similar to those which have formed the enclosing rocks and in general simultaneously with them, and _epigenetic_ for those introduced into preëxisting rocks. in certain cases _syngenetic_ may be roughly synonymous with _primary_, and _epigenetic_ with _secondary_, and yet a primary ore may be epigenetic. for instance, zinc sulphides in the mississippi valley limestones (pp. - ) are epigenetic, and yet are primary with reference to a later enrichment. the two sets of terms are meant to convey somewhat different ideas and are not interchangeable. ransome[ ] has suggested, especially for vein and contact deposits, a series of names which has the considerable advantage of definiteness:--_hypogene ores_, formed in general by ascending non-oxidizing solutions, perhaps hot; _supergene ores_, formed in general by oxidizing and surface solutions, initially cold and downward moving; and _protores_, or metallized rock or vein substances which are too low in tenor to be classed as ores, but which would have been converted into ores had the enriching process been carried far enough. in this connection ransome defines primary ore as unenriched material that can be profitably mined. in view of the general use of the terms primary and secondary as expressing a sequential relation of ore development, it is doubtful whether this more precise definition will supersede the older usage. also it may be noted that commercial conditions might require, under these definitions, the designation of an ore as a protore at one time or place and as a primary ore at another. hypogene ores are dominantly primary, and supergene ores are dominantly secondary, but either may include both primary and secondary ores. the terms of these several classifications overlap, and seek to express different aspects of the same situation. while almost synonymous in certain applications they are not in others. in this text the writer has certainly not escaped the difficulties in regard to names above referred to, nor in fact has he made any exceptional effort to do so. his chief purpose is to convey, in somewhat elementary terms, an understandable idea of the central features of economic geology. in the main, the most widely accepted terms are used. almost at every turn it would be possible, in the interests of precision, to introduce qualifying discussions of names,--but at the expense of continuity and perspective in the presentation of the principal subject-matter. the writer does not wish to minimize the necessity for careful and precise nomenclature; but he regards it important that the student focus his attention on the central objective facts of the subject, and that he do not become misled by the sometimes over-strenuous advocacy of certain names or classifications in preference to others. if the facts are understood, he will ordinarily have no difficulty in judging the significance of the variety of names proposed to express these facts. if, on the other hand, the student approaches the subject with a ready-made set of names and definitions learned by rote, he is in danger of perceiving his facts from one angle only and through a distorted perspective. mineral deposits as magmatic segregations in igneous rocks in this class are included deposits which crystallize within the body of igneous rock, almost, if not quite, simultaneously with the adjacent rock. these deposits form one of the main types of _syngenetic_ deposits. the titaniferous magnetites constitute a widely distributed but at present commercially unavailable class of iron ores. the magnetite crystals of these deposits interpenetrate with the other constituents of an igneous rock, commonly of a gabbro type, and the deposits themselves are essentially igneous rocks. their shapes are for the most part irregular, their boundaries ill-defined, and their concentration varying. while their magmatic origin is clear, there is little agreement as to the precise conditions which determined their segregation in the molten rock. there is often a tendency for the ores to follow certain primary sheeted structures in the igneous mass, a fact for which the reason is not obvious. the sudbury nickel ores, of ontario, canada, the principal source of the world's nickel, lie mainly within and along the lower margin of a great intrusive igneous mass of a basic type called _norite_, and locally the ores project beyond the margin into adjacent rocks. their textures and their intercrystallization with the primary minerals of the igneous rock have suggested that they are essentially a part of the norite mass, and that they crystallized during some segregative processes which were effective before the magma had solidified. near the ores there are likely to be granitic rocks, which, like the ores, seem to be segregations from the norite magma. locally both the ores and the associated granitic rocks replace the main norite body in such a fashion as to indicate their slightly later crystallization. however, the intimate association of the ores with the primary minerals in the magma, together with their absence from higher parts of the norite and from the extraneous rocks far from the contact, indicate to other investigators that they were not brought in from outside in vagrant solutions which followed the intrusion of the main magma, but that they were segregated within the magma essentially in place. the occurrence of these heavy ores near the base of the norite naturally suggests that they were segregated by sinking to the bottom of the molten magma, but this conclusion implies certain physical conditions of the magma which have not yet been proved. again the precise nature of the process and the part played in it by aqueous and gaseous solutions are subject to some doubt and controversy. the settlement of this problem awaits the solution of the more general problem of the origin and crystallization of magmas. in this general class of igneous deposits may be mentioned also diamonds, platinum, chromite, corundum, and other mineral products, although for the formation of commercial ores of many of these substances further concentration by weathering and sedimentation has been required. pegmatites are coarsely crystalline acid dike rocks which often accompany a large igneous intrusion and which have obviously crystallized somewhat later than the main igneous mass. they may constitute either sharply delimited dikes or more irregular bodies which grade into the surrounding igneous mass. they have a composition roughly similar to the associated igneous rock, but usually a different proportion of minerals. they are probably the result of the differentiation of the parent magma. the pegmatites are of especial interest to the economic geologist because of the frequency with which they carry commercial minerals, such as the precious stones, mica, feldspar, cassiterite (tin ore), and others. they show a complete gradation from dikes of definitely igneous characteristics to veins consisting largely of quartz in which evidence of igneous origin is not so clear. the pegmatites thus afford a connecting link between ores of direct igneous sources and ores formed as "igneous after-effects," which are discussed in the next paragraph. aplites are fine-grained acid igneous rocks of somewhat the same composition as the pegmatites and often show the same general relations to ores. mineral deposits within and adjacent to igneous rocks which were formed immediately after the cooling and crystallization of the magmas through the agency of hot magmatic solutions. these deposits are closely associated in place and age with igneous rocks, either intrusive or extrusive, and are usually considered to have come from approximately the same source; and yet they afford distinct evidence of having been deposited after the adjacent igneous rocks were completely crystallized and fractured. they are thus _epigenetic_ deposits. they are not themselves igneous rocks and they do not constitute pegmatites, but they often grade into pegmatites and belong to the same general stage in the sequence of events. they include deposits formed by contact metamorphism. they are sometimes designated by the general term "igneous after-effects"--a term also applied in some cases to pegmatites. some geologists discriminate between "deep vein" deposits (p. ) and "contact-metamorphic" deposits, but the two are so closely related in place and origin that for our purposes they will be considered together. the ores of this class are clearly deposited from vagrant solutions which wander through openings of all kinds in the igneous rock and outward into the adjacent country rocks. they also replace the wall rocks; limestone is especially susceptible. this is a phase of contact metamorphism. some of the most important metalliferous deposits belong in this class, including most of the gold, silver, copper, iron, lead and zinc ores of the western united states and the copper deposits of lake superior. in general, ores of this class are more abundant about intrusive igneous rocks, that is about igneous rocks which have stopped and cooled before reaching the surface,--than in association with extrusive igneous rocks which have poured over the surface as lava flows--but the latter are by no means insignificant, including as they do such deposits as the lake superior copper ores, the kennecott copper ores of alaska, some of the gold-silver deposits of goldfield and other nevada camps, and many others. there is general similarity in the succession of events shown by study of ore bodies related to intrusives. first, the invasion of the magma, resulting in contact metamorphism of the adjacent rocks, sometimes with, and often without conspicuous crowding effects on the invaded rocks; second, the cooling, crystallization, and cracking of both the igneous rock and the adjacent rock; third, the introduction of ore-bearing solutions into these cracks,--sometimes as a single episode, sometimes as a long continued and complex process forming various types of minerals at successive stages. this order may in some cases be repeated in cycles, and overlapping of the successive events is a common feature. one of the interesting facts is the way in which the igneous mass has invaded and extensively altered the country rocks in some mineral districts,--in some cases by crowding and crumpling them, and in others without greatly disturbing their structural attitudes. the latter is illustrated in the bingham district of utah and the philipsburg district of montana. in such cases there is so little evidence of crowding of the country rocks as to raise the question how such large masses of intrusives could be introduced without greater disturbing structural effect. this leads naturally to consideration of the general problem of the manner of progress of magmas through adjacent rocks,--a subject which is still largely in the realm of speculation, but which is not thereby eliminated from the field of controversy. facts of this kind seem to favor the position of certain geologists that magmas may assimilate the rocks they invade. evidence of igneous source no one ever saw one of these deposits in the process of formation; the conclusion, therefore, that they originated from hot solutions, either aqueous or gaseous, or both, which were essentially "after-effects" of igneous activity and came from the same primary source as the associated igneous rocks, is an inference based on circumstantial evidence of the kind below summarized: ( ) the close association both in place and age with igneous rocks. this applies not only to individual deposits, but to certain groups of deposits which have common characteristics, and which constitute a metallogenic province; also to groups of the same geologic age, which indicate a metallogenic epoch (pp. - ). the association with igneous rocks in one place might be a coincidence but its frequent repetition can hardly be so explained. a zonal arrangement of minerals about intrusives is often noted. geologic evidence often shows the processes of ore deposition to have been complete before the next succeeding geologic event,--as for instance in the tonopah district of nevada (p. ), where the ores have been formed in relation to certain volcanic flows and have been covered by later flows not carrying ore, without any considerable erosion interval between the two events. ( ) the general contrast in mineralogical and chemical composition, texture, and mineral associations, between these ore minerals and the minerals known to be formed by ordinary surficial agencies under ordinary temperatures. the latter carry distinctive evidences of their origin. when, therefore, a mineral group is found which shows contrasting evidences, it is clear that some other agencies have been at work; and the natural assumption is that the solutions were hot rather than cold; that they came from below rather than above. ( ) the contrast between the character and composition of these ores (and their associated gangue) and the character and composition of the wall rocks, together with the absence of leaching of the wall rocks, favor the conclusion that the ore minerals are foreign substances introduced from extraneous sources. the source not being apparent above and the processes there observed not being of a kind to produce these results, it is concluded that the depositing solutions were hot and came from below. ( ) the fact that many of the ore minerals are never known to develop under ordinary temperatures at the surface. for some of them, experimental work has also indicated high temperature as a requisite to their formation. quartz, which is a common associate of the ores and often constitutes the principal gangue, serves as a geologic thermometer in that it possesses an inversion point or temperature above which it crystallizes in a certain form, below which in another. in deposits of this class it has often been found to crystallize at the higher temperatures. the quartz sometimes shows bubbles containing liquid, gas, and small heavy crystals, probably of ferric oxide, as in the clifton-morenci district of arizona. it is clear that the ore-bearing solutions in these cavities, before the crystallization of the heavy mineral inclusions, held dissolved not only much larger quantities of mineral substances than can be taken up by water at ordinary temperatures, but also a substance like ferric oxide which is entirely insoluble under ordinary cool conditions. ( ) the association of the ores with minerals carrying fluorine and boron, with many silicate minerals, such as garnet, amphiboles, pyroxenes, mica (sericite) and others, and with other minerals which are known to be characteristic developments within or near igneous masses and which are not known to form under weathering agencies at the surface. various characteristic groupings of these associated minerals are noted. in limestone much of the mass may be replaced by garnet and other silicates in a matrix of quartz. in igneous rock the ore-bearing solutions may have altered the wall rock to a dense mixture of quartz, sericite, and chlorite. where sericite is dominant, the alteration is called sericitic alteration. where chlorite is important, it is sometimes called chloritic or "propylitic" alteration. the chloritic phases are usually farther from the ore deposit than the sericitic phases, indicating less intense and probably cooler conditions of deposition. locally other minerals are associated with the ores, as, for instance, in the goldfield district of nevada (p. ), where alunite replaces the igneous rock. alunite is a potassium-aluminum sulphate, which differs from sericite in that sulphur takes the place of silicon. in the quartzites of the lead-silver mines of the coeur d'alene district of idaho (p. ), siderite or iron carbonate is a characteristic gangue material replacing the wall rock. quartz in some cases, as noted above, gives evidence of high temperature origin and therefore of igneous association. jasperoid quartz, as well illustrated in the tintic district of utah (p. ), may show texture and crystallization suggestive of deposition from colloidal solution,--a process which can occur under both cold and hot conditions, but which is believed to be accelerated by heat. certain minerals, such as magnetite, ilmenite, spinel, corundum, etc., are often found as primary segregations within the mass of igneous rock. these and other minerals, including minerals of tin and tungsten, monazite, tourmaline, rutile, and various precious stones, are characteristically developed in pegmatites, which are known to be igneous rocks, crystallized in the later stages of igneous intrusion. when, therefore, such minerals are found in other ore deposits an igneous source is a plausible inference. for instance, in the copper veins of butte, montana (p. ), are found cassiterite (tin oxide) and tungsten minerals. their presence, therefore, adds another item to the evidence of a hot-water source from below. ( ) the occasional existence of hot springs in the vicinity of these ore deposits. where hot springs are of recent age they may suggest by their heat, steady flow, and mineral content, that they are originating from emanations from the still cooling magmas. in the tonopah camp (p. ), cold and hot springs exist side by side, exhibiting such contrasts as to suggest that some are due to ordinary circulation from the surface and that others may have a deep source below in the cooling igneous rocks. this evidence is not conclusive. hot springs in general fail to show evidence of ore deposition on any scale approximating that which must have been involved in the formation of this class of ore bodies. much has been made of the slight amounts of metallic minerals found in a few hot springs, but the mineral content is small and the conclusion by no means certain that the waters are primary waters from the cooling of igneous rocks below. in this connection the mercury deposits of california (p. ), contribute a unique line of evidence. in areas of recent lavas, mercuric sulphide (cinnabar) is actually being deposited from hot springs of supposed magmatic origin, the waters of which carry sodium carbonate, sodium sulphide, and hydrogen sulphide,--a chemical combination known experimentally to dissolve mercury sulphide. the oxidation and neutralization of these hot-spring solutions near the surface throws out the mercury sulphide. at the same time the sulphuric acid thus formed extensively leaches and bleaches the surrounding rocks. such bleaching is common about mercury deposits. when it is remembered that the mercury deposits contain minor amounts of gold and silver and sulphides of other metals; that they are closely associated with gold and silver deposits; and further that such gold, silver, and other sulphide deposits often contain minor amounts of mercury,--it is easy to assume the possibility that these minerals may likewise have had their origin in hot solutions from below. the presence of mercury in a deposit then becomes suggestive of hot-water conditions. ( ) ores sometimes occur in inverted troughs indicating lodgment by solutions from below, as, for instance, in the saddle-reef gold ores of nova scotia and australia, and in certain copper ores of the jerome camp of arizona (p. .) this occurrence does not indicate whether the solutions were hot or cold, magmatic or meteoric, but in connection with other evidences has sometimes been regarded as significant of a magmatic source beneath. perhaps no one of these lines of evidence is conclusive; but together they make a strong case for the conclusion that the solutions which deposited the ores of this class were hot, came from deep sources, and were probably primary solutions given off by cooling magmas. the conclusion that some ores are derived from igneous sources, based on evidence of the kind above outlined, does not mean necessarily that the ore is derived from the immediately adjacent part of the cooling magma. in fact the evidence is decisive, in perhaps the majority of cases, that the source of the mineral solutions was somewhat below; that these solutions may have originated in the same melting-pot with the magma, but that they came up independently and a little later,--perhaps along the same channels, perhaps along others. possible influence of meteoric waters in deposition of ores of this class it is hardly safe, with existing knowledge, to apply the above conclusion to all ore deposits with igneous associations, or in any case to eliminate entirely another agency,--namely, ground-waters of surface or meteoric origin, which are now present and may be presumed often to have been present in the rocks into which the ores were introduced. such waters may have been heated and started in vigorous circulation by the introduction of igneous masses, and thereby may have been enabled to effectively search out and segregate minutely disseminated ore particles from wide areas. this has been suggested as a probability for the kennecott copper ores of alaska (p. ) and for the copper ores of ely, nevada. in the goldfield camp (p. ) the ores are closely associated with alunite in such a manner as to suggest a common origin. it has been found difficult to explain the presence of the alunite except through the agency of surface oxidizing waters acting on hydrogen sulphide coming from below. in the early days of economic geology there was relatively more emphasis on the possible effectiveness of ground-waters in concentrating ores of this type. with the recognition of evidence of a deeper source related to magmas, the emphasis has swung rapidly to the other extreme. while the evidence is sound that the magmatic process has been an important one, it is difficult to see how and to just what extent this process may have been related to the action of ground-waters,--which were probably present in a heated condition near the contact. it may never be possible to discriminate closely between these two agencies. it seems likely that at some stages the two were so intimately associated that the net result of deposition cannot be specifically assigned either to one or to the other. zonal arrangement of minerals related to igneous rocks evidence is accumulating in many mining districts that ore deposits of these igneous associations were deposited with a rough zonal arrangement about the igneous rock. at bingham, tintic, and butte (pp. , , ), copper ores are on the whole closest to the igneous rock, and the lead, zinc, and silver ores are farther away. furthermore, the quartz gangue near the igneous rock is likely to contain minerals characteristic of hot solutions, while farther away such minerals as dolomite and calcite appear in the gangue, suggestive of cooler conditions. in cornwall (p. ), tin ores occur close to the intrusives, and lead-silver ores farther away. the gradations are by no means uniform; shoots of one class of ore may locally cut abruptly across or through those of another class. the existence of zones horizontally or areally arranged about intrusives suggests also the possibility of a vertical zonal arrangement with reference to the deep sources of the solutions. of course when secondary concentration from the surface, described later, is taken into account, there may be a marked zonal distribution in a vertical direction, but this is not primary zoning. a few veins and districts show evidence of vertical zoning apparently related to primary deposition; for the most part, however, in any one mine or camp there is yet little evidence of primary vertical zoning. on the other hand, certain groups of minerals are characteristic of intense conditions of heat and pressure, as indicated by the coarse recrystallization and high degree of metamorphism of the rocks with which they are associated; and other groups have such associations as to indicate much less intense conditions of temperature and pressure. depth is only one factor determining intensity of conditions, but it affords a convenient way to indicate them; so mineral deposits associated with igneous rocks are sometimes classified by economic geologists on the basis of deep, intermediate, and shallow depths of formation. there are a considerable number of minerals which are formed in all three of these zones, although in differing proportions. there are comparatively few which are uniformly characteristic of a single zone. on the whole, it is possible to contrast satisfactorily mineral deposits representing very intense metamorphic conditions, usually associated with formation at great depth, with those formed at or near the surface; but there are many deposits with intermediate characteristics which it is difficult to place satisfactorily. the accessible deposits of the deep zone are associated with plutonic igneous rocks which have been deeply eroded, and not with surface lavas. they are characterized by minerals of gold, tin, iron, titanium, zinc, and copper, and sometimes of tungsten and molybdenum, in a gangue of quartz, which contains also minerals such as garnet, corundum, amphibole, pyroxene, tourmaline, spinel, and mica. the deep-zone minerals are not unlike the pegmatite minerals in their grouping and associations. deposits formed at shallow depths are related to extrusive rocks and to intrusives near the surface. erosion has not been deep. mercury, silver and gold (tellurides, native metals, and silver sulphides), antimony, lead, and zinc minerals are characteristic, together with alunite, adularia, and barite. metallic copper also is not infrequent. very often the gangue material is more largely calcite than quartz, whereas calcite is not present in the deep zone.[ ] the trend of evidence in recent years has favored the conclusion that the principal ores associated with igneous rocks have not developed at very great depths. even within our narrow range of observation there is a difference in favor of the shallower depths, and the greatest depths we can observe are after all but trivial on the scale of the earth. a survey of the ore deposits of utah has suggested the generalization that ores are more commonly related to intrusive stocks than to the forms known as laccoliths, and that within and about intrusive stocks the ores are much more abundant near the top or apex of a stock than lower down.[ ] in parts of the region where erosion has removed all but the deeper portions of the stocks, ore bodies are less abundant. it will be of interest to follow the testing of this generalization in other parts of the world. the scientist is constantly groping for underlying simple truth. such glimpses of order and symmetry in the distribution of ore around igneous rocks as are afforded by the facts above stated, tempt the imagination to a conception of a simple type or pattern of ore distribution around intrusions. for this reason we should not lose sight of the fact that, in the present state of knowledge, the common and obvious case is one of irregular and heterogeneous distribution, and that there are many variations and contradictions even to the simplest generalization that can be made. the observer is repeatedly struck by the freakish distribution of ores about igneous masses, as compared with their regularity of arrangement under sedimentary processes to be discussed later. it is yet unexplained how an intrusive like the butte granite can produce so many different types of ores at different places along its periphery or within its mass, and yet all apparently under much the same general conditions and range of time. it is difficult also to discern the laws under which successive migrations of magma, from what seems to be a single deep-seated source or melting-pot, may carry widely contrasting mineral solutions. far below the surface, beyond our range of observation, it is clear that there is a wonderful laboratory for the compounding and refinement of ores, but as to its precise location and the nature of its processes we can only guess. other features of distribution of minerals associated with igneous rocks are indicated by their grouping in metallogenic provinces and epochs (see pp. - ). the relation of contact metamorphism to ore bodies of the foregoing class. the deposition of ores of igneous source in the country rock into which the igneous rocks are intruded is a phase of contact metamorphism. ordinarily where this deposition occurs there are further extensive replacements and alterations of the country rock, resulting in the development of great masses of quartz, garnet, pyroxene, amphibole, and other silicates, and in some cases of calcite, dolomite, siderite, barite, alunite, and other minerals. looked at broadly, the deposition of ores at igneous contacts under contact metamorphism is a mere incident in the much more widespread and extensive alterations of this kind. hence it is that the subject of contact metamorphism is of interest to economic geologists. the minerals here formed which do not constitute ores throw much light on the nature of the ore-bearing solutions, the conditions of temperature and pressure, and the processes which locally and incidentally develop the ore bodies. the subject, however, is a complex one, the full discussion of which belongs in treatises on metamorphism.[ ] we may note only a few salient features. for many hundreds of yards the rocks adjacent to the intrusions may be metamorphosed almost beyond recognition. this is especially true of the limestone, which may be changed completely to solid masses of quartz and silicates. the shales and sandstones are ordinarily less vitally affected. the shales become dense, highly crystalline rocks of a "hornstone" type, with porphyritic developments of silicate minerals. the sands and sandstones become highly crystalline quartzites, spotted with porphyritic developments of silicates. occasionally even these rocks may be extensively replaced by other minerals, as in the coeur d'alene district, where quartzites adjacent to the ore veins may be completely replaced by iron carbonate. a question of special interest to economic geologists is the source of the materials for the new minerals in these extensively altered zones. in some cases the minerals are known to be the result of recrystallization of materials already in the rock, after the elimination of certain substances such as carbon dioxide and lime, under the pressures and temperatures of the contact conditions. in such cases there has obviously been large reduction in volume to close the voids created by the elimination of substances. in the majority of cases, the new substances or minerals are clearly introduced from the igneous source, replacing the wall rock volume for volume so precisely that such original textures and structures as bedding are not destroyed. in many cases the result is clearly due to a combination of recrystallization of materials already present and introduction of minerals by magmatic solutions from without. so obvious is the evidence of the introduction of materials from without, that there has been a tendency in some quarters to overlook the extensive recrystallization of substances already present; and the varying emphasis placed on these two processes by different observers has led to some controversy. secondary concentration in place of the foregoing classes of mineral deposits through the agency of surface solutions mineral deposits of direct magmatic segregation are seldom much affected by surficial alteration, perhaps because of their coarse crystallization and their intermingling with resistant crystalline rocks. mineral deposits of the "igneous after-effect" type may be profoundly altered through surficial agencies. the more soluble constituents are taken away, leaving the less soluble. the parts that remain are likely to be converted into oxides, carbonates, and hydrates, through reaction with oxygen, carbon dioxide, and water, which are always present at the surface and at shallow depths. these processes are most effective at the surface and down to the level of permanent ground-water, though locally they may extend deeper. this altered upper part of the ore bodies is usually called the _oxide zone_. it may represent either an enrichment or a depletion of ore values, depending on whether the ore minerals are taken into solution less rapidly or more rapidly than the associated minerals and rocks; all are removed to some extent. in certain deposits, there is evidence that both zinc and copper have been taken out of the upper zone in great quantity; but they happen to be associated with limestone, which has dissolved still more rapidly, with the result that there is a residual accumulation of copper and zinc values. manganese, iron, and quartz are usually more resistant than the other minerals and tend to remain concentrated above. the same is true to some extent of gold and silver. the abundance of iron oxide thus left explains the name "iron cap" or "gossan" so often applied to the upper part of the oxide zone. not infrequently, and especially in copper ores, the upper part of the oxide zone is nearly or entirely barren of values and is called the _capping_. the depth or thickness of the oxide zone depends on topography, depth of water table, climatic conditions, and speed of erosion. a fortunate combination of conditions may result in a deep oxide zone with important accumulations of values. in other cases erosion may follow oxidation so rapidly as to prevent the growth of a thick oxide zone. it is clear from the study of many ore deposits that the process of oxidation has not proceeded uniformly to the present, but has depended upon a fortunate combination of factors which has not been often repeated during geologic time. as illustrative of this, the principal oxidation of the bisbee copper ores of arizona (p. ) occurred before tertiary time, with reference to a place that has since been covered by later sediments. the conditions in the ray, miami, and jerome copper camps of arizona (pp. - ) likewise indicate maximum oxidation at an early period. the lake superior iron ore deposits (pp. - ) were mainly concentrated before cambrian time, during the base-leveling of a mountainous country in an arid or semi-arid climate. the oxide zone of these deposits has no close relation to the present topography or to the present ground-water level. in the kennecott (alaska) copper deposits all oxidation has been stopped since glacial time by the freezing of the aqueous solutions. at butte and at bingham the main concentration of the ores is believed to have occurred in an earlier physiographic cycle than the present one. the _cyclic_ nature of the formation of oxide zones is of comparatively recent recognition, and much more will doubtless be found out about it in the comparatively near future. its practical bearing on exploration is obvious (see p. ). it should be clearly recognized that oxidizing processes are not limited to the zone above the ground-water level. locally oxidizing solutions may penetrate and do effective work to much greater depths, especially where the rocks traversed at higher elevations are of such composition or in such a stage of alteration as not to extract most of the oxygen. consequently the presence of oxide ores below the water table is not necessarily proof that the water table has risen since their formation. on the other hand, the facts of observation do indicate generally a marked difference, in circulation and chemical effect, between waters above and below this horizon, and show that oxidation is dominantly accomplished above rather than below this datum surface. during the formation of the oxide zone, erosion removes some of the ore materials entirely from the area, both mechanically and in solution. part of the material in solution, however, is known to penetrate downward and to be redeposited in parts of the ore body below the oxide zone,--that is, usually below the water table. evidence of this process is decisive in regard to several minerals. copper is known to be taken into solution as copper sulphate at the surface, and to be redeposited as chalcocite where these sulphate solutions come in contact with chalcopyrite or pyrite below. not only has the process been duplicated in the laboratory, but the common coating of chalcocite around grains of pyrite and chalcopyrite below the water level indicates that this process has been really effective. sulphides of zinc, lead, silver, and other metals are similarly concentrated, in varying degrees. the zone of deposition of secondary sulphides thus formed is called the zone of _secondary sulphide enrichment_. ores consisting mainly of secondary sulphides are also called _supergene_ ores (p. ). in some deposits, as in the copper deposits of ray and miami, there is found, below the secondary sulphide zone, a lean sulphide zone which is evidently of primary nature. the mineralized material of this zone, where too lean to mine, has been called a _protore_. with the discovery of undoubted evidence of secondary sulphide enrichment, there was a natural tendency to magnify its importance as a cause of values. continued study of sulphide deposits, while not disproving its existence and local importance, has in some districts shown clearly that the process has its limitations as a factor in ore concentration, and that it is not safe to assume its effectiveness in all camps or under all conditions. at butte for instance, secondary chalcocite is clearly to be recognized. the natural inference was that as the veins were followed deeper the proportion of chalcocite would rapidly diminish, and that a leaner primary zone of chalcopyrite, enargite and other primary minerals would be met. however, the great abundance of chalcocite in solid masses which have now been proved to a depth of feet, far below the probable range of waters from the surface in any geologic period, seems to indicate that much of the chalcocite is primary. the present tendency at butte is to consider as secondary chalcocite only certain sooty phases to be found in upper levels. the solid masses of chalcocite in the kennecott copper mines seem hardly explainable as the result of secondary sulphide enrichment. no traces of other primary minerals are present and the chalcocite here is regarded as probably primary. the possible magnification of the process of secondary enrichment above referred to has had for its logical consequence a tendency to over-emphasize the persistence of primary ores in depth. the very use of the terms "secondary" and "primary" has suggested antithesis between surficial and deep ores. progress in investigation, as indicated on previous pages, seems to indicate that the primary ores are not uniformly deep and that in many cases they are distinctly limited to a given set of formations or conditions comparatively near the surface. in general the processes of oxidation and secondary sulphide enrichment have been studied mainly by qualitative methods with the aid of the microscope and by considerations of possible chemical processes. these methods have disclosed the nature but not the quantitative range and relations of the different processes. much remains to be done in the way of large scale quantitative analysis of ores at different depths, as a check to inferences drawn by other methods. one may know, for instance, that a mineral is soluble and is actually removed from the oxide zone and redeposited below. the natural inference, therefore, is that the mineral will be found to be depleted above and enriched below. in many cases its actual distribution is the reverse,--indicating that this process has been only one of the factors in the net result, the more rapid solution and deposition of other materials being another factor. if one were to approach the study of the concentration of iron ores with the fixed idea of insolubility of quartz from a chemical standpoint, and were to draw conclusions accordingly, he would fail to present a true picture of the situation. while quartz is insoluble as compared with most minerals, it is nevertheless more soluble than iron oxide, and therefore the net result of concentration at the surface is to accumulate the iron rather than the silica. descriptions of enrichment processes as published in many reports are often misleading in this regard. they may be correct in indicating the actual existence of a process, but may lead the reader to assumptions as to net results which are incorrect. residual mineral deposits formed by the weathering of igneous rocks in place igneous rocks not containing mineral deposits may on weathering change to mineral deposits. the lateritic iron ores such as those of cuba (p. ), many bauxite deposits, many residual clays, and certain chromite and nickel deposits are conspicuous representatives of this class. the chemical and mineralogical changes involved in the formation of these deposits are pretty well understood. certain constituents of the original rock are leached out and carried away, leaving other constituents, as oxides and hydrates, in sufficiently large percentage in the mass to be commercially available. the accumulation of large deposits depends on the existence of climatic and erosional conditions which determine that the residual deposit shall remain in place rather than be carried off by erosion as fast as made. in the glaciated parts of the world, deposits of this nature have usually been removed and dispersed in the glacial drift. when the minerals of these deposits are eroded, transported, and redeposited in concentrated form, they come under the class of placer or sedimentary deposits described under the following heading. there are of course many intermediate stages, where the residual deposit is only locally moved and where the distinction between this class of deposits and that next described is an arbitrary one. mineral deposits formed directly as placers and sediments mineral deposits of this class are of large value, including as they do salt, gypsum, potash, sulphur, phosphates, nitrates, and important fractions of the ores of iron, manganese, gold, tin, tungsten, platinum, and precious stones; also many common rocks of commercial importance. the minerals of these deposits are derived from the weathering and erosion of land surfaces, either igneous or sedimentary. they are deposited both under air and under water, both mechanically and chemically (in part by the aid of organisms). these deposits form the principal type of _syngenetic_ deposits (p. ); the term _sedigenetic_ deposits has also been applied to them. mechanically deposited minerals mechanical erosion of preëxisting mineral deposits or rocks and their transportation, sorting, and deposition are responsible for the placers of gold, tin, tungsten, platinum, and various precious stones, and for certain iron sands and conglomerates. sands, sandstones, shales, and certain clays and bauxites also belong in this group. these deposits may be formed under air or under water, and under various climatic and topographic conditions. during the process of formation the minerals of differing density are more or less sorted out and tend to become segregated in layers. the process is not unlike the artificial process of mechanical concentration where ores are crushed, shaken up, and treated with running water. the process is most effective for minerals which are resistant to abrasion and to solution, and of such density as to differentiate them from the other minerals of the parent rock. the origin of deposits of this kind is fairly obvious where they are of recent age and have not been subsequently altered or buried. a considerable amount of experimental work has brought out clearly the main elements of the processes. physiographic and climatic conditions play an important part, and cannot be safely overlooked by anyone studying such deposits. extensive copper deposits exist as sediments (pp. - ). it is not clear to what extent they are mechanically or to what extent chemically deposited. for the most part the concentration of copper in this manner has not been sufficient to yield deposits of large commercial value; the mineral is too much dispersed. relatively small amounts are mined in the mansfield shales of germany and the nonesuch shales and sandstones of the lake superior country. the clinton and similar iron ores of the united states and newfoundland, the pre-cambrian iron ores of brazil, and the jurassic iron ores of england and western europe (pp. - ) are now commonly agreed to be direct sedimentary deposits in which mechanical agencies of sorting and deposition played a considerable part. how far chemical and bacterial agencies have also been effective is not clear. the climatic, topographic, and other physiographic and sedimentary conditions which cause the deposition of this great group of ores present one of the great unsolved problems of economic geology. the study of present-day conditions of deposition affords little clue as to the peculiar combination of conditions which was necessary to accomplish such remarkable results in the past. on the whole, minerals of this mechanically deposited group are not greatly affected by later surficial alteration and concentration, because, having already been subjected to weathering, they are in a condition to resist such influences. chemically and organically deposited minerals the products of surface weathering and erosion are in part carried away in chemical solution and redeposited as sediments. sediments thus formed include limestone and dolomite, siderite, salt, gypsum, potash, sulphur, phosphates, nitrates, and other minerals. precipitation may be caused by chemical reactions, by organic secretion, or by evaporation of the solutions. the processes are qualitatively understood and it is usually possible to ascertain with reasonable accuracy the conditions of depth of water, relation to shore line, climate, nature of erosion, and other similar factors; yet the vast scale of some of these deposits, and their erratic areal and stratigraphic distribution, present unsolved problems as to the precise combinations of factors which have made such results possible. chemically and organically deposited minerals of this class are usually susceptible to further alteration by surface weathering, and some of them, for instance the phosphates and siderites, are thus secondarily concentrated. these processes are discussed under the next heading. in general the great unsolved problem of the origin of the entire group of mineral deposits in placers and sediments relates to the scale of the results. observation of present-day processes and conditions of deposition of these minerals affords satisfactory evidence of their nature, but fails to give us a clear idea of the precise combinations of agencies and conditions necessary to produce such vast results as are represented by the mineral deposits. for example, solution of iron on a land surface and redeposition in bogs and lagoons (as actually observed to be taking place today) show how some iron-ore sediments may be formed; but these processes are entirely inadequate to explain the deposition of iron ores in thick masses over broad areas without intermingling of other sediments--as represented by the clinton iron ores of north america, the jurassic ores of europe and england, and the ancient iron ores of brazil. the paleozoic seas in northern and eastern united states encroached over land areas to the north and east and deposited ordinary sediments such as sandstone, shale, and limestone. suddenly, without, so far as known, tapping any new sources of supply on the ancient land areas, and without any yet ascertainable change in topographic or climatic conditions, they deposited enormous masses of iron ore. there is clearly some cyclic factor in the situation which we do not yet understand. the various deposits of salt, gypsum, potash, sulphur, and other minerals are known to be the result of evaporation, and the deposition of each of these minerals is known to be related to the degree of evaporation as well as to temperature, pressure, and factors such as mass action and crystallization of double salts. the nature of the processes is fairly well understood; but again, observation of the present-day operation of these processes fails to give us much clue to the enormous accumulations at certain times and places in the past. it is difficult to say just what conditions of climate, in combination with particular physiographic factors, could have preserved uniformity of conditions for the long periods necessary to account for some of the enormously thick salt deposits. again some cyclic factor in the situation remains to be worked out. sedimentary mineral deposits which have required further concentration to make them commercially available the conditions for the direct deposition of sedimentary mineral deposits of the foregoing class are also responsible for the deposition of minerals in more dispersed or disseminated form, requiring further concentration through surface agencies to render them commercially available. some of these deposits are discussed below. the lead and zinc ores of the mississippi valley, virginia, tennessee, silesia, belgium, and germany (pp. - , - ) are in sedimentary rocks far removed from igneous sources. lead and zinc were deposited in more or less dispersed form with the enclosing sediments. it is supposed that deposition was originally chemical and was favored by the presence of organic material, which is a rather common accompaniment of the sediments. it is supposed further that these organic participants were originally localized during sedimentation in so-called estuarine channels and shore-line embayments. when subsequently exposed to weathering, the lead and zinc minerals were dissolved and redeposited in more concentrated form in fissures and as replacements of limestone. agreement as to origin of these deposits, so far as it exists, does not go beyond these broad generalizations. there is controversy as to whether the original sources of the ore minerals were the sediments directly above, from which the mineral solutions have been transferred downward during weathering and erosion, or whether the original minerals were below and have been transferred upward by artesian circulation, or whether they were situated laterally and have been brought to their present position by movement along the beds, or whether there has been some combination of these processes. it is the writer's view that the evidence thus far gathered favors on the whole the conclusion of direct downward concentration from overlying sources which have been removed by erosion, although this conclusion fails to explain why certain sulphide deposits give so little evidence of important downward transfer from their present position. this matter is further discussed on pages - . the choice of the various alternatives has some practical bearing on exploration. since these ores were brought into approximately their present position, they have undergone considerable oxidation near the surface and secondary sulphide enrichment below. the chemical and mineralogical changes are pretty well understood, but the quantitative range of these changes and their relative importance in determining the net result are far from known. undoubted evidence of secondary sulphide enrichment has led in some quarters to an assumption of effectiveness in producing values which is apparently not borne out by quantitative tests. a group of mineral deposits in sandstones in utah is regarded as due to chemical concentration of material originally disseminated in the rock. they include silver, copper, manganese, uranium, and radium deposits. the silver reef deposits, including silver, copper, uranium, and vanadium, are commercially the most important of this type.[ ] the ore minerals are commonly associated with carbonized material representing plant remains, and have replaced the calcareous and cementing material of the rock, and also some of the quartz grains. the deposits are regarded as having been formed by circulating waters which collected the minerals disseminated through the sedimentary rocks, and deposited them on contact with carbonaceous matter, earlier sulphides, or other precipitating agents. the circulation in some places is believed to have been of artesian character and to have been controlled to a large extent by structural features. the silver reef deposits are near the crest of a prominent anticline. most of the minerals have been later altered by surface solutions. another great group of ores to be considered under this head are the iron ores of lake superior,--which were originally deposited as sediments, called jaspers or iron formations, with too low a percentage of iron to be of use, and which have required a secondary concentration by surficial agencies to render them valuable. the process of concentration has been a simple one. the iron minerals have been oxidized in place and the non-ferrous minerals have been leached out, leaving iron ores. this process contrasts with the concentration described above, in that there is little evidence of collection of iron minerals from disseminated sources. the lake superior iron ores are essentially residual concentrations in place. the outstanding problems of secondary concentration relate to the structural features which determined the channels through which the oxidizing and leaching waters worked, and to the topographic and climatic conditions which existed at the time the work was done. as with many other classes of ores, it was first assumed that these processes were related to the present erosion surface; but it is now known that concentration happened long ago under conditions far different from those now existing. these deposits contribute to the rapidly accumulating evidence of the _cyclic_ nature of ore concentration. our least satisfactory knowledge of the lake superior ores relates to the peculiar conditions which determined the initial stage of sedimentation of the so-called iron formation. as in the case of the clinton iron ores, no present-day sedimentation gives an adequate clue. students of the problem have fallen back on the association of the iron formation with contemporaneous volcanic rocks, as affording a possible explanation of the wide departure from ordinary conditions of sedimentation evidenced by these formations.[ ] coal deposits are direct results of sedimentation of organic material. they are mainly accumulations of vegetable matter in place. to make them available for use, however, they undergo a long period of condensation and distillation. conditions of primary deposition may be inferred from modern swamps and bogs; but, as in the case of sediments described under the preceding heading, we are sometimes at a loss to explain the magnitude of the process, and especially to explain the maintenance of proper surface conditions of plant growth and accumulation for the long periods during which subsidence of land areas and encroachment of seas are believed to have been taking place. the processes of secondary concentration are also understood qualitatively, but much remains to be learned about the influences of pressure and heat, the effect of impervious capping rocks, and other factors. various oil shales and asphaltic deposits are essentially original sediments which have subsequently undergone more or less decay and distillation. the migration of the distillates to suitable underground reservoirs is responsible for the accumulation of oil and gas pools. oil and gas are distillates from these oil shales and asphaltic deposits, and also from other organic sediments such as carbonaceous limestones. the distillates have migrated to their present positions under pressure of ground-waters. the stratigraphic horizons favorable to their accumulation are generally recognized. the geologist is concerned in identifying these horizons and in ascertaining where they exist underground. he is further concerned in analysis of the various structural conditions which will give a clue to the existence of local reservoirs in which the oil or gas may have been accumulated. so capricious are the oil migrations that the most intensive study of these conditions still leaves vast undiscovered possibilities. anamorphism of mineral deposits mineral deposits formed in any one of the ways indicated above may undergo repeated vicissitudes, both at the surface and deep below the surface, with consequent modifications of character. they may be cemented or replaced by introduction of mineral solutions from without. they may be deformed by great earth pressures, undergoing what is called dynamic metamorphism (pp. - ), which tends to distort them and give them schistose and crystalline characters. they may be intruded by igneous rocks, causing considerable chemical, mineralogical, and structural changes. all these changes may take place near the surface, but on the whole they are more abundant and have more marked effects deep below the surface. in general all these changes of the deeper zone tend to make the rocks more crystalline and dense and to make the minerals more complex. cavities are closed. the process is in the main an integrating and constructive one which has been called _anamorphism_, to contrast it with the disintegrating and destructive processes near the surface, which have been called _katamorphism_ (see also pp. - ). there is little in the process of anamorphism in the way of sorting and segregation which tends to enrich and concentrate the metallic ore bodies. on the contrary the process tends to lock up the valuable minerals in resistant combinations with other substances, making them more difficult to recover in mining. later igneous intrusions or the ordinary ground-waters may bring in minerals which locally enrich ores under anamorphic conditions, but these are relatively minor effects. an illustration of the general effect is afforded by a comparison of the cuban iron ores, which are soft and can be easily taken out, with the cle elum iron ores of washington, which seem to be of much the same origin, but which have subsequently been buried by other rocks and rendered hard and crystalline. in the first case the ores can be mined easily and cheaply with steam shovels at the surface. in the second, underground methods of mining are required, which cost too much for the grade of ore recovered. on the other hand, the same general kind of anamorphic processes, when applied to coal, result in concentration and improvement of grade. the same is true up to a certain point in the concentration of oil; but where the process goes too far, the oil may be lost (pp. - ). conclusion mineral deposits are formed and modified by practically all known geologic processes, but looked at broadly the main values are produced in three principal ways: ( ) as after effects of igneous intrusion, through the agency of aqueous and gaseous solutions given off from the cooling magma. ( ) through the sorting processes of sedimentation,--the same processes which form sandstone, shale, and limestone. organic agencies are important factors in these processes. ( ) through weathering of the rock surface in place, which may develop values either by dissolving out the valuable minerals and redepositing them in concentrated form, or by dissolving out the non-valuable minerals and leaving the valuable minerals concentrated in place. the latter process is by far the more important. the overwhelming preponderance of values of mineral deposits as a whole is found in the second of the classes named. under all these conditions it appears that the maximum results are obtained at and near the surface. on the scale of the earth even the so-called deep veins may be regarded as deposits from solutions reaching the more open and cooler outer portions of the earth. however, valuable mineral deposits are found in the deepest rocks which have been exposed by erosion, and the question of what would be found at still greater depths, closer to the center of the earth, is a matter of pure speculation. ultimately all minerals are derived from igneous sources within the earth. the direct contributions from these sources are only in small part of sufficient concentration to be of value; for the most part they need sorting and segregation under surface conditions. we can only speculate as to causes of the occurrence of valuable minerals in certain igneous rocks and not in others. many granites are intruded into the outer shell of the earth, but only a few carry "minerals"; also, of a series of intrusions in the same locality, only one may carry valuable minerals. it is clear that in some fashion these minerals are primarily segregated within the earth. causes of this segregation are so involved with the problem of the origin of the earth as a whole that no adequate explanation can yet be offered. our inductive reasoning from known facts is as yet limited to the segregation within a given mass of magma, and even here the conditions are only dimly perceived. a discussion of these ultimate problems is beyond the scope of this book. footnotes: [ ] ransome, frederick leslie, copper deposits near superior, arizona: _bull. , u. s. geol. survey_, , pp. - ; the copper deposits of ray and miami, arizona: _prof. paper , u. s. geol. survey_, , p. ; discussion: _econ. geol._, vol. , , p. . [ ] for more specific definitions of vertical zones of ore deposition in association with igneous rocks see spurr, j. e., theory of ore deposition: _econ. geol._, vol. , , pp. - ; lindgren, w., _mineral deposits_, mcgraw-hill book co., d ed., , chapters xxiv-xxvi; and emmons, w. h., _the principles of economic geology_, mcgraw-hill book co., , chapters vi-viii. an excellent discussion of a case of vertical and areal zoning of minerals is contained in _ore deposits of the boulder batholith of montana_, by paul billingsley and j. a. grimes, bull. am. inst. min. engrs., vol. , , pp. - . [ ] butler, b. s., loughlin, g. f., heikes, v. c., and others, the ore deposits of utah: _prof. paper , u. s. geol. survey_, , p. . [ ] leith, c. k., and mead, w. j., _metamorphic geology_, pt. , henry holt and company, new york, . [ ] butler, b. s., loughlin, g. f., heikes, v. c., and others, the ore deposits of utah: _prof. paper , u. s. geol. survey_, , pp. - . [ ] van hise, c. r., and leith, c. k., geology of the lake superior region. _mon. , u. s. geol. survey_, , pp. - ; and references there given. chapter iv mineral resources--some general quantitative considerations of the , known mineral species, perhaps figure in commerce as mineral resources. for the mineral substances used commercially, the term "mineral" is used in this chapter with a broad significance to cover any or all of the materials from which the needed elements are extracted,--whether these materials be single minerals or groups of minerals; whether they be rocks or ores; whether they be liquid or solid. the following figures are generalizations based on the miscellaneous information available. the purpose is to indicate the general perspective rather than the detail which would be necessary for precise statement. world annual production of minerals in short tons exclusive of water, but inclusive of petroleum, the world's annual output of mineral resources amounts to two billions of tons. this figure refers to the crude mineral as it comes from the ground and not to the mineral in its concentrated form. of this total extraction, coal amounts to nearly per cent, stone and clay per cent, iron ore about per cent, petroleum per cent, copper ore per cent, and all the remaining minerals constitute less than per cent. if spread out on the surface in a uniform mass with an estimated average density based on relative proportions of the crude minerals, this annual production would cover a square mile to a depth of , feet. of the total annual production per cent comes from countries bordering the north atlantic basin; per cent is accounted for by the united states, england, and germany; the united states has per cent of the total, england per cent, and germany per cent. by continents, europe accounts for nearly per cent, north america for nearly per cent, asia for nearly per cent, and the remaining continents for nearly per cent. the united states mineral production in recent years has been about , , tons. according to the united states census of , nearly half of all the establishments or businesses engaged in quarrying or mining operations in this country are operating in oil and gas. of the crude materials extracted from the ground perhaps per cent, including gold, silver, copper, lead, zinc, nickel, and other ores, are concentrated mainly at the mine, with the result that this fraction of the tonnage in large part does not travel beyond the mine. about per cent of the total production, therefore, figures largely in the transportation of mineral resources. it is estimated that roughly two-thirds of the annual world production is used or smelted within the countries of origin, the remaining one-third being exported. of the minerals moving internationally, coal and iron constitute per cent of the tonnage. the metal smelting capacity of the world in terms of yearly production of crude metal is estimated at nearly , , short tons. of this amount about per cent is located in the united states, england, and germany. the united states alone has over half of the total. of the oil-refining capacity the united states controls nearly per cent. one of the significant features of the situation above summarized is the concentration of production and smelting in a comparatively few places in the world. this statement applies with even more force to the individual mineral commodities. water may be regarded as a mineral resource in so far as it is utilized as a commodity for drinking, washing, power, irrigation, and other industrial uses. for purposes of navigation and drainage, or as a deterrent in excavation, it would probably not be so classed. while it is not easy to define the limits of water's use as a mineral resource, it is clear that even with a narrow interpretation the total tonnage extracted from the earth as a mineral resource exceeds in amount all other mineral resources combined. world annual production of minerals in terms of value in terms of value, mineral resources appear in different perspective. the annual world value of mineral production, exclusive of water, is approximately $ , , , . this figure is obtained by dividing the annual value of the united states output of each of the principal minerals by the percentage which the united states output constitutes in the world output, and adding the figures thus obtained. the values here used are mainly selling prices at the mines. it is impossible to reduce the figures absolutely to the value of the mineral as it comes from the ground; there are always some items of transportation included. this method of figuring is of course only the roughest approximation; the values as obtained in the united states cannot be accurately exterpolated for the rest of the world because of locally varying conditions. however, the figures will serve for rough comparative purposes. of this total value coal represents roughly per cent, petroleum per cent, iron per cent, copper per cent, and gold per cent. in terms of value, about per cent of the world's mineral production is available for export beyond the countries of origin. of this exportable surplus the united states has about per cent, consisting principally of coal, copper, and formerly petroleum. the value of the united states annual mineral production in recent years has been from about $ , , , to $ , , , . annual imports of mineral products into the united states have averaged recently in the general vicinity of $ , , , the larger items being copper, tin, fertilizers, petroleum, gems and precious stones, manganese, nickel, and tungsten. again the perspective is changed when the value of water resources is considered. as a physiologically indispensable resource, the value of water in one sense is infinite. there is no way of putting an accurate value on the total annual output used for drinking and domestic purposes,--although even here some notion of the magnitude of the figures involved may be obtained by considering the average per capita cost of water in cities where figures are kept, and multiplying this into the world population. this calculation would not imply that any such amount is actually paid for water, because the local use of springs, wells, and streams can hardly be figured on a cash basis; but, if human effort the world over in securing the necessary water is about as efficient as in the average american city, the figures would indicate the total money equivalent of this effort. significance of geographic distribution of mineral production the remarkable concentration of the world's mining and smelting around the north atlantic basin, indicated by the foregoing figures, does not mean that nature has concentrated the mineral deposits here to this extent. it is an expression rather of the localized application of energy to mineral resources by the people of this part of the world. the application of the same amount of energy in other parts of the world would essentially change the distribution of current mineral production. the controlling factor is not the amount of minerals present in the ground; this is known to be large in other parts of the world and more will be found when necessary. controlling factors must be looked for in historical, ethnological, and environmental conditions. this subject is further discussed in the chapters on the several resources, and particularly in relation to iron and steel. the increasing rate of production the extraction of mineral resources on the huge scale above indicated is of comparatively recent date. from to the end of the value of the annual mineral production of the united states has increased from $ , , to more than $ , , , , or nearly fifteen times; measured in another way, it has increased from a little over $ per capita to more than $ .[ ] more coal has been mined in the united states since than in all the preceding history of the country. more iron ore has been mined since than in all the preceding history. the gold production of the united states practically started with the california gold rush in . the great south african gold production began in . production of diamonds in south africa began about . the large use of all fertilizer minerals is of comparatively recent date. the world's oil production is greater now each year than it was for any ten years preceding , and more oil has come out of the ground since than in all the preceding history of the world. the use of bauxite on a large scale as aluminum ore dated practically from the introduction of patented electrolytic methods of reduction in . in one sense the world has just entered on a gigantic experiment in the use of earth materials. the most striking feature of this experiment relates to the vast acquisition of power indicated by the accelerating rate of production and consumption of the energy resources--coal, oil, and gas (and water power). since the per capita consumption of coal in the united states has trebled and the per capita consumption of oil has become five times as great as it was. if the power from these sources used annually in recent years be translated roughly into man power, it appears that every man, woman, and child in the united states has potential control of the equivalent of thirty laborers,--as against seven in . energy is being released on a scale never before approximated, with consequences which we can yet hardly ascertain and appraise. this consideration cannot but raise the question as to the ability of modern civilization to control and coödinate the dynamic factors in the situation. capital value of world mineral reserves it is impossible to deduce accurately the capital value of mineral resources from values of annual output, but again some approximation may be made. the profit on the extraction of mineral resources on the whole, considering the cost of exploration, is probably no greater than in other industries (p. ). if we assume a per cent return, which perhaps is somewhere near the world-wide standard of interest rate for money, and capitalize the value of the world's annual output at this rate, we obtain a world capital value for mineral resources, exclusive of water, of billions of dollars. this assumes an indefinitely long life for reserves. this assumption may need some qualifications, but it is the writer's view (chapter xvii) that it is justified for a sufficiently long period to substantiate the above method of calculation. [illustration: fig. . commercial (financial) control of the mineral resources of the world.] [illustration: fig. . political (territorial) control of the mineral resources of the world.] political and commercial control of mineral resources the occurrence of a mineral resource within a country does not necessarily mean control by that particular political unit. a citizen of the united states may own a mineral resource in south america. commercial control of this sort was demonstrated during the war to be of more far-reaching significance than had been supposed, and it became necessary to ascertain, not only the output of the different countries, but the commercial control of this output. investigation of this subject for twenty-three leading commodities shows that the political and commercial control are by no means the same. these are partly summarized in the accompanying graphs from spurr.[ ] it is to be noted that the graphs show the control of many commodities as it existed in , the last normal year before the war. changes during and since the war have of course largely altered the situation for certain commodities, notably for iron, coal, and potash. these developments are summarized in the discussion of the individual resources. it is also to be noted that the commercial or financial control of the world's minerals, under the influence of the fostering and protective policies of certain governments discussed in chapter xviii, is at present in a state of flux. considerable changes are taking place today and are to be looked for in the future. reserves of mineral resources annual production figures are only to a very partial extent an indication of the distribution of the great reserves of mineral resources. for instance, there are enormous reserves of coal in china which are not yet utilized to any large extent. the minerals of south america and africa are in a very early stage of development. the total world reserves will of course not be known until exploration and development of the world's resources are complete--a time which will probably never come. figures of reserves represent only our present partial state of knowledge and are likely to be considerably modified in the future. furthermore, the quantitative accuracy of knowledge of reserves is so variable in different parts of the world that it is almost impossible to make up world figures which have any great validity. there are, however, certain broad facts ascertainable. every country in the globe is deficient in supplies of some minerals. the united states is better off than any other country, but still lacks many mineral commodities (see pp. - .) no single continent has sufficient reserves of all mineral commodities. for the world, however, it may be stated with reasonable certainty that the reserves of the principal minerals are now known to be ample with the exception of those of oil, tin, and perhaps gold and silver. by _ample_ we mean sufficient to give no cause for worry for the next few decades. for many mineral commodities the amounts now actually in sight will not last long, but the possibilities of extension and discovery are so great that a long future availability of these commodities can be counted upon with reasonable safety. the present shortages in oil, tin, and other minerals mentioned may be only temporary. there is a large part of the world still to be explored, and the present reserves merely mark a stage in this exploration. nevertheless, the ratio of reserves and discovery on the one hand to accelerated use on the other gives cause for much concern. looking forward to the future, the problem of mineral reserves in general is not one of the possible ultimate amount which the earth may contain--presumably in no case is this deficient--but of the success with which the resource may be found and developed to keep up with the rapid acceleration of demand. in the chapter on conservation the suggestion is made that future difficulties are more likely to arise from failure to coödinate the dynamic factors of supply and demand, than from absolute shortage of material in the earth. footnotes: [ ] bastin, edson s., and mccaskey, h. d., the work on mineral resources done by the u. s. geological survey: _min. res. of the united states for , u. s. geol. survey_, pt. , , p. a. [ ] spurr, j. e., who owns the earth?: _eng. and min. jour._, vol. , , pp. - . chapter v water as a mineral resource general geologic relations with the solid earth as the special care of geology, it may seem presumptuous for the geologist to claim the waters thereof, but he does not disclaim this inheritance. water is so all-pervasive that it is more or less taken for granted; and so many and so intricate are its relations that it is not easy to make an objective survey of the water problem in its relation to geology. the original source of water, as well as of air, is in molten magmas coming from below. these carry water and gases,--some of which are released and some of which are locked up in the rocks on cooling, to be later released during the alterations of the rocks. it is supposed, whatever theory of the origin of the earth we favor, that in its early stages the earth lacked both hydrosphere and atmosphere, and that during the growth of the earth these gradually accumulated on and near the surface in the manner stated. during alterations at the surface water is added to the mineral constitution of the rocks, and by alterations deep below the surface it may be subtracted. water is the agent through which most mineral and chemical changes of rocks are accomplished. it is the agent also which is mainly responsible for the segregation of mineral deposits. water, both as running water and in the solid form of ice, plays an important part in determining the configuration of the earth's surface. water is the medium in which most sedimentary rocks are formed. it is an important agent in the development of soil and in organic growth. these various influences of water on geological processes touch the economic field at many points, especially in relation to the concentration of ores and to the development of soils and surface forms. water comes even more directly into the field of economic geology as a mineral resource. water supplies, for the greatest variety of purposes, involve geologic considerations at almost every turn. finally, water may be an aid or a hindrance to excavation and to a great variety of structural operations, both in war and in peace; and in this relation it again affords geologic problems. the part played by water in geologic processes, such as that of mineral segregation, is more or less incidentally discussed in other chapters. we may consider more fully in this chapter the application of geology to the general subject of water supplies. from the geological point of view, water is a mineral,--one of the most important of minerals,--as well as a constituent of other minerals. it becomes a mineral resource when directly used by man. it is ordinarily listed as a mineral resource when shipped and sold as "mineral water," but there is obviously no satisfactory line between waters so named and water supplies in general, for most of them are used for the same purposes and none of them are free from mineral matter. water which is pumped and piped for municipal water supply is as much a mineral resource as water which is bottled and sold under a trade name. likewise water which is used for irrigation, water power, and a wide variety of other purposes may logically be considered a mineral resource. notwithstanding the immense economic importance of water as a mineral resource its value is more or less taken for granted, and considerations of valuation and taxation are much less in evidence than in the case of other mineral resources. water must be had, regardless of value, and market considerations are to a much less extent a limiting factor. economic applications of geology to this resource are rather more confined to matters of exploration, development, total supply, and conservation, than to attempts to fix money value. distribution of underground water free water exists in the openings in rocks where it is sometimes called _hygroscopic_ water. there is also a large amount of water combined molecularly with many of the minerals of rocks, in which form it is called _water of constitution_. this water is fixed in the rock so that it is not available for use, though some of the processes of rock alteration liberate it and contribute it to the free water. the immediate source of underground water, both free and combined, is mainly the surface or rain waters. a subordinate amount may come directly from igneous emanations or from destruction of certain hydrous minerals. ultimately, as already indicated, even the surface water originates from such sources. the openings in rocks consist of joints and many other fractures, small spaces between the grains of rocks (pore space), and amygdaloidal and other openings characteristic of surface volcanic rocks. many of these openings are capillary and sub-capillary in size. most rocks, even dense igneous rocks, are porous in some degree, and certain rocks are porous in a very high degree. the voids in some surface materials may amount to per cent of the total volume. in general the largest and most continuous openings are near the surface,--where rocks on the whole are more largely of the sedimentary type and are more fractured, disintegrated, and decomposed, than they are deep within the earth. the largest supplies of water are in the unconsolidated sediments. the water in igneous and other dense rocks is ordinarily in more limited quantity. approximate quantity of water which will be absorbed by soils and rocks[ ] ------------------------------------------------------ _volume of water asborbed _material_ per of material_ ------------------------------------------------------ sandy soil[ ] . chalk soil[ ] . clay[ ] - . loam[ ] . - . garden earth [ ] . coarse sand [ ] . peat subsoil[ ] . sand - sandstone - limestone and dolomite - chalk - granite .-. ------------------------------------------------------ : mead, daniel w., _hydrology_: mcgraw-hill book co., new york, , p. . : woodward, h. b., _geology of soils and substrata_: edward arnold, london, . immediately at the surface, the openings of rocks may not be filled with water; but below the surface, at distances varying with climatic and topographic conditions, the water saturates the openings of the rocks and forms what is sometimes called the _zone of saturation_ or the _sea of underground water_. the top surface of this zone is called the _water table_, or the _ground-water level_. the space between the water table and the earth's surface is sometimes referred to as the _vadose zone_ or the _zone of weathering_, since it is the belt in which weathering processes are most active. the zone of weathering is not necessarily dry. water from the surface enters and sinks through it and water also rises through it from below; it may contain suspended pockets of water surrounded by dry rocks; it is not continuously and fully saturated. the water table or ground-water level may be near or at the surface in low and humid areas, and it may be two thousand feet or more below the surface in arid regions of high topographic relief. because of the influence of capillarity, the water table is not a horizontal surface. it shows irregularities more or less following the surface contours, though not nearly so sharply accentuated. the lower limit of the ground-water is more irregular than the upper surface and is less definitely known. in general, openings in rocks tend to diminish with depth, due to cementation and to closing of cavities by pressures which are too great for the rock to withstand. but rocks differ so widely in their original character, and in their response to physical and chemical environment, that it is not unusual to find dense and impervious rocks above, and open and porous rocks below. the lower limit of the zone of abundant underground water varies accordingly. a well may encounter nearly dry rock at a comparatively shallow depth, or it may reach a porous water-bearing stratum at considerable depth. at the greater depths pockets of water are sometimes found which have a composition different from that of the surface water, and which evidently are isolated from the surface water by zones of non-pervious rock. attempts have been made to calculate the total volume of underground water by measuring the openings of rocks and making assumptions as to the depth to which such openings may extend. in this manner it has been estimated that, if all the ground-water were assembled in a single body, it would make a shell between eighty and two hundred feet thick (depending on the assumptions) over all the continental areas. movement of underground water availability of water supplies is determined by the movement or flow of water as well as by its distribution and amount. the natural flow of water underground is caused by gravity in the larger openings, but in the smaller openings adhesion and capillarity are also important forces. of all the water falling on the surface, some may not go below the surface at all but may immediately evaporate or join the runoff--that is, the surface streams. another part may penetrate a little distance into the zone of weathering and then join the runoff. of the water which reaches the zone of saturation, a part may soon come to the surface in low areas and join the runoff, and a part may penetrate deeply. above the zone of saturation gravity carries the water downward in devious courses until it reaches the water table. thereafter its course is determined largely by the lowest point of escape from the water table. in other words, the water table is an irregular surface; and under the influence of gravity the water tends to move from the high to the low points of this surface. between the point of entrance and the point of escape from the water table, the water follows various courses, depending upon the porosity and the openings in the rocks. in general it fills all of the available openings, and uses the entire available cross section in making its progress from one point to another. the difference in height or the "head" between the point of entrance and the point of escape, together with the porosity of the rock and other factors, determine the general speed of its movement (see p. ). with equal porosity the flow is at a maximum along a line directly connecting the two points, and on more devious courses the flow is less. the surface water first enters the ground through innumerable small openings. soon, however, it tends to be concentrated into channels of easiest flow, with the result that in the later part of its underground course it may be much concentrated in large trunk channels. these channels may consist of joints, or frequently of very coarse and pervious beds. the sedimentary rocks as a whole contain the most voids, and therefore the largest flow and largest supply of water is often localized in them. of the sedimentary rocks, sandstones and limestones usually contain the largest and most continuous openings, and thus afford the freest circulation for water. the voids in fine-grained shales may equal in volume those in sandstones and limestones, but the openings are so small and discontinuous that the water does not flow freely. regardless of total amount of water, unless there are continuous openings of some size the flow may be small. the relations of more porous rocks to containing impervious strata also profoundly affect the flow of underground water. between impervious strata the circulation may be concentrated and vigorous within the porous bed. where the porous bed is not so contained, the movement may be more dispersed and less vigorous locally. the inclination of the beds, of course, also affects the direction and amount of the flow. the influence of gravity upon underground water may locally tend toward a state of equilibrium in which there is little movement. in such a case the water is substantially ponded, and moves only when tapped by artificial openings. wells and springs underground water becomes available for use by means of springs and through wells or bore holes. water rises to the surface in natural springs at points where the pressure or _head_, due to its entrance into the ground at a higher level, is sufficient to force it to the surface after a longer or shorter underground course. the movement may be all downward and lateral to the point of escape, or it may be downward, lateral, and upward. ordinarily, the course of spring waters does not carry them far below the surface. heat and gases may be added beneath the surface by contact with or contributions from cooling igneous rocks. these may accelerate the upward movement of spring waters, and yield thermal and gas-charged waters, as in the springs and geysers of yellowstone park. when a well is sunk to tap the underground water supply, the water may not rise in the artificial opening but may have to be lifted to the surface. if, however, the water is confined beneath an impervious stratum and is under pressure from the water of higher areas, a well opening may simply allow it to move upward under its own pressure or head. this pressure may carry it upward only a few feet or quite to the surface or beyond, in which latter case the well is called an _artesian_ well. the essential condition for an artesian circulation is a porous zone, inclining downward from the surface beneath an impervious stratum which tends to confine and pond the water. the water at any point in the water-bearing rock is under pressure which is more or less equivalent to the weight of the column of water determined by the difference in height between this point and the point of entrance or feeding area of the water. if the feeding area is higher than the collar of the well, the water will rise quite to the surface; if not, it will rise only part way. capillary resistance, however, may and usually does lessen the theoretical pressure so figured. the flow in deep artesian circulations is ordinarily a slow one. for the artesian wells of southern wisconsin, it has been calculated that waters entering the outcrop of the southward dipping sandstone and limestone layers in the northern part of the state have required two or three hundred years to reach a point in the southern part of the state where they are tapped. because of this slow movement, a large number of wells in any one spot may exhaust the local supply faster than it is replenished from the remainder of the formation. the drilling of additional wells near at hand in such cases does not increase the total yield, but merely divides it among a larger number of wells. the porosity of the rocks, and therefore the flow of an artesian circulation, may in some cases be artificially increased by blasting and shattering. composition of underground waters underground waters are never entirely free from dissolved mineral substances, and seldom are they free from suspended particles. some waters are desired because they contain very small quantities of dissolved mineral matter. others are prized because they have an unusually high content of certain mineral substances. in determining the deleterious or beneficial effect of dissolved substances, much depends on the purpose for which the water is to be used,--whether for drinking, washing, steam boilers, or irrigation. near the surface underground waters may carry bacteria, as well as animal and vegetable refuse, which from a sanitary standpoint are usually objectionable. deeper waters are more likely to lack this contamination because of filtration through rocks and soils. the dissolved mineral substances of underground water are derived for the most part from the solution of rocks with which the waters come in contact, particularly at or near the surface. through the agency of underground water most of the mineral and chemical changes of rocks are produced. the dissolved substances in solution at any time and place may therefore be regarded as by-products of rock alterations. locally they may to some extent be derived from direct emanations from cooling igneous masses. the most common mineral substances contained in waters are lime and magnesia. less common, but abundant locally, are soda, potash, iron, and silica. waters contain also certain acid and gaseous substances, the most common of which is carbon dioxide; and less widespread, but locally abundant, are chlorine and sulphur dioxide. where lime and magnesia are abundant the water is ordinarily classed as a hard water. where absent, or subordinate to soda and potash, the water is ordinarily classed as a soft water. large amounts of the acid substances like chlorine and sulphur are detrimental for most purposes. where there are unusual amounts of carbon dioxide or other gases present, they may by expansion cause the water to bubble. if we were to attempt to describe and define the characteristics, with reference to dissolved mineral content and temperature, which make a given water more desirable than another, we should enter a field of the most amazing complexity and one with many surprising contradictions. for the most widespread use, the most desirable water is a cold water as free from mineral content as possible, and especially one lacking an excess of lime and magnesia which make it hard; also lacking an excess of acid constituents like sulphur dioxide, carbon dioxide, or chlorine, which give the water a taste, or which make impossible its use in boilers. locally and for special reasons, waters of other qualities are in demand. waters so excessively carbonated as to bubble, sulphureted waters, chlorine waters, waters high in iron, high in silica, high in potash, high in soda, or high in magnesia, or waters of high temperature, may come to be regarded as desirable. it is an interesting fact that any water with unusual taste, or unusual mineral content, or unusual temperature, is likely to be regarded as having medicinal value. sometimes this view is based on scientific knowledge; sometimes it is an empirical conclusion based on experience; and again it may be merely superstition. in one case the desirable feature may be the presence of a large amount of carbon dioxide; in another case it may be its absence. in one case the desirable feature may be high temperature; in another case low temperature. the same combination of qualities which in a certain locality may be regarded as highly desirable, may be regarded as highly detrimental somewhere else where certain other types of waters are in vogue. proprietary rights and advertising have brought certain waters into use for drinking purposes which are not essentially different from more widely available waters which are not regarded as having special value. two springs located side by side, or a spring and a deep well, whose waters have exactly the same chemical characteristics, may be used and valued on entirely different scales. any attempt to classify mineral waters sold to the public in any scientific way discloses a most intricate and confused situation. one can only conclude that the popularity of certain waters is not based alone on objective qualities of composition, but rather on causes which lie in the fields of psychology and commerce. the part played by sentiment in putting value on water is well illustrated by the general preference for spring waters as compared with well waters. in the public mind, "spring water" denotes water of unusual purity and of more desirable mineral content than well water. illustrations could be cited of districts in which the surface or spring waters have a composition not different from that of the deeper well waters, and are much more likely to be contaminated because of proximity to the surface; and yet people will pay considerable sums for the spring water in preference to the cheaply available well water. relation of geology to underground water supply it is obvious that a knowledge of geology is helpful in locating an underground water supply. locally the facts may become so well known empirically that the well driller is able to get satisfactory results without using anything but the crudest geologic knowledge; but in general, attention to geologic considerations tends to eliminate failures in well drilling and to insure a more certain and satisfactory water supply. in drilling for water, it is essential to know the nature, succession, and structure of the rocks beneath the surface in order to be able to identify and correlate them from drill samples. the mere identification of samples is often sufficient to determine whether a well has been drilled far enough or too far to secure the maximum results. in order to arrive at any advance approximation of results for a given locality, a knowledge of the general geology of the entire region may be necessary. especially for expensive deep artesian wells it is necessary to work out the geologic possibilities well in advance. it is useless, for instance, to look for artesian water in a granite; but in an area of gently inclined strata, with alternations of porous and impervious layers, the expert may often figure with a considerable degree of certainty the depth at which a given porous stratum will be found, and the pressure under which the water will be in this particular stratum at a given point. even the mineral content of the water may in some cases be predicted from geologic study. one of the most obvious and immediately useful services of the geologist in most localities is the collection and preservation of well samples for purposes of identification and correlation of rock formations, and as a guide to further drilling. failure to preserve samples has often led to useless and expensive duplication of work. the problem of water supply in some localities is comparatively simple and easy. in other areas there is an infinite variety of geologic conditions which affect the problem, and the geologist finds it necessary to bring to bear all the scientific knowledge of any sort which can be used,--particularly knowledge in relation to the type of rock, the stratigraphy and the structure. surface water supplies where underground water is not abundant or not cheaply available, or where larger amounts of water are needed, as in large cities or for irrigation purposes, surface water is used. in general, surface waters are more likely to be contaminated by vegetable and animal matter and to require purification for drinking purposes. surface waters are also used for irrigation, water power, drainage, the carrying of sewage, etc. this great variety of uses brings the consideration of surface waters into many fields other than geology, but an understanding and interpretation of the geological conditions is none the less fundamental. this is evidenced by the inclusion of geologic discussions in most textbooks of hydrology, and in the reports of the hydrographic branch of the u. s. geological survey. the very fact that this important branch of governmental investigation is in a charge of the u. s. geological survey indicates its close relation to geology. the principles of geology used in the study of surface waters relate chiefly to physiography (see chapter i). it is usually necessary to know the total quantity of flow, its annual and seasonal variation, and the possible methods of equalization or concentration; the maximum quantity of flow, the variation during periods of flood, and the possibilities of reduction or control; the minimum flow and its possible modification by storage or an auxiliary supply. these questions are obviously related to the size and shape of the catchment area, the topography, the rock structure, the relation between underground flow or absorption and the runoff, and other physiographic factors. quoting from d. w. mead:[ ] geological conditions are frequently of great importance in their influence on the quantity and regularity of runoff. if the geological deposits of the drainage area are highly impervious, the surface flow will receive and transmit the water into the mass only through the cracks and fissures in the rock. pervious materials, such as sandstones, sands, gravels, and cracked or fissured rocks, induce seepage, retard runoff, and, if such deposits are underlaid with an impervious bed, provide underground storage which impounds water away from the conditions which permit evaporation, and hence tends to increase runoff and equalize flow. on the other hand, if such pervious deposits possess other outlets outside of the stream channel and drainage area, they may result in the withdrawal of more or less of the seepage waters entirely from the ultimate flow of the stream. coarse sands and gravels will rapidly imbibe the rainfall into their structure. fine and loose beds of sand also rapidly receive and transmit the rainfall unless the precipitation is exceedingly heavy under which conditions some of it may flow away on the surface. many of the highly pervious indurated formations receive water slowly and require a considerable time of contact in order to receive and remove the maximum amount. in flat, pervious areas, rainfalls of a certain intensity are frequently essential to the production of any resulting stream flow. in a certain colorado drainage area, the drainage channel is normally dry except after a rainfall of one-half inch or more. a less rainfall, except under the condition of a previously saturated area, evaporates and sinks through the soil and into the deep lying pervious sand rock under the surface which transmits it beyond the drainage area. such results are frequently greatly obscured by the interference of other factors, such as temperature, vegetation, etc. * * * * * the natural storage of any drainage area and the possibilities of artificial storage depend principally upon its topography and geology. storage equalizes flow, although the withdrawal of precipitation by snow or ice storage in northern areas often reduces winter flow to the minimum for the year. both surface and sub-surface storage sometimes hold the water from the streams at times when it might be advantageously used. storage, while essential to regulation, is not always an advantage to immediate flow conditions. underground and surface waters in relation to excavation and construction scarcely more than a mention of this subject is necessary. in mining, the pumping charge is one of the great factors of cost. a forecast of the amount and flow of water to be encountered in mining is based on the geologic conditions. the same is true in excavating tunnels, canals, and deep foundations. detailed study of the amount and nature of water in the rock and soil of the panama canal has been vital to a knowledge of the cause and possibilities of prevention of slides. rock slides in general are closely related to the amount and distribution of the water content. the importance of ground-water as a detriment in military operations was shown during the recent war in trenching and other field works. at the outset, with the possible exception of the german army, a lack of scientific study of ground-water conditions led to much unnecessary difficulty. it soon became necessary to study and map the water conditions in great detail in advance of operations. much of this work was done by geologists (see chapter xix). geological considerations are involved in a great variety of engineering undertakings related to river and harbor improvements, dam sites, etc., mentioned in chapter xx. footnotes: [ ] mead, daniel w., _hydrology_: mcgraw-hill book co., new york, , pp. - , . chapter vi the common rocks and soils as mineral resources economic features of the common rocks under the general heading of common rocks are included the ordinary igneous, sedimentary, and "metamorphic" rocks, and the unconsolidated clays, sands, and gravels characteristic of surface conditions, which are mined and quarried for commercial use. soils are closely related to this group; but since they present special problems of their own, they are discussed under a separate heading at the end of the chapter. names of the common rocks will be used with the general commercial significance given them by the united states geological survey in its mineral resource reports. because of their inexhaustible quantity and ready availability, the value of the common rock products is not large per unit of weight; but in the aggregate it ranks high among mineral products. in respect to tonnage, common rocks constitute perhaps per cent of the world annual output of all mineral commodities (exclusive of water). the greater tonnage of the common rocks is used commercially in crushed or comminuted forms for road material, for railroad ballast, and for cement, brick, concrete, and flux. in blocks and structural shapes, of less aggregate tonnage, they are used as building stone, monumental stone, paving blocks, curbing, flagging, roofing, refractory stone, and for many other building and manufacturing purposes. the common rocks are commodities in which most countries of the globe are self-sufficing. international trade in these commodities is insignificant, being confined to small quantities of materials for special purposes, or to local movements of short distances, allowed by good transportation facilities. the common rocks are so abundant and widespread that the conservation of raw materials is not ordinarily a vital problem. conservational principles do apply, however, to the human energy factor required for their efficient use. in the valuation of common rocks, also, the more important factors are not the intrinsic qualities of the stones, but rather the conditions of their availability for use. because of bulk and comparatively low intrinsic value, the principal commercial factors in the availability of the common rocks are transportation and ease of quarrying, but these are by no means the only factors determining availability. their mineral and chemical composition, their texture and structure, their durability, their behavior under pressure and temperature changes, and other factors enter in to important degrees. the weighting and integration of these factors, for the purpose of reaching conclusions as to the availability of particular rock materials, depend also on the purposes for which these materials are to be used. the problem is anything but simple. the search for a particular rock to meet a certain demand within certain limits of cost is often a long and arduous one. on account of the abundance and widespread distribution of common rocks and their variety of uses, there is a good deal of popular misapprehension as to their availability. many building and manufacturing enterprises have met disastrous checks, because of a tendency to assume availability of stone without making the fullest technical investigation. many quarrying ventures have come to grief for the same reason. it is easy to assume that, because a granite in a certain locality is profitably quarried and used, some other granite in the same locality has equal chances. however, minor differences in structure, texture, and composition, or in costs of quarrying and transportation, may make all the difference between profit and loss. even though all these conditions are satisfactorily met, builders and users are often so conservative that a new product finds difficulty in breaking into the market. a well-established building or ornamental stone, or a limestone used for flux, may hold the market for years in the face of competition from equally good and cheaper supplies. the very size of a quarry undertaking may determine its success or failure. granite the term granite, as used commercially, includes true granite and such allied rocks as syenite and gneiss. in fact even quartzite is sometimes called granite in commerce, as in the case of the baraboo quartzites of wisconsin, but this is going too far. for statistical purposes, the united states geological survey has also included small quantities of diorite and gabbro. the principal uses of granite are, roughly in order of importance, for monumental stone, building stone, crushed stone, paving, curbing, riprap and rubble. thirty states in the united states produce granite, the leaders being vermont, massachusetts, north carolina, maine, wisconsin, minnesota, and california. basalt and related types basalt and related rocks are sometimes included under the name "trap rock," which comprises,--besides typical basalt and diabase,--fine-grained diorite, gabbro, and other basic rocks, which are less common in occurrence and are similar in chemical and physical properties. the principal use of these rocks is as crushed stone for road and ballast purposes and for concrete. they are produced in some fifteen states, the leaders being new jersey, pennsylvania, california, and connecticut. limestone, marl, chalk in the united states limestone is used principally as crushed stone for road material, railroad ballast, concrete, and cement, as fluxing stone for metallurgical purposes, and in the manufacture of lime. minor uses are as building stones, paving blocks, curbing, flagging, rubble, and riprap; in alkali works, sugar factories, paper mills, and glass works; and for agricultural purposes. for the making of cement, in metallurgical fluxes, and in most of the manufacturing and agricultural uses, both limestone and lime (limestone with the co_ driven out by heating) are used. lime is also extensively used in the making of mortar for building operations, in tanning leather, and in a great variety of chemical industries. the total quantity of limestone used for all purposes in the united states nearly equals that of iron ore. nearly every state in the union produces limestone, but the more important producers are pennsylvania (where a large amount is used for fluxing), ohio, indiana, new york, michigan, and illinois. closely associated with limestone in commercial uses, as well as in chemical composition, is calcareous marl, which is used extensively in the manufacture of portland cement. chalk is a soft amorphous substance of the same composition as limestone. the main uses of chalk are as a filler in rubber, and as a component of paint and putty. it is also used for polishing. the principal producers of this commodity are england, denmark, and france, and the chief consumer is the united states. the united states depends upon imports for its supply of chalk for the manufacture of whiting. before the war two-thirds came from england and a third from france. during the war importation was confined to england, with a small tonnage from denmark. no deposits of domestic chalk have been exploited commercially. a somewhat inferior whiting, but one capable of being substituted for chalk in most cases, is manufactured from the waste fine material of limestone and marble quarries. marble marble is limestone which has been coarsely recrystallized by metamorphism. the marble of commerce includes a small quantity of serpentine as quarried and sold in massachusetts, california, maryland, pennsylvania, and vermont, and also a small amount of so-called onyx marble or travertine obtained from caves and other deposits in kentucky and other states. the principal uses of marble are for building and monumental stones. of the twenty-two states producing marble, the leaders are vermont, georgia, and tennessee. a small amount of marble of special beauty, adapted to ornamental purposes, is imported from european countries, especially from italy. marble imports from italy constitute about two-thirds, both in tonnage and value, of all stone imported into the united states. sand, sandstone, quartzite (and quartz) sand is composed mainly of particles of quartz or silica, though sometimes feldspar and other minerals are present. sandstones are partially cemented sands. quartzites are completely cemented sands. to some extent these substances are used interchangeably for the same purposes. the principal uses of sand in order of commercial totals are for building purposes--for mortar, concrete, sand-lime brick, etc.,--as molding sand in foundries, as a constituent of glass, in grinding and polishing, in paving, as engine sand, as fire or furnace sand, in the manufacture of ferrosilicon (a steel alloy), and in filters. reference is made to sand as an abrasive and in the manufacture of steel in chapters xiii and ix. almost every state produces some sand, but for some of the more specialized uses, such as glass sand, molding sand, and fire or furnace sand, the distribution is more or less limited. the united states geological survey has collected information concerning the distribution of various kinds of sand and gravel, and serves a very useful function in furnishing data as to supplies of material for particular purposes. fine molding sands have been imported from france, but during the war domestic sources in new york and ohio were developed sufficiently to meet any requirements. the sandstone of commerce includes the quartzites of minnesota, south dakota, and wisconsin, and the fine-grained sandstones of new york, pennsylvania, and elsewhere, known to the trade as "bluestone." in kentucky most of the sandstone quarried is known locally as "freestone." the principal uses of sandstone are for building stone, crushed stone, and ganister (for silica brick and furnace-linings). other uses are for paving blocks, curbing, flagging, riprap, rubble, grindstones, whetstones, and pulpstones (see also chapter xiii). sandstone is sometimes crushed into sand and is used in the manufacture of glass and as molding-sand. most of the states of the union produce sandstone, the principal producers being pennsylvania, ohio, and new york. "sand and gravel" where sand is coarse and impure and mixed with pebbles, it is ordinarily referred to as "sand and gravel." for sand and gravel the principal uses are for railroad ballast, for road building, and for concrete. sand and gravel are produced in almost every state in the union, the largest producers being pennsylvania, ohio, illinois, new jersey, and north carolina. clay, shale, slate shale is consolidated clay, usually with a fine lamination due to bedding. slate is a more dense and crystalline rock, produced usually by the anamorphism of clay or shale under pressure, and characterized by a fine cleavage which is usually inclined to the sedimentary bedding. clays are used principally for building and paving brick and tile, sewer-pipe, railroad ballast, road material, puddle, portland cement, and pottery. clay is mined in almost every state. ohio, pennsylvania, new jersey, and illinois have the largest production. there has been a considerable importation of high-grade clays, principally from england, for special purposes--such as the filling and coating of paper; the manufacture of china, of porcelain for electrical purposes, and of crucibles; and for use in ultramarine pigments, in sanitary ware, in oilcloth, and as fillers in cotton bleacheries. war experience showed the possibility of substitution of domestic clays for most of these uses; but results were not in all cases satisfactory, and the united states will doubtless continue to use imported clays for some of these special purposes. shales, because of their thinly bedded character and softness, are of no value as building stones, but are used in the manufacture of brick, tile, pottery, and portland cement. slates owe their commercial value primarily to their cleavage, which gives well-defined planes of splitting. the principal uses are for roofing and, in the form of so-called mill stock for sanitary, structural, and electrical purposes. small amounts are used for tombstones, roads, slate granules for patent roofing, school slates, blackboard material, billiard table material, etc. the color, fineness of the cleavage, and size of the flakes are the principal features determining the use of any particular slate. ten states produce slate, the principal production coming from pennsylvania and vermont. the feldspars feldspars are minerals, not rocks, but mention of them is made here because, with quartz, they make up such an overwhelming percentage of earth materials. it is estimated that the feldspars make up per cent of all the igneous rocks and per cent of the sedimentary rocks. as the igneous rocks are so much more abundant than the sedimentary rocks, the percentage of feldspars in the earth approaches the former rather than the latter figure. in most rocks feldspar is in too small grains and is too intimately associated with other minerals to be of commercial importance; in only one type of rock, pegmatite, which is an igneous rock of extremely coarse and irregular texture, are the feldspar crystals sufficiently large and concentrated to be commercially available. feldspar is used principally in the manufacture of pottery, china ware, porcelain, enamel ware, and enamel brick and tile. in the body of these products it is used to lower the fusing point of the other ingredients and to form a firm bond between their particles. its use in forming the glaze of ceramic products is also due to its low melting point. a less widespread use of feldspar is as an abrasive (chapter xiii). one of the varieties of feldspar carries about per cent of potash, and because of the abundance of the mineral there has been much experimental work to ascertain the possibility of separating potash for fertilizer purposes; but, because of cost, this source of potash is not likely for a long time to compete with the potash salts already concentrated by nature. feldspar is mined in eleven states, but the important production comes from north carolina and maine. the united states also imports some feldspar from canada. hydraulic cement (including portland, natural, and puzzolan cements) cement is a manufactured product made from limestone (or marl) and clay (or shale). sometimes these two kinds of substances are so combined in nature (as in certain clayey limestones) that they are available for cement manufacture without artificial mixing. it is not our purpose in this volume to discuss manufactured products; but the cement industry involves such a simple transformation of raw materials, and is so closely localized by the distribution of the raw materials, that a mention of some of its outstanding features seems desirable. hydraulic cement is used almost exclusively as a structural material. it is an essential ingredient of concrete. originally used chiefly for the bonding of brick and stone masonry and for foundation work, its uses have grown rapidly, especially with the introduction of reinforced concrete. it is being used in the construction of roads, and its latest use is in ship construction. with the exception of satisfactory fuels, the raw materials required for the manufacture of cement are found quite generally throughout the world. while practically all countries produce some cement, much of it of natural grade, only the largest producers make enough for their own requirements and as a result there is a large world movement of this commodity. the world trade is chiefly in portland cement. next to the united states, the producing countries having the largest exportable surplus of cement in normal times are germany and great britain. france and belgium were both large producers and exporters before the war, but the war greatly reduced their capacity to produce for the time being. sweden, denmark, austria, japan, and switzerland all produce less extensively but have considerable surplus available for export. italy and spain have large productions, which are about sufficient for their own requirements. holland and russia import large amounts from the other european countries. the far eastern trade absorbs the excess production of japan. in south africa and australasia, production nearly equals demand. in canada, although the industry has been growing very rapidly, the demand still exceeds production. in south and central america, mexico and the west indies, the demand is considerable and will probably increase; production has thus far been insufficient. several modern mills are either recently completed or under construction in these countries, and concessions have been granted for several others. these new mills are largely financed by american capital. the united states is the largest single producer of cement in the world, its annual production being about per cent of the world's total. domestic consumption has always been nearly as great as the production, and exports have usually not exceeded per cent of the total shipments from the mills. south and central america offer fields for exportation of cement from the united states. geologic features of the common rocks to describe the geologic features of the common rocks used in commerce would require a full treatise on the subject of geology. these are the bulk materials of the earth and in them we read the geologic history of the earth. in preceding chapters a brief outline has been given of the relative abundance of the common earth materials and of the processes producing them. in comparison, the metalliferous deposits are the merest incidents in the development of this great group of mineral resources. in this section reference will be made only to a few of the rock qualities and other geologic features which require first attention in determining the availability of a common rock for commercial use. the list is very fragmentary, for the reason that the uses are so many and so varied that to describe all the geologic features which are important from the standpoint of all uses would very soon bring the discussion far beyond the confines of a book of this scope.[ ] building stone for building stones, the principal geologic features requiring attention are structure, durability, beauty, and coloring. the structures of a rock include jointing, sedimentary stratification, and secondary cleavage. nearly all rocks are jointed. the joints may be open and conspicuous, or closed and almost imperceptible. the closed joints or incipient joints cause planes of weakness, known variously as rift, grain, etc., which largely determine the shapes of the blocks which may be extracted from a quarry. where properly distributed, they may facilitate the quarrying of the stone. in other cases they may be injurious, in that they limit the size of the blocks which can be extracted and afford channels for weathering agents. some rocks of otherwise good qualities are so cut by joints that they are useless for anything but crushed stone. the bedding planes or stratification of sedimentary rocks exercise influences similar to joints, and like joints may be useful or disadvantageous, depending on their spacing. the secondary cleavage of some rocks, notably slates, enables them to be split into flat slabs and thus makes them useful for certain purposes. proper methods of extraction and use of a rock may minimize the disadvantageous effects of its structural features. the use of channelling machines instead of explosives means less shattering of the rock. by proper dressing of the surface the opening of small crevices may be avoided. stratified rocks set on bed, so that the bedding planes are horizontal, last longer than if set on edge. the durability of a rock may depend on its perviousness to water which may enter along planes of bedding or incipient fracture planes, or along the minute pore spaces between the mineral particles. the water may cause disastrous chemical changes in the minerals and by its freezing and thawing may cause splitting. for this reason, the less pervious rocks have in general greater durability than the more pervious. highly pervious rocks used in a dry position or in a dry climate will last longer than elsewhere. durability is determined also by the different coefficients of expansion of the constituent minerals of the rock. where the minerals are heterogeneous in this regard, differential stresses are more likely to be set up than where the minerals are homogeneous. likewise a coarse-textured rock is in general less durable than a fine-textured one. expansion and contraction of a stone under ordinary temperature changes, and also under fire and freezing, must necessarily be known for many kinds of construction. minerals resist weathering to different degrees, therefore the mineral composition of a rock is another considerable factor in determining its durability. where pyrite is present in abundance it easily weathers out, leaving iron-stained pits and releasing sulphuric acid which decomposes the rock. abundance of mica, especially where segregated along the stratification planes, permits easy splitting of the rock under weathering. likewise the mica often weathers more quickly than the surrounding minerals, giving a pitted appearance; in marbles and limestones its irregular occurrence may spoil the appearance. flint or chert in abundance is deleterious to limestones and marbles, because, being more resistant, it stands out in relief on the weathered surface, interferes with smooth cutting and polishing, and often causes the rock to split along the lines of the flint concretions. abundance of tremolite may also be disadvantageous to limestones and marbles, because it weathers to a greenish-yellow clay and leaves a pitted surface. the crushing strength of a rock has an obvious relation to its structural uses. the rock must be strong enough for the specified load. most hard rocks ordinarily considered for building purposes are strong enough for the loads to which subjected, and this factor is perhaps ordinarily less important than the structural and mineral features already mentioned. it is often necessary to know the modulus of elasticity and other mechanical constants of a rock, as in cases where it is to be combined with metal or other masonry or to be subjected to exceptional shock. the beauty and coloring of a rock are its esthetic rather than its utilitarian features. they are particularly important in the construction of buildings and monuments for public or ornamental purposes. crushed stone the largest use of rock or stone is in the crushed form for road building, railway embankments, and concrete, and the prospect is for largely increased demands for such uses in the future. for the purpose of road building, it is necessary to consider a stone's resistance to abrasion, hardness, toughness, cementing value, absorption, and specific gravity. limestone cements well, but in other qualities it is not desirable for heavy traffic. shales are soft and clayey, and grind down to a mass which is dry and powdery, and muddy in wet weather. basalt and related rocks resist abrasion, and cement well. granites and other coarse-grained igneous rocks do not cement well and are not resistant to abrasion. many sandstones are very hard and brittle and resist abrasion, but do not cement. the application of geology on a large scale to the study of sources and qualities of crushed stone is now being required in connection with the great state and national projects of highway building. this work is by no means confined to a mere testing of the physical qualities of road-building materials found along the proposed route, but includes a careful study of their geologic occurrence, distribution, and probable amounts. in certain of the northern states specialists in glacial geology are preferred for this purpose. stone for metallurgical purposes the use of limestone and other rock for metallurgical fluxes is dependent very largely on chemical composition. comparatively few limestones are sufficiently pure for this purpose. for furnace linings, the quartzite or ganister must be exceptionally pure. the field search for rocks of the necessary composition has required geologic service. clay for a variety of uses to which clay is put, it is necessary to know its degree of plasticity, tensile strength, shrinkage (both under air and fire), fusibility, color, specific gravity, and chemical properties. the testing of clay for its various possible uses is a highly specialized job, usually beyond the range of a geologist, although certain geologists have been leaders in this type of investigation. more commonly within the range of a geologist are questions concerning origin, field classification, distribution, quantities, and other geologic conditions affecting quality and production. clay originates from the weathering of common rocks containing silicates, by pretty well understood weathering processes (see chapter ii). it may remain in place above the parent rock, or may be transported and redeposited, either on land or under water, by the agencies of air, water, and ice. the kind of parent rock, the climatic conditions and nature of the weathering, and the degree of sorting during transportation, all determine the composition and texture of the resulting clay,--with the result that a classification on the basis of origin may indicate the broad group characteristics which it is desirable to know for commercial purposes. for instance, residual clays from the weathering of granite may be broadly contrasted with residual clays formed by the weathering of limestone, and both differ in group characteristics from clays in glacial deposits. classification according to origin also may be useful in indicating general features of depth, quantity, and distribution. however, a genetic classification of clays is often not sufficient to indicate the precise characteristics which it is necessary to know in determining their availability for narrow and special technical requirements. furthermore, clays suitable for certain commercial requirements may be formed in several different ways, and classification based on specific qualities may therefore not correspond at all to geologic classification based on origin. geologists have been especially interested in the causes of plasticity of clay and in its manner of hardening when dried. in general these phenomena have been found to be due to content of colloidal substances of a clayey nature, which serve not only to hold the substance together during plastic flow but to bind it during drying. the part played by colloids in the formation of clays, as well as of many other mineral products, is now a question which is receiving intensive study. the same processes which produce clay also produce, under special conditions, iron ores, bauxites, the oxide zones of many sulphide ore bodies, and soils, all of which are referred to on other pages. limitations of geologic field in commercial investigation of common rocks in general the qualities of the earth materials which determine their availability for use are only to a minor extent the qualities which the geologist ordinarily considers for mapping and descriptive purposes. the usual geological map and report on a district indicate the distribution and general nature of the common rocks, and also the extent to which they are being used as mineral resources. seldom, however, is there added a sufficiently precise description, for instance of a clay, to enable the reader to determine which, if any, of the many different uses the material might be put to. the variety of uses is so great, and the technical requirements for different purposes are so varied and so variable, that it is almost impossible to make a description which is sufficiently comprehensive, and at the same time sufficiently exact, to give all the information desired for economic purposes. if the geologist is interested in disclosing the commercial possibilities in the raw materials of an area, he may select some of the more promising features and subject them to the technical analysis necessary to determine their availability for special uses. in this phase of his work he may find it necessary to enlist the coöperation of skilled technicians and laboratories in the various special fields. the problem is simplified if the geologist is hunting for a particular material for a specific purpose, for then he fortifies himself with a knowledge of the particular qualities needed and directs his field and laboratory study accordingly. too often the geologist fails to recognize the complexity and definiteness of the qualities required, and makes statements and recommendations on the use of raw materials based on somewhat general geologic observations. on the other hand, the engineer, or the manufacturer, or the builder often goes wrong and spends money needlessly, by failing to take into consideration general geologic features which may be very helpful in determining the distribution, amount, and general characters of the raw materials needed. it is difficult to draw the line between the proper fields of the geologist and those of the engineer, the metallurgist, and other technicians. it is highly desirable that the specialist in any one of these fields know at least of the existence of the other fields and something of their general nature. too often his actions indicate he is not acutely conscious even of the existence of these related branches of knowledge. the extent and detail to which the geologist will familiarize himself with these other fields will of course vary with his training and the circumstances of his work. whatever his limit is, it should be definitely recognized; his work should be thorough up to this limit and his efforts should not be wasted in fields which he is not best qualified to investigate. these remarks apply rather generally to mineral resources, but they are particularly pertinent in relation to the common rock materials which the geologist is daily handling,--for he is likely to assume that he knows all about them and that he is qualified to give professional advice to industries using them. in connection with metallic resources, the metallurgical and other technical requirements are likely to be more definitely recognized and the lines more sharply drawn, with the result that the geologist is perhaps not so likely to venture into problems which he is not qualified to handle. the limits to geologic work here discussed are not necessarily limits separating scientific from non-scientific work. the study and determination of the qualities of rocks necessary for commercial purposes is fully as scientific as a study of the qualities commonly considered in purely geologic work, and the results of technical commercial investigations may be highly illuminating from a purely geological standpoint. when a field of scientific endeavor has been established by custom, any excursion beyond traditional limits is almost sure to be regarded by conservatives in the field as non-scientific, and to be lightly regarded. the writer is fully conscious of the existence of limits and the necessity for their recognition; but he would explain his caution in exceeding these limits on the ground of training and effectiveness, rather than on fear that he is becoming tainted with non-scientific matters the moment he steps beyond the boundaries of his traditional field. soils as a mineral resource soils are not ordinarily listed as mineral resources; but as weathered and altered rock of great economic value, they belong nearly at the head of the list of mineral products. origin of soils soil originate from rocks, igneous, sedimentary, and "metamorphic" by processes of weathering, and by the mixing of the altered mineral products with decayed plant remains or _humus_. the humus averages perhaps or per cent of the soil mass and sometimes constitutes as much as per cent. not all weathered rock is soil in the agricultural sense. for this purpose the term is mainly restricted to the upper few inches or feet penetrated by plant roots. the general process of soil formation constitutes one of the most important phases of katamorphism--the destructive side of the metamorphic cycle, described in chapter ii. processes of katamorphism or weathering, usually accompanied by the formation of soils, affect the surface rocks over practically all the continental areas. the weathering of a highly acid igneous rock with much quartz produces a residual soil with much quartz. the weathering of a basic igneous rock without quartz produces a clay soil without quartz, which may be high in iron. where disintegration has been important the soil contains an abundance of the original silicates of the rock, and less of the altered minerals. the production of soil from sedimentary rocks involves the same processes as alter igneous rocks; but, starting from rocks of different composition, the result is of course different in some respects. sandstones by weathering yield only a sandy soil. limestones lose their calcium carbonate by solution, leaving only clay with fragments of quartz or chert as impurities. a foot of soil may represent the weathering of a hundred feet of limestone. shales may weather into products more nearly like those of the weathering of igneous rocks. silicates in the shales are broken down to form clay, which is mixed with the iron oxide and quartz. in some localities the soil may accumulate to a considerable depth, allowing the processes of weathering to go to an extreme; in others the processes may be interrupted by erosion, which sweeps off the weathered products at intermediate stages of decomposition and may leave a very thin and little decomposed soil. soils formed by weathering may remain in place as residual soils, or they may be transported, sorted, and redeposited, either on land or under water. it is estimated by the united states bureau of soils[ ] that upward of per cent of the soils of the united states which have been thus far mapped owe their occurrence and distribution to transportation by moving water, air, and ice (glaciers), and that less than per cent have remained in place above their parent rock. glaciers may move the weathered rock products, or they may grind the fresh rocks into a powder called _rock flour_, and thus form soils having more nearly the chemical composition of the unaltered rocks. glacial soils are ordinarily rather poorly sorted, while wind and water-borne soils are more likely to show a high degree of sorting. the character of a transported soil is less closely related to the parent rock than is that of a residual soil, because the processes of sorting and mixture of materials from different sources intervene to develop deposits of a nature quite different from residual soils; but even transported soil may sometimes be traced to a known rock parentage. where deposited under water, soil materials may be brought above the water by physiographic changes, and exposed at the surface in condition for immediate use. or, they may become buried by other sediments and not be exposed again until after they have been pretty well hardened and cemented,--in which case they must again undergo the softening processes of weathering before they become available for use. where soils become buried under other rocks and become hardened, they are classed as sedimentary rocks and form a part of the geologic record. many residual and transported soils are to be recognized in the geologic column; in fact a large number of the sedimentary rocks ordinarily dealt with in stratigraphic geology are really transported soils. the development of soils by weathering should not be regarded as a special process of rock alteration, unrelated to processes producing other mineral products. exactly the same processes that produce soils may yield important deposits of iron ore, bauxite, and clay, and they cause also secondary enrichment of many metallic mineral deposits. for instance the weathering of a syenite rock containing no quartz, under certain conditions, as in arkansas, results in great bauxite deposits which are truly soils and are useful as such,--but which happen to be more valuable because of their content of bauxite. the weathering of a basic igneous rock, as in cuba, may produce important residual iron ore deposits, which are also used as soils. weathering of ferruginous limestone may produce residual iron and manganese ores in clay soils. composition of soils and plant growth the mineral ingredients in soils which are essential for plant growth include water, potash, lime, magnesia, nitrates, sulphur, and phosphoric acid--all of which are subordinate in amount to the common products of weathering (pp. - , - ). of these constituents magnesia is almost invariably present in sufficient quantity; while potash, nitrates, lime, sulphur, and phosphoric acid, although often sufficiently abundant in virgin soil, when extracted from the soils by plant growth are liable to exhaustion under ordinary methods of cultivation, and may need to be replenished by fertilizers (chapter vii). some soils may be so excessively high in silica, iron, or other constituents, that the remaining constituents are in too small amounts for successful plant growth. even where soils originally have enough of all the necessary chemical elements, one soil may support plant growth and another may not, for the reason that the necessary constituents are soluble and hence available to the plant roots in one case and are not soluble in the other. plainly the mineral combinations in which the various elements occur are important factors in making them available for plant use. similarly a soil of a certain chemical and mineralogical composition may be fruitful under one set of climatic conditions and a soil of like composition may be barren at another locality--indicating that availability of constituents is also determined by climatic and other conditions of weathering. even with the same chemical composition and the same climatic conditions, there may be such differences in texture between various soils as to make them widely different in yield. the unit of soil classification is the _soil type_, which is a soil having agricultural unity, as determined by texture, chemical character, topography, and climate. the types commonly named are clay, clay loam, silt loam, loam, fine sandy loam, sandy loam, fine sand, and sand. in general the soil materials are so heterogeneous and so remote from specific rock origin, that in such classification the geologic factor of origin is not taken into account. more broadly, soils may be classified into provinces on the basis of geography, similar physiographic conditions, and similarity of parent rocks; for instance, the soils of the piedmont plateau province, of the arid southwest region, of the glacial and loessal province, etc. in such classification the geologic factors are more important. soils within a province may be subdivided into "soil series" on the basis of common types of sub-soils, relief, drainage, and origin. use of geology in soil study while the desirability of particular soils is related in a broad way to the character of the parent rocks, and while by geologic knowledge certain territories can be predicated in advance as being more favorable than others to the development of good soils, so many other factors enter into the question that the geologic factor may be a subordinate one. a soil expert finds a knowledge of geology useful as a basis for a broad study of his subject; but in following up its intricacies he gives attention mainly to other factors, such as the availability of common constituents for plant use, the existence and availability of minute quantities of materials not ordinarily regarded as important by the geologist, the climatic conditions, and the texture. as the geologic factors are many of them comparatively simple, much of the expert work on soils requires only elementary and empirical knowledge of geology. the geologist, although he may understand fully the origin of soils and may indicate certain broad features, must acquire a vast technique not closely related to geology before he becomes effective in soil survey work and diagnosis. for these reasons the mapping and classification of soils, while often started by geologists of state or federal surveys, have in their technical development and application now passed largely into the hands of soil experts in the special soil surveys affiliated with the u. s. department of agriculture and with agricultural colleges. footnotes: [ ] a good summary of this subject may be found in _engineering geology_, by h. ries and t. l. watson, wiley and sons, d ed., . [ ] marbut, curtis f., soils of the united states: _bull. , bureau of soils_, , p. . chapter vii the fertilizer group of minerals general comments soils are weathered rock more or less mixed with organic material. the weathering processes forming soils are in the field of geologic investigation, but the study of soils in relation to agriculture requires attention to texture and to several of their very minor constituents which have little geologic significance. soil study has therefore become a highly specialized and technicalized subject,--for which a geological background is essential, but which is usually beyond the range of the geologist. to supply substances which are deficient in soils, however, requires the mining, quarrying, or extraction of important mineral resources, and in this part of the soil problem the geologist is especially interested. soils may be originally deficient in nitrates, phosphates, or potash; or the continued cropping of soils may take out these materials faster than the natural processes of nature supply them. in some soils there are sufficient phosphates and potash to supply all plant needs indefinitely; but the weathering and alteration processes, through which these materials are rendered soluble and available for plant life, in most cases are unable to keep up with the depletion caused by cropping. a ton of wheat takes out of the soil on an average pounds of nitrogen, pounds of phosphoric acid, pounds of potash. on older soils in europe it has been found necessary to use on an average pounds of mixed mineral fertilizers annually per acre. on the newer soils of the united states the average thus far used has been less than one-seventh of this amount. the united states has thus far been using up the original materials stored in the soil by nature, but these have not been sufficient to yield anything like the crop output per acre of the more highly fertilized soils of europe. in addition to the nitrates, phosphates, and potassium salts, important amounts of lime and sulphuric acid, and some gypsum, are used in connection with soils. lime is derived from crushed limestone (pp. - ), and is used primarily to counteract acidity or sourness of the soil; it is, therefore, only indirectly related to fertilizers. sulphuric acid is used to treat rock phosphates to make them more soluble and available to plant life. it requires the mining of pyrite and sulphur. gypsum, under the name of "land-plaster," is applied to soils which are deficient in the sulphur required for plant life; increase in its use in the future seems probable. there are also considerable amounts of inert mineral substances which are used as fillers in fertilizers to give bulk to the product, but which have no agricultural value. the proportions of the fertilizer substances used in the united states are roughly summarized in figure . the united states possesses abundant supplies of two of the chief mineral substances entering into commercial fertilizers,--phosphate rock and the sulphur-bearing materials necessary to treat it. for potash the united states is dependent on europe, unless the domestic industry is very greatly fostered under protective tariff. for the mineral nitrates the united states has been dependent on chile, and because of the cheapness of the supply will doubtless continue to draw heavily from this source. however, because of the domestic development of plants for the fixation of nitrogen from the air, the recovery of nitrogen from coal in the by-product processes, and the use of nitrogenous plants, the united states is likely to require progressively less of the mineral nitrates from chile. the fertilizer industry of the united states is yet in its infancy and is likely to have a large growth. furthermore much remains to be learned about the mixing of fertilizers and the amounts and kinds of materials to be used. the importance of sulphur as a plant food has been realized comparatively recently. the use of fertilizers in the united states has come partly through education and the activity of agricultural schools and partly through advertising by fertilizer companies. the increased use of potash has been due largely to the propaganda of the german sales agents. an examination of a map showing distribution of the use of fertilizers over the country indicates very clearly the erratic distribution of the effects of these various activities. one locality may use large amounts, while adjacent territory of similar physical conditions uses little. the sudden withdrawal of fertilizers for a period of three or four years during the war had very deleterious effects in some localities, but was not so disastrous as expected in others,--emphasizing the fact that the use of fertilizers has been partly fortuitous and not nicely adjusted to specific needs. [illustration: fig. . fertilizer situation in the united states. smithsonian institution--united states national museum] nitrates economic features there are several sources of nitrogen for fertilizer purposes: mineral nitrates, nitrogen taken from the air by certain plants with the aid of bacteria and plowed into the soil, nitrogen taken directly from the air by combining nitrogen and oxygen atoms in an electric arc, or by combining nitrogen and hydrogen to form ammonia, nitrogen taken from the air to make a compound of calcium, carbon, and nitrogen (cyanamid), nitrogen saved from coal in the form of ammonia as a by-product of coke-manufacture, and nitrogen from various organic wastes. nitrogen in the form of ammonia is also one of the potential products of oil-shales (p. ). while the principal use of nitrogenous materials is as fertilizers, additional important quantities are used in ammonia for refrigerating plants, and in the form of nitric acid in a large number of chemical industries. during the war the use of nitrates was largely diverted to explosives manufacture. the geologist is interested principally in the mineral nitrates as a mineral resource, but the other sources of nitrogen, particularly its recovery from coal, also touch his field. almost the single source of mineral nitrates for the world at present is chile, where there are deposits of sodium nitrate or chile saltpeter, containing minor amounts of potassium nitrate. about two-thirds of the chilean material normally goes to europe and about one-fourth to the united states. the supply has been commercially controlled chiefly by great britain and by chilean companies backed by british and german capital. the dependence of the world on chile became painfully apparent during the war. germany was the only nation which had developed other sources of nitrogenous material to any great extent. the other nations were dependent in a very large degree on the mineral nitrates, both for fertilizer and munition purposes. total demands far exceeded the total output from chile, requiring international agreement as to the division of the output among the nations. the stream of several hundred ships carrying nitrates from chile was one of the vital war arteries. this situation led to strenuous efforts in the belligerent countries toward the development of other sources of nitrogen. the united states, under governmental appropriation, began the building of extensive plants for the fixation of nitrogen from the air, and the building of by-product coke ovens in the place of the old wasteful beehive ovens was accelerated. germany before the war had already gone far in both of these directions, not only within her own boundaries, but in the building of fixation plants in scandinavia and switzerland. war conditions required further development of these processes in germany, with the result that this country was soon entirely self-supporting in this regard. one of the effects was the almost complete elimination in germany of anything but the by-product process of coking coal. war-time development of the nitrogen industry in the united states for munition purposes brought the domestic production almost up to the pre-war requirements for fertilizers alone. with the increasing demand for fertilizers and with the cheapness of the chilean supply of natural nitrates, it is likely that the united states will continue for a good many years to import considerable amounts of chilean nitrates. it may be noted that, although this country normally consumes about one-fourth of the chilean product, american interests commercially control less than one-twentieth of the output. presumably, if for no other purpose than future protection, effort will be made to develop the domestic industry to a point where in a crisis the united states could be independent of chile. particularly may an increase in the output of by-product ammonia from coke manufacture be looked for (see also pp. - ), since nitrogenous material thus produced need bear no fixed part of the cost of production, and requires no protective tariff. the reserves of chilean nitrate are known to be sufficient for world requirements for an indefinitely long future. geologic features mineral nitrates in general, and particularly those of soda and potash, are readily soluble at ordinary temperatures. mineral nitrate deposits are therefore very rare, and are found only in arid regions or other places where they are protected from rain and ground-water. the only large deposits known are those of northern chile and some extensions in adjacent parts of peru and bolivia. these are located on high desert plateaus, where there is almost a total absence of rain, and form blankets of one to six feet in thickness near the surface. the most important mineral, the sodium nitrate or chile saltpeter, is mingled with various other soluble salts, including common salt, borax minerals, and potassium nitrate, and with loose clay, sand, and gravel. the nitrate deposits occur largely around and just above slight basin-like depressions in the desert which contain an abundance of common salt. the highest grade material contains to per cent of sodium nitrate, and material to be of shipping grade must run at least to per cent. the origin of the nitrate beds is commonly believed to be similar to that of beds of rock salt (pp. - ), borax, and other saline residues. the source of the nitrogen was probably organic matter in the soil, such as former deposits of bird guano, bones (which are actually found in the same desert basin), and ancient vegetable matter. by the action of nitrifying bacteria on this organic matter, nitrate salts are believed to have formed which were leached out by surface and ground waters, and probably carried in solution to enclosed bodies of water. here they became mingled with various other salts, and all were precipitated out as the waters of the basins evaporated. deliquescence and later migration of the more soluble nitrates resulted in their accumulation around the edges of the basins. the nitrate beds are thus essentially a product of desiccation. while the origin just set forth is rather generally accepted, several other theories have been advanced. it has been suggested that the deposits were not formed in water basins, but that ground water carrying nitrates in solution has been and is rising to the surface,--where, under the extremely arid conditions, it evaporates rapidly, leaving the nitrates mixed with the surface clays. one group of writers accounts for the deposits by the fixation of atmospheric nitrogen through electrical phenomena. still others note the frequent presence of nitrogen in volcanic exhalations and the association of the chilean nitrate beds with surface volcanic rocks; they suggest that these rocks were the source of the nitrogen, which under unusual climatic conditions was leached out and then deposited by evaporation. phosphates economic features the principal use of natural phosphates is in the manufacture of fertilizers. they are also used in the manufacture of phosphorus, phosphoric acid, and other phosphorus compounds, for matches, for certain metallurgical operations, and for gases used in military operations. the material mined is mainly a phosphate of lime (tricalcium phosphate). to make it available for plant use, it is treated with sulphuric acid to form a soluble superphosphate; hence the importance of sulphuric acid, and its mineral sources pyrite and sulphur, in the fertilizer industry. a small percentage of the phosphate is also ground up and applied directly to the soil in the raw form. other phosphatic materials are the basic slag from phosphatic iron ores made into thomas-process steel, guano from the pacific islands, and bone and refuse (tankage) from the cattle raising and packing countries. these materials are used for the same purposes as the natural phosphates. the united states is the largest factor in the world's phosphate industry, with reference both to production and reserves. the largest and most available of the european sources are in tunis and algeria, under french control, and in egypt, under english control. belgium and northern france have been considerable producers of phosphates, but, with the development of higher grade deposits in other countries, their production has fallen to a very small fraction of the world's total. there also has been very small and insignificant production in spain and great britain. russia has large reserves which are practically unmined. while there is comparatively little phosphate rock in western europe, a considerable amount of the phosphate supply is obtained as a by-product from thomas slag, derived from phosphatic iron ores. these ores are chiefly from lorraine and sweden, but english and russian ores can be similarly used. outside of europe and the united states, there are smaller phosphate supplies in canada, the dutch west indies, venezuela, chile, south australia, new zealand, and several islands of the indian and south pacific oceans. none of these has yet contributed largely to world production, and their distance from the principal consuming countries bordering the north atlantic basin is so great that there is not likely to be any great movement to this part of the world. on the other hand, some of the south sea islands have large reserves of exceptionally high grade guano and bone phosphates, which will doubtless be used in increasing amounts for export to japan, new zealand, and other nearby countries. the most important of these islands are now controlled by great britain, japan, and france. a striking feature of the situation is that the central european countries, which have been large consumers of phosphate material, have lost not only the pacific island phosphates but the lorraine phosphatic iron ores, and are now almost completely dependent on british, french, and united states phosphate. in the united states, reserves of phosphate are very large. they are mined principally in florida, tennessee, and south carolina; but great reserves, though of lower grade, are known in arkansas, montana, idaho, wyoming, and utah. there are possibilities for the development of local phosphate industries in the west, in connection with the manufacture of sulphuric acid from waste smelting gases at nearby mining centers. the anaconda copper mining company has taken up the manufacture of superphosphate as a means of using sulphuric acid made in relation to its smelting operations. the united states is independent in phosphate supplies and has a surplus for export. this country, england, and france exercise control of the greater part of the world's supply of phosphatic material. in competition for world trade, the florida and carolina phosphates are favorably situated for export, but there is strong competition in europe from the immense fields in french north africa, which are about equally well situated. geologic features small amounts of phosphorus are common in igneous rocks, in the form of the mineral apatite (calcium phosphate with calcium chloride or fluoride). apatite is especially abundant in some pegmatites. in a few places, as in the adirondacks where magnetic concentration of iron ores leaves a residue containing much apatite, and in canada and spain where veins of apatite have been mined, this material is used as a source of phosphate fertilizer. the great bulk of the world's phosphate, however, is obtained from other sources--sedimentary and residual beds described below. phosphorus in the rocks is dissolved in one form or another by the ground-waters; a part of it is taken up by land plants and animals for the building of their tissues, and another part goes in solution to the sea to be taken up by sea plants and animals. in places where the bones and excrements of land animals or the shells and droppings of sea animals accumulate, deposits of phosphatic material may be built up. in certain places where great numbers of sea birds congregate, as on desert coasts and oceanic islands, guano deposits have been formed. some of them, like the worked-out deposits of peru and chile, are in arid climates and have been well preserved. others, like those of the west indies and oceania, are subjected to the action of occasional rains; and to a large extent the phosphates have been leached out, carried down, and reprecipitated, permeating and partially replacing the underlying limestones. in this way deposits have been formed containing as high as per cent calcium phosphate. even more important bodies of phosphates have been produced by the accumulation of marine animal remains, probably with the aid of joint chemical, bacterial, and mechanical precipitation. these processes have formed the chief productive deposits of the world, including those of the united states, northern africa, and russia, and also the phosphatic iron ores of england and central europe. the sedimentary features of many phosphate rocks, particularly their oölitic textures, show a marked similarity to the features of the clinton type of iron ores (pp. - ). the marine phosphate beds originally consist principally of calcium phosphate and calcium carbonate in varying proportions. depending on the amount of secondary enrichment, they form two main types of deposits. the extensive beds of the western united states (in the upper carboniferous) are hard, and very little enrichment by weathering has taken place; they carry in their richer portions to per cent calcium phosphate, and large sections range only from about to per cent. in the southeastern deposits (silurian and devonian in tennessee and tertiary in the carolinas and florida), there has been considerable enrichment, the rock is softer, and the general grade ranges from to per cent. both calcium carbonate and calcium phosphate are soluble in ordinary ground waters, but the carbonate is the more soluble of the two. thus the carbonate has been dissolved out more rapidly, and in addition descending waters carrying the phosphate have frequently deposited it to pick up the carbonate. these enriching processes, sometimes aided by mechanical concentration, have formed high-grade deposits both in the originally phosphatic beds and in various underlying strata. concretionary and nodular textures are common. the "pebble" deposits of florida consist of the phosphatic materials broken up and worked over by river waters and advancing shallow seas. pyrite economic features the principal use of pyrite is in the manufacture of sulphuric acid. large quantities of acid are used in the manufacture of fertilizers from phosphate rock, and during war times in the manufacture of munitions. sulphuric acid converts the phosphate rock into superphosphate, which is soluble and available for plant use. other uses of the acid are referred to in connection with sulphur. pyrite is also used in europe for the manufacture of paper from wood-pulp, but in the united states native sulphur has thus far been exclusively used for this purpose. the residue from the roasting of pyrite is a high-grade iron ore material frequently very low in phosphorus, which is desirable in making up mixtures for iron blast furnaces. most of the countries of europe are producers of pyrite, and important amounts are also produced in the united states and canada. the european production is marketed mainly on that continent, but considerable amounts come to the united states from spain. before the war domestic sources supplied a fourth to a third of the domestic demand for pyrite. imports came mainly from spain and portugal to consuming centers on the atlantic seaboard. the curtailment of overseas imports of pyrite during the war increased domestic production by about a third and resulted also in drawing more heavily on canadian supplies, but the total was not sufficient to meet the demand. the demand was met by the increased use of sulphur from domestic deposits (p. ). at the close of the war supplies of pyrite had been accumulated to such an extent that, with the prospect of reopening of spanish importation, pyrite production in the united states practically ceased. war experience has demonstrated the possibility of substitution of sulphur, which the united states has in large and cheaply mined quantities. the future of the pyrite industry in the united states therefore looks cloudy, except for supplies used locally, as in the territory tributary to the great lakes, and except for small amounts locally recovered as by-products in the mining of coal or from ores of zinc, lead, and copper. pyrite production in the past has been chiefly in the appalachian region, particularly in virginia and new york, and in california. geologic features pyrite, the yellow iron sulphide, is the commonest and most abundant of the metallic sulphides. it is formed under a large variety of conditions and associations. marcasite and pyrrhotite, other iron sulphide minerals, are frequently found with pyrite and are used for the same purposes. the great deposits of rio tinto, spain, which produce about half of the world's pyrite, were formed by replacement of slates by heated solutions from nearby igneous rocks. the ores are in lenticular bodies, and consist of almost massive pyrite with a small amount of quartz and scattered grains and threads of chalcopyrite (copper-iron sulphide). they carry about per cent of sulphur, and the larger part carries about per cent of copper which is also recovered. similar occurrences of pyrite on a smaller scale are known in many places. pyrite is very commonly found in vein and replacement deposits of gold, silver, copper, lead, and zinc. in the mississippi valley it is extracted as a by-product from the lead and zinc ores, and in the cordilleran region large quantities of by-product pyrite could easily be produced if there were a local demand. the pyrite deposits of the appalachian region are chiefly lenses in schists; they are of uncertain origin though some are believed to have been formed by replacement of metamorphosed limestones and schists. under weathering conditions pyrite oxidizes, the sulphur forming sulphuric acid,--an important agent in the secondary enrichment of copper and other sulphides,--and the iron forming the minerals hematite and limonite in the shape of a "gossan" or "iron-cap." pyrite is likewise frequently found in sediments, apparently being formed mainly by the reducing action of organic matter on iron salts in solution. in illinois and adjacent states it is obtained as a by-product of coal mining. sulphur economic features sulphur is used for many of the same purposes as pyrite. under pre-war conditions, the largest use in the united states was in the manufacture of paper pulp by the sulphite process. minor uses were in agriculture as a fungicide and insecticide, in vulcanizing rubber, and in the manufacture of gunpowder. about per cent of the sulphur of the united states was used in the manufacture of sulphuric acid. during the war this use was greatly increased because of the shortage of pyrite and the large quantities of sulphuric acid necessary for the manufacture of explosives. the replacement of pyrite by sulphur in the manufacture of sulphuric acid has continued since the war, and in the future is likely to continue to play an important part. sulphuric acid is an essential material for a great range of manufacturing processes. some of its more important applications are: in the manufacture of superphosphate fertilizer from phosphate rock; in the refining of petroleum products; in the iron, steel, and coke industries; in the manufacture of nitroglycerin and other explosives; and in general metallurgical and chemical practice. the united states is the world's largest sulphur producer. the principal foreign countries producing important amounts of sulphur are italy, japan, spain, and chile. europe is the chief market for the italian sulphur. in spite of increased demands in europe the italian production has decreased as the result of unfavorable labor, mining, and transportation conditions, and the deficit has had to be met from the united states. japan's sulphur production has been increasing. normally about half of the material exported comes to the united states to supply the needs of the paper industry in the pacific states, and half goes to australia and other british colonies. spain's production is relatively small and has been increasing slowly; most of it is consumed locally. chile's small production is mainly consumed at home and large additional amounts are imported. the sulphur output of the united states, which in - was second to italy, now amounts to three-fourths of the entire output of the world, and the united states has become a large exporter of sulphur. supplies are ample and production increasing, with the result that the united states can not only meet its own demands, but can use this commodity extensively in world trade. small amounts of sulphur are mined in some of the western states, but over per cent of the production comes from louisiana and texas. geologic features native sulphur is found principally in sedimentary beds, where it is associated with gypsum and usually with organic matter. deposits of this type are known in many places, the most important being those of sicily and of the gulf coast in the united states. in the latter region beds of limestone carry lenses of sulphur and gypsum which are apparently localized in dome-like upbowings of the strata. the deposits are overlain by several hundred feet of loose, water-bearing sands, through which it is difficult to sink a shaft. an ingenious and efficient process of mining is used whereby superheated water is pumped down to melt the sulphur, which is then forced to the surface by compressed air and allowed to consolidate in large bins. the sicilian deposits are similar lenses in clayey limestones containing to per cent of sulphur, associated with gypsum and bituminous marl; they are mined by shafts. concerning the origin of these deposits several theories have been advanced. it has been thought that the materials for the deposits were precipitated at the same time as the enclosing sediments; and that the sulphur may have been formed by the oxidation of hydrogen sulphide in the precipitating waters through the agency of air or of sulphur-secreting bacteria, or that it may have been produced by the reduction of gypsum by organic matter or bacteria. others have suggested that hot waters rising from igneous rocks may have brought in both the sulphur and the gypsum, which in crystallizing caused the upbowing of the strata which is seen in the gulf fields (see also p. ). native sulphur is also found in mineral springs from which hydrogen sulphide issues, where it is produced by the oxidation of the hydrogen sulphide. it likewise occurs in fissures of lava and around volcanic vents, where it has probably been formed by reactions between the volcanic gases and the air. the japanese and chilean deposits are of the volcanic type. potash economic features potash is used principally as a component of fertilizers in agriculture. it is also used in the manufacture of soap, certain kinds of glass, matches, certain explosives, and chemical reagents. for a long time potash production was essentially a german monopoly. the principal deposits are in the vicinity of stassfurt in north central germany (about the harz mountains). stassfurt salts are undoubtedly ample to supply the world's needs of potash for an indefinite future. however, other deposits, discovered in the rhine valley in alsace in , have been proved to be of great extent; and though the production has hitherto been limited by restrictions imposed by the german government, it has nevertheless become considerable.[ ] the grade ( per cent k_{ }o) is superior to the general run of material taken from the main german deposits, and the deposits have a regularity of structure and uniformity of material favorable to cheaper mining and refining than obtains in the stassfurt deposits. other countries have also developed supplies of potash, some of which will probably continue to produce even in competition with the deposits of recognized importance referred to above. noteworthy among the newer developments are those in spain.[ ] these have not yet produced on any large scale, but their future production may be considerable. less important deposits are known in galicia, tunis, russia, and eastern abyssinia, and the nitrate deposits of chile contain a small percentage of potash which is being recovered in some of the operations. prior to the war the united states obtained its potash from germany. the german potash industry was well organized and protected by the german government, which made every effort to maintain a world monopoly. during the war the potash exports from germany were cut off, excepting exports to the neutrals immediately adjoining german territory. the result in the united states was that the price of potash rose so far as to greatly diminish its use as fertilizer. the consequent efforts to increase potash production in the united states met with considerable success, but the maximum production attained was only about one-fourth of the ordinary pre-war requirements. the principal american sources are alkaline beds and brines in nebraska, utah, and california, and especially at searles lake, california. these furnished per cent of the total output. minor amounts have been extracted in utah from the mineral alunite (a sulphate of potassium and aluminum), in wyoming from leucite (a potassium-aluminum silicate), in california from kelp or seaweed, and in various localities from cement-mill and blast-furnace dusts, from wood ashes, from wool washings, from the waste residues of distilleries and beet-sugar refineries, and from miscellaneous industrial wastes. at the close of the war, sufficient progress had been made in the potash industry to indicate that the united states might become self-supporting in the future, though at high cost. the renewal of importation of cheap potash from germany, with probable further offerings from alsace and spain, makes it impossible for the united states potash production to continue; except, perhaps, for the recovery of by-products which will go on in connection with other industries. demand for a protective tariff has been the inevitable result (see chapters xvii and xviii). geologic features potassium is one of the eight most abundant elements in the earth. it occurs as a primary constituent of most igneous rocks, some of which carry percentages as high as those in commercial potash salts used for fertilizers. it is present in some sediments and likewise occurs in many schists and gneisses. various potassium silicates--leucite, feldspar, sericite, and glauconite--and the potassium sulphate, alunite, have received attention and certain of them have been utilized to a small extent, but none of them are normally able to compete on the market. potential supplies are thus practically unlimited in amount and distribution. deposits from which the potash can be extracted at a reasonable cost, however, are known in only a few places, where they have been formed as saline sediments. in the decomposition of rocks the potash, like the soda, is readily soluble, but in large part it is absorbed and held by clayey materials and is not carried off. potash is therefore more sparingly present in river and ocean waters than is soda, and deposits of potash salts are much rarer than those of rock salt and other sodium compounds. the large deposits in the permian beds of stassfurt, as well as those in the tertiary of alsace and spain, have been formed by the evaporation of very large quantities of salt water, presumably sea water. they consist of potassium salts, principally the chloride, mixed and intercrystallized with chlorides and sulphates of magnesium, sodium, and calcium. in the stassfurt deposits the potassium-magnesium salts occupy a relatively thin horizon at the top of about feet of rock salt beds, the whole underlying an area about miles long and miles wide. the principal minerals in the potash horizon are carnallite (hydrous potassium-magnesium chloride), kieserite (hydrous magnesium sulphate), sylvite (potassium chloride), kainite (a hydrous double salt of potassium chloride and magnesium sulphate), and common salt (sodium chloride). the potash beds represent the last stage in the evaporation of the waters of a great closed basin, and the peculiar climatic and topographic conditions which caused their formation have been the subject of much speculation. this subject is further treated in the discussion of common salt beds (pp. - ). in the united states the deposits at searles lake, california, have been produced by the same processes on a smaller scale. in this case evaporation has not been carried to completion, but the crystallization and separation out of other salts has concentrated the potassium (with the magnesium) in the residual brine or "mother liquor." the deposits of this lake or marsh also contain borax (see p. ), and differ in proportions of salts from the stassfurt deposits. this is due to the fact that they were probably derived, not from ocean waters, but from the leaching of materials from the rocks of surrounding uplands, transportation of these materials in solution by rivers and ground waters, and concentration in the desert basin by evaporation. the alkali lakes of nebraska are believed to be of very recent geologic origin. they lie in depressions in a former sand dune area, and contain large quantities of potash supposedly accumulated by leaching of the ashes resulting from repeated burnings of the grass in the adjacent country. of other natural mineral sources, alunite is the most important. the principal deposits worked are at marysville, utah, but the mineral is a rather common one in the western part of the united states, associated with gold deposits, as at goldfield, nevada. alunite occurs as veins and replacement deposits, often in igneous associations, and is supposed to be of igneous source. its origin is referred to in connection with the goldfield ores (p. ). footnotes: [ ] gale, hoyt s., the potash deposits of alsace: _bull. -b, u. s. geol. survey_, , pp. - . [ ] gale, hoyt s., potash deposits in spain: _bull. -a, u. s. geol. survey_, , pp. - . chapter viii the energy resources--coal, oil, gas (and asphalt) coal economic features coal overshadows all other mineral resources, except water, in production, value, and demand. it is the greatest of the energy sources--coal, petroleum, gas, and water power. roughly two-thirds of the world's coal is used for power, one-sixth for smelting and metallurgical industries, and one-sixth for heating purposes. coal constitutes over one-third of the railroad tonnage of the united states and is the largest single tonnage factor in international trade; per cent of the pre-war tonnage of outgoing cargoes from england was coal. =world production and trade.= the great coal-producing countries of the world border the north atlantic basin. the united states produces about per cent of the world's total, great britain about per cent, and germany about per cent. other countries producing coal stand in about the following order: austria-hungary, france, russia, belgium, japan, china, india, canada, and new south wales. there is similarity in the major features of the distribution of coal production and of iron ore production. the great centers of coal production--the pennsylvania and illinois fields of the united states, the midlands district of england, and the lower rhine or westphalian fields of germany--are also the great centers of the iron and steel industries of these countries. as in the case of iron ore, there is rather a striking absence of important coal production in the southern hemisphere and in asia. a significant item in the world's distribution of coal supplies is england's world-wide system of coaling stations for shipping. the principal coal-producing countries all have large reserves of coal. outside of these countries the world's most important reserves are in china, which may be looked to for great future development. for the most part, except for the probable chinese development, it is likely that countries now producing most of the coal will continue to do so in the future, and that outlying parts of the world will continue to be supplied mainly from these countries. the quantity and distribution of the coal reserves of the world have been estimated with perhaps a greater degree of accuracy than those of any other mineral resource. from these estimates it appears that the north american continent contains about half of the world reserves (principally in the united states, with lesser amounts in canada) and asia about one-fourth (principally in china, with some in india). europe contains only one-sixth of the world total, chiefly in the area of the former german empire and in great britain, with smaller quantities in russia, austria-hungary, france, and belgium. australasia (new south wales), africa (british south africa), and south america (chile, brazil, peru, and colombia), together contain less than a tenth of the total reserves. coal being one of the great bases for modern industrialism, the large reserves of high grade-coals in china have led to the belief that china may some day develop into a great manufacturing nation. similarly, the deficiency in coal of most of the south american and african countries seems to preclude their developing any very large manufacturing industries, except where water power is available. coal reserves and the conservation of coal are further discussed in chapter xvii. the war resulted in considerable disturbances in coal production and distribution. there has not yet been a return to normal conditions, and some of the changes are probably permanent. the great overseas movement of coal from germany was stopped and that from england curtailed. to some extent the deficiency was supplied by coal exports from the united states, particularly to south america. the shutting off of the normal german export to france and mediterranean countries, the occupation of the french and belgian coal fields by the germans, and the partial restriction of german exports to scandinavian countries, resulted in europe's absorbing most of the british coal available for export, and in addition requiring coal from the united states. the stress in the world's coal industry to meet the energy requirements of war is too recent and vivid to require more than mention. the world was made to realize almost for the first time the utterly vital and essential nature of this industry. since the war, there has been a gradual resumption of england's export of coal along old lines of international trade. the german overseas export trade has not been reëstablished, and cannot be for a long time to come if germany fulfills the terms of the peace treaty. indeed, because of slow recovery in output of german coal, there is yet considerable lag in the supply available for european countries. the terms of the peace treaty lessened the territory of german coal reserves and required considerable additional contributions of coal to be delivered to france, belgium, luxemburg, and italy. the increased export of coal from the united states during the war is likely to be in part continued in the future, although the great bulk of the united states production will in the future, as in the past, be absorbed locally. most of the coal in the united states available for export is higher in volatile matter than the british and german export coal. this quality will in some degree be a limiting factor in exportation. on the other hand, it may result in wider introduction of briquetting, coking, and other processes, which will tend to improve the local industry and be conservational in their effect. japan will doubtless hold some of the asiatic coal market gained during the war. international coal relations are further discussed in chapter xviii.[ ] =production in the united states.= the main features of the distribution of coal supplies in the united states are: ( ) localization of the anthracite production and reserves in a limited area in the lawton region of pennsylvania. low-grade anthracite coal also occurs in rhode island, north carolina, colorado, and idaho. ( ) localization of the bituminous production in the eastern and interior states of pennsylvania, west virginia, ohio, indiana, illinois, and kentucky. the principal reserves of bituminous coal occur in the same provinces, but important additional reserves are known in texas, in north and south carolina, and in the rocky mountain and pacific coast provinces. ( ) the existence of large tonnages of subbituminous coal in the west, which have not been mined to any extent. ( ) the existence of large fields of lignite in the gulf coast region, and in the northern plains region, which have not been mined. =coke.= about one-sixth of the bituminous coal mined in the united states is made into _coke_, that is, it is subjected to heat in ovens from which oxygen is excluded in order to drive off the volatile gases (chiefly hydrocarbons and water) which constitute about per cent of the weight of the coal. the residual product, the coke, is a light, porous mass with a considerably higher percentage of fixed carbon than bituminous coal. in regard to composition, coking accomplishes artificially somewhat the same result reached by nature in its slow development of high-grade coals, but the texture of coke is far different from that of coal. not all bituminous coals are suitable for coke manufacture; and such coals are frequently divided into two classes, known as _coking_ and _non-coking_ coals. coke is used principally for smelting purposes. because of its spongy, porous texture, it burns more rapidly and intensely than coal. the gases eliminated in coking are wasted in the old-fashioned "beehive" ovens, but in modern "by-product" coke ovens these gases by proper treatment yield valuable coal tar products and ammonia. it is estimated that the sum of the value of the products thus recovered from a ton of coal multiplies the value of the ton of coal at the mine by at least thirteen times. the importance of this fact from the conservational standpoint cannot be too much emphasized. at present over half of the total coke produced in the united states comes from by-product ovens, and this proportion will doubtless increase in the future. balance sheet showing contrast between value of ton of bituminous coal at mine and value of products which it contains, based on conditions prevailing in .[ ] _value at _value at point of mine _ _quantity_ production, _ ------------------------------------------------------------------------- ton ( , pounds) |( , pounds smokeless fuel $ . [ ] bituminous coal |( , cubic feet gas, at contains $ . | c. per , . [ ] |( pounds ammonium sulphate at . c. . |( - / gallons benzol, at c. . [ ] |( gallons tar, at . c. . [ ] total $ . [ ]| $ . ------------------------------------------------------------------------- : gilbert, chester g., and pogue, joseph e., the energy resources of the united states--a field for reconstruction: _bull. , u. s. national museum_, vol. , , p. . : figure based upon approximate selling price of anthracite. : figure based upon average price of city gas. : these figures would be much higher if an adequate coal products industry were in existence. : this figure shows clearly that lowering the cost of production cannot be expected to lower the price of coal. even if the cost of production were eliminated, the price of coal would merely be a dollar less. =classification of coals.= the accurate naming and classification of different varieties of coal is not an easy matter. the three main classes,--anthracite, bituminous, and lignite,--have group characteristics determined by their composition, color, texture, origin, and uses, and for general purposes these names have reasonably definite significance. however, there is complete gradation in coal materials from peat through lignite to bituminous and anthracite coals; many varieties fall near the border lines of the main groups, and their specific naming then becomes difficult. in addition, coal is made up of several substances which vary unequally in their proportions. it is difficult to arrange all of these variables in a graded series in such a fashion as to permit of precise naming of the coal. furthermore, the scientific naming of a coal may not serve the purpose of discriminating coals used for different commercial purposes. even the commercial names vary among themselves, depending on the use for which the coal is being considered. thus it is that the naming and classification of coals is a perennial source of difficulty and controversy. the earliest and most widely used classification is based on the ratio between fixed (or non-volatile) carbon and volatile constituents, called the "fuel ratio." for this purpose "proximate" analyses of coal are made, in terms of fixed carbon, volatile matter, moisture, ash, and sulphur. anthracite has a higher fuel ratio than bituminous coal; that is, it has more fixed carbon in relation to volatile matter. similarly bituminous coal has a higher fuel ratio than lignite. the fuel ratio measures roughly the heat or calorific power of the coal, in other words, its fuel value. however, some bituminous coals have a higher calorific power than some anthracites, because a large part of their volatile matter is combustible and yields more heat than the corresponding weight of fixed carbon in the anthracite. the fuel ratio pretty well discriminates coals of the higher ranks, and gives a classification corresponding roughly with their commercial uses. for the lower ranks of coal it is not so satisfactory, because the volatile constituents of such coals contain large and varying percentages of non-combustible hydrogen, oxygen, and nitrogen. also such coals contain larger and more variable amounts of moisture, which is inert to combustion and requires heat for its evaporation. two coals of the lower ranks with the same fuel ratio may have very different fuel qualities and different commercial uses, because of their different amounts of inert volatile matter and of water. for these coals it is sometimes desirable to supplement the chemical classification by physical criteria. for instance, subbituminous coal may be distinguished from lignite, not by its fuel ratio alone, but by its shiny, black appearance as contrasted with the dull, woody appearance of lignite. bituminous may be distinguished from subbituminous by the manner of weathering. other classifications have attempted to recognize these difficulties and still maintain a purely chemical basis by considering separately the combustible and non-combustible volatile constituents. for this purpose, it is necessary to have not merely approximate analyses, but the ultimate analyses in terms of elements. definitions of the principal kinds of coal by campbell,[ ] of the united states geological survey, are as follows: _anthracite._ anthracite is generally well known and may be defined as a hard coal having a fuel ratio (fixed carbon divided by the volatile matter) of not more than or and not less than . _semianthracite._ semianthracite is also a hard coal, but it is not so hard as true anthracite. it is high in fixed carbon, but not so high as anthracite. it may be defined as a hard coal having a fuel ratio ranging from to . the lower limit is uncertain, as it is difficult to say where the line should be drawn to separate "hard" from "soft" coal and at the same time to divide the two ranks according to their fuel ratio. _semibituminous._ the name "semibituminous" is exceedingly unfortunate, as literally it implies that this coal is half the rank of bituminous, whereas it is applied to a kind of coal that is of higher rank than bituminous--really superbituminous. semibituminous coal may be defined as coal having a fuel ratio ranging from to . its relatively high percentage of fixed carbon makes it nearly smokeless when it is burned properly, and consequently most of these coals go into the market as "smokeless coals." _bituminous._ the term "bituminous," as generally understood, is applied to a group of coals having a maximum fuel ratio of about , and hence it is a kind of coal in which the volatile matter and the fixed carbon are nearly equal; but this criterion cannot be used without qualification, for the same statement might be made of subbituminous coal and lignite. as noted before, the distinguishing feature which serves to separate bituminous coal from coals of lower rank is the manner in which it is affected by weathering. _subbituminous._ the term "subbituminous" is adopted by the geological survey for what has generally been called "black lignite," a term that is objectionable because the coal is not lignitic in the sense of being distinctly woody, and because the use of the term seems to imply that this coal is little better than the brown, woody lignite of north dakota, whereas many coals of this rank approach in excellence the lowest grade of bituminous coal. subbituminous coal is generally distinguishable from lignite by its black color and its apparent freedom from distinctly woody texture and structure, and from bituminous coal by its loss of moisture and the consequent breaking down of "slacking" that it undergoes when subjected to alternate wetting and drying. _lignite._ the term "lignite," as used by the geological survey, is restricted to those coals which are distinctly brown and either markedly woody or claylike in their appearance. they are intermediate in quality and in development between peat and subbituminous coal. [illustration: fig. . diagrams showing the chemical composition and heat efficiency of the several ranks of coal. upper diagram: comparative heat value of the samples of coal represented in the lower diagram, computed on the ash-free basis. lower diagram: variation in the fixed carbon, volatile matter, and moisture of coals of different ranks, from lignite to anthracite, computed on samples as received, on the ash-free basis. after campbell.] geologic features geologic features of coal may be conveniently described in terms of origin or genesis. coal has essential features in common with asphalt, oil, and gas. they are all composed of carbon, hydrogen, and oxygen, with minor quantities of other materials, combined in various proportions. they are all "organic" products which owe their origin to the decay of the tissues of plants and perhaps animals. they have all been buried with other rocks beneath the surface. the common geologic processes affecting all rocks have in the main determined the evolution of these organic products and the forms in which we now find them. originating at the surface, they have participated in the constructive or anamorphic changes of the metamorphic cycle, which occur beneath the surface, and under these influences have undergone various stages of condensation, refinement, distillation, and hardening. all stages in the development of coal have been traced. in brief, the story is this: [illustration: fig. . origin and development of coal. after gilbert.] this exhibit shows the successive chemical stages in the evolution of coal. the striking qualities of the original are lost in the reproduction through the use of designs in the place of realistic coloring, but the effect is retained sufficiently to indicate the nature of the sequence and the directness with which it leads back to an origin in vegetal accumulations. the evolutionary process is seen to take the form of increasing density through the progressive expulsion of volatilizable matters in the course of geologic time. this inference is substantiated beyond reasonable question by the actual presence of organic remains in coal beds. grasses, trees, and other plants growing in swamps and bogs decay and form a vegetable mold in the nature of _peat_. a peat bog from the top downward consists of ( ) living plants, ( ) dead plants, and ( ) a dense brownish-black mass, of decayed and condensed vegetable material, in which the vegetable structure is more or less indistinct. peat consists chiefly of fixed carbon and volatile matter, also of sulphur, moisture, and ash. the volatile matter consists mainly of various combinations of hydrogen and carbon, called hydrocarbons; it goes off in gas or smoke when the peat is heated to a red heat. the fixed carbon is the carbon left after the volatile matter has been driven off. the ash represents the more incombustible mineral matter, usually of the nature of clay or slate. the moisture in peat may be as high as per cent. the essential condition for thick accumulation of peat seems to be abundance of moisture, which favors luxuriant growth and protects the plant remains from complete oxidation or decay. without moisture the vegetable material would completely oxidize, leaving practically no residue, as it does in dry climates. for the formation of thick peat beds, there seems to be implied some sort of a balance between the slow building up of organic accumulations and the settling of the area to keep it near the elevation of the water table. present day bog deposits are known in some cases to have a thickness of forty feet. this thickness is not enough to account for some of the great coal seams within the earth; but there seems to be no escape from the conclusion that the same sort of deposits, formed on a larger scale in the past, were the first step in the formation of the coal seams. flat, swampy coastal plains are believed to furnish the best conditions for thick accumulation of peat. there is good evidence that most of the deposits accumulate essentially in place, without appreciable transportation. in time these surface accumulations of vegetable material may subside and be buried under clay, sand, or other rock materials. the processes of condensation begun in the peat bog are then carried further. they result in the second stage of coal formation, that of _lignite_ or _brown coal_. this is brown, woody in texture, and has a brown streak. it has a higher percentage of fixed carbon, and less volatile matter and water, than peat. continuation of the processes of induration produces _subbituminous coal_, or _black lignite_, which is usually black and sometimes has a fairly bright luster. it is sometimes distinguished from bituminous coal, where weathered or dried, by the manner in which it checks irregularly or splits parallel to the bedding,--the characteristic feature of bituminous coal being columnar fracture. the next stage in coal formation is _bituminous coal_. it has greater density than the lignites or subbituminous coals, is black, more brittle, and breaks with a cubical or conchoidal fracture. it is higher in fixed carbon, lower in volatile matter and water. a variety of bituminous coal, called _cannel coal_, is characterized by an unusually high percentage of volatile matter, which causes it to ignite easily. this material has a dull luster and a conchoidal fracture. it is composed almost entirely of the spores and spore cases, which are resinous or waxy products, of such plants as lived in the parent coal swamp. there are gradations from bituminous coal into _anthracite coal_. _semibituminous_ and _semianthracite_ are names used to some extent for these intermediate varieties. the final stage of coal formation is anthracite,--hard, brittle, black, with high luster and conchoidal fracture. it has a higher percentage of fixed carbon and correspondingly less of the volatile constituents, than any of the other coals. the coals form a completely graded series from peat to the hard anthracite. comparison of the compositions of the coal materials at different stages shows clearly what has happened. moisture has diminished, certain volatile hydrocarbons have been eliminated as gases, and oxygen has decreased. on the other hand, the residual fixed carbon, sulphur, and usually ash, have remained in higher percentage. this change in composition is graphically represented in figure . during this process volume has been progressively reduced and density increased. five feet of wood or plant may produce about one foot of bituminous coal, or six-tenths of a foot of anthracite. the exact physical conditions in the earth which determine the progressive changes in coals, above outlined, cannot be fully specified. time is one of the factors--the longer the time, the greater the opportunity for accomplishing these results. another factor is undoubtedly pressure, due to the weight of overlying sediments, or to earth movements. in peat condensational changes of this nature are accomplished artificially by the pressure of briquetting machines. another factor is believed to be the heat developed by earth movements and vulcanism, which presumably facilitates the elimination of volatile materials, and thus accelerates the gradational changes above described. this is suggested by the fact that in places where hot volcanic lavas have gone through coal beds they have locally produced coals of anthracitic and coke-like varieties. in general, however, it has not been possible to determine the degree to which heat has been responsible for the changes. coals which have been developed in different localities, under what seem to be much the same heat conditions, may show quite different degrees of progress toward the anthracite stage. another factor that has been suggested as possibly contributing to the change, is the degree of permeability of the rocks overlying the coal to the volatile materials which escape from the coal during its refinement. it is argued that in areas of folding or of brittle rock where the cover is cracked, volatile gases have a better chance to escape, and that the change toward anthracite is likely to advance further here than elsewhere. bacterial action is an important factor in the earlier stages, in the partial decay of vegetable matter to form peat; accumulation of waste products from this action, however, appears to inhibit further bacterial activity. coal deposits have the primary shapes of sedimentary beds. they are ordinarily thin and tabular, and broadly lenticular,--on true scale being like sheets of thin paper. at a maximum they seldom run over feet in thickness, and they average less than feet. seldom is a workable coal bed entirely alone; there are likely to be several superposed and overlapping seams of coal, separated by sandstones, shales, or other rocks. in illinois and indiana there are nine workable coal seams, in pennsylvania in some places about twenty, and in wales there are over one hundred, many of which are worked. some of the seams are of very limited extent; others are remarkably persistent, one seam in pennsylvania having an average thickness of to feet over about , square miles of its area. only per cent of the coal-bearing measures of the eastern united states is actually coal. even where not subsequently disturbed by deformation, coal beds are not free from structural irregularity. they are originally deposited in variable thicknesses on irregular surfaces. during their consolidation there is a great reduction of volume, resulting in minor faults and folds. subsequent deformation by earth forces may develop further faults and folds, with the result that the convolutions of a coal bed may be very complex. the beds of a coal-bearing series are usually of differing thickness and competency, and as a consequence they do not take the same forms under folding. shearing between the beds may result in an intricate outline for one bed, while the beds above and below may have much more simple outlines. in short, the following of a coal seam requires at almost every stage the application of principles of structural geology. it is obvious, also, that the identification and location of sedimentary geologic horizons are essential, and hence the application of principles of stratigraphy. the folios of the united states geological survey on coal-bearing areas present highly developed methods of mapping and representing the geologic features of coal beds. on the surface map are indicated the topography, the geologic horizons, and the lines of outcrop of the coal seams. in addition, there are indicated the sub-surface contours of one or more of the coal seams which are selected as datum horizons. the sub-surface structure, even though complex, can be readily read from one of these surface maps. with the addition of suitable cross sections and comparative columnar sections, the story is made complete. in the study of the occurrence of coal seams, the reader cannot do better than familiarize himself with one or more of the geological survey folios. the high-grade coals of the eastern and central united states are found in rocks of carboniferous age. the very name carboniferous originated in the fact that the rocks of this geologic period contain productive coal beds in so many parts of the world. the coal measures of great britain, of germany, belgium, and northern france, of russia, and the largest coal beds of china are all of carboniferous age. deposits of this period include the bulk of the world's anthracite and high-grade bituminous coal. coal deposits of more recent age are numerous, but in general they have had less time in which to undergo the processes of condensation and refinement, and hence their general grade is lower. in the western united states there are great quantities of subbituminous coal of cretaceous age, and of tertiary lignites which have locally been converted by mountain upbuilding into bituminous and semibituminous coals. jurassic coals are known in many parts of the world outside of north america, and lignites of tertiary age are widely distributed through asia and europe. petroleum economic features petroleum is second only to coal as an energy resource. the rapid acceleration in demand from the automobile industry and in the use of fuel oil for power seems to be limited only by the amounts of raw material available. =production and reserves.= the distribution by countries of the present annual production of petroleum, the past total production, and the estimated reserves, is indicated in terms of percentages of the world's total in the table[ ] on the opposite page. this table indicates the great dominance of the united states both in present and past production of petroleum, as well as the concentration of the industry in a few countries. in addition the united states controls much of the mexican production as well as production in other parts of the world, making its total control of production at least per cent. of the world's total. notwithstanding its large domestic production, the united states has recently consumed more oil than it produces. imports of crude oil are about balanced by exports of kerosene, fuel oils, lubricants, etc. the per capita consumption of petroleum in the united states is said to be twenty times greater than in england. on the other hand, the remaining principal producers consume far less than they produce, the excess being exported. the oil from the united states, russia, the dutch east indies, india, roumania, and galicia is for the most part treated at refineries near the source of supply or at tidewater, and exports consist of refined products. the mexican oil is largely exported in crude form to the united states though increasing quantities are being refined within mexico. the figures shown in the table for oil reserves are of course the roughest approximations, particularly for some of the less explored countries. however, they are compiled from the best available sources and may serve at least to show the apparent relative positions of the different countries at this time. further exploration is likely to change the percentages and add very greatly to the totals. the significant feature of these figures is the contrast which they indicate between distribution of reserves and distribution of past production. particularly do they show that the reserves of the united states, which are more closely estimated than those of any other country, are in a far lower ratio to past production than are the reserves in other countries. it was estimated in that about per cent of the united states reserves are exhausted.[ ] present and past production and reserves of oil, by countries, in terms of percentage of world's total -------------------------+--------------+--------------+------------- | | _per cent | _per cent country |_per cent of | of total | of total | production, | production, | oil | _ | - _ | resources_ -------------------------+--------------+--------------+------------- united states and alaska | . | . | . mexico | . | . | . russia (southeastern | | | russia, southwestern | | | siberia, region of the | | | caucasus, northern | | | russia, and saghalien) | . | . | . east indies | . | . | . roumania, galicia, and | | | western europe | . | . | . india | . | . | . persia and mesopotamia | . | . | . japan and formosa | . | . | . egypt and algeria | . | . | . germany | . | . | -- canada | . | . | . northern south america, | | | including peru, | | | trinidad and venezuela | . | . | . southern south america, | | | including bolivia and | | | argentina | . | . | . china | -- | -- | . italy | } | | cuba | } | . | other countries | } | | | ------ | ------ | ------ world total | . | . | . -------------------------+--------------+--------------+------------- looking forward to the future, it is clear that there will be considerable shifts in the centers of principal production of petroleum in the directions indicated by the reserve figures. in particular, conspicuous development of production may be expected in the immediate future in the countries bordering the caribbean sea and the gulf of mexico. in the eastern hemisphere production is rapidly increasing in persia and mesopotamia; and russia, with the stabilization of political conditions, may become ultimately the world's leading oil producer. at the now indicated rate of production, world reserves now estimated would be exhausted in eighty-six years and the peak of production would be passed earlier. with continuing acceleration of production, total reserves would be exhausted in considerably less time,--providing physical conditions would allow the oil to be pumped from the ground at the necessary speed, which they probably will not. these figures taken at face value are alarming; but the earth offers such huge possibilities for further discoveries that the life of oil reserves above indicated is likely to be considerably extended. at many times in the history of the mineral industry the end has apparently been in sight for certain products; but with the increased demand for these products has come increased activity in exploration, with the result that as yet no definite end has been approached for any one of them. the more immediate problems of the petroleum industry seem to the writer to be of rather different nature: first, whether the discovery and winning of the oil can be made to keep pace with the enormous acceleration of demand; and second, the adjustment of political and financial control of oil resources, the possession of which is becoming so increasingly vital to national prosperity. in regard to the first question, it is a much more difficult problem today to locate and develop a supply of oil to replace the annual world production (recently half a billion barrels), than it was twenty years ago, when it was necessary for this purpose to find only one-fifth this amount; and if the demand is unchecked, it will be still more difficult to replace the three-quarters of a billion barrels of oil which will doubtless be required in a very few years. regardless of the amount of oil actually in the ground, it is entirely possible that physical limitations on its rate of discovery and recovery will prevent its being made available as fast as necessary to meet the increasing demand. this fact is likely to make itself felt through increase of price. other natural results should be the development of substitutes, such as alcohol or benzol for gasoline; the larger recovery of oil from oil shales; and the general speeding up of conservational measures of various kinds. these are all palliatives and not essential remedies. to make enough alcohol to substitute for the gasoline now coming from oil would use a very considerable fraction of the world's food supply. to make enough benzol (a by-product of coke) to replace gasoline would necessitate the manufacture of many times the amount of coke now required by the world's industries. to develop the oil shale industry to a point where it could supply anything like the amount of oil now derived from oil pools would mean the building of great plants, including towns, railroads, and other equipment, equivalent to the plants of the coal mining industry. to apply any one of the various conservational measures discussed on later pages would only temporarily alleviate the situation. the question of political and financial control of oil supplies may be illustrated by particular reference to the united states. on present figures it appears that within three to five years the peak of production in this country will be passed; and at the present rate of production the life of the reserves may not be over seventeen to twenty years. of course production could not continue to the end at this rate, and the actual life will necessarily be longer. again the doubtful factor is the possibility for further discoveries. many favorable structures have been mapped which have not yet been drilled, and there are considerable unexplored areas where the outcrops are so few that there is no clue at the surface to the location of favorable structures. the future is likely to see a considerable amount of shallow drilling for the sole purpose of geological reconnaissance. for upwards of ten years important parts of the public domain have not been available for exploration, but congress has now enacted legislation which opens up vast territories for this purpose. even with large allowance for these possibilities, it seems unlikely that production in the united states can increase very long at the accelerating rate of the domestic demand, which is already in excess of domestic production. the supplies of mexico are in a large part controlled by american capital and are thus made available to the united states (subject, of course, to political conditions); but even with these added, the united states is in a somewhat unfavorable situation as compared with certain other countries. this situation is directing attention to the possibility of curtailment of oil exports, and to the possibility of acquiring additional oil supplies in foreign countries. in this quest the united states is peculiarly handicapped in that most foreign countries, in recognition of the vital national importance of the oil resource, have imposed severe restrictions on exploration by outsiders. nationals of the united states are excluded from acquiring oil concessions, or permitted to do so only under conditions which invalidate control, in the british empire, france, japan, netherlands, and elsewhere, and the current is still moving strong in the direction of further exclusion. as the united states fields are yet open to all comers, it has been suggested that some restriction by the united states might be necessary for purposes of self-protection, or as an aid in securing access to foreign fields. the activity of england during and since the war has increased the amount of oil controlled by that country from an insignificant quantity to potentially over half of the world's oil reserves. the problem of future oil supplies for the united states presents an acute phase of the general question of government coöperation or participation in mineral industries, which is further discussed in chapter xviii. the following table summarizes the distribution of the oil production in the united states, together with the salient features of its geologic distribution and character. this table, in conjunction with fig. below, shows clearly that the bulk of the united states production of oil comes from two great sources--the pennsylvanian sandstones of the mid-continent field in kansas and oklahoma, and the cretaceous and tertiary sediments of the southern half of california. phenomenal development of the central and north texas field in increased its yield to about one-sixth of the country's total. the older appalachian oil field, extending from new york to west virginia and tennessee, was the earliest area discovered; it is still one of the more productive fields, though it has long since passed its maximum production. the other principal sources of oil are the gulf coast field in louisiana and texas, the north louisiana field, the southern illinois field, and the rocky mountain region. this last region, containing large amounts of government land recently opened to exploration, bids fair to produce increasing quantities of oil for some time. past production of petroleum in the united states. (figures from u. s. geological survey) -------------+-----------------+----------+-----------+--------------- | | | | _total | _age of | |_production| production | containing | | for |including _state_ | rocks_ | _base_ |(barrels)_ |(barrels)_ -------------+-----------------+----------+-----------+--------------- alaska |east-low. |paraffin | (a) | (a) | tertiary | | | | west-jurassic | | | california |cretaceous: | | | | tertiary |asphalt | , , | , , , colorado |pierre-cretaceous|paraffin | , | , , illinois |mississippian- |paraffin | , , | , , | pennsylvanian | | | indiana |east-ordovician |paraffin | , | , , | (trenton) west-| | | | pennsylvanian | | | kansas |pennsylvanian |par.-asph.| , , | , , kentucky, |mississippian |paraffin | , , | , , tennessee | | | | louisiana |cretaceous-quat. |paraffin | , , | , , | cretaceous- | | | | eocene | | | michigan, |carboniferous |paraffin | (a) | (a) missouri | | | | montana | -- | -- | , | , new mexico |carboniferous- | -- | (a) | (a) | cretaceous | | | new york, |devonian- |paraffin | , , | , , pennsylvania| carboniferous | | | ohio, east |ordovician- |paraffin | , , | , , and west | carboniferous | | | oklahoma |pennsylvanian |paraffin | , , | , , texas |pennsylvanian, |asph.-par.| , , | , , | cretaceous-quat.| | | utah | -- | -- | (b) | (b) west |devonian- | -- | , , | , , virginia | carboniferous | | | wyoming |carboniferous- |asph.-par.| , , | , , | cretaceous | | | other | -- | -- | , | , | | |-----------| ------------- | | | , , | , , , -------------+-----------------+----------+-----------+--------------- (a) included in "other." (b) included in wyoming. [illustration: fig. . chart showing the present tendency of the united states in respect to its unmined reserve of petroleum. data from u.s. geological survey. after gilbert and pogue.] =methods of estimating reserves.= it may be of interest to inquire into the basis on which predictions are made of the life of an oil pool. the process is essentially a matter of platting curves of production, and of projecting them into the future with the approximate slopes exhibited in districts which are already approaching exhaustion.[ ] while no two wells or two districts act exactly alike, these curves have group characteristics which are used as a rough basis for interpreting the future. [illustration: fig. . the annual output of the principal oil fields of the united states for the last twenty years. data from u.s. geological survey.] a less reliable method is to calculate from geologic data the volume and porosity of the oil-bearing reservoirs, and to estimate the percentage of recovery on the basis of current practices and conditions. complete data for this method are often not available; but in the early years of a field, before production curves are established, this method may serve for a rough approximation. [illustration: fig. . curve showing the usual decline in oil field production after the period of maximum output is reached. after ralph arnold. the petroleum resources of the united states, smithsonian report for , p. . compare this theoretical curve of final decrease with the production curve shown in fig. .] =classes of oils.= when crude petroleum is distilled, it gives off in succession various substances and gradually thickens until it leaves a solid residue, which may be largely either paraffin wax or asphalt. the two main classes of oils are determined by the nature of this solid residual. the products given off are natural gas and then liquid hydrocarbons of various kinds, which evaporate in the order of their lightness. petroleum is thus a mixture or mutual solution of different liquids, gases, and solids. nearly one-fifth of the domestic consumption of crude petroleum is burned directly as fuel, and four-fifths are refined. the several principal primary products of refinement are gasoline, kerosene, fuel oil, and lubricating oil; but these may be broken up into other substances, each the starting point of further refinements, with the result that present commercial practice yields several hundred substances of commercial value. with increasing chemical and technical knowledge these products are being multiplied. the rapidly increasing demand for gasoline has led to the use of processes which extract a large proportion of this substance from the raw material, by "cracking" or breaking up other substances; but while, under the stress of necessity, there is possibility of slight modification of the proportions of principal substances extracted from the crude oil, it is not possible to change these proportions essentially. it is, therefore, a problem to adjust relative demands to supplies of the different products. the domestic demand for gasoline is greater than the supply. on the other hand, the demand for kerosene, which must be produced at the same time, is much less than the domestic supply. hence the importance of maintaining export markets for kerosene. the nature or grade of the oil of various fields is an important matter in considering reserves for the future. perhaps half of the united states reserves consist of the asphalt-base oils of the california and certain of the gulf fields, which yield comparatively small amounts of gasoline and other valuable light products, though they are very satisfactory for fuel purposes. similarly the large reserve tonnages of oil in mexico and the caribbean countries, in peru, and probably in russia, are essentially of the heavier, lower grade oils. the oils of the mid-continental and eastern fields of the united states, of ontario, of the dutch east indies, of burma, and of persia and mesopotamia are reported to be largely of the paraffin base type, which, because of its larger yield of gasoline and light oils, is at present considerably more valuable. these generalizations are of course subject to qualifications, in that the oils of a given region may vary considerably, and that some oils are intermediate in character, containing both asphalt and paraffin wax. =conservation of oil.= the rapid increase in demand for oil as compared with discovery of new sources is leading naturally to a more intensive study of the conservational aspects of the industry. this is a complex and difficult subject which we shall not take up in detail, but we may point out some of the phases of the problem which are receiving especial attention. [illustration: fig. . chart showing the relative values of the principal petroleum products manufactured in the united states from to . after gilbert and pogue. note the decreasing importance of kerosene in sustaining the cost of refining, and the necessity of exports for maintaining a balanced outlet of products. data from story b. ladd, petroleum refining. census of manufactures: , bureau of census, washington, , p. .] about per cent of the oil in the porous strata, of oil pools is ordinarily not recovered, because it clings to the rock. efforts are being made along various lines to increase the percentage of recovery,--as, for instance, in preventing infiltration of water to the oil beds and in the use of artificial pressures and better pumping. "casing-head gasoline" is being recovered to an increasing extent from the natural gas which was formerly allowed to dissipate in the air. minute division of the ownership of a pool, with consequent multiplication of wells and unrestricted competition, tends to gross over-production and highly wasteful methods. the more rapid exhaustion of one well than the others may result in the flooding of the oil sands by salt waters coming in from below. various efforts have been made toward a more systematic and coördinated development of oil fields. in general, the organization and technique involved in the development of an oil field are improving in the direction of extracting a greater percentage of the total available oil. better methods of refining the oil, and the refining of a larger percentage of the crude oil, make the oil more available for a greater variety of purposes and therefore more valuable. great advances have been made along these lines, particularly in the application of the "cracking" method for a greater recovery of the more valuable light oils at the expense of the less valuable heavy oils. similarly, modifications of internal combustion engines will probably permit the use, in an increasing number of cases, of products of lower volatility than gasoline. one of the conservational advances in coming years will probably be a restriction in the amount of crude oil used directly for fuel and road purposes without refining. these crude uses cut down the output of much desired products from the distillation of the oil. various other restrictions in the use of oil have been proposed, such as the curtailment of the use of gasoline in pleasure cars. the gasless sundays during the war represented an attempt of this kind. in general, it seems likely that such restrictions will come mainly through increase in the price of oil products. the substitution of oil from oil shales, and of alcohol for gasolene, already mentioned, will be conservational so far as the oil is concerned, though perhaps not so in regard to other elements of the problem. geologic features =organic theory of origin.= according to this theory, accumulations of organic materials in sedimentary beds, usually muds or marls, have been slowly altered and distilled during geologic ages; the products of distillation have migrated chiefly upward to porous strata like sandstones or cavernous limestones, where, under suitable conditions, they have become trapped. the original organic material is believed to have been plants of low order and animal organisms (such as foraminifera) which were deposited as organic detritus with mud and marl in the bottoms of ponds, lakes, estuaries, and on the sea bottom,--in both salt and fresh waters. bacteria are supposed to have played a part in the early stage of alteration, sometimes called the biochemical stage. when the organic matter was buried under later sediments and subjected to pressure, physical conditions were responsible for further volatilization or distillation. this stage is called the geochemical stage. there is much in common as to origin between coal, oil shales, and petroleum. according to white,[ ] whether the ingredient organic matter, be it plant or animal, will be in part transformed to coal of the ordinary type, to cannel, to oil shale, to the organic residues in so-called bituminous shales and carbonaceous shales, or to petroleum and natural gas, is dependent upon the composition of the ingredient organic débris, the conditions of its accumulation or deposition, and the extent of the microbian action. white has further developed the important principle that, in the geochemical stage of development, both coal and oil react to physical influences in much the same way; and that therefore when both are found in the same geologic series, the degree of concentration of the coal, measured by its percentage of carbon, may be an indication of the stage of development of the oil. more specifically where the coal contains more than to per cent of fixed carbon, chances for finding oil in the vicinity are not good (though commercial gaspools may be found), probably for the reason that the geochemical processes of distillation have gone so far as to volatilize the oils, leaving the solid residues in the rock. white also finds that the lowest rank oils, with considerable asphalt, are found in regions and formations where the coal deposits are the least altered, and the lighter, higher rank oils, on the whole, where the coal has been brought to the correspondingly higher ranks; in other words, up to the point of complete elimination of the oil, improvement in quality of the oil accompanies increased carbonization of the coal. the principle, therefore, becomes useful in exploration in geologic series where oil is associated with coal. where the coal is in one series and the oil in another, separated by unconformity (indicating different conditions of development), the principle may not hold, even though there is close geographical association. the oil and gas distillates migrate upward under gas pressure and under pressure of the ground-water. if there are no overlying impervious beds to furnish suitable trapping conditions, or conditions to retard the flow, the oil may be lost. the conditions favorable for trapping are overlying impervious beds bowed into anticlines, or other structural irregularities, due either to secondary deformation or to original deposition, which may arrest the oil in its upward course. a dome-like structure or anticline may be due to stresses which have buckled up the beds, or to unequal settling of sediments varying in character or thickness; thus some of the anticlinal structures of the mid-continent field may be due to settling of shaley sediments around less compressible lenses of sandstone which may act as oil reservoirs, or around islands which stood above the seas in which the oil-bearing sediments were deposited and on the shores of which sands capable of acting as oil reservoirs were laid down. favorable conditions for trapping the oil may be furnished by impervious clay "gouges" along fault planes, or by dikes of igneous rock. favorable conditions may also be merely differences in porosity of beds in irregular zones, determined by differences either in original deposition or in later cementation. the thickness of oil-producing strata may vary between or feet and feet. the porosity varies between and per cent. in sandstones the average is from to per cent. in shales and clays, which are commonly the impervious "cap-rocks," porosity may be equally high, but the pores are too small and discontinuous to permit movement. when the impervious capping is punctured by a drill hole, gas is likely to be first encountered, then oil, and then water, which is usually salty. the gas pressure is often released with almost explosive violence, which has suggested that this is an important cause of the underground pressures. it has been supposed also that the pressures are partly those of artesian flows. the vertical arrangement of oil, gas, and water under the impervious capping is the result of the lighter materials rising to the top. in certain fields, oil and gas have been found in the tops of anticlines in water-saturated rocks, and farther down the flanks of folds or in synclines in unsaturated rocks. the localization of oil pools is evidently determined partly by original organic deposition, often in alignment with old shore lines, and partly by the structural, textural, and other conditions which trap the oil in its migration from the source. =effect of differential pressures and folding on oil genesis and migration.= another organic hypothesis proposed somewhat recently[ ] is that oil is formed by differential movement or shearing in bituminous shales, which are often in close relationship with the producing sand of an oil field, and that the movement of oil to the adjacent sands is accomplished by capillary pressure of water and not by ordinary free circulation of water under gravity. the capillary forces have been shown to be strong enough to hold the oil in the larger pores against the influence of gravity and circulation. the accumulation of the oil into commercial pools is supposed to take place in local areas where the oil-soaked shale, due to jointing or faulting, is in direct contact with the water of the reservoir rock. this suggests lack of wide migration. this hypothesis is based on experimental work with bituminous shales. the general association of oil pools with anticlinal areas is explained on the assumption that anticlines on the whole are areas of maximum differential movement, resulting in oil distillation, and that they are ordinarily accompanied by tension joints or faults, affording the conditions for oil migration. data are insufficient, however, to indicate the extent to which the anticlinal areas are really areas of maximum shearing. as regards the exact nature of the process, it is not clear to what extent differential movement may involve increase in temperature which may be the controlling factor in distillation,--although in mccoy's experiment oil was formed when no appreciable amount of heat was generated. the development of petroleum by pressure alone acting on unaltered shale, as shown by these experiments, has been taken by white[ ] to have a significant bearing on the geochemical processes of oil formation. under differential stresses acting on fine-grained carbonaceous strata under sufficient load, there is considerable molecular rearrangement, as well as actual movement of the rock grains,--thus promoting the distillation of oil and gas from the organic matter in the rocks, and the squeezing out of the oil, gas, and water into adjacent rocks, such as coarse round-grained sandstones and porous limestones, which are more resistant to change of volume under pressure. migration, concentration and segregation of the oil, gas, and water is supposed to be brought about, partly through the effect of capillary forces--the water, by reason of its greater capillary tension, tending to seize and hold the smaller voids, and thus driving the oil and gas into the larger ones--and partly through the action of gravity. white also suggests that the process may go further where the parent carbonaceous strata are of such thickness and under such load of overlying rocks that they undergo considerable interior adjustment and volume change before yielding to stress by anticlinal buckling,--than where the strata yield quickly. it is not clear to the writer that the interior adjustment assumed under this hypothesis is necessarily slowed up or stopped by anticlinal buckling. interior stresses are inherent in any sedimentary formation, when settling and consolidating and recrystallizing under gravity, and these may be independent of regional thrusts from without. the first oils evolved by pressure from the organic mother substance are probably heavy, the later oils lighter, and the oils from formations and regions where the alteration is approaching the carbonization limit are characteristically of the highest grade. this is the reverse of the order of products obtained by heat distillation. whether there is also a natural fractionation and improvement of the first heavy oils as they undergo repeated migrations is not known. =inorganic theory of origin.= another theory of the source of oil has had some supporters, although they are much in the minority. this is the so-called "inorganic" theory, that oil comes from magmas and volcanic exhalations. in support of this theory attention is called to the fact that igneous rocks and the gases associated with them frequently carry carbides or hydrocarbons; that many oil fields have a suggestive geographic relationship with volcanic rocks; and that certain of the oil domes, as for instance in mexico, are caused by plugs of igneous rocks from below. it has been suggested that deep within the earth carbon is combined with iron in the form of an iron carbide, and that from the iron carbide are generated the hydrocarbons of the oil, either by or without the agency of water. iron carbide is magnetic, and significance has been attached to the general correspondence between the locations of oil in the western united states and regions of magnetic disturbance. it seems not unlikely that some inorganic theory of this sort is necessary to explain the ultimate source of oil or of the substances which become oil, but the evidence is overwhelming that organic agencies have been mainly responsible for the principal oil pools now known. =oil exploration.= a simple geographic basis for oil exploration is the fact that the major oil fields of the world are situated between ° and ° north latitude, and that thus far there are no major oil areas within the tropics or within the southern hemisphere. this broad generalization may have little value when exploration is carried further. it has also been suggested that the geographic distribution of oil corresponds roughly with the average annual temperatures, or isotherms, between ° and .°[ ] it is thought that this present distribution of temperatures may indicate roughly the temperatures of the past when the oil was accumulated; and the inference is drawn that there was some sort of limitation of areal deposition within these temperature limits. if this be true, the only reasons why the southern hemisphere is not productive are the relatively small size of the land areas and the lack of exploration to date. in approaching broadly the problem of oil exploration, the geologist considers in a general way the kinds and conditions of rocks which are likely to be petroliferous or non-petroliferous. schuchert[ ] summarizes these conditions for north america as follows: . the impossible areas for petroliferous rocks. (_a_) the more extensive areas of igneous rocks and especially those of the ancient shields; exception, the smaller dikes. (_b_) all pre-cambrian strata. (_c_) all decidedly folded mountainous tracts older than the cretaceous; exceptions, domed and block-faulted mountains. (_d_) all regionally metamorphosed strata. (_e_) practically all continental or fresh-water deposits; relic seas, so long as they are partly salty, and saline lakes are excluded from this classification. (_f_) practically all marine formations that are thick and uniform in rock character and that are devoid of interbedded dark shales, thin-bedded dark impure limestones, dark marls, or thin-bedded limy and fossiliferous sandstones. (_g_) practically all oceanic abyssal deposits; these, however, are but rarely present on the continents. . possible petroliferous areas. (_a_) highly folded marine and brackish water strata younger than the jurassic, but more especially those of cenozoic time. (_b_) cambrian and ordovician unfolded strata. (_c_) lake deposits formed under arid climates that cause the waters to become saline; it appears that only in salty waters (not over per cent?) are the bituminous materials made and preserved in the form of kerogen, the source of petroleum; some of the green river (eocene) continental deposits (the oil shales of utah and colorado) may be of saline lakes. . petroliferous areas. (_a_) all marine and brackish water strata younger than the ordovician and but slightly warped, faulted, or folded; here are included also the marine and brackish deposits of relic seas like the caspian, formed during the later cenozoic. the more certain oil-bearing strata are the porous thin-bedded sandstones, limestones, and dolomites that are interbedded with black, brown, blue, or green shales. coal-bearing strata of fresh-water origin are excluded. series of strata with disconformities may also be petroliferous, because beneath former erosional surfaces the top strata have induced porosity and therefore are possible reservoir rocks. (_b_) all marine strata that are, roughly, within miles of former lands; here are more apt to occur the alternating series of thin and thick-bedded sandstones and limestones interbedded with shale zones. the extent to which marine or brackish water conditions of sedimentation are requisite to the later formation of oil, as is suggested in the above quotation, has long been a debatable question. it may be noted that certain oil shales formed in fresh water basins contain abundant organic matter which is undoubtedly suitable for the generation of oil and gas, and that these shales on distillation yield oil essentially like that obtained from oil shales of marine origin; that certain important oil-bearing sands of the younger appalachian formations were laid down in waters which are believed to have been only slightly saline; that natural gas is present in fresh water basins; and that it has not been demonstrated that salt in appreciable amounts is necessary for the geologic, any more than for the artificial, distillation of oil. most of the great oil fields have been in regions of marine or other saline water deposits, but it has not been proved that this is a necessary condition. white[ ] says: "at the present stage of our knowledge, fresh-water basins appearing otherwise to meet the requirements should be wildcatted without prejudice." the principal oil-bearing horizons in any locality are comparatively few, and it is ordinarily easy to determine by stratigraphic methods the presence or absence of a favorable geologic horizon. by knowing the succession and thicknesses of the beds in a given region it is possible to infer from surface outcrops the approximate depth below the surface at which the desired horizon can be found. to do this, however, the conditions of sedimentation, the initial irregularities of the beds, the structural conditions, including unconformities, and other factors must be studied. in exploration for oil the determination of the existence and location of the proper horizon is but an initial step. for instance, the oil of the midcontinent field of the united states is in the beds of the pennsylvanian, which are known to occupy an enormous area extending from illinois and wyoming south to the gulf of mexico. this information is clearly not sufficiently specific to limit the location of drill holes. sometimes seepages of oil or showings of gas near the surface are sufficient basis for localizing the drill holes.[ ] commonly, however, it is necessary to find some structural feature in the nature of a dome or anticline which suggests proper trapping conditions for an oil pool. this is accomplished by geologic and topographic mapping of the surface. levels and contours are run and outcrops are platted. as the outcrops are usually of different geologic horizons, it is necessary to select some one or more identifiable beds as horizon markers, and to map their elevations at different points as a means of determining the structural contours of the beds. when several key horizons are thus used, their elevations must be reduced to the elevations of one common horizon by the addition or subtraction of the intervals between them. for instance, knowing the succession, an outcrop of a certain sandstone may indicate that the marking horizon is feet below, and the structural contour is then drawn accordingly. observations of strike and dip at the surface are helpful; but where the beds are but slightly flexed, small irregularities in deposition may make strike and dip observations useless in determining major structures. it is then necessary to have recourse to the elevations of the marking horizons. in the selection of key horizons, knowledge of the conditions of sedimentation is very important. for example, some of the oil fields occur in great delta deposits, where successive advances and retreats of the sea have resulted in the interleaving of marine and land deposits. the land-deposited sediments usually show great variations in character and thickness laterally and vertically; and a given bed is likely to thin out and disappear when traced for a short distance, rendering futile its use as a marker. the marine sediments, on the either hand, show a much greater degree of uniformity and continuity, and a bed of marine limestone may extend over a large area and be very useful as a key horizon. over large areas outcrops and records of previously drilled water and oil wells may not be sufficient to give an indication of structure; it then becomes necessary to secure cross sections by drilling shallow holes to some identifiable bed, and to determine the structure from these cross sections, in advance of deeper drilling through a favorable structure thus located. the coöperative effort of the illinois state survey and private interests, cited on page , is a good illustration of this procedure. this method is only in its infancy, because well-drilling has not yet exhausted the possibilities of structures located from surface outcrops. the so-called anticlinal structures, which have been found by experience to be so favorable to the accumulation of oil, are by no means symmetrical in shape or uniform in size. they may be elongated arches with equal dip on the two sides, or one side may dip and the other be nearly flat. in a territory with a general dip in one direction, a slight change in the angle, though not in the direction of dip, sometimes called an arrested dip, may cause sufficient irregularity to produce the necessary trapping conditions. in other cases the anticline may be of nearly equidimensional dome form. the largest anticlines which have been found to act as specific reservoirs are rarely more than a few miles in extent, and in many cases only a mile or two. the "closure" of an anticline is the difference between the height of a given stratum at the highest point and at the edges of the structure. a considerable number of productive anticlines are known in which the beds dip so gently as to give a closure of feet or less. after the structural outlines of beds near the surface have been determined, all possible information should be used in projecting these structures downward to the oil-producing horizons. where a number of wells have been previously drilled in the vicinity, examination of their records may indicate certain lateral variations in the thickness of the beds between the horizon which has been mapped and the producing horizon. the effect of such lateral variations may be either to accentuate the surface structure, or to cause it to disappear entirely and thus to indicate lack of favorable trapping conditions. the possibility of several oil-producing beds, at different depths--a not uncommon condition in many fields--should also be kept in mind. as already indicated, anticlines are not always essential to make the necessary trapping conditions. in the beaumont field of texas, for instance, it has been shown that irregular primary deposition of sediments differing in porosity both vertically and horizontally allowed the oil to migrate upward irregularly along the porous beds and parts of beds, and to be trapped between the more impervious portions of the beds. further questions to be considered in the exploration of an area are the content of organic matter in the sediments which may have served as a source of oil, the presence of impervious cap-rocks or of variations in porosity sufficient to retain the oil, the thickness of sediments and the extent to which they have undergone differential stresses, the amount of erosion and the possibilities that oil, if formed, has escaped from the eroded edges of porous strata, and, where carbonaceous beds are present, their degree of carbonization, and many other similar matters. each field in fact has its own "habit," determined by the interaction of several geologic factors. this habit may be learned empirically. geologists have often gone wrong in applying to a new district certain principles determined elsewhere, without sufficient consideration of the complexity and relative importance of the sundry geologic factors which in the aggregate determine the local habit of oil occurrence. geographically associated fields characterized by similarity of oil occurrence, age, and origin, are known as _petroliferous provinces_. the factors entering into the classification of fields are so numerous that more precise definition of a petroliferous province is hardly yet agreed upon. the part played by the economic geologist in oil exploration and development is a large one for the obvious reasons given above. probably no other single division of economic geology now employs so large a number of geologists. practically no large oil company, or large piece of oil exploration and development, is now handled without geologic advice. quoting from arnold:[ ] it ought to be as obvious that exploration with the drill should be preceded by careful geologic studies as it is that railroad construction should be based on surveys. these studies should include such subjects as topography, stratigraphy, structure, and surface evidence of petroleum in the regions to be tested. the work divides itself into two stages--preliminary reconnaissances and detailed surveys. the preliminary reconnaissance should consist in procuring all the available published and hearsay evidence regarding the occurrence of oil or gas seepages or hydrocarbon deposits in the region; in making preliminary geologic surveys to determine from which formations the oil is to come and the areal distribution of these formations; in determining those general regions in which the surface evidence is supposed to be most favorable for the accumulation of hydrocarbons; and in determining the best routes and methods of transportation. the second stage includes detailed geologic surveys of those regions where the surface evidence indicates that petroleum is most likely to be found and the location of test holes at favorable points. by working out the surface distribution and structure of the formations it is usually possible to select the areas offering the best chances of success. geology should always be the dominant factor in determining the location of test holes, although modifications to meet natural conditions must sometimes be made. oil shales one of the sources of oil which is likely to become important in the future is oil shales,--that is, shales from which oil product can be extracted by distillation. these have already been referred to on previous pages. such shales are now mined only in scotland and in france to a relatively small extent, but there are immense reserves of these shales in various parts of the world which are likely to be drawn upon when commercial conditions require it. in the united states alone it is estimated that the oil shales are a potential source of oil in amounts far greater than all the natural petroleum of this hemisphere.[ ] the solution of the problem of extraction of oil from shales is fairly well advanced technically, and the problem has now become principally one of cost. in order to recover any large amount of oil from this source, operations of stupendous magnitude, approximately on the scale of the coal industry, must be established. as long as there are sufficient supplies of oil concentrated by nature to be drawn upon, it is unlikely that oil shale will furnish any considerable percentage of the world's oil requirements. with the great increase in world demand for oil, however, which may very possibly outstrip the available annual supply in the future, and particularly with the increase in the united states demand relative to domestic supplies, exhaustive surveys of the situation are being made with a view to development of oil shales when warranted by market conditions. oil shales are sedimentary strata containing decomposed products of plants and animals. locally they grade into cannel coal, with which they are genetically related. they may be regarded as representing the kinds of sediments from which the oil of oil pools has in the main originated. the most extensive of the oil shales of the united states are found in the eocene beds of northwestern colorado, northeastern utah, and southwestern wyoming, and in the miocene beds of northern nevada. the largest known foreign deposits occur in brazil and russia. natural gas economic features natural gas is used both for lighting and for fuel purposes. in the united states it has become the basis of a great industry, the value of the product ranging above that of lead and zinc. the united states is the largest producer of natural gas. other producers are canada, dutch east indies, mexico, hungary, japan, and italy. nearly all producing oil fields furnish also some natural gas. in the united states nearly per cent of the total production of natural gas comes from west virginia, about per cent from pennsylvania, about per cent from oklahoma, and less than per cent from each of ohio, california, louisiana, kansas, texas, and several other states. one of the recent interesting developments in this industry is the recovery of gasoline from the natural gas. this is obtained by compression and condensation of the casing-head gas from oil wells, and also, more recently, by an absorption process which is applied not only to "wet" gas from oil wells but also to so-called "dry" gas occurring independently of oil. it is a high-grade product which in recent years has amounted to about per cent of the total output of gasoline for the united states. geologic features natural gas, like oil, originates in the distillation of organic substances in sediments, and migrates to reservoirs capped by impervious strata. it is commonly, though not always, associated with oil and coal. the geologic features of its occurrence have so much in common with oil that a description would essentially duplicate the above account of the geologic features of oil. asphalt and bitumen economic features asphalt and bitumen are not used as energy resources, but they have so much in common with oil in occurrence and origin that they are included in this chapter. asphalt and bitumen find their main use in paving. other important uses are in paints and varnishes, in the manufacture of prepared roofing, for various insulating purposes, and in substitutes for rubber. nearly the entire world's supply of natural asphalt comes from the british island of trinidad and from venezuela. both of these deposits are under united states commercial control probably affiliated with dutch-english interests. prior to the war about half the product went to europe and half to the united states. large amounts of asphaltic and bituminous rock, used mainly in paving, are normally produced in alsace, france, and in italy. prior to the war both the alsatian and italian deposits were under german commercial control. their output is practically all consumed in europe. the united states takes a large part in the world's trade in natural asphalt, by importation from trinidad and venezuela, and by some reëxportation chiefly to canada and mexico. the united states also produces some natural asphalt and bituminous rock for domestic consumption. deposits of natural asphaltic material are widely distributed through the united states, but commercial production is limited to a few localities in kentucky, texas, utah, colorado, oklahoma, and california. the asphalt manufactured from petroleum constitutes a much larger tonnage than natural asphalt though it does not enter so largely into world trade. the manufactured product is largely but not exclusively in american control. large amounts are made in this country and will no doubt be made for the next decade, from oil produced in the southwestern states and in mexico. at the present time as much or more asphalt is made in the united states from mexican as from domestic crude oil. the refineries are located near the gulf coast so that exports can avoid overland shipments. the relative merits of natural asphalt and asphalt manufactured from oil may be subject to some discussion; but it is perfectly clear that the manufactured material is sufficient, both in quantity and variety, to make the united states entirely independent and have an exportable surplus. geologic features natural asphalt and similar products are in the main merely the residuals of oil and gas distillation accumulated by nature under certain conditions already described in connection with oil (pp. - ). in some cases the asphaltic material is found as impregnations of sediments, and appears to have remained in place while the lighter organic materials were volatilized and migrated upward. in other cases it occurs in distinct fissure veins; the fissures and cavities apparently were once filled with liquid petroleum, which has subsequently undergone further distillation. the original liquid character of some of these bitumens is shown by occasional fragments of unworn "country rock" imbedded in the veins. the effect of surface waters, carrying oxidizing materials and sulphuric acid, is believed to have contributed to the drying out and hardening of these veins or dikes. asphalts and bitumens include a wide variety of hydrocarbon materials, such as gilsonite, grahamite, elaterite, ozokerite, etc., which are used for somewhat different purposes. the deposits of the united states show much variety in form, composition, age, and geologic associations. the important kentucky deposits occur as impregnations of carboniferous sandstones at the base of the coal measures of that state. the trinidad asphalt comes from the famous "pitch lake," which is a nearly circular deposit covering about a hundred acres feet above sea level, and which is believed to fill the crater of an old mud volcano. the so-called pitch consists of a mixture of bitumen, water, mineral and vegetable matter, the whole inflated with gas, which escapes to some extent and keeps the mass in a state of constant ebullition. the surface of the lake is hard, and yet the mass as a whole is plastic and tends to refill the excavations. the lake is believed to be on the outcrop of a petroleum-bearing stratum, and the pitch to represent the unevaporated residue of millions of tons of petroleum which have exuded from the oil-sands. the pitch is refined by melting,--the heat expelling the water, the wood and other light impurities rising, and the heavy mineral matter sinking to the bottom. the asphalt of venezuela is similar in nature, but the pitch "lake" is here covered with vegetation and the soft pitch wells up at certain points as if from subterranean springs. footnotes: [ ] for more detailed treatment of international coal movements before the war and of coal movements within the united states, see the u. s. geological survey's _world atlas of commercial geology_, pt. , , pp. - . [ ] campbell, marius r., the coal fields of the united states: _prof. paper -a, u. s. geol. survey_, , pp. , , . [ ] compiled from tables quoted by white, david, the petroleum resources of the world: _annals am. acad. social and political sci._, vol. , , pp. and . [ ] white, david, _loc. cit._, p. . [ ] see arnold, ralph, petroleum resources of the united states: _econ. geol._, vol. , , p. . [ ] white, david, late theories regarding the origin of oil: _bull. geol. soc. am._, vol. , , p. . [ ] mccoy, a. w., notes on principles of oil accumulation: _jour. geol._, vol. , , pp. - . [ ] white, david, genetic problems affecting search for new oil regions: _mining and metallurgy_, _am. inst. of min. engrs._, no. , sec. , feb., . [ ] mehl, m. g., some factors in the geographic distribution of petroleum: _bull. sci. lab._, _denison univ._, vol. , , pp. - . [ ] schuchert, charles, petroliferous provinces: _bull. _, _am. inst. mining and metallurgical engrs._, , pp. - . [ ] loc. cit., p. . [ ] seepages or residual bituminous matter near the surface may be due to upward escape of oil material through joints in the rocks capping a reservoir, and productive pools may be found directly below such showings. in other regions similar surface indications may mean that the stratum in the outcrop of which they are found is oil-bearing; but accumulations of oil, if present, may be several miles down the dip, at places where the structural conditions have been favorable. in still other cases the seepage may have been in existence for such a long time as to exhaust the reservoir. it must also be remembered that gas seeps are common in sloughs and marshes where vegetation is decaying, and may be of no significance in the search for petroleum. [ ] arnold, ralph, conservation of the oil and gas resources of the americas: _econ. geol._, vol. , , pp. - . [ ] oil shales may also be made to yield large quantities of fuel and illuminating gas, and of ammonia (see pp. - ). chapter ix minerals used in the production of iron and steel (the ferro-alloy group) general features iron and steel and their alloys are the most generally used of the metals. the raw materials necessary for their manufacture include a wide variety of minerals. iron is the principal element in this group; but in the manufacture of iron and steel, manganese, chromium, nickel, tungsten, molybdenum, vanadium, zirconium, titanium, aluminum, uranium, magnesium, fluorine, silicon, and other substances play important parts, either as accessories in the furnace reactions or as ingredients introduced to give certain qualities to the products. nearly all parts of the world are plentifully supplied with iron ores for an indefinite period in the future, but their abundant use has thus far been confined mainly to the countries bordering the north atlantic,--the united states, germany, and england,--which, possessing ample coal supplies, have had the initiative to develop great iron and steel industries. china has abundant coal, moderate quantities of iron ore, and a large population, but a low per capita consumption of iron and steel products. development of its iron and steel industry is just beginning. japan has neither coal nor iron in sufficient quantities, and hence the japanese effort in recent years to control the mineral resources of china and other countries. as a result of the war germany has been largely deprived of its iron ores, and france may assume somewhat the rank in iron ore production once held by germany. sweden and spain have been considerable producers of iron ore, but both lack coal, with the result that their ores have been largely exported to england and germany. with increase of per capita consumption in outlying parts of the world, iron and steel industries are beginning to develop locally on a small scale, as in india, south africa, and australia. russia has had sufficient supplies of coal and iron, but the stage of industrial development in that country has not called for great expansion of its iron and steel industry. there has been a tendency for iron and steel manufacture to become concentrated at a comparatively few places on the globe favored by the proper combinations of coal, iron, transportation, proximity to consuming populations, initiative and capacity to take advantage of a situation, and other factors. even though on paper conditions may seem to be favorable in outlying territories for the development of additional plants, this development is often held back by competition from the established centers. on the west coast of the united states, there are raw materials for an iron and steel industry and there has been discussion for years as to the possibilities of starting a successful large scale steel industry. the consuming power of the local population for all kinds of iron and steel would seem to be great enough to warrant such action. however, the demand is for an extremely varied assortment of iron and steel products; and to start an industry, making only a few of the cruder products such as pig iron and semi-finished forms, would not meet this demand. all varieties of finishing plants and associated factories would also need to be started in order to meet the situation. this would require large capital. furthermore the local demand for some of the accessory finished products might not warrant the establishment of the accessory plants. throughout the history of the iron and steel business there has been a marked tendency for the iron ore to move to regions of coal production rather than for the coal to move to the iron ore regions. the coal or energy factor seems ultimately to control. this is due in considerable part to the fact that coal furnishes the basis of a great variety of industries for which iron ore is only one of the feeders, and which are so interrelated that it is not always easy to move the iron and steel industry to a spot near the sources of iron ore where iron and steel alone could be produced. in regard to iron ore supplies of proper grade and quantity, the united states is more nearly self-sufficing than any of its competitors. it imports minor amounts of ore from cuba and canada, and even from chile and sweden, to border points, in the main merely because these imported ores can compete on a price basis with the domestic ores. the entire exclusion of these ores, however, would make comparatively little difference in the total volume of our iron and steel industry; though it would probably make some difference in distribution, to the disadvantage of plants along the coast. there is only one kind of iron ore in which the united states has anything approaching deficiency, and that is ore extremely low in phosphorus, adapted to making the so-called low-phosphorus pig which is needed for certain special steels. ordnance requirements during the war put a premium on these steels. while some of these extremely low-phosphorus ores are mined in the united states, additional quantities have been required from spain and canada and to a lesser extent from north africa and sweden. also the spanish pyrite, imported ordinarily for its sulphur content, on roasting leaves a residue of iron oxide extremely low in phosphorus which is similarly used. the elimination of pyrite imports from spain during the war, therefore, was a considerable contributing factor to the stringency in low-phosphorus iron ores. war experience showed that the united states was dependent on foreign sources for per cent or upwards of its needs in this regard. certain developments in progress, notably the project for concentration of siliceous eastern mesabi range ores, make it likely that future domestic production will more nearly be able to meet the requirements. the equivalent of per cent of the iron ore mined in the united states is exported as ore to canadian ports on the great lakes and in the form of crude iron and steel products to many parts of the world. england and germany are almost the sole competitors in the export trade. when we turn to the minerals used for making the alloys of iron and as accessories in the manufacture of iron, it appears that no one of the principal iron and steel producing countries of the world is self-supporting, but that these "sweeteners" must be drawn in from the far corners of the earth. the importance of these minor constituents is altogether out of proportion to their volume. for instance, only fourteen pounds of manganese are necessary in the making of a ton of steel, yet a ton of steel cannot be made without manganese. the increasing specialization in iron and steel products, and the rapidly widening knowledge of the qualities of the different alloys, are constantly shifting the demand from one to the other of the ferro-alloy minerals. each one of the ferro-alloy minerals may be regarded as being in the nature of a key mineral for the iron and steel industry, and the control of deposits of these minerals is a matter of international concern. control is not a difficult matter, in view of the fact that the principal supplies of practically every one of the alloy minerals are concentrated in comparatively few spots on the globe,--as indicated on succeeding pages. nature has not endowed the united states, nor in fact the north american continent, with adequate high-grade supplies of the principal ferro-alloy minerals,--with the exception of molybdenum, and with the exception of silica, magnesite, and fluorspar, which are used as accessories in the process of steel making. with plenty of iron ore and coal, and with an iron and steel capacity amounting to over per cent of the world's total, the united states is very largely dependent on other countries for its supplies of the ferro-alloy minerals. the war brought this fact home. with the closing of foreign sources of supplies, it looked at one time as if our steel industry was to be very greatly hampered; and extraordinary efforts were made to keep channels of importation open until something could be done in the way of development, even at excessive cost, of domestic supplies. the result of war efforts was a very large development of domestic supplies of practically all the ferro-alloy minerals; but in no case, with the exceptions noted above, did these prove sufficient to meet the total requirements. this development was at great cost and at some sacrifice to metallurgical efficiency, due to the low and variable grades of the raw materials. with the post-war reopening of importation much of the domestic production has necessarily ceased, and large amounts of money patriotically spent in the effort to meet the domestic requirements have been lost. these circumstances have resulted in the demand in congress from producers for direct financial relief and in demand for protective tariffs, in order to enable the new struggling industries to exist, and to permit of development of adequate home supplies. such tariffs might be beneficial to these particular domestic industries if wisely planned; but also, in view of the limited amounts of these particular ores in this country, their general low grade, and the high cost of mining, tariffs might very probably hasten exhaustion of our limited supplies and might handicap our metallurgical industries both in efficiency and cost (see pp. - , - ). iron ores economic features =technical and commercial factors determining use of iron ore minerals.= popularly, an iron ore is an iron ore, and there is little realization of its really great complexity of composition and the difficulty of determining what is or is not a commercial ore. percentage of iron is of course an important factor; but an ore in which the iron is in the mineral hematite is more valuable than one with an equivalent percentage of iron which is in the form of magnetite. substances present in the ore in minor quantities, such as phosphorus, sulphur, and titanium, have a tendency to make the iron product brittle, either when it is cold or when it is being made, so that excessive amounts of these substances may disqualify an ore. excessive quantities of silica, lime, or magnesia may make the ore undesirable. where an acid substance, like silica, is balanced by basic constituents like lime and magnesia, considerable amounts of both may be used. excessive moisture content may spoil an ore because of the amount of heat necessary to eliminate it in smelting. the metallurgical processes of the iron and steel industry are essentially adapted to the principal grades of ore available. the cheapest of the steel-making processes, called the acid bessemer process, requires a very low-phosphorus ore (usually below . per cent in the united states and below . per cent in england.) the basic open-hearth processes, making two-thirds of the steel in the united states, allow higher percentages of phosphorus, but not unlimited amounts. the basic bessemer (thomas) process, used for the "minette" ores of western europe and the swedish magnetites, may use an ore with any amount of phosphorus over . per cent. the phosphatic slag from this process is used as fertilizer. the supply of low-phosphorus bessemer ore in the united states is at present limited as compared with that of the non-bessemer ores, with the result that steel-plant construction for many years past has been largely open-hearth. the open-hearth process is favored also because it allows closer control of phosphorus content in the steel. small but increasing amounts of steel are also made in the electric furnace; for the most part, however, this process is more expensive than the others, and it is used principally for special alloy steels. iron ores are seldom so uniform in quality that they can be shipped without careful attention to sampling and grade. in the lake superior region the ores are sampled daily as mined, and the utmost care is taken to mix and load the ore in such a way that the desired grades can be obtained. ordinarily a single deposit produces several grades of ore. when ores are put into the furnace for smelting the mixtures are selected with great care for the particular purpose for which the product is to be used. the mixture is compounded as carefully as a druggist's prescription. an ore salesman, after ascertaining the nature of the iron and steel products of a plant, has to use great skill in offering particular ores for sale which not only will meet the desired grade in regard to all elements, but also will meet competition in price. in some respects, the marketing of different grades of iron ore is as complex as the marketing of a miscellaneous stock of merchandise. with ores, as with merchandise, custom and sentiment play their part,--with the result that two ores of identical grade mineralogically and chemically may have quite a different vogue and price, simply because of the fact that furnace men are used to one and not to the other and are not willing to experiment. the geologist is ordinarily concerned merely with finding an ore of as good a general grade as possible; but he often finds to his surprise that his efforts have been directed toward the discovery of something which, due to some minor defect in texture, in mineralogical composition, or in chemical composition, is difficult to introduce on the market. there is here a promising field, intermediate between geology (or mineralogy) and metallurgy, for the application of principles of chemistry, metallurgy, and mineralogy, which is occupied at the present time mainly by the ore salesman. both the mineralogist and metallurgist touch the problem but they do not cover it. with increasingly precise and rapidly changing metallurgical requirements, this field calls for scientific development. =geographic distribution of iron ore production.= iron ores are widely distributed over the world, but are produced and smelted on a large scale only in a few places where there is a fortunate conjunction of high grades, large quantity, proximity of coal, cheap transportation to markets, and manufacturing enterprise. over per cent of the iron ore production of the world is in countries bordering the north atlantic basin. the united states produces about per cent, france about per cent, england about per cent, germany before the war to per cent, and spain, russia, and sweden each about per cent. lesser producing countries are luxemburg, austria-hungary, cuba, newfoundland, and algeria; and insignificant amounts are produced in many other parts of the world. of the world's iron and steel manufacturing capacity, the united states has about per cent, germany per cent, england per cent, france per cent, the remainder of europe (chiefly russia, austria-hungary, and belgium) per cent. the absence of important iron ore production and of iron and steel manufacture either in the southern hemisphere or in any of the countries bordering the pacific is a significant feature, when we remember what part iron plays in modern civilization. japan, however, is beginning to develop a considerable iron and steel industry, which promises to use a large amount of ore from china, manchuria, and korea, and possibly to compete in american pacific coast markets. in the united states about per cent of the production, or one-third of the world's production, comes from the lake superior region, a large part of the remainder from the birmingham district, alabama, and smaller quantities from the adirondacks. for the rest of the north american continent, the only largely producing deposit is that at belle isle, newfoundland, which is the basis of the iron industry of eastern canada. cuba supplies some ore to the east coast of the united states. in europe there are only three large sources of high-grade iron ore which have heretofore been drawn on largely,--the magnetite deposits of northern sweden, the hematites and siderites of the bilbao and adjacent districts of northern spain, and the magnetite-hematite deposits of southern russia. the first two of these ores have been used to raise the percentage of iron in the low-grade ores which are the principal reliance of western europe. the swedish ores have also been necessary in order to raise the percentage of phosphorus and thus make the ores suitable for the thomas process; on the other hand the spanish ores and a small part of the swedish material have been desired because of their low phosphorus content, adapted to the acid bessemer process and to the manufacture of low-phosphorus pig. the russian ores have largely been smelted in that country. the largest of the western european low-grade deposits is a geographic and geologic unit spreading over parts of lorraine, luxemburg, and the immediately adjacent briey, longwy, and nancy districts of france. the ores of this region are called "minette" ores. this unit produces about a fourth of the world's iron ore. low-grade deposits of a somewhat similar nature in the cleveland, lincolnshire, and adjacent districts of england form the main basis for the british industry. there is minor production of iron ores in other parts of france and germany, in austria-hungary, and in north africa (these last being important because of their low phosphorus content). comparison of figures of consumption and production of iron ores indicates that the united states, france, russia, and austria-hungary are self-supporting so far as quantity of materials is concerned. certain ores of special grades, and ores of other minerals of the ferro-alloy group required in steel making, however, must be imported from foreign sources; this matter has been discussed above. great britain and germany appear to be dependent on foreign sources, even under pre-war conditions, for part of the material for their furnaces. during the war there was considerable development of the low-grade english ores, but this does not eliminate the necessity for importing high-grade ores for mixture. belgium produces a very small percentage of her ore requirements and is practically dependent on the lorraine-luxemburg field. the principal effect of the war on iron ore production was the occupation of the great french mining and smelting field by the germans, thereby depriving the french of their largest source of iron ore. since the war the situation has been reversed, france now possessing the lorraine field, which formerly supplied germany with per cent of its iron ore. as the german industrial life is largely based on iron and steel manufacture, the problem of ore supplies for germany is now a critical one. it has led to german activity in chile and may lead to german developments in eastern europe and western asia, particularly in the large and favorably located reserves of southern russia. it seems likely, however, that arrangements will also be made to continue the export of ore from the lorraine field down the rhine to the principal german smelting centers. france needs the german coal for coking as badly as germany needs the french iron ore. the rhine valley is the connecting channel for a balanced movement of commodities determined by the natural conditions. these basic conditions are likely in the long run to override political considerations. the lake superior deposits, the swedish magnetites, the spanish hematites, and the russian ores carry to per cent of metallic iron. the birmingham deposits of southeastern united states, the main british supplies, and the main french and german supplies contain about per cent or less. it is only where ores are fortunately located with reference to consuming centers that the low-grade deposits can be used. for outlying territories only the higher-grade deposits are likely to be developed, and even there many high-grade deposits are known which are not mined. the largest single group not yet drawn on is in brazil. others in a very early stage of development are in north africa and chile. =world reserves and future production of iron ore.= the average rate of consumption of iron ore for the world in recent years has been about million tons per year. at this rate the proved ore reserves would last about years. if it be assumed that consumption in the future will increase at about the same rate as it has in the past, the total measured reserve would still last about a century. these calculations of life, however, are based only on the known reserves; and when potential reserves are included the life is greatly increased. and this is not all; for beyond the total reported reserves (both actual and potential), there are known additional large quantities of lower-grade ores, at present not commercially available, but which will be available in the future,--to say nothing of expected future discoveries of ores of all grades in unexplored territories. both geological inference and the history of iron ore exploration seem to make such future discoveries practically certain. iron ore constitutes about per cent of the earth's shell and it shows all stages of concentration up to per cent. only those rocks are called "iron ores" which have a sufficiently high percentage of iron to be adapted to present processes for the extraction of iron. when economic conditions demand it, it may be assumed that iron-bearing rocks not now ordinarily regarded as ores may be used to commercial advantage, and therefore will become ores. not only is an indefinitely long life assured for iron ore reserves as a whole, but the same is true of many of the principal groups of deposits. the question of practical concern to us, therefore, is not one of total iron ore reserves, but one of degrees of _availability_ of different ores to the markets which focus our requirements for iron. the annual production of ore from a given district is roughly a measure of that ore's ability to meet the competitive market, and therefore, of its actual immediate or past availability. annual production is the net result of the interaction of all of the factors bearing on availability. it may be argued that there are ores known and not yet mined which are also immediately available. on the whole, they seem to be less available than ores actually being produced; otherwise general economic pressure would require their use and actual production. in considering the future availability of iron ores, it is obvious that tables of past production afford only a partial basis for prediction. presumably districts which have produced largely in the past may be expected to continue as important factors. in these cases production has demonstrated availability. continued heavy production may thus be expected from the ores of the lake superior region, from the clinton hematites of alabama, from the ores of the lorraine-luxemburg-briey district, from the cleveland ores of england, from the bilbao ores of spain, from the high-grade magnetites of northern sweden, and (assuming political stability) from the ores of southern russia. similarly, also, recent increases in production from certain districts are probably significant of increased use of such ores in the future. among these developments are the increasing production of swedish ores and their importation into england and germany, and the increasing use of clinton hematites and adirondack magnetites in the united states. low-grade ores from the great reserves of cuba are being mined and brought to the east coast of the united states in increasing amounts, and it is highly probable that they will take a larger share of the market. a similar project in chile, which lay dormant during the war because of restricted shipping facilities, is expected in the near future to yield important shipments to the united states. in none of these cases will production be limited in the near future by ore reserves. increased production and use of iron ores are also to be looked for in newfoundland, north africa, china, india, australia, and south africa. on the commercial horizon are ores of still newer districts, the availability of which may not be read from tables of production. their availability must be determined by analysis and measurement of the factors entering into availability. availability of iron ore is determined by percentage of iron, percentages of impurities, percentages of advantageous or deleterious minor constituents, physical texture, conditions for profitable mining, adaptability to present furnace practice, distance from consuming centers, conditions and costs of transportation, geographical and transportational relation to the coal and fluxes necessary for smelting, trade relations, tariffs and taxes, inertia of invested capital, and other considerations. all of these factors are variable. a comparison of ores on the basis of any one of these factors or of any two or three of them is likely to be misleading. a comparison based on the quantitative consideration of all of the several factors seems to be made practically impossible by the difficulty of ascertaining accurately the quantitative range and importance of each factor, and by the difficulty of integrating all of the factors even if they should be determined. however, their combined effect is expressed in the cost of bringing the product to market; and comparison of costs furnishes a means of comparing availability of ores. a high-grade ore, cheaply mined and favorably located with reference to the points of demand, will command a relatively high price at the point of production. the same ore so located that its transportation costs are higher will command a lower price; or it may be so located that the costs of mining and bringing it to places where it can be used are so high that there is no profit in the operation. there are known high-grade iron ores which, because of cost, are not available under present conditions. the availability of an ore, then, depends on its relation to a market,--whether, after meeting the cost of transportation, it can be sold at prevailing market prices at the consuming centers, and can still leave a fair margin of profit for the mining operation. the price equilibrium between consuming centers affords a reasonably uniform basis against which to measure availability of ores. figures of cost are obtainable as a basis for comparison of availability of iron ores of certain of the districts, but not enough are at hand for comparison of the ores of all districts. careful study of costs has demonstrated the availability in the near future of the brazilian high-grade bessemer hematites; and projects which are now under way for exportation to england and the united states will doubtless make this enormous reserve play an important part in the iron industry. iron ore is known but not yet mined in many parts of the western united states and western canada. with the increasing population along the west coast of north america, projects for smelting the ore there are becoming more definite. establishment of smelters on the west coast would make available a large reserve of ore (see also, however, p. ). the list of changes now under way or highly probable for the future might be largely extended. the use of iron and steel is rapidly spreading through populous parts of the world which have heretofore demanded little of these products. this increased use is favoring the development of local centers of smelting, which will make available other large reserves of iron ore. the growth of smelting in india, china and australia illustrates this tendency. iron ore reserves are so large, so varied, and so widely distributed over the globe, that they will supply demands upon them to the remote future. reserves become available and valuable only by the expenditure of effort and money. ores are the multiplicand and man the multiplier in the product which represents value or availability. iron ore can be made available, when needed, almost to any extent, but at highly varying cost and degree of effort. the highest grade ores, requiring minimum expenditure to make them available, are distinctly limited as compared to total reserves. any waste in their utilization will lead more quickly to the use of less available ores at higher cost. one of the significant consequences of the exhaustion of the highest grade reserves will be an increased draft upon fuel resources for the smelting of the lower grade ores. availability of iron ores is limited, not by total reserves, but by economic conditions. geologic features iron rarely exists in nature as a separate element. it occurs mainly in minerals which represent combinations of iron, oxygen, and water, the substances which make up iron rust. very broadly, most of the iron ores might be crudely classified as iron rust. in detail this group is represented by several mineral varieties, principal among which are hematite (fe_{ }o_{ }), magnetite (fe_{ }o_{ }), and limonite (hydrated ferric oxide). iron likewise combines with a considerable variety of substances other than oxygen; and some of these compounds, as for instance iron carbonate (siderite), iron silicate (chamosite, glauconite, etc.), and iron sulphide (pyrite), are locally mined as iron ores. while an ore of iron may consist dominantly of some one of the iron minerals, in few cases does it consist exclusively of one mineral. most ores are mixtures of iron minerals. fully nine-tenths of the iron production of the world comes from the so-called hematite ores, meaning ores in which hematite is the dominant mineral, though most of them contain other iron minerals in smaller quantities. about per cent of the world's iron ores are magnetites, and the remainder are limonites and iron carbonates. iron ores are represented in nearly all phases of the metamorphic cycle, but the principal commercial values have been produced by processes of weathering and sedimentation at and near the surface. =sedimentary iron ores.= over per cent of the world's production of iron ore is from sedimentary rocks. the deposits consist in the main either of beds of iron ore which were originally deposited as such and have undergone little subsequent alteration, or of those altered portions of lean ferruginous beds which since their deposition have been enriched or concentrated sufficiently to form ores. a minor class of iron ores in sediments consists of deposits formed by secondary replacement of limestones by surface waters carrying iron in solution. . deposits of the first class,--originally laid down in much their present form,--are usually either oölitic, _i. e._, containing great numbers of flat rounded grains of iron minerals like flaxseeds, or consist in large part of fossil fragments of sea shells, replaced by iron minerals. the clinton ores of the birmingham district, the wabana ores of newfoundland, the minette ores of the lorraine district in central europe, and the oölitic ores of northern england are all of these types. their principal iron mineral is hematite, although the english ores also contain considerable iron carbonate or siderite. the cementing or gangue materials are chiefly calcite and quartz, in variable proportions. the large reserves of high-grade hematite in the minas geraes district of brazil are also original sediments, but lack the oölitic texture. an insignificant proportion of the world's iron is obtained from "bog ores," which are sedimentary deposits of hydrated iron oxide in swamps and lakes. these ores have been used only on a small scale and chiefly in relatively undeveloped countries. they are of particular interest from a genetic standpoint in that they show the nature of some of the processes of iron ore deposition as it is actually going on today. none of the ores of this class, with the exception of the iron carbonates, have undergone any considerable surface enrichment since their primary deposition. neither, with the exception of the brazilian ores, have they undergone any deep-seated metamorphism. the shapes, sizes, and distribution of the deposits may be traced back to the conditions of original deposition. in england and western europe the principal deposits have been only slightly tilted by folding. in the united states the clinton ores have partaken in the appalachian folding. in brazil, the ores have undergone close folding and anamorphism. . deposits of the second class, which owe much of their value to further enrichment since deposition, are represented by the hematite ores of the lake superior district. these may be thought of as the locally rusted and leached portions of extensive "iron formations," in which oxidation of the iron, and the leaching of silica and other substances by circulating waters, have left the less soluble iron minerals concentrated as ores. the lake superior iron formations now consist near the surface mainly of interbanded quartz (or chert) and hematite, called _jasper_ or _ferruginous chert_ or _taconite_. these are similar in composition to the leaner iron ores of brazil, called _itabirite_, but differ in that the silica is in the form of chemically deposited chert, rather than fragmental quartz grains. [illustration: fig. . alteration of lake superior iron formation to iron ore by the leaching of silica.] when originally deposited the iron was partly hematite (perhaps some magnetite) and largely in the form of iron carbonate (siderite) and iron silicate (greenalite), interbanded with chert. the original condition is indicated by the facts that deep below the surface, in zones protected from weathering solutions, siderite and greenalite are abundant, and that they show complete gradation to hematite in approaching the surface. the ore has been concentrated in the iron formation almost solely by the process of leaching of silica by surface or meteoric waters, leaving the hematite in a porous mass. figure illustrates this change as calculated from analyses and measurements of pore space. during this process a very minor amount of iron has been transported and redeposited. in short, the lake superior iron ores are residual deposits formed by exactly the same weathering processes as cause the accumulation of clays, bauxites, and the oxide zones of sulphide deposits. the development of an iron ore rather than of other materials as an end-product is due merely to the peculiar composition of the parent rock. the solution of silica on such an immense scale as is indicated by these deposits has sometimes been questioned on the general ground that silica minerals are insoluble. however, there is plenty of evidence that such minerals _are_ soluble in nature; and the assumption of insolubility, so often made in geologic discussions, is based on the fact that most other minerals are _more_ soluble than silica minerals, and that in the end-products of weathering silica minerals therefore usually remain as important constituents. iron oxide, on the other hand, is _less_ soluble even than silica,--with the result that when the two occur together, the evidence of leaching of silica from the mixture becomes conspicuous. the fact that these deposits are almost exclusively residual deposits formed by the leaching of silica has an important bearing on exploration. if they have been formed by the transportation and deposition of iron from the surrounding rocks, there is no reason why they should not occasionally be found in veins and dikes outside of the iron formation. as a matter of fact they do not transgress a foot beyond the limits of the iron formation. failure to recognize the true nature of the concentration of these ores has sometimes led to their erroneous classification as ores derived from the leaching and redeposition of iron from the surrounding rocks. the distribution and shapes of ore deposits of this class are far more irregular and capricious than those of the primary sediments, as would be expected from the fact that their concentration has taken place through the agency of percolating waters from the surface, which worked along devious channels determined by a vast variety of structural and lithological conditions. the working out of the structural conditions for the different mines and districts constitutes one of the principal geologic problems in exploration. these conditions have been fully discussed in the united states geological survey reports, and are so various that no attempt will be made to summarize them here. one of the interesting features of the concentration of lake superior iron ores is the fact that it took place long ago in the keweenawan period, preceding the deposition of the flat-lying cambrian formations, at a time when the topography was mountainous and the climate was arid or semi-arid. these conditions made it possible for the oxidizing and leaching solutions to penetrate very deeply, how deeply is not yet known, but certainly to a depth below the present surface of , feet. at present the water level is ordinarily within feet of the surface, and oxidizing solutions are not going much below this depth. this region, therefore, furnishes a good illustration of the intermittent and cyclic character of ore concentration which is now coming to be recognized in many ore deposits. subsequent changes far beneath the surface have folded, faulted, and metamorphosed some of the lake superior iron ores but have not enriched them. the same processes have recrystallized and locked together the minerals of some of the lean iron formations, making them hard and resistant, so that subsequent exposure and weathering have had little effect in enriching them to form commercial ores. the weathering of limestones containing minor percentages of iron minerals originally deposited with the limestones may result in the residual concentration of bodies of limonite or "brown ores" associated with clays near the surface. this process is similar in all essential respects to the concentration of the lake superior ores. such limonitic ores are found rather widely distributed through the appalachian region and in many other parts of the world. because of the ease with which they can be mined and smelted on a small scale they have been used since early times, but have furnished only a very small fraction of the world's iron. . in a third class of sedimentary ores, the iron minerals are supposed to have been introduced as replacements of limestones subsequent to sedimentation. such ores are not always easy to discriminate from ores resulting primarily from sedimentation. this class is represented by the high-grade deposits of bilbao, spain, austrian deposits, and by smaller deposits in other countries. the bilbao ores consist mainly of siderite, which near the surface has altered to large bodies of oxide minerals. they occur in limestones and shales and are not associated with igneous rocks. the deposits are believed to have been formed by ordinary surface waters carrying iron in solution, and depositing it in the form of iron carbonate as replacements of the limestones. the original source of the iron is believed to have been small quantities of iron minerals disseminated through the ordinary country rocks of the district. the action of surface waters, in thus concentrating the iron in certain localities which are favorable for precipitation, is similar to the formation of the lead and zinc ores of the mississippi valley, referred to in the next chapter. deposits formed in this manner may be roughly tabular and resemble bedded deposits, or they may be of very irregular shapes. the sedimentary iron ores in general evidently represent an advanced stage of katamorphism, and illustrate the tendency of this phase of the metamorphic cycle toward simplification and segregation of certain materials. the exact conditions of original sedimentation present one of the great unsolved problems of geology, referred to in chapter iii. =iron ores associated with igneous rocks.= about five per cent of the world's production of iron ore is from bodies of magnetite formed in association with igneous rocks. these are dense, highly crystalline ores, in which the iron minerals are tightly locked up with silicates, quartz, and other minerals, suggestive of high temperature origin. the largest of these deposits is at kiruna in northern sweden; in fact this is the largest single deposit of high-grade ore of any kind yet known in the world. here the magnetite forms a great tabular vertical body lying between porphyry and syenite. in the adirondack mountains of new york and in the highlands of new jersey, magnetites are interbedded and infolded with gneisses, granites, and metamorphic limestones. in the western united states there are many magnetite deposits, not yet mined, at contacts between igneous intrusives and sedimentary rocks, particularly limestones (so-called "contact-metamorphic" deposits). the ores of the cornwall district of pennsylvania and some of the chilean, chinese, and japanese ores are of the same type. magnetites containing titanium, which prevents their use at the present time, are known in many parts of the world as segregations in basic igneous rocks. they are actually parts of the igneous rock itself (p. ). among the large deposits of this nature are certain titaniferous ores of the adirondacks, of wyoming, and of the scandinavian peninsula. in all of these cases, it is clear that the origin of the ores is in some way related to igneous processes, and presumably most of the ores are deposited from the primary hot solutions accompanying and following the intrusion of the igneous rocks; but thus far it has been difficult to find definite and positive evidence as to the precise processes involved. none of these deposits have undergone any important secondary enrichment at the surface. their sizes, shapes, and distribution are governed by conditions of igneous intrusion, more or less modified, as in the adirondacks, by later deformation. =iron ores due to weathering of igneous rocks.= a small part of the world's iron ores, less than per cent of the total production, are the result of surface alteration of serpentine rocks. these ores are mined principally in cuba (fig. ). here they have been developed on a plateau-like area on which erosion is sluggish. the process of formation has been one of oxidation of the iron minerals and leaching of most of the other constituents, leaving the iron concentrated near the surface in blanket-like deposits. the minerals of the original rock contained alumina, which, like the iron, is insoluble under weathering conditions, and hence the cuban iron ores are high in alumina. they also contain small quantities of nickel and chromium which have been concentrated with the iron. a large part of the iron minerals, especially where close to the surface, have been gathered into small shot-like nodules called _pisolites_. it is thought that the solution and redeposition of the iron by organic acids from plant roots may be at least a contributing cause in the formation of this pisolitic texture. [illustration: fig. . representing in terms of weight the mineralogical changes in the katamorphism of serpentine rock to iron ore, on the assumption that alumina has remained constant, eastern cuba.] the cuban iron ores are similar in their origin to _laterites_, which are surface accumulations of clay, bauxite, and iron oxide minerals, resulting from the weathering of iron-bearing, commonly igneous, rocks. the typical laterites carry more clay and bauxite than the cuban iron ores, but this is due merely to the fact that the original rocks commonly carry more materials which weather to clay. in fact the cuban iron ores are themselves, broadly speaking, laterites. =iron ores due to weathering of sulphide ores.= a relatively minute portion of the world's iron ore comes from the "gossans" or "iron caps" over deposits of iron sulphides. the gossans are formed by oxidation and leaching of other minerals from the deposits, leaving limonite or hematite in concentrated masses (see pp. - ). manganese ores economic features manganese ores are used mainly in the manufacture of steel, the alloys spiegeleisen and ferromanganese being added to the molten steel after treatment in the bessemer converter and open-hearth furnace in order to recarburize and purify the metal. the alloy ferromanganese is also used in the production of special manganese steels. manganese ore is used in relatively small amounts in dry batteries, in the manufacture of manganese chemicals, in glass making, and in pigments. steel uses per cent of the total manganese consumed, batteries and chemicals per cent. on an average each ton of steel in the united states requires pounds of metallic manganese, equivalent to pounds of manganese ore. with manganese ores, as with iron ores, the percentage of minor constituents,--phosphorus, silica, sulphur, etc.,--determines to a large extent the manner of use. low-grade manganese ores, ranging from to per cent in manganese, to per cent in iron, and containing less than per cent of silica, are used mainly in the production of the low-grade iron-manganese alloy called _spiegeleisen_ or _spiegel_ ( to per cent manganese). the higher-grade ores, ranging from to per cent in manganese, are used mainly in the production of the high-grade alloy called _ferromanganese_ or _ferro_, in which the manganese constitutes to per cent of the total. to a very limited extent manganese is smelted directly with iron ores, thus lessening the amount to be introduced in the form of alloys; this, however, is regarded as wasteful use of manganese, since its effectiveness as so used is not very great. steel makers usually prefer to introduce manganese in the form of ferromanganese rather than as spiegel. on the other hand, the ores of the united states as a whole are better adapted to the manufacture of spiegel. with the shutting off of foreign high-grade supplies during the war, resulting in the increased use of local ores, it became necessary to use larger amounts of the spiegel which could be made from these ores. metallurgists stated that it was theoretically possible to substitute spiegel for the higher grade alloy up to per cent of the total manganese requirement, but in actual practice this substitution did not get much beyond per cent. the principal manganese ore-producing countries in normal times are russia, india, and brazil. relatively little ore is used in these countries, most of it being sent to the consuming countries of europe and to the united states. the indian ore has been used largely by british steel plants, but much of it also has gone to the united states, belgium, france, and germany. the russian ore has been used by all five of these countries, germany having a considerable degree of commercial control and receiving the largest part; a small quantity is also used in russia. brazilian ore has gone mainly to the united states, and in part to france, germany, and england. smaller amounts of manganese ore have been produced in germany, austria-hungary, spain, and japan. this production has had little effect on the world situation. that produced in austria-hungary and germany is used in the domestic industry. that from spain and japan is in large part exported. the highest grade of manganese ore comes from the russian mines, especially those in the caucasus region. most of the ore used for the manufacture of dry batteries and in the chemical industry, where high-grade ores are required, has come from russia. by far the larger part of the russian production, however, has gone into steel manufacture. indian and brazilian ores have likewise been used mainly in the steel industry. some japanese ore also is of high grade and is used for chemical and battery purposes. nature has not endowed the united states very abundantly with manganese ores, and such as are known are widely scattered, of relatively small tonnage, and of a wide range of grade. the principal producing districts are the philipsburg district of montana and the cuyuna range of minnesota; there are also scattering supplies in virginia, arizona, california, and many other states. the use of domestic ores has sometimes been unsatisfactory, because of frequent failure of domestic producers to deliver amounts and grades contracted for. it has been, on the whole, cheaper, easier, and more satisfactory for the large consumers to purchase the imported ore, which is delivered in any desired amount and in uniform grades, rather than to try to assemble usable mixtures from various parts of the country. before the european war, the united states produced only to per cent of its needed supply of manganese, the rest being imported mainly from india, russia, and brazil, in the form of ore, and from england in the form of ferromanganese (about half of the total requirement). the partial closing of the first two and the fourth of these sources of supply under war conditions made it necessary to turn for ore to brazil and also to cuba, where american interests developed a considerable industry in medium-grade ores. at the same time steps were taken to develop domestic resources; and with the high prices imposed by war conditions, the domestic production, both of high- and low-grade ore, was increased largely, but still was able to supply only per cent of the total requirements of manganese. at the close of the war sufficient progress had been made--in the discovery of many new deposits in the united states, in the use of low-grade domestic ores, which before had not been able to compete with imported ores, and in the increased use of spiegel, allowing wider use of low-grade ores,--to demonstrate that, if absolutely necessary, and at high cost, the united states in another year or two could have been nearly self-sufficing in regard to its manganese requirements. the release of shipping from war demands resulted immediately in larger offerings of foreign manganese ore and of ferromanganese from england, at prices which would not allow of competition from much of the domestic or cuban ore production or from the domestic manufacture of alloys. the result was a rather dramatic closing down of the manganese industry, with much financial loss, the passage of a bill for reimbursement of producers, and a demand on the part of the producers, though not of consumers, for a protective tariff. in the questions thus raised it is desirable that geologists and engineers professionally connected with the industry thoroughly understand the basic facts; for they are liable to be called upon for advice, not only on questions relating to domestic supplies affected by possible future foreign policies, but on the formulation of the policies themselves. conservation, cheaper steel, and future trade relations of the united states all require consideration, before action is taken to protect this one of several similarly situated mineral industries, in the effort to make the country self-supporting. these questions are further dealt with in chapters xvii and xviii. manganese production was also developed during the war in the gold coast of west africa, in costa rica, in panama, in java, and elsewhere; but with the possible exception of java and chile, none of these sources are likely to be factors in the world situation. the war-developed manganese production of italy, france, sweden, and united kingdom is also unlikely to continue on any important scale. geologic features like iron ores, manganese ores consist principally of the oxides of manganese (pyrolusite, psilomelane, manganite, wad, and others), and rarely the carbonate of manganese (rhodochrosite). they are similar in their geologic occurrence to many of the iron ores and are often mixed with iron ores as manganiferous iron ores and ferruginous manganese ores. the higher grade manganese ores are of two general types. those of the caucasus district in russia are sedimentary beds, oölitic in texture, which were originally deposited as rather pure manganese oxides, and which have undergone little secondary concentration. they are mined in many places in much the same manner as coal. those of india and brazil are chiefly surface concentrations of the manganese oxides, formed by the weathering of underlying rocks which contain manganese carbonates and silicates. the origin of the primary manganese minerals in the indian and in some of the brazilian deposits is obscure. in others of the brazilian ores, the manganese was deposited in sedimentary layers interbedded with siliceous "iron formations," and the whole series has subsequently been altered and recrystallized. the manganese ores of philipsburg, montana, the principal large high-grade deposits mined in the united states, were derived by surface weathering from manganese carbonates which form replacements in limestone near the contact with a great batholith of granodiorite. the primary manganese minerals probably owe their origin to hot magmatic solutions, as suggested by the close association of the ores with the igneous rock, the presence of minerals containing chlorine, fluorine, and boron, and the development in the limestone of dense silicates and mineral associations characteristic of hot-water alteration. the manganese ores are mined principally in the oxidized zone. rich silver ores are found below the water table, but mainly in veins independent of the manganese deposits. at butte, montana, a little high-grade manganese material has been obtained from the unoxidized pink manganese carbonate, which is a common mineral in some of the veins. it is associated with quartz and metallic sulphides and is similar in origin to the copper ores of the same district (pp. - ). the lower-grade and the more ferruginous manganese ores are of a somewhat similar origin to the principal high-grade ores, in that they represent surface concentrations of the oxides from smaller percentages of the carbonates and silicates in the rocks below. deposits of this nature have been derived from a wide variety of parent rocks--from contact zones around igneous intrusions, from fissure veins of various origins, from calcareous and clayey sediments, and from slates and schists. the manganese and manganiferous iron ores of the cuyuna district of minnesota, the largest source of low-grade ores in this country, were formed by the action of weathering processes on sedimentary beds of manganese and iron carbonates constituting "iron formations." the process is the same as the concentration of lake superior iron ores described elsewhere. manganese, like iron, is less soluble than most of the rock constituents, and tends to remain in the outcrop under weathering conditions. to some extent also it is dissolved and reprecipitated, and is thus gathered into concretions and irregular nodular deposits in the residual clays. in some cases it is closely associated with iron minerals; in others, due to its slightly greater solubility, it has been separated from the iron and segregated into relatively pure masses. with manganese, as with iron, katamorphic processes are responsible for the concentration of most of the ores. the ores are in general surface products, and rarely extend to depths of over a hundred feet. chrome (or chromite) ores economic features the principal use of chrome ores is in the making of the alloy ferrochrome ( to per cent chromium), used for the manufacture of chrome, chrome-nickel, and other steels. these steels have great toughness and hardness, and are used for armor-plate, projectiles, high-speed cutting tools, automobile frames, safe-deposit vaults, and other purposes. chrome ore is used also both in the crude form and in the form of bricks for refractory linings in furnaces, chiefly open-hearth steel furnaces; and as the raw material for bichromates and other chemicals, which are used in paints and in tanning of leather. in the united states in normal times about per cent of the total chromite consumed is used in the manufacture of ferrochrome, and about per cent for bichromate manufacture, leaving per cent for refractory and other purposes. in the higher commercial grades of chrome ore the percentage of chromic oxide is to per cent, but under war conditions ore as low as per cent in cr_{ }o_{ } was mined. recovery of chrome from slags resulting from the smelting of chromiferous iron ores was one of the war-time developments. the principal chromite-producing countries in normal times are new caledonia, and rhodesia (controlled by french and british interests), and to a somewhat lesser extent russia and turkey (asia minor). small amounts of chromite are mined in greece, india, japan, and other countries. the indian deposits in particular are large and high-grade but have been handicapped by inadequate transportation. the production of chrome ore in new caledonia, rhodesia, russia, and turkey has usually amounted to more than per cent of the total world's production. the ore from new caledonia has been used by france, germany, england, and to some extent by the united states. rhodesian ore has been used by the united states and the principal european consumers. latterly more rhodesian ore has gone to europe and more caledonian ore to the united states. the russian ore has been in part used in russia and in part exported, probably going mainly to france and germany. the turkish ore has been exported to the united states, england, and germany; it probably supplied most of germany's chromite requirements during the war. during the war the united states was temporarily an important producer, as were also canada, brazil, cuba, and to a minor degree guatemala. the richest chrome ore mined at present comes from guatemala, but the mines are relatively inaccessible. the new caledonian, rhodesian, russian, turkish, and indian ores are also of high grade. the ores mined in the united states, canada, brazil, cuba, greece, and japan are of lower grade. the use of domestic chromite supplies in the united states presents much the same problem as does manganese. the ore bodies are small, scattered, and of a generally law grade. war-time experience showed that they could be made to meet a large part of the united states requirements, but at high cost and at the risk of early exhaustion of reserves. california and oregon are the principal sources, and incidental amounts have been produced in washington, wyoming, and some of the atlantic states. with the resumption of competition from foreign high-grade ores at the close of the war, the domestic mining industry was practically wiped out; the consequences being financial distress, partial direct relief from congress, and consideration of the possibilities of a protective tariff,--which in this case would have to be a large one to accomplish the desired results (see chapters xvii and xviii). geologic features the principal chrome mineral is chromite, an oxide of chromium and iron. chromite is a common minor constituent of basic igneous rocks of the peridotite and pyroxenite type. in these rocks it occurs both as disseminated grains, and as stringers, and large irregular masses which probably represent magmatic segregations. alteration, and weathering of the parent rock, forming first serpentine and then residual clays, make the chromite bodies progressively richer and more available, by leaching out the soluble constituents of the rock leaving the chromite as residual concentrates. all the important chromite deposits of the world are associated in somewhat this manner with serpentine or related rocks. they are formed in the same way as the lateritic iron ores of cuba, and from the same sort of rocks (pp. - ). chromite is very insoluble, and the mechanical breaking down of deposits and transportation by streams frequently forms placers of chrome sands and gravels. such placers have not been worked to any extent. katamorphic processes give the important values to chromite deposits. nickel ores economic features the principal use of nickel is in the manufacture of nickel steel, the most important of all alloy steels. ordinary nickel steels carry about - / per cent nickel. nickel is used in all gun and armor-plate steels, and in practically all other good steels except tool steels. it is also extensively alloyed with other metals, particularly with copper to form the strong non-corrosive metal (monel metal) used for ship propellers and like purposes. nickel is also used for electroplating, for nickel coins, for chemicals, etc. of the total production about per cent is used in steels, per cent in non-ferrous alloys and per cent in miscellaneous uses. the ores mined range from to per cent in metallic nickel. canada (sudbury, ontario) produces over three-fourths of the world's nickel and is likely to have an even greater share of the future production. the french supply from new caledonia is second in importance, and minor amounts are produced in norway and in several other countries. the control and movement of the canadian and new caledonian supplies are the salient features of the world nickel situation. nickel leaves the producing countries mostly as matte. canadian matte has been refined mainly in the united states, but the tendency is toward refining a larger proportion in canada. in europe there are refineries in france, england, belgium, germany, and norway, which normally treat the bulk of the new caledonian and some of the canadian production. small quantities of new caledonian matte or ore are also refined in japan, and during the war considerable amounts came to the united states. the united states now produces perhaps per cent of its normal requirements of nickel from domestic sources, principally as a by-product of copper refining. however, the united states has a large financial interest in the canadian deposits, and refines most of the matte produced from sudbury ores in a new jersey refinery. shipments to europe of canadian nickel refined in the united states have been a feature of the world's trade in the past. the nickel-bearing iron ores of cuba, consumed in the united states, constitute a potential nickel supply of some importance, if processes of preparation become commercially perfected. known supplies of nickel in canada and new caledonia are ample for a considerable future, and geologic conditions promise additional discoveries at least in the former field. the probable reserves of the sudbury district have been estimated to be fully , , tons, which would supply the world's normal pre-war requirements for about a hundred years. in recent years the british and canadian governments have taken an active interest in the nickel industry. they organized a joint commission for its investigation, the report[ ] of which furnishes the most comprehensive view of the world nickel situation yet available. the british government has directly invested in shares of the british-american nickel company, and has negotiated european contracts for sale of nickel for this company. the canadian government has exerted some pressure toward larger refining of nickel matte in canada. geologic features the principal ore minerals are the nickel sulphides and arsenides (particularly pentlandite, but also millerite, niccolite, and others), which are found at sudbury intergrown with the iron and copper sulphides, pyrrhotite and chalcopyrite; and the hydrated nickel-magnesium silicates (garnierite and genthite), which are products of weathering. the richer ores of canada contain about or per cent of nickel, the new caledonian ores less than per cent. the sudbury ores carry also an average of about . per cent of copper. nickel, while present in the average igneous rock in greater amounts than copper, lead, or zinc, is apparently not so readily concentrated in nature as the other metals and is rarely found in workable deposits. the few ore bodies known have been formed as the result of unusual segregation of the nickel in highly magnesian igneous rock of the norite or gabbro type, at the time of its solidification or soon after; and in some cases, in order to produce the nickel ore, still further concentration by the agency of weathering has been necessary. thus there are two main types of deposits. the first, the sulphide type, is represented by the great ore bodies of the sudbury district. these are situated in the basal portions of a great norite intrusive, and are ascribed to segregation of the sulphides as the rock solidified. to some extent the segregation was aided by mineralizing solutions following the crystallization of the magma, but in general there is little evidence that the ores were deposited from vagrant solutions of this kind (see pp. - ). these ores owe their value to primary concentration; secondary transportation and reprecipitation by surface waters has not been important. a small amount of the green arsenate, annabergite or "nickel bloom," has been developed by oxidation at the surface. the second, the garnierite or "lateritic" type of nickel ores, is somewhat more common and is represented by the deposits of new caledonia. in this locality the original rock is a peridotite, relatively low in nickel, which has been altered to serpentine. weathering has concentrated the more resistant nickel at the expense of the more soluble minerals, and has produced extensive blanket deposits of clay, which in their lower portions contain nickel in profitable amounts. similar processes, working on material of a somewhat different original composition, have produced the nickel-bearing and chrome-bearing iron ores of cuba (pp. - ). tungsten (wolfram) ores economic features the principal use of tungsten is in the making of high speed tool steels. it is added either as the powdered metal or in the form of ferrotungsten, an alloy containing to per cent of tungsten. tungsten is also used for filaments in incandescent lamps, and in contacts for internal combustion engines, being a substitute for platinum in the latter use. of late years tungsten alloys have also been used in valves of airplane and automobile engines. the average grade of tungsten ores mined in the united states is less than per cent of the metal; before smelting they are concentrated to an average grade of per cent tungsten oxide. germany through its smelting interests controlled the foreign tungsten situation prior to the war; two-thirds of its excess output of ferrotungsten was consumed by england and the balance principally by the united states and france. other consumers in the main satisfied their requirements by imports of tool steel from these four countries. the bulk of the tungsten ore consumed in europe prior to came from british possessions; these were principally the federated malay states, burma, australia, and new zealand. the united states, portugal, bolivia, japan, siam, argentina, and peru were also producers. the great demand for tungsten created by the war added china to the list of important producers and greatly increased the production from burma and bolivia. smelting works were established in england and those of the united states and france were greatly enlarged. england is at present in a position to dominate the world tungsten situation. the question of control of the ores obtainable in china, korea, siam, portugal, and western south america is likely to be an important one for the future. of the annual pre-war world production, the united states used about one-fifth. three-fourths of this requirement was met by domestic production. the balance was obtained by importation, chiefly from germany, from portugal and spain, and from england, both of concentrates and of ferrotungsten. to the considerable demand for high speed tool steels occasioned by munitions manufacture, production in the united states responded quickly. supplies of tungsten came chiefly from california, colorado, arizona, nevada, and south dakota. at the same time importation largely increased, chiefly from the west coast of south america and the orient. consumption reached a half of the world's total. considerable amounts of ferrotungsten were exported to the allies. the end of the war created a possible tungsten shortage in this country into a tungsten surplus. in so far as actual domestic consumption is concerned there has been a return to something like pre-war conditions, as the only known new use to which tungsten may be put--the manufacture of die steel--does not involve the use of any large amount of ferrotungsten. the richer mines of the two chief tungsten-producing districts in the united states have shown impoverishment and at present no important new deposits are known. the grade of the producing deposits is on an average low. the domestic production of tungsten ore will doubtless decrease, owing to the importation of cheaper foreign ores, unless a high tariff wall is erected. importation from the orient and the west coast of south america should continue in reduced amounts, depending upon the ability of domestic manufacturers to obtain and hold foreign markets for ferrotungsten and high speed tool steel. in the commercial control of tungsten ores the united states has at present a strong position, second only to that of england. geologic features tungsten ores contain tungsten principally in the form of the minerals scheelite (calcium tungstate), ferberite (iron tungstate), hübnerite (manganese tungstate), and wolframite (iron-manganese tungstate). all these minerals are relatively insoluble and have high specific gravity, and as a consequence they are frequently accumulated in placers, along with cassiterite and other stable, heavy minerals. a large part of the world's tungsten production in the past has been won from such deposits. placers are still important producers in china, siam, and bolivia, although in these countries vein deposits are also worked. with the exhaustion of the more easily worked placer deposits, increasing amounts of tungsten are being obtained from the primary or fixed deposits. these are found almost exclusively in association with granitic rocks, and have a variety of forms. the most productive deposits are in the form of veins, cutting the granites and the surrounding rocks into which the granites were intruded, and containing quartz, metallic sulphides, and in some cases minerals of tin, gold, and silver. the deposits of the two most important districts in the united states, in boulder county, colorado, and at atolia, california, are of this general nature. the close association of such deposits with plutonic igneous rocks, and the characteristic mineral associations (see pp. - ) suggest strongly that the deposits were formed by hot solutions deriving their material from a magmatic source. other tungsten deposits, which only recently became of importance, are of the contact-metamorphic type--in limestones which have been invaded by hot aqueous and gaseous solutions near the borders of granitic intrusions. in these occurrences the tungsten mineral is almost invariably scheelite, and is associated with calcite, garnet, pyroxene, and other silicates. a magmatic origin of the tungsten is probable. some of the deposits of the great basin area and of japan are of this nature, and it is believed that important deposits of this type may be discovered in many other countries. tungsten is likewise found in original segregations in igneous rocks and in pegmatite dikes, but these deposits are of comparatively small commercial importance. in some tungsten deposits a hydrated oxide called tungstite has been formed as a canary-yellow coating at the surface. on the whole, however, tungsten minerals are very resistant to weathering, and in all their deposits secondary concentration by chemical action at the surface has not played any appreciable part. the disappearance of tungsten minerals from alluvial materials which are undergoing laterization, which has been described in burma,[ ] seems to indicate that the tungsten is dissolved in surface waters to some extent; but in the main it is probably carried completely out of the vicinity and not reprecipitated below. molybdenum ores economic features the main use of molybdenum is in the manufacture of high-speed tool steels, in which it has been used as a partial or complete substitute for tungsten. its steel-hardening qualities are more effective than those of tungsten, but it is more difficult to control metallurgically. it has been used in piston rods and crank shafts for american airplanes. its use in tool steel is mainly confined to europe, where its metallurgical application is in a more advanced stage than in the united states. molybdenum is added to steel either as powdered molybdenum or in the form of ferromolybdenum, an alloy containing to per cent of the metal. molybdenum chemicals are essential reagents in iron and steel analysis and other analytical work; they are also used as pigments. molybdenum metal has been used to a small extent in incandescent lamps and as a substitute for platinum in electric contacts and resistances. molybdenum ores range from considerably less than per cent to about per cent in molybdenum. the world's principal sources of molybdenum ores in approximate order of importance are the united states, canada, norway, australia, korea, austria, peru, and mexico. about half of the world's supply is produced in the united states. production of molybdenum in this country practically began in . most of the production has come from colorado and arizona. it is believed that the united states contains reserves more than sufficient to meet any possible future demand. thus far the demand has not kept up with capacity for production. the principal consuming countries are england, france, and germany. geologic features the chief ore minerals are molybdenite (molybdenum sulphide) and wulfenite (lead molybdate). the larger part of the world's production is from the molybdenite ores. molybdenite occurs principally in association with granitic rocks,--in pegmatite dikes, in veins, and in contact-metamorphic deposits,--in all of which associations its origin is traced to hot solutions from the magma. it is frequently present as an accessory mineral in sulphide deposits containing ores of gold, copper, silver, lead, and zinc. at empire, colorado, one of the principal producing localities, it is found in veins, associated with pyrite, and filling the interstices between brecciated fragments of a wall rock composed of alaskite (an acid igneous rock). in molybdenite deposits secondary concentration has not been important. wulfenite is rather common in the upper oxidized zone of deposits which contain lead minerals and molybdenite. it is probably always secondary. deposits of wulfenite have been worked on a small scale in arizona. vanadium ores economic features vanadium is used mainly in steel, to which it gives great toughness and torsional strength. vanadium steels are used in locomotive tires, frames, and springs, in those parts of automobiles that must withstand special bending strains, in transmission shafts, and in general in forgings which must stand heavy wear and tear. vanadium is also used in high-speed tool steels, its use materially reducing the amount of tungsten necessary. it is added in the form of ferrovanadium, carrying to per cent of vanadium. another use of vanadium is in chrome-vanadium steels for armor-plate and automobiles. minor amounts are used in making bronzes, in medicine, and in dyeing. the low-grade ores of the united states range from to per cent of vanadium oxide, the general mean being nearer the lower figure. the high-grade ores of peru contain from about to as high as per cent of the oxide; the roasted ore as shipped averages about to per cent. two-thirds of the world's supply of vanadium comes from peru, where the mines are under american control. the concentrates are all shipped to the united states and some of the ferrovanadium is exported from this country to europe. the germans during the war supplied their needs for vanadium from the minette iron ores in the briey district in france, and presumably the french will in the future utilize this source. an unrecorded but small quantity is obtained by the english from lead-vanadate mines in south africa. there are some fairly large deposits of vanadium minerals in asiatic russia, which may ultimately become an important source. the united states supplies less than one-half of its normal needs of vanadium, from southwestern colorado and southeastern utah. the grade of these deposits is low and the quantity in sight does not seem to promise a long future. through its commercial control of the peruvian deposits, the united states dominates the world's vanadium situation. geologic features the minasragra vanadium deposit of peru contains patronite (vanadium sulphide) associated with a peculiar nickel-bearing sulphide and a black carbonaceous mineral called "quisqueite," in a lens-shaped body of unknown depth, enclosed by red shales and porphyry dikes. the origin is unknown. the patronite has altered at the surface to red and brown hydrated vanadium oxides. the deposits of colorado and utah are large lens-shaped bodies containing roscoelite (a vanadium-bearing mica) in fissures and brecciated zones and replacing the cementing materials of flat-lying sandstones. locally the sandstones contain as much as per cent of the roscoelite. the deposits contain small amounts of fossil wood which may have been an agent in the precipitation of the vanadium. there is considerable doubt as to their origin, but it is generally supposed that they represent concentrations by surface waters of minute quantities of material originally scattered through the surrounding sediments; it has also been suggested that certain igneous dikes in this region may have had some connection with the mineralization. deposits of carnotite, a potassium-uranium vanadate, which have been worked for their content of uranium and radium and from which vanadium has been obtained as a by-product, are found as impregnations of the sandstone in these same localities (p. ). there are other deposits containing small amounts of vanadium which are not at present available as ores. vanadinite, a lead-vanadate, and descloizite, a vanadate of copper or lead, are found in the oxide zones of a number of lead and copper deposits in the southwestern united states and mexico. titaniferous iron ores, extensive deposits of which are known in many places, usually contain a small percentage of vanadium. outside of the peruvian deposit, the affiliations of which are doubtful, the vanadium deposits of economic importance owe their positions and values mainly to the action of surface processes, rather than to igneous activity. zirconium ores economic features the oxides of zirconium have high refractory properties which make them useful for refractory bricks and shapes for furnace linings, for chemical ware, and for other heat, acid, and alkali resisting articles. for these purposes they find a limited market. experimental work seems to show possibilities of a very considerable use of zirconium as a steel alloy; indeed, results are so suggestive that during the war the government conducted an active campaign of investigation with a view to using it in ordnance and armor steel. for such purposes the alloy ferrozirconium is used, which carries to per cent zirconium metal. the principal known deposits of zirconium ores, in order of commercial importance, are in brazil, in india, and in the united states (pablo beach, florida). the brazilian and indian deposits are also the principal sources of monazite (pp. - ). the united states controls one of the important brazilian deposits. germany before the war controlled the indian deposits, and is reported to have taken much interest in the development of zirconium steels. during the war german influence in india was effectively broken up. the use of zirconium has been in an experimental state, and known sources of supply have been ample for all requirements. geologic features the zirconium silicate, zircon, is a fairly common accessory constituent of granitic rocks and pegmatite veins. from these rocks it is separated by weathering, disintegration, and stream transportation, and, having a high specific gravity, it becomes concentrated in placers. the deposits of southern india, of the coast of brazil, and of pablo beach, florida, all contain zircon along with ilmenite, garnet, rutile, monazite, and other insoluble, heavy minerals, in the sands of the ocean beaches. smaller deposits of zircon-bearing sands exist in rivers and beaches in other parts of the united states and in other countries, but none of these deposits has thus far proved to be of commercial importance. the largest and most important zirconium deposits are on a mountainous plateau in eastern brazil and are of a unique type, entirely different from those just described. they contain the natural zirconium oxide, baddeleyite or brazilite, mixed with the silicate, the ore as produced carrying about per cent zirconia (zro_{ }). the ores consist both of alluvial pebbles and of extensive deposits in place. the latter are associated with phonolite (igneous) rocks, and seem to owe their origin to the agency of hot mineralizing solutions from the igneous rocks. titanium ores economic features titanium is sometimes used in steel manufacture to take out occluded gases and thus to increase the strength and wearing qualities. its effect is to cure certain evils in the hardening of the molten steel, and it is not ordinarily added in amounts sufficient to form a definite steel alloy. aluminum is frequently used in place of titanium. titanium is added in the form of ferrotitanium, containing either about per cent titanium and to per cent carbon, or about per cent titanium and no carbon. titanium compounds are also used in pigments, as electrodes for arc-lights, and by the army and navy for making smoke-clouds. the united states has domestic supplies of titanium sufficient for all requirements. production has come chiefly from virginia. additional quantities have been imported from canada and norway. the recently developed deposits of pablo beach, florida, may produce important amounts of titanium minerals along with the output of zircon and monazite. geologic features the principal titanium minerals are rutile (titanium oxide) and ilmenite (iron titanate). these minerals are formed mainly under high temperatures, either during the original solidification of igneous rocks, or as constituents of the pegmatites which follow the crystallization of the main igneous masses. the virginia production comes from pegmatite dikes cutting through gabbros, syenites, and gneisses. the deposits contain rutile in amounts as high as per cent of the mass, but averaging or per cent, in addition to varying amounts of ilmenite. titaniferous magnetites, formed in many basic igneous rocks by the segregation of certain iron-bearing materials into irregular masses, contain large quantities of ilmenite which are not commercially available under present metallurgical processes. rutile and ilmenite both have high specific gravity and are little affected by weathering. consequently they are not decomposed at the surface, but when carried away and subjected to the sorting action of streams and waves, they form placer deposits. both of these minerals are recovered from the sands at pablo beach, florida. magnesite economic features the most important use of magnesite is as a refractory material for lining furnaces and converters. it is also used in the manufacture of sorel cement for stucco and flooring, in making paper, in fire-resisting paint, in heat insulation, and as a source for carbon dioxide. small amounts are used in epsom salts and other chemicals. as taken from the ground the ore consists principally of the mineral magnesite or magnesium carbonate, with minor impurities ( to per cent) of lime, iron, silica, and alumina. in making magnesite bricks, it is calcined or "dead-burned" to drive out the carbon dioxide. austria-hungary and greece are the large european producers of magnesite and scotland supplies a little. most of the european production is consumed in england and the central european countries, but part has been sent to america. outside the united states there are american supplies in canada, and recent developments in venezuela and mexico (lower california). magnesite is produced in considerable quantities in the united states, in california and washington. some material is imported from canada, and a small amount comes from scotland as return cargo for ballast purposes. before the war only about per cent of the united states requirements of magnesite were met by domestic production. the country was practically dependent on imports from various european countries; chiefly from austria-hungary and greece the austrian magnesite (controlled in large part by american capital) was considered especially desirable for lining open-hearth steel furnaces, because of the presence of a small percentage of iron which made the material slightly more fusible than the pure mineral. when the shipments from this source were discontinued during the war and prices rose to a high figure, experiments were made with american magnesite, and the deposits on the pacific coast were developed on a large scale. a process of treatment was perfected by which the washington magnesite was made as desirable for lining furnaces as the austrian material. at the same time large amounts were imported from canada and venezuela and lesser amounts from lower california. under the high prices which prevailed during the war, dolomite was to some extent substituted for magnesite. dolomite, which may be thought of as a magnesite rock high in lime, occurs in large quantities close to many points of consumption. it is cheaper but less satisfactory than magnesite, and is not likely to be used on any large scale. while the united states has undoubtedly sufficient reserves of magnesite to supply the domestic demands for many years, the mines are far from the centers of consumption and it is expensive to transport the material. since the war, magnesite shipped from canada and overseas has again replaced the american product in the eastern market to some extent. the canadian magnesite is of lower grade than the domestic and european magnesite and is consequently less desirable. deposits in venezuela are also expected to furnish some material for the eastern furnaces, in competition with those of austria and greece. austrian magnesite, however, will be likely to dominate the market in the future if delivered at anything like pre-war prices. this situation has led to agitation for a protective tariff on magnesite. geologic features magnesite, as noted above, is the name of a mineral, the composition of which is magnesium carbonate. the principal magnesite deposits are of two types, of different modes of origin and of somewhat different physical characteristics. the large magnesite deposits of austria and of washington, as well as those of quebec, occur as lenses in beds of dolomite (calcium-magnesium carbonate). they are in fairly close proximity to igneous rocks, and magnesia-bearing solutions issuing from these rocks are believed to have dissolved out the calcium carbonate of the dolomite and replaced it with magnesium carbonate. in these deposits the material is coarsely crystalline and forms fairly large, continuous bodies, which are worked by quarrying. the washington deposits closely resemble marble, and had sometimes been mistaken for that rock until war-time needs resulted in their more thorough investigation. the commoner type of magnesite deposits is represented by those of greece, california, venezuela, and many other countries. these consist of veins and replacements in serpentine. the original rock was a highly magnesian igneous rock of the peridotite type, which is very unstable under weathering conditions, and rapidly alters to serpentine. magnesite is formed both by this process and by the further breaking down of the serpentine itself. the processes are those of katamorphism. under these circumstances the magnesite is characteristically fine-grained or massive, and occurs in veins, lenses, and irregular bodies in cavities and fractured zones. it is usually worked by open cuts. magnesite is also reported to occur in sedimentary beds in which it was primarily deposited in its present form and has not undergone later alteration. such deposits are not important commercially. fluorspar economic features the chief use of fluorspar is as a flux in the manufacture of open-hearth steel. minor uses are in chemical and enameling industries, in the smelting of copper, lead, and iron, and in the manufacture of the ferro-alloys in the electric furnace. in order to be used in steel-making, the fluorspar after being concentrated should contain at least per cent calcium fluoride and less than per cent silica. chemical and enameling industries require material with to per cent calcium fluoride and less than per cent silica. the chief foreign producer of fluorspar is great britain, and much of this product comes to the united states. canada produces a small amount, some of which also comes to the united states. several thousand tons are produced yearly in germany and france, and are largely consumed there. the production of fluorspar in the united states is several times that of any other country. the ore mined comes principally from the southern illinois and western kentucky field, and is used largely for fluxing purposes in open-hearth steel furnaces. minor amounts are produced in colorado, new mexico, and other states. the united states has sufficient supplies of fluorspar to meet all its own demands for this material. small amounts, however, are imported for use in eastern furnaces because the material can be brought over from england very cheaply. the domestic fluorspar is suitable for practically all purposes for which fluorspar is used except for lenses in optical instruments. for this use very small quantities of material imported from japan have been used, but recently fluorspar of a grade suitable for optical purposes has been found in illinois, kentucky, new hampshire, and other states. for fluxing purposes domestic fluorspar is superior to the foreign product. geologic features fluorspar is the trade name for the mineral fluorite, which is composed of calcium fluoride. this is a common mineral in veins and replacements which carry ores of zinc, lead, silver, gold, copper, and tin. it is formed under a variety of conditions, but is always ascribed to solutions coming from nearby igneous rocks. the large fluorspar deposits of illinois and kentucky contain fluorite with calcite, barite, and metallic sulphides, in wide veins filling fissures in limestones and sandstones and replacing the fissure walls. into these sediments there are intruded certain peridotite dikes. the fluorite and associated minerals were probably deposited by hot solutions bringing the material from some large underlying igneous mass of which the dikes are off-shoots. in the western united states many metalliferous deposits carry large amounts of fluorite, which is treated as a gangue or waste mineral, but which could be profitably extracted if there were local markets. in england, fluorite is obtained in this manner as a by-product from lead and zinc mines. silica economic features silicon and its oxide, silica, find important applications in the manufacture of iron and steel. silicon, like manganese, is an important constituent of many steels, the alloy ferrosilicon being added to deoxidize and purify the metal and thus to increase its tensile strength. like titanium, it is added chiefly for its curative effect rather than as a useful ingredient. on an average pounds of to per cent ferrosilicon are used in the united states for each ton of steel produced. a higher grade of ferrosilicon ( to per cent) is used for certain special steels, and during the war considerable quantities were used in making hydrogen gas for balloons. lower grades ( to per cent silicon) are practically a high silicon pig iron. silica has an important use in the form of silica brick or "ganister" for lining furnaces and converters in which acid slags are formed. for this purpose siliceous rocks, chiefly quartzites and sandstones, are ground up, mixed with lime as a binder, and fused and pressed into bricks and shapes. for the most satisfactory results the rock should contain per cent or more of silica, and very little of the alkali materials, which increase the fusibility. in addition to its applications to the iron and steel industry, silica finds an almost universal use in a wide variety of structural and manufacturing operations. the extensive use of sand and gravel--composed chiefly of silica--for road materials and railway ballast is well known. in construction work silica is used in the form of stone, sand-lime brick, cement, mortar, concrete, etc. large quantities of sand, or silica, are used for molds in foundries, for abrasives, for the manufacture of glass, for filters, and for a great variety of other purposes which readily suggest themselves (see pp. , ). for most uses of silica there are local supplies available. for certain purposes requiring material of a particular chemical composition or texture, however, satisfactory deposits are known in only a few places. for example, the material for silica refractories is obtained in the united states chiefly from certain regions in pennsylvania, missouri, and wisconsin. the united states has ample domestic supplies of silica for practically all requirements. ferrosilicon of the higher grades is manufactured principally in electric furnaces at niagara falls. the capacity is ample to meet all demands, but cheap ferrosilicon from canada also enters united states markets. geologic features silicon and oxygen, making up the compound silica, are the two most abundant elements in the earth's crust, and quartz (sio_ ) is a very abundant mineral. the processes of weathering and transportation everywhere operative on the surface of the earth tend to separate quartz from other materials, and to concentrate it into deposits of sand. katamorphism is primarily responsible for most of the deposits of silica which are commercially used. anamorphism--cementing and hardening the sands into sandstones and quartzites--has created additional value for certain uses, as in refractories, building stones, and abrasives (see pp. , ). footnotes: [ ] report of the royal ontario nickel commission. printed by order of the legislative assembly of ontario, toronto, . [ ] campbell, j. morrow, tungsten deposits of burma and their origin, _econ. geol._, vol. , , p. . chapter x copper, lead, and zinc minerals copper ores economic features the electrical industry is the largest consumer of copper. the manufacture of brass, bronze, and other copper alloys constitutes another chief use for the metal. considerable quantities of copper sheets, tubes, and other wares are used outside of the electrical industry, as for instance in roofing, plumbing, and ship bottoms. copper is also used in coinage, particularly in china, where it is the money standard of the working population. the average grade of all copper ores mined in the united states in recent years has been about . per cent metallic copper. ores containing as low as . per cent have been mined in the lake superior country, and bonanza deposits containing to per cent have been found and worked in some places, notably in alaska and wyoming. the lower-grade ores, carrying to per cent copper, are usually concentrated before smelting, while the richer ores, carrying to per cent or more, are generally smelted direct. many of the ores contain values in gold and silver, and also in lead and zinc. an average of about c. worth of gold and silver per ton is obtained from all the copper ores of the united states. in other countries the average grade of copper ores mined is somewhat higher than in the united states,--where large scale operations, particularly the use of steam-shovel methods on extensive bodies of disseminated or "porphyry" copper ores, as well as improvements in concentrating and metallurgical processes, have made possible the use of low-grade ore. the principal sources of copper are the north american continent, chile and peru, japan, south and central africa, australia, and spain and portugal. smaller quantities are produced in russia, germany, norway, cuba, serbia, and a number of other countries. the united states normally produces nearly two-thirds of the world's copper and consumes only about one-third. in addition the great bulk of the south american, mexican, and canadian crude copper comes to the united states for refining. through financial interests abroad and by means of refining facilities, the united states controls a quantity of foreign production which, together with the domestic production, gives it control of about per cent of the world's copper. no other country produces one-sixth as much copper as the united states. england, because of production in the british empire (mainly africa and australia) and british financial control of production in various foreign countries, is not dependent upon the united states for supplies of raw copper. japan, spain, portugal, and norway are able to produce from local mines enough copper for their own needs and for export. but france, italy, russia, germany, and the rest of europe normally are dependent upon foreign sources, chiefly the united states. south america, mexico, canada, africa, and australia are exporters of copper. the control of these countries over their production in each case is political and not financial, except in the case of canada, where about half the financial control is also canadian. it is in these countries and in spain that the united states and england have financial control of a large copper supply. before the war german interests had a considerable control over the american copper industry through close working arrangements with electrolytic refineries. germany was the largest foreign consumer of copper, and german companies bought large quantities of the raw copper in the united states, canada, mexico, and south america, had it refined, and sold the finished material in both the american and foreign markets. during the war this control was broken up. in view of the importance of copper metal as a raw material, particularly in the electrical industry, the strength of the united states in copper as a key resource ranks even above its control of petroleum. in the united states in recent years about per cent of the annual production of copper has come from arizona, chiefly from the bisbee, globe, ray-miami, jerome, and morenci-metcalf districts; about per cent has come from the butte district of montana; about to per cent from keweenaw point, michigan; and about per cent from bingham, utah. from to per cent of the country's output comes from each of the states of new mexico, nevada, alaska, and california. all other states together produce only a little over per cent of the total. the so-called "porphyry" coppers in utah, arizona, nevada, and new mexico, described below, are the source of about per cent of the present production of the united states. the deep mines of butte and michigan are responsible for about per cent of the production, and the ore bodies of arizona (other than porphyry) and of alaska produce about per cent. reserves of copper ore are such as to give no immediate concern about shortage, nor to indicate any large shift in the distribution of production in the near future. development is on the whole considerably in advance of present demands. the principal measured reserves are in the so-called porphyry coppers of the united states and chile. in the united states the life of these reserves now estimated is approximately years. the reserves of the chile copper company are the largest of any known copper deposit in the world, and the braden copper reserve (also in chile) is among the largest. for the deep mines of the united states, the developed reserves have a life of perhaps only five years, but for most of these mines the life will be greatly extended by further and deeper development. the porphyry coppers, because of their occurrence near the surface and the ease with which they may be explored by drilling, disclose their reserves far in advance. the deep mines are ordinarily developed for only a few years in advance of production. geologic features the principal copper minerals may be classified into the sulphide group, the oxide group, and native copper. native copper, mined in the lake superior region, is the source of to per cent of the world's copper supply. the oxide group of minerals--including the copper carbonates, azurite and malachite; the silicate, chrysocolla; the oxide, cuprite; the sulphates, chalcanthite and brochantite; and some native copper associated with these minerals--probably supplies another per cent. the remaining per cent is derived from the sulphide group. of the sulphide group by far the most important mineral is chalcocite (cuprous sulphide), which supplies the bulk of the values in the majority of the mining camps of the western hemisphere. locally, as at butte, enargite (copper-arsenic sulphide) is of great value. other minerals of considerable importance in some districts are chalcopyrite and bornite (copper-iron sulphides), tetrahedrite (copper-antimony sulphide), and covellite (cupric sulphide). very commonly the copper sulphides are associated with large quantities of the iron sulphide, pyrite, as well as with varying amounts of lead and zinc sulphides and gold and silver minerals. the principal copper ores originate in the earlier stages of the metamorphic cycle, in close association with igneous activity. katamorphism or weathering, in place, has played an important part in enriching them. the processes of transportation and sedimentary deposition, which have done so much toward making valuable iron ore deposits, have contributed little to the formation of copper ores. =copper deposits associated with igneous flows.= the copper ores of the lake superior district, and of a few small deposits in the eastern united states, contain small percentages of native copper in pre-cambrian volcanic flows or in sediments between the flows. the ore bodies have the form of long sheets parallel to the bedding, the copper and associated minerals filling amygdaloidal openings and small fissures in the flows, and replacing conglomeratic sediments which lie between the flows. the copper was probably deposited by hot solutions related to the igneous rocks, either issuing from the magmas or deriving heat and dissolved material from them. secondary concentration has not been important. there is practically none of it near the present erosion surface; but it appears in one part of the district near an older erosion surface covered by cambrian sediments, suggesting a different climatic condition at that time. the kennecott copper deposits of alaska have a number of resemblances to the lake superior copper deposits, suggesting similarity in origin. the kennecott deposits occur exclusively in limestone, which rests conformably on a tilted surface of igneous flows ("greenstones") not unlike those of lake superior. the flows carry native copper and copper sulphides in minutely disseminated form and in amygdules, but apparently not in quantities sufficiently concentrated to mine. the flows are supposed to be the original source of the copper now in the limestone. the primary copper mineral in the limestone is chalcocite, in exceptionally rich and solid masses, showing no evidence of having replaced earlier sulphides. it is regarded as a product of primary deposition, under the influence of hot solutions related in some way to the igneous flows; but whether the solutions were magmatic, originating in the lavas or below, or whether they were meteoric waters rendered hot by contact with the extrusives, and thereby made effective in leaching copper from them, is not clear. the oxidation of the kennecott copper ores is not extensive. it presents an interesting feature, in that since glacial time the ground has been frozen and the moisture is now present in the form of ice. the oxidation clearly took place before glacial time. abundant fragments of both the oxide and the sulphide ores are mined from the lateral moraine of a nearby glacier. this is a good illustration of the cyclic nature of secondary concentration which is coming to be recognized in so many camps. the boleo copper deposits of lower california occur in volcanic tuffs and associated conglomerates of tertiary age. they have certain peculiar mineralogic associations--the ores containing large quantities of all the common copper oxide minerals, and a number of rare oxide minerals of copper, lead, silver, and cobalt, together with gypsum, sulphur, and much iron and manganese oxide. the copper oxides and carbonates are in places gathered into rounded concretions called "boleos" (balls). sulphides are present in the lowest beds and may represent the form in which the copper was originally deposited. the copper-bearing beds have been much silicified, and it has been suggested that mineralization was accomplished by hot-spring waters, probably of igneous origin. these deposits have a few marked similarities to the lake superior copper ores. =copper veins in igneous rocks.= a second group of copper ores in igneous rocks is made up of deposits in distinct fissure veins and as replacements along such veins. the chief deposits of this type are at butte, montana--which is, from the standpoint of both past and present production, the greatest single copper district in the world. here a large batholith of tertiary granite was intruded by porphyry dikes; and faulting, accompanying and following the intrusions of the dikes, developed numerous fissures. the fissures were mineralized with copper sulphides and arsenides, iron sulphides, and locally with zinc sulphide and manganese carbonate,--all in a matrix of quartz. at the same time the wall rocks were extensively mineralized and altered; the fissure veins grade off into the wall rock, and in fact the larger part of the ore is simply altered granite with disseminated sulphides. the solutions which deposited the ores are inferred to have been hot from the nature of the wall-rock alterations, from the presence of hot-water minerals like fluorite, cassiterite, and others, and from the general association of the ores in time and place with the porphyry intrusions. the solutions are believed to have originated from the porphyry and possibly from other intrusives. in the butte district, and in the great majority of copper sulphide vein ores throughout the world, secondary concentration by surface waters has played a considerable part in developing ores of commercial value. near the surface the copper is leached out and carried down by waters containing various solvents, particularly sulphuric acid from the oxidation of pyrite. a leached zone is formed containing the ordinary products of rock weathering,--rusty quartz and clay, sometimes black with manganese oxides. a small part of the copper remains in this zone as oxides, carbonates, and silicates. below the oxidized and leached zone there is evidence of deposition of a large amount of secondary copper sulphide in the form of chalcocite. this is supposed to have been formed by the leaching of copper from above as soluble copper sulphate, and its precipitation below by iron and other sulphide minerals which the solutions meet on their downward course--a reaction which has been demonstrated experimentally. it was formerly supposed that most of the chalcocite was of this origin; but as chalcocite is found in important amounts with enargite and chalcopyrite to great depths (now , feet), where the veins are still rich and strong, it begins to appear that much of the chalcocite is of primary origin. the fissures along which the butte ores occur are in three main sets, which in order of age strike roughly east-west, northwest-southeast, and northeast-southwest. two-thirds of the ore is in the first set, about per cent in the second, and the remainder in the third. the mineralization of the several vein systems cannot be discriminated, and it is thought that it was accomplished as a more or less continuous and progressive process. there is some evidence, also, that the fracturing in the several fracture systems was likewise a nearly continuous progressive process, contemporaneous with the ore deposition, and perhaps developing under a single great shear which caused more or less simultaneous and overlapping systems of fractures in the various directions. ="porphyry coppers."= another type of copper deposits in igneous rocks is the disseminated or "porphyry" deposits. the term "porphyry" as commonly used includes true porphyries, monzonites, granites, and other igneous rocks. ores of this type are represented by the great deposits of bingham, utah; ray, miami, and the new cornelia mine of arizona; ely, nevada; santa rita, new mexico; cananea, sonora, mexico; northern chile; and many other districts of importance. they form the greatest known reserves of copper ore. these deposits contain copper minerals, usually in the marginal portions of acid porphyries, in many irregular, closely spaced veins, and in minute seams and spots disseminated through the mass of the rock. in the ray and miami and other districts the mineralization has spread largely through adjacent schists, but these deposits are included with the porphyry copper deposits in commercial parlance. the porphyry deposits are of an undulating blanket form of considerable areal extent and shallow depth. at the surface is a leached and weathered zone, often containing more or less of the oxides, carbonates, and silicates of copper, ranging in thickness up to , feet, but averaging feet or less. below this is a zone carrying copper in the form of chalcopyrite, enriched by chalcocite deposition from above, ranging in thickness up to feet. the ore in this zone varies from one-half of per cent to per cent of copper and ordinarily averages between and per cent. the use of ore of this grade is made possible by the large quantities and by the cheap and efficient mining and metallurgical practices. the ore body grades below into a zone characterized by lean chalcopyrite, which is supposed to represent original or primary deposition from hot waters associated with the porphyry intrusion. this primary ore, or protore, was clearly formed after the solidification of the igneous rocks, though soon after, by solutions from igneous sources which followed fractured and shattered zones. =copper in limestone near igneous contacts.= another great group of copper deposits occurs as replacements of limestone adjacent to porphyry or granitic intrusives. this type is illustrated by some of the deposits at bingham, utah, and at bisbee, arizona. the primary deposition was of chalcopyrite and other copper sulphides, together with garnet, diopside, and other minerals known to have required high temperature in their formation. the ore fills fissures and replaces extensive masses of the limestone. it is likely to show a fairly sharp contact on the side toward the intrusive, and to grade off into the country rock on the other side with numerous embayments and irregularities. these deposits have been enriched by weathering in the same manner as indicated above for the porphyry coppers, but to highly varying degrees. in the bisbee deposits large values were found in the weathered zone, and secondary sulphide enrichment below this zone is also important. in the bingham camp, on the other hand, the weathered zone is insignificant and most of the ore beneath is primary. the weathering of the silicated limestone gangue results in great masses of clay which are characteristic features of the oxide zones of these deposits. =copper deposits in schists.= other copper deposits, as at jerome, arizona, in the foothill and shasta county districts of california, at ducktown, tennessee, etc., are irregular lenticular bodies in schists and other rocks, but all show relationship to igneous rocks. the rio tinto ores of spain and portugal, which belong in this group, have been referred to on page . in the jerome or verde district of central arizona, folded pre-cambrian greenstones and sediments were invaded by masses of quartz-porphyry, and after further deformation, rendering many of the rocks schistose, were intruded by an augite-diorite. contact metamorphism along both the quartz-porphyry and the diorite contacts was practically lacking. the ore bodies were formed as irregular pipe-like replacements of the schists, being localized in one case by a steeply pitching inverted trough of impervious diorite, and in other cases by shear zones which favored vigorous circulation. a later series of small diorite or andesite dikes cut the ore bodies. the primary ores consist of pyrite, chalcopyrite, and other sulphides, with large amounts of jaspery quartz and some calcite and dolomite. they were clearly formed by replacement of the schists particle by particle, as shown by the frequent preservation of the schist structure in a banding of the sulphide minerals, the residual shreds of unreplaced schist material in the ores, and the usual gradual transition from unreplaced schists to those completely replaced by massive sulphides. the localization of the most important mineralization in an inverted trough is good evidence that the solutions came from below, and the nature of the mineral associations suggests an origin through the work of hot waters associated with igneous intrusives. the diorite, being most closely related in time and space with the ore bodies, seems the most logical source of the ore materials. secondary concentration of the jerome ores has proceeded along the general lines previously outlined (pp. - , ). here again the evidence is clear that the ores were concentrated in an earlier period, in this case in pre-cambrian times, probably during the long interval required for the base-leveling of the pre-cambrian mountains. since cambrian times the deposits have been for the most part buried by later sediments. some of the deposits are still protected by this overlying blanket and mining has not yet reached the zone of altogether primary sulphides. others have been faulted up and again exposed by erosion; but since being uncovered, steep slopes and rapid erosion have apparently favored the scattering of the copper rather than its concentration and enrichment. in the united verde mine, oxidizing conditions at present prevail to the bottom of the chalcocite zone. the very large reserves of the katanga copper belt of the belgian congo are in the form of tabular masses in schistose and highly metamorphosed paleozoic sediments. the ore bodies are roughly parallel to the bedding, but in instances follow the schistosity which cuts across the bedding. they consist dominantly of the oxide minerals, though in several ore bodies sulphides have been shown by diamond-drilling. the ores have a high content of cobalt and also carry precious metals. the origin of the deposits is not known, but has been ascribed to granitic masses intrusive into the schists. =sedimentary copper deposits.= in the later phases of the metamorphic cycle, the agencies of transportation (in solution) and sedimentary deposition have resulted in some low-grade deposits of copper sulphides in sedimentary rocks. deposits of this type are found in the rocky mountain region, where they are referred to as the "red beds" coppers, but are of no commercial importance. similar deposits in germany, the mansfield copper-bearing shales, have been worked for some time, and during the war were germany's main source of copper. on keweenaw point, michigan, deposits of native copper formed in this manner in the "nonesuch" beds have been worked on a commercial scale. other copper ores on keweenaw point are replacements of conglomerate beds between igneous flows, and are of a different origin already described (p. ). while much of the copper of sedimentary beds gives evidence that it was deposited from solution in cracks and as replacements of the wall rocks, often through the agency of abundant organic material in the beds, and while also comparatively little of this copper can be identified as having been deposited in detrital flakes or fragments along with the other mineral fragments, there is, nevertheless, considerable evidence that some of these deposits were formed essentially during the sedimentation of the enclosing beds and as incidents to this process. such evidence consists of a close limitation of the copper to certain beds, its wide and uniform distribution within these beds, its absence in similar beds near at hand, the absence of evidence of feeding and escape channels of the kind which would be necessary in case the solutions were introduced long afterward, and often a minute participation of the copper minerals in the minor structures of bedding, false-bedding, and ripple-marks, which would be difficult to explain as due to secondary concentration. the corocoro copper deposits of bolivia occur in beds of sandstone with no igneous rocks in the vicinity. however, they are all closely associated with a fault plane, igneous rocks occur at distances of a few miles, and the general mineralization is coextensive with the belt of igneous rocks; the deposits are therefore ascribed to a magmatic source rather than to sedimentary processes. toward the surface the copper is in part in the form of sulphides, somewhat altered to oxide minerals, and farther down it is entirely native copper, associated with gypsum. this is the only district outside of lake superior where native copper has been mined on an important scale. =general comments.= in general, the commercially prominent copper deposits show a close relationship to igneous rocks in place, time, and origin. seldom do the ores extend more than , feet away from the igneous rock. the common downward order in sulphide deposits is: first, a weathered zone, originally formed mainly above the water table, consisting above of a leached portion and below of oxides and carbonates of copper in a gangue of quartz or clay; second, a zone of secondary sulphide enrichment, characterized by chalcocite coatings, chalcopyrite, and pyrite, with a gangue of quartz and igneous rock or limestone; and third, a zone of primary deposition with similar gangue, characterized by chalcopyrite, and at butte by enargite and chalcocite. the oxide zone as a whole may be rich or lean in values, depending on the nature of the associated gangue material and country rock. when these are more soluble than the copper--as is commonly the case in limestone--the copper may be residually concentrated, notwithstanding the fact that much copper originally present has been carried off in solution. when the associated gangue and country rock are less soluble than the copper--as is common with quartz and igneous rocks--the oxide zone is likely to be depleted of values. the zones formed by weathering and secondary enrichment are extremely irregular, both in distribution and depth, in any one deposit, and they overlap and grade into one another in a very complex fashion. in many places the primary zone is too lean to be mined to commercial advantage; but in other places, as at butte, and in the limestone deposits of bingham, the primary ores are of considerable importance. when evidence of secondary sulphide enrichment was first recognized there was a tendency to magnify its effectiveness, and to assume that in most cases the values were due to this process; that the primary zones would be found to be valueless. in recent years the emphasis is being somewhat changed because of the recognizing in many camps of rich primary zones. while some chalcocite is clearly the result of secondary enrichment from above, other chalcocite seems to have been related closely to the primary deposition. the quantitative discrimination of the two is a matter of great difficulty. it has come to be recognized that the zonal arrangement caused by enrichment from the surface has been imposed usually on a zonal arrangement caused by the primary hot solutions and not related to the surface but to the source of the solutions. in some districts, as illustrated by butte and bingham, the copper-bearing minerals seem to have been deposited nearest the igneous source, while the lead, zinc, gold, and silver minerals have been deposited farther away,--suggesting the cooling of the solutions with increasing distance from the igneous source. the further investigation of this primary zonal arrangement promises interesting results with a practical bearing on exploration and development. one of the newer features of the investigation of copper deposits has been the recognition of the cyclic nature of the secondary concentration. this process has been related not only to the present erosion surface, but to older surfaces now partly buried under later rocks. ransome's[ ] summary of conditions at the ray-miami camp has a somewhat general application. supergene enrichment has generally been treated as a continuously progressive process. there is considerable probability, however, that it is essentially cyclic, although the cyclic character may not be patent in all deposits. a full development of the cycle can take place only under a certain equilibrium of a number of factors, including climate, erosion, topography, and character of rock. the essential fact appears to be that as enrichment progresses and chalcocite increases the process of enrichment becomes slower in action, and erosion may, in some circumstances, overtake it. with the removal of some of the protecting zone of chalcocite the protore is again exposed to oxidation and a second cycle of enrichment begins. although much of the enriched ore is now below ground-water level, it probably was once above that level, and enrichment is believed to have taken place mainly in the zone of rock above any general water table. where the old erosion surface roughly coincides with the present erosion surface, the deposits follow more or less the topography. where the old erosion surface pitches below later sediments, the ores pitch with it, and therefore do not follow the present topography. the recognition of the cyclic nature of secondary concentration is obviously of great significance in exploration and development. although a vast amount of study has been devoted to the origin and enrichment of copper deposits, and although the general conditions and processes are pretty well understood, the results thus far have been largely qualitative rather than quantitative. lead ores economic features the most prominent uses of lead are in the manufacture of alloys, such as type-metal, bearing metal, shot, solder, and casting metal; as the oxide, red lead, and the basic carbonate, white lead, in paints; for lead pipe, cable coverings, and containers of acid active material; and in lead compounds for various chemical and medical uses. of the lead consumed in the united states before the war about per cent was utilized in pigments, per cent in alloys other than shot, per cent in pipe, per cent in shot, and per cent in all other uses. during the war much larger quantities were used in munitions, such as shot and shrapnel. the lead content of commercial ores varies widely. it ranges from as low as . per cent in the joplin district of missouri, to about per cent in the broken hill deposits of australia, and over per cent in the bawdwin mines of burma. in the coeur d'alene district of idaho and the southeastern district of missouri, the two greatest lead producers in the united states, the average grades are about per cent and about - / per cent respectively. the grade of ore which may be profitably worked depends not only upon the economic factors,--such as nearness to consuming centers, and the price of lead,--but also upon the amenability of the ore to concentration, the content of other valuable metals, and the fact that lead is very useful in smelting as a collector of gold and silver. most lead ores contain more or less zinc, and lead is obtained as a by-product of most zinc ores. argentiferous lead ores form one of the principal sources of silver, and also yield some gold. lead and copper are produced together from certain ores. thus the separation of many ores into hard and fast classes, as lead, or zinc, or copper, or silver, or gold ores, cannot be made; in some of the mineral resource reports of the united states geological survey the statistics of these five metals are published together. the main sources of lead ore, named in order of their importance, are the united states, australia, spain, germany, and mexico, which account for over per cent of the world's production. most of the countries of europe outside of spain and germany produce small amounts of lead, but are largely dependent on imports. spain exports argentiferous lead and pig lead mainly to england and france, with minor quantities to other countries of europe and to argentina. before the war germany, which was the largest european consumer, utilized all its own production of lead ores and imported an additional per cent of the world's ores for smelting, as well as considerable amounts of pig lead. its principal deposits were those of silesia; under the peace treaty they may possibly be lost to poland, leaving german smelters largely dependent on imports. australia before the war normally shipped lead concentrates and pig lead to england and also to belgium, germany, and japan. england, the second largest european consumer, before the war had insufficient smelting capacity within the british empire and was partly dependent on foreign-smelted lead. during the war, however, england contracted for the entire australian output, and enlarged its smelting capacity accordingly. this may mean permanent loss to belgium, which had depended mainly on the australian ores for its smelting industry before the war. in north africa there is a small but steady production of lead, most of which goes to france. recent developments in burma have shown large reserves of high-grade lead-zinc-silver-copper ores, and this region may be expected to become an important producer. there are also large reserves of lead in the altai mountains of southwestern siberia and in the andes mountains of south america. england, through control of australian and burman lead mines and smelters, domestic smelting facilities, and some financial control in spain, mexico, and elsewhere, and france, through financial control of spanish and north african mines and spanish, belgian, and domestic smelters, have adequate supplies of lead. the united states produces about a third of the world's lead and twice as much as any other country. normally the domestic production is almost entirely consumed in this country. mexico sends large quantities of bullion and ore to the united states to be smelted and refined in bond. mexican lead refined and exported by the united states equals in amount one-sixth of the domestic production. small quantities of ore or bullion from canada, africa, and south america are also brought into the united states for treatment. through domestic production, smelting facilities for mexican ore, and commercial ownership in mexico and elsewhere, the united states controls over per cent of the world's lead production. before the war germany, through the "lead convention" or international sales association, and through smelting and selling contracts with large producing mines, practically controlled the european lead market as well as exports from mexico and the united states and from australia. during the war german foreign influence was practically destroyed. in the united states about a third of the production of lead comes from southeastern missouri and about a fourth from the coeur d'alene district of idaho. the five states, missouri, idaho, utah, colorado and oklahoma, produce about nine-tenths of the country's total output. reserves of lead ore are not large in proportion to demand, contrasting in this regard with zinc ore. geologic features the principal lead mineral is the sulphide, galena, from which the great bulk of the world's lead is derived. cerussite (lead carbonate) and anglesite (lead sulphate) are mined in some places in the upper part of sulphide deposits, and supply a small fraction of the world's output. the ores of lead are of two general classes: the first class, the so-called "soft" lead ores, nearly free from copper and precious metals, and commonly associated with zinc ores, are found in sedimentary beds independent of igneous intrusion. they are of world-wide distribution, were the first to be extensively exploited, were at one time the dominant factor in world production of lead, and at present produce about per cent of the world's total. they are represented by the deposits of the mississippi valley, of silesia, and some of the spanish deposits. the general description of the origin of the zinc ores of the mississippi valley on pp. - applies to this class of lead ores. it should be noted, however, that in the principal united states lead-producing district, that of southeastern missouri, the lead ores occur almost to the exclusion of the zinc ores, and are more disseminated through the limestone than is characteristic of the zinc ores. ores of this type have been found extending only to shallow depths (not over a few hundred feet), and because of the absence of precious metals their treatment is comparatively simple. the second class consists of ores more complex in nature, which are found in association with igneous rocks, and which usually contain some or all of the metals, zinc, silver, gold, copper, iron, manganese, antimony, bismuth, and rare metals, with various gangue minerals among which quartz, siderite, and silicates are important. today these ores are the source of about per cent of the world's lead. they are represented by the lead deposits of the rocky mountain region (coeur d'alene, idaho; leadville, colorado; bingham, utah; etc.); of broken hill, new south wales; of burma; and of many other places. they are all related to the earlier stages of the metamorphic cycle and occur in close genetic association with igneous activity. they include deposits in the body of igneous rocks,--in the form of well-defined veins, replacements along zones of fissuring and shearing, and disseminated masses,--as well as veins and replacements in the rocks, particularly in limestones, adjoining igneous intrusions. the deposits present a wide variety of shapes depending on the courses of the solutions by which they were formed. the materials of the ore minerals are believed to have been derived from the igneous rocks and to have been deposited by hot solutions. the source of the solutions--whether magmatic or meteoric--presents the same problems which have been discussed elsewhere (pp. - ). the ores are frequently mined to great depths. because of their complexity they require involved processes of treatment to separate out the values. ores of this nature have already been referred to in the discussion of the copper ores of bingham and butte, and will be referred to in connection with the zinc-lead-silver ores of leadville, colorado. special reference may be made here to the coeur d'alene district of idaho, which is the second largest producer of lead in the united states. the coeur d'alene deposits are almost unique in that they contain galena as vein-fillings and replacements in quartzite, with a gangue of siderite (iron carbonate). quartzite (instead of limestone) is an unusual locus of replacement ores, and siderite is an unusual gangue. these ores are believed to owe their origin to acid igneous intrusives, because of the close association of the ores with some of these intrusives, and because of the content of high-temperature minerals. some of the ore bodies are found far from intrusives, but it is supposed that in such cases further underground development may disclose the intrusives below the surface. secondary concentration has been insignificant. in general, weathering of lead ores at the surface and secondary sulphide enrichment below are not so extensive as in the case of copper and zinc. galena is fairly stable in the oxide zone, and even in moist climates it is found in the outcrop of many veins. weathering removes the more soluble materials and concentrates the lead sulphide with the residual clay and other gangue. in some districts cerussite and a little anglesite are also found in the oxide zone. the carrying down of lead in solution and its deposition below the water table as a secondary sulphide is not proved on any extensive scale. in this respect it contrasts with zinc; and when the two minerals occur together, lead is likely to be more abundant in the oxide zone, and zinc in the sulphide zone below. such a change in composition with depth is also found in some cases as the result of primary vertical variations in the mineralization. zinc ores economic features zinc metal has commonly gone under the name of "spelter." brass and galvanized iron contain zinc as an essential ingredient. of the total united states zinc consumption in normal times, about per cent is used in galvanizing iron and steel objects to protect them from rust, per cent is used in the manufacture of brass and other alloys, per cent goes into the form of rolled sheets for roofing, plumbing, etc., per cent is employed in desilverizing lead bullion, and the remaining per cent is used for pigments, electrodes, and other miscellaneous purposes. during the war the use in brass-making was greatly increased. the zinc content of the ores mined today ranges from a little over - / per cent in the joplin district of missouri, to per cent and higher in some of the deposits of the coeur d'alene and other western camps, and over per cent in certain bonanzas in british columbia and russia. the ores usually contain both zinc and lead in varying proportions, and sometimes gold, silver, and copper are present. of the zinc produced in the united states, about per cent is obtained from ores containing zinc as the principal element of value, about per cent from zinc-lead ores, and per cent from copper-zinc and other ores. the average grade of the straight zinc ores is about - / per cent. of the world's zinc ore, the united states produces in normal times about one-third, germany about one-fifth, australia about per cent, italy, north africa and spain each about per cent. the remaining to per cent comes from a large number of scattered sources, including japan, east asia, norway and sweden, canada, mexico, austria, france, greece, siberia, and russia. in the near future the bawdwin mines of burma will probably be increasingly important producers. large reserves of zinc also exist in the altai mountains of southwestern siberia, and in the cordilleran region of south america. in short, zinc is one of the most widely distributed of metallic resources; there is consequently less necessity for great international movements than in the case of many other commodities. the smelting of zinc concentrates is in general carried on close to the points of consumption and where skilled labor is available, rather than at the mines,--although smelters to handle part of the output have recently been built in australia and in burma. in europe the great smelting countries have been germany and belgium, and to a lesser extent england and france. before the war these four countries with the united states produced over nine-tenths of the world's spelter. belgium did principally a custom business, and a large part of its exports went to england. australian and tasmanian zinc ores were the basis of the belgian and english smelting industries, and also supplied about one-third of the german requirements. since the war england has contracted to take practically the entire australian output. this fact, in connection with war-time destruction of belgian smelters, leaves the future of the belgian zinc industry in some doubt. germany may possibly lose to poland its richest zinc mines, those of silesia. german activity in the rich deposits of mexico is to be expected. france controls the deposits of north africa and satisfies a considerable part of its requirements from that source. smaller movements of zinc include exports from italy to england, and a complex interchange among the lesser producers of europe. english and french zinc-smelting capacity was expanded during the war, and the industry in these countries is in a strong position. japan also developed a considerable smelting industry during the war, importing ores from eastern asia and australia. the united states normally smelts and consumes all its large production of zinc ores and does not enter foreign markets to any extent. small amounts of zinc concentrates are brought in from mexico and canada to be smelted in bond. during the war,--when the allies were cut off by enemy operations from the customary belgian and german supplies of spelter, and by shortage of ships from australian zinc ores,--australian, spanish, italian, and other ores were imported into the united states, and large quantities of spelter were exported from this country to europe. mine and smelter capacities were greatly increased, over-production ensued, and with the cessation of hostilities many plants were obliged to curtail or cease operations. the united states has now about per cent of the zinc-smelting capacity of the world. for the present at least the capacity is far in excess of the domestic requirements. before the war german control of the international zinc market was even stronger than in the case of lead. the german zinc syndicate, through its affiliations, joint share-holdings, ownership of mines and smelters, and especially through smelting and selling contracts, controlled directly one-half of the world's output of zinc and three-fourths of the european production. it regulated the australian exports by means of long-term contracts, and had considerable influence in the united states. to some extent it was able to so manipulate the market that zinc outside the syndicate was also indirectly controlled. during the war political jurisdiction was used by the allied countries to destroy this german influence. in the united states the principal zinc-producing regions are the joplin and adjacent districts of missouri, oklahoma, kansas, and arkansas, furnishing about one-third of the country's output; the franklin furnace district of new jersey, and the butte district of montana, each yielding about one-sixth of the total supply; and the upper mississippi valley district of wisconsin, iowa, and illinois, the leadville district of colorado, and the coeur d'alene district of idaho, each producing between one-tenth and one-twentieth of the total. smaller quantities are produced in tennessee, new mexico, nevada, and several other states. reserves of zinc are ample for the future. they are now developed considerably in advance of probable requirements, a fact which causes keen competition for markets and renders zinc-mining more or less sensitive to market changes. geologic features the most important mineral of zinc is the sulphide, sphalerite or "zinc blende." the minerals of the oxide zone are smithsonite (zinc carbonate) and calamine (hydrous zinc silicate), which yield minor amounts of zinc and are especially productive at leadville, colorado. zincite (zinc oxide) and willemite (zinc silicate) are the important minerals in the deposits of franklin furnace, new jersey. the association of most deposits of zinc with more or less lead has been noted. the ores of zinc are of two general classes, corresponding to the two classes of lead ores (pp. - ). zinc ores of the first type are in veins and replacements in sedimentary rocks at shallow depths, independent of igneous association, and are supposed to have been formed by cold solutions. they are found in the mississippi valley, in silesia, and in many of the smaller european deposits. they were formerly the leading zinc-producers, and now produce about per cent of the world's total. zinc ores of the second type consist of veins and replacements related to intrusive rocks, sometimes extending to considerable depths, and of more complex composition. they include most of the deposits of the american cordilleran region (butte, coeur d'alene, leadville, etc.), of franklin furnace, of australia, of burma, and of many other places. the zinc-lead ores of the type found in the mississippi valley are of special interest, in that they are sulphide ores of an origin apparently independent of igneous agencies. these ores occur as fissure-fillings and replacements, mainly in nearly flat-lying paleozoic limestones and dolomites--the bonne terre dolomitic limestone of southeastern missouri, the boone formation of southwestern missouri and oklahoma, the galena dolomite of wisconsin and illinois. they are variously associated with a gangue of dolomite, calcite, quartz, iron pyrite, barite, and chert. not infrequently they are spread out both in sheets and in disseminated form along carbonaceous layers within or at the base of the limestone. the source of the primary sulphides has been a subject of much discussion. all are agreed that they were first deposited with the sediments in minutely dispersed form, through the agency of the organic contents of the sediments, and that such deposition was somewhat generally localized by estuarine conditions which favored the accumulation of organic remains. many years ago, before the evidence of estuarine deposition was recognized, chamberlin suggested an ingenious hypothesis for the northern mississippi valley,--that the organic material had been localized by ocean's currents forming something in the nature of a sargasso sea. differences of opinion become acute, however, when the attempt is made to name the precise sedimentary horizon, out of several available horizons, in which for the most part this primary concentration occurred. judging from the organic contents of the several beds, the primary source may have been below, within, or above the present ore-bearing horizons. if the ore came from the lower horizons, it was introduced into its present situation by an artesian circulation, for which the structural conditions are favorable. if the ore was derived from overlying horizons, downward moving solutions accompanying erosion did the work. if the primary source was within the horizon of present occurrence of the ores, both upward and downward moving waters may have modified and transported them locally. for each of these hypotheses a plausible case can be made; but much of the evidence can be used interchangeably for any one of them. in spite of the wealth of data available, it is astonishingly difficult to arrive at a conclusion which is exclusive of other possibilities. without attempting to argue the matter in detail the writer merely records his view, based on some familiarity with these districts, that, on the whole, the evidence favors the accumulation of these deposits by downward moving meteoric solutions during the weathering of overlying strata; but that it is by no means certain that a part of the ores has not been derived from lower horizons. the great area of the producing districts in comparison with their depth, the uniform association of the ore-bearing zone with the surface regardless of geologic horizon uncovered by erosion, the failure of the ores to extend in quantity under cappings of later formations, and the known efficacy of oxidizing waters in local downward transfers of zinc and lead, seem to suggest concentrating agencies which are clearly related to surface conditions. it is of interest to note that in many places in the limestones of missouri and virginia, and elsewhere in the paleozoic rocks, there are sinks of limonite and clay near the surface, which are likewise believed to have originated through downward movement of waters deriving their mineral contents from the erosion and stripping of overlying sediments. still further, the primary deposition of clinton iron ores in many parts of the mississippi valley and eastward to the appalachians took place in stratigraphic horizons not far removed from the horizons of lead and zinc deposition. when the peculiar conditions controlling the deposition of the clinton ores are understood (see pp. - ) it is entirely possible that they may throw some light on the genesis of the lead and zinc ores. since the ores were introduced into essentially their present locations, secondary concentration has produced an oxide zone of clay, chert, and iron oxide, with varying amounts of zinc carbonate, zinc silicate, lead sulphide, and rarely lead carbonate. this zone is obviously developed above water level, and is seldom as much as feet thick. zinc, and to a less extent lead, have been taken into solution as sulphates, with the aid of sulphuric acid resulting from the oxidation of the associated pyrite. zinc has been carried away from the weathered zone in solution faster than lead, leaving the lead more or less concentrated near the surface. some of the zinc carried down has been redeposited secondarily as zinc sulphide. evidences of this secondary sulphide enrichment can be seen in many places; yet certain broad quantitative considerations raise a doubt as to whether this process has been responsible for the main portion of the values of the sulphide zone. if downward secondary enrichment had been a dominant process, it might be expected that the ores would be richer in places where erosion had cut away more than half the limestone formation carrying the ore, than in places where it had barely cut into the formation. this is not the fact,--which suggests that erosion in its downward progress has carried a large part of the zinc completely out of the vicinity. zinc ores of this same general character are also found in paleozoic rocks (knox dolomite) in virginia and tennessee. their manner of occurrence suggests the same problem of origin as in missouri and wisconsin, but no decisive evidence of their source has been discovered. of the zinc ores associated with igneous intrusions, those of the butte and coeur d'alene districts are described in connection with copper and lead ores on pp. - , , and - . zinc constitutes about per cent by weight of the recoverable metals of the leadville district of colorado. about two-thirds of the zinc occurs as the sulphide and about one-third as the carbonate resulting from weathering of the sulphide. the zinc sulphide is associated with lead, iron, and copper sulphides and gold and silver minerals. in the oxide zone the zinc carbonate is associated with oxides and carbonates of various metals, including those of lead, copper, iron, and manganese. the iron and manganese oxides are mined in considerable tonnage as a flux. it is an interesting fact that, although mining has been carried on in this district for upwards of forty years, only within the last decade has the existence of zinc ores in the oxide zone been recognized. this has been due largely to the fact that the iron and manganese oxides effectively stain and mask the zinc carbonate. the leadville ores occur as replacements and vein-fillings in a gently faulted and folded carboniferous limestone, in deposits of a general tabular shape, parallel to the bedding but with very irregular lower surfaces. the limestone is intruded by numerous sheets of porphyry, mainly parallel to the bedding but sometimes cutting across it, against the under sides of which most of the ore occurs. the primary sulphides are believed to be genetically related in some fashion to these porphyries. the older view was that the agents of deposition were aqueous solutions from the surface above, which derived their mineral content chiefly from the porphyries. later views favor solutions coming directly from the porphyries or deeper igneous sources. while in form and association these ores are characteristic igneous contact deposits, they lack the high-temperature silicates which are so distinctive of many ores of this type. the zinc ores of franklin furnace, new jersey, belong in the group associated with igneous agencies, but have certain unique features. they consist of willemite and zincite, together with large amounts of franklinite (an iron-manganese oxide) and silicates, in a pre-cambrian white crystalline limestone near its contact with a coarse-grained granite-gneiss. the origin of the ores is obscured by later shearing and metamorphism, but it seems best explained by replacement of the limestone by heated solutions coming from the granitic mass. the view has also been advanced that the ores originated in the limestone before the advent of the igneous rocks. secondary concentration is not apparent. footnotes: [ ] ransome, frederick leslie, the copper deposits of ray and miami, arizona: _prof. paper , u.s. geol. survey_, , pp. - . chapter xi gold, silver, and platinum minerals gold ores economic features the principal and most essential use of gold is as a standard of value and a medium of exchange. gold has been prized since the earliest times because of its luster, color, malleability, and indestructibility, and has long been used as a trading medium. at present little of the metal is actually circulated from hand to hand. stocks of gold, however, accumulated by governments and banking interests, form the essential foundation of paper currency and of the vast modern system of credit relations. in the settlement of international trade balances considerable quantities of gold frequently move from debtor to creditor nations. although the amounts thus shipped are frequently great in value, they are very small in volume. it is interesting to note that the entire accumulated gold stocks of the world's governments--about nine billion dollars--cast in a solid block, with the horizontal dimensions of the washington monument, would be only about feet high. other uses of gold are in dentistry, and in the arts for jewelry, gilding, and other forms of ornamentation. consumption for these purposes has been increasing of late years and now takes a third or more of the world's annual production. in the united states, before war-time restrictions were adopted, the consumption for jewelry and similar uses exceeded the consumption in coinage. since the war it has exceeded the total domestic production of gold. an interesting problem for the future is how an adequate supply of gold is to be distributed between monetary uses and the arts. the curve of increase in the requirements of the arts indicates that, unless there is greatly increased production, all the world's gold will be necessary for the arts in a comparatively few years. to retain it for monetary purposes would require government restrictions. of all the mineral commodities, gold has played perhaps the most important and certainly the most romantic part in the world's history. the "lure of gold" has taken men to the remotest corners of the globe. it has been the moving force in the settlement and colonization of new countries, in numerous wars, and in many other strenuous activities of the human race. about two-thirds of the annual gold production of the world comes from the british empire--from south and west africa, australasia, canada, and india. a single colony, the transvaal, produces about per cent of the world's total. british capital, which seems to have a particular affinity for investments in gold mines, controls not only the larger part of the output from the colonies, but also important mines in siberia, mexico, south america, and the united states. russia, mexico, and japan have small gold production. the chief deposits of russia are those of siberia, which have had an important output and have apparent great possibilities of increase. other foreign districts are numerous and widely scattered, but, with the exception of colombia and korea, no one of them yields per cent of the world's gold. french interests control about a tenth of the production of the transvaal, and minor supplies in mexico and south america--in all about per cent of the world's production. germany and austria control less than per cent of the total gold production. german interests formerly had extensive holdings in south africa and australia, but during the war this control was eliminated. the united states, the second largest gold-producing country, supplies about per cent of the world's total. commercially it controls production of another per cent in foreign countries, chiefly in canada, mexico, south america, and korea. about one-fourth of the united states production comes from california. other producing states in order of importance are colorado, alaska, south dakota, nevada, arizona, montana, and utah. these eight states supply per cent of the country's output, and most of the remainder is obtained from other western states. international movements of gold depend chiefly upon its use in the settlement of trade balances, and are not governed by the considerations which control ordinary mineral commodities. imports and exports vary with changing foreign trade balances. large amounts of gold normally go to london, because great britain requires all gold produced in the colonies to be sent to england; but since england ordinarily has an unfavorable balance of trade, much of this gold is reëxported. the united states up to a few years ago was also a debtor nation, and more gold was exported than was imported. during the war, however, this country became the greatest of the creditor nations and imports of gold, chiefly from europe, were several times the exports. the total world's gold production up to has been upwards of billions of dollars, of which about billions have gone into the arts or been hidden and lost, leaving billions in monetary reserve. at the present writing the united states government holds an unusually large fraction of the world's gold reserve, about per cent or billion dollars,--an amount equal to two-thirds of the aggregate production of the united states to date. other large stocks of gold are held, in order, by great britain, france, and russia, these three with the united states holding over a half of the world's total gold reserve. germany has about - / per cent of the total reserve, and, with its tremendous debt and no sources of new production, is of course in a particularly unfavorable position. the total amount of gold now ( ) accounted for by governments as money is not more than per cent of the value of the notes and currency issued against this gold. before the war it was per cent. in the united states the pre-war percentage was - / per cent. since the war it has been per cent. the ratio of gold to currency is now so small that the gold standard is hardly a physical fact, but is to be regarded rather more as a profession of faith. notwithstanding the recent falling off in gold production, an increment of approximately million dollars is potentially available each year to be added to the gold reserves. whether this increment, or a larger increment which may come from new discoveries, is sufficient to maintain a reasonable proportion between gold stocks and the necessary normal increase in paper currency, has been, and doubtless will continue to be, a subject of vigorous discussion and speculation. during and immediately following the war, the gold production of the world showed rather an alarming progressive decrease. about the group of three greatest producers--south africa, united states, and australia,--reached the acme of its production, and output then fell off. simultaneously there was a marked decrease of production in many of the less important districts. this general decline was due in considerable part to the fact that during the war the price of gold was fixed and its use restricted to monetary purposes. the price of gold, which is itself the standard of value, could not rise to offset growing mining costs and to maintain profits, as was the case with iron, copper, and the other metals,--with the result that the margin of profit in gold mining became so small as materially to affect exploration and production. another important cause of decreased production was the actual exhaustion of certain mines, and the lowering of the grades of ore available in many others. new discoveries did not supply these deficiencies. in the united states, for instance, physical conditions of one kind or another were responsible for lessening of production from alaska, cripple creek, and california. minor causes included conflicts in california between agricultural and mining interests over water rights, and a succession of dry seasons which did not afford enough water for the working of placers; and in alaska difficulties due to litigation over the oil-flotation process of recovering gold from its ores. as a result of all these conditions, many of the smaller mines were closed down, others continued operations only by curtailing exploration and by mining solely the richest and most accessible ore bodies, and there was a general discouragement and lack of inducement to engage in gold mining. the gold situation has become a matter of great concern to the various governments, since national financial stability and the confidence of the public in the national credit are based largely upon the acquirement of an adequate gold reserve. both in england and in the united states, committees of experts have been appointed to make exhaustive investigations and present recommendations for measures to stimulate production. the report of the joint committee from the united states bureau of mines and geological survey gives a comprehensive review of the conditions in the gold-mining industry.[ ] during the war there was vigorous demand by gold miners both in the united states and south africa for a bonus on gold. these demands received serious consideration on the part of the governments, but were denied on the general ground of the doubtful adequacy of such a measure to meet the situation, and the danger of upsetting the gold standard of value. in the united states, for instance, a bonus of $ per ounce was asked for. it did not appear likely that this could increase the annual production from the united states by more than per cent, in face of the physical conditions being met in gold mining. the bonus would have had to be paid on all the gold mined, which would make the increment of production very expensive; to secure an added production of ten million dollars would have cost in the neighborhood of forty millions. ten millions is only one-third of per cent of the gold reserve already held by this country, and it would obviously have taken a long time for this small increase in annual production to make itself felt in the size of the gold reserves. since the war gold has gone to a considerable premium in england, due to the action of the british government in establishing a "free" market,--that is, abandoning the restriction that gold marketed in london should be offered to the government or the bank of england at the fixed statutory price for monetary purposes. with the pound sterling at a considerable discount outside of england, other countries could afford to bid, in terms of british currency, far above the british mint price. the result is that the south african miner of gold receives a premium due to depreciation of sterling exchange, while the american miner still receives the regular mint price. the agitation for a bonus therefore continues in the united states. however, with the removal of war-time restrictions gold has been allowed to go to the arts, the demand from which is already equal to one-third of the world's gold production, is rapidly increasing, and is temporarily acute due to the accumulation of requirements resulting from war restrictions. this situation has a general tendency to improve the position of the gold miner, though the outlook is still far from bright. it is an interesting fact that india is absorbing a good half of the free gold. india, in regard to its demand for precious metals and stones, has been described as "an abyss from which there is no return." this is an important contributing cause of the shortage of gold in the rest of the world. looking forward to the future, it seems that increased exploration, which is resulting from the present premium on gold, is likely to bring in new reserves to increase production. because of lack of important discoveries in recent years, there is pessimism in some quarters as to the possibilities of large increase of production; but, considering the history of gold discoveries, and the amount of ground still to be explored both areally and vertically, this pessimism does not seem to be wholly justified from the geologic standpoint. curves representing the world's gold production in past years show periods of increasing annual production as new fields are discovered, followed by periods of decreasing production when no new ore bodies are coming in to replace dwindling reserves. it is entirely possible that in recent years the gold-mining industry has been merely in one of these temporary stagnant periods. there are many regions, both in the vicinity of worked-out lodes and in unsettled and poorly explored countries, where gold may still be discovered; there may be far greater resources of this metal still covered up than all those which man has thus far uncovered. a single new deposit or district may make a great difference in the world's production, as suggested by the experience of the past. regions which are especially attractive for exploration and the discovery of new deposits are in siberia and south america, which in the opinion of many engineers may eventually rival south africa. mexico, with the establishment of a stable government, should also have a greatly increased production. geologic features the principal gold mineral is native or metallic gold. this occurs in nature in small scales, crystals, and irregular masses, and also in microscopic particles mechanically mixed with pyrite and other sulphides. chemically, gold is very inactive and combines with but few other elements. a small part of the world's supply is obtained from the gold-silver tellurides--calaverite, sylvanite, krennerite, and petzite. gold deposits are of two general classes--placers, and veins or lodes. placers, which are in general the more easily discovered and more easily worked deposits, have in the past been the chief source of the world's gold supply. it is estimated that in the first twenty-seven years of the modern era of gold-mining, beginning with the discovery of gold in california in , per cent of the world's production was obtained from placers. at present the placers of recent geologic age supply a tenth to a fifth of the gold, and ancient or fossil placers in the transvaal supply another two-fifths. in the united states about a fourth of the gold production comes from placers, mainly from california and alaska. placers are detrital or fragmental sediments containing the ore in mechanical fragments, which are derived from the erosion and transportation of solid-rock veins or lodes, sometimes called the "mother lode." during the process of transportation and deposition there is more or less sorting, because of differing density of the mineral fragments, resulting in the segregation or concentration of the ore minerals in certain layers or channels. gold, because of its weight, tends to work down toward bedrock, or into scoured or excavated portions of stream channels. in a few cases it is carried in some quantity to the sea and concentrated in beach sands. the processes are not unlike the mechanical concentration of ores by crushing and water sorting. seldom, however, do the processes go far enough in nature to produce an ore which can be used directly without some further mechanical sorting. ore minerals concentrated in placers are those which resist abrasion and chemical solution during the processes of weathering and transportation, and which have a density sufficiently high so that they are partially sorted out and concentrated from the accompanying quartz and other minerals. to warrant their recovery they must also be of such high intrinsic value that it pays to mine small quantities. the most important of such minerals are gold, tin, platinum, and the precious stones. iron, copper, lead, and zinc minerals are often somewhat concentrated as placers, but their intrinsic value is not high enough to warrant the attempt to recover them in the large amounts necessary to make them commercially available. placers are forming now and have formed at all stages of the earth's history. early placers may be reworked and further concentrated by renewal of the proper erosional and transportational conditions. old placers may be buried beneath younger rocks, cemented, and more or less recrystallized. "fossil" placers of this kind are best represented by deposits in the black hills of south dakota and probably by the south african gold deposits. in the witwatersrand deposits of south africa, the gold is concentrated in the lower parts of large conglomerate and quartz sand layers of great areal extent. pebbles of the conglomerate are mainly quartz and quartzite. the gold, in particles hardly visible to the eye, is in a sandy matrix and is associated with chloritoid, sericite, calcite, graphite, and other minerals. the origin of the gold deposits of this district is not entirely agreed on, but the evidence seems on the whole to favor their placer origin. some investigators of these ores believe them to have been introduced into the conglomerate and sand by later solutions, possibly by hot solutions related to certain diabase intrusions that cut the beds. in the vein or lode or hard-rock deposits, the gold is mainly metallic gold, and to a minor extent is in the form of gold tellurides. it is usually closely associated with iron pyrite in a matrix or gangue of quartz. seldom is a gold deposit free from important values in other minerals. about per cent of the gold mined in vein or lode deposits of the united states is associated with silver minerals, the combined value averaging about $ per ton; about per cent comes from copper ores which have an average yield of gold and silver of c. per ton; and per cent comes from zinc and lead ores, with an average gold and silver yield ranging from $ to $ per ton. the geologic occurrence of gold in the copper, lead, and zinc ores has already been referred to in the discussions of these ores. reference will be made here only to the vein deposits in which gold, with silver, constitutes the principal values. because of their common gangue of quartz these are often called "dry" or "siliceous" ores. their principal occurrence is in distinct fissure veins in igneous rocks, with more or less replacement of the wall rock. the igneous rocks are commonly acid intrusives of a granite or porphyry type, less commonly intrusives of gabbro and diabase and surface lavas of rhyolite and basalt. in a few cases the ores are contact-metamorphic deposits of the type described under copper ores. in still rarer cases they are in pegmatites. gold is commonly associated with minerals and wall-rock alterations indicating deposition by hot solutions, which are inferred to have come from the igneous rocks. because of the resistant nature both of ore minerals and gangue, weathering and secondary concentration have had little effect in enriching gold deposits. so far as there has been any noticeable effect on the gold content of the ores, it has been due to the leaching out of other constituents, principally pyrite and other sulphides, leaving the gold present in slightly larger proportions. locally there is evidence of solution of gold in weathered zones and its deposition in the sulphide zones below. solution is believed to be accomplished by chloride solutions, and is favored by the presence of manganese which delays precipitation. the precipitating agent below may be ferrous sulphate, various sulphides, native metals, or organic matter. of the vein or lode gold ores in the united states some of the most productive and best known have the following geologic features: the california gold belt extends north and south along the west slope of the sierra nevada mountains. the ore is in a series of parallel and overlapping veins striking with the trend of the range, associated with granodiorite intrusives in schist and slate. there is no pronounced secondary concentration. these deposits are the source of most of the great placer deposits of california, hence the name "mother lode" applied to a part of them. the principal ore deposits are somewhat removed from the main mass of intrusive which forms the crest of the sierra nevada range, and are more closely related to the smaller similar intrusive masses farther down the slope. the gangue is mainly quartz. at juneau, alaska, great dikes of albite-diorite intrude greenstones and schists, and low-grade gold ores occur in shattered portions of the diorite. these ores were mined on a great scale at the treadwell mine. another famous low-grade deposit is the homestake mine in the black hills of south dakota, where pre-cambrian slates and schists of sedimentary origin are impregnated with gold, associated with quartz, dolomite, calcite, pyrite, and other minerals. the origin is supposed to have some connection with intrusives into the schists; but the relations of the ores to intrusives, both in age and in place, present many puzzling questions which make conclusion as to origin very difficult. in the cripple creek district of colorado, a volcanic neck two or three miles in diameter breaks through pre-cambrian granites, gneisses, and schists. the volcanic rocks consist mainly of tuffs and breccias cut by basic dikes. the ore bodies are in fissures and sheeted zones, principally in the granitic rocks, but associated with these dikes. the ore is mainly gold telluride, in a gangue of quartz together with pyrite and a variety of minerals characteristic of hot-water solutions. also the wall rocks have the characteristic hot-water alterations. there is slight enrichment near the surface. at goldfield, nevada, native gold is found in surface igneous flows of a dacite type, which have undergone extensive hydrothermal alterations characterized by the development of alunite (a potassium-aluminum sulphate), quartz, and pyrite. the ore fills fissures to some extent, but is mainly a replacement of the wall rock. association with typical hot-water minerals and hydrothermal alterations of the wall rock are again believed to indicate the origin of the ores through ascending hot solutions from a deep source. one of the interesting features of this occurrence is the abundance of alunite. sulphate minerals are commonly formed by oxidizing solutions. the abundant presence, therefore, of a sulphate mineral with minerals of a primary deep-seated source has led to much discussion of origin. the hypothesis was developed that these minerals result from the interaction of deep-seated sulphide-bearing solutions with surface oxidizing solutions.[ ] it may be noted that in recent years other sulphate minerals have been occasionally regarded as primary, including gypsum, anhydrite, barite, and others. it has been suggested that if igneous emanations contain free oxygen and sulphur, or sulphur dioxide, it would be expected that as they become cool sulphur trioxide would be formed which would result in the sulphate at suitable temperature.[ ] other deposits containing gold are discussed in connection with silver on following pages. silver ores economic features silver has two important uses--in money and in the arts. as money, it is used in the united states and europe for subsidiary coinage,--silver coins normally circulating at more than their intrinsic value,--but its greatest monetary use is in india and china, where it has been the basis for the settlement of foreign exchange balances. in china also it is the money standard of the country. in the arts, silver is employed chiefly in the making of articles of luxury, such as jewelry and tableware. in the orient this use is closely related to its use as money, since the natives invest their savings both in silver jewelry and silver coins. there is some consumption of silver by certain chemical industries, and quantities of increasing importance are used in the form of silver salts by the photographic and moving picture industries. it has been estimated that before about two-thirds of the new silver produced went into the arts and one-third into money. during the war, however, increasing amounts were used in coinage, and less than one-fifth of the output was used in the arts. demands for silver for monetary purposes will probably continue to take the larger part of the world's production for some time. in this connection it may be noted that india has adopted a gold standard, but that the conservative habits of the population will doubtless continue to call for large amounts of silver. about half of the silver production of the world comes from the dry or siliceous silver ores, which are mined solely for that metal and the associated gold; and about half of the production is obtained as a by-product in the mining of other metals, principally copper and lead. the average grades of these ores, in combined values of gold and silver, were referred to on p. . while the aggregate amount of silver obtained as a by-product of other ores is large, the percentage of silver in the copper or lead in any mine is ordinarily very small. consequently the world output of silver depends to a considerable extent upon conditions in the copper- and lead-mining industries. of the total world output of silver, normally about per cent comes from north america. of this the united states and mexico each produce about two-fifths and canada one-fifth, and minor amounts are produced in central america. in late years, political disturbances in mexico reduced that country's production to less than half the normal figure, and the united states took the place which mexico had held for many years as the leading silver producer. the united states and mexican supply is obtained from the rocky mountain belt, and the canadian production comes chiefly from the cobalt, ontario, district. outside of north america the principal producing areas are australia, south america (peru and to a less extent bolivia and chile), europe (chiefly from spain, germany, and austria-hungary, but with smaller amounts from all the other countries), and japan. thus, while there are sources of silver in many places, the great bulk of the world's output comes from north america. in the financial ownership of mines, including ownership in other countries, the united states controls over half the world's silver, great britain about a third, and germany about a tenth (principally in mexico). all the silver mined in the united states is smelted and refined by domestic plants; and in addition much of the canadian, mexican, and south and central american silver is exported to the united states as ore and base bullion, to be treated in this country. the united states is therefore the great silver-selling country of the world. the great silver-consuming countries are india and china, and normally about a half of the world's output goes to these two countries. this major movement of silver, from america to the far east, takes place through the london market, since england has been the chief nation trading in the orient. the balance of the world's silver consumption is widely distributed among the countries of europe and south america and the united states (which consumes about one-tenth of the total). for the european trade most of the silver also goes through london, which is the great clearing-house and the market where prices are fixed. in the later years of the war and immediately after, the demands for silver were probably twice the world's output. the resulting rise in price was unprecedented. silver actually became worth more as bullion than as currency, and in europe much trouble was experienced because of its withdrawal from currency to be melted up. this condition was later followed by an equally striking drop in price as supply caught up with demand. in the united states, as in many other countries, it was desired during the war to accumulate large stocks of gold as a basis of credit for the flotation of government loans, and the export of gold was prohibited. consequently in the settlement of foreign trade balances, particularly with the nations of the orient, very large amounts of silver bullion had to be used. current production proved inadequate, and it was necessary to utilize the stocks of silver dollars in the united states treasury. to this end the pittman silver act, passed in april, , authorized the melting down and conversion into bullion of , , dollars out of the treasury stock, and the retirement of a corresponding number of silver certificates and the issue of federal reserve bank notes. in this manner old stocks of silver, manila dollars, etc., were called into service--though the stage was not reached, as it was in germany, where it became necessary to melt down silver plate and ornaments. the silver used for exchange and export was to be replaced by the purchase of bullion from american producers at $ per ounce, and its coining into new dollars. a minimum price of $ per ounce was thus established for silver bullion. the immediate result was to increase the price of silver at the mine; but with the continued rise in demands for silver, the price in the open market went far above this figure, the maximum being reached in when the price of silver went to $ . per ounce. naturally, but little silver was then offered to the government at the fixed price of $ under the pittman act. with the more recent slump in the general market for silver to a price below $ , offers to the government under the pittman act have been renewed. that part of the silver production which is a by-product of copper production has been low since the war, because of the stagnation in the copper industry. the production from lead ores, on the other hand, was not handicapped by lack of demand for lead. with the restoration of order in mexico, a presumption of large silver production in that country may be expected. increases may probably be expected also from new mines in burma and from bolivia. on the whole, no large increase in world production can be assumed from present known resources. new discoveries will be necessary to make any considerable change. of the mine production of silver in the united states, about two-thirds of the total comes from the states of montana, utah, idaho, and nevada. other considerable producers are colorado, arizona, california, alaska, and new mexico. all the other states together produce less than per cent of the total. the most important single districts are the butte district of montana, the coeur d'alene district of idaho, and the tonopah district of nevada, supplying respectively about one-fifth, one-eighth, and one-tenth of the country's total silver output. geologic features the most important mineral of silver is the sulphide, argentite or "silver glance." other minerals which yield a minor percentage of the total silver produced are the silver-antimony sulphides, pyrargyrite or "ruby silver," stephanite or "black silver," and polybasite; the silver-arsenic sulphides, proustite or "light ruby silver" and pearcite; and the silver antimonide, dyscrasite. in the oxide zone the most abundant minerals are cerargyrite (silver chloride) and native or "horn" silver. in addition to these definite mineral forms, silver is present in many ores in an undetermined form in other sulphides, notably in galena, sphalerite, and pyrite. silver differs from gold in that it is chemically active and forms many stable compounds, of which only the more important have been mentioned. the fact that half the world's silver is obtained as a by-product in the mining of other metals has been referred to. in the united states about a third of the production comes from dry or siliceous ores, over a third from lead and zinc ores, and a fourth to a third from copper ores. a fraction of per cent of the total is obtained as a by-product of gold placers, and all the remainder is won from lode or hard-rock deposits. the general geologic features of the silver-bearing copper and lead ores, and of the dry or siliceous gold and silver ores, have been described on previous pages. the philipsburg district has been referred to in connection with manganese ores, and the bolivian tin-silver ores will be described in connection with tin. we shall consider here only a few of the more prominent districts which have been primarily silver producers. the cobalt district of northern ontario is the most productive silver district in north america. the ores are found in numerous short, narrow veins, principally in pre-cambrian sediments near a thick quartz-diabase sill. locally they penetrate the sill. native silver and various silver sulphides, arsenides, and antimonides are associated with minerals of cobalt, nickel, bismuth, lead, and zinc, in a gangue of calcite and some quartz. the ore is of very high grade. the ore minerals are believed to have been deposited by hot solutions emanating from deep magmatic sources after the intrusion of the diabase. the present oxidized zone is very shallow, but may have been deeper before being stripped off by glaciation; it is characterized by native silver and arsenates of nickel and cobalt in the form of the green "nickel bloom" and the pink "cobalt bloom." the silver minerals are distinctly later in origin than the cobalt and nickel in the unoxidized zone, as evidenced by the relations of the mineral individuals when seen under the microscope. this fact, together with the abundance of native silver in the oxide zone, has suggested downward concentration of the silver by surface waters; but recent studies have indicated the probability that some of the silver at least was deposited by the later ascending solutions of magmatic origin. in the tintic district of central utah, paleozoic limestones have been intruded by monzonite (an acid granitic or porphyritic igneous rock), and covered by surface flows, the flows for the most part having been removed by subsequent erosion. the sediments have been much folded and faulted, and the ore bodies occur as fissure veins which locally widen into chimneys or pipes in fracture zones, accompanied by much replacement of limestone. there is a rough zonal arrangement of the ore minerals around the intrusive, gold and copper minerals (chiefly enargite and chalcopyrite) being more prominent near the intrusive, and argentiferous galena and zinc blende richer at greater distances. silver constitutes the principal value. the gangue is mainly fine-grained quartz or jasperoid, and barite. the water table is at unusually great depths ( , feet) and there is a correspondingly deep oxidized zone, which is characterized by lead and zinc oxide minerals much as at leadville (p. ). the comstock lode at virginia city, nevada, on the east slope of the sierra nevadas, was one of the most famous bonanza deposits of gold and silver in the world. while the richer ore has all been extracted, lower-grade material is still being mined and the fissure is still being followed, in the hope of some day striking another fabulously rich ore body. the lode occupies a fault fissure parallel to the trend of the range and dipping about degrees to the east, which can be traced about two and a half miles along the strike, with igneous rocks forming both hanging and foot walls. there are no sedimentary rocks in the district. the high-grade part of the vein is several hundred feet in thickness, with many irregular branches; the great thickness has been thought to be at least in part due to the tremendous pressure exerted by growing quartz crystals. the wall rocks have undergone a "propylitic" alteration, with development of chlorite, epidote, and probably sericite, much as at butte. the ore contains rich silver sulphide minerals and native gold, in a gangue composed almost entirely of quartz. the ore was doubtless formed by hot solutions, but the exact nature of these solutions, whether magmatic or meteoric, has not been proven. the hypothesis was early developed that the ores were deposited by surface waters,--which are supposed to have fallen on the summits of the sierra nevadas, to have sunk to great depths where they were heated, enabling them to pick up metallic constituents from the diabase forming one wall of the ore body, and to have risen under artesian pressure along the fault plane, where loss of heat and pressure resulted in deposition. later studies have emphasized the similarity of the ore-depositing conditions with those in other districts where the ores are believed to have come directly from magmatic sources, and this origin is now generally favored for the comstock lode. however, the earlier theory has not been disproved. the tonopah, nevada, district is very similar to the goldfield district (p. ). silver and gold are found in veins and replacements in a series of tertiary volcanic flows and tuffs, all of which have been complexly faulted. silver is the dominant constituent of value. the formation of fissures and faults accompanying and caused by the intrusion and cooling of lavas was first clearly shown in this district. evidences of origin through the work of hot solutions, probably magmatic, are the close association of the ores in place and in time with the igneous rocks--ore deposition in most of the flows having taken place before the next overlying flows were put down,--the presence of fluorine, the nature of the wall-rock alterations, the fact that both hot and cold springs are found close together underground (indicating unusual sources for the hot springs), the contrast in composition between the ores and the country rock, and the general relation of these ores to a large number of similar occurrences in tertiary lavas in the same general area. under weathering conditions, the silver sulphide minerals in general are oxidized to form native silver and cerargyrite, which are relatively insoluble and remain for the most part in the oxide zone. silver is less soluble than copper and zinc, but more soluble than gold; and to some extent it is removed in solution, particularly where the oxidation of pyrite forms ferric sulphate. farther down it may be reprecipitated as native silver, argentite, and the sulpho-salts, by organic matter or by various sulphides. the secondarily enriched ores are in a few districts, as at philipsburg, montana, the most valuable portions of the deposits. in other cases, sulphide enrichment does not appear to have contributed greatly to the values. the zones of oxide ores, secondary sulphide ores, and primary or protores are in most silver deposits much less regular and much less definitely marked than in the case of copper ores. platinum ores economic features the principal uses of platinum are: as a catalytic agent in the contact process for the manufacture of sulphuric acid, and in the making of nitric acid from ammonia; for chemical laboratory utensils that must be resistant to heat and acids; for electrical contacts for certain telephone, telegraph, and electrical control instruments, and for internal combustion engines; in dental work; and for jewelry. in normal times before the war, it is estimated that in the united states the jewelry and dental industries used per cent of the platinum metals consumed, the electrical industry per cent, and the chemical industry per cent. during the war, with the extraordinary expansion of sulphuric and nitric acid plants, these proportions were reversed and the chemical and electrical industries consumed about two-thirds of the platinum. substitutes have been developed, particularly for the electrical uses, and the demand from this quarter may be expected to decrease. about per cent of the world's crude platinum produced annually comes from the ural mountains in russia. the deposits next in importance are those of colombia. small amounts are produced in new south wales, tasmania, new zealand, borneo, british columbia, united states, india, and spain; and as a by-product in the electrolytic refining of the sudbury, canada, nickel ores. the extension of this method of refining to all of the sudbury ores would create an important supply of platinum. the colombian output has been increasing rapidly since . meanwhile the russian production has declined; and from the best information available, it is not likely that russia will be able to maintain production for many more years. estimates of the life of the russian fields are from to years at the pre-war rate of production. the platinum situation is commercially controlled by buying and mine-operating agencies,--the french having, before the war, practically dominated the russian industry, while american interests controlled in colombia. the situation is further influenced by four large refineries, in england, germany, united states, and france. before the war the united states produced less than per cent of the new platinum it consumed annually. production comes principally from california, with smaller amounts from oregon, alaska, and nevada. the many efforts which have been made to develop an adequate domestic supply of this metal do not indicate that the united states can ever hope to become independent of foreign sources for its future supplies of platinum. there is little reason to doubt that the colombia field, commercially dominated by the united states, holds great promise for the future. the output has come largely from native hand labor, and with the installation of dredges can probably be greatly increased. during the war, the need for platinum for war manufactures was so urgent and the production so reduced, that restrictions against its use in jewelry were put into force in all the allied countries. the united states government secured quantities of platinum which would have been sufficient for several years' use if war had continued. with the cessation of hostilities restrictions on the use of platinum were removed, and the accumulated metal was released by the government from time to time in small quantities; but the demands for platinum in the arts were so great that prices for a time tended to even higher levels than during the war. more recently supply is again approaching demand. geologic features platinum, like gold, occurs chiefly as the native metal. this is usually found alloyed with iron and with other metals of the platinum group, especially iridium, rhodium, and palladium. most of the platinum as used in jewelry and for electrical purposes contains iridium, which serves to harden it. paladium-gold alloys are a substitute for platinum, chiefly in dental uses. the original home of platinum is in basic igneous rocks, such as peridotites, pyroxenites, and dunites, where it has been found in small, scattered crystals intergrown with olivine, pyroxene, and chromite. platinum is very dense and highly resistant to oxidation and solution. in the breaking up and washing away of the rocks, therefore, it is concentrated in small grains and scales in stream and beach placers. of the world production of platinum over per cent has been derived from placers. the ural mountain deposits of russia are gold- and platinum-bearing placers, in streams which drain areas of dunite rock containing minute quantities of native platinum. the deposits of colombia and australasia are placers of a similar character. in the united states small quantities of platinum are recovered from the gold-bearing gravels of california and oregon, where the streams have come from areas of serpentine and peridotite. a platinum arsenide, called sperrylite, is sometimes found associated with sulphide minerals in basic igneous rocks. at sudbury, ontario, this mineral, together with palladium arsenide, is found in the nickel ores, especially in the weathered zone where it is concentrated by removal of more soluble materials. it has also been found in the copper mines of rambler, wyoming. in the yellow pine district of southern nevada, metallic gold-platinum-palladium ore shoots are found in association with copper and lead ores, in a fine-grained quartz mass which replaces beds of limestone near a granitic dike. no basic intrusives are known in the district. the deposit is unusual in that it has a comparatively high content of platinum (nearly an ounce to the ton), and is probably genetically related to acid intrusives. from all these deposits, only small quantities of platinum are mined. footnotes: [ ] report of a joint committee appointed from the bureau of mines and the united states geological survey by the secretary of the interior to study the gold situation: _bull. , u. s. bureau of mines_, . see also report of special gold committee to secretary of the treasury, february , . [ ] ransome, f. l., the geology and ore deposits of goldfield, nevada: _prof. paper , u.s. geol. survey_, , p. . [ ] butler, b. s., loughlin, g. f., heikes, v. c., and others, the ore deposits of utah: _prof. paper , u.s. geol. survey_, , p. . chapter xii miscellaneous metallic minerals aluminum ores economic features bauxite (hydrated aluminum oxide) is the principal ore of aluminum. over three-fourths of the world's bauxite production and per cent of the united states production is used for the manufacture of aluminum. on an average six tons of bauxite are required to make one ton of metallic aluminum. other important uses of bauxite are in the manufacture of artificial abrasives in the electric furnace, and in the preparation of alum, aluminum sulphate, and other chemicals which are used for water-purification, tanning, and dyeing. relatively small but increasingly important quantities are used in making bauxite brick or high alumina refractories for furnace-linings. aluminum is used principally in castings and drawn and pressed ware, for purposes in which lightness, malleability, and unalterability under ordinary chemical reagents are desired. thus it is used in parts of airplane and automobile engines, in household utensils, and recently in the framework of airplanes. aluminum wire has been used as a substitute for copper wire as an electrical conductor. aluminum is used in metallurgy to remove oxygen from iron and steel, and also in the manufacture of alloys. powdered aluminum is used for the production of high temperatures in the thermite process, and is a constituent of the explosive, ammonal, and of aluminum paints. deposits of bauxite usually contain as impurities silica (in the form of kaolin or hydrous aluminum silicate), iron oxide, and titanium minerals, in varying proportions. bauxites to be of commercial grade should carry at least per cent alumina, and for the making of aluminum should be low in silica though the content of iron may be fairly high. for aluminum chemicals materials low in iron and titanium are preferred; and for refractories which must withstand high temperatures, low iron content seems to be necessary. the abrasive trade in general uses low-silica high-iron bauxites. the only large producers of bauxite are the united states and france, which supplied in normal times before the war over per cent of the world's total. small amounts are produced in ireland, italy, india, and british guiana. during the war a great deal of low-grade bauxite was mined in austria-hungary and possibly in germany; but on account of the large reserves of high-grade material in other parts of the world, it is doubtful whether these deposits will be utilized in the future. bauxites of good grade have been reported from africa, australia, and many localities in india. from geologic considerations it is practically certain that there are very large quantities available for the future in some of these regions. the international movements and the consumption of bauxite are largely determined by the manufacture of aluminum, and to a lesser extent by the manufacture of abrasives and chemicals. the principal foreign producers of aluminum are france, switzerland (works partly german-owned), norway (works controlled by english and french capital), england, canada, italy, germany, and austria. french bauxite has normally supplied the entire european demands,--with the exceptions that italy procures part of her requirements at home, and that the irish deposits furnish a small fraction of the english demand. the deposits of southern france, controlled largely by french but in part by british capital, have large reserves and will probably continue to meet the bulk of european requirements. france also has important reserves of bauxite in french guiana. the united states produces about half of the aluminum of the world, and is the largest manufacturer of artificial abrasives and probably of aluminum chemicals. most of these are made from domestic bauxite. prior to the war, the united states imported about per cent of the bauxite consumed, but these imports were mainly high-grade french bauxite which certain makers of chemicals preferred to the domestic material. the small production of guiana is also imported into the united states. bauxite is exported to canadian makers of aluminum and abrasives. during the war period domestic deposits were entirely capable of supplying all the domestic as well as canadian demands for bauxite, although these demands increased to two and one-half times their previous figure. at the same time considerable amounts of manufactured aluminum products were exported to europe, whereas aluminum had previously been imported from several european countries. the united states production of bauxite comes mainly from arkansas, with smaller amounts from tennessee, alabama, and georgia. the reserves are large but are not inexhaustible. most of the important deposits are controlled by the large consumers of bauxite, principally the aluminum company of america and its subsidiaries, though certain chemical and abrasive companies own some deposits. the aluminum company of america also controls immense deposits of high-grade bauxite in dutch and british guiana, and further exploration by american interests is under way. with the return to normal conditions since the war, some of the domestic bauxite deposits probably can not be worked at a profit, a situation which is likely to require the development of the tropical american deposits. geologic features aluminum is the third most abundant element in the common rocks and is an important constituent of most rock minerals; but in its usual occurrence it is so closely locked up in chemical combinations that the metal cannot be extracted on a commercial scale. in the crystalline form aluminum oxide constitutes some of the most valuable gem stones. many ordinary clays and shales contain to per cent alumina (al_{ }o_{ }), and the perfection of a process for their utilization would make available almost unlimited aluminum supplies. the principal minerals from which aluminum is recovered today are hydrous aluminum oxides, the most prominent of which are bauxite, gibbsite, and diaspore--the aggregate of all these minerals going commercially under the name of bauxite. prior to the discovery of bauxite ores, cryolite, a sodium-aluminum fluoride obtained from pegmatites in greenland, was the chief source of aluminum. it is only within about the last thirty-five years that bauxite has been used and that aluminum has become an important material of modern industry. cryolite is used today to form a molten bath in which the bauxite is electrolytically reduced to aluminum. bauxite deposits in general are formed by the ordinary katamorphic processes of surface weathering, when acting on the right kind of rocks and carried to an extreme. in the weathering of ordinary rocks the bases are leached out and carried away, leaving a porous mass of clay (hydrous aluminum silicates), quartz, and iron oxide. in the weathering of rocks high in alumina, and low in iron minerals and quartz, deposits of residual clay or kaolin nearly free from iron oxide and quartz are formed. under ordinary weathering conditions the kaolin is stable; but under favorable conditions, such as obtain in the weathered zones of tropical climates, it is broken up, the silica is taken into solution and carried away, and hydrous aluminum oxides remain as bauxite ores. this extreme type of weathering is sometimes called lateritic alteration (see pp. - ). impurities of the bauxite ores are the small quantities of iron and titanium present in the original rocks, together with the kaolin which has not been broken up. the deposits usually form shallow blankets over considerable areas, with irregular lower surfaces determined by the action of surface waters--which work most effectively where joints or other conditions favor the maximum circulation and alteration. a certain degree of porosity in the original rock is also known to favor the alteration. a complete gradation from the unaltered rock through clay to the high-grade bauxite, with progressive decrease in bases and silica, concentration of alumina and iron oxide, and increase of moisture and pore space, is frequently evident (see fig. ). the bauxite is earthy, and usually shows a concretionary or pisolitic structure similar to that observed in residual iron ores (p. ). near the surface there may be an increase in silica,--probably due to a reversal of the usual conditions by a slight leaching of alumina, thus concentrating the denser masses of kaolin which have not been decomposed. the arkansas bauxite deposits, the most important in the united states, are surface deposits overlying nepheline-syenite, an igneous rock with a high ratio of alumina to iron content. the most valuable deposits are residual, and some parts have preserved the texture of the original rock, though with great increase in pore space; most of the ore, however, has the typical pisolitic structure. near the surface the pisolites are sometimes loosened by weathering, yielding a gravel ore, and some of the material has been transported a short distance to form detrital ores interstratified with sands and gravels. the complete gradation from syenite to bauxite has been shown. [illustration: fig. . diagram showing gradation from syenite to bauxite in terms of volume. the columns represent a series of samples from a single locality in arkansas. after mead.] in the appalachian region of tennessee, alabama, and georgia, bauxite occurs as pockets in residual clays above sedimentary rocks, chiefly above shales and dolomites. its origin has probably been similar to that described. the bauxite deposits of southern france occur in folded limestones, and have been ascribed by french writers to the work of ascending hot waters carrying aluminum sulphate. they present some unusual features, and evidence as to their origin is not conclusive. at the present time bauxite is doubtless forming in tropical climates, where conditions are favorable for deep and extreme weathering of the lateritic type. the breaking up of kaolin accompanied by the removal of silica is not characteristic of temperate climates, though many clays in these climates show some bauxite. it is possible that, at the time when the bauxite deposits of arkansas and other temperate regions were formed, the climate of these places was warmer than it is today. in studying the origin of bauxites, it should not be overlooked that they have much in common with clays, certain iron ores, and many other deposits formed by weathering. antimony ores economic features antimony is used mainly for alloying with other metals. over one-third of the antimony consumed in the united states is alloyed with tin and copper in the manufacture of babbitt or bearing-metal. other important alloys include type-metal (lead, antimony, and tin), which has the property of expanding on solidification; "hard lead," a lead-antimony alloy used in making acid-resisting valves; britannia or white metal (antimony, tin, copper, zinc), utilized for cheap domestic tableware; and some brasses and bronzes, solders, aluminum alloys, pattern metals, and materials for battery plates and cable coverings. antimony finds a very large use in war times in the making of shrapnel bullets from antimonial lead. antimony oxides are used in white enameling of metal surfaces, as coloring agents in the manufacture of glass, and as paint pigments; the red sulphides are used in vulcanizing and coloring rubber, as paint pigments, in percussion caps, and in safety matches; and other salts find a wide variety of minor uses in chemical industries and in medicine. antimony ores vary greatly in grade, the chinese ores carrying from to per cent of the metal. the presence of arsenic and copper in the ores is undesirable. several of the more important antimony districts owe their economical production of that metal to the presence of recoverable values in gold. some lead-silver ores contain small quantities of antimony, and "antimonial lead," containing to per cent antimony, is recovered in their smelting. china is by far the most important antimony-producing country in the world, and normally supplies over half the world's total. chinese antimony is exported in part as antimony crude (lumps of needle-like antimony sulphide), and in part as antimony regulus, which is about per cent pure metal. france was the only other important source of antimony before the war ( to per cent of the world production), and mexico and hungary produced small amounts. the large demand for antimony occasioned by the war, besides stimulating production in these countries, brought forth important amounts of antimony ore from algeria (french control) and from bolivia and australia (british control), as well as smaller quantities from several other countries. of the war-developed sources, only algeria and perhaps australia are expected to continue production under normal conditions. before the war, antimony was smelted chiefly in china, england, and france, and to a lesser extent in germany. british and french commercial and smelting interests dominated to a considerable extent the world situation, and london was the principal antimony market of the world. during the war chinese antimony interests were greatly strengthened, and facilities for treating the ore in that country were increased. japan also became important as a smelter and marketer of chinese ore, and increasing quantities of antimony were exported from china and japan directly to the united states. english exports ceased entirely and were replaced in this country by chinese and japanese brands. the united states normally consumes about one-third of the world's antimony. before the war the entire amount was secured by importation, two-thirds from great britain and the rest from the orient, france, and other european countries. domestic production of ore and smelting of foreign ores were negligible. (these statements refer only to the purer forms of antimony; the united states normally produces considerable amounts of antimonial lead, equivalent to somewhat less than per cent of the country's total lead production, but this material cannot be substituted for antimony regulus in most of its uses.) during the war, under the stimulus of rising prices, mining of antimony was undertaken in the united states and several thousand tons of metal were produced--principally from nevada, with smaller amounts from alaska, california, and other western states. the great demands for antimony, however, were met chiefly by increased importation. imports were mainly of regulus from chinese and japanese smelters of chinese antimony; but about a third was contained in ores, including most of the production of mexico which had formerly gone to england, and about per cent of the bolivian output. antimony smelters were developed in the united states to handle these ores. at the close of hostilities there had accumulated in the united states large surplus stocks of antimony and antimonial materials. with a very dull market and low prices, domestic mines and smelters were obliged to close down. the dependence of the united states on foreign sources of antimony and the importance of the metal for war purposes led to some agitation for a protective tariff--in addition to the present import duty of per cent on antimony metal--in order to encourage home production (see pp. - , - ). in summary, the united states is almost entirely dependent upon outside sources for its antimony, although there are inadequately known reserves in this country which might be exploited if prices were maintained at a high level. the future of united states smelters is problematical. china, the world's chief source of antimony, at present dominates the market in this country, largely due to the low cost of production and favorable japanese freight rates. geologic features the antimony sulphide, stibnite, is the source of most of the world's production of this metal. antimony oxides, including senarmontite, cervantite, and others, are formed near the surface, and in some of the deposits of mexico and algeria they supply a large part of the values recovered. jamesonite, bournonite, and tetrahedrite (sulphantimonides of lead and copper), when found in lead-silver deposits, are to some extent a source of antimony in the form of antimonial lead. stibnite is found in a variety of associations and is present in small quantities in many types of deposits. in the commercial antimony deposits, it is in most cases accompanied by minor quantities of other metallic sulphides--pyrite, cinnabar, sphalerite, galena, arsenopyrite, etc.--in a gangue of quartz and sometimes calcite. many of the deposits contain recoverable amounts of gold and silver. the deposits of the hunan province of southern china occur as seams, pockets, and bunches of stibnite ore in gently undulating beds of faulted and fissured dolomitic limestone. in the vicinity of the most important mines no igneous rocks have been observed, and the origin of the ores has not been worked out. in the central plateau of france the numerous antimony deposits are stibnite veins cutting granites and the surrounding schists and sediments. an origin related in some way to hot ascending solutions seems probable. the deposits of the national district of western nevada, the most important war-developed antimony deposits of the united states, consist of stibnite veins with a gangue of fine-grained drusy quartz, cutting through flows of rhyolite and basalt. they are intimately related to certain gold- and silver-bearing veins, and all are closely associated with dikes of rhyolite, which were the feeders to the latest extrusion in the district. the wall rocks have undergone alteration of the propylitic type. these relations, and the presence of the mercury sulphide, cinnabar, in some of the ores (see pp. - ), suggest an origin through the work of ascending hot waters or hot springs. these waters probably derived their dissolved matter from a magmatic source, and worked up along vents near the rhyolite dikes soon after the eruption of this rock. in the weathering of antimony deposits, the stibnite usually alters to form insoluble white or yellowish oxides, which are sometimes called "antimony ocher." these tend to accumulate in the oxide zone through the removal of the more soluble accompanying minerals. secondary sulphide enrichment of antimony deposits, if it occurs at all, is negligible. arsenic ores economic features about two-thirds of the arsenic consumed in recent years has been used in agriculture, where various arsenic compounds--arsenic trioxide or "white arsenic," paris green, lead arsenate, etc.--are used as insecticides and weed killers. arsenic compounds are also used in "cattle-dips" for killing vermin. the only other large use of arsenic is in the glass industry, arsenic trioxide being added to the molten glass to purify and decolorize the product. small quantities of arsenic compounds are used in the preparation of drugs and dyeing materials, and metallic arsenic is used for hardening lead in shot-making. the principal arsenic-producing countries are the united states, germany, france, great britain, canada, and mexico. spain, portugal, japan, and china are also producers, and recent trouble with the "prickly-pear" pest in queensland, australia, has led to local development of arsenic mining in that country. for the most part, european production has been used in europe and american production in the united states. arsenic is recovered almost wholly as a by-product of smelting ores for the metals. the potential supply is ample in most countries where smelting is conducted, but owing to the elaborate plant required to recover the arsenic, apparatus is not usually installed much in advance of the demand for production. rapid expansion is not possible. before the war the arsenic needs of the united states (chiefly agricultural) were supplied by a few recovery plants in the united states, mexico, and canada. several large smelters had not found it profitable to install recovery plants, as the market might have been oversupplied and prices were low. during the war, with the extensive demand for insecticides for gardening, there was a considerable deficiency of arsenic supplies. with rising prices production was stimulated, but was still unable to meet the increased demand. this situation resulted in regulation of the prices of white arsenic by the food administration. production of arsenic in the united states comes chiefly from smelters in colorado, washington, utah, montana, and new jersey. small amounts are produced by arsenic mines in virginia and new york. a mexican plant at mapimi has been shipping important quantities to the united states. the plant at anaconda, montana, is expected to produce an ample supply in the future. the united states is entirely independent in arsenic supplies and will probably soon have an exportable surplus. export trade, after the reconstruction period, will probably meet competition from france and germany where production was formerly large. geologic features arsenic-bearing minerals are numerous and rather widely distributed, but only a few of them are mined primarily for their content of arsenic. arsenopyrite or "mispickle" (iron-arsenic sulphide) has been used intermittently as a source of white arsenic in various places,--notably at brinton, virginia, and near carmel, new york. the former deposits contain arsenopyrite and copper-bearing pyrite impregnating a mica-quartz-schist, adjacent to and in apparent genetic relation with aplite or pegmatite intrusives. in the latter locality arsenopyrite is found associated with pyrite in a gangue of quartz, forming a series of parallel stringers in gneiss close to a basic dike. the orange-red sulphides of arsenic, orpiment and realgar, are formed both as primary minerals of igneous source and as secondary products of weathering. they are rather characteristic of the oxide zones of certain arsenical metallic ores, and are believed in many cases to have formed from arsenopyrite. they are mined on a commercial scale in china. the great bulk of the world's arsenic, as previously stated, is obtained as a by-product of smelting operations. the enargite of the butte copper ores (pp. - ) contains a considerable amount of arsenic, a large part of which will be recovered from the smelter fumes by new processes which are being installed. the gold-silver ores of the tintic district (pp. ) also yield important amounts, the arsenic-bearing minerals being enargite and tennantite (copper-arsenic sulphides) and others. the silver ores of the cobalt district of ontario (pp. - ), containing nickel and cobalt arsenides, produce considerable arsenic. many other metallic ores contain notable amounts of arsenic, which are at present allowed to escape through smelter flues, but which could be recovered under market conditions which would repay the cost of installing the necessary apparatus. bismuth ores economic features bismuth metal is used in alloys, to which it gives low fusibility combined with hardness and sharp definition. bismuth alloys are employed in automatic fire sprinklers, in safety plugs for boilers, in electric fuses, in solders and dental amalgams, and in some type and bearing metals. bismuth salts find a considerable application for pharmaceutical purposes, especially in connection with intestinal disorders, and the best grades of bismuth materials are used for this purpose. the salts are also used in porcelain painting and enameling and in staining glass. bolivia is the most important producer of bismuth ore. the output is controlled entirely by british smelting interests. an important deposit exists in peru, the output of which is limited by the same british syndicate. considerable bismuth is produced in australia, tasmania, and new zealand, all of which likewise goes to england. germany before the war had three smelters which produced bismuth from native ores in saxony; bismuth was one of the few metals of which germany had an adequate domestic supply. recently southern china is reported to be mining increasing amounts of bismuth. the united states produces the larger part of its bismuth requirements, chiefly from plants installed at two lead refineries. a further installation would make this country entirely independent of foreign supplies if occasion required. imports, from england and south america, have been steadily declining, but during the war were somewhat increased. the united states does not export bismuth so far as known. geologic features the principal minerals of bismuth are bismuthinite (bismuth sulphide), bismutite (hydrated carbonate), bismite or bismuth ocher (hydrated oxide), and native bismuth. the native metal and the sulphide are believed to be formed mainly as primary minerals of igneous origin. in the deposits of new south wales they are found associated with molybdenite in quartz gangue, in pipe-like deposits in granite. the oxide and the carbonate are probably products of surface weathering. the bolivian deposits contain the native metal, the oxide, and the carbonate, associated with gold, silver, and tin minerals, in one locality in slates and in another locality in porphyry. the origin is not well known. in the united states, the sulphide, bismuthinite, is found in the siliceous ores of goldfield, nevada (p. ), and in minor amounts in a great number of the sulphide ores of the cordilleran region. the ores of the leadville and tintic districts (pp. and ) yield the larger part of the united states production, the bismuth being recovered as by-product from the electrolytic refining of the lead bullion. large amounts of bismuth pass out of the stacks of smelters treating other western ores, and while it would not be cheap nor easy to save the bismuth thus lost, it could probably be done in case of necessity. cadmium ores economic features cadmium is used in low melting-point alloys--as, for example, those employed in automatic fire-extinguishers and electric fuses,--in the manufacture of silverware, and in dental amalgams. during the war the critical scarcity of tin led to experiments in the substitution of cadmium for tin in solders and anti-friction metals. results of some of these experiments were promising, but the war ceased and demands for tin decreased before the cadmium materials became widely used. future developments in this direction seem not unlikely. cadmium compounds are used as pigments, particularly as the sulphide "cadmium yellow," and to give color and luster to glass and porcelain. cadmium salts are also variously used in the arts, in medicine, and in electroplating. practically the entire cadmium output of the world comes from germany and the united states. in addition, england produces a very small quantity. before the war germany produced about two-thirds of the world's total, and supplied the european as well as a considerable part of the united states consumption. during the war the united states production increased three to four fold, imports ceased, and considerable quantities were exported to the allied nations in europe and to japan. at present the united states is entirely independent as regards cadmium supplies. production is sufficient to supply all the home demand and to permit exports of one-third of the total output. a considerable number of possible cadmium sources are not being used, and the production is capable of extension should the need arise. geologic features nearly the only cadmium mineral known is the sulphide, greenockite, but no deposits of this mineral have been found of sufficient volume to be called cadmium ores. sphalerite almost always contains a little cadmium, probably as the sulphide; and in zinc deposits crystals of sphalerite in cavities are frequently covered with a greenish-yellow film or coating of greenockite. these coatings have probably been formed by the decomposition of cadmium-bearing zinc sulphide in the oxide zone, the carrying down of the cadmium in solution, and its precipitation as secondary cadmium sulphide. the zinc oxide minerals in the surficial zone also are sometimes colored yellow by small amounts of greenockite. in the zinc ores of the joplin district of missouri, cadmium is present in amounts ranging from a trace to per cent and averaging . per cent. germany's cadmium is produced by fractional distillation of the silesian zinc ores, which contain at most . per cent cadmium. in the united states there are large potential sources in the zinc ores of the mississippi valley, and considerable cadmium is recovered in roasting them. much of the american cadmium is also obtained from bag-house dusts at lead smelters. the general geologic conditions of the cadmium-bearing ores are indicated in the discussion of lead and zinc deposits in an earlier chapter. cobalt ores economic features cobalt finds its largest use in the form of cobalt salts, employed in coloring pottery and glass and in insect poisons. cobalt is also used in some of the best high-speed tool steels. "stellite," which is used to a limited extent in non-rusting tools of various sorts, and in considerable quantity to replace high-speed tool steels, is an alloy of cobalt, chromium, and small quantities of other metals. considerable experimental work has been done on the properties and uses of cobalt alloys, and their consumption is rapidly on the increase. cobalt is an item of commerce of insignificant tonnage. there are only two countries, canada (ontario) and the belgian congo, which produce noteworthy amounts. the katanga district in the congo produces blister copper that contains as much as per cent of cobalt, though usually less than per cent. this product formerly went to germany, and now goes entirely to great britain. just how much cobalt is saved is unknown, but probably several hundred tons annually. it is probable that most of the cobalt in these ores will be lost on the installation of a leaching process for recovery of the copper. canada exports most of its product to the united states, though the amount is small. domestic production in this country has been too small to record. the united states has been dependent on imports from canada. geologic features the principal cobalt minerals are smaltite (cobalt arsenide), cobaltite (cobalt-arsenic sulphide), and linnæite (cobalt-nickel sulphide). under weathering conditions these minerals oxidize readily to form asbolite, a mixture of cobalt and manganese oxides, and the pink arsenate, erythrite or "cobalt bloom." cobalt minerals are found principally in small quantities disseminated through ores of silver, nickel, and copper. the production of canada is obtained mainly as a by-product of the silver ores of the cobalt district (described on pp. - ), and smaller amounts are recovered from the sudbury nickel ores (pp. - ). the cobalt of belgian congo is obtained from rich oxidized copper ores which impregnate folded sediments (p. ). mercury (quicksilver) ores economic features uses of mercury are characterized by their wide variety and their application to very many different phases of modern industry; they will be named here in general order of decreasing importance. about one-third of the mercury consumed in this country goes into the manufacture of drugs and chemicals, such as corrosive sublimate, calomel, and glacial acetic acid. mercury fulminate is used as a detonator for high explosives and to some extent for small-arms ammunition--a use which was exceedingly important during the war, but is probably of minor consequence in normal times. mercuric sulphide forms the brilliant red pigment, vermilion, and mercuric oxide is becoming increasingly important in anti-fouling marine paint for ship-bottoms. either as the metal or the oxide, mercury is employed in the manufacture of electrical apparatus (batteries, electrolyzers, rectifiers, etc.), and in the making of thermostats, gas governors, automatic sprinklers, and other mechanical appliances. mercuric nitrate is used in the fabrication of felt hats from rabbits' fur. in the extraction of gold and silver from their ores by amalgamation, large amounts of metallic mercury have been utilized, but of late years the wide application of the cyanide process has decreased this use. minor uses include the making of certain compounds for preventing boiler-scale, of cosmetics, and of dental amalgam. the ores of mercury vary greatly in grade. spanish ores yield an average in the neighborhood of per cent, italian ores . per cent, and austrian ores . per cent of metallic mercury. in the united states the ores of california yield about . per cent and those of texas range from about . to per cent. in almost all cases the ores are treated in the immediate vicinity of the mines, and fairly pure metal is obtained by a process of sublimation and condensation. this is usually marketed in iron bottles or flasks containing pounds each. the large producers of mercury are, in order of normal importance, spain, italy, austria, and united states. mexico, russia, and all other countries produce somewhat less than per cent of the world's total. the largest quicksilver mines of the world are those of almaden in central spain, which are owned and operated by the spanish government. this government, after reserving a small amount for domestic use, sells all the balance of the production through the rothschilds of london. in addition british capital controls some smaller mines in northern spain. england thus largely controls the european commercial situation in this commodity, and london is the world's great quicksilver market, where prices are fixed and whence supplies go to all corners of the globe. reserves of the almaden ore bodies are very large. sufficient ore is reported to have been developed to insure a future production of at least , metric tons--an amount equivalent to the entire world requirements at pre-war rates of consumption for years. the mercury deposits of the monte amiata district of central italy were in large part dominated by german capital, but during the war were seized by the italian government. the mines of idria, austria-hungary, were owned by the austrian government and their ultimate control is at present uncertain. reserves are very large, being estimated at about one-half those of almaden. although england has had a considerable control over the prices and the market for mercury, the italian and austrian deposits have provided a sufficient amount to prevent any absolute monopoly. english interests have now secured control of the italian production, and it is expected that they will also control the austrian production--thus giving england control of something over three-fourths of the world's mercury. in the united states about two-thirds of the mercury is produced in the coast range district of california, and most of the remainder in the terlingua district of texas. smaller quantities come from nevada, oregon, and a few other states. the output before the war was normally slightly in excess of domestic demand and some mercury was exported to various countries. due to the exhaustion of the richer and more easily worked deposits, however, production was declining. during the war, with increased demands and higher prices, production was stimulated, the united states became the largest mercury-producing country in the world, and large quantities were exported to help meet the military needs of england and france. with the end of war prices and with high costs of labor and supplies, production in the united states has again declined. many of the mines have passed their greatest yield, and though discovery of new ore bodies might revive the industry, production is probably on the down grade. future needs of this country will probably in some part be met by imports from spain, italy, and austria, where the deposits are richer and labor is cheaper. this situation has caused much agitation for a tariff on imports. the present tariff of per cent is not sufficient to keep out foreign mercury. outside of the united states large changes in distribution of production of quicksilver are not expected for some time. the reserves of the european producers are all large and are ample to sustain present output for a considerable number of years. it is reported that there will be a resumption of mining in the once very productive huancavelica district of peru and in asia minor, and with restoration of political order there may be an increase in output from mexico and russia,--but these districts will be subordinate factors in the world situation. on geologic grounds, new areas of mercury ores may be looked for in regions of recent volcanic activity, such as the east coast of asia, some islands of oceania, the shores of the mediterranean, and the cordilleras of north and south america,--but no such areas which are likely to be producers on a large scale are now known. geologic features the chief mineral of mercury, from which probably over per cent of the world's mercury comes, is the brilliant red sulphide, cinnabar. minor sources include the black or gray sulphide, metacinnabar, the native metal, and the white mercurous chloride, calomel. the ores are commonly associated with more or less iron sulphide, and frequently with the sulphides of antimony and arsenic, in a gangue consisting largely of quartz and carbonates (of calcium, magnesium, and iron). the precious metals and the sulphides of the base metals are rare. mercury deposits are in general related to igneous rocks, and have associations which indicate a particular type of igneous activity. they are not found in magmatic segregations, in pegmatites, nor in veins which have been formed at great depths and under very high temperatures. on the contrary, the occurrence of many deposits in recent flows which have not been eroded, their general shallow depth (large numbers extending down only a few hundred feet), and the association of some deposits with active hot springs now carrying mercury in solution, suggest an origin through the work of ascending hot waters near the surface. the mercury minerals are believed to have been carried in alkaline sulphide solutions. precipitation from such solutions may be effected by oxidation, by dilution, by cooling, or by the presence of organic matter. being near the surface, it is a natural assumption that the waters doing the work were not intensely hot. at sulphur bank springs, in the california quicksilver belt, deposition of cinnabar by moderately hot waters is actually taking place at present; also these waters are bleaching the rock in a manner often observed about mercury deposits. the coast ranges of california contain a great number of mercury deposits extending over a belt about miles long. the ore bodies are in fissured zones in serpentine and jurassic sediments, and are related in general to recent volcanic flows. a considerable amount of bituminous matter is found in the ores, and is believed to have been an agent in their precipitation. the terlingua ores of texas are found in similar fractured zones in cretaceous shales and limestones associated with surface igneous flows. the occurrence of a few ore bodies in vertical shoots in limestone, apparently terminating upward at the base of an impervious shale, furnishes an additional argument for their formation by ascending waters. in the few deposits (_e. g._, those of almaden, spain, and of the deep mines of new almaden and new idria, california,) where there is no such clear relation to volcanic rocks as generally observed, but where the ores contain the same characteristic set of minerals, it is concluded that practically the same processes outlined above have been active in their formation; and that the volcanic source of the hot solutions either failed to reach the surface or has been removed by erosion. the same line of reasoning is carried a step further, and in many gold-quartz veins in volcanic rocks, where cinnabar and its associated minerals are present, it is believed that waters of a hot-spring nature have again been effective. thus cinnabar, when taken with its customary associations, is regarded as a sort of geologic thermometer. in the weathering of mercury deposits, cinnabar behaves somewhat like the corresponding silver sulphide, argentite. in the oxide zone, native mercury and the chloride, calomel, are formed. in the texas deposits a red oxide and a number of oxychlorides are also present. the carrying down of the mercury and its precipitation as secondary sulphide may have taken place in some deposits, but this process is unimportant in forming values. tin ores economic features the largest use of tin is in the manufacture of tin-plate, which is employed in containers for food, oil, and other materials. next in importance is its use in the making of solder and of babbitt or bearing metal. tin is also a constituent of certain kinds of brass, bronze, and other alloys, such as white metal and type metal. minor uses include the making of tinfoil, collapsible tubes, wire, rubber, and various chemicals. tin oxide is used to some extent in white enameling of metal surfaces. roughly a third of the tin consumed within the united states goes into tin-plate, a third into solder and babbitt metal, and a third into miscellaneous uses. the ores of tin in general contain only small quantities of the metal. tin has sufficient value to warrant the working of certain placers containing only a half-pound to the cubic yard, although the usual run is somewhat higher. the tin content of the vein deposits ranges from about per cent to per cent, and the average grade is much closer to the lower figure. great britain has long controlled the world's tin ores, producing about half of the total and controlling additional supplies in other countries. the production is in small part in cornwall, but largely in several british colonies--the malay states, central and south africa, australia, and others. the malay states furnish about a third of the world's total. another third is produced in immediately adjacent districts of the dutch east indies, siam (british control), and china, and some of the concentrates of these countries are handled by british smelters, especially at singapore. tin is easily reduced from its ores and most of the tin is smelted close to the sources of production. considerable quantities, however, have gone to england for treatment. london has been the chief tin market of the world, and before the war the larger portion of the tin entering international trade went through this port. during the war a good deal of the export tin from straits settlements was shipped direct to consumers rather than via london, but it is not certain how future shipments may be made. significant features of the tin situation in recent years have been a decline of production in the malay states, and a large and growing production in bolivia. malayan output has decreased because of the exhaustion of some of the richer and more accessible deposits; certain governmental measures have also had a restrictive effect. bolivian production now amounts to over a fifth of the world's total and bids fair to increase. about half the output is controlled by chilean, and small amounts by american, french, and german interests. a large portion of the bolivian concentrates formerly went to germany for smelting, but during the war american smelters were developed to handle part of this material; large quantities are also smelted in england. the united states produces a small fraction of per cent of the world's tin, and consumes a third to a half of the total. the production is mainly from the seward peninsula of northwestern alaska. for american tin smelters, bolivia is about the only available source of supplies; metallic tin can be obtained from british possessions, but no ore, except by paying a - / per cent export tax. the united states exports tin-plate in large amounts, and in this trade has met strong competition from english and german tin-plate makers. a world shortage of tin during the war required a division of available supplies through a central international committee. somewhat later, with the removal of certain restrictions on the distribution of tin, considerable quantities which had accumulated in the orient found their way into europe and precipitated a sensational slump in the tin market. geologic features the principal mineral of tin is cassiterite (tin oxide). stannite, a sulphide of copper, iron, and tin, is found in some of the bolivian deposits but is rare elsewhere. about two-thirds of the world's tin is obtained from placers and one-third from vein or "lode" deposits. over per cent of the tin of southeastern asia and oceania is obtained from placers. tin placers, like placers of gold, platinum, and tungsten, represent concentrations in stream beds and ocean beaches of heavy, insoluble minerals--in this case chiefly cassiterite--which were present in the parent rocks in much smaller quantities, but which have been sorted out by the classifying action of running water. the original home of cassiterite is in veins closely related to granitic rocks. it is occasionally found in pegmatites, as in certain small deposits of the southern appalachians and the black hills of south dakota, or is present in a typical contact-metamorphic silicated zone in limestone, as in some of the deposits of the seward peninsula of alaska. in general, however, it is found in well-defined fissure veins in the outer parts of granitic intrusions and extending out into the surrounding rocks. with the cassiterite are often found minerals of tungsten, molybdenum, and bismuth, as well as sulphides of iron, copper, lead, and zinc, and in some cases there is evidence of a rough zonal arrangement. the deposits of cornwall and of saxony show transitions from cassiterite veins close to the intrusions into lead-silver veins at a greater distance. the gangue is usually quartz, containing smaller amounts of a number of less common minerals--including lithium mica, fluorite, topaz, tourmaline, and apatite. the wall rocks are usually strongly altered and in part are replaced by some of the above minerals, forming coarse-grained rocks which are called "greisen." the origin of cassiterite veins, in view of their universal association with granitic rocks, is evidently related to igneous intrusions. the occurrence of the veins in distinct fissures in the granite and in the surrounding contact-metamorphic zone indicates that the granite had consolidated before their formation, and that they represent a late stage in the cooling. the association with minerals containing fluorine and boron, and the intense alteration of the wall rocks, indicate that the temperature must have been very high. it is probable that the temperature was so high as to cause the solutions to be gaseous rather than liquid, and that what have been called "pneumatolytic" conditions prevailed; but evidence to decide this question is not at present available. the most important deposits of tin in veins are those of bolivia, some of which are exceptionally rich. these are found in granitic rocks forming the core of the high cordillera real and in the adjacent intruded sediments, in narrow fissure veins and broader brecciated zones containing the typical ore and gangue minerals described above, and also, in many cases, silver-bearing sulphides (chiefly tetrahedrite). there appear to be all gradations in type from silver-free tin ores to tin-free silver ores, although the extremes are now believed to be rare. in the main the tin ores, with abundant tourmaline, appear to be more closely related to the coarse-grained granites, and to indicate intense conditions of heat and pressure, while the more argentiferous ores, with very little or no tourmaline, are found in relation to finer-grained quartz porphyries and even rhyolites, and seem to indicate less intense conditions at the time of deposition. the ores of the whole area, which is a few hundred miles long, have been supposed to represent a single genetic unit, and the sundry variations are believed to be local facies of a general mineralization. processes of secondary enrichment have in places yielded large quantities of oxidized silver minerals and wood tin near the surface, with accumulations of ruby silver ores at greater depths. the only other vein deposits which are at present of consequence are those of cornwall. here batholiths of granite have been intruded into paleozoic slates and sandstones, and tin ores occur in fissures and stockworks in the marginal zones. with the exhaustion of the more easily mined placers, the lode deposits will doubtless be of increasing importance. cassiterite is practically insoluble and is very resistant to decomposition by weathering. oxide zones of tin deposits are therefore enriched by removal of the more soluble minerals. stannite probably alters to "wood tin," a fibrous variety of cassiterite. secondary enrichment of tin deposits by redeposition of tin minerals is negligible. uranium and radium ores economic features radium salts are used in various medical treatments--especially for cancer, internal tumors, lupus, and birth marks--and in luminous paints. during the latter part of the war it is estimated that over nine-tenths of the radium produced was used in luminous paints for the dials of watches and other instruments. in addition part of the material owned by physicians was devoted to this purpose, and it is probable that the accumulated stocks held by the medical profession were in this way reduced by one-half. the greatly extended use of radium, together with the distinctly limited character of the world's known radium supplies, has led to some concern; and considerable investigation has been made of the possibilities of mesothorium as a substitute for radium in luminous paints. low-grade radium residues are used to some extent as fertilizers. uranium has been used as a steel alloy, but has not as yet gained wide favor. uranium salts have a limited use as yellow coloring agents in pottery and glass. the principal use of uranium, however, is as a source of radium, with which it is always associated. european countries first developed the processes of reduction of radium salts from their ores. most of the european ores are obtained from austria, where the mines are owned and operated by the austrian government, and small quantities are mined in cornwall, england, and in germany. production is decreasing. the european hospitals and municipalities have acquired nearly all of the production. the united states has the largest reserves of radium ore in the world, and the american market has in recent years been supplied from domestic plants. before the war, radium ores were shipped to europe for treatment in germany, france, and england, and radium salts were imported from these countries. there are now radium plants in the united states capable of producing annually from domestic ores an amount several times as large as the entire production of the rest of the world. practically all the production has come from colorado and utah. known reserves are not believed to be sufficient for more than a comparatively few years' production, but it is not unlikely that additional deposits will be found in the same area. geologic features uranium is one of the rarer metals. radium is found only in uranium ores and only in exceedingly small quantities. the maximum amount which can be present in a state of equilibrium is about one part of radium in , , parts of uranium. the principal sources of uranium and radium are the minerals carnotite (hydrous potassium-uranium vanadate) and pitchblende or uraninite (uranium oxide). the deposits of joachimsthal, bohemia, contain pitchblende, along with silver, nickel, and cobalt minerals and other metallic sulphides, in veins associated with igneous intrusions. the important commercial deposits of colorado and utah contain carnotite, together with roscoelite (a vanadium mica) and small amounts of chromium, copper, and molybdenum minerals, as impregnations of flat-lying jurassic sandstones. the ores carry up to per cent uranium oxide (though largely below per cent), and from one-third as much to an equal amount of vanadium oxide. the ore minerals are supposed to have been derived from a thick series of clays and impure sandstones a few hundred feet above, containing uranium and vanadium minerals widely disseminated, and to have been carried downward by surface waters containing sulphates. the ore bodies vary from very small pockets to deposits yielding a thousand tons or so, and are found irregularly throughout certain particular beds without any special relation to present topography or to faults. the association of many of the deposits with fossil wood and other carbonaceous material suggests that organic matter was an agent in their precipitation, but the exact nature of the process is not clear. in a few places in utah the beds dip at steep angles, and the carnotite appears in spots along the outcrops and generally disappears as the outcrops are followed into the hillsides; this suggests that the carnotite may be locally redissolved and carried to the surface by capillary action, forming rich efflorescences. because of the nature of the deposits no large amount of ore is developed in advance of actual mining; but estimates based on past experience indicate great potentialities of this region for future production. in eastern wyoming is a unique deposit of uranium ore in a quartzite which lies between mica-schist and granite. the principal ore mineral is uranophane, a hydrated calcium-uranium silicate, which is believed to be an oxidation product of pitchblende. some of the ore runs as high as per cent uranium oxide, and the ore carries appreciable amounts of copper but very little vanadium. very recently radium ores have been discovered in the white signal mining district of new mexico, which was formerly worked for gold, silver, copper, and lead. the radium-bearing minerals are torbernite and autunite (hydrous copper-uranium and calcium-uranium phosphates), and are found in dark felsite dikes near their intersections with east-west gold-silver-quartz veins. the possibilities of this district have not yet been determined. pitchblende has been found in gold-bearing veins in gilpin county, eastern colorado, and in pegmatite dikes in the appalachians, but these deposits are of no commercial importance. pitchblende is grayish-black, opaque, and so lacking in distinctive characteristics that it may readily be overlooked; hence future discoveries in various regions would not be surprising. chapter xiii miscellaneous non-metallic minerals natural abrasives economic features natural abrasives are less important commercially in the united states than artificial abrasives, but a considerable industry is based on the natural abrasives. silica or quartz in its various crystalline forms constitutes over three-fourths of the tonnage of natural abrasives used in the united states. it is the chief ingredient of sand, sandstone, quartzite, chert, diatomaceous earth, and tripoli. from the sand and sandstone are made millstones, buhrstones, grindstones, pulpstones, hones, oilstones, and whetstones. sand, sandstone, and quartzite are also ground up and used in sand-blasts, sandpaper, and for other abrasive purposes. chert or flint constitutes grinding pebbles and tube-mill linings, and is also ground up for abrasives. diatomaceous (infusorial) earth is used as a polishing agent and also as a filtering medium, an absorbent, and for heat insulation. tripoli (and rottenstone) are used in polishing powders and scouring soaps as well as for filter blocks and many other purposes. other important abrasives are emery and corundum, garnet, pumice, diamond dust and bort, and feldspar. imports of abrasive materials into the united states have about one-third of the value of those locally produced. while all of the various abrasives are represented in these imports, the united states is dependent on foreign sources for important parts of its needs only of emery and corundum, garnet, pumice, diamond dust and bort, and grinding pebbles. emery and corundum are used in various forms for the grinding and polishing of hard materials--steel, glass, stone, etc. the principal foreign sources of emery have been turkey (smyrna) and greece (naxos) where reserves are large and production cheap. production of corundum has come from canada, south africa, madagascar, and india. the domestic production of emery is mainly from new york and virginia, and corundum comes from north carolina. domestic supplies are insufficient to meet requirements, and cannot be substituted for the foreign material for the polishing of fine glass and other special purposes. curtailment of imports during the war greatly stimulated the development of artificial abrasives and their substitution for emery and corundum. garnet is used chiefly in the form of garnet paper for working leather, wood, and brass. garnet is produced mainly in the united states and spain. the united states is the only country using large amounts of this mineral and imports most of the spanish output. the domestic supply comes mainly from new york, new hampshire, and north carolina. pumice is used in fine finishing and polishing of varnished and enameled surfaces, and in cleaning powders. the world's principal source for pumice is the lipari islands, italy. there is a large domestic supply of somewhat lower-grade material (volcanic ash) in the great plains region, and there are high-grade materials in california and arizona. under war conditions these supplies were drawn on, but normally the high-quality italian pumice can be placed in american markets more cheaply. diamond dust is used for cutting gem stones and other very hard materials, and borts or carbonadoes (black diamonds) for diamond-drilling in exploration. most of the black diamonds come from brazil, and diamond dust comes from south africa, brazil, borneo, and india. chert or flint pebbles for tube-mills are supplied mainly from the extensive deposits on the french and danish coasts. the domestic production has been small, consisting principally of flint pebbles from the california beaches, and artificial pebbles made from rhyolite in nevada and quartzite in iowa. war experience demonstrated the possibility of using the domestic supply in larger proportion, but the grade is such that in normal times this supply will not compete with importations. feldspar as an abrasive is used mainly in scouring soaps and window-wash. domestic supplies are ample. the principal use of feldspar is in the ceramic industry and the mineral is discussed at greater length in the chapter on common rocks (p. ). for the large number of abrasives produced from silica, outside of flint pebbles, domestic sources of production are ample. siliceous rocks are available almost everywhere. for particular purposes, however, rocks possessing the exact combinations of qualities which make them most suitable are in many cases distinctly localized. _millstones and buhrstones_, used for grinding cereals, paint ores, cement rock, fertilizers, etc., are produced chiefly in new york and virginia; partly because of trade prejudice and tradition, about a third of the american requirements are imported from france, belgium, and germany. _grindstones and pulpstones_, used for sharpening tools, grinding wood-pulp, etc., come mainly from ohio and to a lesser extent from michigan and west virginia; about per cent of the consumption is imported from canada and great britain. _hones_, _oilstones_, and _whetstones_ are produced largely from a rock called "novaculite" in arkansas, and also in indiana, ohio, and new england; imports are negligible. _flint linings_ for tube-mills were formerly imported from belgium, but american products, developed during the war in pennsylvania, tennessee, and iowa, appear to be wholly satisfactory substitutes. _diatomaceous earth_ is produced in california, nevada, connecticut, and maryland, and _tripoli and rottenstone_ in illinois, missouri, and oklahoma; domestic sources are sufficient for all needs, but due to questions of back-haul and cost of rail transportation there has been some importation from england and germany. geologic features the geologic features of silica (quartz), feldspar, and diamonds are sufficiently indicated elsewhere (chapter ii; pp. , , , - ). diatomaceous earth is made up of remains of minute aquatic plants. it may be loose and powdery, or coherent like chalk. it is of sedimentary origin, accumulated originally at the bottoms of ponds, lakes, and in the sea. tripoli and rottenstone are light, porous, siliceous rocks which have resulted from the leaching of calcareous materials from various siliceous limestones or calcareous cherts in the process of weathering. grinding pebbles are derived from the erosion of limestone or chalk formations which contain concretions of extremely fine-grained and dense chert. under stream and wave action they are rounded and polished. the principal sources are ocean beaches. corundum as an abrasive is the mineral of this name--made up of anhydrous aluminum oxide. emery is an intimate mechanical mixture of corundum, magnetite, and sometimes spinel. corundum is a product of contact metamorphism and also a result of direct crystallization from molten magma. canadian corundum occurs as a constituent of syenite and nepheline-syenite in lower ontario. in north carolina and georgia, the corundum occurs in vein-like bodies at the contact of peridotite with gneisses and schists, and also in part in the peridotite itself. in new york the emery deposits are segregations of aluminum and iron oxides in norite (a basic igneous rock). the emery of greece and turkey occurs as lenses or pockets in crystalline limestones, and is the result of contact metamorphism by intrusive granites. garnets result mainly from contact metamorphism, and commonly occur either in schists and gneisses or in marble. the principal american occurrences are of this type. being heavy and resistant to weathering, they are also concentrated in placers. the spanish garnets are reported to be obtained by washing the sands of certain streams. pumice is solidified rock froth formed by escape of gases from molten igneous rocks at the surface. it is often closely associated with volcanic ash, which is also used for abrasive purposes. in general, the geologic processes entering into the formation of abrasives cover almost the full range from primary igneous processes to surface alterations and sedimentation. asbestos economic features the principal uses of asbestos are in high-pressure packing in heat engines, in thermal and electrical insulation, in fire-proofing, and in brake-band linings. the largest producers of asbestos are canada (quebec) and, to a considerably less extent, russia. united states interests have financial control of about a fourth of the canadian production, and practically the entire export trade of canada goes to the united states. russia exports nearly all her product to germany, austria, united kingdom, belgium, and the netherlands. previous to the war the output was largely controlled by a german syndicate. there is a considerable recent production in south africa, which is taken by england and the united states, and small amounts are produced in italy, cyprus, and australia. the united states has been a large importer of asbestos, from canada and some other sources. domestic production is relatively insignificant, and exports depend chiefly on an excess of import. georgia is the principal local source. arizona and california are also producers, their product being of a higher grade. the united states is the largest manufacturer of asbestos goods, and exports go to nearly all parts of the world. so long as the abundant canadian material is accessible on reasonable conditions, the united states is about as well situated as if independent. some canadian proposals of restriction during the war led to a study of other supplies and showed that several deposits, such as those in russia and africa, might compete with the canadian asbestos. geologic features asbestos consists mostly of magnesium silicate minerals--chrysotile, anthophyllite, and crocidolite. the term asbestos covers all fibrous minerals with some tensile strength which are poor conductors and can be used for heat-protection. like talc, they are derived principally from the alteration of olivine, pyroxene, and amphibole,--or more commonly from serpentine, which itself results from the alteration of these minerals. chrysotile is the most common, and because of the length, fineness, and flexibility of its fibers, enabling it to be spun into asbestos ropes and fabrics, it is the most valuable. anthophyllite fibers, on the other hand, are short, coarse, and brittle, and can be used only for lower-grade purposes. crocidolite or blue asbestos is similar to chrysotile but somewhat inferior in fire-resisting qualities. asbestos deposits occur chiefly as veinlets in serpentine rock, which is itself the alteration of some earlier rock like peridotite. they are clearly formed in cracks and fissures through the agency of water, but whether the waters are hot or cold is not apparent. the veinlets have sometimes been interpreted as fillings of contraction cracks, but more probably are due to recrystallization of the serpentine, proceeding inward from the cracks. in quebec the chrysotile asbestos (which is partly of spinning and partly of non-spinning grade) forms irregular veins of this nature in serpentine, the fiber making up to per cent of the rock. in georgia the asbestos, which is anthophyllite, occurs in lenticular masses in peridotite associated with gneiss. it is supposed to have formed by the alteration of olivine and pyroxene in the igneous rocks. in arizona chrysotile is found in veins in cherty limestone, associated with diabase intrusives. here it is believed to be an alteration product of diopside (lime-magnesia pyroxene) in a contact-metamorphic silicated zone. crocidolite is mined on a commercial scale only in cape colony, south africa. the deposits occur in thin sedimentary layers interbedded with jaspers and ironstones. their origin has not been worked out in detail. the deposits of russia, the transvaal, rhodesia, and australia are of high-grade chrysotile, probably similar in origin to the quebec deposits. the asbestos of italy and cyprus is anthophyllite, more like the georgia material. barite (barytes) economic features barite is used chiefly as a material for paints. for this purpose it is employed both in the ground form and in the manufacture of lithopone, a widely used white paint consisting of barium sulphate and zinc sulphide. ground barite is also used in certain kinds of rubber goods and in the making of heavy glazed paper. lesser amounts go into the manufacture of barium chemicals, which are used in the preparation of hydrogen peroxide, in softening water, in tanning leather, and in a wide variety of other applications. germany is the world's principal producer of barite and has large reserves of high grade. great britain also has extensive deposits and produces perhaps one-fourth as much as germany. france, italy, belgium, austria-hungary, and spain produce smaller but significant amounts. before the war the united states imported from germany nearly half the barite consumed in this country, and produced the remainder. under the necessities of war times, adequate domestic supplies were developed and took care of nearly all the greatly increased demands. production has come from fourteen states, the large producers being georgia, missouri, and tennessee. during the war, also, an important movement of barite-consuming industries to the middle west took place, in order to utilize more readily and cheaply the domestic product. for this reason it is not expected that german barite will play as important a part as formerly in american markets,--although it can undoubtedly be put down on the atlantic seaboard much more cheaply than domestic barite, which requires long rail hauls from southern and middle-western states. geologic features the mineral barite is a heavy white sulphate of barium, frequently called "barytes" or "heavy spar." witherite, the barium carbonate, is a much rarer mineral but is found with barite in some veins. all igneous rocks contain at least a trace of barium, which is probably present in the silicates, and these small quantities are the ultimate source of the more concentrated deposits. barite itself is not found as an original constituent of igneous rocks or pegmatites, but is apparently always formed by deposition from aqueous solutions. it is a common gangue mineral in many deposits of metallic sulphides, both those formed in relation to igneous activity and those which are independent of such activity, but in these occurrences it is of little or no commercial importance. the principal deposits of barite are found in sedimentary rocks, and especially in limestones and dolomites. in these rocks it occurs in veins and lenses very similar in nature to the lead and zinc deposits of the mississippi valley (p. _et seq._), and, like them, probably deposited by cold solutions which gathered together small quantities of material from the overlying or surrounding rocks. the missouri deposits are found in limestones in a region not far from the great southeastern missouri lead district, and vary from the lead deposits in relative proportions rather than in kind of minerals; the veins consist chiefly of barite, with minor quantities of silica, iron sulphide, galena, and sphalerite. the deposits of the southern appalachians occur as lenses in limestones and schists. barite is little affected by surface weathering, and tends to remain behind while the more soluble minerals of the associated rock are dissolved out and carried away. a limited amount of solution and redeposition of the barite takes place, however, resulting in its segregation into nodules in the residual clays. most of the barite actually mined comes from these residual deposits, which owe their present positions and values to katamorphic processes. the accompanying clay and iron oxide are removed by washing and mechanical concentration. certain investigators of the deposits of the mississippi valley are extremely reluctant to accept the idea that the ores are formed by surface waters of ordinary temperatures, and are inclined to appeal to heated waters from a hypothetical underlying magmatic source. the fact that barite is a characteristic mineral of many igneous veins, and the fact that in this same general region it is found in the kentucky-illinois fluorspar deposits,--where a magmatic source is generally accepted,--together with doubts as to the theoretical efficacy of meteoric waters to transport the minerals found in the barite deposits, have led certain writers to ascribe to these barite deposits a magmatic origin. the magmatic theory has not been disproved; but on the whole the balance of evidence seems strongly to indicate that the barite deposits as well as the lead and zinc ores, which are essentially the same in nature though differing in mineral proportions, have been concentrated from the adjacent sediments by ordinary surface waters. borax economic features borax-bearing minerals are used almost entirely in the manufacture of borax and boric acid. fully a third of the borax consumed in the united states is used in the manufacture of enamels or porcelain-like coatings for such objects as bathtubs, kitchen sinks, and cooking utensils. other uses of borax or of boric acid are as a flux in the melting and purification of the precious metals, in decomposing chromite, in making glass, as a preservative, as an antiseptic, and as a cleansing agent. recent developments indicate that the metal, boron, may play an important part in the metallurgy of various metals. it has been used in making very pure copper castings for electrical purposes, in aluminum bronzes, and in hardening aluminum castings; and an alloy, ferroboron, has been shown experimentally to act on steel somewhat like ferrovanadium. the bulk of the world's borax comes from the western hemisphere, the united states and chile being the two principal producers. there are additional large deposits in northern argentina, southern peru, and southern bolivia, which have thus far been little drawn on because of their inaccessibility. english financial interests control most of these south american deposits. the only large european producer of borax is turkey. italy and germany produce small amounts. there has also been small production of borax in thibet, brought out from the mountains on sheep-back. the united states supplies of borax are sufficient for all domestic requirements and probably for export. small quantities of boric acid are imported, but no borax in recent years. the domestic production comes entirely from california, though in the past deposits in nevada and oregon have also been worked. geologic features the element boron is present in various complex boro-silicates, such as datolite and tourmaline, the latter of which is used as a precious stone (pp. , ). none of these are commercial sources of borax. the principal boron minerals are borax or "tincal" (hydrated sodium borate), colemanite (hydrated calcium borate), ulexite (hydrated calcium-sodium borate), and boracite (magnesium chloro-borate). commercially the term borax is sometimes applied to all these materials. these minerals appear in nature under rather widely differing modes of origin. the borax production of italy is obtained from the famous "soffioni" or "fumaroles" of tuscany. these are volcanic exhalations, in which jets of steam carrying boric acid and various borates, together with ammonium compounds, emerge from vents in the ground. the boric acid material is recovered by a process of condensation. borates, principally in the form of borax, occur in hot springs and in lakes of volcanic regions. the thibet deposits, and those formerly worked at borax lake, california, are of this type. certain of the hot-spring waters of the california coast ranges and of nevada carry considerable quantities of boron, together with ammoniacal salts, and in some places they deposit borax along with sulphur and cinnabar. it seems probable (see p. ) that these waters may come from an igneous source not far beneath. most of the borax deposits of california, nevada, and oregon, though not at present the largely producing ones, and probably most of the chilean and adjacent south american deposits, are formed by the evaporation of desert lakes. they are products of desiccation, and in chile are associated with the great nitrate deposits (pp. - ), which are of similar origin. the salts contained in these deposits are mainly borax, ulexite, and colemanite. the sources of these materials are perhaps deposits of the type mentioned in the last paragraph, or, in california, certain tertiary borate deposits described below. whatever their source, the borates are carried in solution by the waters of occasional rains to shallow basins, which become covered with temporary thin sheets of water or "playa lakes." evaporation of these lakes leaves broad flats covered with the white salts. these may subsequently be covered with drifting sands and capillary action may cause the borates to work up through the sands, becoming mixed with them and efflorescing at the surface. one of the largest of the california deposits of this general class is that at searles lake, from which it has been proposed to recover borax along with the potash (pp. - ). the deposits which at present constitute the principal source of domestic borax are not the playa deposits just described, but are masses of colemanite in tertiary clays and limestones with interbedded basaltic flows. the principal deposits are in death valley and adjacent parts of california. the colemanite occurs in irregular milky-white layers or nodules, mingled with more or less gypsum. the deposits are believed to be of the replacement type, rather than ones formed contemporaneously with the sediments. whether they are due to magmatic solutions carrying boric acid from the associated flows, or to surface waters carrying materials leached from other sediments, is not clear. the crude colemanite as mined carries an average of about per cent b_ o_ ; it is treated with soda in the manufacture of borax, or with sulphuric acid in making boric acid. boron is present in minute quantities in sea water. when such water evaporates, it becomes concentrated, along with the magnesium and potassium salts, in the "mother liquor"; and upon complete evaporation, it crystallizes out as boracite and other rarer minerals. thus the stassfurt salts of germany (p. ) contain borates of this type in the carnallite zone of the upper part of the deposits. this is the only important case known of borate deposits of marine origin. bromine economic features bromine finds a considerable use in chemistry as an oxidizing agent, in separating gold from other metals, and in manufacturing disinfectants, bromine salts, and aniline colors. the best known and most widely used bromine salts are the silver bromide, used in photography, and the potassium bromide, used in medicine to depress the nervous system. during the war, large quantities of bromine were used in asphyxiating and lachrymating gases. the chief center of the bromine industry in europe prior to was stassfurt, germany. no other important commercial source in foreign countries is known, though small quantities have been obtained from the mother liquors of chile saltpeter and from the seaweed, kelp, in various countries. india has been mentioned as a possible large producer in the future. the united states is independent of foreign sources for bromine. the entire domestic tonnage is produced from brines pumped in michigan, ohio, west virginia, and pennsylvania. a large part of the output is not actually marketed as bromine, but in the form of potassium and sodium bromides and other salts. during the war considerable quantities of bromine materials were exported to great britain, france, and italy. geologic features bromine is very similar chemically to chlorine, and is found under much the same conditions, though usually in smaller quantities. the natural silver bromide (bromyrite) and the combined silver chloride and bromide (embolite) are fairly common in the oxide zones of silver ores, but are not commercial sources of bromine. bromine occurs in sea water in appreciable amounts, as well as in some spring waters and many natural brines. when natural salt waters evaporate, bromine is one of the last materials to be precipitated, and the residual "mother liquors" or bitterns frequently show a considerable concentration of the bromine. where complete evaporation takes place, as in the case of the stassfurt salt deposits (p. ), the bromine salts are crystallized out in the final stages along with the salts of sodium, magnesium, and potassium. the larger part of the world's bromine has come from the mother liquor resulting from the solution and fractional evaporation of these stassfurt salts. the bromine obtained from salt deposits in the eastern united states is doubtless of a similar origin. it is produced as a by-product of the salt industry, the natural or artificial brines being pumped from the rocks (p. ), and the bromides being extracted either from the mother liquors or directly from the unconcentrated brines. fuller's earth economic features fuller's earth is used chiefly for bleaching, clarifying, or filtering mineral and vegetable oils, fats, and greases. the petroleum industry is the largest consumer. minor uses are in the manufacture of pigments for printing wall papers, in detecting coloring matters in certain food-products, and as a substitute for talcum powder. fuller's earths are in general rather widely distributed. the principal producers are the united states, england, and the other large consuming countries of europe. the only important international trade in this commodity consists of exports from the united states to various countries for treating mineral oils, and exports from england for treating vegetable oils. there is a large surplus production in the united states of fuller's earth of a grade suitable for refining mineral oils, but an inadequate production of material for use in refining edible oils, at least by methods and equipment now in most general use. however, the imports needed from england are more than offset by our exports to europe of domestic earth particularly adapted to the petroleum industry. production in the united states comes almost entirely from the southern states; florida produces over three-fourths of the total and other considerable producers are texas, georgia, california, and arkansas. imports from england are normally equivalent to about a third of the domestic production. geologic features fuller's earth is essentially a variety of clay having a high absorptive power which makes it useful for decolorizing and purifying purposes. fuller's earths are in general higher in water content and have less plasticity than most clays, but they vary widely in physical and chemical properties. chemical analyses are of little value in determining whether a given clay will serve as fuller's earth, and an actual test is the only trustworthy criterion. deposits of fuller's earth may occur under the same variety of conditions as deposits of other clays. the deposits of florida and georgia consist of beds in slightly consolidated flat-lying tertiary sediments, which are worked by open cuts. the arkansas deposits are residual clays derived from the weathering of basic igneous rocks, and are worked through shafts. graphite (plumbago) economic features _crystalline graphite_ is used principally in the manufacture of crucibles for the melting of brass, bronze, crucible steel, and aluminum. about per cent of the quantity and per cent of the value of all the graphite consumed in the united states is employed in this manner. both _crystalline_ and _amorphous graphite_ are used in lubricants, pencils, foundry facings, boiler mixtures, stove-polishes and paint, electrodes, and fillers or adulterants for fertilizers. the most important use of amorphous graphite is for foundry facings, this application accounting for about per cent of the total united states consumption of graphite of all kinds. _artificial graphite_ is not suitable for crucibles or pencils but is adapted to meet other uses to which natural graphite is put. it is particularly adapted to the manufacture of electrodes. the grade of graphite deposits varies widely, their utilization being largely dependent on the size of the grains and the ease of concentration. some of the richest deposits, those of madagascar, contain per cent or more of graphite. the united states deposits contain only to per cent. the graphite situation is complicated by the differences in the quality of different supplies. crucibles require coarsely crystalline graphite, but pencils, lubricants, and foundry facings may use amorphous and finely crystalline material. the largest production of high-grade crucible graphite has come from ceylon, under british control, and about two-thirds of the output has come to the united states. the mines are now worked down to water-level and costs are increasing. in later years a rival supply has come from the french island of madagascar, where conditions are more favorable to cheap production, and where reserves are very large. french, british, and belgian interests are concerned in the development of these deposits. the quality of graphite is different from the ceylon product; it has not found favor in the united states but is apparently satisfactory to crucible makers in europe. most of the output is exported to great britain and france, and smaller amounts to germany and belgium. less satisfactory supplies of crystalline graphite are available in many countries, including bavaria, canada, and japan. large deposits of crystalline material have been reported in greenland, brazil, and roumania, but as yet have assumed no commercial importance. amorphous graphite is widely distributed, being produced in about twenty countries,--chiefly in austria, italy, korea, and mexico. certain deposits have been found to be best for special uses, but most countries could get along with nearby supplies. a large part of the world's needs of crucible graphite will probably continue to be met from ceylon and madagascar, while a large part of the amorphous graphite will come from the four sources mentioned. the united states has been largely dependent upon importations from ceylon for crucible graphite. domestic supplies are large and capable of further development, but for the most part the flake is of such quality that it is not desired for crucible manufacture without large admixture of the ceylon material. restrictions during the war required crucible makers to use at least per cent of domestic or canadian graphite in their mixtures, with per cent of foreign graphite. this created a demand for domestic graphite which caused an increased domestic output. most of the production in the united states comes from the appalachians, particularly from alabama, new york, and pennsylvania, and smaller amounts are obtained from california, montana, and texas. one of the permanently beneficial effects of the war was the improvement of concentrating practice and the standardization of output, to enable the domestic product to compete more effectively with the well-standardized imported grades. whether the domestic production will hold its own with foreign competition under peace conditions remains to be seen. domestic reserves are large but of low grade. the madagascar graphite, in the shape and size of the flakes, is more like the american domestic graphite than the ceylon product. small amounts have been used in this country, but american consumers appear in general to prefer the ceylon graphite in spite of its greater cost. the madagascar product can be produced and supplied to eastern united states markets much more cheaply than any other large supply; and, in view of the possible exhaustion of the ceylon deposits, it may be desirable for american users to adapt crucible manufacture to the use of madagascar material as has already apparently been done in europe. expansion of the american graphite industry during the war, and its subsequent collapse, have resulted in agitation for a duty on imports of foreign graphite. amorphous graphite is produced from some deposits in the united states (colorado, nevada, and rhode island), but the high quality of mexican graphite, which is controlled by a company in the united states, makes it likely that imports from this source will continue. since the war the mexican material has practically replaced the austrian graphite in american markets. the output of korea is divided between the united states and england. artificial graphite, in amounts about equal to the domestic production of amorphous graphite, is produced from anthracite or petroleum coke at niagara falls. geologic features the mineral graphite is a soft, steel-gray, crystalline form of carbon. ceylon graphite occurs in veins and lenses cutting gneisses and limestones. usually the veins consist almost entirely of graphite, but sometimes other minerals occur in important amounts, especially pyrite and quartz. the association of graphite with these minerals, and also with feldspar, pyroxene, apatite, and other minerals, suggests that the veins are of igneous origin, like some of the pegmatite veins in the adirondacks of new york. the graphite is mined from open pits and shafts, and sorted by hand and mechanically. the product consists of angular lumps or chips with a relatively small amount of surface in proportion to their volume. in madagascar the graphite is mainly disseminated in a graphitic schist, though to some extent it is present in the form of veins and in gneiss. most of the graphite is mined from a weathered zone near the surface, and the material is therefore soft and easily concentrated. the product is made up of flakes or scales, and in the making of crucibles requires the use of larger amounts of clay binder than the ceylon graphite. the flake graphite of the united states, principally in the appalachian region, occurs in crystalline graphitic schists, resulting from the anamorphism of sedimentary rocks containing organic matter. certain beds or zones of comparatively narrow width carry from to per cent of disseminated graphite. the graphite is recovered by mechanical processes of sorting. the graphite is believed to be of organic origin, the change from organic carbon to graphite having been effected by heat and pressure accompanying mountain-building stresses. some of the graphite also occurs in pegmatite intrusives and adjacent wall rocks. this graphite is considered to be of inorganic origin, formed by the breaking up of gaseous oxides of carbon in the original magma of the pegmatites. the montana graphite is similar in origin. this inorganic graphite in pegmatite veins resembles ceylon graphite, in breaking into large lumps and chips, but supplies are very limited. amorphous graphite is formed in many places where coal and other carbonaceous materials have undergone extreme metamorphism. it represents simply a continuation in the processes by which high grade coals are formed from plant matter (pp. - ). the mexican deposits are of this type, and occur in beds up to feet in thickness interbedded with metamorphosed sandstones. in general, graphite is primarily concentrated both by igneous processes in dikes, and by sedimentary processes in beds. in the latter case anamorphism is necessary to recrystallize the carbon into the form of graphite. gypsum economic features the principal use of gypsum is in structural materials. about two-thirds of the gypsum produced in the united states is used in the manufacture of various plasters--wall plaster, plaster of paris, and keene's cement (for statuary and decorative purposes),--and about a fifth is used as a retarder in portland cement. another important structural use is in the manufacture of plaster boards, blocks, and tile for interior construction. gypsum is used as a fertilizer under the name of "land plaster," and with the growing recognition of the lack of sulphur in various soils an extension of its application is not unlikely. minor uses are in the polishing of plate glass, in the manufacture of dental plaster, in white pigments, in steampipe coverings, and as a filler in cotton goods. the world's gypsum deposits are widely distributed. of foreign countries, france, canada, and the united kingdom are the principal producers. germany, algeria, and india produce comparatively meager amounts. the united states is the largest producer of gypsum in the world. in spite of its large production, the united states normally imports quantities equivalent to between one-fifteenth and one-tenth of the domestic production, mainly in the crude form from nova scotia and new brunswick for consumption by the mills in the vicinity of new york. this material is of a better grade than the eastern domestic supply, and is cheaper than the western supply for eastern consumption. during the war this importation was practically stopped because of governmental requisition of the carrying barges for the coal-carrying trade, but with the return of normal conditions it was resumed. there is no prospect of importation of any considerable amount from any other sources. the domestic supply is ample for all demands. production of gypsum in the united states comes from eighteen states. four-fifths of the total comes from new york, iowa, michigan, ohio, texas, and oklahoma. there are extensive deposits in some of the western states, the known reserves in wyoming alone being sufficient for the entire world demands for many decades. the united states exports a small amount of crude gypsum to canada, principally for use in portland cement manufacture. this exportation is due to geographic location. the united states is the largest manufacturer of plaster boards, insulating materials, and tile, and exports large quantities of these products to cuba, australia, japan, and south america. geologic features gypsum is a hydrated calcium sulphate. it is frequently associated with minor quantities of anhydrite, which is calcium sulphate without water, and under the proper natural conditions either of these materials may be changed into the other. common impurities in gypsum deposits include clay and lime carbonate, and also magnesia, silica, and iron oxide. in the material as extracted, impurities may range from a trace to about per cent. _gypsite_, or gypsum dirt, is an impure mixture of gypsum with clay or sand found in kansas and some of the western states; it is believed to have been produced in the soil or in shallow lakes, by spring waters carrying calcium sulphate which was leached from gypsum deposits or from other rocks. gypsum deposits, like deposits of common salt, occur in beds which are the result of evaporation of salt water. calcium makes up a small percentage of the dissolved material in the sea, and when sea waters are about per cent evaporated it begins to be precipitated as calcium sulphate. conditions for precipitation are especially favorable in arid climates, in arms of the sea or in enclosed basins which may or may not once have been connected with the sea. simultaneously with the deposition of gypsum, there may be occasional inwashings of clay and sand, and with slight changes of conditions organic materials of a limey nature may be deposited. further evaporation of the waters may result in the deposition of common salt. thus gypsum beds are found interbedded with shales, sandstones, and limestones, and frequently, but not always, they are associated with salt beds. the nature of these processes is further discussed under the heading of salt (pp. - ). the anhydrite found in gypsum deposits is formed both by direct precipitation from salt water and by subsequent alteration of the gypsum. the latter process involves a reduction of volume, and consequently a shrinkage and settling of the sediments. the hydration of anhydrite to form gypsum, on the other hand, involves an increase of volume and may result in the doming up and shattering of the overlying sediments. gypsum is fairly soluble in ground-water, and sink-holes and solution cavities are often developed in gypsum deposits. these may allow the inwash of surface dirt and also may interfere with the mining. all the important commercial gypsum deposits are believed to have been formed by evaporation of salt water in the manner indicated. small quantities of gypsum are formed also when pyrite and other sulphides oxidize to sulphuric acid and this acid acts on limestone. thus gypsum is found in the oxide zones of some ore bodies. these occurrences are of no commercial significance. mica economic features the principal use of sheet mica is for insulating purposes in the manufacture of a large variety of electrical equipment. the highest grades are employed particularly in making condensers for magnetos of automobile and airplane engines and for radio equipment, and in the manufacture of spark plugs for high tension gas engines. sheet mica is also used in considerable amounts for glazing, for heat insulation, and as phonograph diaphragms. ground mica is used in pipe and boiler coverings, as an insulator, in patent roofing, and for lubricating and decorative purposes. india, canada, and the united states are the important sheet mica-producing countries, before the war accounting for per cent of the world's total. india has long dominated the sheet mica markets of the world, and will probably continue to supply the standard of quality for many years. the bulk of the indian mica is consumed in the united states, great britain, and germany. the mica of india and the united states is chiefly muscovite. canada is the chief source of amber mica (phlogopite), though other deposits of potential importance are known in ceylon and south africa. canadian mica is produced chiefly in quebec and ontario, and is exported principally to the united states. important deposits of mica (principally muscovite) are also known in brazil, argentina, and german east africa. large shipments were made from the two former countries during the war, both to europe and the united states, and brazil particularly should become of increasing importance as a producer of mica. the deposits in german east africa were being quite extensively developed immediately before the war and large shipments were made to germany in . the united states is the largest consumer of sheet mica and mica splittings, absorbing normally nearly one-half of the world's production. approximately three-fifths of this consumption is in the form of mica splittings, most of which are made from muscovite in india and part from amber mica in canada. due to the cheapness of labor in india and the amenability of indian mica to the splitting process, india splittings should continue to dominate the market in this country. amber mica is a variety peculiarly adapted to certain electrical uses. there are no known commercial deposits of this mica in the united states, but american interests own the largest producing mines in canada. shipments of brazilian mica are not of such uniformly high quality as the indian material, but promise to become of increasing importance in american markets. of the sheet mica consumed annually, the united states normally produces about one-third. war conditions, although stimulating the production of domestic mica very considerably, did not materially change the situation in this country as regards the dependence of the united states on foreign supplies for sheet mica. about per cent of the domestic mica comes from north carolina and per cent from new hampshire. the deposits are small and irregular, and mining operations are small and scattered. these conditions are largely responsible for the heterogeneous nature of the american product. it is hardly possible for any one mine to standardize and classify its product, although progress was made in this direction during the war by the organization of associations of mica producers. this lack of standardization and classification is a serious handicap in competition with the standard grades and sizes which are available in any desired amounts from foreign sources. for ground mica, the domestic production exceeds in tonnage the total world production of sheet mica, and is adequate for all demands. geologic features mica is a common rock mineral, but is available for commerce only in igneous dikes of a pegmatite nature, where the crystallization is so coarse that the mica crystals are exceptionally large. muscovite mica occurs principally in the granitic pegmatite dikes. the phlogopite mica of canada occurs in pyroxenite dikes. the distribution of mica within the dikes is very erratic, making predictions as to reserves hazardous. the associated minerals, mainly quartz and feldspar, are ordinarily present in amounts greater than the mica. also, individual deposits are likely to be small. for these reasons mining operations cannot be organized on a large scale, but are ordinarily hand-to-mouth operations near the surface. a large amount of hand labor is involved, and the indian deposits are favored by the cheapness of native labor. the output of a district is from many small mines rather than from any single large one. pegmatites which have been subjected to dynamic metamorphism are often not available as a source of mica, because of the distortion of the mica sheets. the mining of a mica is facilitated by weathering, which softens the associated feldspar, making it an easier task to take out the mica blocks. on the other hand, iron staining by surface solutions during weathering may make the mica unfit for electrical and certain other uses. scrap or ground mica is obtained as a by-product of sheet mica and from deposits where the crystals are not so well developed. black mica (biotite) and chlorite minerals, which are soft and flexible but not elastic and are found extensively developed in certain schists, have been used to a limited extent for the same purposes. monazite (thorium and cerium ores) economic features the mineral monazite is the source of the thorium and cerium compounds which, glowing intensely when heated, form the light-giving material of incandescent gas mantles. welsbach mantles consist of about per cent thorium oxide and per cent cerium oxide. cerium metal, alloyed with iron and other metals, forms the spark-producing alloys used in various forms of gas lighters and for lighting cigars, cigarettes, etc. mesothorium, a by-product of the manufacture of thorium nitrate for gas mantles, is used as a substitute for radium in luminous paints and for therapeutic purposes. the alloy ferrocerium is used to a small extent in iron and steel. the world's supply of monazite is obtained mainly from brazilian and indian properties. before the war german commercial interests controlled most of the production, as well as the manufacture of the thorium products. during the war german control was broken up. the united states has a supply of domestic monazite of lower grade than the imports, but is dependent under normal conditions on supplies from brazil and india. the american deposits are chiefly in north and south carolina, and have been worked only during periods of abnormally high prices or of restriction of imports. known reserves are small and the deposits will probably never be important producers. during the war, however, the united states became the largest manufacturer of thorium nitrate and gas mantles and exported these products in considerable quantity. an effort is now being made to secure protective legislation against german thorium products. geologic features monazite is a mineral consisting of phosphates of cerium, lanthanum, thorium, and other rare earths in varying proportions. the content of thorium oxide varies from a trace up to per cent, and commercial monazite sands are usually mixed so as to bring the grade up to at least per cent. yellowish-brown crystals of monazite have been found scattered through granites, gneisses, and pegmatites, but in quantities ordinarily too small to warrant mining. in general the mineral is recovered on a commercial scale only from placers, where it has been concentrated along with other dense, insoluble minerals such as zircon, garnet, ilmenite, and sometimes gold. the indian and brazilian monazite is obtained principally from the sands of ocean beaches, in the same localities from which zircon is recovered (p. ). the north and south carolina monazite has been obtained chiefly from stream beds, and to a slight extent by mining and washing the rotted underlying rock, which is a pegmatized gneiss. monazite, together with a small amount of gold, is also known in the stream gravels of the boise basin, idaho, where a large granitic batholith evidently carries the mineral sparsely distributed throughout. these deposits have not been worked. precious stones economic features precious stones range high in the world's annual production of mineral values. a hundred or more minerals are used to some degree as precious stones; but those most prized, representing upwards of per cent of the total production value, are diamond, pearl, ruby, sapphire, and emerald. in total value the diamonds have an overwhelming dominance. over a ton of diamonds is mined annually. diamonds come mainly from south africa, which produces over per cent of the total. pearls come chiefly from the indian and pacific oceans. burma is the principal source of fine rubies. siam is the principal producer of sapphires. colombia is the principal source of fine emeralds. the united states produces small amounts of sapphires (in montana) and pearls (from fresh-water molluscs). diamonds, rubies, and emeralds are practically absent on a commercial scale. of other precious and semi-precious gem stones produced in the united states, the principal ones are quartz, tourmaline, and turquoise. on the other hand, the united states absorbs by purchase over half of the world's production of precious stones. it is estimated roughly that there are now in the united states nearly one billion dollars' worth of diamonds, or over one-half of the world's accumulated stock, and probably the proportions for the other stones are not far different. value attaches to a precious stone because of its qualities of beauty, coupled with endurance and rarity, or because of some combination of these features which has caught the popular fancy. no one of these qualities is sufficient to make a stone highly prized; neither does the possession of all of them insure value. some beautiful and enduring stones are so rare that they are known only to collectors and have no standard market value. others fail to catch the popular fancy for reasons not obvious to the layman. while the intrinsic qualities go far in determining the desirability of a stone, it is clear that whim and chance have been no small factors in determining the demand or lack of demand for some stones. as in other minerals, value has both its intrinsic and extrinsic elements. for the leading precious stones above named, the values are more nearly standard throughout the world than for any other minerals, with the exception of gold and possibly platinum. highly prized everywhere and easily transported, the price levels show comparatively little variation over the world when allowance is made for exchange and taxes. the valuation of precious stones is a highly specialized art, involving the appraisal not only of intrinsic qualities, but of the appeal which the stone will make to the buying public. in marking a sale price for some exceptional stone not commonly handled in the trade, experts in different parts of the world often reach an almost uncanny uniformity of opinion. it is estimated that the world stock of precious stones approximates three billion dollars, or a third of the world's monetary gold reserve. because of small bulk and standard value, this wealth may be easily secreted, carried, and exchanged. when the economic fabric of civilization is disturbed by war or other conditions, precious stones become a medium of transfer and exchange of wealth of no inconsiderable importance. the beauty of a stone may arise from its color or lack of color, from its translucency or opaqueness, from its high refraction of light, and from the manner of cutting and polishing to bring out these qualities. hardness and durability are desirable qualities. the diamond is the hardest known mineral and the sapphire, ruby, and emerald rank high in this regard. on the other hand the pearl is soft and fragile and yet highly prized. geologic features the principal precious stones above named are of simple composition. diamond is made of carbon; the pearl is calcium carbonate; ruby and sapphire are aluminum oxide--varieties of the mineral corundum; the emerald is silica and alumina, with a minor amount of beryllia. minute percentages of chromite, iron, manganese, and other substances are often responsible for the colors in these stones. carbon also constitutes graphite and is the principal element in coal. lime carbonate is the principal constituent of limestone and marble. alumina is the principal constituent of bauxite, the ore of aluminum, and of the natural abrasives, emery and corundum. silica, the substance of common quartz, also constitutes gem quartz, amethyst, opal, agate, onyx, etc. most of the world's diamonds come from the kimberley and transvaal fields of south africa, where they are found in a much decomposed volcanic rock called "blue ground." this is a rock of dull, greasy appearance consisting largely of serpentine. it was originally peridotite, occurring in necks or plugs of old volcanoes penetrating carbonaceous sediments. when the rock is mined and spread at the surface, it decomposes in the course of six months or a year, allowing it to be washed and mechanically sorted for its diamond content. the amount of ground treated in one of the large mines is about equal to that handled in operating the huge porphyry copper deposit of bingham, utah; the annual production of diamonds from the same mine could be carried in a large suit-case. the diamonds were clearly formed at high temperatures and pressures within the igneous rocks. it has been suggested that the igneous magma may have secured the carbon by the melting of carbonaceous sediments through which it penetrated, but proof of this is difficult to obtain. artificial diamonds of small size have been made in the electric furnace under high-pressure conditions not unlike those assumed to have been present in nature. weathering and transportation of rocks containing diamonds have resulted in the development of diamond-bearing placers. the south african diamonds were first found in stream placers, leading to a search for their source and its ultimate discovery under a blanket of soil which completely covered the parent rock. the proportion of diamonds now mined from placers is very small. the diamonds of brazil come from placer deposits. this is the principal source of the black diamond so largely used in diamond-drilling. the united states produces no diamonds on a commercial scale. small diamonds have been found in peridotite masses in pike county, arkansas, but these are of very little commercial value. a few diamonds have been found in the glacial drift of wisconsin and adjacent states, indicating a possible diamond-bearing source somewhere to the north which has not yet been located (p. ). pearls are concretions of lime carbonate of organic origin, and are found in the shells of certain species of molluscs. their color or luster is given by organic material or by the interior shell surface against which the pearl is formed. the principal supply comes from the indian and pacific oceans, but some are found in the fresh water mussels of north america, in the caribbean, and on the western coast of mexico and central america. from the beginning of history the principal source of rubies has been upper burma, where the stones are found in limestone or marble near the contact with igneous rocks, associated with high-temperature minerals. the weathering of the rock has developed placers from which most of the rubies are recovered. siam is also an important producer. in the united states rubies have been found in pegmatites in north carolina, but these gems are of little commercial importance. sapphires are of the same composition as rubies and are found in much the same localities. most of the sapphires of the best quality come from siam, where they are found in sandy clay of placer origin. in the united states sapphires are recovered from alluvial deposits along the missouri river near helena, montana, where they are supposed to have been derived from dikes of andesite rocks. in fergus county, montana, they are mined from decomposed dikes of lamprophyre (a basic igneous rock). in north carolina sapphire has been found in pegmatite dikes. the principal source of fine emeralds is in the andes in colombia. their occurrence here is in calcite veins in a bituminous limestone, but little seems to be known of their origin. the only other emerald locality of commercial importance is in the ural mountains of siberia. emeralds have been found in pegmatite dikes in north carolina and new england, but the production is insignificant. tourmaline is a complex hydrous silicate of aluminum and boron, with varying amounts of magnesium, iron, and alkalies. it is a rather common mineral in silicated zones in limestones near igneous contacts, but gem tourmalines are found principally in pegmatite dikes. they have a wide variety of colors, the red and green gems being the most prized. maine, california, and connecticut are the principal american producers. turquoise is a hydrated copper-aluminum phosphate. it is found in veinlets near the surface in altered granites and other igneous rocks. it is usually associated with kaolin and frequently with quartz, and is believed to have been formed by surface alterations. in the united states it is produced chiefly in nevada, arizona, and colorado. in general the principal gem minerals, except pearl and turquoise, occur as original constituents in igneous intrusives, usually of a pegmatite or peridotite nature. sapphire, ruby, emerald, and tourmaline result also from contact metamorphism of sediments in the vicinity of igneous rocks. weathering softens the primary rocks, making it possible to separate the gem stones from the matrix. when eroded and transported the gems are concentrated in placers. salt economic features the principal uses of salt are in the preserving and seasoning of foods and in chemical industries. chemical industries require salt for the manufacture of many sodium compounds, and also as a source of hydrochloric acid and chlorine. a minor use of salt is in the making of glazes and enamel on pottery and hardware. because of the wide distribution of salt in continental deposits and because of the availability of ocean and salt-lake brines as other sources, most countries of the world either possess domestic supplies of salt adequate for the bulk of their needs, or are able to obtain supplies from nearby foreign countries. certain sea salts preferred by fish packers and other users are, however, shipped to distant points. about a fifth of all the salt consumed in the world annually is produced in the united states, and other large producers are great britain, germany, russia, china, india, and france. the united states produces almost its entire consumption of salt, which is increasing at a very rapid rate. salt is produced in fourteen states, but over per cent of the total output comes from michigan, new york, ohio, and kansas. reserves are practically inexhaustible. exports and imports of salt form a very minor part of the united states industry, each being equivalent to less than per cent of the domestic production. a large part of the imported material is coarse solar-evaporated sea salt, which is believed by fish and pork packers to be almost essential to their industry. imports of this salt come from spain, italy, portugal, and the british and dutch west indies; during the war, on account of ship shortage, they were confined chiefly to the west indies. a considerable tonnage of specially prepared kiln-dried salt, desired by butter-makers, is imported from liverpool, england. there are also some small imports from canada, probably because of geographic location. exports of domestic salt go chiefly to canada, cuba, and new zealand, with smaller amounts to practically all parts of the world. salt is recovered from salt beds in two ways. about a fourth of the salt produced in the united states is mined through shafts in the same manner as coal, the lumps of salt being broken and sized just as coal is prepared for the market. the larger part of the united states production, however, is derived by pumping water down to the beds to dissolve the salt, and pumping the resulting brine to the surface where it is then evaporated. a considerable amount of salt, also, is recovered from natural brines--which represent the solution of rock salt by ground-waters--and from the waters of salt lakes and the ocean. geologic features common salt constitutes the mineral halite, the composition of which is sodium chloride. it is rarely found perfectly pure in nature, but is commonly mixed with other saline materials, such as gypsum and anhydrite, and occasionally with salts of potassium and magnesium. the general grade of rock-salt deposits, where not admixed with clay, is perhaps to per cent of sodium chloride. the ultimate source of salt deposits is the sodium and chlorine of igneous rocks. in the weathering of these rocks the soda, being one of the more soluble materials, is leached out and carried off by ground-waters, and in the end a large part of it reaches the sea. the chlorine follows a similar course; however, the amount of chlorine in ordinary igneous rocks is so extremely small that, in order to explain the amount of chlorine present in the sea, it has been thought necessary to appeal to volcanic emanations or to some similar agency. ocean water contains about . per cent by weight of dissolved matter, over three-fourths of which consists of the constituents of common salt. chief among the other dissolved materials are magnesium, calcium, potassium, and so_ (the sulphuric acid radical). when sea water evaporates it becomes saturated with various salts, according to the amounts of these salts present and their relative solubilities. in a general way, after per cent of the water has evaporated gypsum begins to separate out, and after per cent has evaporated common salt begins to be deposited. after a large part of the common salt has been precipitated, the residual liquid, called a "bittern" or "mother liquid," contains chiefly a concentration of the salts of magnesium and potassium. still further evaporation will result in their deposition, mainly as complex salts like those found in the stassfurt deposit (p. ). the actual processes of concentration and precipitation in sea water or other salt waters are much more complex than is indicated by the above simple outline. the solubility of each of the various salts present, and consequently the rate at which each will crystallize out as evaporation proceeds, depends upon the kinds and concentrations of all the other salts in the solution. temperature, pressure, mass-action, and the crystallization of double salts are all factors which influence the nature and rate of the processes and add to their complexity. during a large part of the general process, several different salts may be crystallizing out simultaneously. it is evident that gypsum may be precipitated in some quantity, and that external conditions may then change, so that evaporation ceases or so that the waters are freshened, before any common salt is crystallized out. this fact may explain in part why gypsum beds are more widely distributed than beds of common salt. at the same time the much greater amount of sodium chloride than of calcium sulphate in sea water may explain the greater thickness of many individual salt beds. the evaporation of salt waters, either from the ocean or from other bodies of water, is believed to have been responsible for nearly all of the important deposits of common salt. this process has been going on from cambrian time down through all the intervening geologic ages, and can be observed to be actually operative today in various localities. the beds of salt so formed are found interstratified with shales, sandstones, and limestones, and are frequently associated with gypsum. on a broad scale, they are always lens-shaped, though they vary greatly in extent and thickness. the necessary conditions for the formation of extensive salt beds include arid climate and bodies of water which are essentially enclosed--either as lakes, as lagoons, or as arms of the sea with restricted outlets,--where evaporation exceeds the contributions of fresh water from rivers, and where circulation from the sea is insufficient to dilute the water and keep it at the same composition as the sea water. under such conditions the dissolved salts in the enclosed body become concentrated, and precipitation may occur. a change of conditions so that mud or sand is washed in or so that calcareous materials are deposited, followed by a recurrence of salt-precipitation, results in the interstratification of salt beds with shales, sandstones, and limestones. for the formation of very thick beds of salt, and especially of thick beds of fairly pure composition, however, this simple explanation of conditions is insufficient. the deposits of michigan and new york occur in beds as much as feet in thickness, with a considerable number of separate beds in a section a few hundred feet thick. beneath the potash salt deposits of stassfurt, beds of common salt to feet in thickness are found, and beds even thicker are known in other localities. when we come to investigate the volume of salts deposited from a given volume of sea water, we find it to be so small that for the formation of feet of salt over a given area, an equivalent area of water , feet deep would be required. it has therefore been one of the puzzling problems of geology to determine the exact physical conditions under which deposition of these beds took place. one of the most prominent theories, the "bar" theory, suggests that deposition may have taken place in a bay separated from the sea by a bar. sea water is supposed to have been able to flow in over the bar or through a narrow channel, so that evaporation in the bay was about balanced by inflow of sea water. thus the salts of a very large quantity of sea water may have accumulated in a small bay. as the process went on, the salts would become progressively more concentrated, and would be precipitated in great thickness. a final complete separation of the basin from the sea, for instance by the relative elevation of the land, might result in complete desiccation, and deposition of potassium-magnesium salts such as those found at stassfurt (p. ). another suggestion to explain the thickness of some salt beds is that the salts in a very large basin of water may, as the water evaporated and the basin shrank, have been deposited in great thickness in a few small depressions of the basin. other writers believe that certain thick salt deposits were formed in desert basins (with no necessary connection with the sea), through the extensive leaching of small quantities of salt from previous sediments, and its transportation by water to desert lakes, where it was precipitated as the lakes evaporated. over a long period of time large amounts of salt could accumulate in the lakes, and thick deposits could result. such hypotheses also explain those cases where common salt beds are unaccompanied by gypsum, since land streams can easily be conceived to have been carrying sodium chloride without appreciable calcium sulphate; in ocean waters, on the other hand, so far as known both calcium sulphate and sodium chloride are always present, and gypsum would be expected to accompany the common salt. a partial explanation of some great thicknesses found in salt beds is that these beds, especially when soaked with water, are highly plastic and incompetent under pressure. in the deformation of the enclosing rocks, the salt beds will flow somewhat like viscous liquids, and will become thinned on the limbs of the folds and correspondingly thickened on the crests and troughs. the salt deposits of the gulf coast of texas and louisiana should be referred to because of their exceptional features. they occur in low domes in tertiary and more recent sands, limestones, and clays. vertical thicknesses of a few thousand feet of salt have been found, but the structure is known only from drilling. in some of these domes are also found petroleum, gypsum, and sulphur (p. ). no igneous rocks are known in the vicinity. it has been thought by some that the deposits were formed by hot waters ascending along fissures from underlying igneous rocks, and the upbowing of the rocks has been variously explained as due to the expanding force of growing crystals, to hydrostatic pressure of the solutions, and to laccolithic intrusions. on the other hand, the uniform association of other salt and gypsum deposits with sedimentary rocks, and the absence of igneous rocks, suggest that these deposits may have had essentially a sedimentary origin, and that they have been modified by subsequent deformation and alteration. the origin is still uncertain. other mineral deposits formed under much the same conditions as salt are gypsum, potash, borax, nitrates, and minerals of bromine; and in a study of the origin of salt deposits these minerals should also be considered. talc and soapstone economic features soapstone is a rock composed mainly of the mineral talc. popularly the terms _talc_ and _soapstone_ are often used synonymously. the softness, greasy feel, ease of shaping, and resistance to heat and acids of this material make it useful for many purposes. soapstone is cut into slabs for laundry tubs, laboratory table tops, and other structural purposes. finer grades are cut into slate pencils and acetylene burners. ground talc or soapstone is used as a filler for paper, paint, and rubber goods, and in electrical insulation. fine grades are used for toilet powder. pyrophyllite (hydrated aluminum silicate) resembles talc in some of its properties and is used in much the same way. fine english clays (p. ) are sometimes used interchangeably with talc as paper filler. the united states produces nearly two-thirds of the world's talc. the other large producers are france, italy, austria, and canada (ontario). the united states is independent of foreign markets for the bulk of its talc consumption, but some carefully prepared talc of high quality is imported from canada, italy, and france. italy is our chief source of talc for pharmaceutical purposes, though recently these needs have been largely supplied by high-grade talc from california. in the united states, vermont and new york are the leading producers of talc and virginia of soapstone slabs. reserves are large. geologic features talc is hydrated magnesium silicate, as is also serpentine, a mineral with which talc is closely associated. both are common alteration products of magnesian silicate minerals such as olivine, pyroxene, and amphibole. talc is also derived from the recrystallization of magnesian carbonates. talc deposits consist of lenses and bands in metamorphic limestones, schists, and gneisses of ancient age. the talc itself is usually schistose like the wall rocks, and is largely a product of mechanical mashing. in some cases, also, talc results from the alteration of igneous rocks without mashing--as in the case of the large talc and soapstone deposits of virginia, which are the result of rather complete alteration of basic igneous rocks such as peridotites and pyroxenites. talc is known to result from the weathering of magnesian silicates under surface conditions, but the common occurrence of the principal deposits, in highly crystalline rocks which have undergone extensive deep-seated metamorphism, is an indication that processes other than weathering have been effective. it has been suggested that hot ascending solutions have been responsible for the work, but without much proof. a more plausible explanation for many deposits is that the talc results from the dynamic metamorphism or shearing of impure magnesian carbonates (as in highly magnesian limestones), the process resulting in elimination of the carbon dioxide and recrystallization of the residue. certain talc deposits, such as those of ontario, show clearly traces of the original bedding planes of limestone crossing the cleavage of the talc, and the rock bears all the evidence of having formed in the same manner as a common slate. talc and slate are almost the only mineral products which owe their value principally to dynamic metamorphism. chapter xiv exploration and development the general relations of the geologist to exploration and development the economic geologist is more vitally concerned with exploration and development than with any other phase of his work. this comes closest to being his special field. here is a fascinating element of adventure and chance. here is the opportunity to converge all his knowledge of geology and economics to a practical end. the outcome is likely to be definite one way or the other, thus giving a quantitative measure of the accuracy of scientific thinking which puts a keen edge on his efforts. it is not enough merely to present plausible generalizations; scientific conclusions are followed swiftly either by proof or disproof. with this check always in mind, the scientist feels the necessity for the most rigid verification of his data, methods, and principles. the general success of the application of geology to exploration and development is indicated by the rapid increase in demand for such service in recent years, and by the large part it plays in nearly all systematic and large-scale operations. the argument is sometimes made that many mineral deposits have been found without geologic assistance, and that therefore the geologist is superfluous. the answer to this argument is that there are often hundreds of "practical" explorers in the field to one geologist, and that in proportion to numbers the story is quite a different one. the very fact that many large mining organizations, as a result of their experience, now leave these matters of exploration and development largely in the hands of geologists, is a tribute to the usefulness of the science. also, it is to be remembered that not all applications of geology are made by geologists. it is hard to find a prospector or explorer who has not absorbed empirically some of the elements of geology, and locally this may be enough. very often men who take pride in the title of "practical prospectors" are the ones with the largest stock of self-made geological theories. during a prospecting boom it is not uncommon for speculators and promoters to attempt to discount geologic considerations where these run counter to their plans. the catching phrase "bet against the geologist" has a broad appeal to an instinctive preference for the practical as opposed to the theoretical. if the public would stop to note the character of the support behind the geologist, including as it does the larger and more successful operators, it would not be so ready to accept this implication. another aspect of this question might be mentioned. there is scarcely an oil field or mining camp in the world without a cherished tradition to the effect that, prior to discovery, the mineral possibilities had been reported on unfavorably by the geologists,--again implying that success has been due to the hard common sense of the horny-handed prospector. these traditions persist in the face of favorable geological reports published before discovery; they are natural expressions of the instinctive distrust of any knowledge which is beyond the field of empirical experience. in many cases the discoveries were made long before geologists appeared on the scene. in others, possibly one or two geologic reports were unfavorable, while many were favorable. in the aggregate, there can be no question that, in proportion to the scale of its use, geological advice has had more than its proportion of success. even under the most favorable conditions, the chances against the success of an individual drill hole or underground development are likely to be greater than the chances for it. the geologist may not change this major balance; but if he can reduce the adverse chances by only a few per cent, his employment is justified on purely commercial grounds. the above comments refer to sound geological work by competent scientists. the geologic profession, like many others, is handicapped by numbers of ill-trained men and by many who have assumed the title of geologist without any real claim whatever,--who may do much to discredit the profession. the very newness of the field makes it difficult to draw a sharp line between qualified and unqualified men. with the further development of the profession this condition is likely to be improved (see pp. - ). so new is the large-scale application of geology to exploration and development, and so diverse are the scientific methods of approach, that it is difficult to lay out a specific course for a student which will prepare him for all the opportunities he may have later. in the writer's experience, both in teaching and practice, the only safe course for the student is to prepare broadly on purely scientific lines. with this background he will be able later to adapt himself to most of the special conditions met in field practice. partly explored versus virgin territories in selecting an area to work, the geologic explorer will naturally consider various factors mentioned in succeeding paragraphs; but the natural first impulse is to start for some place where no one else has been, and to keep away from the older principal mining camps,--on the assumption that such grounds have been thoroughly explored and that their geological conditions bearing on exploration are fully understood. it is safe to say that very few mineral districts are thoroughly understood and explored. numerous important discoveries of recent years have been in the extensions of old mines and old districts; and when one considers the scale of even the most extensive mine openings in comparison with the vast body of rock available for exploration, it is clear that this will continue to be the situation far into the future. it is the writer's belief that the economic geologist stands at least as good a chance of success in exploration in the older districts as he does in new fields. nature is exceedingly erratic and economical in providing places favorable for mineral production; in a producing district the geologic conditions have been proved to be right, and the explorer starts here with this general pragmatic advantage. the explorer here has another great advantage, that much essential information has been gathered which can be built into his plan of operations. he can start, scientifically and practically, where the other man left off. one of the best-known economic geologists has maintained that the more previous work done, the better, because it furnished him more tools to work with. there is no such thing as "skimming the cream" from a geologic problem; there is no end in sight in the search for more knowledge. this attitude toward the problem of exploration has also proved advantageous on the business or financial side. a successful backer of mineral enterprises once remarked that his best prospecting was done from the rear platform of a private car,--meaning that this mode of transportation had carried him to the center of important mining activities, where the chances for large financial success showed a better percentage than in more general and miscellaneous exploration. the use of all available information effective scientific exploration requires the use of all available information applying to the specific area. this might seem to be too obvious to require mention, yet observance of the methods of explorers seems to call for warning against the rather common tendency to go into a field unprepared with a thorough knowledge of preceding work. it is easy to forget or overlook some investigation made many years previously; or to assume that such work is out of date, and of no special consequence in the application of new thought and method which is the basis of the faith and confidence of each new geologic explorer. a study of the reports on an old camp shows how often the younger generations have ignored the results of the older. many of the same elementary truths are rediscovered by successive generations, after large efforts which could have been saved by means of proper care and investigation of the previous literature and mapping. in outlying parts of the world, the existing information bearing on exploration may be at a minimum. in many of the older mining camps and throughout most civilized countries, however, careful investigation will usually disclose a considerable range of useful information bearing on the territory to be explored. in the united states the natural course to be pursued is to hunt carefully through the reports of the u. s. geological survey, the bureau of mines, various state surveys, universities, and private organizations (so far as these reports are available), and through the technical journals and the reports of technical societies, for something bearing on the district to be explored. even if no specific report or map is to be found, it is usually possible to locate general maps or accounts which are likely to be of use. co�peration in exploration competition in exploration often develops an atmosphere of suspicion and furtiveness which is highly unfavorable to coöperative efforts. individuals and companies may handicap themselves greatly by a desire to play a lone hand, and by failure to take advantage of an exchange of information. this action may be based, particularly on the part of strong mining companies, on the assumption that they know all that is necessary about the problem, and that an outsider has nothing to contribute. financial and other conditions may require this attitude; but in large part it is a result of temperament, as clearly indicated by the difference in methods followed by different groups and in different mining districts. from the scientific point of view this attitude can hardly be justified, in view of the extremely narrow limits of human knowledge as compared with the scientific field to be explored. the sum total of knowledge from all sources is only a small fraction of that necessary for the most effective results. the mutual exchange of information and discussion is usually justified on the basis of self-interest alone, to say nothing of the larger interest to the mineral district, to the country, or to science. national and state survey organizations exercise considerable effort to secure records of drilling. in some cases they have the legal power to command this information, particularly in relation to appraisals for taxation and "blue sky" laws. in a larger number of cases drill records are secured through voluntary coöperation with explorers. a considerable number of records are nevertheless not filed with public agencies and some of these are permanently lost. even where the records are turned in to a public organization, they are in most cases not directly available to explorers. public registration of all drilling records is a highly desirable procedure in the interests of the development of the mineral industry as a whole. a vast amount of unnecessary duplication can thus be avoided. the record of a drill hole, even though barren, may be of vast significance in the interpretation of future developments and should be recorded as carefully as an abstract of land title. the property right of the explorer in such information can be and usually is protected by withholding the record from public inspection until sufficient time has elapsed to give him full opportunity to use the information to his own best advantage. the opportunities for coöperation with specialists of public organizations are almost unlimited. these organizations are likely to have an accumulation of data and experience extending through long periods and over large areas, which the private explorer ordinarily cannot hope to duplicate. with proper restrictions this information may be available for public use. a good illustration of current coöperative effort of this kind is in the deep exploration for oil in the trenton limestone of illinois. outcrops and other specific indications are not sufficient to localize this drilling; but the information along broad geologic and structural lines which has been collected previously by the illinois survey is sufficient so that, with a comparatively small amount of shallow drilling, the locus of the more favorable structural conditions may be determined. in this case the survey is directing the initial exploration, which is financed by private capital. economic factors in exploration the approach to the problem of exploration is very often determined by local requirements and conditions; but if one were to come at the problem from a distance and to keep matters in broad perspective, the first step would be a consideration of what might be called the _economic factors_. let us suppose that the geologist is free to choose his field of exploration. an obvious preliminary step is to eliminate from consideration mineral commodities which are not in steady or large demand and are much at the mercy of market conditions, or which are otherwise not well situated commercially. the underlying factors are many and complex. they include the present nature and future possibilities of foreign competition, the domestic competition, the grades necessary to meet competition, the cost of transportation, the cost of mining under local conditions--including considerations of labor and climatic and topographic conditions,--the probability of increase or decrease in demand for the product, the possible changes in metallurgical or concentrating practice (such as those which made possible the mining of low-grade porphyry copper ores), the size of already available reserves, and the mining laws in relation to ownership and regulation. most of these factors are discussed at some length on other pages. after looking into the economic conditions limiting the chromite, nickel, or tin developments in the united states, the explorer might hesitate to proceed in these directions,--for he would find that past experience shows little promise of quantities and grades equivalent to those available in other countries, and that there is little likelihood of tariffs or other artificial measures to improve the domestic situation. before and during the war, commercial conditions might have shown the desirability of hunting for pyrite, but more recent developments in the situation cast some doubt on this procedure. to go ahead blindly in such a case, on the assumption that the pyrite market would in some fashion readjust itself, would not be reasoned exploration. again, in considering exploration for copper, account should be taken in this country of the already large reserves developed far in advance of probable demand, which require that any new discoveries be very favorably situated for competition. in oil, on the other hand, a very brief survey of the economic factors of the situation indicates the desirability of exploration. the comparative shortage of lead supplies at the present time suggests another favorable field for exploration. in short, before actual field exploration is begun, intelligent consideration of the economic factors may go far toward narrowing the field and toward converging efforts along profitable lines. looked at broadly, this result is usually accomplished by the natural working of general laws of supply and demand; but there are many individual cases of misdirected effort, under the spell of provincial conditions, which might easily be avoided by a broader approach to the problem. geologic factors in exploration coming to the geological aspects of exploration, the procedure in its early stages is again one of elimination. oil and coal, for instance, are found in certain sediments of certain ages, and one would not look for them in an area of granite. for every mineral resource there are broad geologic conditions of this sort, particularly the genetic, structural, and metamorphic conditions, which make it possible to eliminate vast areas from consideration and to concentrate on relatively small areas. after the elimination of unfavorable areas, there comes the hunt for positively favorable geologic conditions--for a definite kind of sediment or igneous rock, for a definite structure, for the right kind of mineralogic and metamorphic conditions, or for the right combination of these and other geologic elements. the geologic considerations used in exploration for the various mineral deposits are so many and so diverse, and they require so much adjustment and interpretation in their local application, that one would be rash indeed to attempt anything in the nature of an exhaustive discussion. it is hardly practicable to do more than to outline, for illustrative purposes, a few of the geologic factors most commonly used in exploration. mineral provinces and epochs mineral deposits may be similar in their mineralogic and geologic characters and relations over a considerable area. they may give evidence of having developed under the same general conditions of origin; perhaps they may even be of the same geologic age. the gold-silver deposits of goldfield, of tonopah, the comstock lode of virginia city, and many other deposits through the great basin area of the southwestern united states and mexico have group characteristics which have led geologists to refer to this area as a "metallogenic" or "metallographic" province. the gold-silver ores on the west slope of the sierra nevadas, for nearly the entire length of california, likewise constitute a metallogenic province. the lake superior copper ores on the south shore of lake superior, the silver ores on the north shore, miscellaneous small deposits of copper, silver, and gold ores to the east of lake superior, the nickel ores of sudbury, and the silver-nickel-cobalt ores of the cobalt district are all characterized by similar groups of minerals (though in highly differing proportions), by similar geologic associations, by similar age, and probably by similar conditions of origin. this area is a metallogenic province. the lead and zinc ores of the mississippi valley constitute another such province. the oil pools of the principal fields are characterized by common geologic conditions over great areas (p. ), which may likewise be considered as forming mineral provinces; for them the term "petroliferous provinces" has been used. the list might be extended indefinitely. knowledge of such group distributions of minerals is a valuable asset to the explorer, in that it tends to localize and direct search for certain classes of ores in certain provinces; also, within a province, it tells the explorer what is to be normally expected as regards kinds and occurrences of mineral deposits. in searching for minerals of sedimentary origin, the explorer will use stratigraphic methods in following definite sedimentary horizons. in searching for ores related to igneous intrusions he will naturally hunt for the intrusions, and then follow the periphery of the intrusions for evidences of mineralization, taking into account possible features of zonal arrangement of minerals about the intrusives (see pp. - ), and the preference of the ores for certain easily replaced horizons like limestones, or for certain planes or zones of fracturing. just as minerals may be grouped by provinces, they may be grouped by geologic ages. such groupings are especially useful in the case of minerals which are closely related to certain stratigraphic horizons, such as coal, oil, and iron. the greater number of the productive coal deposits of the united states are of carboniferous age, and the distribution of sediments of this age is pretty well understood from general geologic mapping. the clinton iron ores all follow one general horizon in the lower-middle paleozoic. the lake superior iron ores are pre-cambrian, and over three-fourths of them occur at one horizon in the pre-cambrian. gold deposits of the united states were formed mainly in the pre-cambrian, the early cretaceous, and the tertiary. copper deposits of the united states were formed chiefly in pre-cambrian, cretaceous, and tertiary time. while there are many exceptions and modifications to general classifications of this sort, they seem to express essential geologic facts which can be made very useful in localizing exploration. classification of mineral lands in recent years there has been considerable development of the practice of classifying mineral lands in given areas for purposes of exploration and valuation, or for purposes of formulation and administration of government laws. this has been done both by private interests and by the government. these classifications take into account all of the geologic and economic factors ascertainable. the classes of mineral land designated vary with the mineral, the district, and the purpose for which the classification is made. common procedure for commercial exploration purposes is to divide the lands of a given territory into three groups--( ) lands which are definitely promising for mineral exploration, ( ) lands of doubtful possibilities, and ( ) lands in which the mineral possibilities are so slight that they may be excluded from practical consideration. each of these classes may be subdivided for special purposes. another commonly used classification is, ( ) proved mineral lands, ( ) probable mineral lands, usually adjacent to producing mines, ( ) possible mineral lands, and ( ) commercially unpromising mineral lands. the classification of the public mineral lands by government agencies is fully discussed by george otis smith and others in a bulletin of the united states geological survey.[ ] the purposes, methods, and results of this classification should be familiar to every explorer. nowhere else is there available such a vast body of information of practical value. quoting from this report: a study of the land laws shows the absolute necessity of some form of segregation of the lands into classes as a prerequisite to their disposition. agricultural entry may not be made on lands containing valuable minerals, nor coal entry on lands containing gold, silver, or copper; lands included in desert entries or selected under the carey act must be desert lands; enlarged-homestead lands must not be susceptible of successful irrigation; placer claims must not be taken for their timber value or their control of watercourses; and lands included in building-stone, petroleum, or salt placers must be more valuable for those minerals than for any other purpose. so through the whole scheme of american land laws runs the necessity for determining the use for which each tract is best fitted. for this purpose the geological survey has made extensive classification of coal lands, oil and gas lands, phosphate lands, lands bearing potash and related salines, metalliferous mineral lands, miscellaneous non-metalliferous mineral lands, and water resources. the scope of the work may be indicated by the factors considered. for instance coal is investigated in relation to its character and heat-giving qualities (whence comes its value), quantity, thickness, depth, and other conditions that effect the cost of its extraction. metalliferous mineral lands are considered in relation to general geology, country rock, intrusions and metamorphism, structure, outcrops and float of lodes, prospects and mines, samples, and history of the region. classifications of this kind have often proved useful to large holders of land as a basis for intelligent handling of problems of sale, taxation, and the granting of rights to explorers. because of the lack of this elementary information, there has been in some quarters timidity about dealing with large holdings, for fear of parting with possible future mineral wealth,--with the result that such tracts are carried at large expense and practically removed from the field of exploration. to the same cause may be attributed some of the long delays on the part of the government in opening lands for mineral entry or in issuing patents on land grants. outcrops of mineral deposits many mineral deposits have been found because they outcrop at the surface; the discoveries may have been by accident or they may have been aided by consideration of geologic factors. there are still vast unexplored areas in which mineral deposits are likely to be found standing out at the surface. for much of the world, however, the surface has been so thoroughly examined that the easy surface discoveries have been made, and the future is likely to see a larger application of scientific methods to ground where the outcrops do not tell an obvious story. mineral deposits may fail to outcrop because of covering by weathered rock or soil, by glacial deposits, or by younger formations (surface igneous flows or sediments), or the outcrop of a deposit may be so altered by weathering as to give little clue to the uninitiated as to what is beneath. mineral deposits formed in older geologic periods have in most cases been deeply covered by later sediments and igneous rocks. such deposits are in reach of exploration from the surface only in places where erosion has partly or wholly removed the later covering. an illustration of this condition is furnished in the great basin district of nevada, where ore bodies have been covered by later lava flows. the ore-bearing districts are merely islands exposed by erosion in a vast sea of lava and surface sediments. beyond reasonable doubt many more deposits are so covered than are exposed, and it is no exaggeration to say that by far the greater part of the mineral wealth of the earth may never be found. where a mineral-bearing horizon is exposed by erosion at the surface, underground operations may follow this horizon a long way below the capping rocks; but, after all, such operations are geographically small as compared with the vast areas over which the covering rocks give no clue as to what is beneath. one of the principal problems of economic geology for the future is to develop means for exploration in territories of this sort. a beginning has been made in various districts by the use of reconnaissance drilling, combined with interpretation of all the geologic and structural features. the discovery of one of the largest nickel deposits in the sudbury district of canada was made by reconnaissance drilling to ascertain the general geologic features, in an area so deeply covered as to give little suggestion as to the proper location for attack. some illustrative cases the use of outcrops in oil exploration has been noted on other pages (pp. - ). outcrops of coal seams may be found in folded or deeply eroded areas. for the most part, however, and especially in areas of flat-lying rocks, the presence of coal is inferred from stratigraphic evidence and from the general nature of the geologic section--which has been determined by outcrops of associated rocks or by information available at some distant point. the structural mapping of coal beds on the basis of outcrops and drill holes has been referred to (pp. - ). iron ores are very resistant to solution. where hard and compact they tend to form conspicuous outcrops, and where soft they may be pretty well covered by clay and soil. in glaciated areas, like the lake superior region, outcrops of iron ore are much less numerous because of the drift covering. certain of the harder iron ores of the marquette, gogebic and menominee districts of michigan and of the vermilion district of minnesota project in places through the glacial drift, and these ores were the first and most easily found. much the greater number of iron ore deposits of lake superior, including the great soft deposits of the mesabi range of minnesota, fail to outcrop. on the other hand the _iron formation_, or mother rock of the ore, is hard and resistant and outcrops are numerous. the hematite ores of brazil have many features in common with the lake superior ores in age and occurrence, but they have not been covered with glacial deposits. outcrops of the iron ore are large and conspicuous, and the surface in this territory gives one some idea of what the lake superior region may have looked like before the glaciers came along. certain of the soft iron ores of the lateritic type, as in cuba, outcrop over great areas where their topographic situation is such that erosion has not swept them off. on erosion slopes they are seldom found. the clinton iron ores of the southeastern united states outcrop freely. some of the lead and zinc deposits of the mississippi valley outcrop at the grass roots as varying mixtures of iron oxide, galena, chert, and clay, though they seldom project above the general surface. the old lead ranges of wisconsin and illinois, found at the surface a century ago by the early explorers and traders, have served as starting points for deeper exploration which has located the zinc deposits. erosion channels have freely exposed these ore bodies, and in the wisconsin-illinois deposits most of the ores thus far found are confined to the vicinity of these channels. the greater number of the lead and zinc deposits of the mississippi valley, however, are covered with weathered material or with outliers of overlying sediments, with the result that underground exploration is necessary to locate them. sulphide deposits in general, including those carrying gold, silver, copper, lead, zinc, and other metals, have many common features of outcrop. the iron sulphide commonly present in these ore bodies is oxidized to limonite at the surface, with the result that prospectors look for iron-stained rocks. these iron-stained rocks are variously called the "gossan," the "iron capping," the "colorado," or the "eiserner hut" (iron hat). the gossan is likely to resist erosion and to be conspicuous at the surface,--though this depends largely on the relative resistance of the wall rocks, and on whether the gangue is a hard material like quartz, or some material which weathers more rapidly like limestone or igneous rock. the gossan does not often carry much value, though it may show traces of minerals which suggest what may be found below. gold, silver, and lead are not easily leached out of the surface outcrops. copper and zinc are much more readily leached, and in the outcrop may disclose their existence only by traces of staining. it happens not infrequently, therefore, that copper and zinc deposits are found through the downward exploitation of oxidized gold, silver, and lead ores. the veins at butte were first worked for silver, and the ore bodies at bingham, utah, and jerome, arizona, were first mined for gold. exceptionally, copper ore in enriched, oxidized form outcrops, as at bisbee, arizona. it is not always true that valuable sulphide deposits have an iron-stained outcrop, for in some of them iron sulphide or pyrite is so scarce that the surface outcrops may be light-colored clayey and siliceous rocks. silver is often represented in the outcrop by silver chloride or cerargyrite, which may be easily identified. the prospecting for such surface ores is sometimes called "chloriding." the presence in the outcrop of dark manganese oxides associated with vein quartz sometimes indicates the presence below of copper and zinc and other minerals, as at butte. extensive alterations of the country rock in the way of silicification and sericitization, and the presence of minerals like garnet, tourmaline, diopside, and others, known to be commonly deposited by the same hot solutions which make many ore deposits, may furnish a clue for exploration below. these characteristics of the country rock, however, are likely to be masked at the outcrop by later weathering, which superposes a kaolinic or clayey alteration. topography and climate as aids in searching for mineral outcrops the topographic expression of a mineral deposit depends upon its hardness and resistance to erosion as compared with the adjacent rocks. if more resistant it will stand out at the surface; if less resistant, it will form a depression. the conditions determining resistance are exceedingly variable, and no broad generalization can be made; but within a local province a given group of mineral deposits may characteristically form depressions or ridges, and thus topographic criteria may be very useful in exploration. even with such limitations, the variations of the topographic factor may be so great as to require much care in its use. sulphide ores in quartzites are likely to develop depressions under erosion. in limestones they are more likely to stand out in relief, because of the softer character of the limestone, though this does not always work out. crystalline magnetite and hematite are more resistant to erosion than almost any other type of rock, and stand out at the surface with proportional frequency. climatic conditions may determine the locus of search for certain surface minerals. bauxite and lateritic iron ores, for instance, are known to favor tropical climates. in exploration for these minerals, the climatic factor must be applied in connection with the topographic considerations already mentioned, and both, in turn, in connection with the character of the country rock as determined by general geologic surveys. a combination of climatic, topographic, and other physiographic conditions may be used also in exploration for certain types of residual clays. size and depth of ore bodies as determined from outcrop where the ore body is harder than the surrounding rock, it stands out in conspicuous outcrops and is likely to show a narrowing below. where it is softer than the surrounding rocks, and outcrops in a topographic depression, it is perhaps more likely to show widening below. these features are due to the general facts that, where the ore body is hard and resistant, the downward progress of erosion is likely to be arrested where the adjacent rocks occupy the larger part of the surface, that is, where the ore body is narrower. this principle is often vaguely recognized in the assumption that an exceptionally large outcrop of an ore vein may be "too good to last." again, such a generalization must be applied to a specific case with much caution. attempts to forecast the depth of veins from their extent at the surface meet with only partial success. in a very general way great persistence horizontally suggests persistence in depth, on the ground that the section exposed on the surface is as likely to be a section of average dimensions as one along vertical lines. faith is the first article of the prospector's creed, and it is hard to shake his conviction that every ore outcrop must widen and improve below. as expressed by the french-canadian prospector in the cobalt district, the "vein calcite can't go up, she must go down." while the scientist may have grounds to doubt this reasoning, he is not often in a position to offer definite negative evidence. the use of placers in tracing mineral outcrops outcrops of ore-bearing rock may occasionally be located by tracing a placer deposit back to its source, or by following up ore fragments in the "wash" on mountain sides to the place of origin, or by noting ore fragments in glacial deposits. the presence of an ore mineral in a placer naturally raises the question as to whence it came. if it is a recent placer, it may be comparatively easy to follow up the stream channels to the head-water territory which is delivering the main mass of sediment, and there to locate a vein in place. the problem is complicated by multiplicity of tributaries and by large size of the drainage areas. in such cases careful panning and testing of the gravels at frequent intervals may show which of several tributaries are contributing most of the values, and thus may further localize the area of search. many important mining districts, including butte, bisbee, the mother lode region of southern california, the diamond fields of africa, and others, have been found by tracing up placers in this manner. in the case of an older placer deposit, where the topography and drainage have been much altered since its formation, or where the deposit has been covered by later sediments, the problem is of course much more difficult. much less than a commercially valuable placer deposit in unconsolidated surface rocks may start a search for the mother lode. a single fragment of ore in the "wash" naturally directs attention up the slope, and the repetition of fragments in a certain direction may lead unerringly to the source. the fragments may not even in themselves carry value, but may consist of detrital material from the leached outcrop--such as iron or manganese oxides, which, because of their red or black color, stand out conspicuously in the rock débris. in the lake superior region large angular fragments of iron ore or iron formation in the glacial drift immediately raise question as to source. if the fragments are rounded and small, they usually indicate a very distant source. the general direction of glacial movement is known in most places, and by tracing up the fragments in this direction the outcrop may be found; or the chain of fragments may be traced to a point where they stop, which point may serve to locate the parent bedrock carrying the ore body, even though it does not outcrop. an interesting suggestion was made some years ago with reference to the diamonds found sporadically in the terminal moraines in wisconsin and other mid-west states. the diamonds are of such size and quality as to indicate surely the existence of a real diamond field somewhere to the north. the locations of these diamond finds were platted on a glacial map, and lines were projected in a general northerly direction along the known lines of the glacial movement. it was found that these lines converged at a point near hudson's bay. the data were too meager and the base line too short for this long projection, and the indicated source of the diamonds can be regarded as the merest speculation. however, with the finding of additional diamonds in the drift, as seems very likely, the refinement of this method might conceivably bring results in time. the use of magnetic surveys in tracing mineral ledges magnetic surveys are often useful in tracing iron-bearing rocks beneath the surface, in the discovery of outcrops of such rocks, and in working out their lines of connection. this method is in general use for the crystalline iron ores in the lake superior region, canada, the adirondacks, and elsewhere in the glaciated portions of the united states. it is not so useful for the brown ores and the clinton ores of the southeastern united states, which are only slightly magnetic and can be commonly located by other methods. where the ore is strongly magnetic, and is associated with other rocks which are non-magnetic, the nature of the magnetic field determined by a surface survey with vertical and horizontal needles may tell something about the shape and size of the ore body. commonly, however, magnetic ores are associated with leaner magnetic rocks,--with the result that the magnetic survey, unless it happens to lead to an outcrop of ore, indicates only the general area through which underground exploration might be warranted. in the hematitic iron ores of lake superior, magnetism is less pronounced than in the magnetites; and in the soft hydrous hematites, like those of the mesabi district, it may cause only slight disturbance of the magnetic needle. this disturbance is usually sufficient to locate the position of the iron-bearing formation, though not the position of the ore. where the iron formation has been highly metamorphosed, and rendered resistant to weathering and erosion so that it will not concentrate into ore, it is likely to have higher magnetic attraction than the richer ores. for this reason an area of strong magnetic attraction is ordinarily regarded as not particularly favorable to the finding of important hematite deposits. however, this attraction may be very useful in tracing out the formation to a place where it is less metamorphic, less resistant to erosion, less likely to outcrop, and yet more promising for the discovery of iron ore. for instance, on the east end of the mesabi and on the east and west ends of the gogebic district, magnetic surveys trace the iron formation with great ease to points where the attraction is low and the conditions for exploration more favorable. the magnetic needle has also been used in the search for nickel ore in the sudbury district of ontario, but without great success, because of the variety of rocks other than nickel which are more or less magnetic, and because of the slight magnetic properties of the nickel ore itself. in a large-scale exploration of this type, conducted some years ago, a favorable magnetic belt was discovered, and a pit was sunk to water level but not to bedrock. years later, the extension of this pit by only a few feet disclosed one of the great ore bodies of the district. experimental work on the use of the magnetic needle on copper deposits has yielded some interesting and suggestive results, but this investigation is still under way and the results have not been published. the use of electrical conductivity and other qualities of rocks in exploration in addition to magnetism, rocks and ores have other properties susceptible to observations made at a distance, such as electrical conductivity, transparency to x-rays, specific induction, elasticity, and density. all these qualities have been of interest to geologists in some connection or another, but none of them have yet been used effectively in exploration for mineral resources. the only one of these properties that has thus far seemed to promise practical results is electrical conductivity. the results yet obtained are slight, and this kind of investigation has rested under something of a cloud, due to extravagant claims of inventors. nevertheless, there has been a considerable amount of scientific work by physicists, geologists, and engineers, supplemented by special war-time investigations of rock and earth conductivity in connection with ground telephones and the tapping of enemy conversations, which seems to indicate a distinct possibility of practical results in the future,--perhaps not so much in locating specific ore bodies as in locating general types of formation and structures,--which may serve to supplement other methods of search.[ ] the transmission and reflection of sound waves in rocks have also been more or less investigated with reference to their possible military use. it seems not impossible that these phenomena may be of some geologic aid in the future, but experimental work is yet in a very early stage. the use of structure and metamorphism in exploration the necessity for careful use of structural data in exploration scarcely requires discussion. references have been made to structural features in connection with coal, oil, iron ore, and other minerals. this phase of study can scarcely be too intensively followed. the tracing of a folded or faulted vein, in a particularly complex system of veins, requires application of all of the methods and principles of structural geology. similarly, the importance of applying the principles of metamorphism, embodied in the _metamorphic cycle_ (pp. - ) is almost self-evident. certain kinds of metamorphism are suggestive of the nature of the mineral deposits with which they are associated. one would not look for minerals known to be caused mainly by surficial processes in rocks which have been altered mainly by deep-seated processes. the presence of metamorphism indicating high temperatures and pressures to some extent limits the kinds of minerals which one may expect to find. on the other hand, minerals known to be primarily formed at great depths, providing they are resistant to surface weathering, may be found in deposits which are the result of surficial alterations or katamorphic processes; that is, they may become concentrated as residual materials in weathered zones or as placers. drilling in exploration in the absence of distinctive outcrops, as well as when outcrops are found, drilling is a widely used method of underground exploration in advance of the sinking of shafts or the driving of tunnels. drilling is more useful in the locating and proving of mineral deposits of large bulk, like deposits of coal, iron, and oil, than mineral deposits of small bulk and high value, like gold and silver deposits. however, it is not always used in the exploration of the first class of deposits and is not always eliminated in the exploration of the second class. with the development of better mechanical devices, better methods of controlling and ascertaining the direction of the drill hole, and more skillful interpretation of drill samples, the use of drilling is rapidly extending into mineral fields where it was formerly thought not applicable. the geologist takes an active part in drilling operations by locating the drill holes, by determining the angle of the holes, by identifying and interpreting the samples, by studying bedding, cleavage, and other structures as shown in the samples, and determining the attitude of these structures in the ground, by determining when the horizon is reached which is most promising for mineral, and by determining when the hole shall be stopped. with a given set of surface conditions, the problem of locating and directing a drill hole to secure the maximum possible results for the amount expended requires the careful consideration of many geologic factors,--and, what is more important, their arrangement in proper perspective and relationship. faulty reasoning from any one of the principal factors, or over-emphasis on any one of them, or failure to develop an accurate three-dimensional conception of the underground structural conditions, may lead to failure or extra expense. success or failure is swiftly and definitely determined. the geologist is usually employed by the company financing the drilling; but in recognition of the importance of his work, some of the large contracting drill companies now employ their own geologists. the technique of the geologic interpretation and direction of drilling has become rather complicated and formidable, and has resulted in the introduction of special college courses in these subjects. the desirability of public registration of drilling records is discussed on another page (pp. - ). quantitative aspects of geologic exploration in recent years there has been a tendency to reduce the geologic factors in exploration to some kind of a quantitative basis. while these factors may be very variable and very complex, their net effect frequently may be expressed in terms of quantitative averages. in various mines and mining districts where operations are of wide extent, local quantitative factors have been worked out which are useful in predicting results from proposed explorations in undeveloped portions. figures of this sort may be useful and practical guides in planning any given exploration, its cost, and its probable outcome. quantitative methods are illustrated in the general account of lake superior iron ore exploration in a later section. curves of production from oil wells and from oil districts have been found to have certain characteristic features in common which are often used in predicting the future output and life of a given well, property, or district. where associated with coal, the percentage of fixed carbon in the coal may be a guide to the presence and nature of the oil (see chapter viii). the geological staff of the netherlands east indies estimated the tin reserves of one of these islands by the use of a factor or coefficient, based on the experience of another island. in the cobalt district of canada a factor for future discoveries and output, based on past experience, was similarly developed. hoover[ ] made a statistical study of several hundred metal mines in various parts of the world, and found that not per cent of the mines that yielded profits ever made them from ore mined below , feet; and that of the mines that paid dividends, per cent did not yield profit below , feet, and most of them died above feet. attempt has been made by a swedish geologist to estimate the iron ore resources of continents by the use of an iron coefficient. this coefficient was obtained by dividing the known iron ore resources of the comparatively well-investigated portions of the world by the number of square miles in which they occurred, and was then multiplied into the area of the continents whose resources were to be determined. the application of quantitative methods of this kind has not yet become very general, nor is it possible to use them in some cases; where applied many of them have been very crude and others have been partly disproved by experience. with increasing knowledge and experience, such methods are becoming more accurate and useful, and are likely to have wider use in the future. origin of mineral deposits as a factor in exploration in exploration, the geologist is keen to ascertain the origin of the mineral deposit. this is often a source of wonder to the layman or "practical" man, and the geologist may be charged with having let his fondness for theory run away with him. a widespread fatalistic conception is expressed in the cornishman's dictum on ore, "where it is, there it is." yet an understanding of the origin of any particular ore, the "why" of it, is coming to be recognized as the most effective means of reaching sound practical conclusions. by ascertaining the approximate origin of the ore, it may be possible at once to infer a whole group of practical considerations based on experience with ores of like origin in other localities. the origin of the ore is the geologist's primary interest, and it is this which gives him his most effective and distinctive tool in exploration. many other phases of exploration work may be picked up empirically by any one familiar with the local conditions; but when the man without sound geologic training attempts to go into this particular field, his lack of background and perspective often leads to fantastic hypotheses which may vitiate the inferences on which he plans his exploration. the scientific investigator, while not accepting the fanciful theories of the local observer, will make a mistake if he fails to recognize the residuum of solid fact on which they are built. many practical explorers are shrewd observers of empirical facts, even though their explanations may show a lack of comprehension of the processes involved. any assumption of superiority, intolerance, or lack of sympathy, on the part of the geologist, toward the inadequate explanations and descriptions given him by the practical man, is likely to indicate a weakness or limitation in his own mental processes. the geologist's business is to sift out the fact from the inference, and not to throw over the whole structure because some of the inferences are faulty. lake superior iron ore exploration as an illustration to illustrate the application of some of the methods of exploration of the kinds described in this chapter, the writer selects an example from his own experience in the lake superior iron fields.[ ] in this region, consideration of the economic aspects of the problem may eliminate from the best explorable field certain canadian portions which are far from water transportation, because the conditions in these sections would prevent the use of anything but an exceptionally large and rich deposit. economic conditions determine in advance also that it is not worth while looking for ores of certain grades, either because they are not usable on account of deleterious constituents or low content of iron, or because these particular grades have already been developed in excess of requirements. having determined what ore is desired, whether bessemer or non-bessemer, whether open-hearth or foundry, further elimination of area is possible on the basis of past experience. coming to the geologic phases of the problem, the first step is to eliminate great areas of rock which are known never to contain iron ore, like the granite areas and the quartzite and limestone areas. within the remaining areas, by examination of the surface outcrops and with the aid of magnetic surveys, iron formations are found which are the mother rock of the ores. in michigan, it has been possible to use certain percentage expectations in the areal location of iron formations within certain series of rocks extending over wide areas. such percentage coefficients have been useful, not only in exploration, but also in the valuation of lands which are so covered with drift that no one knows whether they carry an iron formation or not. examination of the iron formations results in elimination of large parts of them, because their metamorphic condition is not favorable to ore concentration. in the remaining areas more intensive methods are followed. it is scarcely possible to summarize briefly all of the structural and stratigraphic methods used in locating the ore bodies. these have often been described in print.[ ] comparatively recent advances in this phase of exploration work have been in the more detailed application of stratigraphic methods to the iron formation. the group characteristics of the iron formation are fairly uniform and distinctive as compared with all other rocks; yet within the iron formation there are so many different kinds of layers represented that it is possible to use these variations with great effectiveness, in correlating favorable horizons for ore deposition, in interpreting drill records, and in other ways. another method of approach, employed chiefly on the mesabi range, relates to the slumping of the ore layers which results from the leaching of silica during the concentration of the ore. this slumping can be measured quantitatively, and has been used to much advantage in exploration, in correlation of ore horizons, in preparation of sections and ore estimates, etc. early geologic explorations in the lake superior country were based on the assumption that the ores were concentrated by waters working down from the present erosion surface; but recognition of the fact that the waters which did the work were related to a far older and different erosion surface, under conditions which allowed of a far deeper penetration, has modified exploration plans for certain of the districts like the marquette and gogebic. notwithstanding the complexity of the geologic factors involved, their net result has been to concentrate iron ores in a surprisingly uniform ratio to the mass of the formation in different parts of the region,--with the result that on an average it may be predicted for any district, in an exploration of sufficient magnitude, how much ore is likely to be cut in either vertical or horizontal dimension. thirteen per cent of the productive area of the mesabi iron formation is iron ore. for the remainder of the lake superior region five or six per cent is the factor. these figures mean that, if a person could explore a broad enough area of iron formation, any miscellaneous group of drill holes or underground openings would tend to yield these percentage results. such percentages are amply sufficient to pay a large profit on the exploration. the question may be raised why the application of geology is required, if such average results can be secured from miscellaneous undirected work. the answer is that seldom is it possible to conduct an exploration on a sufficiently large scale to be sure of approximating this average, and that geologic study has made it possible in many cases to secure a better percentage result. if the geologist is able to raise the percentage ever so little, the expenditure is amply justified. he is not expected to have per cent success; but he is expected to better the average returns, and in this on the whole he has not failed. applying this method specifically to the gogebic range, it appears that up to january , , exploration and development had covered , acres of iron formation, measured along the dip in the plane of the footwall, within the limits of the area in which the formation is in such condition as to allow concentration of the ore. the total area of the footwall to a depth of , feet is approximately , acres. the range, therefore, was per cent developed to this depth. in the developed area, , , tons of ore had been found, or approximately one ton per square foot of footwall area, or , per acre of footwall explored. the total area of ore measured on the footwall was acres. the ratio of ore area to total explored area, measured in the plane of the footwall, was - / per cent. this may be taken in a rough way to indicate the average exploring possibilities in new ground, where local conditions to the contrary do not exist. this means that over the whole range about one drill hole or cross-cut in five will strike ore on an average. or, looked at in another way, about feet of drifting in every , on the footwall will be in ore. applying this factor to the unexplored area, amounting to , acres, the range had an expectation on january , , to a depth of , feet, over and above ores already discovered, of approximately , , tons. this was sufficient to extend the life of the range by about forty-four years. knowing the average cost of development of ore per foot in the past, and knowing the annual output and its rate of acceleration, it is possible to figure with some accuracy how much expenditure should be planned for annually in the future in order to maintain a safe margin of reserves against output. such quantitative considerations in the lake superior region serve not only to guide the general conduct of the exploration and development work, but in some cases as a basis for valuation both for commercial and taxation purposes. development and exploitation of mineral deposits the search for new ore bodies is closely related to the development, extension, and mining of ore bodies already found. in this field the geologist finds wide application of his science. here he may not be so much concerned with the economic factors or with the broader methods of geologic elimination; his study is more likely to be based mainly on the local geologic conditions. some of the larger and more successful mining companies, perhaps the greater number of them these days, have geologists whose business it is to follow closely the underground operations, with a view to advising on the conduct of the development work. this requires the most precise and intensive study. for instance, the anaconda copper mining company has a staff of several geologists, who follow the underground work in the utmost detail and whose approval must be obtained by the operating department in the formulation of any development plan. the complexity and fault relations of the veins in this company's mines are such that the application of these methods has abundantly justified itself on the cost sheet. too often mining companies leave the planning and execution of the underground development work to the local management, commonly to the underground mining captain, without geologic consultation. this procedure does not eliminate the economic geologist; for when the development fails at any point, or new and unexpected conditions are met, the geologist is likely to be called in. in such cases the practice of a geologist is like that of the ordinary medical practitioner; he is called in only when his patients are in trouble. the use of adequate geologic advice in the planning stages is about as little advanced in some localities as the practice of preventive medicine. the work of the economic geologist may not be ended by the finding and development of the ore; for the moment this is accomplished, he should again consider the economic phases of the problem--the grade of his ore, its probable amount, and other features, in relation to the general economic setting. in his enthusiasm for physical results, he may be carried into expenditures not justified by the economic factors in the problem. some one else may and usually does look out for the economic elements, but the prudent geologist will at least see to it that someone is on the job. footnotes: [ ] smith, george otis, and others, the classification of the public lands: _bull. , u.s. geol. survey_, . [ ] schlumberger, c., _study of underground electrical prospecting_: translated from the french by sherwin f. kelly, paris, . bergstrom, gunnar, and bergholm, carl, "teknisk tidskrift, kemi och bergvetenskap," , book . [ ] hoover, herbert c., _principles of mining_: mcgraw-hill book co., new york, , p. . [ ] leith, c. k., use of geology in iron ore exploration: _econ. geol._, vol. , , pp. - . [ ] van hise, c. r., and leith, c. k., geology of the lake superior region: _mon. , u.s. geol. survey_, . chapter xv valuation and taxation of mineral resources popular conception of mineral valuation the total returns from mining may not in the aggregate be far above the expenditure for exploration, development, and extraction; yet the total mineral wealth of the united states, on the basis of earning power and aside from the industries based on it, cannot be far from sixty billions of dollars, and this wealth has virtually come into existence since the gold rush to california. the mining industry supports a large population. these facts are the solid basis for the widespread popular interest in mineral investment--and mineral speculation. but there are other reasons for this interest,--the gambler's chance for quick returns, the "lure of gold," the possibility of "getting something for nothing," the mushroom nature of certain branches of the industry, the element of mystery related to nature's secrets, and the conception of minerals as bonanzas with ready-made value, merely awaiting discovery and requiring no effort to make them valuable. in the united states a factor contributing to the popular interest is the large freedom allowed by the laws to discover and acquire minerals on the public domain. perhaps no other field of industry comes so near being common ground for all classes of people. the mineral industry is a field in which it is easy to capitalize not only honest and skillful endeavor, but hopes, guesses, and greed. it is not to be wondered at, therefore, that in the popular mind the valuation of a mineral resource is little more than a guess, and sometimes not even an honest one. nevertheless, the mineral industry has become second only to agriculture in its capital value and in its earning capacity. in this industry it is hardly possible to arrive at valuations as securely based as in many other industries, but the elements of hazard are not so hopeless of measurement as might be supposed. the great mineral and financial organizations do not depend on mere guesses, but use well-tried methods. if the general investor were to give more attention to these methods he would doubtless save himself money, and the mineral industry would be rid of a great incumbrance of parasites who live on the credulity of the public. to anyone familiar with the mineral field, it is often surprising to see the rashness with which a conservative business man, who would not think of entering another industrial field without close study of all the factors in the situation, will invest in minerals without using ordinary methods of analysis of values. in the following account of valuation of minerals in the ground, and the closely related subject, taxation of such minerals, the attempt is made to state some of the principles briefly and simply with a view to making them intelligible to the layman. values beyond the mine are concerned with so many factors of a non-geologic nature that they are not here discussed. valuation and taxation of mines intrinsic and extrinsic factors in valuation it is essential to recognize at the outset that the value of a mineral deposit, like the value of any other commercial material, comprises two main elements; an intrinsic element based on the qualities of the material itself, and an extrinsic element based on its availability and the nature of the demands for it. the two elements may not be sharply separated, and neither exists without the other. a mineral deposit in easy reach of a populous community, which has sufficiently advanced methods and requirements to use it, may have high value; an exactly similar deposit, if far removed from points of consumption, handicapped by transportation, or available only to people without developed methods for its use, may have little or no value. intrinsically the deposits are alike; but extrinsically they are far different, and their values are correspondingly unlike. even two adjacent properties, differently managed and controlled, and with different relations to markets, may have somewhat different values depending on the use made of them. the value of a deposit may vary from year to year with changes in demand for its output, or with changes in metallurgical and other processes which make its use possible. minerals of small bulk and high value, as for instance gold, platinum, and diamonds, have a nearly standard value related to their intrinsic properties, because they can be transported so easily to any part of the world. on the other hand, materials of large bulk and low unit value, such as coal, iron ore, and clay, may have highly varying values independently of their physical characteristics, because of their relative immobility. but the values even of gold and precious stones represent a combination of intrinsic qualities and of demand. a diamond is made of carbon but is more valuable than coal or graphite because it appeals to the esthetic taste. it is only because man introduces an element of demand that the diamond takes on value. in short, man is the multiplier and the mineral substance is the multiplicand in the product known as value. recognition of the two elements of value is vital to a clear understanding of the methods and problems of valuation of minerals. it is too often assumed that the physical properties constitute the sole factor. looked at in a large way, the returns from the mineral industry are commensurate with the effort put into discovery and development of mineral resources, even though the returns to lucky individuals have been excessive. in respect to the importance of the human energy element, the mining of minerals is not unlike the cropping of soils. some interesting economic studies have been made of mining districts to ascertain whether the total return has been equal to the total investments by both successful and unsuccessful participants. the results show that, even in some of the most successful districts, there is not a large "social surplus,"--that is, a surplus of receipts over total expenditures. it is difficult to generalize from such studies with any degree of accuracy; but it seems likely that if we could measure the vast amount of fruitless effort which has been expended in non-productive territories, the result would tend to bear out the general conclusion that the social surplus for the mineral industry as a whole is a modest one, if it exists at all. of course, it is to be remembered that the total benefits from mineral resources are not to be measured in terms of gain to the producers,--but that their measurement must take into account the satisfying of all the complex demands of modern civilization. values of mineral deposits not often established by market transfers while minerals as extracted and used may have standard market values, mineral deposits in the ground are not bought and sold on the open market with sufficient frequency to establish standard market values. a sale may establish a criterion of value for the particular deposit, but not for the class of deposits,--for no two mineral deposits are exactly alike. stock quotations may establish a certain kind of market value, but these are often vitiated by extraneous considerations. for these reasons the valuation of a mineral deposit is in each case a special problem. the ad valorem method of valuation the ordinary commercial method of valuing mineral deposits recognizes the two main elements of value above discussed. this method is sometimes called the _rational_ or _ad valorem_ method. the profit per ton (or per other unit) of the product is established, on the basis either of past performance of the property or of experience with other similar properties. this profit is multiplied by the total tonnage estimated in the deposit, the estimate including known reserves, probable reserves, and in some cases possible and prospective reserves. the product of the profit per ton and the total tonnage gives the total net amount which will be received; it does not, however, give the present value, because the commodity cannot all be taken out and sold at once, but must be mined and absorbed by the market through a considerable period of years. the returns receivable some years in the future have obviously a lower proportionate present worth than amounts to be received at once. the interest rate comes into play, making it necessary to discount each annual payment for the number of years which will elapse before it is received. it is evident, therefore, that an estimate of the _life_ of the property is necessary, involving not only knowledge of the reserves, but also a forecast of the annual extraction or _rate of depletion_. as a simple case of _ad valorem_ valuation for illustrative purposes, a deposit containing , , tons in reserve has an estimated output of , tons a year for ten years, on which the profit per ton has in the past averaged $ and is expected to average $ in the future. ten annual instalments or dividends of $ , are to be received. the present value of the total of these instalments is figured by an annuity method. it is the value upon which the series of dividends will pay interest at a predetermined rate, in addition to paying to a sinking fund annual instalments which, safely invested each year at a low rate of interest (usually %), will repay the present value at the end of the ten years. in our hypothetical case, if an interest rate of % be taken, the present value of $ , , , to be received through ten years in ten equal instalments, is $ , . in other words, the sum of $ , will be replaced by the sinking fund at the end of ten years, and will pay % interest during this period,--this requiring total receipts of $ , , in ten equal annual instalments. if the deposit here cited as an illustration were to be worked out in three years, thus yielding three annual instalments of $ , , its value would be $ , . each of the factors entering into this method of valuation covers a wide range of variables, any one of which may be difficult to determine. the profit per ton for a given deposit may have been extremely variable in the past, making it difficult to determine whether the highest or lowest figure should be projected into the future or whether some average should be taken; and if an average, whether the time covered by the average should be long or short. for a small, short-lived deposit obviously the most recent conditions would be taken into account in estimating future profits. for a long-lived property there would be more tendency to consider the long-time average vicissitudes, as reflected in the average profits of the past. for some mineral commodities there are cycles of prices, costs, and profits, of more or less definite length, established during the long past history of the industry; and in such cases it is desirable in calculating averages to use a period covering one or more of these cycles, rather than some shorter or longer period. for many minerals, however, these cycles have been too irregular to afford a sound basis for future estimates. if the experience of the property itself is too short to afford a sufficient foundation for forecasting profits, or if there has been no previous work on the property, then it is necessary to use averages based on other properties or other districts; or if there are none strictly comparable, to build up a hypothetical figure from various estimated costs of labor, supplies, and transportation, selling prices, etc. in the estimate of the profit factor, the geologist is not primarily concerned. in estimating the total reserves in a mine, geological considerations nearly always play a large part. an ore body may in some few cases be completely blocked out by underground work or drilling, eliminating the necessity for inferring conditions beyond those actually seen; but in the huge majority of mineral deposits the reserves are not so definitely known, and it becomes necessary for the geologist, through knowledge of similar occurrences, through study of the structural features of the deposit, its origin, and its history, to arrive at some sort of an estimate of reserves. in estimating the life of a mineral deposit it is necessary to start with the figure of total reserves, and from a study of conditions of mining and of markets to estimate the number of years necessary to exhaust the deposit. this is a more nearly commercial phase of the problem, in which the geologist takes only part of the responsibility. perhaps more estimates of value have gone wrong because of misjudgment of this factor than for any other cause. if the physical conditions are satisfactory, it is easy to assume a rate of extraction and life based on hope, which experience will not substantiate. the choice of the interest rate to be used in discounting future receipts to present worth likewise is a financial and not a geologic matter. again, however, the geologist must give consideration to this factor, in view of the fact that the interest rate must be varied to cover the different degrees of hazard and doubt in the geologic factors. for instance, to the extent to which the estimate of ore reserves is doubtful, it is necessary to use a high rate of interest to allow for this hazard. in a large, well-developed mineral deposit, with the geological factors all well known and the demand and market well established, it is reasonable to use a lower rate of interest. in general, the mineral industry is regarded in financial circles as being more hazardous than many other industrial lines; and money is put into the industry with the expectation of a high rate of interest, no matter how safe the investment may be. in actual practice interest rates used in making valuations vary from to or per cent. it is clear that, where a property has long life, the interest will very materially reduce the present value of the ores to be mined far in the future. reserves to be mined more than thirty years hence have relatively little or no present value. beyond a certain point, therefore, the acquirement and holding of reserves for future use by private companies has little commercial justification. this is a matter which is too often not sufficiently well considered. man's natural acquisitiveness often leads him into investments which, because of the time and interest factor, have little chance of successful outcome. of course a large corporation, anticipating an indefinitely long life, or perhaps aiming at monopoly, may afford to hold reserves as a matter of general insurance longer than a small company,--even though, because of the interest rate, these reserves have no present value on their books. it is likewise true that governments, looking forward to the future of the nation, and without the necessity of paying so much attention to interest and taxes, are not so limited by this consideration. an illustration of the limiting effect of the interest rate on the acquirement of long-lived coal deposits by private interests is discussed in chapter xvii on conservation. investments made many years ago have so augmented, even at low interest rates, as to make it practically impossible to count on a return of capital and interest; or if the return were to be exacted from the public it would mean excessive charges, which are not possible in competition with other mines not so burdened. in the commercial valuation of oil wells and pools, much the same method is used as has been described for mineral resources in the solid form, but the estimate of reserves or life is based on consideration of curves of production of the sort mentioned on pages - . the essence of the _ad valorem_ method of valuation above described is income-producing capacity. this method recognizes the fact that the value of the mineral deposit depends, not only on its physical constitution, but also on what performance can be expected from it. stock quotations on mineral properties in the standard markets are based substantially on estimates of income capacity, more or less on the _ad valorem_ basis. however, the quotations also reflect the hopes and fears of the public, often resulting in valuations quite different from those based on studies of the objective conditions. the war introduced new considerations into the problems of _ad valorem_ valuation. under peace conditions there is a tendency toward the establishment of normal costs, selling prices, and markets, which can be taken more or less for granted by anyone attempting to value mineral deposits. under war and post-war conditions, few of these elements can be taken for granted; it becomes necessary to consider the entire world situation in regard to a mineral commodity, the effects of the peace treaty (which greatly concerns minerals), future international relations, tariffs, and other matters of a similar sort. if a person were today valuing a manganese deposit according to the method above outlined, and were to confine himself solely to a narrow consideration of past markets and profits on individual properties, he would be very likely to go wrong,--for the world manganese situation has an immediate and practical bearing on each local problem (see pp. - ). other methods of mineral valuation and taxation we have discussed the _ad valorem_ method of valuation at some length because it is the one in widest commercial use, and also because the principles involved underlie practically all other methods of mineral valuation. the _ad valorem_ method is used in appraisals for taxation in some districts and for some commodities, as, for instance, the iron mines of michigan and wisconsin. its application, however, requires skill and judgment if equitable results are to be secured. for taxation purposes, therefore, it is not uncommon to adopt purely arbitrary or empirical methods which eliminate the element of judgment, and which often result in valuations quite different from those used commercially. the state of minnesota divides its iron ore deposits into a series of classes, on each of which a more or less arbitrary flat value per ton is placed, based on the spread between cost and selling price. the adjustments of flat values on the several classes through a series of years, however, as well as the assigning of specific ores to the different classes, have been based on the same factors as are used in _ad valorem_ valuations. the state of wisconsin uses a so-called "equated income" method of valuation and taxation for the lead and zinc deposits of the southwestern part of the state. under this method the state puts such a tax on the mine incomes for the preceding year as will yield approximately the same total return as under the _ad valorem_ method,--the whole being based on the assumption that each deposit has about the average life figured for the mines of the entire district. so far as individual ore deposits vary from this average life, the value fixed departs from the true or _ad valorem_ value. several states impose specific taxes based on the operations of the mines for the preceding year or for some combination of preceding years, as expressed in tonnage output or net profits or net proceeds, regardless of life or reserves. so far as output or net proceeds for a year are proportional to the real value of the property, a rough approximation to equitable taxation as between mines is accomplished. often, however, the valuation thus obtained has little relation to the true value, because it does not take into account the great differences between properties in reserves, in life, and in capacity for future profit. income taxes, national and state, are of course based on the profits of the preceding year; but in the collection of these taxes from mineral operations, it is recognized that mineral deposits are wasting assets, and therefore a considerable part of the income may under the law be regarded as a distribution of capital assets, and be deducted from taxable income. the amount to be deducted obviously depends on the size of the reserves and the life,--with the result that progressive adjustment of income tax valuations tends to take into consideration exactly the same factors as are used in the _ad valorem_ method. it is obviously unjust, for instance, to collect the same proportion of tax from the annual income of a mine which has a life of only two years as from a mine which has a life of fifty years. under the federal income tax a capital value is placed on the mineral deposit as of march , , which total capital value may be increased with subsequent discoveries. as the ore is taken out of the ground and sold, income tax is paid only on the difference between the assigned capital value per unit and the selling profit. if, for instance, the capital value as of march , , is placed at c. per ton of mineral in the ground, and ten years later a ton is sold for a profit of $ , income tax is paid on c. the figure of c. per ton as value in the ground is actually obtained by estimating a profit, when the ore is ultimately mined and sold, of $ per ton, and discounting this dollar to present worth as of march , . therefore the total amounts on which taxes are paid during the life of the mine should represent approximately the total accruals of interest from march , . in this manner the proportion of annual income to be taxed becomes larger with the length of the life period. with a deposit having a life of thirty years the net result is that about half of the aggregate income is taxed, though this figure of course varies somewhat with the interest rate used. in the collection of income taxes from coal mines in england, and in the collection of certain state income taxes in the united states, a considerably smaller allowance is made for the retirement of capital value (or for _depletion_, as this is commonly called). in these cases the deduction allowed is a small fixed percentage of the capital value, regardless of the actual life of the property. the treatment of mineral resources as wasting assets in the united states income tax law meets one considerable practical difficulty--namely, that the law really requires physical or _ad valorem_ valuation of every mineral property by the government, as a check on the claims for depletion allowance. this immense and expensive task is too much for the tax collection agencies as now organized, and it may be questionable whether it will ever be desirable to expand these agencies to the extent required for such a purpose. this is the principal argument for the use of arbitrary depletion factors such as those sometimes used abroad. there are many advocates of the straight tonnage tax on mineral deposits, on the ground that it is simple, definite, and easily applied. the present tendency is to extend the application of this form of tax. it is clear, however, that to assume the same value per ton for taxing purposes on a property making a large profit, and on another property which, because of physical conditions, is barely able to operate at a profit, imposes a relative injustice. to meet this difficulty, it is sometimes proposed that the tonnage tax should be graded in such a manner as to allow for differences in physical conditions and in profit at different mines. when one attempts to apply a graded tonnage tax, however, it soon becomes apparent that, in order to make such a valuation equitable as between properties, it is necessary to use all of the factors of the _ad valorem_ method for each of the properties. the wide appeal of arguments for a flat tonnage tax is based partly on popular misconception of the complexity of elements entering into mineral valuations. there are many forms of more or less indirect tax which are substituted in different parts of the world for direct taxes. for instance, certain states in south america do not tax ores in the ground, but collect the revenue in the form of mining licenses or export taxes. general comments on taxation of mineral resources there has been a noticeable tendency in recent years to regard mineral resources as a heritage of the people, to be held in trust, rather than as property to be acquired and managed solely for private interest. this tendency has been indicated by the adoption in various parts of the world of laws affecting rights to explore and acquire minerals on the public domain; laws relating to the right of eminent domain over minerals already alienated from the government; laws regulating the exploitation of minerals in the interests of conservation; laws relating to tariffs and other restrictions on the export of mineral commodities; and laws relating to taxation. the feeling that mineral resources really do not belong in private hands has undoubtedly been an underlying factor in the imposition of heavy taxes. contributing to this action also are the popular belief in the intrinsic bonanza values in mineral resources, the failure to recognize the large element of value which is put into such resources by human efforts, and the failure to realize that the social surplus in the aggregate is small. to some tax officials an ore is an ore, more or less regardless of situation, of conditions of mining, of the demand for the product, and of the time when the demand will allow the ore to be mined,--in short, more or less regardless of what the ore may be made to yield as a going business. in this way heavy taxes are sometimes imposed on mineral reserves, which are based on unwarrantably high appraisals of future possibilities, and which cannot be paid out of earnings. ultimately, a tax must be adjusted to the capacity of the mine to pay out of its earnings, and this capacity in turn is determined both by the physical characters of the ore and by the success with which it may be made available for consumption. this view of valuation for taxing purposes is sometimes opposed by mining men on the grounds that it taxes brains, skill, and initiative, and that it puts a premium on shiftless management. the same argument might be applied to the valuing of any business or profession. to the writer the argument is not sound, in that it fails to recognize the element of human energy in resource values. if value were to be confined solely to the intrinsic character of the ore itself, there would be required an almost impossible degree of discrimination on the part of taxing officials to dissociate this value from other considerations; and there would be required further the differentiation between efficient and inefficient management, which involves so many considerations that the conclusion would be worthless. in the application of income taxes to mining operations, there is sometimes another tendency toward over-taxation in that the income is regarded as more or less permanent, and insufficient allowance is made for exhaustion of the mineral deposit. under the united states income tax, mineral deposits are definitely recognized as wasting assets and this factor is allowed for; but in state income taxes and in england and other parts of the world, allowances for this purpose are small. there is wide belief that heavy taxation of mineral resources, particularly on the _ad valorem_ basis, retards exploration and prevents the development of the reserves which are necessary to stabilize the mineral industry. high taxes have undoubtedly had this effect in some cases, especially where taxes have been imposed on resources long prior to development; but, in the writer's view, this tendency in general has not yet passed the danger point, and is not likely to do so until taxes become positively confiscatory of the industry. to argue that increase of taxes may even have certain beneficial results on the mineral industry may lead to suspicion of one's mental soundness; but it is hard to escape the conclusion that the incidence of high taxes has led to a much more careful study of the question of reserves, has eliminated in some cases the expenditure of money for development of excessive reserves to be used far in the future, and has tended to prevent over-production. where mineral reserves are developed too far ahead of demand, the interest on the investment piles up an economic loss to be charged against the industry. it may be assumed that the urge for exploration will continue as long as there is demand for mineral resources; and that, to keep the industry on a sound basis, a certain amount should be set aside and charged to cost for the purpose of keeping up reserves in a proper ratio to production. much remains to be learned about the most desirable ratio between reserves and production. in many camps, before the incidence of high taxes, this ratio was not properly determined; and there was a tendency, due to natural acquisitiveness and in the absence of anything to hinder it, to build up reserves indefinitely. the first effect of high taxes in such camps has frequently been the curtailment of exploration and development. later, as production has begun to approach the end of the reserves, exploration has been resumed, but only on a scale necessary to insure production for a limited period in advance. the argument that high taxes inhibit exploration is good only beyond the point where the industry itself becomes no longer profitable. if there is sufficient demand for the resource, it is obvious that such a condition cannot long continue; for, as production and the development of reserves fall off, the resulting increase in the price received for the product is likely to offset any effect of taxes, and to restimulate production and exploration. nevertheless, in this period of high taxes following the war, there is much discouragement in the matter of exploration, suggesting that the danger point is being approached. some relief has been afforded by recent special provisions of the federal income tax law, recognizing mineral resources as wasting assets, allowing recent discoveries to be included with total assets for depletion purposes, and recognizing special and peculiar circumstances with reference to each mine. also a certain amount of exploration goes on through the momentum gained from past conditions, without sufficiently full recognition of the effect of present high taxes. this is not surprising when it is remembered that the people actively engaged in field exploration often do not think sufficiently fully of the tax situation, until after a discovery or development has brought them face to face with it. because of the vital importance of the reserve factor in mineral valuation, geologic aid and advice are extensively sought by both public and private organizations. mining geologists are playing an important part in the application of the national income tax. a larger number are acting for private companies in appraisals required by this tax. many geologists are used in making valuations for state taxes, and in two cases the state geological surveys have complete charge of appraisals. these appraisals include not only examinations of specific properties, but general surveys of large regions, to ascertain possible values of undeveloped lands and to establish broad principles of valuation based on a consideration of all the physical factors in the situation. chapter xvi laws relating to mineral resources this heading is likely to suggest mining law and the vast literature devoted to it. mining law has mainly to do with questions of the ownership and leasing of mineral deposits. in addition, there are laws relating to the extraction of mineral products, including those having to do with methods of mining and with safety and welfare measures. there are laws affecting the distribution of mineral products, such as those relating to tariffs, duties, international trade agreements, and many other matters. there are laws relating to underground water, to shore lines, and to various geologic engineering fields. in the formulation of these laws, as well as in the litigation growing out of their infraction, basic geologic principles are involved; and thus it is that the geologist finds much practice in the application of his science to legal questions. it will be convenient to consider some of the laws relating to mineral resources under three headings: first, ownership and control; second, extraction; and third, distribution. i laws relating to ownership and control of mineral resources large use of mineral resources is of comparatively recent date. some of the mineral industries are not more than a decade or two old and the greater number of them are scarcely a century old. in the united states the mineral industry dates mainly from the gold rush to california in . the formulation of laws relating to the ownership of minerals has on the whole followed rather than preceded the development of the mineral industries; and hence mining laws relating to ownership are not of great age, although historical precedent may be traced far back. on alienated lands where lands came into private ownership, or were "alienated" from the governments before the formulation of mining laws, varied procedures have been followed in different countries. in england and the united states, under the old régime in russia, and to a slight extent in other parts of the world, mineral titles remain with the owner of the land and the government does not exercise the right of eminent domain. but even in england, where private property rights have been held peculiarly sacred, the discovery of oil during the later years of the war led to an attempt to expropriate the oil rights for the government. because of the objection of landowners this attempt has not reached the statute books, but the movement is today an extremely live political question in england. a somewhat similar question is involved also in the movement to nationalize the coal resources of england, now being so vigorously urged by the labor party. in the united states, no serious attempt has yet been made to take over mineral resources from private ownership. other countries have gone farther in retroactive measures in regard to alienated lands. under the leadership of france, most of the countries of western europe have appropriated to their governments the undiscovered mineral resources on private ground, particularly those beneath the surface, except where previously they had been specifically conveyed to the private owners, or with the exception of certain designated areas and minerals which had been conveyed to private ownership prior to certain dates. some minerals occurring at the surface, variously specified and defined in different countries, are allowed to remain with the private owners, although often subject to government regulation in regard to their development and use. in varying degree this treatment of mineral resources on alienated lands is followed in the british colonial laws--in south africa, australia, new zealand, and canada--and in the latin-american laws. the laws are usually based on specified classifications of minerals. those occurring at or near the surface, and called "quarries," "placer deposits," "non-mines," or "surface deposits," usually remain with the surface owners. those beneath the surface, called "sub-surface deposits" or "mines," in general belong to the government. in some of the countries of south america the state exercises eminent domain even over the surface deposits; and in others even sub-surface minerals remain in private ownership, where specifically granted, or where the transfer of property took place prior to certain dates. where the government has acquired mineral ownership of lands previously alienated, the resources are open for development either by the owners of the surface or by others, on a rental, lease, specific tax, labor, or concession basis. the government holds the title, exacts tribute, and more or less directs and controls the operation. exceptionally, as in ontario, british columbia, quebec, and newfoundland, the government grants patents, that is, it disposes of its rights to purchasers. on the public domain where the development of mineral resources began before the lands had passed from governmental ownership, special mining laws were enacted. looked at broadly, these laws may be regarded as based on two partly conflicting considerations. ( ) the assumption that mineral resources, which are wasting assets, accumulated through long geologic periods, are peculiarly public property,--not to be allowed to go into private ownership, but to be treated as a heritage for the people as a whole and to be transferred to posterity in the best possible condition. some of the early minerals to be developed were used either for money or for war purposes, leading naturally to the acceptance of the idea that these belonged to the government or to the sovereign. ( ) the assumption that the discovery and development of mineral resources requires a free field for individual initiative, and that the fewest possible obstacles are to be put in the way of private ownership. governments have not as a rule been greatly interested nor particularly successful in exploration. therefore, in framing laws of ownership, concessions have been made to encourage private initiative in exploration and development. in the case of the united states this idea was coupled with the broad doctrine that the government held public lands only in the interest of the people, and that its people were entitled to secure these lands for private ownership with the least possible restriction. a survey of the mining laws affecting the public domain or non-alienated lands of different parts of the world, as well as the history of changes in the mining laws, indicates a wide range of relative emphasis on these two underlying considerations. in the united states, at one extreme, the laws have been such as to give the maximum possible freedom to private initiative, and to allow easy acquirement of mineral resources from the government. at the other extreme, in south africa, australia, and south america, it is impossible for the individual to secure title in fee simple from the government; he must develop the mineral resources on what amounts to a lease or rental basis, the ownership remaining in the government. the trend of events in mineral laws is toward the latter procedure. this is evidenced in the united states by the withdrawal of large areas of public lands from entry, and by the recent enactment substituting leasing privileges for specified minerals for the outright ownership which was allowed under the federal law before the lands were withdrawn from entry. the withdrawal of oil lands from public entry in other parts of the world is another illustration (see pp. - ). nationalization of mineral resources nationalization, as this term is popularly understood, means financial control and management of mineral resources by the government, either through actual ownership or through measures of public control designed to eliminate private interest from the active direction of the resources. in a broader sense, it may be used to include a considerable variety of restrictive and coercive measures adopted by the government in the proposed interests of public welfare,--as illustrated by the war-time measures instituted by the united states and other governments relating to the mining and distribution of coal, and to coal prices. in this broader sense various aspects of nationalization are indicated under other headings in this and other chapters. it is clear that other countries of the world have gone farther in the direction of nationalization of mineral resources than the united states. the tendency was manifest before the war, and has been strongly emphasized during and since the war. in the united states, notwithstanding war-time measures, the subject has not yet come prominently forward, at least by name. on the other hand, there has been growing recognition of the dependence of public welfare on the proper handling of mineral resources--particularly of the energy resources, coal and oil,--as evidenced by a variety of proposals and measures under consideration in legislative and administrative branches of our national and state governments. even taxation, both local and national, has in effect reached a stage where private interest has become considerably minimized by the increasing burdens laid on the industry by government requirements. the immediate purpose of taxation is to raise money for the needs of the government; but in the formulation of tax measures there is clearly to be discerned a growth of underlying sentiment that natural resources belong in some fashion to the public, and that private control is to be regarded not as a sacred property right but as a trust held on sufferance of the public. in view of the obvious trend toward nationalization in other parts of the world and the significant tendencies in the united states, it seems likely that the subject of nationalization of mineral resources will come prominently to the front in this country in the comparatively near future. if so, it is time that students of mineral resources should recognize the comprehensiveness of this problem, and should attempt to develop basic principles to serve as a guide in the direction and formulation of the numerous and complex measures which are sure to be proposed. at present there is no government or technical organization related to the industry which is studying the problem in its broader aspects and is in a position to advise wisely with public officials interested in this problem. it is beyond the scope of this book to discuss the pro and con of an economic question of this magnitude. the writer would, however, record his belief, which is implied also in discussions in other chapters, that the discovery and intelligent management of mineral resources by their very nature and infinite variety require private initiative, and that the history of government efforts in this field in this and other countries does not promise that nationalization can supply sufficient advantages to counterbalance the loss of this element. with this view the problem of nationalization becomes one of determining what steps, if any, can be taken by a government to the advantage of public welfare, which will at the same time preserve and foster private initiative, exercised with the hope of reward, which seems alone to be capable of meeting the variable, elastic, and complex problems inherent in the development of a natural resource. a first step toward a broad scientific attack on this problem would be the recognition of the fact that tariffs, taxes, conservation, international mineral questions, leasing laws, and various technical investigations of minerals are but parts of a great unit problem. with this recognition there should follow naturally an attempt to correlate and direct the many government agencies, legislative and administrative, now concerned with different aspects of the problem. under present conditions, the various elements of the problem are considered by different groups of persons, without sufficient contacts or correlation to promise the development of a broad, underlying policy. effect of ownership laws on exploration the nature and the progress of exploration (and development) in different countries have been more or less related to the character of the mining laws. where the mineral resource has passed from government control into private ownership, exploration is a matter of commercial arrangement between the explorer and the owner. there is often some lag in exploration, especially where the lands are held in considerable blocks. the owner is often not inclined, or unable, to institute effective exploration himself; and even though he is willing to offer favorable exploration terms to others, the inducement is often less attractive than on government lands. for instance, it is stated that in england, due to the many requirements of law and custom, it takes on an average eight years, and in some cases even longer, to close a coal lease after the terms have been agreed upon. the slowness of exploration and development on the great land grants in the united states, and on the tracts of the large timber companies, also illustrates the retarding effect of private ownership. it is partly this situation that is making governments increasingly careful about parting with mineral ownership, and that is leading to the introduction of more or less coercive measures, either to regain control or to make it easier for the public to explore and develop minerals on privately owned lands. under the great land grants to railroads in the united states it is becoming increasingly difficult to secure mineral patents from the government; and there has been litigation between government and grantees, as in the case of certain oil lands of the southern pacific railway. the taxation in some states of mineral rights which have been reserved by large owners is indirectly resulting in appraisal of these rights by the owners and in efforts to utilize them. as long as mineral rights were not taxed independently of surface rights, they were often reserved in selling surface rights on the mere chance that mineral might be found in the future, and thereby general exploration and development were held back. in the united states, minerals on the public domain have been open to exploration and acquirement with minimum restrictions, except for the considerable areas later withdrawn from entry. after long delay a part of these withdrawn lands are again open to private exploration, but not to fee ownership. specified minerals--coal, oil, phosphates, and potash--may be explored for, and may be leased under certain restrictions as to amount and time of development. the effect of this act on exploration is yet to be proved; but since many of the lands have now been shown to be favorable for minerals which are in great demand, there is little doubt that exploration will be resumed on a large scale. on the whole, under the federal mining laws of the united states the individual prospector has maximum leeway,--and from the standpoint of development of resources this procedure probably has been justified. in other countries where the mineral resources are owned by the government, there is in most cases considerable restriction, through licenses and other regulative measures, upon the activities of prospectors. this restriction, together with the fact that it is usually not possible to secure title to the land, but only to secure rights through rental or leasing, is to some extent a deterring influence on the penniless prospector. it does not follow that under these conditions exploration and development are absent. the charges imposed are light, and in the early stages require comparatively small contributions as evidence of good faith. it is to be remembered that exploration has become concentrated more and more into the hands of persons financially able to meet such conditions. exploration is passing from the highly hazardous stage of individual effort into a systematic business with calculable returns. use of geology in relation to ownership laws the contacts between geology and laws relating to mineral ownership are many and varied; a few illustrative examples are offered. many difficulties arise from the loose use of mineral names in these laws. the laws governing location of mineral deposits in cuba are so framed that iron ores may be located and claimed from the government either as "iron ores" or as "bog ores and yellow ochers." some of the important ores of eastern cuba, now being extensively used in the united states, came into litigation because rival claimants had overlapping claims under the two classifications. the wording of the law is of course ambiguous, and suggests that geologists did not have a hand in its framing. to establish title to these claims it was necessary to show whether these ores had been rightfully located as iron ores, or whether they should have been located as bog ores and yellow ochers. this involved an analysis of the geological conditions, to show that the ores are the result of normal weathering and concentration in place of the underlying rocks--an origin common to many iron ore deposits,--and that they do not have the characteristic origin of bog ores. in short, the question was settled on the scientific principles of origin of ores and of metamorphic geology. the efforts of our federal government to frame and apply mining laws to public lands have involved extensive geological and mining surveys by the united states geological survey and the bureau of mines. the land classification work for this purpose by the geological survey has been of wide scope. the recently enacted leasing law, which opens up government lands for exploration of coal, oil, potash, and phosphate, requires carefully prepared geologic data for its proper administration. state governments also have initiated surveys of an exploring nature for taxing and other public purposes (see pp. , ). in the united states there is a wide use of geologists as witnesses in litigation affecting "extralateral rights." the federal mining law gives the owner of the claim containing the "apex" or top of a mineral vein or lode the right to follow the vein down the dip, with certain limitations, even though this takes him on to adjacent properties under other ownership. where two branches of a vein are followed down from separate claims, the owner of the oldest claim is entitled to the vein below the point of junction. the law was framed to validate a procedure more or less established by mining custom. it was obviously framed with a very simple and precise conception in mind--namely, a simple vein definitely and easily followed, without much interruption or contortion. in nature, however, veins or lodes have a most astonishing variety of form and occurrence, making it difficult to frame a definition that is comprehensive and at the same time sufficiently precise for all cases. a commonly used definition of a vein or lode is a mineralized mass of rock which is followed for purposes of finding ore. the mineral matter may be continuous or discontinuous. there may be one definite wall, or two walls, or none at all. there may be associated gouges and altered or mineralized rock. the vein may consist of almost any combination of the elements of mineral matter, walls, gouges, and mineralized rock. instead of being a simple tabular sheet, a vein may have almost any conceivable shape; it may consist of multiple strands of most complex relations; it may have branches and cross-over connections. it may be a more or less mineralized sedimentary formation with limits determined by original deposition. it is very often bent or folded, and even more often faulted; the faulting may be of great complexity, making it extremely difficult to follow the vein. the vein may be cut by other veins of different ages, which in places may be hard to distinguish one from another. erosion working down on a complex vein displaced by faulting and folding may bring several parts of the same vein to the surface, developing what seem to be separate vein apices. where there are many veins close together, it may be difficult to determine whether the entire mass should be considered a unit vein or lode (a "broad lode"), or whether each vein should be considered independently under the law. the geologic aspects of these problems are obvious. there are few mining districts where the vein conditions are so simple that no geological problems are left to be solved with relation to extralateral rights. in the early stages of the mining, separate operations may be carried on for a considerable time in a district without mutual interference; but as mining is carried down the dip, what seemed to be separate veins may be found to be parts of the same vein or parts of a complex vein system, and separate mining organizations are thus brought into conflict. it then becomes necessary either to consolidate the ownerships or to go to the courts to see which claim has the extralateral rights. in either case, the geologist is called on to play a large part,--in the valuation of rights for the purpose of combination, or in litigation to settle apex rights. a geologic survey of the conditions is a prerequisite. in order to get the needed information for the courtroom, it may be necessary to go further, and to conduct extensive underground exploration under geologic direction. some of the most intensive and complete geological surveys of mineral resources in existence have been done for litigation purposes. the study in these cases is not empirical, but goes into every conceivable scientific aspect of the situation which may throw any light on the underground conditions--the source of the ores, the nature and source of the solutions which deposited them, their paths of travel, the structural and metamorphic conditions, the mineralogical and chemical character of the ores and rocks, and even broader questions of geologic age. the many volumes of testimony which have accumulated during famous apex trials cover almost every phase of geology, and are important primary sources for the student of economic geology. it is often argued that strictly scientific, impartial geologic work is impossible in connection with one of these trials, because the viewpoint is warped by the desire to win. the sharp contrast in the views of experts on the two sides is cited in evidence. there is no denying the fact that the conditions of a trial tend toward a certain warp in scientific perspective. on the other hand, the very existence of competitive and opposing interests leads to the most intensive detailed study, and to complete disclosure of the facts. in most cases there are no substantial differences in the statements of scientific fact by reputable experts on the two sides, although there may be wide differences in the inferences drawn from these facts. the failure to note a fact, or any distortion or misstatement of a fact, is followed so quickly by correction or criticism from the other side, that the professional witness usually takes the utmost pains to make his statement of fact scientific and precise as far as his ability goes. few scientific treatises in geology contain any more accurate accounts of mineral deposits than testimony in cases of this sort. if every student of geology, early in his career, could have a day on the witness stand on a geologic problem, under both direct and cross examination, he would learn once and for all the necessity for close and accurate thinking, the difference between a fact and an inference, and the difference between inductive study of facts and the subjective approach to a problem. it is a common assumption that a witness called to testify on scientific matters is on a somewhat different basis from the eye-witness to an event or transaction. we are not sure that this assumption is justified. seldom is it possible in mining operations to disclose the facts in three dimensions so completely that they may be empirically observed and platted by the layman. the grouping and presentation of the facts in adequate perspective require an analysis of the origin of the ores and rocks, the rock alterations, the structural systems, and other facts. no one ever saw the vein or lode in the process of formation. the true nature of the event and of its physical results must be inferred inductively from circumstantial evidence. if it be conceded that it is necessary and right to call an eye-witness to an event involved in litigation, it is equally necessary where there are no eye-witnesses to call the persons best qualified to interpret the circumstantial evidence. it is to be remembered that apex cases are only one kind of a vast variety of cases affecting mineral resources. at one time or another, and in some connection or another, practically every geologist of considerable experience has found it necessary to testify on geologic matters in court. the wide interest attaching to certain spectacular apex cases has led in some quarters to hasty criticism of the participation of geologists therein, without apparent recognition of the fact that the criticism applies in principle to many other kinds of litigation and to practically all economic geologists. this criticism also fails to take cognizance of the fact that, for every case tried, there are many settled out of court through the advice and coöperation of geologists. while there may be in the geologic profession, as in others, a very few men whose testimony can be bought outright, in general it must be assumed that geologists will appear on the witness stand only when, after careful examination, they are satisfied that there is a legitimate point of view to be presented. geologists and engineers understand more clearly than almost any other group the extent to which the complexities of nature vary from the conditions indicated in the simple wording of the law of extralateral rights. almost to a man, they favor either modification or repeal of the law. on the other hand, the law has been in force since , it has been repeatedly interpreted and confirmed by the courts, and a vast body of property rights has been established under it. lawyers see great legal difficulties in the way of its repeal or serious modification. mining men for the most part are not primarily interested one way or another, unless there is potential application of the extralateral-rights provision to their particular properties. of those who are thus interested, some hope to gain and some fear they may lose in the application of the law. the general public naturally has little direct interest in the problem. there is thus no effective public sentiment favoring the repeal or modification of the law. it seems likely that for some time to come the law, in spite of its recognized defects, must be applied, and the best geological effort must be directed toward reaching interpretations which come most near to meeting its intent. to refuse to lend geologic science to the aid of justice because the law was improperly framed is hardly a defensible position. presumably it will never be possible to frame laws with such full knowledge of nature's facts as to eliminate the necessity for scientific advice in their interpretation. it has been suggested that the courts, and not the litigants, should employ the geologists. the practical objection to this proposition lies in the difficulty encountered by the judge in the proper selection of geologists. on the assumption that the judge would select only men in whom he had confidence, it is not likely that he would override their conclusions. the outcome of the case, therefore, would be largely predetermined at the moment the selection of experts was made. it is to be doubted whether courts can have the knowledge of the scientific field and of the requirements of the situation necessary to make the wisest selection of men to interpret the given condition. the competitive element would be eliminated. from a judicial standpoint, there seems to be an equally good chance of getting at the best interpretation of the facts by listening to presentations from different standpoints, with the accompanying interplay of criticism and questioning. another practical objection to appointment of experts by the court is the limitation of court costs, which would make it impossible to secure the highest grade men. so far as these men are public employees, such as members of the federal or state geological surveys, this might be arranged. for others, it might be suggested that they should be willing to sacrifice their energy and time in the interests of justice; but as long as human nature and conditions are what they are, it is perhaps futile to argue this question. if it is right to apply science to practical affairs, in other words, if the profession of economic geology is a legitimate one, it seems inevitable that the application must be in some part directed by the geologist himself, in order to avoid mistakes and confusion. the contention that the scientist must isolate himself in a rarified atmosphere to avoid contamination from a non-scientific, commercial, or legal atmosphere, seems to the writer practically untenable, if we recognize any obligation on the part of science to the practical conduct of human affairs. the fact that the geologist in making these applications may occasionally find himself in a non-scientific atmosphere may be deplored from the standpoint of maximum creativeness in science, and from this standpoint there may be reason for limitation of time given to this kind of work,--but to stay out entirely on this ground is to deny his obligation to make his science helpful to his fellows. the problem cannot be solved by staying out. it calls rather for an especial effort on the part of the scientist to establish and maintain his standards of science and ethics in the applied fields. some doubtless fail in this effort. others are strengthened scientifically and ethically, and contribute important aid in raising general standards. the principle of non-participation in such activities for fear of lowering scientific standards may make the geologist's problem easier, but at the expense of non-fulfillment of duties. such a course has for its logical consequence an abandonment of the application of his science to untrained men without the ethical anchorage of scientific achievement. in short, there may be legitimate criticism of individual geologists for their methods and ethics in the applied field, and this is desirable as an aid to maintaining and improving standards; but it is not a logical step from this to the conclusion that, to avoid unfortunate incidents, economic geologists must cloister themselves and thus deny the very implication of their title. ii laws relating to extraction of mineral resources under this heading come a wide variety of laws and regulations,--national, state, and local,--affecting the manner in which mineral resources shall be mined or quarried. such laws may specify the number of shafts or outlets, the use of safety and prevention devices, miners' compensation and insurance, and many other features. most of these laws are framed for the purpose of conserving human life and energy, but they directly affect the mining or extraction of the mineral resources themselves. geology plays but little part in relation to such laws. where the government retains ownership and leases or rents the resources, there are often provisions regarding the manner of mining and the quality and quantity of the material to be mined, in the interests of efficient operation and conservation. the geologist is often called into consultation both in framing and in dealing with the infraction of such provisions. it may be noted that the control thus exercised on the operator by government ownership is very much the same as that often exercised by the private fee owner. it is not unusual for fee owners of mineral rights to maintain a geological staff in order to follow intelligently underground developments, to see that the best methods of exploration and mining are followed, and that ores are either extracted or left in accordance with the best conservational practice. iii laws relating to distribution and transportation of mineral resources under this heading come governmental regulations affecting directly or indirectly the transportation and the destination of mineral products. transportation rates, tariffs, zoning, duties, and international trade agreements of all sorts have vital effects on distribution. in framing any of these measures for a mineral resource, it is desirable to know all about the character of the raw material, its physical occurrence and distribution, and the possibilities for future development. in adjusting the scientific naming and classification of mineral materials with the crude names and classifications used commercially--as in tariffs, in import and export laws, in reports of revenue collectors, in railway and ship rates, etc.--the geologic information is likewise necessary. heretofore, the formulation of measures concerning mineral distribution has often not been done on a scientific and impartial basis; but in recent years geologists have been called on more frequently for aid and advice, as a means of checking or verifying the special pleadings of the different industries. the rude disturbance of trade routes during the war brought home the necessity of basing control of distribution of mineral products on fundamental facts of geology and geography; thus it was that geologists had a considerable voice in the vast number of special measures taken for war purposes by such organizations as the shipping board, the war trade board, the war industries board, and other public organizations. the same was true in relation to the mineral resource questions at the peace conference. in the reconstructive measures of the future, a still larger use of scientific considerations may be looked for. further suggestions as to the relation of geology to laws affecting distribution appear in the chapter on international aspects (chapter xviii). iv other relations of geology to law it is often assumed that the economic geologist is exclusively interested in mineral resources. however, there are varied applications of geology outside of the mineral resource field,--to many kinds of engineering and construction operations, to soils, to water resources, and to transportation,--any of which may develop legal problems requiring geologic service. a few illustrative cases follow. the classification of mineral materials in contracts presents many difficulties. a contract for a railway cut, for a canal, or for any other kind of excavation may specify different prices for removing different mineral materials. too often these are stated in extremely crude and arbitrary terms, such as _rock_, _hard rock_, _hardpan_, _earth_, _dirt_, etc., without regard to the actual variety of materials to be dealt with. when, therefore, in the case of the chicago drainage canal, the contractor encountered a soft shale and claimed compensation for rock excavation, geologists played a considerable part in the extensive litigation that followed in the attempt to define the facts of nature in terms of a contract which did not recognize them. in a railway cut through glacial drift or till, a contractor came suddenly upon a mass of till which had been so thoroughly cemented in place as to have all the resistance of rock. litigation was then necessary to decide whether this should be classified as dirt or rock. rock and dirt slides of all kinds, met with in open-pit mining, canals, and other excavations, present engineering problems with a geologic basis. the kinds of rocks, their strength, porosity, and moisture content, the effects of weathering, and the structural conditions must be determined in order to ascertain the cause of the slides, and are features which figure largely in litigation arising from troubles of this sort. both federal and state laws give the right to lateral and vertical support. when, therefore, adjacent or underlying excavations cause earth movements in a neighbor's property, litigation is likely to ensue and the geologist is likely to be called in. the long-wall method of coal mining, extensively practiced in certain parts of the united states, is slowly withdrawing support from the ground overlying the coal seams, resulting in damages to surface structures and in some cases to overlying mineral deposits. extensive litigation has been the result, and the future seems to promise more of it. in certain metal-mining camps, where considerable amounts of materials have been mined to great depths, caves and cracking in the surface are reaching over unexpectedly wide areas, again threatening litigation. the laws relating to the use of surface and underground waters touch the geologic conditions in many ways. the permanent lowering or raising of a water level through mining or damming may require a careful geological analysis of the underground conditions affecting the movements of ground-water. the use of streams for placer mining, as in california, has resulted in formulation of laws and in extensive litigation, again requiring analysis of geologic conditions. in fact geologists, perhaps more than any other group, have come to realize how many and how varied are the ways in which people get into conflict in using the earth on which they live. chapter xvii conservation of mineral resources the problem conservation of mineral resources may be defined as an effort to strike a proper balance between the present and the future in the use of mineral raw materials. mineral resources have been used to some extent as far back as evidences of man go, but great drafts on our resources have come in comparatively recent years. the use of many minerals has started within only a few years, and for others the acceleration of production within the past two or three decades has been rapid (see pp. - ). in general, the use of mineral resources on a large scale may be said to have started within the lifetime of men still active in business. the wide use of power necessary to an industrial age, the development of metallurgy, the increasing size and complexity of demands for raw material, mean that the intensive development and use of our mineral resources is in its infancy, and is in many respects in an experimental stage. as nations have awakened to their need of mineral raw materials and to the recent rapid depletion of these materials, they have been naturally led to inquire how long the reserves may last, and to consider prevention of waste and the more efficient use of materials, with a view to planning more prudently for future national supplies. the first inquiries seemed to reveal such shortage of mineral supplies as to call for immediate and almost drastic steps to prevent waste, and possibly even to limit the use of certain minerals in the interests of posterity. more careful study of the problem, as might be expected, revealed new factors and greater complexity. the conservational idea has a wide sentimental appeal, but the formulation and application of specific plans meet many difficulties. in its practical aspects the problem is now a live one, the solution of which is requiring the attention of mining men, engineers, geologists, economists, and public officials. it is a question which is coming more and more into the field of actual professional practice of the economic geologist. it is our purpose to indicate the general nature of the conservation problem. we may assume agreement to the desirability of preventing waste, of making a wise present use of mineral products, and of striking a proper balance between the present and future in their use. nature has taken many long geologic periods to build up these reserves. we, of the present generation, in a sense hold them in trust; they are entailed to our successors. with this general thought in mind, how shall we proceed to formulate definite plans for conservation? an initial step is obviously a careful taking of stock. with increasing knowledge of mineral resources, it is becoming apparent that early estimates of supplies were too low. many of these estimates failed to take into account mining to great depths, and wide use of low-grade ores, rendered possible by improved methods; and especially they failed to put sufficient emphasis on the probabilities of new discoveries to replace exhausted supplies. early predictions have already been upset in regard to a number of mineral resources. the recognition of the general fact that the world is far from explored in two dimensions, to say nothing of three, of the fact that known geologic conditions do not yet indicate definite limits to the possibilities of exploration for most mineral resources, and of the consequent fact that for a long time in the future, as in the past, discoveries of new mineral deposits will be roughly proportional to the effort and money spent in finding them,--which means, also, proportional to the demand,--makes it impossible, for most of the mineral resources, to set any definite limits on reserves. it is comparatively easy to measure known reserves; but a quantitative appraisal of the probable and possible reserves for the future is extremely difficult. successive revisions of estimates have, with but few exceptions, progressively increased the total mineral supplies available. the result is that the time of exhaustion has been pushed far into the future for most of the important minerals, thus minimizing the urge for immediate and drastic conservational action, which followed naturally from early estimates of very limited supplies. for both coal and iron, supplies are now known for hundreds or even thousands of years. for oil and lead, on the other hand, the reserves now known have a life of comparatively few years, but the possibilities for successful exploration make it probable that their life will be greatly extended. notwithstanding this tendency to lengthen the exhaustion period, the limits of mineral resource life are still small as compared with the life of the nation or of civilization,--and the fundamental desirability of conservation is not materially affected. it is not easy to predict the rate of production for the future. at the present rate of coal production in the united states, the supplies to a depth of , feet might last , years; but if it be assumed that the recent _acceleration_ of production will be continued indefinitely into the future, the result would be exhaustion of these supplies in less than years. it is generally agreed that exhaustion will come sooner than , years, but will require more time than years. the range between these figures offers wide opportunity for guessing. it is supposed that per capita consumption may not increase as fast in the future as in the past, that possibly an absorption point will be reached, and that there will be limits to transportation and distribution; but how to evaluate these factors no one knows. in the case of some of the metallic resources, such as iron, the fact that the world's stock on hand is constantly increasing--losses due to rusting, ship-wrecks, etc., being only a small fraction of the annual output--suggests that a point will be reached where new production will cease to accelerate at the present rate and may even decline. but again, the factors are so complex and many of them so little known, that no one can say how soon this point will be reached. for the immediate future, there is little to be feared from shortage of mineral supplies in the ground. the difficulties are more likely to arise from the failure of means to extract and distribute these supplies fast enough to keep up with the startling acceleration in future demand indicated by the figures of recent years. the speed and magnitude of recent material developments in many lines cannot but raise question as to whether we have the ability to understand and coödinate the many huge, variable, and accelerating factors we have to deal with, or whether some of the lines of development may not get so far ahead of others as to cause serious disturbance of the whole material structure of civilization. coal alone, which now constitutes a third of our railway tonnage, may with increased rate of production require two-thirds of present railway capacity. will railway development keep up? it may be noted that national crises and failures in the past history of the world have seldom, if ever, been due to shortage of raw materials, or in fact to any failure of the material environment. in its early stages the conservation movement in this country concerned itself principally with the raw material. later there came the recognition of the fact that conservation of raw materials is closely bound up with the question of conservation of human energy. the two elements in the problem are much like the two major elements in mineral resource valuation (see pages - ). if in saving a dollar's worth of raw material, we spend two dollars worth of energy, it naturally raises question as to the wisdom of our procedure. it might be wiser in some cases to waste a certain amount of raw material because of the saving of time and effort. it might be better for posterity to have the product of our energy multiplied into raw material than to have the raw material itself. the valuation of these two major elements of conservation is again almost impossible of quantitative solution. we do not know what is the best result to be aimed for. we cannot foresee the requirements of the future nor the end toward which civilization is moving--or should move. the extravagance of the united states is often contrasted unfavorably with the thriftiness of europe. when considered in relation to raw materials alone, there seems to be basis for this charge. when considered in relation to the product of human energy into raw materials, the conclusion may be far different; for the output per man in the industries related to mineral resources is far greater in the united states than in europe. in the case of iron, it has been estimated that the output per man in the united states is two and one-half times as great as in the rest of the world. which is best in the true interests of conservation, we are not yet able to see. our view of what is desirable in the way of conservation depends somewhat on the limitations imposed by self-interest or location. by devoting ourselves exclusively to one mineral resource, we might work out a conservation program very disadvantageous to the best use of some other mineral commodity. we might take steps to conserve chromite in the united states which would have a disastrous effect on the iron and steel industry. we might conserve coal by the substitution of oil, when the procedure is hardly warranted by the supplies of oil available. we might work out a program for the united states which would not be the best conservational plan for the world as a whole, and which would ultimately react to the disadvantage of the united states. the wisest and most intelligent use of mineral resources seems to call unquestionably for their consideration in their world relations, rather than for a narrow interpretation of local requirements. differences between private and public efforts in conservation it appears that a wide range of effective conservational practices has resulted solely from the effort to make more money through more efficient operations, and this is likely to be true in the future. many improvements in mining, grading, sorting, concentration, and metallurgy of minerals, to yield larger financial returns, are coming naturally through private initiative, under the driving power of self-interest. another considerable group of conservational practices is possible only to governments or other public agencies. this group of practices on the whole requires some sacrifice of the immediate financial interest of the individual, in the interests of the community as a whole, or in the interests of posterity. in this group may be mentioned the compulsory use of methods of mining, sorting, and metallurgy which tend to conserve supplies but result in higher prices; the control of prices; the elimination or lowering of the so-called resource or royalty value (p. ); and the removal of restrictions on private combination or coöperation, leading to more efficient methods, lessening of cost, and better distribution of the product; or, what might amount to the same thing, the acquirement by the government of the resources to be operated on this larger scale. the most effective conservation measures yet in effect are the ones dictated by self-interest and instituted by private initiative. governmental measures are not yet in effective operation. illustrations of these two types of conservational effort are cited in relation to coal on later pages. the interest rate as a guide in conservation in striking a balance between the present and the future, economists have emphasized the importance of recognizing the interest rate as a guiding, if not a controlling consideration. it is obviously difficult for private capital to make investments of effort and money for the purpose of conservation which will not be returned with interest some time in the future. for the present, at least, this consideration furnishes the best guide to procedure in the field of private endeavor. so far as conservational measures, such as investment in an improved process of concentrating low-grade ores, promise return of capital and an adequate interest rate in the future, they are likely to be undertaken. it is clear that governments are not so closely bound by this economic limitation. they can afford to carry their investments in raw materials and processes at a lower interest rate than the private investor. their credit is better. taxes do not figure so directly. they can balance losses in one field against gains in another. as a matter of insurance for the future of the nation, a government may feel justified in inaugurating conservational measures for a particular resource without hope of the interest return which would be necessary to the private investor. in appraising the iron ores of lorraine taken over by france from germany at the close of the war, the actual commercial value of these ores, as figured by the ordinary _ad valorem_ method, was only ninety millions of dollars. it is clear, however, that to france as a nation the reserves were worth more. they could afford to pay more for them, and could afford to spend more money on conservational practice than under ordinary commercial limitations, because of the larger intangible and more or less sentimental interest. the valuation of this larger interest, as a means of determining the limit to which conservational investments may be made, lies in the political field. it may be suggested, however, that a desirable first step in any governmental program of conservation is to ascertain the cost and the possibility of an adequate return of capital and interest. these determinations at least afford a definite point of departure, and a means for measuring the cost to the people of measures which are not directly self-supporting. anti-conservational effects of war experience during the recent past indicates that the exploitation of mineral resources for war purposes is on the whole anti-conservational. it is true that the vast amount of war-time exploration and development, as well as the thoroughgoing investigations of the utilization of various minerals, have led to better knowledge of the mineral resources and their possibilities. it is also true that the war required a much more exhaustive census of mineral possibilities than ever before attempted. the immediate and direct effect of the war, however, was the intensive use of mineral resources without careful regard to cost, grade, or many other factors which determine their use in peace times. for instance, in ordinary times considerable quantities of high-phosphorus iron ores are mined; but, because of the fact that such ores require more time for conversion into steel, war-time practice concentrated on the higher-grade, low-phosphorus ores, resulting in an unbalanced production which in some cases amounted almost to robbing of ore deposits. in the case of coal, quantity was almost the only consideration; it was impossible to grade and distribute the coal to meet the specialized demands of industry. the results were a general lowering of the standards of metallurgical and other industrial practices, and increased cost. high-grade coals were used where lower-grade coals were desirable for the best results. in the making of steel, it is the custom to select the coal and coke with great care in regard to their content of phosphorus, sulphur, ash, and other constituents which affect the composition of the steel product; but during the war it became necessary to accept almost any kind of coal, with a resulting net loss in quantity and in grade of output. for a considerable number of mineral resources, such as the ferro-alloys, foreign sources of supply were cut off during the war, requiring the development and use, at high cost, of low-grade scattered supplies in the united states. it was found possible to produce enough chromite in the united states for domestic requirements, but at two or three times the normal price of imported chromite. the grade was low and the loss in efficiency to the consuming interests was a high one. the extremely limited natural supplies were raided almost to the point of exhaustion. with the post-war resumption of importation of minerals of this kind, producers naturally began a fight for a protective tariff, and the question is yet unsettled. the tariff, if enacted, would in most cases have to be a high one in order to permit the use of domestic supplies. the results would be a large increase in cost to other industries, decreased efficiency, and the early exhaustion of limited supplies in this country. most of the mineral resources have been concentrated by nature in a comparatively few places in the world; and when the two elements of conservation are considered--the materials themselves and the human energy expended in obtaining and using them--it is clear that any measure which interferes with the natural distribution of the favored ores is anti-conservational from the world standpoint. conservation of coal in the sections on mineral resources, there are many casual references to conservation of specific minerals. here we shall not go further than to introduce a brief discussion of the conservation of coal as illustrative of the general problem of conservation of mineral resources. it has been estimated that the united states possesses, to a depth of , feet, in beds inches or over, , , , , tons of coal, and an additional reserve between , and , feet of , , , tons.[ ] if all the unmined coal to a depth of , feet could be placed in one great cubic pile, the pile would be miles long, miles wide, and miles high. of the original amount of coal to this depth only about . of per cent has been mined or wasted in mining. the wastage is estimated at about per cent. if the annual production of coal were to remain the same as in recent years, the total life of the coal reserves (to a depth of , feet) would be between , and , years; but if the acceleration of production of recent years were to be maintained in the future, the life would be but little over years, and the life of the highest-grade coal now being mined might not be over years. all agree that the acceleration of production is not likely to continue indefinitely, which will mean that the life of coal reserves to , feet will be somewhere between the two extremes named. it seems clear that actual shortage of coal will not be felt for some hundreds of years; but this period of years is short as compared with the probable life of the race. measures introduced or proposed to conserve coal the following list of measures for conservation of coal is taken from several sources. the exhaustive report of the british coal commission,[ ] published in , contains a considerable number of specific recommendations for conservation of the coal of great britain. the reports of the national conservation commission[ ] of the united states, published in , treat of the conservation of the coal of the united states and naturally follow some of the recommendations of the british report. the coal section of the national conservation report was prepared by m. r. campbell and e. w. parker of the u. s. geological survey, and is contained in u. s. geological survey bulletin . the recommendations there given are amplified and developed by van hise[ ] in his book on conservation, published in . since that time the subject has been discussed by smith, chance, burrows, haas,[ ] and others, and certain additional conservational methods have been proposed. a considerable number of men have also discussed the sociologic and economic aspects of the question. the report of the conservation commission of canada,[ ] published in , treats rather fully of the conservation of mineral resources. it will suit our purpose, and avoid some repetition, if we group most of these recommendations without regard to authorship. in general, these recommendations can be grouped under the heads: (a) methods of mining and preparation of coal; (b) improvement of labor and living conditions at the mines; (c) introduction or modification of laws to regulate or to remove certain restrictions on the coal industry; (d) distribution and transportation of coal; (e) utilization of coal; (f) substitutes for coal as a source of power. =(a) mining and preparation of coal.= under this heading may be included a large number of proposals which concern primarily the engineering treatment of the coal underground and in the mine plants. some of the more important measures are: . introduction of the long-wall system of mining in places where the conditions allow it, in order to minimize the waste underground. . modification of the room-and-pillar system of mining, by which larger pillars are left while the mine advances, and are recovered in the retreat,--thereby recovering a larger percentage of coal than under the old system, where small, thin pillars were left, which failed and were permanently lost. it has been argued that the great loss of coal by leaving it in pillars could be saved by using other material to support the roof; but an elementary calculation of the cost of this procedure shows that it is cheaper to use the coal. chance[ ] says: the coal left as pillars to support the roof is thus utilized and performs a necessary and useful function, yet the principal part (perhaps two-thirds) of the , , tons our friends the conservationists claim is wilfully and avoidably wasted every year is this coal that is left in pillars to support the roof. i think we can safely claim that this is not waste, but, on the contrary, is engineering efficiency of the highest type, in that it utilizes the cheapest and least valuable material available to support the roof and saves the whole labor cost of building supports of other materials. investigation as to what becomes of that part of the , , tons claimed as wasted, which is not utilized as pillars to support the roof, will disclose the fact that a very large portion is coal that is left in mine workings that are abandoned because the roof is unsafe and because a continuance of operation would result in injuries or loss of life. coal left in the mines in order to conserve human lives cannot be classed as avoidable waste. a small part of the , , tons is lost because it is intimately mixed with refuse and because the labor cost of recovering it and separating it from the refuse would be greater than its value. . mining of shallow bituminous beds by means of the steam shovel. progress has been made along this line in the last few years, and valuable deposits are thus mined which can be mined profitably by no other method. . new methods of filling mined-out spaces with sand, and new methods of mine survey and design. according to haas[ ] the greatest advance in the question of method was the system of mine survey and design perfected in both the anthracite and bituminous fields. the relatively new method of filling old spaces with sand, etc., has also achieved success. . use of methods by which coal is not left in the roof for the support where the roof is weak, and by which coal of inferior quality is not left in the roof. . wider use of coal-cutting machines by which the wasting of thinner beds may be avoided. . where conditions allow it, the working of the upper beds before the lower, in order not to destroy the upper ones by caving. the mining of a lower coal seam has often so broken up the overlying strata as to render it impossible to recover the upper coal seams contained therein. there are certain difficulties, however, in the way of this conservational measure. in some localities the seams are under separate ownership, and there is a resulting conflict of interests. also, if the better coal seam happens to be below and the poorer seams above, market conditions may require that the lower seam be mined regardless of the destruction of the upper ones. . elimination of coal barriers to mark the limits between properties. this involves more coöperation. . improvement of mining machinery, power drills, etc. . centralization of power stations, rather than the use of many small units. . elimination of the wasting of slack or fine coal, through more careful methods of mining, through limitations on the excessive use of powder and larger use of wedges, through the abolition of laws for the payment of miners on a run-of-mine basis, and in the case of anthracite through recovery of the "silt" or dust caused by mining and sorting. it has been argued that the excessive use of powder ("shooting from the solid") means loss of coal, owing to the fact that it shatters the coal and makes a relatively large amount of slack, besides being accompanied by increased danger from fire and explosion and from weakening of the roof. although the excessive use of powder makes a large amount of slack, it does not necessarily result in waste, for this fine coal is carefully saved and for certain purposes is as valuable as the lump coal. so far as the procedure endangers life, it is of course objectionable. . better use of fine coal. it has been recommended that infirm and finely broken coal be washed and compressed, thus avoiding the wasting of slack coal, which was formerly thrown away or burned. however, in recent years there has been comparatively little waste of this kind, for slack coal in general finds nearly as ready a market as lump coal and the use of slack is increasing. there has been much discussion also of the possibilities of using the coal waste on the ground to make power for electric transmission. . more careful attention to sorting and sizing of all grades of coal coming from the mine and to preparation of coals for special uses. on the other hand, some operators say that the ends of conservation will be best met by limiting the sorting and sizing now practiced. the large number of sizes now put on the market greatly increases the cost of production. . wider use of the lower-grade fuels of the west, particularly with the aid of briquetting. =progress in above methods.= methods of mining and preparation of coal have been improved. campbell and parker state:[ ] a much greater proportion of the product hoisted is now being sent to market in merchantable condition. part of this is due to better and more systematic methods of handling, and part to the saving of small sizes which formerly went to the culm banks. the higher prices of coal and the development of methods for using these small sizes have also made it possible, through washing processes, to rework the small coal formerly thrown on the culm banks, and these are now furnishing several millions of tons of marketable coal annually. in general there is increase in the percentage of recovery of coal. whereas in the past the loss in mining was said by campbell and parker[ ] to average per cent, now an extraction of to per cent may be looked for. quoting from smith and lesher:[ ] observation of the advances made in mining methods in the last decade or two affords slight warrant for belief in any charge of wasteful operation. as consumers of coal we might do well to imitate the economy now enforced by the producers in their engineering practice. in the northern anthracite field machine mining in extracting coal from - and -inch beds, and throughout the anthracite region the average recovery of coal in mining is per cent., as against per cent. only twenty years ago. nor are the bituminous operators any less progressive in their conservation of the coal they mine. in anthracite mining, powdered coal or "silt" has accumulated in stockpiles and in stream channels to many tens of millions of tons. it is estimated that this constitutes nearly per cent of the coal mined. significant progress has been made recently in the recovery and use of this silt as powdered fuel for local power purposes. however, physical and commercial conditions do not in all cases allow of the full application of these new methods. once a mine has been opened up on a certain plan, it is difficult to change it. as a whole the longer and better organized companies are better able to change than the smaller companies. conservation measures of the above kinds, as so far applied, have come mainly from private initiative based on self-interest,--though the coöperation of the government has been effective, particularly along educational and publicity lines. =(b) improvement of labor and living conditions at the mines.= under this heading should be mentioned the improvement of housing, sanitation, and living conditions; improvements in the efficiency of labor, through making living conditions such as to attract a higher-grade labor supply and through educational means; the introduction of safety methods; the introduction of workmen's compensation and insurance; and other measures of a similar nature. all these measures as a class are sometimes grouped under the name of "welfare work." much thought and discussion have been devoted to the possibilities of improvement of labor and living conditions from the standpoint of conservation of human energy. in some quarters this subject has been treated as being independent of the physical conservation of mineral resources, and it has been the tendency to assume that conservation of human energy might be more or less inimical to conservation of mineral resources. certain of the changes already introduced have undoubtedly increased the cost of mining; and, until there was a general increase in selling price, this increased cost may have had the effect of eliminating certain practices of mineral conservation which might otherwise have been possible. for instance, according to smith and lesher:[ ] the increased safety in the coal mines that has come through the combined efforts of the coal companies, the state inspectors, and the federal bureau of mines necessarily involves some increase in cost of operation, but the few cents per ton thus added to the cost is a small price to pay for the satisfaction of having the stain of blood removed from the coal we buy. that form of social insurance which is now enforced through the workmen's compensation laws alone adds from to cents a ton to the cost of coal. on the other hand, there can be no doubt that large advances have been made in welfare movements which were introduced for the purpose of insuring a steadier, better, and larger supply of labor, and that the general gain in efficiency of operation thereby obtained has absorbed a large part of the increased cost. in general, conservation measures of this class have been developed coöperatively by private and public efforts, without important sacrifice of private interest. there is obviously room for much wider application of such measures, especially in some of the bituminous fields where conditions are still far from satisfactory. =(c) introduction or modification of laws to regulate or to remove certain restrictions on the coal industry.= it has been proposed: . to modify the laws so as to take care of situations where vertically superposed beds are owned by different parties, preventing the proper mining of the coal by either party. . to modify the laws so as to eliminate conflict in mining practice in cases where the coal is associated with oil and gas pools. . to allow larger ownership by companies utilizing the coal (now only per cent owned by such companies). . to place restrictions on over-capitalization, which leads to wasteful mining in order to secure quick and large returns on large capital. . to remove restrictions on concentration of control. this means, as a corollary proposition, virtual restriction of competition. concentration of control into comparatively few hands has undoubtedly favored conservation. it is easy to see that the stronger financial condition of the large companies makes it possible for them to take fuller advantage of modern methods of extraction, distribution, and marketing. this proposal was especially urged for the bituminous coal industry before the war in order to avoid over-production and over-development. the very wide distribution of the bituminous coals, their enormous quantity, and their exceedingly diversified ownership had led to over-development of coal properties. quoting from smith and lesher:[ ] in estimating the aggregate losses incurred by society by reason of the large number of mines not working at full capacity, the facts to be considered are that the capital invested in mine equipment asks a wage based on a year of days of hours, while labor's year averaged last year only days in the anthracite mines and only days in the bituminous mines, with only five to eight hours to the day. these conditions prevented in some cases even the most modest introduction of better methods, or of changes that would enhance the average profits through a relatively short period of ten or fifteen years at the expense of the present year. it was necessary to get at the best of the coal available in the cheapest possible way, regardless of the losses of coal left in the ground. to some extent the force of this argument was minimized by war and post-war conditions, but even yet development of coal mines is ahead of transportation and distribution. . to allow coöperation in the limitation of output, in the avoidance of cross freights, in gauging the market in advance, and in division of territory, all of which would allow cheaper mining and thus give larger leeway to conservational measures. this necessarily would be accompanied by government regulation. according to van hise,[ ] who was active before the war in advocating this conservational measure, such a procedure is neither regulated competition, nor regulated monopoly; but the retention of competition, the prohibition of monopoly, permission for coöperation and regulation of the latter. in chicago there cannot be one selling agency for the different coal companies which operate in illinois, but there must be many selling agencies, and the coal of pittsburgh must come into illinois and the illinois coal go toward pittsburgh; every one of which things makes unnecessary costs, but all of which are inevitable under the extreme competitive system. because of these facts it is necessary to waste the coal. if at the very same prices the different mines could coöperate in the limitation of the output, avoidance of cross freights, gauging the market in advance, and division of territory, they could mine their coal more cheaply, have a greater profit for themselves and conserve our resources. to some extent the plan here advocated was put into effect during the war by the united states coal administration; but the conditions of this trial were so complicated by special war requirements, that the conservational advantages of unified control were not demonstrated. . to reduce the excessive royalties paid to fee owners. smith and lesher[ ] have recently called attention to the relatively high resource cost in some of the coal fields, represented by the payment of royalties to fee owners. in the case of anthracite the payment averages to cents per ton, and exceptionally runs as high as a dollar per ton. for the bituminous coal the average resource cost is probably not much over five cents a ton. they suggest the possibility of lowering this cost by governmental regulation; and make an especially strong argument for not allowing the government-owned coal lands to go to private owners, who in the future, with the accumulation of interest on the investment, will feel justified in asking for a large "resource" return in the way of royalty. if the resource cost could be lowered, further introduction of conservational methods by the operators would be possible without greatly increasing the cost to the public. . to require or allow, by government regulation, a raising of the price of coal to the consumer, thereby allowing wider application of conservational practices. some of the increased recoveries of coal above noted have been made possible only by increase in the market price. if coöperation were permitted in the manner described in paragraph , the same results might be accomplished without increasing the price. recent high prices caused by the war situation are reflected in the introduction of many conservational changes which were not before possible. however, in some cases the demand for quick results under present conditions has an opposite effect, because of the desire to realize quick profits regardless of conservation. . the local conservation of coal at the expense of heavier drafts on coal of other parts of the world, by imposition of export taxes and preferential duties, has been discussed. while the effect of such a measure would doubtless be conservational from the standpoint of the united states, it is doubtful if it could be so regarded from the broader standpoint of world civilization. under present world conditions such a step would be disastrous. . government ownership has been proposed as a means of facilitating the introduction of conservation measures. in the united states there is yet no major movement in this direction. in england the question of nationalization of coal mines is an extremely live political problem (see pp. , - ). little progress has been made in conservation measures which involve legal enactments of the kinds above listed. =(d) distribution, and transportation of coal.= it has been argued that conservational results would ensue from: . cheaper transportation. . larger use of waterways. . improvement in distribution of the product by partition of the market and by larger use of local coals. for effectiveness this proposition would have to include control of the agencies of distribution, in order to minimize excessive profits of middlemen. . purchasing and storage of coal by consumers during the spring and summer months in anticipation of the winter requirements, in order to equalize the present highly fluctuating seasonal demands on the mines and railroads, and to eliminate the recurring shortages of coal in the winter months. this was particularly recommended by the united states bituminous coal commission in a recent report.[ ] . where conditions allow it, conversion of coal into power at the mine and delivery of power rather than coal to consuming centers. this type of conservation is being put into practice on a large scale above wheeling, on the ohio river, where there has recently been built a two hundred thousand kilowatt installation for steam-generated electric power. some of the power will be delivered to canton, ohio, over fifty miles away. this plant uses local coal and the cost of coal is figured at two mills per kilowatt-hour. under this heading of distribution and transportation of coal, might be considered certain international relations. the international movements of coal are summarized in another place (pp. - ). anything in the way of tariffs or trade agreements which would tend to interfere with or to limit the great natural international movements of coal--which in a free field are based on suitability of grade, cost, location, transportation, etc.--would be anti-conservational from the world's standpoint, although they might be of local and temporary advantage. for instance, the coal exported from england, which has heretofore dominated the international trade of the world, is of a high grade. american coal available for export is on the whole of considerably lower grade, being higher in volatile matter. unless this coal is beneficiated at home, it can replace the english coal in the export field only at increased cost of transportation and lower efficiency in use. the time may come when it will be desirable to ship lower-grade coals long distances; but when the two factors of conservation are considered--the intrinsic qualities of the coal, and the efforts necessary to utilize it--it would seem to be conservational at this stage to ship to long distances only the coal which nature seems specially to have prepared for this purpose. =(e) utilization of coal.= conservational proposals of this kind are: . substitution of retort coke-ovens for beehive ovens, to save not only a larger quantity of coke but also valuable by-products (see pp. - ). additional improvements in coking ovens may make possible the manufacture of some sort of coke from a much wider range of bituminous coals than can be used at present. . larger use of smoke consumers and mechanical stokers. . larger use of central heating plants, with higher efficiency than many local plants. . substitution of gas engines for steam engines, and improvement of the steam engine. . improvement in methods of smelting, leading to larger output of metal per ton of coke used. also the development of electric smelting for certain metals. . more careful study and classification of the qualities of coals, in order to avoid use of higher-grade coals where inferior coals would serve the purpose. . more consumption at the collieries. . larger use of powdered coal as fuel. . improvement of force-draft furnaces. . larger use of gas, a by-product of coal mining, and extraction of other by-products. . more efficient transformation of peat and coal into power and light. . the possible use of oil flotation to eliminate foreign mineral matter. most of the conservation measures above proposed have already been applied with good results, and with promise of large results for the future. the stimulus has come largely from self-interest. war conditions in some ways aided and in others hindered these developments. one of the conspicuous gains was the building of many by-product coke plants, under the necessity of securing the nitrates and hydrocarbons for munition and other purposes. =(f) substitutes for coal as a source of power.= some of the more prominent measures along this line which have been discussed are: . larger use of water power. this has sometimes been popularly assumed to be, at least potentially, a complete solution of the problem; but nevertheless it has its distinct limitations. water power has the advantages that its sources are not exhausted by use, and that the relatively greater initial cost of a hydro-electric plant is frequently more than compensated for by the saving in man power required and by the lower operating expense. however, the total amount of water power which can be developed on a commercial basis is rather closely limited, and much of the available power is so distributed geographically that it cannot be economically supplied to the industries which need it. of the total water-power resources of the united states which have been estimated by the geological survey to be available for ultimate development, over per cent is west of the mississippi,--whereas over per cent of the horse-power now installed in prime movers is east of the mississippi. electric power cannot at present be economically transmitted more than a few hundred miles. furthermore, for many uses of coal, as in metallurgical and chemical processes which require the heat or reducing action of burning coal, and in its use as fuel for ships, hydro-electric power cannot be substituted. it seems clear that while the use of water power will increase, particularly as rising prices of coal make possible the development of new sites, it can never take the place of the mineral fuels in any large proportion. for the immediate future, measures which have been suggested to extend the use of water power include: the more complete utilization of water powers already in use through more efficient machinery and methods; a certain degree of redistribution of industries, so that those requiring large amounts of power may be located in areas where water power is cheap and abundant; and the interconnection of hydro-electric plants so that their full capacity may be used. some water powers which have been developed are not being fully utilized because the plants are not connected with distribution systems large enough to use all the power. during the war the united states geological survey, in coöperation with the fuel administration and the war industries board, collected the information required to prepare maps showing the locations and relations of power stations and transmission lines throughout the country. this survey of the situation showed many possibilities, which had before been but vaguely realized, of interconnections which would increase the efficiency of the plants. . substitution of lower-grade coals--of bituminous for anthracite, and of low-grade bituminous for high-grade bituminous coals. larger use of low-grade western coals. war and post-war conditions have shown germany the way to a wide and effective use of its lignites. this has been accomplished by coöperation of the government and private interests. this vast improvement in methods of treatment and recovery of heating elements and by-products will doubtless have a widespread effect on utilization of lignites in other parts of the world. . substitution of alcohol and natural gas, oil, oil shales, peats, etc., as a source of power. this merely concentrates the conservation problem more largely on these minerals, in some of which, at least, it is already considerably more acute than in the case of coal; it is not a solution of the problem, but merely a shifting of emphasis. business conditions have limited private enterprise in this class of measures, but some progress has been made. more rapid introduction of these measures would require sacrifice of private interest and probably may be accomplished only by application of public power. division of responsibility between government and private interests in the conservation of coal a review of the conservation measures above listed indicates that many of them are already in operation, and that the initiative for such measures has been largely supplied by private ownership endeavoring to advance its own interest. in this category are to be included most of the improvements in physical methods of mining, preparation, and utilization of coal, the use of substitutes for coal, the concentration of control into larger groups better able to introduce new methods, and the improvement of labor and living conditions; also, under recent conditions, the increase in selling price, allowing for a wider application of these measures. another group of conservation proposals, which have not yet been put into substantial effect, are obviously beyond the power of private interests; and must be introduced, if at all, by the application of government power. these include the elimination of resource or royalty costs, the control of over-capitalization, the removal of restrictions on concentration of control, the granting of permission for coöperation among competitive units, the regulation of selling price minimums in order to insure during normal times the use of better physical practices, and the control of distribution. in short, it appears that there are two great spheres of conservational activity--one within the field of private endeavor, and the other possible only by collective action through the government. the principal advances thus far made have been in the field of private endeavor. the government has aided greatly in the advancement of conservation measures arising within the field of private endeavor. one need only refer to many governmental investigations, to the spreading of information as to best methods, and to local compulsory requirements that the best practices be made uniform and that backward interests thereby be brought into line. recognition of the fact that there is a large body of sound conservational practice in the coal industry which falls within the range of self-interest seems essential in planning further changes in the direction of conservation. conservational measures do not all require sacrifice of the individual to the public, nor of the present to the future generations. an exercise of public power is not in all cases essential to the advancement of conservation. the respective limits of the fields of public and private endeavor are not sharply defined, and vary from place to place and time to time, depending upon local conditions and special requirements. in general, the sphere of private interest includes measures which will bring adequate commercial return. the interest rate is the limiting and controlling factor. when it is possible--by improvement of methods of mining, better planning, better preparation of coal, better transportation and distribution, or better utilization--to secure a larger average return on the investment, or to insure return through a longer period of years, self-interest naturally requires the introduction of such methods as rapidly as financial conditions allow. even some of the improvements in labor and welfare conditions have been introduced in this way, with a view to securing a more permanent and more efficient labor supply, and thereby aiding the enterprise from the commercial standpoint. within the sphere of government activity lie the removal of unnecessary restrictions on private initiative, and such conservation measures as involve some sacrifice of individual returns--in other words, a reduction of the normal interest rate. exercise of government power may be directly helpful within the field of private endeavor without materially sacrificing private interests; but beyond this point there are additional large possibilities of conservational activity which are clearly beyond the control of private interests. the introduction of any of these latter changes would evidently be so far-reaching in effect, and would require such broad readjustments not only within but without the mineral industry, that the necessity or desirability is not in all cases so clear as in the case of measures already introduced for private interest. the most obviously helpful step possible to the government in the immediate future is to permit coöperative arrangements under private ownership,--which would make it possible to use common selling agencies, thereby reducing the cost of selling; to divide the territory to be served, thereby avoiding excessive cross freights; and to allot the output in proportion to the demand from various territories, thus eliminating excessive competition and over-production. all of these measures could be accomplished without detriment to the public if properly regulated by the government. the very large saving possible by this means would allow the introduction of conservational methods at the mines without raising the cost to the public. war conditions required even more immediate and sweeping application of government power than above indicated, but conservational purposes were quite overshadowed by other considerations. where the mineral resources are already owned by the government, or can be acquired by the government, some of the troublesome factors in the problem are removed. in such cases it is possible to work out an intelligent plan for government control without the difficulties which arise in dealing with private ownership,--although, of course, new difficulties are introduced (see also pp. - .) the fact that there are conservational measures possible only to governments has been widely used as an argument for introducing government ownership or control. recent vigorous demands for the nationalization of natural resources in europe, and the increasing discussion of the subject in this country, may be regarded as phases of the conservation problem. it is not the purpose here to argue either for or against the drastic exercise of government power in the conservation of natural resources, but merely to call attention to the measures which are being discussed. conservation of minerals other than coal the discussion of conservation as applied to specific minerals might be extended almost indefinitely; but perhaps enough has been said to indicate the general nature of the field. before the war careful estimates of world supplies had been made for comparatively few minerals, although these included some of the most important, such as coal, oil, and iron. war conditions required a hasty estimate of world reserves of most of the mineral products. the reader interested in the problem will find an extremely interesting body of literature issued by the various governments on this subject. of especial interest to the american reader will be the reports of the u. s. geological survey and of the bureau of mines. in recent years there has been increasing recognition of the possibilities of conservational saving by concentration, refinement, and even manufacture of mineral commodities at or near the point of origin,--thus lessening the tonnage involved in transportation of the crude products. limitations of fuel and other conditions often make this procedure difficult; but considerable progress is being made both through private initiative and, especially in international trade, through governmental regulations of great variety. footnotes: [ ] campbell, m. r., the coal fields of the united states: _prof. paper -a_, _u. s. geol. survey_, , p. . [ ] final report of the royal commission on coal supplies: house of commons, london, vol. , . [ ] report of the national conservation commission: senate document no. , th congress, d session, govt. printing office, washington, . [ ] van hise, c. r., _the conservation of natural resources in the united states_: macmillan co., new york, . [ ] haas, frank, the conservation of coal through the employment of better methods of mining: abstract of paper presented to pan-american scientific congress, washington, dec., -jan., . [ ] adams, frank d., our mineral resources and the problem of their proper conservation: _ th ann. rept., commission of conservation_, _canada_, , pp. - . [ ] chance, h. m., address before the mine engineering class of the pennsylvania state college, quoted by f. w. gray, the conservation of coal: _bull. _, _can. mining inst._, , p. . [ ] _loc. cit._ [ ] campbell, m. r., and parker, e. w., coal fields of the united states, papers on the conservation of mineral resources: _bull. , u. s. geol. survey_, , p. . [ ] _loc. cit._ p. . [ ] smith, george otis, and lesher, c. e., the cost of coal: _science_, vol. , , p. . [ ] _loc cit._, pp. - . [ ] _loc. cit._, p. . [ ] van hise, charles r., _coöperation in industry_, pp. - , address given before annual meeting of the national lumber manufacturers' association, chicago, illinois, may , . [ ] _loc. cit._, p. . [ ] stabilization of the bituminous coal industry, extracts from the award and recommendations of the united states bituminous coal commission, government printing office, washington, . chapter xviii international aspects of mineral resources world movement of minerals of the annual world production of minerals about two-thirds are used within the countries where the minerals are produced and one-third is shipped to other countries. in this chapter we are concerned primarily with the part which moves between countries. it may be assumed that the consumption within the countries of origin is a matter of national rather than international concern. in pre-war times minerals constituted about per cent[ ] of the value of the total foreign trade of the united states, and per cent of the foreign trade of germany. figures are not available to show the proportion of mineral tonnage to that of other commodities. one of the several interesting facts in this world movement of minerals is that the movement of most of them shows a rather remarkable concentration. for instance, manganese moves from three principal sources to four or five consuming centers. chromite moves from two principal sources; tungsten also from two. even for certain commodities which are widely distributed and move in large amounts, the concentration of movement is rather marked; for instance, the world movement of coal is controlled by england, the united states, and germany. in other words, although the world movement of mineral commodities is widespread and exhibits many complex features, most of the individual minerals follow two or three salient lines of movement. this means in general that for each mineral there are certain sources of limited geographic extent, which, because of location, grade, relation to transportation, cost--in short, all the factors that enter into availability--are drawn upon heavily for the world's chief demands. the convergence of these materials toward a few consuming centers indicates generally concentration of coal production necessary to smelting, high development of manufacturing, large per capita use, concentration of facilities, strong financial control, and, not least, a large element of enterprise which has taken advantage of more or less favorable conditions. if a nation were fully supplied with mineral resources, without excess, the mineral problem might be almost exclusively domestic in its nature. but no country is so situated. for most of the mineral products the dominant supply is likely to be controlled by one or two nations, the other nations being correspondingly deficient and dependent. even the united states, which is more nearly self-sustaining in mineral resources than any other country, is almost wholly dependent on other countries for certain mineral supplies; and in the case of minerals of which it has an excess it is dependent on other countries for markets. the view that the mineral resource problem is solely a local and national one, of no concern to outsiders, ignores this fundamental fact of distribution of raw materials. control of smelting facilities makes it possible for certain countries to exercise considerable influence over the production and distribution of minerals in other countries, and thus presents many difficult international questions. even more difficult are the international problems created by the commercial ownership and control of minerals in the ground by nationals of other countries. the national and international aspects of mineral resources are difficult to separate, so intimately do they react on each other. to some extent there may be conflict of interest between the two, but in the main the international questions may be logically approached from the standpoint of national self-interest; for, in the conduct of the national industry along broad and enlightened lines, world conditions must necessarily be considered. a clearer comprehension of the world mineral relations, and an understanding of our own opportunities and limitations in comparison with those of our neighbors, cannot but eliminate some of the unnecessary handicaps to the best use of the world mineral resources, and result in a lessening of causes of international discord. a brief survey of the mineral conditions preceding, during, and following the war may serve as a convenient means of approach to a study of the present international aspects of the mineral problem. movement of minerals under pre-war conditions of international trade if the world pre-war movement of minerals is considered broadly, it may be regarded as conforming essentially to normal trade conditions of supply and demand. there have been barriers to overcome, such as tariffs and trade controls and monopolies of various kinds, but these barriers have not prevented the major movements between the best sources of supply and the principal consuming centers. these movements may be regarded as a more or less spontaneous internationalization of mineral resources by private enterprise. the aim of free trade or unrestricted commerce was equality of trade opportunities; but such conditions of unrestricted competition tended to concentrate trade in the hands of the strongest interests and to prevent equality of opportunity. the efforts made to promote or hinder international mineral movements by tariffs, bonuses, embargoes, subsidies, transport control, patents, government management, financial pressure, and other means have been incited mainly by national or imperial self-interest, and have thus been to some extent inimical to an internationalization based on the principle of the greatest good to the greatest number. it may be supposed that, in any effort to attain supernational or international control, motives and measures based on national self-interest of the sort here mentioned will continue to play an important part. changes during the war the war wrought fundamental changes in the world movement of minerals. the character and distribution of the demands changed. customary sources of supply were cut off. financial disturbances and ship shortage profoundly modified the nature, distribution, and extent of the world movement. our domestic mineral industry was abruptly brought to a realization of its vital relations with international trade. to illustrate, the large movement of manganese from india and russia to the united states was abruptly stopped, and we had to develop a source of supply in brazil. the stoppage of pyrite importations from spain as a means of saving ships required the development of pyrite and sulphur supplies in the united states. the export of oil from the united states to european countries was greatly stimulated, and the export to other countries was correspondingly decreased. the world movements of coal were vitally affected, principally by the limitation of the coal shipments from england and the united states to south america and the concentration of shipments to european countries. the closing of german coal supplies to nearby countries also had far-reaching consequences. the cutting off of the german potash left the world for the time being almost unsupplied with this vital fertilizing ingredient. the chilean nitrates, on which the world had relied for fertilizer purposes, were diverted almost exclusively to the manufacture of powder. the total annual imports of mineral commodities into the united states were reduced by , , tons. our exports, though they continued in large volume, were mainly concentrated in europe. the story of these disturbances in the world movement of minerals, though highly interesting, is too long to be told here. out of these sweeping and rapid changes in the world movement of mineral commodities there arose, partly as cause and partly as effect, international agreements for the allocation of minerals, as a means of insuring the proper proportions of supplies to the different countries for the most effective prosecution of the war. inter-allied purchasing committees in london and in paris found it necessary to make an inter-allied allocation of the output of chilean nitrate, because the sum of the demands exceeded the total supply by a considerable fraction, and to agree on the distribution and prices of the world's supplies of tin, tungsten, and platinum. for many other commodities agreements of various sorts were made. for instance, the united states entered into an agreement with england and france for the purchase of iron ore and molybdenum from scandinavia to keep it out of germany. the united states and england agreed as to supplying canada with ferromanganese. new problems of world allocation came up almost daily. another war change in mineral conditions, of a more permanent nature, was the liquidation of german ownership and control of minerals in allied countries, and in some cases even in neutral countries. post-war condition of the mineral trade the mineral industry has by no means reverted to its pre-war condition. the old movements have been only partially resumed, and new elements have entered. shipping is still disturbed. governments have been coöperating in various ways in the liquidation of government stocks of minerals. the german commercial control of minerals outside of its boundaries, as noted above, has been much weakened. the reparations committee created by the peace treaty has enormous powers over the use and distribution of the mineral resources of germany, which directly and indirectly affect the mineral supplies of europe and all the world. the terms of the peace treaty changed in fundamental ways the international channels of mineral movement. the mineral situation of europe is in such a state of chaos that the combined efforts of governments will be necessary for many years to bring order. this will be accomplished partly through the reparations committee, but may require other forms of coöperation. an international coal commission has already been formed to look after the distribution of coal through europe. international coöperation in mineral distribution is not merely a theoretical possibility for the future,--it is now the outstanding fact with reference to the european situation. the recognition of their dependence on neighbors for important mineral resources has led to earnest efforts on the part of nations to supply deficiencies. the great activity of the british government in acquiring oil is one example. the falling off of gold production the world over, together with the increased disparity between gold reserves and the currency issued against them, is causing serious consideration of government action to encourage the gold industry by financial measures tending to increase the profit of the miners (see pp. - ). before and since the war most countries of the globe, outside of england and the united states, have gone far in the exercise of the right of eminent domain over mineral resources within their own boundaries. even in england the recent movement to nationalize the coal and oil resources is an indication of the general tendency. in the united states the movement has manifested itself thus far only in the increasing reluctance on the part of the government to part with mineral resources on the public domain,--as is clear from the terms of its new leasing law to cover oil, coal, gas, potash, and phosphates on public lands. before the war only the german government was clearly identified with private interests in international trade and in the acquirement of mineral reserves. since the war all governments except that of the united states are taking an active part in these fields, both directly and in coöperation with private capital. the british government has taken a direct financial interest in certain companies, such for instance as the anglo-persian and shell oil companies, and in some cases is actively interested in the acquirement of selling contracts. in england there is a wider use of voting trusts in controlling private companies, with the purpose of preventing the control from falling into alien hands. government control of shipping in certain countries is involving various degrees of control of mineral movements. also, through loans and bonds, mineral resources in certain countries have been tied up by the loaning governments. there has been wide extension of government control of minerals in mandatory territories and elsewhere through many new loans and regulations. these steps are in effect closing important parts of the world to private initiative, and particularly to nationals of other countries. whether these activities of governments are economically desirable or not, they are the actual conditions, not theories. if this situation continues, it raises the question whether our government will not be forced, in protection of its own mineral industries, also to take a direct part; for under present conditions, our importers and exporters find themselves dealing single-handed with governments or with private groups so closely identified with governments as to have much the same power. in matters of shipping, credits, exchange, tariffs, embargoes, and opportunity to acquire foreign reserves, the actual and potential disadvantage to american interests is obvious. tendencies toward international co�peration and possibility of international control[ ] of minerals under the pre-war conditions, unrestricted competition in world trade by private enterprise had led to a certain kind of internationalization of mineral deposits based on natural conditions of availability. there is a natural tendency to work back as quickly as possible to this condition, but new elements have entered which seem to make it difficult for governments to keep their hands off. the participation of governments in world mineral trade, when not modified by international coöperation or some other higher form of control, seems to be having a tendency in the opposite direction--to be closing the doors of equal opportunity and preventing the natural world use of the world's resources. these new conditions, together with others outlined in the preceding section, have made it necessary to pay more attention to the possibilities of international coöperation than ever before,--not as a restrictive measure, except temporarily in regard to the central european powers,--but as a means of insuring open channels of movement for raw materials, and of insuring equal economic opportunities to all. many of our mineral industries have already appealed to our government for coöperation and aid in their international dealings. further, mineral industries in private hands in the various allied countries have attempted to get together to arrange for private coöperation, and appealed to the peace conference for authority to do so. in certain cases the necessity for coöperative action became so apparent that pressure was brought to bear on the peace conference for the forming of some sort of international economic body which would make possible some of these steps. these movements were all dictated by considerations of self-interest, but self-interest broadened and educated by a knowledge of the world's situation. just as the increasing size of the units engaged in the mineral trade within national boundaries has led to discussion of the possibilities of government control in the interest of the public, so the increasing size of the units in the international mineral trade, the units in many cases being governments, is leading to discussion of the possibility of some international or supernational control in the interest of the world good. just as national interest is the lengthened shadow of individual interest, so international interest may be regarded in some aspects as the lengthened shadow of national interest. the general purpose of the suggested control is to minimize international friction; but more specifically it has been suggested that some sort of international coöperation is necessary in order to insure equality of opportunity among nations, both in supplies and in markets, and thereby to prevent the crowding of the weaker by the stronger nations. this is the gist of one of the famous fourteen points. the purpose might be accomplished by direct allocation of supplies or by control of tariffs and exchange. one of the conditions which seems to require international coöperation is the exploitation of mineral deposits in backward countries. unrestricted competition among nations in such exploitation has been an important cause of international controversy. it was planned at peace conference that the mineral resources in countries taken over by the great powers under mandatories should be developed and used in the interest of the group of nations, rather than for the special interest of the nation taking the mandatory. one of the natural functions of any international or supernational organization would be the adjustment and settlement of difficulties arising from this provision. this topic brings up the question as to the right of any nation or group of nations to exert any force on weaker nations in the exploitation of mineral resources. on the principal of self-determination and of the complete freedom of action of nations, this procedure seems unjustified. on the other hand, whether rightly or wrongly, civilization has created great material demands which must be satisfied. the individuals, companies, and governments which use force to exploit resources in weaker countries are merely the agents in supplying the demand created by all of us. while their methods are often indefensible, the exploiters cannot be regarded merely as irresponsible buccaneers who are projecting themselves unnecessarily into somebody else's business. whatever the sentimental and ethical aspects of the question, it seems almost inevitable that the demands of civilization will continue to require the exploitation of weaker countries; and in proportion as these countries are backward in coöperating, they must feel the world pressure. an agreement for international coöperation in such matters, therefore, is not to be regarded as merely a cold-blooded attempt to rob weaker nations,--but rather as a means of improving methods in satisfying the actually existing material demands of civilization. for illustration, the criticism of england's attempt to develop the oil industry of mesopotamia and persia has to a large extent confused the methods with the aim sought for. it is the writer's view that development of these resources is inevitable, and that criticism should not be directed toward nations and groups attempting to attain these results, but rather to the methods applied. for the purposes of this discussion, it is not necessary to go beyond the acceptance of the fact of demand, nor to argue the question as to whether the material demands of civilization should be curbed and progress restricted to matters of mind and human happiness. methods of international co�peration the first step in international consideration of minerals is obviously one of fact-finding. this became painfully evident during the great war, when the sudden cutting off of outside supplies and markets brought home the fact that the mineral question is only in part a domestic one. the average mining man had come to take the established marketing and commercial conditions more or less for granted, and had not looked into the underlying factors. there had been a tendency to assume that a kind providence was in some manner looking after these elements in the situation. the nearest approach to providence, as a matter of fact, was a small group of importers and exporters, possessing special knowledge of the international movements of certain commodities,--which knowledge was of unsuspected importance to the mineral industry. war conditions showed that neither the general public nor the mineral industry as a whole, much less the government, had even an elementary grasp of the important elements of the world mineral situation. the mobilizing of this information under high pressure, through the coöperation of government and private agencies, was an interesting and important feature in the complex activities back of the firing line. it is vastly to the credit of the men interested in the mineral industry in this country, and presumably also in other countries, that almost without exception they contributed their bits of knowledge to the common pool, even though these bits had been in a sense their private capital. certain importers, who by their knowledge of international phases of the mineral situation had been able to exercise a profound influence on domestic markets, voluntarily sacrificed their own interest for the common cause and pointed out ways in which reductions of imports could be made. the problems of the peace conference, and of other international agreements now pending, have required a still further systematizing of international information. one of the results has been the establishment of organizations of an international fact-finding character in our own and in certain other governments. in the chapters on the several minerals in this book, are summarized some of the salient features of the international situation developed by study of the kind indicated. knowledge of the physical facts of the world mineral situation is only a first step. their interpretation and correlation, the study of the underlying principles, the formulation of the necessary international agreements and regulations, constitute even more difficult problems, which are far from solved. there always has been some coöperation of governments in the mineral trade through the ordinary diplomatic channels. the question is now prominent whether, in view of the new conditions, it may not be necessary to develop better machinery--in the form of some international or supernational organization, possibly patterned on war procedure--in order to expedite the negotiations and to minimize possibilities of friction. during the war, when the world demand exceeded the total world supply of certain commodities, such as nitrate and tin, international commissions were formed in order to make an equitable distribution of these minerals and prevent favored strong nations from taking too large a proportion of the total. this procedure presented no insurmountable difficulties. a canvass of the total supplies available and of the demands of the various countries ordinarily led to voluntary compromise in the allocation of supplies. most of the regulations of these commissions were applied to mineral industries which were unable to meet the total demand. they were not tried out in cases where there were excess supplies; this process obviously would have been much more difficult, though perhaps not impossible. the general success of international attempts to allocate mineral supplies during the war suggests the lines along which results might be accomplished during peace. the process is essentially a matter of getting at the facts, and then discussing the situation around a table,--thus eliminating the long delays and misunderstandings arising from the procedure through the older established diplomatic channels. how far such a procedure might be possible without the compelling common interest of war is debatable. the great powers of the reparations committee, previously noted, and of the recently formed european coal commission, already indicate the general nature of the machinery for international control which might be exercised through a league of nations. it is not our purpose to argue for international control or for any specific plan of control, but rather to outline the problem. the question is not an academic one. various kinds of international control are present facts, and the problem relates to the possibilities of more effective organization of existing agencies. conservation in its international relations the interests of conservation, considering both its physical and its human energy phases (p. ), seem to call for an international understanding in the use of mineral resources which will result in the minimum hindrance to their free movements along natural channels of trade. the essential fact of the concentration of mineral supplies in comparatively few world localities, and the fact that no nation is supplied with enough of all varieties of minerals, mean that artificial barriers to their distribution cannot but impose unnecessary handicaps on certain localities, which may be anti-conservational from a world standpoint. if the few countries possessing adequate supplies of high-grade ferro-alloy minerals, for instance, were to restrict their distribution by tariffs or other measures, the resulting cost to civilization through the handicapping of the steel industry would be a large one. or if, for the general purpose of making the united states entirely self-supporting in regard to mineral supplies, sufficiently high import tariffs were imposed on these minerals to permit the use of the low-grade deposits in the united states, earlier exhaustion of the limited domestic supplies would follow, and in the meantime the cost to the domestic steel industry would be serious. cost may be taken to represent the net result of human energy multiplied into raw material. the movement would therefore be anti-conservational. if each state in the united states were to start out to become entirely self-sustaining in regard to minerals, and by various regulations were able to prohibit the use of minerals brought in from without, or the export of its excess of minerals, the waste in effort and materials would be obvious. nature has clearly marked out fields of specialization for different localities, and the effective use of mineral supplies is just as much a matter of specialization as the effective use of man's talents. if the united states, because of its vast copper deposits, is in a position to specialize in this line and to aid the world thereby, this should involve recognition of the fact that other countries are better able to specialize in other commodities,--thereby forming a basis for mutual exchange, which is desirable and necessary for world development. this conservational argument against artificial barriers does not necessarily imply complete elimination of tariffs or other restricting or fostering measures. within limits these may be necessary or desirable in order to maintain differences in the standard of living, or in order to permit the growth of infant industries; but to carry these measures to a point where they interfere with essential mineral movements determined by nature is obviously anti-conservational. for some mineral commodities, international coöperation may prevent duplication in efforts and the development of excessive supplies in advance of the capacity of the world to use them. partly because of lack of such coöperation, certain mineral commodities have been developed in such large quantities in various parts of the world that it may be many years before demand catches up with development. in the meantime, large and unnecessary interest charges are piling up. this financial loss measures the loss in effectiveness of collective human effort. in the above discussion, little reference has been made to shortage of total world supplies as an argument for international coöperation. this is an argument often cited, and with some effectiveness during the war. it is the writer's view that this phase of the problem has been much exaggerated. except for certain periods during the war, in considering the world as a whole adequate supplies of all mineral commodities have been available at all times. they have been developed as rapidly as needed, in some cases more rapidly; and geological conditions seem to indicate that this condition will continue for some time in the future, through national and individual effort. combined efforts of governments seem hardly necessary as yet to accomplish this purpose. in fact, there is rather more danger of over-development, without due regard to the working of the interest rate, which might be prevented by international coöperation. the main problem now is not one of total supplies, but of their effective and equitable distribution. exploration in its international relations when an explorer or prospector leaves his own country to discover and acquire minerals in other countries, with a view to exportation, it is reasonably obvious that he must first acquire a sound knowledge of at least some of the elements of international trade in minerals,--such as shipping facilities, rates, tariffs, attitude of the government toward ownership, toward export, etc. for example, the prospector for oil in foreign countries will not get very far without considering the recent steps taken by foreign governments, and mentioned on pp. - . the necessity of study of the international situation in conducting domestic exploration is not so generally recognized; and yet anyone today who confines his attention solely to the local physical facts of the situation, and who ignores international considerations, may find himself in difficulties. the investigation of international questions is not merely desirable from the standpoint of general information, but may be vital to the business or professional success of the explorer. for instance, he might take up the exploration and development in the united states of fertilizers and ferro-alloy minerals which are ordinarily imported; and without understanding the severe limitations imposed by the foreign situation, he might find himself with a property, sound from a physical standpoint, but financially a failure. it is comparatively easy, by running over the long list of mineral commodities used in the united states, to eliminate, on international grounds, a considerable number from the field inviting financial success, and to concentrate on others whose economic relations are sound. in the rapid changes during and since the war, the necessity for consideration of world conditions has been brought home at heavy expense to many business and professional men engaged in the mineral industry. valuation in its international relations for mineral commodities of limited supply and steady demand, market conditions may be more or less taken for granted, and valuation may be based on local considerations. for a large number of mineral resources, however, the competitive market conditions are anything but stable, because of foreign competition. it is necessary not only to know the basis for this competition, but also to be able to follow intelligently its various changes. the value of many of our mineral deposits in recent years has varied widely with changes in the foreign situation. relative position of the united states in regard to supplies of minerals the united states is more nearly self-sustaining in regard to mineral commodities as a whole than any other country on the globe. the following statement summarizes qualitatively our position: . minerals of which our exportable surplus dominates the world situation: copper. petroleum has belonged in this class until recently. in the future imports will be required (see following). . minerals of which our exportable surplus constitutes an important but not a dominant factor in the world trade: cement. coal. iron and steel. phosphates. silver. sulphur. uranium and radium. . minerals of which our exportable surplus is not an important factor in world trade. small amounts of most of these minerals have been and will doubtless continue to be imported because of special grades, back-haul, or cheaper sources of foreign supply, but these imports are for the most part not essential as a source of supply: aluminum and bauxite. arsenic. artificial abrasives and emery (except naxos emery). asphalt and bitumen. barite. bismuth. borax. bromine. building stone (except italian marble). cadmium. feldspar. fluorspar. fuller's earth. gold. gypsum. lead. lime. magnesite. mineral paints (except umber, sienna, and ocher from france and spain). molybdenum. pyrite. salt (except special classes). talc. titanium. tripoli and diatomaceous earth. zinc. . minerals for which the united states must depend almost entirely on other countries: cobalt. nickel. platinum and metals of the platinum group. tin. . minerals for which the united states will depend on foreign sources for a considerable fraction of the supply: antimony. asbestos. ball clay and kaolin. chalk. chromite. corundum. diamond dust and bort. garnet. graphite. grinding pebbles. manganese. mercury. mica. monazite. naxos emery. nitrates. petroleum (see below). potash. precious stones. pumice. tungsten. vanadium. zirconium. in the past the production of petroleum in the united states has dominated the world petroleum situation; but domestic consumption has now overtaken production, and unless discoveries of oil come along at a rapid rate the domestic deficiency seems likely to increase, with corresponding increase in our dependence on foreign sources (see pp. - ). some of the minerals of this last class, such as potash, manganese, and chromite were developed under war conditions in the united states to such an extent as to materially lessen the demand for importation; but in normal times domestic sources can supply a considerable fraction of the demand only at high cost and with the aid of a protective tariff. no attempt will be made here to present the detailed figures on which the above generalizations are based. in view of the present disturbed conditions of production and consumption, any judgment as to future demands or available surplus must take into account several factors which cannot be accurately measured,--such as financial control in foreign countries, possible tariffs, and foreign competition. for this reason the above statement should be regarded as only tentative, though it is the result of a rather exhaustive study of conditions in relation to the world control of shipping. the classes named overlap to some extent, and it is to be expected that some of the commodities placed in one class may in the near future be transferred to another. in terms of value, the united states has a potential export surplus of minerals about twice as large as that of all the rest of the world put together. countries which were neutral during the war have the remaining export surplus. great britain, france, and italy have net import requirements considerably in excess of their exports. germany has almost as large a deficit of minerals as the united states has a surplus. from the above facts it is clear that, in any scheme of international control or coöperation, the united states would have by far the heaviest stake, and perhaps the most to lose by restriction. it seems equally clear that the preponderance of exportable surplus of minerals over necessary imports justifies the united states in taking a broad and liberal view of the importation of needed minerals. the war-time necessity of making our country as nearly self-sustaining as possible does not seem to obtain in peace times. to carry that principle to an extreme means not only the expensive use of low-grade domestic supplies, but the elimination of the imports which are so necessary to balance our export trade. these facts also raise the question as to how far the united states is justified in exploiting the rest of the world to add to its already great preponderance of control,--as, for instance, in copper. any further aggrandizement of our position in regard to such minerals may be directly at the expense of neighbors who are already far less well supplied than ourselves, and is to be justified only on the basis of adding to the world's supply for common use, and of lending our expert assistance to neighbors to make them more nearly self-supporting. to carry out our campaign in these cases without regard to the needs of other countries will obviously not hasten the ideal of a democratic world with equal opportunity for all. on the other hand, the great freedom allowed by our laws in regard to foreign commercial control of our minerals, as compared to the restriction on such control in other countries, suggests the desirability of exerting our pressure for the open door policy in all parts of the world, in the interest of desirable reciprocal relations. in this connection there has been a tendency to criticise england's post-war activity in securing oil reserves for the future. self-interest has clearly dictated the necessity for improving england's weak position in regard to this vital energy resource. the success of this movement obviously means a lessening of the future preponderance of the united states in the oil industry, and calls for increased activity on the part of the united states in maintaining the desirable leading position it has long held. from the writer's viewpoint, however, the fair success of a rival does not call for criticism of motives. if there is any just criticism, it applies to methods (see pp. - ). whatever action may be taken by the united states in regard to international mineral questions, it is clear that the war has brought this country into such world relations that it has become imperative for us to study and understand the world mineral situation much more comprehensively than before,--in the interest not only of intelligent management of our own industries, but of far-sighted handling of international relations. under the stress of war the government, especially through the geological survey, the bureau of mines, and the several war boards, found it necessary to use extraordinary efforts to obtain even elementary information on the international features of mineral trade. much progress has been made, but only a start. the geologist or engineer who fails to follow these investigations may be caught napping in the economic phases of his work. the coal and iron situation of western europe under the terms of the peace treaty a mineral problem of special international importance at the present time relates to the disposition of the coal and iron resources of germany. germany's coal and iron have been the basis for its commanding position in industry and commerce. in fact, its development of these resources has been probably the most vital element in the european economic situation. the terms of the peace treaty in regard to these commodities have far-reaching consequences, not only for germany but for all europe, and indirectly, for the world. germany (westphalia) outclasses all other european sources in grades of metallurgical coal, in quantities produced, and in cheapness of production. both france and belgium must continue to be dependent on this source for important parts of the coking coal for metallurgical purposes, notwithstanding france's acquisition of the saar basin, which produces mainly non-coking coal, and the development of new reserves in belgium. germany's command of coal is wrecked in several ways. the french take over full and absolute possession of the coal of the saar basin, though germany has the right to repurchase it at the end of fifteen years, in case this territory then elects for union with germany. the coal of upper silesia, with a production of about per cent of the total of all german hard coal, is to be ceded to poland, subject, however, to plebiscite. germany undertakes to deliver to france each year, for not to exceed ten years, an amount of coal equal to the difference between the annual pre-war production of the french coal mines destroyed as a result of the war, and the production of the mines of the same area during the years in question,--such delivery not to exceed , , tons in any one year of the first five, nor , , in any one year of the succeeding five years. in addition, germany agrees to deliver coal, or its equivalent in coke, as follows: to france , , tons annually for ten years; to belgium , , tons annually for ten years; to italy an annual quantity rising by annual increments from , , tons in - to , , tons in each of the six years - to - ; and to luxemburg, if required, a quantity of coal equal to the pre-war annual consumption of german coal in luxemburg. the total pre-war coal production of germany in was , , tons. the diminution of production due to loss of territory in alsace-lorraine, in the saar basin, and in upper silesia amounts to about , , tons. the further required annual distribution of coal to france, italy, belgium, and luxemburg amounts to about , , tons. this leaves about , , tons for germany's domestic use, as compared with a pre-war domestic use of , , tons. even then, these calculations make no allowance for coal to be used in export trade to neutrals or other countries, some part of which seems vital to germany's trade. they make no allowance for the deterioration of plant and machinery in the mines, which will delay resumption of coal production. they make no allowance for the diminution in working hours and the lack of transportation. in short, unless there is a miraculous recovery and development of germany's coal industry, impossible conditions have been imposed. some recognition of this fact appears in the great powers to adjust terms which have been vested in the reparations committee. successive revisions of requirements by the reparations committee have already reduced the direct contributions of coal from germany nearly fifty per cent. the entire european coal situation is in a state of chaos. it was found necessary in to appoint a coal commission under international control, to attempt to allocate and distribute supplies. it seems inevitable that the physical facts of the situation will prevail, and that the control of the allies will resolve itself into efforts to distribute and coördinate supplies so as to keep the european machinery going, more or less regardless of the terms of the peace treaty. one of the important outcomes of this situation has been the recent rapid development of german lignite production, based on newly worked-out methods of treatment and utilization. by taking over alsace-lorraine, france acquires about per cent of the iron ore reserves and annual production of germany. this production was in minor part smelted locally,--the larger part moving down the rhine to the vicinity of the ruhr coal fields, and ruhr coal coming back for the smelting in lorraine. this great channel of balanced exchange of commodities has been determined by nature, and is not likely to be permanently affected by political changes. for the time being, however, the drawing of a political boundary across this trade route hinders the full resumption of the trade. self-interest will require both germany and france to keep these routes open. france requires german coal to supply the local smelters near the iron fields, and german markets for the excess production of iron ore. on the other hand, germany's great smelting district in the ruhr basin is largely dependent on the lorraine iron ore, and the movement of this iron ore requires coal from down the rhine as a balance. the intelligent handling of this great coal and iron problem is of far-reaching consequence to the mineral industries of the world. conclusion in the foregoing discussion it is not our purpose to argue for any specific national or international plan or procedure, but rather to show something of the nature of the problem,--and particularly to show that intelligent and broadened self-interest requires a definite national policy in regard to world mineral questions. realization of this fact is a long step toward the solution of the international problems. no geologist, engineer, or business man is safe, in the normal conduct of his affairs, without some attention to these matters. it is our purpose further to bring home the fact that international coöperation in the mineral field is not merely an academic possibility, but that in many important ways it is actually in existence. the terms of the peace treaty alone have far-reaching consequences to the explorer or mining man in all parts of the world. the modifications of these terms, which are inevitable in the future, will not be of less consequence. it is necessary not only to know what these are, but to aid in their intelligent formulation. literature a vast new literature on the subject of international mineral relations has sprung into existence during and following the war, and anyone may easily familiarize himself with the essentials of the situation. some of the international features are noted in the discussion of mineral resources in this book. for fuller discussion, the reader is especially referred to the following sources: the reports of the united states geological survey. note especially _world atlas of commercial geology_, . the reports of the united states bureau of mines. _political and commercial geology_, edited by j. e. spurr, mcgraw-hill book co., new york, . _strategy of minerals_, edited by george otis smith, d. appleton and co., new york, . _coal, iron and war_, by e. c. eckel, henry holt and company, new york, . _the iron and associated industries of lorraine, the sarre district, luxemburg, and belgium_, by alfred h. brooks and morris f. lacroix, bull. u. s. geological survey, . _the lorraine iron field and the war_, by alfred h. brooks, eng. and min. journ., vol. , , pp. - . munitions resources commission of canada, final report, . footnotes: [ ] umpleby, joseph b., _strategy of minerals--the position of the united states among the nations_: d. appleton and co., new york, , p. . [ ] control is here used in a very general sense to cover activities ranging from regulation to management and ownership. the context will indicate in most cases that the word is used in the sense of regulation when referring to governmental relationships. chapter xix geology and war geology behind the front the experience of the great war disclosed many military applications of geology. the acquirement and mobilization of mineral resources for military purposes was a vital necessity. in view of the many references to this application of geology in other parts of this volume, we shall go into the subject in this chapter no further than to summarize some of the larger results. as a consequence of the war-time breakdown in international commercial exchange, the actual and potential mineral reserves of nations were more intensively studied and appraised than ever before, with the view of making nations and belligerent groups self-sustaining. this work involved a comprehensive investigation of the requirements and uses for minerals, and thus led to a clearer understanding of the human relations of mineral resources. it required also, almost for the first time, a recognition of the nature and magnitude of international movements of minerals, of the underlying reasons for such movements, and of the vital inter-relation between domestic and foreign mineral production. the domestic mineral industries learned that market requirements are based on ascertainable factors and that they do not just happen. large new mineral reserves were developed. metallurgical practices were adapted to domestic supplies, thus adding to available resources. better ways were found to use the products. some of these developments ceased at the end of the war, but important advances had been made which were not lost. one of the advances of permanent value was the increased attention to better sampling and standardization of mineral products, as a means of competition with standardized foreign products. for instance, the organization of the southern graphite association made it possible to guarantee much more uniform supplies from this field, and thereby to insure a broader and more stable market. such movements allow the use of heterogeneous mineral supplies in a manner which is distinctly conservational, both in regard to mineral reserves and to the human energy factors involved. in another war the possibilities and methods of meeting requirements for war minerals will be better understood. in these activities, geologists had a not inconsiderable part. the u. s. bureau of mines, the u. s. geological survey, state geological surveys, and many other technical organizations, public and private, turned their attention to these questions. one of the special developments was the organization by the shipping board of a geologic and engineering committee whose duty it was to study and recommend changes in the imports and exports of mineral commodities, with a view to releasing much-needed ship tonnage. this committee was also officially connected with the war industries board and the war trade board. it utilized the existing government and state mineral organizations in collecting its information. over a million tons of mineral shipping not necessary for war purposes were eliminated. this work involved also a close study of the possibilities of domestic production to supply the deficiencies caused by reduction of foreign imports. other special geological committees were created for a variety of war purposes. in the early stages of the war a war minerals committee, made up of representatives of government and state organizations and of the american institute of mining engineers, made an excellent preliminary survey of mineral conditions. a joint mineral information board[ ] was created at washington, composed of representatives of more than twenty government departments which were in one way or another concerned with minerals. it was surprising, even to those more or less familiar with the situation, to find how widely mineral questions ramified through government departments. for instance, the department of agriculture had men specially engaged in relation to mineral fertilizers and arsenic. sulphur and other mineral supplies were occupying the attention of the war department. mica and other minerals received special attention from the navy department. the tariff board, the federal trade commission, the commerce department, even the department of state, had men who were specializing on certain mineral questions. all these departments had delegates on the joint mineral information board, in which connection they met weekly to exchange information for the purpose of getting better coördination and less duplication. the national academy of sciences established a geologic committee, with representatives from the u. s. geological survey, the state geological surveys, the geological society of america, and other organizations. this committee did useful work in correlating geological activities, mainly outside of washington, and in coöperation with the war department kept in touch with the geologic work being done at the front. while the activities of geologists for government, state, and private organizations were for the most part in relation to mineral resource questions, this was by no means the total contribution. the u. s. geological survey and other organizations, in coöperation with the war department, did a large amount of topographic and geologic mapping of the eastern areas for coast-defense purposes. this work involved consideration of the topography for strategic purposes, as well as the stock-taking of mineral resources--including road materials and water supplies. the revision of geological survey folios, with these requirements in mind, brought results which should be of practical use in peace time. studies were likewise made of cantonment areas, with reference to water supplies and to surface and sub-surface conditions. many geologists were engaged in the military camps at home and abroad, and in connection with the student army training corps at the universities, in teaching the elements of map making, map interpretation, water supply, rock and soil conditions in relation to trenching, and other phases of geology in their relation to military operations. the textbook on military geology,[ ] prepared in coöperation by a dozen or more geologists for use in the courses of the student army training corps, is an admirable text on several phases of applied geology. the name of the book is perhaps now unfortunate, because most of it is quite as well adapted to peace conditions as to those of war. there is no textbook of applied geology which covers certain phases of the work in a more effective and modern way. the topics treated in this book are rocks, rock weathering, streams, lakes and swamps, water supply, land forms, map reading and map interpretation, and economic relations and economic uses of minerals. another book,[ ] on land forms in france, prepared from a physiographic standpoint, was a highly useful general survey of topographic features and was widely used by officers and others. geology at the front[ ] perhaps the most spectacular and the best known use of geology in the war was at and near the front. this use reached its earliest and highest development in the german army, but later was applied effectively by the british and british colonial armies, and by the american expeditionary force. one of the first intimations to the american public of the use of geology at the front appeared in the publication of german censorship rules in ,--when, among the prohibitions, there was one forbidding public reference to the use of earth sciences in military operations. a leading american paper noted this item and speculated at some length editorially as to what it meant. it was discovered that geologists to the number of perhaps a hundred and fifty were used by the germans to prepare and interpret maps of the front for the use of officers. features represented on these maps included topography; the kinds of rocks and their distribution; their usefulness as road and cement materials; their adaptability for trench digging, and the kinds and shapes of trenches possible in the different rocks; the manner in which material thrown out in trenching would lie under weathering; the ground-water conditions, and particularly the depth below the surface of the water table at different times of the year and in different rocks and soils; the relation of the ground-water to possibilities of trench digging; water supplies for drinking purposes; the behavior of the rocks under explosives, and the resistance of the ground to shell-penetration; the underground geological conditions bearing on tunnelling and underground mines; and the electrical conductivity of rocks of different types, presumably in connection with sound-detection devices and groundings of electric circuits. some of the captured german maps were models of applied geology. they contained condensed summaries of most of the features above named, together with appropriate sketches and sections. during the argonne offensive by the american army the captured german lines disclosed geologic stations at frequent intervals, each with a full equipment of maps relating to that part of the front. from these stations schools of instruction had been conducted for the officers in the adjacent parts of the front. the british efforts were along similar lines, although they came late in the war, under the leadership of an australian geologist. their efforts were especially useful in connection with the large amount of tunnelling and mining done on the british front. among the many unexpected and special uses of geology might be cited the microscopical identification of raw materials used in the german cement. it became necessary for certain purposes to know where these came from. the microscope disclosed a certain volcanic rock known to be found in only one locality. in the palestine campaign, the knowledge of sources of road material and water supply based on geologic data was an important element in the advance over this arid region. wells were drilled and water pipes laid in accordance with prearranged plans. in spite of the fact that the usefulness of geology had been clearly indicated by the experience of the german and british armies, the american expeditionary force was slow to avail itself in large measure of this tool; but after some delay a geologic service was started on somewhat similar lines under the efficient leadership of lieutenant-colonel alfred h. brooks, director of the division of alaskan resources in the u. s. geological survey. the work was organized in september, , and during the succeeding ten months included only two officers and one clerk. for the last two months preceding the armistice there was an average of four geologic officers on the general staff, in addition to geologists attached to engineering units engaged in road building and cement making, and plans had been approved for a considerable enlargement of the geologic force. the work was devoted to the collection and presentation of geologic data relating to ( ) field works; ( ) water supply; and ( ) road material. of these the first two received the most attention. maps were prepared, based somewhat on the german model, for the french defenses of the vosges and lorraine sectors, and for the german defenses of the st. mihiel, pont-a-mousson, and vosges sectors. water supply reports covered nearly , square kilometers. the following description of the formations, taken from the legend of one of the geologic maps, shows the nature of the data collected: _silt, clay and mud, with some limestone gravel_, usually more or less saturated, except during dry season (june to september), in many places subject to flooding. surface usually soft except during summer. these deposits are / to meters thick in the small valleys, and to meters in the ---- valleys. unfavorable to all field works on account of ground-water and floods, and not thick enough for cave shelters. _silts with some clay and fine sands and locally some fine gravel and rock débris._ these deposits occur principally on summits and slopes, and are probably from to meters thick. even during dry season (june to september) they retain moisture and afford rather soft ground. in wet season the formation is very soft and often muddy. in many places water occurs along bottom of these deposits. favorable for trenches, but which require complete revetment, and ample provision for drainage, not thick enough for cave shelters; cut and cover most practical type of shelter. _clay at surface with clay shales below._ this deposit occurs in flats and is usually saturated for a depth of to - / meters, during wet season, for most of the year the surface is soft, but in part dries out in summer. deep trenches usually impossible, and even shallow trenches likely to be filled with water; defensive works will be principally parapets revetted on both sides. cave shelter construction usually impracticable, unless means be provided for sinking through saturated surface zone into the dry ground underneath. cut and cover usually the most practical type of shelter in this formation. _clay at surface with calcareous clay shale and some thin limestone layers below._ this formation occurs in low rounded hills; surface saturated during wet weather, but terrain permits of natural drainage, and dries out during summer; during wet season (october to may) the surface zone is more or less saturated, and ground may be muddy to a depth of a meter or more, ground-water level usually within two or three meters of surface. trench construction easy, but requires complete revetment, and ample provision for surface drainage. cave shelters can be constructed in this formation where the slope is sufficient to permit of drainage tunnels. the depth to ground-water level should always be determined by test shafts or bore holes in advance of dugout construction. _surface formation usually clay to meters in depth; below this is soft clay shales or soft limestone._ surface usually fairly well drained, and fairly hard ground. in general, favorable for trenches and locally favorable for cave shelters. in some localities underground water prevents cave shelter construction. the presence or absence of underground water should always be determined by test shafts or bore holes in advance of dugout construction. _surface formation consisting of weathered zone / to - / meters thick, made up of clay with limestone fragments and broken rock. below is compact limestone formation._ the surface of this formation is usually fairly hard, and well drained except in wettest season. trenches built in it require little revetting; very favorable for cave shelters, but requires hard rock excavation. some thin beds of clay occur in some of the limestone, and at these a water bearing horizon will be found. where a limestone formation rests on clay as near ---- a line of springs or seepages is usually found. such localities should be avoided, or the field works placed above the line of springs or seepages. this formation is best developed in the plateau west of ----. here it is covered by only a thin layer of soil, hard rock being close to the surface. the limestones afford the only rock within the quadrangle which can be used for road metal. _quarries_ (in part abandoned). _limestone gravel pits._ _locus of springs and seepages._ these should be avoided as far as possible in the location of field works, especially of dugouts. field works should be placed above the lines of springs. the water supply maps with accompanying engineer field notes are models of concise description of water supply conditions, with specific directions for procedure under different conditions. a few paragraphs taken from these notes are as follows: ground overlying rock, such as limestone, compact sandstone, granites, etc., which are usually fractured, is from the standpoint of underground water, most favorable for siting of field works. clay shales and clay hold both surface and underground water, and are, therefore, unfavorable for field works. the contact between hard rocks resting on clay or clay shales is almost invariably water bearing, and should be avoided in locating field works. at localities where impervious formations (clay, etc.) occur at or near the surface, they hold the water and form a superficial zone of saturation. this condition makes trench construction and maintenance difficult, and cave shelters can usually only be made by providing means of sinking through the saturated zone. the surface saturated zone often dries out in summer. in pervious, or almost pervious rocks, the zone of saturation, or ground-water level, lies at much lower depth, and may permit of the construction of field works as well as cave shelters above it. underground water bearing horizons and water bearing faults should be avoided in locating field works. wherever there is any uncertainty about the underground water conditions, test shafts or bore holes should always be made in advance of the construction of extensive deep works. effect of the war on the science of economic geology in general, the war required an intensive application of geology along lines already pretty well established under peace conditions. much was done to make the application more direct and effective, and a vast amount of geologic information was mobilized. the general result was a quickened appreciation of the possibilities of the use of geology for practical purposes. perhaps the most important single result was a wider recognition of the real relations of mineral resources to human activities, and of the international phases of the problem. more specifically, there was a most careful stock-taking of mineral resources and a consideration of the "why" of their commercial use. many new resources were found, as well as new ways to utilize them. footnotes: [ ] now known as economic liaison committee. [ ] _military geology and topography_, herbert e. gregory, editor. prepared and issued under the auspices of division of geology and geography, national research council, yale univ. press, new haven, . [ ] davis, w. m., _handbook of northern france_, harvard univ. press, cambridge, . [ ] for more detailed description of this subject the reader is referred to the use of geology on the western front, by alfred h. brooks, _prof. paper -d_, _u. s. geol. survey_, . chapter xx geology and engineering construction economic applications of geology are by no means confined to mineral resources (including water and soils). the earth is used by the human race in many other ways. human habitations and constructions rest on it and penetrate it. it is the basis for transportation, both by land and water. its water powers are used. in these various relations the applications of geology are too numerous to classify, much less to describe. while only a few of these activities have in the past required the participation of geologists, the growing size of the operations and increasing efficiency in their planning and execution are multiplying the calls for geologic advice. the nature of such applications of geology may be briefly indicated.[ ] foundations the foundations of modern structures such as heavy buildings, especially in untried localities, require much more careful consideration of the substrata than was necessary for lighter structures. in planning such foundations, it is necessary to know the kinds of rocks to be excavated, their supporting strength, their structures, the difficulties which are likely to be caused by water, and other geologic features. failure to give proper attention to these factors has led to some disastrous results. the planning of foundations and abutments of bridges requires similar geologic knowledge. in addition, there must be considered certain physiographic factors affecting the nature and variation of stream flow and the migration of shore lines. surface waters construction of great modern dams is preceded by a careful analysis of sub-surface conditions, in regard to both the rocks and the water. it is necessary to know the supporting strength of the rocks in relation to the weight of the dam; to know whether the rocks will allow leakage around or beneath the dam; and to know whether there are any zones of weakness in the rocks which will allow shearing of foundations under the weight of the dam in combination with the pressure of the ponded water. it is necessary to know whether the valley is a rock valley or whether it is partially filled with rock débris; if the latter, how deep this débris is, and its behavior under load and in a saturated condition. here again physiographic factors are of vital importance, both in relation to the history of development of the valley, and to questions of stream flow and reservoir storage.[ ] construction of dams is only an item in the long list of engineering activities related to surface waters. river and harbor improvements of a vast range likewise involve geologic factors. problems of wave action, shore currents, shifting of shores, erosion, and sedimentation, which are of great importance in such operations, have long occupied the attention of the geologist. they belong especially in the branch of the science known as physiography. geology in relation to underground water supplies is discussed in chapter v. tunnels the digging of tunnels for transportation purposes, for aqueducts, and for sewage disposal requires careful analysis of geologic conditions in regard to both the rocks and the underground water. knowledge of these conditions is necessary in planning the work, in inviting bids, and in making bids. it is necessary during the progress of the work. too often in the past disastrous consequences, both physical and financial, have resulted from lack of consideration of elemental geologic conditions. the building of the great new york aqueducts and subways through highly complex crystalline rocks has been under the closest geological advice and supervision. the detailed study of the geology of manhattan island through a long series of years has resulted in an understanding of the rocks and their structures which has been of great practical use. in the aqueduct construction the kinds of rock to be encountered in the different sections, their water content, their hardness, their joints and faults, were all platted and planned for, and actual excavation proved the accuracy of the forecasts. an interesting phase of this work was the tunneling under the hudson at points where the pre-glacial rock channel was buried to a depth of nearly a thousand feet by glacial and river deposits,--this work requiring a close study of the physiographic history of the river. slides slides of earth and rock materials, both of the creeping and sudden types, have often been regarded as acts of providence,--but studies of the geologic factors have in many cases disclosed preventable causes. a considerable geologic literature has sprung up with reference to rock slides, which is of practical use in excavation work of many kinds. the cause of such movements is gravity. the softer, unconsolidated rock materials yield of course more readily than the harder ones, but even strong rocks are often unable to withstand the pull of gravity. the relative weakness of rock masses on a large scale was graphically shown by chamberlin and salisbury,[ ] in a calculation indicating that a mass of average hard rock a mile thick, domed to the curvature of the earth, can support a layer of only about ten feet of its own material. the structural geologist, through his study of folds, faults, and rock flowage, comes to regard rocks essentially as failing structures. disturbances of equilibrium, resulting in rock movements under gravity, may be caused by local loading, either natural or artificial. natural loading may be due to unusual rainfall, or raising of water level, or increased barometric pressure. artificial loading may come from construction of heavy buildings or dams. movement may also result from excavation, which takes away lateral support--and such excavation again may be caused by natural processes of erosion or by artificial processes involved in construction. movement may be caused by mere change in the moisture content of rocks, or by alterations of their mineral and chemical character, affecting their resistance to gravity. in still other cases, earthquakes are the initiating cause of movement. in unconsolidated rocks, a frequent cause of movement is the presence of wet and slippery clay layers. the identification and draining of these clay layers may eliminate this cause. in certain sands, on the other hand, water may actually act as a cement and tend to increase the strength of the rock. planes of weakness in the rock, such as bedding, joints, and cleavage, are also likely to localize movement. earth materials, and even fairly hard rocks, may creep under gravity at an astonishingly low angle. the angle from the horizontal at which loose material will stand on a horizontal base without sliding is called the angle of rest or repose. it is often between ° and °, but there is wide variation from this figure, depending on the shapes and sizes of the particles and on other conditions. it has been suggested that even the slight differences in elevation of continents and sea bottoms may, during long geologic eras, have caused a creep of continental masses in a seaward direction. in problems relating to slides, the geologist is concerned in determining the kinds of rocks, their space relations, their structures and textures, their metamorphic changes, their water content and the nature of the water movement, their strength, both under tension and compression, and other factors. in the digging of the panama canal, a geological staff was employed in the study of the rock and earth formations to be met. however, had more attention been paid to geologic questions in the planning stages, this great undertaking, so thoroughly worked out from a purely engineering standpoint, would have avoided certain mistakes due to lack of understanding of the geological conditions. it is a curious fact that in these early stages no strength tests of rocks were made, and that no thorough detailed study was made of the geologic factors affecting slides and their prevention. it was only after the slides had become serious that the geological aspects of the subject were intensively considered. the results of the geologic study, therefore, are useful only for preventive measures for the future and for other undertakings. one of the interesting features of this investigation was the discovery that certain soft rock formations were rendered weaker rather than stronger by the draining off of the water. it had been more or less assumed that the water had acted as a lubricant rather than as a cement. subsidence not the least important application of geology to slides is in relation to deep mining operations. while the mining geologist has been principally engaged in exploration and development of ores, he is now beginning to be called in to interpret the great earth movements caused by the sinking of the ground over mining openings. for instance, the long-wall method of coal mining has resulted in a slow progressive subsidence of the overlying rock, affecting overlying mineral beds and surface structures over great areas. detailed studies have been made of this movement, in order to ascertain its relation to the strength and structure of the rocks, its relation to the nature of the excavation, its speed of transmission, and the possible methods of prevention. german scientists have perhaps gone further with this kind of study than anyone else. in an elaborate investigation of subsidence over a coal mine in illinois,[ ] unusually complete data were obtained as to the nature, direction, and speed of the transmission of strains through large rock masses, and as to their effect in producing secondary rock structures. railway building in railway building, the planning and estimation of cuts and fills is now receiving geologic consideration, in order to make sure that no geologic condition has been overlooked which will affect costs, the stability of the road, or the accurate formulation of contracts. the location of best sources of supply for ballast is also a geologic problem (see pp. - ). the physiographic phases of geology also are finding important applications to railroad building. the physiographer studies the surface forms with a trained eye, which sees them not as lawless or heterogeneous units but as parts of a topographic system, and he is able to eliminate much unnecessary work in the location of trial routes. further study of some of the older railroads from this standpoint has led to considerable improvements. physiographic study has also been applied to railway bridge construction, in the appraisal of the difficulties in surmounting stream barriers. a still broader use of physiography or geography, not popularly understood, is illustrated in the case of certain transcontinental railroads, in the study of the probable future development of the territory to be served--many features of which can be predicted with some accuracy from a study of the rocks, soils, topography, conditions of transportation, and natural conditions favoring localization of cities. the location of new towns in some cases has been based on this kind of preliminary study. in locating an alaskan railway close to the end of a momentarily quiescent glacier, troubles were not long in appearing, due to the fact that the glacier was really not as stable as it seemed to the layman. a specialist on glaciers, knowing their behavior, their relations to precipitation, their relations to earthquakes, the speed of their movement, and the periodicity of their movement, was ultimately called into consultation on the location of the railroad. road building road building in recent years has become a stupendous engineering undertaking, which is requiring geologic aid to locate nearby sources of supply for road materials. a considerable number of geologists are now devoting their attention to this work. it relates not only to the hard-rock geology but to the gravel and surface geology. certain northern states are using specialists in glacial geology to aid in locating proper supplies of sand and gravel. geology in engineering courses many engineering courses include elementary geologic studies, in recognition of the close relationship between geology and engineering. men so trained, though not geologists, have been responsible for many applications of geology to engineering. with the increasing size and importance of operations, calling for more specialization, the professional geologist is now being called in to a larger extent than formerly. a logical trend also is the acquirement of more engineering training on the part of the geologist, for the purpose of pursuing these applications of his science. footnotes: [ ] excellent texts on this subject may be found in _military geology and topography_, herbert e. gregory, editor, prepared and issued under the auspices of division of geology and geography, national research council, yale univ. press, new haven, , and _engineering geology_, by h. ries and t. l. watson, wiley and sons, new york, d ed., . [ ] atwood, w. w., relation of landslides and glacial deposits to reservoir sites in the san juan mountains, colorado: _bull. _, _u. s. geol. survey_, . [ ] chamberlin, t. c., and salisbury, r. d., _geology_, vol. , , pp. - . [ ] schultz, robert s., jr., _bull. am. inst. mining and metallurgical engrs._ in preparation. chapter xxi the training, opportunities, and ethics of the economic geologist economic geology is now an established and well-recognized profession, but there is yet nothing approaching a standardized course of study leading to a degree in economic geology. there are as many different kinds of training as there are institutions in which geology is taught. within an institution, also, it is seldom that any two persons take exactly the same groups of geologic studies. this situation allows wide latitude of training to meet ever changing requirements, but in other respects it is not so desirable. pure versus applied science in no institution are all the applied branches of geology taught. there is constant pressure for the introduction of more applied courses; this seems to be the tendency of the times. the economic geologist, fresh from vivid experiences in his special field, is often insistent that a new course be introduced to cover his particular specialty. any attempt, however, to put into a college course a considerable fraction of the applied phases of geology would mean the crowding out of more essential basic studies. to yield wholly to such pressure would in fact soon develop an impossible situation; for, on the basis of time alone, it would be quite impossible to give courses on all of the applied subjects in a training period of reasonable length. on the other hand, the failure to introduce a fair proportion of applied geology, on the ground that the function of the college is to teach pure science and that in some way economic applications are non-scientific, seems to the writer an equally objectionable procedure,--because it does not take into account the unavoidable human relations of the science, which vivify and give point and direction to scientific work. the development of science in economic directions does not necessarily mean incursion into less scientific or non-scientific fields. it is true that many of the economic applications of geology are so new and so constantly changing that they are not yet fully organized on a scientific basis; but this fact is merely an indication of the lag of science, and not of the absence of possibilities of developing science in such directions. there is today a considerable tendency among geologists of an academic type, whose lives have been spent in purely scientific investigation and teaching, to assume that anything different from the field of their activities is in some manner non-scientific, and therefore less worthy. many economic geologists have been made to feel this criticism, even though seldom expressed openly. for the good of geologic science, this tendency seems to the writer extremely unfortunate. the young man entering the field of economic geology should be made to understand that his is the highest scientific opportunity; and that if parts of his field are not yet fully organized, the greater is his own opportunity to participate in the constructive work to be done. under war requirements many geologists were called upon to extend their efforts to bordering fields of endeavor. in some quarters these activities were regarded as non-scientific, and as subtracting from efficiency in purely geological work,--and yet out of this combined effort came a wider comprehension of new scientific fields, between the established sciences and between sciences and human needs. it is inevitable that in the future these fields, now imperfectly charted, will be occupied and developed, perhaps not by the men who are already well established in their particular fields of endeavor, but by coming scientists. in this light, it was a privilege for geologists to participate in the discovery and charting activities of the war. still another attempt to discriminate between scientific and non-scientific phases of geologic effort has been the assumption by certain scientific organizations with reference to standards of admission,--that work done for practical purposes may be regarded as scientific only if it leads to advancement of the science through the publication of the results. there is by no means any general agreement as to the validity of this distinction. on this basis, some of the most effective scientific work which is translated directly into use for the benefit of civilization is ruled out as science, because it is expressed on a typewritten rather than on a printed page. while applied phases of the geologist's work may be truly scientific in the broader sense, it is undoubtedly easy in this field to drift into empirical methods, and to emphasize facility and skill at the expense of original scientific thought. the practice of geology then becomes an art rather than a science. this remark is pertinent also to much of non-applied geologic work in recent years. a considerable proportion of this empirical facility is desirable and necessary in the routine collection of data and in their description; but where, as is often the case, the geologist's absorption in such work minimizes the use of his constructive faculties, it does not aid greatly in the advancement of science. geology is by no means the only science in which there has been controversy as to the relative merits of the so-called pure and applied phases; but as one of the youngest sciences, which heretofore has been pursued mainly from the standpoint of "pure science," it is now, perhaps more than any other science, in the transition stage to a wider viewpoint. in the past there was doubt about the extension of chemistry toward the fields of physics and engineering, and of physics toward the fields of chemistry and engineering, and of both physics and chemistry toward purely economic applications; but out of these fields have grown the great sciences of physical chemistry, chemical engineering, and others,--and few would be rash enough to attempt to draw a line between the pure and applied science, or between the scientific and non-scientific phases of this work. this general tendency means a broadening of science and not its deterioration. course of study suggested there are almost as many opinions on desirable training for economic geology as there are geologists, and the writer's view cannot be taken as representing any widely accepted standard. on the basis of his own experience, however, both in teaching and in field practice, he would lay emphasis on the fundamental branches both of geology and of the allied sciences,--general geology, stratigraphy, paleontology, physiography, sedimentation, mineralogy, petrology, structural and metamorphic geology, physics, chemistry, mathematics, and biology. after these are covered, as much attention should be given to economic applications as time permits. the time allowance for training, at a maximum, is not sufficient to cover both pure and applied science. subsequent experience will supply the deficiencies in applied knowledge, but will not make up for lack of study of basic principles. it is safe advice to a student wishing to prepare for economic geology that there is no royal road to success; that his best chance lies in the effort to make himself a scientist, even though he cover only a narrow field; that if he is successful in this, opportunities for economic applications will almost inevitably follow. to devote attention from the start merely to practical and commercial features, rather than to scientific principles, brings the student at once into competition with mining engineers, business men, accountants, and others, who are often able to handle the purely empirical features of an economic or practical kind better than the geologist. in the long run the economic geologist succeeds because he knows the fundamentals of his science, and not because he has mere facility in the empirical economic phases of his work. of course there are exceptions to this statement,--there are men with a highly developed business sense who are successful in spite of inadequate scientific training, but such success should be regarded as a business and not a professional success. geology is sometimes described as the application of other sciences to the earth. this statement might be made even broader, and geology described as the application of all knowledge to the earth. in the writer's experience, the best results on the whole have been obtained from students who, before entering geology, have had a broad general education or have followed intensively some other line of study. whether this study has been the ancient languages, law, engineering, economics, or other sciences, the results have usually been good if the early training has been sound. to start in geology without some such background, and without the resulting power of a well-trained mind, is to start with a handicap in the long race to the highest professional success. it follows, then, that intensive study of geology should in most cases not begin until late in the undergraduate course, and preferably not until the graduate years. two or three years of graduate work may then suffice to launch the geologist on his career, but so great is the field, and so rapid the growth of knowledge within it, that there is no termination to his study. it is not enough to settle back comfortably on empirical practice based solely on previously acquired knowledge. each problem develops new scientific aspects. it is this ever renewing interest which is one of the great charms of the science. however, whether the student has a general training in geology, a specialized knowledge of certain branches, or takes it up incidentally in connection with engineering and other sciences, he will find opportunities for economic applications. the frequent success of the mining engineer in the geological phases of his work is an indication that even a comparatively small amount of geological knowledge is useful. the writer is inclined to emphasize also the desirability of what might be called the quantitative approach to the subject,--that is, of training in mathematics and laboratory practice, which gives the student facility in treating geologic problems concretely and in quantitative terms. geology is passing from the descriptive and qualitative stages to a more precise basis. for this reason the combination of geology with engineering often proves a desirable one. it is not uncommon for the student trained solely in the humanities and other non-quantitative subjects to have difficulty in acquiring habits of mind which lead to sufficient precision in the application of his science. he may have a good grasp of general principles and be able to express himself well, but he is handicapped in securing definite results. this does not necessarily mean that a large amount of time should be given to study of quantitative methods; exact habit of mind is more important in the early stages than expert facility with methods. the teacher of economic geology finds his data so voluminous that it is difficult to present all the essential facts and yet leave sufficient time for discussion of general principles or for drill in their constructive application. it is difficult to lay down any rule as a guide to the proper division of effort; but from the writer's point of view, it is a mistake to attempt to crowd into a course too many facts. at best they cannot all be given; and in the attempt to do so, the student is brought into a passive and receptive attitude, requiring maximum use of his memory and minimum use of his reasoning power. presentation of a few fundamental facts, combined with vigorous discussion tending to develop the student's ability to use these facts, and particularly tending to develop a constructive habit of investigation, seems to be the most profitable use of time during the course of training. the acquirement of facts and details will come fast enough in actual practice. the variety, amount, and complexity of the data available in geology tend in themselves toward generalizations in teaching--toward the deductive rather than the inductive method. a certain amount of generalization is desirable, but its over-emphasis develops bad habits of mind on the part of the student, and requires radical readjustment of his ideas in subsequent field investigations. to retain a proper emphasis on inductive methods, it is necessary to limit the amount of data presented. good results have been obtained by using the "case system," now common in the teaching of law--that is, by starting with a specific fact or situation as a basis for developing principles. another advantage in the restriction of data is the opportunity thus afforded for spending more time in the study of original reports rather than of the short textbook summaries. the student thus learns where the best primary sources of information are, how to find them, and how to extract essentials from them. field work field work is an essential part of any course of geologic training. not only should it be taken at every opportunity during the regular school year, but no summer should be allowed to pass without geologic practice in the field. opportunities for such work are offered in the summer field courses given by various institutions. in recent years it has usually been possible, also, for the student with elementary training to take part in summer geological survey work for state, national, or private organizations. in fact, after two or three years of geologic training, it is comparatively easy for the student to earn at such intervals during the year a fair fraction of his year's expenses. the ideal arrangement, from the writer's viewpoint, would be about an equal division of time between indoor and outdoor study. the alternation from one to the other supplies a much needed corrective to clear thinking. it is impossible to bring all the subject materials into the classroom and laboratory; such study must inevitably be more or less deductive and generalized. if the student at frequent intervals is not able to acquire and renew a mental picture of field conditions, there is likely to be a faulty perspective even in regard to principles, and a considerable gap between the theoretical and applied phases of his knowledge. it may be possible in the classroom, for instance, to discuss faults in great detail with the aid of maps, diagrams, and pictures; and yet it is extremely difficult to get a real three-dimensional conception of the problems without actually standing on the ground. specialization in studies with the increasing size and efficiency of human operations has come an inevitable tendency to specialization. where, in the past, the necessary geologic work might be passably done by the mining engineer, the local superintendent or operator, it is now being intrusted to specialists. even within the more strictly engineering phases of the mining engineer's work, there is the same tendency toward specialization; his work is being divided up among the electrical engineers, the mechanical engineers, the hydraulic engineers, and others. the opportunities for geologic work, therefore, are distinctly in the direction of specialization. the student in determining the field he shall enter needs to take this fact into account and to prepare accordingly, but not at the sacrifice of the broad basal training. only a small part of the specialization can be accomplished in college. the remainder will come with experience. in the future there is likely to be increasing specialization among the different educational institutions in the phases of applied geology which are taught. geographic location has a good deal to do with this tendency. where an institution is located near a coal or oil field, it is likely, as a matter of course, to specialize to some extent in the application of geology to these resources. or, the specialization may arise from the fact that the teachers have had special training in certain phases of applied geology, and such training naturally and properly determines the emphasis to be placed. courses in engineering geology are finding a natural development in the leading engineering colleges. in view of the fact that it is impossible for any one institution to cover all phases of applied geology, because of lack of time, and in view of the fact that even if this were attempted the results would be very unequal, because of the varied experience of teachers or because of geographic location, it would seem wise definitely to recognize these limitations and for each institution to play up the work it can do best. with freedom of migration among universities, a student by moving from place to place can thus secure any combination of specialized courses which best fits his requirements. a degree of economic geology there has been some agitation in recent years for standardization of courses in economic geology, and for the granting of a special degree in evidence of the completion of such a course. the principal argument for this procedure is that it would tend to insure a better average of training and would draw a line between worthy geologists and a host of ill-trained pseudo-geologists. the earth is so accessible, and its use so varied, that geology is handicapped perhaps more than any other science by persons who really have no valid claim to a scientific title. the writer doubts whether a special degree in economic geology would go far toward improving this situation. even if the courses were the same in different institutions, the manner of treatment and the ability of the teachers would be so varied that in the future, as in the past, anyone inquiring into the real standing of a geologist would be likely to consider his individual training rather than the degree attached to his name. there would be no guarantee that institutions not qualified to give the degree might not do so. however, the principal objection in the writer's mind to a degree of economic geology is the assumption that it is possible for anybody, in the present stage of knowledge, to formulate a standardized course adequate or best to meet the varied requirements. considering the breadth and the variety of the field, any such attempt at standardization would have to be highly arbitrary. once established, it would be a hindrance to the natural development of new courses to meet the ever changing requirements. when, if ever, the science of economic geology becomes fully organized, a standardized course may be possible. in the present stage of the science, more elasticity is required than seems to be possible in any of the courses proposed. one of the purposes of the introduction of a degree of economic geology, to separate the sheep from the goats, may be accomplished in another way,--namely, by the establishment and maintenance of high standards of admission and high aims on the part of the various professional societies having to do with geology and mining. if this is done, membership in such societies may be regarded as evidence of sound training and achievement. to some extent this procedure may relieve the pressure on universities for uniformity of courses and degrees, leaving them free to develop in such manner as seems best. scientific organizations, overlooking the entire field, are in a position to take into account the greatest variety of factors of training and experience in selecting their members. failure of any university course to make men eligible for such recognition will obviously react on the course in a desirable way. the opportunities of the economic geologist it has been the aim in this book to present a general view of the fields of activity of the economic geologist; and the list of chapter headings in itself summarizes the variety of his opportunities. the rapidly increasing use of earth materials promises far greater calls for geologic aid in the future than in the past. the profession is in its infancy. opportunities for employment are ordinarily found in three main directions--in educational institutions, in the federal and state geological surveys, and in private organizations. connection with the united states geological survey excludes participation in private work, and in recent years even in teaching. in the state surveys there is ordinarily more latitude in this regard. in the educational institutions, it is rather the common procedure for the instructor to secure his field practice and experience through private agencies, or through part time connection with state surveys,--an arrangement with advantages to all concerned. the educational institution secures the benefit of the field experience which it cannot afford to provide, and is enabled to hold geologists at salaries far below their earning capacity. the geologist gains by the opportunity to alternate between office and field study, and to correct his perspective by the constant checking of theory with field conditions. the combination tends to keep the clearly scientific and the applied phases in a proper relative proportion; it minimizes the danger of drifting into purely empirical field methods on the one hand, and of losing touch with actualities on the other. geologists devoting their attention solely to field work often complain that they do not have time to digest and correlate their results, nor to keep up with what others are doing. on the other hand, geologists without current field practice are likely to develop too strongly along subjective, deductive, and theoretical lines. the teacher gains in freshness and force in the presentation of his subject in the classroom, and the very effort necessary for presentation requires better analysis and coördination of his field observations. the private or state organization gains in this combination by drawing on the general and varied knowledge which has necessarily been accumulated for teaching and investigative purposes. temperament and circumstances will determine in which of these directions the student will turn. however, in view of the present natural tendency to be attracted by the large financial rewards in the commercial field, it may not be out of place to emphasize the fact that these rewards are perhaps more likely to be gained through perfected training and experience in state and national surveys and in educational institutions, than through early concentration in the commercial field. in any case, the financial side will take care of itself when sufficient knowledge and proficiency have been attained in any branch of the science. the world is the geologist's laboratory; it is the only limit to his activities. the frontiers are near at hand, both physically and intellectually. there are few fields so attractive from the scientific standpoint. there are few in which the successful prosecution of the science can be of so much direct benefit to civilization and can yield such large financial rewards. if, in addition, the opportunities for travel and adventure are taken into account, what profession promises a more interesting and useful life? so far we have discussed geology as a profession. it has proved its value also as a training for administrative and other public careers. the profession contributes its full share of men to these activities. the practice of geology deals with a wide variety of factors, and requires the constant exercise of judgment in balancing, correlating, and integrating these factors in order to reach sound conclusions. this objective treatment of complex situations is valuable training for the handling of human affairs. ethics of the economic geologist ethical questions involved in the practice of economic geology have called out much discussion, and, in some cases, marked differences of opinion among men equally desirous of doing the right thing. in the plain choice between right and wrong, there is of course no difference of opinion. unfortunately in many of the questions which arise the alternatives are not so clearly labeled. the lure of discovery and quick returns always has, and doubtless always will, draw into the field large numbers of persons without sound ethical anchorage or standards. fortunately, these are not the persons in control of the mineral industries; they are mere incidents in the great and stable business built up by legitimate demands for raw materials. the view is sometimes expressed that the geologist should hold himself aloof from the business or applied phases of his profession, because of the danger of being tainted with commercialism. this argument would apply to the engineer as well as to the geologist. to carry such a procedure through to its logical conclusion would mean substantially the withdrawal of scientific aid from industry,--which, to the writer, is hardly a debatable question. circumstances are trending inevitably to the larger use of geologic science in the commercial field. the problems of ethics cannot be solved by staying out. the economic geologist is rather called upon to do his part in raising the standards of ethics in that part of the field in which he has influence. this he can do by careful appraisal of all the conditions relating to a problem which he is asked to take up, and by refusing to act where questionable ethical standards are apparent or suspected. he must understand fully the purposes for which his report is to be used; merely as a matter of professional self-interest, there is no other course open to him. in a field in which there is so much danger from loose ethical conceptions, the premium on rigid honesty and nice appreciation of professional ethics is proportionately higher. the extreme care taken in this matter by acknowledged leaders in the profession of economic geology should be carefully considered by the young man entering the profession. there is a reason. in other chapters reference is made to certain special ethical questions, such as the use of geology in mining litigation (pp. - ), and the necessity of the geologist's recognizing his own limitations (pp. - ), but no attempt has been made to cover the variety of such questions that may come up. it is safe to assume that no special ethical code can be made sufficiently comprehensive, detailed, and elastic to cover all the contingencies which are likely to be met in the practice of economic geology; nor is it likely that any such code, if attempted, would be any improvement on the spirit of the golden rule. simple decency and common sense in their broader implications are essential to the practice of the profession. index abrasives, - , abyssinia, potash, adams, frank d., adirondacks, new york, graphite, iron ores, , , , phosphate from magnetic ores, - use of magnetic surveys in tracing iron rocks, ad valorem method of valuation of mineral deposits, - africa, bauxite, coal, cobalt, copper, - , tin, _see also_ south africa; north africa; east africa; west africa. alabama, bauxite, , graphite, iron, - , , , , - alaska, antimony, copper, , , , , , - gold, , , silver, tin, , algeria, antimony, , gypsum, iron, , , , petroleum, phosphates, , , _see also_ north africa. almaden, spain, mercury ores, - , alsace, potash, - alsace-lorraine, coal and iron of, under peace treaty, - aluminum company of america, aluminum ores, - , _see also_ bauxite. alunite, , - , , , anaconda, montana, arsenic production, anaconda copper mining company, manufacture of phosphate, use of geology in development and exploration, - anamorphism, defined, , anamorphism of mineral deposits, , - anhydrite, occurrence in gypsum deposits, - anticlines, occurrence of oil in, - , - antimonial lead, antimony ores, - , apex law, - , aplites, appalachians, barite, bauxite, graphite, - petroleum, , pitchblende, pyrite, tin, _see also_ under individual states. argentina, borax, mica, petroleum, tungsten, arizona, asbestos, , copper, , , , , , - , , - , , , gold, manganese, molybdenum, , silver, tungsten, turquoise, arkansas, bauxite, , , - , diamonds, fuller's earth, hones, oilstones and whetstones, phosphates, zinc, arnold, ralph, , , - arsenic ores, - , artesian wells, asbestos, - , asphalt and bitumen, , - , atolia, california, tungsten ores, atwood, w. w., australasia, cement, coal, gold, australia, antimony, arsenic, asbestos, , bauxite, bismuth, coal, copper, - gold, , , iron, , , lead, - , molybdenum, phosphates, silver, tin, tungsten, zinc, - , australia, laws relating to ownership of mineral resources, , austria, cement, graphite, mercury, , molybdenum, talc, uranium and radium, zinc, austria-hungary, barite, coal, , iron, , magnesite, - manganese, silver, _see also_ hungary. austria-hungary, commercial and political control of various minerals, ball clay, , "bar" theory of formation of thick salt beds, baraboo, wisconsin, quartzites of, barite, - , basalt, , , , bauxite, , , , - , bavaria, graphite, bawdwin mines, burma, lead and zinc, , beaumont field, texas, occurrence of oil, belgian congo, cobalt, copper, belgium, barite, cement, coal, - , , flint linings, iron, - lead, - , millstones and buhrstones, phosphates, zinc, - , belgium, commercial and political control of various minerals, , belle isle, newfoundland, iron ores, - , , bergholm, carl, bergstrom, gunnar, bessemer processes of steel making, , bilbao, spain; iron ores, , billingsley, paul, and grimes, j. a., bingham, utah, copper and lead ores, , , , , , , , , , birmingham, alabama, iron ores, , , , - _see also_ clinton iron ores. bisbee, arizona, copper ores, , , , , bismuth ores, - , bitumen and asphalt, , - , black hills, south dakota, gold ores, , tin ores, "blue ground," occurrence of diamonds in, "bluestone," bohemia, uranium and radium ores, boise basin, idaho, monazite deposits, boleo, lower california, copper ores, bolivia, antimony, bismuth, , borax, copper, nitrates, petroleum, silver, tin, , - tungsten, , bolivia, commercial and political control of various minerals, bonne terre limestone, missouri, zinc ores, boone formation, missouri, zinc ores, borax, - , borax lake, california, borax deposits, borneo, diamond dust, platinum, bort, , , boulder batholith, montana, ore-deposits of, boulder county, colorado, tungsten ores, braden copper ores, chile, brazil, chromite, coal, diamonds and diamond dust, , graphite, iron, - , , , , manganese, - , mica, monazite, , oil shales, zirconium, - brazil, commercial and political control of various minerals, briey district, france, iron ores, , vanadium, brinton, virginia, arsenic ores, british coal commission, british columbia, laws relating to mineral resources, british empire. _see_ great britain. british guiana, bauxite, , british south africa, coal, broken hill, new south wales, lead and zinc ores, , bromine, - , brooks, alfred h., , brooks, alfred h., and lacroix, morris f., buhrstones, building stone, - , - , bureau of mines, , burma, lead, , , rubies, , silver, tungsten, , zinc, , burrows, j. s., butler, b. s., loughlin, g. f., and heikes, v. c., , , butte, montana, arsenic in copper ores, copper ores, , , , - , - , , manganese ores, , silver ores, , use of placers in locating ores, zinc ores, - zonal arrangement of minerals, , cadmium ores, - , california, antimony, asbestos, asphalt and bitumen, basalt, borax, , - chromite, copper, , diatomaceous earth, fuller's earth, gold, , , , , , , granite, graphite, grinding pebbles, magnesite, - manganese, mercury, , , , natural gas, petroleum, , , , potash, , - pyrite, serpentine, silver, , tourmaline, tungsten, campbell, j. morrow, campbell, m. r., , , campbell, m. r., and parker, e. w., , - canada, arsenic, asbestos, - , cement, chromite, coal, , cobalt, copper, - corundum, , feldspar, fluorspar, , gold, graphite, - grindstones and pulpstones, gypsum, - iron, - , , , , magnesite, - mica, , molybdenum, natural gas, nickel, - petroleum, phosphates, , platinum, pyrite, - salt, silver, , - talc, , titanium, zinc, , canada, laws relating to ownership to mineral resources, use of magnetic surveys in tracing iron rocks, cananea, sonora, mexico, copper ores, cannel coal, cape colony, south africa, asbestos, capillarity, effect on ground-water level, effect on petroleum migration, - capital value of mineral resources, , "capping," of copper ores, carbonado, carey act, classification of public lands under, carmel, new york, arsenic ores, casing-head gasoline, , caucasus region, russia, manganese ores, , cement, - , cementation, mineral products resulting from, cementing materials, source of, central america, cement, , silver, _see also_ costa rica, guatemala, panama. central powers. _see_ germany, austria-hungary. cerium ores, _see_ monazite. ceylon, graphite, - mica, chalk, , chamberlin, t. c., chamberlin, t. c., and salisbury, r. d., chance, h. m., , chert, use for abrasives, , , chile, borax, , bromine, coal, copper, - , iron, , , , , manganese, nitrates, , - phosphates, , potash, silver, sulphur, - chile, commercial and political control of various minerals, , china, antimony, - , arsenic, , bismuth, coal, , , , iron, , , , , petroleum, salt, silver, tin, tungsten, , china, commercial and political control of various minerals, "chloriding" for silver ores, chrome (or chromite) ores, - , , - , clarke, f. w., , , classification of mineral deposits, - of mineral lands, - of mineral materials, adjustment of scientific to commercial names, clays, , , - , cle elum, washington, iron ores, cleavage, cleveland district, england, iron ores, clifton-morenci district, arizona, copper ores, , climate, as a factor in exploration, effect of in formation of bauxites, clinton iron ores, , - , , - , , , coal, conservation of, , - european international situation, - , , , , - general economic and geologic features, , - , , reserves, , - , - cobalt district, ontario, arsenic, cobalt, silver ores, , - , , use of coefficient to estimate future output, cobalt ores, - , coeur d'alene district, idaho, lead-silver ores, , , , - , , coke, - colloids, content of in clays, colombia, coal, emeralds, , gold, platinum, colombia, commercial and political control of various minerals, "colorado," colorado, arsenic, asphalt and bitumen, bismuth, coal, fluorspar, gold, , graphite, lead, , molybdenum, oil shales, petroleum, silver, tungsten, , turquoise, uranium and radium, - , vanadium, - zinc, , - commercial and political control of mineral resources, , , _see also_ under individual resources. common rocks, as mineral resources, - comstock lode, nevada, silver ores, - , congo. see belgian congo connecticut, basalt, diatomaceous earth, tourmaline, conover, julian d., conservation, - , - application of economic geology to, - of coal, - of common rocks, of human energy, international aspects, - , , - , - of petroleum, - conservation commission of canada, contact metamorphism, , , - , - _see also_ igneous after-effects. contracts, classification of earth materials in, - copper ores, , - , - , , , , , - , - , , cornwall, england, tin ores, , , , uranium and radium ores, corocoro, bolivia, copper ores, corundum, - , , costa rica, manganese, "cracking" processes for refining petroleum, , cripple creek district, colorado, gold ores, cuba, chromite, copper, iron, - , , , , , , , - , , manganese, nickel, petroleum, cuyuna range, minnesota, manganese ores, , cycle, erosion or topographic, - cyclic nature of ore concentration, - , - , , , , , , cyprus, asbestos, , dams, geologic problems involved in construction, davis, w. m., death valley, california, borax deposits, degree of economic geology, - denmark, cement, chalk, grinding pebbles, depletion of mineral deposits, as factor in valuation and taxation, , , depth as a factor in mineral deposition, , , - diamond dust, , , diamonds, - , , diatomaceous earth, , , diorite, dolomite, , domes, occurrence of oil in. _see_ anticlines. domes, salt and sulphur, gulf coast, , drilling, exploration of mineral deposits by, - drilling records, public registration of, - ducktown, tennessee, copper ores, dutch east indies, natural gas, petroleum, , tin, use of coefficient to estimate tin reserves, dutch guiana, bauxite, dutch west indies, phosphates, , dynamic metamorphism, - east africa, mica, east indies. see dutch east indies. eckel, e. c., economic liaison committee, egypt, petroleum, phosphates, eiserner hut, electrical conductivity, use in exploration of mineral deposits, ely, nevada, copper ores, , emeralds, , , emery, - , , , emmons, w. h., empire, colorado, molybdenum ores, energy resources, - accelerating production of, , - , , - engineering, application of economic geology to, , - england. _see_ great britain enrichment, secondary, - , , - . _see also_ under copper ores, silver ores, etc. epigenetic ore deposits, use of term, , "equated income" method of taxation, - erosion, relation to oxide zones, - erosion cycle, description of, - ethics, questions of, - europe, coal and iron situation under terms of peace treaty, - expert witnesses, use of geologists as, - , - exploitation of mineral deposits, functions of geologist, - exploration of mineral deposits, - effect of ownership laws on, - effect of taxation on, - quantitative aspects of, - , - relation to international conditions, - extralateral rights, litigation affecting, - extrusive rocks, formation of, federated malay states. _see_ malay states. feldspar, , , - , ferro-alloy minerals, - , - , , - , - , - , - ferroboron, ferrocerium, ferrochrome, ferromanganese, - ferromolybdenum, ferrosilicon, ferrotitanium, ferrotungsten, - ferrovanadium, ferrozirconium, ferruginous chert, fertilizer minerals, - field work for students of economic geology, - flint linings for tube mills, florida, fuller's earth, phosphates, , titanium, , zirconium, flowage, rock, , fluorspar, - , foothill district, california, copper ores, formosa, petroleum, foundations, application of geology to, france, antimony, , arsenic, - asphalt and bitumen, barite, bauxite, , cement, chalk, coal, - , coal and iron situation under peace treaty, - fluorspar, grinding pebbles, gypsum, iron, , - , , - , - manganese, millstones and buhrstones, molding sand, oil shales, phosphates, , potash, - salt, talc, vanadium, zinc, france, control of various minerals in other countries, , - , , , , , , , , , laws relating to ownership of mineral resources, relative position in regard to supplies of minerals, franklin furnace, new jersey, zinc ores, - , "freestone," french guiana, bauxite, fuel ratio of coal, defined, fuller's earth, - , gabbro, , gale, hoyt s., galena dolomite, wisconsin, zinc ores, galicia, petroleum, , potash, ganister, , , garnet, , , , gas, natural, , georgia, asbestos, , barite, bauxite, , corundum, fuller's earth, marble, georgia granite, volume change in weathering of, germany, arsenic, - barite, - bismuth, borax, , bromine, , cadmium, , cement, coal, - , , - copper, , , - , fluorspar, gypsum, iron, , - , - lead, - , - lignites, , millstones and buhrstones, nitrates, manufactured, - petroleum, potash, - salt, , silver, tripoli and rottenstone, uranium and radium, zinc, - , - , zirconium, germany, control of various minerals in other countries, , , , , , , , , , , , , , participation of government in mineral trade, relative position in regard to supplies of minerals, geysers, gilbert, chester g., gilbert, chester g., and pogue, joseph e., , , gilpin county, colorado, uranium ores, glacial geology, application to railroad building, application to road materials, , glacial soils, globe, arizona, copper ores, gneissic structure, gogebic district, michigan, iron ores, , , - gold, monetary reserves, gold coast, west africa, manganese, gold ores, - , , - , - , - , goldfield, nevada, alunite, - , bismuth, gold-silver ores, , , , gossan, , , , government ownership and control. _see_ nationalization. governments, participation in mineral ownership and international trade, - granite, , , , graphite, - , graphite association, southern, gravel, sand and, - gray, f. w., great basin, nevada, covering of mineral deposits by lavas, - gold-silver ores, occurrence in a metallogenic province, tungsten ores, great britain, arsenic, barite, cadmium, cement, chalk, clay, coal, - , , fluorspar, - fuller's earth, - grindstones and pulpstones, gypsum, iron, , - , manganese, salt, tripoli and rottenstone, uranium and radium, great britain, control of various minerals outside of british isles, , , - , , , , , , , , , , , , , , , , - , , , income taxes on mineral properties, , laws relating to ownership of mineral resources, participation of government in mineral trade, relative position, in regard to supplies of minerals, tendencies toward nationalization, great plains, lignite, pumice, greece, chromite, - emery, , magnesite, - zinc, greenland, graphite, gregory, herbert, , grimes, j. a., and billingsley, paul, grinding pebbles, , , , grindstones, ground-waters, composition of and relation to commercial use, - distribution and movement of, - influence in deposition of ore deposits, - relation to military operations, - , , - relation to rock slides, , - source of, ground-water level, description of, relation to oxide zone, relation to zone of weathering, ground-water supply, relation of geology to, - guano, , guatemala, chromite, guiana, bauxite, - gulf coast region, lignite, petroleum, , , salt, sulphur, _see also_ louisiana, texas, etc. gypsum, , - , haas, frank, , "head" of underground water, - heikes, v. c., butler, b. s., and loughlin, g. f., , , highway building, application of geology to, - holland, cement, commercial and political control of various minerals, _see also_ dutch east indies, etc. homestake mine, south dakota, gold ores, hones, hoover, herbert c., hot springs, relation to ore-deposits, , - hot waters, evidence of formation of ores by, - huancavelica district, peru, mercury ores, hudson river, physiographic problems in tunneling under, hudson's bay, possible diamond field, humus, hunan province, china, antimony ores, hungary, antimony, natural gas, _see also_ austria-hungary. hydrosphere, hypogene ores, use of term, - idaho, coal, lead, , , , , - monazite, phosphates, silver, zinc, , idria, austria-hungary, mercury ores, igneous after-effects, ore-deposits formed as, - , - igneous rocks, formation of, mineral deposits associated with, - , - principal minerals of, - proportions of principal types, relative abundance of, weathering of, illinois, clay, coal, , , fluorspar, limestone, petroleum, , , pyrite, sand and gravel, tripoli and rottenstone, zinc, illinois geological survey, coöperative exploration for oil, , income tax, application to mineral properties, - india, bauxite, india, bromine, chromite, - coal, , corundum, diamond dust, gypsum, iron, , , manganese, - mica, monazite, , petroleum, , platinum, salt, zirconium, indiana, coal, , hones, oilstones and whetstones, limestones, petroleum, , interest rate, as a guide in conservation, choice of for valuation purposes, limiting effect on acquirement of reserves, international aspects of mineral resources, , - international coal commission, , , international trade, in common rocks, in minerals, - participation of governments, - intrusive rocks, formation of, iowa, flint linings, grinding pebbles, gypsum, zinc, ireland, bauxite, iron and coal, situation of western europe under terms of peace treaty, - iron and steel, metallurgical processes, - iron and steel industry, possible establishment on west coast of united states, , iron cap, of sulphide deposits, , , iron ores, anti-conservational effect of war, attempt to estimate reserves of continents, exploration of in lake superior region, - general geologic and economic features, - , , , , , , - , - , , , - , - , litigation concerning cuban, metallogenic provinces and epochs, - outcrops, - taxation of in lake superior region, use of magnetic surveys, - world reserves, - , - itabirite, italy, asbestos, , asphalt and bitumen, barite, bauxite, borax, cement, graphite, manganese, marble, mercury, - natural gas, petroleum, pumice, salt, sulphur, - talc, zinc, - italy, coal situation under peace treaty, commercial and political control of various minerals, relative position in regard to supplies of minerals, japan, arsenic, cement, chromite, - coal, , copper, - gold, graphite, iron, , manganese, natural gas, petroleum, silver, sulphur, - tungsten, , zinc, japan, control of various minerals in other countries, , , , jasper, java, manganese, jerome, arizona, copper ores, , , , - , joachimsthal, bohemia, uranium and radium ores, joint mineral information board, joplin district, missouri, cadmium, lead and zinc ores, - , , , , , - juneau, alaska, gold ores, kansas, gypsite, natural gas, petroleum, , , salt, zinc, kaolin, , katamorphism, defined, , katanga, belgian congo, cobalt, copper ores, kennecott, alaska, copper ores, , , , , - kentucky, asphalt and bitumen, , coal, fluorspar, marble, petroleum, sandstone, kimberley, south africa, diamonds, - knox dolomite, tennessee, zinc ores, korea, gold, graphite, , iron, molybdenum, tungsten, lacroix, morris f., and brooks, alfred h., lake superior copper ores, , , , lake superior copper, silver, gold ores, occurrence in a metallogenic province, lake superior iron ores, , , - , , , , - , , - lake superior region, iron ore exploration in, - , - land grants in united states, retarding effect on exploration, "land-plaster", laterites, - laws relating to mineral resources, - lawton region, pennsylvania, coal, lead and zinc, wisconsin, equated income method of taxation, - lead ores, - , - , - , , , - , , leadville, colorado, bismuth, lead and zinc ores, , , - leasing law, on public lands in western united states, leith, c. k., leith, c. k., and mead, w. j., leith, c. k., and van hise, c. r., , lesher, c. e., and smith, george otis, , , , lignite, , , , german development of, , lime, , - , limestone, , , , - , - , lincolnshire district, england, iron ores, lindgren, w., lipari islands, italy, pumice, lithosphere, principal elements of, principal minerals of, - principal rocks of, - litigation, use of geologists in, - , - lode, application of legal term to diverse mineral deposits, long-wall system of coal mining, conservational aspect, subsidence of overlying ground and resulting litigation, , longwy, france, iron ores, lorraine, iron ores, - , - , , , , - phosphate from thomas slag, loughlin, g. f., butler, b. s., and heikes, v. c., , , louisiana, natural gas, petroleum, , , salt, sulphur, lower california, copper, magnesite, - luxemburg, coal situation under peace treaty, iron ores, - , _see also_ under lorraine, iron ores madagascar, corundum, graphite, - magmatic segregation, mineral deposits thus formed, - , magmatic waters, evidence of formation of ores by, - magnesite, - , magnetic surveys in tracing mineral ledges, - magnetite deposits, , , , - maine, feldspar, granite, tourmaline, malay states, tin, - tungsten, manchuria, iron, mandatory countries, exploitation of minerals in, - manganese ores, , , - , , , mansfield shales, germany, copper ores, , , mantle rock, mapimi, mexico, arsenic production, marble, , - marbut, curtis f., marl, marquette district, michigan, iron ore outcrops, maryland, diatomaceous earth, serpentine, marysville, utah, alunite deposits, mashing, - massachusetts, granite, serpentine, mccoy, a. w., mead, daniel w., , - mead, w. j., mead, w. j., and leith, c. k., mehl, m. g., menominee district, michigan, iron ore outcrops, mercury ores, , - , mesabi district, minnesota, concentration of siliceous iron ores, exploration for iron ores, , , , mesopotamia, petroleum, - , , mesothorium, metallogenic provinces and epochs, - metamorphic cycle and its relation to classification of mineral deposits, - "metamorphic rocks," defined, metamorphism, relation to economic geology, use of principles of in exploration for mineral deposits, - _see also_ katamorphism, anamorphism, contact metamorphism, dynamic metamorphism, weathering, etc. metasomatic replacement, metcalf-morenci district, arizona, copper ores, , meteoric waters, influence of in deposition of ore deposits, , - mexico, antimony, - arsenic, cement, copper, - , , gold, graphite, - , lead, - magnesite, - mercury, , molybdenum, natural gas, petroleum, , , , silver, - , vanadium, zinc, - mexico, commercial and political control of various minerals, miami, arizona, copper ores, , , , , , mica, - , michigan, bromine, copper, grindstones and pulpstones, gypsum, iron. _see_ lake superior iron ores, gogebic district, etc. limestone, salt, , michigan, taxation of iron ores, midcontinent field, petroleum, , , , , military geology, preparation of textbook, military operations, relation of ground-waters to, - millstones, minas geraes, brazil, iron ores, - , , , , mineral deposits, classification and general features of origin, - exploration and development, - origin as a factor in economic problems, - , - outcrops, - secondary concentration, - , - _see also_ under iron ores, copper ores, etc. zonal arrangement, - mineral industry, basis for popular interest in, "social surplus" of, mineral lands, classification, - mineral paints, relative position of united states, mineral provinces and epochs, - mineral resources, conservation, - general quantitative considerations, - international aspects, - laws relating to, - nationalization, - , - , - , political and commercial control, relative position of the united states in regard to supplies, - valuation and taxation, - world movement, - world reserves, - mineralogy, relation to economic geology, "minette" iron ores, , , mining law, - mining methods, control of by government or owners in interests of conservation, minnesota, granite, iron. _see_ lake superior iron ores, mesabi district, etc. manganese, , minnesota, taxation of iron ores, mississippi valley, cadmium, lead and zinc ores, - , , - , , - , , missouri, barite, - cadmium, lead, , silica for refractories, tripoli and rottenstone, zinc, , , - molybdenum ores, - , monazite, - , montana, arsenic, - copper, , , , , - , - , , gold, graphite, , manganese, , - petroleum, phosphates, sapphires, silver, , , , zinc, , , monte amiata district, italy, mercury ores, morenci-metcalf district, arizona, copper ores, , mother lode district, california, gold ores, , , munitions resources commission of canada, nancy, france, iron ores, national academy of sciences, national conservation commission, national district, nevada, antimony ores, nationalization of mineral resources - , - , - , , natural abrasives, - , natural gas, , nebraska, potash, , netherlands. _see_ holland, dutch east indies, etc. nevada, alunite, , - , antimony, , bismuth, borax, , copper, , , diatomaceous earth, gold, , , , , - graphite, grinding pebbles, mercury, oil shales, platinum, - silver, , , , - , , - tungsten, turquoise, zinc, new almaden, california, mercury ores, new brunswick, gypsum, - new caledonia, chromite, - nickel, - new cornelia, arizona, copper ores, newfoundland, iron ores, - , , laws relating to ownership of mineral resources, new hampshire, fluorspar, garnet, mica, new idria, california, mercury ores, new jersey, arsenic, basalt, clay, iron, sand and gravel, zinc, , new mexico, copper, , fluorspar, silver, uranium and radium, - zinc, new south wales, australia, bismuth, - coal, , lead, , , platinum, zinc, , new york, arsenic, , emery, , garnet, graphite, , gypsum, iron, , , , limestone, millstones and buhrstones, petroleum, , pyrite, salt, , sandstone, talc, new zealand, bismuth, phosphates, platinum, tungsten, new zealand, laws relating to ownership of mineral resources, nickel ores, - , - , , , , nitrates, - , - , , , nonesuch beds, michigan, copper ores, , north africa, iron, , , , lead, phosphates, , , potash, zinc, - north carolina, coal, corundum, , emeralds, feldspar, garnet, granite, mica, monazite, , rubies, sand and gravel, sapphires, northern plains, coal, norway, copper, - molybdenum, nickel, titanium, zinc, _see also_ scandinavia. nova scotia, gypsum, - saddle-reef gold ores, oceania, mercury, phosphates, , tin, ohio, bromine, clay, coal, grindstones and pulpstones, gypsum, hones, oilstones and whetstones, limestone, natural gas, petroleum, salt, sand and gravel, sandstone, oil. _see_ petroleum. oil shales, , , - oilstones, oklahoma, asphalt, and bitumen, gypsum, lead, natural gas, petroleum, , , tripoli and rottenstone, zinc, ontario, canada, arsenic, cobalt, corundum, mica, nickel, - , - , , , platinum, , silver, , - , , talc, , ontario, canada, laws relating to ownership of mineral resources, onyx marble, open-hearth process of steel making, - ore deposits. _see_ mineral deposits. oregon, borax, , chromite, mercury, origin of mineral deposits, as a factor in economic problems, - , - outcrops of mineral deposits, - ownership laws, effect on exploration of mineral deposits, - relation of geology to, - oxide zones, , - , - _see also_ under copper ores, silver ores, etc. pablo beach, florida, titanium ores, - zirconium ores, pacific coast, possible establishment of iron and steel industry, , pacific coast province, coal, palegeography, relation to economic geology, paleontology, relation to economic geology, palestine campaign, use of geologic data, panama, manganese, panama canal, slides, - parker, e. w., and campbell, m. r., , - peace conference, use of geologists in advisory capacity, , peace treaty, coal and iron situation of western europe under terms of, , - effect of terms on valuation problems, silesian lead and zinc ores, , pearls, - peat, formation of, - pegmatites, - , , peneplains, formation of, pennsylvania, basalt, clay, coal, , , flint linings, graphite, iron, limestone, natural gas, petroleum, sand and gravel, sandstone, serpentine, silica for refractories, slate, persia, petroleum - , , peru, bismuth, borax, coal, copper, - mercury, molybdenum, nitrates, petroleum, , phosphates, silver, tungsten, vanadium, , petroleum, , - , , , , , petroliferous provinces, , petrology, relation to economic geology, philipsburg, montana, manganese and silver ores, , , - , phosphates, - , - , physiography, general discussion and relations to economic geology, - _see also_ topography. physiography, relation to bridge building, relation to hudson river tunnels, relation to railway construction, relation to river and harbor improvements, pisolites, pitch. _see_ asphalt. pittman silver act, placers, formation of, gold deposits in, _see also_ monazite, platinum, tin, tungsten, and other minerals. use in tracing mineral outcrops, - plasticity of clay, platinum ores, , - , , plumbago. _see_ graphite. pogue, joseph e., pogue, joseph e., and gilbert, chester g., , , poland, lead and zinc, , political and commercial control of mineral resources, , - _see also_ under individual resources. porosity of rocks, , porphyry copper ores, , , portland cement. see cement. portugal, arsenic, copper, - , pyrite, - salt, tungsten, potash, , - , - , , precious stones, - , primary ore deposits, use of term, primary ores, relation to depth, propylitic alteration, , protore, use of term, , "proximate" analyses of coal, public domain, laws relating to ownership of mineral resources on, - pulpstones, pumice, , , , puzzolan cement. see cement. pyrite, , - , , , pyrophyllite, quartz, as geologic thermometer, geologic occurrence, , - , , , , - , production and use, , , quartzite, , quebec, canada, asbestos, - magnesite, mica, quebec, laws relating to ownership of mineral resources, queensland, australia, arsenic, quicksilver ores. _see_ mercury ores. radium ores, , - , railway construction, application of geology to, - rambler, wyoming, occurrence of platinum, ransome, f. l., , , ray, arizona, copper ores, , , , , , "red beds" copper ores, , registration, public, of drilling records, - regulus, reparations committee, , , replacement, metasomatic, reserves of mineral resources, - , - , - _see also_ under individual resources. "resource cost" of coal, reduction of in interests of conservation, , rhode island, coal, graphite, rhodesia, asbestos, chromite, - ries, h., and watson, t. l., rio tinto, spain, copper ores, pyrite, road building, application of geology to, - , "rock flour," defined, rock slides, , - rocks, common, as mineral resources, - rocky mountain region, coal, petroleum, , room-and-pillar system of coal mining, modification for conservational purposes, - rottenstone, , roumania, graphite, petroleum, , royal ontario nickel commission, royalties on coal, reduction of in interests of conservation, , rubies, , - russia, asbestos, - , cement, chromite, - coal, , copper, - gold, iron, , - , manganese, - mercury, , oil shales, petroleum, - , phosphates, , platinum, , potash, salt, zinc, russia, commercial and political control of various minerals, laws relating to ownership of mineral resources, russia, asiatic, vanadium, _see also_ siberia. saar basin, coal of, under peace treaty, salisbury, r. d., and chamberlin, t. c., salt, - , salt domes of gulf coast, sand, , , sand and gravel, - sandstone, , , , , , , santa rita, new mexico, copper ores, sapphires, , , sargasso sea theory, of deposition of lead and zinc sulphides, saxony, bismuth, tin, scandinavia, molybdenum, nitrogen-fixation plants, schistose structure, schlumberger, c., schuchert, charles, schultz, robert s., jr., scotland, magnesite, oil shales, searles lake california, borax deposits, potash deposits, , - secondary enrichment, - , , - _see also_ under copper ores, silver ores, etc. secondary ore deposits, use of term, sedigenetic deposits, use of term, sedimentary mineral deposits, unsolved problems, , , sedimentary rocks, formation of, - , mineral deposits associated with, , - principal minerals of, - proportions of principal types, relative abundance of, weathering of, sedimentation, relation to economic geology, segregation, magmatic, - , sericitic alteration, serpentine, seward peninsula, alaska, tin ores, , shale, , , , , shasta county, california, copper ores, shipping board, , siam, sapphires, , tin, tungsten, , siberia, emeralds, gold, , lead, vanadium, zinc, silesia, cadmium, coal, under peace treaty, lead and zinc ores, - , , - , - , - silica, - , , _see also_ quartz, quartzite, sand, sandstone, etc. "silt" (fine coal), use of, , silver ores, - , , - , , - , silver reef, utah, deposits, slate, , slides, earth and rock, , , - smelting capacity of world, smith, george otis, , , smith, george otis and lesher, c. e., , , , smyrna, turkey, emery, soapstone, - societies, professional, standards of admission, - , soils, classification, composition, - , origin, - use of fertilizer minerals on, - use of geology in study of, - sound waves, possible use in exploration, south africa, asbestos, , cement, coal, cobalt, copper, - , corundum, diamond dust, diamonds, , - , gold, - , iron, , mica, tin, vanadium, south africa, laws relating to ownership of mineral resources, , south america, cement, - coal, lead, , mercury, zinc, _see also_ under individual countries. south america, laws relating to ownership of mineral resources, - , south carolina, coal, monazite, , phosphates, , south dakota, gold, , , quartzite, tin, tungsten, southern graphite association, southern pacific railway, litigation in regard to oil lands, spain, arsenic, barite, cement, copper, - , garnet, , iron, , , - , , lead, , - manganese, mercury, - , phosphates, , platinum, potash, - pyrite, - salt, silver, sulphur, - zinc, - spain, commercial and political control of various minerals, spiegeleisen, - springs, spurr, j. e., , , stassfurt, germany, borax, bromine, potash, - , , - salt, common, - steel. _see_ iron and steel stone. _see_ building stone, common rocks. storage of coal, stratigraphy, relation to economic geology, structural geology, relation to economic geology, use of principles of in exploration for mineral deposits, - structures of rocks, relation to earth stresses, relation to topography, subsidence of ground over mining operations, geologic study of, , sudbury, ontario, cobalt, nickel ores, - , - , , , platinum, , sulphide enrichment. _see_ secondary enrichment. sulphur, - , - , sulphur bank springs, california, deposition of mercury by hot waters, supergene ores, use of term, , , surface water supplies, - surface waters, application of geology to use of, relation to excavation and construction, - sweden, cement, iron, , , , , , , , manganese, phosphate from thomas slag, zinc, _see also_ scandinavia. switzerland, cement, nitrogen fixation plants, syngenetic ore deposits, use of term, , , taconite, talc and soapstone, - , tankage, use of phosphate content, tariffs, proposed, on mineral resources, - , , , , , - tariffs and duties, anti-conservational effect of, - , , , , - tasmania, bismuth, platinum, zinc, taxation of mineral resources, , - tennessee, barite, bauxite, , copper, flint linings, marble, petroleum, , phosphates, , zinc, - , , terlingua district, texas, mercury, , texas, asphalt and bitumen, coal, fuller's earth, graphite, gypsum, mercury, , , natural gas, petroleum, , , , salt, sulphur, thermal metamorphism. _see_ contact metamorphism. thermal waters, thibet, borax, , thomas process of steel making, , use of slag for phosphate content, , tin ores, - , , - , , , , , tintic, utah, silver ores, , , , , titaniferous magnetites, , , titanium ores, - , tonopah, nevada, gold silver ores, , , - , topographic cycle, description of, topography, relation to mineral deposits, - , - relation to rock structures, tourmaline, , training in economic geology, - transvaal, africa, asbestos, diamonds, gold, , - , trap-rock, travertine, treadwell mine, alaska, gold ores, trenches, military, application of geology to, , - trinidad, asphalt, , petroleum, tripoli, , , tungsten ores, , - , , tunis, phosphates, - potash, _see also_ north africa. tunnels, application of geology to construction, - turkey, borax, chromite, - emery, , turquoise, , tuscany, italy, borax deposits, umpleby, joseph b., underground waters. see ground-waters. united kingdom. see great britain. united states, abrasives, natural, - , , aluminum, - , antimony, - , , arsenic, - , asbestos, - , asphalt and bitumen, , barite, - , bauxite, - , bismuth, - , borax, , , bromine, , , cadmium, - , cement, - , chalk, , chromite, , coal, - , , , - , common rocks, - , copper, - , corundum, - , , diatomaceous earth, , emery, - , , feldspar, , ferro-alloy minerals, general, - fertilizers, general, - fluorspar, , fuller's earth, - , garnet, , , gold, - , graphite, - , grinding pebbles, , gypsum, - , iron, - , - , lead, - , lime, - , magnesite, - , manganese, - , mercury, - , mica, - , mineral paints, molybdenum ores, - , monazite, , , natural abrasives, - , , natural gas, nickel, , nitrates, , oil shales, - petroleum, - , , phosphates, - , platinum, - , potash, - , precious stones, , - , pumice, , pyrite, - , salt, - , silica, - silver, - , stone, - , sulphur, - , talc, , , tin, , , titanium, - , tripoli, , tungsten, - , uranium and radium, - , vanadium, , , zinc, - , zirconium, , united states, control of various minerals in other countries, , , , , - , , , - , , , , , , , , , , laws relating to ownership of mineral resources, - quantitative feature of mineral production, - relative position in regard to supplies of minerals, - tendencies toward nationalization of mineral resources, - united states bituminous coal commission, united states bureau of mines, activities in the war, literature or international mineral relations, united states geological survey, activities in the war, , classification of mineral lands, - employment by, literature on international mineral relations, united states shipping board, , uranium ores, , - , utah, arsenic, , asphalt and bitumen, bismuth, copper, , , , , , , , , , gold, , lead, , , manganese, oil shales, phosphates, potash, , silver, , , , uranium and radium, , , vanadium, , - utah, ore deposits, relation to intrusive stocks, vadose zone, valuation of lorraine iron ores at peace conference, valuation of mineral resources, , - , value, capital, of mineral resources, , value of united states mineral production and imports, value of world mineral production, - vanadium ores, , - , van hise, c. r., , van hise, c. r., and leith, c. k., , vein, application of legal term to diverse mineral deposits, venezuela, asphalt, , magnesite, - petroleum, phosphates, verde district, arizona. _see_ jerome district. vermilion district, minnesota, iron ore outcrops, vermont, granite, marble, serpentine, slate, talc, virginia, arsenic, , emery, manganese, millstones and buhrstones, pyrite, talc and soapstone, , titanium, zinc, - , virginia city, nevada. _see_ comstock lode volcanic ash, use as abrasive, wabana, newfoundland, iron ores, - , , wales, coal, war, anti-conservational effects of, - application of geology to, - effect on ad valorem valuations, war industries board, , war minerals committee, war trade board, , "wash," use in tracing mineral outcrops, - washington, arsenic, chromite, magnesite, - water, applications of economic geology to, as a mineral resource, , , - general geologic relations, - hygroscopic, defined, of constitution, defined, quantity absorbed by soils and rocks, relative abundance of, source of, use of, litigation arising from, - _see also_ ground-waters, surface waters, hot waters, meteoric waters, magmatic waters. water power, possibilities of substituting for coal, - water supplies, - water supply maps for military use, - water table, defined, _see also_ ground-water level. waters, thermal, watson, t. l., and ries, h., weathering, of igneous rocks and veins, - of igneous rocks, formation of mineral deposits by, of mineral deposits, - of sedimentary rocks, - production of clay by, production of soils by, - zone of, welfare work, in interests of conservation, - wells, - west africa, gold, manganese, west indies, cement, phosphates, , salt, west virginia, bromine, coal, grindstones and pulpstones, natural gas, petroleum, , whetstones, white, david, , , , , white signal district, new mexico, uranium and radium ores, - wisconsin, artesian wells, diamonds in glacial drift, , granite, iron. _see_ lake superior iron ores, gogebic district, etc. quartzite, , , zinc, wisconsin, equated income method of taxation, - taxation of iron ores, witwatersrand, south africa, gold ores, wolfram ores. _see_ tungsten ores. woodward, h. b., wyoming, chromite, oil shales, petroleum, phosphates, platinum, potash, uranium and radium ores, yellow pine district, nevada, platinum ores, - yellowstone park, springs and geysers of, zinc and lead ores, wisconsin, equated income method of taxation, - zinc ores, - , - , - , , - , zinc syndicate, german, zirconium ores, - , *-------------------------------------------------+ | transcriber's note | | | | some inconsistent spelling in the text has | | been retained. | | | | page in the symbol feco_{ } the _{ } is | | subscript. | | | | page x developmnet changed to development | | page unites changed to united | | page heterogenous changed to heterogeneous | | page guatemela changed to guatemala | | paqe familar changed to familiar | | page afrcia changed to africa | | page winconsin changed to wisconsin | | page westtern changed to western | | page ownnership changed to ownership | *-------------------------------------------------* distributed proofreaders the story of a piece of coal what it is, whence it comes, and whither it goes by edward a. martin, f.g.s. preface. the knowledge of the marvels which a piece of coal possesses within itself, and which in obedience to processes of man's invention it is always willing to exhibit to an observant enquirer, is not so widespread, perhaps, as it should be, and the aim of this little book, this record of one page of geological history, has been to bring together the principal facts and wonders connected with it into the focus of a few pages, where, side by side, would be found the record of its vegetable and mineral history, its discovery and early use, its bearings on the great fog-problem, its useful illuminating gas and oils, the question of the possible exhaustion of british supplies, and other important and interesting bearings of coal or its products. in the whole realm of natural history, in the widest sense of the term, there is nothing which could be cited which has so benefited, so interested, i might almost say, so excited mankind, as have the wonderful discoveries of the various products distilled from gas-tar, itself a distillate of coal. coal touches the interests of the botanist, the geologist, and the physicist; the chemist, the sanitarian, and the merchant. in the little work now before the reader i have endeavoured to recount, without going into unnecessary detail, the wonderful story of a piece of coal. e.a.m. thornton heath, _february_, . contents. i. the origin of coal and the plants of which it is composed ii. a general view of the coal-bearing strata iii. various forms of coal and carbon iv. the coal-mine and its dangers v. early history--its use and its abuse vi. how gas is made--illuminating oils and bye-products vii. the coal supplies of the world viii. the coal-tar colours chart shewing the products of coal general index list of illustrations. fig. . _stigmaria_ " . _annularia radiata_ " . _rhacopteris inaequilatera_ " . frond of _pecopteris_ " . _pecopteris serlii_ " . _sphenopteris affinis_ " . _catamites suckowii_ " . _calamocladus grandis_ " . _asterophyllites foliosa_ " . _spenophyllum cuneifolium_ " . cast of _lepidodendron_ " . _lepidodendron longifolium_ " . _lepidodendron aculeatum_ " . _lepidostrobus_ " . _lycopodites_ " . _stigmaria ficoides_ " . section of _stigmaria_ " . sigillarian trunks in sandstone " . _productus_ " . _encrinite_ " . encrinital limestone " . various _encrinites_ " . _cyathophyllum_ " . _archegosaurus minor_ " . _psammodus porosus_ " . _orthoceras_ " . _fenestella retepora_ " . _goniatites_ " . _aviculopecten papyraceus_ " . fragment of _lepidodendron_ " . engine-house at head of a coal-pit " . gas jet and davy lamp " . part of a sigillarian trunk " . inside a gas-holder " . filling retorts by machinery " . "condensers" " . "washers" " . "purifiers" chapter i. the origin of coal and the plants of which it is composed. from the homely scuttle of coal at the side of the hearth to the gorgeously verdant vegetation of a forest of mammoth trees, might have appeared a somewhat far cry in the eyes of those who lived some fifty years ago. but there are few now who do not know what was the origin of the coal which they use so freely, and which in obedience to their demand has been brought up more than a thousand feet from the bowels of the earth; and, although familiarity has in a sense bred contempt for that which a few shillings will always purchase, in all probability a stray thought does occasionally cross one's mind, giving birth to feelings of a more or less thankful nature that such a store of heat and light was long ago laid up in this earth of ours for our use, when as yet man was not destined to put in an appearance for many, many ages to come. we can scarcely imagine the industrial condition of our country in the absence of so fortunate a supply of coal; and the many good things which are obtained from it, and the uses to which, as we shall see, it can be put, do indeed demand recognition. were our present forests uprooted and overthrown, to be covered by sedimentary deposits such as those which cover our coal-seams, the amount of coal which would be thereby formed for use in some future age, would amount to a thickness of perhaps two or three inches at most, and yet, in one coal-field alone, that of westphalia, the most important seams, if placed one above the other in immediate succession, would amount to no less than feet of coal. from this it is possible to form a faint idea of the enormous growths of vegetation required to form some of our representative coal beds. but the coal is not found in one continuous bed. these numerous seams of coal are interspersed between many thousands of feet of sedimentary deposits, the whole of which form the "coal-measures." now, each of these seams represents the growth of a forest, and to explain the whole series it is necessary to suppose that between each deposit the land became overwhelmed by the waters of the sea or lake, and after a long subaqueous period, was again raised into dry land, ready to become the birth-place of another forest, which would again beget, under similarly repeated conditions, another seam of coal. of the conditions necessary to bring these changes about we will speak later on, but this instance is sufficient to show how inadequate the quantity of fuel would be, were we dependent entirely on our own existing forest growths. however, we will leave for the present the fascinating pursuit of theorising as to the how and wherefore of these vast beds of coal, relegating the geological part of the study of the carboniferous system to a future chapter, where will be found some more detailed account of the position of the coal-seams in the strata which contain them. at present the actual details of the coal itself will demand our attention. coal is the mineral which has resulted, after the lapse of thousands of thousands of years, from the accumulations of vegetable material, caused by the steady yearly shedding of leaves, fronds and spores, from forests which existed in an early age; these accumulated where the trees grew that bore them, and formed in the first place, perhaps, beds of peat; the beds have since been subjected to an ever-increasing pressure of accumulating strata above them, compressing the sheddings of a whole forest into a thickness in some cases of a few inches of coal, and have been acted upon by the internal heat of the earth, which has caused them to part, to a varying degree, with some of their component gases. if we reason from analogy, we are compelled to admit that the origin of coal is due to the accumulation of vegetation, of which more scattered, but more distinct, representative specimens occur in the shales and clays above and below the coal-seams. but we are also able to examine the texture itself of the various coals by submitting extremely thin slices to a strong light under the microscope, and are thus enabled to decide whether the particular coal we are examining is formed of conifers, horse-tails, club-mosses, or ferns, or whether it consists simply of the accumulated sheddings of all, or perhaps, as in some instances, of innumerable spores. in this way the structure of coal can be accurately determined. were we artificially to prepare a mass of vegetable substance, and covering it up entirely, subject it to great pressure, so that but little of the volatile gases which would be formed could escape, we might in the course of time produce something approaching coal, but whether we obtained lignite, jet, common bituminous coal, or anthracite, would depend upon the possibilities of escape for the gases contained in the mass. everybody has doubtless noticed that, when a stagnant pool which contains a good deal of decaying vegetation is stirred, bubbles of gas rise to the surface from the mud below. this gas is known as marsh-gas, or light carburetted hydrogen, and gives rise to the _ignis fatuus_ which hovers about marshy land, and which is said to lure the weary traveller to his doom. the vegetable mud is here undergoing rapid decomposition, as there is nothing to stay its progress, and no superposed load of strata confining its resulting products within itself. the gases therefore escape, and the breaking-up of the tissues of the vegetation goes on rapidly. the chemical changes which have taken place in the beds of vegetation of the carboniferous epoch, and which have transformed it into coal, are even now but imperfectly understood. all we know is that, under certain circumstances, one kind of coal is formed, whilst under other conditions, other kinds have resulted; whilst in some cases the processes have resulted in the preparation of large quantities of mineral oils, such as naphtha and petroleum. oils are also artificially produced from the so-called waste-products of the gas-works, but in some parts of the world the process of their manufacture has gone on naturally, and a yearly increasing quantity is being utilised. in england oil has been pumped up from the carboniferous strata of coalbrook dale, whilst in sussex it has been found in smaller quantities, where, in all probability, it has had its origin in the lignitic beds of the wealden strata. immense quantities are used for fuel by the russian steamers on the caspian sea, the baku petroleum wells being a most valuable possession. in sicily, persia, and, far more important, in the united states, mineral oils are found in great quantity. in all probability coniferous trees, similar to the living firs, pines, larches, &c., gave rise for the most part to the mineral oils. the class of living _coniferae_ is well known for the various oils which it furnishes naturally, and for others which its representatives yield on being subjected to distillation. the gradually increasing amount of heat which we meet the deeper we go beneath the surface, has been the cause of a slow and continuous distillation, whilst the oil so distilled has found its way to the surface in the shape of mineral-oil springs, or has accumulated in troughs in the strata, ready for use, to be drawn up when a well has been sunk into it. the plants which have gone to make up the coal are not at once apparent to the naked eye. we have to search among the shales and clays and sandstones which enclose the coal-seams, and in these we find petrified specimens which enable us to build up in our mind pictures of the vegetable creation which formed the jungles and forests of these immensely remote ages, and which, densely packed together on the old forest floor of those days, is now apparent to us as coal. [illustration: fig. .--_annularia radiata._ carboniferous sandstone.] a very large proportion of the plants which have been found in the coal-bearing strata consists of numerous species of ferns, the number of actual species which have been preserved for us in our english coal, being double the number now existing in europe. the greater part of these do not seem to have been very much larger than our own living ferns, and, indeed, many of them bear a close resemblance to some of our own living species. the impressions they have left on the shales of the coal-measures are most striking, and point to a time when the sandy clay which imbedded them was borne by water in a very tranquil manner, to be deposited where the ferns had grown, enveloping them gradually, and consolidating them into their mass of future shale. in one species known as the _neuropteris_, the nerves of the leaves are as clear and as apparent as in a newly-grown fern, the name being derived from two greek words meaning "nerve-fern." it is interesting to consider the history of such a leaf, throughout the ages that have elapsed since it was part of a living fern. first it grew up as a new frond, then gradually unfolded itself, and developed into the perfect fern. then it became cut off by the rising waters, and buried beneath an accumulation of sediment, and while momentous changes have gone on in connection with the surface of the earth, it has lain dormant in its hiding-place exactly as we see it, until now excavated, with its contemporaneous vegetation, to form fuel for our winter fires. [illustration: fig. .--_rhacopteris inaequilatera._ carboniferous limestone.] although many of the ferns greatly resembled existing species, yet there were others in these ancient days utterly unlike anything indigenous to england now. there were undoubted tree-ferns, similar to those which thrive now so luxuriously in the tropics, and which throw out their graceful crowns of ferns at the head of a naked stem, whilst on the bark are the marks at different levels of the points of attachment of former leaves. these have left in their places cicatrices or scars, showing the places from which they formerly grew. amongst the tree-ferns found are _megaphyton_, _paloeopteris_, and _caulopteris_, all of which have these marks upon them, thus proving that at one time even tree-ferns had a habitat in england. [illustration: fig. .--frond of _pecopteris._ coal-shale.] one form of tree-fern is known by the name of _psaronius_, and this was peculiar in the possession of masses of aerial roots grouped round the stem. some of the smaller species exhibit forms of leaves which are utterly unknown in the nomenclature of living ferns. most have had names assigned to them in accordance with certain characteristics which they possess. this was the more possible since the fossilised impressions had been retained in so distinct a manner. here before us is a specimen in a shale of _pecopteris_, as it is called, (_pekos_, a comb). the leaf in some species is not altogether unlike the well-known living fern _osmunda_. the position of the pinnules on both sides of the central stalk are seen in the fossil to be shaped something like a comb, or a saw, whilst up the centre of each pinnule the vein is as prominent and noticeable as if the fern were but yesterday waving gracefully in the air, and but to-day imbedded in its shaly bed. [illustration: fig. .--_pecopteris serlii_. coal-shale.] _sphenopteris_, or "wedge-fern," is the name applied to another coal-fern; _glossopteris_, or "tongue-leaf"; _cyclopteris_, or "round-leaf"; _odonlopteris,_ or "tooth-leaf," and many others, show their chief characteristics in the names which they individually bear. _alethopteris_ appears to have been the common brake of the coal-period, and in some respects resembles _pecopteris_. [illustration: fig. .--_sphenopteris affinis._ coal-shale.] in some species of ferns so exact are the representations which they have impressed on the shale which contains them, that not only are the veins and nerves distinctly visible, but even the fructification still remains in the shape of the marks left by the so-called seeds on the backs of the leaves. something more than a passing look at the coal specimens in a good museum will well repay the time so spent. what are known as septarian nodules, or snake-stones, are, at certain places, common in the carboniferous strata. they are composed of layers of ironstone and sandstone which have segregated around some central object, such as a fern-leaf or a shell. when the leaf of a fern has been found to be the central object, it has been noticed that the leaf can sometimes be separated from the stone in the form of a carbonaceous film. experiments were made many years ago by m. goppert to illustrate the process of fossilisation of ferns. having placed some living ferns in a mass of clay and dried them, he exposed them to a red heat, and obtained thereby striking resemblances to fossil plants. according to the degree of heat to which they were subjected, the plants were found to be either brown, a shining black, or entirely lost. in the last mentioned case, only the impression remained, but the carbonaceous matter had gone to stain the surrounding clay black, thus indicating that the dark colour of the coal-shales is due to the carbon derived from the plants which they included. another very prominent member of the vegetation of the coal period, was that order of plants known as the _calamites_. the generic distinctions between fossil and living ferns were so slight in many cases as to be almost indistinguishable. this resemblance between the ancient and the modern is not found so apparent in other plants. the calamites of the coal-measures bore indeed a very striking resemblance, and were closely related, to our modern horse-tails, as the _equiseta_ are popularly called; but in some respects they differed considerably. most people are acquainted with the horse-tail (_equisetum fluviatile)_ of our marshes and ditches. it is a somewhat graceful plant, and stands erect with a jointed stem. the foliage is arranged in whorls around the joints, and, unlike its fossil representatives, its joints are protected by striated sheaths. the stem of the largest living species rarely exceeds half-an-inch in diameter, whilst that of the calamite attained a thickness of five inches. but the great point which is noticeable in the fossil calamites and _equisetites_ is that they grew to a far greater height than any similar plant now living, sometimes being as much as eight feet high. in the nature of their stems, too, they exhibited a more highly organised arrangement than their living representatives, having, according to dr williamson, a "fistular pith, an exogenous woody stem, and a thick smooth bark." the bark having almost al ways disappeared has left the fluted stem known to us as the calamite. the foliage consisted of whorls of long narrow leaves, which differed only from the fern _asterophyllites_ in the fact that they were single-nerved. sir william dawson assigns the calamites to four sub-types: _calamite_ proper, _calamopitus, calamodendron_, and _eucalamodendron_. [image: fig. .--root of _catamites suckowii_. coal-shale.] [image: fig .--_calamocladus grandis_. carboniferous sandstone.] having used the word "exogenous," it might be as well to pay a little attention, in passing, to the nomenclature and broad classification of the various kinds of plants. we shall then doubtless find it far easier thoroughly to understand the position in the scale of organisation to which the coal plants are referable. [illustration: fig. .--_asterophyllites foliosa_. coal-measures.] the plants which are lowest in organisation are known as _cellular_. they are almost entirely composed of numerous cells built up one above the other, and possess none of the higher forms of tissue and organisation which are met with elsewhere. this division includes the lichens, sea-weeds, confervae (green aquatic scum), fungi (mushrooms, dry-rot), &c. the division of _vascular_ plants includes the far larger proportion of vegetation, both living and fossil, and these plants are built up of vessels and tissues of various shapes and character. all plants are divided into ( ) cryptogams, or flowerless, such as mosses, ferns, equisetums, and ( ) phanerogams, or flowering. flowering plants are again divided into those with naked seeds, as the conifers and cycads (gymnosperms), and those whose seeds are enclosed in vessels, or ovaries (angiosperms). angiosperms are again divided into the monocotyledons, as the palms, and dicotyledons, which include most european trees. thus:-- ------------------------------------------------------------------- | (m.a. brongniart). | |(lindley). | |cellular | | | | _cryptogams_ (flowerless) |fungi, seaweeds, |thallogens | | | lichens | | | | | | |vascular | | | | _cryptogams_ (flowerless) |ferns, equisetums, |acrogens | | | mosses, lycopodiums| | | _phanerogams_ (flowering) | | | | gymnosperms (having |conifers and |gymnogens | | naked seeds) | cycads | | | two or more cotyledons | | | | angiosperms (having | | | | enclosed seeds) | | | | monocotyledons |palms, lilies, |endogens | | | grasses | | | dicotyledons |most european |exogens | | | trees and shrubs | | ------------------------------------------------------------------- adolphe brongniart termed the coal era the "age of acrogens," because, as we shall see, of the great predominance in those times of vascular cryptogamic plants, known in dr lindley's nomenclature as "acrogens." [illustration: fig. .--_spenophyllum cuneifolium._ coal-shale.] two of these families have already been dealt with, viz., the ferns (_felices_), and the equisetums, (_calamites_ and _equisetites_), and we now have to pass on to another family. this is that which includes the fossil representatives of the lycopodiums, or club-mosses, and which goes to make up in some coals as much as two-thirds of the whole mass. everyone is more or less familiar with some of the living lycopodiums, those delicate little fern-like mosses which are to be found in many a home. they are but lowly members of our british flora, and it may seem somewhat astounding at first sight that their remote ancestors occupied so important a position in the forests of the ancient period of which we are speaking. some two hundred living species are known, most of them being confined to tropical climates. they are as a rule, low creeping plants, although some few stand erect. there is room for astonishment when we consider the fact that the fossil representatives of the family, known as _lepidodendra_, attained a height of no less than fifty feet, and, there is good ground for believing, in many cases, a far greater magnitude. they consist of long straight stems, or trunks which branch considerably near the top. these stems are covered with scars or scales, which have been caused by the separation of the petioles or leaf-stalks, and this gives rise to the name which the genus bears. the scars are arranged in a spiral manner the whole of the way up the stem, and the stems often remain perfectly upright in the coal-mines, and reach into the strata which have accumulated above the coal-seam. [illustration: fig. .--cast of _lepidodendron_ in sandstone.] count sternberg remarked that we are unacquainted with any existing species of plant, which like the _lepidodendron_, preserves at all ages, and throughout the whole extent of the trunk, the scars formed by the attachment of the petioles, or leaf-stalks, or the markings of the leaves themselves. the yucca, dracaena, and palm, entirely shed their scales when they are dried up, and there only remain circles, or rings, arranged round the trunk in different directions. the flabelliform palms preserve their scales at the inferior extremity of the trunk only, but lose them as they increase in age; and the stem is entirely bare, from the middle to the superior extremity. in the ancient _lepidodendron_, on the other hand, the more ancient the scale of the leaf-stalk, the more apparent it still remains. portions of stems have been discovered which contain leaf-scars far larger than those referred to above, and we deduce from these fragments the fact that those individuals which have been found whole, are not by any means the largest of those which went to form so large a proportion of the ancient coal-forests. the _lepidodendra_ bore linear one-nerved leaves, and the stems always branched dichotomously and possessed a central pith. specimens variously named _knorria, lepidophloios, halonia_, and _ulodendron_ are all referable to this family. [illustration: fig. .--_lepidodendron longifolium._ coal-shale.] [illustration: fig. .--_lepidodendron aculeatum_ in sandstone.] in some strata, as for instance that of the shropshire coalfield, quantities of elongated cylindrical bodies known as _lepidostrobi_ have been found, which, it was early conjectured, were the fruit of the giant club-mosses about which we have just been speaking. their appearance can be called to mind by imagining the cylindrical fruit of the maize or indian corn to be reduced to some three or four inches in length. the sporangia or cases which contained the microscopic spores or seeds were arranged around a central axis in a somewhat similar manner to that in which maize is found. these bodies have since been found actually situated at the end of branches of _lepidodendron_, thus placing their true nature beyond a doubt. the fossil seeds (spores) do not appear to have exceeded in volume those of recent club-mosses, and this although the actual trees themselves grew to a size very many times greater than the living species. this minuteness of the seed-germs goes to explain the reason why, as sir charles lyell remarked, the same species of _lepidodendra_ are so widely distributed in the coal measures of europe and america, their spores being capable of an easy transportation by the wind. [illustration: fig. .--_lepidostrobus._ coal-shale.] one striking feature in connection with the fruit of the _lepidodendron_ and other ancient representatives of the club-moss tribe, is that the bituminous coals in many, if not in most, instances, are made up almost entirely of their spores and spore-cases. under a microscope, a piece of such coal is seen to be thronged with the minute rounded bodies of the spores interlacing one another and forming almost the whole mass, whilst larger than these, and often indeed enclosing them, are flattened bag-like bodies which are none other than the compressed sporangia which contained the former. [illustration: fig. .--_lycopodites_. coal sandstone.] now, the little scottish or alpine club-moss which is so familiar, produces its own little cones, each with its series of outside scales or leaves; these are attached to the bags or spore-cases, which are crowded with spores. although in miniature, yet it produces its fruit in just the same way, at the terminations of its little branches, and the spores, the actual germs of life, when examined microscopically, are scarcely distinguishable from those which are contained in certain bituminous coals. and, although ancient club-mosses have been found in a fossilised condition at least forty-nine feet high, the spores are no larger than those of our miniature club-mosses of the present day. the spores are more or less composed of pure bitumen, and the bituminous nature of the coal depends largely on the presence or absence of these microscopic bodies in it. the spores of the living club-mosses contain so much resinous matter that they are now largely used in the making of fireworks, and upon the presence of this altered resinous matter in coal depends its capability of providing a good blazing coal. at first sight it seems almost impossible that such a minute cause should result in the formation of huge masses of coal, such an inconceivable number of spores being necessary to make even the smallest fragment of coal. but if we look at the cloud of spores that can be shaken from a single spike of a club-moss, then imagine this to be repeated a thousand times from each branch of a fairly tall tree, and then finally picture a whole forest of such trees shedding in due season their copious showers of spores to earth, we shall perhaps be less amazed than we were at first thought, at the stupendous result wrought out by so minute an object. another well-known form of carboniferous vegetation is that known as the _sigillaria_, and, connected with this form is one, which was long familiar under the name of _stigmaria_, but which has since been satisfactorily proved to have formed the branching root of the sigillaria. the older geologists were in the habit of placing these plants among the tree-ferns, principally on account of the cicatrices which were left at the junctions of the leaf-stalks with the stem, after the former had fallen off. no foliage had, however, been met with which was actually attached to the plants, and hence, when it was discovered that some of them had long attenuated leaves not at all like those possessed by ferns, geologists were compelled to abandon this classification of them, and even now no satisfactory reference to existing orders of them has been made, owing to their anomalous structure. the stems are fluted from base to stem, although this is not so apparent near the base, whilst the raised prominences which now form the cicatrices, are arranged at regular distances within the vertical grooves. when they have remained standing for some length of time, and the strata have been allowed quietly to accumulate around the trunks, they have escaped compression. they were evidently, to a great extent, hollow like a reed, so that in those trees which still remain vertical, the interior has become filled up by a coat of sandstone, whilst the bark has become transformed into an envelope of an inch, or half an inch of coal. but many are found lying in the strata in a horizontal plane. these have been cast down and covered up by an ever-increasing load of strata, so that the weight has, in the course of time, compressed the tree into simply the thickness of the double bark, that is, of the two opposite sides of the envelope which covered it when living. _sigillarae_ grew to a very great height without branching, some specimens having measured from to feet long. in accordance with their outside markings, certain types are known as _syringodendron_, _favularia_, and _clathraria_. _diploxylon_ is a term applied to an interior stem referable to this family. [illustration: fig. .--_stigmaria ficoides_. coal-shale.] but the most interesting point about the _sigillariae_ is the root. this was for a long time regarded as an entirely distinct individual, and the older geologists explained it in their writings as a species of succulent aquatic plant, giving it the name of _stigmaria_. they realized the fact that it was almost universally found in those beds which occur immediately beneath the coal seams, but for a long time it did not strike them that it might possibly be the root of a tree. in an old edition of lyell's "elements of geology," utterly unlike existing editions in quality, quantity, or comprehensiveness, after describing it as an extinct species of water-plant, the author hazarded the conjecture that it might ultimately be found to have a connection with some other well-known plant or tree. it was noticed that above the coal, in the roof, stigmariae were absent, and that the stems of trees which occurred there, had become flattened by the weight of the overlying strata. the stigmariae on the other hand, abounded in the _underclay_, as it is called, and were not in any way compressed but retained what appeared to be their natural shape and position. hence to explain their appearance, it was thought that they were water-plants, ramifying the mud in every direction, and finally becoming overwhelmed and covered by the mud itself. on botanical grounds, brongniart and lyell conjectured that they formed the roots of other trees, and this became the more apparent as it came to be acknowledged that the underclays were really ancient soils. all doubt was, however, finally dispelled by the discovery by mr binney, of a sigillaria and a stigmaria in actual connection with each other, in the lancashire coal-field. stigmariae have since been found in the cape breton coal-field, attached to lepidodendra, about which we have already spoken, and a similar discovery has since been made in the british coal-fields. this, therefore, would seem to shew the affinity of the sigillaria to the lepidodendron, and through it to the living lycopods, or club-mosses. some few species of stigmarian roots had been discovered, and various specific names had been given to them before their actual nature was made out. what for some time were thought to be long cylindrical leaves, have now been found to be simply rootlets, and in specimens where these have been removed, the surface of the stigmaria has been noticed to be covered with large numbers of protuberant tubercles, which have formed the bases of the rootlets. there appears to have also been some special kind of arrangement in their growth, since, unlike the roots of most living plants, the tubercles to which these rootlets were attached, were arranged spirally around the main root. each of these tubercles was pitted in the centre, and into these the almost pointed ends of the rootlets fitted, as by a ball and socket joint. [illustration: fig. --_section of stigmaria_.] "a single trunk of _sigillaria_ in an erect forest presents an epitome of a coal-seam. its roots represent the _stigmaria_ underclay; its bark the compact coal; its woody axis, the mineral charcoal; its fallen leaves and fruits, with remains of herbaceous plants growing in its shade, mixed with a little earthy matter, the layers of coarse coal. the condition of the durable outer bark of erect trees, concurs with the chemical theory of coal, in showing the especial suitableness of this kind of tissue for the production of the purer compact coals."--(dawson, "structures in coal.") there is yet one other family of plants which must be mentioned, and which forms a very important portion of the constituent _flora_ of the coal period. this is the great family of the _coniferae_, which although differing in many respects from the highly organised dicotyledons of the present day, yet resembled them in some respects, especially in the formation of an annual ring of woody growth. the conifers are those trees which, as the name would imply, bear their fruit in the form of cones, such as the fir, larch, cedar, and others. the order is one which is familiar to all, not only on account of the cones they bear, and their sheddings, which in the autumn strew the ground with a soft carpet of long needle-like leaves, but also because of the gum-like secretion of resin which is contained in their tissues. only a few species have been found in the coal-beds, and these, on examination under the microscope, have been discovered to be closely related to the araucarian division of pines, rather than to any of our common firs. the living species of this tree is a native of norfolk island, in the pacific, and here it attains a height of feet, with a girth of feet. from the peculiar arrangement of the ducts in the elongated cellular tissue of the tree, as seen under the microscope, the fossil conifers, which exhibit this structure, have been placed in the same division. the familiar fossil known to geologists as _sternbergia_ has now been shown to be the cast of the central pith of these conifers, amongst which may be mentioned _cordaites, araucarites_, and _dadoxylon._. the central cores had become replaced with inorganic matter after the pith had shrunk and left the space empty. this shrinkage of the pith is a process which takes place in many plants even when living, and instances will at once occur, in which the stems of various species of shrubs when broken open exhibit the remains of the shrunken pith, in the shape of thin discs across the interval cavity. we might reasonably expect that where we find the remains of fossil coniferous trees, we should also meet with the cones or fruit which they bear. and such is the case. in some coal-districts fossil fruits, named _cardiocarpum_ and _trigonocarpum_, have been found in great quantities, and these have now been decided by botanists to be the fruits of certain conifers, allied, not to those which bear hard cones, but to those which bear solitary fleshy fruits. sir charles lyell referred them to a chinese genus of the yew tribe called _salisburia_. dawson states that they are very similar to both _taxus_ and _salisburia._. they are abundant in some coal-measures, and are contained, not only in the coal itself, but also in the sandstones and shales. the under-clays appear to be devoid of them, and this is, of course, exactly what might have been expected, since the seeds would remain upon the soil until covered up by vegetable matter, but would never form part of the clay soil itself. in connection with the varieties which have been distinguished in the families of the conifers, calamites, and sigillariae, sir william dawson makes the following observations: "i believe that there was a considerably wide range of organisation in _cordaitinae_ as well as in _calamites_ and _sigillariae_, and that it will eventually be found that there were three lines of connection between the higher cryptogams (flowerless) and the phaenogams (flowering), one leading from the lycopodes by the _sigillariae_, another leading by the _cordaites_, and the third leading from the _equisetums_ by the _calamites_. still further back the characters, afterwards separated in the club-mosses, mare's-tails, and ferns, were united in the _rhizocarps_, or, as some prefer to call them, the heterosporous _filicinae_." in concluding this chapter dealing with the various kinds of plants which have been discovered as contributing to the formation of coal-measures, it would be as well to say a word or two concerning the climate which must have been necessary to permit of the growth of such an abundance of vegetation. it is at once admitted by all botanists that a moist, humid, and warm atmosphere was necessary to account for the existence of such an abundance of ferns. the gorgeous waving tree-ferns which were doubtless an important feature of the landscape, would have required a moist heat such as does not now exist in this country, although not necessarily a tropical heat. the magnificent giant lycopodiums cast into the shade all our living members of that class, the largest of which perhaps are those that flourish in new zealand. in new zealand, too, are found many species of ferns, both those which are arborescent and those which are of more humble stature. add to these the numerous conifers which are there found, and we shall find that a forest in that country may represent to a certain extent the appearance presented by a forest of carboniferous vegetation. the ferns, lycopods, and pines, however, which appear there, it is but fair to add, are mixed with other types allied to more recent forms of vegetation. there are many reasons for believing that the amount of carbonic acid gas then existing in the atmosphere was larger than the quantity which we now find, and professor tyndall has shown that the effect of this would be to prevent radiation of heat from the earth. the resulting forms of vegetation would be such as would be comparable with those which are now reared in the green-house or conservatory in these latitudes. the gas would, in fact, act as a glass roof, extending over the whole world. chapter ii. a general view of the coal-bearing strata. in considering the source whence coal is derived, we must be careful to remember that coal itself is but a minor portion of the whole formation in which it occurs. the presence of coal has indeed given the name to the formation, the word "carboniferous" meaning "coal-bearing," but in taking a comprehensive view of the position which it occupies in the bowels of the earth, it will be necessary to take into consideration the strata in which it is found, and the conditions, so far as are known, under which these were deposited. geologically speaking, the carboniferous formation occurs near the close of that group of systems which have been classed as "palaeozoic," younger in point of age than the well known devonian and old red sandstone strata, but older by far than the oolites, the wealden, or the cretaceous strata. in south wales the coal-bearing strata have been estimated at between , and , feet, yet amongst this enormous thickness of strata, the whole of the various coal-seams, if taken together, probably does not amount to more than feet. this great disproportion between the total thickness and the thickness of coal itself shows itself in every coal-field that has been worked, and when a single seam of coal is discovered attaining a thickness of or feet, it is so unusual a thing in great britain as to cause it to be known as the "nine" or "ten-foot seam," as the case may be. although abroad many seams are found which are of greater thicknesses, yet similarly the other portions of the formation are proportionately greater. it is not possible therefore to realise completely the significance of the coal-beds themselves unless there is also a knowledge of the remaining constituents of the whole formation. the strata found in the various coal-fields differ considerably amongst themselves in character. there are, however, certain well-defined characteristics which find representation in most of the principal coal-fields, whether british or european. professor hull classifies these carboniferous beds as follows:-- upper carboniferous. _upper coal-measures._ reddish and purple sandstones, red and grey clays and shales, thin bands of coal, ironstone and limestone, with _spirorbis_ and fish. _middle coal-measures._ yellow and gray sandstones, blue and black clays and shales, bands of coal and ironstone, fossil plants, bivalves and fish, occasional marine bands. middle carboniferous. _gannister beds_ or _lower coal-measures._ _millstone grit._ flagstone series in ireland. _yoredale beds._ upper shale series of ireland. lower carboniferous. _mountain limestone_. _limestone shale_. each of the three principal divisions has its representative in scotland, belgium, and ireland, but, unfortunately for the last-named country, the whole of the upper coal-measures are there absent. it is from these measures that almost all our commercial coals are obtained. this list of beds might be further curtailed for all practical purposes of the geologist, and the three great divisions of the system would thus stand:-- upper carboniferous, or coal-measures proper. millstone grit. lower carboniferous, or mountain limestone. in short, the formation consists of masses of sandstone, shale, limestone and coal, these also enclosing clays and ironstones, and, in the limestone, marbles and veins of the ores of lead, zinc, and antimony, and occasionally silver. [illustration: fig. .--sigillarian trunks in current-bedded sandstone. st etienne.] as the most apparent of the rocks of the system are sandstone, shale, limestone, and coal, it will be necessary to consider how these were deposited in the waters of the carboniferous ages, and this we can best do by considering the laws under which strata of a similar nature are now being deposited as sedimentary beds. a great proportion consists of sandstone. now sandstone is the result of sand which has been deposited in large quantities, having become indurated or hardened by various processes brought to bear upon it. it is necessary, therefore, first to ascertain whence came the sand, and whether there are any peculiarities in its method of deposition which will explain its stratification. it will be noticed at once that it bears a considerable amount of evidence of what is called "current-bedding," that is to say, that the strata, instead of being regularly deposited, exhibit series of wedge-shaped masses, which are constantly thinning out. sand and quartz are of the same chemical composition, and in all probability the sand of which every sandstone in existence is composed, appeared on this earth in its first solid form in the shape of quartz. now quartz is a comparatively heavy mineral, so also, therefore, will sand be. it is also very hard, and in these two respects it differs entirely from another product of sedimentary deposition, namely, mud or clay, with which we shall have presently to deal when coming to the shales. since quartz is a hard mineral it necessarily follows that it will suffer, without being greatly affected, a far greater amount of wearing and knocking about when being transported by the agency of currents and rivers, than will a softer substance, such as clay. an equal amount of this wearing action upon clay will reduce it to a fine impalpable silt. the grains of sand, however, will still remain of an appreciable average size, and where both sand and clay are being transported to the sea in one and the same stream, the clay will be transported to long distances, whilst the sand, being heavier, bulk for bulk, and also consisting of grains larger in size than grains of clay, will be rapidly deposited, and form beds of sand. of course, if the current be a violent one, the sand is transported, not by being held in suspension, but rather by being pushed along the bed of the river; such an action will then tend to cause the sand to become powdered into still finer sand. when a river enters the sea it soon loses its individuality; it becomes merged in the body of the ocean, where it loses its current, and where therefore it has no power to keep in suspension the sediment which it had brought down from the higher lands. when this is the case, the sand borne in suspension is the first to be deposited, and this accumulates in banks near the entrance of the river into the sea. we will suppose, for illustration, that a small river has become charged with a supply of sand. as it gradually approaches the sea, and the current loses its force, the sand is the more sluggishly carried along, until finally it falls to the bottom, and forms a layer of sand there. this layer increases in thickness until it causes the depth of water above it to become comparatively shallow. on the shallowing process taking place, the current will still have a certain, though slighter, hold on the sand in suspension, and will transport it yet a little further seaward, when it will be thrown down, at the edge of the bank or layer already formed, thus tending to extend the bank, and to shallow a wider space of river-bed. as a result of this action, strata would be formed, shewing stratification diagonally as well as horizontally, represented in section as a number of banks which had seemingly been thrown down one above the other, ending in thin wedge-shaped terminations where the particular supply of sediment to which each owed its formation had failed. the masses of sandstone which are found in the carboniferous formation, exhibit in a large degree these wedge-shaped strata, and we have therefore a clue at once, both as to their propinquity to sea and land, and also as to the manner in which they were formed. [illustration: fig. .--_productus_. coal-measures.] there is one thing more, too, about them. just as, in the case we were considering, we could observe that the wedge-shaped strata always pointed away from the source of the material which formed them, so we can similarly judge that in the carboniferous strata the same deduction holds good, that the diagonally-pointing strata were formed in the same way, and that their thinning out was simply owing to temporary failure of sediment, made good, however, by a further deposition of strata when the next supply was borne down. it is scarcely likely, however, that sand in a pure state was always carried down by the currents to the sea. sometimes there would be some silt mixed with it. just as in many parts large masses of almost pure sandstone have been formed, so in other places shales, or, as they are popularly known by miners, "bind," have been formed. shales are formed from the clays which have been carried down by the rivers in the shape of silt, but which have since become hardened, and now split up easily into thin parallel layers. the reader has no doubt often handled a piece of hard clay when fresh from the quarry, and has remembered how that, when he has been breaking it up, in order, perhaps, to excavate a partially-hidden fossil, it has readily split up in thin flakes or layers of shaly substance. this exhibits, on a small scale, the chief peculiarity of the coal shales. the formation of shales will now demand our attention. when a river is carrying down with it a quantity of mud or clay, it is transported as a fine, dusty silt, and when present in quantities, gives the muddy tint to the water which is so noticeable. we can very well see how that silt will be carried down in greater quantities than sand, since nearly all rivers in some part of their course will travel through a clayey district, and finely-divided clay, being of a very light nature, will be carried forward whenever a river passes over such a district. and a very slight current being sufficient to carry it in a state of suspension, it follows that it will have little opportunity of falling to the bottom, until, by some means or other, the current, which is the means of its conveyance, becomes stopped or hindered considerably in its flow. when the river enters a large body of water, such as the ocean or a lake, in losing its individuality, it loses also the velocity of its current, and the silt tends to sink down to the bottom. but being less heavy than the sand, about which we have previously spoken, it does not sink all at once, but partly with the impetus it has gained, and partly on account of the very slight velocity which the current still retains, even after having entered the sea, it will be carried out some distance, and will the more gradually sink to the bottom. the deeper the water in which it falls the greater the possibility of its drifting farther still, since in sinking, it would fall, not vertically, but rather as the drops of rain in a shower when being driven before a gale of wind. thus we should notice that clays and shales would exhibit a regularity and uniformity of deposition over a wide area. currents and tides in the sea or lake would tend still further to retard deposition, whilst any stoppages in the supply of silt which took place would give the former layer time to consolidate and harden, and this would assist in giving it that bedded structure which is so noticeable in the shales, and which causes it to split up into fine laminae. this uniformity of structure in the shales over wide areas is a well ascertained characteristic of the coal-shales, and we may therefore regard the method of their deposition as given here with a degree of certainty. there is a class of deposit found among the coal-beds, which is known as the "underclay," and this is the most regular of all as to the position in which it is found. the underclays are found beneath every bed of coal. "warrant," "spavin," and "gannister" are local names which are sometimes applied to it, the last being a term used when the clay contains such a large proportion of silicious matter as to become almost like a hard flinty rock. sometimes, however, it is a soft clay, at others it is mixed with sand, but whatever the composition of the underclays may be, they always agree in being unstratified. they also agree in this respect that the peculiar fossils known as _stigmariae_ abound in them, and in some cases to such an extent that the clay is one thickly-matted mass of the filamentous rootlets of these fossils. we have seen how these gradually came to be recognised as the roots of trees which grew in this age, and whose remains have subsequently become metamorphosed into coal, and it is but one step farther to come to the conclusion that these underclays are the ancient soils in which the plants grew. no sketch of the various beds which go to form the coal-measures would be complete which did not take into account the enormous beds of mountain limestone which form the basis of the whole system, and which in thinner bands are intercalated amongst the upper portion of the system, or the true coal-measures. now, limestones are not formed in the same way in which we have seen that sandstones and shales are formed. the last two mentioned owe their origin to their deposition as sediment in seas, estuaries or lakes, but the masses of limestone which are found in the various geological formations owe their origin to causes other than that of sedimentary deposition. in carboniferous times there lived numberless creatures which we know nowadays as _encrinites_. these, when growing, were fixed to the bed of the ocean, and extended upward in the shape of pliant stems composed of limestone joints or plates; the stem of each encrinite then expanded at the top in the shape of a gorgeous and graceful starfish, possessed of numberless and lengthy arms. these encrinites grew in such profusion that after death, when the plates of which their stems consisted, became loosened and scattered over the bed of the sea, they accumulated and formed solid beds of limestone. besides the encrinites, there were of course other creatures which were able to create the hard parts of their structures by withdrawing lime from the sea, such as _foraminifera_, shell-fish, and especially corals, so that all these assisted after death in the accumulation of beds of limestone where they had grown and lived. [illustration: fig. .--encrinite.] [illustration: fig. .--encrinital limestone.] there is one peculiarity in connection with the habitats of the encrinites and corals which goes some distance in supplying us with a useful clue as to the conditions under which this portion of the carboniferous formation was formed. these creatures find it a difficult matter, as a rule, to live and secrete their calcareous skeleton in any water but that which is clear, and free from muddy or sandy sediment. they are therefore not found, generally speaking, where the other deposits which we have considered, are forming, and, as these are always found near the coasts, it follows that the habitats of the creatures referred to must be far out at sea where no muddy sediments, borne by rivers, can reach them. we can therefore safely come to the conclusion that the large masses of encrinital limestone, which attain such an enormous thickness in some places, especially in ireland, have been formed far away from the land of the period; we can at the same time draw the conclusion that if we find the encrinites broken and snapped asunder, and the limestone deposits becoming impure through being mingled with a proportion of clayey or sandy deposits, that we are approaching a coast-line where perhaps a river opened out, and where it destroyed the growth of encrinites, mixing with their dead remains the sedimentary dêbris of the land. [illustration: fig. .--encrinites: various. mountain limestone.] we have lightly glanced at the circumstances attending the deposition of each of the principal rocks which form the beds amongst which coal is found, and have now to deal with the formation of the coal itself. we have already considered the various kinds of plants and trees which have been discovered as contributing their remains to the formation of coal, and have now to attempt an explanation of how it came to be formed in so regular a manner over so wide an area. each of the british coal-fields is fairly extensive. the yorkshire and derbyshire coal-fields, together with the lancashire coal-field, with which they were at one time in geological connection, give us an area of nearly square miles, and other british coal-fields show at least some hundreds of square miles. and yet, spread over them, we find a series of beds of coal which in many cases extend throughout the whole area with apparent regularity. if we take it, as there seems every reason to believe was the case, that almost all these coal-fields were not only being formed at the same time, but were in most instances in continuation with one another, this regularity of deposition of comparatively narrow beds of coal, appears all the more remarkable. the question at once suggests itself, which of two things is probable? are we to believe that all this vegetable matter was brought down by some mighty river and deposited in its delta, or that the coal-plants grew just where we now find the coal? formerly it was supposed that coal was formed out of dead leaves and trees, the refuse of the vegetation of the land, which had been carried down by rivers into the sea and deposited at their mouths, in the same way that sand and mud, as we have seen, are swept down and deposited. if this were so, the extent of the deposits would require a river with an enormous embouchure, and we should be scarcely warranted in believing that such peaceful conditions would there prevail as to allow of the layers of coal to be laid down with so little disturbance and with such regularity over these wide areas. but the great objection to this theory is, that not only do the remains still retain their perfection of structure, but they are comparatively _pure,--i.e.,_ unmixed with sedimentary depositions of clay or sand. now, rivers would not bring down the dead vegetation alone; their usual burden of sediment would also be deposited at their mouths, and thus dead plants, sand, and clay would be mixed up together in one black shaly or sandy mass, a mixture which would be useless for purposes of combustion. the only theory which explained all the recognised phenomena of the coal-measures was that the plants forming the coal actually grew where the coal was formed, and where, indeed, we now find it. when the plants and trees died, their remains fell to the ground of the forest, and these soon turned to a black, pasty, vegetable mass, the layer thus formed being regularly increased year by year by the continual accumulation of fresh carbonaceous matter. by this means a bed would be formed with regularity over a wide area; the coal would be almost free from an admixture of sandy or clayey sediment, and probably the rate of formation would be no more rapid in one part of the forest than another. thus there would be everywhere uniformity of thickness. the warm and humid atmosphere, which it is probable then existed, would not only have tended towards the production of an abnormal vegetation, but would have assisted in the decaying and disintegrating processes which went on amongst the shed leaves and trees. when at last it was announced as a patent fact that every bed of coal possessed its underclay, and that trees had been discovered actually standing upon their own roots in the clay, there was no room at all for doubt that the correct theory had been hit upon--viz., that coal is now found just where the trees composing it had grown in the past. but we have more than one coal-seam to account for. we have to explain the existence of several layers of coal which have been formed over one another on the same spot at successive periods, divided by other periods when shale and sandstones only have been formed. a careful estimate of the lancashire coal-field has been made by professor hull for the geological survey. of the feet of carboniferous strata here found, spread out over an area of square miles, there are on the average eighteen seams of coal. this is only an instance of what is to be found elsewhere. eighteen coal-seams! what does this mean? it means that, during carboniferous times, on no less than eighteen occasions, separate and distinct forests have grown on this self-same spot, and that between each of these occasions changes have taken place which have brought it beneath the waters of the ocean, where the sandstones and shales have been formed which divide the coal-seams from each other. we are met here by a wonderful demonstration of the instability of the surface of the earth, and we have to do our best to show how the changes of level have been brought about, which have allowed of this game of geological see-saw to take place between sea and land. changes of level! many a hard geological nut has only been overcome by the application of the principle of changes of level in the surface of the earth, and in this we shall find a sure explanation of the phenomena of the coal-measures. great changes of the level of the land are undoubtedly taking place even now on the earth's surface, and in assuming that similar changes took place in carboniferous times, we shall not be assuming the former existence of an agent with which we are now unfamiliar. and when we consider the thicknesses of sandstone and shale which intervene beneath the coal-seams, we can realise to a certain extent the vast lapses of years which must have taken place between the existence of each forest; so that although now an individual passing up a coal-mine shaft may rapidly pass through the remains of one forest after another, the rise of the strata above each forest-bed then was tremendously slow, and the period between the growth of each forest must represent the passing away of countless ages. perhaps it would not be too much to say that the strata between some of the coal-seams would represent a period not less than that between the formation of the few tertiary coals with which we are acquainted, and a time which is still to us in the far-away future. the actual seams of coal themselves will not yield much information, from which it will be possible to judge of the contour of the landmasses at this ancient period. of one thing we are sure, namely, that at the time each seam was formed, the spot where it accumulated was dry land. if, therefore, the seams which appear one above the other coincide fairly well as to their superficial extent, we can conclude that each time the land was raised above the sea and the forest again grew, the contour of the land was very similar. this conclusion will be very useful to go upon, since whatever decision may be come to as an explanation of one successive land-period and sea-period on the same spot, will be applicable to the eighteen or more periods necessary for the completion of some of the coal-fields. we will therefore look at one of the sandstone masses which occur between the coal-seams, and learn what lessons these have to teach us. in considering the formation of strata of sand in the seas around our river-mouths, it was seen that, owing to the greater weight of the particles of the sand over those of clay, the former the more readily sank to the bottom, and formed banks not very far away from the land. it was seen, too, that each successive deposition of sand formed a wedge-shaped layer, with the point of the wedge pointing away from the source of origin of the sediment, and therefore of the current which conveyed the sediment. therefore, if in the coal-measure sandstones the layers were found with their wedges all pointing in one direction, we should be able to judge that the currents were all from one direction, and that, therefore, they were formed by a single river. but this is just what we do not find, for instead of it the direction of the wedge-shaped strata varies in almost every layer, and the current-bedding has been brought about by currents travelling in every direction. such diverse current-bedding could only result from the fact that the spot where the sand was laid down was subject to currents from every direction, and the inference is that it was well within the sphere of influence of numerous streams and rivers, which flowed from every direction. the only condition of things which would explain this is that the sandstone was originally formed in a closed sea or large lake, into which numerous rivers flowing from every direction poured their contents. now, in the sandstones, the remains of numerous plants have been found, but they do not present the perfect appearance that they do when found in the shales; in fact they appear to have suffered a certain amount of damage through having drifted some distance. this, together with the fact that sandstones are not formed far out at sea, justify the safe conclusion that the land could not have been far off. wherever the current-bedding shows itself in this manner we may be sure we are examining a spot from which the land in every direction could not have been at a very great distance, and also that, since the heavy materials of which sandstone is composed could only be transported by being impelled along by currents at the bed of the sea, and that in deep water such currents could not exist, therefore we may safely decide that the sea into which the rivers fell was a comparatively shallow one. although the present coal-fields of england are divided from one another by patches of other beds, it is probable that some of them were formerly connected with others, and a very wide sheet of coal on each occasion was laid down. the question arises as to what was the extent of the inland sea or lake, and did it include the area covered by the coal basins of scotland and ireland, of france and belgium? and if these, why not those of america and other parts? the deposition of the coal, according to the theory here advanced, may as well have been brought about in a series of large inland seas and lakes, as by one large comprehensive sea, and probably the former is the more satisfactory explanation of the two. but the astonishing part of it is that the changes in the level of the land must have been taking place simultaneously over these large areas, although, of course, while one quarter may have been depressed beneath the sea, another may have been raised above it. in connection with the question of the contour of the land during the existence of the large lakes or inland seas, professor hull has prepared, in his series of maps illustrative of the palaeo-geography of the british islands, a map showing on incontestible grounds the existence during the coal-ages of a great central barrier or ridge of high land stretching across from anglesea, south of flint, staffordshire, and shropshire coal-fields, to the eastern coast of norfolk. he regards the british coal-measures as having been laid down in two, or at most three, areas of deposition--one south of this ridge, the remainder to the north of it. in regard to the extent of the former deposits of coal in ireland, there is every probability that the sister island was just as favourably treated in this respect as great britain. most unfortunately, ireland has since suffered extreme denudation, notably from the great convulsions of nature at the close of the very period of their deposition, as well as in more recent times, resulting in the removal of nearly all the valuable upper carboniferous beds, and leaving only the few unimportant coal-beds to which reference has been made. [illustration: fig. .--_cyathophyllum_. coral in encrinital limestone.] we are unable to believe in the continuity of our coal-beds with those of america, for the great source of sediment in those times was a continent situated on the site of the atlantic ocean, and it is owing to this extensive continent that the forms of _flora_ found in the coal-beds in each country bear so close a resemblance to one another, and also that the encrinital limestone which was formed in the purer depths of the ocean on the east, became mixed with silt, and formed masses of shaly impure limestone in the south-western parts of ireland. it must be noted that, although we may attribute to upheaval from beneath the fact that the bed of the sea became temporarily raised at each period into dry land, the deposits of sand or shale would at the same time be tending to shallow the bed, and this alone would assist the process of upheaval by bringing the land at least very near to the surface of the water. each upheaval, however, could have been but a temporary arrest of the great movement of crust subsidence which was going on throughout the coal period, so that, at its close, when the last coal forest grew upon the surface of the land, there had disappeared, in the case of south wales, a thickness of , feet of material. of the many remarkable things in connection with coal-beds, not the least is the state of purity in which coal is found. on the floor of each forest there would be many a streamlet or even small river which would wend its way to meet the not very distant sea, and it is surprising at first that so little sediment found its way into the coal itself. but this was cleverly explained by sir charles lyell, who noticed, on one of his visits to america, that the water of the mississippi, around the rank growths of cypress which form the "cypress swamps" at the mouths of that river, was highly charged with sediment, but that, having passed through the close undergrowth of the swamps, it issued in almost a pure state, the sediment which it bore having been filtered out of it and precipitated. this very satisfactorily explained how in some places carbonaceous matter might be deposited in a perfectly pure state, whilst in others, where sandstone or shale was actually forming, it might be impregnated by coaly matter in such a way as to cause it to be stained black. in times of flood sediment would be brought in, even where pure coal had been forming, and then we should have a thin "parting" of sandstone or shale, which was formed when the flood was at its height. or a slight sinking of the land might occur, in which case also the formation of coal would temporarily cease, and a parting of foreign matter would be formed, which, on further upheaval taking place, would again give way to another forest growth. some of the thicker beds have been found presenting this aspect, such as the south staffordshire ten-yard coal, which in some parts splits up into a dozen or so smaller beds, with partings of sediment between them. in the face of the stupendous movements which must have happened in order to bring about the successive growth of forests one above another on the same spot, the question at once arises as to how these movements of the solid earth came about, and what was the cause which operated in such a manner. we can only judge that, in some way or other, heat, or the withdrawal of heat, has been the prime motive power. we can perceive, from what is now going on in some parts of the earth, how great an influence it has had in shaping the land, for volcanoes owe their activity to the hidden heat in the earth's interior, and afford us an idea of the power of which heat is capable in the matter of building up and destroying continents. no less certain is it that heat is the prime factor in those more gradual vertical movements of the land to which we have referred elsewhere, but in regard to the exact manner in which it acts we are very much in the dark. everybody knows that, in the majority of instances, material substances of all kinds expand under the influence of heat, and contract when the source of heat is withdrawn. if we can imagine movements in the quantity of heat contained in the solid crust, the explanation is easy, for if a certain tract of land receive an accession of heat beneath it, it is certain that the principal effect will be an elevation of the land, consequent on the expansion of its materials, with a subsequent depression when the heat beneath the tract in question becomes gradually lessened. should the heat be retained for a long period, the strata would be so uplifted as to form an anticlinal, or saddle-back, and then, should subsequent denudation take place, more ancient strata would be brought to view. it was thus in the instance of the tract bounded by the north and south downs, which were formerly entirely covered by chalk, and in the instance of the uprising of the carboniferous limestone between the coal-fields of lancashire, staffordshire, and derbyshire. how the heat-waves act, and the laws, if any, which they obey in their subterranean movements, we are unable to judge. from the properties which heat possesses we know that its presence or absence produces marked differences in the positions of the strata of the earth, and from observations made in connection with the closing of some volcanoes, and the opening up of fresh earth-vents, we have gone a long way towards establishing the probability that there are even now slow and ponderous movements taking place in the heat stored in the earth's crust, whose effects are appreciably communicated to the outside of the thin rind of solid earth upon which we live. owing to the great igneous and volcanic activity at the close of the deposition of the carboniferous system of strata, the coal-measures exhibit what are known as _faults_ in abundance. the mountain limestone, where it outcrops at the surface, is observed to be much jointed, so much so that the work of quarrying the limestone is greatly assisted by the jointed structure of the rock. faults differ from joints in that, whilst the strata in the latter are still in relative position on each side of the joint, they have in the former slipped out of place. in such a case the continuation of a stratum on the opposite side of a fault will be found to be depressed, perhaps a thousand feet or more. it will be seen at once how that, in sinking a new shaft into a coal-seam, the possibility of an unknown fault has to be brought into consideration, since the position of the seam may prove to have been depressed to such an extent as to cause it to be beyond workable depth. many seams, on the other hand, which would have remained altogether out of reach of mining operations, have been brought within workable depth by a series of _step-faults_, this being a term applied to a series of parallel faults, in none of which the amount of down-throw is great. the amount of the down-throw, or the slipping-down of the beds, is measured, vertically, from the point of disappearance of a layer to an imaginary continuation of the same layer from where it again appears beyond the fault. the plane of a fault is usually more or less inclined, the amount of the inclination being known as the _hade_ of the fault, and it is a remarkable characteristic of faults that, as a general rule, they hade to the down-throw. this will be more clearly understood when it is explained that, by its action, a seam of coal, which is subject to numerous faults, can never be pierced more than once by one and the same boring. in mountainous districts, however, there are occasions when the hade is to the up-throw, and this kind of fault is known as an _inverted fault_. lines of faults extend sometimes for hundreds of miles. the great pennine fault of england is miles long, and others extend for much greater distances. the surfaces on both sides of a fault are often smooth and highly polished by the movement which has taken place in the strata. they then show the phenomenon known as _slicken-sides_. many faults have become filled with crystalline minerals in the form of veins of ore, deposited by infiltrating waters percolating through the natural fissures. in considering the formation and structure of the better-known coal-bearing beds of the carboniferous age, we must not lose sight of the fact that important beds of coal also occur in strata of much more recent date. there are important coal-beds in india of permian age. there are coal-beds of liassic age in south hungary and in texas, and of jurassic age in virginia, as well as at brora in sutherlandshire; there are coals of cretaceous age in moravia, and valuable miocene tertiary coals in hungary and the austrian alps. again, older than the true carboniferous age, are the silurian anthracites of co. cavan, and certain norwegian coals, whilst in new south wales we are confronted with an assemblage of coal-bearing strata which extend apparently from the devonian into mesozoic times. still, the age we have considered more closely has an unrivalled right to the title, coal appearing there not merely as an occasional bed, but as a marked characteristic of the formation. the types of animal life which are found in this formation are varied, and although naturally enough they do not excel in number, there are yet sufficient varieties to show probabilities of the existence of many with which we are unfamiliar. the highest forms yet found, show an advance as compared with those from earlier formations, and exhibit amphibian characteristics intermediate between the two great classes of fishes and reptiles. numerous specimens proper to the extinct order of _labyrinthodontia_ have been arranged into at least a score of genera, these having been drawn from the coal-measures of newcastle, edinburgh, kilkenny, saärbruck, bavaria, pennsylvania, and elsewhere. the _archegosaurus,_ which we have figured, and the _anthracosaurus,_ are forms which appear to have existed in great numbers in the swamps and lakes of the age. the fish of the period belong almost entirely to the ancient orders of the ganoids and placoids. of the ganoids, the great _megalichthys hibberti_ ranges throughout the whole of the system. wonderful accumulations of fish remains are found at the base of the system, in the bone-bed of the bristol coal-field, as well as in a similar bed at armagh. many fishes were armed with powerful conical teeth, but the majority, like the existing port jackson shark, were possessed of massive palates, suited in some cases for crushing, and in others for cutting. [illustration: fig. .--_archegosaurus minor_. coal-measures.] [illustration: fig. .--_psammodus porosus_. crushing palate of a fish.] [illustration: fig. .--_orthoceras_. mountain limestone.] in the mountain limestone we see, of course, the predominance of marine types, encrinital remains forming the greater proportion of the mass. there are occasional plant remains which bear evidence of having drifted for some distance from the shore. but next to the _encrinites_, the corals are the most important and persistent. corals of most beautiful forms and capable of giving polished marble-like sections, are in abundance. _polyzoa_ are well represented, of which the lace-coral (_fenestella_) and screw-coral (_archimedopora_) are instances. _cephalopoda_ are represented by the _orthoceras_, sometimes five or six feet long, and _goniatites_, the forerunner of the familiar _ammonite_. many species of brachiopods and lammellibranchs are met with. _lingula_, most persistent throughout all geological time, is abundant in the coal-shales, but not in the limestones. _aviculopecten_ is there abundant also. in the mountain limestone the last of the trilobites (_phillipsia_) is found. [illustration: fig. .--_fenestella retipora_. mountain limestone.] [illustration: fig. .--_goniatites_. mountain limestone.] we have evidence of the existence in the forests of a variety of _centipede_, specimens having been found in the erect stump of a hollow tree, although the fossil is an extremely rare one. the same may be said of the only two species of land-snail which have been found connected with the coal forests, viz., _pupa vetusta_ and _zonites priscus_, both discovered in the cliffs of nova scotia. these are sufficient to demonstrate that the fauna of the period had already reached a high stage of development. in the estuaries of the day, masses of a species of freshwater mussel (_anthracosia_) were in existence, and these have left their remains in the shape of extensive beds of shells. they are familiar to the miner as _mussel-binds_, and are as noticeable a feature of this long ago period, as are the aggregations of mussels on every coast at the present day. [illustration: fig. .--_aviculopecten papyraceus_. coal-shale.] chapter iii. various forms of coal and carbon. in considering the various forms and combinations into which coal enters, it is necessary that we should obtain a clear conception of what the substance called "carbon" is, and its nature and properties generally, since this it is which forms such a large percentage of all kinds of coal, and which indeed forms the actual basis of it. in the shape of coke, of course, we have a fairly pure form of carbon, and this being produced, as we shall see presently, by the driving off of the volatile or vaporous constituents of coal, we are able to perceive by the residue how great a proportion of coal consists of carbon. in fact, the two have almost an identical meaning in the popular mind, and the fact that the great masses of strata, in which are contained our principal and most valuable seams of coal, are termed "carboniferous," from the latin _carbo_, coal, and _fero_, i bear, tends to perpetuate the existence of the idea. there is always a certain, though slight, quantity of carbon in the air, and this remains fairly constant in the open country. small though it may be in proportion to the quantity of pure air in which it is found, it is yet sufficient to provide the carbon which is necessary to the growth of vegetable life. just as some of the animals known popularly as the _zoophytes_, which are attached during life to rocks beneath the sea, are fed by means of currents of water which bring their food to them, so the leaves, which inhale carbon-food during the day through their under-surfaces, are provided with it by means of the currents of air which are always circulating around them; and while the fuel is being taken in beneath, the heat and light are being received from above, and the sun supplies the motive power to digestion. it is assumed that it is, within the knowledge of all that, for the origin of the various seams and beds of coaly combinations which exist in the earth's crust, we must look to the vegetable world. if, however, we could go so far back in the world's history as the period when our incandescent orb had only just severed connection with a gradually-diminishing sun, we should probably find the carbon there, but locked up in the bonds of chemical affinities with other elements, and existing therewith in a gaseous condition. but, as the solidifying process went on, and as the vegetable world afterwards made its appearance, the carbon became, so to speak, wrenched from its combinations, and being absorbed by trees and plants, finally became deposited amongst the ruins of a former vegetable world, and is now presented to us in the form of coal. we are able to trace the gradual changes through which the pasty mass of decaying vegetation passed, in consequence of the fact that we have this material locked up in various stages of carbonisation, in the strata beneath our feet. these we propose to deal with individually, in as unscientific and untechnical a manner as possible. first of all, when a mass of vegetable matter commences to decay, it soon loses its colour. there is no more noticeable proof of this, than that when vitality is withdrawn from the leaves of autumn, they at once commence to assume a rusty or an ashen colour. let the leaves but fall to the ground, and be exposed to the early frosts of october, the damp mists and rains of november, and the rapid change of colour is at once apparent. trodden under foot, they soon assume a dirty blackish hue, and even when removed they leave a carbonaceous trace of themselves behind them, where they had rested. another proof of the rapid acquisition of their coaly hue is noticeable in the spring of the year. when the trees have burst forth and the buds are rapidly opening, the cases in which the buds of such trees as the horse-chestnut have been enclosed will be found cast off, and strewing the path beneath. moistened by the rains and the damp night-mists, and trodden under foot, these cases assume a jet black hue, and are to all appearance like coal in the very first stages of formation. but of course coal is not made up wholly and only of leaves. the branches of trees, twigs of all sizes, and sometimes whole trunks of trees are found, the last often remaining in their upright position, and piercing the strata which have been formed above them. at other times they lie horizontally on the bed of coal, having been thrown down previously to the formation of the shale or sandstone, which now rests upon them. they are often petrified into solid sandstone themselves, whilst leaving a rind of coal where formerly was the bark. although the trunk of a tree looks so very different to the leaves which it bears upon its branches, it is only naturally to be supposed that, as they are both built up after the same manner from the juices of the earth and the nourishment in the atmosphere, they would have a similar chemical composition. one very palpable proof of the carbonaceous character of tree-trunks suggests itself. take in your hand a few dead twigs or sticks from which the leaves have long since dropped; pull away the dead parts of the ivy which has been creeping over the summer-house; or clasp a gnarled old monster of the forest in your arms, and you will quickly find your hand covered with a black smut, which is nothing but the result of the first stage which the living plant has made, in its progress towards its condition as dead coal. but an easy, though rough, chemical proof of the constituents of wood, can be made by placing a few pieces of wood in a medium-sized test-tube, and holding it over a flame. in a short time a certain quantity of steam will be driven off, next the gaseous constituents of wood, and finally nothing will be left but a few pieces of black brittle charcoal. the process is of course the same in a fire-grate, only that here more complete combustion of the wood takes place, owing to its being intimately exposed to the action of the flames. if we adopt the same experiment with some pieces of coal, the action is similar, only that in this case the quantity of gases given off is not so great, coal containing a greater proportion of carbon than wood, owing to the fact that, during its long burial in the bowels of the earth, it has been acted upon in such a way as to lose a great part of its volatile constituents. from processes, therefore, which are to be seen going on around us, it is easily possible to satisfy ourselves that vegetation will in the long run undergo such changes as will result in the formation of coal. there are certain parts in most countries, and particularly in ireland, where masses of vegetation have undergone a still further stage in metamorphism, namely, in the well-known and famous peat-bogs. ireland is _par excellence_ the land of bogs, some three millions of acres being said to be covered by them, and they yield an almost inexhaustible supply of peat. one of the peat-bogs near the shannon is between two and three miles in breadth and no less than fifty in length, whilst its depth varies from feet to as much as feet. peat-bogs have in no way ceased to be formed, for at their surfaces the peat-moss grows afresh every year; and rushes, horse-tails, and reeds of all descriptions grow and thrive each year upon the ruins of their ancestors. the formation of such accumulations of decaying vegetation would only be possible where the physical conditions of the country allowed of an abundant rainfall, and depressions in the surface of the land to retain the moisture. where extensive deforesting operations have taken place, peat-bogs have often been formed, and many of those in existence in europe undoubtedly owe their formation to that destruction of forests which went on under the sway of the romans. natural drainage would soon be obstructed by fallen trees, and the formation of marsh-land would follow; then with the growth of marsh-plants and their successive annual decay, a peaty mass would collect, which would quickly grow in thickness without let or hindrance. in considering the existence of inland peat-bogs, we must not lose sight of the fact that there are subterranean forest-beds on various parts of our coasts, which also rest upon their own beds of peaty matter, and very possibly, when in the future they are covered up by marine deposits, they will have fairly started on their way towards becoming coal. peat-bogs do not wholly consist of peat, and nothing else. the trunks of such trees as the oak, yew, and fir, are often found mingled with the remains of mosses and reeds, and these often assume a decidedly coaly aspect. from the famous bog of allen in ireland, pieces of oak, generally known as "bog-oak," which have been buried for generations in peat, have been excavated. these are as black as any coal can well be, and are sufficiently hard to allow of their being used in the manufacture of brooches and other ornamental objects. another use to which peat of some kinds has been put is in the manufacture of yarn, the result being a material which is said to resemble brown worsted. on digging a ditch to drain a part of a bog in maine, u.s., in which peat to a depth of twenty feet had accumulated, a substance similar to cannel coal itself was found. as we shall see presently, cannel coal is one of the earliest stages of true coal, and the discovery proved that under certain conditions as to heat and pressure, which in this case happened to be present, the materials which form peat may also be metamorphosed into true coal. darwin, in his well-known "voyage in the _beagle_" gives a peculiarly interesting description of the condition of the peat-beds in the chonos archipelago, off the chilian coast, and of their mode of formation. "in these islands," he says, "cryptogamic plants find a most congenial climate, and within the forest the number of species and great abundance of mosses, lichens, and small ferns, is quite extraordinary. in tierra del fuego every level piece of land is invariably covered by a thick bed of peat. in the chonos archipelago where the nature of the climate more closely approaches that of tierra del fuego, every patch of level ground is covered by two species of plants (_astelia pumila_ and _donatia megellanica_), which by their joint decay compose a thick bed of elastic peat. "in tierra del fuego, above the region of wood-land, the former of these eminently sociable plants is the chief agent in the production of peat. fresh leaves are always succeeding one to the other round the central tap-root; the lower ones soon decay, and in tracing a root downwards in the peat, the leaves, yet holding their places, can be observed passing through every stage of decomposition, till the whole becomes blended in one confused mass. the astelia is assisted by a few other plants,--here and there a small creeping myrtus (_m. nummularia_), with a woody stem like our cranberry and with a sweet berry,--an empetrum (_e. rubrum_), like our heath,--a rush (_juncus grandiflorus_), are nearly the only ones that grow on the swampy surface. these plants, though possessing a very close general resemblance to the english species of the same genera, are different. in the more level parts of the country the surface of the peat is broken up into little pools of water, which stand at different heights, and appear as if artificially excavated. small streams of water, flowing underground, complete the disorganisation of the vegetable matter, and consolidate the whole. "the climate of the southern part of america appears particularly favourable to the production of peat. in the falkland islands almost every kind of plant, even the coarse grass which covers the whole surface of the land, becomes converted into this substance: scarcely any situation checks its growth; some of the beds are as much as twelve feet thick, and the lower part becomes so solid when dry that it will hardly burn. although every plant lends its aid, yet in most parts the astelia is the most efficient. "it is rather a singular circumstance, as being so very different from what occurs in europe, that i nowhere saw moss forming by its decay any portion of the peat in south america. with respect to the northern limit at which the climate allows of that peculiar kind of slow decomposition which is necessary for its production, i believe that in chiloe (lat. ° to °), although there is much swampy ground, no well characterised peat occurs; but in the chonos islands, three degrees farther southward, we have seen that it is abundant. on the eastern coast in la plata (lat. °) i was told by a spanish resident, who had visited ireland, that he had often sought for this substance, but had never been able to find any. he showed me, as the nearest approach to it which he had discovered, a black peaty soil, so penetrated with roots as to allow of an extremely slow and imperfect combustion." the next stage in the making of coal is one in which the change has proceeded a long way from the starting-point. _lignite_ is the name which has been applied to a form of impure coal, which sometimes goes under the name of "brown coal." it is not a true coal, and is a very long way from that final stage to which it must attain ere it takes rank with the most valuable of earth's products. from the very commencement, an action has being going on which has caused the amount of the gaseous constituents to become less and less, and which has consequently caused the carbon remaining behind to occupy an increasingly large proportion of the whole mass. so, when we arrive at the lignite stage, we find that a considerable quantity of volatile matter has already been parted with, and that the carbon, which in ordinary living wood is about per cent. of the whole, has already increased to about per cent. in most lignites there is, as a rule, a comparatively large proportion of sulphur, and in such cases it is rendered useless as a domestic fuel. it has been used as a fuel in various processes of manufacture, and the lignite of the well-known bovey tracey beds has been utilised in this way at the neighbouring potteries. as compared with true coal, it is distinguished by the abundance of smoke which it produces and the choking sulphurous fumes which also accompany its combustion, but it is largely used in germany as a useful source of paraffin and illuminating oils. in silesia, saxony, and in the district about bonn, large quantities of lignite are mined, and used as fuel. large stores of lignite are known to exist in the weald of the south-east of england, and although the mining operations which were carried on at one time at heathfield, bexhill, and other places, were failures so far as the actual discovery of true coal was concerned, yet there can be no doubt as to the future value of the lignite in these parts, when england's supplies of coal approach exhaustion, and attention is turned to other directions for the future source of her gas and paraffin oils. beside the bovey tracey lignitic beds to which we have above referred, other tertiary clays are found to contain this early promise of coal. the _eocene_ beds of brighton are an important instance of a tertiary lignite, the seam of _surturbrand_, as it is locally called, being a somewhat extensive deposit. we have now closely approached to true coal, and the next step which we shall take will be to consider the varieties in which the black mineral itself is found. the principal of these varieties are as follows, against each being placed the average proportion of pure carbon which it contains:-- splint or hard coal, per cent.; cannel, candle or parrott coal, per cent.; cherry or soft coal, per cent.; common bituminous, or caking coal, per cent.; anthracite, blind coal, culm, glance, or stone coal, from south wales, per cent. as far as the gas-making properties of the first three are concerned, the relative proportions of carbon and volatile products are much the same. everybody knows a piece of cannel coal when it is seen, how it appears almost to have been once in a molten condition, and how it breaks with a conchoidal fracture, as opposed to the cleavage of bituminous coal into thin layers; and, most apparent and most noticeable of all, how it does not soil the hands after the manner of ordinary coal. it is at times so dense and compact that it has been fashioned into ornaments, and is capable of receiving a polish like jet. from the large percentage of volatile products which it contains, it is greatly used in gasworks. caking coal and the varieties of coal which exist between it and anthracite, are familiar to every householder; the more it approaches the composition of the latter the more difficult it is to get it to burn, but when at last fairly alight it gives out great heat, and what is more important, a less quantity of volatile constituents in the shape of gas, smoke, ammonia, ash and sulphurous acid. for this reason it has been proposed to compel consumers to adopt anthracite as _the_ domestic coal by act of parliament. certainly by this means the amount of impurities in the air might be appreciably lessened, but as it would involve the reconstruction of some millions of fire-places, and an increase in price in consequence of the general demand for it, it is not likely that a government would be so rash as to attempt to pass such a measure; even if passed, it would probably soon become as dead and obsolete and impotent as those many laws with which our ancestors attempted, first to arrest, and then to curb the growth in the use of coal of any sort. anthracite is not a "homely" coal. if we use it alone it will not give us that bright and cheerful blaze which english-speaking people like to obtain from their fires. it is a significant fact, and one which proves that the various kinds of coal which are found are nothing but stages begotten by different degrees of disentanglement of the contained gases, that where, as in some parts, a mass of basalt has come into contact with ordinary bituminous coal, the coal has assumed the character of anthracite, whilst the change has in some instances gone so far as to convert the anthracite into graphite. the basalt, which is one of the igneous rocks, has been erupted into the coal-seam in a state of fusion, and the heat contained in it has been sufficient to cause the disentanglement of the gases, the extraction of which from the coal brings about the condition of anthracite and graphite. the mention of graphite brings us to the next stage. graphite, plumbago, or, as it is more commonly called, black-lead, which, we may say in passing, has nothing of lead about it at all, is best known in the shape of that very useful and cosmopolitan article, the black-lead pencil. this is even purer carbon than anthracite, not more than per cent. of ash and other impurities being present. it is well-known by its grey metallic lustre; the chemist uses it mixed with fire-clay to make his crucibles; the engineer uses it, finely powdered, to lubricate his machinery; the house-keeper uses it to "black-lead" her stoves to prevent them from rusting. an imperfect graphite is found inside some of the hottest retorts from which gas is distilled, and this is used as the negative element in zinc and carbon electricity-making cells, whilst its use as the electrodes or carbons of the arc-lamp is becoming more and more widely adopted, as installations of electric light become more general. one great source of true graphite for many years was the famous mine at borrowdale, in cumberland, but this is now almost exhausted. the vein lay between strata of slate, and was from eight to nine feet thick. as much as £ , is said to have been realised from it in one year. extensive supplies of graphite are found in rocks of the laurentian age in canada. in this formation nothing which can undoubtedly be classed as organic has yet been discovered. life at this early period must have found its home in low and humble forms, and if the _eozoön_ of dawson, which has been thought to represent the earliest type of life, turns out after all not to be organic, but only a deceptive appearance assumed by certain of the strata, we at least know that it must have been in similarly humble forms that life, if it existed at all, did then exist. we can scarcely, therefore, expect that the vegetable world had made any great advance in complexity of organism at this time, otherwise the supplies of graphite or plumbago which are found in the formation, would be attributed to dense forest growths, acted upon, after death, in a similar manner to that which awaited the vegetation which, ages after, went to form beds of coal. at present we know of no source of carbon except through the intervention and the chemical action of plants. like iron, carbon is seldom found on the earth except in combination. if there were no growth of vegetation at this far-away period to give rise to these deposits of graphite, we are compelled to ask ourselves whether, perchance, there did not then exist conditions of which we are not now cognisant on the earth, and which allowed graphite to be formed without assistance from the vegetable kingdom. at present, however, science is in the dark as to any other process of its formation, and we are left to assume that the vegetable growth of the time was enormous in quantity, although there is nothing to show the kind of vegetation, whether humble mosses or tall forest trees, which went to constitute the masses of graphite. geologists will agree that this is no small assumption to make, since, if true, it may show that there was an abundance of vegetation at a time when animal life was hidden in one or more very obscure forms, one only of which has so far been detected, and whose very identity is strongly doubted by nearly all competent judges. at the same time there _may_ have been an abundance of both animal and vegetable life at the time. we must not forget that it is a well-ascertained fact that in later ages, the minute seed-spores of forest trees were in such abundance as to form important seams of coal in the true carboniferous era, the trees which gave birth to them being now classed amongst the humble _cryptogams_, the ferns, and club-mosses, &c. the graphite of laurentian age may not improbably have been caused by deposits of minute portions of similar lowly specimens of vegetable life, and if the _eozoön_ the "dawn-animalcule," does represent the animal life of the time, life whose types were too minute to leave undoubted traces of their existence, both animal life and vegetable life may be looked upon as existing side by side in extremely humble forms, neither as yet having taken an undoubted step forward in advance of the other in respect to complexity of organism. [illustration: fig .--_lepidodendron_. portion of sandstone stem after removal of bark of a giant club-moss] there is but one more form of carbon with which we have to deal in running through the series. we have seen that coal is not the _summum bonum_ of the series. other transformations take place after the stage of coal is reached, which, by the continued disentanglement of gases, finally bring about the plumbago stage. what the action is which transforms plumbago or some other form of carbon into the condition of a diamond cannot be stated. diamond is the purest form of carbon found in nature. it is a beautiful object, alike from the results of its powers of refraction, as also from the form into which its carbon has been crystallised. how nature, in her wonderful laboratory, has precipitated the diamond, with its wonderful powers of spectrum analysis, we cannot say with certainty. certain chemists have, at a great expense, produced crystals which, in every respect, stand the tests of true diamonds; but the process of their production at a great expense has in no way diminished the value of the natural product. the process by which artificial diamonds have been produced is so interesting, and the subject may prove to be of so great importance, that a few remarks upon the process may not be unacceptable. the experiments of the great french chemist, dumas, and others, satisfactorily proved the fact, which has ever since been considered thoroughly established, that the diamond is nothing but carbon crystallised in nearly a pure state, and many chemists have since been engaged in the hitherto futile endeavour to turn ordinary carbon into the true diamond. despretz at one time considered that he had discovered the process, which consisted in his case of submitting a piece of charcoal to the action of an electric battery, having in his mind the similar process of electrolysis, by which water is divided up into the two gases, hydrogen and oxygen. he obtained a microscopic deposit on the poles of the battery, which he pronounced to be diamond dust, but which, a long time after, was proved to be nothing but graphite in a crystallised state. this was, however, certainly a step in the right direction. the honour of first accomplishing the task fell to mr hannay, of glasgow, who succeeded in producing very small but comparatively soft diamonds, by heating lampblack under great pressure, in company with one or two other ingredients. the process was a costly one, and beyond being a great scientific feat, the discovery led to little result. a young french chemist, m. henri moissau, has since come to the front, and the diamonds which he has produced have stood every test for the true diamond to which they could be subjected; above all, the density of the product is . , _i.e._, that of the diamond, that of graphite reaching only. he recognised that in all diamonds which he had consumed--and he consumed some £ worth in order to assure himself of the fact--there were always traces of iron in their composition. he saw that iron in fusion, like other metals, always dissolves a certain quantity of carbon. might it not be that molten iron, cooling in the presence of carbon, deep in volcanic depths where there was little scope for the iron to expand in assuming the solid form, would exert such tremendous pressure upon the particles of carbon which it absorbed, that these would assume the crystalline state? he packed a cylinder of soft iron with the carbon of sugar, and placed the whole in a crucible filled with molten iron, which was raised to a temperature of ° by means of an electric furnace. the soft cylinder melted, and dissolved a large portion of the carbon. the crucible was thrown into water, and a mass of solid iron was formed. it was allowed further to cool in the open air, but the expansion which the iron would have undergone on cooling, was checked by the crucible which contained it. the result was a tremendous pressure, during which the carbon, which was still dissolved, was crystallised into minute diamonds. these showed themselves as minute points which were easily separable from the mass by the action of acids. thus the wonderful transformation from sugar to the diamond was accomplished. it should be mentioned that iron, silver, and water, alone possess the peculiar property of expanding when passing from the liquid to the solid state. the diamonds so obtained were of both kinds. the particles of white diamond resembled in every respect the true brilliant. but there was also an appreciable quantity of the variety known as the "black diamond." these diamonds seem to approximate more closely to carbon as we are most familiar with it. they are not considered as of such value as the transparent form, but they are still of considerable commercial value. the _carbonado_, as this kind is called, possesses so great a degree of hardness that by means of it it is possible to bore through the hardest rocks. the diamond drill, used for boring purposes, is furnished around the outer edge of the cylinder of the "boring bit," as it is called, with perhaps a dozen black diamonds, together with another row of brazilian diamonds on the inside. by the rotation of the boring tool the sharp edges of the diamonds cut their way through rocks of all degrees of hardness, leaving a core of the rock cut through, in the centre of the cylindrical drill. it is found that the durability of the natural edge of the diamond is far greater than that of the edge caused by _artificial_ cutting and trimming. the cutting of a pane of glass by means of a ring set with an artificially-cut diamond, cannot therefore be done without injuring to a slight extent the edge of the stone. the diamond is the hardest of all known substances, leaving a scratch on any substance across which it may be drawn. yet it is one whose form can be changed, and whose hardness can be completely destroyed, by the simple process of combustion. it can be deprived of its high lustre, and of its power of breaking up by refraction the light of the sun into the various tints of the solar spectrum, simply by heating it to a red heat, and then plunging it into a jar of oxygen gas. it immediately expands, changes into a coky mass, and burns away. the product left behind is a mixture of carbon and oxygen, in the proportions in which it is met with in carbonic-anhydride, or, carbonic acid gas deprived of its water. this is indeed a strange transformation, from the most valuable of all our precious stones to a compound which is the same in chemical constituents as the poisonous gas which we and all animals exhale. but there is this to be said. probably in the far-away days when the diamond began to be formed, the tree or other vegetable product which was its far-removed ancestor abstracted carbonic acid gas from the atmosphere, just as do our plants in the present day. by this means it obtained the carbon wherewith to build up its tissues. thus the combustion of the diamond into carbonic-anhydride now is, after all, only a return to the same compound out of which it was originally formed. how it was formed is a secret: probably the time occupied in the formation of the diamond may be counted by centuries, but the time of its re-transformation into a mass of coky matter is but the work of seconds! there is another form of carbon which was formerly of much greater importance than it is now, and which, although not a natural product, is yet deserving of some notice here. charcoal is the substance referred to. in early days the word "coal," or, as it was also spelt, "cole," was applied to any substance which was used as fuel; hence we have a reference in the bible to a "fire of coals," so translated when the meaning to be conveyed was probably not coal as we know it. wood was formerly known as coal, whilst charred wood received the name of charred-coal, which was soon corrupted into charcoal. the charcoal-burners of years gone by were a far more flourishing community than they are now. when the old baronial halls and country-seats depended on them for the basis of their fuel, and the log was a more frequent occupant of the fire-grate than now, these occupiers of midforest were a people of some importance. we must not overlook the fact that there is another form of charcoal, namely, animal charcoal or bone-black. this can be obtained by heating bones to redness in closed iron vessels. in the refining of raw sugar the discoloration of the syrup is brought about by filtering it through animal-charcoal; by this means the syrup is rendered colourless. when properly prepared, charcoal exhibits very distinctly the rings of annual growth which may have characterised the wood from which it was formed. it is very light in consequence of its porous nature, and it is wonderfully indestructible. but its greatest, because it is its most useful property, is undoubtedly the power which it has of absorbing great quantities of gas into itself. it is in fact what may be termed an all-round purifier. it is a deodoriser, a disinfectant, and a decoloriser. it is an absorbent of bad odours, and partially removes the smell from tainted meat. it has been used when offensive manures have been spread over soils, with the same object in view, and its use for the purification of water is well known to all users of filters. some idea of its power as a disinfectant may be gained by the fact that one volume of wood-charcoal will absorb no less than volumes of ammonia, volumes of carbonic anhydride, and volumes of sulphurous anhydride. other forms of carbon which are well-known are ( ) coke, the residue left when coal has been subjected to a great heat in a closed retort, but from which all the bye-products of coal have been allowed to escape; ( ) soot and lamp-black, the former of which is useful as a manure in consequence of ammonia being present in it, whilst the latter is a specially prepared soot, and is used in the manufacture of indian ink and printers' ink. chapter iv. the coal-mine and its dangers. it is somewhat strange to think that where once existed the solitudes of an ancient carboniferous forest now is the site of a busy underground town. for a town it really is. the various roads and passages which are cut through the solid coal as excavation of a coal-mine proceeds, represent to a stranger all the intricacies of a well-planned town. nor is the extent of these underground towns a thing to be despised. there is an old pit near newcastle which contains not less than fifty miles of passages. other pits there are whose main thoroughfares in a direct line are not less than four or five miles in length, and this, it must be borne in mind, is the result of excavation wrought by human hands and human labour. so great an extent of passages necessarily requires some special means of keeping the air within it in a pure state, such as will render it fit for the workers to breathe. the further one would go from the main thoroughfare in such a mine, the less likely one would be to find air of sufficient purity for the purpose. it is as a consequence necessary to take some special steps to provide an efficient system of ventilation throughout the mine. this is effectually done by two shafts, called respectively the downcast and the upcast shaft. a shaft is in reality a very deep well, and may be circular, rectangular or oval in form. in order to keep out water which may be struck in passing through the various strata, it is protected by plank or wood tubbing, or the shaft is bricked over, or sometimes even cast-iron segments are sunk. in many shafts which, owing to their great depth, pass through strata of every degree of looseness or viscosity, all three methods are utilised in turn. in westphalia, where coal is worked beneath strata of more recent geological age, narrow shafts have been, in many cases, sunk by means of boring apparatus, in preference to the usual process of excavation, and the practice has since been adopted in south wales. in england the usual form of the pit is circular, but elliptical and rectangular pits are also in use. on the continent polygonal-shaped shafts are not uncommon, all of them, of whatever shape, being constructed with a view to resist the great pressure exerted by the rock around. [illustration: fig. .--engine-house and buildings at head of a coal-pit.] if there be one of these shafts at one end of the mine, and another at a remote distance from it, a movement of the air will at once begin, and a rough kind of ventilation will ensue. this is, however, quite insufficient to provide the necessary quantity of air for inhalation by the army of workers in the coal-mine, for the current thus set up does not even provide sufficient force to remove the effete air and impurities which accumulate from hundreds of perspiring human bodies. it is therefore necessary to introduce some artificial means, by which a strong and regular current shall pass down one shaft, through the mine in all its workings, and out at the other shaft. this is accomplished in various ways. it took many years before those interested in mines came thoroughly to understand how properly to secure ventilation, and in bygone days the system was so thoroughly bad that a tremendous amount of sickness prevailed amongst the miners, owing to the poisonous effects of breathing the same air over and over again, charged, as it was, with more or less of the gases given off by the coal itself. now, those miners who do so great a part in furnishing the means of warming our houses in winter, have the best contrivances which can be devised to furnish them with an ever-flowing current of fresh air. amongst the various mechanical appliances which have been used to ensure ventilation may be mentioned pumps, fans, and pneumatic screws. there is, as we have said, a certain, though slight, movement of the air in the two columns which constitute the upcast and the downcast shafts, but in order that a current may flow which shall be equal to the necessities of the miners, some means are necessary, by which this condition of almost equilibrium shall be considerably disturbed, and a current created which shall sweep all foul gases before it. one plan was to force fresh air into the downcast, which should in a sense push the foetid air away by the upcast. another was to exhaust the upcast, and so draw the gases in the train of the exhausted air. in other cases the plan was adopted of providing a continual falling of water down the downcast shaft. these various plans have almost all given way to that which is the most serviceable of all, namely, the plan of having an immense furnace constantly burning in a specially-constructed chamber at the bottom of the upcast. by this means the column of air above it becomes rarefied under the heat, and ascends, whilst the cooler air from the downcast rushes in and spreads itself in all directions whence the bad air has already been drawn. on the other hand, to so great a state of perfection have ventilating fans been brought, that one was recently erected which would be capable of changing the air of westminster hall thirty times in one hour. having procured a current of sufficient power, it will be at once understood that, if left to its own will, it would take the nearest path which might lie between its entrance and its exit, and, in this way, ventilating the principal street only, would leave all the many off-shoots from it undisturbed. it is consequently manipulated by means of barriers and tight-fitting doors, in such a way that the current is bound in turn to traverse every portion of the mine. a large number of boys, known as trappers, are employed in opening the doors to all comers, and in carefully closing the doors immediately after they have passed, in order that the current may not circulate through passages along which it is not intended that it should pass. the greatest dangers which await the miners are those which result, in the form of terrible explosions, from the presence of inflammable gases in the mines. the great walls of coal which bound the passages in mines are constantly exuding supplies of gas into the air. when a bank of coal is brought down by an artificial explosion, by dynamite, by lime cartridges, or by some other agency, large quantities of gas are sometimes disengaged, and not only is this highly detrimental to the health of the miners, if not carried away by proper ventilation, but it constitutes a constant danger which may at any time cause an explosion when a naked light is brought into contact with it. fire-damp may be sometimes heard issuing from fiery seams with a peculiar hissing sound. if the volume be great, the gas forms what is called a _blower_, and this often happens in the neighbourhood of a fault. when coal is brought down in any large volume, the blowers which commence may be exhausted in a few moments. others, however, have been known to last for years, this being the case at wallsend, where the blower gave off feet of gas per minute. in such cases the gas is usually conveyed in pipes to a place where it can be burned in safety. in the early days of coal-mining the explosions caused by this gas soon received the serious attention of the scientific men of the age. in the _philosophical transactions of the royal society_ we find a record of a gas explosion in . the amusing part of such records was that the explosions were ascribed by the miners to supernatural agencies. little attention seemed to have been paid to the fact, which has since so thoroughly been established, that the explosions were caused by accumulations of gas, mixed in certain proportions with air. as a consequence, tallow candles with an exposed flame were freely used, especially in britain. these were placed in niches in the workings, where they would give to the pitman the greatest amount of light. previous to the introduction of the safety-lamp, workings were tested before the men entered them, by "trying the candle". owing to the specific gravity of fire-damp (. ) being less than that of air, it always finds a lodgement at the roofs of the workings, so that, to test the condition of the air, it was necessary to steadily raise the candle to the roof at certain places in the passages, and watch carefully the action of the flame. the presence of fire-damp would be shown by the flame assuming a blue colour, and by its elongation; the presence of other gases could be detected by an experienced man by certain peculiarities in the tint of the flame. this testing with the open flame has almost entirely ceased since the introduction of the perfected davy lamp. the use of candles for illumination soon gave place in most of the large collieries to the introduction of small oil-lamps. in the less fiery mines on the continent, oil-lamps of the well-known etruscan pattern are still in use, whilst small metal lamps, which can conveniently be attached to the cap of the worker, occasionally find favour in the shallower scotch mines. these lamps are very useful in getting the coal from the thinner seams, where progress has to be made on the hands and feet. at the close of the last century, as workings began to be carried deeper, and coal was obtained from places more and more infested with fire-damp, it soon came to be realised that the old methods of illumination would have to be replaced by others of a safer nature. it is noteworthy that mere red heat is insufficient in itself to ignite fire-damp, actual contact with flame being necessary for this purpose. bearing this in mind, spedding, the discoverer of the fact, invented what is known as the "steel-mill" for illuminating purposes. in this a toothed wheel was made to play upon a piece of steel, the sparks thus caused being sufficient to give a moderate amount of illumination. it was found, however, that this method was not always trustworthy, and lamps were introduced by humboldt in , and by clanny in . in these lamps the air which fed the flame was isolated from the air of the mine by having to bubble through a liquid. many miners were not, however, provided with these lamps, and the risks attending naked lights went on as merrily as ever. in order to avoid explosions in mines which were known to give off large quantities of gas, "fiery" pits as they are called, sir humphrey davy in invented his safety lamp, the principle of which can be stated in a few words. if a piece of fine wire gauze be held over a gas-jet before it is lit, and the gas be then turned on, it can be lit above the gauze, but the flame will not pass downwards towards the source of the gas; at least, not until the gauze has become over-heated. the metallic gauze so rapidly conducts away the heat, that the temperature of the gas beneath the gauze is unable to arrive at the point of ignition. in the safety-lamp the little oil-lamp is placed in a circular funnel of fine gauze, which prevents the flame from passing through it to any explosive gas that may be floating about outside, but at the same time allows the rays of light to pass through readily. sir humphrey davy, in introducing his lamp, cautioned the miners against exposing it to a rapid current of air, which would operate in such a way as to force the flame through the gauze, and also against allowing the gauze to become red-hot. in order to minimise, as far as possible, the necessity of such caution the lamp has been considerably modified since first invented, the speed of the ventilating currents not now allowing of the use of the simple davy lamp, but the principle is the same. during the progress of sir humphrey davy's experiments, he found that when fire-damp was diluted with per cent. of air, and any less proportion, it simply ignited without explosion. with between per cent. and per cent. of air, fire-damp assumed its most explosive form, but afterwards decreased in explosiveness, until with - / per cent. of air it again simply ignited without explosion. with between and per cent. of fire-damp the mixture was most dangerous. pure fire-damp itself, therefore, is not dangerous, so that when a small quantity enters the gauze which surrounds the davy lamp, it simply burns with its characteristic blue flame, but at the same time gives the miner due notice of the danger which he was running. [illustration: fig. .--gas jet and davy lamp.] with the complicated improvements which have since been made in the davy lamp, a state of almost absolute safety can be guaranteed, but still from time to time explosions are reported. of the cause of many we are absolutely ignorant, but occasionally a light is thrown upon their origin by a paragraph appearing in a daily paper. two men are charged before the magistrates with being in the possession of keys used exclusively for unlocking their miners' safety-lamps. there is no defence. these men know that they carry their lives in their hands, yet will risk their own and those of hundreds of others, in order that they may be able to light their pipes by means of their safety-lamps. sometimes in an unexpected moment there is a great dislodgement of coal, and a tremendous quantity of gas is set free, which may be sufficient to foul the passages for some distance around. the introduction or exposure of a naked light for even so much as a second is sufficient to cause explosion of the mass; doors are blown down, props and tubbing are charred up, and the volume of smoke, rushing up by the nearest shaft and overthrowing the engine-house and other structures at the mouth, conveys its own sad message to those at the surface, of the dreadful catastrophe that has happened below. perhaps all that remains of some of the workers consists of charred and scorched bodies, scarcely recognisable as human beings. others escape with scorched arms or legs, and singed hair, to tell the terrible tale to those who were more fortunately absent; to speak of their own sufferings when, after having escaped the worst effects of the explosion, they encountered the asphyxiating rush of the after-damp or choke-damp, which had been caused by the combustion of the fire-damp. "choke-damp" in very truth it is, for it is principally composed of our old acquaintance carbonic acid gas (carbon dioxide), which is well known as a non-supporter of combustion and as an asphyxiator of animal life. it seems a terrible thing that on occasions the workings and walls themselves of a coal-mine catch fire and burn incessantly. yet such is the case. years ago this happened in the case of an old colliery near dudley, at the surface of which, by means of the heat and steam thus afforded, early potatoes for the london market, we are told, were grown; and it was no unusual thing to see the smoke emerging from cracks and crevices in the rocks in the vicinity of the town. from fire on the one hand, we pass, on the other, to the danger which awaits miners from a sudden inrush of water. during the great coal strike of , certain mines became unworkable in consequence of the quantity of water which flooded the mines, and which, continually passing along the natural fractures in the earth's crust, is always ready to find a storage reservoir in the workings of a coal-mine. this is a difficulty which is always experienced in the sinking of shafts, and the shutting off of water engages the best efforts of mining engineers. added to these various dangers which exist in the coal-mine, we must not omit to notice those accidents that are continually being caused by the falling-in of roofs or of walls, from the falling of insecure timber, or of what are known as "coal-pipes" or "bell-moulds." then, again, every man that enters the mine trusts his life to the cage by which he descends to his labour, and shaft accidents are not infrequent. the following table shows the number of deaths from colliery accidents for a period of ten years, compiled by a government inspector, and from this it will be seen that those resulting from falling roofs number considerably more than one-third of the whole. ------------------------------------------------------------------- | causes of death. | no. of | proportion | | | deaths. | per cent. | ------------------------------------------------------------------- | deaths resulting from fire-damp | | | | explosions | | . | | | | | | deaths resulting from falling | | | | roofs and coals | | . | | | | | | deaths resulting from shaft | | | | accidents | | . | | | | | | deaths resulting from miscellaneous | | | | causes and above ground | | . | | |------------|------------| | | | . | ------------------------------------------------------------------| every reader of the daily papers is familiar with the harrowing accounts which are there given of coal-mine explosions. this kind of accident is one, which is, above all, associated in the public mind with the dangers of the coal-pit. yet the accidents arising from this cause number but per cent. of those recorded, and granted there be proper inspection, and the use of naked lights be absolutely abolished, this low percentage might still be considerably reduced. a terrific explosion occurred at whitwick colliery, leicestershire, in , when two lads were killed, whilst a third was rescued after a very narrow escape. the lads, it is stated, _were working with naked lights_, when a sudden fall of coal released a quantity of gas, and an immediate explosion was the natural result. accidents had been so rare at this pit that it was regarded as particularly safe, and it was alleged that the use of naked lights was not uncommon. this is an instance of that large number of accidents which are undoubtedly preventable. an interesting commentary on the careless manner in which miners risk their lives was shown in the discoveries made after an explosion at a colliery near wrexham in . near the scene of the explosion an unsecured safety lamp was found, and the general opinion at the time was that the disaster was caused by the inexcusable carelessness of one of the twenty victims. besides this, when the clothing of the bodies recovered was searched, the contents, taken, it should be noted, with the pitmen into the mines, consisted of pipes, tobacco, matches, and even keys for unlocking the lamps. it is a strange reflection on the manner in which this mine had been examined previous to the men entering upon their work, that the under-looker, but half an hour previously, had reported the pit to be free from gas. another instance of the same foolhardiness on the part of the miners is contained in the report issued in regard to an explosion which occurred at denny, in stirlingshire, on april th, . by this accident thirteen men lost their lives, and upon the bodies of eight of the number the following articles were found; upon patrick carr, tin matchbox half full of matches and a contrivance for opening lamps; john comrie, split nail for opening lamps; peter conway, seven matches and split key for opening lamps; patrick dunton, split nail for opening lamps; john herron, clay pipe and piece of tobacco; henry m'govern, tin matchbox half full of matches; robert mitchell, clay pipe and piece of tobacco; john nicol, wooden pipe, piece of tobacco, one match, and box half full of matches. the report stated that the immediate cause of the disaster was the ignition of fire-damp by naked light, the conditions of temperature being such as to exclude the possibility of spontaneous combustion. henry m'govern had previously been convicted of having a pipe in the mine. with regard to the question of sufficient ventilation it continued:--"and we are therefore led, on a consideration of the whole evidence, to the conclusion that the accident cannot be attributed to the absence of ventilation, which the mine owners were bound under the mines regulation act and the special rules to provide." the report concluded as follows:-- "on the whole matter we have to report that, in our opinion, the explosion at quarter pit on april th, , resulting in the loss of thirteen lives, was caused by the ignition of an accumulation or an outburst of gas coming in contact with a naked light, 'other than an open safety-lamp,' which had been unlawfully kindled by one of the miners who were killed. in our opinion, the intensity of the explosion was aggravated, and its area extended, by the ignition of coal-dust." we have mentioned that accidents have frequently occurred from the falling of "coal-pipes," or, as they are also called, "bell-moulds." we must explain what is meant by this term. they are simply what appear to be solid trunks of trees metamorphosed into coal. if we go into a tropical forest we find that the woody fibre of dead trees almost invariably decays faster than the bark. the result is that what may appear to be a sound tree is nothing but an empty cylinder of bark. this appears to have been the case with many of the trees in coal-mines, where they are seen to pierce the strata, and around which the miners are excavating the coal. as the coaly mass collected around the trunk when the coal was being formed, the interior was undergoing a process of decomposition, while the bark assumed the form of coal. the hollow interior then became filled with the shale or sandstone which forms the roof of the coal, and its sole support when the coal is removed from around it, is the thin rind of carbonised bark. when this falls to pieces, or loses its cohesion, the sandstone trunk falls of its own weight, often causing the death of the man that works beneath it. sir charles lyell mentions that in a colliery near newcastle, no less than thirty _sigillaria_ trees were standing in their natural position in an area of fifty yards square, the interior in each case being sandstone, which was surrounded by a bark of friable coal. [illustration: fig. --part of a trunk of _sigillaria_, showing the thin outer carbonised bark, with leaf-scars, and the seal-like impressions where the bark is removed.] the last great danger to which we have here to make reference, is the explosive action of a quantity of coal-dust in a dry condition. it is only now commencing to be fully recognised that this is really a most dangerous explosive. as we have seen, large quantities of coal are formed almost exclusively of _lepidodendron_ spores, and such coal is productive of a great quantity of dust. explosions which are always more or less attributable to the effects of coal-dust are generally considered, in the official statistics, to have been caused by fire-damp. the act regulating mines in great britain is scarcely up to date in this respect. there is a regulation which provides for the watering of all dry and dusty places within twenty yards from the spot where a shot is fired, but the enforcement of this regulation in each and every pit necessarily devolves on the managers, many of whom in the absence of an inspector leave the requirement a dead letter. every improvement which results in the better ventilation of a coal-mine tends to leave the dust in a more dangerous condition. the air, as it descends the shaft and permeates the workings, becomes more and more heated, and licks up every particle of moisture it can touch. thorough ventilation results in more greatly freeing a mine of the dangerous fire-damp, but the remedy brings about another disease, viz., the drying-up of all moisture. the dust is thus left in a dangerously inflammable condition, acting like a train of gunpowder, to be started, it may be, by the slightest breath of an explosion. there is apparently little doubt that the presence of coal-dust in a dry state in a mine appreciably increases the liability of explosion in that mine. so far as great britain is concerned, a royal commission was appointed by lord rosebery's government to inquire into and investigate the facts referring to coal-dust. generally speaking, the conclusion arrived at was that fine coal-dust was inflammable under certain conditions. there was considerable difference of opinion as to what these conditions were. some were of opinion that coal-dust and air alone were of an explosive nature, whilst others thought that alone they were not, but that the addition of a small quantity of fire-damp rendered the mixture explosive. an important conclusion was come to, that, with the combustion of coal-dust alone, there was little or no concussion, and that the flame was not of an explosive character. coal-dust was, however, admittedly dangerous, especially if in a dry condition. the effects of an explosion of gas might be considerably extended by its presence, and there seems every reason to believe that, with a suitable admixture of air and a very small proportion of gas, it forms a dangerous explosive. legislation in the direction of the report of the commission is urgently needed. we have seen elsewhere what it is in the dust which makes it dangerous, how that, for the most part, it consists of the dust-like spores of the _lepidodendron_ tree, fine and impalpable as the spores on the backs of some of our living ferns, and the fact that this consists of a large proportion of resin makes it the easily inflammable substance it is. nothing but an incessant watering of the workings in such cases will render the dust innocuous. the dust is extremely fine, and is easily carried into every nook and crevice, and when, as at bridgend in , it explodes, it is driven up and out of the shaft, enveloping everything temporarily in dust and darkness. in some of the pits in south wales a system of fine sprays of water is in use, by which the water is ejected from pin-holes pricked in a series of pipes which are carried through the workings. a fine mist is thus caused where necessary, which is carried forward by the force of the ventilating current. a thorough system of inspection in coal-mines throughout the world is undoubtedly urgently called for, in order to ensure the proper carrying out of the various regulations framed for their safety. it is extremely unfortunate that so many of the accidents which happen are preventable, if only men of knowledge and of scientific attainments filled the responsible positions of the overlookers. chapter v. early history--its use and its abuse. the extensive use of coal throughout the civilised world for purposes of heating and illumination, and for the carrying on of manufactures and industries, may be regarded as a well-marked characteristic of the age in which we live. coal must have been in centuries past a familiar object to many generations. people must have long been living in close proximity to its outcrops at the sides of the mountains and at the surface of the land, yet without being acquainted with its practical value, and it seems strange that so little use was made of it until about three centuries ago, and that its use did not spread earlier and more quickly throughout civilised countries. a mineral fuel is mentioned by theophrastus about b.c., from which it is inferred that thus early it was dug from some of the more shallow depths. the britons before the time of the roman invasion are credited with some slight knowledge of its industrial value. prehistoric excavations have been found in monmouthshire, and at stanley, in derbyshire, and the flint axes there actually found imbedded in the layer of coal are reasonably held to indicate its excavation by neolithic or palaeolithic (stone-age) workmen. the fact that coal cinders have been found on old roman walls in conjunction with roman tools and implements, goes to prove that its use, at least for heating purposes, was known in england prior to the saxon invasion, whilst some polygonal chambers in the six-foot seam near the river douglas, in lancashire, are supposed also to be roman. the chinese were early acquainted with the existence of coal, and knew of its industrial value to the extent of using it for the baking of porcelain. the fact of its extensive existence in great britain, and the valuable uses to which it might be put, did not, however, meet with much notice until the ninth century, when, owing to the decrease of the forest-area, and consequently of the supply of wood-charcoal therefrom, it began to attract attention as affording an excellent substitute for charcoal. the coal-miner was, however, still a creation of the future, and even as peat is collected in ireland at the present day for fuel, without the laborious process of mining for it, so those people living in coal-bearing districts found their needs satisfied by the quantity of coal, small as it was, which appeared ready to hand on the sides of the carboniferous mountains. till then, and for a long time afterwards, the principal source of fuel consisted of vast forests, amidst which the charcoal-burners, or "colliers" as they were even then called, lived out their lonely existence in preparing charcoal and hewing wood, for the fires of the baronial halls and stately castles then swarming throughout the land. as the forests became used up, recourse was had more and more to coal, and in the first charter dealing with and recognising the importance of the supplies was granted to the freemen of newcastle, according them permission to dig for coals in the castle fields. about the same time a coal-pit at preston, haddingtonshire, was granted to the monks of newbattle. specimens of newcastle coal were sent to london, but the city was loth to adopt its use, objecting to the innovation as one prejudicial to the health of its citizens. by the end of the th century, two ships only were found sufficient to satisfy the demand for stone-coal in london. this slow progress may, perhaps, have been partially owing to the difficulties which were placed in the way of its universal use. great opposition was experienced by those who imported it into the metropolis, and the increasing amount which was used by brewers and others about the year , caused serious complaints to be made, the effect of which was to induce parliament to obtain a proclamation from the king prohibiting its use, and empowering the justices to inflict a fine on those who persisted in burning it. the nuisance which coal has since proved itself, in the pollution of the atmosphere and in the denuding of wide tracts of country of all vegetation, was even thus early recognised, and had the efforts which were then made to stamp out its use, proved successful, those who live now in the great cities might never have become acquainted with that species of black winter fog which at times hangs like a pall over them, and transforms the brightness of day into a darkness little removed from that of night. at the same time, we must bear in mind that it is universally acknowledged that england owes her prosperity, and her pre-eminence in commerce, in great part, to her happy possession of wide and valuable coal-fields, and many authorities have not hesitated to say, that, in their opinion, the length of time during which england will continue to hold her prominent position as an industrial nation is limited by the time during which her coal will last. the attempt to prohibit the burning of coal was not, however, very successful, for in the reign of edward iii. a license was again granted to the freemen of newcastle to dig for coals. newcastle was thus the first town to become famous as the home of the coal-miner, and the fame which it early acquired, it has held unceasingly ever since. other attempts at prohibition of the article were made at various times subsequently, amongst them being one which was made in elizabeth's reign. it was supposed that the health of the country squires, who came to town to attend the session of parliament, suffered considerably during their sojourn in london, and, to remedy this serious state of affairs, the use of stone-coal during the time parliament was sitting was once more prohibited. coal was, however, by this time beginning to be recognised as a most valuable and useful article of fuel, and had taken a position in the industrial life of the country from which it was difficult to remove it. rather than attempt to have arrested the growing use of coal, parliament would have been better employed had it framed laws compelling the manufacturers and other large burners to consume their own smoke, and instead of aiming at total prohibition, have encouraged an intelligent and more economical use of it. in spite of all prohibition its use rapidly spread, and it was soon applied to the smelting of iron and to other purposes. iron had been largely produced in the south of england from strata of the wealden formation, during the existence of the great forest which at one time extended for miles throughout surrey and sussex. the discovery of coal, however, and the opening up of many mines in the north, gave an important impetus to the smelting of iron in those counties, and as the forests of the weald became exhausted, the iron trade gradually declined. furnace after furnace became extinguished, until in that at ashburnham, which had lingered on for some years, was compelled to bow to the inevitable fate which had overtaken the rest of the iron blast-furnaces. in referring to this subject, sir james picton says:--"ironstone of excellent quality is found in various parts of the county, and was very early made use of. even before the advent of the romans, the forest of dean in the west, and the forest of anderida, in sussex, in the east, were the two principal sources from which the metal was derived, and all through the mediaeval ages the manufacture was continued. after the discovery of the art of smelting and casting iron in the sixteenth century, the manufacture in sussex received a great impulse from the abundance of wood for fuel, and from that time down to the middle of the last century it continued to flourish. one of the largest furnaces was at lamberhurst, on the borders of kent, where the noble balustrade surrounding st paul's cathedral was cast at a cost of about £ , . it is stated by the historian holinshed that the first cast-iron ordnance was manufactured at buxted. two specialities in the iron trade belonged to sussex, the manufacture of chimney-backs, and cast-iron plates for grave-stones. at the time when wood constituted the fuel the backs of fire-places were frequently ornamented with neat designs. specimens, both of the chimney-backs and of the monuments, are occasionally met with. these articles were exported from rye. the iron manufacture, of course, met with considerable discouragement on the discovery of smelting with pit-coal, and the rapid progress of iron works in staffordshire and the north, but it lingered on until the great forest was cut down and the fuel exhausted." in his interesting work, "sylvia," published in , evelyn, in speaking of the noxious vapours poured out into the air by the increasing number of coal fires, writes, "this is that pernicious smoke which sullies all her glory, superinducing a sooty crust or furr upon all that it lights, spoiling movables, tarnishing the plate, gildings and furniture, and corroding the very iron bars and hardest stones with those piercing and acrimonious spirits which accompany its sulphur, and executing more in one year than the pure air of the country could effect in some hundreds." the evils here mentioned are those which have grown and have become intensified a hundred-fold during the two centuries and a half which have since elapsed. when the many efforts which were made to limit its use in the years prior to are remembered; at which time, we are informed, two ships only were engaged in bringing coal to london, it at once appears how paltry are the efforts made now to moderate these same baneful influences on our atmosphere, at a time when the annual consumption of coal in the united kingdom has reached the enormous total of millions of tons. the various smoke-abatement associations which have started into existence during the last few years are doing a little, although very little, towards directing popular attention to the subject; but there is an enormous task before them, that of awakening every individual to an appreciation of the personal interest which he has in their success, and to realise how much might at once be done if each were to do his share, minute though it might be, towards mitigating the evils of the present mode of coal-consumption. probably very few householders ever realise what important factories their chimneys constitute, in bringing about air pollution, and the more they do away with the use of bituminous coal for fuel, the nearer we shall be to the time when yellow fog will be a thing of the past. a large proportion of smoke consists of particles of pure unconsumed carbon, and this is accompanied in its passage up our chimneys by sulphurous acid, begotten by the sulphur which is contained in the coal to the amount of about eight pounds in every thousand; by sulphuretted hydrogen, by hydro-carbons, and by vapours of various kinds of oils, small quantities of ammonia, and other bodies not by any means contributing to a healthy condition of the atmosphere. a good deal of the heavier carbon is deposited along the walls of chimneys in the form of soot, together with a small percentage of sulphate of ammonia; this is as a consequence very generally used for manure. the remainder is poured out into the atmosphere, there to undergo fresh changes, and to become a fruitful cause of those thick black fogs with which town-dwellers are so familiar. sulphuretted hydrogen (h_{ }s) is a gas well known to students of chemistry as a most powerful reagent, its most characteristic external property being the extremely offensive odour which it possesses, and which bears a strong resemblance to that of rotten eggs or decomposing fish. it tarnishes silver work and picture frames very rapidly. on combustion it changes to sulphurous acid (so_{ }), and this in turn has the power of taking up from the air another atom of oxygen, forming sulphuric acid (so_{ } + water), or, as we more familiarly know it, oil of vitriol. yet the smoke itself, including as it does all the many impurities which exist in coal, is not only evil in itself, but is evil in its influences. dr siemens has said:--"it has been shown that the fine dust resulting from the imperfect combustion of coal was mainly instrumental in the formation of fog; each particle of solid matter attracting to itself aqueous vapour. these globules of fog were rendered particularly tenacious and disagreeable by the presence of tar vapour, another result of imperfect combustion of raw fuel, which might be turned to better account at the dyeworks. the hurtful influence of smoke upon public health, the great personal discomfort to which it gave rise, and the vast expense it indirectly caused through the destruction of our monuments, pictures, furniture, and apparel, were now being recognised." the most effectual remedy would result from a general recognition of the fact that wherever smoke was produced, fuel was being consumed wastefully, and that all our calorific effects, from the largest furnace to the domestic fire, could be realised as completely, and more economically, without allowing any of the fuel employed to reach the atmosphere unburnt. this most desirable result might be effected by the use of gas for all heating purposes, with or without the additional use of coke or anthracite. the success of the so-called smoke-consuming stoves is greatly open to question, whilst some of them have been reported upon by those appointed to inspect them as actually accentuating the incomplete combustion, the abolition of which they were invented to bring about. the smoke nuisance is one which cuts at the very basis of our business life. the cloud which, under certain atmospheric conditions, rests like a pall over our great cities, will not even permit at times of a single ray of sunshine permeating it. no one knows whence it rises, nor at what hour to expect it. it is like a giant spectre which, having lain dormant since the carboniferous age, has been raised into life and being at the call of restless humanity; it is now punishing us for our prodigal use of the wealth it left us, by clasping us in its deadly arms, cutting off our brilliant sunshine, and necessitating the use in the daytime of artificial light; inducing all kinds of bronchial and throat affections, corroding telegraph and telephone wires, and weathering away the masonry of public buildings. the immense value to us of the coal-deposits which lie buried in such profusion in the earth beneath us, can only be appreciated when we consider the many uses to which coal has been put. we must remember, as we watch the ever-extending railway ramifying the country in every direction, that the first railway and the first locomotive ever built, were those which were brought into being in by george stephenson, for the purpose of the carriage of coals from the killingworth colliery. to the importance of coal in our manufactures, therefore, we owe the subsequent development of steam locomotive power as the means of the introduction of passenger traffic, and by the use of coal we are enabled to travel from one end of the country to the other in a space of time inconceivably small as compared with that occupied on the same journey in the old coaching days. the increased rapidity with which our vessels cross the wide ocean we owe to the use of coal; our mines are carried to greater depths owing to the power our pumping-engines obtain from coal in clearing the mines of water and in ensuring ventilation; the enormous development of the iron trade only became possible with the increased blast power obtained from the consumption of coal, and the very hulls and engines of our steamships are made of this iron; our railroads and engines are mostly of iron, and when we think of the extensive use of iron utensils in every walk in life, we see how important becomes the power we possess of obtaining the necessary fuel to feed the smelting furnaces. evaporation by the sun was at one time the sole means of obtaining salt from seawater; now coal is used to boil the salt pans and to purify the brine from the salt-mines in the triassic strata of cheshire. the extent to which gas is used for illuminating purposes reminds us of another important product obtained from coal. paraffin oil and petroleum we obtain from coal, whilst candles, oils, dyes, lubricants, and many other useful articles go to attest the importance of the underground stores of that mineral which has well and deservedly been termed the "black diamond." chapter vi. how gas is made--illuminating oils and bye-products. accustomed as we are at the present day to see street after street of well-lighted thoroughfares, brilliantly illuminated by gas-lamps maintained by public authority, we can scarcely appreciate the fact that the use of gas is, comparatively speaking, of but recent growth, and that, like the use of coal itself, it has not yet existed a century in public favour. valuable as coal is in very many different ways, perhaps next in value to its actual use as fuel, ranks the use of the immediate product of its distillation--viz., gas; and although gas is in some respects waning before the march of the electric light in our day, yet, even as gas at no time has altogether superseded old-fashioned oil, so we need not anticipate a time when gas in turn will be likely to be superseded by the electric light, there being many uses to which the one may be put, to which the latter would be altogether inapplicable; for, in the words of dr siemens, assuming the cost of electric light to be practically the same as gas, the preference for one or other would in each application be decided upon grounds of relative convenience, but gas-lighting would hold its own as the poor man's friend. gas is an institution of the utmost value to the artisan; it requires hardly any attention, is supplied upon regulated terms, and gives, with what should be a cheerful light, a genial warmth, which often saves the lighting of a fire. the revolution which gas has made in the appearance of the streets, where formerly the only illumination was that provided by each householder, who, according to his means, hung out a more or less efficient lantern, and consequently a more or less smoky one, cannot fail also to have brought about a revolution in the social aspects of the streets, and therefore is worthy to be ranked as a social reforming agent; and some slight knowledge of the process of its manufacture, such as it is here proposed to give, should be in the possession of every educated individual. yet the subjects which must be dealt with in this chapter are so numerous and of such general interest, that we shall be unable to enter more than superficially into any one part of the whole, but shall strive to give a clear and comprehensive view, which shall satisfy the inquirer who is not a specialist. the credit of the first attempt at utilising the gaseous product of coal for illumination appears to be due to murdock, an engineer at redruth, who, in , introduced it into his house and offices, and who, ten years afterwards, as the result of numerous experiments which he made with a view to its utilisation, made a public display at birmingham on the occasion of the peace of amiens, in . more than a century before, however, the gas obtained from coal had been experimented upon by a dr clayton, who, about , conceived the idea of heating coal until its gaseous constituents were forced out of it. he described how he obtained steam first of all, then a black oil, and finally a "spirit," as our ancestors were wont to term the gas. this, to his surprise, ignited on a light being applied to it, and he considerably amused his friends with the wonders of this inflammatory spirit. for a century afterwards it remained in its early condition, a chemical wonder, a thing to be amused with; but it required the true genius and energy of murdock to show the great things of which it was capable. london received its first instalment of gas in , and during the next few years its use became more and more extended, houses and streets rapidly receiving supplies in quick succession. it was not, however, till about the year that its use throughout the country became at all general, st james' park being gas-lit in the succeeding year. this is not yet eighty years ago, and amongst the many wonderful things which have sprung up during the present century, perhaps we may place in the foremost rank for actual utility, the gas extracted from coal, conveyed as it is through miles upon miles of underground pipes into the very homes of the people, and constituting now almost as much a necessity of a comfortable existence as water itself. the use of gas thus rapidly extended for illuminating purposes, and to a very great extent superseded the old-fashioned means of illumination. [illustration: fig. .--inside a gas-holder.] the gas companies which sprang up were not slow to notice that, seeing the gas was supplied by meter, it was to their pecuniary advantage "to give merely the prescribed illuminating power, and to discourage the invention of economical burners, in order that the consumption might reach a maximum. the application of gas for heating purposes had not been encouraged, and was still made difficult in consequence of the objectionable practice of reducing the pressure in the mains during daytime to the lowest possible point consistent with prevention of atmospheric indraught." the introduction of an important rival into the field in the shape of the electric light has now given a powerful impetus to the invention and introduction of effective gas-lamps, and amongst inventors of recent years no name is, perhaps, in this respect so well known as the name of sugg. as long as gas retained almost the monopoly, there was no incentive to the gas companies to produce an effective light cheaply; but now that the question of the relative cheapness of gas and electricity is being actively discussed, the gas companies, true to the instinct of self-preservation, seem determined to show what can be done when gas is consumed in a scientific manner. in order to understand how best a burner should be constructed in order that the gas that is burnt should give the greatest possible amount of illumination, let us consider for a moment the composition of the gas flame. it consists of three parts, ( ) an interior dark space, in which the elements of the gas are in an unconsumed state; ( ) an inner ring around the former, whence the greatest amount of light is obtained, and in which are numerous particles of carbon at a white heat, each awaiting a supply of oxygen in order to bring about combustion; and ( ) an outer ring of blue flame in which complete combustion has taken place, and from which the largest amount of heat is evolved. the second of these portions of the flame corresponds with the "reducing" flame of the blow-pipe, since this part, if turned upon an oxide, will reduce it, i.e., abstract its oxygen from it. this part also corresponds with the jet of the bunsen burner, when the holes are closed by which otherwise air would mingle with the gas, or with the flame from a gas-stove when the gas ignites beneath the proper igniting-jets, and which gives consequently a white or yellow flame. the third portion, on the other hand, corresponds with the "oxidising" flame of the blow-pipe, since it gives up oxygen to bodies that are thirsting for it. this also corresponds with the ordinary blue flame of the bunsen burner, and with the blue flame of gas-stoves where heat, and not light, is required, the blue flame in both cases being caused by the admixture of air with the gas. thus, in order that gas may give the best illumination, we must increase the yellow or white space of carbon particles at a white heat, and a burner that will do this, and at the same time hold the balance so that unconsumed particles of carbon shall not escape in the way of smoke, will give the most successful illuminating results. with this end in view the addition of albo-carbon to a bulb in the gas-pipe has proved very successful, and the incandescent gas-jet is constructed on exactly the same chemical principle. the invention of burners which brought about this desirable end has doubtless not been without effect in acting as a powerful obstacle to the widespread introduction of the electric light. without entering into details of the manufacture of gas, it will be as well just to glance at the principal parts of the apparatus used. the gasometer, as it has erroneously been called, is a familiar object to most people, not only to sight but unfortunately also to the organs of smell. it is in reality of course only the gas-holder, in which the final product of distillation of the coal is stored, and from which the gas immediately passes into the distributing mains. the first, and perhaps, most important portion of the apparatus used in gas-making is the series of _retorts_ into which the coal is placed, and from which, by the application of heat, the various volatile products distil over. these retorts are huge cast-iron vessels, encased in strong brick-work, usually five in a group, and beneath which a large furnace is kept going until the process is complete. each retort has an iron exit pipe affixed to it, through which the gases generated by the furnace are carried off. the exit pipes all empty themselves into what is known as the _hydraulic main_, a long horizontal cylinder, and in this the gas begins to deposit a portion of its impurities. the immediate products of distillation are, after steam and air, gas, tar, ammoniacal liquor, sulphur in various forms, and coke, the last being left behind in the retort. in the hydraulic main some of the tar and ammoniacal liquor already begin to be deposited. the gas passes on to the _condenser_, which consists of a number of u-shaped pipes. here the impurities are still further condensed out, and are collected in the _tar-pit_ whilst the gas proceeds, still further lightened of its impurities. it may be mentioned that the temperature of the gas in the condenser is reduced to about ° f., but below this some of the most valuable of the illuminants of coal-gas would commence to be deposited in liquid form, and care has to be taken to prevent a greater lowering of temperature. a mechanical contrivance known as the _exhauster_ is next used, by which the gas is, amongst other things, helped forward in its onward movement through the apparatus. the gas then passes to the _washers_ or _scrubbers_, a series of tall towers, from which water is allowed to fall as a fine spray, and by means of which large quantities of ammonia, sulphuretted hydrogen, carbonic acid and oxide, and cyanogen compounds, are removed. in the scrubber the water used in keeping the coke, with which it is filled, damp, absorbs these compounds, and the union of the ammonia with certain of them takes place, resulting in the formation of carbonate of ammonia (smelling salts), sulphide and sulphocyanide of ammonia. [illustration: fig. .--filling retorts by machinery.] [illustration: fig. .--condensers.] hitherto the purification of the gas has been brought about by mechanical means, but the gas now enters the "_purifier_," in which it undergoes a further cleansing, but this time by chemical means. [illustration: fig. .] the agent used is either lime or hydrated oxide of iron, and by their means the gas is robbed of its carbonic acid and the greater part of its sulphur compounds. the process is then considered complete, and the gas passes on into the water chamber over which the gas-holder is reared, and in which it rises through the water, forcing the huge cylinder upward according to the pressure it exerts. the gas-holder is poised between a number of upright pillars by a series of chains and pulleys, which allow of its easy ascent or descent according as the supply is greater or less than that drawn from it by the gas mains. [illustration: fig. .] when we see the process which is necessary in order to obtain pure gas, we begin to appreciate to what an extent the atmosphere is fouled when many of the products of distillation, which, as far as the production of gas is concerned, may be called impurities, are allowed to escape free without let or hindrance. in these days of strict sanitary inspection it seems strange that the air in the neighbourhood of gas-works is still allowed to become contaminated by the escape of impure compounds from the various portions of the gas-making apparatus. go where one may, the presence of these compounds is at once apparent to the nostrils within a none too limited area around them, and yet their deleterious effects can be almost reduced to a minimum by the use of proper purifying agents, and by a scientific oversight of the whole apparatus. it certainly behoves all sanitary authorities to look well after any gas-works situated within their districts. now let us see what these first five products of distillation actually are. firstly, house-gas. everybody knows what house-gas is. it cannot, however, be stated to be any one gas in particular, since it is a mechanical mixture of at least three different gases, and often contains small quantities of others. a very large proportion consists of what is known as marsh-gas, or light carburetted hydrogen. this occurs occluded or locked up in the pores of the coal, and often oozes out into the galleries of coal-mines, where it is known as firedamp (german _dampf_, vapour). it is disengaged wherever vegetable matter has fallen and has become decayed. if it were thence collected, together with an admixture of ten times its volume of air, a miniature coal-mine explosion could be produced by the introduction of a match into the mixture. alone, however, it burns with a feebly luminous flame, although to its presence our house-gas owes a great portion of its heating power. marsh-gas is the first of the series of hydro-carbons known chemically as the _paraffins_, and is an extremely light substance, being little more than half the weight of an equal bulk of air. it is composed of four atoms of hydrogen to one of carbon (ch_{ }). marsh-gas, together with hydrogen and the monoxide of carbon, the last of which burns with the dull blue flame often seen at the surface of fires, particularly coke and charcoal fires, form about per cent. of the whole volume of house-gas, and are none of them anything but poor illuminants. the illuminating power of house-gas depends on the presence therein of olefiant gas (_ethylene_), or, as it is sometimes termed, heavy carburetted hydrogen. this is the first of the series of hydro-carbons known as the _olefines_, and is composed of two atoms of carbon to every four atoms of hydrogen (c_{ }h_{ }). others of the olefines are present in minute quantities. these assist in increasing the illuminosity, which is sometimes greatly enhanced, too, by the presence of a small quantity of benzene vapour. these illuminants, however, constitute but about per cent. of the whole. added to these, there are four other usual constituents which in no way increase the value of gas, but which rather detract from it. they are consequently as far as possible removed as impurities in the process of gas-making. these are nitrogen, carbonic acid gas, and the destructive sulphur compounds, sulphuretted hydrogen and carbon bisulphide vapour. it is to the last two to which are to be attributed the injurious effects which the burning of gas has upon pictures, books, and also the tarnishing which metal fittings suffer where gas is burnt, since they give rise to the formation of oil of vitriol (sulphuric acid), which is being incessantly poured into the air. of course the amount so given off is little as compared with that which escapes from a coal fire, but, fortunately for the inmates of the room, in this case the greater quantity goes up the chimney; this, however, is but a method of postponing the evil day, until the atmosphere becomes so laden with impurities that what proceeds at first up the chimney will finally again make its way back through the doors and windows. a recent official report tells us that, in the town, of st helen's alone, sufficient sulphur escapes annually into the atmosphere to finally produce , tons of sulphuric acid, and a computation has been made that every square mile of land in london is deluged annually with tons of the same vegetation-denuding acid. it is a matter for wonder that any green thing continues to exist in such places at all. the chief constituents of coal-gas are, therefore, briefly as follows:-- / ( ) hydrogen, | ( ) marsh-gas (carburetted hydrogen or fire-damp), | ( ) carbon monoxide, | ( ) olefiant gas (ethylene, or heavy carburetted hydrogen), with \ other olefines, / ( ) nitrogen, | ( ) carbonic acid gas, | ( ) sulphuretted hydrogen, \ ( ) carbon bisulphide (vapour), the last four being regarded as impurities, which are removed as far as possible in the manufacture. in the process of distillation of the coal, we have seen that various other important substances are brought into existence. the final residue of coke, which is impregnated with the sulphur which has not been volatilised in the form of sulphurous gases, we need scarcely more than mention here. but the gas-tar and the ammoniacal liquor are two important products which demand something more than our casual attention. at one time regarded by gas engineers as unfortunately necessary nuisances in the manufacture of gas, they have both become so valuable on account of materials which can be obtained from them, that they enable gas itself to be sold now at less than half its original price. the waste of former generations is being utilised in this, and an instance is recorded in which tar, which was known to have been lying useless at the bottom of a canal for years, has been purchased by a gas engineer for distilling purposes. it has been estimated that about , tons of coal-tar are distilled annually. tar in its primitive condition has been used, as every one is aware, for painting or tarring a variety of objects, such as barges and palings, in fact, as a kind of protection to the object covered from the ravages of insects or worms, or to prevent corrosion when applied to metal piers. but it is worthy of a better purpose, and is capable of yielding far more useful and interesting substances than even the most imaginative individual could have dreamed of fifty years ago. in the process of distillation, the tar, after standing in tanks for some time, in order that any ammoniacal liquor which may be present may rise to the surface and be drawn off, is pumped into large stills, where a moderate amount of heat is applied to it. the result is that some of the more volatile products pass over and are collected in a receiver. these first products are known as _first light oils_, or _crude coal-naphtha_, and to this naphtha all the numerous natural naphthas which have been discovered in various portions of the world, and to which have been applied numerous local names, bear a very close resemblance. such an one, for instance, was that small but famous spring at biddings, in derbyshire, from which the late mr young--paraffin young--obtained his well-known paraffin oil, which gave the initial impetus to what has since developed into a trade of immense proportions in every quarter of the globe. after a time the crude coal-naphtha ceases to flow over, and the heat is increased. the result is that a fresh series of products, known as _medium oils_, passes over, and these oils are again collected and kept separate from the previous series. these in turn cease to flow, when, by a further increase of heat, what are known as the _heavy oils_ finally pass over, and when the last of these, _green grease_, as it is called, distils over, pitch alone is left in the still. pitch is used to a large extent in the preparation of artificial asphalte, and also of a fuel known as "briquettes." the products thus obtained at the various stages of the process are themselves subjected to further distillation, and by the exercise of great care, requiring the most delicate and accurate treatment, a large variety of oils is obtained, and these are retailed under many and various fanciful names. one of the most important and best known products of the fractional distillation of crude coal-naphtha is that known as _benzene_, or benzole, (c_{ }h_{ }). this, in its unrefined condition, is a light spirit which distils over at a point somewhat below the boiling point of water, but a delicate process of rectification is necessary to produce the pure spirit. other products of the same light oils are toluene and xylene. benzene of a certain quality is of course a very familiar and useful household supplement. it is sometimes known and sold as _benzene collas_, and is used for removing grease from clothing, cleaning kid gloves, &c. if pure it is in reality a most dangerous spirit, being very inflammable; it is also extremely volatile, so much so that, if an uncorked bottle be left in a warm room where there is a fire or other light near, its vapour will probably ignite. should the vapour become mixed with air before ignition, it becomes a most dangerous explosive, and it will thus be seen how necessary it is to handle the article in household use in a most cautious manner. being highly volatile, a considerable degree of cold is experienced if a drop be placed on the hand and allowed to evaporate. benzene, which is only a compound of carbon and hydrogen, was first discovered by faraday in ; it is now obtained in large quantities from coal-tar, not so much for use as benzene; is for its conversion, in the first place, by the action of nitric acid, into _nitro-benzole,_ a liquid having an odour like the oil of bitter almonds, and which is much used by perfumers under the name of _essence de mirbane_; and, in the second place, for the production from this nitro-benzole of the far-famed _aniline_. after the distillation of benzene from the crude coal-naphtha is completed, the chief impurities in the residue are charred and deposited by the action of strong sulphuric acid. by further distillation a lighter oil is given off, often known as _artificial turpentine oil_, which is used as a solvent for varnishes and lackers. this is very familiar to the costermonger fraternity as the oil which is burned in the flaring lamps which illuminate the new cut or the elephant and castle on saturday and other market nights. by distillation of the _heavy oils_, carbolic acid and commercial _anthracene_ are produced, and by a treatment of the residue, a white and crystalline substance known as _naphthalin_ (c_{ }h_{ }) is finally obtained. thus, by the continued operation of the chemical process known as fractional distillation of the immediate products of coal-tar, these various series of useful oils are prepared. the treatment is much the same which has resulted in the production of paraffin oil, to which we have previously referred, and an account of the production of coal-oils would be very far from satisfactory, which made no mention of the production of similar commodities by the direct distillation of shale. oil-shales, or bituminous shales, exist in all parts of the world, and may be regarded as mineral matter largely impregnated by the products of decaying vegetation. they therefore greatly resemble some coals, and really only differ therefrom in degree, in the quantity of vegetable matter which they contain. into the subject of the various native petroleums which have been found--for these rock-oils are better known as petroleums--in south america, in burmah (rangoon oil), at baku, and the shores of the caspian, or in the united states of america, we need not enter, except to note that in all probability the action of heat on underground bituminous strata of enormous extent has been the cause of their production, just as on a smaller scale the action of artificial heat has forced the reluctant shale to give up its own burden of mineral oil. however, previous to , although native mineral oil had been for some years a recognised article of commerce, the causes which gave rise to the oil-wells, and the source, probably a deep-seated one, of the supply of oil, does not appear to have been well known, or at least was not enquired after. but in that year mr young, a chemist at manchester, discovered that by distilling some petroleum, which he obtained from a spring at riddings in derbyshire, he was able to procure a light oil, which he used for burning in lamps, whilst the heavier product which he also obtained proved a most useful lubricant for machinery. this naturally distilled oil was soon found to be similar to that oil which was noticed dripping from the roof of a coal-mine. judging that the coal, being under the influence of heat, was the cause of the production of the oil, mr young tested this conclusion by distilling the coal itself. success attended his endeavour thus to procure the oil, and indelibly young stamped his name upon the roll of famous men, whose industrial inventions have done so much towards the accomplishment of the marvellous progress of the present century. from the distillation he obtained the well-known young's paraffin oil, and the astonishing developments of the process which have taken place since he obtained his patent in , for the manufacture of oils and solid paraffin, must have been a source of great satisfaction to him before his death, which occurred in . cannel coal, boghead or bathgate coal, and bituminous shales of various qualities, have all been requisitioned for the production of oils, and from these various sources the crude naphthas, which bear a variety of names according to some peculiarity in their origin, or place of occurrence, are obtained. boghead coal, also known as "torebanehill mineral," gives boghead naphtha, while the crude naphtha obtained from shales is often quoted as shale-oil. in chemical composition these naphthas are closely related to one another, and by fractional distillation of them similar series of products are obtained as those we have already seen as obtained from the crude coal-naphtha of coal-tar. in the direct distillation of cannel-coal for the production of paraffin, it is necessary that the perpendicular tubes or retorts into which the coal is placed be heated only to a certain temperature, which is considerably lower than that applied when the object is the production of coal-gas. by this means nearly all the volatile matters pass over in the form of condensible vapours, and the crude oils are at once formed, from whence are obtained at different temperatures various volatile ethers, benzene, and artificial turpentine oil or petroleum spirit. after these, the well-known safety-burning paraffin oil follows, but it is essential that the previous three volatile products be completely cleared first, since, mixed with air, they form highly dangerous explosives. to the fact that the operation is carried on in the manufactories with great care and accuracy can only be attributed the comparative rareness of explosions of the oil used in households. after paraffin, the heavy lubricating oils are next given off, still increasing the temperature, and, the residue being in turn subjected to a very low temperature, the white solid substance known as paraffin, so much used for making candles, is the result. by a different treatment of the same residue is produced that wonderful salve for tender skins, cuts, and burns, known popularly as _vaseline_. probably no such widely-advertised remedial substance has so deserved its success as this universally-used waste product of petroleum. we have noticed the fact that in order to procure safety-burning oils, it is absolutely necessary that the more volatile portions be completely distilled over first. by act of parliament a test is applied to all oils which are intended for purposes of illumination, and the test used consists of what is known as the flashing-point. many of the more volatile ethers, which are highly inflammable, are given off even at ordinary temperatures, and the application of a light to the oil will cause the volatile portion to "flash," as it is called. a safety-burning oil, according to the act, must not flash under ° fahrenheit open test, and all those portions which flash at a less temperature must be volatilised off before the residue can be deemed a safe oil. it seems probable that the flashing-point will sooner or later be raised. one instance may be cited to show how necessary it is that the native mineral oils which have been discovered should have this effectual test applied to them. when the oil-wells were first discovered in america, the oil was obtained simply by a process of boring, and the fountain of oil which was bored into at times was so prolific, that it rushed out with a force which carried all obstacles before it, and defied all control. in one instance a column of oil shot into the air to a height of forty feet, and defied all attempts to keep it under. in order to prevent further accident, all lights in the immediate neighbourhood were extinguished, the nearest remaining being at a distance of four hundred feet. but in this crude naphtha there was, as usual, a quantity of volatile spirit which was being given off even at the temperature of the surrounding atmosphere. this soon became ignited, and with an explosion the column of oil was suddenly converted into a roaring column of fire. the owner of the property was thrown a distance of twenty feet by the explosion, and soon afterwards died from the burns which he had received from it. such an accident could not now, however, happen. the tapping, stopping, and regulating of gushing wells can now be more effectually dealt with, and in the process of refining; the most inflammable portions are separated, with a result that, as no oil is used in the country which flashes under ° f. open test, and as our normal temperature is considerably less than this, there is little to be feared in the way of explosion if the act be complied with. when the results of mr young's labours became publicly known, a number of companies were started with the object of working on the lines laid down in his patent, and these not only in great britain but also in the united states, whither quantities of cannel coal were shipped from england and other parts to feed the retorts. in , according to the statistics furnished, some seventy factories were established in the united states alone with the object of extracting oil from coal and other mineral sources, such as bituminous shale, etc. when young's patent finally expired, a still greater impetus was given to its production, and the manufacture would probably have continued to develop were it not that attention had, two years previously, been forcibly turned to those discoveries of great stores of natural oil in existence beneath a comparatively thin crust of earth, and which, when bored into, spouted out to tremendous heights. the discovery of these oil-fountains checked for a time the development of the industry, but with the great production there has apparently been a greatly increased demand for it, and the british industry once again appears to thrive, until even bituminous shales have been brought under requisition for their contribution to the national wealth. were it not for the nuisance and difficulty experienced in the proper cleaning and trimming of lamps, there seems no other reason why mineral oil should not in turn have superseded the use of gas, even as gas had, years before, superseded the expensive animal and vegetable oils which had formerly been in use. although this great development in the use of mineral oils has taken place only within the last thirty years, it must not be thought that their use is altogether of modern invention. that they were not altogether unknown in the fifth century before christ is a matter of certainty, and at the time when the persian empire was at the zenith of its glory, the fires in the temples of the fire-worshippers were undoubtedly kept fed by the natural petroleum which the districts around afforded. it is thought by some that the legend which speaks of the fire which came down from heaven, and which lit the altars of the zoroastrians, may have had its origin in the discovery of a hitherto unknown petroleum spring. more recently, the remarks of marco polo in his account of his travels in a.d. and following years, are particularly interesting as showing that, even then, the use of mineral oil for various purposes was not altogether unknown. he says that on the north of armenia the greater is "zorzania, in the confines of which a fountain is found, from which a liquor like oil flows, and though unprofitable for the seasoning of meat, yet is very fit for the supplying of lamps, and to anoint other things; and this natural oil flows constantly, and that in plenty enough to lade camels." from this we can infer that the nature of the oil was entirely unknown, for it was a "liquor like oil," and was also, strange to say, "unprofitable for the seasoning of meat"! in another place in armenia, marco polo states that there was a fountain "whence rises oil in such abundance that a hundred ships might be at once loaded with it. it is not good for eating, but very fit for fuel, for anointing the camels in maladies of the skin, and for other purposes; for which reason people come from a great distance for it, and nothing else is burned in all this country." the remedial effects of the oil, when used as an ointment, were thus early recognised, and the far-famed vaseline of the present day may be regarded as the lineal descendent, so to speak, of the crude medicinal agent to which marco polo refers. the term asphalt has been applied to so many and various mixtures, that one scarcely associates it with natural mineral pitch which is found in some parts of the world. from time immemorial this compact, bituminous, resinous mineral has been discovered in masses on the shores of the dead sea, which has in consequence received the well-known title of lake asphaltites. like the naphthas and petroleums which have been noticed, this has had its origin in the decomposition of vegetable matter, and appears to be thrown up in a liquid form by the volcanic energies which, are still believed to be active in the centre of the lake, and which may be existent beneath a stratum, or bed, of oil-producing bitumen. in connection with the formation of this substance, the remarks of sir charles lyell, the great geologist, may well be quoted, as showing the transformation of vegetable matter into petroleum, and afterwards into solid-looking asphalt. at trinidad is a lake of bitumen which is a mile and a half in circumference. "the orinoco has for ages been rolling down great quantities of woody and vegetable bodies into the surrounding sea, where, by the influence of currents and eddies, they may be arrested, and accumulated in particular places. the frequent occurrence of earthquakes and other indications of volcanic action in those parts, lend countenance to the opinion that these vegetable substances may have undergone, by the agency of subterranean fire, those transformations or chemical changes which produce petroleum; and this may, by the same causes, be forced up to the surface, where, by exposure to the air, it becomes inspissated, and forms those different varieties of earth-pitch or asphaltum so abundant in the island." it is interesting to note also that it was obtained, at an ancient period, from the oil-fountains of is, and that it was put to considerable use in the embalming of the bodies of the egyptians. it appears, too, to have been employed in the construction of the walls of babylon, and thus from very early times these wonderful products and results of decayed vegetation have been brought into use for the service of man. aniline has been previously referred (p. ) to as having been prepared from nitro-benzole, or _essence de mirbane_, and its preparation, by treating this substance with iron-filings and acetic acid, was one of the early triumphs of the chemists who undertook the search after the unknown contained in gas-tar. it had previously been obtained from oils distilled from bones. the importance of the substance lies in the fact that, by the action of various chemical reagents, a series of colouring matters of very great richness are formed, and these are the well-known _aniline dyes_. as early as , it was discovered that aniline, when heated with chloride of lime, acquired a beautiful blue tint. this discovery led to no immediate practical result, and it was not until twenty-one years after that a further discovery was made, which may indeed be said to have achieved a world-wide reputation. it was found that, by adding bichromate of potash to a solution of aniline and sulphuric acid, a powder was obtained from which the dye was afterwards extracted, which is known as _mauve_. since that time dyes in all shades and colours have been obtained from the same source. _magenta_ was the next dye to make its appearance, and in the fickle history of fashion, probably no colours have had such extraordinary runs of popularity as those of mauve and magenta. every conceivable colour was obtained in due course from the same source, and chemists began to suspect that, in the course of time, the colouring matter of dyer's madder, which was known as _alizarin_, would also be obtained therefrom. hitherto this had been obtained from the root of the madder-plant, but by dint of careful and well-reasoned research, it was obtained by dr groebe, from a solid crystalline coal-tar product, known as _anthracene_, (c_{ }h_{ }). this artificial alizarin yields colours which are purer than those of natural madder, and being derived from what was originally regarded as a waste product, its cost of production is considerably cheaper. we have endeavoured thus far to deal with ( ) gas, and ( ) tar, the two principal products in the distillation of coal. we have yet to say a few words concerning the useful ammoniacal liquor, and the final residue in the retorts, _i.e._, coke. the ammoniacal liquor which has been passing over during distillation of the coal, and which has been collecting in the hydraulic main and in other parts of the gas-making apparatus, is set aside to be treated to a variety of chemical reactions, in order to wrench from it its useful constituents. amongst these, of course, _ammonia_ stands in the first rank, the others being comparatively unimportant. in order to obtain this, the liquor is first of all neutralised by being treated with a quantity of acid, which converts the principal constituent of the liquor, viz., carbonate of ammonia (smelling salts), into either sulphate of ammonia, or chloride of ammonia, familiarly known as sal-ammoniac, according as sulphuric acid or hydrochloric acid is the acid used. thus carbonate of ammonia with sulphuric acid will give sulphate of ammonia, but carbonate of ammonia with hydrochloric acid will give sal-ammoniac (chloride of ammonia). by a further treatment of these with lime, or, as it is chemically known, oxide of calcium, ammonia is set free, whilst chloride of lime (the well-known disinfectant), or sulphate of lime (gypsum, or "plaster of paris" ), is the result. thus: sulphate of ammonia + lime = plaster of paris + ammonia. or, sal-ammoniac + lime = chloride of lime + ammonia. ammonia itself is a most powerful gas, and acts rapidly upon the eyes. it has a stimulating effect upon the nerves. it is not a chemical element, being composed of three parts of hydrogen by weight to one of nitrogen, both of which elements alone are very harmless, and, the latter indeed, very necessary to human life. ammonia is fatal to life, producing great irritation of the lungs. it has also been called "hartshorn," being obtained by destructive distillation of horn and bone. the name "ammonia" is said to have been derived from the fact that it was first obtained by the arabs near the temple of jupiter ammon, in lybia, north africa, from the excrement of camels, in the form of sal-ammoniac. there are always traces of it in the atmosphere, especially in the vicinity of large towns and manufactories where large quantities of coal are burned. coke, if properly prepared, should consist of pure carbon. good coal should yield as much as per cent. of coke, but owing to the unsatisfactory manner of its production, this proportion is seldom yielded, whilst the coke which is familiar to householders, being the residue left in the retorts after gas-making, usually contains so large a proportion of sulphur as to make its combustion almost offensive. no doubt the result of its unsatisfactory preparation has been that it has failed to make its way into households as it should have done, but there is also another objection to its use, namely, the fact that, owing to the quantity of oxygen required in its combustion, it gives rise to feelings of suffocation where insufficient ventilation of the room is provided. large quantities of coke are, however, consumed in the feeding of furnace fires, and in the heating of boilers of locomotives, as well as in metallurgical operations; and in order to supply the demand, large quantities of coal are "coked," a process by which the volatile products are completely combusted, pure coke remaining behind. this process is therefore the direct opposite to that of "distillation," by which the volatile products are carefully collected and re-distilled. the sulphurous impurities which are always present in the coal, and which are, to a certain extent, retained in coke made at the gas-works, themselves have a value, which in these utilitarian days is not long likely to escape the attention of capitalists. in coal, bands of bright shining iron pyrites are constantly seen, even in the homely scuttle, and when coal is washed, as it is in some places, the removal of the pyrites increases the value of the coal, whilst it has a value of its own. the conversion of the sulphur which escapes from our chimneys into sulphuretted hydrogen, and then into sulphuric acid, or oil of vitriol, has already been referred to, and we can only hope that in these days when every available source of wealth is being looked up, and when there threatens to remain nothing which shall in the future be known as "waste," that the atmosphere will be spared being longer the receptacle for the unowned and execrated brimstone of millions of fires and furnaces. chapter vii. the coal supplies of the world. as compared with some of the american coal-fields, those of britain are but small, both in extent and thickness. they can be regarded as falling naturally into three principal areas. the northern coal-field, including those of fife, stirling, and ayr in scotland; cumberland, newcastle, and durham in england; tyrone in ireland. the middle coal-field, all geologically in union, including those of yorkshire, derbyshire, shropshire, staffordshire, flint, and denbigh. the southern coal-field, including south wales, forest of dean, bristol, dover, with an offshoot at leinster, &c., and millstreet, cork. thus it will be seen that while england and scotland are, in comparison with their extent of surface, bountifully supplied with coal-areas, in the sister island of ireland coal-producing areas are almost absent. the isolated beds in cork and tipperary, in tyrone and antrim, are but the remnants left of what were formerly beds of coal extending the whole breadth and length of ireland. such beds as there remain undoubtedly belong to the base of the coal-measures, and observations all go to show that the surface suffered such extreme denudation subsequent to the growth of the coal-forests, that the wealth which once lay there, has been swept away from the surface which formerly boasted of it. on the continent of europe the coal-fields, though not occupying so large a proportion of the surface of the country as in england, are very far from being slight or to be disregarded. the extent of forest-lands still remaining in germany and austria are sufficing for the immediate needs of the districts where some of the best seams occur. it is only where there is a dearth of handy fuel, ready to be had, perhaps, by the simple felling of a few trees, that man commences to dig into the earth for his fuel. but although on the continent not yet occupying so prominent a position in public estimation as do coal-fields in great britain, those of the former have one conspicuous characteristic, viz., the great thickness of some of the individual seams. in the coal-field of midlothian the seams of coal vary from feet to feet in thickness. one of them is known as the "great seam," and in spite of its name attains a thickness only of from to feet thick. there are altogether about thirty seams of coal. when, however, we pass to the continent, we find many instances, such as that of the coal-field of central france, in which the seams attain vast thicknesses, many of them actually reaching and feet, and sometimes even feet. one of the seams in the district of st. etienne varies from to feet thick, whilst the fifteen to eighteen workable seams give a thickness of feet, although the total area of the field is not great. again, in the remarkable basin of the saône-et-loire, although there are but ten beds of coal, two of them run from to feet each, whilst at creusot the main seam actually runs locally to a thickness varying between and feet. the belgian coal-field stretches in the form of a narrow strip from to miles wide by about miles long, and is divided into three principal basins. in that stretching from liége to verviers there are eighty-three seams of coal, none of which are less than feet thick. in the basin of the sambre, stretching from namur to charleroi, there are seventy-three seams which are workable, whilst in that between mons and thulin there are no less than one hundred and fifty-seven seams. the measures here are so folded in zigzag fashion, that in boring in the neighbourhood of mons to a depth of yards vertical, a single seam was passed through no less than six times. germany, on the west side of the rhine, is exceptionally fortunate in the possession of the famous pfalz-saarbrücken coal-field, measuring about miles long by miles wide, and covering about square miles. much of the coal which lies deep in these coal-measures will always remain unattainable, owing to the enormous thickness of the strata, but a careful computation made of the coal which can be worked, gives an estimate of no less than millions of tons. there is a grand total of two hundred and forty-four seams, although about half of them are unworkable. beside other smaller coal-producing areas in germany, the coal-fields of silesia in the southeastern corner of prussia are a possession unrivalled both on account of their extent and thickness. it is stated that there exist feet of coal, all the seams of which exceed - / feet, and that in the aggregate there is here, within a workable depth, the scarcely conceivable quantity of , million tons of coal. the coal-field of upper silesia, occupying an area about miles long by miles broad, is estimated to contain some , feet of strata, with feet of good coal. this is about three times the thickness contained in the south wales coal-field, in a similar thickness of coal-measures. there are single seams up to feet thick, but much of the coal is covered by more recent rocks of new red and cretaceous age. in lower silesia there are numerous seams - / feet to feet thick, but owing to their liability to change in character even in the same seam, their value is inferior to the coals of upper silesia. when british supplies are at length exhausted, we may anticipate that some of the earliest coals to be imported, should coal then be needed, will reach britain from the upper waters of the oder. the coal-field of westphalia has lately come into prominence in connection with the search which has been made for coal in kent and surrey, the strata which are mined at dortmund being thought to be continuous from the bristol coal-field. borings have been made through the chalk of the district north of the westphalian coal-field, and these have shown the existence of further coal-measures. the coal-field extends between essen and dortmund a distance of miles east and west, and exhibits a series of about one hundred and thirty seams, with an aggregate of feet of coal. it is estimated that this coal-field alone contains no less than , millions of tons of coal. russia possesses supplies of coal whose influence has scarcely yet been felt, owing to the sparseness of the population and the abundance of forest. carboniferous rocks abut against the flanks of the ural mountains, along the sides of which they extend for a length of about a thousand miles, with inter-stratifications of coal. their actual contents have not yet been gauged, but there is every reason to believe that those coal-beds which have been seen are but samples of many others which will, when properly worked, satisfy the needs of a much larger population than the country now possesses. like the lower coals of scotland, the russian coals are found in the carboniferous limestone. this may also be said of the coal-fields in the governments of tula and kaluga, and of those important coal-bearing strata near the river donetz, stretching to the northern corner of the sea of azov. in the last-named, the seams are spread over an area of , square miles, in which there are forty-four workable seams containing feet of coal. the thickest of known russian coals occur at lithwinsk, where three seams are worked, each measuring feet to feet thick. an extension of the upper silesian coal-field appears in russian poland. this is of upper carboniferous age, and contains an aggregate of feet of coal. at ostrau, in upper silesia (austria), there is a remarkable coal-field. of its seams there are no less than workable ones, and these contain feet of coal. the coals here are very full of gas, which even percolates to the cellars of houses in the town. a bore hole which was sunk in to a depth of feet, gave off a stream of gas, which ignited, and burnt for many years with a flame some feet long. the zwickau coal-field in saxony is one of the most important in europe. it contains a remarkable seam of coal, known as russokohle or soot-coal, running at times feet thick. it was separated by geinitz and others into four zones, according to their vegetable contents, viz.:-- . zone of ferns. . zone of annularia and calamites. . zone of sigillaria. . zone of sagenaria (in silesia), equivalent to the culm-measures of devonshire. coals belonging to other than true carboniferous age are found in europe at steyerdorf on the danube, where there are a few seams of good coal in strata of liassic age, and in hungary and styria, where there are tertiary coals which approach closely to those of true carboniferous age in composition and quality. in spain there are a few small scattered basins. coal is found overlying the carboniferous limestone of the cantabrian chain, the seams being from feet to feet thick. in the satero valley, near sotillo, is a single seam measuring from feet to feet thick. coal of neocomian age appears at montalban. when we look outside the continent of europe, we may well be astonished at the bountiful manner in which nature has laid out beds of coal upon these ancient surfaces of our globe. professor rogers estimated that, in the united states of america, the coal-fields occupy an area of no less than , square miles. here, again, it is extremely probable that the coal-fields which remain, in spite of their gigantic existing areas, are but the remnants of one tremendous area of deposit, bounded only on the east by the atlantic, and on the west by a line running from the great lakes to the frontiers of mexico. the whole area has been subjected to forces which have produced foldings and flexures in the carboniferous strata after deposition. these undulations are greatest near the alleghanies, and between these mountains and the atlantic, whilst the flexures gradually dying out westward, cause the strata there to remain fairly horizontal. in the troughs of the foldings thus formed the coal-measures rest, those portions which had been thrown up as anticlines having suffered loss by denudation. where the foldings are greatest there the coal has been naturally most altered; bituminous and caking-coals are characteristic of the broad flat areas west of the mountains, whilst, where the contortions are greatest, the coal becomes a pure anthracite. it must not be thought that in this huge area the coal is all uniformly good. it varies greatly in quality, and in some districts it occurs in such thin seams as to be worthless, except as fuel for consumption by the actual coal-getters. there are, too, areas of many square miles in extent, where there are now no coals at all, the formation having been denuded right down to the palaeozoic back-bone of the country. amongst the actual coal-fields, that of pennsylvania stands pre-eminent. the anthracite here is in inexhaustible quantity, its output exceeding that of the ordinary bituminous coal. the great field of which this is a portion, extends in an unbroken length for miles n.e. and s.w., and includes the basins of ohio, maryland, virginia, kentucky, and tennessee. the workable seams of anthracite about pottsville measure in the aggregate from to feet. some of the lower seams individually attain an exceptional thickness, that at lehigh summit mine containing a seam, or rather a bed, of feet of good coal. a remarkable seam of coal has given the town of pittsburg its name. this is feet thick at its outcrop near the town, and although its thickness varies considerably, professor rogers estimates that the sheet of coal measures superficially about , square miles. what a forest there must have existed to produce so widespread a bed! even as it is, it has at a former epoch suffered great denudation, if certain detached basins should be considered as indicating its former extent. the principal seam in the anthracite district of central pennsylvania, which extends for about miles along the left bank of the susquehanna, is known as the "mammoth" vein, and is - / feet thick at wilkesbarre, whilst at other places it attains to, and even exceeds, feet. on the west of the chain of mountains the foldings become gentler, and the coal assumes an almost horizontal position. in passing through ohio we find a saddle-back ridge or anticline of more ancient strata than the coal, and in consequence of this, we have a physical boundary placed upon the coal-fields on each side. passing across this older ridge of denuded silurian and other rocks, we reach the famous illinois and indiana coal-field, whose coal-measures lie in a broad trough, bounded on the west by the uprising of the carboniferous limestone of the upper mississippi. this limestone formation appears here for the first time, having been absent on the eastern side of the ohio anticline. the area of the coal-field is estimated at , square miles. in connection with the coal-fields of the united states, it is interesting to notice that a wide area in texas, estimated at square miles, produces a large amount of coal annually from strata of the liassic age. another important area of production in eastern virginia contains coal referable to the jurassic age, and is similar in fossil contents to the jurassic of whitby and brora. the main seam in eastern virginia boasts a thickness of from to feet of good coal. very serviceable lignites of cretaceous age are found on the pacific slope, to which age those of vancouver's island and saskatchewan river are referable. other coal-fields of less importance are found between lakes huron and erie, where the measures cover an area of square miles, and also in rhode island. in british north america we find extensive deposits of valuable coal-measures. large developments occur in new brunswick and nova scotia. at south joggins there is a thickness of , feet of strata, in which are found seventy-six coal-seams of feet in total thickness. at picton there are six seams with a total of feet of coal. in the lower carboniferous group is found the peculiar asphaltic coal of the albert mine in new brunswick. extensive deposits of lignite are met with both in the dominion and in the united states, whilst true coal-measures flank both sides of the rocky mountains. coal-seams are often encountered in the arctic archipelago. the principal areas of deposit in south america are in brazil, uruguay, and peru. the largest is the candiota coal-field, in brazil, where sections in the valley of the candiota river show five good seams with a total of feet of coal. it is, however, worked but little, the principal workings being at san jeronimo on the jacahahay river. in peru the true carboniferous coal-seams are found on the higher ground of the andes, whilst coal of secondary age is found in considerable quantities on the rise towards the mountains. at porton, east of truxillo, the same metamorphism which has changed the ridge of sandstone to a hard quartzite has also changed the ordinary bituminous coal into an anthracite, which is here vertical in position. the coals of peru usually rise to more than , feet above the sea, and they are practically inaccessible. cretaceous coals have been found at lota in chili, and at sandy point, straits of magellan. turning to asia, we find that coal has been worked from time to time at heraclea in asia minor. lignites are met with at smyrna and lebanon. the coal-fields of hindoostan are small but numerous, being found in all parts of the peninsula. there is an important coal-field at raniganj, near the hooghly, miles north of calcutta. it has an area of square miles. in the raniganj district there are occasional seams feet to feet in thickness, but the coals are of somewhat inferior quality. the best quality amongst indian coals has come from a small coal-field of about square miles in extent, situated at kurhurbali on the east indian railway. other coal-fields are found at jherria and on the sone river, in bengal, and at mopani on the nerbudda. much is expected in future from the large coal-field of the wardha and chanda districts, in the central provinces, the coal of which may eventually prove to be of permian age. the coal-deposits of china are undoubtedly of tremendous extent, although from want of exploration it is difficult to form any satisfactory estimate of them. near pekin there are beds of coal feet thick, which afford ample provision for the needs of the city. in the mountainous districts of western china the area over which carboniferous strata are exposed has been estimated at , square miles. the coal-measures extend westward to the mongolian frontier, where coal-seams feet thick are known to lie in horizontal plane for miles. most of the chinese coal-deposits are rendered of small value, either owing to the mountainous nature of the valleys in which they outcrop, or to their inaccessibility from the sea. japan is not lacking in good supplies of coal. a colliery is worked by the government on the island of takasima, near nagasaki, for the supply of coals for the use of the navy. the british possession of labuan, off the island of borneo, is rich in a coal of tertiary age, remarkable for the quantity of fossil resin which, it contains. coal is also found in sumatra, and in the malayan archipelago. in cape colony and natal the coal-bearing karoo beds are probably of new red age. the coal is reported to be excellent in quantity. in abyssinia lignites are frequently met with in the high lands of the interior. coal is very extensively developed throughout australasia. in new south wales, coal-measures occur in large detached portions between ° and ° s. latitude. the newcastle district, at the mouth of the hunter river, is the chief seat of the coal trade, and the seams are here found up to feet thick. coal-bearing strata are found at bowen river, in queensland, covering an area of , square miles, whilst important mines of cretaceous age are worked at ipswich, near brisbane. in new zealand quantities of lignite, described as a hydrous coal, are found and utilised; also an anhydrous coal which may prove to be either of cretaceous or jurassic age. we have thus briefly sketched the supplies of coal, so far as they are known, which are to be found in various countries. but england has of late years been concerned as to the possible failure of her home supplies in the not very distant future, and the effects which such failure would be likely to produce on the commercial prosperity of the country. great britain has long been the centre of the universe in the supply of the world's coal, and as a matter of fact, has been for many years raising considerably more than one half of the total amount of coal raised throughout the whole world. there is, as we have seen, an abundance of coal elsewhere, which will, in the course of time, compete with her when properly worked, but britain seems to have early taken the lead in the production of coal, and to have become the great universal coal distributor. those who have misgivings as to what will happen when her coal is exhausted, receive little comfort from the fact that in north america, in prussia, in china and elsewhere, there are tremendous supplies of coal as yet untouched, although a certain sense of relief is experienced when that fact becomes generally known. if by the time of exhaustion of the home mines britain is still dependent upon coal for fuel, which, in this age of electricity, scarcely seems probable, her trade and commerce will feel with tremendous effect the blow which her prestige will experience when the first vessel, laden with foreign coal, weighs anchor in a british harbour. in the great coal lock-out of , when, for the greater part of sixteen weeks scarcely a ton of coal reached the surface in some of her principal coal-fields, it was rumoured, falsely as it appeared, that a collier from america had indeed reached those shores, and the importance which attached to the supposed event was shown by the anxious references to it in the public press, where the truth or otherwise of the alarm was actively discussed. should such a thing at any time actually come to pass, it will indeed be a retribution to those who have for years been squandering their inheritance in many a wasteful manner of coal-consumption. thirty years ago, when so much small coal was wasted and wantonly consumed in order to dispose of it in the easiest manner possible at the pitmouths, and when only the best and largest coal was deemed to be of any value, louder and louder did scientific men speak in protest against this great and increasing prodigality. wild estimates were set on foot showing how that, sooner or later, there would be in britain no native supply of coal at all, and finally a royal commission was appointed in , to collect evidence and report upon the probable time during which the supplies of great britain would last. this commission reported in , and the outcome of it was that a period of twelve hundred and seventy-three years was assigned as the period during which the coal would last, at the then-existing rate of consumption. the quantity of workable coal within a depth of feet was estimated to be , millions of tons, or, including that at greater depths, , millions of tons. since that date, however, there has been a steady annual increase in the amount of coal consumed, and subsequent estimates go to show that the supplies cannot last for more than years, or, taking into consideration a possible decrease in consumption, years. most of the coal-mines will, indeed, have been worked out in less than a hundred years hence, and then, perhaps, the competition brought about by the demand for, and the scarcity of, coal from the remaining mines, will have resulted in the dreaded importation of coal from abroad. in referring to the outcome of the royal commission of , although the commissioners fixed so comparatively short a period as the probable duration of the coal supplies, it is but fair that it should be stated that other estimates have been made which have materially differed from their estimate. whereas one estimate more than doubled that of the royal commission, that of sir william armstrong in gave it as years, and professor jevons, speaking in concerning armstrong's estimate, observed that the annual increase in the amount used, which was allowed for in the estimate, had so greatly itself increased, that the years must be considerably reduced. one can scarcely thoroughly appreciate the enormous quantity of coal that is brought to the surface annually, and the only wonder is that there are any supplies left at all. the great pyramid which is said by herodotus to have been twenty years in building, and which took , men to build, contains , , cubic yards of stone. the coal raised in would make a pyramid which would contain , , cubic yards, at the low estimate that one ton could be squeezed into one cubic yard. the increase in the quantity of coal which has been raised in succeeding years can well be seen from the following facts. in there were raised in great britain about millions of tons. by this amount had increased to - / millions. in this again had increased to millions, whilst twenty years after, viz., in , this had increased to no less than millions, such were the giant strides which the increase in consumption made. in the return for , this amount had farther increased to - / millions of tons, an advance in eight years of a quantity more than equal to the total raised in , and in the total reached - / millions; this was produced by , persons, employed in and about the mines. chapter viii. the coal-tar colours. in a former chapter some slight reference has been made to those bye-products of coal-tar which have proved so valuable in the production of the aniline dyes. it is thought that the subject is of so interesting a nature as to deserve more notice than it was possible to bestow upon it in that place. with abstruse chemical formulae and complex chemical equations it is proposed to have as little as possible to do, but even the most unscientific treatment of the subject must occasionally necessitate a scientific method of elucidation. the dyeing industry has been radically changed during the last half century by the introduction of what are known as the _artificial_ dyes, whilst the _natural_ colouring matters which had previously been the sole basis of the industry, and which had been obtained by very simple chemical methods from some of the constituents of the animal kingdom, or which were found in a natural state in the vegetable kingdom, have very largely given place to those which have been obtained from coal-tar, a product of the mineralised vegetation of the carboniferous age. the development and discovery of the aniline colouring matters were not, of course, possible until after the extensive adoption of house-gas for illuminating purposes, and even then it was many years before the waste products from the gas-works came to have an appreciable value of their own. this, however, came with the increased utilitarianism of the commerce of the present century, but although aniline was first discovered in by unverdorben, in the materials produced by the dry distillation of indigo (portuguese, _anil_, indigo), it was not until thirty years afterwards, namely, in , that the discovery of the method of manufacture of the first aniline dye, mauveine, was announced, the discovery being due to the persistent efforts of perkin, to whom, together with other chemists working in the same field, is due the great advance which has been made in the chemical knowledge of the carbon, hydrogen, and oxygen compounds. scientists appeared to work along two planes; there were those who discovered certain chemical compounds in the resulting products of reactions in the treatment of _existing_ vegetation, and there were those who, studying the wonderful constituents in coal-tar, the product of a _past_ age, immediately set to work to find therein those compounds which their contemporaries had already discovered. generally, too, with signal success. the discovery of benzene in by faraday was followed in the course of a few years by its discovery in coal-tar by hofmann. toluene, which was discovered in by pelletier, was recognised in the fractional distillation of crude naphtha by mansfield in . although the method of production of mauveine on a large scale was not accomplished until , yet it had been noticed in , the actual year of its recognition as a constituent of coal-tar, that, when brought into contact with chloride of lime, it gave brilliant colours, but it required a considerable cheapening of the process of aniline manufacture before the dyes commenced to enter into competition with the old natural dyes. the isolation of aniline from coal-tar is expensive, in consequence of the small quantities in which it is there found, but it was discovered by mitscherlich that by acting upon benzene, one of the early distillates of coal-tar, for the production of nitro-benzole, a compound was produced from which aniline could be obtained in large quantities. there were thus two methods of obtaining aniline from tar, the experimental and the practical. in producing nitrobenzole (nitrobenzene), chemically represented as (c_{ }h_{ }no_{ }), the nitric acid used as the reagent with benzene, is mixed with a quantity of sulphuric acid, with the object of absorbing water which is formed during the reaction, as this would tend to dilute the efficiency of the nitric acid. the proportions are parts of purified benzene, with a mixture of parts of concentrated nitric acid (hno_{ }) and parts of concentrated sulphuric acid. the mixture is gradually introduced into the large cast-iron cylinder into which the benzene has been poured. the outside of the cylinder is supplied with an arrangement by which fine jets of water can be made to play upon it in the early stages of the reaction which follows, and at the end of from eight to ten hours the contents are allowed to run off into a storage reservoir. here they arrange themselves into two layers, the top of which consists of the nitrobenzene which has been produced, together with some benzene which is still unacted upon. the mixture is then freed from the latter by treatment with a current of steam. nitrobenzene presents itself as a yellowish oily liquid, with a peculiar taste as of bitter almonds. it was formerly in great demand by perfumers, but its poisonous properties render it a dangerous substance to deal with. in practice a given quantity of benzene will yield about per cent of nitrobenzene. stated chemically, the reaction is shown by the following equation:-- c_{ }h_{ } + hno_{ } = c_{ }h_{ }no_{ }, + h_{ }o (benzene) (nitric acid) (nitrobenzene) (water). the water which is thus formed in the process, by the freeing of one of the atoms of hydrogen in the benzene, is absorbed by the sulphuric acid present, although the latter takes no actual part in the reaction. from the nitrobenzene thus obtained, the aniline which is now used so extensively is prepared. the component atoms of a molecule of aniline are shown in the formula c_{ }h_{ }nh_{ }. it is also known as phenylamine or amido-benzole, or commercially as aniline oil. there are various methods of reducing nitrobenzene for aniline, the object being to replace the oxygen of the former by an equivalent number of atoms of hydrogen. the process generally used is that known as béchamp's, with slight modifications. equal volumes of nitrobenzene and acetic acid, together with a quantity of iron-filings rather in excess of the weight of the nitrobenzene, are placed in a capacious retort. a brisk effervescence ensues, and to moderate the increase of temperature which is caused by the reaction, it is found necessary to cool the retort. instead of acetic acid hydrochloric acid has been a good deal used, with, it is said, certain advantageous results. from to per cent. of aniline on the quantity of nitrobenzene used, is yielded by béchamp's process. stated in a few words, the above is the process adopted on all hands for the production of commercial aniline, or aniline oil. the details of the distillation and rectification of the oil are, however, as varied as they can well be, no two manufacturers adopting the same process. many of the aniline dyes depend entirely for their superiority, on the quality of the oil used, and for this reason it is subject to one or more processes of rectification. this is performed by distilling, the distillates at the various temperatures being separately collected. when pure, aniline is a colourless oily liquid, but on exposure rapidly turns brown. it has strong refracting powers and an agreeable aromatic smell. it is very poisonous when taken internally; its sulphate is, however, sometimes used medicinally. it is by the action upon aniline of certain oxidising agents, that the various colouring matters so well known as aniline dyes are obtained. commercial aniline oil is not, as we have seen, the purest form of rectified aniline. the aniline oils of commerce are very variable in character, the principal constituents being pure aniline, para- and meta-toluidine, xylidines, and cumidines. they are best known to the colour manufacturer in four qualities-- (_a_) aniline oil for blue and black. (_b_) aniline oil for magenta. (_c_) aniline oil for safranine. (_d_) _liquid toluidine. from the first of these, which is almost pure aniline, aniline black is derived, and a number of organic compounds which are further used for the production of dyes. the hydrochloride of aniline is important and is known commercially as "aniline salt." the distillation and rectification of aniline oil is practised on a similar principle to the fractional distillation which we have noticed as being used for the distillation of the naphthas. first, light aniline oils pass over, followed by others, and finally by the heavy oils, or "aniline-tailings." it is a matter of great necessity to those engaged in colour manufacture to apply that quality oil which is best for the production of the colour required. this is not always an easy matter, and there is great divergence of opinion and in practice on these points. the so-called aniline colours are not all derived from aniline, such colouring matters being in some cases derived from other coal-tar products, such as benzene and toluene, phenol, naphthalene, and anthracene, and it is remarkable that although the earlier dyes were produced from the lighter and more easily distilled products of coal-tar, yet now some of the heaviest and most stubborn of the distillates are brought under requisition for colouring matters, those which not many years ago were regarded as fit only to be used as lubricants or to be regarded as waste. it is scarcely necessary or advisable in a work of this kind to pursue the many chemical reactions, which, from the various acids and bases, result ultimately in the many shades and gradations of colour which are to be seen in dress and other fabrics. many of them, beautiful in the extreme, are the outcome of much careful and well-planned study, and to print here the complicated chemical formulae which show the great changes taking place in compounds of complex molecules, or to mention even the names of these many-syllabled compounds, would be to destroy the purpose of this little book. the rosanilines, the indulines, and safranines; the oxazines, the thionines: the phenol and azo dyes are all substances which are of greater interest to the chemical students and to the colour manufacturer than to the ordinary reader. many of the names of the bases of various dyes are unknown outside the chemical dyeworks, although each and all have complicated; reactions of their own. in the reds are rosanilines, toluidine xylidine, &c.; in the blues--phenyl-rosanilines, diphenylamine, toluidine, aldehyde, &c.; violets--rosaniline, mauve, phenyl, ethyl, methyl, &c.; greens--iodine, aniline, leucaniline, chrysotoluidine, aldehyde, toluidine, methyl-anilinine, &c.; yellows and orange--leucaniline, phenylamine, &c.; browns--chrysotoluidine, &c.; blacks--aniline, toluidine, &c. to take the rosanilines as an instance of the rest. aniline red, magenta, azaleine, rubine, solferino, fuchsine, chryaline, roseine, erythrobenzine, and others, are colouring matters in this group which are salts of rosaniline, and which are all recognised in commerce. the base rosaniline is known chemically by the formula c_{ }h_{l }n_{ }, and is prepared by heating a mixture of magenta aniline, toluidine, and pseudotoluidine, with arsenic acid and other oxidising agents. it is important that water should be used in such quantities as to prevent the solution of arsenic acid from depositing crystals on cooling. unless carefully crystallised rosaniline will contain a slight proportion of the arseniate, and when articles of clothing are dyed with the salt, it is likely to produce an inflammatory condition of skin, when worn. some years ago there was a great outcry against hose and other articles dyed with aniline dyes, owing to the bad effects which were produced, and this has no doubt proved very prejudicial to aniline dyes as a whole. again, the base known as mauve, or mauveine, has a composition shown by the formula c_{ }h_{ }n_{ }. it is produced from the sulphate of aniline by mixing it with a cold saturated solution of bichromate of potash, and allowing the mixture to stand for ten or twelve hours. a blue-black precipitate is then formed, which, after undergoing a process of purification, is dissolved in alcohol and evaporated to dryness. a metallic-looking powder is then obtained, which constitutes this all-important base. mauve forms with acids a series of well-defined salts and is capable of expelling ammonia from its combinations. mauve was the first aniline dye which was produced on a large scale, this being accomplished by perkin in . the substance known as carbolic acid is so useful a product of a piece of coal that a description of the method of its production must necessarily have a place here. it is one of the most powerful antiseptic agents with which we are acquainted, and has strong anaesthetic qualities. some useful dyes are also obtained from it. it is obtained in quantities from coal-tar, that portion of the distillate known as the light oils being its immediate source. the tar oil is mixed with a solution of caustic soda, and the mixture is violently agitated. this results in the caustic soda dissolving out the carbolic acid, whilst the undissolved oils collect upon the surface, allowing the alkaline solution to be drawn from beneath. the soda in the solution is then neutralised by the addition of a suitable quantity of sulphuric acid, and the salt so formed sinks while the carbolic acid rises to the surface. purification of the product is afterwards carried out by a process of fractional distillation. there are various other methods of preparing carbolic acid. carbolic acid is known chemically as c_{ }h_{ }(ho). when pure it appears as colourless needle-like crystals, and is exceedingly poisonous. it has been used with marked success in staying the course of disease, such as cholera and cattle plague. it is of a very volatile nature, and its efficacy lies in its power of destroying germs as they float in the atmosphere. modern science tells us that all diseases have their origin in certain germs which are everywhere present and which seek only a suitable _nidus_ in which to propagate and flourish. unlike mere deodorisers which simply remove noxious gases or odours; unlike disinfectants which prevent the spread of infection, carbolic acid strikes at the very root and origin of disease by oxidising and consuming the germs which breed it. so powerful is it that one part in five thousand parts of flour paste, blood, &c., will for months prevent fermentation and putrefaction, whilst a little of its vapour in the atmosphere will preserve meat, as well as prevent it from becoming fly-blown. although it has, in certain impure states, a slightly disagreeable odour, this is never such as to be in any way harmful, whilst on the other hand it is said to act as a tonic to those connected with its preparation and use. the new artificial colouring matters which are continually being brought into the market, testify to the fact that, even with the many beautiful tints and hues which have been discovered, finality and perfection have not yet been reached. a good deal of popular prejudice has arisen against certain aniline dyes on account of their inferiority to many of the old dye-stuffs in respect to their fastness, but in recent years the manufacture of many which were under this disadvantage of looseness of dye, has entirely ceased, whilst others have been introduced which are quite as fast, and sometimes even faster than the natural dyes. it is convenient to express the constituents of coal-tar, and the distillates of those constituents, in the form of a genealogical chart, and thus, by way of conclusion, summarise the results which we have noticed. coal. | .----------+-----------+----+-------------------+--------+----. | | | | | | water house-gas coal-tar ammoniacal coke | | liquor | .---------+-------+---------+---------. | sulphur | | | | | | (sulphurreted first second heavy anthracene pitch | hydrogen: light light oils (green | sulphurous oils oils (creosote oils) | acid: oil | (crude oils) | | of vitriol) .----+----. naphtha) | anthracene | | | | | | | ammoniacal benzene | | alizarin or | liquor toluene,| | dyer's madder | &c. | | | | | | | | sulphuric acid=carbonate of=hydrochloric | | | ammonia acid | | | (smelling | | | salts) | | | | | lime=sulphate of lime=chloride of | | | ammonia | ammonia (sal | | | | ammoniac) | | | | | | .----+----. .----+----. | | | | | | | | ammonia sulphate ammonia chloride | | of lime of lime. | | (plaster of paris) | | | .--+-----+----------. | | | | | crude carbolic naphthalin | creosote acid | .--------------+---+--+-------+--------+-----------. | | | | | benzene=nitric acid toluene nylene artificial burning | turpentine oils nitrobenzene= } iron filings oil (solvent (essence de | } and acetic acid naphtha) mirbane) | | aniline=various reagents | aniline dyes index. a. accidents, causes of mining "age of _acrogens_" _alethopteris_ alizarin american coal-fields ammoniacal liquor aniline aniline dyes aniline oil, commercial aniline salt aniline "tailings" anthracene anthracite artificial turpentine oil asphalt australian coals _aviculopecten_ b. béchamp's process benzene bind bitumen in trinidad "blower" a boghead coal bog-oak boring diamonds borrowdale graphite mine bovey tracey lignite british coal-fields british north-american coal-measures briquettes c. _calamites_, extinct horsetails carbolic acid carboniferous formation, the _cardiocarpum_, fossil fruit carelessness of miners causes of earth-movements changes of level charcoal as a disinfectant chemistry of a gas-flame chinese coals clanny's safety-lamp clayton's experiments with gas clay, regularity in deposition of club-mosses, great height of fossil coal-dust, danger from coal formed in large lakes or closed seas coal formation, geological position of coal formed by escape of gases coal-mine, the coal not the result of drifted vegetation coal-period, climate of "coal-pipes" coal-plants, classification of coal-seam, each, a forest growth coals of non-carboniferous age coal, vegetable origin of coke "cole" "condensers" cones of _lepidodendra_ conifers in coal-measures current-bedding in sandstone d. davy-lamp dangers of benzene darwin on the chonos archipelago diamonds, how made artificially disintegration of vegetable substances disproportion in relative thickness of coal and coal-measures e. early use of coal effects of an explosion encrinital limestone _equiseta_ "essence de mirbane" european coal-fields evelyn on the use of coal experiments illustrating fossilisation f. filling retorts by machinery firedamp fire, mines on first light oils first record of an explosion flashing-point of oil flooding of pits fog and smoke _foraminifera_ fossil ferns fructification on fossil-ferns furnace, ventilating g. gas, coal gasholder, the gas, house, constituents of _glossopteris_ graphite "green grease" h. hannay, of glasgow heavy oils humboldt's safety-lamp hydraulic main i. impurities in house-gas indian coals insertion of rootlets of _stigmaria_ insufficiency of modern forest growths ireland denuded of coal-beds iron, supplies of l. _lepidodendra_ _lepidostrobi_ lignite london lit by gas m. mammoth trees marco polo marsh gas medium oils metamorphism of coal by igneous agency methods of ventilation mountain limestone murdock's use of gas mussel beds n. napthalin _neuropteris_ newcastle, charters to nitro-benzole o. objections to use of coal oils from coal and lignite oil-wells of america olefiant gas _orthoceras_ p. paraffins peat _pecopteris_ pennsylvanian anthracite persian fire-worshippers pitch plumbago _polyzoa_ prejudice against aniline dyes prohibitions of the use of coal proportions of explosive mixtures _psaronius_ "purifiers" pyrites in coal q. quantity of coal raised in great britain r. reptiles of the coal-era resemblance of american and british coal-_flora_ retorts roman use of coal rosanilines, the royal commission of s. sandstone, how formed shales _sigillaria_ south american coals spores of _lepidodrendron_ spores, resinous matter in spores, inflammability of steel-mill _sternbergia_ _stigmaria_ subsidence throughout coal-era surturbrand at brighton sussex iron-works t. tar testing pits by the candle texas coal toluene, discovery of torbanehill mineral trappers u. underclays uses to which coal is put v. vaseline vegetation of the coal age ventilation of coal-pits w. "washers" waste of fuel wealden lignite westphalian coal-field y. young's paraffin oil z. zoroastrians transcriber's notes : ( ) obvious misspellings, punctuation faults and misprints have been corrected. ( ) italic text is denoted by _underscores_ ( ) subscripts are denoted by an _underscore followed by the symbol in {braces} ( ) "par/share" = par value per share, in the table of share values [illustration: utah copper company's open pit mine, bingham, utah. this mountain is copper ore.] the business of mining a brief, non-technical exposition of the principles involved in the profitable operation of mines by arthur j. hoskin, m.e., consulting and general mining engineer; western editor, "mines and minerals"; formerly professor of mining, colorado school of mines; member, american institute of mining engineers; member, colorado scientific society _with full page illustrations and one chart_ [illustration: publisher's logo] philadelphia & london j. b. lippincott company copyright, , by j. b. lippincott company published july, printed by j. b. lippincott company at the washington square press philadelphia, u.s.a. contents chapter page introduction i. what is a mine? ii. what is mining? iii. the antiquity of mining iv. mining's place in commerce v. the finding of mines vi. mining claims vii. placering viii. open mining ix. considerations preceding the opening of mines x. mine openings xi. types of ore bodies xii. the questions of depth and grades of ore xiii. valuation of mining property xiv. the mine promoter xv. incorporation and capitalization xvi. mining investments xvii. mine equipments xviii. mine management xix. prices of metals xx. mine accounting xxi. investment in mining stocks xxii. the men of the future in mining xxiii. miscellaneous considerations capitalization and dividends of north american metal mines index illustrations page utah copper company's open pit mine, bingham, utah _frontispiece_ hackett mine and mill, joplin, mo. coal washing plant, pana, illinois universal mine, clinton, ind. kennedy mine, jackson, cal. a gilpin county, col., scene dredges of yuba consolidated goldfields, hammonton, cal. the snowstorm placer, fairplay, col. steam shovels and churn drills, copper flat, ely, nev. mill of the pittsburg-silver peak gold mining co., blair, nev. mills and shaft house of daly west mine, park city, utah shaft no. , tamarack mining co., calumet, mich. smeltery of the balaklala consolidated copper co., coram, cal. washoe reduction works of the anaconda copper mining co., anaconda, mont. mill of the roodepoort-united mines, transvaal, south africa spray shaft house of copper queen consolidated mining co., bisbee, ariz. diagram of metal market for one-third of a century florence mine and mill, goldfield, nev. the business of mining introduction there is probably no line of human activity that is not beset with malicious and ignorant intruders. the fact that any occupation or business is really legitimate seems often to stimulate the operations of these disreputable persons. mining does not escape the application of this postulate. for ages, the industry has afforded most fertile opportunities for the machinations of the unscrupulous and the erring. somehow, there weaves throughout the history of mining a sort of magnetism rendering us unduly susceptible to the allurements which are presented with every mining proposition. it is not, however, always intentional deceit that is perpetrated upon the unwary. often, mining failures result from actual ignorance of the business upon the part of those entrusted with its conduct, or if not from actual lack of knowledge, then from erroneous conceptions with the consequent misapplication of honest endeavor. a victim of such misplaced faith is perhaps more leniently inclined than is the person who has been duped by a "shark," but the effect upon the great industry is hurtful in either case. the purpose of this short monograph will be served if the author can feel assured that his readers will finish its perusal with the belief that mining may be followed as a business with just as much assurance of success as attaches to any one of the many lines of industrial activity. many persons who have sustained losses in mining ventures deserve no sympathy whatever, since they have not exercised even the simplest precautions. so long as men--or women--will take as fact the word of any untrained or inexperienced individual concerning investments, just so long will there be resultant financial losses, no matter what the line of business. because there have been elements of chance observed in the records of mining, this business appeals to the speculative side of our human natures, with the result that untold numbers of individuals have had ample reason to regret their ventures. but, as will be found in the text matter, mining can be relied upon with precisely as much assurance as can any other business. nothing of a technical or engineering sort has been attempted herein, the sole aim of the writer being to establish the reliability and the credit of the mining industry as a whole by pointing out the lines of conduct which should be followed by those who enter its precincts as business people. when investors of small or large means will put their money into mining projects with the same precautions that they would exercise in placing their cash in other enterprises, they will be rewarded with corresponding remuneration. in this firm conviction, then, this little work is dedicated to the intelligence of american laymen in mining matters. i what is a mine? before entering into a discussion of the economic features of the mining industry, it will be well to be sure that we understand, definitely, what is meant by mining. as one investigates the question, he is bound to run across varying shades of meaning for the words _mine_ and _mining_, and so we must pause long enough to define these words according to the best usages. a search through works on mining written at various periods reveals differing ideas that have prevailed among authors. less than a hundred years ago, it was said that a mine "consists of subterranean workings from which valuable minerals are extracted." one early writer said that a mine is one only when the operations are conducted in the absence of daylight. as time has created new fields for the industry, we find that ideas concerning the meaning of the word mine have necessarily altered, until now (according to the coal and metal miners' pocketbook), we may think of a mine as "any excavation made for the extraction of minerals." under this definition, we properly think of the rather unusual operations of marketing coal right from the surface of the earth, in eastern kansas, as mining. there is, in this case, no covering of earth above the workmen; neither are the operations necessarily carried on at night to avoid the illumination of the sun. so, also, placers are now correctly spoken of as mines, although but a few years ago there was drawn a strict line, eliminating such worked deposits from the category of mines. one may still run across a few men who are sticklers upon the point that a placer is not a mine. throughout the world, at the present time, there are many places where immense deposits of valuable minerals are being excavated from open pits by out-of-doors methods, and our common term for these places is mines. thus, in minnesota, in that wonderful lake superior country, that is famous as the world's greatest known producer of iron ore, tremendous tonnages are handled every year by the modern steam shovel, which works in natural light by day and by electric lamps at night. in utah and nevada we find similar operations conducted in the excavation of copper ores. in australia, the famous mount morgan mine is using open air methods in the mining of precious metal ore. but what about quarries from which are taken building stone, salt, kaolin or clay? are not such substances of the mineral kingdom? here we run across a hitch in the definition quoted above; for while we hear of "salt mines" (not "salted mines"), our parlance has not, as yet, warranted this term except for such excavations of salt as are carried on in subterranean deposits; and it is quite out of place to speak of stone or clay mines. evidently we must pass through another transition in our conceptions about mines, or we must permit quarries and pits to be included within our realm of mines. at the present time, the prevailing practice of the men best qualified in such matters is to designate as mines those workings from which only coal, metallic ores, or gems are extracted. hence, we should not speak of a slate, sulphur, mica, clay or phosphate mine. and yet, with all the above restriction in our nomenclature, we have not reached one very important consideration, one which we have been approaching for a number of years and which, of late, has been met and forcibly applied by the best men in the profession of mining engineering. an excavation that will produce coal, metals or gems is not necessarily a mine. the simple fact that a man can get some gold-bearing dirt from a hole in the ground does not mean that he has a mine. the occasional finding of a diamond on the sidewalks of a great city does not give anybody the impression that city sidewalks are diamond mines. there are many places in which small amounts of combustible coal can be scratched from its natural depository, but no company appears to think highly enough of these seams to install machinery and to carry on operations. in the eastern part of kentucky there are well-defined deposits of lead-bearing baryta, though, up to date, their development has not proved successful. in brazil there are known to be very rich areas of placer ground, and still the deposits are not worked. a friend of the writer discovered some very good gold-bearing gravels in alaska, but he was unable to mine. there is something besides the presence of valuable minerals and the ability to win them from their natural matrices that is essential to a mine. it is here, in our considerations of the mining industry, that we come into real economic notions for the first time. yes, according to the latest ideas, we are wrong in stating that any worked or workable mineral deposit is a mine, _if it does not contain possibilities of profitable working_. this is now the prime thought of every up-to-date mining manager or engineer. it is this notion that will distinguish a mine from a prospect. the prospect may become a mine by proving itself profitably workable: if it simply carries values which cannot be realized to advantage, then it must continue as a mere prospect. there are cases of properties which possess rich deposits and which are loosely called mines. these properties may be observed to be erratic in their productiveness, owing to the very pockety nature of the deposits; and the owners, although they do, indeed, strike occasional handsome bonanzas, expend all the profits of such finds--or even greater amounts--in searching for other pockets. is such work profitable? is it mining? the trouble with the cited placers of south america is that climatic, hygienic and political conditions have been antagonistic to successful working: the ground is rich, but it cannot be handled to make money. in the case of the alaska gravels, there was no available, though essential, water supply. the kentucky galena cannot be economically separated from the containing heavy spar. coal, which is sold at comparatively low figures per ton, must be handled at the mines in large quantities to pay, so that a thin seam or a scattered deposit is not suitable for mining. under these restrictions of our new definitions, we run across many interesting points. for instance, one may ask the question about the old abandoned hole in the ground which is occasionally found by prospectors, "is it a mine?" the answer can be simply another query as to whether the hole was abandoned because it contained no value, or because, containing value, it could not be profitably worked. as we think of mines nowadays, we can conceive several reasons why, before the advent of transportation lines and the invention of modern metallurgical processes and many forms of labor-saving machinery now so common in and about mines, many very rich deposits may have been necessarily forsaken by their discoverers. but such a property would, if now worked, probably prove highly profitable. we thus note that there exists some elasticity in the meaning of the word mine. an unprofitable project at one time may develop into a mine at a later period. many gold mines have become worthless propositions merely through changes in the ore that have rendered further work unremunerative. ii what is mining? having considered the accepted definition of a mine, let us now extend our reasoning a little and inquire just what is meant by mining. at first thought, one would say that mining is, in a broad sense, the art or practice of excavating, at a profit, the ores of metals, the beds of coal, the gravels of placers and the deposits containing precious stones. are we justified in letting this definition stand as it is? if we do not make any change, we must exclude all quarries, sand banks, clay pits, and the numerous sorts of works that are producing the non-metallic minerals of commerce. very well, since we find good usage will warrant us, we will do so. [illustration: hackett mine and mill, joplin, missouri.] still, there are other pertinent questions arising. does the practice of mining cover the treatment of the excavated products? here we run across a mooted point. the british and the american uses of the word mining seem to be a bit different in this regard. upon the rand, south africa, a territory dominated by englishmen, every mine is equipped with its own mill, and all notions of mining cover the inseparable idea of local ore treatment. here, in our country, there are many, many mines which have absolutely no means of treating their own products and the managers give no thought whatever to metallurgical or milling lines. there are, on the other hand, many companies that have erected private plants at their mines for the extraction of metallic contents from the ores. here it may, or it may not, happen that the operations of mining are considered as distinct from those of treatment. in some instances, as at the tonopah mining company's plants, there is separate superintendence of the milling and the mining; but in the joplin, missouri, zinc region one superintendent looks after the running of a mine and its omnipresent mill. there may be drawn a sharp distinction between what is really mining and what is the subsequent treatment of the ores for the extraction of values. the latter field is denoted _metallurgy_ when the operations are of such a nature as to actually recover or extract metallic products or metals. if the treatment process has for its object merely the rejection of some of the worthless materials in the original ore, thus causing a concentration of the valuable minerals, but without actually obtaining any metal, then the term _ore dressing_ is warranted. at some mines, there is maintained a practice of culling out, often by hand, a certain percentage of the obviously worthless ingredients of the ore before shipping the products to treatment plants. this is neither milling, metallurgy, nor ore dressing, but is more properly called _sorting_. it is one of the operations connected with mining. milling may be either ore dressing or metallurgy. in the operations of placering, there is a simultaneous _excavation_ of a deposit and an _extraction_ of the valuable contents. in this case, shall we call the process mining or metallurgy? if it is a gold placer, one may see the recovery of the metallic values. here, the usage of the majority of practical mining men will uphold us in always speaking of the work as mining. in its original significance and use, metallurgy involved the use of fire for the concentration and recovery of metals. with recent advances in chemistry, there have been numerous discoveries of wet or fireless methods for arriving at equivalent results, so that it is now perfectly proper to allow the word metallurgy to cover such processes as cyanidation, chlorination, electrolysis, and the host of new inventions that are continually appearing. the writer has consulted a number of authorities on mining lines to ascertain just what sort of a position to give to the practice of ore dressing. prof. robert h. richards, the head of the mining department in the massachusetts institute of technology, and the inventor of machines which have made him famous among mining men, says, "ore dressing is an essential part of mining. the whole object of ore dressing is to remove gangue before shipment and so save in freight and treatment charges." mr. a. g. charleton, the eminent english mining engineer and author of numerous books, in discussing this question, writes, "personally, i am of the opinion that ore dressing should be included in mining." one has but to look through the catalogues of most of the american and foreign mining schools to find that little or no line is drawn between the courses in mining and metallurgy, and almost universally the dressing of a mine's product is taken up as an inseparable part of mining. in a very few exceptions, the courses of study are so planned as to draw an imaginary line between mining and metallurgy, and in these instances, ore dressing is placed with metallurgy only for convenience in the use and arrangement of college laboratories. but, since it is a common practice for mining companies to install plants right at the mines for the purpose of diminishing the bulk of ore shipped and to thus save in freight and custom treatment charges, mine superintendents and even the common miners have become accustomed to thinking of such plants as but units of the "mining" plants. at bituminous and anthracite mines whose products contain objectionable amounts of impurities, it is a common practice to subject the output to a _washing_ to remove the deleterious substances before shipment to the market. [illustration: coal washing plant, pana, illinois.] in view, then, of these reasons, it is proper to decide that mining is a term broad enough to cover the operations of extracting coal and metallic ores from the ground and of preparing them for shipment or metallurgical treatment. coal is always coal, no matter in what thickness of deposit it is found. it may not be minable coal because in thin seams or because so intercalated with layers of slate or "bone," that the mine's mixture, or so-called "run of mine," is not salable. but with metallic ores, we run across an idea that is occupying the attention of many prominent geologists and mining men. what is ore? this is a question to which there have been many attempted answers. there has been an evolution of ideas, with a corresponding gradation of definition. to set a uniform standard of thought upon this point, officers of the united states geological survey, a few years ago, proposed the following definition. it must be conceded that this definition, while embodying many splendid features, is not altogether exempt from criticism; but in the absence of anything better, we shall not be very far in error if we use it: _ore_ is a _natural_ aggregation of one or more _minerals_ from which useful _metal_ may be _profitably_ extracted. there is, then, no such thing as "pay ore" or "non-pay ore," expressions still quite common among miners and prospectors of the uneducated types. prof. james f. kemp, probably america's best-posted writer upon the subject, in an attempt to formulate one acceptable and unchangeable meaning for the word ore, says, "in its technical sense, an ore is a metalliferous mineral or an aggregate of such minerals, more or less mixed with gangue, and capable of being won and treated at a profit. the test of _yielding the metal or metals at a profit_ seems to me, in the last analysis, the only feasible one to employ." this definition eliminates one of the weak points in the first definition, namely, that an ore must be an association of minerals: there are some common ores (as for example, magnetite) which are not associations, but single minerals. we now reach certain fundamental concepts which must be accepted by the mining man who desires to be recognized as abreast of modern ideas. following the publication of kemp's definition of ore, there was much comment--as was anticipated--with the result that there has been noted a vacancy in scientific matters and it has been thought proper to permit another definition for purely scientific uses. this other definition of ore will cover the materials or aggregates of minerals from which gem stones and other valuable, but not metallic, substances are recovered. let us recapitulate. an _ore_ must be an aggregate or association of natural minerals, or a single mineral, from which metal may be profitably recovered. _mines_ are excavations in the earth from which ore, coal or gems are taken. _mining_ is the art or practice of operating mines. throughout the subject, we see the inseparable idea of _profit_. the work of carrying on operations in a railroad tunnel is not mining; the driving of adits through barren rocks to reach ore bodies is not mining; the sinking of shafts through worthless "wash" or rocks with a view of opening avenues for the removal of ore is not mining. mining is carried on only when ore is being produced. the wildcat practice of erecting small, temporary plants and digging prospect holes can be condemned as not being real mining. [illustration: universal mine (bituminous), clinton, indiana.] there is usually little question about the validity of a coal mining proposition, since "the goods show for themselves." comparatively few cases of fraudulent ventures in coal properties are of record. the product of a coal mine is ready for market just as soon as it is loaded into railroad cars, the mining company receiving its pay, commonly, upon its own recorded weights. there is no freight to pay, no waiting for assays or analyses, and no settlements with mills or smelteries. there are not the allurements for getting rich quickly in coal mining that are so beguiling to the class of investors generally approached by the promoters of mines(?). this must not be construed as stating that nobody has ever been deceived in a coal mine proposition, for, indeed, there have been many failures; however, they have been due, chiefly, to auto-deception as to area, thickness or quality of the coal measures. iii the antiquity of mining. mining is believed to have been one of man's earliest occupations. in historical writings, many of which date back into antiquity, there are allusions, as well as direct statements, concerning the art and tasks of obtaining valuable metals from mother earth. we are told that the very ancient egyptians made common use of metals and that they possessed knowledge of certain metallurgical and metal-working processes (as for example, the tempering of copper) which we, of today, cannot claim. six thousand years ago egypt became a world power through her mining of copper in the sinai peninsula. iron implements found in the great gizeh pyramid are supposed to date back to , b.c. copper tools have been found in the ruins of ancient troy. in assyria, a very good steel saw, inches long, was taken from the ruins of nimrod. iron was utilized by the chinese some , years b.c. near delhi, india, there exists an iron pillar, feet long and weighing six tons, dating back to b.c. it is chiefly interesting in exhibiting an ancient knowledge of welding which is the envy of our modern iron workers. if we accept the hebrew scriptures, we must believe that mining was carried on in the time of tubalcain, spoken of in genesis. the old testament contains numerous verses referring to the mining of metals, the land of perfect abundance being paraphrased in deuteronomy thus: "where the stones are of iron and out of its hills are digged mines of brass." coal was mined and used in greece in b.c. it is quite probable that gold was the earliest metal to be worked. there are two good reasons for this assumption: first, gold was to be found in the native state or as nuggets, thus requiring no reduction process. second, the ores of gold are usually less refractory than are the ores of other metals. this is especially true of the oxidized ores such as would naturally be discovered by primitive man. these facts, together with the further properties of gold, _viz._, that its color is attractive, that it resists corrosion or tarnish, and that it is easily worked into ornaments or coin merely by hammering, make it highly probable that humans early made use of this yellow material. we read in job : , that "gold is refined;" and modern investigations tend to prove that the ophir of biblical reference is the southern portion of matabeleland or the rhodesia of present fame among mining regions. it is possible and quite probable that the great quantities of gold used in the building and furnishing of king solomon's temple came from the vicinity of the present city of johannesburg. the "golden fleece" of literature has been explained as a figure of speech for the skins of sheep which were laid in troughs to catch gold upon the principle of the riffle in a modern sluice-box. copper was perhaps the second metal to be worked by man. as a rule, it, also, is easily smelted from its ores; and, as above mentioned, we have relics that give evidence of wonderful skill in working this metal in times of remote antiquity. however, other metals are believed to have been mined, upon commercial scales, before the christian era. silver and lead were handled in large quantities from the mines of laurium, greece, in the sixth century b.c., and the same mines are being worked to this day, the principal values now being in the lead rather than, as formerly, in the white metal. the phoenicians, about b.c., invaded spain for gold, copper and mercury, and cornwall for tin and copper. the almaden quicksilver mines of spain have been operated, almost incessantly, since b.c., and in the th century, a.d., the wealth of europe's greatest family of financiers, the fügers, was based upon the operation of this remarkable deposit. del mar, in his _history of the precious metals_, says, "desire for the precious metals, rather than geographical researches or military conquest, is the principal motive which has led to the dominion of the earth by civilized races. gold has invariably invited commerce, invasion has followed commerce, and permanent occupation has completed the process. it is the history of the past as well as of the present. scipio went to africa, cæsar to gaul, columbus to america, cortez to mexico, pizarro to peru, clive to the conquest and hastings to plunder bengal." our own day has witnessed the subjugation of the boer. because of mexico's mineral wealth, many optimistic americans are beginning to prophesy the annexation of our sister republic. for gold, englishmen populated australia in , about the same time ( ) that we witnessed the rush to california gold fields. spaniards settled central and south american countries merely to gain the precious metals. it is mining which has been responsible for the population of the arid, southwestern portion of our own domain. in this, as in every other age of the world's development, we shall find that the mining industry lies at the heart of all commerce. it is well for the student of mining economics to fully appreciate this fact, for it will whet his interest in this great world industry. "truly, it has been a great seeking and finding. the story of mining may have been staled by commonplace, and the romance of it dulled, often enough, by greed; yet, in the main, it has linked the generations of earth as with a golden thread--and if not golden only, then there has been the red glint of copper or the white sheen of silver. mining districts may come and go, but mining remains."--(editorial, _engineering and mining journal_). iv mining's place in commerce. it is said that upon two of the world's commercial industries, every other form of activity depends. these two fundamental industries are agriculture and mining. statisticians prove the above statement and the further fact that these two dissimilar branches of civilization's business are so closely related as to be quite inter-dependent. strides are made by one of these industries only when advance is noted in the other. while it may not be possible to explain just why this is so, it is worth our attention to consider some brief figures that show this condition of affairs. the agitation conducted during the past few years, leading to the establishment of a bureau of mines in the department of the interior, attracted the thoughts of many students of economics who had not previously or seriously considered the industry of mining. the delivery of brilliant addresses showed that mining had been unjustly retarded. while agriculture has for years been fostered by the government and with remarkably satisfactory results, the great sister industry has been required, until recently, to struggle along without any governmental recognition in the matter of support. yet it has forged its way in unmistakable terms of progress and there was an insistent demand, among those men particularly interested in the welfare of mining, for the protection and the assistance which would and has now come through the establishment of a governmental department. various states have long recognized the importance of the mining industry by the establishment of departments. the canadian and mexican governments maintain very creditable departments of mines. it was but a question of time until the shortsightedness of our politicians (not our statesmen) was revealed, and the mining industry has now come under the auspices of a federal department. taking the world as a whole, it would be hard to conceive the sum total of annual mineral productions. the middle of the past century seems to have been a critical period in the mining industry of the earth. there was a great impetus given to mining by the greed for gold which caused the settlement of our western states and the australian states, as already mentioned. but there gradually followed the opening up of mining in many other and hitherto unpopulated and uncivilized portions of the globe. the search for gold was successful. prior to , the production of gold had not kept pace with the increase in population. soon, however, it began to take leaps, in almost geometrical ratios, until, by , the annual production of gold throughout the world was some , per cent. of the production for (as nearly as may be ascertained). the gold production was of a weight of about tons, in round figures. during , the world produced approximately $ , , (about tons) in new gold bullion. it is estimated that with a continuance of the remarkable progress, the next years will duplicate _the amount of gold now known in the world_. _this means that the amount of gold which has been accumulating from mining during the world's ages will be doubled during a fraction of our lifetime._ this is significant of the world's progress, in gold mining, at least. [illustration: kennedy mine, jackson, california.] it seems coincidental that the rush for gold in - should have been almost simultaneous with the remarkable development of our other mineral resources. all of our great discoveries of coal, oil, silver, iron, lead, copper, and zinc can be said to have followed closely upon the discovery of gold in california. it is not supposed that the discovery of iron in northern michigan in the early eighties had any connection with the "pike's-peak-or-bust" expeditions, nor that the opening and development of the vast coal beds of pennsylvania had any bearing on the discoveries of lead and zinc in the great mississippi valley. but, on the other hand, there can be traced a very intimate relation between the finding of gold, silver, copper, and lead in the rocky mountain states and the search for gold in california: the pioneers en route to the coast were the discoverers and settlers in colorado, wyoming, utah, and montana. figures are not available for arriving at such striking or reliable conclusions in regard to the world's production of metals other than gold, but there is no logical reason to doubt that such increases have been just as pronounced as in the case of the yellow metal. in fact, there are good grounds for assuming that the figures for silver, lead, iron, and zinc would show up even more spectacularly; while with coal, we know that we are now in the greatest period of the world's production. the united states leads the world in the production of the base metals, such as copper, iron, manganese, lead, and zinc, taken collectively or separately. our country stands second in the production of the precious metals, gold, platinum, and silver. we have the greatest variety of mineral products, as well as the greatest production of complex ores, or those carrying more than one valuable metal. we produce more copper than the rest of the world combined. although we stand in second place when considering the production of gold, we still possess the homestake mine in the black hills, famous as being the gold mine with the greatest tonnage in the world; and the camp bird mine, in the san juan district of colorado, famous the world over for its highest average value of gold ore. this great mine is now nearly exhausted and is about to close down after making a wonderful record. south africa produces the greatest amount of, and the purest, natural gold in the world. great britain has an insignificant production of both gold and copper, and still it is noteworthy that the english-speaking nations control the world's production of both these metals. british and american citizens own seven-eighths of the world's gold mines. england stands second in the consumption of copper, which, of course, is mainly imported. russia controls the world's output of platinum, with very little competition. in a similar manner, canada has the control of nickel production. mexico, although not commonly regarded as a gold mining country, is rapidly coming to the front and possesses the esperanza mine, said to be one of the most profitable gold mines in the world. to more emphatically show the importance of the mining industry, especially in our own country, the following facts are taken from census returns: agriculture produces annually about $ per capita; mining, $ , ; and manufacturing, which is dependent upon the others, $ . _the national banker_ has said: "statistics show that the combined dividends paid by the gold and silver mining companies of the united states are greater than the combined dividends paid by all of the banking institutions of the country; and the combined dividends paid by the copper mining companies of the united states exceed the combined dividends paid by all of our railroads." there is one thought that will always comfort any person who is engaged in furthering legitimate mining: wealth acquired from a mine is not wrested from any being but mother earth, and it is not, therefore, in the class with the much discussed "tainted money" that is said to be wrung from unfortunate human beings. the following tables are presented to give the reader ideas concerning the productions of gold and silver during recent years. among the interesting points that may be noted are the following: the gold production of the world took a sudden drop in , but it immediately resumed its upward climb. during the decade from to , this production increased over per cent. there is a remarkable similarity noticeable in the gold productions of the united states during the years and . without the notable increase in the gold output of the transvaal in , the world's total gold production for that year would have shown a decrease. the silver production of the united states remained practically unchanged during . gold production of the world for years $ , , $ , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , united states silver production (in fine ounces) alabama alaska , , arizona , , , , california , , , , colorado , , , , georgia idaho , , , , illinois , , michigan , , maryland ...... missouri , , montana , , , , nevada , , , , n. mexico , , , n. carolina , , oklahoma ...... , oregon , , pennsylvania , s. carolina ...... s. dakota , , tennessee , , texas , , utah , , , , virginia washington , , wyoming , , porto rico ...... philippines , , miscellaneous ...... , ---------- ---------- total , , , , united states gold production (in value) alabama $ , $ , alaska , , , , arizona , , , , california , , , , colorado , , , , georgia , , idaho , , , , illinois ------ , michigan ------ maryland ------ montana , , , , nevada , , , , new mexico , , n. carolina , , oklahoma ------ , oregon , , pennsylvania , , s. carolina , , s. dakota , , , , tennessee , , texas , utah , , , , virginia , washington , , wyoming , , porto rico , , philippines , , miscellaneous ------ , ----------- ----------- total $ , , $ , , gold production of the world transvaal $ , , $ , , united states including alaska , , , , australia , , , , russia , , , , mexico , , , , rhodesia , , , , india , , , , canada , , , , china , , , , japan, east indies, etc. , , , , west africa , , , , madagascar , , , , france , , , , central and south america , , , , other countries , , , , ------------ ------------ total $ , , $ , , v the finding of mines. mines are discovered in many ways. one hears much about prospecting, and since this is a practice which is rapidly changing from a mystical to a scientific basis, a few considerations will here be in order. persons who have lived in mining communities are familiar with two types of prospector, the roving and the settled. somehow, when we think of the former, there comes to mind a bearded, roughly clad man, usually accompanied by a "jack" and both packing the outfit consisting of a few tools, a pan, some blankets, a gun, and a supply of "grub." if we have in mind the other type of prospector, we imagine him as living an isolated life in a log cabin up in the hills, spending his daytime in putting in a few, short drill-holes and blasting down a ton or two of usually worthless rock in a "tunnel" or shallow shaft, confident that each succeeding shot will disclose a treasure. both of these types represent the utmost in optimism. these men endure many hardships and privations, they can have little converse with other humans, often they can see no provisions for the next day; in fact, they receive few of the benefits of modern civilization--if we except the food-preserving features. still, a typical, old-style prospector keeps on with absolute faith that fortune will smile tomorrow. we must reach the conclusion that these uneducated men are led on by subtle beliefs which, to a technically-trained man, seem like the rankest folly. they are diviners, dreamers. they are disappearing now and, a generation hence, there will be but memories of them. they are giving way to successors of a different type. the newer kind of prospector is well educated, and, perchance, he is rather youthful. his chances of success are many times those of the man he supplants. why? because he is taking advantage of the work that has been done by all former prospectors. he is guided by theories deduced from observations through ages, and he has the advice of the best contemporary men of experience in matters of geology as applied to mining. in other words, he is a scientific prospector. the prospector of today has a general understanding of mineralogy and geology; he must have knowledge of mining methods, so that he may know whether a deposit, once found, can be exploited at a profit; he must be ready to account for all discovered mineral bodies, and he must be capable of applying theories to actualities. there are so many metals and minerals sought for the markets of the world today that we see there are many fields of study and practice open to prospectors. it is not the purpose here to explain the details of scientific prospecting, for the study of this one subject would, in itself, fill a volume. the object of the above remarks is to draw to the attention of the economist the propriety (amounting almost to a necessity) of giving heed to the findings of the educated, trained searcher for mineral bodies, in preference to those of the illiterate man who has furnished themes for artists, narrators, and dramatists, because of his quaint characteristics. some writers have classified mineral discoveries into search, chance and adventitious. _search_ discoveries, being the rewards of earnest seeking, it is not surprising that, under the past guide of notions and mysticism, the percentage of such discoveries has been small. under the new order of things, with science as a guide, the percentage is growing and, in the future, this kind of discovery will undoubtedly strongly outnumber the others. _chance_ discoveries are those that are made purely without premeditation. they have been a dominant factor in the mineral development of the past. the discovery of _gold_ in california came about through the noticing of shiny, yellow flakes of metal in a ditch leading to a saw-mill. the great _iron_ mines of the mesabi range were found by the ore clinging to the roots of an overturned tree. the wallaroo _copper_ mine, the greatest in australia, was discovered by the green minerals brought to the surface in the excavations of a wombat. the famous sudbury _nickel-silver_ ore bodies were disclosed when making a railroad cut on the canadian pacific railroad. the reddington _quicksilver_ mine, in california, was similarly opened in a cut for a wagon road. the mining of _silver_ at catorce, mexico, followed the discovery of shining silver nuggets in the camp-fire of a native, who had camped right upon a rich outcrop. the kimberly _diamond_ mines are said to have been disclosed by the burrowings of an ichneumon, which fetched a brilliant stone to the sunlight. _adventitious_ finds are such as occasionally occur when, while really searching for, or actually mining, one metal, discovery is made of a different metal, or possibly the same metal is found in an entirely different kind of ore. the comstock lode of nevada was originally a _search_ gold discovery, the gold having been sought and found by two prospectors with ordinary gold pans. in their working to recover gold, a black mineral and a yellow sand were discarded from the pans and rockers. curiosity of one man resulted in the identification of these two minerals as ores of silver which henceforth were held as valuable as the native gold. the anaconda mine, at butte, montana, was located, and for some time worked as a silver proposition; but the values gradually changed with depth from silver to copper, until now silver is only a valuable by-product. the rich lead-silver ores of leadville were discovered as _adventitious_ to the operation of the rich gold placers in california gulch. a heavy, troublesome rock which accumulated in the sluices, much to the disgust of the miners, turned out to be cerussite, a fine ore of lead. this same district now produces in commercial amounts gold, silver, lead, iron, zinc, copper, and manganese. the treadwell mine on douglas island, alaska, was first worked as a placer and the values were found to extend downward into the underlying rock in a place which proved to be an immense deposit of eruptive, gold-bearing ore. as the old-fashioned, venturesome kind of prospecting has but recently been crowded off the scene by the better, scientific kind, let us not overlook the great discoveries that were made in the past before we had applied "organized common sense" to such a field of activity. those original prospectors were searchers, hunters. they had no guides, but they did accomplish a great deal, and their discoveries were rewards for diligence and hard labor which were, to a great extent, often misdirected. vi mining claims. the process of acquiring title to mining property may be viewed from a number of points. such property is real estate and, as such, it may be bought and sold or otherwise transferred exactly the same as farms or city lots. the united states has constructed an elaborate system for the disposal of its public lands to individuals, under various classifications, such as homestead, desert land, timber and stone, timber culture, coal, placer, and lode claims. different rules apply to the filing upon, improvement and patenting (acquiring deed from the government) of these various kinds of claims. the character of the lands in the public domain is decided by the surveyors who execute contracts from the general land office for subdividing or staking the country off into townships and sections, according to our american system. in the return of each surveyor's notes, he recommends the sale of the land according to his judgment as to its highest value. there has naturally been a good deal of erroneous conception upon these points, with the result that, often, land has been later shown to be entirely different in its character from the classification given to it by the contracting surveyor; for the qualifications of such a person are not always of a high grade, when it comes to geological questions. and yet, on the whole, the scheme has worked out well and much fraud against the government has been prevented by the rigid practice. the government prices for some of the various classes of land have been as follows: agricultural, $ . per acre; coal, $ per acre when the land was not closer to a railroad than miles, and $ per acre when it lay within this limit; placer, $ . per acre; lode, $ per acre. these have been the prices demanded for the land only; the payment of these amounts, in many cases, has constituted a small fraction of the expense of securing the original deeds from the federal government. coal lands may be located very much the same as a homestead, with the exception that residence upon the ground is not required, nor are improvements essential. in cases of dispute as to priority of location, the land office will recognize those claimants who have expended the greater amounts in improvements. one citizen may locate but one claim of acres. since april , , the government has been disposing of its public coal lands under a classification that takes note of many details. the kind, grade, thickness, and purity of coal; the number of workable seams; the depth; the features of local supply; transportation facilities; and the average prices at which similar private tracts are held, are among the items recognized in the classification. probably no two tracts will be sold at the same rate. in general, the new prices are higher than the flat prices that formerly prevailed and some pieces of land are now estimated as high as $ per acre. in every case of application to purchase coal land, hereafter, the area in question will undergo inspection by government experts and a price will then be assessed. this law is being severely opposed as being unreasonably severe, and its amendment may be looked for. placer lands were formerly permitted to be taken up in any shape, the boundary stakes being placed upon the ground in such a manner as to include only the desirable area, which is usually of an alluvial nature along some valley or gulch. this practice has been forbidden, however, and a locator is now obliged to take up his land in quadrilateral tracts conforming to the subdivisions of the so-called public survey. by this rule, it is permissible to file upon land which is laid off into lots of not less than / of a quarter section--or ten acres--and a claim may be composed of such lots as lie contiguously and which may thus be considered as one complete workable area. the claims are often of zigzag or l shapes, but the locator is enabled, at the extra expense of subdivision surveying, to avoid filing upon, and paying for, much ground that he feels is not desirable in a placer claim. the government does not survey public domain into smaller tracts than quarter sections of acres each, so that in the taking up of placers it often involves a great deal of expense to carry the subdivisions upon the ground into sufficient detail to ascertain the location of boundary corners. one person is entitled to as many placer claims as he desires. each claim of a single individual may contain not to exceed acres and, as said, it must be of one continuous area. associations of citizens to the number of eight may unite in the location of acres, which will then be held in equal and common interest by the several locators. the restraint placed upon greed in the matter of locations, either placer or lode, lies in certain expenses entailed in work or improvements upon the land before patent may be issued and the legal requirement of the performance of labor upon each claim amounting to $ per annum. also, it is required that _bona fide_ values be disclosed upon the ground. for each acres located under the placer laws of the united states, not less than $ worth of improvements must be made before the issuance of a patent. the legal (not the technical) definition of lode land covers all grounds containing deposits of ore in its natural and original place of deposit. under the laws, therefore, a citizen may file upon a tract of land to include a vein, lode, mass, chimney or any other form of ore body. the laws were framed at a time when miners were familiar only with the steep, tabular forms, synonymously termed veins or lodes in their nomenclature, and there were introduced features which time and progress in geological investigations have proved to be entirely unsuited to the needs of locators in many districts. our statutes provide that a lode claim may not exceed an area of , acres, this being the area of a parallelogram , feet long by feet wide. the intention is to permit a discoverer to lay off a "lode line" along the outcrop of his vein for a distance of , feet and, at each end, to measure off, at right angles, a distance of feet each way, merely as assurance that he covers the entire thickness of his lode. since the surface contours of rugged country will crook the outcrop of a dipping plane (such as we may imagine a vein to be) the laws were constructed to permit a claim being laid off with angles or bends in the boundaries so that the outcrop might be kept closely along the middle of the claim. the above dimensions and area are the maximum permissible under the federal laws. the government does not say that claims may not be less in extent, anywhere, nor does it prevent states, counties or even mining districts from making further limitations. in most of the western mining states and territories that have applied the mining law, the full maximum is allowed; but in colorado no claim is legal if it exceeds a width of feet, while in four counties of the same state claims have been restricted in width to feet. by legislative enactment, since september , , claims in all counties of colorado are permitted to be taken up feet in width. the citizens or miners of any new district, in any state or territory, may elect to limit claims to any size less than the maximum granted by the statutes and such a decision will be recognized by courts as binding upon all comers. this is an example of the rights of custom in establishing common law. in all shapes and widths of lode claims, there is now the rigid restriction that the two end-lines must be laid off exactly parallel. [illustration: a gilpin county, colorado, scene, showing the prize, gunnell, concrete, gold collar, and eureka mines.] the laws of our country contemplate the right of any locator of a vein to follow such vein down upon its dip, even if it extends beyond vertical planes passed through the side boundaries. the vertical planes through the end-lines, however, may not lawfully be penetrated in the extraction of ore bodies. the application of this doctrine of "extra-lateral rights" has led to innumerable controversies that have crippled many worthy mining enterprises. the inevitable habit of different veins to intersect, branch, unite, and in many other ways to cause complications, has served no purpose but to delay operations, cause legal warfare and embitter neighbors. so unjust have been courts' decisions in interpreting the lax laws that various mining districts have taken unto themselves the prerogative of deciding for themselves what is justice to all concerned; and we therefore find that many "camps" have unwritten laws under which claimants are restrained in their underground operations, to the ground contained between vertical planes _through all boundaries_, whether end or side. this is obviously the only fair plan, and it is hoped that, whenever the legislators at washington get time to give to the matter the attention it deserves, our nation will be favored with a revision of this and a number of other objectionable mining laws which have retarded the industry. ours is the only country having laws permitting extra-lateral rights and, upon this score, we are criticized by all foreigners. the canadian government appears to leave the framing of mining laws to the several provincial governments. ontario and quebec have very good and simple laws relative to mining claims. in some respects the laws of the two provinces are similar. for example, in each province a claim must be laid out as a subdivision of the usual public survey and is normally acres in extent. again, no prospecting or locating may be done except by persons holding so-called miners' licenses or miners' certificates, which cost $ to $ per year. no extra-lateral rights are recognized. in ontario, a patent may be applied for any time within - / years of the date of certificate of record, and the land is purchased outright by the payment of $ per acre. the patent thus obtained conveys no rights to timber or water on the property. in quebec, patents are never issued and mining claims are held by a sort of lease, as it were. a license to hold a mining claim costs a flat fee of $ , plus an extra fee of one dollar per acre. at times, arrangements are made for holding and working mining property upon a per cent royalty basis. the mexican laws permit the location of any number of claims by individuals. a locator is required to employ an expert (_perito_) to make a careful survey of his claims (_pertinencias_), which are taken up in rectangular form. measurements are according to the metric system, and the unit of area is the _hectara_, which is the area of a square with -meter ( -feet) sides, and is equivalent to . acres. the government's sale price for mineral ground is _pesos_ (about $ . ) per hectare, or approximately one dollar, united states money, per acre. the unit size of a claim is a hectare, and it thus comes about that the words _pertinencia_ and _hectara_ are used somewhat synonymously. under united states laws, the owner of agricultural land, if he has not committed perjury in perfecting his title, will hold all minerals which may be disclosed subsequently to the granting of his deed. the proof of false representations will rescind any such patent and the ground will revert to the government and be again open to location. in the surveying and laying off of mineral claims for patent purposes, the united states laws require the claimant to put the work into the hands of a mineral surveyor. such a surveyor may usually be engaged in any mining district and he will hold a commission from the department of the interior authorizing him to do this sort of work. he will have passed certain examinations as to his capabilities and he will have filed bonds in the sum of $ , for the faithful performance of his duties to both the government and his client. he receives no compensation from the government, and each claimant may make such terms with him as are equitable. he must hold no interest, directly or otherwise, in the property he surveys, nor is he permitted to file upon any mineral land. if he undertakes a case for a client his duties require him to survey the boundaries of every other mineral claim which may be contiguous to, or conflicting with, the one in question, and his maps must accurately show all such claims. his notes will contain sufficient data to accurately convey the exact location, the chief topographical features, the conflicts with all other locations, the position, and description of all mining improvements, and many other details which will be required in the final purchase of the land from the government. the surveyor's fee will vary from $ to possibly $ for a single claim, much depending upon the nature of the survey, whether simple or difficult, and upon local financial conditions and competition. after the filing of the mineral surveyor's notes and plats with the surveyor-general, critical examination of the documents is made, and if they are found to conform with all requirements, the case is "approved" and it may then pass to the local land office of the district. next begins a publication period of sixty days, during which opportunity is offered the public to enter objections to the issuance of a patent, either for reasons of conflict or because of fraud. if no such adverse proceedings are instituted, the patent will follow, in due time. the ultimate expense of securing a patent to a claim of, say, the maximum area will not be less than $ , and it may run as high as $ if in a region difficult to survey or if there are a good many conflicting surveys. a mineral surveyor is prohibited from acting as attorney for the claimant in presenting his claims before the land office, so an attorney's fee must be added to the above rough estimates. as a matter of fact, although the surveyor does not nominally appear as the attorney, in many a case it is he who makes out all of the documents to be then signed by an attorney in fact. the laws are faulty in this respect. the lawyer recognizes this fact and he asks the surveyor to make out the many legal forms; for who is so fully cognizant of the property and the desires of the claimant as the surveyor who has become intimately acquainted with the premises, its workings, its desirable features and everything concerned with the adjustment of conflicts? it is to be expected that he could best protect the claimant's interests, and it is wrong to retire him at this very critical time prescribed by a foolish law. the fee of an additional man in the case is an unjust burden upon the client. land office officials have recognized this fact. they know that the best documents reaching their offices are those prepared by mineral surveyors. vii placering. different writers hold the following slightly different definitions of a placer: one says, "a placer is a surface _accumulation_ of minerals in the wash of streams and seas," while another writes that a placer is "a _place_ where surface depositions _are washed_ for valuable minerals, such as gold, tin, tungsten, gems, etc." one definition conveys no notion of the operations of mining, but is merely geological, while the other involves the thought of the recovery of values. no matter how or where found, placers were all originally of surface deposition. they are now found in gulches, cañons, valleys, ocean and lake beaches, glacial drifts, and sometimes beneath eruptive flows. such placers as occupy the courses of streams are spoken of as gulch, valley, bar, and bench placers. the meanings of the first three names are obvious. by a bench placer is understood a deposit that was originally the bed of a stream, but which, in the course of time, has been cut down, or through, in such a manner as to leave a shelf or bench of the "wash" hanging up some distance above the present base of the gulch or valley. when such deposits that have been covered by lava flows are disclosed and worked, they go by the name of "buried placers." they are, by no means, uncommon, and typical "drift mines" of this sort are operated in california and new zealand. they present the novelty of working alluvial deposits under cover of solid rocks, and they thus conform to one of the early definitions of a mine, as previously given. since the workings of such subterranean placers are generally confined to an approximately horizontal zone, the mine passages, to a certain degree, resemble those of a coal mine. placer deposits, being of a secondary nature, the materials are not in the place nor form of the original components. the gravels and sands, together with the valuable contents, probably originally existed in some solid forms such as rocks or massive minerals. the primary structures, in the course of ages and by atmospheric agencies, have been disintegrated and carried by gravity and flowing water to lower levels. the finer the decomposed material, the further it has been transported. if the original rocks carried gold, the flakes of the metal, being of high specific gravity, would tend to settle to the bottom of the channels and to be carried shorter distances than would the lighter, non-metallic particles. the finer the gold, the more evenly will it be distributed in the bed of gravel. likewise, placers near the heads of gulches, as a rule, carry coarser gold than those farther down stream. the valuable materials found in placers must, of necessity, be those that possess the property of resisting corrosion and disintegration. the minerals and metals are, therefore, of a very permanent character. every find of "values" in a placer is unquestioned evidence that somewhere, above the present deposit, there originally existed primary depositions containing the valuable metals or minerals. the trail can frequently be traced back to them. these so-called "mother lodes" are not necessarily rich. in the case of gold, for instance, these original deposits of ore may not carry the metal in coarse enough particles to be visible and yet the placers may contain nuggets. there are numerous theories proposed to account for this observed phenomenon, but we will not discuss them here. the fact remains that nuggets have been actually produced artificially in flowing water under conditions similar to nature's. the methods of prospecting and working placer ground have undergone many improvements, but there are still many men practicing the primitive ways of a generation ago. the use of devices of simple construction and for operation by muscular effort is still familiar in many regions; and there are good miners who cling to such practice in the belief that it is the cheapest and truest way in which to ascertain the values of wash deposits. also, there are many placers of limited areas and irregular shapes that cannot be well handled in any other manner. with a "pan," a man can wash, in ten hours, not over one cubic yard of dirt; and to accomplish this amount of washing the ground must be very loose and favorable. an ordinary ten-hour day's work is about pans. this is equivalent to about one-half of a cubic yard, which is the unit of volume in all placering operations. one may thus readily arrive at the cost of carrying on operations in this way. a cubic yard of ordinary placer dirt is the equivalent of less than two tons. a _batea_ is the mexican equivalent for the american iron gold pan. it is a sort of broad, conical, wooden bowl and its capacity is not equal to the pan. a "rocker" or "cradle" is a trough on rockers somewhat like the old-fashioned child's cradle. in using it, a stream of water is caused to flow into the device which has been nearly filled with gravel and the miner gives it a rocking motion that causes the contents to classify or stratify according to the laws of specific gravity. the valuable particles, being the heaviest, will settle to the bottom, whence they may be subsequently removed. a "long tom" is an inclined, narrow box set stationary with a constant stream of water entering at the upper end. gravel is also shoveled into the device at the same point. the process is more continuous than the preceding ones, the values accumulating at the bottom of the lower end, while the upper layers of gravel are carefully removed by skimming with shovels. the work will keep two men busy and the capacity is correspondingly greater. with a long tom, two men will ordinarily handle about five or six cubic yards in ten hours. whenever deposits of a broad area, with considerable and uniform depth, are thought to be valuable, it has become a practice to prove their value by "prospect drilling." this is a mechanical method and one form of apparatus employed is of the churn-drill type common throughout oil and coal regions. with these portable machines, holes are put down to bed-rock at intervals across the ground. as they are sunk, the holes are cased with iron pipes, the drillings are carefully saved and washed, and the values are estimated for each foot of descent. from the summation and averages obtained from all the holes, a very fair knowledge of the ground's worth can be obtained. intensive placering is now the order of things and the marvelous increase in the use of dredges attests the success which these "gold ships" have attained. it is very interesting to watch the operations of these huge boats loaded with ponderous machines, especially when they are installed in inland regions or up in high mountain gulches. yet numbers of them are thus in steady use. wherever suitable beds with a tolerably uniform size of boulders and gravel are found, dams are built to retain the flows of streams until ponds are created of sufficient size to contain and float the barges. [illustration: dredges of yuba consolidated goldfields, hammonton, california.] continual improvements are being made in the construction of these mammoth machines with a view to economy in operations that will result from greater capacities. all costs of placering are reckoned per cubic yard washed. costs have been rapidly dropping during the past decade until now some companies, with extensive operations, are handling dirt at not to exceed three cents per cubic yard for excavating, washing, wasting the refuse, maintenance, repairs, labor, taxes, interest on investment, and the depreciation of equipment. such figures will hold good only under very favorable natural conditions of ground and climate such as prevail in california; they have not been attained in the frigid regions of alaska nor in the torrid south american interior. in view of the wonderful improvements brought forth by mechanical engineers, it is improper to deny that the future will bring still further reductions in placer costs. on the contrary, the signs are good for material reductions. dredges are very costly in their installation. they are usually designed to handle so many thousands of cubic yards per day. it has been stated, as a fair but rough rule, that "bucket" dredges will average, in initial cost, one dollar for every cubic yard the boats will handle per month. thus, if a dredge of this type is built to treat fifty or seventy thousand cubic yards in a month, working steadily, the costs will be respectively $ , or $ , . other types of dredges, known as the "dipper" and the "suction," will cost less than the bucket type, but have not gained general usage. "hydraulicking" is extensively practiced. this term signifies the working of placer deposits by water which is conducted through flumes and pipe-lines and, by means of nozzles called "giants" or "monitors," is directed, in huge jets, against the banks of gravel. these banks or walls are thus torn down and, by the same water, the loosened, disintegrated materials are caused to flow into and through long, wooden, box-like troughs known as "sluices." the floors of these sluices are paved with ribs, cleats or other obstructions termed "riffles" whose function it is to retard and collect the heavy particles which may, later, during the process of cleaning up, be removed as the valuable product. the word "sluicing" is frequently used quite synonymously with hydraulicking. costs of this latter sort of placering are considerably higher than those of dredging; but there are many deposits not adapted to dredging operations that may be nicely worked by sluicing, so that there will always be a field for this scheme. average costs are difficult to obtain since it happens that most of the companies now operating hydraulically are secretive in their accounts. more labor is entailed, more time is required, greater delay is occasioned in cleaning up, and the amount of water used is much greater. where water is abundant, this last item need not be considered. it is well to remember that even a very large dredge, while requiring a continual and large flow of water through its devices, can still operate with just the water in which it floats, this water being pumped and used repeatedly; whereas, in the case of hydraulic mining, the water may be used but once and, consequently, there must be a large supply and at a good head or pressure. but, in spite of these disparaging points, we find instances in which, under peculiarly favorable conditions, hydraulicking has been carried on at very low figures. e. b. wilson says: "the yield of the gravel at north bloomfield was . cents per cubic yard; the cost of mining, . cents per cubic yard. the yield per cubic yard of gravel at la grange was . cents, the cost of mining, cents. the costs of mining at these two mines would analyze about as follows: labor, per cent; supplies, per cent; water, per cent; office, per cent. ground carrying but . cents per cubic yard has been worked at a profit at the first mine. with such a small margin to work on, it is evident that skill and executive ability must be provided from the pipemen up." it is claimed that an idaho mine was worked profitably with less than two cents value in the dirt, but this is to be regarded with some doubt. [illustration: the snowstorm placer, fairplay, colorado. a typical hydraulic mine.] there are large deposits in the arid portions of the globe where water for working is not obtainable. to meet such conditions, numerous inventions continue to be placed upon the market. these devices are all planned in such a way as to use very little or no water. if water is required at all, the machines are expected to use it repeatedly. the machines are built to effect the segregation of the precious contents gravitationally, electrostatically, pneumatically, and by amalgamation with mercury. it is too early to say how successful such devices will prove in commercial operations. because some of them have not "made good" does not mean that genius will not yet cope with the situation; and we look into the future to see large operations efficiently and economically conducted by dry placer machinery. there are now no authentic figures obtainable upon this question of dry placering costs. viii open mining. some mention has been already made of open mining. the greatest development of this sort of mining has come about since the application of the modern steam shovel to the excavation of ore. this practice was an american innovation and it is being adopted throughout the world wherever natural conditions will warrant. within the past few years, immense bodies of iron ore have been discovered in northern minnesota and the adoption of these immense, mechanically operated shovels has worked such economies in the mining of this kind of ore that entirely new cost figures have been established and tonnages are being produced which, a few years ago, would have seemed unbelievable. there are about a dozen mines of this "open pit" type that have each produced over a million tons of ore per year in a season that must cease with the close of navigation on the great lakes. one mine has shipped over three million tons a season. at the utah copper company's mine in bingham cañon, utah, a great deposit of low grade, copper-bearing eruptive rock is being handled upon a steep mountain-side by this same scheme. this ore averages a little less than two per cent. in copper, but so economical is the handling of it in such vast amounts that a neat profit is made above all mining, transportation and milling charges. when the red metal sells at thirteen cents per pound, the gross value of this ore is about $ . per ton. this mine has maintained an output of ten thousand tons or more per day over long periods. a famous gold mine in queensland, australia--the mount morgan--is also being worked by steam shovel methods. the deposit is here in the form of a small mountain and the operations are gradually razing this landmark to the level of the surrounding plains. the mining of low-grade _gold_ ores by open-pit methods has taken hold in america, and an example of the practice may be found at the wasp no. mine in the black hills. according to published accounts of the operations of this company, all of the costs of mining and treating the ore amount to only $ . per ton. the ore body is a bed of quartzite lying nearly flat, and averaging in the neighborhood of only $ . per ton in gold, the only mineral of value. the recovery of this metal is at the rate of between and per cent. efficiency, or about $ from each ton. the net profit is therefore close to one dollar per ton. this very modern scheme of mining has been made possible through the recent advances made in the cyanidation of ore, and it is going to pave the way for many more such mining plants. [illustration: steam shovels and churn drills, copper flat, ely, nevada.] the nevada consolidated copper company has conducted vast mining operations "in the open" at ely, nevada, by the use of -ton shovels having a capacity of two and one-half cubic yards per dip. one shovel has handled as high as , cubic yards (the equivalent of about , tons) in nine hours; but this must be recognized as an exceptional run, and cannot be taken as an average. the ore has a thickness of about feet and covers many acres. as in the majority of such properties, there is here a large amount of "overburden" to be removed and disposed of before the ore can be excavated. this process of uncovering the ore body by the removal of the overburden is called "stripping." the cost per ton of ore mined is said to average cents. in an open mine there must be maintained a system of continually changing tracks placed upon grades (sometimes rather steep) and with sharp curves. with multiple switches, numbers of small locomotives are kept busy pulling and pushing up and down the tracks with their strings of loaded cars and replacing the "loads" with "empties." when such operations are upon a mountain-side, a very beautiful panoramic view may be had from the opposite side of the gulch. generally, the ore material is disintegrated to some extent. in some cases, it will actually crumble down before the advance of a steam shovel. in other mines, it is necessary to drill large holes which are loaded and blasted. it is becoming more and more important for the active mining man to post himself upon the methods and economies of this latter-day mining practice. the development of this open or surface mining has introduced entirely new economic ideas. with no costs for timbering of mine passages, for ventilation, or for hoisting, and with a very material decrease in manual labor per ton mined, immense masses of rocks are now really ore, although a few years ago they were nothing but lean, country rock. in consequence of the success attained by the pioneers in this kind of mining, there has been created a demand for properties possessing large deposits of low grade ore that is workable on this intensive scale. copper properties have been holding a prominent place recently and stockbrokers carry regular lists of "porphyries," this nickname having been coined to cover the companies operating in the low grade porphyry ores of the western united states. not all of these porphyry companies will use surface mining methods. some companies in the globe district of arizona have started extensive underground schemes for mining large tonnages very cheaply by "caving" methods. ix considerations preceding the opening of mines. the word "exploitation" is used by many mining men and engineers to signify a plan of so opening up ore deposits as to render the contents removable. the same persons use the word "mining" to mean the operations involved in the actual extraction of the ore exploited. it is sometimes difficult to draw any line between the meanings of these two words for, as handled by different men, with varying shades of intention, they are sometimes synonymous. thus, if exploiting an underground mine, which carries ore right from the surface, means developing the mine in such a way as to provide for a large, steady production, it is difficult to see why the ore taken out in this process cannot be said to be "mined." by "dead work" is usually meant that work of opening up a mine which will put or keep it in a producing condition but which does not supply any remuneration in the shape of ore (or coal). again, as used by some men, there is little distinction between this work and exploitation. there may, however, be lines reasonably drawn between these three terms, and therefore the following definitions are proposed: _dead work_ is such work as is necessary to develop an ore body, but it does not produce any ore. it may be prosecuted for drainage or ventilation purposes or for creating passage-ways for men and products. _exploitation_ is also work performed in opening up or developing a property, but it does not contemplate the value of the extracted materials which may, or may not, be of any commercial importance. indeed, much ore might be extracted during work which was carried on merely to define extents or boundaries of ore bodies. in this last supposition, the original sense of exploration is brought out and this should serve to fix the definition clearly in mind. _mining_ may be restricted to mean the methods and work involved in the profitable production of the mine's ore (or coal). the term would not be used to cover operations of shaft-sinking, tunneling, and the like, unless such work be in the valuable materials. mining may be said to begin whenever there is produced an output upon which there is some profit. exploitation may be in valuable ground. if so, we may say that mining is in progress during the exploitation. the driving of levels or drifts in an ore body--or of entries in a bed of coal--produces the valuable products of the mine, and we may, therefore, consider that mining is taking place. the driving of a crosscut through barren rock to reach an ore body is dead work; but the driving of a drift or level in a vein is either exploitation or mining. dead work produces _no_ ore. exploitation may, or may not, produce ore. mining must produce ore. throughout all of the above and the following discussion of this chapter, the reader should bear in mind the point that the word "coal" may be substituted for the word "ore" without altering the substance of the definitions or the conclusions. before a mine is opened up, the economist-manager will consider many items. in the first place, care must be exercised in the _examination of the title_ to the property. a mineral property may have passed through the most complicated kind of transfers of fractional interests in the title, just as is true with ordinary real estate. the abstract must be traced back clear to the issuance of patent from the government, and then on back to the original location. with an undeveloped property (a prospect), this precaution is essential to estop any possible pretensions to ownership, by outside parties, in case the ground subsequently turns out to be exceptionally valuable. it has often been the case that no obstructions from any adverse claimants have been met until owners have, in good faith and at great expense, developed splendid mines. then suits for possession or partial ownership have been instituted, sometimes with marked success for the plaintiffs. there are persons who make it a special line of business to examine titles to mining property, and it is economy for the average manager to employ such experienced men to attend to these matters. _topographical considerations_ will hold a place in the study preceding the opening of a new mine. the nature of the surface of the property and the surrounding country will largely influence in the selection of the proper site for the mine's mouth. neglect upon this point has been a common cause of failure in mining operations. a mine opening must be away from all dangers of snow-slides, rock-slides, cloud-bursts and deluges from overflowing streams or breaking dams. it may make a difference in the mine's ventilation as to which direction the prevailing winds blow and therefore upon which side of a hill the mouth be opened. _transportation_ facilities must be given due thought. if means are not already at hand, one must inquire into the feasibility of constructing some form of carrier; and here, again, will enter the question of the surface's contour. if a railroad is out of question, possibly an aerial tramway may be constructed. these modern conveyances stop at no obstacles of surface configuration and are dependent only upon the necessity of having the point of delivery lower in altitude than the point of loading at the mine. with some of the modern improvements in these installations, mine products are being transported up-hill as well as down-hill through the application of power. in mining regions, it is generally the case that the mines, themselves, are above the settlements in which are the railroads or treatment plants, so that the mine products will transport readily by the natural force of gravity. _climate_ holds an important place in the economics of mining. the working of very rich pieces of ground may prove a losing proposition in some portions of the world where the climatic conditions are such as to render operations possible during only a very small portion of the year. extremes of heat or cold, malaria or other pestilential obstacles, long rainy seasons with floods, and the hostility of native humans, beasts or insects have accounted for the abandonment of seemingly attractive mining projects. the question of _labor_ must be given due thought. it is true that the best miners on earth are americans. we do not deny that many of our miners are of foreign birth, but the fact remains that they perform better and more intelligent service than do their fellow countrymen who have not been adopted into our country. our men are in demand in the mining development of foreign countries. an american mine manager will always experience dissatisfaction while endeavoring to get, from natives in foreign parts, the same efficiency that he is accustomed to receive from the miners "at home." he may be paying a good deal less per capita for such labor, but he finds he is actually paying more per ton of output. even within a single country, there are notable differences in the worth of labor. the natives of some of the mexican states are far preferable to those of other states. within the united states, there may be discerned material differences between the efficiencies of the citizens of various sections, when it comes to mining. one cannot procure as competent miners in some of the agricultural states as in the typical mining states. this is but to be expected. for instance, there are deposits of lead ore in the "moonshine" regions of kentucky which have never been successfully worked, and the real cause of failure, in the writer's belief, lies in the inability of superintendents to obtain real miners either in that region or from the outside. the residents will never become miners; outsiders will not enter for work under existing sociological conditions. the question of _unionism_ is sometimes held by managers as a deciding one when debating the opening of a mine. while there are those who will broadly denounce such organizations, there may be found other and just as successful mine operators who declare that the effects of union control over their miners are beneficial to their companies' interests. probably the greatest objection to unionism raised by operators is that they resent the dictation that accompanies the inauguration of union rules in their mines. the owners and managers prefer to run their own business to suit themselves. some managers are so imbued with this conviction of their own rights that they will refuse to open up mines or, if they are operating, they will close down their mines before they will submit to the demands made upon them by the union officials. on the other hand, there are mine managers who prefer the presence of some central, labor-controlling body; for they believe that the men who belong to such a large federation or organization will, and do, have less complaint to make and therefore work more freely than is the case with the independent laborers. the argument is that these union men are satisfied because they feel that their interests are being looked after with a sort of attention that they, individually, could not give. this is not a place to discuss the crimes that have been laid at the doors of both the labor organizations and the mine owners' associations. it is safe to assume that wrong has probably been done by both sides. but it is furthermore right to believe that most of the crimes were not authorized, nor recognized, by the officers or the majority of members of either side. individual members must not be taken as averages of the membership in any kind of civil, social or political organization. it seems entirely wrong that _politics_ should enter into the considerations of a mine manager whose operations are apparently so apart from affairs of state; but the fact remains that there are places where mining operations cannot be carried on without the good will of certain officials of the state or national governments. it is not advisable to enter into any compromising terms to gain privileges for carrying on any legitimate business for there are other, better ways, generally, of attaining the justice that is deserved. one must not omit to investigate the _sources of supply_ for all the needs of a mine and its camp. there are many kinds of materials needed to keep a mine going. fuel, machinery, timber, water, food for men and beasts, lumber, and all household furnishings and necessities must come from some markets or natural sources. it behooves the cautious manager to see that all these things may be had in ample amount and at figures which will not prove annihilating to his business. in utah, there are mines which have all their timbers framed in and shipped from the forests of oregon, the sawing and framing being done before shipment to save on freight. the fir of oregon is shipped to distant australia for mining purposes. the arid camps of nevada get their supplies of timber from the sister state, california. the michigan mines are fortunate in being in a lumber region. colorado's metal mines are more favored in the matter of timbers than are the coal mines of the same state. most of the coal mines are upon the barren plains, while the metal mines are chiefly in the wooded mountains. [illustration: mill of the pittsburg-silver peak gold mining co., blair, nevada.] water may be too scarce for the needs of a mine or its community. there may not be sufficient to supply boilers or a mill, or for the domestic purposes of the workers. on the other hand, water may be so abundant in the mine workings as to prove a deterrent factor in profitable operation. with shaft mines, having deep workings and low grades of ore, if water must be delivered mechanically, the costs for such drainage are frequently prohibitive of mining. some mines, in arid regions, have been fortunate in striking such flows of underground water that it has been possible to operate mills right at the mines. in this way, the cost of water hoisting has been more than compensated in the milling benefits which, in turn, have decreased freights and treatment charges. _machinery_ is usually purchased at centres of mining supplies and manufactures. san francisco, los angeles, salt lake city, denver and chicago are the principal _rendezvous_ in the west for mining men in need of machinery. mexico city is, similarly, the outfitting point for the mines of southern mexico. the united states holds the supremacy of the world in the matter of equipping mines and mills, large orders of american-made mining machinery being shipped to even the antipodes. the nearer a property is to a depot of supplies, the less is bound to be the cost of getting goods onto the ground. it is this last item--the delivery of goods--that must be recognized as a very pertinent, and sometimes a critical, factor upon the cost side of mining accounts. mines that are remote or in rugged countries are frequently dependent upon animal transportation. in some cases, machinery going to the mines must be so built that it may be taken apart into small portions suitable for loading upon the backs of horses or burros, or even, in the andes, upon the frail llamas. operations, if planned to be conducted for a long term of years and therefore warranting the installation of large and expensive plants, should be based upon the holding of extensive ore-bearing ground. here enters the notion of the _shape and size of a mining property_. with some kinds of mining ground, the best form for the holdings would probably be a compact, approximately equilateral tract, covering a reasonably large acreage. this would be the case with ores that occur in sedimentary beds, for instance, where it is advisable to have the mining plant centrally located so as to work expeditiously the entire area. this would apply to a region like the cripple creek district, which contains innumerable veins running in all directions but displaying no outcrops. in other instances, the most desirable shape might be long, narrow strips so laid off as to contain the strikes of persistent lodes or veins, as those of the wonderful comstock lode region. it is not acreage that counts here so much as lineal extent. in the transvaal, land is held in rectangular blocks. the first owners of the ground took it up for agricultural purposes. this same statement is also true of the mining properties in the joplin district of missouri and kansas. in the case of the south african properties, every company has definite boundaries to which operations may be planned. hence it is possible for the management to so plant any mine as to operate it at a given rate for a predetermined life of the enterprise. the work is planned to maintain a certain output that will exhaust the ore bodies in just so many years, and all the equipment may thus be purchased with the forecast that it will serve its purpose and perform its economic share within the prescribed time. this notion will be more readily understood when we consider the various types of ore bodies. with properties wherein there is no possible way of predicting the number, size, and worth of discoverable ore bodies, the life is wholly problematical and it is therefore difficult for a manager to decide how much he should expend in the initial equipment. x mine openings. in every new mining project, there is much to be considered concerning the expediency of opening up through shafts, inclines or adits. more attention has lately been given to this subject than formerly. there are very good reasons for the selection of any one of these kinds of mine openings. the words shaft, incline, and tunnel have been handled with careless meanings by mining men. it is time that some definitions be accepted so that everybody will use these terms with the same meanings. a shaft has loosely been any steep opening sunk through the ground. an incline--sometimes spoken of also as an incline shaft--has been taken to mean an opening resembling a shaft, but not very steep and not approaching verticality. right here, there has been too much latitude of speech and it has entailed the necessity of many awkward explanations. by a tunnel has been intended any (approximately) horizontal passageway driven from the natural surface. objection to this use of the word rests in the strict definition of a tunnel, which states that it must have both ends open to the natural surface of the earth, as for example, an irrigation or a railroad tunnel. a level passageway which has but one end open to daylight is not properly spoken of as a tunnel. in mining practice, practically every horizontal opening of this nature is open at only one end, and it is an adit rather than a tunnel. if the precaution of speaking of it as a "mining tunnel" is observed, very well, for this may be taken to be an expression synonymous with adit. the latter term is, however, shorter and more correct. for the sake of a uniform usage, the following definitions are proposed. their use will conform with the usages of those well-informed persons who adhere to correct speech. a _shaft_ is a truly vertical mine passage which may, or may not, be sunk in or along an ore or a coal body. an _incline_ is any mine passage which occupies a sloping position and which may, or may not, maintain a uniform inclination throughout its length. it may be sunk along, or in, a pitching vein or seam and it may thus conform to the irregularities of the dip of such body. it is neither horizontal nor vertical. such an inclined passage following a seam of coal is known as a _slope_. it sometimes happens, especially in coal mining, that a sloping passageway is driven through barren rock either to get at known bodies by the shortest means or to establish uniform grades for tracks. in a strict sense, these are not inclines or slopes, for they do not even approximately follow, nor parallel, bodies of value. the miner's term for such an opening is _rock slope_. an _adit_ or _mining tunnel_ is a horizontal opening driven from the surface. if it be driven along an ore body, as a vein, it is properly called a _vein adit_; if it is driven _across_ barren country to intercept presumed or known bodies, it is spoken of as a _crosscut adit_. all adits must be given a small amount of grade for drainage necessities. before getting underground we should consider what is required in the way of opening our mine; what is positively known about our body of coal or ore; and what conditions are liable to confront us later on. we must consider the type of ore body; character of material to be extracted; average thickness and hardness of the body; desired tonnage; power facilities; probable surface and underground drainage to be maintained; and dozens of other things which only the experienced man will think of and appreciate. the right kind of a manager will know that he cannot afford to overlook such points. every case involves different contingencies, and therefore extreme forethought must be given to the subject before deciding upon any particular kind of an opening into the ground for mining purposes. this remark does not apply to such openings as prospect drill-holes, openings which are not for mining purposes, but for exploitation. assuming that sufficient data are known concerning the property to warrant the expenditures incident to the making of a mine, the question remains as to the best way of proceeding. it is a well-established fact that it is much cheaper to drive an adit than to sink a shaft of equal transporting capacity. it is also cheaper to drive an adit than to sink an incline. if the topography is such that an adit can be driven into or beneath an ore body and thus expose it from a low elevation, the temptation is strong and along lines of good practice to do so. if the country is quite flat or nearly so, or, if the surface is such that, while rough, an adit of reasonable length cannot be driven to tap the valuable mineral and handle it economically, then it is good practice to decide upon a shaft mine. an adit will not only be cheaper, foot for foot, than a shaft or incline, but, if given the proper, slight grade, it will afford a natural drainage outlet for all subsequent workings above its level. the cost of pumping, as already suggested, may be a considerable item and it may be a deciding factor in favor of an adit when this form of opening is possible. furthermore, an adit will obviate the installation and use of hoisting machinery, and thus there may be maintained a greater efficiency in the operating expense of the mine than would be possible with a shaft. again, it is a simpler and cheaper matter to maintain a mining tunnel in working shape than it is a shaft, particularly in bad ground. by the settling or "working" of the ground, a shaft may be thrown perhaps but slightly out of alignment and annoying interferences will be experienced in hoisting, especially when rapid and uninterrupted hoisting is necessary to maintain the desired output. while the same amount of disturbance does take place in an adit, it is an easy matter to readjust track grades while continuing regular haulage operations. the timbers, in the case of either a shaft or an adit, will require occasional renewal, but the expense of such repairs is less in adits than in shafts or inclines, while the delay to other operations of mining, in the case of the adit, will be inappreciable. topography has been referred to above, but it must be again briefly mentioned. there are some places in which ore bodies extend to, or exist at, such depths that adits could not be projected to get beneath enough of the ore to warrant their construction. an adit mine is not a practicable thing in a flat country like nevada or the rand, but in the rough country of the san juan it is the customary kind of a mine. in the very early days of comstock lode mining, shafts were sunk by each of the hundreds of companies. before a great while, the advantages that would accrue from having a deep "tunnel" became evident, and the famous sutro tunnel, with its historic, checkered career, was driven. although it loomed up like a gigantic undertaking for that period, the immense prospective or future value of it could not be denied. the following relative advantages of the several types of mine mouths are in addition to those already given and are worth consideration: with an incline, the value of a tabular deposit is determined as work progresses; the course and dip of the body will be known at all depths along the incline; the body may be explored from the incline in both directions, simultaneously, with a resulting doubling of the development and production; all, or nearly all, the material removed is "vein stuff" and its value may repay the sinking expenses; there is no losing of the ore body unless a geological fault is met. with a shaft, more rapid hoisting is possible than with an incline; the timbering labor is less than in the case of an incline, but greater than in the case of an adit; with ground containing ore bodies in irregular masses and at no uniform intervals, vertically or horizontally, stations and levels may be started wherever desirable; the crosscuts which are usually necessary to reach the bodies may disclose otherwise unknown bodies. [illustration: mills and shaft house of daly west mine, park city, utah.] with a vein adit, the vein is prospected as work advances; the ore removed may pay its own way, as it were; the drainage is automatic; ore is transportable from the mine by haulage rather than by hoisting; the ore in place is above the level and will handle itself to the outgoing passage by gravity. with a crosscut adit, in addition to the last three advantages noted for the vein adit, there is bound to be exploration of the ground upon at least one side of the known body; there will generally be easier haulage because of the straighter track, since an adit driven along a vein will conform to the geological irregularities and the track is bound to be more or less crooked. without counting upon the doubtful success of the numerous propositions in tunneling machines, but judging only from past experiences, we may say that a shaft will cost about three times as much as a "tunnel" of equal transporting capacity. if the ground is wet, the discrepancy in first costs becomes much larger. in a remote region, with difficult transportation of machinery and fuel, it may be better to drive and use a long adit rather than a shallow shaft. an adit will transport more product than will a shaft of equal dimensions. an adit may be driven to intercept a shaft and to serve as a sort of artificial surface, as it were, and thus save expenses in pumping and in hoisting up to the original collar of the shaft at the surface of the ground. no matter how crooked an incline may be, it is possible to hoist ore in conveyances known as skips, although the hoisting may be necessarily somewhat slow. these same conveyances are useful for lowering and hoisting men, and the parody, "men go down to the mine in skips," here finds its significance. the usual hoisting conveyances used in shafts are known as cages. they usually produce less friction than do incline skips. a skip in an incline must travel upon a track, while a cage, somewhat resembling a passenger elevator, has no wheels, but slides upon guides. however, an incline skip, because of the inclination of the passage, does not exert the same dead weight upon the cable and hoisting engine and hence these parts of the equipment may be made correspondingly lighter. skips for shafts are similar to cages in their lack of wheels. complete estimates of probable future requirements should be made before a shaft is sunk. when it becomes necessary to enlarge a single-compartment shaft to one with two compartments, the expense has been found to exceed one-half the original cost of sinking; while, to convert a one-compartment shaft into a three-compartment shaft costs fully three-fourths of the original sinking expense. approximately the same ratios of cost will hold in the case of enlarging inclines. character of ore sometimes influences the selection of the kind of passageway. some high grade, brittle ores must not be dumped nor handled repeatedly, since values are lost in the "fines." iron and copper ores will not probably be injured by any amount of dumping. coal should be handled as few times as possible. in view of this fact, other things being equal, adopt that system that will injure the ore or coal the least. as a rule, workmen are safer in tunnels than in shafts, since there is little danger from objects falling any great distance. tiny bits of rock have been known to kill men in shafts. on the other hand, there is less liability of injury from falls of large rocks in shafts than in adits. roof falls are a very prolific source of mine accidents. the workmen of neighboring mines will often be able to give much valuable information as to the proper procedure in opening a new property. for instance, water levels, amounts and kinds of gases that may be expected, the nature of the wall rocks, and other pertinent points may be learned by interviewing the men who are employed in adjacent mines. still better information may be obtained by personal visits to the underground workings of the nearby mines. in this connection, one must not permit himself to be unduly influenced by the prejudices or hobbies of the neighboring operators or their employés if there is reason to suppose that such notions are contrary to good practice. due consideration must always be given to the selection of some method of opening up what might be supposed will never amount to a great mine, so that, should subsequent disclosures exceed expectations, enlargement of the scale of operations can be advantageously effected. always bear in mind that legitimate mining is just as much a commercial enterprise as is any other kind of business. the utmost concern for financial showings must be constantly borne in mind. select a scale of operations consistent with the known--not the hoped-for--bodies of coal or ore; but have a certain feature of elasticity about the plans that may take care of future increase in business if found desirable. do not "over-plant." never plant, at all, _prematurely_. it is better to postpone the installation of the equipment until some specific facts are available. many companies have met defeat in the exhaustion of capital through the purchase and installation of elaborate plants which were never warranted. after a mine is once opened and preparations have all been perfected to operate upon a certain scale of output, it is quite essential that exploitation and production be maintained without material fluctuations, if the greatest economy is to be attained. exploitation, _i.e._, development work, must be kept well in advance of actual mining operations to assure plenty of working space for the extraction of the normal output. xi types of ore bodies. it has been necessary, a number of times in this discussion, heretofore, to make mention of kinds of ore bodies. it is well, at this time, to get some fixed ideas concerning the leading types of bodies of minerals which are extracted as ores. because of the laxity in type differentiation which has prevailed among miners and writers, the same geologists who have framed definitions of ore, have also defined the various types of ore bodies. the definitions, having been accepted by the leading mining geologists and engineers of the present day, it is well for us to fall into line and to agree with the authorities in such matters. a _vein_ is a _single, ore-bearing fissure_, generally, though not necessarily, with at least one well-defined wall. when we run across a tabular-shaped deposit of ore that looks as though it may have been put into a pre-existing fissure or chasm, the chances are that it is a vein. but a vein must not be confounded with a dike. a dike is a filling that has been injected, while molten or fluid, into an open passageway or rupture across rocks, or into an opening which it created for itself. a little examination of the material should tell, to even the novice, whether or not the substance is of plutonic origin. the filling of a vein is not eruptive, at all. veins have been filled from circulating aqueous solutions, by slow depositions, that have occupied very long periods. a vein may be any thickness, since a fissure may have been opened to any width. hence, a vein may be as thin as a sheet of paper, or it may be a hundred feet across. however, it is true that some wide veins have resulted by a sort of enlargement from original thin seams. very few of the notable wide veins of the world are believed to have been created by the filling up of chasms originally as wide as the present ore bodies. but, in all cases of real veins, there were original fissures, fractures or crevices which acted as channels for circulating solutions that contained the materials which were left to make the vein matter. a _lode_ is an _assemblage of veins_ so closely spaced that the ground between the veins becomes, in places, ore-bearing, and the entire width of the aggregation becomes an ore body. a zone of sheeted rocks like schist or slate, if sufficiently mineralized to warrant mining, would be a lode. sometimes, in certain districts, the earth's crust has been subjected to many approximately parallel, closely-spaced fractures, and by the subsequent filling of these cracks, with the accompanying corrosion of the walls and their replacement by ore, extraction of the entire mass of rocks across a considerable distance will be found to yield a profit. any such body is a lode. in the cripple creek district, the ground is criss-crossed in every direction by tiny fissures which have resulted from the contraction of the country rock, just as a bed of mud is fissured in the process of drying up after a rain. wherever these fissures are found in aggregates that are closely spaced and in which a majority of the cracks have a general trend so that the whole assemblage can be readily worked as one mass, this whole body of fractured rock may be found worth mining and it will then constitute a lode. it may be mentioned here that the so-called ore of this district is not really ore according to the accepted definition. the true ore, the filling of these innumerable, tiny cracks, really constitutes but about five per cent. of the material that is shipped as ore, but which is principally the "country rock" broken down with the small volume of ore. in _legal_ phraseology, the word lode has come to include all sorts of ore bodies. when the word is thus used, in a legal sense, it should not be confused with the strictly technical meaning. it has been the fashion for prospectors to dilate upon the fact that they have located "true fissure veins." this expression, formerly on the tongues of most mining men in districts possessing veins at all, is now obsolete and hence should be placed in the discard. there can be no such thing as an "untrue" vein nor an "untrue" fissure. neither can there be any vein without a fissure. therefore, if there is any vein, it must be a real or true vein. accordingly, the verbiage is to be discouraged. the intention of a miner, in using this pet phrase, has been to convey the impression that his vein extended downward, indefinitely; there having arisen a notion that some veins are rather superficial and liable to "peter out" at slight depths, while others--the kind he invariably has located--persist both in size and value to extreme depths. there are districts in which are found short fissures, generally confined to certain horizons in sedimentary rocks, such as the limestones of the great mississippi valley, from which are mined lead and zinc ores. these are called "gash veins." these are always readily recognized and there is not the slightest excuse for confusing them with the fissures which are common to other kinds of rock formations. a _bed_ or _blanket vein_ is the term applied to any nearly flat deposit conforming to the bedding. such a body of ore must be in a sedimentary series of rocks. coal bodies are all of this type. many bodies of iron ore are also of this type. a _chimney_ is an ore body which has not the tabular form of a vein but is rudely elliptical in outline, horizontally, and with a very considerable vertical extent. a _stock_ is a similar body but it is of still greater irregularity of boundary. these bodies are usually the filling of extinct volcanoes or geysers, and therefore they are presumed to extend to very great depths. the diamond mines of kimberly, africa, are of this type and the ore is a sort of hardened geyserite or mud in which are enclosed the precious gems. in custer county, colorado, the ore body of the bassick mine is a conglomerate of rounded boulders of all sizes cemented together, somewhat like concrete, by the materials which really carry the values. this mass occupies an ancient volcanic neck or throat of a geyser, probably the latter. the main portion of the cripple creek district is the crater of a great prehistoric volcano. it might be called a great chimney, but custom seems to limit the use of the word chimney to a smaller body such as might be included in a single mining property. a _mass_ is a deposit whose irregularity of shape is so great that it cannot be recognized as belonging to any of the types already mentioned. masses conform to no rules as to shape or size. they are usually the result of a chemical dissolving of the original barren rocks with a simultaneous or subsequent substitution of valuable materials. there are many instances of ores that have been deposited, molecule by molecule, replacing equal volumes of the previous rock, much upon the order of the petrifaction of wood. again, there are immense masses which are believed to have accumulated in caves already dissolved out of the containing rocks. while recent geological study of the districts in which such ore bodies abound have disclosed numerous facts about their occurrence, there still remains much conjecture concerning their origins, and we may still believe that they do not conform to any rules as to regularity or size. the ore bodies of leadville are of this type, and they may be described by the homely similes that they are as like and as unlike, and their occurrences are about as regular, as potatoes in a hill. the potato-tops give the farmer a suggestion as to where to dig. so, also, do certain geological relations guide the miner. and yet a shaft may be sunk hundreds of feet down among masses and not happen to penetrate a single one. there are numerous recognized types of ore body not enumerated here; but it is sufficient for the average layman in mining matters to understand these few distinct types and to believe that all other types are rarities, and are, as a general thing, but intermediate forms of those defined. [illustration: shaft no. , tamarack mining company, calumet, michigan.] [illustration: smeltery of the balaklala consolidated copper co., coram, california.] xii the questions of depth and grades of ore. the prevailing belief of a few years ago that ore bodies always improve with depth has been discredited. not a single mining geologist will longer maintain such a notion. the evidence of many thousands of mines has refuted this older belief and it has been proven that quite the opposite view is the correct one concerning changes of value with depth. values, instead of getting better, do actually, in the majority of cases, grow poorer as depth is gained. president c. r. van hise, of the university of wisconsin, was among the early expounders of the newer theories to account for this fact. the writer heard him state, years ago, before a scientific gathering (which, at that time, was not quite ready to agree with him), that if he were given his choice, he would much prefer to own the upper thousand feet of the earth's crust than all the rest of the globe. in this remark, he was referring only to mineral values, of course. this belief that the best values are to be found not far from the surface has since become popular, for it is based upon proven facts. it is not claimed that values are never mined below an elevation that is a thousand feet from the surface. there are many mines, and great ones, too, that are operating at depths greatly exceeding this distance; but in these same mines there will be found valid reasons for not applying the general statement to their particular cases. for instance, the great copper mines of the keweenaw peninsula are productive at depths of a mile or more from the surface; but we believe that here the ore must have been originally deposited at, or near, the surface, that it was then overlain with rock strata; and subsequently steeply tilted by earth movements which carried some of the ore bodies down to the depths where they are now found. the "reefs" or bankets of the rand are so termed because these ore bodies were undoubtedly ancient coast beaches or sea placers. the gravel, sand, and gold particles were cemented together into a conglomerate, then covered with many later sedimentaries, and finally the continent of africa was so raised or altered in some manner as to bring these gold deposits into their present inland and tilted positions. in veins or lodes, it is not supposed that ore-making minerals could have been precipitated from solutions travelling either upward or downward and obeying chemical laws if the depth were sufficient to furnish great temperature or high rock and hydrostatic pressures. therefore minerals which were deposited from aqueous solutions rising from depths, for example, must have retained their dissolved condition until they ascended to horizons in which both pressure and temperature were low enough to permit the precipitation and crystallization that create ores. contrarily, descending solutions must have given off their contents before reaching the deep zones of heat and pressure, or not at all. it is a quite common phenomenon to observe that the richest _gold_ ore in a mine is found close to the surface, if not actually at "grass roots." the explanation is simple. the gold, being the most stable of the aggregate of minerals composing the original ore, has the better resisted the corrosive attacks of atmospheric agencies and has remained nearly intact, while its associated minerals have been dissolved or altered and carried away. the same amount of gold remaining with a diminished quantity of the worthless, non-metallic minerals--the "gangue"--inevitably renders the ore richer per unit of weight (such as a ton), although per unit of volume the value remains constant, or nearly so, so far as the gold is concerned. but with other kinds of ore, as, for example, copper, the best grades are found, not close to the surface but some two hundred or more feet down. the explanation is that the minerals of copper are considerably more soluble than the ordinary gangues and therefore the weathering and oxidation that takes place in the upper horizons of ore bodies will dissolve out the cupriferous compounds and thus deplete the superficial ore. but, by the flowing of the copper solutions to a lower zone, there occur certain reactions that reprecipitate the salts of copper upon compounds of the metal already formed and we have instances of the phenomenon known as "secondary enrichment." [illustration: concentrator division, washoe reduction works of the anaconda copper mining co., anaconda, montana. largest copper works in the world.] it was this very process that effected the changes in the character of the ore in the famous anaconda mine, previously mentioned (page ). the locator's discovery was upon an outcrop rich in silver. probably the original compounds of the vein were of both silver and copper. the silver was more stable against dissolution than was the copper, with the result that the base metal was removed more rapidly and completely than was the precious metal. the upper portion of the vein was therefore left rich in silver, and low in copper. but, as depth of mining increased, there was found a gradual diminution of the silver content with a simultaneous increase in the copper. the mines of butte have become known as copper mines, and the wonderful records they have made are ample testimony to the fact that the change in the prevailing metallic values has not wrought serious havoc in the mining industry of the district. regarding the probability of veins persisting to great depths, there is this thought suggested by j. e. spurr: "owing to the pressure exerted by gravity, it is doubtless more difficult for a fissure to stay open in depth than near the surface. the tendency is to press the sides together. at a certain depth, it is probably the case that the pressure and the plasticity resulting from this, together with the increase in heat, makes it impossible for fissures, fractures or any openings to exist." there are still many persons who are reluctant to let go of the cherished notion about the improvement of ores with depth. but there is no economy in deceiving one's self, and the wise thing to do is to accept the truths as they are daily proven. it may be worth while to again refer to the wonderful camp bird mine. this mine was discovered in its true worth years after it had been abandoned by early prospectors because it lacked showy, base-metal minerals. however, since its true merit has been recognized, it has maintained large and remarkably rich annual outputs. as values were beginning to show a material decrease, about five years ago, an experienced mining engineer of recognized standing was engaged to give advice concerning the future exploitation of the property. after exhaustive investigation of the ground, and in the face of adverse opinions, he recommended the discontinuance of further development in depth. at the same time, however, he advised the exploitation of the ground laterally or along the strike of the very persistent vein. his advice was followed and the company's stockholders had reason to be advocates of the new theory; for a very reasonable amount of horizontal development work opened up vast stores of rich gold ore. and yet, notwithstanding this disquieting feature that seems to apply to mining, there is comfort to be found in the consideration of the exceptional cases. every man may hope that when he locates a new mine he is taking possession of a property that will have as extensive ore bodies as those that have been proven to exist in the lead-silver mines of laurium, greece, the quicksilver mines of spain, or the copper and tin mines of cornwall. these mines are in lodes which have persisted and have been mineralized to comparatively great depths, so that their bottoms have not been reached. there is a modern idea that has taken root in the minds of mining men of the last generation to the effect that the mines with rich ore are not necessarily the ones with big profits. there are many men looking for investments in mines whose contents are of low grade but in large bodies readily worked. if a mine with rich ore can be found and the ore abounds in such liberal amounts as to warrant the inauguration of a company with the essential working equipment, such a proposition will naturally not be turned down. however, the faith of some men is placed in those mines that may be operated upon very large scales for long periods even if the profit per ton be very small. with a large plant, the unit of expense, _i.e._, the cost of mining per ton, is less than with a small mine. with the assurance of regular outputs of ore of a reasonably uniform grade, the milling equipment can be planned to handle a mine's product to the greatest advantage. the alaska-treadwell mine, on douglas island, is an instance of a splendid property that has been continuously operated for about a third of a century. the ore is low grade in gold but immense dividends have been declared because the ore body, a tremendous mass of eruptive rock, has lain in such a position that the owners found it possible to excavate the stuff, to a great extent, by open-pit methods, although not by using steam shovels. the ore is treated in a vast mill contiguous to the mine. the homestake, another gold mine, has an ore body quite dissimilar geologically from, but of dimensions approximating those of, the treadwell. it is a great body of mineralized, crushed shales, standing steeply in the shape of a lode and carrying about $ . per ton. it has been followed down considerably over one thousand feet and although the grade has dropped somewhat with depth, there are known to still be millions of tons in reserve. according to estimates, the mine has enough positive ore in reserve to keep the mill running at the rate of , tons per day for several years even if no more ore were to be opened up. this ore nets but cents per ton above all mining and milling expenses; but a little arithmetic will show that this mine is worth twice as much as the mine that is producing, with more or less regularity, an average daily output of, say, forty tons of high grade ore upon which there is a net gain of $ per ton, a figure that is rather high for the average of so-called "high grade" mines. we must, therefore, decide that it is always wise to think twice before condemning a mine because its grade of product is low. it is only recently and by virtue of marked improvements in metallurgical processes that many bodies of mineral have become "ore." hence it is but natural that many of the older miners fail to grasp the possibilities that lie in such deposits. what is the line of value separating a low grade from a high grade of precious metal ore? there is no uniform practice along this line. one will notice that ores are nowadays spoken of as high grade that, before the practice of mining these described meagre deposits, were reckoned as low grade. this fact is due to two reasons, viz., the cheapening of metallurgical operations, and the greater respect that is entertained for ores of low metallic content. the esperanza mine, in mexico, is called a high-grade gold mine. its ore has averaged about $ per ton and the profit therefrom about $ . the oroya-brownhill mine, in western australia, has had ore that carried a value of about $ per ton and from it a profit of about $ per ton was made. in the cripple creek district, ores that run above $ per ton are considered high grade. this means that the average rich ore shipments of the district have a gold content of about - / ounces per ton. the expenses of mining, freight, and treatment will probably total close to one-half the gross value, or about $ per ton. when one speaks of $ or $ ore as rich or high grade, it is not to be inferred that there is no ore in the shipments which is not worth a great deal more than this amount per ton. such lots of ore will, no doubt, contain a great many chunks that would assay many times the average value. such selected materials would not, however, be samples; they would be what are called "specimens." the specimen has its place in mine economic discussions because it furnishes the basis of operations for the ubiquitous "high grader" with which nearly every new and rich mining camp must contend. some writers claim that the high grader is a product of modern conditions; but we find that he has existed for such a long time that he was given mention by the scotch historian and scientist andrew ure, who wrote of the precautions that were exercised in working the graphite mines of england, a century ago, to prevent the pilfering of even this comparatively low-grade material. even the ignorant african natives of today cannot be trusted to wear clothing while working in the diamond mines. no, the cause of high grading is the innate greed of human beings and it has existed from prehistoric time and among all peoples. in this discussion as to grades of ore, the question may arise as to what might be reasonably considered the most attractive kind of a mining proposition. this is too knotty a query to be answered in a few words. there are so many different phases that must be given due weight. every mine is a problem in itself. the minnesota mines afford the best examples of profitable iron mining. under the classification of underground, tabular deposits such as veins or lodes, no matter in what metals their values are found, mr. t. a. rickard believes that the ideal mine would be one carrying ore worth $ per ton, in a body five feet thick, with costs not exceeding $ per ton, and so mined as to keep one million tons continually in reserve. according to these restrictions, he thinks the robinson mine, of johannesburg, will about fill the bill as an ideal _gold_ mine. it has a deposit of about the right thickness to avoid excessive timbering expense and this ore body is in such a vast, continuous sheet that its superintendent can depend upon maintaining a systematic development that will assure a constant supply of ore to the immense mill for ten or twelve years in advance. this same ore averages about fourteen pennyweights (approximately $ ) per ton and upon this there is assured a profit of over five dollars per ton. xiii valuation of mining property. whenever a piece of mining property is to change hands, it is the proper procedure to employ an expert engineer to investigate the ground and the improvements and so arrive at some estimate concerning its intrinsic value. nobody is infallible and it is a trite saying that "nobody can see into a mine farther than the last drill hole." but there is a great difference in the reliabilities of reports made by trained and by untrained men. a self-styled "expert" of the type which is so abundant in every new mining centre and about cities frequented by mining investors will probably not be able to comprehend anything beyond his vision; but the mining geologist and engineer--the man who has devoted the better part of his life to study and experience along these lines--will be able to reach conclusions upon which much reliance may be placed. this fact has come to be recognized by the men who exercise business judgment in their mining investments. the sampling of mines has been studied and improved upon by succeeding engineers, until one may say that it is conducted along strictly scientific lines. the old method of taking a sample of a mine by scratching ore from the sides of a shaft from top to bottom and letting the collected material at the bottom represent a fair average of the ore body, has been relegated to its proper place in the evolution of mine valuation. without entering into a description of the methods now employed by the best examiners of mines, let it be said that every scientific precaution is taken to obtain representative portions of the ore bodies, at such intervals as seem best in each particular case; that measurements and assays are made for each and every sample taken and not for the aggregate of all the samples; that no opportunity is allowed unscrupulous persons to vitiate results in any manner; that a professional engineer will not hold nor acquire, in any way, an interest in any proposition which he examines; and that the report of a reputable engineer is equally acceptable to the seller and to the purchaser, no matter for whom the work is done. much discussion has prevailed as to the best means of estimating the amount and the value of ore in unbroken reserves. associated with these beneficial disputes, there has been a further controversy as to the correct classification for reserves of unbroken ore. it is now conceded among mining men and engineers to be improper to longer make use of the meaningless but tongue-worn expression "ore in sight" as signifying any known or unknown volumes of ore in the ground. the only ore in sight is that which has been hoisted or which has been broken and stored underground. well-known engineers have proposed the following expressions: to denote the contents of ore bodies which have been exposed on four sides, we may say _ore blocked out_, _positive ore_ or _ore developed_; for bodies exposed upon three sides, it is considered correct to describe the contents as _ore partly blocked_; for such bodies as are proved upon two sides only, the terms _ore faces_, _ore developing_ or _probable ore_ are appropriate; while in speaking of all ore that may be expected or suspected, but which is beyond the last exposures, we may use the expressions _ore expectant_ and _possible ore_. when it comes to the question of placing a value upon an undeveloped property--one in which there is little, or no, development work or exploitation--it takes more than the ability of the common "expert" of the curbstone variety to arrive at any dependable figures. without any exposures, except those that may have been produced by nature, and perhaps with no guidance from facts that might be obtainable were there adjoining mines, one might suppose that the whole matter would resolve itself into mysticism. right here is where the trained man best shows his ability. the greatest error of the usual investor in mining schemes is to rely upon either no report at all or upon a worthless one furnished by an impostor. _in no sort of a mining proposition is a reliable report so essential as when one is contemplating the purchase of a "prospect."_ successful engineers, whose predictions concerning such properties have come true, are sometimes complimented (?) by being accused of possessing intuition or prophetic vision. call this ability what we will, we must admit that _education and training_ give certain qualifications that will enable a man to arrive at conclusions which, in the majority of cases, will be found to wear. xiv the mine promoter. with the thought that has justly been given to the place occupied (or that should be occupied) in the world's financial and economic affairs by legitimate mining, there has developed a well-founded stigma upon the operations of a class of persons who have styled themselves by what was formerly considered a worthy title, that of "promoters." since men have found that it is as possible to go into a mining deal with the same chances for success as attach to any other line of investment; since it has been proved that real, worthy mining property does not require the exertions of many middlemen to obtain capital for its development; and since it has usually turned out that these "promoters" have handed the hot end of deals to their investors, it is not to be wondered that some sort of a brand would attach itself to the men who are not in the business to benefit the industry of mining in the least, but really for the selfish gains which they can pocket at the expense of the industry. these men are legion. the mails are laden with their seductive letters and "literature." brokerage firms are numbered among these leeches on legitimate mining. charlatans appear almost daily upon mining scenes. the men who engage in these deplorable practices are not from any one walk in life: they spring up from various branches of our social structure. the general public has learned that a very prominent boston magnate will not scruple to promote a mining property even though it lacks the merit essential in attracting the conservative capitalist. thousands of people of small means throughout the united states and canada have been recipients of nicely worded and familiarly-addressed letters signed by the son of a famous american author. this son, himself a writer of some repute, presumed to speak to his "friends" concerning a mining property which he promoted and into which he was glad to allow them to get with him "on the ground floor." he frankly stated that he was not offering such privileges to the big capitalists. he inwardly knew that such men do not require holdings in the cobalt or any other region. through the splendid work carried on by the government postal authorities many of these frauds have been exposed and the perpetrators brought to justice. in january, , the above-mentioned author, together with a number of his ilk, were brought before the federal grand jury, and found guilty. it is not the men of great capital who are induced, as a rule, into the deals of the "promoter." it is usually the common people, the persons of small means who have saved up a little spare money from which they hope to realize competencies for rainy days--a class of beings inexperienced in investments--who become the dupes of the promoter. there have been notable exceptions to the statement that capitalists do not yield to the seductions of these men, but recurrences are liable to be few. the great business man is fortified by experience against forms of treachery and he is, therefore, not so susceptible to the allurements of any "promotion," be it mining or otherwise. if one investigates these advertised mining "promotions," he will often find that the money paid in by the small investors purchases a very small portion only of the capitalization. the men who conceived the scheme of "promoting" a concern have carefully arranged to hold a majority of the stock, so that should there, by any chance, prove to be a mine, they are the ones who will reap the greatest benefits. further, it often transpires that the contributions of cash that purchase the small interests do not perform the function of development for which the stock was ostensibly put upon the market. perhaps somebody has a desire to get rich quickly. the operations of such frauds are so obscured and so complex to the average individual that sufficient evidence can seldom be procured to prove any violation of law. a witty newspaper paragrapher once remarked that out in nevada the old adage "death loves a shining mark" was changed to "death loves a mining shark." it would seem, however, that if death were to love the person bearing the odious, well-understood title of "shark" enough to claim him early, the business of mining would be materially benefited. the post-office officials of the united states are to be commended for their efforts at curbing the despicable operations of these fakirs. occasionally the papers come out with the news that a firm's offices have been raided and their business stopped. these news items fall as awakeners upon the hundreds of gullible, middle-class persons all over the country who are known to actually force their cash remittances upon these fraudulent operators, much upon the plan of a department store's supposed bargain sale. in spite of the "bad name" that has been attached to the persons engaged in starting up enterprises, there is a real need for more activity in the matter of inaugurating real, legitimate mining enterprises. persons who devote their brains and energies in the direction of furthering worthy mining propositions do really "promote" the interests of such companies. what shall such persons be called if not "promoters"? there does not seem to be any other word that expresses the occupation of such persons. the real solution of this dilemma in which the honest men engaged in such work find themselves placed is to denounce, forcefully, the charlatan as being not a real promoter but a gross misrepresentation of one. let us, therefore, remove the odium from this title and give our approbation to those persons who are earnestly endeavoring, by honest means, to place mining enterprises upon strictly business-like footings. the mining industry needs promotion and promoters. xv incorporation and capitalization. let us consider the legitimate financing of a new or a reorganized, worthy, mining proposition. it is the universal custom to own and work a mine under the laws that govern a corporation and, for this reason, the mining man of the day is familiar with the practices of incorporating. it is something of a question at the start to decide what is a fair price to fix upon a property as a whole--that is, to decide what the capitalization should be. there is no rule to be followed in this matter. some organizers will decide to capitalize at what is expected will be the value of the property after some time. other men will stick to the idea that it is the proper thing to capitalize for what the property will invoice at the time. the higher the capital stock, the greater number of shares there are for sale, usually. with a conservative capitalization, there may be fewer shares for sale, but each share is worth correspondingly more and the chances are much better for an advance in the price per share whenever the mine becomes productive. there are investors who will carefully investigate this feature and will shun any mining stock which has any appearance of over-capitalization. it would be well if all investors were to follow this precaution. but what about the price at which to capitalize a prospect? by a prospect we here mean a property that has been favorably reported upon as worthy of development but in which, up to date, there is little, if any, showing of values or reserves. the engineer's report has recommended the property as containing the possibilities of a mine. how much is it worth? can he or can anybody even roughly estimate the sum? an engineer frequently does fix the sale-purchase price of a property, but it is not so usual for him to decide upon a valuation for capitalization. a very good guess may be made, perhaps, if there are similar and neighboring properties which have been developed. assuming a prospect that has been reliably reported to the owners as possessing the earmarks of a mine and as warranting expenditures for exploitation, upon what basis should a company be capitalized? if the owners of the property have capital, the chances are that they will not care to share their holdings with other parties. but very frequently worthy "prospects" are held by men of no means, and in order to develop their mines the owners feel the necessity of coöperation with parties who can furnish working funds. in every such instance, there will arise this debate as to the proper basis of capitalization. there is no human means of arriving at a _close_ valuation of any prospect, so it becomes a matter of pure judgment as to future probabilities and the possibility of placing the stock at the most advantageous price. a company will, therefore, be stocked for some round number of shares, say , , upon which some empirical par valuation, say $ , is placed per share. this is not to be understood as stating nor assuming that the property has a present valuation equalling the par of the entire capitalization. who would assert that any mere prospect ever had such a value as $ , ? no, it is not the intention of the organizers to claim that the ground is worth the par valuation; but some start must be made and so, in the absence of something precise, round numbers are made to do service. stock is then offered at figures much below the par valuation and in such quantities as will maintain sufficient capital in the treasury of the new concern to get the property's exploitation under way and to so sustain it as to make the prospect grow into a mine. if shares are offered at cents, it does not mean that a prospect is worth even that valuation. it does mean (we are considering now only the operations of honest concerns) that the men who are managing affairs believe that the sale of so many shares at ten cents each will furnish adequate means for the development and equipment of the mine. therefore, there is a _prospective_ valuation placed upon all such enterprises. is an investment in such a company to be considered as gambling? if there have been sound assurances from reliable examiners concerning the likelihood of the ground carrying the essentials of a mine and the only uncertain element is the ultimate magnitude of the mine, then we might say that the investment is not a gamble at all, since there is no chance to lose. the purchase of such stock is a very sane investment and there is no telling what the returns may reach. when incorporating a new company, it has become the fashion for the owners of the ground to exchange their titles for certain specified fractional interests in the company. this is effected usually by going through the formality of having the owners sell their holdings outright for the entire issue of the capital stock. then, according to prearranged agreements, these owners donate to the treasury of the company a portion of this capital stock to be henceforth termed "treasury stock." the first step makes the capital stock "fully paid for," since it has been accepted in full payment for the property. the second step supplies the company with the necessary means for raising funds to develop. there can be no reasonable objection to this practice. but there is much criticism of the usual apportionment of the owners' and the treasury stock. it is agreed that the incorporators are, as a rule, greedy in this respect, since they generally issue more than per cent. (and frequently per cent.) of the capital stock to themselves and expect to float the project to success upon the money derivable from the sale of the balance or treasury stock. is a mere prospect, even under the best natural conditions, plus the effort incidental to the organization of a mining company, worth one-half or more of a producing mine? during an extended experience in the business of converting discoveries into patented claims and prospects into mines, the writer has found that _there is never an owner who is willing to sell a developed mine for twice the price he had set upon the original prospect_. the valuation of his holdings goes up by greater multiples than mere doubling or even trebling and it is a rare thing to find a man willing to sell out a proved mine at less than ten times the prevailing valuation that would have been placed upon the same piece of property before its development. hence, there is no propriety in the act of self-appropriating half the capital stock by the organizers. investors should be wary about taking interests in companies which have been so organized. if an owner believes that a mine is worth ten times as much as a prospect, let him be consistent and offer his undeveloped property for a tithe of the capital stock in the anticipated mine. if he has a worthy piece of ground, he will reap the same benefits as the holders of the stock who place their cash against his title to a tract of virgin territory. if he will not thus act fairly, it indicates either a questionable piece of property or an avidity undesirable in a partner. it is accordingly advisable to shun offerings in such concerns. another matter to be considered here is that of overloading a fairly good mining enterprise with so much capital investment that the property cannot be made to pay proper dividends and fair interest on the capital. many worthy, though perhaps small, mining concerns have made failures through a disregard for this economic feature. the proper adjustment of this matter is a serious thing and it should not be passed over lightly. investors should look into this phase of mining thoroughly. xvi mining investments. one should be able to establish, in his mind, a distinction between the value of investments in operating mines and in prospective mines; and he should likewise be competent to fix some difference in his attitude when purchasing the stocks in these dissimilar projects. one should invest in an established mine with the same business precautions that would guide him in buying an interest in a mercantile establishment. it is possible to obtain, through competent engineers, the approximate present valuation and the probable life of any mine and thus to arrive at conservative figures that will govern one's investments. but, when debating the purchase of stock in a prospect, a man should learn all the available facts concerning the geology and the organizers and should then decide, in his own way, whether he cares to make the purchase. even the prospects offering the finest inducements have been known to disappoint, just as some less promising prospects have occasionally exceeded expectations. [illustration: mill of the roodepoort-united mines, transvaal, south africa.] so, while there are certain safeguards to investments, there should also be accepted the uncertainties which must accompany the placing of faith in unseen things. the same general rules for business success will attend both commercial and mining enterprises. any incorporation must be handled according to recognized, successful methods, no matter what its scope or activity. in most lines of business, there is a likelihood of growth with longevity, there being no reason to limit the life of the usual mercantile business. with advancing years, a manufacturing company, for instance, with good management, will establish a reputation and will gradually increase its business and its stock in trade. but with a mine, the business is one which is most successful only when actually depleting the assets at the most rapid rate. with some kinds of mines such as coal, placer, iron or the "reef" gold mines of the rand, the life can be very accurately forecast and all activities may be planned for specified periods. in some kinds of mining ground--as for instance, the irregular masses of leadville or the crooked and uncertain veins of tonopah--there can be no predictions that will reliably or even approximately decide the probable life of the mining activities of any company. the duration of mines of this second class is wholly problematical. a few years ago, there was much discussion of this subject and one writer, who had collected statistics over an extended period and covering various kinds of mines, arrived at the conclusion that the average life of a mine is about eleven years. j. p. wallace, in his work, _ore deposits for the practical miner_, in discussing this point says, "the average mine, if continuously worked, seldom lasts longer than three to five years. a mine is valuable not for what it has produced, but for what it is capable of producing." this opinion cannot be borne out by facts, for the brevity he ascribes to the average mine is altogether unreasonable and his statement is pessimistic. the cases of mines which have petered out in three or five years are exceptionally few. it must be that the experiences of this author have been in "pockety" districts, for he could not have lived in any of the worthy mining camps of the world very long and have come away with any such notion. to take care of this intrinsic feature of mining, and to place propositions fairly before the public, there should be attention given to the matter of recovering the invested capital before the expiration of activities through the exhaustion of mining assets, the ore bodies. this practice, known as "amortization," is being given more and more consideration as people come to realize this peculiarity of mining. some companies are now so organized and managed that there is a guaranteed refund, at stated periods, or whenever profits have accrued, of fractions of the invested capital with accumulated interest thereon. these funds are calculated to continue over the number of years which it is presumed the mines will live so that upon the cessation of mining, the owners of the stocks will have been completely reimbursed with their original outlay in addition to the dividends that have resulted from the success of the enterprise. it is here that the problem of the life of a mine enters into economics, and it is important that it be given its due share of study. amortization is not of american origin and it has not been adopted in this country to the extent which it is bound to be in the future. one means of providing against an extinction of a mining company's activity with the exhaustion of the ore bodies in the mines is to provide new mining territory to which operations may be transferred at the proper time. this plan has been very successfully carried out by a number of large mining companies. when a mining company has been maintaining its identity for a considerable period, it has reached a very desirable stage of economy in the make-up of its various lists of officials, superintendents and engineers. all this efficiency can be very readily transferred to the operation of virgin mining property. often much of the equipment of a mine can be moved and used again. when a mine is known to be nearing its finish, there is a hesitancy on the part of the owners in replenishing the equipment and sometimes the mining is kept up through the use of worn-out, inefficient apparatus when, were the owners expecting to continue mining, they would purchase and install the new equipment when it is needed. one company in the san juan region of colorado prepared for the contingency by purchasing neighboring property to which it moved its operations. another large company bought a large piece of mining property in mexico, although its initial operations were in colorado. placer mining companies frequently dismantle, move and re-erect dredges. xvii mine equipments. there is a constant tendency toward the adoption of machinery for the performance of every mining act which, formerly, was done by manual or animal labor. there are good reasons for this tendency. good, trained labor is scarce; wages are slowly but gradually rising; ores of lower grade must be mined, and the tonnages must be correspondingly greater. the increased economy in production can be brought about by the adoption of devices that will supplant, and even excel, muscular effort. a machine can now be installed and can be operated by a single man to perform the work formerly done by many men. there have been machines invented to entirely, or partially, perform every operation in and around mines, and one might imagine an ideal mine in which all such machines were installed. but even there, we should have to grant the presence of some few men, for it would not be possible to keep all the machines working without human, intelligent control. in such a mine, it might be possible to maintain a large production with very few laborers or overseers. fewer men means less wages, less labor trouble, fewer fatalities, and less time occupied in handling men into and out of the workings. in some ways, copper mines are ahead of gold mines in their equipment. coal mines have adopted car loaders which as yet and without any very good reasons metal mines have not. plants for mines must utilize the same sources of power as are used by any other plants. steam and water have been the usual forms, but electricity is gaining in favor in places where it can be cheaply obtained. at a coal mine, we naturally expect to see all the power generated through the combustion of coal under boilers. at metal mines--which are frequently remote from sources of coal supply--we run across the use of expensive coal for all power purposes. when it is possible to obtain a sufficient supply and head, water is adopted to furnish the required power for operation. at mines, with water sufficient to produce a part only of the needed power, we may see both steam and water power utilized. in the cases of some mines which are distant from sources of both coal and water supply, power is generated at points where stores of natural energy are available for use and the power is transmitted (usually as electricity, sometimes as compressed air) over long distances to the mines. some mines cannot be economically operated without the treatment of the ores upon, or close to, the mining property. with certain sorts of low-grade ore, or with those kinds of ores that may be concentrated before shipment, provision should be early made for the erection of appropriately designed mills. we say the subject should be considered early, but we do not advocate the premature erection of any mill. the hills of the western mining states are dotted with monuments to men's error in this particular. here and there (not in our own country alone, but throughout the mining world) one may run across an abandoned mine plant, a complete mill, a smeltery, a railroad or an aerial tramway, all prematurely provided for outputs which failed to materialize. there are men still trying to succeed in the mining business while thinking it is essential in mining that a complete plant be the first thing given attention. upon the showing in a ten-foot hole, such men will induce capital to take interests enough to provide the wherewithal for purchasing and installing an equipment capable of handling and treating the output of a big mine. this is a grievous mistake that comes about through misconceptions. it is often true that ores of the kind these mines are expected to produce should be treated upon the ground. but it is also true, and far more essential, that there be enough ore to supply the treatment works. it is rank folly then to spend the money needed to make a mine upon a plant to handle the product. money should be spent, first, in exploitation and proving the value of a property. if the proof is forthcoming, it is then time enough to erect the plant. meanwhile, during the development stages of a mine, the proper amount of experimentation can be conducted to ascertain the correct process for treating the ore. if ores are produced in abundance, they may be shipped for treatment in custom works until such time as the company's own plant is ready; or the ores may be stocked up for emergency mill supply at future times when it may be compulsory to curtail the mine production because of accidents or other unforeseen causes. one who considers these matters from an economic standpoint will recognize that there must exist some proper ratio of mine output to treatment capacity. just what this relationship is constitutes a serious problem for each particular mine and there cannot be stated any ironclad rules that may be applied to all cases. in the first place, we believe _a mine will be operated at its greatest economy when it is making its largest and most regular output_. this being the case, we must agree that the plant and mill must be capable of taking care of this maximum output. it would then seem axiomatic that the equipment must be calculated according to the mine's capabilities. but, in the youth of a mine, how are we to know what its mature capacity will be? here comes the rub. very nice discussions along this line have been indulged in by british and american representative mining men. when speaking of operations that are typical of some foreign mining districts and especially those that possess ore-bodies whose extents are readily calculated, no clever prophecy is required to ascertain the proper amount of equipment. but there are many regions, especially in our own country, where nobody can predict, with any degree of accuracy, how extensive will prove to be the natural reserves of any mine. it is in such places as these that hard study and careful guessing are needed, and we are inclined to agree with george j. bancroft when he says, "to my mind, there is more credit due to those who take up the hard propositions and make them pay than to those who exploit bonanzas along purely scientific lines. the first usually require energy, sagacity, perseverance and, very often, daring; while the others need chiefly cool calculation." it is a safe practice, throughout the world, whenever there is no absolute means of reaching figures of a mine's ultimate production, to erect the treatment installations in units. by a "unit" is here meant the outfit of machinery and the other equipment which will handle a specified round number of tons per day. in some districts, a unit will be for the treatment of tons; in other districts this number may run up to tons. in the plans provisions are made for additions, from time to time, as mining development warrants. very much the same scheme should be followed in the erection of the plant for carrying on the operations, which are strictly those of obtaining the ore from the earth. that is, mining equipment, as well as the milling equipment, should be on a flexible plan so as to be readily adapted to an increased scale of operation. there must be space provided for harmonious additions to the initial plant whenever such extra parts are required. [illustration: spray shaft house of copper queen consolidated mining co., bisbee, arizona.] xviii mine management. no matter how splendid a company's holdings may be naturally, there cannot be expected any profits from the workings of the deposits if there be not a sound business management. h. c. hoover, the prominent mining engineer and mine manager, says, "good mine management is based upon three elements: first, sound engineering; second, proper coördination and efficiency of every human unit; third, economy in the purchase and consumption of supplies." and he goes on to emphasize the fact that "no complete manual will ever be published upon 'how to become a good mine manager.'" in view of this damper upon good intentions one might possess, and granting that the subject is one that cannot be taught (except along very general lines possibly), no attempt will be made to enter into arguments concerning this important subject of mine management. good administrative ability can be improved by cultivation just as can an individual of the vegetable kingdom; but there must first be the existent, innate ability. no man should attempt such a hard proposition as the management of a mine, with its varied phases of activity, unless he has found himself possessing the fundamentals that go to assure success in managerial positions. furthermore, he should not think, because he has been successful in running a clothing business or any other mercantile line, that he is certain to succeed in running a mine. the duties of directors and president are pretty much the same in all sorts of incorporations. but, while there are many mining companies--and successful ones, too--that hold upon their directorates men who probably never saw a mine prior to their present ventures, it may still be stated that it is obviously advisable to select for such places men who have knowledge and sound ideas concerning the industry of mining. to be sure, if they are ignorant along mining lines, they can, and often do, place the blame for their shortcomings upon their manager, their consulting engineer, or their superintendent. but this is not an auspicious state of affairs and it were well for stockholders to see to it that they elect to the directorate men who are cognizant of mining economics. the well-organized mining concerns of today maintain their engineering staffs just as completely as do other great technical businesses. the engineer is a very important man in mining affairs. his duties are probably more varied than those that appertain to any other sort of engineering. his operations will extend into the realms of the mechanical, the civil, the chemical, the metallurgical, the hydraulic, and the electrical engineers. he must be posted along the latest conceptions in geology, mineralogy, and physics. besides he should be an accurate and rapid mathematician and draftsman. the manager finds in the engineer his most helpful and trusted aid. often the engineer performs many of the functions usually attaching to the office of manager and, in the absence of the latter person, he may attend to all of the management. as stated above, the qualities that make a good manager are inherent; hence, to a certain extent, we may hold the deduction that good mining engineers, also, must possess innate qualities. yet there may be pointed out this distinction between the make-up of a good man for manager and that of a good mining engineer: one, as said, cannot learn his business except through his own experience, while the other can receive vast benefit by _study_ of a theoretical nature and by _practice_. lately, there is much said about the _consulting_ mining engineer. his field of usefulness is broad. he can be asked to add his opinions and recommendations to those of the regular engineer, at any time; he can be used at times when the duties are too much for the resident engineer; he can be called upon to substitute; he need not live near the property, but may visit it periodically. thus, while his retention is deemed remunerative, his services are available at a fractional part of what he would demand if he were employed exclusively by the company. under ordinary working conditions, it should be considered just as essential for a mine to take an occasional inventory as it is for a mercantile establishment. in truth, there is far more need in mining operations of the knowledge thus derived than in any other business. in mining, as already suggested, the business is one of selling off the stock in trade without replenishing it. the opening of more reserves of ore is not bringing more goods into the stock, but it may be likened to simply unpacking more goods in the storehouse. no new reserve can be added--they can simply be found and unpacked, as it were. this finding entails the greatest amount of concern, and upon its successful practice depends the life of the mine. the presumption is strong that many mines have been abandoned while they really contained possibilities; but lack of knowledge of things geological, or perhaps failures to explore, permitted the operators to remain ignorant of the splendid assets that were available. proof of this error has been found in many mines that have been subsequently re-opened. the work of sizing up the quantity and the value of available ore is known as sampling. it is not well to limit the practice of sampling to the times only when a sale is contemplated. reports based upon careful sampling should be issued frequently. some companies employ men whose sole occupation is the daily sampling of every working face. the assay results obtained from the collected samples inform the superintendent just "how the stuff is holding up" throughout the mine and he governs his work accordingly. at longer intervals, the engineer should go into the work more thoroughly by not only taking very careful, scientific samples (not the usual "grab" samples taken by the daily sampler) but also by making careful memoranda of the physical appearances of the ore with its thickness and all geological data that will tend to throw light upon the permanency of each body. the engineer's monthly report will then be a substantial guide to the manager and the directors. managers, too, are expected to make periodical reports--monthly, quarterly, or annually--to the directors who, in turn, issue reports to the stockholders. the reports of managers and directors are not usually technical in their nature, although sometimes it is the practice of a manager to attach the engineer's report to his own for the perusal of such readers as may desire to dip into the technical affairs of the operations. usually, the directors' reports are of a simple, financial nature, stating the conditions of affairs in plain business language to the persons whose cash has been invested in the enterprise. it may happen that, for some reason, a special report is desired by the directors who may be contemplating some consolidation or other financial move and both the manager and the engineer will be required to furnish detailed statements concerning their respective branches. if a sale is planned, it may be that not only the company's engineer, but very probably another engineer engaged by the contemplative purchaser, will make examinations. they may work together or separately, as best suits them mutually, but it is upon the reports issued by them that the satisfactory price for the exchange of title is based. xix prices of metals. there is only one product of mines that has a constant market value, viz., gold. the precious metals, gold, silver, and platinum, are sold by the troy ounce: the base metals are all handled and dealt with on avoirdupois weights. copper, lead, zinc, tin, and nickel are quoted in cents per pound avoirdupois. iron and manganese are curiously sold by mines to smelting companies on the ton of ore basis. since gold has been found in every known rock of every geologic age and is of world-wide distribution; since it possesses physical properties that long ago placed it at the head of the list of desirable metals; and further, since it does not occur in very condensed amounts, generally; this metal was selected as the standard of value by which the worth of every other commodity in the world is fixed. it must therefore be possessed of a fixed market value, and one never looks for quotations on pure gold. the price of pure gold is set at $ . . this very peculiar value is known as the "mint value," and is the price which the government of the united states pays for all of its coinage gold. among miners, as a rule, the price is thought of as $ per ounce, and this is probably because this is more nearly the actual return the miner has been accustomed to obtain from companies who have bought and treated his ores. most all the gold produced in the world is associated with other metals, such as silver, copper, or platinum, so that the bullion recovered in milling or smelting will usually contain the gold alloyed with such other metals and the gold is said to be not "fine," or pure. the fineness of gold in the metallic state is expressed in two ways. jewelers have the carat system, while mints use the decimal system in expressing such degrees of purity. pure gold is -carat fine. an alloy of parts gold and part copper would be considered as -carat gold. in the decimal system, pure gold is called , fine, and the various degrees of purity are then expressed in their true proportional amounts. thus the same alloy as cited above would be called fine gold. silver has a fluctuating market value although attempts have been made, at times, to establish its value at some fixed ratio to the value of gold. in fact, a reader may occasionally run across statistics of silver production in which it appears as though there were a fixed value for the metal, but this will be found to be due to the use of what is known as the "coinage value," which is $ . . this figure will be recognized as our old acquaintance, " to ," _i.e._, this price for silver being one-sixteenth of the fixed price for gold. there is actually no such fixation, and prices for silver are established every business day of the year in the great metal markets of the world, london and new york. platinum has been increasing in market value during recent years and the quotations have ranged up so high that it is now more than twice as valuable as gold. the reasons for this high price are that the production of the metal is limited, whereas the uses for the metal have been increasing. the greatest production of this metal is in the ural mountains of russia, and the output from this region is handled by a few concerns who virtually possess a monopoly. these companies are able to maintain the production practically constant and to cause the market price to fluctuate. tin is found in commercial amounts in but very few regions. there is but one mineral mined as an ore of tin, viz., cassiterite, the oxide, which is per cent tin. tin is found in both veins and placers and the great bulk of the metal is now being derived from the latter type of bodies in the malay peninsula and the straits of the east indies. formerly, cornwall produced the world's supply, from veins. although the united states consumes per cent to per cent of the world's production, the country does not produce per cent of this production. since the main source of our tin is british territory, the markets are controlled by london, and quotations are issued daily from that center. such quotations are given in units of english money per long ton ( pounds) of metal. however, prices are also quoted at new york, daily, in cents per pound, and there is a real difference in value between the two quotations to take care of freights and duty. for instance, on a certain date, quotations were £ s, and c. the average price during in new york was . cents. the chief supply of nickel now comes from the canadian districts of cobalt and sudbury, where this metal occurs accompanying rich silver deposits. the metal is sold by the pound avoirdupois and prices in january, , ranged from c. to c. tungsten is a metal which has been finding more and more uses of late years, but the production has remained quite limited. three-quarters of the world's total production in came from a small district in boulder county. colorado. the quotations on this metal are given in dollars per ton of concentrated ore, and the price is for a certain percentage of wo_{ }, the oxide of wolfram (tungsten). the schedule of prices announced in april, , for boulder county ores and concentrates provides as follows, a unit being understood to mean per cent or pounds per ton: for material assaying per cent wo_{ }, $ . per unit; for per cent wo_{ }, $ . per unit; for per cent and more, $ . per unit. ore containing, say, per cent of the tungsten radical is thus salable at $ per ton, the mineral itself thus bringing a price of - / cents per pound. although copper is used and sold in very large lots commercially, it continues to be quoted upon the pound basis. the united states produces about per cent of the whole amount mined in the world and the prices are made in new york daily. the amount of copper mined in this country in was , , , pounds and the price varied between . cents and . cents. there are always at least two quotations every day on copper, one being on "lake" and another on "electrolytic". by these terms are meant, respectively, copper produced in the lake superior region and the copper from other mines. the lake superior copper is the purest in the world and it always sells for a fraction of a cent per pound more than the other coppers which are refined by electrolysis. metallic iron is reduced from a number of different ores, but by far the bulk of pig-iron is made from the oxides and carbonates of iron. such ores, in the united states, are obtained principally in minnesota, michigan, wisconsin, and alabama. as already stated, the quotations on iron are based upon the ores rather than the pig-iron, and there are two types of such ore recognized. if the ore is suitable for the making of bessemer steel, it is given a certain quotation per ton, while if it cannot be used for such a purpose, it is given a non-bessemer rating and is used for casting. the greatest iron-mining region in the world is in the lake superior country. here are a number of districts that are known as "ranges." in some of these ranges mining is by underground methods, while in others the excavation is entirely in the open by the use of great steam shovels. the outputs of these ranges go by rail and water to the great smelting points along the great lakes and at pittsburg. the metallic zinc on the market is known as spelter. all quotations on this metal are given in two systems, the "pounds sterling per long ton" and the "cents per pound." the average prices during were respectively, £ . and . c. the american quotations are frequently given in the unit of dollars per hundredweight. this offers no confusion, whatever, for under this nomenclature, the average price for would be stated as $ . . in the zinc-mining regions of the mississippi valley, the producers of ore have a practice of putting the mines' products through their own mills at the mines and making concentrates of the zinc mineral, which is usually blende or "jack," and this concentrated stuff is then sold to smelting companies at the daily quotations per ton of per cent ore. during the average price paid in the joplin district was $ . . since this amount bought , pounds of metallic zinc, it is evident that the miner received only about . cents per pound for his metal, the discrepancy between this sum and the new york quotation being consumed in costs of smelting and shipment and in profits to the middlemen. lead is sold upon a plan exactly similar to zinc. it has the same various quotations. for example, the prices in london, new york, and joplin averaged, respectively, £ . , . c., and $ . . quicksilver is sold by the "flask" of pounds. the price ranges in the neighborhood of $ to $ . there are numerous other metals, but the more common ones are given above. below is given a graphical exhibit of the course of the prices of lead, spelter, standard (electrolytic) and lake copper, pig-iron, and tin for a number of years. a study of this chart is interesting in noting the waves or fluctuations that have covered periods of years. this chart is reproduced from _the engineering and mining journal_. [illustration: diagram of metal market for one-third of a century] xx mine accounting. while there has been a great deal of attention given to the matter of keeping systematic mine accounts, both in the main offices and those at the works, there still is a lack of uniformity in practice. in the bookkeeping of manufacturing and mercantile institutions, uniform practices or systems have become a feature. but there have been good reasons for the absence of similar methods in mine offices. there will be found to exist some uniformity in the accounting as practised by the mines of a particular district which are operating under similar conditions; but when one considers that the mines of various districts have quite dissimilar conditions throughout almost every phase of the business, it is not surprising that different methods must be employed in the keeping of their accounts. it is unavoidable. mines extracting different metals or different kinds of coal will find it necessary to keep quite unlike records. mines with their own mills will likewise require a different system of accounting from those that ship their products to custom works. open and underground mines will need quite different styles of accounts. so, it is not possible to recommend any one method of mine accounting. the best way to become posted upon this subject is to investigate the schemes, the blank forms and the books of some of the established, successful companies here and there about the world. in this way, ideas will be collected, and it will be possible for the investigator to evolve his own schemes for recording the accounts of his company. it has come to be recognized as contributing to economy to maintain systems of accounts that will enter into minutiæ concerning every branch of the business. just how far this can be carried without creating office expenses that will exceed the benefits to be derived from the detailed information remains a question to be decided by each manager. there are companies with accounts so perfected that it is possible to quickly ascertain, to a fraction of a cent, what the expenditures of any day have been for any particular part of the operations, as for instance, the haulage per ton underground, or the fuse employed in the blasting of a particular stope. such details are highly useful since they prevent leaks in the costs; but it is a problem to decide to what extent it is economy to carry them. these data also furnish the superintendent information concerning the efficiency of his many laborers and the machinery. labor-saving inventions, such as the printed blank form, and the loose leaf, are put to excellent use in mining offices. there are strong companies operating great mining plants whose records are open to the perusal of any individual, be he stockholder or not. in the office of such a company, a person may turn to the accounts and see for himself how much it costs to maintain each and all of the operations and he can learn the size and the value of all shipments of products of any sort--ore, concentrates, coal, matte, or bullion. again, there are those companies that are so secretive about everything connected with their work that even the government is unable to learn any particulars, except at very great trouble. the portland gold mining company, operating a great property at victor, in the cripple creek district, is an instance of the first sort, while the united verde mine, at jerome, arizona, may be taken to represent the second sort. both of these mines have made splendid records. it cannot be seen wherein the second mine is required to maintain secrecy, for there is no danger of litigation from neighboring property holders, the one company controlling, practically, the mining in its neighborhood. the presumption is that the owners hold their business to be nobody's else and they have a right to keep their affairs secret if they desire. on the other hand, the portland is surrounded by good mines which profit by knowing the details of operating costs and incomes of their neighbor; but it is found to cost no more to be open and above board than to keep things under guard. the colorado fuel and iron company will not divulge any particulars concerning its mining movements; but there are other just as great mining companies that will explain every detail. the clark copper companies, of butte, montana, did not permit much information to escape their offices, while the neighboring amalgamated companies gave particulars freely. the question of secrecy should be considered, and if there is no very good excuse for maintaining a privacy it should not be instituted. the trend of all modern thought is along the line of publicity in all our dealings. the only persons who have a reasonable right to be secretive are those who have something they do not care to share or divulge to their fellow-men. law breakers, tax dodgers, and trespassers, could be put into one class; persons doing research work which it is premature to publish are a more respectable class; manufacturers with strong competition in the sales markets are in a measure excusable; even a mine which is producing some material in the sale of which it attempts to maintain a monopoly might be excusable. but it is hard to see what excuse or benefit there is for a coal or a copper mining company to prevent a knowledge of its affairs, if the business is being conducted along strictly legitimate lines. xxi investment in mining stocks. as a feature of investment in mining stocks, there has always been a more or less open lure. generally much larger returns are promised or are expected than in other kinds of investments. there may be absolutely no intention on the part of the seller to create this impression; but there does, somehow, exist in the memories of people accounts of wonderful fortunes that have been made in mining. there is an amount of uncertainty about any mine or prospect that appeals to the speculative proclivities in humans and it is hard for most persons to resist the notion that greater or richer bodies of ore may, at any time, be discovered in their particular mining properties. concerning the average stock purchaser, then, we may conclude that it is speculation rather than true investment that he is seeking. the writer hopes that, even in the short preceding discussions, the reader will have come to agree with him and to understand that safe investments are as possible in mining as in any other business. it would be a great benefit to this great industry of mining were the public taught to take interests--that is, financial interests--in mining concerns with the same precautions and with the same sound business sense that accompany the purchases of interests in other enterprises. writing along this line of thought, mr. p. a. leonard has this to say in _the mining world_: "one very general difficulty seems to be that the man unacquainted with mines who is asked to invest either expects an unreasonable return for his money, or he blindly closes his eyes and takes what he calls a 'flyer,' expecting little more from it than he would if he bought margins on 'change or bet on a horse race." about the first thing that the promoters of a new mining company do is to issue a neat, attractive prospectus. it is a bait, no matter how reliable these men may be nor how worthy the property they desire to work. many of these documents are written in absolutely good faith and every representation is intended to be accurate. there are occasionally offered for sale stocks in mining properties that warrant the fullest confidence of the promoters and the investors. however, careful perusal of a great many of these pamphlets has led the writer to the conclusion that at least per cent. of them are unreliable from the fact that they either wilfully misrepresent or because they grossly exaggerate the probabilities of success beyond all reason. exaggeration is a habit with some people and it is used many times with no real criminal intent or even consciousness upon the part of the offender. but its effect is just as baneful when innocently inflicted as when it is used in a premeditated manner. good, worthy mining property does not need to be hawked, usually. there have been periods of financial unrest when it has seemed quite impossible for honest men to dispose of interests in what were unquestionably reliable mining enterprises. at such times, there has been nothing to gain by any amount of teasing the public, and any attempts at forceful disposal of interests in the concerns have but served to kill any small remnants of confidence that the public may have possessed. prospectuses are usually prepared for the reading of small investors who may feel inclined to risk a few dollars or, in other words, to speculate upon the representations contained in the seductive pamphlets. there are a few "don'ts" which it would be well for any person inclined to invest in mining stocks to read, consider, and follow. for instance, never invest in any new stock whose company _guarantees_ specific dividends. profits in mining, except in rare cases, cannot be so accurately foretold as to warrant such a guarantee. we should remember that the success of any mine depends upon many, very many, contingencies and that some of them are invisible and are among nature's secrets. again, avoid placing any confidence in those companies that are simultaneously selling treasury stock and declaring dividends. this is a very common practice of the numerous "get-rich-quick" concerns which uncle sam has been routing the past few years. such crooked practice is difficult to eradicate, although severe penalties are awarded the transgressors. the success which has been met in the operation of the _great_ mining companies of the world can, in the majority of cases, be traced to the common sense which was exercised in the business management. the _business of mining is legitimate_. if mining is one of the basic industries of the world, how could the operation of a real mine be anything but a legitimate business? the mere fact that there have been neat opportunities for, and the practice of, fraud in the growth of this tremendous industry does not by any means, argue that the whole thing is founded upon unstable premises. what is needed is a presentation of the industry in its legitimate aspect before all kinds of investors and this can be done properly and effectively only by the rank and file of men interested in mining. these men should place themselves boldly on record as combating all sorts of deals that smack of fraud, and they should do their utmost to discourage all delusions that may exist in the mind of the public with reference to the supposed lure offered by mining. there have been too many causes of failure in mining for even a partial enumeration of them. there have been many errors in getting started, both on the part of the organizers and the investors. there have been many mistakes in management. many blunders have been evidenced in the operation of mines which made very good starts. all of these failures are attributable to something outside of the mine's intrinsic worth; they are mistakes due to inexperience or misconception. such shortcomings should not be tolerated in the make-up of a mine's managerial staff. perhaps one of the most common mistakes of mine managers is to submit to a condition of nepotism that is often furthered by directors or stockholders. no responsible position around a mine should be filled by a novice. just because a director has two or three sons needing situations does not make it incumbent upon a superintendent or a manager to jeopardize his reputation by employing these young men. percy williams, a veteran mining man, advised "don't take your son or nephew or your clerk out of your store or business house and send him to arizona or colorado to run things for you at the mine. sell out first. if you are a director in a mining company, do not force the manager or superintendent to find a job for all your unsuccessful friends and relatives. let him hire his own men. don't convert your mine into an asylum for ne'er-do-wells." as already stated, there is protection obtainable by every investor in mining. one may always secure, at reasonable cost, the services of competent engineers whose business consists in sizing up the worth of mining property. if the services of these men were more generally appreciated and secured, there would be a great diminution in the number of disappointments following investments in mining. an eastern man of means complained to the writer about the way in which he had been "stung" in various mining investments. a little catechizing brought forth the facts that he knew absolutely nothing about mining in general and that, worse still, he had never investigated--that is, in a business-like manner--any of the propositions which had absorbed his ready money. receiving no sympathy during the recital of his troubles but, instead, the assurance that he "got what was coming to him," he was prepared to sit up, take notice, and listen to a severe roasting which opened his eyes about mining matters. now, this man has proved successful in other lines of business. he is a prominent lawyer and banker in his own city and has numerous, scattered, money-making interests. but he was content to go into mining without the investigation which it is certain he would have given to any other sort of an investment. the time should come when there would not be such a prevalent "slaughter of the innocents" in mining investments. people must learn to curb their gullibility in such affairs. but this has proved almost impossible. just as it is in the nature of some persons to gamble, and it takes something more than misfortune at gaming to wean them from the vice, so it is with a certain class of men who can not overcome the temptations of dabbling in mining. such men will not desist even when they have suffered several delusions, and will continue to "send their good money after their bad," absolutely defiant of the well-meant advice of friends who are often in position to judge of the merits of any contemplated investment. probably every mining engineer of any extended experience can tell of instances in which he has endeavored to discourage clients from investment in unworthy mining enterprises but in which the gambling instinct of the clients has overridden the sound advice. during the early days of the wonderful cripple creek district, all sorts of wildcat tricks were successfully practiced upon the "tenderfeet" and the "down-east suckers." in one case, stock was readily unloaded upon the representation that a person could stand in the door of the cabin on the property and "look right into the shaft-house of the independence mine." this statement was not untrue, although grossly misleading; for while it was actually quite possible by the use of a telescope to span the intervening three or four miles, visually, the prospect lacked the propinquity to the famous mine that was the bait implied by the statement in the prospectus. this is but one of many ingenious tricks that were played. did the outcome of this one fraud cure the victims of irrational mining investment? railroads, too, have, in the past, added their troubles to the mining men. recent laws have, however, to a great extent, mitigated the annoyances and unjust practices that the common carrying companies have been in the habit of committing. it is now obligatory upon a railroad company to treat all shippers without favor or discrimination, so that the difficulties formerly experienced by one mining company in getting enough ore cars to transport its shipments while its rival company could have cars in abundance, is now almost a thing of the past. it takes time to right all wrongs of this sort. it is a slow matter to get laws framed, passed through the necessary legislation, and made effective. but the outlook is favorable, along this line. the leasing system has exercised an influence upon the mining activity of many districts. by this system is meant the custom of renting or letting the whole, or fractional parts, of a mining property to miners who enter upon and work the premises, extract the ores, and pay to the owners a specified percentage of the receipts from the marketing of the ore. this practice has frequently been the only successful way of operating some mines. it has, at times, been the manner of operating practically every mine in certain districts. in districts carrying pockets of very rich ore, "high grading" has been discouraged in this way, for the "leasers" (incorrect, though common, word for lessees) do their own mining and there is much less object in stealing. in other instances of mines which have been operated by the owning companies until they were past a profitable stage, it has been proved possible to prolong the life of operations very materially by leasing the property to miners, who always work with more diligence and economy for themselves than they ever do when working under "day's pay." this feature of leasing has been quite a factor in the lives of some of the mines of the cripple creek district. until the recent drainage of the district through the roosevelt tunnel, there were numerous small--and even some large--properties that had worked all the ore bodies previously known to exist above the water level of the district, and had been obliged to shut down because of the heavy pumping expenses. company operation did not longer pay. but the plain "leaser" and his partner could go into such old workings and they could prospect and find ore bodies that had escaped the observation of the superintendents. the expenses incurred in leasing are low. it is true that lessees will not probably take as good care of mine workings and equipment as will "company men," and often a property may be seriously crippled through the lack of sufficient timbering after having been in the hands of a set of lessees for some time. but, on the whole, there has probably been more benefit than loss through the letting of leases. when, a few years ago, the plans of the national forestry service were put into effect, there was great complaint recorded concerning the rulings that were made against various miners. some very well authenticated cases of wrongs were cited. however, it is now believed by all fair-minded men that there has been no intention, on the part of the officials of the forest service, to interfere with any legitimate mining enterprise. there was a well-founded object, viz., to put a stop to dishonest practices in obtaining title to timber lands by the misrepresentation of mineral finds. the general land office passed a rule authorizing foresters and assistant foresters to make inspections of all mining claims within their reserves and to report to the secretary of the interior. the idea embodied in this rule was that these men, being agents of the government and upon the ground, are able to investigate the facts concerning every mining claim and its claimant and so to run across any evidences of fraud that might be attempted in the securing of title. trouble immediately arose because the foresters were not all experienced miners and prospectors and so were not thoroughly qualified to pass judgment upon the merits of mineral lands. this weakness has been admitted by the officers of the service but the excuse has been offered that there was an immediate need for a great many foresters and it was not possible to secure men trained in both forestry and mining at such short notice. "just as soon as conditions became better understood, and money was available to allow the service to hire men whose judgment in mining matters could not be gainsaid, such men were employed," says paul g. reddington, recently forester for the rocky mountain regions. it is true that much fraud has been prevented in the practice of taking up government lands and it is also quite true that the forest service is endeavoring to uplift the mining industry in the western portions of the united states. mining is bound to become a still stronger factor in civilization as metallurgical processes multiply and there are discovered means of more economically extracting the valuable contents of ores. minerals which are not now ores--according to the accepted, scientific definition, because the values cannot be recovered at a profit--will, at some future period, become ores. it is not safe to make any close predictions along this line, for such marked reductions in treatment costs have been going on during the last few years that mining men are entertaining great expectations. inventions for improvement in metallurgical lines are being placed upon the market so frequently that it is difficult for even the professional metallurgist to keep posted. this being true, it is clear that the layman cannot expect to keep abreast of the metallurgical advance. at the same time, it is well for everybody to be slightly conversant with the wonderful advances being made in the reduction and dressing of ores. conspicuous in this field are the improvements that have been effected in cyanidation, electrolytic amalgamation and extraction, and flotation. these processes are applicable to the lower grades of ore. among the very recent successes in the treatment of very low-grade gold ores are the operations conducted in the new mills of the portland gold mining company, stratton's independence, and the ajax gold mining company, all in the cripple creek district. all of these mills are now treating old mine dumps, the contents of which were considered as absolutely waste matter at the time it was excavated. this stuff is now ore and its treatment is making fine profits. there is still a demand for cheaper methods of reducing ores of zinc. there are vast quantities of stuff that contains very good percentages of zinc, but the material cannot be mined and treated at a profit under existing conditions. with the invention of something radically new in the metallurgy of this metal, there will be opened an entirely different aspect in the zinc-mining regions. the leadville district possesses great reserves of this material that is being held until it may become "ore." [illustration: florence mine and mill, goldfield, nevada.] xxii the men of the future in mining. the mining of the future will probably be largely in the hands of young men. to arrive at any conclusions concerning the probabilities of success, therefore, we are obliged to recognize the dual conditions. in other words, there is to be an interdependence between men and mining. up to this point in our discussion, we have dwelt upon the probabilities as viewed from the standpoints of natural resources and of human capability. in a certain degree, we have already covered the ground of this present chapter; and yet there are some points that must be given special consideration. what is the true status of metal mining? alarmists would have us believe that civilization is rapidly exhausting the world's reserves of available metals. conservative investigation, however, repudiates such notions. the best that can be claimed for the reliability of such disconcerting statements is that they may apply in _some_ districts, to _some_ grades of _some_ kinds of desirable mineral matter. it may be true that the early miners have removed the "cream" from nature's deposits in some districts, in the sense that they have skimmed off, as it were, the rich surface portions. but this does not signify the exhaustion of deeper ore bodies, nor does it mean that the pioneers were the only capable prospectors. why should we have any reason to deny the ability of present or future generations to find just as good mineral deposits as did our predecessors? persons in some of the older of the western mining states--as for instance, colorado or california--are apt to carry a misconception along this line. they can see a number of idle "camps" that are mere relics of former thriving mining communities and they are liable to jump to the conclusion that the day of mining at such places is past, forever. however, as we look at the subject in a more rational light, we shall see that there is no more authority for such an assumption than there is for one to the effect that a farm in the wintertime is a worthless proposition simply because, temporarily, it is not producing its customary summer yield. just as nature brings about changing conditions for the farmer, so will economic forces establish varying degrees of attractiveness to the miner. it is unfair to judge one of the pioneer mining districts by its activity at the present time, if the productiveness happens to be small. let us look for the reasons of the apparent decline. the chances are that the inactivity will be shown to be due, not to an exhaustion of ore bodies, but to some needed changes in mining or metallurgical methods. very likely, under a readjustment of our notions about that particular district there will appear to be as great latent possibilities as ever cheered the earlier operators. the prospects may appear to be even better than this, and the future may appear to extend greater opportunities than were ever manifested in the past. investigation may disclose great bodies of ore that could not be seriously considered in the earlier working of the region. in fact, speaking technically, the stuff in question was not ore at the time of previous operations, for it could not then be made to yield a profit. and yet, by introducing some changes in equipment or methods of working or treatment, there may be possibilities of making a great deal of money from an abandoned property; and the chances are good that this same profit may be won at a much more rapid rate than was ever before possible and that therefore the economic conditions are enhanced. for we must not lose sight of the fact that the greatest profits in mining usually accrue from the most rapid exhaustion of the ore bodies. a mine, or even a whole district, may have been deserted because of failure on the part of original miners to recognize the value of certain minerals. the recent revival of activity that has been noted in leadville mining circles is but an instance in point. in this district, miners have given a delayed recognition to some important minerals of zinc, and the indications are that leadville has entered upon another of its eras of mining activity. but, it is not necessary to restrict our thoughts to the old mining regions, for if we can observe how easy it has been to overlook valuable deposits in a country that has been subjected to severe mining work, for years and years, what must we conclude concerning the possibilities of the many and vast undeveloped areas in remote portions of the globe? it would seem that there is indeed very small cause for alarm about the exhaustion of the earth's metals. no, it can be shown that mining, which is one of the very fundamental industries of the world and the one upon which every other form of commercialism rests, will be carried on with a continual increase in magnitude just as long as man exists. as the richer and more easily mined ore reserves of nature are exhausted, improved and cheaper methods of mining, transportation, and treatment will be introduced and at a pace that will equalize this exhaustion. we, of the present generation, see the eminently successful handling of copper ores of grades so low that they were not given passing consideration ten years ago. the outlook would appear to be that the improvements in methods and costs will not only keep abreast of needs in such matters, but the probabilities are that they will take a very marked lead, with the result of a continually increasing scope to the mining industry. let us then entertain optimistic views about the _future of mining_. now, as to the future of the young man who engages in mining there is just as much to be said as there is concerning the career of a young man in any other line of business. this word "business" is used advisedly, for the day is past when any person has a right to say that mining is anything but strictly legitimate business. we look to the young men of the present and future to correct all of the shortcomings that have hindered the establishment of mining upon its deserved plane of stability in the minds of the general public. young blood will take a lead in the dissemination of the correct thoughts about mining. the successful man in mining will be, as heretofore, the one with the right qualifications in his make-up. is a college education an essential prerequisite to success in mining? no, the writer is not one to declare that young men cannot succeed in the business without college training. however, there can be no avoidance of the proposition that the chances of the college-trained man are better than are those of the man who has not had the benefits of such a career. a man may be said to engage in mining in three different ways. thus, he may operate mining property; or he may perform any of the manifold lines of mining engineering; or he may be an investor in mining property or mining stocks. to prove a success when enrolled in either of the first two classes, there is no denying the advantages of technical, mining education. the successful investor likewise will do well to make a consistent study of mining economics, and the more attention he gives to the many phases of approved modern mining, the greater will be his ultimate achievement, financially. just as education along usual school branches is of immeasurable benefit to any man of business, so is it to the mining man. and in just as great ratio is the possession of innate business ability. education and natural ability are the two elements that will count in the future of any young man in mining. space might be devoted to the discussion of the possibilities of young men in the field of research work along scientific lines that would add materially to the economy and scope of mining. such a career offers inducements looking to the achievement of honor as well as fortune. the field for such service is ready. xxiii miscellaneous considerations. there are regions producing ores that are too refractory for the simple treatments that might be given by company plants located at the mines. there are districts that have many small gold and silver mines with ores that do not yield to simple milling processes and which must therefore be shipped to custom smelteries. even were the ores amenable to milling of some sort, it is often the case that the mines are not of sufficient magnitude to warrant the maintenance of their own treatment plants. under proper trade and commercial conditions, there is no impropriety in shipping ore to a custom plant or in selling it outright to a company owning such a plant. but, contemporaneously with much of the mining in the west, there has been such a monopoly on ore treatment that great injustice has been wrought to the shippers of small lots of ore. not only has this accusation been true of smelting concerns but also of milling companies. once in a while representatives of such corporations will arise and attempt to refute these statements, but the evidence is overwhelmingly against them, and their arguments of being benefactors of the miner fall flat. by consolidation of companies and the elimination of competition, arrogant methods and unreasonable charges have been put into force; and the managers of mines have been obliged to accept whatever rates the monopolists saw fit to charge for treatment and whatever arbitrary prices they cared to pay for the metallic contents of the shipped ores. very gross extortion has been practised and even yet there are many mining camps which are so absolutely under the control of these concerns that properties which should pay well, under just and favorable conditions, are forced to remain idle. these conditions could not be expected to prevail forever, and the time is now at hand when the extortionate smelting and milling trusts are meeting with pronounced opposition and a greatly diminished business. the state of utah has demonstrated the ability of ore producers to bring the oppressors to time and the mine owners of that state are in a much more favored position right now than are the miners of colorado, for instance, who really have been the greater sufferers. the utah mining men have benefited by the sad experiences of the miners of the sister state. in colorado, the american smelting and refining co. has been a domineering factor in the mining industry for years, and the decrease of mining in colorado has been contemporaneous with the oppression of this great corporation. the real cheating that has been practised by the ore-buying and ore-treating companies is well understood by all mining men who have been within their clutches. it seems to be a fact that every tyrant eventually proves his own undoing. in the case of the oppressive smelter trust, the greed resulted in an immense income for the time being; but as mines were obliged to close down because of the unjust charges imposed for handling the ores, the quantities of ore handled continued to diminish. during the past few years when mining has been so unusually dull in many of the western mining camps, it has been very difficult for the smelting company to secure enough ore to keep running, and the present outlook is not encouraging. statistics will show that the production of the metals is not really so low as the decrease in tonnages would seem to indicate, and the discrepancy is accounted for in the fact that very many mining companies have installed their own plants for either actually recovering their metals or for reducing their bulk of ores by concentration before shipping to the custom treatment plants. thus the smelting company may still be turning out a large amount of metallic lead, for example, but it is smelted from concentrates instead of from crude ore and the tonnage, the principal basis for estimating smelting charges, is very much less than was formerly handled in obtaining the same amount of the same sort of product. the investigations started by the oppressed ones in their efforts to evade the oppressor have led to wonderful results, and it is no longer necessary for the miner to depend upon the smelter. some similar sharp practice against the mining fraternity was attempted and for a short time successfully carried on by what was termed, in colorado, the milling trust. this concern handled the ores from cripple creek, principally. the larger mining companies soon began the erection of their individual plants and the practice has been extending until it is now common for cripple creek mines to own and operate their own reduction works, much on the order of the practice in the transvaal country. as a final word in this discussion, the author wishes to reiterate his belief in the legitimacy of investment in mines and mining stocks. when mining is placed upon sound business principles and every detail of the work is carried on with strict attention to sound economy, there can be few failures. this means that business judgment and expert advice must be used from the very start--in other words, that no false starts must be permitted. then, after getting under way in a worthy enterprise, the successful mine operator will exercise just as close scrutiny of every operation, method, and employee as do the men who conduct other successful lines of business. this little work has been prepared primarily for the perusal of men and women who are not personally acquainted with details of mining, but who entertain notions of becoming financially interested. it is hoped that the simple descriptions of some of the elementary details will prove of use to a great many persons. capitalization and dividends of north american metal mines. =============================================================================== company | state or | metals | capitali- | par/ |dividends to | country | produced | zation |share|jan. , -----------------------+----------+------------+-----------+------+------------ alaska-mexican |alaska |gold | $ , , | $ | $ , , alaska-treadwell |alaska |gold | , , | | , , amalgamated |montana |copper | , , | | , , anaconda |montana |copper | , , | | , , arizona |arizona |copper | , , | . | , , baltic |michigan |copper | , , | | , , boston & montana cons. |montana |copper | , , | | , , bullion-beck & champion|utah |silver, gold| , , | | , , bunker hill & sullivan |idaho |silver, lead| , , | | , , butte coalition |montana |copper | , , | | , , calumet & arizona |arizona |copper | , , | | , , calumet & hecla |michigan |copper | , , | | , , camp bird |colorado |gold | , , | | , , centennial-eureka |utah |gold, silver| , , | | , , champion |michigan |copper | , , | | , , colorado |utah |silver, lead| , | . | , , copper range con. |michigan |copper | , , | | , , crown reserve |ontario |silver | , , | | , , daly |utah |gold, lead, | , , | | , , | | silver | | | daly-west |utah |gold, lead, | , , | | , , | | silver | | | delamar |idaho |gold, silver| , | | , , doe run |missouri |lead | , , | | , , elkton con. |colorado |gold | , , | | , , el oro |mexico |gold, silver| , , | | , , esperanza |mexico |silver, gold| , , | | , , federal |idaho |silver, lead| , , | | , , gemini-keystone |utah |gold, silver| , | | , , goldfield con. |nevada |gold, silver| , , | | , , granby con. |b. c. |copper,gold,| , , | | , , | | silver | | | greene con. |mexico |copper | , , | | , , guggenheim exploration |mexico |all metals | , , | | , , hecla |idaho |silver, lead| , | . | , , hercules |idaho |silver, lead| , , | | , , homestake |s. dakota |gold | , , | | , , hond. rosario |c. a. |gold | , , | | , , horn silver |utah |silver | , , | | , , iron silver |colorado |all metals | , , | | , , kerr lake |ontario |silver | , , | | , , la rose con |ontario |silver | , , | $ | , , mammoth |utah |gold,silver,| , , | | , , | | copper | | | mohawk |michigan |copper | , , | | , , mountain |california|copper | , , | | , , naica |mexico |silver, lead| , | | , , nevada con |nevada |copper | , , | | , , nipissing |ontario |silver | , , | | , , north butte |montana |copper,gold,| , , | | , , | | silver | | | north star |california|gold | , , | | , , ontario |utah |silver, lead| , , | | , , osceola |michigan |copper | , , | | , , panuco |mexico |gold, silver| , , | | , , parrot |montana |copper | , , | | , , penoles |mexico |silver, gold| , , | | , , phelps, dodge & co |u. s. |copper | , , | | , , plumas, eureka |california|gold | , , | | , , portland |colorado |gold | , , | | , , la rose con |ontario |silver | $ , , | $ | $ , , mammoth |utah |gold,silver,| , , | | , , | | copper | | | mohawk |michigan |copper | , , | | , , mountain |california|copper | , , | | , , naica |mexico |silver, lead| , | | , , nevada con |nevada |copper | , , | | , , nipissing |ontario |silver | , , | | , , north butte |montana |copper,gold,| , , | | , , | | silver | | | north star |california|gold | , , | | , , ontario |utah |silver, lead| , , | | , , osceola |michigan |copper | , , | | , , panuco |mexico |gold, silver| , , | | , , parrot |montana |copper | , , | | , , penoles |mexico |silver, gold| , , | | , , phelps, dodge & co |u. s. |copper | , , | | , , plumas, eureka |california|gold | , , | | , , portland |colorado |gold | , , | | , , quincy |michigan |copper | , , | | , , richmond |nevada |gold, silver| , , | | , , | | lead | | | san rafael |mexico |gold, silver| , | | , , sta. gertrudis |mexico |gold, silver| , , | | , , sta. maria del paz |mexico |gold, silver| , | . | , , st. joseph |missouri |lead | , , | | , , silver king coalition |utah |silver | , , | | , , smuggler |colorado |silver,lead,| , , | | , , | | zinc | | | standard con |california|gold, silver| , , | | , , stratton's ind |colorado |gold | , , | | , , strong |colorado |gold | , , | | , , tamarack |michigan |copper | , , | | , , tennessee |tennessee |copper | , , | | , , tomboy |colorado |gold, silver| , , | | , , tonopah |nevada |gold, silver| , , | | , , united |montana |copper | , , | | , , united verde |arizona |copper | , , | | , , utah copper |utah |copper | , , | | , , utah con |utah |copper | , , | | , , vindicator con |colorado |gold | , , | | , , wolverine |michigan |copper | , , | | , , -----------------------+----------+------------+-----------+------+------------ index accidents, adit, advantages of, , , , adit, defined, ajax mine, alaska, , , , amortization, anaconda mine, , arizona, australia, , bancroft, geo., bankets, bassick mine, batea, bingham cañon dist., black hills, , blanket vein, brazil placers, , buried placers, butte district, , cages, california mining, , , , , camp bird mine, , canadian mining claims, , capitalization, , charleton, a. g., chimneys, churn drilling, climatic influences, coal mining, , coal washing, colorado fuel & iron co., colorado lode claims, comstock lode, , , concentration, , consulting engineer, copper mining, , , copper, price of, cornwall, , cost of patenting claims, cradle, cripple creek district, , , , , , , , crosscuts, custom treatment, dead work, dikes, directors' functions, dividends of n. amer. mines, dry placers, egypt, ely district, esperanza mine, examination of mines, , exploitation, , extralateral rights, failures in mining, gash veins, gangue, giants, gold, price of, gold production, to golden fleece, explained, grab samples, greece, mining in, , high-grading, , homestake mine, , hoover, h. c., hydraulicking, , inclines, , incorporation, iron ore prices, joplin district, , kansas coal mining, kemp, jas. f., kentucky lead mining, , keweenaw peninsula, kimberly diamond mines, , , labor considerations, , lead, prices of, leadville, , , , , leasing, leonard, p. a., life of a mine, , lode defined, , , long tom, low-grade mining, , machinery, , management, mass, defined, metallurgy, mexico, , , mexican mining claims, milling, mine accounts, mine, definition of, , , mine promotion, , , , mine reports, miner's licenses and certificates, miner's pan, mine sampling, , mine timbers, mining, defined, , mining engineer's functions, , mining plants, , , , , minnesota iron ranges, , , , monitors, mount morgan mine, , nevada cons. copper co., , new zealand, nickel mining, , nickel, price of, ore defined, , ore deposition, ore dressing, , ore in sight, ore reserves, oroya-brownhill mine, open pit mining, ophir, location, _pertinencia_, placer dredging, , placer defined, placering, platinum mining, platinum, price of, political considerations, porphyry mines, portland mine, , prospecting, prospects, prospect drilling, prospectuses, , quicksilver mining, quicksilver, price of, reddington mine, reddington, p. g., reefs, richard, r. h., rickard, t. a., riffles, robinson mine, rocker, roosevelt tunnel, san juan region, , , secondary enrichment, secrecy in operations, shafts, , , silver, price of, silver production, skips, slope, defined, sluices, , sorting, south africa, , , , , spain, spurr, j. e., steam shovelling, , stock, defined, stratton's independence mine, , stripping, sudbury district, supplies, mine, , surveyor-general offices, sutro tunnel, tin, price of, title to property, tonopah district, , topographical considerations, , transportation considerations, , transvaal, , treadwell mine, , treasury stock, treatment monopolies, , tungsten, price of, tunnel, defined, unionism, united verde mine, u. s. bureau of mines, u. s. coal claims, , u. s. forestry service, u. s. lode claims, , u. s. mineral output, to u. s. mineral surveyors, , u. s. placer claims, u. s. postal dept., , utah copper co., , van hise, c. r., vein, defined, wallace, j. p., wallaroo mine, wasp no. mine, wildcatting, , williams, percy, zinc, price of, produced from scanned images of public domain material from the google print project.) [illustration: _frontispiece_: the miners' hall, durham] a history of the durham miners' association - by alderman john wilson, j.p. _corresponding secretary to the association, chairman of durham county council, and member of parliament for mid-durham division_ "a tale should be judicious, clear, succinct; the language plain, and incidents well link'd; tell not as new what everybody knows, and, new or old, still hasten to a close." cowper. durham printed and published by j. h. veitch & sons, and north road _price three shillings and sixpence_ to my colleagues the miners of durham this outline of their associated history is respectfully dedicated by one who knows the hardships and dangers of their lives, who understands their character and esteems it, who has been with them in their struggles for freedom, equality, and a better life, whose greatest pride is that from early youth he has been (and still is) one of them, whose highest honour is that he is trusted by them to take part in the varied and important duties of their association, and whose hope is, that avenues of greater good may by their united and individual efforts be opened out to them. contents page prefatory explanation xi the preparation laying the foundation rearing the building the leaders opposition to the building history after words changes in memoriam au revoir appendix i " ii " iii index index to illustrations miners' hall, durham _frontispiece_ n. wilkinson _facing page_ t. ramsey " j. h. veitch " the first deputation " w. crawford, m.p. " w. golightly " j. forman " w. h. patterson " alderman j. wilson, m.p. " j. johnson, m.p. " t. h. cann " alderman w. house " alderman s. galbraith " h. f. heath " prefatory explanation it is necessary that i should set forth the reason why this attempt has been made to place on record, in a compact form, the rise and progress of our association, with the changes which have taken place in our position. the inception lies in a letter received from one of our lodges, and addressed to the executive committee: "seeing that matters of a definite nature relating to the history of the trade union movement in the county of durham, in its social, political, and industrial aspects, are difficult to obtain, we would suggest to our executive that it would be opportune at this juncture to ask mr wilson, on behalf of the association, to write a short, concise history of the movement in the county, giving the social and industrial changes that have followed its progress, and that the executive issue the same free or at cost price to lodges for distribution amongst the members." this was considered by the committee. it met with their approval so far as the history was concerned, but they, with very generous feelings, remembered the many things i have on hand. they felt confident that such a work would be appreciated by our members, but they were loath to impose more work upon me. their desire that i should prepare such a work was expressed in such a kind and considerate manner--not as a committee dictating business to its secretary--that i could not have refrained from taking the task, even if it had been irksome; but the request was in harmony with my own desire, and therefore, if the labour had been more arduous, it would still have been one of pure love and pleasure. yet, although it is pleasant, it is well to recognise a difficulty which meets us at the start. it arises from the fact that at the commencement of our association no records were kept, or, if kept, have been lost. the first minutes that can be found commence with , and even the minutes for the years - are not all in existence, and some which are, have been mutilated by portions of them, and circulars, being cut out. in the period referred to we were in the same position as other similar bodies or nations. at the rise of these there is always the vague and uncertain period where tradition plays the part of accurate historical record. in the struggle for a position there is no time for systematic book-keeping, or, if books are kept, there is no care in preserving them. this is borne out fully in our inception and our early existence, and therefore for facts in relation to our commencement and the first few years of our existence as a trades union body we must depend upon outside sources wherever such are available. in this some little assistance will come from "fynes' history," which, of course, cannot supply much, as it deals with matters largely anterior to our commencement. if we turn to the files of newspapers we by diligent and close search can gather from published reports of meetings and proceedings of that time useful information. there is another source of information--viz. the books of the employers. in respect to this matter i cannot too strongly express my thanks to the proprietors and editor of _the durham chronicle_ for the kind and ready manner in which they placed at my disposal the whole of the files of their paper, commencing with , and allowed me to have them for use in our office. they have very largely helped me to fill in the hiatus up to . my thanks and yours are due to the employers and mr guthrie for the free access they gave me to their books at any time and in the fullest manner. they have not only allowed me facilities for examination, but mr guthrie has assisted me in my search, and has copied out portions which i deemed necessary for our purpose. the difficulty has therefore been lessened, and the work lightened by the help mentioned, but if this had not been so the work would still have been commenced, as the object lies near my heart, for two reasons--first, because to me there is no dearer or more attractive institution in the whole country than our association. i will not say it is superior to all others, but i will assert it has none, or not many equals. from very small beginnings, from very unlikely conditions, and in the face of bitter and opposing circumstances and forces, there has been reared not merely a strong trades union as strong as any extant, but one as beneficial as it is strong. the second reason is the usefulness of the record. if, as pope says, the "proper study of mankind is man," then, if on a slightly lower plane, it must be an important matter for a man to know the history of the class to which he belongs and of any institution of which he is a member. it is useful, too, in showing our young men the condition we have come from, the toil and anxiety those who were the initiators had to face, and the large amount of unremunerative labour they had to perform. our present position has been bought with a price, the amount of which is unknown to this generation, many of whom are like the prodigal, who inheriting a fortune and knowing nothing of the hardships involved in the accumulation, squanders with indifference that which has cost bitter years and much hardship. let me conclude this preface by saying i offer no plea for inability. that is too well known, by myself at least. if he is a wise man who knows his own limits and failings, then i am a very wise man. but one other thing i know as well: i have a full knowledge of your toleration, and that you are ready to give full credit for good intentions. the history shall be the best that i can do, keeping in view all the circumstances. i remember that we do not want a mere comment upon our history; that i could make from my experience, but it might not be accepted as reliable, and therefore what we must aim at (even if it be tedious) is a matter-of-fact statement, because that is all we desire. i fear the history will not be very concise; but that, like all other words, is relative. if it is not as short as some would desire, it shall not be verbose. we will waste no words nor use any useless verbal padding; we will "nothing extenuate nor write down aught in malice." each general event shall have its place and mention. this note may be added, that at the commencement of the association it was embracive of all sections of labour in and about the mines. before we had been long in existence there was a desire for the formation of separate organisations, as it was felt that there were certain peculiarities connected with the other occupations which the miners could not technically deal with. the first to leave were the enginemen, then followed the mechanics, and then the cokemen at the end of . with this notice it will be understood that i deal with the miners alone, only mentioning the others as they come into play with us, and especially after the federation was formed. i propose to deal with the work with regard to the chronological order of the events rather more than in symmetrical chapters, and therefore after we get the association formed we will take a year or more, just as the business is great or small, as a definite period. history of durham miners' association the preparation the association was not a sudden and startling phenomenon, but was a pure evolution. it was no growth of a day like jonah's gourd, but it was the outcome and the harvest of a long, painful sowing-time. in our hall we have two busts. these are no doubt looked upon (if noticed at all) with casual indifference. few of us regard them as expressions of important periods in our struggle for right and equality, and as part of the preparatory process, the consummation of which is our grand institution, of which we are justly proud, for our history fully illustrates the sentiment: "truth struck to earth will rise again." it is not my intention to take a long and detailed retrospect, but just to enumerate a few of the events happening after , all of which were assisting in clearing the ground, and inciting our formation and preparing men's minds gradually for, such an institution. these i will place in chronological order. first, there was the mines act which came into force in july , which amongst other important provisions provided that no boy should go down the mine under twelve unless he could produce a certificate that he could read and write; that boys under twelve should go to school five hours per day; that minerals should be weighed, and that the workmen should be at liberty to appoint a checkweighman. another of the series was the hartley calamity on the th of january --a calamity which is unique in the history of mining disasters, which moved the heart of the nation, and turned the minds of men everywhere to two very important matters--first, the sinking of two shafts to every mine; and second, to the provision for the relatives of those who lose their lives, or for the workmen who are injured. and thus it has ever been: our industry has offered up its human sacrifices before necessary reforms have been introduced. death has in many instances opened the gateway to life and blessing. it is sad, but yet true. then we had two very notable strikes--one at the brancepeth collieries, which is known as the "rocking strike." the name arose from the custom which obtained of setting out the tubs if they were not level full when they came to bank. in order that this might be attained the hewer used to walk around the tub and strike it with his "mell," or rock and shake it so that the jolting on the road out-by might not lower the coals below the rim of the tub, and thus result in the forfeiture of the entire contents. this system was enforced even after the act of , and in such a glaring manner, that the master's weighman was paid a commission upon every light tub he found. the demands of the workmen were payment by weight and an advance in wages. those whose memory goes back to that period will remember the meetings that were held, and especially one not far from mr love's (the owner of the collieries) house, just outside durham city, then called mount beulah, now by the more earthly name of springwell hall. at that meeting on the platform was a working model of a miner rocking a tub, and a song composed by a local poet (mr cooke of trimdon grange) was sung. part of the refrain was, as near as i can remember, as follows:-- "the rocking so shocking long, long we have bore, farewell to the rocking, we will rock them no more." the second strike took place at wearmouth, and was the real, although not formal, starting-point of our union. this strike commenced about the middle of april , and arose out of the conditions contained in the "bond" of that year, which was brought out as usual in the month of march, when the hewers were told that, owing to the depressed condition of trade, there would have to be a considerable reduction in prices. in one instance the score price was reduced from s. to s. d., and the yard price from s. to d. there was no opposition offered at the time, as the men were willing to give the lower rate a fair trial. afterwards they found they were not able to make a fair day's wage. they worked on until the th of may, when after going into the pit they all came out, and held a meeting on the green, and appointed a deputation of six to wait upon the manager and mr stobart. no concession being made the report was given, when the men declared it was impossible to maintain their families, and resolved that they would not resume work until the previous prices were paid. it is not part of my purpose to enter into all the phases of the strike, but one thing i will set forth, as it shows the method adopted to break the ranks of the workmen. the manager of the colliery was a man well-known in the north of england coal trade, mr r. heckles. he, believing there was great power in the beer jug, when the strike had continued for a fortnight sent six notes for fifty men each to get a quart of ale per man. these were placed before a meeting of men. "on the offer of the beer being announced the men replied that the notes were to be sent back, as the day had gone by when the men were to be bought with beer, but that beef and bread would be better, and a resolution was carried not to resume work except at last year's prices." the breaking of the bond brought the workmen into collision with the law, and four of them were summoned to appear at the sunderland court, on the st of june . they were charged under the masters and servants act. one of the cases, that of thomas fenwick, was taken. the magistrates were told they could impose a fine of £ , or commit to prison for three months. the defence was conducted by mr roberts, the "pitmen's attorney-general." the bench decided that the defendant should give sureties of £ to return to work, or be committed to prison for one month. mr roberts took objection, and pointed out that there was no attesting witness to the signing of the contract, and asked for a case to the queen's bench on the point. on that being raised the case was adjourned for a fortnight. on the th of july the case again came up for hearing. the objection raised by mr roberts was then gone into. it was to the effect that the defendant was a marksman (that is, made his mark and did not sign his name), and that the bond was never read over to him. the matter was contested for a considerable time. eventually mr roberts said he had "been told by the most influential men among the workmen that they wanted to be free from the villainous and iniquitous bond, and they would undertake to leave the houses within nine days." on that promise being made and accepted by the solicitor for the owners the bond by mutual consent was cancelled. the men immediately arranged for vacating the houses and handing in their lamps. in one instance this was done in a unique and striking manner. the men formed in procession, over in number, each man carrying his lamp and a copy of the colliery rules. marching to the colliery they handed in their lamps, and returned the rules to the overman. the effect of the trial was speedily seen in the solidifying of the whole of the workmen at wearmouth, as the deputies and others (while passively remaining from work, had never taken active part in the strike) now threw themselves into the struggle, and made common cause with the hewers, and the further effect was the impetus given to the cause of unionism throughout the county until it consummated in the durham miners' union. another element assisting our formation was the desire for association which was burning in the breast of a few men whose ardour could not be damped by repeated failures or retarded by opposition or hardship. the last of the series of these attempts was in , the meeting being held in the victoria hotel, newcastle. there were delegates present-- from northumberland, and only from durham, whitworth, washington, and usworth, the membership being slightly over . we are told by fynes in his history that it was resolved to hold meetings in durham "with the view of moving the men of this county to join them." at the next meeting mr crawford was appointed agent and secretary, with mr joseph sheldon as a colleague. in that capacity the writer first saw mr crawford. he was the principal speaker at a meeting held on sherburn hill. he was on his way from the leeds national conference, and we find by reference to the report of that meeting that he was chairman of the committee on law. this union of the two counties continued until the northumberland men felt that to them it was like being connected with a body of death, and they realised that the connection would in the end be fatal, and in resolved to separate. this resolution was carried into effect, and county organisations were formed. the two agents were allotted as follows:--mr crawford being kept in northumberland, and mr sheldon became the agent in durham. his term of office was very short, as the union here very soon died out. at the united meeting, embracing the two counties, held on november st, e. rhymer was the only delegate, and he delivered a very characteristic speech, of which the following is a portion:-- "with respect to the county of durham he was sorry that they appeared as a black spot in england respecting the miners' association. they numbered about , but there were only represented at that meeting. the hours of the men were eight hours working. the average wage being from s. to s. d. the hours of the boys upon an average were fourteen per day. the system with respect to the boys was the most wretched in the civilised world. they never saw the light of the blessed sun from sabbath to sabbath. he had authority to tell them that the district which he represented begged of them through him to send help to save them from starvation and misery." these are very strong words and true, for the state throughout was deplorable. here and there small societies existed having no federal connection, but they were of no earthly use. they only showed in darker colours the disorganisation which had set in. to use milton's illustration, they made the darkness more visible. still, there were some brave spirits who not only deplored the condition, but, as fynes says, "set themselves the almost herculean task of revising the union and substituting harmony for the discord which then prevailed." for that purpose meetings were held in various parts of the county. the speakers who attended them ofttimes found themselves sleeping in a room whose walls were the horizon and the roof studded with the stars of heaven. prominent we find the names of w. crake and j. richardson (two men who were sacrificed as the result of the wearmouth strike), w. patterson, t. ramsey, and n. wilkinson. not only were there local men at these meetings, but strangers were sent from other districts, seeking to infuse new life into the apathetical and indifferent men of durham. the most notable of these meetings was held at thornley on saturday, the th of september . amongst the speeches delivered i find two given at great length in _the durham chronicle_ of the st of october by mr t. burt and mr w. brown, who was then residing in yorkshire, but who afterwards became the agent for the north staffordshire miners. the chair was occupied by mr w. patterson (our patterson), and there were about men in attendance. if it were convenient i would place on record in this history those speeches in full, as they were worthy of the men and the occasion. one or two sentences may be quoted from mr burt's speech. he urged that "there were many reasons why men should be united: wages, better conditions, and safety at work." their wages were not so high as they ought to be, neither was their social condition what it might have been, and he would candidly confess that the miners themselves were most to blame that such was the state of affairs. had they worked together and exercised confidence where they displayed little else but petty jealousy, had they not spent their money for naught, their position might have been different that day. if proof were needed let them look at other classes and districts. "if the miners of the county of durham compared their condition with any of the great combined bodies of english workmen they would at once see how different their position might have been had they been united. if they compared non-union districts with union districts they would contrast the rate of wages paid in lancashire, wales, yorkshire, and northumberland; and they would see a striking example of the effects of union and non-union." these remarks suggest a curious contrast between our relative position compared with other districts now and then, and the comparison proves the force and wisdom of mr burt's exhortation. in this connection i find a letter from mr crawford bearing on the same subject, and published in _the durham chronicle_ of the th of october , which i insert in full. sir,--seeing that the durham miners are again trying to form amongst themselves an organisation for mutual protection, you will perhaps allow me to say a few words, having had some experience in connection with their last one some six years ago. many of your readers will remember the strenuous efforts then made to organise the whole county, and at least the partial success which attended that undertaking. a great portion of the county did become united, and at one time promised satisfactory success. but those who expected such an accomplishment were doomed to be disappointed. after a short time the whole fabric collapsed, and miners were again subjected to all those difficulties and impositions which necessarily follow in the train of disorganisation. since that time my mind has often been occupied in trying to ascertain the cause or causes of that disastrous downfall, and i have long since concluded that the following were the main if not the only causes which led to such a direful result:-- st. yearly hirings. for years before the union began, these had existed in the county, and their baneful effects had been to reduce the wages of the miners from fifteen to thirty per cent. the coal was no better to get, and its market value ranged about the same. what, then, was the cause of men being reduced in some instances from s. d. to s. per score? it may be truly attributed to disorganisation and yearly hirings. when the union began these still continued, and hence the impossibility of men gradually recovering that which they had lost. these yearly hirings had brought the county to the lowest possible social condition, and when brought, kept it there, rendering organisation difficult, and when attained making its continuance more difficult still. they have been the curse, the withering blighting curse, of thousands of miners in that county. again, the county is too wide and extensive for one association. to make the work not only practical, but effective, it ought to be divided into three, or perhaps four separate districts. these districts ought to be thoroughly independent of each other; not only doing their own business, but being self-supporting. of course, in many instances, one district would find its interests best furthered by rendering assistance to a neighbouring one. in such cases let relief be unsparingly given. the more mutual support and sympathy there existed between the districts, the greater the chance of permanent success. yet, in their working, collecting, and distribution of their finances, let an entire separation exist. we have not space to go fully into this matter here; but if the past will prove anything, it will prove what i have just said. and, if an instance is wanted, it will be found in the two _distinct_, but _successful_ associations, which for years have existed in yorkshire. other causes operated to make short the existence of the last organisation; but these were unquestionably the main ones, and ought, therefore, to be avoided this time, especially the latter, that power being now with themselves, to put into immediate effect, while the former must be a work of time, at least for a few months. the present condition of the durham miners calls aloud for a change, and the power to effect that change is with themselves. let them bestir, set to work in right earnest, and if that work be characterised by prudence and determination, i doubt not but that ultimate and entire success will crown their efforts. william crawford. bedlington, northumberland, _october th, ._ laying the foundation currently with these meetings arising out of the wearmouth strike, and the other matters mentioned, the young union was gathering strength. delegate meetings were being held, the machinery of the association was taking shape, and the constitution outlined. the first of these was held on saturday the rd of july , the chairman being mr j. richardson of wearmouth. in his opening remarks he said: "they had met not as delegates of an organised body of miners, but as representatives of collieries not yet united, to devise means whereby an organisation could be established throughout the county of durham." no attempt was made to transact any business, but a number of addresses were delivered. the speakers were mr lynney of wearmouth, mr b. irving and mr scranghann of houghton, mr noull, windy nook, and mr g. parker of spennymoor. all spoke of the deplorable condition of the county, and expressed their firm belief that nothing but union would bring about an amelioration. the next meeting was held in the market hotel, durham. i again quote from _the durham chronicle_ report: at the hour named there was only a limited attendance of delegates and, no others coming up as time passed on, no business was done, and the delegates present merely contented themselves with discussing the project of a county union, to which the delegates from thornley and houghton stated the men in their respective districts gave perfect accordance, uniting with the union in both cases the scheme of a benefit society. mr richardson of wearmouth thought they ought to form their union first, and leave the question of benefit and emigration societies in connection with it to a future time. a resolution that wearmouth, thornley, and houghton form the nucleus of an organisation or union among the miners of the county, and that a paid agent be appointed to explain to the men the aim, object, and principles of the proposed association, was then passed. the following is the district set out for the lecturer to visit:--ryhope, seaton (and seaham), hetton, south hetton, haswell, shotton, castle eden, wingate, trimdon, fire houses (trimdon grange), and thornley. the agitation of the proposed organisation to be directed against the yearly bond. the next account available is that of a meeting held at the half-way house near thornley on the rd of september. it was held in connection with the demonstration referred to above, at which mr burt and mr brown spoke. the following are the names of the delegates who answered the roll, with the collieries represented:-- w. crake, wearmouth. h. robson, ryhope. w. h. patterson, heworth. t. ramsey, trimdon. j. wylde, quarrington hill. e. furneval, felling. r. bousfield, houghton. j. colledge, murton. a. cairns, thornley. n. wilkinson, trimdon grange. c. flynn, shiny row. c. nicholson, seaham. this meeting was the most ambitious of any held, as a properly arranged business programme was before the delegates. the items discussed were the wages and expenses of the agent. the point discussed was not merely the amount per week, but whether he should be charged for stamps and all cost of correspondence. the meeting was equally divided, when the question was remitted to the lodges. next came the "formation of a central fund." in this matter there was great fear as to the permanency of the movement. the predominant feeling was that it was better to wait until the roll of members reached a few thousands. mr patterson was among those who hesitated, and expressed himself in the following terms:-- "they had several times tried to form a union, but had failed, the men appearing somehow to have little confidence in them." the wearmouth delegate was more optimistic. he did not think it was necessary that they should have members before the fund was formed. mr patterson had hinted the union might fail, but there was not the least fear in his mind that such would be the case. following these came the persons to attend the delegate meetings (whether strangers should be admitted), the pay for attending (this was fixed at s. d. and third-class fare), the appointment of a committee to draw up rules, the adoption of a "pass card" as a guarantee of membership, the collieries for the agent to visit, and the appointment of an agent, secretary, and treasurer. these offices were filled as follows:--mr j. richardson, agent for three weeks; mr isaac parks, secretary; and mr n. wilkinson, treasurer for three months. the next meeting was held on saturday, th november. it is important that we should note this meeting, as it was the real beginning of the association. the following is the full report from _the durham chronicle_:-- durham miners' mutual association "a meeting of the delegates of this association was held in the market hotel in this city on saturday, when the delegates present represented members. the following resolutions were passed:--( ) resolved that stanley be exempted from paying any contributions this day. ( ) that all members receive rules free. ( ) that each delegate speak in rotation as on the list, and not to speak more than five minutes each time. ( ) the following were appointed trustees:--alan murray, w. crake, isaac parks, w. patterson, r. carr, w. wilson, john armstrong, and t. noble. ( ) that each delegate have one vote. ( ) that mr john richardson be agent and secretary, and be paid s. per week, and allowed third-class railway fare when on the business of the association when such business calls him more than four miles from his residence, the delegates to decide his place of residence. ( ) that the delegates should manage the business at present, and that in future a president should be chosen at each meeting of delegates who shall have a casting vote. ( ) that each delegate be prepared with security for the person proposed by his district for the office of treasurer. ( ) that all suggestions be sent in at least seven days before the meeting. ( ) that the miners of the county of durham have their attention called to the objects contemplated by the association by hand-bills, and that be printed. ( ) that the agent go into the crook and spennymoor districts and explain the advantages of the society." here we have the union for the whole county fairly established on a weak foundation. sufficient to dishearten, looking from our present proud position, but it must be remembered that there were giants in those days--brave, hopeful men, who were not to be turned from their purpose by any hindrance. they felt that united effort was the breath of our life, and they kept their eyes on that goal. a united durham was their battle-cry and inspiration. if there had been any possibility of diverting them, the next meeting, which was held on th december , was sufficient. that meeting was held again in the market hotel. there were delegates from only collieries, representing ½ members. the outlay for the previous fortnight was £ , s. d., and there was a saving of £ , s. ½d. mr n. wilkinson was appointed treasurer. rules were submitted from various collieries. the agent was instructed to visit the derwent district, and a very wise provision was made that no suggestion should be put on the programme that infringed the general rules. it was a little anticipatory, seeing the rules were not formed, but those men knew well that without order and law it was impossible to have any useful progress. later experience proves the wisdom of their provision. rearing the building the end of saw the foundation of the structure laid. the beginning of found the builders hard at work raising it. the first move made was to hold fortnightly delegate meetings. these appear to have been of the nature of committee and council meetings combined, and were usually held in the market hotel, durham. the first in the year was held on saturday, st january. the first business, even in this early stage, was to deal with that permanent disease of trades unionism, the unfinancial member; for from the origin of things there have been men who were ready to take all and give nothing. various schemes were suggested for dealing with such people, many of which were crude, but in the end the means most favoured by the delegates was analogous to, but somewhat more drastic than, the rule at present in operation for compelling members to keep themselves straight on the books. the other questions dealt with were the proposed formation of a sick fund, with sundry minor or local matters. passing over the meeting held on january th, except to note that the number of men represented was , and the fortnightly contributions amounted to £ , s. ½d., we come to an important one held on the th. the numbers in union were the same as a fortnight before. the meeting was important, because it is the first time we find the yearly bond as part of the business of the council. there was a very lengthy discussion upon, or rather expression of condemnation of, the bond. the most noteworthy portion of the proceedings was a letter from mr a. macdonald, as president of the miners' national association. the letter is worthy of note, because it is the first recorded instance of his official connection with durham, and because of its opposition to the system of yearly bindings. he was desirous to ascertain what were the views of the miners in the county upon it. the government were pledged to bring in a mines regulation bill during the next session of parliament, and it was necessary that their views should be expressed with a view to insert a clause in the new bill to provide for fortnightly or monthly agreements. in mr macdonald's opinion, as in that of other leading gentlemen connected with the organised coal districts in great britain, it was useless to attempt to better the condition of the miners in durham so long as that system existed. the unanimous agreement of the meeting upon the subject was "that mr macdonald should be informed that the miners of the county of durham considered the bond to be a great evil, and would hail with the greatest gratification any legislative enactment providing for its abolition." at the meeting held on th february a much more satisfactory report was presented. the membership had increased to ½, and the contributions to £ , s. d. there had been a deposit of £ , making the banking account £ . in addition to this large increase in funds and numbers encouraging reports were given by the delegates as to the requests which were made from unorganised collieries for someone to attend to assist in inducing the men to join. in connection with this desire there came a question from mr macdonald and mr burt asking whether the young association would take an active part in arranging for meetings, passing of resolutions, and getting up petitions in furtherance of the mines bill about to be introduced into parliament. these gentlemen were extremely desirous that a series of meetings should be held, and they were willing to attend them if arranged. the result of the request was an agreement to hold three meetings at sunderland, bishop auckland, and durham, and the appointment of a committee to make the necessary arrangements. at this meeting we have the first mention of an entrance fee, which was to be d. for a month, the payment of delegates out of the local funds, the attendance of trustees at every delegate meeting, and the most important appointment of president and executive committee. the custom had been to appoint a president from each delegate meeting _pro tem_., but now it was deemed advisable to elect for a longer period. the appointments were as follows:-- _president_ w. crake, monkwearmouth. _committee_ christopher nicholson, seaham. isaac parks, trimdon. martin thompson, murton. john jackson, thornley. mr allonby, south hetton. w. h. patterson, heworth. w. anderson, murton. these with the treasurer formed the committee. it was further arranged that the delegate meetings should be held once a month, and that the contributions be forwarded fortnightly to the general treasurer. as a result of the arrangements for holding mass meetings in the county, two were held: on the th of february at bishop auckland, and on the th at sunderland. these were addressed by messrs burt and macdonald. both meetings were very well attended; the object was to discuss the proposed new mines bill. strong speeches were made against it. "it was too narrow in its application. it would permit a boy to be employed for hours in the mine, and he would have to work a length of time equal to days in the year, more than the child in the factory. there was a deficiency with regard to weighing. that they demanded should be remedied, because the system of measuring and gauging simply meant robbery and double robbery. in some districts the arithmetical tables had been altered to make a ton equal to and even cwt. then there was a great need for more inspectors and for properly trained managers, for the absence of competent men had been a fruitful source of colliery accidents. deputies and overlookers were not chosen, as they all knew, because of their excellence and skill, or their high moral qualities, but more because they were sycophants and tyrants in the hands of those who owned the mines." there came a powerful appeal from mr burt on behalf of the union. "every great movement in the world was carried on by combined efforts. single individuals had never been able to accomplish much. in all parts of the world one heard the declaration made that workmen were doing too much work, and receiving too little remuneration, and it needed but the organisation of this great army to gain for themselves justice. if they joined that army they would have education, temperance, prudence, and virtue rising up in the place of moral degradation; happiness in the place of misery; and comfort in every home where wretchedness now only prevailed." at the monthly meeting held on the th of march there were delegates from collieries, with a membership of , being an increase for the month of over . the monthly income was £ , s. d. of that sum £ was paid for collecting the signatures for the petition to parliament _re_ the mines bill, and a balance of £ was added to the banking account. two petitions were in evidence, one being and the other yards long--the cost in the former case being over £ , and in the latter over £ . a deputation attended this meeting from yorkshire soliciting subscriptions for a colliery on strike in that county. in response to the appeal £ was sent, so that very early in its history the young society was learning the luxury that comes from doing good to your neighbour--a lesson it has not forgotten in its older and stronger days. the next monthly meeting was held on the th of april. there was a sad falling off in the membership represented. the chairman was able to "congratulate the meeting on the fact that the bindings had passed off so satisfactorily, and that a slight increase in price had been secured." there were only collieries represented, with a membership of . the variation in the number of delegates may be accounted for by the system of paying the delegates, it being borne by the lodges, and not as at present. a complaint was made by the delegates in regard to the dismissal of men at the late bindings. it was said that there were at trimdon grange who had been treated in that manner. the owners had shifted of them, but a claim was made for removal allowance from the union at the rate of s. for the first mile and s. per mile afterwards. the meeting held on the rd of april had a very full programme of business. the county was called upon to deal with another serious strike at wearmouth, and the support of the men severely taxed the energies of the union. a great deal depended upon the result of that contest. the business part of the meeting, apart from wearmouth, was the appointment of a secretary and extra agents. the points under consideration were the number to be appointed, whether they should be in districts or be centralised, and what should be the salary. the decision was there should be two agents, and the salary s. d. per week, with house and firing. with respect to the secretary, it was resolved to appoint one--the choice in this, as in the agents, being left to a subsequent meeting. on the th of may a full detailed list of the collieries and members was given, which it may be interesting to set forth. number of name of colliery members income for month trimdon ½ £ trimdon grange ½ shiney row philadelphia murton ½ ludworth south hetton whitworth addison norwood evenwood shildon lodge page bank black boy tudhoe adelaide thornley heworth seaham felling quarrington hill and coxhoe derwent the appointment of agents and secretary was then taken, the following being the result:-- as agents, mr munson, philadelphia; mr crawford bedlington, and mr j. richardson; the secretary being a. cairns, thornley. mr richardson was assigned to north east, mr crawford, central, and mr munson, south-west. each district to have a sub-delegate meeting, birtley, thornley and bishop auckland being the places of meeting. mr crawford was not long in the county before he began to make himself felt, and let the people know he was around, as the yankee would say. in _the durham chronicle_ for the rd of june there is a very striking letter in his best style. those of us who knew him are well aware what his best meant in . he was writing in defence of trades unions--some writers had been speaking about the "terrible tyranny" of these unions. he turned on them, and showed that, "if there were tyranny anywhere, it lay on the side of the employers, and that the workmen were at all times inclined to act in a right and courteous manner. still, while they so act, they have to be utterly and fiercely condemned, and the employing class applauded and eulogised for acting in a manner diametrically opposite, and about as near an approximation to truth and right, as are the north and south poles. this seems a most anomalous condition of things, that with one class right should be called wrong, while with an opposite class that which is really wrong should be called right. but i have no hesitation in saying that, if the doings of working men's associations be closely and impartially sought into, it will be found that, instead of any of their members receiving full licence to do as they like, every action is closely watched, and not over-considerately examined, and that, if there be a fault, it often is in the executive power pressing rather too hardly any portion of their fellows who may wish to seek for an amelioration of their wrongs. let the general public examine both the origin and mode of conducting our trade disputes, and, as a rule, it will be found that, instead of the toiling population deserving their unsparing contumely, the employing class are alone the undivided cause of these struggles, and the course they generally afterwards pursue ought to call forth the bitterest indignation, and often does beget in the heart of the working men a feeling of dislike and disregard not unmixed with contempt." at the meeting held on the th of june a fourth district was formed. it was called the south-western, and mr patterson was appointed agent to it. as a further consequence of this additional district the executive committee was increased from seven to nine, the wages of the agents being fixed at s. d. and expenses. at this meeting we have the first safeguarding rule against collieries striking illegally: "that any colliery coming out on strike in an unconstitutional way be not allowed any support from the central fund, or have their case considered at the central board." the next delegate meeting was held on the th of july. there was an attendance of thirty-two delegates. the only matters needing a place in our history were the appointment of another agent or assistant, and an increase in the wages of the agents. [illustration: n. wilkinson] it was decided to appoint "tommy ramsey," and his wage to be s. per week. the wage of the other agents was fixed at s. per week, with s. travelling expenses and s. per week house rent. these sums to include all expenses within their respective districts. the first annual meeting was held on december rd, , in the market hotel, durham, and the proceedings and programme occupy three columns of _the durham chronicle_. the reason arises out of the dual nature of the meeting, it being council and committee. the secretary's report showed that there were financial members on the books, and the total worth of the society was s. ½d. per member. our purpose will be met if we select the main points, leaving those of a local and temporary character. first, in that general category we have a request for durham to join the amalgamated association of miners. this was not acceded to, but copies of the rules were written for. second, the appointment of treasurer and his payment. mr n. wilkinson was appointed, and his salary was to be s. per quarter (much less than many of our local treasurers receive now). yet mr wilkinson felt proud of the office, and promised to merit their confidence during the year. third, the question of sending a delegate to the miners' national conference, and the business, which was to discuss the mines bill. it is very obvious that the county was feeling its way very carefully, and with great regard to economy, for one delegate said it would take one-twelfth of the income to send a representative, independently of the entrance fee. it was finally agreed to send mr crawford. fourth, the question of cumulative voting was brought forward by murton as follows:--"that each delegate have an additional vote for every members he represented." the proposal, however, was lost by fourteen to eight. fifth, the appointment of the officers for the year. these were elected as follows:-- secretary, a. cairns; treasurer, n. wilkinson; president, w. crawford; vice-president, w. h. patterson; the committee being mr munson, t. mitcheson, m. thompson, m'mann, j. jackson, w. coulthard, and i. perks. a very fitting finish to the year will be a reference to another letter by mr crawford. the object of his attack was the rev. mr blagdon, newbottle. this gentleman had said he hated and detested unions, and this roused the temper of crawford, and plainly he talked to him. he reminded the parson of the condition of the miner, and he pointed to the contrast between his conduct and that of christ. "but i suppose," said crawford, "things are changed. of course, we live in an age of progression, and we ought to leave behind us those old and antiquated practices of practical philanthropy. christ always spoke the truth too. when he made a promise it was always kept." then he asks: "what wrong are the workmen doing? our only aim is the establishment of common justice amongst mankind. we have myriads of men, women, and children who but seldom receive an approximate sufficiency of the commonest necessaries of life. and it is a self-evident fact that nothing will render human existence so miserable and short as social destitution, bringing, as a matter of consequence, mental pressure or anxiety of mind. even comparative want is prejudicial to physical health. this brings care and anxiety. they act and react on each other, often doing their deadly work ere men have passed half their allotted threescore years and ten. that these things exist are incontrovertible facts. and does their removal by moral and philosophical means not _in part_ pertain to the work which this gentleman has chosen for himself in life? history and observation alike teach that, where a people are socially depressed, moral culture is a most difficult matter, and, where moral cultivation is no easy task, to spiritualise is next to an utter impossibility. so that in reality, when rightly viewed, there is a very near kinship, and ought to be, in working a very close connection between the union to which the philadelphia society belongs and the work in which this reverend gentleman is engaged. whether or not mr blagdon will endorse these sentiments i cannot say; however, be that as it may, when in future he makes a promise let him keep it, and likewise cease to give utterance to such vehement expressions as hating and detesting that about which he seems to understand but little indeed. by pursuing such a course he will in future save himself the merited contempt of his parishioners." this quotation will serve a twofold purpose: it will give an example of mr crawford's vigorous style of writing when roused and at his best, and it will indicate the kind of opposition the young association was met with at this very delicate and important period of its existence. those who should have welcomed all effort towards better things should have assisted instead of thwarting and maligning. the year found the builders of the association untiring in their efforts, but still meeting great discouragements. these came mainly from the apathy of the people whom they were trying to help. like nehemiah they had their sanballats, who did their best to prevent the work; but, inspired by the belief in the power of a united people to better their own condition, they fought and built, making headway but slowly. in the early part of january a miners' conference was held in manchester to consider the mines regulation bill, the trades union bill, the truck bill, and kindred subjects. the delegate from durham was mr w. crawford, and the number he represented was , . before proceeding further with the account of the building we will place on record the first collective action taken by the young association. this was in relation to the inundation which happened at wheatley hill on thursday, the th of january . the colliery had been in operation about six months; there were thirteen hewers, five putters, and three helpers up, with the necessary deputies and others, at the time it occurred. there were five lives lost, and others had a very narrow escape. there is no need to describe in detail the whole circumstances. it will be sufficient to say that a man named roberts was in a place which was being driven in the main coal at thornley for the purpose of tapping some water which was lying on the thornley side in order that it might be run to the other colliery which lies to the "dip." in addition to those who lost their lives, other two were rescued after being in the mine fifty-four hours. the miners' association was not slow in taking part in the subsequent proceedings, and at the inquest which opened on the th at the colliery office, wheatley hill, by mr crofton maynard (whose able services are still given to inquiries into the sad accidents in the easington ward), the association was represented by mr w. crawford. on his application that witnesses should be summoned on behalf of the workmen the coroner readily consented to an adjournment until wednesday, the th of february. the adjourned inquest was held at wingate grange, when mr a. cairns, secretary, and mr w. crawford, agent, were present on behalf of the association, with mr kewney, solicitor, of north shields, to watch the proceedings. after a very long and exhaustive inquiry the verdict was "that the deceased were killed on the th of january by a burst of water in the wheatley hill pit, through the gross negligence of w. spencer, head viewer, w. hay, resident viewer, and thomas watson, overman; and that the said w. spencer, w. hay, and t. watson did kill and slay the five deceased previously mentioned by neglecting to put in proper bore holes for the safe working of the mine." on that verdict the coroner committed the accused for trial at the assizes on a charge of manslaughter. the trial took place at the march assizes before baron martin. the counsel for the association were mr herschell (afterwards lord chancellor) and mr j. edge. the writer of this history was in court, and heard the trial, and the able speech made by mr herschell, whose object was to show that there had been a violation of the mines act of , the fifteenth rule of which was to the effect "that bore holes should be kept in advance, and if necessary on both sides, on approaching places likely to contain a large quantity of water." the grand jury had thrown out the bill, but the case was still proceeded with. it was clear the judge was against the proceedings after the throwing out of the bill; and eventually the workmen's counsel withdrew the case, because the judge was of the opinion that roberts (the hewer in whose place the water broke away) should have known as well as the manager how near the water was to them, and because, on the technical point, it was quite clear how the judge would direct the jury. the accused were therefore acquitted. one little piece of funny puzzling of the judge is very vividly remembered. roberts was not a native of the county, but was doing his best to train himself in the peculiarities of a dialect which, when spoken by a durham man, is to a stranger difficult to understand, but more so when it comes from a welsh tongue. at one part of the proceedings the judge asked roberts what he was doing when the water broke in. the reply was: "aw hed getten me jud korved, and the hole marked off, and was gannen back for the drills." with surprise the judge repeated the question, and received the same answer. perplexed, but not enlightened, a second query was put: "what did you do then?" "aw run doon the board and up the stenton." innocently the judge put a supplementary question: "was it a wide plank you ran along?" thinking the word board meant a piece of timber laid for roberts to walk on. upon an explanation being given he confessed that, in the whole of his experience, he had never been so much puzzled before. in our review of the building of the association it will not be necessary to mention the work in the county except so far as it relates to the object we are dealing with: the raising and strengthening of the organisation and the changes in policy and procedure. the first council in was held on march th. the attendance of delegates was moderate, and mr crawford, the president of the association, was called to the chair. at this meeting we have the first mention of the yearly demonstration. it was moved "that the council take into consideration the desirability of holding a general meeting of miners in the central district, the expenses of such to be paid from the central fund." the time named was shortly after easter. it was likewise arranged for the agents to live in durham. mr crawford at that time was residing in sunderland, and mr patterson in bishop auckland. this, it was felt, interfered very much with the necessary consultation and arranging of work. a series of resolutions was brought forward by mr crawford. first, that "minerals be weighed only, seeing that measuring and gauging are sources of endless losses to the hewers." second, "that miners ought to be allowed to place on the pit bank as checkweighman a man of their own choice, whether such person be one of the workmen or not." third, the appointment of an additional number of inspectors or sub-inspectors is required--the number of pits in in the whole country being , and only inspectors, which gave an average of pits each. the following resolution was carried:-- "we believe that to make inspection thoroughly effective, mines ought to be inspected at intervals not exceeding three months." the fourth resolution was "that no boy should be allowed to work more than ten hours a day." the murton delegate seconded the resolution, and said: "miners were often referred to as an ignorant set of men, but if they received more attention than they did in the seed-time of life perhaps better fruit would be received. at present their boys went to work at half-past four in the morning, and did not leave the mine till half-past five in the evening. by the time they got home, washed themselves, and had a little refreshment it was seven o'clock. certainly night schools were provided for the boys, but he could not see the utility of them, as the minds of the lads after being so many hours in the pit were incapable of receiving instruction. providing schools under these circumstances for pit lads was like preparing food for persons who had no appetite." that speech is worth quoting and remembering, because it gives us so clearly the condition in that year and shows so graphically the change since then. the young men at least will do well to ponder the lesson. to them it means much, and tells them the benefit they have (in this alone) received from the labours of those men who so unselfishly toiled in the early days. at this time a question arose which evoked great feeling in the thornley district in particular, and throughout the county in general. this was the refusal by mr cooper, the manager at thornley, to bind mr a. cairns, the secretary of the association, who was checkweighman, and mr j. jackson, one of the executive committee. at that time, it should be remembered, a man to be a checkweighman must be, and remain, a workman on the colliery, and therefore be "bound" as all other men were. the situation is interesting for two points--first, because it was productive of some very strong letter writing by mr crawford in defence of the two men; and second, because it is the first recorded instance of an offer from the men to apply arbitration as a means of settling disputes between employers and workmen under this association. the offer was contained in a resolution passed at a special council held in the market hotel, durham, on th april. the following is a portion of the resolution:-- "this meeting strongly urges on the thornley workmen the propriety of offering to submit the whole case to arbitration, the members of the board chosen to be composed of an equal number from both sides; the arbitrators to elect an umpire whose decision shall be final." i quote two sentences from one of mr crawford's letters: "the entire transactions both on the part of the masters, and these perfidious hirelings [certain blacklegs] is contemptible in the extreme, clearly showing to working men that where they have not, by combination, the power to protect themselves they will only be endured so long as they are passive slaves in the hands of grasping greediness. men need to arise, and by an active concentration of organised power frustrate that intolerance so rampant among them, an intolerance diametrically opposed to the spirit of the age, and one that will not hesitate to build its own advancement on the spoliation and desolation, and if necessary the damnation, of myriads of immortal beings." our first gala the first in the long series of meetings was held in wharton's park, durham, on saturday, the th of august . for some time prior district meetings had been held in different parts of the county, and great efforts made to secure a good gathering. in addition, a "sum amounting to £ was offered in three prizes for a band contest, and liberal money prizes for various athletic sports." there was a charge for admission, and it was estimated that between and paid for admission. the speakers outside the association were a. macdonald, w. brown, staffordshire, and john normansell, yorkshire. the local speakers were mr w. h. patterson, mr hendry, addison colliery; mr t. ramsey, mr n. wilkinson, mr allens, mr young, addison colliery; and mr ferguson, edmondsley. the platform was decorated with the thornley banner, and in the arena was a banner bearing the inscription: "a fair day's wage for a fair day's work." the chairman was mr w. crawford. his first words were: "this is the first great gala day of the durham miner's mutual confident association, and i only pray that it will not be the last." he reminded them that he and his colleagues had only been trying to organise the county. they had met with great difficulties, but they were still alive, and more likely to continue alive than ever. "i can assure you," he said, "that on this, the th day of august , the durham miners' association was never in a more healthy position; never more healthy with regard to its feeling and determination to carry on its great work of organising the county; never more healthy with respect to its funds; and never more healthy in reference to the general progressive tendency of its operations, since the first day the association was established." to quote the speeches would be foreign to the purpose of this history. the speakers were men who did great work in the trades union movement in the period with which we are now dealing. william brown had peculiar methods, partaking more of a religious revivalist. he ofttimes at home opened his meetings with prayer, and had a small collection of songs (entitled melodies and poems), from which he would sing before he commenced to speak (and he was a singer). for some months it was the privilege of the writer to be engaged as a lecturer in the midlands by the miners' national union in , three weeks of which were spent with brown in north stafford, and therefore there was a good opportunity of judging. at this first gala brown sang two of these songs, and recited the following poem:-- working men "think what power lies within you, for what triumphs you are formed; think, but not alone of living like the horse from day to day; think, but not alone of giving health for pelf, and soul for pay. think, oh! be machines no longer, engines made of flesh and blood; thought will make you fresher, stronger, link you to the great and good; thought is a wand of power, power to make oppression shrink, grasp ye then the precious dower, poise it, wield it, work and think." these men, heroes of the highest order, who inaugurated one of the finest series of labour meetings ever held in this or any other county, who saw the possibilities which lay within us, and who spoke such words of hope, have all passed to the reward which awaits the good and the true who battle for the right in whatever clime or sphere of life. their spirits still live and move and have being in many to-day, bearing testimony that "the good men do lives after them." a delegate meeting was held on the th of september , mr crawford presiding, at which three general matters were transacted. it was decided to retain a solicitor to transact the legal business of the association and act as adviser. arrangements were to be made to open a proper banking account, and it was resolved to join the miners' national association. the next delegate meeting of importance was held in the shakespeare hall, north road, durham. mr j. forman was now chairman (although still continuing to live at roddymoor)--mr crawford being appointed secretary, mr wilkinson treasurer, and mr patterson agent. the matter under discussion was the wage settlement, some dissatisfaction being manifested at the difference between the men underground and those at bank, and a report was made of the first case settled by arbitration. this was at the lizzie colliery, the arbitrators being t. taylor-smith and mr w. crawford. the leaders with the council meeting held on tuesday, march th, , by the election of mr forman as president and mr crawford as secretary, and the regular meetings with the employers being recognised, we have the association fully and solidly established. before we proceed further it will be in natural order if we take a short glance at the men who were at the head of it. there is no need to enlarge upon them; a bare outline will be sufficient. the first in prominence and force was mr w. crawford. when appointed he was outside the county, but owing to his having been secretary of the combined counties he was known to the durham men as an able and forcible trades unionist. when the separation between the two counties took place he was engaged as secretary of the northumberland association. this post, says fynes in his history, he filled "with great ability until june , and made himself a great favourite in northumberland, but he then left the association in order to take the secretaryship of the cowpen co-operative store at blyth." mr burt was elected to succeed him. in , when mr crawford applied for the position of agent in durham, he was selected from a number of candidates. it was at this time that the writer had the pleasure of making his acquaintance, and had large opportunities of forming an estimate of his ability. never had any man more force of character or more executive power. his individuality was very large. he had no love for platform work, and the love for that sphere lessened as he grew older; but he had no superior and few equals in his grasp of, and power to find a solution of, the peculiar difficulties and complications which arise in an occupation like the miners. he was a solver of difficulty and a manager of men, and in every way fitted for the post of secretary of a trades organisation. from his appointment to his death he filled it with a skill few men can command. _n. wilkinson_, the first treasurer of the association, had worked at trimdon grange as a fireman. at the date of his appointment he was earning a living by tea selling, having lost his employment on account of his trades union principles. his first appointment was temporary, and when elected permanently he was living at coxhoe. as soon as the union was fairly started he was made treasurer permanently, and so acted till . as a speaker he was of a blunt, straightforward order. as othello says: "his was a round unvarnished tale and he told it right on." at the commencement, when announced on the bills it was as "nicky wilkinson," and no man could be in the least doubt but that when he spoke to them on the union and its usefulness it was from the heart. as a man in those stern and trying times he was, as those who were his colleagues would testify, a man upon whom they could depend in any testing circumstances. _mr j. forman._--he was the first regular chairman. at the time of his appointment he was checkweighman at roddymoor, and when spoken of it was as "forman of roddymoor." he came from northumberland to annfield plain when a young man. he acted as president of the association for a time, and followed his occupation as checkweighman; then in he was appointed a permanent official, and removed to durham. he continued in that position until his death on the nd of september , at the age of seventy-seven. he was an ideal president. it is not saying too much--his superior could not be found. the fact of his appointment to that position indicated the prominent part he took in the formation of the union. he was more of an adviser than a platform speaker. he preferred a quiet, retiring life in which he could be useful rather than ornamental. although shunning public notoriety he was no shirker when danger demanded the presence of men, for in all the explosions which happened during the term of his office he was one of the foremost; and almost single-handed he stood out for the dust theory when men of noted scientific knowledge were against him. _w. h. patterson._--his life's work, from start to finish, was the most conclusive testimony as to the sincerity of his purpose. there were men then, as now, whose motive is the loaves and fishes, willing to gather where they strew not and reap where they have not sown; but patterson was not one of these. from the time when, but a mere boy living at windy nook, he threw himself into the work, with earnestness and energy, until his death, when a comparatively young man, he devoted himself and the best he could give to the establishment of and care for the union. when it prospered no man was more cheerful, and when dark times came upon it his sorrow was genuine and large. he was not a crawford (few were), yet for persistent plodding he was equal to any. with youthful buoyancy, and a heart full of desire and determination, he was the very man for the position in which he was placed. it would have been a useful addition to our own literature if he had placed on record the hardships he, with "tommy ramsey" endured in - . they lodged many a time in a room the walls of which were the horizon and the lamps the stars above them. money was not plentiful, and it was not every person who dared to take an agitator in to lodge. it was in many quarters considered a crime almost deserving of capital punishment. "_tommy ramsey._"--what can be said of "tommy"? he was a most perfect type of an old school miner, and a sound trades unionist, one of the heroes of ' . there are numbers of men in the county who will remember the rugged old warrior in the noble cause, just as the picture hanging in the hall describes him--a rough but true diamond of the first water. with bills under his arm and crake in hand he went from row to row announcing the meetings and urging the men to attend. his words were few, but forcible; not polished, but very pointed--and they went home. like longfellow's arrow shot in the air, they found a resting-place. he had one speech, the peroration of which was something like the following:--"lads, unite and better your condition. when eggs are scarce, eggs are dear; when men are scarce, men are dear." it was impossible to miss the meaning in those words. their simplicity was their greatest eloquence. his work was far from pleasant or safe. the writer of this was witness of a brutal attack on the old man by a bully who would disgrace any place in which he lived. this antipodes of a man, to curry favour with the manager, and to please those who bought him body and what soul he had, ill used ramsey, and burnt his crake. at the subsequent meeting crawford was wild in his denunciations. the words still ring in my ears. brave old "tommy" cared not; he got a new crake, and turned it with more emphasis. grand old ramsey, you are right now; if not, many of us have a poor chance. you in your way, in accordance with your ability, tried to open the prison doors to those who were bound, and to stir up a love of freedom in the breast of those who were in willing slavery. [illustration: t. ramsey] the opposition to the building this was fourfold, and it may be interesting to look at these _seriatim_. the first was not in the least unexpected. at that time capital and labour were looked upon as being natural enemies, and all their relations were on that principle. we see now how foolish is that idea. then conflict and doubt formed the atmosphere which surrounded the two great parties in the industrial world. if men having common interest joined themselves, in order that they might act for the common welfare, the leaders were to be dealt with harshly, and if necessary banished. it was no infrequent occurrence, when the spirit of union was abroad, for men to be driven away from localities they loved and from associations endeared by years of enjoyment. this was done with the view that terror might be struck into the hearts of others. the principle was: drive away the shepherd and the sheep will flee. so much was that spirit abroad that in many places the establishment of the permanent relief fund was treated coldly, obstacles thrown in its way, if not bitterly opposed, because it was regarded as the thin edge of the union wedge. what more natural than for fierce opposition to rear itself, with threats for the braver spirits, and bribes and allurements for those whose nature was susceptible to such influences? ale-houses were used as a means for preventing unionism taking root and spreading. the sorrow of it is there have always been spirits who are ready to act meanly when required. this opposition was, therefore, to meet and bear down and convince that a trades organisation was not an institution prone to evil, and set up for no other purpose. the men who are alive to-day, and who took part in that opposition, would, we may assert with confidence, confess their mistake if they were interviewed on the subject. then the law was against the trades unionists. we complain now, but they had more reason in those days. we must lift ourselves into the condition of things prior to the act, which did a great deal towards equalising the positions of the employer and employed. the master and servants act, with all its one-sided applications, was in force. for a long time an agitation was carried on for its repeal, but after twenty years the only result was the appointment of a select committee to inquire into the operation of the law. the law was very unequal. it had been framed on the principle that the workman alone was inclined to do wrong, and therefore wanted hedging in and punishing. in the year there were arrests under the act in the country. eight hundred of the accused were sent to prison. an amending act was passed in , but between that time and , were convicted. "the state of the law was simply infamous. its provisions made it a criminal act if a workman broke a contract, even under the most justifiable circumstances. he was arrested by warrant, and if the breach of contract was proved the magistrate was bound to inflict the punishment of imprisonment with hard labour. if, on the other hand, the employer broke the contract, ever so flagrantly, he could only be summoned by a civil process, and his punishment was simply a fine." [illustration: j. h. veitch] then they were hindered by a system of boycotting before the word became proverbial. it was not merely difficult, but impossible in some places to get a meeting-place. the writer knows of one colliery where a place could not be got. even the co-operative hall was closed against the union, and the union money had to be taken in the corner of a field. beyond this, in durham the printers refused to do the union printing--all except mr j. h. veitch, who dared almost social ostracism and took the work, and the connection then formed has continued up till now. the refusal arose from two reasons--first, there was a fear that the union would not be able to pay for the printing; and second, trades unions were in bad odour in the county generally, and none the less in durham. there was none of the respectability about the institutions there is now, and little hope of them. broadheadism at sheffield, with its destructive policy, had filled men's minds with fear. the form of reasoning was: "trades unions are guilty of these evil things; this is a trades union, therefore it will be guilty of doing evil." just as logical as if a man had said: "murder is committed in england; these people are english, therefore they will commit murder." mr j. h. veitch (all honour to him) had none of those fears, nor that false logic. he took the work when social ostracism was in the air. we cannot forget the act nor the man. another great obstacle against which they had to contend was a host of anonymous writers, who wrote behind a variety of _nom de plumes_--such as "geordie close," which covered w. p. shield, and "jacky close," but none under their own names. these writers used the most scurrilous and slanderous language about, and attributed the vilest motives to the men who were at the head of the movement. the situation was a complete analogue to that when nehemiah commenced to build the walls of jerusalem. sanballat and tobiah and geshem laughed him to scorn, and despised him, and said: "what is this thing that ye do; will ye rebel against the king?" but as those sneerers in the far-off jewish times had no effect on the builders of that day, so in those days the founders of our association, the builders of our broken walls, heeded not those snarlers of thirty-six years ago, and the result is an all-round benefit. the greatest of all the species of opposition they had to meet arose from the apathy and indifference of the people. although the condition was bad in the extreme, yet often the earnest spirits and others scattered about the county had to ask each other, in the query of the prophet: "who hath believed our report?" the state of apathy was quite natural. it was not because there was no real love of union; it was the outcome of repeated failures. "hope deferred maketh the heart sick." there had been spasmodic attempts at associated effort. the result was a feeling of hopelessness. like men of whom we read in waterlogged ships or analogous situations on land, having tried oft to save themselves, they give up in despair, and say "kismet," like an eastern fatalist. the hold this feeling had on the mind is seen in the small results for a considerable time after the association commenced. a thousand or two was their whole membership, their council was their committee as well, and the numbers so small that a room in an ordinary hotel could with ease contain them. at their meetings, sparse in attendance, they were often insulted and sometimes maltreated by the men they had come to help. in this alone there was sufficient to deter them, and to lead men of talent and energy (such as they were) to turn themselves to other objects in life; but they loved their class, and, while they had aspirations for better conditions, they desired to raise their fellows with themselves. any one of them could have made a position in other directions if their aims had been selfish; but they were men of different mould, and they were inspired by the love of the cause, and confident in its ultimate success if once they could clear away the dark pessimism which had fixed itself in the minds of the workmen. for this they endured the hardship and faced the opposition, until finally men saw the solidity and permanency of their work, with the result that the institution they founded occupies a rightly deserved foremost place among trades unions. the coal owners' association--the abolition of the bond--first general advance--formation of the joint committee--first gala--mines regulation act--second advance _the coal owners' association._--one of the results of the formation of the organisation was the commencement of the durham coal owners' association. there had been an association under the name of "the north of england united coal trade association," but its functions were vastly different from those of the present organisation. then the sphere of operations was parliamentary and legal, but the new body was formed for trade purposes. the first meeting to consider such a step was held on february st, . there was an adjournment for a fortnight, when a set of rules was submitted setting forth the conditions of membership, contributions, the assistance to be rendered, and the appointment of officers. the chairman and vice-chairman were respectively hugh taylor and w. stobart, and the secretary was t. w. bunning. no sooner was the association formed than communications were opened with the miners' association, as the following letter will show:-- neville hall, coal trade office, newcastle-on-tyne, _feb. th, ._ mr crawford, my dear sir,--i am directed to inform you that, at a large meeting of the representatives of the household coal collieries, held here last saturday, it was resolved-- that it is considered desirable that a meeting should be held between the coal owners and a deputation of the representatives of the workmen, at one o'clock on saturday, the th instant, at the coal trade office, to discuss the various questions now in agitation by the workmen, with a view to their adjustment, and that a copy of this resolution be forwarded to mr crawford. will you be as kind as to acknowledge the receipt of this letter, and let me have the names of the deputation who will attend. i beg to remain, dear sir, very respectfully yours, theo. wood bunning. [illustration: (back row).--n. wilkinson. (_treasurer._) w. h. patterson. (_vice-president._) m. thompson. t. ramsey. g. jackson. j. forman. (front row).--w. askew. w. crawford. (_president and secretary._) j. handy. t. mitcheson. the first deputation from the durham miners' association to the coal trade office, newcastle-upon-tyne, february , ] there were about a score of representatives of the employers present during the meeting, while ten delegates, representing , workmen, took part in the conference on the latter's behalf. mr hugh taylor occupied the chair, and the delegates were introduced by mr crawford. the first question for discussion by the conference was then brought forward--viz. the yearly bindings. at the outset the employers intimated that they were perfectly willing to abolish the bond, and establish in its place either monthly or fortnightly agreements, giving preference to the former. the workmen's delegates at once intimated their readiness to abolish the yearly bond, and thanked the masters most kindly for the manner in which they had met them on that question. the men proposed in the place of the yearly bond to establish a fortnightly agreement, and it was ultimately decided to discuss the terms of the agreement at a second meeting to be held shortly. the next matter was the question of the hours of boy labour, but after a short conversation it was also agreed to allow this question to stand over until the second meeting. the next question was with reference to an advance of wages. on this point the owners admitted that the men ought to share the present prosperous condition of the trade, the only difference of opinion that arose being what that share ought to be. the employers were of opinion that they and the men ought to meet as two associations--the combined masters on the one side and the combined workmen on the other--and discuss the question as to what would be fair to both parties. it was suggested at the same time that any advance asked or conceded should be based on prices in force at bound and unbound collieries of the county of durham in april . on the part of the employers it was pointed out that a great many collieries had at the present time presented petitions for an advance of wages, and in some cases they had intimated their decision of laying the pits idle in case their demands were not conceded, and it was now suggested that the delegates from the workmen present should do their utmost to get the petitions placed in abeyance until the next conference was held. this was readily agreed to, and the meeting then terminated. it is satisfactory to note that during the continuance of the conference a most pleasant and amicable feeling prevailed on both sides. the association being formed and officered preparation was made for the removal of grievances. the first to which attention was turned was the abolition of the "yearly bond." for a long time there had been a protest against the system of partial slavery implied in a contract covering a year. the system was as follows:--on a saturday near the th of march the whole of the workmen were called to the colliery office, and there the manager would read over (nearly always in tones inaudible to all except those who were close to him) the conditions of labour for the next twelve months. there was usually a balancing of the prices. as an inducement to the men there was, say, a sovereign given to the first man bound, ten shillings to the second, five shillings to the third, and then two shillings and sixpence to every man after. the crush to secure the first place was generally so great that the manager was fortunate if he were not carried off his feet. as a preparation for this rush certain men would be bribed to incite, and thus induce men to act in an unthinking manner. this bare outline will suffice to show the evil of the "bond," and that it was a wise step on the part of the newly-formed organisation to attempt to substitute a shorter term of contract. the first meeting for that purpose between the employers and workmen was held on february th, . as this was the first united meeting in a series which has been for the benefit of all concerned it will be interesting to place on record the letter from the employers inviting the representatives of the miners' association to meet them. of course, the employers were made aware of the desire amongst the people for this and other reforms, and that knowledge induced them to arrange matters amicably if possible. another thing was in favour of the workmen: not only was their union gathering strength, but the state of trade was in their favour. one result of the war between france and prussia was to increase the demand for british coal, the result being a coal famine and excessive prices. the old pit heaps even were sent away, and a common saying at the time was: "anything black was sold for coal." a conflict, therefore, would have been a dangerous and destructive thing. (_first general advance_) important conference of colliery owners and miners' agents in newcastle (_durham chronicle account_) agreeably to an arrangement made at the conference between the colliery owners and the miners' delegates held on the th inst. an adjourned meeting between the two bodies took place on saturday at the wood memorial hall, newcastle. there was a large attendance of the masters, mr hugh taylor, chipchase, being in the chair. mr w. crawford, president of the durham miners' mutual confident association, acted as principal spokesman for the miners' delegates, who were eight in number. it will be remembered that at the last meeting the masters agreed to the abolition of the yearly bond, and the first question, therefore, taken into consideration at the present conference, was the nature of the future agreement between the masters and the men. on the one hand, the employers suggested monthly notices on both sides; but the men on the other hand were unanimous in the request for a fortnightly notice, with the option of either giving or receiving the same on any day except sunday. after some discussion, the masters acceded to the wishes of the men on this point. the next question taken into consideration was the advance in pay demanded by the men. a proposition for an increase of per cent. on all prices paid in april last was submitted by the delegates, who, in answer to questions by the owners, admitted that the advance requested appeared to be a large one, but they urged that it was made in consequence of the low rate of remuneration received by the miners of the county at the time referred to. to this advance the owners objected on the ground that it was excessive. they also urged that for several years past coal had been low in the market, and the working of pits had been unremunerative, and submitted that it was unfair on the part of the workmen, when a slightly better price had been obtained, to make an exorbitant demand. they also pointed out that the advance asked for was greatly in excess of that obtained by the miners in other parts of the country. to this argument the delegates replied that they were of opinion that the advance asked for was not greater than the excessive profits of the masters would allow to pay; in fact they only wanted a reasonable ratio of the profits made by their labour, and they were also of opinion that the per cent. advance would not place the miners of the county of durham on an equality with the workmen of other counties. after some further discussion, the delegates intimated that they would be satisfied, if the owners did not feel disposed to give the increase asked for, with the average score price paid in northumberland and south yorkshire. they were willing, if the masters would divide the two last mentioned counties into four quarters each, and would select, according to arrangement, two collieries from each of the eight quarters, to accept the averages of the prices paid at the sixteen collieries as the standard scale in the county of durham. the owners, after hearing this proposition, asked the deputation if the average would be accepted by the men at those collieries in the county who were at present working for only per cent. less than the proposed standard. the delegates replied that every such colliery would accept the average if the masters would give it to the men of those collieries who were at present working for per cent. less than the average named. after some further discussion the delegates retired. on being called back into the room they were informed by the chairman that the owners did not think it was desirable to go to either northumberland or south yorkshire for an average, as they were of opinion that they were quite competent to manage their own affairs; and that they had agreed, in a spirit of conciliation, to offer an advance of per cent. on all prices over and above all consideration money paid on april last. the deputation stated that they had no authority to accept the offer of the owners, but they would in due course communicate it to the general body of the men. the conference shortly afterwards broke up. the day fixed for a meeting on this question was the nd of march. in the meantime a special council meeting was held in the town hall, durham, mr w. crawford, as president, occupying the chair. there were present delegates, and the members represented were about , . the business was the discussion of the matters to come before the employers and the appointment of a deputation to attend the meeting. the adjourned conference was held on thursday, march st, and for the purpose of giving a proper knowledge i herewith record the press report from _the durham chronicle_. conference between durham coal owners and workmen another conference between the durham coal owners and a deputation of the workmen of the county took place on thursday sennight in the wood memorial hall, newcastle. the chair was occupied by mr j. b. simpson, low hedgefield, and there was a good attendance of the representatives of the owners, the deputation being, as at previous meetings, headed by mr w. crawford. before proceeding to the disposal of the questions for which the conference had been convened, it was intimated to the deputation that haswell colliery was idle. it was explained that the workmen at that colliery had received an advance of d. per score on last april's prices in november last, and they now wanted an advance of per cent. on that concession. a telegram was also produced which intimated that a strike on the same ground had occurred that morning at castle eden colliery. the course adopted by these two collieries was utterly opposed to the arrangement which had been made between the two associations of employers and workmen at their conference, and the representatives of the former body intimated that if such constant violations of the arrangements arrived at at these interviews were to continue, it would be better to break off all negotiations at once, and each side follow its own policy. the members of the deputation expressed their utter surprise and utter ignorance of the events that had occurred at the collieries named, the first intimation of which they had received was at that meeting, and they desired to be allowed a private consultation before they proceeded further. after a short consultation in private, the deputation drew up the following telegram, the substance of which they communicated to the employers:-- we regret to hear that haswell and castle eden collieries are idle. you must know that you are wrong, and we strongly advise you to commence work to-morrow, otherwise steps will be taken to repudiate such reprehensible conduct, and if necessary the strongest action will be taken in the matter. this was deemed satisfactory, and the conference then proceeded to the business which had drawn them together--viz. the remuneration of the offhanded men and boys. the employers stated that they had agreed to give all offhanded men and boys who work underground per cent. advance on last april's prices, the same as they had conceded to the hewers. to the men who work above ground--viz. to the cinder drawers, joiners, blacksmiths, firemen, screenmen, and banksmen, and all other men and boys, with the exception of the enginemen and a few rare cases of cinder drawers--they offered an advance of ½ per cent. on last april's prices. the deputation, while expressing their perfect satisfaction with the underground men and boys' advance, suggested the propriety of the same advance being extended to all those men, as enumerated, who work above bank. on the part of the employers, however, it was stated that the reason only ½ per cent. was offered to the above-bank men was that a reduction of per cent. in their working hours had been conceded; and further that their work was not of so risky and dangerous a nature as that of the underground men, and also that there was always a superabundance of men willing to work on the screens, and to do other work above bank. after a conversation, the terms offered by the employers for both descriptions of men were accepted. the report of the interview was given to a delegate meeting, mr crawford again presiding. the number of delegates was very large. the points under discussion were the two offers contained in the report above. it was agreed that the offer of the owners should be accepted, with the understanding that it come into operation at once. this was the whole of the important business discussed. it will serve no useful purpose to deal with every local strike, they are incidental to the main course. mention will only be made when any incident cognate to the general purpose be connected with them. with that idea in view i refer to the strike at seaham. this strike commenced on monday, th may. the main causes of the stoppage were the length of the hours of the hewers and the time when the shifts should be worked. the hours of the putters had been reduced from twelve to ten, the pit at the time being a single or day shift. with the reduction of the hours the employers wanted to arrange for two shifts of putters and three shifts of hewers. against this the workmen not only protested, but stopped work without notice. two things are noticeable, and of interest to us. we have the first breach of discipline, and the first instance of censure of the general officials, because, in accordance with the obligations of their office, they enforced the rules of the association, and candidly and clearly told the men their opinion. the cause of complaint with reference to mr crawford and the officials of the union, was a telegram sent to the lodge, which, with slight verbal variation, has formed the model of all sent since under the same circumstances. it read as follows:--"do go to work. you must know you are wrong. you will get no support. liable to punishment. do return." for sending that message mr crawford was subject to some very scurrilous remarks at the meetings which were held in connection with the strike. these remarks called forth a public reply. in the press of that day is found a letter which contains an unflinching and manly statement of the facts of the case: the cause of the strike, the illegal position of the men, and an extenuation of the action of himself and his colleagues. i quote the concluding words. after pointing out how expeditious the agents had been in their attendance to the matter in dispute, how they (the men) were striking against their own agreement, how he had been vilified, and how his views were still unchanged, he wrote: the report of yesterday's proceedings at seaham colliery has not changed my views on this matter. i repeat it, the men are in the wrong, and even liable to punishment. a miner characterised the telegram as an insult to the men at that colliery. of this i have not the slightest doubt. i have recently been accused of both insults and incivility; and why? because, as in the case of seaham, my opinion has been asked, or advice sought, and where such opinion or advice has been adverse to their own preconceived ideas of right or wrong, and they have been told so decisively but courteously, then i became uncivil! these are the men who can prate about liberty of speech and freedom of action, and yet, because they are supposed to subscribe their mite towards a person's maintenance,--every penny of which is doubly worked for,--would only allow his tongue to utter words in accordance with their own crude and contracted views, even though such words were a mere utterance of the most glaring untruths, and a flagrant violation of all the rules now in operation as between masters and servants in their respective relations to each other. i willingly admit that these are but a small minority among the , members now composing our association. from the men i have received the utmost consideration, demonstrating by their conduct, that they will give to those whom they employ that treatment which they would like to receive from those by whom they themselves are employed. i commenced my present agency amongst the miners of durham on may th, . from then, till now, i have done my utmost to protect and further their interests in a fair and equitable manner. where i have deemed the doings of owners or agents to be wrong, i have not been slow to condemn them, and what i have done will do again; and where i have found the workmen to be wrong, i have pursued the same course, unhesitatingly making known my views without the slightest hesitation. if any man or number of men are mean and cowardly enough to think that i shall sit and become a mere machine of repetition, i beg to clearly intimate that they are sadly mistaken. i shall retain my individuality intact, holding myself free to unreservedly express my opinion of all matters which in any way may effect the welfare of our association, being always willing to retrace my steps, if shown wherein i am wrong; but holding on, amid the folly of fools and the abuse of knaves, if convinced that i am right. and in conclusion, allow me to say that, if such doings are not in keeping with those of the men, the sooner i am replaced the better. a council meeting was held on the th of may in the town hall, durham. the only thing of note was a proposition for the establishment of an institution for the benefit of old men. nothing definite was done in the matter. after discussing it the council decided to refer the matter to the executive committee, with instructions to draw up a plan or plans to be submitted to the county for acceptance or rejection. in this we have the germ which eventually developed, through the permanent relief fund, into the superannuation fund, which has been such a blessing to hundreds of aged miners in the northern counties. on saturday, june st, an important conference was held between the coal owners and a deputation of representatives of the association. the deputation consisted of j. forman (president), w. crawford (secretary), w. h. patterson (agent), n. wilkinson (treasurer), t. mitcheson, coundon, m. thompson, murton, g. jackson, and h. davison, thornley. the first question was the dispute at seaham and the night shift in general. there was a long discussion, and eventually the employers promised not to commence any more night-shift pits unless it were a case of absolute necessity. the conference next turned its attention to the first rank for pony putters. the proposal of the men was that the distance should be yards. it will be as well to say here that afterwards the distance was fixed at that number of yards. the next subject was as to how many tubs should constitute a score. there was no uniformity in the county. although twenty of anything is generally reckoned a score, yet at some collieries it was as high as twenty-five. the object was to reduce it to twenty, and the deputation was willing to rearrange the prices wherever the number was reduced. the owners thought it unwise to alter the arrangements, and suggested an adjournment, which was agreed to. the last question was the arrangement of a uniform time for the foreshift men to go down. the custom varied; at some places it was as early as one or two in the morning. the hour named by the representatives of the workmen was from four o'clock. the employers had no very strong objection, except that of interfering with other classes of labour--such as cokemen, waiters-on, and others who would have to commence later, and therefore be later at work. the deputation replied by instancing the peases firm, where the system had been introduced and was working satisfactorily. the employers asked for time to consult the trade, and promised to inform the coal trade how emphatic the workmen were in their desire for the change. the first gala on the race-course, durham beyond this gala, which may be truly classed as the first, there will not be any need to mention the yearly gatherings in this history. its importance compels notice. important it was, for two reasons--first, its place in the series; and second, because of the public feeling, and in many quarters fear, which was felt as to the consequence of bringing such a large number of the miners and massing them in the city. as showing the state of feeling i will insert a portion of an article which appeared in _the durham chronicle_ for friday, june th, . the coming demonstration has occasioned not a few timid residents much uneasiness during the past few days, on account, as they imagine, of the extreme likelihood of the affair resulting in a scene of riot and disorder, and two or three nervous females in business in the town have so far given way to their fears that they have actually consulted their friends as to the propriety of closing their shops in order to protect their persons and property from "those horrid pitmen!" even the borough magistrates, too, seem to have had an idea that the dog-fighting and pitch-and-toss portion of the mining community was going to be introduced into the city by the approaching gathering, for they declined when first requested to grant the usual licences to the proprietors of the refreshment booths. a full meeting of the borough magistrates was, however, subsequently held, and the bench after hearing a statement from mr crawford, the principal agent of the durham miners' association, relative to the object of the miners in assembling together agreed to issue the required certificates. for our own part, we have not the slightest doubt of the proceedings being characterised by anything but the best of feeling and order on the part of the men taking part in the demonstration, which we are sure is intended to partake more of the character of a monster "outing" of a class of men whose only desire is to discuss amongst themselves the best means of improving, in a rational and legal manner, their condition, rather than an assemblage of either political or social conspirators and agitators. almost the worst contingency, however, has been anticipated, as there will be a force of policemen on the ground, the expense of the attendance of of whom will be borne by the miners' association, whilst the remuneration of the remaining will be defrayed from the funds of the borough watch rate. in addition to this, many tradesmen barricaded their shop windows, and an urgent request was made to the mayor to have soldiers in readiness. mr j. fowler stood in defence. his reply was characteristic, but correct: "i know the pitmen better than you, and there is no fear." he was borne out by the proceedings, which were in the highest degree satisfactory. the first part of the procession came in at . a.m., and from first to last the most complete good order obtained. there were in all collieries present--the membership of the association being , . the speakers were a. m'donald, then president of the national association of miners; w. brown, stafford; and t. burt, northumberland. the local speakers were w. crawford, w. h. patterson, h. davison (thornley), n. wilkinson, t. mitcheson, g. ("general") jackson, t. ramsey, and w. askew. the following resolutions were submitted:-- . the change which during the past twelve months has taken place in the position of the durham miners' association, both numerically and financially, ought to be encouraging to all who take an interest in its welfare. during that period differences, as in other places, have arisen; but, so far, they have been managed without a single pit having been stopped, or the loss of any work whatever. this is a condition of things which, taken all together, ought to give the utmost satisfaction to all parties concerned. . this meeting begs to utter its indignant protest against the action of the select committee in the way they have amended the payment of wages bill. it at the same time most earnestly calls upon government to restore it to its original form by amendment whilst it is under the consideration of the committee of the whole house. it further begs to state that no measure will be satisfactory to the miners of the county of durham that does not contain payment of wages weekly without any reduction whatever. . that this meeting also has learnt with surprise that it has been stated that the miners of durham do not want weekly payment of their wages, and that they are not aggrieved with the present reduction. they beg to give the statement, by whomsoever made, an unqualified denial. . this meeting likewise looks upon the criminal law amendment act of as an insult to the working classes of this country. it at the same time pledges itself to every legal means to have the law repealed or so modified as that all classes in the country will be alike in the eye of the law. . that this meeting regards arbitration as a logical way of settling those differences which in trade necessarily arise between employers and employed. arbitration recognises the right of both parties to put forth views, and leads to examination or investigation, which tends to avoid strikes and lockouts, with all their commercial ruin and social misery. it has now for a short time been in operation amongst the miners of durham, and we are able to speak to beneficial results; and we most heartily wish to have a continuance and extension of the principle. . that a copy of the foregoing resolutions be sent to the prime minister and home secretary. with this all too brief reference we must leave this, our first race-course gathering. if anyone be desirous of reading a very full description of the collieries attending, with their numbers on the books, the banners with their inscriptions and designs, and the speeches, let him refer to _the durham chronicle_ for june st of that year. suffice it here to say that the day was all that could be desired. the old city was enlivened and its trade enhanced. the great crowd came and went in good order. the fears of the fearful were shown to be groundless, and the good behaviour initiated that day, amid the firing of the cannons in wharton park, has never varied up to the last of this series of gatherings. the cannons were fired at the expense of t. ramsey. the second advance in wages on friday, the th of july , a meeting took place between the employers' and workmen's representatives. the meeting was arranged in response to a request for an advance of fifteen per cent. on the rate of wages. mr h. taylor occupied the chair. the deputation was headed by mr w. crawford. at the outset of the meeting the owners complained that the men were neglecting work to a very great extent, causing a diminution in the output of not less than twenty per cent. as compared with the previous twelve months. statistics showed that the average working time of the hewers was not more than eight days per fortnight. that entailed heavy loss on the owners, and while such neglect of work continued they could not grant the advance asked for, and they suggested the propriety of having a clause inserted in all agreements, that the men should be compelled to work at least thirty-five hours per week before claiming the highest price paid at the colliery. that meant the system of bonus money paid at many collieries, and the deputation emphatically refused it, and said they were not asking because of the state of trade only, but because of the very low condition of their wages which had obtained in durham for so long, and which they hoped to raise, even if trade became depressed. the deputation was asked to retire, and on their return were handed the following resolution:-- the association [owners'] has decided to give per cent. advance to all underground workmen, including banking-out men; but excepting pony putters, who are to be dealt with after the putting question has been settled in northumberland; and ½ per cent. to the whole of the above-ground labour; enginemen, both above and below ground, to be excepted. this advance to be on present prices, and to date from the pay commencing nearest the first day of august. this offer was brought before a special council meeting held on saturday, the th, mr john forman presiding. the report of the meeting with the employers was given by mr crawford, who went very fully into the reasons why the advance of fifteen per cent. was claimed. the council adopted the following series of resolutions:-- . that in the opinion of this meeting we are more than justified in asking the per cent. on present prices, which is being sought by our association. there never was a time when the price of coals approximated to what they are at the present time, and in justice we believe that we ought to fully share in that increase and increasing prosperity. on the th day of the present month the following are quotations from the london coal market:--kelloe, s. d.; south hetton and lambton, s.; and hetton, s. d. having seen coals sold in the same market for as little as s. per ton, or more than cent. per cent. less than now, we certainly conclude that we are more than justified in seeking d. or even s. out of s. or s. this being so, we abide by the per cent. now being asked for all classes of workmen, above and below ground. . that the owners be requested to meet our deputation on friday next for the purpose of reconsidering the per cent. advance, or if possible on a more early day. . that this meeting deplores the oft-repeated statement of coal owners and others relative to the amount of work at present lost by the miners in the county of durham. we cannot with our present knowledge admit the accuracy of these statements, but believe, on the contrary, that such statements are very greatly overdrawn, and thus an entire false impression is being conveyed to the public mind, and a positive injury done to a large body of men. we have again and again declared that in our opinion men ought to attend their work as regularly as possible, believing that to do so is for the benefit of themselves as well as the employers, and we again urge our members to be as regular as possible in their attendance at work, so as alike to benefit themselves and deprive all parties from so maligning them. the adjourned meeting with the owners took place on friday, july th, when mr h. taylor again occupied the chair. the owners repeated their complaint about the loss of work, and asked whether the deputation were willing to give any guarantee that the men would in future work more regularly. they could not give such a guarantee, but said their council meeting had agreed to recommend the men to work as regularly as possible. with this assurance the owners then handed the following resolution to the deputation:-- we have decided to give per cent. advance to all underground workmen--including banking-out men--except pony putters (who are to be dealt with after the putting question has been settled in northumberland), and per cent. to the whole of the above-ground workmen, enginemen (both above and below) excepted. this advance to be on present prices, and to date from pays commencing nearest to monday the nd and monday the th of july. the deputation were not satisfied with the reservation as to the putters, and after some further discussion it was agreed to make the advance applicable to them as to the other underground workmen. formation of joint committee it will be interesting to give this important step in detail. it was first mentioned in connection with certain meetings which were held mainly on the wages question or the abolition of the yearly bond. while discussing these matters mr crawford, on behalf of the deputation, mentioned the advisability of forming a committee of six on either side to consider local disputes and changes in wages. the first formal action taken by the employers was on july th, , when the following resolution was adopted at their meeting:-- joint committee.--mr crawford was also informed that on the motion of mr lindsay wood, seconded by mr hunter, a committee consisting of the following gentlemen:--hugh taylor, w. stobart, w. hunter, c. berkley, r. f. matthews and lindsay wood had been appointed to meet a committee from the miners' union, to draw up rules for guiding the association in receiving demands from the workmen. it was arranged with mr crawford, that the committee from the miners' union should meet the above-formed committee at . on friday, the th inst. the suggested meeting was held on th july, when the following recommendation was agreed to:-- joint committee.--it was agreed to recommend--that six members of each association should meet every fortnight and discuss all demands except cases of consideration in temporary bad places, the consideration to be given in such places to be settled from fortnight to fortnight by the agents of the collieries affected. all demands to come through mr crawford, who is to give the agents of the colliery and the secretary of this association, at least three clear days' notice of the nature of the demands that it is intended to prefer at the next meeting. as a result of this recommendation a meeting was held on the nd of august, and the first code of rules was arranged. the names of the parties at the meeting are in the following list:-- _owners_ hugh taylor. w. stobart. lindsay wood. john taylor. j. b. simpson. c. berkley. p. cooper. w. hunter. r. f. matthews. t. t. smith. _workmen_ w. crawford. w. h. patterson. n. wilkinson. j. jackson. j. forman. t. mitcheson. r. b. sanderson occupied the chair. the following rules were agreed to:-- the object of the committee shall be to arbitrate, appoint arbitrators, or otherwise settle all questions (except such as may be termed county questions or questions affecting the general trade) relating to matters of wages, practices or working, or any other subject which may arise from time to time at any particular colliery, and which shall be referred to the consideration of the committee by the parties concerned. the committee shall have full power to settle all disputes, and their decision shall be final and binding upon all parties in such manner as the committee may direct. the committee shall consist of six representatives chosen by the miners' union and six representatives chosen by the coal owners' association. at meetings of this committee it shall be deemed that there shall be no quorum unless at least three members of each association be present. each meeting shall nominate its own chairman, who shall have no casting vote. in case of equality of votes upon any question, it shall be referred to two arbitrators, one to be chosen by the members of each association present at the meeting. these arbitrators to appoint an umpire in the usual way. each party to pay its own expenses. the expenses of the umpire to be borne equally by the two associations. should any alteration of or addition to these rules be desired, notice of such change shall be given at the meeting previous to its discussion. if any member of the committee is directly interested in any question under discussion, he shall abstain from voting, and a member of the opposite party shall also abstain from voting. when any subject is to be considered by the committee, the secretary of the association by whom it is brought forward shall give notice thereof to the secretary of the other association, at least three clear days before the meeting at which it is to be considered. the committee to meet every alternate friday at half-past eleven o'clock. the first meeting of joint committee was held on th august. the members were: _owners_ r. b. sanderson, chairman. c. berkley. j. b. simpson. j. taylor. p. cooper. r. f. matthews. _workmen_ w. crawford. w. h. patterson. j. forman. n. wilkinson. j. jackson. t. mitcheson. there were in all six cases, which, with their decisions, are as follows:-- _august th, ._ murton (_stonemen_).--demand for an advance of from d. to d. per day. to stand over for a fortnight to ascertain the average wages of the district. oakenshaw.--demand for s. per score on the broken and a sliding scale similar to that in the whole. the s. per score in the broken was granted to date from (uncertain?). the sliding scale was waived by mr crawford and his committee. seaham.--mr matthews' report objected to,--referred, together with a question of removing bottom coal (mr t. taylor was chosen arbitrator by the association); any concessions made by the arbitrators to date from monday the th august. etherley.--complaint that the banksmen and others have not received the different advances granted by the association. mr lishman was desired to carry out the resolutions of the association in their entirety. south derwent.--complaint that the deputies have not got the per cent. advance. mr dickenson, having stated the circumstances of the case and the wages paid, the complaint was withdrawn; it being considered that the deputies are fully in the receipt of the advances decided upon. wardley.--longwall skirting.--this turned upon the question as to whether it was intended by the arbitrators to include skirting in their award of the th march , but it was decided that it was not so included, and that d. per yard extra should be given for skirting. shifters' wages.--demand withdrawn. ramble.--to be considered at the next meeting. it was agreed that full particulars of subjects to be discussed before the meeting should be given at least three clear days before the meeting. the mines regulation act in the session of a mines bill was under discussion, but was not carried through its various stages. it was again introduced in the session of , and for a long time its fate was uncertain. men from all the districts were up lobbying on behalf of the bill. mr crawford was sent from durham. a council meeting was held on saturday, th july. while the meeting was in progress a telegram was received from mr crawford as follows:-- crawford, london, to mr john forman, town hall, durham.--many hours in the lords last night. happily disappointed. bill passed satisfactory. weighing clause safe. boys ten hours from bank to bank. a vote of thanks was carried to mr crawford, the government, and to the home secretary for the able manner in which he had conducted the bill through parliament. claim for advance of fifteen per cent. at the ordinary council meeting held on saturday, th september, the number of members reported was , . mr crawford gave the result of a conference which had taken place with the coal owners with respect to another advance of fifteen per cent. nothing definite had been done, as the employers were indisposed to comply with the request, and it was adjourned for a fortnight. that meeting was held on friday, september th, in newcastle. the deputation was informed that the subject had been fully considered. coals were falling in price, the demand was declining, and the commercial prospects were assuming a more unfavourable aspect, and therefore they could not give any further advance in wages. the meeting terminated, but the deputation expressed their dissatisfaction with the result, and they were supported in their objection by a council which was held on saturday, september th, and they were instructed to again meet the employers. the mines act--the third advance--death of "tommy" ramsey--the drawing hours--the second gala--advance in wages on january st the new mines act came into force. it is no part of this history to enter into all the changes made by the new measure, but there are three portions of it which deserve a brief notice--these are the weighing of minerals, the position of the checkweighman, and the hours of the boys. the weighing of minerals clause was to provide against the "rocking" customs such as had obtained at the brancepeth collieries, and which had caused the "rocking" strike. the new act set forth that: where the amount of wages paid to any of the persons employed in a mine to which this act applies depends on the amount of mineral gotten by them, such persons shall, after the first day of august one thousand eight hundred and seventy-three, unless the mine is exempted by a secretary of state, be paid according to the weight of the mineral gotten by them, and such mineral shall be truly weighed accordingly. the clause further provided for deductions and for exemptions by the secretary of state from the weighing clause if it were proved that the exigencies of the mine warranted it. in a note to this section mr maskell w. peace, solicitor to the mining association of great britain, warned the employers that: "this is an entirely new enactment. care must be taken to provide the necessary machines for carrying out the provisions by the st of august ." the portion of the act relating to the appointment of the checkweighman was a great advance in the direction of freedom of choice. prior to this the choice of the workmen was confined to those employed on the colliery subject to the confirmation of the manager, and the man chosen was as liable to be discharged as any other of the workmen for any reason. the new act provided that one of the workmen could be chosen either from the mine or under the firm. he need not be sanctioned by the manager, and could only be removed "on the ground that such checkweigher has impeded or interfered with the working of the mine, or interfered with the weighing or has otherwise misconducted himself." the last provision gave rise to some very glaring removals for acts done away from the mine. these anomalies were corrected by the act of . the hours of boys there were two provisions in the new act relating to the hours of boys. one was for those between the ages of ten and twelve, and they were for the purpose of employment in thin seams; their time was to be for only "six hours in any one day." the other provision (which still exists) was for boys between twelve and sixteen years. the weekly hours were fixed at fifty-four. this latter provision was the cause of some confusion, seeing the hours of drawing coal were twelve, and the difficulty was to bring these boys away without interfering with that. a very important council was held in the town hall, durham. there were two questions before the meeting--first, the demand for fifteen per cent. advance; and second, the working hours under the new mines regulation act. as stated in the review of the previous year, meetings had been held on the advance in september, but the employers would not give way, and asked us to wait. in consequence there was a very strong feeling in the county which found expression at the council. there was some complaint that the executive committee had not been so energetic in the matter as they ought to have been. mr crawford defended the committee. an attempt was made to increase the amount claimed to thirty-five per cent., but in the end the original request was confirmed. the question of the number of hours the pits should draw coal was next considered. the employers were asking for eleven hours, but this was felt to be difficult because of the act in its application to the boys under sixteen. there was a desire on the part of many delegates that the coal drawing should be limited to ten. during the discussion mr crawford said: no more important question could occupy their attention than that before the meeting. not even the question of an advance exceeded it in importance, because whether or not that was given a great deal depended on how they settled the question of the hours. he might hold views very different to what were entertained by many in that room, but he was bound to state them. the question had occupied his attention, and he was of the opinion that the owners would be unable to keep the men fully employed for eleven hours. they had, however, requested to be allowed to work those hours, and they had a perfect right to do so if they could employ the men. at the same time, he did not believe they could keep the men employed during the last hour after the lads had gone to bank. eventually it was resolved that the employers should have the unreserved right to draw coal eleven hours per day, providing they did not violate the mines act relative to the boys under sixteen, nor keep the men in the pit the last hour doing nothing. the meeting with the employers on the advance was held on february th, mr hugh taylor presiding. in a very long statement he reviewed the state of the coal trade. he reminded the deputation that, although there had been delay, there had not been any breach of faith. he brought before them the question of short time, which was an evil not only to those engaged in the coal trade, but to the country at large. he urged again the request of the employers that there should be an agreement binding men to work so many hours at the coal face. the mines act had been passed. it did not satisfy anyone. all they asked was that the men should do their duty. in the face of these difficulties, but in the hope that the men would help them, they had decided on an all-round advance of fifteen per cent. there were some of the lodges who refused to carry out the eleven hours' arrangement, and with a view to induce them to do so the following circular was issued:-- to the members of the durham miners' association fellow-workmen,--in the inauguration of any new system, difficulties always occur; whether these difficulties are easily overcome, or otherwise, will much depend on the manner and extent to which men, or classes, are affected thereby. as a matter of consequence, we have found these difficulties amongst ourselves in putting into operation the new "mines regulation bill." these have arisen from various causes. we have, first, a very erroneous impression gone forth, to the effect, that after the commencement of the new mines bill, on the first day of the present year, no pit, or no person in a pit, must work more than hours per day, or hours in any one week. in the minutes of committee meeting, held on the th inst., we clearly and distinctly stated that this view was a wrong one. we again beg to emphatically state that the law, in this particular, affects only boys under years of age, and that so far as regards all parties above this age, matters remain identically as they have been. it would appear, however, that in the face of this intimation, some collieries of men are still insisting on the general adoption of the hours per day, and hours per week. in addition to this, we have existing at many collieries, both where men work two and three shifts per day, difficulties as to what the working hours ought to be. under these circumstances, the owners asked your deputation to meet them last week, for the purpose of discussing, and if possible arranging, some understood mode of action. this meeting took place, at newcastle, on friday last. the first question asked was, what objection we had to owners working their pits hours per day, and or days per fortnight as usual, so long as they did not violate the act of parliament relative to boys under years of age? after talking over the matter for a long time, we retired, and in consulting among ourselves, failed to see any reason why pits should not draw coals hours per day as heretofore they had done. we returned and told them that we could see nothing to prevent them from working the pits hours per day, if they thought desirable to do so, and they could find men or boys to bring the coals to bank; but that, in trying to carry this into effect, they must not keep men laying at their work for the last hour doing absolutely nothing, as, if such cases did occur, they would most certainly be complained of, and a remedy sought by an appeal to the joint committee, in which case they would be exposed to the entire county throughout. respecting boys being brought into the pit an hour or two after work commences, or sent home an hour or two before the pit is done at night, we cannot see that any difficulties should exist. the question was asked, should a boy be sent home for the first days, having worked less by far than the allotted hours' per day, and such boy should purposely remain at home on the saturday, would such boy claim his days' pay, remembering that for days he had worked short time for the very purpose of going to work on the saturday? to this the owners demurred, when we suggested the desirability of seeing boys, or their parents, and making with them necessary arrangements. we may be told that the boys are sent home to suit the owner's convenience, but we must not forget, for whatever purpose sent home, that while they worked short time they were paid full hours, and we certainly cannot see the wisdom of preventing boys from receiving days' pay for working hours, when, but a short time ago, they worked hours for the same money. the employers, by act of parliament, are compelled to reduce the working hours of boys under years of age, but we cannot expect them to reduce the hours of all datal men, if work can be found for them for the ordinary time. we must not lose sight of one very important fact, viz., that a reduction of working hours to those who are paid a datal wage means an advance of price, a reduction of hours, from to per day, is equal to per cent., which practically means per cent. advance, seeing that the productive powers are lessened by so much. in this manner it must be seen too, that no boy under years of age is allowed to be in the pit more than hours in any one single day, or hours in any one week. if this is strictly seen to, a great work has been accomplished, and don't let us spoil that which is really good by trying to accomplish too much. those lodges who object to the pit drawing coal hours per day, ought to bear in mind that a reduction to hours is a very serious curtailment in the drawing or producing powers of the pit, and as such only tends to lessen the power of owners to pay good wages. the profits arising from the produce of any article are up to a given quantity consumed in paying current expenses; and, therefore, the more the produce is restricted, the less means are there at command wherewith to pay all classes of workmen. the disadvantages arising from the operation of the new mines act must necessarily tell heavily on the mine owners in the two northern counties, where the double-shift system is worked, and it would be an act of imprudence--not to say injustice--and materially militate against our own interests, to increase drawbacks beyond an absolutely necessary point. we would, therefore, strongly urge on all our associated collieries to allow the employers ( ) to work their pits hours per day, where they can find men or boys to keep them going that time, without, of course, infringing the law, relative to boys under years of age. and ( ) to allow boys to be sent home on one or more days, so as to make up six nine-hour shifts in the week. by this plan no workman can lose, while the boys would materially gain thereby. we have so far worked successfully, but that success has been greatly, if not altogether, owing to the caution we have exercised, and the general reasonableness of our requests, having at all times a respect for the right, while we have tried to bring into active operation the duties of capitalists. let us not then mar that success by an imprudent or forward act of ours, particularly at a time when a change which must tell very severely on the interests of mine owners, and which, moreover, is of our own seeking, is just being introduced amongst us, and from which boys at least must gain immense advantages. by order of the committee, wm. crawford, _secretary_. offices-- north road, durham. _jan. th, ._ while these questions were claiming and received the attention of mr crawford and his colleagues a foul attack was made upon him by g. ("general") jackson of nettlesworth. he published a number of letters, which were not very choice in language, but prolific in the lowest form of abuse. he spoke of "that fellow crawford," "that bully" who was feathering his nest by defrauding. this went on until the executive came to the defence of mr crawford. they published a circular, pointing out the false charges which had been made, and that jackson was a member of the committee during the period in which he alleged the misappropriation of money had taken place. they reminded him of the neglect of duty implied in his not exposing such things before, and ended the circular by saying: "further this committee begs respectfully to say that they have the greatest esteem for their secretary, mr crawford, and are fully convinced that he has always acted in harmony with the highest principles of moral rectitude." on thursday, th of may, the first of the pioneers who crossed the border line, "tommy" ramsey, died at the house of his brother at blaydon at the age of sixty-two. he was buried in the cemetery at blaydon on monday, the th. the number of people attending his funeral was a proof of the high esteem in which he was held. according to the account there were fifty of the trimdon miners, where he worked last, present, while from collieries around durham large numbers also attended. the procession was headed by the blaydon main banner. we have made a note about him, as one of the leaders, but we may add a few words from an obituary which was published at the time of his death. "old tommy," as his brother miners of every degree loved to call him, was chiefly known to the pitmen at large as a unionist. with a face furrowed with care and the hardships of his laborious calling, and scarred by many an accident in the pits, he was never afraid to stand up before his brethren and agitate for that amelioration in the condition of the working pitmen which has at length been conceded. his style of oratory, if it were not strictly grammatical, was gifted with a warmth of expression that told forcibly on his hearers of his own class, and his perfect knowledge of the one subject he engaged upon--the danger and the excessive toil of the miner's life--caused him to be held in respect by masters and men alike. in every movement that had for its object the freedom from the bondage the miner was held in, ramsey was always to the front, and none mourned in bygone years more sincerely than he did the failure to establish on a firm and lasting basis the union, by which alone he maintained were they likely to obtain their rights as workmen. when the present association was started, amongst the dozen delegates or so who assembled at the market hall, durham, bent if they could on forming a union, was "old tommy"; and there he attended every meeting, when to be identified as a delegate was to almost sign his own death warrant so far as employment was concerned. "men and brothers," he said, addressing a public meeting near thornley a few weeks after the association was formed, "i've been a unionist all my days, and with the help of god i will remain one to the end of the chapter." at the council meeting held on st may we have the first mention of a hall for the use of the association, with offices and agents' houses. after a lengthy discussion the project was endorsed, the money to be taken from the general funds, and the executive were appointed a building committee. the committee immediately commenced operations by purchasing a block of houses known as monks buildings, the site of the hall and houses, and offering a premium of £ for the best design for hall and offices. this was won by mr t. oliver, architect, of newcastle. the other important question was the eleven hours' drawing of coals. the system received general condemnation. at the conclusion of the consideration a very long resolution was adopted. it set forth that when the mines act came into operation the workmen did not think it right to curtail the producing powers of the pits, and they, therefore, fell in with the views of the owners. having tried the system they had no hesitation in pronouncing it an utter failure on the following grounds:-- " . because of the great difficulty, if not impossibility, of working the pits full time on both the first and last hour of the day, thus inflicting a positive injustice on large bodies of men. we have the testimony of lindsay wood, esq., in his evidence before the coal committee that the system of eleven hours' work entails great danger on the boys going and coming out of the mine while the pit is at full work. we regret to say that this system has already borne fruit in the slaughter of one or more boys in going and coming out of the mine during the day. this being so we now find ourselves compelled to make an emphatic appeal to the mine owners of the county to work their pits only ten hours per diem in order to obviate both this injustice and danger." as i have said, it will not assist the history we have on hand if we dwell upon the whole series of our galas, and therefore we will only make a reference to the second one in the series. it was held on saturday, the th of june, and the gathering was larger than the year prior. there were three platforms. the chairmen were j. cowen, j. laverick, and j. fowler. the speakers outside were p. casey, yorkshire; a. m'donald, scotland; b. pickard, yorkshire; lloyd jones, london; j. shepherd, cleveland; t. burt, northumberland; and r. fynes, blyth, with the addition of the executive committee. the speeches need not be referred to beyond the references by mr crawford, as indicating the progress of the association during the year. they had added to their numbers, bringing the membership up to , , and they had increased their funds from £ , to £ , . they had proved their leading principle was amicability. "that principle had been not to get a thing because they had the power, but first of all to ask the question was it right that they ought to have it." the ordinary council meeting was held in the town hall on july th. it is important because of the attempt that was made to censure mr crawford. for some weeks a personal controversy had been taking place between mr e. rhymer and mr crawford. mr rhymer had complained that, although the miners had invited him to the demonstration, yet mr crawford had stood in his way. this was denied very strongly, and some very curious epithets were applied to him (mr crawford) for making the statement. at the council a resolution was on the programme from ushaw moor as follows:-- "that mr crawford receive three months' notice from next delegates' meeting, for his behaviour to e. rhymer and also the bearpark men." in a note he sent out with the programme he said "he was prepared to account for all he had done in open day, and after that, if the association was so minded, he was prepared to leave them not in three months, but in three days or three hours." the result of the discussion was the withdrawal of the ushaw moor resolution and the carrying of one from hetton which not only exonerated him, but expressed their high approval of his conduct and work in the county. on the th of october a council meeting was held. the object of the meeting was to consider the advisability of applying for a twenty per cent. advance. in the end the resolution was carried, and mr crawford was instructed to arrange for a meeting with the employers. this meeting was held on october th, but was refused by the owners, and in refusing they intimated that, as the state of trade was, they would shortly be making a claim for a reduction. the refusal was reported to a special council, when the deputation was again instructed to meet the employers. the second meeting was held on november th. after the question had been discussed the following resolution was handed the deputation:-- "this association cannot accede to the application of the durham miners' association for an advance in wages, but is prepared to refer to arbitration the question of whether since the last settlement of wages in february there has been such a change in the condition of the durham coal trade as to call for an alteration in the wages now paid, and if so whether by way of advance or reduction and the amount in either case." this offer was discussed at a council meeting, when the arbitration was agreed to; but the submission was disapproved of, and the executive committee instructed to draw up a counter proposal, to be submitted to a subsequent meeting for approval. another meeting with the employers was held on friday, the th of december. at the conclusion of the meeting the employers intimated that they would send their decision to mr crawford. on the th a council meeting was held. a letter was read from the employers, in which they objected to accede to the request of the workmen for an alteration of the submission they had proposed. after a further discussion the following resolution was proposed:-- "having fully considered the objections of the employers to our suggested basis for arbitration we fail to see the soundness of such objections. nevertheless in order that no difficulties may arise in carrying out this matter, we are willing to alter that basis by leaving the question entirely open. allowing both parties to bring forward all reliant matter which may bear upon their respective positions, leaving it to the arbitrator to say whether any advance ought to be given and that the durham coal owners' association be urgently requested to consider this matter on the earliest day possible." there are two matters which deserve a brief notice here, although not essentially part of the association. these were the royal commission to inquire into the coal supply and the causes of the high prices, and the rise of the franchise association. the former of these was appointed on st february by the following resolution of the house of commons:-- "that a select committee be appointed to inquire into the causes of the present dearness and duration of coal, and report thereon to the house." this committee examined a large number of witnesses, including all classes connected with the coal trade. the following is a portion of their report:-- " . considering the great extent of the coal fields in great britain, the number of collieries at work, and the variety of coals produced, which though primarily used for particular purposes, will, at certain prices, be used for others, your committee, notwithstanding intermittent and startling fluctuations in price due to temporary causes, do not believe that any combination either of employers or workmen can by artificial means succeed in permanently affecting the ordinary results of the relations of demand and supply in adjusting the quantity of coal produced to the demand, or can permanently affect the price resulting from the state of the market; nor do your committee believe that the interference of parliament with the course of industry and trade in coal could produce any useful or beneficial result to the public beyond what has been arrived at in recent legislation, namely, the prevention of injury to the health and morals of young children and young persons, and the prevention of accidents from wilful neglect of recognised precautions. " . much evidence has however been given to show the great increase in the rate of wages, and the earnings of the working miners; but whilst it is true that in some cases the earnings have enormously increased, and have been improvidently spent, your committee conclude that in general the condition of the workmen has been much improved, and that the rise in the rate of wages has not, under the exceptional circumstances, been unreasonable, nor been unattended with considerable benefit to the workers; indeed in some cases the workmen have preferred improving the conditions under which they work to increasing the amount of their wages in money. " . it is clearly shown that the real order of events has been the rise in the price of iron, the rise in the price of coal, and the rise in the rate of wages. the increased payment per ton for labour employed in getting the coal cannot therefore be considered as the primary cause of the large increase in the price of coal; a rise in wages followed upon rather than preceded a rise in the price of coal. to the extent to which increased rates of wages have induced workmen to labour for a shorter number of hours than heretofore, resulting in a reduced output per man, a higher payment for labour has contributed indirectly in an important degree to maintain the high price of coal, but having regard to the great danger to which coal miners are exposed, and the character of their labour, the average rate of wages in collieries has not been more than sufficient to attract the requisite labour to the mine. the workmen, like all others connected with coal mining, should only regard their present earnings as a temporary profit, which may, at no distant day, approach towards former rates." with respect to the franchise association, during the year there was a strong agitation in favour of an extension of the franchise to the householders in the county, as such had been done by the act of to those in the borough. the spirit of reform found ready response in the minds of the durham miners, and a very active association was formed. although incidental to the labour organisation, and with a voluntary contribution, it was managed by the leading men in that association. the names found prominently in one are found in the other. a council meeting of the miners' association was held in november of this year, at which it was proposed that mr crawford should be nominated for one of the county divisions, and the matter was remitted to the franchise association. there were but two of these divisions at that time--the north and south, each having two members. there was a general election in prospect, and it was deemed advisable to run mr crawford as a liberal candidate. to anticipate a little, he was duly put forward on wednesday, the th of january . his candidature was publicly announced, but on friday, the th, at a meeting of the ex-committee, he withdrew. his aim in so doing was to avoid a division of the liberal forces. there were two tories in the field and three liberals, and it was highly necessary that this should be avoided. this decision was reported to a council held on the st. there was a general consensus of opinion that he had acted wisely, although the delegates regretted the necessity. some of them had brought money--as much as £ in one instance--towards the election expenses. a resolution was adopted which had for its object the formation of an election fund with the view to strengthen the hands of the franchise association, and it was agreed that whenever there was a vacancy in the county, where there was a chance of success, he should be at once brought forward. the first reduction--co-operative colliery--the strike of --the wheatley hill revolt and evictions--second reduction--first arbitration we finished with a demand for an advance and a difference as to the submission for a reference to arbitration. during the interval the trade had declined to such an extent that the employers sent a claim for a reduction, and thus the young society was beginning to find itself entering its first dark cloud of depression. up to that moment the booming times arising out of the franco-prussian war had been with it, but now the relapse which generally follows a fever in trade had set in, and the demand for coals had fallen off seriously; and whereas a month or two previously they had expected another advance, it was felt by mr crawford and his colleagues that it would not be possible to stave off a reduction. before coming to the consideration of the first reduction let us, for the sake of chronological order, note one or two matters of some importance. the first of these is the demand for men being trained before being left to themselves in a mine. at the council meeting held on saturday, st march, the following resolution was carried:-- "we have again to protest against the introduction of strangers into our mines--men to whom mining with all its dangers is thoroughly unknown, whereby the limbs and lives of other men are constantly endangered. we therefore emphatically ask the owners to put such men under the care of some practical miner for a period of not less than six months, who will be responsible for any danger arising from such person's ignorance of mines." another point worthy of note was the resolve to join in the movement to form a co-operative mining company. at the council meeting on th april it was resolved: "that we take £ out of the general fund, and invest it in the co-operative mining co., as we believe productive co-operation to be the only solution to the many difficulties that exist between capital and labour." at the same council a copy of the owners' request for a reduction was read. it conveyed the decision of their full meeting: "that the state of the durham coal trade imperatively calls for a reduction of twenty per cent. in all colliery wages, both above and below ground, to take effect from the th of next month." a meeting was held between the two associations on the th of april, when the employers stated the reasons for their demand. they held "( ) that there was no connection between profit and wages, and the workmen had, therefore, no legitimate right to interfere in such a matter; ( ) that trade was vastly more dull, and prices materially less, than was supposed; ( ) that in various parts of our own country and also in germany, reductions had taken place, in the latter per cent., and having to compete in the same markets with firms and districts so brought down, they had no choice but to enforce the reduction." this was brought before a council meeting on april th, but the delegates refused to discuss it then, and referred the question to a special meeting to be held on the th. steps were taken to prepare for a stop should a reduction take place, and men were arranged to visit various districts. those going to ireland and scotland had £ each. the owners had in the meantime given notice at certain collieries, and the workmen were told to remain at their own collieries. on the th the executive committee issued the following circular:-- april th, . fellow workmen,--according to arrangement, messrs patterson, wilkinson and crawford, saw messrs burt and nixon yesterday, and from information received it appears that the per cent., or a reduction from to , has to affect all, both above and below ground. we cannot but call your attention to our present position. the adjoining county, much more compact than ours, and many years older in organisation,--two elements of strength and power,--have just accepted a reduction of wages. miners, immediately south of us,--west yorkshire,--have expressed their willingness to accept a reduction of ½ per cent. on wages all round. this, however, the owners refused to accept. they seek a reduction of per cent., and the matter is, therefore, going to arbitration. with these facts before us, is it possible that we can, at the present time, by any means, which we might adopt, altogether stave off a reduction, more or less, without referring it to arbitration, in some way or other? we will not attempt to point out all the terrible effects which must arise from anything like a general strike. many of you experimentally know the direful effect and heartrending destitution which has arisen from partial strikes amongst ourselves. suppose a general stop now ensues, what are the probabilities of success? can we make our efforts successful? suppose we should strike against a receding market, and a surplus number of men, and lose, what would be the consequences? these are questions worthy your earnest consideration, because on them depend your weal or woe for years to come. we have to-day very fully thought over the matter, and considering everything, we think it wise, if not absolutely necessary, to make some advances, with a view to a settlement of this important question. we, therefore, strongly advise that an offer of per cent. reduction be made to the owners; and should they refuse this, let the whole matter go to arbitration. if arbitration be offered and accepted, we would suggest the appointment of two men on both sides, and let these four men find a basis or starting-point for arbitration. should they fail to agree as to what such basis ought to be, let the matter go to an umpire, appointed by the four arbitrators. let no one regard this as in the slightest degree dictatorial. we have too much respect for your collective judgment to attempt anything of the kind. but we think it our duty to point out that, if not careful, we may drift amongst shoals and quicksands, which may endanger the very existence of our association. and if this should come to pass, we need not name--not our probable, but certain condition, for years to come. on the th of april the special council was held, which approved of the committee's circular by offering a reduction of ten per cent. this decision was conveyed by telegram to mr bunning, the employers' secretary. no sooner was it known in the county than a general protest was made, not only by the miners, but by the mechanics and enginemen. they objected to being included in the reduction. these bodies held meetings in durham on the race-course on may nd, and passed resolutions not to accept any reduction. the spirit of revolt was rampant in the county amongst the members of the miners' association. meetings to protest against it were held throughout the county. circulars were sent out by district councils, in which the executive committee was held up to ridicule. to these the agents replied, boldly pointing out the danger of the course which was being adopted and the disaster which would assuredly follow if more moderate action were not taken. some of the members of the executive committee were found amongst the protestors and the loudest in their condemnation of mr crawford, who came in for a large share of abuse. it was calculated that at one of those meetings in houghton there were , people present. on may th the coal owners held a meeting. the resolutions dealt mainly with the action of the enginemen. from these the employers offered to accept five per cent. if acceded promptly, but no man should be allowed to work for less reduction than that offer. during the owners' meeting a telegram was read from mr crawford as follows:-- "for reasons previously given both to the standing committee and full meeting of owners, we shall begin on monday to work five days per week or pits be laid idle on saturday, so far as the working and drawing of coal is concerned." to that telegram the owners sent the following reply:-- "the provisional committee give notice to the durham miners' association that unless the owners' association receive before the end of the week a satisfactory assurance that collieries will continue to work the same number of days per fortnight, as heretofore, they will advise the coal owners' association to insist upon the full twenty per cent.--first demanded; such demand only having been withdrawn on the condition that no change whatever was to be made in the usual mode of working." on the th of may a council meeting was held, when the ten per cent. was under consideration. by a majority of the delegates decided in favour of the ten per cent., voting for it and against. this brought the dispute to an end so far as the wages were concerned. the strike, if it could be called such, was of the most desultory kind, there being a division as to the acceptance of the ten per cent. reduction. it is generally known as the "week's strike"; but even the executive were in ignorance of the time off, and sent out a slip asking the lodges to tell them "what number of days they were off, when they stopped, and when they resumed work and the reasons why they were off." the returns show that there were none off more than a week. none of them were entitled to strike pay seeing that a colliery had to be off a fortnight before they could claim. the executive by their minute of june th, , said the strike commenced on may th and ended on the th. the strike being settled generally, all the collieries commenced work except wheatley hill, thornley, and ludworth. these were in a peculiar position. for some time they had been ten-day collieries, and at wheatley hill the hours of stonemen, shifters, and wastemen had been six every day. when the strike ended the executive committee sent word out to the county that work should be resumed under the same conditions as obtained before the strike. the workmen at the three collieries claimed they should work the ten days. that position the following minute of the executive committee bears out:-- "we have again had the case of thornley, ludworth and wheatley hill brought before us, and beg to give the following statement: as will be understood by all lodges, before the stop these places were working ten days under protest. after the settlement of the working days matter at our council, the question arose between the manager and men whether these were ten or eleven day collieries, the men holding to the former, while the manager held to the latter. on friday, may th, mr bunning telegraphed, stating that the owners still held these to be eleven-day places. we replied that they had been working ten days under protest, and that in some way or other they ought to recommence on the same conditions." the three collieries, on the strength of the notice to resume work, corroborated by the above minute, refused to start except as ten-day collieries. the owners offered arbitration, but conditioned it by asking for the men to work eleven days, and suspended the joint committee until the case was settled. the letter from mr bunning contained the words: "the action of the thornley etc. men renders the resumption of the joint committee impossible," and asked whether the executive were supporting them or not. the men were willing to go to arbitration, but asked to be allowed to start at the ten days. the executive ordered them to work on the employers' terms, summoned a representative from each colliery to the committee, and sent out large deputations to attend meetings. still the men stood firm. on monday, june st, the evicting of the men from the houses commenced. a very large contingent of "candymen" were imported, and a force of seventy or eighty policemen, in charge of superintendent scott, to maintain order. there never was an occasion where better humour prevailed throughout and where there was so little need of police. it would afford a break in this dry matter-of-fact history if some of the incidents were related: how a jew who had come to gather his fortnightly instalments wrung his hands, and, shylock-like, cried about his "monish"; how some of the women were to carry out in arm-chairs, and one of them stuck hat pins in the candymen, to the hilarity of all but themselves; how once in a while a "candyman," sick of the work, broke through the crowd, and ran off, chased by the police and the cheers of the crowd; and how the people dwelt in tents for three weeks, having continuous sunshine by day and jollity by night, making a continual round of "picnicking." we must, however, leave the pleasurable for the historical. the lodge made an attempt at council to get strike pay on an appeal against the committee. the merits of the case were with them, but their case was prejudiced by the temper of the delegate, mr j. wood. during the discussion of the question some contention rose as to wood (who could write shorthand) taking notes. mr wilkinson (the treasurer) expressed himself in doubt as to wood's honesty, and the latter struck at the treasurer on the platform--the consequence being the council decided against, and the men were left to their own resources. an attempt was made to settle the strike by the rev. w. mayor of thornley. he called upon some of the leading men, and asked them to meet mr cooper, the manager, who with mr bunning agreed to allow the pit to resume work on the old conditions with regard to the number of days, and that the dispute should be left to the two associations. the arrangement was come to on the monday, and on the tuesday the horses and ponies were sent down, and about men commenced. it then transpired that mr cooper objected to three of the leading men, and the men alleged that there had been some reduction in prices. the result was the stoppage again. the dispute was as to the submission for the arbitration. the difference lay in this: the owners wanted the men to start as an eleven-hour colliery, and then arbitrate. the workmen were willing to start as at ten hours, and arbitrate. in the end that was accepted. the arbitrators decided that the men were right in considering their collieries ten-day collieries and refusing to resume work except as such; but they concluded that the collieries should work eleven days, "although at the same time we strongly censure the conduct of mr cooper, the manager, throughout the entire struggle." they further awarded that the whole expense of the arbitration should be borne by the owners, thus proving the men to be right in their contention as to starting. [illustration: william crawford, m.p.] we now come to the second claim for a reduction in wages. on july th mr crawford read to the committee a resolution he had received from the employers making a claim for a reduction: "that the durham coal miners' association, through mr crawford, be informed that the associated coal owners consider that it is necessary to reduce wages substantially and promptly. that the amount of such reduction, as well as the date of the commencement, will be considered by the owners on the th day of august next, and that in the meantime the association will be ready to give their best consideration to anything the representatives of the workmen may desire to lay before it." to this request the executive committee could not accede, and on th august the employers sent another claim for a reduction of twenty per cent. they said "that the best policy to pursue in the exigencies of the trade, and to restore the activity of the coal and iron trades, was for the men to submit to a twenty per cent. reduction." in the event of the workmen not agreeing to such a reduction the owners would be prepared to leave the whole case to the arbitration of any gentleman mutually appointed, each party being left free to produce such evidence as they may think fit and satisfactory, arrangement being made for prompt decision, and for securing the operation of the arbitrator's award from the th of this month. mr crawford was instructed by the executive committee to inform the employers that, while they did not offer any opinion on the reduction, they would call the attention of the owners to the last portion of their resolution, wherein the date of the reduction was fixed, and said: "in seeking advances we never yet fixed a date, even when coal was going up in an unparalleled manner and certainly very much more rapidly than ever it has come down. both in march last and now you wish to fix the date in what seems to us rather an arbitrary manner. had we in seeking advances pursued this course, you would have been more than justified in doing the same thing, but having pursued a course diametrically opposite, we fail to see the grounds of your justification for the course you are at present pursuing." a council meeting was held on august nd, when the first question discussed was the owners' application for the twenty per cent. reduction. the following resolution was carried:-- ( ) we cannot see where in the cleveland, or the coasting, or other markets the prices of coal and coke are down sufficiently low to warrant a further reduction of wages. ( ) the stacking of coal and coke may be made to have--but ought not to have--any very material effect on the workmen's wages, seeing that, if too much is being produced, we have no objection to be put on short time, or any other fair process whereby a reduction of wages can be averted. we fail to see why the employers ought to seek arbitration. we are now in the same position which they were in during the last two and a half years. they were at that time so fully certain that trade would not give any further advance that arbitration was pointedly refused. we are now so sure that the present, as compared with past prices of coal and coke, does not warrant any further reduction, that we think arbitration is only an unnecessary waste of time and money, causing no end of annoyance without any good resulting therefrom. this resolution was sent, accompanied by a demand for fifteen per cent. advance, to the employers, who held a meeting on th august, under the presidency of mr stobart, for the purpose of considering it and what action they should take. after considerable discussion a resolution was passed to enforce the twenty per cent. reduction and to give the men fourteen days' notice, to expire on the th of september, seeing that their claim and arbitration had been refused. the notices were issued in keeping with that resolve, but not to all men alike. the form of notice was as follows:-- on behalf of----colliery i do hereby give you notice to determine your existing hiring on the nineteenth day of september eighteen hundred and seventy-four, and that the wages and prices heretofore paid at this colliery will from that date be reduced to the rate of twenty per cent. and that if your service be continued, it must be on these terms. in these circumstances the executive committee issued a circular and called a special council. the lodges were asked to send their delegates prepared to discuss and decide upon three questions: " . ought bankmen, horsekeepers, furnacemen, etc., to give in their notices? " . ought collieries of men (hewers included) who have not received any notice to give in their notices? " . the matter of arbitration." we will quote a portion or two of the circular. it is very serious and impressive: "it must be clear to all that we are passing through the most important crisis which has marked the history of the present organisation on the need or otherwise of a further reduction; we here offer no opinion, that being a matter which will take the collective wisdom of the county to determine. we wish, however, to point out what seems to us to be one of two ultimatums to the present unpleasant condition of matters in the county. if a stolid and unreasoning resistance be persevered in, a strike is inevitable. we feel certain that nothing can or will prevent a stop. how long such struggle might continue it is impossible to say. but whether it might be for a longer or a shorter period an immense amount of suffering would be entailed. we want you therefore to very carefully consider the whole matter. view the entire position with an unbiased mind, not from the standpoint of mere abstract justice, but from that of probabilities or even possibilities. we are offered arbitration. if we refuse, the press and public will most assuredly say that our position is untenable. if we persistently refuse to submit the entire matter to arbitration, we must prepare to cope with the following difficulties in conducting a struggle. "( ) the strongest combination of employers the north of england ever saw. "( ) stacks of coal and coke laid up in every direction of the county. "( ) coal and coke brought from other districts to supply what we may be short of supplying from our own heaps. "( ) the press and public opinion would be against us." the dispute was brought to an amicable settlement by the whole question being referred to open arbitration. by that decision the association passed out of the era of negotiations into that of arbitration re underground wages. as that was the first step in the path of conciliation it may be useful to give in detail the proceedings. the inquirer after further information may very usefully consult the printed proceedings of the case. there were for arbitrators mr g. leeman and mr d. dale acting for the owners, and mr l. jones and mr t. burt for the workmen. the case was conducted by mr w. armstrong and mr l. wood (now sir lindsay wood) on behalf of the employers. mr w. crawford and mr j. forman were for the employed. there were with these arbitrators and conductors other gentlemen, whose names we can find no record of either in the press, the owners' books, or in ours. the first meeting was held on tuesday, th october, in the queen's head hotel (now the liberal club), newcastle. after a long sitting the case was adjourned until the th, when mr forman on behalf of the workmen, and because there had not been sufficient time to prepare a reply to the employers' case, asked for an adjournment. mr crawford said they had "sat twenty-eight consecutive hours, and never moved the whole of the time." it was therefore decided to adjourn until the th. during the discussion mr crawford made the request that the owners should produce their books in order that both costs of production and the selling prices of coal might be obtained. the fourth day's proceedings was held on the th. the arbitrators met on the th in london. failing to agree, they agreed to refer the question to the right hon. russell gurney, m.p., whom they met on the th in the abbey hotel, malvern. on november rd he gave his award. without giving the whole of the award it will be explained by a quotation from a circular sent out by mr crawford: "the reduction is as follows:--at present time our advances amount to per cent. over prices. this by mr gurney's award is reduced to . that is a reduction of per cent. on the gross wages and will take effect from monday, november nd." at that time the attention of the county was turned to the sanitary condition of the mining villages. the committee took a return in which they asked eleven questions: "what is the size of your best houses? what size are the rooms, and how many to a house? size of single houses? is there attached to your houses or on the colliery any private accommodation? are there any channels or underground sewers to take away the dirty water and other refuse made in the houses? are the houses damp and incompatible with health, or dry and healthy? are there many of the members who have houses of their own? what number of double and single houses have you? have you a good or bad supply of water and whence supplied? what is your school accommodation, national or colliery? have you a mechanics' institute? is it colliery or private property? are there any gardens to the houses?" on saturday, november th, the owners made a claim for a reduction from all the men at bank. this was before the executive committee. they by resolution expressed their surprise, and their opinion that they had not been treated fairly, as the employers ought to have dealt with the classes now to be affected in the arbitration just concluded. they considered that "such a mode of procedure cannot but have an injurious effect on that good and desirable understanding which has so long existed between the two associations." the owners gave the surface men notice to terminate their engagement on th december. a special council meeting was called. the questions to be decided were--first, should the miners' committee act for the cokemen, seeing those men were forming an association of their own, and over two-thirds of that class had joined it? of the other classes three questions were asked: "ought these men to follow russell gurney's award? ought the reduction to be resisted or ought arbitration to be sought?" the council decided on saturday, december th, that the cokemen's association meet the employers themselves, but "that the members of the joint committee should meet them on the banksmen, screeners, labourers, etc." the arrangement come to by the joint committee was: "the banking-out men having been generally classed with the underground men, should in all cases be dealt with strictly according to the terms of mr gurney's award, that is, remain per cent. in excess of march and it was recommended that the case of men earning less than s. per diem be left to the consideration of individual owners." there are two matters not dealt with in the general statement of this year. these are the appointment of mr forman as permanent president on nd may and the appointment of the first clerk. the first was mr a. hall shotton; but his stay was short, and he was succeeded by mr w. golightly, who was in the office for over thirty-one years. [illustration: w. golightly] the third reduction--co-operative colliery--the demand for better houses--the fourth reduction early in the year the association was called upon to face another reduction in wages. the executive committee had sent some requests with respect to hewers putting in the foreshifts and working hard places. the owners sent a reply on january th refusing the requests, and at the same time saying, such things being asked of them in depressed times were offensive, and would not have to be repeated. in the same letter mr crawford was told that the employers had that day "unanimously decided to ask for a reduction in the wages of all men employed about coal mines and that the standing (joint) committee be instructed to discuss the matter of such reductions and the date when it should commence." to this the executive committee replied that they would pass over the question of reduction as it was premature to interfere with it, but they complained of the tone of the letter sent to them, which was very unbecoming, to say the least. they had a perfect right to send the requests. no doubt they were annoying. "but however annoying a request properly made may be, it ought, in keeping with the common courtesies of life, to be denied without imperiousness. it was annoying to them as workmen to receive an application for a reduction." the response to that reached mr crawford on the th. it informed him that they (the owners) felt it needful to claim such reduction as will leave the wages of both underground and surface men ten per cent. in excess of , to take effect from the pay ending th march. mr bunning added: "as it is our usual custom not to carry out a resolution of this nature without first having a consultation with you, i am requested to ask you to make such arrangements with your clients as may enable you to meet our committee at an early date to decide." a special council meeting was called for the th of february to consider whether a deputation should meet the employers; if so, how many and whom they should be. the council decided that as a deputation the members of the joint committee should meet the employers, and mr crawford was deputed to go to south wales to inquire into the condition of things amongst the miners there. at an adjourned council held on february th it was again considered, and the following resolution carried:-- in looking at the last reduction, and the undue advantage the coal owners have taken on us in making a call on the bankmen so soon after the arbitration case, that we in future entertain no more reductions on one separate class of workmen, without knowing their intentions as to the rest of the workmen in our association. the meeting with the employers took place on th february, when six reasons were given by them why the reduction was needed: many collieries were working at ruinous losses; a terribly increased cost of production; at many collieries the men were restricting their work; a greatly increased number of men were needed; the increased cost owing to the great decrease in the working hours; and the fact that mr gurney's award was delayed two months. the employers again issued notices, but not to all men or all collieries. the committee immediately called a council, and drew the attention of the lodges to two resolutions which were passed on april st and december th, . that in future when there are notices given for a reduction of wages throughout the county, and where a colliery or collieries of men do not get their notices, they be requested to give them in. where men who are members of our association and who have not received notice should these refuse to give in their notices, their names be struck from our books and never again re-entered. in addition to this the committee issued a circular in which they reviewed the condition of trade, and pointed out that in many districts life and death struggles were taking place. these men were being supported by voluntary contributions from other mining districts and the public. if durham came out large support would be cut off, and the state here rendered more dangerous. in northumberland and cleveland arbitrations were proceeding. there was only two weeks' money in the funds, therefore the best policy was to accept arbitration. facing these circumstances they advised the acceptance of arbitration. the employers would be compelled to show sufficient reasons for a reduction. if this were not done no umpire would reduce the wages. this advice was accepted at the council on th march, and it was resolved to refer the whole matter to arbitration on the prices and wages ruling at hearing of the last case, that mr l. jones and w. crawford be arbitrators, and the preparing and conducting of the case be left to the executive committee. on march th they met the employers, and made arrangements for the proceedings and the withdrawal of the notices, and they informed the members that in every case where the workmen had given notices they must at once be withdrawn. the first meeting on the arbitration case was held on april th in the queen's head hotel, newcastle. the right hon. w. e. forster, m.p., was the umpire. the arbitrators for the employers were mr w. armstrong and mr d. dale; for the workmen mr l. jones and mr w. crawford. the case was a dual one, a combination of the miners' and cokemen's associations. the latter agreed to accept the statement made by the employers in the miners' case and then put in a separate reply. the following was the order of the procedure:--the employers stated their case. then the miners replied on the first day. second day, the owners' reply to the miners, the miners' rejoinder; the cokemen's reply to the employers, then their reply to the cokemen. the third day's sitting was taken up by the cokemen's rejoinder. the same arbitrators acted in both cases, but mr jackson wilson presented the cokemen's case. the umpire gave his award on the rd of april--the reduction being five per cent. from the underground wages and four per cent. from those of the surface men. at the council meeting held on may th a resolution was carried urging upon the miners' national association to use their influence to have established an important board of arbitration, such board to say: "first, what amount of interest ought to be claimed for capital invested in coal-mining operations; secondly, whether or not the books showing the profit and loss accounts of the employers ought to be laid before the arbitrators in deciding a matter in dispute as to the rise or fall of the wages of their workmen; and thirdly, what portion of the profits ought to go to the capitalist and what portion to the labourer." the programme for a council meeting held on st august contained a resolution dealing with the providing of a better class of houses. "that we appeal to the owners to have better houses right throughout the county for the members of the durham miners' association, and not to make such difference between brakesmen and members of the association. we believe that one man has the same right to a good house as another." in the balance sheet for the first quarter of the year is found an item relating to the coop colliery-- shares in the coop mining company, £ , . for some time, and especially during , the idea of a co-operative mine had been agitating the two northern counties. meetings were held in various parts, addressed chiefly by gentlemen from northumberland. the idea fell upon good ground in durham, for from time to time it was found on the council programme, and, so far as the association is concerned, bore fruit in the shares mentioned. the fruit was not merely collective, but on every hand those who could took out shares, even to the extent of all their savings. the committee of management were: dr j. h. rutherford, chairman. mr t. burt, m.p. mr j. nixon. mr r. young. mr j. brown. mr r. cramon. mr w. crawford. mr j. forman. mr w. h. patterson. mr j. byson. mr g. fryer. e. lowther, secretary. --all good men, and, if it could have been established, would have been. they were all tried co-operators and ardent believers in productive co-operation. but the enterprise was doomed from the first. the name of the colliery was monkwood, near chesterfield, derbyshire. on the th of september the committee submitted a balance sheet for the year ending th june. the auditors were benson, eland & co. they informed the members that after depreciation as per rule the net loss up to date was £ , , s. d. the committee in presenting the balance sheet said it had arisen from circumstances over which they had no control. the output of the colliery had never reached to their anticipations. the cost of production, and the unsatisfactory state in which the society found the colliery, had occasioned the loss. the vendor had not truthfully represented the output. they had filed a bill in chancery against him for the recision of the contract and the return of the purchase money. the loss to durham was £ , . on th november the ex-committee was called upon to face the fourth reduction. they received a letter on that date from the employers conveying to them a demand for twenty per cent. reduction from all underground earnings, including banksmen, and twelve and a half per cent. off all above-ground labour, to take effect from the th. the committee replied protesting against the imperative way in which the demand was made, and resolved to ask the county whether a deputation should attend newcastle to hear the reasons assigned for the reduction. the county agreed to send a deputation and offer open arbitration, the deputation being the joint committee, and that a council meeting be held on the th to hear the report. the committee met the owners on monday, the nd, and the offer of open arbitration was accepted, the court to consist of four arbitrators and an umpire. death of burdon sanderson--appointment of mr meynell--the third arbitration--the general treasurer and executive--the new hall--deputies' association joint committee chairman in january the joint committee chairman, mr r. b. sanderson, was in a serious railway collision on the great northern railway at abbots ripton. he was not killed outright, but was so seriously injured that he died shortly afterwards. he was the first chairman, and sat all through the meetings up to his death. the joint committee at their meeting on january th passed a resolution paying high respect to his character and to his ability and impartiality in his decisions. from that time until th september the chairman was selected from the meeting _pro tem_. on that date mr meynell was appointed, and from that time until his death in he occupied that position to his credit and with fairness to everyone concerned. it would be incorrect to say that no fault was ever found with him; but it is well known that at his death all who had been at the joint committee regretted it, and he has been sorely missed, because he had years of experience--experience which is worth a great deal in that position. the proceedings in the arbitration did not proceed further in , but rested over until january . the arbitrators were the same as in the previous case, and the umpire chosen by them was c. h. hopwood, m.p. the advocates for the owners were mr h. t. morton, mr lindsay wood, and mr t. wood bunning, the secretary of the owners' association, and for the workmen mr j. forman and mr w. h. patterson. the names of the committee who assisted were: n. wilkinson. j. holliday. m. thompson. w. prentice. g. parker. j. cummings. c. kidd. c. cooper. j. crowther. f. smith. g. jackson. j. day. g. newton. the first meeting was held on tuesday, th january , in the queen's head hotel, newcastle. there were two days' sittings. at the close of the sittings in newcastle the arbitrators and umpire held a meeting in london on th february, when the umpire gave his award that there should be a reduction of seven per cent. underground and four per cent. on the surface. out of this case and the meeting in london there arose a serious disturbance. the treasurer (mr wilkinson) refused to pay the committee for going to london. he alleged that they went without authority. they went on the vote of seven out of seventeen members of the committee, the rest being either absent or lying neutral. their going, he said, was a waste of public money. he finally showed there had been an extravagant expenditure and charges for unnecessary meetings. along with his explanation he sent out a detailed statement in which it is shown that for one fortnight they had received sums varying from £ , s. d. to £ , s. d., or an average of £ , s. d. per man. for another fortnight the average worked out at £ , s. each. to this the committee made a long reply, but all unavailing, for at the council meeting held on march th, , the following resolution was carried:-- "that the members of executive committee who went to london be expelled, and that they have no payment for going." by another resolution the number of the committee was reduced to nine. the result was to leave only three committee men to transact the business until a new committee was elected. a word of explanation may be necessary. at the election of committee in december three new men were elected. these were c. simpson, w. gordon, and j. wilson. as the arbitration was proceeding when the election of took place the executive committee asked the members whether they should be allowed to continue in office until it was finished. this was granted, and as a consequence the newly elected members did not take their places until the decision was given. the durham miners' triumvirate ruled until may th, when the full committee was elected. as a further result of the dispute between the treasurer and committee certain rules were suggested by the executive committee and approved by council on th april. ( ) that in future there be no night sittings of the committee. ( ) for a long time, a custom has existed of the committee, asking questions on their reassembling after dinner hours. these questions were put on paper during the forenoon and handed in to be read after dinner. it will be seen, that this practice can be abused, and made to lengthen out committee meetings to any extent. that this practice be entirely abolished unless it be a mere asking a question from the secretary. the question and answer to be printed on the minutes; but no discussion whatever to be held on the matter. ( ) that the general secretary alone have the power both to call and disperse committee meetings. ( ) that the committee have no power to either shorten their hours or alter modes of payment. in a letter bearing date may th the employers made another demand for a considerable reduction of wages both above and below ground, and fixing saturday, the th, as the date for a meeting upon the matter. on that date nothing definite was done, and an adjournment took place until th june. a special council was called for june th, when lodges were asked to instruct their representatives what should be done in the matter. in the meantime the committee issued a circular, giving an account of the meeting with the employers, and informing the members that the owners' demand was for fifteen per cent. off underground labour and ten per cent. off surface labour, or they were willing to refer the whole question to arbitration in order to avoid a stoppage of work. they (the committee) then urged the acceptance of arbitration at once. to refuse it would be to run counter to the efforts of working men in the past who "had fought some of their most severe struggles in trying to enforce arbitration as a means of settling their trade disputes." many hundreds of thousands of pounds had to be spent before the employers would even recognise the right of the workmen to the merest inquiry in advances or reductions of wages. the employers claimed the right to be the sole judges in matters of that kind. "when the employers arrogated to themselves the right to judge both for them and us, we were not slow in applying the words tyranny, despotism, and even villainy to their actions. don't let us then be guilty of an imprudence, both by a repudiation of our own principles and going into a battle when everything is against us." the committee supported that bold and candid statement by drawing attention to the success which had attended the arbitration in the past. "if ever a body of men ought to be satisfied with a means of adjusting differences we ought with arbitration. it has in every instance so far immensely reduced the application of the owners. there is no other means by which we could have fared better. on every occasion the owners complained about the insufficient amount awarded them." the alternative to arbitration was a strike. that course would be madness. there was a complete stagnation in trade, nowhere more felt than in durham. pits were working half time, and there were hundreds of men who could not find an hour's work. to strike would be to jeopardise "an organisation which in the very short space of time has done more for its members than any other trades' organisation that ever existed." they urged other reasons in as forcible a manner, and concluded by saying, if arbitration were refused and a struggle entered upon, there could be but one end, "that of utter and terrible defeat for the miners of this county." towards the end of may preparations were being made for opening the new hall, and a return was taken as to the mode of procedure. the place of meetings had been on a movable plan. at first the committee meetings were held in north road, durham. then both councils and committees were held in the market hall. as the organisation increased the councils alternated between the shakespeare hall and the town hall, and the committees in the western hotel, western hill, durham. the opening of the hall took place on saturday, june rd, the occasion being the consideration of a ten per cent. reduction at a special council meeting. the cost of the buildings was £ , and the architect, mr t. oliver, newcastle--the council-room fifty-two feet by thirty-four; the tower thirty feet above the body of the hall. the clock cost £ . the arrangements as to the lighting of the clock are: the city authorities pay for the gas, while the miners keep the clock in repair. for some time the city council refused to bear the charge for lighting, and at first only agreed for six months as a trial. there was no opening ceremony beyond a few words from the president, mr forman. the delegates took their places as per number of seat. mr forman then said he was glad to welcome them to their new hall. "the noble building had been built with the money of the working miners of the county of durham. it was a great example of their forethought, their economy, industry, enterprise and unity, and he hoped that it would be one more link that would bind them together in the cause of mutual help and mutual endeavour, and be another great supporting prop to the noble edifice they had reared in their association. he was sorry that the first business at the opening was to be the unpleasant one of discussing a ten per cent. reduction." the first council meeting was held in the new hall on th june, and the first resolution was "that we refuse to send the reduction question to arbitration." the spirit of war was in the air, at least among the men who attended the lodge meeting to consider the subject at first. during the next week, however, a ballot of the members was taken, the result of which was declared at a special council meeting--the voting being for arbitration, , ; against, , ; majority for, , . there were resolutions passed to remit the question to open arbitration: that the committee get up the case, but "if any person has to accompany the arbitrators out of the county, only the two men who conduct the case do so." at the same meeting mr n. thompson and t. mitcheson (two of the london committee) were removed from the trusteeship, and their places filled by john wilson, wheatley hill, and w. gordon, ravensworth. the arbitration commenced on th august in the queen's head hotel, newcastle, the umpire being g. j. shaw-lefevre, m.p. the arbitrators for the employers were mr w. armstrong and h. t. morton, mr l. jones and mr w. crawford acting again for the workmen. the advocates on the owners' side were mr lindsay wood and mr j. b. simpson and mr t. w. bunning; for the workmen were mr j. forman and mr n. wilkinson. there were two sittings. there is no need to review the arguments or facts in these cases, as that would extend our work too much, but there is one interesting point advanced by the employers in their rejoinder to the workmen's case. it refers to the cost of production at that time over . the increase was thirty-seven or thirty-five per cent. higher than --the items being, wages . per cent., and the effect of the mines bill . per cent. assuming that the cost arising from the operation of the mines was divided between employers and workmen--eleven per cent. to each--there was still . per cent. to the disadvantage of the employer. on the credit side coal was only ½ or . per cent. higher than in , and therefore their conclusion was that the claim for fifteen and ten per cent. reduction was amply justified. at the conclusion of the two days' sitting it was agreed that the arbitrators should meet on the th of september, and if they failed to agree the umpire would decide. that meeting took place, and the umpire was asked to decide, which he did on september th, and awarded a reduction of six per cent. in the wages underground and four per cent. in the wages paid to surface men. no sooner was the arbitration finished than the association found itself face to face with a difficulty of a different but yet perplexing nature. the employers conceived the idea of separating the deputies from the miners. their reasons for taking this step are stated in a subsequent letter. the mode of procedure they adopted was to exempt the deputies from the six per cent. reduction, providing a majority of the deputies on any colliery would leave the miners' association. the employers said their action was in response to a request by some of the deputies. the action drew from the executive committee a strong remonstrance. they pleaded with the deputies and protested against the action of the owners. the circular they issued was a lengthy one. our object will be served if we quote a few portions. addressing the deputies, they said: "it appears in response to some application made by some of you the owners' committee have agreed that where a majority of deputies on any colliery are not members of ours, they will recommend that such deputies be freed from the recent reduction. call this offer by what name you will it is neither more nor less than a special kind of bribery held out to you and we regret to hear, that some of you have been imprudent enough to accept it. why make this difference between those who belong and those who do not belong to our association? it is not because they respect the one party more than the other, or that the party who have left us are any better workmen or in any way more useful to the owners than those deputies who still belong to our association. the most unknown amongst you as to your past history, or the most casual observer of present doings, ought to know that the motive which has induced the owners' committee to make this offer is not respect for you as a class, is not because they think your responsibilities are increased more than heretofore, neither is it because they think you underpaid, but it is because they want to induce you to sever your connection with an association which has hitherto been able to gain many advantages for members and for none more than for your class. they offer you an inch now in order that they may take from you a foot hereafter. most of you can remember the time (only five years ago) when your wages varied from s. d. to s. d. per day of eight hours' working, while with the recent reduction of six per cent. your wages are now s. d. for ½ hours' working, or an advance in time and money of . per cent." the circular then draws attention to a portion of a letter from the deputies who had left the miners to those of another colliery, and to the resolution of the owners' association. the portion of the deputies' letter said: "if any member of our [the deputies'] association leaves and starts to hew, and has to go back to the hewers' association, the two pounds' entrance fee will be paid out of the deputies' association." the resolution of the owners read: that this association thinks that deputies, like overmen, should be the agents of the masters, and that under these circumstances it is imperative that they should not be restricted by any trades union resolutions. in relation to these the committee point out that they (the deputies) could not honestly be members even of the deputies' association, for by the stipulation of the employers they were not to be restricted by any trade union regulations. "it will thus be seen that if you do this, you sell your birthright, your independence, your manhood, your all, not even for a necessitous 'mess of pottage' but for an insignificant present advantage, in order that you may bring upon yourselves a future permanent and great evil." some of the deputies were desirous of serving two masters: they wanted to remain in the miners' and at the same time enter the deputies' association for the sake of the six per cent. at the council held on saturday, th september, a resolution was carried declaring "that the deputies be not allowed to remain in our association and also become members of what is called the deputies' association." at the same time a sharp correspondence took place between the owners' association and the miners', in which mr bunning sent a letter, bearing date rd november, which contained a protest and an extenuation. _november rd, ._ resolution of coal owners the members of this association regret that the representatives of the miners' association after five years' amicable correspondence, should have thought it necessary to communicate to them so uncourteous and offensive a document as that bearing date th october , and relating to the resolution passed respecting the deputies, on october th, . and, as this resolution was arrived at after mature deliberation, and from the conviction that both the safety of the mine, and discipline of the pits, are seriously endangered, by having the deputies subject to the restrictions imposed by the miners' union, no good can possibly arise from any discussion of the subject at a meeting of the two associations. [illustration: john forman] the reply sent by the executive repudiated all intention to be uncourteous or offensive in language, but at the same time they repeated the charge of bribery, for, said they, "viewed from the most favourable standpoint, your action in the matter can only be characterised as that of holding out a manifestly unfair inducement to the deputies." they asked what the employers would have thought, if, having the power, the miners' association had held out inducements to charge men? they reminded the owners that they asked for a reduction off all wages, and the award of six per cent. applied to all underground labour. considering these facts they could not but look upon the action as a covert attack on the association. the executive acting on instruction from council took a return, which resulted as follows:-- total number of deputies-- . total number in our association-- . total number in deputies' association-- . total number paid old wage-- . total number paid reduced wage-- . deputies--sliding scale--relief fund--emigration the dispute about the deputies opened the year. a very lengthy correspondence took place on the subject between the employers' and miners' associations. on january rd the whole of it was sent to the lodges. they were informed that the committee had done all they could to avert a conflict on the question. in keeping with a resolution of council, the owners had been offered arbitration, which they had refused. the resolution referred to contained the alternative of giving the whole of the notices providing arbitration was refused. now, to carry out the instructions contained in that resolution the committee forwarded the ballot tickets for the purpose of taking the vote in accordance with the rule. they concluded by saying: "whatever the result may be arising out of this case the entire onus of blame must rest with the owners themselves." a resolution was placed on the programme for council on february rd by the ex-committee asking "that the deputies who are still with us be paid the per cent. out of the general fund of the association," but it lost. in addition, the subject was laid before the central board of the miners' national union. they expressed regret and surprise at the action of the employers in paying one portion of the deputies more than the others, and were of the opinion "that there can only be one object in view in this policy, the disruption of the miners' union. the board earnestly appeal to the mine owners to withdraw from the position they have taken up. should they fail to do this the board will feel called upon to ask the members of the national union to yield all the support to the durham miners' association they can under the circumstances." nothing further was done in the matter during except an occasional council resolution. we shall, however, meet the same question in a few years. the first sliding scale early in the year the association was entering seriously into a new phase of our industrial relation with the employers and taking another step in the path of amicability by the arrangement of the sliding scale. for some time there had been an inclination in that direction. by the minutes of the executive committee members were informed that negotiations were proceeding with a view to establishing a scale, and at the council meeting held on december th, , the following resolution was on the programme:--"seeing that coals are up, we ask for per cent. advance." the decision was that the question rest over until the sliding scale question is settled. on february th a letter was received from the employers containing the following resolution:-- "this association having anxiously considered the further serious depression in the durham coal trade and the necessity for endeavouring to avert in some prompt and thorough manner the complete collapse which has set in to the ruin of many owners, and the casting adrift of large bodies of men, feels compelled to ask the miners' association to concur in a further reduction in wages and readjustment of hours." the executive committee met the owners on thursday, february nd, when they were informed that the depressed trade and lower prices demanded a reduction of ten per cent. from underground and six per cent. from the bank workmen, "coupled with an increase in the working hours which would, in a great measure, compensate the men for the reduction in their wages." the committee could neither see the necessity for a reduction nor could they see the compensation in the lengthening of hours. they, however, arranged another meeting for friday, th march, when they would further discuss the sliding scale, and, failing that, the reduction. in the statement explaining these proceedings the committee placed before the members two scales--one proposed by them and the other by the owners. it will be interesting and instructive to give these scales. _december nd, ._ sliding scale proposed by the durham coal owners price wage s. d. per cent. s. d. . . . . . . . . . . . . . _january nd, ._ sliding scale as proposed by the durham miners' association price wage s. d. per cent. s. d. in the explanation sent out it was shown that each scale would carry a minimum wage. theirs would be five shillings, while the employers' would be s. d. the wages in the scale were for coal hewers only. the reduction the employers were asking for would bring the wages down twopence per man below the lowest wages offered in the owners' scale. they asked the members to leave the question entirely in their hands, as in their opinion a better settlement would be got than by any other way. a special council was called for the th of march, and two subjects were sent out for discussion--( ) should a sliding scale be adopted; if so, under what condition? ( ) should the owners be offered arbitration? the result was that the arranging of the scale was placed in the hands of the committee, and on th march the first sliding scale was signed for two years. the first scale the following scale shall regulate the wages of hewers and labour below ground:-- scale price at and above but below wage ½ per cent. reduction " " present rate per cent. advance " " " " " " " " " " " " " " " " " " " " " " and so on. it will be observed that the grades were eightpence, and for that amount the change in wages was four per cent. next, there was to be a minimum wage of s. ½d. per day. this is worthy of special notice in the light of subsequent events, especially during the time the minimum existed, which was until , and especially in view of the desire of many people to have a minimum established again. another point was the amount of reduction, which would depend upon an ascertainment by accountants. messrs monkhouse, goddard & miller acted for the owners, and messrs benson, eland & co. for the workmen. the ascertainment was made known on the st of march, the average net price realised being certified at s. . d. the committee accompanied the ascertainment with a short circular, and informed the members "that a reduction of ½ per cent. on underground men and boys and 'banksmen' wages and per cent. on 'bankmen's' wages will take place on the pays commencing april nd and april th." the first relief fund as a consequence of the depressed state of trade very large numbers of men were thrown out of work, and the rules of the association made no provision for them. opinion had been ripening for some months, and the committee realising that the time was opportune, and acting on a council resolution, suggested the formation of a relief fund. in furtherance of the object they sent out the following:-- suggestions for relief fund fellow workmen,--at last council meeting, you put into the hands of the committee, the work of suggesting some plan to relieve the numbers of men now idle at various collieries in the county. after mature consideration, they suggest the following as a means of forming a relief fund:-- . to take from the general fund the sum of five thousand pounds to form the nucleus of such relief fund. . that this fund be afterwards kept up by the payment of a levy, or extra contribution, of d. per member per fortnight. these two are the basis of their suggestions, details can be discussed and arranged afterwards. but to make these suggestions--and especially the second one--a success, the committee believe that the county will require to have brought before them our exact position. the best, if not the only, means of doing this is to hold a series of public meetings at the various lodges and districts in the county, grouping lodges together where such can be done. what they now ask is, can they have your consent to assist the agents in attending such a series of public meetings? it is the only means of rendering successful the getting of necessary means and would not cost more than an ordinary council meeting. in support of their proposals they adopted two modes of advocacy--first, to issue a circular, and second, to hold a series of meetings at all the lodges. this latter step they considered most essential, as they would thus be enabled to state the matter more clearly by speech and answer to the members. this view they placed before the lodges, and received sanction with very little objection; and, acting upon it, they arranged themselves into deputations of two each, and for about three weeks either addressed lodge meetings or groups of collieries where convenient, and as a consequence the relief fund was formed on the lines suggested. while it existed it proved itself a very useful institution for that period, which was the darkest through which the association had to pass. the amount paid, although small, was useful to the public as well as the members--to the latter by easing off the pinch of poverty, and to the former by the help to the rates, which would assuredly have been much more heavily weighted if the fund had not existed. it only existed a year, however, for the committee placed a statement before the county on november nd which showed that, while there had only been £ contributed to the relief fund, the expenditure had been £ , and that, adding the £ grant from the general fund, the expenditure had exceeded by £ the whole amount paid into it. emigration agency during and up to july the agents had acted as emigration agents, and had been very useful in their advice to people who were inclined to emigrate by giving them advice upon points and matters of importance to them. all they did was done free of charge, and only with the view to help those who were members of the association; but as in every movement there are men of the "viler sort," whose envy prompts them to attribute ill motives to those they envy, so in this case there were some who, instead of giving the agents credit for good motives, were not slow to charge them with selfishness and exploiting the volume of emigration for their own benefit. the agents bore this until the council meeting held on july st, when mr crawford and his colleagues resolved to give it up. in doing so they gave their reasons in the following circular:-- emigration agency _to the members._ gentlemen,--as announced at council meeting on saturday last, we intend to give up the agency. it was taken with two objects--( ) to have ourselves well posted up in emigration news, so that we might be able to give the best advice possible; ( ) to aid our members by allowing them the commission money, which is a very important item indeed. it was not taken with the view of making one penny of profit, but solely to assist our members by advice and also an abatement of their fares. but as some poltroon fellows, who are directly interested in getting emigrants in order that they may get the commission money, are causing some stir, and as, further, some of our lodges are listening to their statements, we think it necessary to give it up. you will be the only losers by it, but remember that it is amongst our own members that the real grumblers are found. the hours arbitration--position of the association--federation board the first item of interest in was initiated on th march by a letter received from the employers _re_ the lengthening of the coal-drawing hours. it was addressed to mr crawford as follows:-- dear sir,--i am desired to inform you that the present state of the coal trade in durham seems to render it imperative to extend the hours of work and increase the facilities for drawing coal. and that the members of this association would be glad to discuss the matter with you and your committee with a view to arriving at some decision on the subject. could you fix thursday next, the st, at two o'clock to meet our committee here? an answer at your earliest convenience will oblige. the executive met the employers as requested, and found that the change was to increase from ten hours to eleven all the collieries working ten hours, that drawing time being the outcome of an arrangement. the owners were reminded that it was inconsistent with the sliding scale, and the demand should be withdrawn. they replied by quoting a portion of the scale: "both parties shall remain at liberty to raise any question not inconsistent with the maintenance of the sliding scale." "should any dispute arise as to the carrying out of these arrangements the question in dispute shall be submitted to the chairman of the joint committee, who, if he cannot act, shall appoint some other umpire to act in his place. the award in either case to be final." these were discussed at great length; finally three proposals suggested by the executive committee, subject to the approval of their members, were agreed to: st. is it consistent with the sliding scale to even discuss a lengthening of the hours? nd. if it is consistent with the sliding scale to discuss the matter, is it necessary to lengthen such hours? rd. if the hours are lengthened, should there follow any increase in wages, and if so, how much? the committee were not sure whether the full body of owners would agree to them, as those present at the meeting objected to no. being a question of reference. they informed the lodges that mr meynell had fixed th april for the hearing of the case. they were convinced that the employers could make the demand under the arrangements, and therefore all that was necessary was to say how many persons should attend and who they should be. the question was eventually placed in the hands of the members of joint committee to make the best settlement they could. on th april mr meynell gave the following award:-- coal drawing (_award_) whereas the durham coal owners' association, being of opinion, that it is absolutely necessary that the working hours of all men and boys above years of age should be increased, if they thought fit to place it before me, and to leave me to decide the question. and whereas it was also agreed that the following questions should be left to me for my decision:-- st. is it consistent with the sliding scale to discuss a lengthening of the hours? nd. if it is consistent with the sliding scale to discuss the matter, is it necessary to lengthen such hours? rd. if the hours are lengthened, should there follow any increase in wages, and, if so, how much? now, having heard and carefully considered the arguments on each side, i award, decide, and determine that it is not inconsistent with the sliding scale to discuss the question of lengthening the working hours; nd. that it is necessary to lengthen such hours; rd. that there should be an increase in the wages where the hours are lengthened. i award and decide that the working hours of all men and boys above years of age shall, or may be increased in accordance with my award, that the minimum wage to be paid to the hewers shall be, when the pit works ½ hours, s. ½d.; and when the pit works hours, s. ½d.; and that the wages of the datal men shall be increased in strict arithmetical proportion to the wages they are earning at the time of such increase in the hours. i determine that the increased hours shall or may commence on and after the first pays after the date of this my award. as witness my hand, this th day of april . e. j. meynell. there immediately arose some dispute as to the application of the award, and he was called upon to define it, which he did in a decision given at joint committee on may th. _may th, ._ "i further award and decide that where the working hours shall be increased in accordance with my award, that the minimum wages to be paid to the miners shall be where the pit works hours and a half, s. ½d. and where the pit works hours, s. ½d. is intended to mean--that where the hewers are increased one quarter hour per shift, the county average wage shall, in that case, be considered as s. ½d. instead of s. ½d. as hithertofore; and where their hours are increased half-an-hour per shift, the county average wage shall be s. ½d. instead of the present average of s. ½d. it is also intended that the working hours of any or all classes of workmen may be increased on the payment to them of proportionate increased rates as set out in the award; and that the maximum working hours for drawing coals be hours per day in day-shift pits, and double shifts proportionately." the employers then asked that there should be an allowance for the time taken by boys under age descending and ascending. with the ten hours the boys under sixteen came out after coal drawing was done, but under the eleven hours some were taken in at six a.m. and "rode" at four p.m. some were taken at seven a.m. and came out at five p.m., when the coal drawing finished. there was, therefore, a loss of time at either seven or at four, and this should be allowed for. the matter was arranged on the following principle:--whatever time was taken either at seven to send the under-age boys down, or at four to bring them up, should be added to the eleven hours. if it took ten minutes, then the coal drawing would be from six a.m. to five-ten p.m., but in no case was the time allowed to be more than a quarter of an hour. position of the association as the year progressed the trade became more depressed. pits were being laid in or batches of men were being discharged. the price of coals was rushing down; the ascertainment for the four months ending november showed the average was s. . d. per ton, a reduction of . d. per ton since the scale was established without any reduction in wages. the evil of this was seen in the numbers of men being discharged and in the sad falling away in the membership. the extent of this may be gathered by a reference to the executive committee minutes for may th. without mentioning names here, suffice it to say that at one large colliery a deputation was sent from the executive with power to "appoint someone to act as checkweighman and secretary and to guarantee his wages for six months," and that if the men at that colliery wished "the president attend as either steward or treasurer." the state of the county was growing so desperate that the committee issued two circulars, the object being to place it clearly before the members. in the first they dealt with the relief fund. they commenced by saying: "we are passing through a crisis in the coal trade, and during its continuance every step we take requires careful watching. we may even find it necessary to retrace our steps, by undoing what we have hithertofore done. we are well aware, that to many men this kind of conduct seems to portray a want of stability and necessary perseverance. perseverance in a good and successful cause is highly commendable, but to persevere in a course of conduct, where perseverance means ultimate ruin is neither wise nor commendable. a renowned writer has said that "while fools persevere in their ways, wise men change their opinions and course of conduct." a body of men who either cannot or will not adapt themselves to existing exigencies must not expect success to attend their efforts." passing from these calm, wise words of warning they bring before the members the position of the relief fund. a year prior they (the committee) had asked them to subscribe to assist those thrown out of employment by the bad condition of trade. to this there had been a response of twopence per fortnight. that had not been adequate to meet the demand, and the twopence had been increased to fivepence. still the income did not keep pace with the outlay. for the six weeks previous there had been a loss of £ . there was not only this monetary loss, but there was the more serious one, its effect on the membership. thousands of members are refusing to pay the fivepence per fortnight, and great numbers of men have left the association, so that we are not only losing the fivepence but their ordinary labour contributions. this being our position, we would strongly advise you to at once abolish the payment of the relief fund levy. while this was their opinion they would continue the benefits for three months. at the council held on th june it was decided "that the benefits of the relief fund be continued for weeks longer, but the contributions cease forthwith and the money required to meet the demands thereof be taken from the general fund." this was done in order that the men in receipt of relief should not suddenly have their small resources cut off, but should have a little time to look round. the second circular dealt with the general fund in its relation to the demands upon it. as a preface to their suggested alteration they said: the history of trades unions during the last years would form a very curious chapter in the annals of our country. the vicissitudes which have happened to organised bodies of workmen have been manifold, and varied; but the disastrous consequences which have so often overtaken them have generally been the result of a want of policy, prudence, and forethought, on the part of those who have composed such associations. it is just as much the study of those who have the more direct management of associations like ours to look facts fully in the face before it is too late, as it is that of the head of a household to weigh his position and measure his stores both present and prospective, before he rushes into irretrievable ruin. believing this to be our duty we now place before you our position both present and prospective. they then point out that the expenditure was just double the income. during the previous nine months there had been £ , drawn from the deposit account. in the face of these facts there needed to be retrenchment. they then show that in the contribution was fixed at d. per fortnight, while the strike and breakage allowance was s. per week (and a colliery must be off two weeks before receiving anything), and the sacrificed allowance was s. per week, with s. per week for each child. these benefits continued until , when work was plentiful and wages good. then the strike and breakage allowance was raised to s. (and only to be off a week before being entitled), and the sacrificed allowance was made s., with s. d. for each child, per week. they therefore suggested a reversion to the original payment (except in the case of the week) and the reduction of the death legacy for children from £ to £ , and they wound up by saying: "it is not now a matter of choice, but one of positive compulsion. an association wanting money is like a ship wanting a rudder in a boisterous sea. we would soon find ourselves driven on to the rocks of discontent, disaffection, and disunion, and in all probability shattered to pieces in the struggle. to pursue longer the course we are now pursuing must shortly leave us in that pitiable and helpless condition." a special council meeting was held on th october which gave sanction to the whole of the committee's recommendation. formation of the federation board as soon as the other sections of labour had formed themselves into separate organisations in - , there sprang up a desire for a federation of forces, and from time to time there appeared resolutions on the council programme all aiming at that end. in this year it took a more definite shape. on the committee minutes for january th there is a resolution as follows:-- that a deputation of three agents attend a meeting of cokemen, mechanics and enginemen as to the amalgamation of all those associations. in october a meeting was held at which a set of rules was drawn up and sent out to the county with an explanation. the members were informed that the suggestions were not unalterable, but in their crude form were submitted subject to their approval or amendment. and they were informed that: "the federation was formed to protect their joint interests. there might have been divisions but these must be forgotten. the workmen were unconnected, whilst acting against a thoroughly organised body of owners. there had been no cohesion, nor the remotest understanding, while at the same time they were dealing with the same combined body of capitalists. it must be clear to everyone that while in our present divided condition and negotiating with owners who act as one body we must be placed at a very serious disadvantage." the county approved of the idea, and on november th the rules were issued to the county. at the annual meeting held on th december the first members of the board were elected. their names were j. forman, w. crawford, w. h. patterson, n. wilkinson, j. wilson, and w. johnson. slightly anticipating the events happening in , and for the purpose of keeping ourselves in as close sequence as possible, it may be stated here that the first meeting of the board was held on january th, , when mr crawford was appointed secretary, and mr j. dover (mechanic) treasurer. with respect to the chairman, it was decided to appoint an independent one for six months. he should only have a casting vote, and be paid s. per day and expenses. at the meeting held on february th mr john coward of durham was elected to that position, and occupied it for some months, and during the strike of , assisted by his counsel. by being unaffected in wage by that stoppage he was able to bring a cool and dispassionate feeling to bear upon the questions in dispute. it is due to him to say he took no remuneration for his services. demand for reduction--strike of --dual arbitration--renewal of sliding scale the board was just formed when it was called upon to face one of the most serious crises in our history. at the council meeting held on december th, , it was decided that the average wages in the county should be taken, and that the formation of another scale should be remitted to the committee, with power to renew it. the committee were not satisfied with that indefinite resolution, and asked for more explicit instructions. there were certain alterations required, and therefore they asked for "full and uncontrolled power." they knew that in adopting that course they would risk a large amount of unpleasantness, but they were willing to risk it if they were assured of the confidence of the majority of the members. further, they asked that the retiring members of the committee should be allowed to remain in office until the scale was arranged and the crisis over. these requests as to power and suggestion as to the committee were both accepted. the formation of the federation board, however, somewhat altered, and at first complicated, the situation, for the result was a complex and dual authority. the board was not then, as now, the sole conductor of the wages disputes, but the various committees acted collaterally, the miners' committee taking the leading part in the negotiations. the demands made by the employers were handed to the miners' committee on february th. the conditions were as under: ( ) that a reduction of per cent. on present underground wages is a condition precedent to the re-establishment of a sliding scale. ( ) that a reduction of ½ per cent. should be made in surface labour, but so that the wages of able-bodied men be not brought below s. d. per day. ( ) in the event of a scale being established, it shall have no limit upward or downward, and shall be subject to termination on months' notice. the committee could not grant the request, but at once made an offer of seven and a half per cent., to take effect on monday, the th, or they would submit the entire matter to arbitration. these offers were refused by the owners, and as a consequence the meeting was adjourned until the th. the committee called a council for the th of february. on the th the federation board met, and passed the following resolution:-- this board feels that the position of the county in reference to wages is anomalous. the owners having as a body demanded a reduction of wages, and as such reduction includes all classes of labour in connection with collieries, we recommend that each association call a council meeting to discuss the advisability of adjusting a sliding scale for the regulation of wages, consistent with all our interests. that the secretary write and ask that at the meeting on the th inst. all the four associations be represented. the miners' council decided against the seven and a half per cent., but by the following resolution offered arbitration:-- "that having heard the report of the committee on their interview with the owners on the reduction now asked by the latter, this meeting is of opinion that the best means of settling the difficulty is, to refer it to open arbitration as heretofore." the owners refused to meet the federation board as a whole, and as a consequence the miners' committee met them on the th, in keeping with the board minute, on february th. at that meeting the owners modified their demand. owners' modified offer _february nd, ._ " . that a reduction of per cent. in underground, and ½ per cent. in surface labour, be brought into operation in the first pay beginning march next. . that the additional per cent. in underground, and per cent. in surface labour, claimed by the owners in their minute of january th, be referred to arbitration in the following manner, viz.:-- representatives of the two associations to meet within the first week of march, and if they can agree on a sole arbitrator, the matter to be forthwith referred to him; and if they cannot so agree, each side to appoint an arbitrator, which two arbitrators shall forthwith appoint an umpire, and if they fail to do so by march th, such umpire shall, on the application of either arbitrator, be appointed by mr meynell, county court judge of durham. in the event of there being two arbitrators and an umpire, they shall sit together to hear the case; and the award shall take effect in the first pay in april. . the expediency of re-establishing a sliding scale, to be left for consideration after the award has been given." this was submitted to the federation board, who met the modification by the following:-- federation board's offer _march th, ._ st. to offer the owners the per cent. for underground workmen, and ½ per cent. for bank workmen as a settlement of the whole question. nd. to offer them ½ per cent. from underground, and per cent. from above-bank workmen, and to refer any further claim they might make to arbitration. the miners' committee supported the board, and did this in a circular which contained some very plain and urgent statements. "at best, the lookout is but a gloomy one, and we must try to bridge over the difficulty as best we can, and if possible, without the pits being stopped. we have no wish to descant on the generally depressed condition of trade, or the evil effects producible by a large surplus number of men. at the present time, both these things are operating amongst us, and the owners know this, and seem determined to use them in this crisis. looking at the general condition of things, we would very strongly advise you to adopt one of the suggestions contained in this circular. they are the best we can get at the present time, and a refusal of one of the methods suggested cannot result in better terms for the great body of our members. you must remember that these are times when prudent men do the best, and get the most they can without running all the risks which always attend a stoppage of the pits when trade is paralysed and men both suffering and disorganised." immediately these offers were made known there arose a fierce agitation in the county, and on every hand mass meetings were held protesting against the terms. as is the case in matters of this kind, orators vehement if not polished sprang up from every quarter, whose stock-in-trade consisted of foul epithets which they hurled at the committee and federation board. so desperate was the situation that certain of the committee were in fear, and came into public view as little as possible. a personal incident may be excused here. a mass meeting was held on the sands in durham. the writer, as chairman of the wheatley hill lodge, marched to it. the first words heard were: "there's one of the----; let us put him in the river." the crowd surged and rocked. what the consequence might have been it is hard to tell, but just when the feeling ran highest and he was most in danger a man was knocked back over on to a drum which stood end up, and it went off with a loud report, and the cry was: "they are firing guns." in a moment a panic seized the people, and, as is recorded of the battle of stanhope over the moor hen, "those who ran fastest got soonest out of town." there was a low wall (low on one side, high on the other) over which hundreds fell head foremost, and a good, kind lady who had come from wheatley hill to take care of her husband (the man whose presence was the cause of all the hubbub) was carried away by the crowd, and was so rushed along by the panic-stricken stream of humanity that she was with twenty others landed in a stable, the door of which stood invitingly open like a city of refuge. and so the result was the meeting was disturbed, and the culprit, one of the malodorous committee, was left unhurt, providence in the shape of a drum being the means of saving him. apart from the ludicrous incident of the bursting drum the feeling manifested towards the committee there was only on a par with that found everywhere throughout the county. if one of those at the head of affairs appeared in the street and passed a group of men insult was rampant--slander, being cowardly, feels safe in a crowd. still the committee were not to be driven from their task. they regretted the action of the employers in refusing open arbitration, and who, knowing the condition of the union, were determined to force their full demand; and they were sorry for the opposition of their members, but they knew they were moved by sheer desperation, and played upon by designing men who cared more for popularity, even if it were fleeting, than the welfare of the union, and who would not hesitate to bring ruin if perchance small gain would come to them from it. the committee prepared for the struggle which they saw was inevitable if the employers did not move from the position they had taken up. knowing this they set themselves to ascertain the true state of affairs in the county. they took the actual average of the hewers and reductions which at each colliery had been suffered at joint committee, or had been forced upon them since march , with the hewing prices. it was found that while there was a nominal minimum wage of s. ½d. where the drawing hours were ten, s. ½d. where the hours were ten and a half, and s. ½d. where the eleven hours prevailed, the actual average of the hewers throughout the entire county was only s. ¾d. it was therefore about d. per day or seven per cent. below the theoretical minimum. this is worth considering when we are desirous of establishing it again. it may work in the summer of trade, but not in the winter of depression. this state of things was brought about as the result of local reductions. there were well-known instances where whole collieries of men petitioned the executive committee to be allowed to work at twenty per cent. below the minimum wage. in the final arbitration of , before lord derby, the employers admitted the actual average was only s. ¾d. this they had taken just prior to the strike. they likewise stated in their case that many and considerable reductions were privately agreed to, and particularly where the owners possessed little capital or worked inferior or costly seams. the average taken by the committee harmonised with the s. ¾d. _quotation from owners' case_ . at separate pits arrangements for abatements of wages were made in the working of different seams, varying from ½ per cent. to per cent. and upwards, and this state of things continued up to the close of the period to which the sliding scale applied, when negotiations for a general reduction of wages were entered into by the two associations which eventually ended in the strike. . these local arrangements, as we have stated, were private, and between the individual worker owner and his workmen, and without the official knowledge of the owners' association. it is believed that, if not in every case, certainly very many of the private agreements had the approval of the miners' executive, for some of these negotiations were conducted personally by their staff, who had the strong motive in thus keeping their constituents employed at the best wages they could obtain for them, of saving the union funds from supporting every man, who, under the rules of the association, was entitled to support when thrown out of employment. the committee in their reply before lord derby acknowledged that these reductions took place, but to strengthen their case they charged the whole blame on the employers. they said: sometimes this was done by threatening to stop the pits and sometimes by the more reprehensible practice of dismissing portions of men, in proof of which we can testify that men were personally canvassed, and if not found pliable were threatened and coerced. that reductions took place, and, as the owners state, in some cases they amounted to per cent., is correct, thus making the wages of numerous bodies of hewers (in place of reaching the owners asserted s. d. or s. per day) fall far below even s. per day and proving what we have all along stated, that the average wages of the best paid class of men in the county, viz.--the hewers, are at least per cent. and even more below the rate named by the owners. this proves the inability of our men to suffer any further reduction. in their rejoinder the employers returned to the subject. they asserted that for two years the great bulk of the owners had kept faith with the workmen, at a loss to themselves when the selling price fell below the scale. in the cases where arrangements had been made they had been assisted and concurred in by the miners' executive. "we assert and challenge contradiction that the executive were parties, if not to every abatement of wage in - , most certainly they were parties to many, and hence the folly of accusing the owners of conniving at the reductions when the executive were straining every nerve to assist them, with the object, as we again assert, of saving their union funds." in addition to the general poverty of the workmen through low wages and slack work the committee had to face a serious disorganisation. at some very large collieries the numbers had decreased very much. this fact was as well known to the owners as the committee, for it was brought out very prominently at the meeting with the employers, when the committee made the offer of ten and seven and a half per cent. as a full settlement. one of the employers, urging the acceptance of their claim, said: "there are a large number of men outside the union, and these are not with you. the logic of events will decide the issue." the reply of one of the executive was: "you mean the logic of circumstances, the logic of the cupboard. you have a good ally in our poverty." then there was a sadly depleted fund, which in itself was sufficient to fill them with pessimism, for every man deserving of being at the head of trade unions is bound to feel when faced by these circumstances--not in a cowardly manner, but a feeling evolved out of the dark background of poverty and hunger, not of men, but of the children. there was only £ , in property and bank. from this was to be deducted £ as money invested in the industrial bank and houghton and shotton workmen's hall, which was not available for strike purposes; therefore the war chest was very small, especially to enter upon a struggle such as lay before them. in the face of these adverse circumstances--owners persistent in their demands, wages very low, partial disorganisation, small resources, and an angry people--the committee stood firm. their attitude was unflinching, and their advice fearless and clear, as witness the following quotation from a circular:-- the time has now come when there must be unmistakably plain speaking. it is now clear, beyond a doubt, that if you persist in your adherence to open arbitration alone, the owners will allow the sliding scale to run out without further interference or negotiation and at the end of that time they will take all that they can get, either along the whole line or piecemeal, whichever course may best suit their purpose, by enabling them to punish you by lowering wages and reintroducing pernicious practices. to attempt to fight at the present time without offering the terms which we shall further on advise you to offer, would be suicidal. look around you, and what do you find? on every hand you can count idle men by hundreds and thousands. many of these men have been idle for weeks and months. all their means have long since been spent, and they are waiting for work, begging for work, and cannot find it. we have spent in two years over strikes amongst our own members, at large and small collieries, nearly one hundred thousand pounds and there is not a single strike, either of large or small dimensions, where we have not signally failed. the offer mentioned in the above was a ten per cent. off underground men and seven and a half per cent. off surface men as a final settlement, or seven and a half per cent. off underground wages and six per cent. off surface wages, and any further claim referred to open arbitration. the circular was submitted to a council, and refused, but mr crawford was instructed to offer open arbitration on the whole question. this was done by telegram: to t. w. bunning, coal trade hall, newcastle. open arbitration having for many years been resorted to by your association and ours in the settlement of wages questions, our members again wish to have recourse to it in the settlement of your present demand for a further reduction of wages. on the same day a reply was received: w. crawford, north road, durham. the following resolution was passed by a full meeting of the employers' association before the receipt of your telegram and has since been unanimously confirmed--at a meeting of this body held to-day arrangements were made for giving notice to expire on april th to all men whose wages have been hitherto regulated by the durham miners' sliding scale, that from that date underground wages will be reduced fifteen and surface wages ten per cent. it will be seen the offer of the owners confines it to the miners, as they alone were in the scale. this modification of demand and threat of notice was sent out in a circular on the th of march. they reviewed the whole situation both at home and in other counties. at home, within the previous six days, four collieries had received notice for depression of trade. in south wales heavy reductions had taken place. in scotland nearly the whole of the notices had been served for further reductions, while wages were as low as s. d. per day. in other parts of the country a similar state of things existed. in stating these matters there was no attempt to terrify. it was a simple statement of facts. it would require the pen of a master to place before them a true picture of "all the comparative and positive destitution to be found in the houses of thousands of men at the present time. with this dreadfully adverse condition of things is it possible to go into a struggle with a body of men, strong in their own cause, determined to fight, and who have every possible advantage on their side? to do so can only end in results the most damaging to our organisation and ruinous to ourselves and families. true valour is not shown in reckless and heedless action, but by waiting until a foe can be met on at least equal terms." it was no use offering arbitration, for the owners had persistently refused that. they urged the whole matter should be left in the hands of somebody chosen by themselves to make the best settlement they could. the voting at the council was taken on the two questions: the committee's suggestion or arbitration. the result was for the former and for the latter--being a majority of for open arbitration on the whole question. it will be obvious that the tendency of the owners' offer only being made to the miners would be to disintegrate. it would not be right to say such was the intention, yet that was assuredly the bias. the justification lies in this, the miners were the only parties to the scale at its formation. none of the other sections were parties to it, and therefore the negotiations only applied to them. the terms of the requests were very embracive: they are "underground wages" and "surface wages." this is certain, that no division took place. the action, right or wrong, was as solid as could be expected. the voting on the questions, committee suggestion or arbitration, did not give a satisfactory decision, and a second ballot was taken on the questions: "strike" or "owners' terms," with a result that the workmen refused the terms. the strike was entered upon, the notices terminating on th april. some of the managers threatened to withhold the wages until the houses were vacant, and it was feared that this might provoke disturbance. notice was sent out by the committee, in which the action of such managers was condemned as "not only an illegal, but also an inhuman act." "but whatever course they may adopt, either in this or any other matter, be very careful not to be guilty of any breach of the law. let nothing induce you to pursue a course which at all times is to be deplored, but which just now would be aggravated into the most heinous of crimes." as a result the conduct during the strike was most commendable, the only persons suffering being the committee and federation board. there were certain collieries to whom notice was not given, and the committee felt it necessary to ask whether these should continue working or give in their notices. the returns of the voting were for stopping the whole of the collieries and only for working on. they were, therefore, ordered to give in their notices, and instructions were sent out as to the mode of procedure. that vote was taken on april nd, but on the th at a special council meeting it was qualified by the following resolution:-- "this meeting deems it highly necessary that all those firms ought to be allowed to work their pits who will agree to arbitration as a settlement of their difficulties, or who will agree to a continuation of present prices without being affected by any county change." an offer was made to the enginemen, which their representative brought before the federation board. at the meeting on april st they were advised "to only take such a reduction as the sliding scale would have warranted them in asking, had it been operative downwards as well as upwards. should this be refused by the owners, this board would further recommend the enginemen, mechanics and cokemen who are yet employed to give in their notices and thus legally terminate their agreement." the board met again on the th of april, when the enginemen reported a change in their position, and the following resolution was passed:-- this meeting has heard with satisfaction that the owners on saturday last offered the enginemen open arbitration in the settlement of their present wages difficulty. but it cannot but express its surprise at the conduct of the owners in so determinedly refusing to adopt the same principle in the settlement of the wages difficulty now existing between the miners and them. if the adoption of arbitration in the enginemen's case would have been a right and equitable way of settling, it surely must be right also in the case of the miners. so the strike proceeded. the committee were formed into a strike committee, with full power to manage it. they were called upon to defend themselves in the press. every effort was made to get help from other districts. on the th of may a communication was received from the owners. copy of a resolution unanimously passed at a meeting of the durham coal owners' association, may rd, the durham coal owners' association recognising ( ) that the public, as well as private interests, so seriously prejudiced by the strike, render it a duty to adopt a course most likely to bring about a settlement; ( ) that the proposition for each side appointing a committee with the full powers seems to have met with general approval; ( ) that such committee would undoubtedly provide the means by which difficult negotiations can be most successfully conducted; resolves: that a committee of members of this association be and are hereby appointed to meet a similar committee, if such should be appointed by the miners' association, with full power to settle the matter at issue. that the foregoing resolution be communicated to the miners' association, and they be invited to adopt a similar course. the committee in response to that resolution met the owners' committee on saturday, the th of may, but failed to come to any agreement, and the meeting was adjourned until the th. the county was informed of the failure, and told to remain as they were until they heard from the committee again. mr forman and mr crawford met mr l. wood and mr d. dale on the th. no settlement was come to as to amount of reduction, but it was arranged there should be a _pro tem_. arbitration, with mr bradshaw, county court judge, as umpire. the arrangement was that there should be an arbitration to say how the collieries should commence, and a second case after work was resumed to decide what further reduction should be granted. the preliminary case was heard on may th, and judge bradshaw, after passing in review the various stages of the dispute, decided "that there should be an absolute reduction in wages of ¾ per cent. on underground and of ¾ per cent. on surface labour, to take effect from that date, and the question whether any further reduction should be made be left to a future arbitration." award in the matter of disputes relating to wages between the coal owners, members of the durham coal owners' association, and their workmen, members of the durham miners' association: whereas the owners claimed a considerable reduction of wages, to take effect from the fifth day of april last, and the miners refusing to accept such reductions the collieries in the county of durham have for some time been, and still are idle. and whereas, with a view of settling the matter in difference between them, the owners' association appointed a committee of persons, and the miners' committee appointed a committee of like number, with full power to determine the question at issue. and whereas, after long negotiations, the owners' committee deputed to messrs lindsay wood and david dale, and the miners' committee deputed to messrs william crawford and john forman, their respective powers. and whereas, the said lindsay wood, david dale, william crawford, and john forman having applied to me, the undersigned, for my advice and decision in the premises, and have laid before me the following statements, which are admitted by the parties on both sides, namely:-- . that on february th last, the owners offered to accept an absolute reduction in wages of per cent. on underground, and ½ per cent. on surface labour, and to leave to arbitration the question whether any, and what further reduction should be made. . that on april nd last, the miners' association offered to concede an absolute reduction in wages of ½ per cent. on underground, and per cent. on surface labour, and to leave to arbitration the question, whether any, and what further reduction should be made. . that on the th inst., the owners' committee offered to accept an absolute reduction in wages of ¾ per cent. on underground and ¾ per cent. on surface labour, and to leave to arbitration the question, whether any, and what further reduction should be made. . that on the th inst., the miners' committee offered to concede an absolute reduction in wages of ¼ per cent. on underground, and per cent. on surface labour, and to leave to arbitration whether any, and what further reduction should be made. now, i, the undersigned, having duly weighed and considered the foregoing statement, and what has been alleged before me by the respective parties, _do decide and award_, that there be an absolute reduction in wages of ¾ per cent. on underground, and of ¾ per cent. on surface labour, to take effect from the date of these presents; and the question, whether any, and what further reduction should be made, be left to future arbitration. in witness whereof, i have hereunto set my hand, in duplicate, this fifteenth day of may, one thousand eight hundred and seventy-nine. thos. bradshaw. then there arose a dispute as to whether it were competent for the men to show cause before the future arbitrator why there should be a rebatement of the eight and three quarters and six and three quarters per cent. it was again referred to the umpire. he decided that the contention of the workmen's representatives could not be sustained. the employers accepted his decision as an instalment of their claim, and to get the pits to work, but they in no way waived or relinquished their right to refer to arbitration, whether or not they were entitled to any, and if any, what further reduction over and above the absolute reduction by his award. that definition the committee accepted. immediately the spirit of revolt ran through the county, and for a few days some lodges objected to resume work. whenever the executive appeared they were greeted with cries of "judge bradshaw" and "eight and three quarters." gradually the resumption of work became universal, and on the nd of july the arbitration was opened, with lord derby as umpire, in great george street, london. mr w. armstrong and mr d. dale were arbitrators for the employers, with mr l. jones and mr w. crawford for the workmen. advocates for the owners were h. t. morton, l. wood, and w. t. bunning; for the employees j. forman, n. wilkinson, and w. h. patterson. the names of the executive committee were: w. johnson. g. newton. j. scott. j. bell. w. r. fairley. w. robinson. w. longstaff. g. parker. w. gordon. j. wilson. there were two days' sittings, and on the th of july lord derby gave his award. he said it was agreed that the award should apply to all underground and surface men, except enginemen, firemen, joiners, smiths, masons, labourers, and cokemen. he awarded a reduction of one and a quarter per cent. in the present rate of wages paid to underground and surface men affected by his award. thus ended a stoppage of work--it is a misnomer to call it a strike--which should never have taken place. the men from the first were ready to appeal to reason, and the final decision proved the executive committee right in their offer. there is a closer spirit abroad now. the county has been in an atmosphere of amicability. may that better state take full possession and the day of strikes be gone for ever. [illustration: w. h. patterson] the strike ended, the committee set themselves to work to repair the broken places and put the association on to a solid foundation again. they found themselves financially insolvent and shattered numerically. they were unable to meet the benefits provided by rule, and there was a great cry of distress from those who were out of work owing to depression of trade. a return was taken as to a levy to meet the latter class, but it was very unsatisfactory, not one half of the votes being cast, and the suggestions included levies varying from d. up to s. they therefore decided to call a special council, warning the members that these people could not be paid from the general fund. they had been compelled to pay those who were on the funds short allowance. the position was so desperate that "either the contributions must be increased or the benefits reduced," and at the council the two questions were--first, the general question of contributions and outlay; second, the men idle from depression: how to raise money for their support and how much should they be paid? the council acting on the advice of the committee decided that the benefits for strike, lockout, and breakage should be s. and s. per week for members and half members respectively, and that these payments should only be paid for six months, when they should cease without appeal, the sacrificed allowance being reduced to s. per week without a reduction in time. their next difficulty was the unconstitutional district meetings which were held. at these the wildest statements were made, and as a consequence the minds of the members (as will always be the case when these meetings are in vogue) became unsettled, and disunion followed. amid the natural difficulties of the situation the committee were called upon to defend themselves. a circular was sent out which, after renewing the argument of the promoters of the meetings, said: "if you determine to let those men go on, doing their endeavours to undermine your association, then be prepared to accept with that choice all the evil consequences which must arise therefrom. these are the men who would "_rather rule in_ hell than serve in heaven!" they have yet to learn the most important of all attainments--viz. how to rule themselves, before presuming to guide the thousands of people in this county. if complaints are to be made, let them be made regularly and right. if reformations are needed, let them be sought in keeping with the constitution." history is apt to repeat itself in this mode of procedure as in others. nothing but evil can result. we are not in russia; we are a democracy, and have a free tribunal. there were other four questions calling for arrangement: the fixing of the county average; the arranging for official recognition and the operation of the federation board; the rearrangement of the sliding scale; and the resumption of the joint committee. a dispute as to the average for hewers arose in reference to the figures from which the eight and three quarters per cent. and one and a quarter per cent. should be taken. the employers contended they should be deducted from the actual wage of the county for the three pays prior to the strike, which was found to be s. ¾d. the committee contended they should be deducted from the nominal minimum wage of s. ½d. for the eleven-hour pits and s. ½d. for the ten-hour pits. these were the wages from which the reductions were sought. if they were averaged as per the number of pits at each it worked out at s. d. it was therefore obvious that there would be a great difference in the result. if the two reductions were taken from the s. d. the average would be s. . d.; if from the s. ¾d. it would be s. . d., or . d. of a difference. it was finally agreed that the average for hewers should be s. d. for the eleven and s. d. for the ten hour pits. the official recognition of the federation board was at first objected to by the employers. at a meeting of the board held on the rd of september the details of the sliding scale were discussed. they were in doubt as to whether the owners would discuss it with them, or the miners alone. eventually a joint meeting was held, and the second sliding scale was arranged on october th. the date of its commencement was fixed for december. sliding scale, there shall be made the following percentage additions when the net to, or deductions average selling from, the now prevailing price of coal tonnage rates and wages reaches but does not reach additions deductions s. d. s. d. none none ½ per cent. " " " ½ " " " " " " ½ " " " " and so on upwards, ½ per cent. for each d.; the per cent. variation for the d. range in price between s. d. and s. d. being limited to that special range. s. d. s. d. deductions. ½ per cent. " and so on downwards. * * * * * the difference between this and the previous one consists in the lessened grades. the d. grade was reduced to d. for two and a half per cent. change in underground wages and two per cent. in surface wages. another variation was the giving up of the minimum wage. all parties were agreed on this point, as all had felt the evil arising from the operation of it during the two years of its existence. long may it be before such another condition arises here, for the days were dark indeed; as witness the first ascertainment, which showed the average selling price of coal to be s. . d. per ton. the accountants were, as now ( ), e. spark, and monkhouse, goddard & co. the joint committee was suspended at the commencement of the strike on april th, and did not resume its sittings until december th. during the time intervening the rules were revised. a special committee (which might be called an interregnum committee) met, and transacted business of the same nature as that within the purview of the joint committee. before leaving the strike and the consequences it may be of interest to quote from mr crawford's first monthly circular his estimate of it. the strike which took place in the months of april and may last will ever remain an epoch in the history of the association. a more complete success never took place. at its beginning, strong doubts were expressed and great fears entertained as to what would be the ultimate consequences of such a step. i was amongst those who doubted, but did not despair, and the end more than justified the expectations of the most sanguine. if we take the entire history of trade disputes, it will be found that not one ever commanded so much public sympathy. we had justice and right on our sides, and we took the only wise course--viz. to let the public know it. we deplore strikes as much as anyone can do, but there are times when they become necessary and such a climax had we arrived at in april . numbers of men who were outside our association then came forward and joined with us and fought the battle side by side. there never was a more complete stoppage of work or one which to the workmen, at least, ended more satisfactorily. we may fittingly close the year by a reference to the strong tide of emigration that was running. a miners' conference to consider a scheme to assist prospective emigrants and draw up a code of rules was called in manchester in november. such a scheme was formulated and the rules suggested, but nothing ever came of it. in connection with this large volume of emigration from the mining districts mr crawford took a trip to america in one of the inman liners, and wrote an account of it in a pamphlet entitled "in the steerage." a report was circulated in the press describing what purported to be the foul condition of the accommodation provided for the third-class passengers. with a desire to ascertain the truth or otherwise of these statements mr crawford went to new york in one of the inman boats, and completely exposed the untruthfulness of it, and did a great deal towards easing the minds of many of the miners who were preparing for leaving the country. violations of scale--restriction of labour--working hours arbitration--deputies' wage arbitration--employers' liability by the end of the consequence of the strike, as seen in disarranged collective machinery, had been reconstructed. one beneficial effect of the stoppage was the great number of men who joined the union. when the notices terminated there were collieries where the numbers were few; but these men, as if moved by the instinct of self-preservation, ceased work, and to a very large extent became members, remaining until this day. it was the greatest piece of missionary effort ever seen. instead of disunion and isolated action there were manifest loyal adhesion and solidity. there were sure to be exceptions to this as to all rules, and early in the year the federation board was called upon to meet a class of trouble which was entirely illegal, and which arises occasionally now. without specifying places (but dealing generally) it will suffice to say that in a few instances notices were given for advances beyond what the sliding scale gave. the employers requested the board to meet them. this they did, and two resolutions, one dealing with the cokemen and the other with the miners at one colliery, were unanimously carried. the workmen were told that they had violated the rules of the federation board and sliding scale agreement. they were told (by a circular sent out by the federation board) that they were parties to the arrangement, and yet had given in their notices for an advance in direct contravention of its provisions. having been parties to the scale they ought not to violate it with impunity. if this individual or lodge action were allowed it would end in disruption, and therefore it must be checked. the wisdom of that advice is obvious, and not only in that day, but for the present time. if agreements are made for men they should be adhered to. to violate them is lawlessness, which in the end is hurtful beyond the immediate act. if conditions are forced upon people it is right to repudiate, but for the last thirty-four years in this county there has been freedom and equality. restriction of labour at the council meeting held on january th it was decided that there should be a restriction, and that no coal hewer should make more than s. d. or s. d. per shift, but this was never carried out in any general manner. on march th the council again dealt with it, and declared all lodges unfinancial where it was not put in force. in furtherance of that resolution the seaham lodge put a notice on the pit heap to inform the members "that the restriction had commenced, and that a list be drawn up stating the number of tubs each man had to fill in his respective district or flat, no man to make more than the county average in any one day." to that notice the owners' association took objection. a letter was sent to mr crawford asking him whether the workmen had determined to enforce restriction, and if so, were they then acting on it. these questions mr crawford did not answer, but brought them before the committee. as a result a circular was issued reviewing the whole case. they pointed out that when the council carried it very few of the lodges put it in force, and the few who did soon left off, and that at the council to enforce it the voting was for, against. they reminded the majority that "surely a minority so strong ought to have led to a reconsideration of a matter not only so vitally important, but which has at all times been found so very difficult to carry out in practice." lodges were sending in resolutions refusing to carry out the council resolution. that resolution said those lodges should be expelled. the position would be that whole collieries of men would be cut off from the association because they were determined to abide by the scale agreement. in view of these facts, they resolved to call a special council. they pointed out that one or two lodges had sent in motions of censure because advice had been given, and they met the censures by saying: one or two lodges have sent motions seeking to pass a vote of censure on us for issuing the last circular. it would seem that these lodges would like to see us sit and do nothing, even though we were certain that an impending evil was threatening our very existence. we cannot regard this as our province. what we did was for the preservation of the association. the moment we see that our efforts have not ended more satisfactorily we have called a special council meeting to further consider the matter. take our advice, and inasmuch as we have only done our duty, spare your censures. we have quite enough to do at present without wasting our energies in useless and pernicious quarrelling amongst ourselves. the result of the special meeting proved the committee right. a tabulated vote was taken--the voting being against restriction , for ; majority against, . thus ended the only county attempt to carry out a uniformity in piecework. it ended as all such will end. human nature is too strong for such arrangements. working hours arbitration this case arose out of the hewers' hours at some of the collieries. amongst them were gurney pit, leasingthorne, letch, and wingate. these were eleven-hour pits, but during the depression of - the hewers had been induced or coerced to go in at three a.m. instead of four a.m. the executive committee in their negotiations contended that this was a violation of mr meynell's award, and therefore ought not to exist. on the employers' side it was held that the award named only dealt with the coal drawing. after attempts to settle it was finally agreed to refer it to arbitration, with lord rowton as umpire. the arbitrators on the owners' side were mr r. f. mathews and mr w. t. hall, and for the workmen mr l. jones and mr w. crawford. there were two days' sitting in the westminster palace hotel, london. on the th of august the umpire decided that the hours complained of should remain as they were. the deputies' arbitration this question of the deputies being paid a higher wage if they were not in the miners' association came up in a renewed application for uniformity of wage. this was sent to the owners amongst a number of other requests. the reply was that they were strongly of the opinion that the deputies should not be members of the miners' association. the executive could not accept that reply. they had never asked about the associations, but a just wage, and they considered the reply was an insult. they recommended to their members that it should be sent to the federation board. this was done, and on the th of march the board offered to submit the matter to arbitration. the offer was refused by the following resolution:-- miners' request and reply forwarded to mr crawford _june th, ._ _deputies._--that deputies who are not members of the deputies' association be paid the same wages as those who are. considering the position in which the deputies stand to the hewers and other workmen, any change in the present arrangement is undesirable. on the receipt of this the board notified the county, and resolved to call a joint meeting of the four associations. their advice was that the whole of the notices be given in, and work to cease until the claim was conceded or arbitration granted. the meeting was held on august th. negotiations proceeded, and in november the employers agreed to accept arbitration. the case was not heard until february . the umpire on that occasion was mr i. hinde palmer, m.p.; the advocates were mr l. wood, mr w. armstrong, mr l. jones, and mr w. crawford. the hearing lasted two days, and was held in the westminster hotel, london. the umpire decided upon two points: ( ) that it is competent under the sliding scale agreement of october for the deputies who are members of the miners' association to require that their wages be advanced. ( ) that the advance shall be such a sum as will make the amount of their wages respectively the same as the wages paid to those deputies who are not members of the miners' association. the employers' liability act it is not intended to review the introduction and passing of acts of parliament, but mention may be made of the employers' liability of , not with a view to explain its provisions, but to indicate steps which were taken towards contraction out of it. in lancashire contracting out was made one of the conditions of hiring, and a strike took place in an attempt to resist it. with us in the north (for the two counties worked together) the same end was sought, but by different means. the aim of the employers here was to avoid litigation if possible, and, with that end in view, would have increased their contributions to the permanent relief fund. the officials of that fund were desirous of bringing an arrangement about, believing it would strengthen their position. there were a few men outside the ranks of those officials who advised the miners to enter into a contract. at a meeting of the permanent fund committee it was just on the point of being carried when a suggestion was made to the effect "that it was not a matter pertaining to the fund, but belonged to the workmen's associations, and that a joint meeting should be held." such did take place, with the result that the proposal was defeated. the leaders of the associations were very strong against it. among the strongest was mr crawford, whose monthly circular for december contained some very clear and explicit reasons in opposition to the idea. there were threats from some employers as to smart money and subscriptions to the permanent relief fund, but still the workmen refused to give way. - deputies' wage again--third sliding scale--death of mr macdonald--change in the treasurership in february this question was again in evidence. by reference to the award as given above it will be seen that the umpire decided clearly in the workmen's favour, but there arose a complication in the mode of application adopted by the owners. the mode of calculation was skilful and peculiar. the dispute arose in when, as an inducement for the deputies to form an organisation of their own, they were to be exempt from the six per cent. reduction; therefore, said the employers, we will give those deputies who are in the miners' union the six per cent. given in , and then deduct all the reductions since, by this process bringing them to s. ½d. per day. they seemed to forget that the deputies' arbitration was for the difference between the actual wages at that time--the difference being d. or d. per day. the anomaly was that two men might be doing the same work with equal responsibilities (in some cases the lower paid the best workman) and yet one have a much higher wage than the other. mr bunning (on behalf of the owners) sent a copy of the instructions to the managers to mr crawford, asking him if they met with his approval. the answer was sharp. instead of agreeing with them he considered them a clear violation of mr palmer's award. it was not based upon shaw lefevre's award, but upon the existing difference in the wages. and he informed the owners, that they would demand the higher wages. the negotiations continued until may, when the umpire by joint letter was asked to meet mr l. wood and mr crawford. he informed them he would write each of them an explanation, and save the journey. this he did, and said the award was clear and intelligible, and that he meant those who were in the miners' association to be paid the highest wages. on the strength of that interpretation the owners paid the wage, with everything kept off since the award. third sliding scale as the two years for which the sliding scale was definitely fixed drew near completion it was obvious that there was a strong feeling against it. the circumstances were against it. introduced at the conclusion of a very disastrous strike the whole of its operation was in the worst times--trade bad, wages low. there was no wonder that the men had little love for it. recognising the opposition the committee placed a motion on the council programme suggesting that notice be given to terminate it at the end of the two years. this was adopted, and notice given at the proper time. in the meantime the miners generally were turning their attention to the question. a sliding scale conference was held on april th, , in the midland hotel, birmingham. the conference affirmed "that the principle of sliding scales is an equitable mode of settling wages questions, if rightly worked out in detail: that the best mode of taking out the selling price will generally be to take the price of coal sold, but that no coals should be taken which were sold on contract; only those sold at the current market price." in the matter of leaving firms out each district was left to its own option. it was considered desirous that the accountants should have more freedom in regard to the matters they were permitted to divulge. a second conference on the same question was called for october th in birmingham, with a programme on very similar lines. a council meeting was held, and two delegates selected to represent durham. certain instructions were given them: sliding scales were the best arrangements for regulating wages; the open markets were preferable to the existing mode of ascertainment, with others of a kindred nature. on january th the federation board had under discussion a proposal from the employers. it was not accepted, but they were told the board was ready to meet them at any time. at a special council held on th february the situation was complicated by the miners deciding to ask for an advance of twenty per cent. if the owners refused the sliding scale drawn up by the federation board, and that body was instructed to meet the employers. the meeting took place on march th on the two questions, when the owners gave the board the following:-- owners' offer _march th, ._ the durham coal owners' association is unable to accept either of the propositions suggested in the federation board minutes of february th, that is to say,-- . the association cannot regard "the sliding scale drawn up by the federation board as just and equitable," and consequently cannot adopt it. . the association cannot grant "an immediate advance of per cent. in the wages of all men and boys," nor admit "that trade warrants such an application," or any advance at all. having regard to the difference of view between the owners' association and the federation board, the association can only suggest that the question whether wages shall be varied, and if so, to what extent, and in what direction, shall be left to open arbitration. the miners' council then decided to take a ballot on the twenty per cent. if the question were not carried by a two-thirds majority, to arbitrate on the advance. when this was sent to the owners they replied that the advance could not be granted, but they were quite ready to leave it to open arbitration. the federation board as a whole considered itself in an anomalous position if any section were allowed to act as the miners were doing. if this were allowed to proceed, then on wage questions there was an end to all usefulness. either the power must be taken away altogether, or they must unreservedly trust them. as the position was, they were in a crippled condition. "this renders our work on general questions nil, and the federation instead of being a tower of strength is a source of weakness, inasmuch as it exposes to the owners our want of agreement and diversity of thought and action." they had, therefore, come to the conclusion to take a vote, with the view to have the matter settled. the response of the county was in favour of the board by a large majority. immediately they decided to ask for a scale with a minimum wage, and that the variations should be two and one and a half per cent. a meeting between the board and the owners was held on april th, when the workmen asked for an advance of seven and a half per cent. to this the employers objected, but said they would pay a wage as if the coals had reached s. d., which was equal to an advance of three and three quarters per cent., and would be an advantage of two and a half per cent., during the continuance of the scale. the board strongly urged the acceptance of the offer, which in their opinion was preferable to arbitration. the workmen accepted their advice, and the following scale was signed on april th:-- third sliding scale there shall be made the following percentage of additions to, or deductions from, the standard tonnage when the net rates and datal wages, average selling being those prevailing at price of coal november reaches but does not reach additions deductions s. d. s. d. none none ¼ " ½ " ¾ " " ¼ " ½ " ¾ " " ¼ " ½ " ¾ " ¼ " ¾ " " ¼ " ½ " and so on upwards, ¼ per cent. for each d., the ½ per cent. variations for the two ranges of d. each in price between s. d. and s. d. being limited to those special ranges. -- ¼ -- ½ and so on downwards. it had to continue in force until th june , to be terminated by six months' notice given any time after that date. it will be of interest if we insert the scales proposed by the owners and board before the agreement. owners' scale there shall be made the following percentage of additions to, or deductions from, the standard when the net tonnage rates and datal average selling wages, being those prevailing price of coal at november reaches but does not reach additions deductions s. d. s. d. none none ¼ " ½ " ¾ " " ¼ " ½ " ¾ " " ¼ " ¾ " ¼ " ½ " ¾ " " and so on upwards, ¼ per cent. for each d., the ½ per cent. variations for the two ranges of d. each in price between s. d. and s. d. being limited to those special ranges. -- ¼ -- ½ -- ¾ -- and so on downwards. workmen's scale there shall be made the following additions to the when the net standard tonnage rates and average selling datal wages, being those at price of coal november reaches but does not reach additions s. d. s. d. ( s. minimum wage) ½ ½ ½ ½ ½ ½ and so on upwards, ½ per cent. for every d. it will be obvious that the difference between the two is very wide. the workmen sought to renew the minimum wage, although but two years had intervened since the dark experience of - , and when it was impossible for the condition to have been forgotten. death of mr macdonald on october st, , mr macdonald, m.p., died at wellhall, near hamilton, scotland. he was the ablest leader the miners of scotland had, and one of the first labour representatives in the house, being elected with our good friend mr burt in . he was often called the "miners' friend." although not a durham man he was so intimately and closely connected with our early history and progress up to his death that there would be a great hiatus if no mention were made of him. the executive committee was represented at his funeral, and the first council meeting after his death passed a resolution expressing deep sorrow at his death, and regarding it as an irreparable loss and national calamity to the mining population of england, scotland, and wales. his self-sacrificing efforts for a number of years on their behalf cannot be fully known, but his memory will ever be held dear by a grateful people. a movement was immediately started to commemorate his work, the result of which was the statue which is in front of the hall in durham. as mr crawford said, "it is the last tribute of respect we can pay to one who through good and evil report kept steadily in view the one object of his life--viz. to reduce the misery, and alleviate the sorrows of the mining population, while following their hazardous occupation." it will be interesting to place on record an outline of his life. he was born in the year , and began work at eight years of age. when he was born the condition of the mining population was dreadful. there was no law to protect the miner, and there was little regard for health or life. the hours were fearfully long. women worked in the mines under the most debasing conditions. in the midst of this he set himself the uphill task of self-education--uphill now, but how much more so then! in early life he left the mines, and became a teacher. the knowledge he acquired he determined to devote to bettering the condition of the miners. between and he was assiduous in procuring amended miners' acts, and those of and were mainly due to his efforts. from that time until his death he was earnestly working in efforts to ameliorate the conditions of the life he knew so well, and at his death was busily engaged in further amending the mines act. he was a sample of men who have been endowed with splendid powers, and who might have made a fortune if they had followed commercial pursuits as eagerly as they followed after reform and better temporal conditions for others, but who, when there was nothing to gain, counted it their highest good if they could in any way assist their class on to a higher platform and into brighter conditions of life. they chose rather to suffer with the people in their affliction, and help those who needed it, than to make for themselves monetary positions. when he died a truly great man left the ranks of reformers, and to the honour of englishmen be it said, they honoured him in death as they appreciated him in life, as witness the splendid statue which was unveiled on th november by his colleague in union and labour representation in parliament, mr t. burt. in the beginning of a matter arose which, were it not for the fact that it would leave an incompleteness in our record, might have been passed over unnoticed. some doubts were felt as to the state of the accounts, and it was resolved to have a thorough inquiry into and examination of the books. mr john staton, the accountant, was employed for the purpose. his report was to the effect that the treasurer was indebted to the association to the amount of £ , s. d. this examination covered the period commencing with december . he not only described the amount, but he suggested a system of book-keeping. the result of the affair was the suspension of the treasurer (mr forman acting _pro tem._), and his removal on the th of may, and the appointment of mr j. wilson. the whole circumstance was unfortunate. there were many (the writer among them) who doubted if there had been any defrauding, and who were convinced he had only been careless. he was an earnest worker in the association. [illustration: alderman john wilson, j.p., m.p.] - five days per week movement--fourth sliding scale--second relief fund--wheatley hill "putt pay" the question of restriction of the output was again brought under discussion at the beginning of the year. it was not peculiar to nor spontaneous in durham, but was of extraneous suggestion. it was the result of a miners' conference in leeds, and was set forth under two phases: the reduction in the hours per day and the days per week to five--all the pits being off on the saturday. the members were told plainly by mr crawford what the real issue was and what was the condition of the mining districts. while in other districts the hours had to be reduced, in durham they would remain, but the days per week would apply to all alike. he, however, pointed out that there was only one-sixth of the miners of the county represented. a special council was called, and the matter placed before it, when it was decided "that pits ought to work not more than five days per week and draw coal not more than ten hours per day--each and every pit being idle every saturday, irrespective of how many of the preceding days of the week have been worked." a second national conference was held on the question. a report was issued by the representatives, messrs crawford and wilson, which showed the fallacy of attempting any national movement. the conference was called to hear how far the decision had been carried out. the report showed that there were only , paying members in the districts represented, the total number employed being about , ; that there were only persons who had adopted the leeds resolution of restriction, and some districts positively refused to carry it out. in the face of these facts the conference reaffirmed the restriction resolution, and resolved that the ballot should be taken in each district, and that there should be an adjournment to hear the result. in the meantime a meeting was held between the executive committee in durham and the owners. the committee stated their reasons for requesting the meeting, and hoped the owners would assist them to carry the conference decisions into effect. the reply was that the question was so important to both employers and employed that it would require serious consideration. could the workmen point out any probable good which would result? how far it had been carried out? unless it were generally adopted it would mean ruin to those districts attempting it. they were willing to take part in a national conference for the purpose of discussing the subject. the matter was again brought before a conference in birmingham on april th. there were twenty-seven delegates present from districts where , men were employed. the only item of business was the appointment of a committee to meet the mine owners' national association, each district to appoint its own representative on the committee. mr crawford was afterwards appointed to act for durham. the request for a meeting was sent to mr maskell w. peace, the owners' secretary. it was refused, as they considered it outside their province. beyond the disorganisation in the other districts it was found in durham to be incompatible with the sliding scale, and as a consequence the attempt at a national regulation of labour proved abortive. that which oft looks easy when at a distance is often found impracticable when we are brought face to face with it. if a national restriction be ever carried out it will need solid unions, and all men of one mind, or it will fail at the start. the fourth sliding scale as the period approached when the definite year of the scale would end there were growing signs that the requisite six months' notice would be given. at a meeting of the federation board held on may rd it was decided to give such notice to terminate the scale at the end of the year, and the board prepared to meet the emergency, and if possible renew the scale or modify it. a resolution was come to at their meeting in october, expressive of their opinion that "a sliding scale is the best mode of adjusting the wages questions." they further resolved that each section should meet the owners for the purpose of discussing any alteration peculiar to themselves. acting on that arrangement the executive committee sent out a circular urging the maintenance of the principle. in addition they called a special council, and asked for suggested amendments. in response there were seventy-seven suggestions returned, embracing every kind of alteration or grievance, to be considered before the scale was re-established. these were sent to the employers, who replied by sending a counter list containing (if not as many) a very large number of questions. the federation board asked why they were making so many claims. these reasons were supplied, each section being taken _seriatim_. the various committees and the federation board were doing their best to get the settlement placed in the hands of some body of men, so that the scale might be rearranged. this advice was not accepted, for at a special council the power to settle was retained by the county so far as the miners were concerned. the reasons assigned by the owners in support of their claims were unacceptable to the board. they felt justified, they said, in refusing, but were willing to meet to discuss the respective alterations. the meeting took place, but it was found that the representatives of the miners could not proceed, as their council had refused to accept the scale until all the notices of men who were discharged for depression of trade were withdrawn and all the pits recommenced. "the owners said that such a thing was an impossibility, seeing that a want of trade was the only cause of pits being stopped and men dismissed. if the pits could be worked they would work them, but this they could not do in consequence of the terrible depression of trade. it was nonsense to say that the pits were stopped by an arrangement among the owners. that was a monstrous absurdity." these remarks were sent out to the miners with a most earnest appeal not to delay the matter any longer, because it could only result in danger. a form accompanied the circular upon which the lodges were asked to vote whether they would place the question of a sliding scale in the hands of the federation board. this appeal was successful, and the board was instructed to proceed with it by a majority of . at the earliest possible moment a meeting was arranged, and the scale agreed to on the lines of the previous one, to commence on st august , and to continue for two years certain, subject to two calendar months' notice. but such notice was to be given on a date to permit of a termination on the st of july. this fourth sliding scale was similar to the third one, which appears on page , so we need not reproduce it. second relief fund the formation of the second relief fund was forced upon the county by the fact that there were so many men out of work, and their poverty was a peril to those who were in employment. men's necessities are a strong force, oft compelling them to do things they would otherwise shrink from. it was thought, therefore, it would be sound economy to ease off the poverty, if luxury could not be afforded, and thus save men from overcrowding the labour market, or at least from accepting conditions which, if once established, would prove a general injury. then there was a feeling of sympathy for the distress seen on all hands, and a desire to alleviate, if not obliterate it; for the miners of durham may have little, but they never hesitate to share it. they are not the men "who, seeing their brother in distress, shut up their bowels of compassion against him." the sight of distress, or a knowledge that someone is in danger, never appeals in vain. the council meeting held on may rd, , dealt with the question of providing for the relief of those men who were discharged through depression of trade. it decided that a special council should be called on the th for the purpose of discussing the best means, and in the meantime suggestions might be sent in--"motions of all kinds, including levies, to be admissible." without describing these in detail, suffice it to say that there were eighty-eight in number, covering all phases of the subject, both as to means of raising money and amount of benefit. the council decided for a levy of d. per full and ½d. per half member per fortnight. that £ should be advanced from the general fund, to be redeemed by the levy, and "that the amount of money the levy will bring be equally divided by the executive committee amongst the men idle or who may be idle." it was soon found that the income from the levy would not give anything near s., and often it was found to run as low as s., per week. wheatley hill "putt pay" as this, although belonging to an individual colliery, is yet of a peculiar character, it will be well to note it here. on the pay friday falling on april th it was found that the company had become bankrupt, and the wages of the workmen were not forthcoming. this being the second occasion at these collieries, and only half the amount for the previous occasion having been paid, there was great consternation, and the presence of an agent was urgently requested. the treasurer immediately went out, and found the people ready for a riot. this, of course, was to be expected. mr ramsay, the agent of the colliery, desirous to meet in part the wants of the people, sold a branch engine, but when the n.e.r. engine came to take it away men, women, and children commenced and pulled the rails up, thus keeping both engines as it were in "pound." it was arranged that there should be a mass meeting the next day (saturday), and the treasurer was to attend to persuade the men to allow the sale to proceed, and accept the money as an instalment of their wages. the meeting was held in a field. the day was fine, there was a large crowd, and the treasurer was in his most eloquent mood, when a very laughable incident occurred. there was a pigeon-flying match from newcastle to thornley. it was about the time when the birds were expected. some of the men were watching the heavens more closely than they were listening to the speaker or at the time thinking about their wages. just when the orator was in the midst of one of his best sentences a voice was heard (which was the descent from the sublime to the ridiculous): "haud thee hand till th' 'slate cock' comes in." in a moment speaker and occasion were lost, and the gathering generally watched the bird, hero of the hour, as, like an arrow shot from some great bow, he came right on to his "ducket." then in deliberate manner the same voice was heard exclaiming: "there, he's landed; thoo can gan on wi' thee speech." but rhetoric and reason were both ineffective after the "slate cock" had landed. the executive committee, however, were quick in their action, and put in men as bailiffs at each colliery to prevent anything being taken away. after a year had been taken up by the process of law, and £ spent in money, the entire wages, slightly over £ , with the colliery pay sheets, were handed over to the treasurer. that sum included the wages of union and non-union men alike, and was paid to all with this difference, that the members got their money free of cost, but the non-members were charged s. each towards the cost incurred in procuring the money. this sum was all paid out as per the pay sheets. the last man to turn up was five years after. industrial remuneration conference--extension of the franchise--labour representation--lloyd jones in january a peculiar but very useful conference was held in london. it was, and is, known as the "industrial remuneration conference." in the preface to the proceedings, which were published, we are told why the conference was called. "in the spring of , a gentleman of edinburgh determined to devote a considerable sum of money to the purpose of keeping before the public mind this vital question, viz.: what are the best means, consistent with justice and equity, for bringing about equal division of the daily products of industry between capital and labour, so that it may become possible for all to enjoy a fair share of material comfort and intellectual culture, and possible for all to lead a dignified life, and less difficult for all to lead a good life?" for the purpose indicated he gave £ , vested in seven trustees, mr t. burt being one of them. to the trustees there was a committee added, and mr crawford was, by the consent of the miners' council, amongst the number. that committee considered that the best means of carrying out the trust was by organising a conference and inviting all sorts and conditions of opinion. there were two main branches of inquiry: "is the present system or manner whereby the products of industry are distributed between the various persons and classes of the community satisfactory; or if not, are there any means by which that system could be improved?" these general propositions were divided into many branches. the purpose of this historical outline is served by mentioning the connecting link being mr crawford's appointment on the committee. the chairman of the conference was sir c. dilke. while these important industrial matters were taking place the political affairs had not been neglected. the franchise association had kept up a close and instructive agitation not only at home, but outside the county, pressing the demand for an assimilation of county to borough. they urged that it was a glaring anomaly for a man to be eligible to vote in a borough, and because he passed over an arbitrary line (yet in all respects the same man in trade and duties of citizenship) he was not permitted to do so. at the trades union congress held in nottingham in the following resolution was proposed by the representatives from durham:-- that, without accepting an equalisation of the county with the borough franchise as a final solution of the great question of parliamentary reform, this congress is of opinion that the government should lose no time in introducing their promised measure, and calls upon the organised trades of the country to assist by every means in their power in promoting the popular movement in support of this long-expected reform, and authorises the parliamentary committee to join with the durham franchise association and other associations of all kinds in the proposed deputation to the prime minister. the result of this resolution was the reception by mr gladstone of a very large deputation, representative of all the trades unions in the country, on january rd, . three speakers--j. arch, a. wilkie, and j. wilson--were selected, and they received the assurance that the government would introduce the bill. it was introduced, and occupied nearly the whole of the session; was carried through the commons, but was defeated by the lords, or as mr gladstone said, they put "an effectual stoppage on the bill; or in other words, they did practically reject it." the liberals, however, were determined that the matter should be settled, and for that purpose summoned an autumn session. by the tact and eloquence of the prime minister the great measure was carried in spite of the most bitter opposition, in which constitutional means were stretched to their utmost limit, and the deepest depths of vulgarity were ransacked for the foulest epithets to use against the working classes, some of whom appear to have very short memories, as they forget this and other great acts done for them by the liberals. the passing of the act did not take the miners of durham or their colleagues over the tyne by surprise, but found them expectant, and ready to use their newly acquired power. the twelve years of the teaching of the franchise association bore fruit at once. during the summer of numerous district meetings were held. the miners' executive and the committee of the franchise worked together. the two great questions were the political right withheld and the action of the irresponsible house of lords in thwarting the will of the nation as expressed by the duly elected representatives of the people. the th of october was the appointed day to hold district meetings simultaneously all over the county. the people were urged to make them a success. the committee was appointed to take charge, and the owners were notified that all the collieries would be off on that day. the whole county was in a political fever. john morley had uttered his memorable words, which have passed into one of our epigrams: "end them or mend them." the political creed of the progressives was "down with the lords" and "faith in gladstone." one sentence may be quoted from mr crawford's circular of that time: mr gladstone and the government deserve the highest praise for their action in this matter, and with the support of the people they will yet carry the bill against the organised and determined opposition of a class of men who have amassed immense wealth by, in past times, taking that which belonged to the people. the practical effect of the act in durham was seen on january th, , when the federation board called a special council to consider the following programme:-- programme, ( ) shall there be labour representatives? ( ) if so, how many? ( ) if it be decided to have labour representatives, who shall he or they be? ( ) the ways and means of supporting such person or persons from the associations. ( ) what should the salary of such man or men be? ( ) should we nominate men other than labour representatives? that is, men who hold similar views to ourselves, but who will pay their own costs, both in contesting and otherwise. ( ) if this be done, who should they be? ( ) the selection of divisions. the resolutions come to were--( ) there should be labour representatives; ( ) there should be _bona fide_ labour candidates selected from the workmen, but run in connection with the liberals; ( ) the candidates should be j. wilson, w. crawford, and l. trotter; ( ) the ways and means should be left in the hands of the federation board, and that the salaries should be £ per year. on the same day the board met, and decided to select the bishop auckland, mid-durham, and houghton-le-spring divisions--mr trotter for bishop auckland; mid-durham, w. crawford; houghton-le-spring, j. wilson. they further decided to inform the north and south durham liberal associations what had been done, and asked them if they would co-operate with the board. a meeting between the representatives of the liberal associations, the federation board, and the franchise association was held in the county hotel, durham, when the following resolutions were agreed to:-- resolutions, that it is highly desirable for all sections of the new electorate to arrange for the object of securing the return of liberal members at the next election, and that this meeting is prepared to give support to the persons nominated by the miners' federation board, providing their candidature is endorsed by the liberals in each division. that this meeting requests the constituencies to form liberal organisations, and that small committees from the south and north durham liberal associations, the federation board, and the miners' franchise association be appointed to aid such organisations. _january th, ._ so far as the mid-durham and the houghton divisions were concerned, all went on smoothly. the candidates were accepted with complete unanimity, but in the auckland division the feeling in some quarters was in strong opposition. the board were asked to withdraw mr trotter, which they refused to do. there were other two gentlemen in nomination, and he was asked to put himself in competition with them, and if rejected retire. he refused, and they, the board, approved of his refusal, and arranged a meeting of the lodges in the division for the purpose of explaining the situation. at this point there arose a complication of a different order. at their meeting on october nd, , the board decided "that each candidate must be responsible for the returning officer's fees in their respective divisions." shortly after this was made known mr trotter withdrew, the reason assigned being the refusal of the board to pay the returning officer's fees, although all the candidates were treated alike. as a consequence the division was vacant, and open to any candidate. this only need be added, that at the general election in november mr crawford and mr wilson were both returned by great majorities--the latter being defeated in , but succeeding mr crawford in as the member for mid-durham. this may be a fitting place to try to remove a false impression, which has lingered in some minds unto this day, as to what they are pleased to call "the shameful treatment" of mr lloyd jones, while in the chester-le-street division, by the federation board. there never was a grosser misstatement. the board did nothing but what was fair and honourable throughout the whole proceedings, although they were made the object of a somewhat bitter attack by _the newcastle chronicle_, which attack was entirely founded upon a too slight knowledge of the facts. as mentioned above, an arrangement was made whereby the workmen were to have their divisions undisputed, and with the rest there was no claim for interferences set up. mr j. (now lord) joicey was selected by the liberals for the chester-le-street division, the federation board having no part or lot in the transaction. mr jones, who was an intimate friend of mr j. cowen, was brought out, it is well known, as mr cowen's nominee, and as such, contested the division. the board, as such, did nothing in it in any way. if they had, their action would have been dishonourable in the light of the agreement. this, however, they did do: as soon as mr trotter withdrew from bishop auckland, they sent a deputation to interview mr jones and to make him an offer of that division. the writer was one of the deputation, and with the others did all possible to persuade him, but he refused. it was felt he was not free, or he would have accepted. this can be said without fear of contradiction: the board as a whole regretted the refusal, for mr jones was a great orator, respected very much by the miners in durham, as witness their continual choice of him for their arbitration cases, and he could have had a safe seat. - in dark days--the eight hours--the sliding scale--advance of ten per cent.--second advance of ten per cent.--death of the scale--the county council the year passed over uneventfully, and in a routine manner, except in the matter of trade, which continued very much depressed, and wages very low. at the beginning of the average selling price at the pit mouth was s. . d. the relief fund (even with the principle of division of income) was in debt to the general fund £ , s. d. as per the balance sheet for quarter ending december . the condition of trade was so bad generally that a royal commission was appointed to inquire into it, the present county court judge of durham being one of the members. he differed from the majority report, and signed a minority report. this objection was in relation to the fragmentary character of the evidence. in the coal and iron industries the witnesses were entirely from the employers. without stating the whole of his able report, dealing as it did with every phase of our industrial life, a portion may be mentioned. four causes of depression and low wages upon which he laid emphasis, were the land question and the royalties, way leaves and dead rents. those who hold the land, claim these from the employers and employed who risk their capital and their lives to get the mineral which he, as landlord, does nothing to assist. in the midst of the dark times the executive committee was compelled to face two evils: a small banking account, and a heavy expenditure. the banking account for the quarter ending december was £ , , exclusive of the deposit and shares in the industrial bank, which amounted to £ , but which were nominal and, so far as use was concerned, simply on paper. in addition, there was a sum nearing £ invested in buildings. in a short circular the committee placed the whole financial position before the members. for the year the income was £ , , with an expenditure of £ , . "you will thus see that we cannot exist long at the rate of £ on the wrong side of the ledger. soon all our funds will be gone, and nothing left for the members who have paid so long." they were compelled by rule to keep £ , in the funds, and were therefore driven to consider two propositions: either to increase the subscription by d. a fortnight or reduce the benefits. for that purpose they proposed to call a special council to consider the questions. the reductions suggested would reduce the expenditure by £ per quarter. at the council meeting an all-round reduction of s. per week for sickness, breakage, strikes, and sacrificed allowance was made, and £ off the death legacies, to take place from the rising of the council, which was held on th april. happily, however, the trade began to turn and the position of the association to amend, for on august th a slip was sent out informing the members "that the funds have so far recouped as to enable the society to pay all benefits according to rule from monday the th." the eight hours--a restriction on october th, , and three following days a miners' conference was held in edinburgh. the main purpose of the conference was the limitation of the output. there were a large number and variety of propositions discussed: five days per week, a week or fortnight's holiday, and the eight hours per day. part of the resolution on the last question was in words that have become familiar to durham in these later years: "that no miner be allowed to work more than eight hours in the twenty-four." the first resolution on the question did not appeal to the state, but on the fourth day it was brought forward containing an appeal to the legislature, and carried. the position of durham was the same then as now ( ), and the opposition of to-day is based upon the thought of that day. before the conference was held the executive committee gave their opinion upon the various questions on the programme of business. on the eight hours they said: eight hours' resolution _eight hours._--this is to be sought for by act of parliament. to seek to fix the hours of men by act of parliament is, in the year , a monstrous and illogical proceeding. if you fix the working hours by act of parliament, why not fix the rate of wages also? in the old feudal times wages were so fixed by act of parliament. under such laws, men were serfs and slaves, and became as much the property of their employers as the horses that filled his stables. to demand eight hours, and even less, is in the hands of all men if they will only utilise their own organised power. but if such an act were passed, it would result in our own county in one of two ways, ( ) the turning off of , or , hands; or ( ) the adoption of two shifts of hewers, and two shifts of offhanded men and lads, and thus increase the hewers' hours by one hour, and, in many cases, one and a half hours per day. again, if you seek by act of parliament an eight hours' bill, it logically follows that you regard eight hours as the number of hours men should work. in such a case, you endanger your own position, and would strongly tend to bring upon you an eight hours' system. but why is this sought? it is sought because men are indifferent, apathetic, and consequently disorganised. if this law passed to-morrow, it would be an inducement to indifference and disorganisation, and as such materially injure you. in september the trades union congress decided to take a ballot of all the unions on the general eight hours. the questions submitted were: should an eight hours' day be sought; if so, by what means, by trades union effort or by law? again the executive committee advised the members to vote against it, which they did. "if this became law to-morrow," they said, "you could not make it operative. to do so you must turn off some thousands of coal hewers, or have two shifts of offhanded men and boys, and draw coals sixteen hours per day instead of as now drawing them ten and eleven hours. if this be sought it follows by clear implication that the men voting for it regard eight hours as a normal and fair time to work per day." the congress of decided in favour of eight hours by law. the question came again before a miners' conference held in birmingham on th october . there were three items discussed: "the international miners' congress, an advance in wages, and the eight hours." the delegates from durham, mr j. johnson and mr j. wilson, drew up a report of the proceedings, which was sent out to the members. they were sent to the conference with definite instructions from the council: "that we don't take any part in the agitation for an eight hours' day for underground workmen." the representatives in the report say: beyond that we could not (nor desired to) go. when the conference came to discuss the question we laid our position before the meeting, and told them we could not take any part in the agitation. we make no remarks about the sarcastic reflections which were made by some of the delegates on our position. they were no doubt natural reflections, although their repetition was galling, and evoked from us replies which were not of the calmest order. we stood firm to our instructions, and abstained from either voting or speaking, except in self-defence. the conference resolved that on the st of january all men and boys represented there should commence working eight hours from bank to bank. northumberland and the forest of dean voted against, with durham neutral. then followed a resolution pledging all the districts to give in notices to terminate with the year. this placed the conference in a dilemma. they were ready to pass resolutions, but few were prepared to say their members would give their notices in for it. then it was decided to take a ballot and hold another conference in november. at our council meeting on november th it was decided not to be represented. the sliding scale the programme for the council to be held on february nd, , contained a resolution asking for a ballot to be taken for or against the sliding scale. in their notes on the questions to be discussed the committee strongly urged the maintenance of the scale. it steadied trade, made work and wages more regular than any other means. where sliding scales existed the districts were in better condition. they (the committee) were as much interested as the members. the gain or loss was alike. having fully considered the question they were convinced that it was the most just and equitable way of fixing and settling wages. the resolution to ballot was carried. about the same time the mechanics decided to give notice to have the scale amended. the federation board not only found themselves called upon to consider the scale, but they had to deal with a demand for an advance in wages. a meeting was held on june th. the employers placed before the board three propositions: arbitration, two and a half per cent. to commence on july st, and two and a half on september st. these advances would raise the wages to ten per cent. above the standard, or they were willing to arrange for a new scale. the board were reminded that the scale would run until july st, and therefore their application was in violation of that agreement. these offers were recommended to the members, with a request that they, the board, should be vested with full power to negotiate a settlement, which should be submitted to the county. the offer and request were refused, and another meeting took place on july th. the employers then modified their offer, and were willing to give five per cent. advance for the months of august, september, and october, and a further five per cent. for november, december, and january, or they would refer it to open arbitration. again the question was submitted to the members. the board said: "there were three courses to pursue: accept the owners' offer, go to arbitration, or ballot the county." of the three they strongly preferred the offer, as to take the ballot was a repudiation of arbitration as a means of settlement. arbitration was a lingering and uncertain course. it would last three months, and they would thus lose for that time a clear five per cent., or something like from four to five thousand pounds per week in wages. "remembering all the difficulties which now surround us, and looking at all the facts, we would very strongly advise you, as men alike interested with yourselves, to accept the offer the owners now make." the reply of the county was to demand twenty per cent. advance. the federation board was driven to take the ballot. the result of the ballot was for pressing the demand, and the miners' executive made preparation for giving in the notices on august st. the employers made another offer: instead of giving two fives they offered a full and immediate ten per cent. durham coal owners' association the owners' wages committee is unable to recommend its association to give an advance of per cent. the actual invoice price of coals and coke has not yet materially advanced. recent contracts at high prices can only have a gradual and deferred influence. the owners have already given a special advance of per cent., which has been in operation less than four months. any advance which they now give must, like that previous advance, be in anticipation of the higher prices which will alone allow of higher wages being paid. they are willing to stretch a point in this respect in the expectation that wages will be thereby settled for a period which will allow of equivalent prices being actually realised, but they are not prepared to do more than recommend a general advance of per cent. on the basis rates, to take effect in the first pay commencing after the date of acceptance of this offer. reginald guthrie, _secretary_. newcastle-on-tyne, _november rd, ._ the federation board urged the acceptance of that offer. "everyone (unless it be the unobservant and inexperienced) must be fully alive to all the dangers to our social, and it may be our permanent condition, which always follows a strike, such as we should have in this county. it does not mean a few hands, but the entire county, comprising , folks laid commercially prostrate; and who can conceive the social and moral disaster arising from such a state of things." they felt confident that it would be for the good of the whole county, for they would reap an immediate and certain gain of from £ to £ , per week. the ballot was taken. the miners' vote was in favour of a strike, but the whole vote of the federation was in favour of accepting the ten per cent. within three months of the acceptance the miners' council on september th decided that the committee should demand a further advance of fifteen per cent., to commence on november st; if refused, the county to be balloted at once. that request was forwarded to the employers from the federation board. they were informed that, after very carefully considering the improved condition of trade and the increased prices at which coal and coke were sold in the open market, the board considered that they had a just claim for an advance of fifteen per cent. the reply of the employers was contained in the following resolution:-- the owners' association, taking an account of the fact that the ascertained price of coal for the quarter just ended is only s. . d. (or . d. above the price of the previous quarter), is not prepared to give an advance approaching that which is asked, but is willing to appoint a committee to confer with the federation board, having full authority to negotiate for a settlement of wages, to begin at such a date, and extend over such period, as may afford a reasonable opportunity of actually realising those higher prices which would alone allow higher wages to be paid. the question arose whether the miners should seek the advances themselves or through the medium of the federation board, as that was the only regular and effective means. it was at the same time pointed out to the workmen that their claim for the fifteen per cent. was in violation of the understanding that three months must elapse from the date of a previous change before a new application could be considered. the voting on the body to negotiate resulted in favour of the board, but there was a further question to decide. what was to be the line of procedure? had the board to make the best settlement, or should they press for the full fifteen per cent., and, if refused, the members be balloted? the miners' special council voted by a large majority for the full demand or strike, the voting being for strike and for placing the power in the hands of the board. it was found that the other three sections had remitted the question absolutely to the federation by large majorities, and the miners' executive naturally felt the advance was being delayed for weeks, whereas the board might have settled it, and the workmen have got an early increase in wages. it was, therefore, felt imperative that the miners should be asked to reconsider their position, seeing that in the other sections there was unanimity. the committee resolved to again submit it to a council meeting, but there was no change, the instruction of the previous one being repeated, the majority being slightly decreased. that council was held on november th. the federation board met the same night, and on the th mr crawford handed mr r. guthrie (who had been appointed secretary as successor to mr bunning, deceased) a request for a meeting. that was fixed for the rd of november. when the board met the owners they were asked what power they had, and the reply was simply to ask for the fifteen per cent. mr l. wood, the owners' chairman, then said: "we only agreed to meet the federation board on condition that they had power to settle the entire matter. have you that power?" the board had to give the humiliating answer: "no." an adjournment for three hours took place, when an offer of ten per cent. was handed to the board. they then resolved to take a ballot of the whole of the sections, the decision being to accept the offer. there are two remarks necessary anent the industrial matters of --first, the termination of the sliding scale, which happened on the st of july; several attempts were made to revive it again. the latest in the year was a new scale submitted by the enginemen's association. it was drawn up by mr t. hindmarsh, the treasurer of that association (who was a very useful man), but it was never proceeded with. the scales had been in existence twelve years. the misfortune was that the trial of the system took place in a series of years which covered the most unbroken period of depression within the experience of the association. the ascertainment showed that prices never reached (except at the last stage) higher than s. per ton, being most of the time below s. d. we are so much inclined to judge from appearances and not righteous judgment that the blame for bad trade was thrown entirely upon the scale, as if its existence or non-existence could influence the coal markets and their prices. to the superficial observer the collateral conditions of the scale would appeal with force; but men who look at the fitness of things, and who do not measure that fitness by a small period or single phase of our industrial life, are fully aware that all kind of trade seasons are required to supply a proper test--these recognise that the scale, with proper adjustments, is bound to be an equitable means of adjusting wages. there was this coincidence which strengthened the position of the objector: the scale ended just when a boom in trade set in, and many men believed that it had been the incubus which had in an evil manner weighted the trade and kept wages down. "see," they said, "how the conditions have altered since its removal, and shall we not be foolish if we give it another lease of life?" the second remark applied to the delay in securing the advance through not trusting those at the head to negotiate a settlement, and this in spite of urgent appeals. this remark applies not merely to the distrust of that day, but to all such occasions. the foolishness is not merely for a day, but for all time. it is a great check upon men's ardour to find themselves doubted, and it is a grand incitant and inspiration to feel they have the confidence of their people behind them. if a leader is not such as can be relied upon to do his best he is not fit to be in the position. generals win battles most assuredly when the men trust them. there is always danger when with suspicion those in the ranks are watching the head. the county councils' act for a considerable time prior to there had been a great desire amongst the people for a more active part in local affairs. this was running currently with the national and parliamentary idea. the opposition which reared itself against the national was found striving to prevent an extension of home affairs. it was in relation to this that the marquis of salisbury, "that master of jeer and gibe," said what the people wanted was a circus, as they were more eager for that class of amusement than seriously taking part in the management of parish or county business. however, as in the parliamentary suffrage, so in the transferring of the local affairs from the parish magnates and the petty sessions to the people; the spirit of reform, the friends of freedom, and the trustees of the people were too strong. those who were in power--the masters in the art of "grasping the skirts of happy chance"--those skilful plagiarisers of other people's ideas, calling them their original property, those who have always waited to be forced to do right, introduced and carried the "local government act." as the men of durham were eager and expectant in with reference to the extension of the suffrage--not merely eager to receive, but to use--so in relation to the county affairs, they were earnestly desiring to receive the long withheld right and to put it into operation. in this matter they were and are unique. the system of political teaching carried on by their franchise association had not been in vain. while in other parts of the country men had been at fever heat until they were incorporated into the electorate, and then lapsed into indifference or misuse, in durham the same keen zest was manifest after the passing of the act as before. between the royal assent being given and the time of operation a serious preparation took place. a very large number of meetings were held, and in a business manner the election was prepared for, with the result that about one-fourth of the new-formed council were working men, and fully seventy per cent. of the parish and district councillors were from their ranks. in this respect the county occupied a proud and peculiar position, for in no other county was any such use made of the act. instead of that, the lethargy seen in other counties was such as to justify the salisburian jeer as to the circus. it may be said without fear of contradiction that no selfish or ill use was made of the power thus gained. no county anywhere more needed reform in matters pertaining to the home life of the people, for in matters of convenience and sanitation the condition of many parts was deplorable. there was a general idea that these working men when they were placed in this responsible and new position, with the public purse to draw upon, would act the part of prodigals, and run into all kinds of waste. those who said that, based their reasoning on a very false position. they said (and no doubt believed) that the miners did not contribute to the rates, and therefore would rush into useless expenditure. some of the miners asked where the rates came from if not from them. the fear has been falsified. there was great need in the home surroundings for rushing, but with all that, gradual reforms were the order of the day, and no one suffered. another advance sought--death of mr crawford--the ten hours' drawing and hewers' hours--the second advance--international miners' conference this year opened with another claim for an advance. in the federation minutes for january th is the following:-- that the secretary write to the secretary of the coal owners' association asking a meeting requesting an advance of per cent. on all classes. that motion was the outcome of a resolution passed at the miners' council on the th. not merely was the amount of advance named, but the st of february was to be the date of its commencement, with the alternative that the ballot be taken if it were refused. the board met the owners on the st of january, when they were given the following resolution:-- the durham coal owners' association is unable to make any further advance in wages unless, or until, a much higher invoice price of coal is realised than has yet been attained. the owners' accountants have ascertained the selling price for the last three months (ending december st, ) and they certify the net average invoice price to be s. . d. this, according to the recent sliding scale agreement, would make wages ¾ per cent. above the standard of . wages are, as a matter of fact, now per cent. in advance of that standard brought up to this point, by the special advance of per cent. given only or weeks ago, in anticipation, as the owners then declared, of higher prices yet to be got. the owners invite the federation board to verify these figures, and to join in a further ascertainment for the first three months of this year, with a view to thus determining whether any advance in wages is justified, either now or in april next. the owners regard it as all-important that the men employed in the collieries in the county of durham should be afforded, and should avail themselves of, an opportunity of correcting the serious misapprehension under which they labour from regarding the prices quoted in the newspapers for what is but a small proportion of the output as representing the entire volume of trade. lindsay wood, _chairman_. coal trade office, newcastle, _january st, ._ the federation board resolved to submit the question to a ballot, as it was found that the miners were not in favour of either joining the owners in an ascertainment, or allowing their representatives to meet the employers. the result of the miners' ballot was most perplexing. at that time there were only , full members, and of these only , voted for a strike, those against the strike and neutrals amounting to , . taking the federation as a whole, the situation was unsatisfactory. for a strike there were , , and against , . there were more than , unrecorded votes. under these circumstances they considered their best policy was to call sectional councils, to be held on february th. the voting at the miners' council was a very large majority for giving in the notices on the th. the federation board met on the same day, when it was found that the enginemen refused to give in their notices; but the board decided that the other three sections should tender theirs, and the owners should be informed of the same. great regret was shown at the refusal of the enginemen. mr crawford, acting on the instruction of the board, at once notified the employers, and received from them a long reply. they were surprised to find no reference made, either in the letter or in the submission to the members, as to the joint ascertainment of the selling price of coal. they reaffirmed their statement that the average price did not warrant the advance. if a strike were entered upon, the responsibility would rest with the side which refused to avail themselves of the full opportunities offered for ascertaining the condition and prospects of the trade. they were prepared to consider whether by arbitration, or by any other course, a strike might be averted, and they invited the board to meet them again on february nd. at that meeting the owners offered an advance of five per cent., making the underground men thirty, and the surface men twenty-seven, per cent. above the standard of . another ballot was taken--( ) upon this offer; ( ) open arbitration; ( ) strike. the result of the ballot was to accept the offer of five per cent. on the th of may another demand was made for fifteen per cent. advance. this meeting was in response to a letter sent by mr crawford from the executive committee notifying the employers of the demand. this they could not accede to. their reasons were the serious reaction which had set in in the coal trade. whether it would continue, or there would be a recovery, was uncertain. the most they could offer was to leave wages where they were, and reconsider them in a month. for some time there had been a growing desire for shorter hours, and it was felt by some of the leaders of the union that instead of pressing for wages it would be better to devote all their attention to the shortening of the hours, and even going so far as giving up the advance. in keeping with that idea the question was introduced to the owners; but the executive felt that these two subjects were too much for successful consideration at the same time, and they therefore asked the lodges to send delegates to a special council on may st to say whether--( ) they had to press for the entire programme--viz. fifteen per cent., with ten hours' drawing and seven hours from bank to bank; ( ) should the cases be separated; ( ) which one should be preferred. finally, it was agreed that the claim for an advance should be withdrawn and the whole attention of the county placed upon the shortening of the hours. a more beneficial decision has never been come to in the whole of our history. in this case time has meant money, and has proved the wisdom of applying the spirit of compromise and arrangement to these matters by men who know the technicalities of the trade. death of mr crawford we must stay our record of industrial changes to consider a serious blow which fell upon the association in the death of mr crawford on july st . it was a blow the force of which can only be realised by those who were intimately acquainted with him, and whose good fortune it was to be colleagues with him. never yet had an association a stronger or more capable leader. to see him at his best one had to be with him in a complex question and in a committee. he was not an eloquent orator, moving men's minds by speech, but he was a pilot skilful in guiding their affairs through the perilous times. no man was ever more attacked by men who were never able to reach his excellence in the sphere of life in which he was placed; but this was always certain, those who made the attack were sure to receive cent per cent. in return. his ability was only fully known by those who were in close contact with him. his temper was sudden, fierce for a short time, but soon burnt out. ofttimes, therefore, he was apt to give offence. he had his failings. is he to be for that condemned, for where is there a man without them? the pecksniffs of life may pose as being pure, but _men_ know how far they fall short of that state. pure spirits are a terror to common mortals, and beyond their reach, and especially to men whose lives, like crawford's, are cast amid the complexities and complications of an earnest trades union leader. let us place on record the opinion of his colleagues in the circular notifying the county of his death: "it is our sorrowful duty to announce to you that mr crawford died this morning at a.m. on this occasion our words will be few, but they must not be taken as the measure of our feelings. we are in a position which enables us to form an estimate of his worth to us as secretary of our association, and we are therefore the more fully conscious of the loss sustained. he has died doing his duty--as he was at newcastle at joint committee on monday the th of june, and took part both in discussions inside and settling cases outside. he went to that meeting in opposition to the persuasions of his colleagues, who saw the delicate state of his health, and how dangerous it was for him to go to the meeting." he died comparatively young, aged only fifty-eight. if any of the young men want to see his style let them turn to his circulars, which are scattered profusely through our documents. he had been feeble for some time before his death, but when in health he was ready and vigorous with his pen. he passed from us, but his work still lives, and will live so long as the durham miners' organisation remains; and if the workmen in folly should allow it to fall, then the work he did for them will be their greatest condemnation. the vacancies caused by his death were filled up by mr patterson becoming corresponding secretary, mr wilson being made financial secretary, and mr johnson being elected treasurer. the political vacancy was supplied by the nomination and election of mr wilson for mid-durham. [illustration: john johnson, m.p.] the shortening of hours at the executive committee meeting on july rd this matter was under discussion, and it was resolved to ask for a meeting with the owners "on the seven hours' and ten hours' drawing." the interview did not effect a settlement, and the committee decided to ballot the county. it was submitted as "strike," "no strike," and the result was, for strike , , with against. this result was sent to the employers, with a request for an early meeting. it was held on august th. the original request was a reversion to the hours worked prior to mr meynell's award: "foreshift men to go down at a.m., back-shift to be loosed to commence to ride at p.m., and no colliery to draw coals more than ten hours per day, for two shifts of hewers. the drawing hours in the night-shift collieries to be in proportion to the day shift." in that request there is no mention of the seven hours. this omission the committee explained. if they had asked for seven hours they would have lengthened the hours of those men who were loosed by their marrows in the face. in their opinion the plain request of seven hours would have increased the hours in those cases on an average of at least half-an-hour per day, and would have compelled a system of overlapping in all such cases, because a signed agreement would supersede all customs. as a counter proposal the employers submitted the following:-- _august th, ._ seven hours' and ten hours' coal drawing the owners' committee offer as a settlement that hewers' shifts be on an average of foreshift, and back shift not more than seven hours, reckoned from the last cage descending to the first cage ascending, and from the last cage descending to the last cage ascending; the present coal-drawing arrangements remaining unchanged. the custom of shifts changing in the face to be maintained. failing the acceptance of this offer, the owners' committee propose that the whole question of hours be referred to arbitration. you, on the other hand, have urged that there should be simply a return to the drawing hours, and arrangements consequent thereon, prevailing prior to mr meynell's award in april . it will be the duty of the owners' committee to report this to a general meeting, but in order that that meeting may fully understand what such a proposal means, it is necessary to obtain information from each colliery as to its hours and arrangements prior to april . the owners' committee will proceed to ascertain this, and it suggests that your deputation meet the owners' committee on friday, the th inst., at . , for a further discussion prior to the owners' general meeting which will be called for this day fortnight. yours faithfully, reginald guthrie, _secretary_. the whole subject was placed before a special meeting, and sundry questions were asked. should the question stand adjourned as the owners requested? should the seven hours be withdrawn? should the owners' offer be accepted? should arbitration be offered? should the notices go in; if so, when? the conclusions of the council were to wait for another meeting with the employers, and to withdraw the seven hours as a separate question. at the meeting held on august th the employers placed before the committee their proposals. their chief objection lay in the serious loss of output which would follow a reduction of one hour in the coal-drawing time. in any case it would be impossible to bring the change into operation till the contract engagements could be adapted to new conditions; that the change should not take effect till the first pay in january; that if there were a reduction in hours there should be a proportionate reduction in wages; that the committees of the two associations should have full power to settle certain points: "mode of reckoning the hours in ten and twenty hour pits; for coal drawing; for offhanded men and boys above and below ground; arrangements in cases of accidental stoppage; drawing hours on saturdays; changing at the face; 'led tubs'; travelling time in relation to distance; co-operation of miners in making the ten hours of coal drawing as full and effective as possible." the council meeting before which these were placed decided to accept the owners' offer of ten hours, to operate on january st, , and that the executive committee meet the owners, with full power to settle the conditions. the appointment of the committee resulted in the "ten hours' agreement," which need not be inserted here, but a difference arose as to the number of hours the double-shift pits should draw coals. finding they could not agree, the committees arranged to refer the matter to an umpire, and two on either side were appointed to place the case before him. the umpire chosen was mr j. r. d. lynn, coroner in northumberland. he decided as follows on december nd, :-- durham coal owners' association and the durham miners' association _re_ drawing hours of double-shift pits whereas, by an agreement between the durham miners' association and the durham coal owners' association, the question of whether the coal-drawing hours of double-shift pits should be or hours per day was left to my decision; mr hall and mr parrington on behalf of the owners' association; and mr forman and mr patterson on behalf of the miners' association. now having taken upon myself the said reference, and heard what was alleged by messrs hall and parrington and messrs forman and patterson, on behalf of the said parties respectively, and having heard and considered all the evidence produced to me, and duly weighed and considered the terms of the request of the miners' association, contained in their resolution of august th, --the terms of the offer of the owners--the terms of the agreement or qualified acceptance of the owners' offer by the council of the miners' association--the agreed working hours of the datal men and boys--the time occupied by the different classes of men and boys descending and ascending the pits--the prevailing custom of the county and all the matters and things bearing upon the question referred to me--i am forced to the conclusion that the drawing hours of double-shift collieries can only be reduced in proportion to the agreed reduction of the drawing hours of the single-shift collieries, and not in proportion to the number of hewers' shifts; and now make and publish this, my award, in writing, as follows:-- i do award and determine that the coal-drawing hours of double-shift pits shall be twenty hours per day. j. r. d. lynn. _dec. nd, ._ the negotiations were complicated and a settlement hindered by the action of the wearmouth lodge. it arose out of the seven hours' resolution. when the council carried the resolution that the hewers' day should be seven hours, that lodge, without waiting for any general action on the question, commenced to put it into operation. we need not mention the circumstances beyond saying that the colliery was on strike, causing great friction between them and the committee, and delaying a settlement of the general question, although they were told repeatedly that they were violating rule, and retarding progress. before the hours agreement was come to another advance was asked for. as usual, it emanated from the miners. the amount claimed was twenty per cent., and again the date was fixed for commencing, with the alternative of the ballot, and notices if refused. the resolution was brought before the federation board, accepted by them, and sent on to the owners, with a request for an early meeting. the discussion on the subject took place on october th, when the employers said: "as the application was based upon an alleged increase in the price of coal they must have time to verify the price by the accountants' ascertainment, and as soon as this was done they would meet the board and give a definite answer." the federation board, feeling the anomaly of their position, and being loath to meet the owners with restricted powers, resolved to ask their constituents to give them full power to negotiate as to the amount of the advance. the result of this voting was a large majority in favour of placing the whole matter in their hands. as soon as possible (november th) a meeting with the employers was held. the first question asked of the board was what was the extent of their powers, and they, the owners, were informed the workmen had placed the matter entirely in the hands of the board to settle. this, the owners said, cleared the ground and prepared for a settlement, as they had resolved not to make any offer if such had not been the case. it was, however, ultimately resolved to give an advance of five per cent., making the percentage above the standard of thirty-five for the underground workmen, banksmen, mechanics, enginemen, and cokemen, and thirty-two per cent. for the surface workmen, the agreement to take effect with the pays commencing december th, , and january th, , according to the pays at the various collieries. by that arrangement the shortened hours and the increase in wages were simultaneous. before leaving we will notice a very important step taken by the miners of great britain --the holding of the first international miners' conference at jolimont in belgium. as this was the first of the series it will be interesting if we give the origin. the first idea originated in . in that year two labour congresses were held in paris: the marx or socialist, and the possibilist or trades unionist. to the latter the northumberland miners sent messrs burt and fenwick. prior to the meeting of the congress those gentlemen sent a joint letter inviting the miners' representatives attending either the marx or trades union congress to meet for the purpose of a friendly interchange of opinions on questions relating to the condition of the miners. some eighteen delegates responded, and the meeting took place in a dingy coffee-house in a back street. the interpreter on that occasion was miss edith simcox. the result was the miners of great britain were requested to take the initiative in the formation of an international. this request was conveyed to the central board of the national miners' union (mr crawford being at that time secretary). the matter was brought forward at a subsequent miners' conference at birmingham. the outcome was the congress held at jolimont in belgium in . - silksworth strike--claim for a reduction--the general strike--aftermath of the strike--the eight hours again the year opened with a strike at silksworth. it is mentioned here because of its being connected with, and being the last of, the disputes about the deputies. in order that there may be a proper understanding it will be necessary to retrace our steps a little. at the miners' council held on august th, , a resolution was carried giving the silksworth lodge power "to take the ballot with a view of giving in their notices to compel the deputies to join the union." the ballot resulted in the notices being tendered. they expired on november nd, and on november th, at a federation board meeting, it was reported that the dispute between the deputies and the lodge had been settled amongst themselves, and they were ready to return to work. this had been forwarded to the employers by mr patterson and mr forman, from whom they had received a reply acknowledging the receipt of the information. they having, however, been informed "that many of the deputies, non-members of the miners' association, have been compelled by coercion and violence to join that association, are not prepared to take any further steps with regard to the strike until they have consulted a general meeting of the owners, and this they will take an early opportunity of doing." mr patterson and mr forman wrote denying all knowledge of any force, reminding the owners that in all previous cases, whether general or local, the withdrawal of notices had always been mutual, and that they had instructed the workmen to present themselves for work. this action produced a deadlock, and three meetings were held between the federation board and the owners--on november th in durham, and on december st and nd in newcastle. the owners said they were convinced that some of the deputies had been driven through fear to join the miners' association, and therefore they could not sanction the resumption of work at silksworth until the federation agreed to provide for the security and freedom of the deputies who refused to join the miners' association pending the consideration of the question "whether it is consistent with the duties and responsibilities of deputies to belong to the miners' association, and that the deputies at silksworth should have the opportunity, under proper safeguards, of freely declaring whether they wished to remain in the miners' association." to these the workmen made reply that the action of the owners was against all former arrangements made between the two associations. "in every case that has taken place the men either before or after giving the notices have had to agree to resume work" before the urgency committee was appointed, and yet the employers were asking, in the silksworth case, to reverse that well-established practice, and were demanding that the pit should stand until a settlement was come to. that course of action the board repudiated, and expressed their willingness to join any body or committee as soon as the pit started. the employers then modified the claim, and asked that a joint committee should be formed, and the deputies who had been compelled to join the miners should be allowed to appear before that committee, and say whether they wanted to remain in such association. with that understanding the pit should go to work as soon as got ready, and the committee meet within the next three days, which would mean prior to work being resumed, except very partially. the board was willing to agree to form the committee. no settlement was come to, although strong endeavours were made. at last the employers decided to evict the men from the houses. the evictions commenced on february th, , and in all there were families turned out, many of whom found shelter with their friends and in the places of worship. to effect that purpose a very large contingent of police was drafted in from other parts of the country, with the usual accessories to these circumstances, the "candymen," to whom the occasion was a harvest, and just the kind of work their natures were akin to, and their minds eagerly desiring, and therefore ready to accept. there were most serious riots, and at one time a violent collision took place, between the crowd and the police. it was not the result of any action on the part of the silksworth people, but was owing to the presence of strangers. it was customary for the police to escort the candymen out of the village to a large house a short distance off, which afterwards was given the name of "candy hall" because of the use it was put to. on a certain night when the escorting took place, the police and their charge were followed by a large concourse of people, some of whom threw stones and various kinds of missiles. in a few instances the officers were hurt. this they bore until they got outside the village, when suddenly wheeling they charged with their batons upon the crowd, many of whom were seriously injured. before the whole of the people were evicted negotiations re-opened, and the proceedings stayed, which eventuated in the following agreement:-- it is agreed that the owners' committee advise the silksworth deputies who joined the durham miners' association after the notices were handed in to pay up at once their arrears of subscriptions to the present date, on the distinct understanding that they are to be at perfect liberty from this date to be members or non-members of the miners' or any other association pending the settlement of the general question of deputies between the two associations. on the arrears being paid work to be resumed at silksworth, seaham, and rainton, all men being reinstated in the positions occupied by them before work ceased. that ended the last of the privileges given to deputies. the claim for a reduction in the beginning of july the federation board met the owners. the employers had made a claim for a reduction on april th which the board met by asking for an advance. as this is the first of the series of events and negotiations which led up to the strike of it will enable us to better understand that occurrence if we record it in detail. at the meeting referred to, the employers said that as the board had asserted that the state of trade did not warrant a reduction, but, on the contrary, an advance, they would officially ascertain present and prospective invoice prices, and would then ask the board to meet and consider them. if that did not lead to an agreement they would ask that the question should be submitted to arbitration. the matter was delayed until november th, when another meeting took place. the following statement was handed to the federation board:-- owners' statement the durham coal owners' association feel that the time has come when they must press for a substantial reduction of wages. they are paying per cent. above the standard rates, whilst the ascertainment of selling prices for the quarter ending september th last brought out results corresponding with wages only ¾ per cent. above the standard. the excess measured in this manner is therefore ¼ per cent.; but prices are continuing to decline, and this should also be taken into account in considering what reduction ought to be made. the last advance of per cent. arranged in november , to take effect from january st, , was given in the expectation that prices were likely to rise; instead of this proving to be the case they have declined to an extent equivalent to a per cent. reduction in wages, thus placing the owners in a worse position to the extent of per cent. as compared with this time last year. this is the smallest amount of reduction that the owners feel ought to at once be conceded, and they are willing either to accept this as an instalment of the relief that the state of trade imperatively calls for, or to submit to open arbitration the question of what change in wages ought to be made. lindsay wood, _chairman_. coal trade office, _november th, ._ the board promised to place the statement before the members as soon as they had time to examine it, and at the same time they would send the employers a statement with regard to the application for an advance. nothing more was heard of the subject until the th of december, when the owners wrote to the federation board as follows:-- i am desired to ask you when the owners' association may expect the reply to the proposal as to the reduction of wages made to your federation board at the meeting on november th. this was brought before the board, when they suggested that the questions should lie in abeyance until the new year, after which they would be prepared to arrange for an early meeting. on january th, , the board met the owners' wages committee, when three propositions were handed to them--( ) an immediate reduction of ten per cent.; ( ) to submit to open arbitration the question of what change in wages ought to be made; ( ) to submit any proposal the board might have to make to the coal owners' association. failing to receive an intimation from the board at the earliest date that they accepted one of those propositions, then the wage committee must at once lay the position of affairs before their association, and obtain instructions as to the steps to be taken to press for an immediate reduction. these questions were at once placed before the workmen by the board. they, in the first instance, said they did not consider they had the power to make any settlement, and therefore were compelled to take that course. then they reminded their constituents that when the markets were advancing (and on sufficient reason being shown) the employers gave advances by mutual arrangement, and therefore that mutuality should be reciprocated. they hoped the members would not be rash nor doubtful, for these were dangerous and destructive to their interests. "we must meet these situations like business men. the greatest safeguard is confidence in each other, and, as in the past, we have done all we could to merit that confidence from you, so in this most critical period, if you entrust us with the care of this matter, we shall do all we can to bring about the greatest benefit for our various associations." there were three modes of settlement open to them: the first to grant the immediate reduction of ten per cent.--this they would not recommend; the second was arbitration; and the third to place the matter in the hands of the board to negotiate the best settlement possible. they pointed to the last advance of five per cent., which was got so speedily by acting in the latter manner. upon these three questions the ballot would be taken, the papers to be returned on or before february rd. the voting was: for accepting the ten per cent., ; arbitration, ; board to have power to settle, ; for refusing the whole, , . the board then put in operation rule , which gives them power to call the committees of the four sections if they deem it necessary. they arranged for such a meeting, and laid before it an amended offer made by the employers: an immediate reduction of seven and a half per cent., or five per cent. immediate, and five per cent. on the first of may. if neither of these was accepted then notices would be given on february th. with these offers the united committees sent out a circular. in it they supplemented the one sent out by the board in january, prior to the last voting being taken, and they warned the county not to be deceived, because it was quite clear that the owners were in earnest, and resolved not to be put off any longer. the question had waited six months. if they accepted one of the alternatives the dispute would be arranged. if they chose a strike, then they must prepare for taking the consequences. on the th of february, the day upon which the notices were given, they met and decided: "that all members of any of the four sections who have not received notice from the owners must put them in at once, except the collieries who are not associated with the durham coal owners' association, who must work on, providing their wages are not interfered with." these instructions were altered three days after, and the members were informed that "all workmen, whether employed at associated or non-associated collieries, and who have not received notices, must give them in at once." the voting on the amended proposals of the employers was largely in favour of a strike. for agreeing to the seven and a half per cent. voted, for the two five per cents. ; for giving the board full power , , and for strike , . it was then resolved to submit the two highest to another ballot. in the meantime the board endeavoured to induce the owners to modify their demand still further. on the th of march, two days before the notices expired, numerous telegrams passed between the two parties. those from the board were urgent; those from the employers as if inspired by indifference, the last one reading: "owners regret position, but have no suggestion to make." the board then turned their attention to the prevention of the filling of the coals that were stacked, and they promised that, if any man or men refused to fill at the pits in the county during the strike, they would see them reinstated into their former work. in some places the colliery officials interfered with the enginemen. the committee of that association entered their protest, and brought the matter before the board, who decided: that we endorse the action of the enginemen's association in the prompt means taken by them in reference to officials of collieries tampering with the enginemen, and should any action be taken against the enginemen they will have the protection of this board. on march th the miners' executive decided to call a special council meeting of their members on the th to consider the situation, and informed the federation board of their decision. after a long discussion the council decided against any reduction, and on the th the votes of the whole federation as per ballot showed: strike federation to settle miners , , enginemen mechanics , , cokemen , , ------- ------ , , in spite of all these efforts to prevent the strike and induce the members to settle there were some who charged the leaders with not giving the members full information and not daring to put the matter as clearly and as forcibly as they should. in defence they asked the lodge secretaries to look at the circulars and minutes which had been sent to them, and they would find these people were speaking either without full knowledge of the facts or maliciously stating that which they knew was untrue. the board had placed before the members the various offers, and had in an unequivocal manner advised them that the most beneficial mode of procedure was to give the board power to settle. "to this we still adhere, as the wisest, surest, and best course to be pursued, and we have no doubt that, were it adopted, a speedy settlement might be arrived at, and all the misery and hardships that are necessarily attached to a strike or lockout, whether it be long or short, would be obviated." the question of the sick members was somewhat perplexing, for the members of the sick department who were not receiving anything beyond the small amount of strike pay, found they could not keep their payments up, and the question was brought before the council, when the following resolution was carried:-- this meeting deems it advisable to let the sick members who are now on strike cease paying their contributions for the present, and at the same time they be not allowed to come on to the sick fund. but those who are now on the sick fund have their sick pay continued until they recover from such illness, and at the same time they will have to continue paying their contributions, but death benefits to be paid to all. the banking account as per the balance sheet for december was £ , . there was £ , in property in the various halls in the county, and there had been so much money spent in local strikes that it had been impossible to accumulate money to the extent they should have done. the members were informed that the amount available would only enable the committee to pay s. to each full member and s. to each half member, for they were compelled by rule to reserve £ , for the sick fund. the strike being fairly started the federation board found themselves in a position analogous to that of . the best they did receive (from a large number of people) was slander and vile names, and all because they, realising the dangers of the situation, dared to advise the county and take an unpalatable but manly stand. meetings were held everywhere, and the speeches delivered were interlarded with epithets of the lowest order; and if the estimate of the agents was even only approximately true they were fit for no place outside a prison, for the most corrupt motives were attributed to them. they were betrayers of their trust, and were selling the interest of the men for their own gain. the main spreaders of those untruths were men from the outside: sailors who loved to sail on land better than sea, and coal porters from london, who thought they knew more about the miners' affairs than the men of the county did. in addition, there were those who believed in brotherhood, and thought the most effective means to establish it was by sowing discord broadcast among a people engaged in an industrial death struggle. the severity of the struggle may be gathered from the fact that s. per member and s. per half member was all that was available in the funds, and after being off nearly eight weeks the money gathered in from helping friends amounted to s. and s. d. respectively. it took £ to give each member of the federation d. each. after being off work close upon eight weeks the federation board sought a meeting with the owners for the purpose of talking "over the situation with a view of putting before the members of the various associations any suggestions that might arise." three days after the parties met, when the whole question was fully discussed. the position taken up by the board was that, according to joint committee rules, no question could be negotiated during a stoppage, and therefore the owners should open the pits, after which the men would consider their demands for a reduction. that offer was refused, and a reduction of s. in the £ was pressed. in connection with it they suggested the formation of a wage board as a means of preventing the recurrence of a suspension of work. they were then asked if they would refer the question to arbitration. their reply was very short and decisive: "no; thirteen and a half per cent. reduction must be conceded before we will agree to open the pits." when asked why they increased their demand they said they had done so because the stoppage of the pits had entailed a great loss upon them, and they thought the men should pay for it. in addition, they chided the board with simply being message carriers instead of men of influence. there were three results from the action of the owners. the first was to bring the federation board and committees into closer relations with the people as a whole. there had been a tendency towards peace, when the employers took the false step. they had an idea that the workmen were beaten, and there is no doubt there would have been a much earlier settlement but for that mistake. before, the leaders were doing their best to persuade their people to let them settle the dispute, but afterwards they were in determined opposition to the settlement on the lines of the increased demand. the second result was to throw public sentiment against the owners. it was very clear that, so long as the employers stood by their original demand, there was at least a silent condemnation of the workmen for refusing to place confidence in their leaders, but after the thirteen and a half per cent. was asked for the public veered round to the side of the workmen. the third result was to change the feeling of the miners in relation to their trust in the leaders. what persuasion could not do the extreme demand did. at a miners' council held on may th it was decided to leave the entire case in the hands of the board. on the th, at a united meeting of the four committees, the subject was discussed for a considerable time, when it was decided that the board meet the owners, but the committees to be in attendance. a telegram was sent to mr guthrie informing him that: "the federation board having received full power to settle the wages question, can you fix a day as soon as possible for us to meet your wages committee? board waiting reply." to this mr guthrie replied that he would call a meeting for the th, and lay the message before their members. the meeting took place on the th of may. the owners stood firm to their thirteen and a half per cent. the united committees offered to give five per cent. that offer was refused. the committees then proposed the following:-- workmen's offer _may th, ._ that we, the united committees, representing the four sections of the workmen employed in the county, cannot accede to the demands of the owners for a thirteen and a half per cent., but in order that we may end this dispute, with the consequent stoppage of trade and deprivation amongst the people, we are willing to accept an immediate reduction of seven and a half per cent. from the thirty-five per cent., leaving the wages twenty-seven and a half per cent. above the basis; and further, that we are willing at the earliest moment after the starting of work to recommend to our members the formation of a wages board for the settlement of all county wage questions in the future. w. h. patterson. owners' reply the owners' wages committee regrets that it is impossible to accept the offer of the united committees for an immediate reduction of seven and a half per cent. only. in other respects the committees' proposal is acceptable. the wages committee must again point out that the ascertainment of selling price for the month of february showed that the owners are entitled--according to the relation of wages to prices that so long prevailed, and which the owners still regard as fairly and fully measuring the rates that can be afforded--to a reduction of fifteen per cent. from the standards. in asking for thirteen and a half per cent. only the owners feel that this is the smallest reduction that they would be justified in accepting. they believe, having regard to the deepening depression of trade, that any higher rate of wages than would be thus established must lead to a serious diminution in the amount of employment that could be afforded. reginald guthrie. these were sent out with a statement of the case, with three questions upon which the members were asked to vote: should the owners' terms be accepted? should the strike continue? what suggestion had they to offer? in the circular sent out four days after these questions the federation board pointed out the seriousness of the position. it was difficult to carry on the struggle much longer. arbitration had been offered to the employers, the pits commencing at the old rate. that had been emphatically refused, although it might have been accepted, if agreed to at the first. one suggestion had come to them--viz. to offer to accept a reduction of ten per cent. this was sent out as from themselves, and was carried by a majority of nearly four to one. when forwarded to the owners it was refused. the following is the resolution:-- _may rd, ._ resolution that we, the united committees, representing the four sections of the workmen employed in the county, adhere to our refusal to accede to the demand of the owners for a thirteen and a half per cent. reduction, but in order that we may end this dispute, with the consequent stoppage of trade and deprivation amongst the people, we are willing to accept ten per cent. reduction from the thirty-five per cent., leaving the wages twenty-five per cent. above the basis; and further, that we will at the earliest moment after the starting of work recommend to our members the formation of a wages board for the settlement of all county wage questions in the future. seeing the owners' committee have refused our offer of ten per cent. reduction, and press for their full claim of thirteen and a half per cent. in wages as a settlement of the present dispute, we offer to submit the whole question to open arbitration, providing the pits be opened out at once. on the refusal of this offer it became clear to the workmen that they were being most harshly dealt with, and as a natural consequence there were a few outbursts of temper and disturbances. there were numbers of policemen imported into the county. against this the united committees protested, and pointed out that the massing of these men was likely to cause disturbance, where otherwise there would be peace. they likewise thought the rate-payers should demand the withdrawal of the policemen, as they were an unnecessary burden upon the county. at the same time they placed before the county a detailed account of the whole proceedings from the initiation of it. they showed that they had done all they could in the interests of peace. they had offered to submit to a reduction, the justice of which had never been sufficiently proved; in fact, they were willing to give two and a half more than the owners asked for when they came out, which was equal to the fullest demand before the stoppage. they concluded by saying: the future of this awful struggle is with the owners. we have done our part. we cannot and do not ask you to accept the unjust and exorbitant demand made upon you. so far as we can see, the struggle must continue, that is, unless you are prepared to submit to the unjust demands of the owners. are you prepared to do this? we implore you to be patient under the strain placed upon you by the latest action of the owners, from which it is evident that they would crush you, and reduce your manhood to the level of serfdom. we urge you to be law-abiding and still continue to show, as you have done in the past, that the men of durham are a credit, not only to trade unionism, but to the country at large. the owners are aware that our ability to successfully resist their demands depends upon our being able to procure the necessaries of life. it is a matter which they have no need to personally fear, but which they appear determined to use as a weapon to force us to accept their terms. we must all do our best to defeat their projects, and nothing shall be left undone that we can do to secure subscriptions in order that our people may have food. we are thankful to those friends who have helped us, and we hope that workmen and all lovers of justice will respond to our appeal. as committees, we tender our thanks to the leaders and friends at our local lodges, who have so untiringly and unceasingly given their labours for that purpose. they are in a good cause, and we are sure they will not weary in their well-doing. their action is made more necessary by the determination of the owners. the offer of the employers (thirteen and a half per cent.) was submitted to the county along with the alternative of strike, with the result that every section voted by large majorities for a continuance of the strike, the least majority of any section being near four to one, and in one section nine to one. the resources of the men were gone, but their spirit of determination was strong. the owners by a statement tried to put themselves right with the public, but the board replied by a counter statement. then some of the influential men in the county (including bishop westcott) thought it was time to interfere, and letters were written by them to the board, for which thanks were sent in reply. among the communications was one from n. wood, esq., m.p., in which he expressed his regret at the failure to settle and the great misery among the people, and suggested that the board should make an offer of eleven and a half. a letter of thanks was sent to him, expressing surprise that he should make the suggestion, and informing him that they would feel glad if he would try to get the owners to see that they were preventing a settlement by their stubborn refusal to shift from their demand for thirteen and a half per cent. the good bishop, however, was not satisfied, and persisted in his endeavours to get the parties together. he was told that as soon as the owners were willing the board would meet, and an arrangement was made on june st at auckland castle. a very long joint meeting took place, and then each party met in a separate room, the bishop passing from room to room, full of solicitude for a settlement. at nearly the final stage of the proceedings he tried his best to persuade the workmen to offer eleven per cent., and he was told that, while he had their most profound respect, and they were sorry to refuse him, yet if they thought ten and a half would settle the dispute they would refuse, and continue the strike. at that point the parties met jointly again, when the following resolution was handed to the workmen:-- owners' offer the federation board have offered explanations as to the establishment of a system of conciliation in the future, which the bishop of durham recommends the owners to accept as satisfactory, and the bishop having strongly appealed to the owners--not on the ground of any judgment on his part of the reasonableness or otherwise of the owners' claim of ½ per cent., but solely on the ground of consideration for the impoverished condition of the men and of the general prevailing distress--to reopen the pits at a present reduction of per cent. (that is, from to above standard), with the full expectation that wages will hereafter be amicably settled by the system of conciliation contemplated, the owners yield to the bishop's appeal on these grounds, and assent thereto. bishop auckland, _june st, ._ it was thought desirable to settle certain details before work was resumed. amongst these was the restarting of all men as they came out. some of the owners demurred, and thereupon the meeting broke up, and adjourned until friday, the rd. the workmen at that meeting asked for a plain statement that every man would be engaged at his own work. the proposal of the owners was as follows:-- owners' resolution . the owners' association have decided that no person shall be refused employment in consequence of having taken part in the affairs of the workmen's associations during the strike; they cannot, however, give a pledge to re-employ all their workmen, but they will recommend their members to employ as large a number as possible, and that the re-engagement of hewers be as follows:--that the places in each pit be cavilled for according to the last cavilling sheet, and that men cavilled to the places not intended to commence again shall be the ones not to be employed, it being understood that one hewer in a family being cavilled to a place that is to work is equal to the engagement of the whole family. in cases where a whole seam is stopped, it having been previously cavilled separately, the men belonging to such seam shall not be entitled to have a cavil put in for any other seam. this mode of re-engagement shall not be adopted as precedent in future cases, either in discharging or employing workmen. . that the owners are not prepared to discharge or remove the workmen whom they have employed during the strike for the purpose of reinstating other workmen who were previously employed, but will use their best endeavours to re-engage those previously employed as vacancies occur. reginald guthrie, _secretary_. durham coal owners' association, _june rd, ._ the united committees objected to the second portion, but were willing to accept the first. no definite agreement was come to, but there was an understanding that the matter would be allowed to adjust itself smoothly, which it did, and no disturbance whatever took place in the absence of an agreement. the united committees guarded themselves by drawing up a resolution, in which they interpreted the owners' resolution to mean that every man would be re-employed as before the stoppage. at the same time they informed their members that if any case of refusal took place, then all the other men must refuse to work. thus ended one of the most memorable strikes in this or any other country, not on account of its length, but the circumstances which were connected with it. the workmen were poor in funds at the start, and the help (although generous from some quarters) was small per individual; the total benefit for the three months did not exceed s. each full member. with these poor resources and prospects they entered upon what was felt would be a strike of a very determined kind--this, too, with the minimum amount of friction. the only event of much importance happened at castle eden. the disturbance took place on may th. it arose in reference to a man named stogdale, who would not abstain from working during the strike. four of the workmen at castle eden were tried for intimidation. their names were michael forbes, w. r. robbins, t. jones, and t. h. cann. they were tried at the durham assizes in july , before judge day. they were tried under the intimidation act. the judge summed up in a very strong manner against all the men except robbins, who was discharged, but the other three were sent to prison. the judge said they had been found guilty by the jury of the offence with which they were charged--namely, with the object of preventing a certain person from pursuing his legal occupation "you in a disorderly manner, with other people, followed him along the road." after making a long speech in a similar strain, to show how beneficent the law was in his opinion and what a trio of desperadoes they were, he sentenced forbes to a month, jones to six weeks, and cann, because the judge thought he was the ringleader, to two months. the aftermath of the strike if the strike was unique in its endurance and order it was none the less important in its lessons. in it, as in , was seen the result that followed the lack of confidence. a strike is the harvest field of the agitator, who cares not what is destroyed so long as he prospers. what would have been the gain to the individual member and to the association if the resolve taken in the last few weeks had been taken before the tools were brought to bank? the funds, such as they were, would have been kept intact instead of being wasted. the great loss in individual income would have been avoided; in that respect the savings banks and co-operative societies (which in many cases are the poor man's bank) could have told a tale of hardly saved stores used up which had been kept for a "rainy day" of unavoidable troubles. the unnecessary and destructive friction which is sure to arise in these matters, no matter how peaceably the struggle be conducted, would have been avoided. two great bodies, such as the two great associations in durham, are two great armies, and in the struggle and strivings anger will arise, and regrettable things will be said in the heat of the moment. these have a more far-reaching effect than people are apt to credit. then the loss in wages. this was twofold. there was the three months' irredeemable loss and there was the lessening of the reduction. it was admitted on all hands that less than the ten per cent. would have kept the pits working if the federation board had been trusted with power to settle, even up to the eve of the strike. in saying this there is no intention of measuring the result of a strike by the money loss or gain. the world would not have been so far as it is in the path of reform and better life if the forlorn hopes of labour had not been fought, but it would be a piece of false logic if we were to infer that strikes should, therefore, be entered upon at all times. and certainly no one who in was able to appreciate the situation then would say it was one of those necessities of our industrial life. it was far from that; the gain would have been greater by the avoidance of the quarrel. if in writing our history this is emphasised, it is not in the spirit of reflection, but rather that we may learn wisdom; for in these matters it cries aloud in the street, and we can from a remembrance of such events escape the like evils. if this be done, then the strike of that day will be useful in the greatest degree to those of us who are active in this. using longfellow's figure, it is part of our dead selves, of which we can make a ladder, by which we can rise to higher things. another part of the aftermath was the burden which was thrown upon the funds. this was twofold. there were the men who could not get started, in the first instance, because of the state some of the pits were in; and second, because of the dislocation of trade, which was sure to follow a stoppage of work for three months. business connections are liable to break, and the difficulty is to heal them again. the consequence was that there were men out of work for a long time after the actual strike was settled, and these were to maintain for a considerable time, many of them so long that they had to be transferred to the relief fund. the money paid to them was the outcome of a levy, which pressed heavily on those at work. then there was another burden, the result of the strike, but which was not any portion of the obligations of rule, the payment of the back rent of those who were living in rented houses. there was one peculiar and pleasing feature in connection with that strike, as with that of , there was no interference with the men who were living in the colliery houses. there was in one or two places some little talk of a rent obligation from such men, but it came to nothing. perhaps it was never intended that it should. this much it is our duty to state, to the credit of the employers: the men who were in battle with them were allowed to live in their houses, and were not prevented from gathering coal wherever such was lying about. to the men who were in rented houses the case was vastly different. every week off work added to their debt, which they were bound to pay when they resumed work. with a spirit of generosity which is not restricted the whole of the members recognised the debt of those men as belonging to the whole county, and resolved to pay a levy for the purpose of paying the back rent. the resolution was carried at the council meeting on june th, : "that a levy of d. per full member and ½d. per half member throughout the county be made to help to pay the house rent of the members living in rented houses." at the same meeting the present ( ) relief fund was formed, to support men who were out of work. the system adopted in paying rent was to cavil the collieries, and pay them as they were drawn, with this provision, that if any colliery were drawn, but had not paid the levy, no rent was allowed until the levy was paid. the eight hours again the only remaining subject in was the ballot on the legal eight hours. we have noted previously how and when this was first introduced, with some plain advice given by mr crawford--advice which has never been shown to be wrong. it was decided at the council meeting held on august th "that the county be balloted for and against the eight hours." on september st the committee took the ballot, and issued a circular setting forth their views on the subject. as we have now ( ) reached a crucial stage in the discussion, it will be useful to place on record what the committee of that date thought of the question and the difficulties it involved. in their opinion there were two modes of procedure by which the hours of labour might be shortened: legal interference and trades union effort. the latter was the one they had adopted, and it had been successful. no man could think they were against short hours; any opportunity to shorten them would be welcomed. they referred the members to the action in : how they had given up a claim for ten per cent. and accepted a shorter day. "we are not now to set up a show of weakness, and sacrifice our manhood and independence, by handing ourselves over to the supervision and control of the house of commons, which is not acquainted with the peculiarities of our occupation." if it were the function of the state to fix hours of labour, was it not logically its function to fix the wages of the workman? "it is said that some of the organisations are weak, and therefore the state should protect." the reply was: "where weak organisations exist low wages are found. it is therefore necessary for the state to fix the amount of wages men should be paid, for men require bread as well as hours." they then turned to the difficulty. eight hours those who favour legal eight hours must consider how it would work. there would be serious alteration needed in our present mode of working. we must either have two shifts of hours, making hours' coal drawing and hours' shifts, increasing the hours of hewers by to ½ hours per diem, and deputies half hour per day. this would increase the output, and consequently the price of coal, and necessarily the wages of all men. the other alternative is an hours' shift for all men and boys, which would throw into the labour market thousands of men. consequently, competition amongst ourselves such as we experienced in ' and ' would arise, and thus we would have a repetition of the hardships we underwent in those disastrous times. much is made of the hours of boys; these we will shorten at the earliest opportunity. under our present system, and taking a number of years, we work less than we should do under eight hours by law. we therefore strongly urge on you to vote to a man against any parliament fixing the hours of labour, as in our opinion it would be injurious to the working classes generally, and to ourselves in particular. do not be led away by the idea that the short hours we have obtained for the hewers will be maintained. the request is eight hours from bank to bank for all and every man who works down the pit. to this, it may be said, it is a maximum number of hours, and that, therefore, some might be allowed to work less. that will depend upon the arrangement. if the employers get the sanction of the law, and they require us to work eight hours, we shall be expected to so work. there is another point which demands consideration. it is a question of wages. let us suppose the act passed, and those who work ten hours (both below and above ground) were reduced to eight, how much should the wages be reduced? if we shorten the hours by negotiation, it will be done gradually, and wages could be arranged. the result of the ballot was: for parliamentary eight hours, , ; against it, , . the wages board--the miners' federation the wages board during the negotiations for a settlement of the strike in the employers laid emphasis upon what they designated the wages board, but which afterwards was known as the conciliation board. their idea (commendable in every point) was to bring the parties closer together, and avoid the recurrence of the stoppage, which they felt (as all must feel) had been a disaster to the whole of them. the question rested over until the beginning of the year, when the owners made application for a reduction in wages, and at the same time asked that the formation of the board might be taken into consideration. the meeting took place, and on february th the executive committee issued a circular, putting the whole position before the members. the miners at the time were in a complicated position, being connected with the durham federation, and they had a short time before become members of the miners' federation of great britain. under rule that federation claimed to have control of the wages disputes in all the districts identified with them. in order that the position may be properly understood we will insert the rule. . that whenever any county, federation, or district is attacked on the wage question, or any action taken by a general conference, all members connected with the society shall tender a notice to terminate their contracts, if approved by a conference called to consider the advisability of such action being taken. the application of that rule to durham, in the situation it was in, would have been to leave the whole matter in the hands of the miners' federation, which would have taken full charge of the question, and have told the durham association what they must do--whether to accept or reject. the complication arose from the fact that they were members of the home federation as well, and there would be confusion if two bodies, one in the county and the other at a distance, were to have supervision. it was impossible to go on in that state. one body was on the spot, and knew the whole bearings of the case; the other was at a distance, and therefore bound to be in comparative ignorance of the facts of the situation. the executive committee felt they were compelled to put the position clearly before the federation board and the county, and inform them they were members of the miners' federation. in addition, they resolved to call a special council, and place before it the plain issue. "let us state the position to you," they said. "prior to our becoming members of the federation of great britain we acted on all general and wage questions with the durham federation board. our action was a whole one with the cokemen, mechanics, and enginemen, the last strike being the most recent and clearest illustration of that. you will remember with what loyalty the four sections worked together on that occasion." if they were resolved to remain members of the miners' federation, and accept rule , they must prepare for leaving the county federation. that would result in sectional action in durham, for the other sections would naturally seek to make the best of themselves they could. it was not reasonable to ask them to wait until the miners' federation had decided, as per rule , for durham to strike, and then ask the cokemen, mechanics, and enginemen to join in it. there was needed some definiteness on the point, and the council would be asked to decide two questions: first, "shall it be settled by the federation of great britain?" second, "shall it be settled by the durham federation board and the united committees?" at the council held on march th the decision was in favour of the latter question. in accordance with that resolution the united committees met the owners on march th, and asked them to reduce their demand for ten per cent. to five, and they (the committee) would at once accept it. the employers accepted the offer, the following being their resolution:-- the durham coal owners' wages committee feels the responsibility of accepting a less reduction than the per cent. claimed, because upon an adequate reduction really depends the extent of employment that can be afforded. whilst, therefore, the owners' judgment is that the true interest of both parties lies in at once bringing into operation a reduction of at least per cent., the owners, desiring to show a spirit of conciliation, accept the federation board's offer to submit to a reduction of per cent., to come into operation from the next pay of each colliery; but in doing so the owners feel it their duty to point out that so small a reduction as per cent. falls far short of meeting the urgent necessities of the trade, and can therefore be regarded only as a temporary settlement. this reduction brought the percentage above the standard down to twenty. but the employers were not satisfied; they pressed upon the board the formation of a wages board. on may th mr guthrie wrote to mr patterson as follows:-- i am directed by the durham coal owners' association to press strongly upon you the honourable obligation we come under to the bishop of durham, and to each other, to endeavour to establish a wages board which would secure by conciliation or arbitration the pacific settlement of all questions outside the jurisdiction of the joint committee. that honourable obligation has been more than once reaffirmed by your federation board, but no steps have been mutually taken to give effect to it, and my association feels that such steps should not be longer delayed, and therefore instructs me to ask your board to meet the owners' committee in order to advance the matter. the members of the federation board were eager, as individuals, to come to an arrangement, but were not sure how the membership would receive it. it was a new but necessary departure in an industry such as the durham coal trade, but in order that it might be acceptable they were desirous that some scheme (beyond a mere name) should be outlined at least, and placed before the various sections for consideration. they asked the owners, therefore, for certain information: "( ) the allocation of the s. d. basis price of coal under the following heads:--wages, salaries, material, royalties, and profits. ( ) the proportion of coal required to make a ton of coke in as compared with . ( ) the cost of producing a ton of coke in as compared with the same in . ( ) a statement setting forth the various objects to which the d. per ton was allocated. ( ) a statement showing the percentage of steam coal, gas coal, household coal, manufacturing coal, and coal converted into coke. ( ) the average lengths of contracts, with the periods when they are ordinarily made." a reply to these questions was received on december th. this was in conjunction with an application for an advance made by the federation board. they were informed that the owners' committee was willing to meet and discuss the question at the same meeting when the proposed wages board was considered. in reference to the list of questions the letter contained the following:-- "the meaning of some of your questions does not seem clear, and generally my committee failed to understand how they bear on the expediency or otherwise of forming the proposed board, or arise prior to its establishment, but the committee accepts your suggestion that a meeting should be held to discuss your communication." the meeting was held on december th. nothing was done in relation to the wages board, but an arrangement was made with respect to the advance. the owners' committee were convinced that the tendency of prices was downward. these had been somewhat higher during the strike in the midlands, but the effect of that was passing away, and they had very grave reasons to doubt whether the first quarter in would justify the rate of wages then paid. they had given a temporary advance in october for six pays only, and they were prepared to make that permanent, and bring the wages to twenty-five and twenty-two per cent. respectively above basis rates. durham and the miners' federation in order that we may make the chronology of our history as close and sequential as possible, we will postpone the wages board until , and take up a subject which is within the year we are dealing with. in the autumn of durham decided to join the miners' federation of great britain. the membership continued without any difference (except that arising from the eight hours, and the case of the reduction in durham mentioned above) until the month of july , when a demand was made upon the miners' federation for a reduction of twenty-five per cent. in connection therewith a conference was held in birmingham (the proverbial hen and chickens' conference) to consider the situation. two delegates were sent from durham (mr j. johnson and mr j. wilson). it was found that in some districts organisation was in a very poor condition. the delegates from durham were sent to move the whole question be referred to arbitration, but when they brought it forward as the best mode of procedure, they were prevented for some time, but finally were permitted, with the result that, by a majority of four to one, they were outvoted. a resolution was carried pledging all the districts within the federation area to give in notices. if they had suffered reductions within two years, then they had to apply for an advance equal to the amount lost, without regard to the state of trade or any other consideration. the absolute order was to give in notices, the aim being to bring all into the struggle which was impending, and these had to be given within a fortnight. when these proceedings were reported to the county a circular was sent out by the executive committee, in which they commented upon the situation, and asked the members what should be done. they said there were two questions for them to decide upon--first, the position in the south; and second, the demand they had to make for fifteen per cent. advance, as per the birmingham resolution. these could have been sent out in a bald form, but it was their duty to give the county guidance, for if a committee be appointed for anything at all, it is to watch, warn, and guide the members of the organisation. there could be no doubt but that durham was in favour of arbitration, for the last vote taken on the instructions to the delegates proved that. this was refused, and instead they were ordered to make a demand for fifteen per cent. advance. the question which they must answer first was: is trade favourable for such a demand? unless trade is prosperous now, could they expect to succeed in such a claim? what support could they get? their own funds were gone entirely. if the federation strike took place, then there was no source of income anywhere. there were at that moment men out of work, some of whom had never started since the late strike. the small support these men had been receiving would be cut off. they would have to commence a strike, not in comparative, but absolute poverty. where, then, was the hope? but suppose notice was not given in for an advance, then durham must give in notice to terminate their engagement when they had no dispute with their employers. if they were asked "what they were striking about" what answer could be given, except the following:--"nothing whatever in our own county; we have no difference." further, if the employers were to offer a ten per cent. advance, it could not be taken without the leave of the federation. neither could they accept arbitration, for they had been told the no. rule of the federation would not admit of it. therefore they must strike, or be expelled from the federation. but, said the committee, "much as we desire national federation, and may regret our expulsion from that body, we cannot urge you to a course that would in our opinion be disastrous." the questions involved were then placed before a special council, when it was decided to ask for an advance of fifteen per cent., but that they would not join the miners' federation in the strike. the council likewise resolved to ask the cokemen, mechanics, and enginemen to join them in their demand for the fifteen per cent. if not, then the miners' executive should apply themselves. the federation board considered the decision of the miners. they regretted the circumstances which had led to the great dilemma in which they were found, but, having a desire to keep the solidity of the board, they would accede to the request, and meet the owners, but if it were refused, it would be desirable to refer the question to their respective sections for further instructions, and at the same time they would ask the united committees to accompany the board. the owners could not accede to the request, and it was necessary that the will of the members should be ascertained by the miners. this was the position: they had been ordered by the birmingham conference to make a demand for fifteen per cent., and if not conceded, to give in their notices. none of the other sections had received the same orders. the questions were: should there be a strike to force the demand, or should they work on? but before that stage was reached, it was necessary that they should ascertain whether the ballot should be the whole of the durham federation, or simply the miners. the voting was: for the whole federation board, ; for the miners' vote alone to decide, . it was then found that the other sections could not join the ballot until they had consulted their members, and the executive committee determined to take a ballot of their members alone. the result of the ballot was: for a strike, , ; against, , . the rule, therefore, was against a strike. the consequence of that vote was to place durham in direct conflict with the miners' federation. that body had a conference arranged for august nd in london. messrs johnson and wilson were sent to it by a nearly unanimous vote. the first business of the conference was to consider the action of durham, and the following resolution was moved and carried with great unanimity:-- that we, the representatives of this federation, cannot allow the durham delegates to sit in this conference, seeing that this district through its officials has not carried out the resolution of the birmingham conference. there are two very notable things in the resolution and its setting. durham was expelled from the federation, and the officials of that organisation were charged with preventing the carrying out of the birmingham resolution. the first of these is very clear, for on that point the motion is specific; but it will be seen the second is not correct when we consider the two votes recorded above--the first placing it in the hands of the federation board and the second by a ballot being against the strike. this is a history, and not a record of any man's opinion. it is necessary that the state of things that existed should be recorded, not a mere theory as to how things should be. the history would be incomplete if we were not to follow the sequence a little further. no sooner had the expulsion taken place than there was an introduction of speakers from the miners' federation, who came with the avowed object of trying to induce the county to continue its membership. the only complete illustration of that circumstance would be for a man to kick another out of his house, and the next minute go himself, or send some of his relations, to ask the man to come in again, doing his best to show that he who was kicked out was the offender, and ought to feel thankful for the usage he had received, and to supplicate to be taken in again. it was a curious mode of procedure, to say the least, and, most surprising of all, they were assisted by some of the people in the county, who did not feel the slightest ignobleness in the treatment they had received by the expulsion. - the conciliation board--lord davey's arbitration the formation of a conciliation board was again brought forward by a request from bishop westcott to the federation board asking them to meet him for the purpose of discussing the subject. the board acceded to his request, but did not appoint a definite deputation except the four secretaries, leaving any others to join them who thought proper. the result of the interview was the calling of the four committees to discuss the proposal. the decision of the miners' council on march th was: that the committee meet the owners and discuss the advisability of forming a joint board for fixing the correct selling price of coal, and the other sections of the federation (county) be asked to join the negotiations and report to the county; that there be a conciliation board formed, to consist of members from the owners on the one part and members of the durham federation board on the other part. the said board shall be formed of equal representatives of the before-named parties, who shall meet on terms of absolute equality. this resolution was brought before the federation board, when it was found that the other three sections had not been instructed by their members, and it was resolved that the question be deferred until "they had an opportunity of bringing the matter before their associations, and that the board recommend the acceptance of the principle for their adoption, and the four secretaries meet and draw up a code of rules for the guidance of the conciliation board." a difficulty arose from a resolution passed by the cokemen's association. dr r. s. watson had given an award in a cokeman's case shortly before, which in the opinion of the cokemen was not being carried out by the owners, and therefore, while they were in favour of the principle of conciliation, they decided not to take any part in the formation until the owners brought the award into practical operation. the federation board regretted the action of the cokemen, as in their opinion "such a board would be the most effective means of bringing a full recognition of that award. as, however, the other three sections were in favour of proceeding with the formation of the board, we ask the employers for an early meeting, and we would urge upon the cokemen to reconsider their resolution of march st, and give their representatives power to proceed with us in that formation." the owners were desirous that the board should join them in meeting the bishop, but they were informed that a previous understanding had been come to, by which it was arranged that each side should meet him separately, and then the joint meeting should take place. they had carried out their part of the bargain, and were ready to meet jointly as soon as his lordship should ask them, as they were very wishful not to throw any obstacle in the way of the formation of the board. on july th the formalities were settled, and the rules were left to the four secretaries, with instructions to draw up a circular recommending such rules to the members. proposed conciliation board gentlemen,--we hereby desire your attention and consideration to the rules of the "proposed conciliation board," which you instructed us to form. we have always told you that, however carefully we might draft such rules, the acceptance, amendment, or rejection thereof is with you. we were proud to receive the commission of the duty, and we place before you the result of our work, and are hopeful that great benefits will accrue to the trade of the county if these rules are adopted. we do not claim perfection for them, but we do assert that they are in advance of any method ever arranged here for the settlement of disputes. we will not trouble you by any lengthy statement by way of urging you to accept the rules, for in our opinion their fitness is clear, but we will in as brief a manner as possible draw your attention to three of their leading features or principles. first, the scope of the operations of the board; second, its duration; and third, the machinery by which it arrives at its decisions. the scope of the board is set forth under the headings of "objects." we do not quote those objects, but ask you to refer to and consider them carefully. they are clear in their intention and comprehension. what can be more interesting and important to us than the prevention of disputes? we speak for you, as well as ourselves, and say we desire them not, and welcome any mode of settlement which will minimise friction, and help both employers and employed to avoid any irritating action, while it does not interfere with the right of and justice to either party. you will observe that the board is intended to be _more than a wages board_. it will take into its cognisance and decision any questions which may arise and for which the joint committee rules do not provide. you know as well as we do the numerous cases that arise which have no standing at the joint committee, and you will, therefore, easily recognise the value and importance of any tribunal which will deal with such matters in a ready and expeditious manner. there is no need to enumerate those questions. we hope you will not merely glance at the latter portion of the "objects," but give it your careful attention. the duration is fixed by rule three. the limit is , and, therefore, if the rules should fail to meet our views, we can terminate the existence of the board in less than a year and a half from now, which is a short time in the history of our industrial relations. a shorter time than this will not give us the opportunity of testing the usefulness of the arrangement, neither is it long enough to allow any serious evil to arise therefrom. the machinery or mode of operation is contained in rule four and subsequent rules. if you examine these rules you will see, that while they provide for the appointment of an umpire (which is necessary), yet his services are not to be called in until the board have tried to settle by negotiation and conciliation. we recommend to your special notice the main features of this portion of the rules. these are the provisions for the play of conciliation and mutual confidence. anything that will beget a feeling of trust and mutuality, that will remove the desire to overreach and withhold on the one hand, and of suspicion and doubt on the other, should be welcomed and tried, and if possible strengthened. there were a number of suggested objects and provisions sent in, which were afterwards commented upon by the united committees. amongst these was a minimum wage. the committees, in relation to that question, drew attention to the period between - , when, in little more than a year and a half, the miners spent £ , in the maintenance of men out of work; that, so severe was the pressure, they were compelled to abolish the relief fund; that there were collieries where the men asked to be allowed to work at twenty per cent. below the minimum; and that the actual average went down to nearly d. per day below the minimum. the second suggestion was "a voice in the selling price of coals." this, the committees thought, was a very good ideal, but it was yet a great way off. it implied more mutuality than was in existence, and it was a state which must evolve, rather than be fixed arbitrarily. "the voting to be by ballot at the board meetings." this was thought to be unbusiness-like, as secret voting was a strange thing for a business meeting. then it was thought by some lodges that the question of sacrificed men, and arranging for all men to be in the associations, were matters to come within the purview of the board, but it was found that they were not compatible with its objects. the rules as framed were not perfect, but were far in advance of any to be found in the country. "many other districts and trades have adopted the principle, but we venture to say that in no instance has a conciliation board been formed which, for breadth of scope in its operation and dealing with questions that can arise, is in any way equal to that proposed for this county. we have had the opportunity of studying the rules of all the boards already formed, we have watched the work of those, and we unhesitatingly declare that in no single instance have such equitable rules been found." when these views were put before the four sections they were accepted by the other three, but the miners hesitated. the executive pointed out to them that by a council resolution the power had been given to the board to arrange rules and conditions, and therefore theirs was an anomalous position for them to take up by their objection. under the circumstances they had resolved to call a special council, in order that the matter might be fully considered. they were confident that if the common good were the aim, and all were imbued by that idea, the conciliation board would be formed on the lines suggested by the united committees. the result of the council was the acceptance of the proposed constitution, with the alteration of the number of members from fifteen to eighteen on each side, and the owners were informed that the federation board was ready to meet and sign the rules. the rules were signed on the th of february . there is no need to insert the rules here, as they can at all times be seen in the office, if any person feels desirous of doing so. the election of the first members took place on the th february , the following persons being elected:-- j. wilson. j. johnson. j. forman. w. h. patterson. t. h. cann. w. golightly. s. galbraith. w. house. h. jemison. at the first meeting of the conciliation board the employers asked for a reduction of wages. many people thought they were in a hurry. such a conclusion was hardly justifiable when we remember that they had been pressing for a reduction for some time, and the delay had arisen from the length of time taken in the negotiations to establish the board. the employers felt themselves injured by the delay, and therefore took the first opportunity of having their claim put forward and settled. the federation board in their circular on the situation acknowledged that, for they said: we cannot but regret that the first meeting of the board should have been convened to consider a reduction of wages, yet we feel confident that, however distasteful and unpleasant it may be to submit to a fall in percentage, all who have observed the condition of trade, taken note of the prices prevailing generally, and the serious lessening of the number of hands, during the past six months, could not be otherwise than prepared for a reduction in the rates of wages which were got when the condition of trade was different and prices higher. while the board were prepared for a demand for a reduction they were not prepared for the amount asked. the demand was for fifteen per cent., which would bring the wages down to a point to which the scale of would have brought them. the price of coal in was s. d., in it was s. d. wages had risen thirty-five per cent., and therefore they had a claim (said the owners) for at least fifteen per cent. the arguments against that claim we need not state in full. the main one was that, taking the whole period since , wages had been between seven and nine per cent. higher than the periodically quoted net selling prices would have given. that argument, as all are aware, was of great weight, and that it influenced the decision, there is not the slightest doubt. the decision of the umpire was a reduction of seven and a half per cent., but it left the wages higher by that amount than the old arrangement would have done. under it s. d. per ton would have given a wage ten per cent. above the standard; the award of lord davey in may left it seventeen and a half above the standard. although they had been called upon to suffer this reduction so early in the era of conciliation, the federation board did not lose faith in it as an advance in wage settlements. they said: it may not be out of place to allude to a feature or two of the newly adopted method of dealing with wages regulations as disclosed by recent applications, and we may modestly, yet rightly, claim for it a superiority of character and practice over preceding modes. as already stated, it has by its earliest results confirmed the conviction previously held, that the standard relation of wages to prices governing previous methods was not correct, and established the increased average amount obtained by the negotiations of the past years. at the next meeting of the board the owners made another application for a reduction. when the july meeting took place the claim was brought forward. it was objected to at first, on the grounds that there had not been sufficient time, seeing the three months had not elapsed. the notice was withdrawn and renewed. the reasons assigned were the declension in the markets and the inadequacy of the previous reduction. these reasons were not accepted, and the umpire was again called in. his decision, after two days' hearing, was a reduction of two and a half per cent. in spite of this adverse circumstance the federation board were still strong in their belief in the utility of the system. they said: we are not going to say that its course, so far as it has gone, has been pleasant, for there have been two reductions, but these do not shake our confidence in it. it is an unfortunate coincidence, the initiation of a new system when circumstances are unfavourable and its changes are downward. the true test of institutions, as of men, is their action in a variety of conditions. no arrangement can make trade prosperous. they are dreamers who think so, and are liable to a rude awakening. wise men recognise the ever-recurring changes, and employ the means which are most expeditious, easy, and equitable in their responses. friction between employer and employed is a foe to any trade, uncertainty is a sure and hurtful detriment, hastening and enlarging the times of adversity. our opinion is that, if we have not the best system, we have one which will ward off friction, allay uncertainty, and induce steadiness in the trade of the county. that clear and bold statement of their confidence in the board was not effective in maintaining it, for at the miners' council held on november th it was resolved to take a ballot to test its continuance. the federation board, on being informed of that action, resolved to take it of all the sections. they at the same time advised their members to keep it intact. they did not find fault with the decision to take the ballot. their advice was therefore not prompted by a spirit of complaint. it was right that these matters should rest on the will of the members. their duty, however, was to guide the members and advise, even on subjects that were unpalatable. in october they placed before them their views in as clear a manner as possible. those views they adhered to, and did not swerve from their belief in conciliation as the best system yet tried. it was condemned, because there had been reductions. if advances had come there would have been loud praise. would wages not have been reduced if the board had never been formed? "without hesitation we tell you that, in our opinion, he is a foolish or a designing man, or ignorant of commercial relations, who attempts to teach such a doctrine. we have never told you such an absurdity. when we asked you in the spring of the year to adopt conciliation we never dreamt of it as a fixed, immovable machine. to us it was (and is) a more mutual, closer, and smoother principle than we have ever had, taking within its comprehension other and important matters outside wages." in spite of this pleading on the part of the federation board the voting was: for the conciliation board, , ; against it, , ; neutrals, , , as a result of the miners' vote. the whole federation vote was: for, , ; against, , ; neutrals, , . on the strength of that vote notice was given to terminate the conciliation board in accordance with rule. the conciliation board--death of mr patterson the federation board were still in hope that the decision to terminate the conciliation board might be reconsidered, and they again brought the question before the members. they asked what system was to be substituted for it. they were firm in their belief in conciliation, but, if the members still persisted in abolishing it, what other form was to be adopted? "the situation in which we as a county find ourselves makes it imperative that we should address you. we do not refer to our own organisations, for these are strong, but to our relation with the employers and the settlement of our transactions with them. how are these to be managed in the future? has our attitude to be one of repulsion or attraction? have the employers and ourselves to act like two antagonistic forces, looking with suspicion upon each other, and ready to take every advantage, as if we were in a continual wrestling match on the catch-who-can principle, where those who get the hold win, whether their cause be righteous or not? if the members persisted in their resolve to have no conciliation board, or some substituted machinery, who would suffer most? if there were two parties before you of equal strength and similarly conditioned, then the issue would be uncertain, and the victory would depend upon some unforeseen circumstances. such is not the case with us. given a solid organisation of labour, and the same of employers numerically--still the balance of the chances in a wear-and-tear and struggling policy will he on the side of the party who is the best ammunitioned and provisioned. in this case, which in your opinion as the advantage?" they pointed out that they were mutual sufferers with the members, if there were suffering; that there was not time in the lodge meetings to discuss the utility of such a system; and that as a consequence they, as one of the obligations of their office, were bound to have a fuller knowledge of the subject than the members. it was an unfortunate circumstance that the system had been tried in a receding market, but the proper test was not by one condition of trade. if conciliation were tested by an increasing as well as a falling market it would then be seen how useful it was. some people seemed to charge the conciliation board with being the cause of the depression. "there cannot be a greater fallacy. the causes of the reductions lie outside the purview of any system yet arranged, and the control of them is not within the possibility of an arrangement yet thought of. but the question that faces us now, and demands an answer from us, is, would they have come if the board had never been formed? there needs no philosophical knowledge to satisfy the mind on that point, except it be the philosophy of matter-of-fact, everyday life, which in these matters is not an unsafe test. let experience guide, and it will afford a sure refutation of the unfounded idea that it is possible to fix, firmly and permanently, wages by any scheme within the knowledge of man." they were desirous of giving them another chance, as the ballot on the previous occasion was very unsatisfactory, and some of the sections had made a request for such to be done. and they were hopeful that, before the notice of termination ran out, the conciliation board would be reaffirmed, as "the hope of all true reformers is centred in the cultivation of amicability and friendly intercourse between employers and employed, with a conciliatory method of settling any difference that may arise, monetary or otherwise, and in the ultimate blending of the two forces--capital and labour--for the mutual and equal benefit of all concerned. consider seriously every step we as an organisation take, and let all we do tend towards the attainment of the much-needed object." the result of the second ballot was against the board, the numbers being in close similarity to the previous vote--the miners being very largely against, while the other three sections were in favour. we may add here that it terminated on august th, and for a short time the county entered the region of uncertainty again, which all must acknowledge is no help to trade or district. death of mr patterson the month of july had been fatal to the organisation, for in it, in , mr crawford died, and on july th of this year mr patterson passed away from the labour to which he gave his youth and manhood. he had filled the position of agent and financial secretary for twenty-five years. it will not be out of place if we insert a portion of the _monthly circular_ for the month in which he died. it contains the sincere estimate of one who knew him intimately, who had the highest respect for him while he lived, and who now has pleasant recollections of his manly and reliable actions. he was no self-seeker or panderer for self-profit; he was the antipodes of that mean and despicable character. you might have difference of opinion with patterson, but you could at all times depend upon the open honesty of his nature. monthly circular _july ._ my first word must be a note of sorrow. july to us, as regards the agency, has been a fatal month. in it we lost crawford, and now patterson has joined the great majority. this is the common lot of all. happy is the man who leaves this world for the next without regret, feeling that his life has been of some service to his kind, and that the people amongst whom he has lived express their recognition of his worth by their sorrow and appreciation of his labours. such was our friend. if we, who stood by his bedside in the last moments of the final struggle, could have been cognisant of his thoughts there would have been no regret; for w. h. patterson was the enemy of no living man, but the friend of all. we were not so privileged, but we were so glad to see the large crowd of people who gathered to pay a tribute to his memory. the gathering was diversified in its character, spontaneous in its gathering, and truly sympathetic in its manner and spirit. but from our regret for his loss let us turn to the influence of his life. the true test of a man is his work. our friend stood the test. the real measure of a man's life is its actions; he was full measure. he was not showy, but solid, and as such, being dead, yet speaketh--speaks in no uncertain sounds; let us turn no indifferent ear. the main work of his life, in conjunction with others, was the inception, promotion, and solidifying of our organisation. it will be the most real expression of our sorrow if we do our best to carry forward that upon which he set his mind, and which he endeavoured on all occasions to enforce. would it not be sham sorrow and unreal regret on the part of a son who on the death of a father ... a father who by the toil and care of his life had made a position ... if he were careless of that work, and had regard only to self-indulgence? little as we may think of it, there has a fortune come to this generation and a position been gained for it by the labours of our friend and others which cannot be estimated in money. we are apt to test everything by a monetary standard, but in this case the test fails. within the life of mr patterson there have been effected changes which he outside the range of wages, but which are none the less valuable to us. these are only known to those whose working life commenced anterior to thirty years ago. there are many who have not the experience, and who cannot, therefore, realise to the full, the contrast. lightly as these may be inclined to look upon the changed conditions, and think because these conditions exist now they have always existed, there are numbers who know, and who are able to compare, and rejoice in the change made. i would not say that all is attributable to the labours of our lost friend. no man would have protested more strongly against such an idea than himself; but he did what he could; he never devolved his share of work upon others. he was earnest and determined at the foundation of the society, and anxious for its welfare during the whole course of our existence. we shall best show our respect to his memory by doing what we can to preserve and perfect the institution. the loss of mr patterson was followed by the election of mr t. h. cann to the office of treasurer, mr wilson being appointed corresponding secretary, and mr johnson financial secretary. we will close our reference to our friend by placing on record the estimate placed upon him by the committee who knew him. [illustration: t. h. cann] committee notice (_death of mr w. h. patterson_) gentlemen,--it is with very great regret that we announce to you the death of mr w. h. patterson, which took place at - p.m. on july th. our regrets on this occasion are not those of formality, but are prompted by a recognition of his worth as an official of our organisation and his character as a fellow-worker and a man. never yet had any organisation a more earnest officer, nor any body of men a more willing colleague, nor any community a more upright, honest, and straightforward man, than our friend who has been taken from us. he has not lived the years allotted to man, but the best part, and by far the largest part, of his life has been spent in the cause of his fellows. he has gone to his rest at the age of forty-nine years. twenty-eight of these have been spent in active, diligent service--and useful service. he was one of the band of men who twenty-seven years ago, in the face of difficulty, laid the foundation of our organisation; and since that time he has been watchful over its interests, consistent in his desire to benefit the members, and unwearied and uncomplaining in his endeavours to strengthen the structure he helped to rear. it was not his privilege "to die in harness," as we are confident it would have been his pleasure; but those of us who had the opportunity of judging know how anxious he was, so long as he could get about, to do and advise whenever he could. the name of w. h. patterson is wove into the web of our institution, and his life will be a blessing after he has gone from our midst. the good that he has done will live after him. happy shall we be if the same be said of us when death gathers us in. _july th, ._ miners' federation--washington strike the year was memorable for two things: the refusal of the miners' federation to accept durham as a member unless the county would agree to support a legislative eight hours' bill, and the conflict between the executive committee and washington lodge, which settled the question once for all whether money could be paid if a colliery were stopped illegally, even if the council decided to pay. these we will take in the order stated. towards the end of it was decided to join the miners' federation. the information was sent to mr ashton, the secretary of the federation, and the application was accepted. then arose the question as to the meaning of object : "to seek and obtain an eight hours' day from bank to bank in all mines for all persons working underground." in order that the intention might be made clear the executive passed the following resolution:-- that mr ashton be written to, asking whether object in the miners' federation rules means that the eight hours have to be obtained by state interference alone, or by organised efforts, and whether the districts have any option or choice in the matter. mr ashton replied that object was to be brought about by organised effort or legislation, or both. as far as the district having option or choice was concerned all members were expected to be loyal to the federation, to be guided by the rules, and assist in carrying out the resolutions passed at the conferences of the federation. that was interpreted to mean that if durham became a member, as all the other districts were voting for legislative action, it would be virtually bound to join in the demand for eight hours by state, and the executive placed the question on the programme for the council held on february th in the following form:-- that the county having decided to join the miners' federation, and we having been informed that we must agree to support a legislative eight hours as a condition of membership, and as we remember that the county has decided, by ballot in and by resolution in , not to support such a measure, we cannot agree to accept that condition until the county alter the previous resolution on the question, either by council, motion, or ballot. will delegates come prepared to say what shall be done in this matter? ( ) shall we rescind the previous resolutions? ( ) shall we support an eight hours' bill? ( ) shall a ballot be taken on the subject? the council passed a general resolution: "we adhere to the resolutions now standing in the association's minute-books--viz. that we do not go in for the parliamentary eight hours' day, and that there be no ballot taken on the question." that decision was sent to mr ashton on february th, the following being the letter:-- at our council meeting held on february th our members decided to abide by their previous resolution to oppose any state interference with the hours of labour. i am instructed by our committee to inform you of this decision and to ask you to let us know whether under these conditions your executive committee accept us as members of the miners' federation of great britain. on the presumption that you will accept us as members on those conditions, i enclose you a cheque on the national provincial bank, value £ (fifty-nine pounds), being our entrance fee at one pound per thousand members.--i am yours, john wilson. the receipt for the entrance fee not being sent the executive committee wrote again on february th: if you do not send the receipt the inference on all sides must be that you do not accept us on the conditions stated (our opposition to state interference with hours). if you do send a receipt, then we shall conclude that you do accept us on the conditions, and there will be no need to repeal the resolution of exclusion of . two days after that was sent mr ashton sent a receipt, and said: i have no desire to delay the matter of your district becoming connected with the federation. i enclose receipt for the entrance fee. as this was written two days after the committee placed the alternative before the federation it was assumed that durham was not to be bound to the legal eight hours. this impression was communicated to mr ashton on february th, and on the th the committee was surprised to be told: "in reply to your letter of yesterday, durham has been accepted into the federation as all other districts have been. whatever resolutions you may pass on general questions in your council or committee meetings you must be governed by majorities at the federation." then there arose a dispute about some contributions which were sent to mr ashton. the amount was £ , s. d. the dispute was as to the period which was covered by the payment. on june th, in a letter dealing with the disputed point, mr ashton said: i think you will agree with me that the difference on the hours question is so great that until durham can agree to withdraw their opposition to the miners' eight hours' bill, it is most unwise to keep their connection with the federation. and on july th the cheque for the £ , s. d. was returned to durham, and the separation mentioned above was effected by the return of the contributions. the executive committee then summarised the situation as follows:-- we decided to join the federation. we then found that we had resolutions standing against the eight hours. by our own decision of february th we resolved to abide by those previous resolutions. we then informed mr ashton, as secretary of the federation, that we had so resolved, and enclosed the cheque for our entrance fee, with the understanding that if the receipt were sent we were accepted on those conditions. our council again on may th reaffirmed our opposition to the eight hours, and we wrote to mr ashton and sent our quarter's contributions, and said we were desirous of remaining members on wage questions. we were then asked to say whether we could pledge the county to come out on strike, which we could not do. the conclusion of the whole matter then is, because we could not give a pledge to come out on strike on every occasion when so ordered, and because we were resolved to oppose the eight hours by state interference, our contributions are returned, and we are told by actions--which speak louder than words--that we are not to be members. we are not to be allowed to judge of our own circumstances and peculiarities, but must submit the most important part of the conditions of our labour to those whose conditions are widely different from ours, and who, knowing nothing of our circumstances, would force us to be guided by the changes they require in the hours of labour. the washington strike it will be observed that there has been no mention of local strikes except there be some peculiarity related to them. there is such in connection with this strike. it was of great importance to the association and the maintenance of the rules. there had been numbers of illegal stoppages, and although the leaders and members at the lodges affected knew they were breaking the rule, yet they persisted, and were enabled to carry a vote in council that they should be paid from the general fund. it was felt that once and for all the question should be decided, and it should be shown that where the constitution of the association was violated the violation should entail forfeiture of benefit, or else of what use was it to have rules or committee of management? to go on in such a loose manner was to make the rules a byword and a mockery. it was time they should have the seal of reality, and be placed on a sure foundation, so that order should be maintained, or at least those who with open eye did wrong should know that their action would not receive condonement, and they be paid the benefit of the association, as if they had obeyed its provisions. that was the question to be decided. should the rule be the guide, and the executive committee have the management, or should lodges be allowed to stop their colliery in opposition to the constitution, and suffer none of the consequences? the washington case afforded the opportunity for the settlement, and that is the reason why it is made part of this history. the dispute arose about the application of an agreement made by themselves. the nature of the agreement is of no import now. the action of the lodge and its relation to the rule is what we have to consider. the manager put one interpretation on the agreement, the workmen another, and they were the signatories. numbers of agreements had been disputed prior to that, and had been brought before joint committee or some other properly arranged tribunal, and managed by the agents, or executive, in accordance with rule. washington, however, set rule aside, disregarded the committee, and stopped the pit on the th of august. on the th the corresponding secretary met their deputation in newcastle, and told them they were acting illegally, and that they could not be paid from the funds. the deputation, however, were confident the council would grant them strike pay, although they admitted they were breaking the rule. other means were adopted to induce them to resume work. the lodge appealed to the council for a grant; it was not put on the programme. the trustees objected to the treasurer paying the money. they had taken the opinion of mr atherley jones previously. the question submitted to the counsel was: "supposing a lodge came out on strike in violation of the rule, without first having obtained the permission of the committee or council, would the fact that the council, after the men came out on strike, approved of their action alter the position or liability of the trustees?" the opinion was as follows:-- mr jones' opinion _august th, ._ with regard to the question raised, whether, under the circumstances described, the trustees have power to allow payments to be made to the men on strike who have violated rule , i am of opinion that they have no such powers, and any payment so made would appear to be a direct breach of trust. nor do i think the position or liability of the trustees would in any way be altered by the subsequent vote of the council approving such payments. the wording of rule is quite clear:-- "any lodge ceasing work" "under the circumstances which have happened" "shall forfeit all claims on this association"; and even though the whole association were to vote in favour of strike pay being granted, i cannot see how the effect of that rule could be removed. standing upon that advice, the trustees refused to allow the money to be paid. the lodge requested the executive to call a special council to consider whether a grant should be given them. the request was refused, because, as the rules had been violated and the trustees had decided that no money should be paid, it was no use calling the council, seeing, if the vote were given to pay, the decision could not be carried out. however, the question was brought forward at the conclusion of a council, and the delegates decided to pay a grant equal to strike allowance, but the trustees refused to allow the money to be drawn from the bank. the executive then placed the position before the members. they said the giving of a grant was but a form of evading the provisions of the constitution. the decision of the council placed the treasurer in a dilemma: either he had to refuse to pay, or face a prosecution in court for paying money contrary to rule. the committee had, therefore, either to leave the treasurer to his own devices, or call the trustees together, and place the whole question before them. the meeting was held in the office of dr r. s. watson, who was one of the trustees. they decided to take the case to the court of chancery, and to inform the washington lodge of their intention, and give them the opportunity of being parties to the case. mr isaacs (the association lawyer) was instructed to write the lodge, which he did. he said he was instructed to inquire whether they wished "to be a party to the proceedings, and if so, to kindly supply me with the name and address of any one of your members whom you may appoint to represent the lodge." after some negotiations, and with the view to make the matter mutual, the executive agreed to bear the cost of the trial for both sides. the hearing did not take place until the th of february , but in order that we may keep it in close connection it will be well to consider it here. it was heard in the chancery court, before justice cozens hardy. the association was represented by mr i. isaacs, its legal adviser, and the lodge by mr c. w. newlands of south shields. there were able barristers on both sides. the judge decided: if these men came within section it must be because these particular men must be considered deserving, and also within the objects of the association. he thought unless there was something to strike them out the argument on their behalf was well founded. the real question was whether, although the language of rule defining the objects of the association included them, they had not by been removed. he thought that was the case. he did not think he could limit the effect of that rule so as to make it mean that they should forfeit only the absolute right to have s. per week under rule , which it was admitted they had lost. he thought the exclusion applied not merely to claims as of right, but to all protection from the association, and they could not be deemed legally or properly objects of the benefits of the association. so far as the executive and trustees were concerned that trial and decision were satisfactory, but the lodge said they wanted it taken to the court of appeal. so far as bearing the cost of the trial was concerned the pledge had been carried out, and the committee were surprised when it was suggested to carry the case to a higher court. however, as they were desirous to have the case properly decided, and that there should be no room for doubt (the welfare of the association being their great consideration), they agreed, and guaranteed the payment of the entire costs. the appeal was heard on november th and th, the judges being rigby, romer, and vaughan williams. a strong effort was made to reverse the decision. all the skill, plausibility, and sophistry of very able lawyers were used. the rules were purposely disparaged and travestied, in order that a prejudice might be created against them, but the judges unanimously agreed with the finding of the court of chancery. this is a bare record of facts of a dispute and trial which was fraught with importance to the association. it generated a great deal of bitterness. the leaders could have had no personal ends to serve. their aim will be truly set forth by a quotation from the _monthly circular_ for november . monthly circular, (_the lessons of the trial_) the trial is over, and, so far as any personal feelings are concerned, the sooner it is forgotten the better it will be for our association. to guard and strengthen that should be our first thought and care. but while it will be beneficial for us to forget any attribution of ill motives, and evil speaking or ruffled feelings consequential thereto, we shall be wise men if we gather up the lessons which come to us. this battle has been fought for one purpose only, and that is to support the authority of the rules. to that end, and that alone, have our efforts been devoted. the great question at this moment is: whether it is better to have a set of rules which requires that the committee of picked men (responsible year by year to the will of the members) should have a knowledge of, and be called in to assist in, the settlement of disputes before a large colliery is stopped, and a serious expenditure thrown upon the association; or whether a lodge shall have a free hand to stop a colliery at will, and then run a chance of creating a favourable feeling, and receiving large sums from the funds, when, if the committee had been consulted, the matter might have been settled; or if not, a strike entered upon legally. another lesson is that, having received the sanction of the courts to our rules, and having lifted them out of the uncertainty by which they were surrounded, we shall do well to keep them in the certainty in which they have been placed. it is very clear that an attempt will be made to alter the rules which guide this matter. if so, a lax (and ruinous) state of things will be introduced. for the last two or three years the same attempts have been made, and again this year resolutions with the same object are sent in. the rules which place the affairs of the association in the hands of the committee (before a stoppage) have to be erased or mutilated, and rendered useless. surely it is better, and more conducive to the welfare of the society, to have our affairs placed on business lines, than to have a code of rules which will admit of loose procedure, and spending illegally large sums of money, which will be wanted whenever the depression of trade sets in. my advice to you is to consider carefully every amendment which may come before you. trades organisations will prosper most when they are founded upon, and guided by, business principles. the wages question--the compensation act the uncertainty which the federation board had pointed out as the inevitable result of the abolition of the conciliation board soon made itself manifest. there were continual demands being made upon the federation board to seek advances, but they felt how difficult it was to get reliable data upon which to found a claim. on march nd they gave the county an account of an interview they had with the employers on the th of that month. the suggestion as to the claim for an advance being made was not supported by any data, and when they met, the employers pointed out that the indications were in the direction of depression more than the expansion of trade, and therefore the wage committee could not recommend to the owners to concede an advance. that refusal the board advised the workmen to accept until there was some better trade prospects. "like prudent men, and, acting upon the lines you would have us proceed upon, we are convinced it will be more hurtful than useful to initiate or press a demand for an advance unless the state of the markets warrant such a course." another meeting on the wages question was held on may th. a strike took place in south wales in the beginning of april, the effect of which was felt in an increased demand for the class of coal produced in this district. their supply being cut off consumers turned to other sources, and as a consequence there was a natural feeling of unrest in durham among the workmen. they had the impression that the whole of the produce of the county would be affected by the demand, and therefore the increase in price would be an all-round one. the federation board met that "false impression which we fear rests in the minds of many of our members" in a statement they sent out on the th of may. they pointed out two very important considerations, which the generality of members would lose sight of. there was a large amount of coal sold under contract, which would not be affected by the temporarily increased price, even if all the output of durham had been steam coal, but it must be remembered that only nine per cent. was of that class. they then gave a calculation to show how a rise on a small percentage would affect the whole. the steam coal being the only part feeling the increase, and that class forming only nine per cent. of the total, what would be its universal effect? "without contending for the accuracy of the quantities let us give a calculation which may suggest a key to the position. of the nine per cent. of steam coal let us suppose two-thirds of it was sold under contract at a normal market price. we should then have only three per cent. of the entire output getting a higher price. let us further suppose that this three per cent. secured an advance in the abnormal state of the market of s. per ton during the strike; we should only have realised a general increase equal to, say, . d. per ton over the whole of the coals produced." considering, then, the purely temporary nature of the rise in price the board agreed to accept an advance of five per cent.--two and a half on basis rates under the usual conditions, and, with the view of meeting the exceptional circumstances, a temporary advance of two and a half for six pays. the advances were to date back for a fortnight in each case, the understanding being that if the prices fell at the end of the six pays the temporary two and a half would be discontinued. on july nd the board met the employers, when the temporary advance was continued for other six pays. a subsequent meeting was held on october th. the employers offered to increase the temporary advance of two and a half to five for a further period of six pays. the board was willing to take the five per cent. if it were considered a permanent advance. the settlement agreed to was an advance of two and a half, and a continuance of the temporary advance of two and a half for six pays more. the compensation act during the parliamentary session of the first compensation act was passed. the date of commencement was fixed for the st of july . while the act was under discussion the representative of the durham miners in parliament urged strongly that, not only should facilities be given for the formation of committees, but means should be adopted to induce employers and employed to take steps in that direction as a means of avoiding the friction and litigation which the new law involved. the idea of a compensation committee was from the very commencement very favourably received by the members of the association, and the employers were as desirous on their part to join in the endeavour. there was a natural desire on the part of the permanent fund officials to formulate a scheme to strengthen their fund. it was found that the attempt between the trade unions of northumberland, the federation board, and the permanent relief fund to arrange a scheme was a failure. a number of meetings of joint committees and sub-committees, representative of the various associations, and between those sub-committees and the employers, were held. the failure arose from the character of the proposition--that there should be an insurance fund, which would take over all the liabilities of the owners, and insure all the workmen, which, said the employers, was the primary condition. the miners' executive in durham could not accept such a scheme, and they turned to the formation of a committee representative of their association alone, and the owners. negotiations went on with the owners, and finally the executive committee asked for full power on lines which they indicated. this the county agreed to give, and an agreement was come to in time for the commencement of the act on july st. the system of class average obtaining in the county lent itself to the formation and working of such a committee. this the men readily adopted, and it was another illustration of the hold mutuality and compromise had on the men of the county as a whole. some men would have made above the average wage, and have worked more than the agreed number of days, and as a consequence their compensation would have been greater, but it would have entailed a large amount of labour if it had been on an individual basis. but by the committee arrangement the system worked automatically. in the formation of the compensation committee durham stood alone. there was nothing like it in any other district or trade, and its action was of the greatest benefit to employers and workmen alike. election of mr house--the wages again--the second conciliation board--the aged miners' homes--deputies' basis wage for some time there had been a growing desire for a further subdivision of the labour in connection with the agency. it was thought that it might be useful if, instead of the joint committee business being in the corresponding secretary's department, an agent was appointed, who should have sole charge of that committee. this rearrangement was hastened by the passing of the compensation act. the work thrown upon the organisation as a result of that measure was immense owing to the very great liability there is to accidents in the miners' occupation, and consequently the large number of delicate questions that were sure to arise in the application of a complex and complicated measure such as the new act. the executive committee felt that it was imperative something should be done, and, acting on their suggestion, a new department was formed. mr w. house was the gentleman selected to fill the new office. mr house brought to the work a very essential qualification. his ability was unquestioned, but he was also experienced, having served on the executive and joint committees for some years, and was thus thoroughly prepared for taking upon himself the duties of the new office. [illustration: alderman w. house] the wages again in considering the wage negotiations for mention was made of a temporary advance of two and a half per cent., which was given for six pays, and then carried forward other two periods of the same duration, and extended into . on the th of january the federation board met the owners, their errand being to get if possible the temporary advance (which would terminate on january st) incorporated into the ordinary percentage. that request the employers could not grant, as the ascertained price for october and november was less than for the three months previous. "they are willing, however, to continue the temporary advance for a further period of six pays, or as an alternative they suggest that this meeting be adjourned until saturday, the th inst., by which time the selling price for the quarter ending st of december will be ascertained." the federation board chose the extension for a further six pays, as they believed it was the most beneficial course. the next meeting was held on april th. nothing was arranged, and there was an adjournment for three weeks. at that meeting the owners said there had been a declension in the prices. after a long discussion they offered an advance of three and three quarters, bringing the percentage above the standard up to twenty-six and a quarter; and, in consideration of special circumstances, to give a temporary advance for three months of one and a quarter, and they were prepared to date it back a fortnight. the arrangement was a very unique one, and, said the federation board in their explanation to the members, "it arises from the operation of the two and a half temporary advance, and the fact that the adjourned meeting was not held until after the dates fixed for its termination." the second conciliation board the delay and uncertainty, both as to time for making application for, and the data upon which to found, the claim, turned the minds of the members to a renewal of the conciliation board, or some similar system by which wages could be regulated more smoothly and expeditiously than the policy they were pursuing. on the programme for the council held on may th there appeared a resolution from marley hill: "we move that the county be balloted for and against forming a conciliation board." the executive committee in their note on that resolution strongly recommended its adoption. it was highly desirable that the feeling of the county should be ascertained. they said: we have previously expressed the opinion that the steadier we can make our trade, and the more certainty we can infuse into our industrial relationship with our employers, the better it will be for the workmen; and there is nothing more calculated to foster this desirable condition than the principle of conciliation. it was a mistake when we terminated the previous board, and this has been revealed more fully in our negotiations with the owners in a rising market. we feel sure we would have done better, and it would have saved a great deal of friction, if we had had the board. there are other questions of great importance besides the wage question which a conciliation board could deal with. we therefore advise that you carry this resolution. acting on that advice the council adopted the ballot, and by a majority of in a total vote of , the board was re-established. the bishop (westcott), who had been anxiously watching the course of events, came forward to offer his congratulations and assistance if required. no time was lost. the four sections were called together, and they recommended that the old rules should be adopted, and that a circular be sent out urging the acceptance of the same as the constitution of the new board. the objects may be inserted here. "by conciliatory means to prevent disputes and to put an end to any that may arise, and with this view to consider and decide upon _all claims_ that either party may, from time to time, make for a change in county wages or county practices, _and upon any other questions_ not falling within the jurisdiction of the joint committee that it may be agreed between the parties to refer to the board." the following was the voting on the adoption of the old rules:-- for the old rules against majority miners enginemen -- cokemen mechanics -- at the earliest moment after the result of the vote was known a meeting was arranged with the employers. at that meeting the employers wanted to alter the rules in one or two particulars, but the federation board informed them that their powers only extended to the adoption of the old rules, and if any alterations were made they would have to be referred to the members for sanction. "it was agreed that the employers should take the statement to a full meeting of their members, and if they persisted in desiring amendments a further meeting should be held, but if not, then the two secretaries should get the rules signed by the owners' committee and the federation board." the latter alternative was adopted. the old rules were signed as suggested. the first meeting of the board was held on november th. the officers elected were sir david dale, chairman; w. h. lambton, vice-chairman; r. guthrie and j. wilson, secretaries of their respective associations; and lord davey, umpire. it was further resolved: "that with pays commencing th and th of november , wages should be advanced by ¾ per cent., making the wages of underground men, mechanics, enginemen, cokemen, and banksmen to be ¾ per cent. above the basis of , other classes of surface labour ¾ per cent. above the basis." the aged miners' homes in october was initiated a movement of which durham may justly claim to be the pioneers--viz. the provision (as far as it can possibly be done) of free houses and coal for the aged mine workers. for a few years the subject had been assuming shape. vague in its inception, by the perseverance of the originators it was inaugurated in this year. the first to make mention of such a movement was mr j. hopper, who subsequently became secretary and clerk of the works. to him was soon joined mr h. wallace, land steward to earl ravensworth; and then other three: the rev. canon moore ede, j. johnson, and j. wilson. their first step was to secure a large hall and two acres of ground near boldon which could be made into tenements. the building was the property of the ecclesiastical commissioners, but was rented at an easy rent. that was taken over by the boldon workmen for their own old men. then the committee turned to the ecclesiastical commissioners again. without entering into all the stages of the negotiations, the final result was the renting of nine acres of land in three plots situated in three different parts of the county. just at this juncture there was an opportunity to purchase the colliery village known as haswell moor, consisting of houses, to each of which was attached a garden. the whole of it was freehold. this fortunate bargain gave inspiration to the committee, as it was very cheap, and an impetus to the effort, as it formed a very nice colony of old people, the cost per house being about £ . the scheme rested on a voluntary basis. the committee in initiating the movement resolved to keep it clear of all compulsion. their proposition was s. per member from all in the miners' association per year, which would give £ . the lodges responded very readily to the appeal, and were soon joined by the other three sections of the federation board and the deputies. in addition, the outside public sent large and generous help. one very striking letter was received, enclosing a cheque for £ , which we will record. "mrs graham and i are very pleased to find that you are making such good progress with this most useful and laudable scheme. we are quite sure that the old folks would be more at _home_ and more comfortable in cottages such as they have been used to all their lives instead of being placed in specially built almshouses or hospitals. "we would like to feel that we have made one old couple happy by paying the cost of one of the haswell moor cottages, as intended to be made fit for habitation, and therefore propose to subscribe £ ." that encouraging letter and generous gift were from coroner graham of findon hill, near durham, and was soon followed by other expressions of sympathy and substantial help. bishop westcott rendered great assistance, and opened his castle at auckland for one of the sectional meetings the committee called as a means of bringing the question before the lodges. his lordship allowed the use of his splendid drawing-room, and presided over the meeting, and on every hand the workmen were praised for their grand work. the best commendation, however, was the comfort of the old people, and when the opening day came there could not have been found prouder men anywhere than the committee of management. the opening of the first batch of houses took place at haswell moor in october. the ceremony was performed by mr j. wilson, the chairman of the general committee, and the inaugural address was delivered by the bishop. a quotation from the _monthly circular_ giving an account of the proceedings will be fitting here. it was a great occasion, and the address was worthy of it. there was a very large company in the tent to listen to the eloquent remarks, but there was a larger outside who were excluded from the privilege. to the men of mature years there was the rejoicing coming from the past, and an exhortation to act in unity, and not to be simply receivers, but givers of strength to the common cause. they were not alone, not isolated separate units, but members of the great body; strong with the strength of all, and glad with the service which they could render to their fellows. a man who received all and gave nothing was like the dead sea. however rich the floods might be that flowed into it, it retained no life-giving, no glad force--all was lost. in addition, there was the urging to avoid despair and have hope. nothing could be more fatal than to declare that, because we were not moving with greater rapidity, the goal was unattainable. "do not listen to such a vision of despair, cherish the full vigour of hope." let me finish with the words to the young men. i wish all could have heard the words of wisdom as they fell from the lips of our respected and honoured bishop. as they could not, let me quote them, "they had received a splendid inheritance, splendid with noble achievements and noble traditions, and they--as men who had mastered themselves and realised their obligations--would use it well, guard it well, and hand it down to those who came after, enriched by the fulfilment of hopes cherished long ago, and illuminated by the brightness of hopes which those who came after them would perhaps be allowed to fulfil." on that day, by the inauguration, the durham miners took a long step in the path of benevolence, and raised themselves to a proud and prominent position amongst true reformers. it was a grand illustration of the truth that they who most practise self-help are best able and most eager to help others. a working man's income limits the possibility of giving large sums; but the many small rills make the large river. there is large philanthropy in a small gift. the volume and value of it lies in the spirit and intent which prompts it; and the ultimate success of a movement like the aged miners' homes scheme lies in the willingness of the thousands of workmen in and about the mines to assist. based on that, the county can be studded with homes where the aged and worn-out miner and his partner can find home comfort and warmth when the sun of their life is nearing the setting and the shadows of life's evening are gathering thick around them. no young man can measure the full meaning of such provision, but all can feel the rich mental luxury which will assuredly result from taking part in the providing. deputies' wages we will close this year by a reference to a settlement made during it. this was in respect to the fixing of a basis wage for deputies. prior to the agreement there had been a fixed wage, which was altered by adding a penny or twopence, or more, to it, or reducing in that way if the wages were decreased. it was a very unsatisfactory mode of procedure, and always involved a meeting between the owners' and the deputies' association after the federation board had dealt with the wages. for some time there had been a strong desire on the part of the deputies who were in the miners' association to have their wages regulated by a percentage, the same as the other classes of workmen. in july the following agreement was signed:-- it is hereby agreed that with pays commencing th and st of july the basis wage of deputies shall be fixed at s. ½d. (four shillings and eightpence halfpenny) per shift for back-bye shifts, and that these basis rates shall be subject to the same percentage, advances, and reductions as may be from time to time arranged with regard to the wages of the miners. death of mr forman--election of mr galbraith--agreements made during the year on the nd of september death made another inroad upon the original leaders of the organisation by carrying off the president, mr j. forman. for over twenty-seven years he had been in that position, and from first to last he carried out the obligations of the office in a manner equalled by few and excelled by none. he was fitted at all points for being president of an organisation of workers such as the durham miners. the best estimate of his character will be found in quotations from the _monthly circular_ and the executive committee's minute. death of our respected president i am sorry to say death has made one of its most serious inroads into our ranks, and taken from us one of the most prominent figures in our association. our much respected and gentlemanly president is no more, and his services, over more than the average length of a generation, are ended. we long for the sound of a voice that is for ever still, and the touch of a hand that had a friendly grasp. for nearly thirty years the name of forman has been a household word amongst the miners of durham. he was not ambitious of "spreading a sounding name abroad," but he had a deep desire to do his duty to his own people. his was a quiet nature; but among men, as in nature, the quiet forces are the most productive of good. in the movements that make for progress in men, as in our physical surroundings, the clamour of violent action and noise are not the most useful. in the history of our association, from its very commencement, our departed friend has been one of the binding and consolidating influences. wise in counsel, when a spirit of rashness and impatience seized some of us, he has many a time helped to steady the mind and temper, and tone the action. prolific in suggestion he has oft pointed a way out of difficulty in the time of stress and strain; in fact, he was well and amply equipped and qualified for the important position he filled amongst us. he took upon himself the office when times were vastly different from what they are now; when capital and labour were in this county like two opposing forces, separated by a spirit of doubt and animosity; and he has done much to establish a better feeling between employers and employed. he knew by experience the position of inferiority and harsh conditions in which our lot was cast before the foundations of the society were laid. he has assisted and rejoiced over every step towards equality and relationship, and he was very anxious lest anything should be done to mar our usefulness. mr forman was more than an agent, he was a friend and an example. a man may be appointed to a position and do his work in a mechanical and perfunctory manner, like a hireling waiting for the shadow of the day, but that is not sufficient, and it did not satisfy him whose loss we mourn. he was an example in conduct and in mental cultivation worthy of imitation by all our young men. he looked upon the workmen as something more than machines, and he was desirous that they should pay more attention to the improvement of their minds, and the formation of thrifty and studious habits. in that he was no theorist, for he was a man of very extensive reading, especially upon scientific subjects, and, as a consequence, he was able to approach and deal with our questions in a most intelligent manner. he has gone, but his work is with us. it is our heritage, not merely for enjoyment, but for employment. we can best show our respect for his memory by our acceptance and proper use of that legacy. these men whose lives like his stretch back into the dark days are decreasing in number year by year. let us do nothing to damage the institution they helped to establish and consolidate, and let our effort be to strive for the goal they sought to attain. death of mr john forman (_executive committee's notice_) _september, ._ our regrets on this occasion are not those of formality, but are prompted by a recognition of his worth as an official of our organisation and his character as a fellow-worker and a man. never yet had any organisation a more earnest officer, any body of men a more willing colleague, nor any community a more upright, honest, and straightforward man than our friend who has been taken from us. he was privileged to live to the ripe old age of years, and for more than a quarter of a century has devoted the whole of his time and the best of his energies to the upbuilding and consolidation of our society, and the betterment of the working classes generally. we shall miss his genial presence and guiding counsel from all our business meetings. he was on all occasions a reliable guide and counsellor in our deliberations on complicated questions, and in the general matters pertaining to the work of the association in the midst of dark times and difficult circumstances. we feel that by his death we have not only lost an able and efficient president and colleague, but the workers in and about the mines in durham have been deprived of a friend whose lifelong services have been devoted to the bettering of their conditions as wage earners. and further, we would tender to the family our sympathy in the great bereavement which has fallen upon them, and the hope that they may be strengthened by the assurance that, although dead, he still lives in the grateful remembrance of the people amongst whom he lived, and for whom he laboured. [illustration: alderman s. galbraith] the vacancy caused by his death was filled by mr house being transferred from the joint committee agency to the presidency, and the election of mr s. galbraith as his successor in the joint committee. in the election the county chose a well-tried and very trustworthy man. he had been checkweighman at the browney colliery for twenty-one and a half years. those workmen placed absolute reliance in him, and without reserve allowed him to manage the affairs of the lodge. the condition of the colliery, the peace and harmony which obtained, and the fact that only one deputation visited them to make inquiry into a grievance during the whole time he was there, are clear proof that he had great care for the interests of the men, and that they were well repaid for their confidence in him. his tactful management of the local business specially fitted him for the wider sphere of labour. the members reasoned safely when they concluded that he who had been faithful in the local would be faithful in the general. those who knew mr galbraith were in perfect agreement as to the opinion formed by the men who had been in such long and profitable business contact with him. agreements screenmen--labourers--datal wage--hewers' datal--houses and house rent--boys' advance the first of these was the raising of the basis wage of the screenmen and labourers. that wage was fixed by an arbitration at s. ½d., but was never quite accepted by the county. negotiations had been proceeding, and on st march it was agreed "that the basis wage of _bona fide_ screenmen and labourers on and about the pit-heap and on the colliery branches should be s. d. per day." this was a clear advance of ½d. per day, and meant nearly a day's wage increase in the fortnight. the second was in reference to the hewers' datal wage. there was no settled or uniform principle of payment for the back-bye work. on august th it was arranged that: "when coal hewers are taken from hewing to do other work for a shift or shifts (or portions of a shift), during which they would otherwise have been employed at coal hewing, they shall, for not exceeding three consecutive shifts employed at such other work, be paid the hewers' county average wage." the third settlement was the "houses and house rent." this had been on hand for six or seven years. it was placed on the agenda of the conciliation board in . after that board terminated the question lapsed, but was brought forward by the owners at the board meeting on may st, . it was at first part of a general application, but shortly before the meeting the mechanics introduced a house question, and therefore the request of the owners was made to apply solely to miners. the subject was adjourned to give the employers a chance to rearrange their claim. before the meeting held on august rd the owners' and miners' committee held two meetings, and an agreement had been come to, subject to the approval of the miners' lodges. the conciliation board was informed of this; further, that a return was being taken, and that the agreement was being strongly recommended. it was adjourned on the understanding that the owners could put it on the next agenda, if not settled in the meantime, and could then ask the board or umpire to decide. the request of the owners was as follows:-- that the general question of the supply of houses and coals be considered by the board of conciliation with a view to the points of difference between the owners' and miners' associations being decided by the board. the return mentioned above resulted in a refusal of the agreement, although large material changes had been made in it to the advantage of the workmen. the return was most unsatisfactory, as fifty-two collieries, representing votes, did not vote. the executive committee decided to call a special council, and informed their members of the position. the subject was sure to be settled at the next conciliation board meeting. "we have pointed out to you on one or two occasions that if it is not settled by us it will come before the next conciliation board, who will be asked by the owners to deal with it or refer it to the umpire." the special council was held, and a discussion took place on the agreement, but no vote was taken. in due course the subject came before the board. it was felt that the refusal was caused by the exclusion of the shifters and wastemen. the owners were willing to include these, and the board agreed to the list of classes and conditions contained in the agreement of november . the agreement settled a long-standing dispute, and established for twelve classes the right to a free house, or rent if houses were not found. in respect to the other classes not specifically named in the list, their right would rest on the custom of the colliery obtaining on the st of june . under the circumstances the agreement was the best that could be got, and was a very long way ahead of the uncertain condition of things which existed prior to its signing. there was this to be considered: if the board had not settled it then the umpire would have been called in, and there was no assurance that he would have gone so far. with respect to the rent, which was dependent upon the custom of the colliery, the right of the classes named to a rent (if not the amount) was guaranteed. before the arrangement was made, if there were not sufficient houses, the men belonging to the colliery had to prove, at joint committee, it was the custom to pay rent at that colliery. if they failed to establish the custom, then they were non-suited, and without rent. that which was indefinite and uncertain was lifted out of the region of contention once and for all, and that in itself was no small advantage. in judging of the merits of the "houses and house rent agreement" it must be remembered that the executive committee and federation board had to contend against time and precedent. these were no mean forces. practices which in some cases had existed for thirty years were difficult to alter by the party seeking the alteration. if the effort had been made twenty-five years before it would have been comparatively easy: "customs would have admitted of easy proof, and the data would have been new and readily substantiated." keeping those things in remembrance, the conclusion will be that the agreement was a good one. on the th of december other two small agreements were signed. one of them had reference to boys whose wages were below s. and those having a basis wage of s. and d. or less. the former were raised to s., and the latter had to have d. increase. the other change was in relation to smart money for beat hands. it was agreed that, as the compensation act did not cover that injury, the smart money should be continued where it had been the custom to pay it before the act was passed. the coal tax--the death of bishop westcott--the appointment of an accountant in the spring of the year the whole of the mining industry was startled by a proposal made by the chancellor of the exchequer to place an export duty of s. per ton upon all exported coal. it was done to enable him to meet the heavy expenditure which had been thrown upon the nation by the boer war. the entire cost was over £ , , . the year or two previous the coal trade had been prosperous. the profits of the employers and the wages of the miners loomed up very large, and he being in a desperate position (having a deficit of £ , , to meet) thought it safe to make an attack on the trade. his proposition was a very disastrous one. the arguments advanced in support were uneconomic and fallacious, but were forced upon the house of commons by the sheer weight and force of a great and obedient majority--a majority whose party loyalty covered a large number of political sins. his main arguments (upon which the changes were rung) were as follows:--coals were a great national asset, and the exportation should be checked, and even if exported under the s. tax the foreigners would pay it. to say the least, the former of these arguments was too narrow to be considered at all seriously, because if the necessities of the nation demanded a preservation of our coal supply, then it could only be done by a total prohibition of the export. further, it lost sight of the large mining population, the amount of capital sunk in the mines, the ships and sailors employed in the carrying of coal, and the interchange of trade, which would be interfered with if the policy were effected. the argument as to the foreigners paying the s. was fallacious and selfish; fallacious because it assumed the foreign consumer would not seek the cheapest market, which would be opened out to him by the development of the continental coal fields; and selfish because, if correct, it was an endeavour to throw upon him a part of the cost of a mad and wasteful war, when he took no part in the initiation of it. his proposal was met by fierce opposition in all the mining districts, both exporting and non-exporting, but in none more than in durham. employer and employed united in opposing it. to such an extent was this joint action carried that the pits were all laid idle for the purpose of affording the workmen an opportunity to hold mass meetings. in a circular issued on april nd the executive committee informed the lodges that they intended to hold seven simultaneous meetings, and to join the northumberland miners on the town moor, newcastle. in the circular they said: the occasion is important. time is short. the question is urgent. a more injurious tax was never proposed. if carried, it will cripple our trade, but more especially that of northumberland and south wales. our export trade is not so large as theirs, but we are so closely bound together that we are sure to suffer with them. let our protest be as large and emphatic as the tax will be injurious, and then the pressure of public opinion will compel a withdrawal of the chancellor's proposal. in connection with the national protest large conferences were held. the first of these took place on april th and th, at which a deputation was appointed to meet the chancellor on the th; but he held out no hope. the conference was resumed on the th, and on may st. there was a very strong feeling in favour of stopping all the mines in the country, and a resolution in that direction was adopted. the main obstacle to an immediate stoppage was the fact that certain districts had not considered it, and the conference was adjourned for a week to give them time to call council meetings and consult their members. the adjourned meeting took place on may th, but it was found that there was a more peaceful spirit abroad. durham was in favour of the stoppage, and the delegates, acting on instruction from the council, voted for that course of action. the conference was against it. an arrangement was come to in view of any district being asked to submit to a reduction in consequence of the coal tax. if that occurred, then "another conference should be called to consider and determine whether the whole of the mines of the country should be laid idle until such intimated reduction is withdrawn." so far as any stoppage of work was concerned, the agitation was at an end, but the protest did not cease with it, for year after year it was brought forward, and at all the galas it was made part of the resolutions. deputations met the chancellor, and in parliament the spokesmen of the miners brought forward the question on every opportunity. at the very outset they compelled him to exempt all coals sold for s. per ton and under. and (to anticipate a little) one of the first effects of the return of the liberal party in was the removal of the tax, to take effect on the st of november that year. the death of the bishop of durham the history would be incomplete if we did not make a reference to the death of bishop westcott. he was known amongst us as "the pitmen's bishop," and well he deserved the designation, for from the time of his coming to the county he sought on all occasions to make himself acquainted with our conditions, and was ever ready to assist in the work of amelioration. in every effort in that direction he was ready to counsel. he was one of england's greatest scholars, but his learning did not blunt his sympathies nor check his desires to help the people in their struggles. he was highly religious, but it was not the religion of the visionary. it found expression in actions. he proved his faith by his works, and demonstrated it by that higher and truer exponent of a man's creed, his active participation in every movement which tended to purify the conditions of our working and home life. his death was a unique circumstance. at the gala held on july th he delivered a masterly address in the cathedral. his closing words were prophetic. he informed the large gathering, mainly miners, that it would be the last time he would address them. whether this was the presentiment of the coming of the last messenger or not we cannot tell, but it is certain that the kindly heart and eloquent tongue were both stilled by death, and the miners were in sorrow longing for the sound of a voice that was gone, within a short week after he had thrilled the hearts of his hearers, and a great sorrow fell upon the county without regard to class, creed, or social status. the following resolution passed by the executive committee will show the appreciation of his worth expressed by them in the name of the miners:-- that we, the executive committee of the durham miners' association, in the name of our members, express our universal sorrow at the death of our respected bishop and friend, the late bishop westcott. we recognise that we have lost a sympathiser, counsellor, and helper in all our efforts for better conditions both in our home surroundings and our working life. from the first day of his residence amongst us we felt that it was his desire to be the bishop of the diocese in the truest and best sense of the term; and as the years have passed that feeling has been strengthened by the words of kindly counsel he has given us and by his generous and helpful actions. while, therefore, we share in the loss that has fallen upon the whole community we join in the expression of regret and sorrow which will be felt in every portion of the sphere in which he moved, and we tender our sympathy to the relations of the truly great and kindly christian, who has been taken from a life in which he lived usefully and well to a reward which awaits all who try to correct the wrongs and brighten the darkness of this life. appointment of the accountant under the sliding scale there were joint ascertainments of prices by each side having a firm of accountants, who agreed to the average realised selling price of coals. when the scales terminated the services of the accountants on the miners' side were dispensed with, and the selling price was gathered by the federation board visiting various depôts, the ports whence coal was exported, and the coal exchange in london. now it was obvious that such a system was at its best very uncertain, and while the data gathered might be asserted it never could be put forward as accurate. without the accountants, the mode adopted was necessary, but it was difficult, expensive, and unreliable. the federation board, upon whom the burden of seeking the prices fell, was never satisfied, and in the end the members came round to that way of thinking. on the miners' council programme for september th the following resolution appeared:-- accountant be engaged for the purpose of ascertaining the price of coal, the mode of procedure to be arranged by the executive committee. the resolution was carried, and was sent to the federation, and by them placed before the other sections, and finally adopted. at the board meeting held on november th it was decided "that mr e. sparks be appointed as the accountant for the board in the ascertainment of coal prices on the terms which obtained under the sliding scale, and that he be asked to meet the board at the next meeting." between the loose system which obtained prior to his appointment and that which resulted from it there was a very great contrast. without the definite figures he was able to supply the workmen were always in an atmosphere of uncertainty on two points--first, the time when to apply for an advance; and second, as to the amount to ask for. further, whatever demand the owners might make it was a matter of guesswork as to the accuracy of the change in the markets. with the quarterly ascertainment the state of the trade was given to the very smallest decimal, it gave reliability as to data, and guaranteed the stability of trade and the regularity of work, which is a great consideration to the workmen. - hours of datal boys and firemen--bank holiday--mr patterson's statue--ballot on eight hours--coal drawing after loose--agreement of th august--surface firemen's wages on monday, the th of january, the executive committee met the employers' committee on six requests. three of them were the hours of timber leaders and others, putters at datal work, and the hours of firemen at the week-ends. those three were settled by the allowing agreement:-- it is hereby agreed between the durham coal owners' association and the durham miners' association as follows:-- _putters at datal work._--that the hours of putters when sent to datal work shall be those applicable to the particular class of work which they are required to perform. _firemen's week-end shifts._--that the hours of firemen employed at boilers attached to stationary colliery engines which work continuously between a.m. on saturday and a.m. on monday shall be eight per shift between these hours. _timber and water leaders._--that the hours of the following classes of boys shall be in future eight per day--namely, timber leaders, stone putters and water leaders, and those boys who for a full shifter's shift may be working with shifters whose hours are eight. those whose hours are reduced to suffer a proportionate reduction of wage. this agreement to take effect with pays commencing the rd and th february . for the durham coal owners' association, reginald guthrie, _secretary_. for the durham miners' association, john wilson. the result of the settlement so far as it affects the young men will be seen by the following table, and it must be remembered that the total number of days reduced was for any one day, and not for a fortnight:-- timber leaders water leaders stone putters number of putters at datal work on any given day other boys so engaged ---- total days reduced these figures were taken from the associated collieries. there were a number of others, which would increase the total somewhat. it will be observed that the hours shortened did not in any way affect the coal-drawing time, and were indications of the willingness to meet the shortening of the hours if it were expedient to do so. it was in complete harmony with the general policy of the association--self-effort even if the end were a little longer in being reached, and negotiation in preference to an appeal to the legislature. further, the settlement proved that the inexpediency and difficulty of applying the eight hours a day was the only obstacle in the way of the durham men, and not their unwillingness to shorten the working time, as was alleged by many outside the county. the bank holiday for some years there had been complaints from the employers in reference to the pits being laid idle on bank holidays, without any arrangement being made for the same. the logic of their position was incontrovertible. they stated it in the following manner:-- as associations we have had business relations for over thirty years. we have in that time made many agreements, and have arranged tribunals for every class of difference, and yet you, one of the associations, have deliberately set all that machinery to a side, have ruthlessly broken all precedents and procedure, and have for some years laid the pits idle, without even consulting the owners' side. they then brought the subject before the conciliation board in august , but while they were wishful to call in the umpire they agreed to defer it for three months. their request was in the following form:-- the owners complain of the action of the workmen in laying collieries idle on august and december bank holidays, and ask that the conciliation board take this matter into consideration with a view of requiring the workmen to continue previously existing county arrangements until such are altered, either through negotiations between the owners' and workmen's associations or by the conciliation board. after being discussed it was decided that: the claim of the owners, that this board shall restrain the growing practice of laying pits idle on the august and december bank holidays, is to be considered and dealt with at the november meeting of the board. at that meeting the question was again brought forward; but it was thought desirable that the miners and the employers should have a chance of settling without a reference to the umpire, and for that purpose another adjournment took place, it being understood that if no arrangement were come to the reference should be made as soon as possible. the umpire was not called in until the th of july . the hearing of the case took place in london in the westminster palace hotel. on the th lord davey gave his award: "on the question referred to me at the meeting on july th i award that the workmen be allowed the august bank holiday, but go to work on the day after christmas day." mr patterson's statue the statue was unveiled on saturday, st of january , at two p.m. the ceremony consisted of a formal unveiling in front of the hall, and a meeting in the council chamber immediately after. the executive committee, in a short circular sent out to inform the members of the event, said: it will not be necessary to urge upon you to send a deputation to represent you, and thus show respect to a man who did as much as he could to establish our association and to promote its usefulness. don't let this be a mere ceremonial function, but let us show by our presence as much as by the statue we are placing in front of the hall how we appreciate the labours of men like our departed friend. there was a great response to the circular, and both the unveiling and the meeting inside were well attended. the ceremony was performed by the corresponding secretary (j. wilson), who gave the address. the proceedings were presided over by mr w. house, the president of the association, and a number of speeches were delivered by representative men, and many who had been with him during the greater part of his life, and throughout the highest testimony was given to the good qualities and disinterestedness of mr patterson. his would be a narrow mind who could say anything else. if true virtue consists of desire to do good, and he is only great who loves his fellow-men, then patterson was truly great. and that was the standard by which the county judged him, and on that he carried their appreciation. it will be fitting to quote in connection with the unveiling a portion of the _monthly circular_ written by one who had lived and worked with mr patterson and knew him. but the most cheering part of the unveiling to me does not lie in the appreciation as expressed by the marble, but in the numbers who attended the ceremony and the feeling manifested during the whole of it. if it showed our respect for a colleague and friend, it reflected honour upon us because there was nothing of the cold and formal about it. the gathering was truly representative, and from first to last friendship was in the air and in every heart. there were very few lodges (if any) that were not represented, and in addition there were gentlemen who, although outside our ranks as trades unionists, came uninvited to pay a last tribute to a man who in life they had known and learned to respect, and warm were their words in reference to him. the eight hours--second ballot this question assumed a new and more prominent shape at the annual council meeting in . it was decided "to seek for a living wage for all workers in and about the mines and for no man or lad to be more than eight hours from bank to bank in one day." it will be observed that the county had to seek, but it did not define by what means the object had to be sought. the executive was in a strait between the legal eight hours and negotiation with the employers. they therefore resolved to take the opinion of the county by submitting the question to the ballot. on june th they issued the voting papers, accompanied by the following circular:-- gentlemen,--it will be observed that the word "seek" is the word we invariably use when we send cases before the owners for negotiation. it would have been competent for the executive committee to have interpreted the new object in that light, and have looked upon it as being a point to aim at, rather than take it as absolute, and especially when you remember that, recognising the evils of a sudden introduction of a shortening of the hours from ten to eight hours, we have always been against the state regulation of hours, and by ballot before we have so decided. the committee, however, think it will be best to submit the question to you to say whether we are to proceed by negotiation, or by an appeal to the state, and for that purpose the ballot papers have been drawn up, so that we may have a plain issue upon the two methods. there can be no mistake. there are three things i would like to mention. first, let every full member (and no other) vote, as it affects all, and will affect all; second, i ask the lodge officials to let the ballot be such in nature more than name. let it be as secret as possible; and third, let me urge upon you not to be led away by sentiment, but consider the effect it may have upon the position of every man, lest we may make things worse than they are. it will be too late to regret after. we had better weigh well the result before the step is taken. j. wilson. _june th, ._ the result of the ballot was as follows:--for trades union effort, , ; for state interference, , ; majority, , . there were lodges voted. some lodges refused to vote, expressing their opposition to any change in the hours, but some refused without assigning any reason. the vote, however, was very decisive, and reaffirmed the opposition to legal enactment in respect to the eight hours. coal-drawing agreement the question of drawing coals after loose had been for some time in dispute between the two associations. a number of meetings were held. in the discussion the employers claimed the right to draw coals, if it suited their convenience, at any time. this could not be granted. then they asked for an arrangement which would allow them to draw coals if it were the custom prior to , and in case of a break up to draw coals to make up the loss. if this were granted they would concede four of the requests the workmen were making. the executive committee was not willing to retrospect so far as , but was willing to date back to , and to allow the employers the opportunity for proper preparation for the pit starting the day after an accident, if it were long. this concession formed the basis of settlement, and the following agreement was made:-- it is this day agreed between the durham coal owners' and the durham miners' association as follows:-- . that at all collieries where at the end of december it was customary for coals to be drawn at other times than the ordinary coal-drawing hours, such customs shall continue to the same extent. . that at all collieries the owners shall have the right of drawing after the or hours' coal drawing time, as the case may be, such of the coals standing in the shaft sidings as owing to accident it may be necessary to send to bank for any of the following purposes:-- (_a_) to enable stones to be drawn; (_b_) to enable pit timber or other material to be got down and clear of the shaft sidings. . that at all collieries, in case of an accident or breakdown which is not remedied one hour before loose, such coals shall be drawn as may be necessary to prepare the pit for working the next shift, such preparations to mean drawing such a quantity of coal as will enable one empty set (or tubs where endless rope haulage is employed) to be taken to each landing affected by the accident. for the durham coal owners' association, reginald guthrie. for the durham miners' association, john wilson. john johnson. three of the concessions on the part of the employers are contained in the following agreement:-- it is hereby agreed between the durham coal owners' association and the durham miners' association as follows:-- _hand putters' basis wage._--that the basis wage for hand putters when employed on datal work shall be s. d. per day. _stone putters' short shifts._--that stone putters when working with stonemen and shifters shall be allowed the same short shifts as those granted to the men with whom they are working. _boys' minimum wage._--that the minimum basis wage of boys employed at bank shall be one shilling per day. for the durham coal owners' association, reginald guthrie. for the durham miners' association, john wilson. broken price there was a fourth question which was not put in the agreement because it was so complicated--viz. the fixing of a relative price between the whole and broken prices. the custom at some collieries had been to fix a whole and broken price for the seam, the definite figure being named of, say, d. per ton difference. in every case where a future broken started it was at the original price, no matter how much the whole prices might have increased. the effect was that there were men who might be working at s. or s. d. per ton on the saturday, and through the area of goaf being taken out they would have a reduction of in some cases s. and s. d. per ton on monday. it was always difficult to get a rectification at joint committee, and it was thought best to arrange a uniform or relative price between the whole and broken prices, so that, no matter how the prices in the former might alter, the relative difference would never vary. the arrangement removed a very great anomaly and grievance, it being left to the joint committee to decide. surface firemen's wages this was a settlement made by the conciliation board. some years prior, by an arbitration, it was decided "that the standard or basis average wage of firemen at bank working twelve hours per day is s. d. per day of twelve hours." the operation of that award was that before a man could claim the s. d. he must be working the full twelve hours per day; if not, the employer could claim a proportionate reduction. the arrangement made on november th, , reduced the time to eleven hours for the s. d., those above that time receiving an advance of d. per day. by a return taken at the time the number of men and hours at the associated collieries was found to be as follows:-- hours per shift men ½ " " " man " " " men ½ " " " " " " " " " " " " --- average hours per shift, . ; and the result, therefore, was an all-round increase of d. per day. labour representation--mr johnson and gateshead--suspension of joint committee--conciliation board--the fillers' agreement it will be necessary to retrace our steps a year or two to keep this question in consecutive order. the action taken in has been set forth, with the result thereof. the matter rested with one representative until the council meeting held on june th, , when the executive committee placed on the programme the following resolution:-- the time is now opportune for considering the question of increased labour representation in parliament for the county of durham. on the council programme for september th, , the committee placed another resolution: with a view of giving effect to council resolution, with regard to further labour representation, we ask that the whole matter be relegated to the sections comprising the federation board. on november st that resolution came before the federation board, when it was resolved as follows:-- that we express our belief that the time has fully arrived when we ought to have increased labour representation in parliament, and that the other three sections be requested to consult their members on the subject, and as soon as they intimate their decision to the secretary a meeting of the board be called. the course of action indicated in that resolution was followed. the idea was accepted nearly universally. the federation board, therefore, resolved to place the matter before the four committees on january st in the miners' hall, durham. it was decided to call a special delegate meeting, to be held in the town hall, durham, the following programme to be submitted:-- ( ) shall there be an increase in the number of labour representatives in the county? ( ) if so, how many more shall be chosen? ( ) who shall they be? ( ) that the selections of divisions be left to the four committees. ( ) ways and means. the united committees advised that there should be an increase of two. this was not done because they believed it to be a mathematically fair proportion of the county, but because it was best to move safely. they left the choice of candidates to the council, but suggested that the selection of divisions should be remitted to them (the four committees), and that as regards the ways and means the same system as obtained in the case of mr wilson should apply to those chosen. having regard to our space we need not enlarge upon the various steps in the procedure. it will be sufficient to say that the council accepted the advice, leaving the carrying out of the details to the four committees. the candidates selected were mr j. johnson and mr j. w. taylor. shortly after the selection was made, and while the committees were trying to arrange for the division, a communication was received from the south-east durham liberal association asking that mr j. johnson should be sent there as a candidate. in the end the request was acceded to, but before much was done beyond the acceptance sir w. allan, m.p. for gateshead, died suddenly, and within a day or two the liberal association made overtures, and invited mr johnson. a meeting was called, and in response he was transferred to gateshead. it would not serve any good purpose nor assist our history if notice were made of some objections and some objectors. it will be sufficient if we record that he was returned on january th, , by a majority of , and we make mention of two matters--first, a resolution of the federation board: that we, the federation board, representing the whole of the workers in and about the mines in durham, desire to tender our thanks to the electors of gateshead for the splendid majority with which they have returned mr johnson as member of parliament for their borough, and all who worked to secure his return. second, a portion of the _monthly circular_ for january: there are many matters worthy of notice this month, but the one nearest your hearts and mine is _our_ success at gateshead. mr johnson is the m.p. for that borough, but the victory is _ours_. i have no envy for the state of mind of any man or men who can find room for carping or faddism in connection with the election. we are the last people among whom such should be found. the invitation to contest the seat was spontaneous. the workers were numerous, energetic, and of all classes, and the rejoicing when the result was known was of the most enthusiastic nature. it was encouraging to receive from a number of our lodges good wishes during the contest, and their congratulations since the victory was secured. suspension of joint committee through a dispute which arose over a decision given by the chairman of joint committee the meetings were entirely suspended, the employers alleging that the decision was against the rules of the joint committee. this objection was not taken until after the decision was given. the federation board, as the authority dealing with the joint committee, considered the question, and decided: that in the opinion of this board the protest entered by the owners' side of the joint committee on january th, , is entirely in opposition to the tenth rule of the joint committee constitution, and that whatever stoppage there may be in the proceedings of that board the blame rests only with them. and further, we protest against the refusal of the owners to meet the other sections of the board, as in our opinion it is in violation of all past procedure, and cannot conduce to the harmonious relation between the employers' and workmen's associations; and we hope that, whether the difference between the miners and employers be settled or not, no objection will be raised to the business of the other sections being proceeded with. in the opinion of the federation board there was something lying behind the objection to the decision. "if," said they, "that was the sole cause for the suspension, why not go on with the other sections?" they felt (rightly or wrongly) that the main objection was against the chairman. it was time for the appointment or reappointment of the chairman, and by the refusal of the owners to reappoint judge o'connor the board was strengthened in their opinion that it was the man--more than the single decision--the objection was taken to. the secretary received a letter from mr guthrie asking the board to meet for the purpose of appointing a chairman, and he was instructed to say they were ready to meet at any time convenient to the owners. that reply was repeated again on april th. the business was suspended from january th until july th, when it was resumed, the chairman being appointed _pro tem_. until the appointment of colonel blake, who occupied the position for the first time on october st. conciliation board a mention of this is made here because of a unique circumstance which arose at the august meeting of the board. the ascertainment showed a fall in price sufficient to warrant a reduction of one and a quarter per cent. the federation board objected to it. then the employers asked for the umpire to be called in, and requested it should be done as speedily as possible. there was a difficulty in the way. mr wilson was arranging to go to america, and had paid an instalment of his passage money. either he must forfeit the money he had paid or the meeting must be delayed. in their circular for november the federation board placed the following statement of the case:-- neither of these alternatives was acceptable, and in order to meet the situation the following resolution was submitted by the owners and accepted by us:-- in order to meet the convenience of mr wilson it is agreed that consideration of the claim for a reduction of wages be postponed until the meeting of the board in november, when lord davey shall be invited to attend and, failing agreement, to decide on the claim after consideration of the information which may then be put before him as to the state of trade, a preliminary meeting of the board to be held on october th, in order if possible to effect a settlement without the intervention of the umpire. in harmony with that resolution we met on the th of october. there were two courses open to us, as you will see: either we must consider the circumstances warranted the reduction asked for, or on the th of november--which is the date of the ordinary quarterly meeting--meet the umpire. one thing more let us point out: on the th of october we received the accountants' ascertainment for the quarter ending september, which showed a further fall in the realised selling price of coal. you will easily perceive the force of the situation which he had to meet. let us enumerate the circumstances. in august the employers claimed a reduction on the result of the ascertainment then obtained. although they were (as they said) convinced of the validity of their claim, we have kept the higher wage for three months, and you will know how much that means to us as a county, with our large wage fund and the thousands of men and boys employed. furthermore, there had been another fall in price. if we had gone to the umpire these facts faced us. these facts were fully considered, and the probabilities of the case carefully investigated, and we were convinced that the course most conducive to the best interest of those we represent was the acceptance of the one and a quarter per cent. reduction, and we are as fully convinced that the action will carry your general approval. as is seen by the circular, a settlement was made without the umpire. lord davey was informed, and replied as follows:-- brook street, w., _october , ._ dear sirs,--i deplore the existence of the circumstances which have admittedly rendered some reduction of wages necessary. but i congratulate both parties on having been able to settle the question themselves by amicable discussion without the intervention of a third party. nothing affords me greater pleasure than to hear that they have done so. i say this not from any desire to spare myself any trouble in your service, but because it is the best earnest for future harmony and co-operation in which the joint claims both of capital and of labour will be recognised.--i am, dear sirs, yours very faithfully, davey. the joint secretaries, durham board of conciliation. the fillers' agreement with this notice we will conclude our history. for some time there had been a gradual introduction of "mechanical coal cutters," and it was necessary that an arrangement should be made for a new class of workmen known as "fillers," whose work consisted solely of filling the coals after they had been got down. one main feature had obtained from the commencement in the policy of the association--viz. the permission to the employers to work the mines as they thought proper (consistent with the safety of the workmen), providing the workmen were paid a recognised wage; and second, no objection was ever raised to the introduction of new machinery, if regard were had to safety and wage. when these machines were brought in their utility was recognised. it was seen they were to ease the heaviest portion of the hewers' work, and the attention was turned to the two considerations named. after many meetings and much negotiation the following agreement was made:-- agreement made this day, th day of november , between the durham coal owners' and durham miners' association:-- . that the standard basis piece rate of wages for "fillers" who follow mechanical coal cutters shall be four shillings and sixpence per shift, and that the length of shift shall be eight hours from bank to bank, except on saturdays, when it shall be less in proportion to the reduced coal-drawing hours on that day at the respective collieries. . that the above standard piece rate shall be the basis for joint committee purposes, or for the purpose of any adjustment of "filling" prices, either as to advance, reduction, or revision thereof as the case may be, provided that each one and a quarter per cent. advance or reduction in the county percentage shall be held for joint committee purposes to vary the wages of "fillers" by three farthings per shift. . that the duties of "fillers" shall be held to embrace, according to the requirements of the management of the particular colliery concerned, breaking up, casting, and filling (into such receptacle as may be provided by the said management) coal kirved by mechanical coal cutters; the squaring of the coal face so as to leave it straight and perpendicular; the picking out and casting back under an agreed "laid-out" penalty of all material which the hewers are expected to pick out at the respective collieries; timbering in the absence of the deputy and according to the special and timbering rules; preparing the face and leaving it clean and free for the subsequent operations of the coal cutter. . that the "fillers" shall be included among the classes of men entitled to free houses or the customary allowance for house rent under the conditions of the conciliation board resolution of november th, , regarding "houses and house rent." for the durham coal owners' association, reginald guthrie. for the durham miners' association, john wilson. the noticeable features in the agreement are--first, the wages, which are d. per day (as a basis wage) higher than those of the coal getter, the hours being eight from bank to bank; second, the percentage is regulated as it is for the hewers, five per cent. in price meaning d. per day in wages; third, the duties they are called upon to perform are plainly set forth; and fourth, they are entitled to free houses or the customary allowance for rent as the other acknowledged classes. * * * * * _p.s._--inadvertently the death of mr meynell, chairman of the joint committee, and the appointment of judge o'connor to that office has been omitted and this _p.s._ supplies the omission. the last meeting at which mr meynell presided was held on december th, . the first under the presidency of mr o'connor was on april th, ; the chair in the _interim_ being filled _pro tem_. after words the lawyers--the changes we leave the history of the organisation for the time being, but before closing the volume, it would leave a vacuum if there were not some mention (even if it were little) of the legal advisers who have been connected with the association, and have helped it in the questions of law which from time to time are inevitable in such a large organisation. the first regular lawyer was mr "harry" marshall, the leading solicitor in the city of durham. he was well on in life when the association was founded, but he was retained until the time of his death. his offices were in the market place, durham. he was followed by mr h. forrest, who was heir to the business and offices of mr marshall, and by a natural sequence the legal matters of the organisation fell into his practice; but they did not remain there long. gradually mr i. isaacs of sunderland was called in, until finally he was appointed officially to the position. in mr isaacs the association had a very skilful and painstaking adviser, and a gentleman who stood well with the magistrates in every district in the county. he died a young man, but he had attained to a position which was one of the envied positions by the whole of the legal gentlemen in the county. he was made clerk to the castle eden magistrates, but, unfortunately, died shortly after; in fact, before he had rightly taken over his duties. he was a man of the highest type, a jew by religion, upright in all his dealings. the standard he lived up to was high enough for all to aim at. [illustration: h. f. heath] to keep the succession complete we may insert here a notice of his successor, mr h. f. heath. he was in mr isaacs' office until a very short time prior to the decease of the latter, and from the time of his appointment has proved himself a reliable guide. his advice is given for the good of the association, and not on the low ground of personal profit. he is as skilful in the stating of a case, or detecting the weak places in the position of his opponents, as he is versed in law. having to deal with mining matters he has made himself thoroughly acquainted with the technicalities of the mine, and is most desirous for the success of the business which is placed in his hands. no member of the durham miners' association has more regard to its welfare and prosperity than has the miners' solicitor and advocate. changes within the period of our associated life there have been many changes, a few of which we may with profit enumerate. the "yearly bond" has been dealt with as one of the first actions of the associations. it was considered a species of slavery, and a remnant of the old feudal times when men were part of the estate. we need not dwell further upon it nor its abolition. the change in the "first caller" is no mean one, apart from its implied shortening of the hours. it uniformed the time for men commencing work in the foreshift, and it gave them two or three hours more time to rest when it was most natural and most needed. the writer of this (as all men who were hewers at that time would go) went to work, if in the whole, at one in the morning. the "caller" made his rounds then, but there were many men who never waited until he came. they were at the pit and down before the time. at some collieries the back shift men went in at six or six-thirty a.m. if they were out until the latter time they were the last to go in. it was not considered necessary to suspend the coal-drawing to send them down. the man and his picks were put into an empty tub, and went down against the full tubs coming up. the engineman was told there was a "man on," and the only difference in the running was the easing up a little at the bottom. when the back shift hewer got to the face he had the company of his marrow for some two or three hours. in the calling time was changed, and the loosing in the face established. take the position of checkweighmen. prior to the commencement of the union (and at the time) the workmen's choice of their weighman was merely nominal. they selected, but the selection was subject to the approval of the employer or manager, and he was at all times liable to receive his notice, not from the men for whom he worked, but from the manager--and it could be given for anything which did not harmonise with the will of the manager. a breach of the law was not considered except it was colliery-made law. it will be obvious that his freedom of action (so far as the advocacy of the rights of workmen was concerned) would be very much restricted. in the generality of cases the policy was to "lie low." in this there has been a great and useful change. now the checkweighman is employed by the workmen, and can only be removed by them, except he violates the conditions of the mines' regulation act; and now he is (with rare exceptions) the mouthpiece of the men when meeting the manager, the leader in public movements, and the most prominent in matters relating to the association. no less important is the facility for meeting the employers, and the spirit of equality which obtains. what a contrast between and ! then it was truly a meeting of the superior with his inferiors, and as a natural consequence there was an absence of free discussion, which is so essential to the proper settlement of the questions arising between employers and workmen. happily, that feeling has died out. there is less of the dictator and dictated to, and more of the meeting of equals. then it was thought to employ men was to confer a favour upon them, and that consequently they were to consider themselves under patronage, and be satisfied with the treatment meted out to the patronised. now it is realised that if the employers employ a man's labour the workmen employ their capital, that reciprocity and mutuality form the platform upon which the two sides can meet, and that free, unrestrained, courteous expression is not merely the right, but the safest and most beneficial course. there has not only been an economic benefit accruing to both sides alike, as a result of this equality, but there has been a mental stimulus given to the workmen. it is true that, concurrently with the life of the association, the schoolmaster has been more abroad amongst the people. the boys commence work later in life, and with a larger mental capital, and that as a consequence there is more ability at command for the use of workmen, but it is a safe assertion that the fact of the organisation operating in our midst has been no mean factor in stimulating the use of the learning so acquired. the young men think it no small attainment to take part in the various offices which are held out to them in the union, and they know as well that they must be prepared to fill those offices in an intelligent manner. it would be a difficult, but yet a most interesting, calculation if it could be shown how many men have been incited to mental activity in the manner indicated. from the very inception the association has demonstrated that the industrial relations in this county were passing out of the region of brute force into that of reason, and the play of mind against mind, and that the body of working men who desire to hold their own, and progress, must do so by the mental force they could command. the greater that force the safer the position, and the more assured the amelioration of their conditions. by that will they conquer. the contrast between the number of able men now and in is encouraging. it gives the young assurance, and rejoices the heart of the aged, who in their youth saw this day as in a vision, but desired it. a natural corollary from the equality in meeting and the mental impetus is the amended mode of settling disputes and conducting our negotiations. we have come from a chronic state of open and avowed antagonism to (if not complete conciliation) at least a great approach to it. the history in describing the various stages in our path, will prove that the old era of contention was wearying and wasteful, as it was sure to be when the two parties considered themselves as two armies, and their strength of numbers and increase in capital were for purposes of crushing the other side. these ideas, like that of national superiority and large armaments, were hard to destroy on either side. their presence made the attempts at compromise more difficult, and often helped those who were wishful to retrograde. they brought about the abolition of the sliding scales and the first conciliation board. it may be at some future stage they will effect the same with the second. this will not be, if the past teaches any lessons and the workmen of durham recognise the tendency of the times. that is towards conciliation, and no step should be taken except to perfect it. if wisdom rules, that backward action will be avoided as a great danger. a very pleasing change is the greater care for life manifest during the last thirty-six years. the county has had its share of explosions in the period indicated. the following table will give us a view as to the extent of the life-saving in the mines of the nation. the table deals with three decades, and singly, and gives the deaths per year, the numbers of persons employed, with the number of tons, the average of each ten years being taken. ten years deaths per number of number of ending year persons employed tons , , , , , , , , , , , , the table is very cheering. the full value of it will be realised if we take the decade ending and compare it with . there we have thirty more deaths, but we have , more people employed, and an increase of over , , tons in output. the proportionate reduction in the saving of life is great. three more changes remain to be noted. first, the political change. in the political power in the hands of the miners (as of all county dwellers) was a very small quantity. the logic of the situation was curious. above a certain monetary position or size of a house, or possession of land, or living on one side of a line, men were allowed to vote; without those, and being over the line, they were prohibited. the law of england was an open declaration that houses, money, land, all insensate, could guarantee a man a qualification for doing that which alone can be done properly by the operation of mind, and living within an arbitrary area imparted to him full competency for the right of citizenship. he might have them to-day, and live on the borough side of the line, and be qualified; but the vicissitudes of life might strip him of his possessions--or the necessities of his occupation might compel him to move to-morrow--and he would be considered unfit to take part in the election of those who had to make the laws he was bound to obey, which is certainly a most sacred right. that anomaly was swept away. the durham miners took their share of the work, and set the example as to the proper use of the power. another of the changes we note is the strong desire there is for an improved home life. it is not an extraneous feeling forced upon the miners by outsiders, but is within them. there is a great change in that respect. there has been much done in the direction of the much-needed reform. the present is a long way from being satisfactory, but it is far in advance of the state at the inception of the association. that only existed because it was born of use. the old-time houses are a standing witness of the opinion those who built them had of the workmen. how should we know that the merciful man regarded the life of his beast except by the manner of his feeding and _housing_? there is a change in that respect, but there is a more hopeful one, and that is the desire on the part of those who live in them for betterment. the man who is _content_ with a hovel, or room in a slum, will never look higher. to be dissatisfied with them is healthy, and is the sure road to a better state. may the feeling grow until bad houses and insanitation are removed; but it should never be forgotten that a house itself does not make a home--the life in it alone can do that. the last of the changes, but not the least, is the altered opinion about, and the more accurate knowledge of, the miner there is in the country. forty years ago, to many of the people of london the northern miner was a dweller in remote regions, and a man of uncouth and rude speech and habits. some believed he remained down in the mine, never coming to bank except for a holiday. the writer was once asked by a man not far from london how long he had been in the mines. he replied eight or nine years. then said the querist: "have you never been up till now?" he was informed that the miner came up every day. with surprise he exclaimed: "i thought you lived down in the mines altogether." that is only one of the numerous instances which could safely be quoted expressive of the ignorance about the miner and his life. they knew his product because it warmed them and cooked their food, but that was the extent of their correct information. but the change in the geographical and domestic knowledge is not all, nor the most important; the altered opinion of the miner as a man is more. the common name was the "geordies," and that was used as being indicative of something low rather than a class cognomen. it was the idea as seen in the attitude of many in durham when the first gala was held--as stated above. that is all changed during the thirty-six years we have existed as an association. the man who speaks lightly of the class does it in the face of the clearest light, and from malice. it is of the class we speak here. if we reason from the individual our logic will be unsound, and all classes stand condemned. taken in the bulk, as compared with our start, the miner has been raised on to a pedestal of respect. that is a result of his own self-respect. without the latter the former will never be attained. it is the compelling force. it is the philosophy of shakespeare's "to thine own self be true," which finds exemplification in every sphere and grade of life. the durham miners have shown this in a marked degree. they may be void of some of the polish which is to be found amid the complaisances and conventionalities of the finer trades or higher walks of life--their battle for bread is a rough one--but he who wants honesty, uprightness, and bravery will not be disappointed if he turns to them. he need not seek far. in memoriam we have finished our history for the present, and traced it in rapid outline for thirty years. with the benefits we are enjoying from it, the enjoyment must not induce forgetfulness of the brave men who laid the foundations of our little kingdom, for such it is. we enter into their labours, but we will do so with gratitude, and not indifference. their memory deserves more than a mere casual place with us. we should not be true men if we gave it only that. let us remember that in reality the position we have realised and the solidity of our association have been won and made possible by their spirit and foresight, and because we have kept ourselves close to the lines of their procedure. ours is a great organisation, not because of its numbers (bulk may be weakness), but because of its principles. if it were not so, instead of standing out prominently as we do we should be in a dwarfed and stunted condition, and comparatively useless. the structure we now possess has risen by slow growth from very small beginnings and opposing forces. every new idea, all the teaching of experience, were used as blocks by those patient builders laying the foundation for those who were to follow them. it is true there might be some mistake and bungling in the building. but in spite of these the structure has arisen with solidity, and from the rubble of that time we have reared up great walls and fair outlines, giving promise of future strength, durability, and usefulness. truly the little one has become a great nation, and the weak one a strong force, and as long as we do not harm ourselves no power outside can. how shall we show our respect for them? we have no possible way except by carrying on their work and seeking to give effect and volume to it. the end of their policy was reform, not revolution--not only in a political way, but in every direction where it was needed. every hindrance in the whole round of working conditions was to them an evil, and as such should be removed. where immediate abolition was not possible they tried to reduce its magnitude. they preached the ideal life, seized the possible, and made the best of circumstances. and is the wisdom of their action not evident? the spasmodic has been succeeded by the settled and the orderly. where hate was endangering the general weal by its unreasoning action we now have regular business relations. no doubt to many whose main feature is ardency and rush they were slow-paced. these would have gone faster, but there would have been slower progress. to the israelites moses was slow-paced, but the wilderness was their portion as a result of their grumbling. there were grumblers in our start from egypt to a better position (some of them remain to this day), but these are not the spirits who would either lay foundations or rear structures. the live men before us now were not grumblers. they were too busy; the work before them was too imperative. they were discontented; but in essence there is a wide difference between that and a grumbler. never since the world began has any grievance been removed by the latter class. they may have hindered, but never helped. they are the drags on the wheels, and complain because more speed is not made. the men of were men of different mettle, or the fear is we should never have had the association we have, nor stood in the proud position we enjoy among the trades organisations of the nation. we are reaping where they sowed, and while we enjoy the harvest let us remember the sowers. we have placed their statues in a prominent position; but what do they mean to us? they are reminders of a state of things in a large part passed away, and as suggesters of a hope of a larger life in the future they contain a recognition and a resolve--a recognition of their work and a resolve to carry it forward: a recognition of the debt we owe to them, which can only be paid by service rendered to others. it is a debt which no statue, no matter how costly or lifelike, can liquidate. it can only be paid in kind. that is a truth we should not forget, but on all occasions give expression to. it is that expression which stamps real dignity upon the life of any man. position, rank, title, wealth are all useless, for the true index is manliness and useful service. the true reformers have been (and are) men who assisted the good and resisted the evil, not simply because it would pay or bring preferment or popularity, but because they felt in their hearts the impulses (and compulsions, if you will) of duty. the love of man constrained them, and the imperative _i must_ forced them onward. the world's progress has not depended on the acts of the so-called great men, but on the endeavours and self-denials of men who were lost often amid the mists and struggles and poverty of life, and to whom its heavy burdens were not theoretical, but terribly near in their contact, and fearful in their weight and trial. the deeds of the workers of the race are not recorded to decorate history, but for strengthening the generations to come. for such purpose has prominence been given here to our workers. "the measure of a nation's civilisation is the number of the brave men it has had, whose qualities have been harvested for children and youth." we have had our brave men. they did not live to themselves. in this we must be their imitators. au revoir i have had many pleasant occupations in connection with our association, and the writing of this outline of our history is not the least pleasing among them. it has taken much time, but the result has been (not to be burdensome, but) to impart a somewhat hurried and loose character to the writing, and perhaps some slight omissions of facts, not material to the general course of the history. it has been compiled in the rush of other matters, and in odd minutes as they offered themselves, but its purpose will be attained if a desire to form a closer acquaintance with our growth and transactions be provoked, especially in the minds of our young men, in the hope that they may be rooted and grounded in their faith in trades unionism. the dependence of the future is upon them. what is more important than for them to have a full knowledge of our policy and procedure? the subject is to me of the most interesting nature. from start to finish it has been running the current of my own life, because in nearly all the incidents i have had some small share--as one in the ranks at first, and in these later years as one of the officials. i saw the start, have seen the growth, and feel proud of its position. with those who helped to form it i shared the evil speaking and unfair treatment when we made the attempt, and have never hesitated to be a partner in the blame and slanders which small-minded men have seen fit to bestow upon those who were doing their duty. the narrow mind always feels a pleasure in censuring others. i say nothing of the work which has been done except this: in all i have had any part in there has been pleasure, and none of the hireling waiting for the shadow of the day. i have shared the regrets of those who regretted the failures, and now i am thankful there is large room to rejoice over the progress made and the position attained. this feeling, you will permit me to say, is bound to be stronger in me than in most men. it is part of my life. thirty-seven years is a long time. a man is a fool, or worse, if, living in contact with an institution (one in which he has lived and moved and had his being), it has not made more than a mechanical impression upon him. i have passed from youth to age in that contact. it commenced in the prime of manhood, and continues when life's day is declining, and the gathering shades indicate the sun has dipped far to the west, and to find myself in active service, even with the limited powers resulting from the weight of threescore years and ten, is the crown of my rejoicing. i have been a long time the colleague of some of you. in the battle we have been shoulder to shoulder, and our hair has turned grey in the fight. we have been together in good and evil, for the web of our life has been of mingled yarn. good and evil together have been mixed, but the good has predominated--how much we alone can tell. i rejoice with you that we have lived to see this day, and that we are still fighting the good fight, with the hopeful spirit, if the physical energies are less than when we commenced. there is a great distance between the point we have attained and the valley whence we started--a distance not measured by time. the true standard is an experience such as our life alone can supply. my final word is to my young brothers. it is that of exhortation to appreciate not merely the conditions you enjoy, but the possibilities opened out to you. the thought of these should stir you up to the enjoyment of one and the use of the other. believe me, about this i am very anxious, and shall rejoice if something in this book, or suggested by it, tends to stir you to good and profitable use of the facilities and time the association has opened out to you. the opening out of these devolves upon you a twofold duty: to yourselves first, and then devoting yourselves to the improvement, solidifying, strengthening, and perfecting of the organisation. let me quote a few words i have written to you before: to omit the duty you owe to yourselves; to neglect the opportunities which are open to you; to think all of pleasure and sport, and nothing of mental culture; to leave the institutes which are opening out to you, with their libraries, and which with their stores of knowledge bring you into living, thoughtful contact with the mental giants of the race; to live only for present enjoyment, with no preparation for to-morrow, which will need and make demands upon you, is surely a lack of forethought, which is condemnable for two reasons, because it stunts your own nature (for no uneducated man is complete), and hinders your usefulness when matured manhood calls upon you to take your place in the affairs of your class and nation, to assist in the progress of one and the rectification of the national evils. put not your trust in other people entirely; look not to some power outside yourselves to raise you higher in the social scale, whether it be parliamentary or otherwise. the most effective means for further progress lies in us. we want to be true to ourselves, resting not satisfied with foul conditions and surroundings nor ignorance. an educated people is a powerful people; for where is there a man who knows what is due to a man who will be satisfied with less than what a man requires and deserves? these thoughts form the _raison-d'être_ of this history. the aim is to make it a reliable record of facts and an inspiration to those who read. there has been no attempt at literary display. there has been a desire to give prominence to the principles of the founders, and to urge adherence to them, for by them we have come, and by them we shall progress. our course has been gradual, but it has been safe. we have a record of which all may justly feel proud. it has not been rushing nor spasmodic. in these ofttimes lies ruin, and this we have found when we as an association have tried that method. carefulness and caution are not cowardice. these feelings may not be heroic, but they have proved their fitness in the years that are gone. "discretion is the better part of valour." "more firm and sure the hand of courage strikes when it obeys the watchful eye of caution." this was the leading feature of those who made our present possible. no one would dare charge them with lack of true heroism. let me urge upon you the same spirit. the road may seem longer, and the processes more painful and slow, but these need not damp your spirits. they should brace you for the struggle, strengthen your purpose, fix more firmly your hopes, give you larger faith in the future, induce you to realise your place in life and not be drifters with the current. there are too many who are satisfied to merely exist. they have no aspiration nor ideal nor hope. no man has a right to pass through life indifferent to the wrongs around him. two things we must avoid: impetuosity in associated work and stagnation in the individual life. each life should be a clear current, invigorating, not a mere moral miasmatic pool, but cleansing, elevating, ennobling. there are three voices calling upon this generation: the past with the work done for us; the present with its demands upon our help for rectification; and the future with its possibilities of a better and purer life. there are many powers opened out to you, but there are three which stand out prominently: sobriety, education, association. these used, the darkness will disperse, the downtrodden be raised, and england made truly a home for her people. the continuous sunshine in which some dwell and the dark poverty in which thousands exist will be blended, every soul-enslaving fetter be bruised and broken and cast away, and the world be brighter for our living in it; and we, when called to our account, will feel cheered that we have done what we could to cast out the old and cruel conditions and ring in the christ that is to be, when want and hunger shall be no more and that state which the rich provision in nature and the wonderful production around us provides for shall be realised. appendix i the galas, with the day and date upon which they were held saturday, august th, at wharton park, durham. " june th, on race-course, durham. " june th " " " august th " " " july rd " " monday july rd " " " july th " " saturday july th " " " july th " " " july st " " " july th " " " july st " " " july th " " " july th " " " july th " " " july st " " " july rd " " " july th " " " july th " " " july th " " " july th " " " july rd " " " july th " " " july st " " " july th " " " july th " " " july th " " " july th " " " july nd " " " july th " " " july th " " " july th " " " july th " " " july rd " " " july th " " " july st " " appendix ii changes in wages from date of change advance reduction taking effect per cent. per cent. february -- july -- february -- april -- november -- april -- february -- september -- april -- ½ may -- ¾ july -- ¼ december ½ -- april ¾ -- august -- ¼ november ¼ -- february ¼ -- august -- ¼ may -- ¼ may -- ¼ february ¼ -- may -- ¼ august -- ¼ november ¼ -- february ¼ -- august -- december -- march - , -- december , -- january , -- -- june , -- march -- [ ]october , -- may - , -- ½ october - , -- ½ august - , ½ -- [ ]may - , ½ -- may - , ½ -- oct. -nov. , ½ -- [ ]april - , ½ -- july - , ½ -- november - , ¾ -- february - , -- may - , ½ -- august - , -- november - , -- february - , -- ¼ may - , -- ¼ august - , -- ½ november - , -- february - , -- ¼ may - , -- ½ august - , -- ½ february - , ¼ -- may - , -- ¼ august - , -- ¼ february - , -- ¼ may - , -- ½ november - , -- ¼ february - , ¼ -- august - , ½ -- november - , ¼ -- [footnote : originally given as a temporary advance for six pays, afterwards converted into an ordinary advance.] [footnote : originally given for six pays, afterwards continued for further period of six pays, and again extended until pays ending th and nd april ; it was then continued as an ordinary advance.] [footnote : of this advance one and a quarter per cent. was given for seven pays, and afterwards merged in the ordinary percentage.] appendix iii table showing the explosions and inundations, with the date and number of lives lost, since the beginning of , in durham, brought down to the end of , with two statements on the dust theory by mr j. forman. lives lost --may , monkwearmouth --october , seaham --july , craghead exploded --september , seaham colliery exploded --february , trimdon colliery exploded --april , tudhoe exploded --april , west stanley exploded --march , usworth exploded --june , houghton-le-spring --december , elemore --november , hebburn --december , eppleton --april , brancepeth a pit --may , east hetton, inundation --august , brandon c pit --may , deaf hill --november , sacriston, inundation --october , wingate, explosion --december , urpeth busty, explosion a theory showing how coal dust is ignited and exploded in a coal mine, more especially on in-take air roads in the first place, there must be a considerable quantity of very fine and dry coal dust in the immediate proximity of a shot when fired; and if the shot is a strong one the concussion will be very great. this force, acting on the air, throws the finest particles of coal dust into the circulating current, in a finely divided state, with orbid motion, thereby causing each particle of coal dust to be surrounded with air, and these particles of dust in this condition coming in contact with the flame of a shot, are easily ignited. at the moment of ignition the temperature of the particles of dust is low, but as the ignition extends to other particles, and they become ignited in quantity, the temperature rises, so that the motion of the heated particles becomes more rapid by expanding and compressing the air, until their velocity is so great that the temperature of the burning dust is raised to the temperature of gas flame, exploding the coal dust in its course. at this high temperature, the expansion of the air will develop great force, which acting on the dust at rest, will whirl it into the air current, and this will be continued so long as there is a sufficient quantity of coal dust and air to feed the flame. john forman. * * * * * to j. wilson, esq., secretary to the royal commission on explosions from coal dust in mines. dear sir,--in october an explosion occurred at seaham colliery, and my attention was called to it; and, after considering all the circumstances of the case, i eventually came to the conclusion that the shot fired by the two simpsons ignited the coal dust and caused the explosion. in september another explosion took place at seaham colliery. i went down the pit in the evening of the day of the explosion with mr stratton (the manager) and other mining engineers, and i remained at seaham colliery for months, until the last body was found, and was, during that time, down the pit almost every day as an explorer. i also attended the inquest and gave evidence. i was satisfied from what i saw that the shot fired by simpson and brown ignited the coal dust and caused the explosion. in february an explosion occurred at trimdon grange colliery. i went down the pit and attended the inquest, and from what i saw and heard i concluded that the explosion was caused by a flushed kitty or straw at maitland's shot firing a small quantity of fire-damp, which ignited the coal dust and caused the explosion. in april an explosion occurred at west stanley colliery. i attended the inquest, and from what i could learn the shot fired by the two men (douglas and hutchinson) ignited a small portion of fire-damp, which fired the coal dust, and brought on an explosion. in march an explosion happened at usworth colliery. i attended the inquest, and came to an opinion that the shot fired by the two men, named brown, ignited the coal dust, which produced an explosion. in december an explosion occurred at elemore colliery. i went down the pit and attended the inquest. i was satisfied, in my mind, that the shot fired by the three men (johnson, appleby and luke) ignited the coal dust, thereby causing the explosion.--yours, etc. john forman. _december ._ index a accountants, , , aftermath of strike, agents' districts, - alteration of the "first caller," , amicability in disputes, arbitration, deputies', -- earliest, -- first general, , -- second, -- third, -- fourth, -- owners refuse, -- working hours, armstrong, w., , attempts to form union, average, county, -- theoretical and real, award, , _pro tem_., -- j. r. lyn's, awards, lord davey's, , - award, lord davey's, , b bank holiday, banking account, benefits, reduction of, blagdon, rev. m., bond, yearly, , , boys' wages, , broken price agreement, brown, w., , building, the, bunning, t. w., burt, t., , , , c cairns, a., , , "caller, first," , candymen, cann, t. h., appointed treasurer, care for life, changes, checkweighmen, , clerk, first appointed, coal-drawing agreement, coal owners' association formed, coal tax, commission, royal, committee, , compensation act , conciliation board, -- first members of, -- renewed, , co-operative colliery, , -- committee, county council, crake, w., , crawford, w., , , , , , , , , -- attack on, -- censure on, -- candidature of, -- death of, d dale, d., sir, , , dark days, deputies' basis wage fixed, -- difference as to, -- hours, , -- wage, , -- wage, derby, lord, desire for better houses, e educational benefit of union, emigration, , employers' liability act, entrance fee, first, , equality, evictions, wheatley hill, ex-committee condemned, -- expelled, -- rules, f federation board formed, -- condemned, -- first members of the, federation, miners', -- durham miners and the, , -- expulsion from the, -- refuses durham, fillers' agreement, firemen's week-end shifts, five days per week, forman, j., , , , , -- death of, forsters', w. e., award, fowler, j., franchise association, -- extension of, g gala, first, - -- first on the race-course, galbraith, s., appointed, golightly, w., gordon, w., , graham, coroner, gurney's, russell, award, guthrie, r., h hall, the new, , hand putters' basis wage, heath, mr, hewers' datal wage, homes, aged miners', hopwood's, c. h., award, hours arbitration, hours', arrangement, ten, , -- eight, -- ballot on, -- second ballot on, -- of boys, , , , , houses and house rent, housing condition, , house, w., appointed to joint committee, -- appointed president, i imprisonment of messrs cann, jones, and forbes, increased knowledge of the miners, industrial remuneration conference, isaacs, mr, j johnson, j., appointed treasurer, -- fin. secretary, johnson, mr, and gateshead, joint committee, formation of, -- first meeting, -- suspended, , jones, l., , , , , judge, a, puzzled, l labourers' basis wage, labour representation, , leaders, the first, lords, house of, m macdonald, a., -- death of, meynell, mr e., , -- award, miners' demand for trained miners, -- international congress, formed, -- national conference, , -- act , -- act , -- act , , n negotiations of , notices given to enforce a reduction, -- again given by owners, o o'connor, judge, , officers, first, opposition, , , , p patterson, w. h., , , , , -- appointed corres. secretary, -- death of, patterson's, mr, statue, political power, position of the association, president, first, president, permanent, putters' hours at datal work, -- short shift, stone, r ramsey, t., , , reduction, first, , -- second, -- third, -- fourth, -- fifth, -- of bankmen, -- of , reductions, private, relief fund, first, -- second, rent paying in , resolutions, first gala, restriction of output, rhymer, e., , richardson, j., , rocking strike, s salary of first treasurer, sanderson, r. b., , screenmen's basis wage, seaham strike, shaw lefevre's award, simpson, c., sliding scale, first, -- second, -- third, -- fourth, -- abolished, -- violation of, smart money, stobart, w., strike at silksworth, -- at wheatley hill, -- of , -- of , -- of , strikes illegal, surface firemen's wages, t taylor, hugh, , -- j. w., thornley meeting, timber leaders' hours, trotter, l., trustees, first, w wage board, first mention of, , , wages, advance in, , , , , wages in - , , washington strike, water leaders' hours, wearmouth strike, westcott, bishop, , , -- death of, wheatley hill inundation, -- "putt pay," wilkinson, n., , , , , , wilson, j., , , , -- appointed fin. secretary, -- appointed corres. secretary, wood, lindsay, mr, , , , j. h. veitch and sons durham * * * * * transcriber's notes obvious typographical errors have been silently corrected. hyphenation has been rationalised. variations in spelling and punctuation have been retained. words in _italics_ are denoted thus. the repetition of the title on page has been removed. generously made available by the canadian institute for historical microreproductions (www.canadiana.org)) geological report on asbestos, and its indications, in the province of quebec, canada. london: e. forster groom, , charing cross, s.w. . [_all rights reserved._] geological report on asbestos, and its indications in the province of quebec, canada. having been called upon to make a close and careful examination of the geological formations in the eastern townships of garthby, wolf'stown, and coleraine, situated in the province of quebec, canada, i gave special attention to the distribution of the asbestos-bearing rocks (serpentine), which have been, in my opinion, heretofore only partially traced. perhaps this was owing to the difficulties which had to be encountered from the thick undergrowth which in many places rendered it almost impossible to penetrate sufficiently in order to make a _true_ report as regards the "existence," "location," and "association" of these rocks. admirable reports have been written by r. e. ellis, ll.d., dr. hunt, and others, on the origin and distribution of the serpentines, and have been fully discussed and ventilated. still, though various opinions have been expressed upon the subject, they appear to differ in many respects. i mention these facts as possibly one inexperienced or unacquainted with the country might consider it strange that a thorough examination of the asbestos properties had not been followed. yet the causes i have mentioned above, as well as the difficulties i had to contend with during the months of heavy snowfall, lead me to believe that my _confrères_ (geologists) were disinclined to follow up a correct and actual prospectus of these valuable serpentinous localities. before locating, or going into details of these classes of rock as a mineral repository, i intend to treat on the subject as regards their mode of existence and origin. serpentine is diffused under the head of "metamorphic rocks," while, in the widest sense, according to studor and others, mineral metamorphism means every change of aggregation, structure, or chemical condition, which rocks have undergone subsequently to their deposition and stratification, or the effects which have been produced by forces other than gravity and cohesion. there fall under this definition the discolouration of the surface of, for instance, black limestone, by the loss of its carbon, the formation of brownish red crusts in rocks of limestone, sandstone, many slatestones, shales, granite, &c., by the decomposition of compounds of iron, finely disseminated in the mass of the rock, the change in rocks consequent in the absorption of water, and the crumbling of many granites and porphyries into gravel, occasioned by the decomposition of the mica and felspar. in its more limited sense the term "metamorphic" is confined to those changes of rock which are produced directly or indirectly by agencies seated in the interior of the earth. in many cases the mode of change may be explained by our physical or chemical theories, and may be viewed as the effects of temperature or of electro-chemical actions adjoining rocks or connecting communications with the interior of the earth, also distinctly point out the seat from which this change proceeds. in many other cases the metamorphic process itself remains a mystery, and from the nature of the products alone do we conclude that such a metamorphic action has taken place. serpentine is generally believed to have been originally deposited as a sediment, and to have acquired its present compact crystalline character through the subsequent action of various chemical, or mechanical, agencies. it is known to be a _hydrated silicate of magnesia_ with about equal parts of silica and magnesia, and contains per cent. of water with varying proportions of iron, chromium manganese, alumina and lime, has a specific gravity of . , and weighs about lbs. to the cubic foot. it is found both in a soft and very compact state, of a waxy lustre, with many different shades of beautiful green which give it a mottled appearance like a serpent, hence the origin of its name "serpentine," or ophite. it is called "ranocchia" by the italians, from the appearance it bears to the "frog," and, on account of its susceptibility to a high polish, is greatly valued as a marble for interior ornamental purposes, more than exterior, as it weathers rapidly. in galway, ireland, it is found in large quantities, and called "serpentinous marble," or "ophi-calcite." it is also to be found in other parts of the world, as in the pyrenees, alps of dauphing, mount st. gothard, italy, sweden, ural mountains, silesia, new south wales, savoy, corsica, cornwall, scotland, and other places too numerous to mention; but in canada the finest and most crystalline serpentine is to be found forming great belts of over miles long and several thousand feet in breadth. there it associates with the dioretic, or volcanic, rocks, and is, according to dr. ells, without any doubt, "an alteration product of a dioretic rock rich in olivine." it is sometimes very difficult to distinguish the mineral constituents in many of the metamorphic rocks, but diorite is always considered to be composed chiefly of felspar and hornblende, which composition enters largely into the serpentines. actinolite, tremolite, &c., and many other minerals, are sometimes found associating with it. there are many valuable properties attributed to serpentine, and i am of opinion that the time is not far distant when it will be commercially considered an invaluable substance, and this on account of its refractory properties. i may also mention that it can be extensively used in the manufacture of crucibles, &c. its soft and unctuous qualities (especially where it is found associated with "steatite," or "soapstone," which is often to be seen in large quantities) renders it easy to be worked, and, if reduced to a powder, could be moulded in bricks which the most intense heat will not affect. one of the chief properties it contains, and one which the serpentine of lower canada is so famous for, is the asbestos, crysotile, or fibrous serpentine. this valuable and important mineral product is found in paying quantities only at certain points in the extensive serpentine reefs, and was first mined as an article of commerce in canada in , and has now become a regular and rapidly-developing industry. on account of its incombustible and indestructible qualities, is extensively used in steam, hydraulic, and electrical machinery. it has been adopted by the admiralty for engine packing, in her majesty's war-ships. it is spun into six-fold yarn, with a tensile strength of lbs. and upwards, is manufactured into cloth, as clothing for firemen, and covering hose-pipes, in fire brigades, and also engine purposes, as well as drop-curtains, and general stage scenery, and is employed by the principal railway and steamship companies, collieries, ironworks and all classes of factories, and, in the manufacture of the new asbestos grates and stoves, is finding for itself a large market. messrs. bell & company of london, who are the largest asbestos users in the world, have adopted it in the manufacture of over special purposes in connection with steam engines and general machinery, and, as a lubricant, asbestoline ranks in the first degree. there have been many mines started in canada by people of the farming class, as well as by companies, and "cotton," as asbestos is locally termed, has been found in large quantities within a few feet from the surface, in veins from / to inches and more in length of fibre. in italy, asbestos is found, measuring up to feet, in fibre, and chemically speaking, there is no difference between it and canadian, except that the latter, though shorter in fibre, is much more compact and crystalline, and purer in every sense of the word than can be obtained in italy, so much so, as i understand, that users of italian material have virtually abandoned it for canadian. although i have no doubt but that italian asbestos has its own special purposes. the greatest depth reached in canada is feet in open workings. no timbering or extensive machinery is used in the manipulation of the mines, as the "cuts"--being usually in the mountain side--afford a natural drainage, and dumpage. having blasted the rock, the first process of extraction is termed "cobbing," which means breaking off the adhering serpentine from the asbestos vein, this being manual work done by boys. the fibre is packed in sacks, each weighing lbs., and in some cases lbs. are shipped by the local railroad company to montreal or new york at something about cents and cents per sack. asbestos is sorted into three qualities, and priced thus:-- st quality, selling at mine $ to $ , per ton of , lbs. nd " " " " , " " " rd " " " " , " " " some inferior quality, at a very low price, is used by the asbestos mining and manufacturing company of quebec. the workmen are principally french canadians belonging to the neighbouring villages, and the wages paid them are-- miners (without board), $ . ( / ) to $ . ( / ), per day. pickers and cobbers, $ . ( / ) " $ . ( / ), " the cost of extraction is taken from $ to $ per ton; this includes local administrations and all other expenses connected with the mine, and with the adoption of machinery and the use of air-compressed drills the cost of actual mining will be reduced to at least per cent.; so taking an average price of about $ per ton, a net profit of from £ to £ , or $ , is obtainable per ton of raw material. in the total amount of asbestos, taken from all the mines, may be estimated at , tons, and of the amount returned last year ( ), all but tons were from the quebec province mines, and of these thetford turned out , tons, and black lake , or together three-fourths of the whole out-put. the tons were from bridgewater, in the province of ontario, a somewhat different class of mineral, which is generally used in the manufacture of fire-proof roofing. as regards the indications of asbestos, it is a general recognised fact, and one that may be depended on, that not alone in canada, but indeed all other places where asbestos-bearing serpentine is found, the existence of asbestos, or "amianthus," is noticed when the serpentine is exposed, and presents a rusted, sometimes greyish and broken appearance, due to decomposition or weathering, or covered with a thin layer of soil. small veins of asbestos are to be seen forming a network on the surface of the rock. if closely examined there may be noticed the indications of a fault which, in the eastern townships of quebec, has generally a direction of n. ° e., this fault appearing in all openings where a good show of mineral is to be seen, presenting a wall either in a vertical position or at an angle, which is preferred to be not greater than °. from this wall, at a varying distance of from to feet, will be found another, sometimes parallel to, or at an opposite angle; in this latter case, if these walls be worked down, they will be found to either meet, forming a trough-like appearance, or to change their course in a downward direction, leaving only a few feet from each other at the narrowest point, and then diverge to an unlimited depth. in this case their faces will have a slicken appearance, smeared over with thin layers of imperfect asbestos, or crysotile, now and then compact, fibrous hornblende, up to inches in length, of various colours, and rich deposits of olivine, in rare cases small quantities of "ground ivory" with many other admixtures. the condition of the serpentine within these walls is greatly distorted, containing many small veins of asbestos varying from mere threads to and inches in thickness, and sometimes deposits of grains of magnetic iron or magnetite with traces of chromic iron, which in some localities break the continuity of the fibre, veins of rich white crystalline matter (perhaps calcareous) with large deposits of "soapstone," or steatite, associated with "serpentite." such contorted out-crops are indications of rich veins of asbestos, which will be found to both increase in quantity and quality the deeper they are worked. and in the case where the walls are parallel and the filling matter in the same contorted condition, it is inevitable, in order to obtain a good fibre, considerable depth should be reached. the serpentine, which constitute these walls, will also be found to proportionally become more compact, and less associated with impurities, and contain the finest quality and lustre of fibre. a very interesting phenomenon may be noticed at some of the mines in connection with this contorted matter. it is the transposition of the serpentine into asbestos fibre, by the action of the atmosphere. this is to be seen on the dumps where the filling matter and cobbed rock is exposed. in one or two cases i have seen large quantities of broken rock changed into fibre after a few years, by atmospherical chemical agencies. in so many cases i find people are prejudiced from going deeper than a few feet from the surface, as not finding a copious supply of asbestos there, when _good_ indications are shown they become disheartened. therefore, from these practical facts it will be seen that in order to get the best results it is necessary to work at the lowest possible level when a favourable out-crop is shown, as, possibly, working at a high elevation on the out-crop may be a mistake, where a lower point is available. there are good indications of asbestos where the serpentine is crossed by quartzose, gneiss, or "traverse dykes," and some valuable finds have been made at the junction with the dioretic rocks. when the serpentine is found dark in colour, to have a granular appearance, containing many dark grains of, perhaps, felspathic crystals, the asbestos will be of a dark, dull, translucent lustre, very compact, and easily fluffed to a fine silken fibre. the admixtures of hard and soft serpentine, where not effected by a fault, may sometimes be regarded as a doubtful indication of an immediate find, but if its hardness increases on descending, and colour becomes more uniform, from a light emerald green with a whitish admixture, to a dark olive, and containing numerous small veins of fibre, the conclusions may be considered as favourable to rich deposits of asbestos. in conclusion i may add that the foregoing remarks, as regards the indications of this valuable mineral, are based on my personal geological experience, and the reliable information of the managers of the various asbestos mines in canada, whose opinions have greatly aided me in my recent prospection, and i trust that this pamphlet will not alone be a benefit to them, but to the asbestos industry, which i feel assured will be one of the most prominent in the province of quebec. lucius j. boyd, c.e., f.r.g.s.i. georgius agricola de re metallica translated from the first latin edition of with biographical introduction, annotations and appendices upon the development of mining methods, metallurgical processes, geology, mineralogy & mining law from the earliest times to the th century by herbert clark hoover a. b. stanford university, member american institute of mining engineers, mining and metallurgical society of america, société des ingéniéurs civils de france, american institute of civil engineers, fellow royal geographical society, etc., etc. and lou henry hoover a. b. stanford university, member american association for the advancement of science, the national geographical society, royal scottish geographical society, etc., etc. _dover publications, inc._ new york to john caspar branner ph.d., _the inspiration of whose teaching is no less great than his contribution to science._ this new edition of de re metallica is a complete and unchanged reprint of the translation published by the mining magazine, london, in . it has been made available through the kind permission of honorable herbert c. hoover and mr. edgar rickard, author and publisher, respectively, of the original volume. printed in the united states of america translators' preface. there are three objectives in translation of works of this character: to give a faithful, literal translation of the author's statements; to give these in a manner which will interest the reader; and to preserve, so far as is possible, the style of the original text. the task has been doubly difficult in this work because, in using latin, the author availed himself of a medium which had ceased to expand a thousand years before his subject had in many particulars come into being; in consequence he was in difficulties with a large number of ideas for which there were no corresponding words in the vocabulary at his command, and instead of adopting into the text his native german terms, he coined several hundred latin expressions to answer his needs. it is upon this rock that most former attempts at translation have been wrecked. except for a very small number, we believe we have been able to discover the intended meaning of such expressions from a study of the context, assisted by a very incomplete glossary prepared by the author himself, and by an exhaustive investigation into the literature of these subjects during the sixteenth and seventeenth centuries. that discovery in this particular has been only gradual and obtained after much labour, may be indicated by the fact that the entire text has been re-typewritten three times since the original, and some parts more often; and further, that the printer's proof has been thrice revised. we have found some english equivalent, more or less satisfactory, for practically all such terms, except those of weights, the varieties of veins, and a few minerals. in the matter of weights we have introduced the original latin, because it is impossible to give true equivalents and avoid the fractions of reduction; and further, as explained in the appendix on weights it is impossible to say in many cases what scale the author had in mind. the english nomenclature to be adopted has given great difficulty, for various reasons; among them, that many methods and processes described have never been practised in english-speaking mining communities, and so had no representatives in our vocabulary, and we considered the introduction of german terms undesirable; other methods and processes have become obsolete and their descriptive terms with them, yet we wished to avoid the introduction of obsolete or unusual english; but of the greatest importance of all has been the necessity to avoid rigorously such modern technical terms as would imply a greater scientific understanding than the period possessed. agricola's latin, while mostly free from mediæval corruption, is somewhat tainted with german construction. moreover some portions have not the continuous flow of sustained thought which others display, but the fact that the writing of the work extended over a period of twenty years, sufficiently explains the considerable variation in style. the technical descriptions in the later books often take the form of house-that-jack-built sentences which have had to be at least partially broken up and the subject occasionally re-introduced. ambiguities were also sometimes found which it was necessary to carry on into the translation. despite these criticisms we must, however, emphasize that agricola was infinitely clearer in his style than his contemporaries upon such subjects, or for that matter than his successors in almost any language for a couple of centuries. all of the illustrations and display letters of the original have been reproduced and the type as closely approximates to the original as the printers have been able to find in a modern font. there are no footnotes in the original text, and mr. hoover is responsible for them all. he has attempted in them to give not only such comment as would tend to clarify the text, but also such information as we have been able to discover with regard to the previous history of the subjects mentioned. we have confined the historical notes to the time prior to agricola, because to have carried them down to date in the briefest manner would have demanded very much more space than could be allowed. in the examination of such technical and historical material one is appalled at the flood of mis-information with regard to ancient arts and sciences which has been let loose upon the world by the hands of non-technical translators and commentators. at an early stage we considered that we must justify any divergence of view from such authorities, but to limit the already alarming volume of this work, we later felt compelled to eliminate most of such discussion. when the half-dozen most important of the ancient works bearing upon science have been translated by those of some scientific experience, such questions will, no doubt, be properly settled. we need make no apologies for _de re metallica_. during years it was not superseded as the text-book and guide to miners and metallurgists, for until schlüter's great work on metallurgy in it had no equal. that it passed through some ten editions in three languages at a period when the printing of such a volume was no ordinary undertaking, is in itself sufficient evidence of the importance in which it was held, and is a record that no other volume upon the same subjects has equalled since. a large proportion of the technical data given by agricola was either entirely new, or had not been given previously with sufficient detail and explanation to have enabled a worker in these arts himself to perform the operations without further guidance. practically the whole of it must have been given from personal experience and observation, for the scant library at his service can be appreciated from his own preface. considering the part which the metallic arts have played in human history, the paucity of their literature down to agricola's time is amazing. no doubt the arts were jealously guarded by their practitioners as a sort of stock-in-trade, and it is also probable that those who had knowledge were not usually of a literary turn of mind; and, on the other hand, the small army of writers prior to his time were not much interested in the description of industrial pursuits. moreover, in those thousands of years prior to printing, the tedious and expensive transcription of manuscripts by hand was mostly applied to matters of more general interest, and therefore many writings may have been lost in consequence. in fact, such was the fate of the works of theophrastus and strato on these subjects. we have prepared a short sketch of agricola's life and times, not only to give some indication of his learning and character, but also of his considerable position in the community in which he lived. as no appreciation of agricola's stature among the founders of science can be gained without consideration of the advance which his works display over those of his predecessors, we therefore devote some attention to the state of knowledge of these subjects at the time by giving in the appendix a short review of the literature then extant and a summary of agricola's other writings. to serve the bibliophile we present such data as we have been able to collect it with regard to the various editions of his works. the full titles of the works quoted in the footnotes under simply authors' names will be found in this appendix. we feel that it is scarcely doing agricola justice to publish _de re metallica_ only. while it is of the most general interest of all of his works, yet, from the point of view of pure science, _de natura fossilium_ and _de ortu et causis_ are works which deserve an equally important place. it is unfortunate that agricola's own countrymen have not given to the world competent translations into german, as his work has too often been judged by the german translations, the infidelity of which appears in nearly every paragraph. we do not present _de re metallica_ as a work of "practical" value. the methods and processes have long since been superseded; yet surely such a milestone on the road of development of one of the two most basic of human industrial activities is more worthy of preservation than the thousands of volumes devoted to records of human destruction. to those interested in the history of their own profession we need make no apologies, except for the long delay in publication. for this we put forward the necessity of active endeavour in many directions; as this book could be but a labour of love, it has had to find the moments for its execution in night hours, weekends, and holidays, in all extending over a period of about five years. if the work serves to strengthen the traditions of one of the most important and least recognized of the world's professions we shall be amply repaid. it is our pleasure to acknowledge our obligations to professor h. r. fairclough, of stanford university, for perusal of and suggestions upon the first chapter; and to those whom we have engaged from time to time for one service or another, chiefly bibliographical work and collateral translation. we are also sensibly obligated to the printers, messrs. frost & sons, for their patience and interest, and for their willingness to bend some of the canons of modern printing, to meet the demands of the th century. _july , ._ the red house, hornton street, london. introduction. biography.[ ] georgius agricola was born at glauchau, in saxony, on march th, , and therefore entered the world when it was still upon the threshold of the renaissance; gutenberg's first book had been printed but forty years before; the humanists had but begun that stimulating criticism which awoke the reformation; erasmus, of rotterdam, who was subsequently to become agricola's friend and patron, was just completing his student days. the reformation itself was yet to come, but it was not long delayed, for luther was born the year before agricola, and through him agricola's homeland became the cradle of the great movement; nor did agricola escape being drawn into the conflict. italy, already awake with the new classical revival, was still a busy workshop of antiquarian research, translation, study, and publication, and through her the greek and latin classics were only now available for wide distribution. students from the rest of europe, among them at a later time agricola himself, flocked to the italian universities, and on their return infected their native cities with the newly-awakened learning. at agricola's birth columbus had just returned from his great discovery, and it was only three years later that vasco da gama rounded cape good hope. thus these two foremost explorers had only initiated that greatest period of geographical expansion in the world's history. a few dates will recall how far this exploration extended during agricola's lifetime. balboa first saw the pacific in ; cortes entered the city of mexico in ; magellan entered the pacific in the same year; pizarro penetrated into peru in ; de soto landed in florida in , and potosi was discovered in . omitting the sporadic settlement on the st. lawrence by cartier in , the settlement of north america did not begin for a quarter of a century after agricola's death. thus the revival of learning, with its train of humanism, the reformation, its stimulation of exploration and the re-awakening of the arts and sciences, was still in its infancy with agricola. we know practically nothing of agricola's antecedents or his youth. his real name was georg bauer ("peasant"), and it was probably latinized by his teachers, as was the custom of the time. his own brother, in receipts preserved in the archives of the zwickau town council, calls himself "bauer," and in them refers to his brother "agricola." he entered the university of leipsic at the age of twenty, and after about three and one-half years' attendance there gained the degree of _baccalaureus artium_. in he became vice-principal of the municipal school at zwickau, where he taught greek and latin. in he became principal, and among his assistants was johannes förster, better known as luther's collaborator in the translation of the bible. during this time our author prepared and published a small latin grammar[ ]. in he removed to leipsic to become a lecturer in the university under his friend, petrus mosellanus, at whose death in he went to italy for the further study of philosophy, medicine, and the natural sciences. here he remained for nearly three years, from to . he visited the universities of bologna, venice, and probably padua, and at these institutions received his first inspiration to work in the sciences, for in a letter[ ] from leonardus casibrotius to erasmus we learn that he was engaged upon a revision of galen. it was about this time that he made the acquaintance of erasmus, who had settled at basel as editor for froben's press. in agricola returned to zwickau, and in he was chosen town physician at joachimsthal. this little city in bohemia is located on the eastern slope of the erzgebirge, in the midst of the then most prolific metal-mining district of central europe. thence to freiberg is but fifty miles, and the same radius from that city would include most of the mining towns so frequently mentioned in _de re metallica_--schneeberg, geyer, annaberg and altenberg--and not far away were marienberg, gottesgab, and platten. joachimsthal was a booming mining camp, founded but eleven years before agricola's arrival, and already having several thousand inhabitants. according to agricola's own statement[ ], he spent all the time not required for his medical duties in visiting the mines and smelters, in reading up in the greek and latin authors all references to mining, and in association with the most learned among the mining folk. among these was one lorenz berman, whom agricola afterward set up as the "learned miner" in his dialogue _bermannus_. this book was first published by froben at basel in , and was a sort of catechism on mineralogy, mining terms, and mining lore. the book was apparently first submitted to the great erasmus, and the publication arranged by him, a warm letter of approval by him appearing at the beginning of the book[ ]. in he published _de mensuris et ponderibus_, through froben, this being a discussion of roman and greek weights and measures. at about this time he began _de re metallica_--not to be published for twenty-five years. agricola did not confine his interest entirely to medicine and mining, for during this period he composed a pamphlet upon the turks, urging their extermination by the european powers. this work was no doubt inspired by the turkish siege of vienna in . it appeared first in german in , and in latin--in which it was originally written--in , and passed through many subsequent editions. at this time, too, he became interested in the god's gift mine at abertham, which was discovered in . writing in , he says[ ]: "we, as a shareholder, through the goodness of god, have enjoyed the proceeds of this god's gift since the very time when the mine began first to bestow such riches." agricola seems to have resigned his position at joachimsthal in about , and to have devoted the next two or three years to travel and study among the mines. about he became city physician of chemnitz, in saxony, and here he resided until his death in . there is but little record of his activities during the first eight or nine years of his residence in this city. he must have been engaged upon the study of his subjects and the preparation of his books, for they came on with great rapidity soon after. he was frequently consulted on matters of mining engineering, as, for instance, we learn, from a letter written by a certain johannes hordeborch[ ], that duke henry of brunswick applied to him with regard to the method for working mines in the upper harz. in he married anna, widow of matthias meyner, a petty tithe official; there is some reason to believe from a letter published by schmid,[ ] that anna was his second wife, and that he was married the first time at joachimsthal. he seems to have had several children, for he commends his young children to the care of the town council during his absence at the war in . in addition to these, we know that a son, theodor, was born in ; a daughter, anna, in ; another daughter, irene, was buried at chemnitz in ; and in his widow and three children--anna, valerius, and lucretia--were still living. in began the publication of the series of books to which agricola owes his position. the first volume comprised five works and was finally issued in ; it was subsequently considerably revised, and re-issued in . these works were: _de ortu et causis subterraneorum_, in five "books," the first work on physical geology; _de natura eorum quae effluunt ex terra_, in four "books," on subterranean waters and gases; _de natura fossilium_, in ten "books," the first systematic mineralogy; _de veteribus et novis metallis_, in two "books," devoted largely to the history of metals and topographical mineralogy; a new edition of _bermannus_ was included; and finally _rerum metallicarum interpretatio_, a glossary of latin and german mineralogical and metallurgical terms. another work, _de animantibus subterraneis_, usually published with _de re metallica_, is dated in the preface. it is devoted to animals which live underground, at least part of the time, but is not a very effective basis of either geologic or zoologic classification. despite many public activities, agricola apparently completed _de re metallica_ in , but did not send it to the press until ; nor did it appear until a year after his death in . but we give further details on the preparation of this work on p. xv. during this period he found time to prepare a small medical work, _de peste_, and certain historical studies, details of which appear in the appendix. there are other works by agricola referred to by sixteenth century writers, but so far we have not been able to find them although they may exist. such data as we have, is given in the appendix. as a young man, agricola seems to have had some tendencies toward liberalism in religious matters, for while at zwickau he composed some anti-popish epigrams; but after his return to leipsic he apparently never wavered, and steadily refused to accept the lutheran reformation. to many even liberal scholars of the day, luther's doctrines appeared wild and demagogic. luther was not a scholarly man; his addresses were to the masses; his latin was execrable. nor did the bitter dissensions over hair-splitting theology in the lutheran church after luther's death tend to increase respect for the movement among the learned. agricola was a scholar of wide attainments, a deep-thinking, religious man, and he remained to the end a staunch catholic, despite the general change of sentiment among his countrymen. his leanings were toward such men as his friend the humanist, erasmus. that he had the courage of his convictions is shown in the dedication of _de natura eorum_, where he addresses to his friend, duke maurice, the pious advice that the dissensions of the germans should be composed, and that the duke should return to the bosom of the church those who had been torn from her, and adds: "yet i do not wish to become confused by these turbulent waters, and be led to offend anyone. it is more advisable to check my utterances." as he became older he may have become less tolerant in religious matters, for he did not seem to show as much patience in the discussion of ecclesiastical topics as he must have possessed earlier, yet he maintained to the end the respect and friendship of such great protestants as melanchthon, camerarius, fabricius, and many others. in , when he was at the age of , began agricola's activity in public life, for in that year he was elected a burgher of chemnitz; and in the same year duke maurice appointed him burgomaster--an office which he held for four terms. before one can gain an insight into his political services, and incidentally into the character of the man, it is necessary to understand the politics of the time and his part therein, and to bear in mind always that he was a staunch catholic under a protestant sovereign in a state seething with militant protestantism. saxony had been divided in between the princes ernest and albert, the former taking the electoral dignity and the major portion of the principality. albert the brave, the younger brother and duke of saxony, obtained the subordinate portion, embracing meissen, but subject to the elector. the elector ernest was succeeded in by frederick the wise, and under his support luther made saxony the cradle of the reformation. this elector was succeeded in by his brother john, who was in turn succeeded by his son john frederick in . of more immediate interest to this subject is the albertian line of saxon dukes who ruled meissen, for in that principality agricola was born and lived, and his political fortunes were associated with this branch of the saxon house. albert was succeeded in by his son george, "the bearded," and he in turn by his brother henry, the last of the catholics, in , who ruled until . henry was succeeded in by his protestant son maurice, who was the patron of agricola. at about this time saxony was drawn into the storms which rose from the long-standing rivalry between francis i., king of france, and charles v. of spain. these two potentates came to the throne in the same year ( ), and both were candidates for emperor of that loose confederation known as the holy roman empire. charles was elected, and intermittent wars between these two princes arose--first in one part of europe, and then in another. francis finally formed an alliance with the schmalkalden league of german protestant princes, and with the sultan of turkey, against charles. in maurice of meissen, although a protestant, saw his best interest in a secret league with charles against the other protestant princes, and proceeded (the schmalkalden war) to invade the domains of his superior and cousin, the elector frederick. the emperor charles proved successful in this war, and maurice was rewarded, at the capitulation of wittenberg in , by being made elector of saxony in the place of his cousin. later on, the elector maurice found the association with catholic charles unpalatable, and joined in leading the other protestant princes in war upon him, and on the defeat of the catholic party and the peace of passau, maurice became acknowledged as the champion of german national and religious freedom. he was succeeded by his brother augustus in . agricola was much favoured by the saxon electors, maurice and augustus. he dedicates most of his works to them, and shows much gratitude for many favours conferred upon him. duke maurice presented to him a house and plot in chemnitz, and in a letter dated june th, [ ] in connection therewith, says: "... that he may enjoy his life-long a freehold house unburdened by all burgher rights and other municipal service, to be used by him and inhabited as a free dwelling, and that he may also, for the necessities of his household and of his wife and servants, brew his own beer free, and that he may likewise purvey for himself and his household foreign beer and also wine for use, and yet he shall not sell any such beer.... we have taken the said doctor under our especial protection and care for our life-long, and he shall not be summoned before any court of justice, but only before us and our councillor...." agricola was made burgomaster of chemnitz in . a letter[ ] from fabricius to meurer, dated may th, , says that agricola had been made burgomaster by the command of the prince. this would be maurice, and it is all the more a tribute to the high respect with which agricola was held, for, as said before, he was a consistent catholic, and maurice a protestant prince. in this same year the schmalkalden war broke out, and agricola was called to personal attendance upon the duke maurice in a diplomatic and advisory capacity. in also he was a member of the diet of freiberg, and was summoned to council in dresden. the next year he continued, by the duke's command, burgomaster at chemnitz, although he seems to have been away upon ducal matters most of the time. the duke addresses[ ] the chemnitz council in march, : "we hereby make known to you that we are in urgent need of your burgomaster, dr. georgius agricola, with us. it is, therefore, our will that you should yield him up and forward him that he should with the utmost haste set forth to us here near freiberg." he was sent on various missions from the duke to the emperor charles, to king ferdinand of austria, and to other princes in matters connected with the war--the fact that he was a catholic probably entering into his appointment to such missions. chemnitz was occupied by the troops of first one side, then the other, despite the great efforts of agricola to have his own town specially defended. in april, , the war came to an end in the battle of mühlberg, but agricola was apparently not relieved of his burgomastership until the succeeding year, for he wrote his friend wolfgang meurer, in april, ,[ ] that he "was now relieved." his public duties did not end, however, for he attended the diet of leipzig in and in , and was at the diet at torgau in . in he was again installed as burgomaster; and in , for the fourth time, he became head of the municipality, and during this year had again to attend the diets at leipzig and dresden, representing his city. he apparently now had a short relief from public duties, for it is not until , shortly before his death, that we find him again attending a diet at torgau. agricola died on november st, . a letter[ ] from his life-long friend, fabricius, to melanchthon, announcing this event, states: "we lost, on november st, that distinguished ornament of our fatherland, georgius agricola, a man of eminent intellect, of culture and of judgment. he attained the age of . he who since the days of childhood had enjoyed robust health was carried off by a four-days' fever. he had previously suffered from no disease except inflammation of the eyes, which he brought upon himself by untiring study and insatiable reading.... i know that you loved the soul of this man, although in many of his opinions, more especially in religious and spiritual welfare, he differed in many points from our own. for he despised our churches, and would not be with us in the communion of the blood of christ. therefore, after his death, at the command of the prince, which was given to the church inspectors and carried out by tettelbach as a loyal servant, burial was refused him, and not until the fourth day was he borne away to zeitz and interred in the cathedral.... i have always admired the genius of this man, so distinguished in our sciences and in the whole realm of philosophy--yet i wonder at his religious views, which were compatible with reason, it is true, and were dazzling, but were by no means compatible with truth.... he would not tolerate with patience that anyone should discuss ecclesiastical matters with him." this action of the authorities in denying burial to one of their most honoured citizens, who had been ever assiduous in furthering the welfare of the community, seems strangely out of joint. further, the elector augustus, although a protestant prince, was agricola's warm friend, as evidenced by his letter of but a few months before (see p. xv). however, catholics were then few in number at chemnitz, and the feeling ran high at the time, so possibly the prince was afraid of public disturbances. hofmann[ ] explains this occurrence in the following words:--"the feelings of chemnitz citizens, who were almost exclusively protestant, must certainly be taken into account. they may have raised objections to the solemn interment of a catholic in the protestant cathedral church of st. jacob, which had, perhaps, been demanded by his relatives, and to which, according to the custom of the time, he would have been entitled as burgomaster. the refusal to sanction the interment aroused, more especially in the catholic world, a painful sensation." a brass memorial plate hung in the cathedral at zeitz had already disappeared in , nor have the cities of his birth or residence ever shown any appreciation of this man, whose work more deserves their gratitude than does that of the multitude of soldiers whose monuments decorate every village and city square. it is true that in a marble tablet was placed behind the altar in the church of st. jacob in chemnitz, but even this was removed to the historical museum later on. he left a modest estate, which was the subject of considerable litigation by his descendants, due to the mismanagement of the guardian. hofmann has succeeded in tracing the descendants for two generations, down to , but the line is finally lost among the multitude of other agricolas. to deduce georgius agricola's character we need not search beyond the discovery of his steadfast adherence to the religion of his fathers amid the bitter storm of protestantism around him, and need but to remember at the same time that for twenty-five years he was entrusted with elective positions of an increasingly important character in this same community. no man could have thus held the respect of his countrymen unless he were devoid of bigotry and possessed of the highest sense of integrity, justice, humanity, and patriotism. agricola's intellectual attainments and position in science. agricola's education was the most thorough that his times afforded in the classics, philosophy, medicine, and sciences generally. further, his writings disclose a most exhaustive knowledge not only of an extraordinary range of classical literature, but also of obscure manuscripts buried in the public libraries of europe. that his general learning was held to be of a high order is amply evidenced from the correspondence of the other scholars of his time--erasmus, melanchthon, meurer, fabricius, and others. our more immediate concern, however, is with the advances which were due to him in the sciences of geology, mineralogy, and mining engineering. no appreciation of these attainments can be conveyed to the reader unless he has some understanding of the dearth of knowledge in these sciences prior to agricola's time. we have in appendix b given a brief review of the literature extant at this period on these subjects. furthermore, no appreciation of agricola's contribution to science can be gained without a study of _de ortu et causis_ and _de natura fossilium_, for while _de re metallica_ is of much more general interest, it contains but incidental reference to geology and mineralogy. apart from the book of genesis, the only attempts at fundamental explanation of natural phenomena were those of the greek philosophers and the alchemists. orthodox beliefs agricola scarcely mentions; with the alchemists he had no patience. there can be no doubt, however, that his views are greatly coloured by his deep classical learning. he was in fine to a certain distance a follower of aristotle, theophrastus, strato, and other leaders of the peripatetic school. for that matter, except for the muddy current which the alchemists had introduced into this already troubled stream, the whole thought of the learned world still flowed from the greeks. had he not, however, radically departed from the teachings of the peripatetic school, his work would have been no contribution to the development of science. certain of their teachings he repudiated with great vigour, and his laboured and detailed arguments in their refutation form the first battle in science over the results of observation _versus_ inductive speculation. to use his own words: "those things which we see with our eyes and understand by means of our senses are more clearly to be demonstrated than if learned by means of reasoning."[ ] the bigoted scholasticism of his times necessitated as much care and detail in refutation of such deep-rooted beliefs, as would be demanded to-day by an attempt at a refutation of the theory of evolution, and in consequence his works are often but dry reading to any but those interested in the development of fundamental scientific theory. in giving an appreciation of agricola's views here and throughout the footnotes, we do not wish to convey to the reader that he was in all things free from error and from the spirit of his times, or that his theories, constructed long before the atomic theory, are of the clear-cut order which that basic hypothesis has rendered possible to later scientific speculation in these branches. his statements are sometimes much confused, but we reiterate that their clarity is as crystal to mud in comparison with those of his predecessors--and of most of his successors for over two hundred years. as an indication of his grasp of some of the wider aspects of geological phenomena we reproduce, in appendix a, a passage from _de ortu et causis_, which we believe to be the first adequate declaration of the part played by erosion in mountain sculpture. but of all of agricola's theoretical views those are of the greatest interest which relate to the origin of ore deposits, for in these matters he had the greatest opportunities of observation and the most experience. we have on page reproduced and discussed his theory at considerable length, but we may repeat here, that in his propositions as to the circulation of ground waters, that ore channels are a subsequent creation to the contained rocks, and that they were filled by deposition from circulating solutions, he enunciated the foundations of our modern theory, and in so doing took a step in advance greater than that of any single subsequent authority. in his contention that ore channels were created by erosion of subterranean waters he was wrong, except for special cases, and it was not until two centuries later that a further step in advance was taken by the recognition by van oppel of the part played by fissuring in these phenomena. nor was it until about the same time that the filling of ore channels in the main by deposition from solutions was generally accepted. while werner, two hundred and fifty years after agricola, is generally revered as the inspirer of the modern theory by those whose reading has taken them no farther back, we have no hesitation in asserting that of the propositions of each author, agricola's were very much more nearly in accord with modern views. moreover, the main result of the new ideas brought forward by werner was to stop the march of progress for half a century, instead of speeding it forward as did those of agricola. in mineralogy agricola made the first attempt at systematic treatment of the subject. his system could not be otherwise than wrongly based, as he could scarcely see forward two or three centuries to the atomic theory and our vast fund of chemical knowledge. however, based as it is upon such properties as solubility and homogeneity, and upon external characteristics such as colour, hardness, &c., it makes a most creditable advance upon theophrastus, dioscorides, and albertus magnus--his only predecessors. he is the first to assert that bismuth and antimony are true primary metals; and to some sixty actual mineral species described previous to his time he added some twenty more, and laments that there are scores unnamed. as to agricola's contribution to the sciences of mining and metallurgy, _de re metallica_ speaks for itself. while he describes, for the first time, scores of methods and processes, no one would contend that they were discoveries or inventions of his own. they represent the accumulation of generations of experience and knowledge; but by him they were, for the first time, to receive detailed and intelligent exposition. until schlüter's work nearly two centuries later, it was not excelled. there is no measure by which we may gauge the value of such a work to the men who followed in this profession during centuries, nor the benefits enjoyed by humanity through them. that agricola occupied a very considerable place in the great awakening of learning will be disputed by none except by those who place the development of science in rank far below religion, politics, literature, and art. of wider importance than the details of his achievements in the mere confines of the particular science to which he applied himself, is the fact that he was the first to found any of the natural sciences upon research and observation, as opposed to previous fruitless speculation. the wider interest of the members of the medical profession in the development of their science than that of geologists in theirs, has led to the aggrandizement of paracelsus, a contemporary of agricola, as the first in deductive science. yet no comparative study of the unparalleled egotistical ravings of this half-genius, half-alchemist, with the modest sober logic and real research and observation of agricola, can leave a moment's doubt as to the incomparably greater position which should be attributed to the latter as the pioneer in building the foundation of science by deduction from observed phenomena. science is the base upon which is reared the civilization of to-day, and while we give daily credit to all those who toil in the superstructure, let none forget those men who laid its first foundation stones. one of the greatest of these was georgius agricola. de re metallica agricola seems to have been engaged in the preparation of _de re metallica_ for a period of over twenty years, for we first hear of the book in a letter from petrus plateanus, a schoolmaster at joachimsthal, to the great humanist, erasmus,[ ] in september, . he says: "the scientific world will be still more indebted to agricola when he brings to light the books _de re metallica_ and other matters which he has on hand." in the dedication of _de mensuris et ponderibus_ (in ) agricola states that he means to publish twelve books _de re metallica_, if he lives. that the appearance of this work was eagerly anticipated is evidenced by a letter from george fabricius to valentine hertel:[ ] "with great excitement the books _de re metallica_ are being awaited. if he treats the material at hand with his usual zeal, he will win for himself glory such as no one in any of the fields of literature has attained for the last thousand years." according to the dedication of _de veteribus et novis metallis_, agricola in already looked forward to its early publication. the work was apparently finished in , for the dedication to the dukes maurice and august of saxony is dated in december of that year. the eulogistic poem by his friend, george fabricius, is dated in . the publication was apparently long delayed by the preparation of the woodcuts; and, according to mathesius,[ ] many sketches for them were prepared by basilius wefring. in the preface of _de re metallica_, agricola does not mention who prepared the sketches, but does say: "i have hired illustrators to delineate their forms, lest descriptions which are conveyed by words should either not be understood by men of our own times, or should cause difficulty to posterity." in the completed book was sent to froben for publication, for a letter[ ] from fabricius to meurer in march, , announces its dispatch to the printer. an interesting letter[ ] from the elector augustus to agricola, dated january , , reads: "most learned, dear and faithful subject, whereas you have sent to the press a latin book of which the title is said to be _de rebus metallicis_, which has been praised to us and we should like to know the contents, it is our gracious command that you should get the book translated when you have the opportunity into german, and not let it be copied more than once or be printed, but keep it by you and send us a copy. if you should need a writer for this purpose, we will provide one. thus you will fulfil our gracious behest." the german translation was prepared by philip bechius, a basel university professor of medicine and philosophy. it is a wretched work, by one who knew nothing of the science, and who more especially had no appreciation of the peculiar latin terms coined by agricola, most of which he rendered literally. it is a sad commentary on his countrymen that no correct german translation exists. the italian translation is by michelangelo florio, and is by him dedicated to elizabeth, queen of england. the title page of the first edition is reproduced later on, and the full titles of other editions are given in the appendix, together with the author's other works. the following are the short titles of the various editions of _de re metallica_, together with the name and place of the publisher:-- latin editions. _de re metallica_, froben basel folio . " " " " " " . " " " ludwig könig " " . " " " emanuel könig " " . in addition to these, leupold,[ ] schmid,[ ] and others mention an octavo edition, without illustrations, schweinfurt, . we have not been able to find a copy of this edition, and are not certain of its existence. the same catalogues also mention an octavo edition of _de re metallica_, wittenberg, or , with notes by joanne sigfrido; but we believe this to be a confusion with agricola's subsidiary works, which were published at this time and place, with such notes. german editions. _vom bergkwerck_, froben, folio, . _bergwerck buch_, sigmundi feyrabendt, frankfort-on-main, folio, . " " ludwig könig, basel, folio, . there are other editions than these, mentioned by bibliographers, but we have been unable to confirm them in any library. the most reliable of such bibliographies, that of john ferguson,[ ] gives in addition to the above; _bergwerkbuch_, basel, , folio, and schweinfurt, , octavo. italian edition. _l'arte de metalli_, froben, basel, folio, . other languages. so far as we know, _de re metallica_ was never actually published in other than latin, german, and italian. however, a portion of the accounts of the firm of froben were published in [ ], and therein is an entry under march, , of a sum to one leodigaris grymaldo for some other work, and also for "correction of agricola's _de re metallica_ in french." this may of course, be an error for the italian edition, which appeared a little later. there is also mention[ ] that a manuscript of _de re metallica_ in spanish was seen in the library of the town of bejar. an interesting note appears in the glossary given by sir john pettus in his translation of lazarus erckern's work on assaying. he says[ ] "but i cannot enlarge my observations upon any more words, because the printer calls for what i did write of a metallick dictionary, after i first proposed the printing of erckern, but intending within the compass of a year to publish georgius agricola, _de re metallica_ (being fully translated) in english, and also to add a dictionary to it, i shall reserve my remaining essays (if what i have done hitherto be approved) till then, and so i proceed in the dictionary." the translation was never published and extensive inquiry in various libraries and among the family of pettus has failed to yield any trace of the manuscript. footnotes: [ ] for the biographical information here set out we have relied principally upon the following works:--petrus albinus, _meissnische land und berg chronica_, dresden, ; adam daniel richter, _umständliche ... chronica der stadt chemnitz_, leipzig, ; johann gottfried weller, _altes aus allen theilen der geschichte_, chemnitz, ; freidrich august schmid, _georg agrikola's bermannus_, freiberg, ; georg heinrich jacobi, _der mineralog georgius agricola_, zwickau, ; dr. reinhold hofmann, _dr. georg agricola_, gotha, . the last is an exhaustive biographical sketch, to which we refer those who are interested. [ ] _georgii agricolae glaucii libellus de prima ac simplici institutione grammatica_, printed by melchior lotther, leipzig, . petrus mosellanus refers to this work (without giving title) in a letter to agricola, june, . [ ] _briefe an desiderius erasmus von rotterdam._ published by joseph förstemann and otto günther. _xxvii. beiheft zum zentralblatt für bibliothekswesen_, leipzig, . p. . [ ] _de veteribus et novis metallis._ preface. [ ] a summary of this and of agricola's other works is given in the appendix a. [ ] _de veteribus et novis metallis_, book i. [ ] printed in f. a. schmid's _georg agrikola's bermannus_, p. , freiberg, . [ ] op. cit., p. . [ ] archive , chemnitz municipal archives. [ ] baumgarten-crusius. _georgii fabricii chemnicensis epistolae ad w. meurerum et alios aequales_, leipzig, , p. . [ ] hofmann, op. cit., p. . [ ] weber, _virorum clarorum saeculi xvi. et xvii. epistolae selectae_, leipzig, , p. . [ ] baumgarten-crusius. op. cit., p. . [ ] hofmann, op. cit., p. . [ ] _de ortu et causis_, book iii. [ ] _briefe an desiderius erasmus von rotterdam._ published by joseph förstemann & otto günther. _xxvii. beiheft zum zentralblatt für bibliothekswesen_, leipzig, , p. . [ ] petrus albinus, _meissnische land und berg chronica_, dresden, , p. . [ ] this statement is contained under " " in a sort of chronicle bound up with mathesius's _sarepta_, nuremberg, . [ ] baumgarten-crusius, p. , letter no. . [ ] principal state archives, dresden, cop. , folio . [ ] jacob leupold, _prodromus bibliothecae metallicae_, , p. . [ ] f. a. schmid, _georg agrikola's bermannus_, freiberg, , p. . [ ] _bibliotheca chemica_, glasgow, , p. . [ ] _rechnungsbuch der froben und episcopius buchdrucker und buchhändler zu basel_, - , published by r. wackernagle, basel, . p. . [ ] _colecion del sr monoz_ t. , fol. _en la acad. de la hist._ madrid. [ ] sir john pettus, _fleta minor_, the laws of art and nature, &c., london, , p. . [illustration xix (title page from first edition)] georgius fabricius in libros metallicos georgii agricolae philosophi præstantissimi.[ ] ad lectorem. si iuuat ignita cognoscere fronte chimæram, semicanem nympham, semibouemque uirum: si centum capitum titanem, totque ferentem sublimem manibus tela cruenta gygen: si iuuat Ætneum penetrare cyclopis in antrum, atque alios, vates quos peperere, metus: nunc placeat mecum doctos euoluere libros, ingenium agricolae quos dedit acre tibi. non hic uana tenet suspensam fabula mentem: sed precium, utilitas multa, legentis erit. quidquid terra sinu, gremioque recondidit imo, omne tibi multis eruit ante libris: siue fluens superas ultro nitatur in oras, inueniat facilem seu magis arte uiam. perpetui proprijs manant de fontibus amnes, est grauis albuneæ sponte mephitis odor. lethales sunt sponte scrobes dicæarchidis oræ, et micat è media conditus ignis humo. plana nariscorum cùm tellus arsit in agro, ter curua nondum falce resecta ceres, nec dedit hoc damnum pastor, nec iuppiter igne: vulcani per se ruperat ira solum. terrifico aura foras erumpens, incita motu, sæpe facit montes, antè ubi plana uia est. hæc abstrusa cauis, imoque incognita fundo, cognita natura sæpe fuere duce. arte hominum, in lucem ueniunt quoque multa, manuque terræ multiplices effodiuntur opes. lydia sic nitrum profert, islandia sulfur, ac modò tyrrhenus mittit alumen ager. succina, quâ trifido subit æquor vistula cornu, piscantur codano corpora serua sinu. quid memorem regum preciosa insignia gemmas, marmoraque excelsis structa sub astra iugis? nil lapides, nil saxa moror: sunt pulchra metalla, croese tuis opibus clara, mydaque tuis, quæque acer macedo terra creneide fodit, nomine permutans nomina prisca suo. at nunc non ullis cedit germania terris, terra ferax hominum, terraque diues opum. hic auri in uenis locupletibus aura refulget, non alio messis carior ulla loco. auricomum extulerit felix campania ramum, nec fructu nobis deficiente cadit. eruit argenti solidas hoc tempore massas fossor, de proprijs armaque miles agris. ignotum graijs est hesperijsque metallum, quod bisemutum lingua paterna uocat. candidius nigro, sed plumbo nigrius albo, nostra quoque hoc uena diuite fundit humus. funditur in tormenta, corus cum imitantia fulmen, Æs, inque hostiles ferrea massa domos. scribuntur plumbo libri: quis credidit antè quàm mirandam artem teutonis ora dedit? nec tamen hoc alijs, aut illa petuntur ab oris, eruta germano cuncta metalla solo. sed quid ego hæc repeto, monumentis tradita claris agricolae, quæ nunc docta per ora uolant? hic caussis ortus, & formas uiribus addit, et quærenda quibus sint meliora locis. quæ si mente prius legisti candidus æqua: da reliquis quoque nunc tempora pauca libris. vtilitas sequitur cultorem: crede, uoluptas non iucunda minor, rara legentis, erit. iudicioque prius ne quis malè damnet iniquo, quæ sunt auctoris munera mira dei: eripit ipse suis primùm tela hostibus, inque mittentis torquet spicula rapta caput. fertur equo latro, uehitur pirata triremi: ergo necandus equus, nec fabricanda ratis? visceribus terræ lateant abstrusa metalla, vti opibus nescit quòd mala turba suis? quisquis es, aut doctis pareto monentibus, aut te inter habere bonos ne fateare locum. se non in prærupta metallicus abijcit audax, vt quondam immisso curtius acer equo: sed prius ediscit, quæ sunt noscenda perito, quodque facit, multa doctus ab arte facit. vtque gubernator seruat cum sidere uentos: sic minimè dubijs utitur ille notis. iasides nauim, currus regit arte metiscus: fossor opus peragit nec minus arte suum. indagat uenæ spacium, numerumque, modumque, siue obliqua suum, rectaúe tendat iter. pastor ut explorat quæ terra sit apta colenti, quæ bene lanigeras, quæ malè pascat oues. en terræ intentus, quid uincula linea tendit? fungitur officio iam ptolemæe tuo. vtque suæ inuenit mensuram iuraque uenæ, in uarios operas diuidit inde uiros. iamque aggressus opus, uiden' ut mouet omne quod obstat, assidua ut uersat strenuus arma manu? ne tibi surdescant ferri tinnitibus aures, ad grauiora ideo conspicienda ueni. instruit ecce suis nunc artibus ille minores: sedulitas nulli non operosa loco. metiri docet hic uenæ spaciumque modumque, vtque regat positis finibus arua lapis, ne quis transmisso uiolentus limite pergens, non sibi concessas, in sua uertat, opes. hic docet instrumenta, quibus plutonia regna tutus adit, saxi permeat atque uias. quanta (uides) solidas expugnet machina terras: machina non ullo tempore uisa prius. cede nouis, nulla non inclyta laude uetustas, posteritas meritis est quoque grata tuis. tum quia germano sunt hæc inuenta sub axe, si quis es, inuidiæ contrahe uela tuæ. ausonis ora tumet bellis, terra attica cultu, germanum infractus tollit ad astra labor. nec tamen ingenio solet infeliciter uti, mite gerát phoebi, seu graue martis opus, tempus adest, structis uenarum montibus, igne explorare, usum quem sibi uena ferat, non labor ingenio caret hic, non copia fructu, est adaperta bonæ prima fenestra spei. ergo instat porrò grauiores ferre labores, intentas operi nec remouere manus. vrere siue locus poscat, seu tundere uerras, siue lauare lacu præter euntis aquæ. seu flammis iterum modicis torrere necesse est, excoquere aut fastis ignibus omne malum, cùm fluit æs riuis, auri argentique metallum, spes animo fossor uix capit ipse suas. argentum cupidus fuluo secernit ab auro, et plumbi lentam demit utrique moram. separat argentum, lucri studiosus, ab ære, seruatis, linquens deteriora, bonis. quæ si cuncta uelim tenui percurrere uersu, ante alium reuehat memnonis orta diem. postremus labor est, concretos discere succos, quos fert innumeris teutona terra locis. quo sal, quo nitrum, quo pacto fiat alumen, vsibus artificis cùm parat illa manus: nec non chalcantum, sulfur, fluidumque bitumen, massaque quo uitri lenta dolanda modo. suscipit hæc hominum mirandos cura labores, pauperiem usque adeo ferre famemque graue est, tantus amor uictum paruis extundere natis, et patriæ ciuem non dare uelle malum. nec manet in terræ fossoris mersa latebris mens, sed fert domino uota precesque deo. munificæ expectat, spe plenus, munera dextræ, extollens animum lætus ad astra suum. diuitias christus dat noticiamque fruendi, cui memori grates pectore semper agit. hoc quoque laudati quondam fecere philippi, qui uirtutis habent cum pietate decus. huc oculos, huc flecte animum, suauissime lector, auctoremque pia noscito mente deum. agricolae hinc optans operoso fausta labori, laudibus eximij candidus esto uiri. ille suum extollit patriæ cum nomine nomen, et uir in ore frequens posteritatis erit. cuncta cadunt letho, studij monumenta uigebunt, purpurei donec lumina solis erunt. misenæ m. d. li. èludo illustri. footnotes: [ ] for completeness' sake we reproduce in the original latin the laudation of agricola by his friend, georgius fabricius, a leading scholar of his time. it has but little intrinsic value for it is not poetry of a very high order, and to make it acceptable english would require certain improvements, for which only poets have licence. a "free" translation of the last few lines indicates its complimentary character:-- "he doth raise his country's fame with his own and in the mouths of nations yet unborn his praises shall be sung; death comes to all but great achievements raise a monument which shall endure until the sun grows cold." to the most illustrious and most mighty dukes of saxony, landgraves of thuringia, margraves of meissen, imperial overlords of saxony, burgraves of altenberg and magdeburg, counts of brena, lords of pleissnerland, to maurice grand marshall and elector of the holy roman empire and to his brother augustus,[ ] george agricola s. d. most illustrious princes, often have i considered the metallic arts as a whole, as moderatus columella[ ] considered the agricultural arts, just as if i had been considering the whole of the human body; and when i had perceived the various parts of the subject, like so many members of the body, i became afraid that i might die before i should understand its full extent, much less before i could immortalise it in writing. this book itself indicates the length and breadth of the subject, and the number and importance of the sciences of which at least some little knowledge is necessary to miners. indeed, the subject of mining is a very extensive one, and one very difficult to explain; no part of it is fully dealt with by the greek and latin authors whose works survive; and since the art is one of the most ancient, the most necessary and the most profitable to mankind, i considered that i ought not to neglect it. without doubt, none of the arts is older than agriculture, but that of the metals is not less ancient; in fact they are at least equal and coeval, for no mortal man ever tilled a field without implements. in truth, in all the works of agriculture, as in the other arts, implements are used which are made from metals, or which could not be made without the use of metals; for this reason the metals are of the greatest necessity to man. when an art is so poor that it lacks metals, it is not of much importance, for nothing is made without tools. besides, of all ways whereby great wealth is acquired by good and honest means, none is more advantageous than mining; for although from fields which are well tilled (not to mention other things) we derive rich yields, yet we obtain richer products from mines; in fact, one mine is often much more beneficial to us than many fields. for this reason we learn from the history of nearly all ages that very many men have been made rich by the mines, and the fortunes of many kings have been much amplified thereby. but i will not now speak more of these matters, because i have dealt with these subjects partly in the first book of this work, and partly in the other work entitled _de veteribus et novis metallis_, where i have refuted the charges which have been made against metals and against miners. now, though the art of husbandry, which i willingly rank with the art of mining, appears to be divided into many branches, yet it is not separated into so many as this art of ours, nor can i teach the principles of this as easily as columella did of that. he had at hand many writers upon husbandry whom he could follow,--in fact, there are more than fifty greek authors whom marcus varro enumerates, and more than ten latin ones, whom columella himself mentions. i have only one whom i can follow; that is c. plinius secundus,[ ] and he expounds only a very few methods of digging ores and of making metals. far from the whole of the art having been treated by any one writer, those who have written occasionally on any one or another of its branches have not even dealt completely with a single one of them. moreover, there is a great scarcity even of these, since alone of all the greeks, strato of lampsacus,[ ] the successor of theophrastus,[ ] wrote a book on the subject, _de machinis metallicis_; except, perhaps a work by the poet philo, a small part of which embraced to some degree the occupation of mining.[ ] pherecrates seems to have introduced into his comedy, which was similar in title, miners as slaves or as persons condemned to serve in the mines. of the latin writers, pliny, as i have already said, has described a few methods of working. also among the authors i must include the modern writers, whosoever they are, for no one should escape just condemnation who fails to award due recognition to persons whose writings he uses, even very slightly. two books have been written in our tongue; the one on the assaying of mineral substances and metals, somewhat confused, whose author is unknown[ ]; the other "on veins," of which pandulfus anglus[ ] is also said to have written, although the german book was written by calbus of freiberg, a well-known doctor; but neither of them accomplished the task he had begun.[ ] recently vannucci biringuccio, of sienna, a wise man experienced in many matters, wrote in vernacular italian on the subject of the melting, separating, and alloying of metals.[ ] he touched briefly on the methods of smelting certain ores, and explained more fully the methods of making certain juices; by reading his directions, i have refreshed my memory of those things which i myself saw in italy; as for many matters on which i write, he did not touch upon them at all, or touched but lightly. this book was given me by franciscus badoarius, a patrician of venice, and a man of wisdom and of repute; this he had promised that he would do, when in the previous year he was at marienberg, having been sent by the venetians as an ambassador to king ferdinand. beyond these books i do not find any writings on the metallic arts. for that reason, even if the book of strato existed, from all these sources not one-half of the whole body of the science of mining could be pieced together. seeing that there have been so few who have written on the subject of the metals, it appears to me all the more wonderful that so many alchemists have arisen who would compound metals artificially, and who would change one into another. hermolaus barbarus,[ ] a man of high rank and station, and distinguished in all kinds of learning, has mentioned the names of many in his writings; and i will proffer more, but only famous ones, for i will limit myself to a few. thus osthanes has written on [greek: chymeutika]; and there are hermes; chanes; zosimus, the alexandrian, to his sister theosebia; olympiodorus, also an alexandrian; agathodæmon; democritus, not the one of abdera, but some other whom i know not; orus chrysorichites, pebichius, comerius, joannes, apulejus, petasius, pelagius, africanus, theophilus, synesius, stephanus to heracleus cæsar, heliodorus to theodosius, geber, callides rachaidibus, veradianus, rodianus, canides, merlin, raymond lully, arnold de villa nova, and augustinus pantheus of venice; and three women, cleopatra, the maiden taphnutia, and maria the jewess.[ ] all these alchemists employ obscure language, and johanes aurelius augurellus of rimini, alone has used the language of poetry. there are many other books on this subject, but all are difficult to follow, because the writers upon these things use strange names, which do not properly belong to the metals, and because some of them employ now one name and now another, invented by themselves, though the thing itself changes not. these masters teach their disciples that the base metals, when smelted, are broken up; also they teach the methods by which they reduce them to the primary parts and remove whatever is superfluous in them, and by supplying what is wanted make out of them the precious metals--that is, gold and silver,--all of which they carry out in a crucible. whether they can do these things or not i cannot decide; but, seeing that so many writers assure us with all earnestness that they have reached that goal for which they aimed, it would seem that faith might be placed in them; yet also seeing that we do not read of any of them ever having become rich by this art, nor do we now see them growing rich, although so many nations everywhere have produced, and are producing, alchemists, and all of them are straining every nerve night and day to the end that they may heap a great quantity of gold and silver, i should say the matter is dubious. but although it may be due to the carelessness of the writers that they have not transmitted to us the names of the masters who acquired great wealth through this occupation, certainly it is clear that their disciples either do not understand their precepts or, if they do understand them, do not follow them; for if they do comprehend them, seeing that these disciples have been and are so numerous, they would have by to-day filled whole towns with gold and silver. even their books proclaim their vanity, for they inscribe in them the names of plato and aristotle and other philosophers, in order that such high-sounding inscriptions may impose upon simple people and pass for learning. there is another class of alchemists who do not change the substance of base metals, but colour them to represent gold or silver, so that they appear to be that which they are not, and when this appearance is taken from them by the fire, as if it were a garment foreign to them, they return to their own character. these alchemists, since they deceive people, are not only held in the greatest odium, but their frauds are a capital offence. no less a fraud, warranting capital punishment, is committed by a third sort of alchemists; these throw into a crucible a small piece of gold or silver hidden in a coal, and after mixing therewith fluxes which have the power of extracting it, pretend to be making gold from orpiment, or silver from tin and like substances. but concerning the art of alchemy, if it be an art, i will speak further elsewhere. i will now return to the art of mining. since no authors have written of this art in its entirety, and since foreign nations and races do not understand our tongue, and, if they did understand it, would be able to learn only a small part of the art through the works of those authors whom we do possess, i have written these twelve books _de re metallica_. of these, the first book contains the arguments which may be used against this art, and against metals and the mines, and what can be said in their favour. the second book describes the miner, and branches into a discourse on the finding of veins. the third book deals with veins and stringers, and seams in the rocks. the fourth book explains the method of delimiting veins, and also describes the functions of the mining officials. the fifth book describes the digging of ore and the surveyor's art. the sixth book describes the miners' tools and machines. the seventh book is on the assaying of ore. the eighth book lays down the rules for the work of roasting, crushing, and washing the ore. the ninth book explains the methods of smelting ores. the tenth book instructs those who are studious of the metallic arts in the work of separating silver from gold, and lead from gold and silver. the eleventh book shows the way of separating silver from copper. the twelfth book gives us rules for manufacturing salt, soda, alum, vitriol, sulphur, bitumen, and glass. although i have not fulfilled the task which i have undertaken, on account of the great magnitude of the subject, i have, at all events, endeavoured to fulfil it, for i have devoted much labour and care, and have even gone to some expense upon it; for with regard to the veins, tools, vessels, sluices, machines, and furnaces, i have not only described them, but have also hired illustrators to delineate their forms, lest descriptions which are conveyed by words should either not be understood by men of our own times, or should cause difficulty to posterity, in the same way as to us difficulty is often caused by many names which the ancients (because such words were familiar to all of them) have handed down to us without any explanation. i have omitted all those things which i have not myself seen, or have not read or heard of from persons upon whom i can rely. that which i have neither seen, nor carefully considered after reading or hearing of, i have not written about. the same rule must be understood with regard to all my instruction, whether i enjoin things which ought to be done, or describe things which are usual, or condemn things which are done. since the art of mining does not lend itself to elegant language, these books of mine are correspondingly lacking in refinement of style. the things dealt with in this art of metals sometimes lack names, either because they are new, or because, even if they are old, the record of the names by which they were formerly known has been lost. for this reason i have been forced by a necessity, for which i must be pardoned, to describe some of them by a number of words combined, and to distinguish others by new names,--to which latter class belong _ingestor_, _discretor_, _lotor_, and _excoctor_.[ ] other things, again, i have alluded to by old names, such as the _cisium_; for when nonius marcellus wrote,[ ] this was the name of a two-wheeled vehicle, but i have adopted it for a small vehicle which has only one wheel; and if anyone does not approve of these names, let him either find more appropriate ones for these things, or discover the words used in the writings of the ancients. these books, most illustrious princes, are dedicated to you for many reasons, and, above all others, because metals have proved of the greatest value to you; for though your ancestors drew rich profits from the revenues of their vast and wealthy territories, and likewise from the taxes which were paid by the foreigners by way of toll and by the natives by way of tithes, yet they drew far richer profits from the mines. because of the mines not a few towns have risen into eminence, such as freiberg, annaberg, marienberg, schneeberg, geyer, and altenberg, not to mention others. nay, if i understand anything, greater wealth now lies hidden beneath the ground in the mountainous parts of your territory than is visible and apparent above ground. farewell. _chemnitz, saxony, december first, ._ footnotes: [ ] for agricola's relations with these princes see p. ix. [ ] lucius junius moderatus columella was a roman, a native of cadiz, and lived during the st century. he was the author of _de re rustica_ in books. it was first printed in , and some fifteen or sixteen editions had been printed before agricola's death. [ ] we give a short review of pliny's _naturalis historia_ in the appendix b. [ ] this work is not extant, as agricola duly notes later on. strato succeeded theophrastus as president of the lyceum, b.c. [ ] for note on theophrastus see appendix b. [ ] it appears that the poet philo did write a work on mining which is not extant. so far as we know the only reference to this work is in athenæus' ( a.d.) _deipnosophistae_. the passage as it appears in c. d. yonge's translation (bonn's library, london, , vol. ii, book vii, p. ) is: "and there is a similar fish produced in the red sea which is called stromateus; it has gold-coloured lines running along the whole of his body, as philo tells us in his book on mines." there is a fragment of a poem of pherecrates, entitled "miners," but it seems to have little to do with mining. [ ] the title given by agricola _de materiae metallicae et metallorum experimento_ is difficult to identify. it seems likely to be the little _probier büchlein_, numbers of which were published in german in the first half of the th century. we discuss this work at some length in the appendix b on ancient authors. [ ] pandulfus, "the englishman," is mentioned by various th and th century writers, and in the preface of mathias farinator's _liber moralitatum ... rerum naturalium_, etc., printed in augsburg, , there is a list of books among which appears a reference to a work by pandulfus on veins and minerals. we have not been able to find the book. [ ] jacobi (_der mineralog georgius agricola_, zwickau, , p. ) says: "calbus freibergius, so called by agricola himself, is certainly no other than the freiberg doctor rühlein von kalbe; he was, according to möller, a doctor and burgomaster at freiberg at the end of the th and the beginning of the th centuries.... the chronicler describes him as a fine mathematician, who helped to survey and design the mining towns of annaberg in and marienberg in ." we would call attention to the statement of calbus' views, quoted at the end of book iii, _de re metallica_ (p. ), which are astonishingly similar to statements in the _nützlich bergbüchlin_, and leave little doubt that this "calbus" was the author of that anonymous book on veins. for further discussion see appendix b. [ ] for discussion of biringuccio see appendix b. the proper title is _de la pirotechnia_ (venice, ). [ ] hermolaus barbarus, according to watt (_bibliotheca britannica_, london, ), was a lecturer on philosophy in padua. he was born in , died in , and was the author of a number of works on medicine, natural history, etc., with commentaries on the older authors. [ ] the debt which humanity does owe to these self-styled philosophers must not be overlooked, for the science of chemistry comes from three sources--alchemy, medicine and metallurgy. however polluted the former of these may be, still the vast advance which it made by the discovery of the principal acids, alkalis, and the more common of their salts, should be constantly recognized. it is obviously impossible, within the space of a footnote, to give anything but the most casual notes as to the personages here mentioned and their writings. aside from the classics and religious works, the libraries of the middle ages teemed with more material on alchemy than on any other one subject, and since that date a never-ending stream of historical, critical, and discursive volumes and tracts devoted to the old alchemists and their writings has been poured upon the world. a collection recently sold in london, relating to paracelsus alone, embraced over seven hundred volumes. of many of the alchemists mentioned by agricola little is really known, and no two critics agree as to the commonest details regarding many of them; in fact, an endless confusion springs from the negligent habit of the lesser alchemists of attributing the authorship of their writings to more esteemed members of their own ilk, such as hermes, osthanes, etc., not to mention the palpable spuriousness of works under the names of the real philosophers, such as aristotle, plato, or moses, and even of jesus christ. knowledge of many of the authors mentioned by agricola does not extend beyond the fact that the names mentioned are appended to various writings, in some instances to mss yet unpublished. they may have been actual persons, or they may not. agricola undoubtedly had perused such manuscripts and books in some leading library, as the quotation from boerhaave given later shows. shaw (a new method of chemistry, etc., london, . vol. i, p. ) considers that the large number of such manuscripts in the european libraries at this time were composed or transcribed by monks and others living in constantinople, alexandria, and athens, who fled westward before the turkish invasion, bringing their works with them. for purposes of this summary we group the names mentioned by agricola, the first class being of those who are known only as names appended to mss or not identifiable at all. possibly a more devoted student of the history of alchemy would assign fewer names to this department of oblivion. they are maria the jewess, orus chrysorichites, chanes, petasius, pebichius, theophilus, callides, veradianus, rodianus, canides, the maiden taphnutia, johannes, augustinus, and africanus. the last three are names so common as not to be possible of identification without more particulars, though johannes may be the johannes rupeseissa ( ), an alchemist of some note. many of these names can be found among the bishops and prelates of the early christian church, but we doubt if their owners would ever be identified with such indiscretions as open, avowed alchemy. the theophilus mentioned might be the metal-working monk of the th century, who is further discussed in appendix b on ancient authors. in the next group fall certain names such as osthanes, hermes, zosimus, agathodaemon, and democritus, which have been the watchwords of authority to alchemists of all ages. these certainly possessed the great secrets, either the philosopher's stone or the elixir. hermes trismegistos was a legendary egyptian personage supposed to have flourished before , b.c., and by some considered to be a corruption of the god thoth. he is supposed to have written a number of works, but those extant have been demonstrated to date not prior to the second century; he is referred to by the later greek alchemists, and was believed to have possessed the secret of transmutation. osthanes was also a very shadowy personage, and was considered by some alchemists to have been an egyptian prior to hermes, by others to have been the teacher of zoroaster. pliny mentions a magician of this name who accompanied xerxes' army. later there are many others of this name, and the most probable explanation is that this was a favourite pseudonym for ancient magicians; there is a very old work, of no great interest, in mss in latin and greek, in the munich, gotha, vienna, and other libraries, by one of this name. agathodaemon was still another shadowy character referred to by the older alchemists. there are mss in the florence, paris, escurial, and munich libraries bearing his name, but nothing tangible is known as to whether he was an actual man or if these writings are not of a much later period than claimed. to the next group belong the greek alchemists, who flourished during the rise and decline of alexandria, from b.c. to a.d., and we give them in order of their dates. comerius was considered by his later fellow professionals to have been the teacher of the art to cleopatra ( st century b.c.), and a mss with a title to that effect exists in the bibliothèque nationale at paris. the celebrated cleopatra seems to have stood very high in the estimation of the alchemists; perhaps her doubtful character found a response among them; there are various works extant in mss attributed to her, but nothing can be known as to their authenticity. lucius apulejus or apuleius was born in numidia about the nd century; he was a roman platonic philosopher, and was the author of a romance, "the metamorphosis, or the golden ass." synesius was a greek, but of unknown period; there is a mss treatise on the philosopher's stone in the library at leyden under his name, and various printed works are attributed to him; he mentions "water of saltpetre," and has, therefore, been hazarded to be the earliest recorder of nitric acid. the work here referred to as "heliodorus to theodosius" was probably the mss in the libraries at paris, vienna, munich, etc., under the title of "heliodorus the philosopher's poem to the emperor theodosius the great on the mystic art of the philosophers, etc." his period would, therefore, be about the th century. the alexandrian zosimus is more generally known as zosimus the panopolite, from panopolis, an ancient town on the nile; he flourished in the th century, and belonged to the alexandrian school of alchemists; he should not be confused with the roman historian of the same name and period. the following statement is by boerhaave (_elementa chemiae_, paris, , chap. i.):--"the name chemistry written in greek, or _chemia_, is so ancient as perhaps to have been used in the antediluvian age. of this opinion was zosimus the panopolite, whose greek writings, though known as long as before the year to george agricola, and afterwards perused ... by jas. scaliger and olaus borrichius, still remain unpublished in the king of france's library. in one of these, entitled, 'the instruction of zosimus the panopolite and philosopher, out of those written to theosebia, etc....'" olympiodorus was an alexandrian of the th century, whose writings were largely commentaries on plato and aristotle; he is sometimes accredited with being the first to describe white arsenic (arsenical oxide). the full title of the work styled "stephanus to heracleus caesar," as published in latin at padua in , was "stephan of alexandria, the universal philosopher and master, his nine processes on the great art of making gold and silver, addressed to the emperor heraclius." he, therefore, if authentic, dates in the th century. to the next class belong those of the middle ages, which we give in order of date. the works attributed to geber play such an important part in the history of chemistry and metallurgy that we discuss his book at length in appendix b. late criticism indicates that this work was not the production of an th century arab, but a compilation of some latin scholar of the th or th centuries. arnold de villa nova, born about , died in , was celebrated as a physician, philosopher, and chemist; his first works were published in lyons in ; many of them have apparently never been printed, for references may be found to some different works. raymond lully, a spaniard, born in , who was a disciple of arnold de villa nova, was stoned to death in africa in . there are extant over works attributed to this author, although again the habit of disciples of writing under the master's name may be responsible for most of these. john aurelio augurello was an italian classicist, born in rimini about . the work referred to, _chrysopoeia et gerontica_ is a poem on the art of making gold, etc., published in venice, , and re-published frequently thereafter; it is much quoted by alchemists. with regard to merlin, as satisfactory an account as any of this truly english magician may be found in mark twain's "yankee at the court of king arthur." it is of some interest to note that agricola omits from his list avicenna ( - a.d.), roger bacon ( - ), albertus magnus ( - ), basil valentine (end th century?), and paracelsus, a contemporary of his own. in _de ortu et causis_ he expends much thought on refutation of theories advanced by avicenna and albertus, but of the others we have found no mention, although their work is, from a chemical point of view, of considerable importance. [ ] _ingestor_,--carrier; _discretor_,--sorter; _lotor_,--washer; _excoctor_,--smelter. [ ] nonius marcellus was a roman grammarian of the th century b.c. his extant treatise is entitled, _de compendiosa doctrina per litteras ad filium_. book i. many persons hold the opinion that the metal industries are fortuitous and that the occupation is one of sordid toil, and altogether a kind of business requiring not so much skill as labour. but as for myself, when i reflect carefully upon its special points one by one, it appears to be far otherwise. for a miner must have the greatest skill in his work, that he may know first of all what mountain or hill, what valley or plain, can be prospected most profitably, or what he should leave alone; moreover, he must understand the veins, stringers[ ] and seams in the rocks[ ]. then he must be thoroughly familiar with the many and varied species of earths, juices[ ], gems, stones, marbles, rocks, metals, and compounds[ ]. he must also have a complete knowledge of the method of making all underground works. lastly, there are the various systems of assaying[ ] substances and of preparing them for smelting; and here again there are many altogether diverse methods. for there is one method for gold and silver, another for copper, another for quicksilver, another for iron, another for lead, and even tin and bismuth[ ] are treated differently from lead. although the evaporation of juices is an art apparently quite distinct from metallurgy, yet they ought not to be considered separately, inasmuch as these juices are also often dug out of the ground solidified, or they are produced from certain kinds of earth and stones which the miners dig up, and some of the juices are not themselves devoid of metals. again, their treatment is not simple, since there is one method for common salt, another for soda[ ], another for alum, another for vitriol[ ], another for sulphur, and another for bitumen. furthermore, there are many arts and sciences of which a miner should not be ignorant. first there is philosophy, that he may discern the origin, cause, and nature of subterranean things; for then he will be able to dig out the veins easily and advantageously, and to obtain more abundant results from his mining. secondly, there is medicine, that he may be able to look after his diggers and other workmen, that they do not meet with those diseases to which they are more liable than workmen in other occupations, or if they do meet with them, that he himself may be able to heal them or may see that the doctors do so. thirdly follows astronomy, that he may know the divisions of the heavens and from them judge the direction of the veins. fourthly, there is the science of surveying that he may be able to estimate how deep a shaft should be sunk to reach the tunnel which is being driven to it, and to determine the limits and boundaries in these workings, especially in depth. fifthly, his knowledge of arithmetical science should be such that he may calculate the cost to be incurred in the machinery and the working of the mine. sixthly, his learning must comprise architecture, that he himself may construct the various machines and timber work required underground, or that he may be able to explain the method of the construction to others. next, he must have knowledge of drawing, that he can draw plans of his machinery. lastly, there is the law, especially that dealing with metals, that he may claim his own rights, that he may undertake the duty of giving others his opinion on legal matters, that he may not take another man's property and so make trouble for himself, and that he may fulfil his obligations to others according to the law. it is therefore necessary that those who take an interest in the methods and precepts of mining and metallurgy should read these and others of our books studiously and diligently; or on every point they should consult expert mining people, though they will discover few who are skilled in the whole art. as a rule one man understands only the methods of mining, another possesses the knowledge of washing[ ], another is experienced in the art of smelting, another has a knowledge of measuring the hidden parts of the earth, another is skilful in the art of making machines, and finally, another is learned in mining law. but as for us, though we may not have perfected the whole art of the discovery and preparation of metals, at least we can be of great assistance to persons studious in its acquisition. but let us now approach the subject we have undertaken. since there has always been the greatest disagreement amongst men concerning metals and mining, some praising, others utterly condemning them, therefore i have decided that before imparting my instruction, i should carefully weigh the facts with a view to discovering the truth in this matter. so i may begin with the question of utility, which is a two-fold one, for either it may be asked whether the art of mining is really profitable or not to those who are engaged in it, or whether it is useful or not to the rest of mankind. those who think mining of no advantage to the men who follow the occupation assert, first, that scarcely one in a hundred who dig metals or other such things derive profit therefrom; and again, that miners, because they entrust their certain and well-established wealth to dubious and slippery fortune, generally deceive themselves, and as a result, impoverished by expenses and losses, in the end spend the most bitter and most miserable of lives. but persons who hold these views do not perceive how much a learned and experienced miner differs from one ignorant and unskilled in the art. the latter digs out the ore without any careful discrimination, while the former first assays and proves it, and when he finds the veins either too narrow and hard, or too wide and soft, he infers therefrom that these cannot be mined profitably, and so works only the approved ones. what wonder then if we find the incompetent miner suffers loss, while the competent one is rewarded by an abundant return from his mining? the same thing applies to husbandmen. for those who cultivate land which is alike arid, heavy, and barren, and in which they sow seeds, do not make so great a harvest as those who cultivate a fertile and mellow soil and sow their grain in that. and since by far the greater number of miners are unskilled rather than skilled in the art, it follows that mining is a profitable occupation to very few men, and a source of loss to many more. therefore the mass of miners who are quite unskilled and ignorant in the knowledge of veins not infrequently lose both time and trouble[ ]. such men are accustomed for the most part to take to mining, either when through being weighted with the fetters of large and heavy debts, they have abandoned a business, or desiring to change their occupation, have left the reaping-hook and plough; and so if at any time such a man discovers rich veins or other abounding mining produce, this occurs more by good luck than through any knowledge on his part. we learn from history that mining has brought wealth to many, for from old writings it is well known that prosperous republics, not a few kings, and many private persons, have made fortunes through mines and their produce. this subject, by the use of many clear and illustrious examples, i have dilated upon and explained in the first book of my work entitled "_de veteribus et novis metallis_," from which it is evident that mining is very profitable to those who give it care and attention. again, those who condemn the mining industry say that it is not in the least stable, and they glorify agriculture beyond measure. but i do not see how they can say this with truth, for the silver mines at freiberg in meissen remain still unexhausted after years, and the lead mines of goslar after years. the proof of this can be found in the monuments of history. the gold and silver mines belonging to the communities of schemnitz and cremnitz have been worked for years, and these latter are said to be the most ancient privileges of the inhabitants. some then say the profit from an individual mine is unstable, as if forsooth, the miner is, or ought to be dependent on only one mine, and as if many men do not bear in common their expenses in mining, or as if one experienced in his art does not dig another vein, if fortune does not amply respond to his prayers in the first case. the new schönberg at freiberg has remained stable beyond the memory of man[ ]. it is not my intention to detract anything from the dignity of agriculture, and that the profits of mining are less stable i will always and readily admit, for the veins do in time cease to yield metals, whereas the fields bring forth fruits every year. but though the business of mining may be less reliable it is more productive, so that in reckoning up, what is wanting in stability is found to be made up by productiveness. indeed, the yearly profit of a lead mine in comparison with the fruitfulness of the best fields, is three times or at least twice as great. how much does the profit from gold or silver mines exceed that earned from agriculture? wherefore truly and shrewdly does xenophon[ ] write about the athenian silver mines: "there is land of such a nature that if you sow, it does not yield crops, but if you dig, it nourishes many more than if it had borne fruit." so let the farmers have for themselves the fruitful fields and cultivate the fertile hills for the sake of their produce; but let them leave to miners the gloomy valleys and sterile mountains, that they may draw forth from these, gems and metals which can buy, not only the crops, but all things that are sold. the critics say further that mining is a perilous occupation to pursue, because the miners are sometimes killed by the pestilential air which they breathe; sometimes their lungs rot away; sometimes the men perish by being crushed in masses of rock; sometimes, falling from the ladders into the shafts, they break their arms, legs, or necks; and it is added there is no compensation which should be thought great enough to equalize the extreme dangers to safety and life. these occurrences, i confess, are of exceeding gravity, and moreover, fraught with terror and peril, so that i should consider that the metals should not be dug up at all, if such things were to happen very frequently to the miners, or if they could not safely guard against such risks by any means. who would not prefer to live rather than to possess all things, even the metals? for he who thus perishes possesses nothing, but relinquishes all to his heirs. but since things like this rarely happen, and only in so far as workmen are careless, they do not deter miners from carrying on their trade any more than it would deter a carpenter from his, because one of his mates has acted incautiously and lost his life by falling from a high building. i have thus answered each argument which critics are wont to put before me when they assert that mining is an undesirable occupation, because it involves expense with uncertainty of return, because it is changeable, and because it is dangerous to those engaged in it. now i come to those critics who say that mining is not useful to the rest of mankind because forsooth, gems, metals, and other mineral products are worthless in themselves. this admission they try to extort from us, partly by arguments and examples, partly by misrepresentations and abuse of us. first, they make use of this argument: "the earth does not conceal and remove from our eyes those things which are useful and necessary to mankind, but on the contrary, like a beneficent and kindly mother she yields in large abundance from her bounty and brings into the light of day the herbs, vegetables, grains, and fruits, and the trees. the minerals on the other hand she buries far beneath in the depth of the ground; therefore, they should not be sought. but they are dug out by wicked men who, as the poets say, are the products of the iron age." ovid censures their audacity in the following lines:-- "and not only was the rich soil required to furnish corn and due sustenance, but men even descended into the entrails of the earth, and they dug up riches, those incentives to vice, which the earth had hidden and had removed to the stygian shades. then destructive iron came forth, and gold, more destructive than iron; then war came forth."[ ] another of their arguments is this: metals offer to men no advantages, therefore we ought not to search them out. for whereas man is composed of soul and body, neither is in want of minerals. the sweetest food of the soul is the contemplation of nature, a knowledge of the finest arts and sciences, an understanding of virtue; and if he interests his mind in excellent things, if he exercise his body, he will be satisfied with this feast of noble thoughts and knowledge, and have no desire for other things. now although the human body may be content with necessary food and clothing, yet the fruits of the earth and the animals of different kinds supply him in wonderful abundance with food and drink, from which the body may be suitably nourished and strengthened and life prolonged to old age. flax, wool, and the skins of many animals provide plentiful clothing low in price; while a luxurious kind, not hard to procure--that is the so called _seric_ material, is furnished by the down of trees and the webs of the silk worm. so that the body has absolutely no need of the metals, so hidden in the depths of the earth and for the greater part very expensive. wherefore it is said that this maxim of euripides is approved in assemblies of learned men, and with good reason was always on the lips of socrates: "works of silver and purple are of use, not for human life, but rather for tragedians."[ ] these critics praise also this saying from timocreon of rhodes: "o unseeing plutus, would that thou hadst never appeared in the earth or in the sea or on the land, but that thou didst have thy habitation in tartarus and acheron, for out of thee arise all evil things which overtake mankind"[ ]. they greatly extol these lines from phocylides: "gold and silver are injurious to mortals; gold is the source of crime, the plague of life, and the ruin of all things. would that thou were not such an attractive scourge! because of thee arise robberies, homicides, warfare, brothers are maddened against brothers, and children against parents." this from naumachius also pleases them: "gold and silver are but dust, like the stones that lie scattered on the pebbly beach, or on the margins of the rivers." on the other hand, they censure these verses of euripides: "plutus is the god for wise men; all else is mere folly and at the same time a deception in words." so in like manner these lines from theognis: "o plutus, thou most beautiful and placid god! whilst i have thee, however bad i am, i can be regarded as good." they also blame aristodemus, the spartan, for these words: "money makes the man; no one who is poor is either good or honoured." and they rebuke these songs of timocles: "money is the life and soul of mortal men. he who has not heaped up riches for himself wanders like a dead man amongst the living." finally, they blame menander when he wrote: "epicharmus asserts that the gods are water, wind, fire, earth, sun, and stars. but i am of opinion that the gods of any use to us are silver and gold; for if thou wilt set these up in thy house thou mayest seek whatever thou wilt. all things will fall to thy lot; land, houses, slaves, silver-work; moreover friends, judges, and witnesses. only give freely, for thus thou hast the gods to serve thee." but besides this, the strongest argument of the detractors is that the fields are devastated by mining operations, for which reason formerly italians were warned by law that no one should dig the earth for metals and so injure their very fertile fields, their vineyards, and their olive groves. also they argue that the woods and groves are cut down, for there is need of an endless amount of wood for timbers, machines, and the smelting of metals. and when the woods and groves are felled, then are exterminated the beasts and birds, very many of which furnish a pleasant and agreeable food for man. further, when the ores are washed, the water which has been used poisons the brooks and streams, and either destroys the fish or drives them away. therefore the inhabitants of these regions, on account of the devastation of their fields, woods, groves, brooks and rivers, find great difficulty in procuring the necessaries of life, and by reason of the destruction of the timber they are forced to greater expense in erecting buildings. thus it is said, it is clear to all that there is greater detriment from mining than the value of the metals which the mining produces. so in fierce contention they clamour, showing by such examples as follow that every great man has been content with virtue, and despised metals. they praise bias because he esteemed the metals merely as fortune's playthings, not as his real wealth. when his enemies had captured his native priene, and his fellow-citizens laden with precious things had betaken themselves to flight, he was asked by one, why he carried away none of his goods with him, and he replied, "i carry all my possessions with me." and it is said that socrates, having received twenty minae sent to him by aristippus, a grateful disciple, refused them and sent them back to him by the command of his conscience. aristippus, following his example in this matter, despised gold and regarded it as of no value. and once when he was making a journey with his slaves, and they, laden with the gold, went too slowly, he ordered them to keep only as much of it as they could carry without distress and to throw away the remainder[ ]. moreover, anacreon of teos, an ancient and noble poet, because he had been troubled about them for two nights, returned five talents which had been given him by polycrates, saying that they were not worth the anxiety which he had gone through on their account. in like manner celebrated and exceedingly powerful princes have imitated the philosophers in their scorn and contempt for gold and silver. there was for example, phocion, the athenian, who was appointed general of the army so many times, and who, when a large sum of gold was sent to him as a gift by alexander, king of macedon, deemed it trifling and scorned it. and marcus curius ordered the gold to be carried back to the samnites, as did also fabricius luscinus with regard to the silver and copper. and certain republics have forbidden their citizens the use and employment of gold and silver by law and ordinance; the lacedaemonians, by the decrees and ordinances of lycurgus, used diligently to enquire among their citizens whether they possessed any of these things or not, and the possessor, when he was caught, was punished according to law and justice. the inhabitants of a town on the tigris, called babytace, buried their gold in the ground so that no one should use it. the scythians condemned the use of gold and silver so that they might not become avaricious. further are the metals reviled; in the first place people wantonly abuse gold and silver and call them deadly and nefarious pests of the human race, because those who possess them are in the greatest peril, for those who have none lay snares for the possessors of wealth, and thus again and again the metals have been the cause of destruction and ruin. for example, polymnestor, king of thrace, to obtain possession of his gold, killed polydorus, his noble guest and the son of priam, his father-in-law, and old friend. pygmalion, the king of tyre, in order that he might seize treasures of gold and silver, killed his sister's husband, a priest, taking no account of either kinship or religion. for love of gold eriphyle betrayed her husband amphiaraus to his enemy. likewise lasthenes betrayed the city of olynthus to philip of macedon. the daughter of spurius tarpeius, having been bribed with gold, admitted the sabines into the citadel of rome. claudius curio sold his country for gold to cæsar, the dictator. gold, too, was the cause of the downfall of aesculapius, the great physician, who it was believed was the son of apollo. similarly marcus crassus, through his eager desire for the gold of the parthians, was completely overcome together with his son and eleven legions, and became the jest of his enemies; for they poured liquid gold into the gaping mouth of the slain crassus, saying: "thou hast thirsted for gold, therefore drink gold." but why need i cite here these many examples from history?[ ] it is almost our daily experience to learn that, for the sake of obtaining gold and silver, doors are burst open, walls are pierced, wretched travellers are struck down by rapacious and cruel men born to theft, sacrilege, invasion, and robbery. we see thieves seized and strung up before us, sacrilegious persons burnt alive, the limbs of robbers broken on the wheel, wars waged for the same reason, which are not only destructive to those against whom they are waged, but to those also who carry them on. nay, but they say that the precious metals foster all manner of vice, such as the seduction of women, adultery, and unchastity, in short, crimes of violence against the person. therefore the poets, when they represent jove transformed into a golden shower and falling into the lap of danae, merely mean that he had found for himself a safe road by the use of gold, by which he might enter the tower for the purpose of violating the maiden. moreover, the fidelity of many men is overthrown by the love of gold and silver, judicial sentences are bought, and innumerable crimes are perpetrated. for truly, as propertius says: "this is indeed the golden age. the greatest rewards come from gold; by gold love is won; by gold is faith destroyed; by gold is justice bought; the law follows the track of gold, while modesty will soon follow it when law is gone." diphilus says: "i consider that nothing is more powerful than gold. by it all things are torn asunder; all things are accomplished." therefore, all the noblest and best despise these riches, deservedly and with justice, and esteem them as nothing. and this is said by the old man in plautus: "i hate gold. it has often impelled many people to many wrong acts." in this country too, the poets inveigh with stinging reproaches against money coined from gold and silver. and especially did juvenal: "since the majesty of wealth is the most sacred thing among us; although, o pernicious money, thou dost not yet inhabit a temple, nor have we erected altars to money." and in another place: "demoralising money first introduced foreign customs, and voluptuous wealth weakened our race with disgraceful luxury."[ ] and very many vehemently praise the barter system which men used before money was devised, and which even now obtains among certain simple peoples. and next they raise a great outcry against other metals, as iron, than which they say nothing more pernicious could have been brought into the life of man. for it is employed in making swords, javelins, spears, pikes, arrows--weapons by which men are wounded, and which cause slaughter, robbery, and wars. these things so moved the wrath of pliny that he wrote: "iron is used not only in hand to hand fighting, but also to form the winged missiles of war, sometimes for hurling engines, sometimes for lances, sometimes even for arrows. i look upon it as the most deadly fruit of human ingenuity. for to bring death to men more quickly we have given wings to iron and taught it to fly."[ ] the spear, the arrow from the bow, or the bolt from the catapult and other engines can be driven into the body of only one man, while the iron cannon-ball fired through the air, can go through the bodies of many men, and there is no marble or stone object so hard that it cannot be shattered by the force and shock. therefore it levels the highest towers to the ground, shatters and destroys the strongest walls. certainly the ballistas which throw stones, the battering rams and other ancient war engines for making breaches in walls of fortresses and hurling down strongholds, seem to have little power in comparison with our present cannon. these emit horrible sounds and noises, not less than thunder, flashes of fire burst from them like the lightning, striking, crushing, and shattering buildings, belching forth flames and kindling fires even as lightning flashes. so that with more justice could it be said of the impious men of our age than of salmoneus of ancient days, that they had snatched lightning from jupiter and wrested it from his hands. nay, rather there has been sent from the infernal regions to the earth this force for the destruction of men, so that death may snatch to himself as many as possible by one stroke. but because muskets are nowadays rarely made of iron, and the large ones never, but of a certain mixture of copper and tin, they confer more maledictions on copper and tin than on iron. in this connection too, they mention the brazen bull of phalaris, the brazen ox of the people of pergamus, racks in the shape of an iron dog or a horse, manacles, shackles, wedges, hooks, and red-hot plates. cruelly racked by such instruments, people are driven to confess crimes and misdeeds which they have never committed, and innocent men are miserably tortured to death by every conceivable kind of torment. it is claimed too, that lead is a pestilential and noxious metal, for men are punished by means of molten lead, as horace describes in the ode addressed to the goddess fortune: "cruel necessity ever goes before thee bearing in her brazen hand the spikes and wedges, while the awful hook and molten lead are also not lacking."[ ] in their desire to excite greater odium for this metal, they are not silent about the leaden balls of muskets, and they find in it the cause of wounds and death. they contend that, inasmuch as nature has concealed metals far within the depths of the earth, and because they are not necessary to human life, they are therefore despised and repudiated by the noblest, and should not be mined, and seeing that when brought to light they have always proved the cause of very great evils, it follows that mining is not useful to mankind, but on the contrary harmful and destructive. several good men have been so perturbed by these tragedies that they conceive an intensely bitter hatred toward metals, and they wish absolutely that metals had never been created, or being created, that no one had ever dug them out. the more i commend the singular honesty, innocence, and goodness of such men, the more anxious shall i be to remove utterly and eradicate all error from their minds and to reveal the sound view, which is that the metals are most useful to mankind. in the first place then, those who speak ill of the metals and refuse to make use of them, do not see that they accuse and condemn as wicked the creator himself, when they assert that he fashioned some things vainly and without good cause, and thus they regard him as the author of evils, which opinion is certainly not worthy of pious and sensible men. in the next place, the earth does not conceal metals in her depths because she does not wish that men should dig them out, but because provident and sagacious nature has appointed for each thing its place. she generates them in the veins, stringers, and seams in the rocks, as though in special vessels and receptacles for such material. the metals cannot be produced in the other elements because the materials for their formation are wanting. for if they were generated in the air, a thing that rarely happens, they could not find a firm resting-place, but by their own force and weight would settle down on to the ground. seeing then that metals have their proper abiding place in the bowels of the earth, who does not see that these men do not reach their conclusions by good logic? they say, "although metals are in the earth, each located in its own proper place where it originated, yet because they lie thus enclosed and hidden from sight, they should not be taken out." but, in refutation of these attacks, which are so annoying, i will on behalf of the metals instance the fish, which we catch, hidden and concealed though they be in the water, even in the sea. indeed, it is far stranger that man, a terrestrial animal, should search the interior of the sea than the bowels of the earth. for as birds are born to fly freely through the air, so are fishes born to swim through the waters, while to other creatures nature has given the earth that they might live in it, and particularly to man that he might cultivate it and draw out of its caverns metals and other mineral products. on the other hand, they say that we eat fish, but neither hunger nor thirst is dispelled by minerals, nor are they useful in clothing the body, which is another argument by which these people strive to prove that metals should not be taken out. but man without metals cannot provide those things which he needs for food and clothing. for, though the produce of the land furnishes the greatest abundance of food for the nourishment of our bodies, no labour can be carried on and completed without tools. the ground itself is turned up with ploughshares and harrows, tough stalks and the tops of the roots are broken off and dug up with a mattock, the sown seed is harrowed, the corn field is hoed and weeded; the ripe grain with part of the stalk is cut down by scythes and threshed on the floor, or its ears are cut off and stored in the barn and later beaten with flails and winnowed with fans, until finally the pure grain is stored in the granary, whence it is brought forth again when occasion demands or necessity arises. again, if we wish to procure better and more productive fruits from trees and bushes, we must resort to cultivating, pruning, and grafting, which cannot be done without tools. even as without vessels we cannot keep or hold liquids, such as milk, honey, wine, or oil, neither could so many living things be cared for without buildings to protect them from long-continued rain and intolerable cold. most of the rustic instruments are made of iron, as ploughshares, share-beams, mattocks, the prongs of harrows, hoes, planes, hay-forks, straw cutters, pruning shears, pruning hooks, spades, lances, forks, and weed cutters. vessels are also made of copper or lead. neither are wooden instruments or vessels made without iron. wine cellars, oil-mills, stables, or any other part of a farm building could not be built without iron tools. then if the bull, the wether, the goat, or any other domestic animal is led away from the pasture to the butcher, or if the poulterer brings from the farm a chicken, a hen, or a capon for the cook, could any of these animals be cut up and divided without axes and knives? i need say nothing here about bronze and copper pots for cooking, because for these purposes one could make use of earthen vessels, but even these in turn could not be made and fashioned by the potter without tools, for no instruments can be made out of wood alone, without the use of iron. furthermore, hunting, fowling, and fishing supply man with food, but when the stag has been ensnared does not the hunter transfix him with his spear? as he stands or runs, does he not pierce him with an arrow? or pierce him with a bullet? does not the fowler in the same way kill the moor-fowl or pheasant with an arrow? or does he not discharge into its body the ball from the musket? i will not speak of the snares and other instruments with which the woodcock, woodpecker, and other wild birds are caught, lest i pursue unseasonably and too minutely single instances. lastly, with his fish-hook and net does not the fisherman catch the fish in the sea, in the lakes, in fish-ponds, or in rivers? but the hook is of iron, and sometimes we see lead or iron weights attached to the net. and most fish that are caught are afterward cut up and disembowelled with knives and axes. but, more than enough has been said on the matter of food. now i will speak of clothing, which is made out of wool, flax, feathers, hair, fur, or leather. first the sheep are sheared, then the wool is combed. next the threads are drawn out, while later the warp is suspended in the shuttle under which passes the wool. this being struck by the comb, at length cloth is formed either from threads alone or from threads and hair. flax, when gathered, is first pulled by hooks. then it is dipped in water and afterward dried, beaten into tow with a heavy mallet, and carded, then drawn out into threads, and finally woven into cloth. but has the artisan or weaver of the cloth any instrument not made of iron? can one be made of wood without the aid of iron? the cloth or web must be cut into lengths for the tailor. can this be done without knife or scissors? can the tailor sew together any garments without a needle? even peoples dwelling beyond the seas cannot make a covering for their bodies, fashioned of feathers, without these same implements. neither can the furriers do without them in sewing together the pelts of any kind of animals. the shoemaker needs a knife to cut the leather, another to scrape it, and an awl to perforate it before he can make shoes. these coverings for the body are either woven or stitched. buildings too, which protect the same body from rain, wind, cold, and heat, are not constructed without axes, saws, and augers. but what need of more words? if we remove metals from the service of man, all methods of protecting and sustaining health and more carefully preserving the course of life are done away with. if there were no metals, men would pass a horrible and wretched existence in the midst of wild beasts; they would return to the acorns and fruits and berries of the forest. they would feed upon the herbs and roots which they plucked up with their nails. they would dig out caves in which to lie down at night, and by day they would rove in the woods and plains at random like beasts, and inasmuch as this condition is utterly unworthy of humanity, with its splendid and glorious natural endowment, will anyone be so foolish or obstinate as not to allow that metals are necessary for food and clothing and that they tend to preserve life? moreover, as the miners dig almost exclusively in mountains otherwise unproductive, and in valleys invested in gloom, they do either slight damage to the fields or none at all. lastly, where woods and glades are cut down, they may be sown with grain after they have been cleared from the roots of shrubs and trees. these new fields soon produce rich crops, so that they repair the losses which the inhabitants suffer from increased cost of timber. moreover, with the metals which are melted from the ore, birds without number, edible beasts and fish can be purchased elsewhere and brought to these mountainous regions. i will pass to the illustrations i have mentioned. bias of priene, when his country was taken, carried away out of the city none of his valuables. so strong a man with such a reputation for wisdom had no need to fear personal danger from the enemy, but this in truth cannot be said of him because he hastily took to flight; the throwing away of his goods does not seem to me so great a matter, for he had lost his house, his estates, and even his country, than which nothing is more precious. nay, i should be convinced of bias's contempt and scorn for possessions of this kind, if before his country was captured he had bestowed them freely on relations and friends, or had distributed them to the very poor, for this he could have done freely and without question. whereas his conduct, which the greeks admire so greatly, was due, it would seem, to his being driven out by the enemy and stricken with fear. socrates in truth did not despise gold, but would not accept money for his teaching. as for aristippus of cyrene, if he had gathered and saved the gold which he ordered his slaves to throw away, he might have bought the things which he needed for the necessaries of life, and he would not, by reason of his poverty, have then been obliged to flatter the tyrant dionysius, nor would he ever have been called by him a king's dog. for this reason horace, speaking of damasippus when reviling staberus for valuing riches very highly, says: "what resemblance has the grecian aristippus to this fellow? he who commanded his slaves to throw away the gold in the midst of libya because they went too slowly, impeded by the weight of their burden--which of these two men is the more insane?"[ ] insane indeed is he who makes more of riches than of virtue. insane also is he who rejects them and considers them as worth nothing, instead of using them with reason. yet as to the gold which aristippus on another occasion flung into the sea from a boat, this he did with a wise and prudent mind. for learning that it was a pirate boat in which he was sailing, and fearing for his life, he counted his gold and then throwing it of his own will into the sea, he groaned as if he had done it unwillingly. but afterward, when he escaped the peril, he said: "it is better that this gold itself should be lost than that i should have perished because of it." let it be granted that some philosophers, as well as anacreon of teos, despised gold and silver. anaxagoras of clazomenae also gave up his sheep-farms and became a shepherd. crates the theban too, being annoyed that his estate and other kinds of wealth caused him worry, and that in his contemplations his mind was thereby distracted, resigned a property valued at ten talents, and taking a cloak and wallet, in poverty devoted all his thought and efforts to philosophy. is it true that because these philosophers despised money, all others declined wealth in cattle? did they refuse to cultivate lands or to dwell in houses? there were certainly many, on the other hand, who, though affluent, became famous in the pursuit of learning and in the knowledge of divine and human laws, such as aristotle, cicero, and seneca. as for phocion, he did not deem it honest to accept the gold sent to him by alexander. for if he had consented to use it, the king as much as himself would have incurred the hatred and aversion of the athenians, and these very people were afterward so ungrateful toward this excellent man that they compelled him to drink hemlock. for what would have been less becoming to marcus curius and fabricius luscinus than to accept gold from their enemies, who hoped that by these means those leaders could be corrupted or would become odious to their fellow citizens, their purpose being to cause dissentions among the romans and destroy the republic utterly. lycurgus, however, ought to have given instructions to the spartans as to the use of gold and silver, instead of abolishing things good in themselves. as to the babytacenses, who does not see that they were senseless and envious? for with their gold they might have bought things of which they were in need, or even given it to neighbouring peoples to bind them more closely to themselves with gifts and favours. finally, the scythians, by condemning the use of gold and silver alone, did not free themselves utterly from avarice, because although he is not enjoying them, one who can possess other forms of property may also become avaricious. now let us reply to the attacks hurled against the products of mines. in the first place, they call gold and silver the scourge of mankind because they are the cause of destruction and ruin to their possessors. but in this manner, might not anything that we possess be called a scourge to human kind,--whether it be a horse, or a garment, or anything else? for, whether one rides a splendid horse, or journeys well clad, he would give occasion to a robber to kill him. are we then not to ride on horses, but to journey on foot, because a robber has once committed a murder in order that he may steal a horse? or are we not to possess clothing, because a vagabond with a sword has taken a traveller's life that he may rob him of his garment? the possession of gold and silver is similar. seeing then that men cannot conveniently do all these things, we should be on our guard against robbers, and because we cannot always protect ourselves from their hands, it is the special duty of the magistrate to seize wicked and villainous men for torture, and, if need be, for execution. again, the products of the mines are not themselves the cause of war. thus, for example, when a tyrant, inflamed with passion for a woman of great beauty, makes war on the inhabitants of her city, the fault lies in the unbridled lust of the tyrant and not in the beauty of the woman. likewise, when another man, blinded by a passion for gold and silver, makes war upon a wealthy people, we ought not to blame the metals but transfer all blame to avarice. for frenzied deeds and disgraceful actions, which are wont to weaken and dishonour natural and civil laws, originate from our own vices. wherefore tibullus is wrong in laying the blame for war on gold, when he says: "this is the fault of a rich man's gold; there were no wars when beech goblets were used at banquets." but virgil, speaking of polymnestor, says that the crime of the murderer rests on avarice: "he breaks all law; he murders polydorus, and obtains gold by violence. to what wilt thou not drive mortal hearts, thou accursed hunger for gold?" and again, justly, he says, speaking of pygmalion, who killed sichaeus: "and blinded with the love of gold, he slew him unawares with stealthy sword."[ ] for lust and eagerness after gold and other things make men blind, and this wicked greed for money, all men in all times and places have considered dishonourable and criminal. moreover, those who have been so addicted to avarice as to be its slaves have always been regarded as mean and sordid. similarly, too, if by means of gold and silver and gems men can overcome the chastity of women, corrupt the honour of many people, bribe the course of justice and commit innumerable wickednesses, it is not the metals which are to be blamed, but the evil passions of men which become inflamed and ignited; or it is due to the blind and impious desires of their minds. but although these attacks against gold and silver may be directed especially against money, yet inasmuch as the poets one after another condemn it, their criticism must be met, and this can be done by one argument alone. money is good for those who use it well; it brings loss and evil to those who use it ill. hence, very rightly, horace says: "dost thou not know the value of money; and what uses it serves? it buys bread, vegetables, and a pint of wine." and again in another place: "wealth hoarded up is the master or slave of each possessor; it should follow rather than lead, the 'twisted rope.'"[ ] when ingenious and clever men considered carefully the system of barter, which ignorant men of old employed and which even to-day is used by certain uncivilised and barbarous races, it appeared to them so troublesome and laborious that they invented money. indeed, nothing more useful could have been devised, because a small amount of gold and silver is of as great value as things cumbrous and heavy; and so peoples far distant from one another can, by the use of money, trade very easily in those things which civilised life can scarcely do without. the curses which are uttered against iron, copper, and lead have no weight with prudent and sensible men, because if these metals were done away with, men, as their anger swelled and their fury became unbridled, would assuredly fight like wild beasts with fists, heels, nails, and teeth. they would strike each other with sticks, hit one another with stones, or dash their foes to the ground. moreover, a man does not kill another with iron alone, but slays by means of poison, starvation, or thirst. he may seize him by the throat and strangle him; he may bury him alive in the ground; he may immerse him in water and suffocate him; he may burn or hang him; so that he can make every element a participant in the death of men. or, finally, a man may be thrown to the wild beasts. another may be sewn up wholly except his head in a sack, and thus be left to be devoured by worms; or he may be immersed in water until he is torn to pieces by sea-serpents. a man may be boiled in oil; he may be greased, tied with ropes, and left exposed to be stung by flies and hornets; he may be put to death by scourging with rods or beating with cudgels, or struck down by stoning, or flung from a high place. furthermore, a man may be tortured in more ways than one without the use of metals; as when the executioner burns the groins and armpits of his victim with hot wax; or places a cloth in his mouth gradually, so that when in breathing he draws it slowly into his gullet, the executioner draws it back suddenly and violently; or the victim's hands are fastened behind his back, and he is drawn up little by little with a rope and then let down suddenly. or similarly, he may be tied to a beam and a heavy stone fastened by a cord to his feet, or finally his limbs may be torn asunder. from these examples we see that it is not metals that are to be condemned, but our vices, such as anger, cruelty, discord, passion for power, avarice, and lust. the question next arises, whether we ought to count metals amongst the number of good things or class them amongst the bad. the peripatetics regarded all wealth as a good thing, and merely spoke of externals as having to do with neither the mind nor the body. well, let riches be an external thing. and, as they said, many other things may be classed as good if it is in one's power to use them either well or ill. for good men employ them for good, and to them they are useful. the wicked use them badly, and to them they are harmful. there is a saying of socrates, that just as wine is influenced by the cask, so the character of riches is like their possessors. the stoics, whose custom it is to argue subtly and acutely, though they did not put wealth in the category of good things, they did not count it amongst the evil ones, but placed it in that class which they term neutral. for to them virtue alone is good, and vice alone evil. the whole of what remains is indifferent. thus, in their conviction, it matters not whether one be in good health or seriously ill; whether one be handsome or deformed. in short: "whether, sprung from inachus of old, and thus hast lived beneath the sun in wealth, or hast been poor and despised among men, it matters not." for my part, i see no reason why anything that is in itself of use should not be placed in the class of good things. at all events, metals are a creation of nature, and they supply many varied and necessary needs of the human race, to say nothing about their uses in adornment, which are so wonderfully blended with utility. therefore, it is not right to degrade them from the place they hold among the good things. in truth, if there is a bad use made of them, should they on that account be rightly called evils? for of what good things can we not make an equally bad or good use? let me give examples from both classes of what we term good. wine, by far the best drink, if drunk in moderation, aids the digestion of food, helps to produce blood, and promotes the juices in all parts of the body. it is of use in nourishing not only the body but the mind as well, for it disperses our dark and gloomy thoughts, frees us from cares and anxiety, and restores our confidence. if drunk in excess, however, it injures and prostrates the body with serious disease. an intoxicated man keeps nothing to himself; he raves and rants, and commits many wicked and infamous acts. on this subject theognis wrote some very clever lines, which we may render thus: "wine is harmful if taken with greedy lips, but if drunk in moderation it is wholesome."[ ] but i linger too long over extraneous matters. i must pass on to the gifts of body and mind, amongst which strength, beauty, and genius occur to me. if then a man, relying on his strength, toils hard to maintain himself and his family in an honest and respectable manner, he uses the gift aright, but if he makes a living out of murder and robbery, he uses it wrongly. likewise, too, if a lovely woman is anxious to please her husband alone she uses her beauty aright, but if she lives wantonly and is a victim of passion, she misuses her beauty. in like manner, a youth who devotes himself to learning and cultivates the liberal arts, uses his genius rightly. but he who dissembles, lies, cheats, and deceives by fraud and dishonesty, misuses his abilities. now, the man who, because they are abused, denies that wine, strength, beauty, or genius are good things, is unjust and blasphemous towards the most high god, creator of the world; so he who would remove metals from the class of blessings also acts unjustly and blasphemously against him. very true, therefore, are the words which certain greek poets have written, as pindar: "money glistens, adorned with virtue; it supplies the means by which thou mayest act well in whatever circumstances fate may have in store for thee."[ ] and sappho: "without the love of virtue gold is a dangerous and harmful guest, but when it is associated with virtue, it becomes the source and height of good." and callimachus: "riches do not make men great without virtue; neither do virtues themselves make men great without some wealth." and antiphanes: "now, by the gods, why is it necessary for a man to grow rich? why does he desire to possess much money unless that he may, as much as possible, help his friends, and sow the seeds of a harvest of gratitude, sweetest of the goddesses."[ ] having thus refuted the arguments and contentions of adversaries, let us sum up the advantages of the metals. in the first place, they are useful to the physician, for they furnish liberally the ingredients for medicines, by which wounds and ulcers are cured, and even plagues; so that certainly if there were no other reasons why we should explore the depths of the earth, we should for the sake of medicine alone dig in the mines. again, the metals are of use to painters, because they yield certain pigments which, when united with the painter's slip, are injured less than others by the moisture from without. further, mining is useful to the architects, for thus is found marble, which is suitable not only for strengthening large buildings, but also for decoration. it is, moreover, helpful to those whose ambition urges them toward immortal glory, because it yields metals from which are made coins, statues, and other monuments, which, next to literary records, give men in a sense immortality. the metals are useful to merchants with very great cause, for, as i have stated elsewhere, the use of money which is made from metals is much more convenient to mankind than the old system of exchange of commodities. in short, to whom are the metals not of use? in very truth, even the works of art, elegant, embellished, elaborate, useful, are fashioned in various shapes by the artist from the metals gold, silver, brass, lead, and iron. how few artists could make anything that is beautiful and perfect without using metals? even if tools of iron or brass were not used, we could not make tools of wood and stone without the help of metal. from all these examples are evident the benefits and advantages derived from metals. we should not have had these at all unless the science of mining and metallurgy had been discovered and handed down to us. who then does not understand how highly useful they are, nay rather, how necessary to the human race? in a word, man could not do without the mining industry, nor did divine providence will that he should. further, it has been asked whether to work in metals is honourable employment for respectable people or whether it is not degrading and dishonourable. we ourselves count it amongst the honourable arts. for that art, the pursuit of which is unquestionably not impious, nor offensive, nor mean, we may esteem honourable. that this is the nature of the mining profession, inasmuch as it promotes wealth by good and honest methods, we shall show presently. with justice, therefore, we may class it amongst honourable employments. in the first place, the occupation of the miner, which i must be allowed to compare with other methods of acquiring great wealth, is just as noble as that of agriculture; for, as the farmer, sowing his seed in his fields injures no one, however profitable they may prove to him, so the miner digging for his metals, albeit he draws forth great heaps of gold or silver, hurts thereby no mortal man. certainly these two modes of increasing wealth are in the highest degree both noble and honourable. the booty of the soldier, however, is frequently impious, because in the fury of the fighting he seizes all goods, sacred as well as profane. the most just king may have to declare war on cruel tyrants, but in the course of it wicked men cannot lose their wealth and possessions without dragging into the same calamity innocent and poor people, old men, matrons, maidens, and orphans. but the miner is able to accumulate great riches in a short time, without using any violence, fraud, or malice. that old saying is, therefore, not always true that "every rich man is either wicked himself, or is the heir to wickedness." some, however, who contend against us, censure and attack miners by saying that they and their children must needs fall into penury after a short time, because they have heaped up riches by improper means. according to them nothing is truer than the saying of the poet naevius: "ill gotten gains in ill fashion slip away." the following are some of the wicked and sinful methods by which they say men obtain riches from mining. when a prospect of obtaining metals shows itself in a mine, either the ruler or magistrate drives out the rightful owners of the mines from possession, or a shrewd and cunning neighbour perhaps brings a law-suit against the old possessors in order to rob them of some part of their property. or the mine superintendent imposes on the owners such a heavy contribution on shares, that if they cannot pay, or will not, they lose their rights of possession; while the superintendent, contrary to all that is right, seizes upon all that they have lost. or, finally, the mine foreman may conceal the vein by plastering over with clay that part where the metal abounds, or by covering it with earth, stones, stakes, or poles, in the hope that after several years the proprietors, thinking the mine exhausted, will abandon it, and the foreman can then excavate that remainder of the ore and keep it for himself. they even state that the scum of the miners exist wholly by fraud, deceit, and lying. for to speak of nothing else, but only of those deceits which are practised in buying and selling, it is said they either advertise the veins with false and imaginary praises, so that they can sell the shares in the mines at one-half more than they are worth, or on the contrary, they sometimes detract from the estimate of them so that they can buy shares for a small price. by exposing such frauds our critics suppose all good opinion of miners is lost. now, all wealth, whether it has been gained by good or evil means, is liable by some adverse chance to vanish away. it decays and is dissipated by the fault and carelessness of the owner, since he loses it through laziness and neglect, or wastes and squanders it in luxuries, or he consumes and exhausts it in gifts, or he dissipates and throws it away in gambling: "just as though money sprouted up again, renewed from an exhausted coffer, and was always to be obtained from a full heap." it is therefore not to be wondered at if miners do not keep in mind the counsel given by king agathocles: "unexpected fortune should be held in reverence," for by not doing so they fall into penury; and particularly when the miners are not content with moderate riches, they not rarely spend on new mines what they have accumulated from others. but no just ruler or magistrate deprives owners of their possessions; that, however, may be done by a tyrant, who may cruelly rob his subjects not only of their goods honestly obtained, but even of life itself. and yet whenever i have inquired into the complaints which are in common vogue, i always find that the owners who are abused have the best of reasons for driving the men from the mines; while those who abuse the owners have no reason to complain about them. take the case of those who, not having paid their contributions, have lost the right of possession, or those who have been expelled by the magistrate out of another man's mine: for some wicked men, mining the small veins branching from the veins rich in metal, are wont to invade the property of another person. so the magistrate expels these men accused of wrong, and drives them from the mine. they then very frequently spread unpleasant rumours concerning this amongst the populace. or, to take another case: when, as often happens, a dispute arises between neighbours, arbitrators appointed by the magistrate settle it, or the regular judges investigate and give judgment. consequently, when the judgment is given, inasmuch as each party has consented to submit to it, neither side should complain of injustice; and when the controversy is adjudged, inasmuch as the decision is in accordance with the laws concerning mining, one of the parties cannot be injured by the law. i do not vigorously contest the point, that at times a mine superintendent may exact a larger contribution from the owners than necessity demands. nay, i will admit that a foreman may plaster over, or hide with a structure, a vein where it is rich in metals. is the wickedness of one or two to brand the many honest with fraud and trickery? what body is supposed to be more pious and virtuous in the republic than the senate? yet some senators have been detected in peculations, and have been punished. is this any reason that so honourable a house should lose its good name and fame? the superintendent cannot exact contributions from the owners without the knowledge and permission of the bergmeister or the deputies; for this reason deception of this kind is impossible. should the foremen be convicted of fraud, they are beaten with rods; or of theft, they are hanged. it is complained that some sellers and buyers of the shares in mines are fraudulent. i concede it. but can they deceive anyone except a stupid, careless man, unskilled in mining matters? indeed, a wise and prudent man, skilled in this art, if he doubts the trustworthiness of a seller or buyer, goes at once to the mine that he may for himself examine the vein which has been so greatly praised or disparaged, and may consider whether he will buy or sell the shares or not. but people say, though such an one can be on his guard against fraud, yet a simple man and one who is easily credulous, is deceived. but we frequently see a man who is trying to mislead another in this way deceive himself, and deservedly become a laughing-stock for everyone; or very often the defrauder as well as the dupe is entirely ignorant of mining. if, for instance, a vein has been found to be abundant in ore, contrary to the idea of the would-be deceiver, then he who was to have been cheated gets a profit, and he who has been the deceiver loses. nevertheless, the miners themselves rarely buy or sell shares, but generally they have _jurati venditores_[ ] who buy and sell at such prices as they have been instructed to give or accept. seeing therefore, that magistrates decide disputes on fair and just principles, that honest men deceive nobody, while a dishonest one cannot deceive easily, or if he does he cannot do so with impunity, the criticism of those who wish to disparage the honesty of miners has therefore no force or weight. in the next place, the occupation of the miner is objectionable to nobody. for who, unless he be naturally malevolent and envious, will hate the man who gains wealth as it were from heaven? or who will hate a man who to amplify his fortune, adopts a method which is free from reproach? a moneylender, if he demands an excessive interest, incurs the hatred of men. if he demands a moderate and lawful rate, so that he is not injurious to the public generally and does not impoverish them, he fails to become very rich from his business. further, the gain derived from mining is not sordid, for how can it be such, seeing that it is so great, so plentiful, and of so innocent a nature. a merchant's profits are mean and base when he sells counterfeit and spurious merchandise, or puts far too high a price on goods that he has purchased for little; for this reason the merchant would be held in no less odium amongst good men than is the usurer, did they not take account of the risk he runs to secure his merchandise. in truth, those who on this point speak abusively of mining for the sake of detracting from its merits, say that in former days men convicted of crimes and misdeeds were sentenced to the mines and were worked as slaves. but to-day the miners receive pay, and are engaged like other workmen in the common trades. certainly, if mining is a shameful and discreditable employment for a gentleman because slaves once worked mines, then agriculture also will not be a very creditable employment, because slaves once cultivated the fields, and even to-day do so among the turks; nor will architecture be considered honest, because some slaves have been found skilful in that profession; nor medicine, because not a few doctors have been slaves; nor will any other worthy craft, because men captured by force of arms have practised it. yet agriculture, architecture, and medicine are none the less counted amongst the number of honourable professions; therefore, mining ought not for this reason to be excluded from them. but suppose we grant that the hired miners have a sordid employment. we do not mean by miners only the diggers and other workmen, but also those skilled in the mining arts, and those who invest money in mines. amongst them can be counted kings, princes, republics, and from these last the most esteemed citizens. and finally, we include amongst the overseers of mines the noble thucydides, the historian, whom the athenians placed in charge of the mines of thasos.[ ] and it would not be unseemly for the owners themselves to work with their own hands on the works or ore, especially if they themselves have contributed to the cost of the mines. just as it is not undignified for great men to cultivate their own land. otherwise the roman senate would not have created dictator l. quintius cincinnatus, as he was at work in the fields, nor would it have summoned to the senate house the chief men of the state from their country villas. similarly, in our day, maximilian cæsar would not have enrolled conrad in the ranks of the nobles known as counts; conrad was really very poor when he served in the mines of schneeberg, and for that reason he was nicknamed the "poor man"; but not many years after, he attained wealth from the mines of fürst, which is a city in lorraine, and took his name from "luck."[ ] nor would king vladislaus have restored to the assembly of barons, tursius, a citizen of cracow, who became rich through the mines in that part of the kingdom of hungary which was formerly called dacia.[ ] nay, not even the common worker in the mines is vile and abject. for, trained to vigilance and work by night and day, he has great powers of endurance when occasion demands, and easily sustains the fatigues and duties of a soldier, for he is accustomed to keep long vigils at night, to wield iron tools, to dig trenches, to drive tunnels, to make machines, and to carry burdens. therefore, experts in military affairs prefer the miner, not only to a commoner from the town, but even to the rustic. but to bring this discussion to an end, inasmuch as the chief callings are those of the moneylender, the soldier, the merchant, the farmer, and the miner, i say, inasmuch as usury is odious, while the spoil cruelly captured from the possessions of the people innocent of wrong is wicked in the sight of god and man, and inasmuch as the calling of the miner excels in honour and dignity that of the merchant trading for lucre, while it is not less noble though far more profitable than agriculture, who can fail to realize that mining is a calling of peculiar dignity? certainly, though it is but one of ten important and excellent methods of acquiring wealth in an honourable way, a careful and diligent man can attain this result in no easier way than by mining. end of book i. footnotes: [ ] _fibrae_--"fibres." see note , p. . [ ] _commissurae saxorum_--"rock joints," "seams," or "cracks." agricola and all of the old authors laid a wholly unwarranted geologic value on these phenomena. see description and footnotes, book iii., pages and . [ ] _succi_--"juice," or _succi concreti_--"solidified juice." ger. trans., _saffte_. the old english translators and mineralogists often use the word juices in the same sense, and we have adopted it. the words "solutions" and "salts" convey a chemical significance not warranted by the state of knowledge in agricola's time. instances of the former use of this word may be seen in barba's "first book of the art of metals," (trans. earl sandwich, london, , p. , etc.,) and in pryce's _mineralogia cornubiensis_ (london, , p. , ). [ ] in order that the reader should be able to grasp the author's point of view as to his divisions of the mineral kingdom, we introduce here his own statement from _de natura fossilium_, (p. ). it is also desirable to read the footnote on his theory of ore-deposits on pages to , and the review of _de natura fossilium_ given in the appendix. "the subterranean inanimate bodies are divided into two classes, one of which, because it is a fluid or an exhalation, is called by those names, and the other class is called the minerals. mineral bodies are solidified from particles of the same substance, such as pure gold, each particle of which is gold, or they are of different substances such as lumps which consist of earth, stone, and metal; these latter may be separated into earth, stone and metal, and therefore the first is not a mixture while the last is called a mixture. the first are again divided into simple and compound minerals. the simple minerals are of four classes, namely earths, solidified juices, stones and metals, while the mineral compounds are of many sorts, as i shall explain later. "earth is a simple mineral body which may be kneaded in the hands when moistened, or from which lute is made when it has been wetted. earth, properly so called, is found enclosed in veins or veinlets, or frequently on the surface in fields and meadows. this definition is a general one. the harder earth, although moistened by water, does not at once become lute, but does turn into lute if it remains in water for some time. there are many species of earths, some of which have names but others are unnamed. "solidified juices are dry and somewhat hard (_subdurus_) mineral bodies which when moistened with water do not soften but liquefy instead; or if they do soften, they differ greatly from the earths by their unctuousness (_pingue_) or by the material of which they consist. although occasionally they have the hardness of stone, yet because they preserve the form and nature which they had when less hard, they can easily be distinguished from the stones. the juices are divided into 'meagre' and unctuous (_macer et pinguis_). the 'meagre' juices, since they originate from three different substances, are of three species. they are formed from a liquid mixed with earth, or with metal, or with a mineral compound. to the first species belong salt and _nitrum_ (soda); to the second, chrysocolla, verdigris, iron-rust, and azure; to the third, vitriol, alum, and an acrid juice which is unnamed. the first two of these latter are obtained from pyrites, which is numbered amongst the compound minerals. the third of these comes from _cadmia_ (in this case the cobalt-zinc-arsenic minerals; the acrid juice is probably zinc sulphate). to the unctuous juices belong these species: sulphur, bitumen, realgar and orpiment. vitriol and alum, although they are somewhat unctuous yet do not burn, and they differ in their origin from the unctuous juices, for the latter are forced out from the earth by heat, whereas the former are produced when pyrites is softened by moisture. "stone is a dry and hard mineral body which may either be softened by remaining for a long time in water and be reduced to powder by a fierce fire; or else it does not soften with water but the heat of a great fire liquefies it. to the first species belong those stones which have been solidified by heat, to the second those solidified (literally 'congealed') by cold. these two species of stones are constituted from their own material. however, writers on natural subjects who take into consideration the quantity and quality of stones and their value, divide them into four classes. the first of these has no name of its own but is called in common parlance 'stone': to this class belong loadstone, jasper (or bloodstone) and _aetites_ (geodes?). the second class comprises hard stones, either pellucid or ornamental, with very beautiful and varied colours which sparkle marvellously; they are called gems. the third comprises stones which are only brilliant after they have been polished, and are usually called marble. the fourth are called rocks; they are found in quarries, from which they are hewn out for use in building, and they are cut into various shapes. none of the rocks show colour or take a polish. few of the stones sparkle; fewer still are transparent. marble is sometimes only distinguishable from opaque gems by its volume; rock is always distinguishable from stones properly so-called by its volume. both the stones and the gems are usually to be found in veins and veinlets which traverse the rocks and marble. these four classes, as i have already stated, are divided into many species, which i will explain in their proper place. "metal is a mineral body, by nature either liquid or somewhat hard. the latter may be melted by the heat of the fire, but when it has cooled down again and lost all heat, it becomes hard again and resumes its proper form. in this respect it differs from the stone which melts in the fire, for although the latter regain its hardness, yet it loses its pristine form and properties. traditionally there are six different kinds of metals, namely gold, silver, copper, iron, tin and lead. there are really others, for quicksilver is a metal, although the alchemists disagree with us on this subject, and bismuth is also. the ancient greek writers seem to have been ignorant of bismuth, wherefore ammonius rightly states that there are many species of metals, animals, and plants which are unknown to us. _stibium_ when smelted in the crucible and refined has as much right to be regarded as a proper metal as is accorded to lead by writers. if when smelted, a certain portion be added to tin, a bookseller's alloy is produced from which the type is made that is used by those who print books on paper. each metal has its own form which it preserves when separated from those metals which were mixed with it. therefore neither electrum nor _stannum_ is of itself a real metal, but rather an alloy of two metals. electrum is an alloy of gold and silver, _stannum_ of lead and silver (see note , p. ). and yet if silver be parted from the electrum, then gold remains and not electrum; if silver be taken away from _stannum_, then lead remains and not _stannum_. whether brass, however, is found as a native metal or not, cannot be ascertained with any surety. we only know of the artificial brass, which consists of copper tinted with the colour of the mineral calamine. and yet if any should be dug up, it would be a proper metal. black and white copper seem to be different from the red kind. metal, therefore, is by nature either solid, as i have stated, or fluid, as in the unique case of quicksilver. but enough now concerning the simple kinds. "i will now speak of the compounds which are composed of the simple minerals cemented together by nature, and under the word 'compound' i now discuss those mineral bodies which consist of two or three simple minerals. they are likewise mineral substances, but so thoroughly mixed and alloyed that even in the smallest part there is not wanting any substance that is contained in the whole. only by the force of the fire is it possible to separate one of the simple mineral substances from another; either the third from the other two, or two from the third, if there were three in the same compound. these two, three or more bodies are so completely mixed into one new species that the pristine form of none of these is recognisable. "the 'mixed' minerals, which are composed of those same simple minerals, differ from the 'compounds,' in that the simple minerals each preserves its own form so that they can be separated one from the other not only by fire but sometimes by water and sometimes by hand. as these two classes differ so greatly from one another i usually use two different words in order to distinguish one from the other. i am well aware that galen calls the metallic earth a compound which is really a mixture, but he who wishes to instruct others should bestow upon each separate thing a definite name." for convenience of reference we may reduce the above to a diagram as follows: . fluids and gases. { { earths { (a) simple { solidified juices { minerals { stones { { metals { a. homogenous { { bodies { { { (b) compound { being heterogeneous mixtures { { minerals { of (a) { . mineral { bodies { { { b. mixtures. being homogenous mixtures of (a) [ ] _experiendae_--"a trial." that actual assaying in its technical sense is meant, is sufficiently evident from book vii. [ ] _... plumbum ... candidum ac cinereum vel nigrum_. "lead ... white, or ash-coloured, or black." agricola himself coined the term _plumbum cinereum_ for bismuth, no doubt following the roman term for tin--_plumbum candidum_. the following passage from _bermannus_ (p. ) is of interest, for it appears to be the first description of bismuth, although mention of it occurs in the _nützlich bergbüchlin_ (see appendix b). "_bermannus_: i will show you another kind of mineral which is numbered amongst metals, but appears to me to have been unknown to the ancients; we call it _bisemutum_. _naevius_: then in your opinion there are more kinds of metals than the seven commonly believed? _bermannus_: more, i consider; for this which just now i said we called _bisemutum_, cannot correctly be called _plumbum candidum_ (tin), nor _nigrum_ (lead), but is different from both and is a third one. _plumbum candidum_ is whiter and _plumbum nigrum_ is darker, as you see. _naevius_: we see that this is of the colour of _galena_. _ancon_: how then can _bisemutum_, as you call it, be distinguished from _galena_? _bermannus_: easily; when you take it in your hands it stains them with black, unless it is quite hard. the hard kind is not friable like _galena_, but can be cut. it is blacker than the kind of _rudis_ silver which we say is almost the colour of lead, and thus is different from both. indeed, it not rarely contains some silver. it generally indicates that there is silver beneath the place where it is found, and because of this our miners are accustomed to call it the 'roof of silver.' they are wont to roast this mineral, and from the better part they make metal; from the poorer part they make a pigment of a kind not to be despised." [ ] _nitrum._ the ancients comprised many salts under this head, but agricola in the main uses it for soda, although sometimes he includes potash. he usually, however, refers to potash as _lixivium_ or salt therefrom, and by other distinctive terms. for description of method of manufacture and discussion, see book xii., p. . [ ] _atramentum sutorium_--"shoemaker's blacking." see p. for description of method of manufacture and historical footnote. in the main agricola means green vitriol, but he does describe three main varieties, green, blue, and white (_de natura fossilium_, p. ). the blue was of course copper sulphate, and it is fairly certain that the white was zinc vitriol. [ ] _lavandi_--"washing." by this term the author includes all the operations of sluicing, buddling, and wet concentration generally. there is no english equivalent of such wide application, and there is some difficulty in interpretation without going further than the author intends. book viii. is devoted to the subject. [ ] _operam et oleum perdit_--"loss of labour and oil." [ ] in _veteribus et novis metallis_, and _bermannus_, agricola states that the mines of schemnitz were worked years before that time ( ), or about a.d., and, further, that the lead mines of goslar in the hartz were worked by otho the great ( - ), and that the silver mines at freiberg were discovered during the rule of prince otho (about ). to continue the argument to-day we could add about years more of life to the mines of goslar and freiberg. see also note , p. , and note , p. . [ ] xenophon. essay on the revenues of athens, i., . [ ] ovid, _metamorphoses_, i., to . [ ] diogenes laertius, ii., . the lines are assigned, however, to philemon, not euripides. (kock, _comicorum atticorum fragmenta_ ii., ). [ ] we have not considered it of sufficient interest to cite the references to all of the minor poets and those whose preserved works are but fragmentary. the translations from the greek into latin are not literal and suffer again by rendering into english; we have however considered it our duty to translate agricola's view of the meaning. [ ] diogenes laertius, ii. [ ] an inspection of the historical incidents mentioned here and further on, indicates that agricola relied for such information on diogenes laertius, plutarch, livy, valerius maximus, pliny, and often enough on homer, horace, and virgil. [ ] juvenal. _satires_ i., l. , and vi., l. . [ ] pliny, xxxiv., . [ ] horace. _odes_, i., , ll. - . [ ] horace. _satires_, ii., , ll. - . [ ] virgil. _Æneid_, iii., l. , and i., l. . [ ] horace. _satires_, i., l. ; and epistle, i., , l. . [ ] theognis. maxims, ii., l. . [ ] pindar. _olymp._ ii., - . [ ] antiphanes, . [ ] _jurati venditores_--"sworn brokers." (?) [ ] there is no doubt that thucydides had some connection with gold mines; he himself is the authority for the statement that he worked mines in thrace. agricola seems to have obtained his idea that thucydides held an appointment from the athenians in charge of mines in thasos, from marcellinus (_vita_, thucydides, ), who also says that thucydides obtained possession of mines in thrace through his marriage with a thracian woman, and that it was while residing on the mines at scapte-hyle that he wrote his history. later scholars, however, find little warrant for these assertions. the gold mines of thasos--an island off the mainland of thrace--are frequently mentioned by the ancient authors. herodotus, vi., - , says:--"their (the thasians') revenue was derived partly from their possessions upon the mainland, partly from the mines which they owned. they were masters of the gold mines of scapte-hyle, the yearly produce of which amounted to eighty talents. their mines in thasos yielded less, but still were so prolific that besides being entirely free from land-tax they had a surplus of income derived from the two sources of their territory on the mainland and their mines, in common years two hundred and in best years three hundred talents. i myself have seen the mines in question. by far the most curious of them are those which the phoenicians discovered at the time when they went with thasos and colonized the island, which took its name from him. these phoenician workings are in thasos itself, between coenyra and a place called aenyra over against samothrace; a high mountain has been turned upside down in the search for ores." (rawlinson's trans.). the occasion of this statement of herodotus was the relations of the thasians with darius ( - b.c.). the date of the phoenician colonization of thasos is highly nebular--anywhere from to b.c. [ ] agricola, _de veteribus et novis metallis_, book i., p. , says:--"conrad, whose nickname in former years was 'pauper,' suddenly became rich from the silver mines of mount jura, known as the _firstum_." he was ennobled with the title of graf cuntz von glück by the emperor maximilian (who was emperor of the holy roman empire, - ). conrad was originally a working miner at schneeberg where he was known as armer cuntz (poor cuntz or conrad) and grew wealthy from the mines of fürst in leberthal. this district is located in the vosges mountains on the borders of lorraine and upper alsace. the story of cuntz or conrad von glück is mentioned by albinus (_meissnische land und berg chronica_, dresden, , p. ), mathesius (_sarepta_, nuremberg, , fol. xvi.), and by others. [ ] vladislaus iii. was king of poland, - , and also became king of hungary in . tursius seems to be a latinized name and cannot be identified. book ii. qualities which the perfect miner should possess and the arguments which are urged for and against the arts of mining and metallurgy, as well as the people occupied in the industry, i have sufficiently discussed in the first book. now i have determined to give more ample information concerning the miners. in the first place, it is indispensable that they should worship god with reverence, and that they understand the matters of which i am going to speak, and that they take good care that each individual performs his duties efficiently and diligently. it is decreed by divine providence that those who know what they ought to do and then take care to do it properly, for the most part meet with good fortune in all they undertake; on the other hand, misfortune overtakes the indolent and those who are careless in their work. no person indeed can, without great and sustained effort and labour, store in his mind the knowledge of every portion of the metallic arts which are involved in operating mines. if a man has the means of paying the necessary expense, he hires as many men as he needs, and sends them to the various works. thus formerly sosias, the thracian, sent into the silver mines a thousand slaves whom he had hired from the athenian nicias, the son of niceratus[ ]. but if a man cannot afford the expenditure he chooses of the various kinds of mining that work which he himself can most easily and efficiently do. of these kinds, the two most important are the making prospect trenches and the washing of the sands of rivers, for out of these sands are often collected gold dust, or certain black stones from which tin is smelted, or even gems are sometimes found in them; the trenching occasionally lays bare at the grass-roots veins which are found rich in metals. if therefore by skill or by luck, such sands or veins shall fall into his hands, he will be able to establish his fortune without expenditure, and from poverty rise to wealth. if on the contrary, his hopes are not realized, then he can desist from washing or digging. when anyone, in an endeavour to increase his fortune, meets the expenditure of a mine alone, it is of great importance that he should attend to his works and personally superintend everything that he has ordered to be done. for this reason, he should either have his dwelling at the mine, where he may always be in sight of the workmen and always take care that none neglect their duties, or else he should live in the neighbourhood, so that he may frequently inspect his mining works. then he may send word by a messenger to the workmen that he is coming more frequently than he really intends to come, and so either by his arrival or by the intimation of it, he so frightens the workmen that none of them perform their duties otherwise than diligently. when he inspects the mines he should praise the diligent workmen and occasionally give them rewards, that they and the others may become more zealous in their duties; on the other hand, he should rebuke the idle and discharge some of them from the mines and substitute industrious men in their places. indeed, the owner should frequently remain for days and nights in the mine, which, in truth, is no habitation for the idle and luxurious; it is important that the owner who is diligent in increasing his wealth, should frequently himself descend into the mine, and devote some time to the study of the nature of the veins and stringers, and should observe and consider all the methods of working, both inside and outside the mine. nor is this all he ought to do, for sometimes he should undertake actual labour, not thereby demeaning himself, but in order to encourage his workmen by his own diligence, and to teach them their art; for that mine is well conducted in which not only the foreman, but also the owner himself, gives instruction as to what ought to be done. a certain barbarian, according to xenophon, rightly remarked to the king of persia that "the eye of the master feeds the horse,"[ ] for the master's watchfulness in all things is of the utmost importance. when several share together the expenditure on a mine, it is convenient and useful to elect from amongst their own number a mine captain, and also a foreman. for, since men often look after their own interests but neglect those of others, they cannot in this case take care of their own without at the same time looking after the interests of the others, neither can they neglect the interests of the others without neglecting their own. but if no man amongst them be willing or able to undertake and sustain the burdens of these offices, it will be to the common interest to place them in the hands of most diligent men. formerly indeed, these things were looked after by the mining prefect[ ], because the owners were kings, as priam, who owned the gold mines round abydos, or as midas, who was the owner of those situated in mount bermius, or as gyges, or as alyattes, or as croesus, who was the owner of those mines near a deserted town between atarnea and pergamum[ ]; sometimes the mines belonged to a republic, as, for instance, the prosperous silver mines in spain which belonged to carthage[ ]; sometimes they were the property of great and illustrious families, as were the athenian mines in mount laurion[ ]. when a man owns mines but is ignorant of the art of mining, then it is advisable that he should share in common with others the expenses, not of one only, but of several mines. when one man alone meets the expense for a long time of a whole mine, if good fortune bestows on him a vein abundant in metals, or in other products, he becomes very wealthy; if, on the contrary, the mine is poor and barren, in time he will lose everything which he has expended on it. but the man who, in common with others, has laid out his money on several mines in a region renowned for its wealth of metals, rarely spends it in vain, for fortune usually responds to his hopes in part. for when out of twelve veins in which he has a joint interest one yields an abundance of metals, it not only gives back to the owner the money he has spent, but also gives a profit besides; certainly there will be for him rich and profitable mining, if of the whole number, three, or four, or more veins should yield metal. very similar to this is the advice which xenophon gave to the athenians when they wished to prospect for new veins of silver without suffering loss. "there are," he said, "ten tribes of athenians; if, therefore, the state assigned an equal number of slaves to each tribe, and the tribes participated equally in all the new veins, undoubtedly by this method, if a rich vein of silver were found by one tribe, whatever profit were made from it would assuredly be shared by the whole number. and if two, three, or four tribes, or even half the whole number find veins, their works would then become more profitable; and it is not probable that the work of all the tribes will be disappointing."[ ] although this advice of xenophon is full of prudence, there is no opportunity for it except in free and wealthy states; for those people who are under the authority of kings and princes, or are kept in subjection by tyranny, do not dare, without permission, to incur such expenditure; those who are endowed with little wealth and resources cannot do so on account of insufficient funds. moreover, amongst our race it is not customary for republics to have slaves whom they can hire out for the benefit of the people[ ]; but, instead, nowadays those who are in authority administer the funds for mining in the name of the state, not unlike private individuals. some owners prefer to buy shares[ ] in mines abounding in metals, rather than to be troubled themselves to search for the veins; these men employ an easier and less uncertain method of increasing their property. although their hopes in the shares of one or another mine may be frustrated, the buyers of shares should not abandon the rest of the mines, for all the money expended will be recovered with interest from some other mine. they should not buy only high priced shares in those mines producing metals, nor should they buy too many in neighbouring mines where metal has not yet been found, lest, should fortune not respond, they may be exhausted by their losses and have nothing with which they may meet their expenses or buy other shares which may replace their losses. this calamity overtakes those who wish to grow suddenly rich from mines, and instead, they become very much poorer than before. so then, in the buying of shares, as in other matters, there should be a certain limit of expenditure which miners should set themselves, lest blinded by the desire for excessive wealth, they throw all their money away. moreover, a prudent owner, before he buys shares, ought to go to the mine and carefully examine the nature of the vein, for it is very important that he should be on his guard lest fraudulent sellers of shares should deceive him. investors in shares may perhaps become less wealthy, but they are more certain of some gain than those who mine for metals at their own expense, as they are more cautious in trusting to fortune. neither ought miners to be altogether distrustful of fortune, as we see some are, who as soon as the shares of any mine begin to go up in value, sell them, on which account they seldom obtain even moderate wealth. there are some people who wash over the dumps from exhausted and abandoned mines, and those dumps which are derived from the drains of tunnels; and others who smelt the old slags; from all of which they make an ample return. now a miner, before he begins to mine the veins, must consider seven things, namely:--the situation, the conditions, the water, the roads, the climate, the right of ownership, and the neighbours. there are four kinds of situations--mountain, hill, valley, and plain. of these four, the first two are the most easily mined, because in them tunnels can be driven to drain off the water, which often makes mining operations very laborious, if it does not stop them altogether. the last two kinds of ground are more troublesome, especially because tunnels cannot be driven in such places. nevertheless, a prudent miner considers all these four sorts of localities in the region in which he happens to be, and he searches for veins in those places where some torrent or other agency has removed and swept the soil away; yet he need not prospect everywhere, but since there is a great variety, both in mountains and in the three other kinds of localities, he always selects from them those which will give him the best chance of obtaining wealth. in the first place, mountains differ greatly in position, some being situated in even and level plains, while others are found in broken and elevated regions, and others again seem to be piled up, one mountain upon another. the wise miner does not mine in mountains which are situated on open plains, neither does he dig in those which are placed on the summits of mountainous regions, unless by some chance the veins in those mountains have been denuded of their surface covering, and abounding in metals and other products, are exposed plainly to his notice,--for with regard to what i have already said more than once, and though i never repeat it again, i wish to emphasize this exception as to the localities which should not be selected. all districts do not possess a great number of mountains crowded together; some have but one, others two, others three, or perhaps a few more. in some places there are plains lying between them; in others the mountains are joined together or separated only by narrow valleys. the miner should not dig in those solitary mountains, dispersed through the plains and open regions, but only in those which are connected and joined with others. then again, since mountains differ in size, some being very large, others of medium height, and others more like hills than mountains, the miner rarely digs in the largest or the smallest of them, but generally only in those of medium size. moreover, mountains have a great variety of shapes; for with some the slopes rise gradually, while others, on the contrary, are all precipitous; in some others the slopes are gradual on one side, and on the other sides precipitous; some are drawn out in length; some are gently curved; others assume different shapes. but the miner may dig in all parts of them, except where there are precipices, and he should not neglect even these latter if metallic veins are exposed before his eyes. there are just as great differences in hills as there are in mountains, yet the miner does not dig except in those situated in mountainous districts, and even very rarely in those. it is however very little to be wondered at that the hill in the island of lemnos was excavated, for the whole is of a reddish-yellow colour, which furnishes for the inhabitants that valuable clay so especially beneficial to mankind[ ]. in like manner, other hills are excavated if chalk or other varieties of earth are exposed, but these are not prospected for. there are likewise many varieties of valleys and plains. one kind is enclosed on the sides with its outlet and entrance open; another has either its entrance or its outlet open and the rest of it is closed in; both of these are properly called valleys. there is a third variety which is surrounded on all sides by mountains, and these are called _convalles_. some valleys again, have recesses, and others have none; one is wide, another narrow; one is long, another short; yet another kind is not higher than the neighbouring plain, and others are lower than the surrounding flat country. but the miner does not dig in those surrounded on all sides by mountains, nor in those that are open, unless there be a low plain close at hand, or unless a vein of metal descending from the mountains should extend into the valley. plains differ from one another, one being situated at low elevation, and others higher, one being level and another with a slight incline. the miner should never excavate the low-lying plain, nor one which is perfectly level, unless it be in some mountain, and rarely should he mine in the other kinds of plains. with regard to the conditions of the locality the miner should not contemplate mining without considering whether the place be covered with trees or is bare. if it be a wooded place, he who digs there has this advantage, besides others, that there will be an abundant supply of wood for his underground timbering, his machinery, buildings, smelting, and other necessities. if there is no forest he should not mine there unless there is a river near, by which he can carry down the timber. yet wherever there is a hope that pure gold or gems may be found, the ground can be turned up, even though there is no forest, because the gems need only to be polished and the gold to be purified. therefore the inhabitants of hot regions obtain these substances from rough and sandy places, where sometimes there are not even shrubs, much less woods. the miner should next consider the locality, as to whether it has a perpetual supply of running water, or whether it is always devoid of water except when a torrent supplied by rains flows down from the summits of the mountains. the place that nature has provided with a river or stream can be made serviceable for many things; for water will never be wanting and can be carried through wooden pipes to baths in dwelling-houses; it may be carried to the works, where the metals are smelted; and finally, if the conditions of the place will allow it, the water can be diverted into the tunnels, so that it may turn the underground machinery. yet on the other hand, to convey a constant supply of water by artificial means to mines where nature has denied it access, or to convey the ore to the stream, increases the expense greatly, in proportion to the distance the mines are away from the river. the miner also should consider whether the roads from the neighbouring regions to the mines are good or bad, short or long. for since a region which is abundant in mining products very often yields no agricultural produce, and the necessaries of life for the workmen and others must all be imported, a bad and long road occasions much loss and trouble with porters and carriers, and this increases the cost of goods brought in, which, therefore, must be sold at high prices. this injures not so much the workmen as the masters; since on account of the high price of goods, the workmen are not content with the wages customary for their labour, nor can they be, and they ask higher pay from the owners. and if the owners refuse, the men will not work any longer in the mines but will go elsewhere. although districts which yield metals and other mineral products are generally healthy, because, being often situated on high and lofty ground, they are fanned by every wind, yet sometimes they are unhealthy, as has been related in my other book, which is called "_de natura eorum quae effluunt ex terra_." therefore, a wise miner does not mine in such places, even if they are very productive, when he perceives unmistakable signs of pestilence. for if a man mines in an unhealthy region he may be alive one hour and dead the next. then, the miner should make careful and thorough investigation concerning the lord of the locality, whether he be a just and good man or a tyrant, for the latter oppresses men by force of his authority, and seizes their possessions for himself; but the former governs justly and lawfully and serves the common good. the miner should not start mining operations in a district which is oppressed by a tyrant, but should carefully consider if in the vicinity there is any other locality suitable for mining and make up his mind if the overlord there be friendly or inimical. if he be inimical the mine will be rendered unsafe through hostile attacks, in one of which all of the gold or silver, or other mineral products, laboriously collected with much cost, will be taken away from the owner and his workmen will be struck with terror; overcome by fear, they will hastily fly, to free themselves from the danger to which they are exposed. in this case, not only are the fortunes of the miner in the greatest peril but his very life is in jeopardy, for which reason he should not mine in such places. since several miners usually come to mine the veins in one locality, a settlement generally springs up, for the miner who began first cannot keep it exclusively for himself. the _bergmeister_ gives permits to some to mine the superior and some the inferior parts of the veins; to some he gives the cross veins, to others the inclined veins. if the man who first starts work finds the vein to be metal-bearing or yielding other mining products, it will not be to his advantage to cease work because the neighbourhood may be evil, but he will guard and defend his rights both by arms and by the law. when the _bergmeister_[ ] delimits the boundaries of each owner, it is the duty of a good miner to keep within his bounds, and of a prudent one to repel encroachments of his neighbours by the help of the law. but this is enough about the neighbourhood. the miner should try to obtain a mine, to which access is not difficult, in a mountainous region, gently sloping, wooded, healthy, safe, and not far distant from a river or stream by means of which he may convey his mining products to be washed and smelted. this indeed, is the best position. as for the others, the nearer they approximate to this position the better they are; the further removed, the worse. now i will discuss that kind of minerals for which it is not necessary to dig, because the force of water carries them out of the veins. of these there are two kinds, minerals--and their fragments[ ]--and juices. when there are springs at the outcrop of the veins from which, as i have already said, the above-mentioned products are emitted, the miner should consider these first, to see whether there are metals or gems mixed with the sand, or whether the waters discharged are filled with juices. in case metals or gems have settled in the pool of the spring, not only should the sand from it be washed, but also that from the streams which flow from these springs, and even from the river itself into which they again discharge. if the springs discharge water containing some juice, this also should be collected; the further such a stream has flowed from the source, the more it receives plain water and the more diluted does it become, and so much the more deficient in strength. if the stream receives no water of another kind, or scarcely any, not only the rivers, but likewise the lakes which receive these waters, are of the same nature as the springs, and serve the same uses; of this kind is the lake which the hebrews call the dead sea, and which is quite full of bituminous fluids[ ]. but i must return to the subject of the sands. springs may discharge their waters into a sea, a lake, a marsh, a river, or a stream; but the sand of the sea-shore is rarely washed, for although the water flowing down from the springs into the sea carries some metals or gems with it, yet these substances can scarcely ever be reclaimed, because they are dispersed through the immense body of waters and mixed up with other sand, and scattered far and wide in different directions, or they sink down into the depths of the sea. for the same reasons, the sands of lakes can very rarely be washed successfully, even though the streams rising from the mountains pour their whole volume of water into them. the particles of metals and gems from the springs are very rarely carried into the marshes, which are generally in level and open places. therefore, the miner, in the first place, washes the sand of the spring, then of the stream which flows from it, then finally, that of the river into which the stream discharges. it is not worth the trouble to wash the sands of a large river which is on a level plain at a distance from the mountains. where several springs carrying metals discharge their waters into one river, there is more hope of productive results from washing. the miner does not neglect even the sands of the streams in which excavated ores have been washed. the waters of springs taste according to the juice they contain, and they differ greatly in this respect. there are six kinds of these tastes which the worker[ ] especially observes and examines; there is the salty kind, which shows that salt may be obtained by evaporation; the nitrous, which indicates soda; the aluminous kind, which indicates alum; the vitrioline, which indicates vitriol; the sulphurous kind, which indicates sulphur; and as for the bituminous juice, out of which bitumen is melted down, the colour itself proclaims it to the worker who is evaporating it. the sea-water however, is similar to that of salt springs, and may be drawn into low-lying pits, and, evaporated by the heat of the sun, changes of itself into salt; similarly the water of some salt-lakes turns to salt when dried by the heat of summer. therefore an industrious and diligent man observes and makes use of these things and thus contributes something to the common welfare. the strength of the sea condenses the liquid bitumen which flows into it from hidden springs, into amber and jet, as i have described already in my books "_de subterraneorum ortu et causis_"[ ]. the sea, with certain directions of the wind, throws both these substances on shore, and for this reason the search for amber demands as much care as does that for coral. moreover, it is necessary that those who wash the sand or evaporate the water from the springs, should be careful to learn the nature of the locality, its roads, its salubrity, its overlord, and the neighbours, lest on account of difficulties in the conduct of their business they become either impoverished by exhaustive expenditure, or their goods and lives are imperilled. but enough about this. the miner, after he has selected out of many places one particular spot adapted by nature for mining, bestows much labour and attention on the veins. these have either been stripped bare of their covering by chance and thus lie exposed to our view, or lying deeply hidden and concealed they are found after close search; the latter is more usual, the former more rarely happens, and both of these occurrences must be explained. there is more than one force which can lay bare the veins unaided by the industry or toil of man; since either a torrent might strip off the surface, which happened in the case of the silver mines of freiberg (concerning which i have written in book i. of my work "_de veteribus et novis metallis_")[ ]; or they may be exposed through the force of the wind, when it uproots and destroys the trees which have grown over the veins; or by the breaking away of the rocks; or by long-continued heavy rains tearing away the mountain; or by an earthquake; or by a lightning flash; or by a snowslide; or by the violence of the winds: "of such a nature are the rocks hurled down from the mountains by the force of the winds aided by the ravages of time." or the plough may uncover the veins, for justin relates in his history that nuggets of gold had been turned up in galicia by the plough; or this may occur through a fire in the forest, as diodorus siculus tells us happened in the silver mines in spain; and that saying of posidonius is appropriate enough: "the earth violently moved by the fires consuming the forest sends forth new products, namely, gold and silver."[ ] and indeed, lucretius has explained the same thing more fully in the following lines: "copper and gold and iron were discovered, and at the same time weighty silver and the substance of lead, when fire had burned up vast forests on the great hills, either by a discharge of heaven's lightning, or else because, when men were waging war with one another, forest fires had carried fire among the enemy in order to strike terror to them, or because, attracted by the goodness of the soil, they wished to clear rich fields and bring the country into pasture, or else to destroy wild beasts and enrich themselves with the game; for hunting with pitfalls and with fire came into use before the practice of enclosing the wood with toils and rousing the game with dogs. whatever the fact is, from whatever cause the heat of flame had swallowed up the forests with a frightful crackling from their very roots, and had thoroughly baked the earth with fire, there would run from the boiling veins and collect into the hollows of the grounds a stream of silver and gold, as well as of copper and lead."[ ] but yet the poet considers that the veins are not laid bare in the first instance so much by this kind of fire, but rather that all mining had its origin in this. and lastly, some other force may by chance disclose the veins, for a horse, if this tale can be believed, disclosed the lead veins at goslar by a blow from his hoof[ ]. by such methods as these does fortune disclose the veins to us. but by skill we can also investigate hidden and concealed veins, by observing in the first place the bubbling waters of springs, which cannot be very far distant from the veins because the source of the water is from them; secondly, by examining the fragments of the veins which the torrents break off from the earth, for after a long time some of these fragments are again buried in the ground. fragments of this kind lying about on the ground, if they are rubbed smooth, are a long distance from the veins, because the torrent, which broke them from the vein, polished them while it rolled them a long distance; but if they are fixed in the ground, or if they are rough, they are nearer to the veins. the soil also should be considered, for this is often the cause of veins being buried more or less deeply under the earth; in this case the fragments protrude more or less widely apart, and miners are wont to call the veins discovered in this manner "_fragmenta_."[ ] further, we search for the veins by observing the hoar-frosts, which whiten all herbage except that growing over the veins, because the veins emit a warm and dry exhalation which hinders the freezing of the moisture, for which reason such plants appear rather wet than whitened by the frost. this may be observed in all cold places before the grass has grown to its full size, as in the months of april and may; or when the late crop of hay, which is called the _cordum_, is cut with scythes in the month of september. therefore in places where the grass has a dampness that is not congealed into frost, there is a vein beneath; also if the exhalation be excessively hot, the soil will produce only small and pale-coloured plants. lastly, there are trees whose foliage in spring-time has a bluish or leaden tint, the upper branches more especially being tinged with black or with any other unnatural colour, the trunks cleft in two, and the branches black or discoloured. these phenomena are caused by the intensely hot and dry exhalations which do not spare even the roots, but scorching them, render the trees sickly; wherefore the wind will more frequently uproot trees of this kind than any others. verily the veins do emit this exhalation. therefore, in a place where there is a multitude of trees, if a long row of them at an unusual time lose their verdure and become black or discoloured, and frequently fall by the violence of the wind, beneath this spot there is a vein. likewise along a course where a vein extends, there grows a certain herb or fungus which is absent from the adjacent space, or sometimes even from the neighbourhood of the veins. by these signs of nature a vein can be discovered. there are many great contentions between miners concerning the forked twig[ ], for some say that it is of the greatest use in discovering veins, and others deny it. some of those who manipulate and use the twig, first cut a fork from a hazel bush with a knife, for this bush they consider more efficacious than any other for revealing the veins, especially if the hazel bush grows above a vein. others use a different kind of twig for each metal, when they are seeking to discover the veins, for they employ hazel twigs for veins of silver; ash twigs for copper; pitch pine for lead and especially tin, and rods made of iron and steel for gold. all alike grasp the forks of the twig with their hands, clenching their fists, it being necessary that the clenched fingers should be held toward the sky in order that the twig should be raised at that end where the two branches meet. then they wander hither and thither at random through mountainous regions. it is said that the moment they place their feet on a vein the twig immediately turns and twists, and so by its action discloses the vein; when they move their feet again and go away from that spot the twig becomes once more immobile. the truth is, they assert, the movement of the twig is caused by the power of the veins, and sometimes this is so great that the branches of trees growing near a vein are deflected toward it. on the other hand, those who say that the twig is of no use to good and serious men, also deny that the motion is due to the power of the veins, because the twigs will not move for everybody, but only for those who employ incantations and craft. moreover, they deny the power of a vein to draw to itself the branches of trees, but they say that the warm and dry exhalations cause these contortions. those who advocate the use of the twig make this reply to these objections: when one of the miners or some other person holds the twig in his hands, and it is not turned by the force of a vein, this is due to some peculiarity of the individual, which hinders and impedes the power of the vein, for since the power of the vein in turning and twisting the twig may be not unlike that of a magnet attracting and drawing iron toward itself, this hidden quality of a man weakens and breaks the force, just the same as garlic weakens and overcomes the strength of a magnet. for a magnet smeared with garlic juice cannot attract iron; nor does it attract the latter when rusty. further, concerning the handling of the twig, they warn us that we should not press the fingers together too lightly, nor clench them too firmly, for if the twig is held lightly they say that it will fall before the force of the vein can turn it; if however, it is grasped too firmly the force of the hands resists the force of the veins and counteracts it. therefore, they consider that five things are necessary to insure that the twig shall serve its purpose: of these the first is the size of the twig, for the force of the veins cannot turn too large a stick; secondly, there is the shape of the twig, which must be forked or the vein cannot turn it; thirdly, the power of the vein which has the nature to turn it; fourthly, the manipulation of the twig; fifthly, the absence of impeding peculiarities. these advocates of the twig sum up their conclusions as follows: if the rod does not move for everybody, it is due to unskilled manipulation or to the impeding peculiarities of the man which oppose and resist the force of the veins, as we said above, and those who search for veins by means of the twig need not necessarily make incantations, but it is sufficient that they handle it suitably and are devoid of impeding power; therefore, the twig may be of use to good and serious men in discovering veins. with regard to deflection of branches of trees they say nothing and adhere to their opinion. [illustration (divining rod): a--twig. b--trench.] since this matter remains in dispute and causes much dissention amongst miners, i consider it ought to be examined on its own merits. the wizards, who also make use of rings, mirrors and crystals, seek for veins with a divining rod shaped like a fork; but its shape makes no difference in the matter,--it might be straight or of some other form--for it is not the form of the twig that matters, but the wizard's incantations which it would not become me to repeat, neither do i wish to do so. the ancients, by means of the divining rod, not only procured those things necessary for a livelihood or for luxury, but they were also able to alter the forms of things by it; as when the magicians changed the rods of the egyptians into serpents, as the writings of the hebrews relate[ ]; and as in homer, minerva with a divining rod turned the aged ulysses suddenly into a youth, and then restored him back again to old age; circe also changed ulysses' companions into beasts, but afterward gave them back again their human form[ ]; moreover by his rod, which was called "caduceus," mercury gave sleep to watchmen and awoke slumberers[ ]. therefore it seems that the divining rod passed to the mines from its impure origin with the magicians. then when good men shrank with horror from the incantations and rejected them, the twig was retained by the unsophisticated common miners, and in searching for new veins some traces of these ancient usages remain. but since truly the twigs of the miners do move, albeit they do not generally use incantations, some say this movement is caused by the power of the veins, others say that it depends on the manipulation, and still others think that the movement is due to both these causes. but, in truth, all those objects which are endowed with the power of attraction do not twist things in circles, but attract them directly to themselves; for instance, the magnet does not turn the iron, but draws it directly to itself, and amber rubbed until it is warm does not bend straws about, but simply draws them to itself. if the power of the veins were of a similar nature to that of the magnet and the amber, the twig would not so much twist as move once only, in a semi-circle, and be drawn directly to the vein, and unless the strength of the man who holds the twig were to resist and oppose the force of the vein, the twig would be brought to the ground; wherefore, since this is not the case, it must necessarily follow that the manipulation is the cause of the twig's twisting motion. it is a conspicuous fact that these cunning manipulators do not use a straight twig, but a forked one cut from a hazel bush, or from some other wood equally flexible, so that if it be held in the hands, as they are accustomed to hold it, it turns in a circle for any man wherever he stands. nor is it strange that the twig does not turn when held by the inexperienced, because they either grasp the forks of the twig too tightly or hold them too loosely. nevertheless, these things give rise to the faith among common miners that veins are discovered by the use of twigs, because whilst using these they do accidentally discover some; but it more often happens that they lose their labour, and although they might discover a vein, they become none the less exhausted in digging useless trenches than do the miners who prospect in an unfortunate locality. therefore a miner, since we think he ought to be a good and serious man, should not make use of an enchanted twig, because if he is prudent and skilled in the natural signs, he understands that a forked stick is of no use to him, for as i have said before, there are the natural indications of the veins which he can see for himself without the help of twigs. so if nature or chance should indicate a locality suitable for mining, the miner should dig his trenches there; if no vein appears he must dig numerous trenches until he discovers an outcrop of a vein. a _vena dilatata_ is rarely discovered by men's labour, but usually some force or other reveals it, or sometimes it is discovered by a shaft or a tunnel on a _vena profunda_[ ]. the veins after they have been discovered, and likewise the shafts and tunnels, have names given them, either from their discoverers, as in the case at annaberg of the vein called "kölergang," because a charcoal burner discovered it; or from their owners, as the geyer, in joachimsthal, because part of the same belonged to geyer; or from their products, as the "pleygang" from lead, or the "bissmutisch" at schneeberg from bismuth[ ]; or from some other circumstances, such as the rich alluvials from the torrent by which they were laid bare in the valley of joachim. more often the first discoverers give the names either of persons, as those of german kaiser, apollo, janus; or the name of an animal, as that of lion, bear, ram, or cow; or of things inanimate, as "silver chest" or "ox stalls"; or of something ridiculous, as "glutton's nightshade"; or finally, for the sake of a good omen, they call it after the deity. in ancient times they followed the same custom and gave names to the veins, shafts and tunnels, as we read in pliny: "it is wonderful that the shafts begun by hannibal in spain are still worked, their names being derived from their discoverers. one of these at the present day, called baebelo, furnished hannibal with three hundred pounds weight (of silver) per day."[ ] end of book ii. footnotes: [ ] xenophon. essay on the revenues of athens, iv., . "but we cannot but feel surprised that the state, when it sees many private individuals enriching themselves from its resources, does not imitate their proceedings; for we heard long ago, indeed, at least such of us as attended to these matters, that nicias the son of niceratus kept a thousand men employed in the silver mines, whom he let on hire to sosias of thrace on condition that he should give him for each an obolus a day, free of all charges; and this number he always supplied undiminished." (see also note ). an obolus a day each, would be about oz. troy of silver per day for the whole number. in modern value this would, of course, be but about s. per day, but in purchasing power the value would probably be to (see note on p. ). nicias was estimated to have a fortune of talents--about , troy ounces of silver, and was one of the wealthiest of the athenians. (plutarch, life of nicias). [ ] xenophon. _oeconomicus_ xii., . "'i approve,' said ischomachus, 'of the barbarian's answer to the king who found a good horse, and, wishing to fatten it as soon as possible, asked a man with a good reputation for horsemanship what would do it?' the man's reply was: 'its master's eye.'" [ ] _praefectus metallorum._ in saxony this official was styled the _berghauptmann_. for further information see page and note on page . [ ] this statement is either based upon apollodorus, whom agricola does not mention among his authorities, or on strabo, whom he does so include. the former in his work on mythology makes such a statement, for which strabo (xiv., , ) takes him to task as follows: "with this vain intention they collected the stories related by the scepsian (demetrius), and taken from callisthenes and other writers, who did not clear them from false notions respecting the halizones; for example, that the wealth of tantalus and of the pelopidae was derived, it is said, from the mines about phrygia and sipylus; that of cadmus from the mines of thrace and mount pangaeum; that of priam from the gold mines of astyra, near abydos (of which at present there are small remains, yet there is a large quantity of matter ejected, and the excavations are proofs of former workings); that of midas from the mines about mount bermium; that of gyges, alyattes, and croesus, from the mines in lydia and the small deserted city between atarneus and pergamum, where are the sites of exhausted mines." (hamilton's trans., vol. iii., p. ). in adopting this view, agricola apparently applied a wonderful realism to some greek mythology--for instance, in the legend of midas, which tells of that king being rewarded by the god dionysus, who granted his request that all he touched might turn to gold; but the inconvenience of the gift drove him to pray for relief, which he obtained by bathing in the pactolus, the sands of which thereupon became highly auriferous. priam was, of course, king of troy, but homer does not exhibit him as a mine-owner. gyges, alyattes, and croesus were successively kings of lydia, from to b.c., and were no doubt possessed of great treasure in gold. some few years ago we had occasion to inquire into extensive old workings locally reputed to be croesus' mines, at a place some distance north of smyrna, which would correspond very closely to the locality here mentioned. [ ] there can be no doubt that the carthaginians worked the mines of spain on an extensive scale for a very long period anterior to their conquest by the romans, but whether the mines were worked by the government or not we are unable to find any evidence. [ ] the silver mines of mt. laurion formed the economic mainstay of athens for the three centuries during which the state had the ascendency in greece, and there can be no doubt that the dominance of athens and its position as a sea-power were directly due to the revenues from the mines. the first working of the mines is shrouded in mystery. the scarcity of silver in the time of solon ( - b.c.) would not indicate any very considerable output at that time. according to xenophon (essay on revenue of athens, iv., ), written about b.c., "they were wrought in very ancient times." the first definite discussion of the mines in greek record begins about b.c., for about that time the royalties began to figure in the athenian budget (aristotle, constitution of athens, ). there can be no doubt that the mines reached great prosperity prior to the persian invasion. in the year b.c. the mines returned talents (about , oz. troy) to the treasury, and this, on the advice of themistocles, was devoted to the construction of the fleet which conquered the persians at salamis ( b.c.). the mines were much interfered with by the spartan invasions from to b.c., and again by their occupation in b.c.; and by b.c., when xenophon wrote the "revenues," exploitation had fallen to a low ebb, for which he proposes the remedies noted by agricola on p. . by the end of the th century, b.c., the mines had again reached considerable prosperity, as is evidenced by demosthenes' orations against pantaenetus and against phaenippus, and by lycurgus' prosecution of diphilos for robbing the supporting pillars. the domination of the macedonians under philip and alexander at the end of the th and beginning of the rd centuries b.c., however, so flooded greece with money from the mines of thrace, that this probably interfered with laurion, at this time, in any event, began the decadence of these mines. synchronous also was the decadence of athens, and, but for fitful displays, the state was not able to maintain even its own independence, not to mention its position as a dominant state. finally, strabo, writing about b.c. gives the epitaph of every mining district--reworking the dumps. he says (ix., , ): "the silver mines in attica were at first of importance, but are now exhausted. the workmen, when the mines yielded a bad return to their labour, committed to the furnace the old refuse and scoria, and hence obtained very pure silver, for the former workmen had carried on the process in the furnace unskilfully." since , the mines have been worked with some success by a french company, thus carrying the mining history of this district over a period of twenty-seven centuries. the most excellent of many memoirs upon the mines at laurion, not only for its critical, historical, and archæological value, but also because of its author's great insight into mining and metallurgy, is that of edouard ardaillon (_les mines du laurion dans l'antiquité_, paris, ). we have relied considerably upon this careful study for the following notes, and would refer others to it for a short bibliography on the subject. we would mention in passing that augustus boeckh's "silver mines of laurion," which is incorporated with his "public economy of athens" (english translation by lewis, london, ) has been too much relied upon by english students. it is no doubt the product of one acquainted with written history, but without any special knowledge of the industry and it is based on no antiquarian research. the mt. laurion mining district is located near the southern end of the attic peninsula. the deposits are silver-lead, and they occur along the contact between approximately horizontal limestones and slates. there are two principal beds of each, thus forming three principal contacts. the most metalliferous of these contacts are those at the base of the slates, the lowest contact of the series being the richest. the ore-bodies were most irregular, varying greatly in size, from a thin seam between schist planes, to very large bodies containing as much as , cubic metres. the ores are argentiferous galena, accompanied by considerable amounts of blende and pyrites, all oxidized near the surface. the ores worked by the ancients appear to have been fairly rich in lead, for the discards worked in recent years by the french company, and the pillars left behind, ran % to % lead. the ratio of silver was from to ounces per ton of lead. the upper contacts were exposed by erosion and could be entered by tunnels, but the lowest and most prolific contact line was only to be reached by shafts. the shafts were ordinarily from four to six feet square, and were undoubtedly cut by hammer and chisel; they were as much as feet deep. in some cases long inclines for travelling roads join the vertical shafts in depth. the drives, whether tunnels or from shafts, were not level, but followed every caprice of the sinuous contact. they were from two to two and a half feet wide, often driven in parallels with cross-cuts between, in order to exploit every corner of the contact. the stoping of ore-bodies discovered was undertaken quite systematically, the methods depending in the main on the shape of the ore-body. if the body was large, its dimensions were first determined by drives, crosscuts, rises, and winzes, as the case might require. if the ore was mainly overhead it was overhand-stoped, and the stopes filled as work progressed, inclined winzes being occasionally driven from the stopes to the original entry drives. if the ore was mainly below, it was underhand-stoped, pillars being left if necessary--such pillars in some cases being thirty feet high. they also employed timber and artificial pillars. the mines were practically dry. there is little evidence of breaking by fire. the ore was hand-sorted underground and carried out by the slaves, and in some cases apparently the windlass was used. it was treated by grinding in mills and concentrating upon a sort of buddle. these concentrates--mostly galena--were smelted in low furnaces and the lead was subsequently cupelled. further details of metallurgical methods will be found in notes on p. and p. , on metallurgical subjects. the mines were worked by slaves. even the overseers were at times apparently slaves, for we find (xenophon, _memorabilia_, ii., ) that nicias paid a whole talent for a good overseer. a talent would be about troy ounces of silver. as wages of skilled labour were about two and one half pennyweights of silver per diem, and a family income of ounces of silver per annum was affluence, the ratio of purchasing power of attic coinage to modern would be about to . therefore this mine manager was worth in modern value roughly £ , . the mines were the property of the state. the areas were defined by vertical boundaries, and were let on lease for definite periods for a fixed annual rent. more ample discussion of the law will be found on p. . [ ] xenophon. (essay on the revenues, iv., ). "i think, however, that i am able to give some advice with regard to this difficulty also (the risk of opening new mines), and to show how new operations may be conducted with the greatest safety. there are ten tribes at athens, and if to each of these the state should assign an equal number of slaves, and the tribes should all make new cuttings, sharing their fortunes in common, then if but one tribe should make any useful discovery it would point out something profitable to the whole; but if two, three, or four, or half the number should make some discovery, it is plain that the works would be more profitable in proportion, and that they should all fail is contrary to all experience in past times." (watson's trans. p. ). [ ] agricola here refers to the proposal of xenophon for the state to collect slaves and hire them to work the mines of laurion. there is no evidence that this recommendation was ever carried out. [ ] _partes._ agricola, p. - , describes in detail the organization and management of these share companies. see note , p. . [ ] this island in the northern Ægean sea has produced this "earth" from before theophrastus' time ( - b.c.) down to the present day. according to dana (system of mineralogy ), it is cimolite, a hydrous silicate of aluminium. the ancients distinguished two kinds,--one sort used as a pigment, and the other for medicinal purposes. this latter was dug with great ceremony at a certain time of the year, moulded into cubes, and stamped with a goat,--the symbol of diana. it thus became known as _terra sigillata_, and was an article of apothecary commerce down to the last century. it is described by galen (xii., ), dioscorides (v., ), and pliny (xxxv., ), as a remedy for ulcers and snake bites. [ ] _magister metallorum_. see note , p. , for the reasons of the adoption of the term _bergmeister_ and page for details of his duties. [ ] _ramenta_. "particles." the author uses this term indifferently for fragments, particles of mineral, concentrates, gold dust, black tin, etc., in all cases the result of either natural or artificial concentration. as in technical english we have no general term for both natural and artificial "concentrates," we have rendered it as the context seemed to demand. [ ] a certain amount of bitumen does float ashore in the dead sea; the origin of it is, however, uncertain. strabo (xvi., , ), pliny (v., and ), and josephus (iv., ), all mention this fact. the lake for this reason is often referred to by the ancient writers by the name _asphaltites_. [ ] _excoctor_,--literally, "smelter" or "metallurgist." [ ] this reference should be to the _de natura fossilium_ (p. ), although there is a short reference to the matter in _de ortu et causis_ (p. ). agricola maintained that not only were jet and amber varieties of bitumen, but also coal and camphor and obsidian. as jet (_gagates_) is but a compact variety of coal, the ancient knowledge of this substance has more interest than would otherwise attach to the gem, especially as some materials described in this connection were no doubt coal. the greeks often refer to a series of substances which burned, contained earth, and which no doubt comprised coal. such substances are mentioned by aristotle (_de mirabilibus_. , , ), nicander (_theriaca_. ), and others, previous to the nd century b.c., but the most ample description is that of theophrastus ( - ): "some of the more brittle stones there also are, which become as it were burning coals when put into a fire, and continue so a long time; of this kind are those about bena, found in mines and washed down by the torrents, for they will take fire on burning coals being thrown on them, and will continue burning as long as anyone blows them; afterward they will deaden, and may after that be made to burn again. they are therefore of long continuance, but their smell is troublesome and disagreeable. that also which is called the _spinus_, is found in mines. this stone, cut in pieces and thrown together in a heap, exposed to the sun, burns; and that the more, if it be moistened or sprinkled with water (a pyritiferous shale?). but the _lipara_ stone empties itself, as it were, in burning, and becomes like the _pumice_, changing at once both its colour and density; for before burning it is black, smooth, and compact. this stone is found in the pumices, separately in different places, as it were, in cells, nowhere continuous to the matter of them. it is said that in melos the pumice is produced in this manner in some other stone, as this is on the contrary in it; but the stone which the pumice is found in is not at all like the _lipara_ stone which is found in it. certain stones there are about tetras, in sicily, which is over against lipara, which empty themselves in the same manner in the fire. and in the promontory called erineas, there is a great quantity of stone like that found about bena, which, when burnt, emits a bituminous smell, and leaves a matter resembling calcined earth. those fossil substances that are called coals, and are broken for use, are earthy; they kindle, however, and burn like wood coals. these are found in liguria, where there also is amber, and in elis, on the way to olympia over the mountains. these are used by smiths." (based on hill's trans.). dioscorides and pliny add nothing of value to this description. agricola (_de nat. fos._, p. - ) not only gives various localities of jet, but also records its relation to coal. as to the latter, he describes several occurrences, and describes the deposits as _vena dilatata_. coal had come into considerable use all over europe, particularly in england, long before agricola's time; the oft-mentioned charter to mine sea-coal given to the monks of newbottle abbey, near preston, was dated . amber was known to the greeks by the name _electrum_, but whether the alloy of the same name took its name from the colour of amber or _vice versa_ is uncertain. the gum is supposed to be referred to by homer (od. xv. ), and thales of miletus ( - b.c.) is supposed to have first described its power of attraction. it is mentioned by many other greek authors, Æschylus, euripides, aristotle, and others. the latter (_de mirabilibus_, ) records of the amber islands in the adriatic, that the inhabitants tell the story that on these islands amber falls from poplar trees. "this, they say, resembles gum and hardens like stone, the story of the poets being that after phaeton was struck by lightning his sisters turned to poplar trees and shed tears of amber." theophrastus ( ) says: "amber is also a stone; it is dug out of the earth in liguria and has, like the before-mentioned (lodestone), a power of attraction." pliny (xxxvii., ) gives a long account of both the substance, literature, and mythology on the subject. his view of its origin was: "certainly amber is obtained from the islands of the northern ocean, and is called by the germans _glaesum_. for this reason the romans, when germanicus cæsar commanded in those parts, called one of them _glaesaria_, which was known to the barbarians as _austeravia_. amber originates from gum discharged by a kind of pine tree, like gum from cherry and resin from the ordinary pine. it is liquid at first, and issues abundantly and hardens in time by cold, or by the sea when the rising tides carry off the fragments from the shores of those islands. certainly it is thrown on the coasts, and is so light that it appears to roll in the water. our forefathers believed that it was the juice of a tree, for they called it _succinum_. and that it belongs to a kind of pine tree is proved by the odour of the pine tree which it gives when rubbed, and that it burns when ignited like a pitch pine torch." the term amber is of arabic origin--from _ambar_--and this term was adopted by the greeks after the christian era. agricola uses the latin term _succinum_ and (_de nat. fos._, p. - ) disputes the origin from tree gum, and contends for submarine bitumen springs. [ ] the statement in _de veteribus et novis metallis_ (p. ) is as follows:-- "it came about by chance and accident that the silver mines were discovered at freiberg in meissen. by the river sala, which is not unknown to strabo, is hala, which was once country, but is now a large town; the site, at any rate, even from roman times was famous and renowned for its salt springs, for the possession of which the hermunduri fought with the chatti. when people carried the salt thence in wagons, as they now do straight through meissen (saxony) into bohemia--which is lacking in that seasoning to-day no less than formerly--they saw galena in the wheel tracks, which had been uncovered by the torrents. this lead ore, since it was similar to that of goslar, they put into their carts and carried to goslar, for the same carriers were accustomed to carry lead from that city. and since much more silver was smelted from this galena than from that of goslar, certain miners betook themselves to that part of meissen in which is now situated freiberg, a great and wealthy town; and we are told by consistent stories and general report that they grew rich out of the mines." agricola places the discovery of the mines at freiberg at about . see note , p. . [ ] diodorus siculus (v., ). "these places being covered with woods, it is said that in ancient times these mountains were set on fire by shepherds, and continued burning for many days, and parched the earth, so that an abundance of silver ore was melted, and the metal flowed in streams of pure silver like a river." aristotle, nearly three centuries before diodorus, mentions this same story (_de mirabilibus_, ): "they say that in ibernia the woods were set on fire by certain shepherds, and the earth thus heated, the country visibly flowed silver; and when some time later there were earthquakes, and the earth burst asunder at different places, a large amount of silver was collected." as the works of posidonius are lost, it is probable that agricola was quoting from strabo (iii., , ), who says, in describing spain: "posidonius, in praising the amount and excellence of the metals, cannot refrain from his accustomed rhetoric, and becomes quite enthusiastic in exaggeration. he tells us we are not to disbelieve the fable that formerly the forests having been set on fire, the earth, which was loaded with silver and gold, melted and threw up these metals to the surface, for inasmuch as every mountain and wooded hill seemed to be heaped up with money by a lavish fortune." (hamilton's trans. i., p. ). or he may have been quoting from the _deipnosophistae_ of athenaeus (vi.), where posidonius is quoted: "and the mountains ... when once the woods upon them had caught fire, spontaneously ran with liquid silver." [ ] lucretius, _de rerum natura_ v. . [ ] agricola's account of this event in _de veteribus et novis metallis_ is as follows (p. ): "now veins are not always first disclosed by the hand and labour of man, nor has art always demonstrated them; sometimes they have been disclosed rather by chance or by good fortune. i will explain briefly what has been written upon this matter in history, what miners tell us, and what has occurred in our times. thus the mines at goslar are said to have been found in the following way. a certain noble, whose name is not recorded, tied his horse, which was named ramelus, to the branch of a tree which grew on the mountain. this horse, pawing the earth with its hoofs, which were iron shod, and thus turning it over, uncovered a hidden vein of lead, not unlike the winged pegasus, who in the legend of the poets opened a spring when he beat the rock with his hoof. so just as that spring is named hippocrene after that horse, so our ancestors named the mountain rammelsberg. whereas the perennial water spring of the poets would long ago have dried up, the vein even to-day exists, and supplies an abundant amount of excellent lead. that a horse can have opened a vein will seem credible to anyone who reflects in how many ways the signs of veins are shown by chance, all of which are explained in my work _de re metallica_. therefore, here we will believe the story, both because it may happen that a horse may disclose a vein, and because the name of the mountain agrees with the story." agricola places the discovery of goslar in the hartz at prior to . see note , p. . [ ] _fragmenta_. the glossary gives "_geschube_." this term is defined in the _bergwerks' lexicon_ (chemnitz, , p. ) as the pieces of stone, especially tin-stone, broken from the vein and washed out by the water--the croppings. [ ] so far as we are able to discover, this is the first published description of the divining rod as applied to minerals or water. like agricola, many authors have sought to find its origin among the ancients. the magic rods of moses and homer, especially the rod with which the former struck the rock at horeb, the rod described by ctesias (died b.c.) which attracted gold and silver, and the _virgula divina_ of the romans have all been called up for proof. it is true that the romans are responsible for the name _virgula divina_, "divining rod," but this rod was used for taking auguries by casting bits of wood (cicero, _de divinatione_). despite all this, while the ancient naturalists all give detailed directions for finding water, none mention anything akin to the divining rod of the middle ages. it is also worth noting that the monk theophilus in the th century also gives a detailed description of how to find water, but makes no mention of the rod. there are two authorities sometimes cited as prior to agricola, the first being basil valentine in his "last will and testament" (xxiv-viii.), and while there may be some reason (see appendix) for accepting the authenticity of the "triumphal chariot of antimony" by this author, as dating about , there can be little doubt that the "last will and testament" was spurious and dated about years after agricola. paracelsus (_de natura rerum_ ix.), says: "these (divinations) are vain and misleading, and among the first of them are divining rods, which have deceived many miners. if they once point rightly they deceive ten or twenty times." in his _de origine morborum invisibilium_ (book i.) he adds that the "faith turns the rod." these works were no doubt written prior to _de re metallica_--paracelsus died in --but they were not published until some time afterward. those interested in the strange persistence of this superstition down to the present day--and the files of the patent offices of the world are full of it--will find the subject exhaustively discussed in m. e. chevreul's "_de la baguette divinatoire_," paris, ; l. figuier, "_histoire du merveilleux dans les temps moderne ii._", paris, ; w. f. barrett, proceedings of the society of psychical research, part , , and , ; r. w. raymond, american inst. of mining engineers, , p. . of the descriptions by those who believed in it there is none better than that of william pryce (_mineralogia cornubiensis_, london, , pp. - ), who devotes much pains to a refutation of agricola. when we consider that a century later than agricola such an advanced mind as robert boyle ( - ), the founder of the royal society, was convinced of the genuineness of the divining rod, one is more impressed with the clarity of agricola's vision. in fact, there were few indeed, down to the th century, who did not believe implicitly in the effectiveness of this instrument, and while science has long since abandoned it, not a year passes but some new manifestation of its hold on the popular mind breaks out. [ ] exodus vii., , , . [ ] odyssey xvi., , and x., . [ ] odyssey xxiv., , etc. the _caduceus_ of hermes had also the power of turning things to gold, and it is interesting to note that in its oldest form, as the insignia of heralds and of ambassadors, it had two prongs. [ ] in a general way _venae profundae_ were fissure veins and _venae dilatatae_ were sheeted deposits. for description see book iii. [ ] these mines are in the erzgebirge. we have adopted the names given in the german translation. [ ] the quotation from pliny (xxxiii., ) as a whole reads as follows:-- "silver is found in nearly all the provinces, but the finest of all in spain; where it is found in the barren lands, and in the mountains. wherever one vein of silver has been found, another is sure to be found not far away. this is the case of nearly all the metals, whence it appears that the greeks derived _metalla_. it is wonderful that the shafts begun by hannibal in spain still remain, their names being derived from their makers. one of these at the present day called baebelo, furnished hannibal with three hundred pounds' weight (of silver) per day. this mountain is excavated for a distance of fifteen hundred paces; and for this distance there are waterbearers lighted by torches standing night and day baling out the water in turns, thus making quite a river." hannibal dates - b.c. and was therefore dead years when pliny was born. according to a footnote in bostock and riley's translation of pliny, these workings were supposed to be in the neighbourhood of castulo, now cazlona, near linares. it was at castulo that hannibal married his rich wife himilce; and in the hills north of linares there are ancient silver mines still known as los pozos de anibal. book iii. previously i have given much information concerning the miners, also i have discussed the choice of localities for mining, for washing sands, and for evaporating waters; further, i described the method of searching for veins. with such matters i was occupied in the second book; now i come to the third book, which is about veins and stringers, and the seams in the rocks[ ]. the term "vein" is sometimes used to indicate _canales_ in the earth, but very often elsewhere by this name i have described that which may be put in vessels[ ]; i now attach a second significance to these words, for by them i mean to designate any mineral substances which the earth keeps hidden within her own deep receptacles. [illustration a (vein in mountain): a, c--the mountain. b--_vena profunda_.] first i will speak of the veins, which, in depth, width, and length, differ very much one from another. those of one variety descend from the surface of the earth to its lowest depths, which on account of this characteristic, i am accustomed to call "_venae profundae_." [illustration b (vein in mountain): a, d--the mountain. b, c--_vena dilatata_.] another kind, unlike the _venae profundae_, neither ascend to the surface of the earth nor descend, but lying under the ground, expand over a large area; and on that account i call them "_venae dilatatae_." [illustration (veins in mountain): a, b, c, d--the mountain. e, f, g, h, i, k--_vena cumulata_.] another occupies a large extent of space in length and width; therefore i usually call it "_vena cumulata_," for it is nothing else than an accumulation of some certain kind of mineral, as i have described in the book entitled _de subterraneorum ortu et causis_. it occasionally happens, though it is unusual and rare, that several accumulations of this kind are found in one place, each one or more fathoms in depth and four or five in width, and one is distant from another two, three, or more fathoms. when the excavation of these accumulations begins, they at first appear in the shape of a disc; then they open out wider; finally from each of such accumulations is usually formed a "_vena cumulata_." [illustration a (veins in mountain): a--_vena profunda_. b--_intervenium_. c--another _vena profunda_.] [illustration b (veins in mountain): a & b--_vena dilatatae_. c--_intervenium_. d & e--other _venae dilatatae_.] the space between two veins is called an _intervenium_; this interval between the veins, if it is between _venae dilatatae_ is entirely hidden underground. if, however, it lies between _venae profundae_ then the top is plainly in sight, and the remainder is hidden. [illustration (veins in mountain): a--wide _vena profunda_. b--narrow _vena profunda_.] _venae profundae_ differ greatly one from another in width, for some of them are one fathom wide, some are two cubits, others one cubit; others again are a foot wide, and some only half a foot; all of which our miners call wide veins. others on the contrary, are only a palm wide, others three digits, or even two; these they call narrow. but in other places where there are very wide veins, the widths of a cubit, or a foot, or half a foot, are said to be narrow; at cremnitz, for instance, there is a certain vein which measures in one place fifteen fathoms in width, in another eighteen, and in another twenty; the truth of this statement is vouched for by the inhabitants. [illustration a (veins in mountain): a--thin _vena dilatata_. b--thick _vena dilatata_.] _venae dilatatae_, in truth, differ also in thickness, for some are one fathom thick, others two, or even more; some are a cubit thick, some a foot, some only half a foot; and all these are usually called thick veins. some on the other hand, are but a palm thick, some three digits, some two, some one; these are called thin veins. [illustration b (seams in the rocks): a, b, c--vein. d, e, f--seams in the rock (_commissurae saxorum_).] _venae profundae_ vary in direction; for some run from east to west. [illustration a (seams in the rocks): a, b, c--vein. d, e, f--_seams in the rocks_.] others, on the other hand, run from west to east. [illustration b (seams in the rocks): a, b, c--vein. d, e, f--_seams in the rocks_.] others run from south to north. [illustration (seams in the rocks): a, b, c--vein. d, e, f--_seams in the rocks_.] others, on the contrary, run from north to south. the seams in the rocks indicate to us whether a vein runs from the east or from the west. for instance, if the rock seams incline toward the westward as they descend into the earth, the vein is said to run from east to west; if they incline toward the east, the vein is said to run from west to east; in a similar manner, we determine from the rock seams whether the veins run north or south. [illustration (compass)] now miners divide each quarter of the earth into six divisions; and by this method they apportion the earth into twenty-four directions, which they divide into two parts of twelve each. the instrument which indicates these directions is thus constructed. first a circle is made; then at equal intervals on one half portion of it right through to the other, twelve straight lines called by the greeks [greek: diametroi], and in the latin _dimetientes_, are drawn through a central point which the greeks call [greek: kentron], so that the circle is thus divided into twenty-four divisions, all being of an equal size. then, within the circle are inscribed three other circles, the outermost of which has cross-lines dividing it into twenty-four equal parts; the space between it and the next circle contains two sets of twelve numbers, inscribed on the lines called "diameters"; while within the innermost circle it is hollowed out to contain a magnetic needle[ ]. the needle lies directly over that one of the twelve lines called "diameters" on which the number xii is inscribed at both ends. when the needle which is governed by the magnet points directly from the north to the south, the number xii at its tail, which is forked, signifies the north, that number xii which is at its point indicates the south. the sign vi superior indicates the east, and vi inferior the west. further, between each two cardinal points there are always five others which are not so important. the first two of these directions are called the prior directions; the last two are called the posterior, and the fifth direction lies immediately between the former and the latter; it is halved, and one half is attributed to one cardinal point and one half to the other. for example, between the northern number xii and the eastern number vi, are points numbered i, ii, iii, iv, v, of which i and ii are northern directions lying toward the east, iv and v are eastern directions lying toward the north, and iii is assigned, half to the north and half to the east. one who wishes to know the direction of the veins underground, places over the vein the instrument just described; and the needle, as soon as it becomes quiet, will indicate the course of the vein. that is, if the vein proceeds from vi to vi, it either runs from east to west, or from west to east; but whether it be the former or the latter, is clearly shown by the seams in the rocks. if the vein proceeds along the line which is between v and vi toward the opposite direction, it runs from between the fifth and sixth divisions of east to the west, or from between the fifth and sixth divisions of west to the east; and again, whether it is the one or the other is clearly shown by the seams in the rocks. in a similar manner we determine the other directions. [illustration (compass with winds)] now miners reckon as many points as the sailors do in reckoning up the number of the winds. not only is this done to-day in this country, but it was also done by the romans who in olden times gave the winds partly latin names and partly names borrowed from the greeks. any miner who pleases may therefore call the directions of the veins by the names of the winds. there are four principal winds, as there are four cardinal points: the _subsolanus_, which blows from the east; and its opposite the _favonius_, which blows from the west; the latter is called by the greeks [greek: zephyros], and the former [greek: apêliôtês]. there is the _auster_, which blows from the south; and opposed to it is the _septentrio_, from the north; the former the greeks called [greek: notos], and the latter [greek: aparktias]. there are also subordinate winds, to the number of twenty, as there are directions, for between each two principal winds there are always five subordinate ones. between the _subsolanus_ (east wind) and the _auster_ (south wind) there is the _ornithiae_ or the bird wind, which has the first place next to the _subsolanus_; then comes _caecias_; then _eurus_, which lies in the midway of these five; next comes _vulturnus_; and lastly, _euronotus_, nearest the _auster_ (south wind). the greeks have given these names to all of these, with the exception of _vulturnus_, but those who do not distinguish the winds in so precise a manner say this is the same as the greeks called [greek: euros]. between the _auster_ (south wind) and the _favonius_ (west wind) is first _altanus_, to the right of the _auster_ (south wind); then _libonotus_; then _africus_, which is the middle one of these five; after that comes _subvesperus_; next _argestes_, to the left of _favonius_ (west wind). all these, with the exception of _libonotus_ and _argestes_, have latin names; but _africus_ also is called by the greeks [greek: lips]. in a similar manner, between _favonius_ (west wind) and _septentrio_ (north wind), first to the right of _favonius_ (west wind), is the _etesiae_; then _circius_; then _caurus_, which is in the middle of these five; then _corus_; and lastly _thrascias_ to the left of _septentrio_ (north wind). to all of these, except that of _caurus_, the greeks gave the names, and those who do not distinguish the winds by so exact a plan, assert that the wind which the greeks called [greek: koros] and the latins _caurus_ is one and the same. again, between _septentrio_ (north wind) and the _subsolanus_ (east wind), the first to the right of _septentrio_ (north wind) is _gallicus_; then _supernas_; then _aquilo_, which is the middle one of these five; next comes _boreas_; and lastly _carbas_, to the left of _subsolanus_ (east wind). here again, those who do not consider the winds to be in so great a multitude, but say there are but twelve winds in all, or at the most fourteen, assert that the wind called by the greeks [greek: boreas] and the latins _aquilo_ is one and the same. for our purpose it is not only useful to adopt this large number of winds, but even to double it, as the german sailors do. they always reckon that between each two there is one in the centre taken from both. by this method we also are able to signify the intermediate directions by means of the names of the winds. for instance, if a vein runs from vi east to vi west, it is said to proceed from _subsolanus_ (east wind) to _favonius_ (west wind); but one which proceeds from between v and vi of the east to between v and vi west is said to proceed out of the middle of _carbas_ and _subsolanus_ to between _argestes_ and _favonius_; the remaining directions, and their intermediates are similarly designated. the miner, on account of the natural properties of a magnet, by which the needle points to the south, must fix the instrument already described so that east is to the left and west to the right. [illustration (veins in mountain): a, b--_venae dilatatae_. c--_seams in the rocks_.] in a similar way to _venae profundae_, the _venae dilatatae_ vary in their lateral directions, and we are able to understand from the seams in the rocks in which direction they extend into the ground. for if these incline toward the west in depth, the vein is said to extend from east to west; if on the contrary, they incline toward the east, the vein is said to go from west to east. in the same way, from the rock seams we can determine veins running south and north, or the reverse, and likewise to the subordinate directions and their intermediates. [illustration a (veins in mountain): a--straight _vena profunda_. b--curved _vena profunda_ [should be _vena dilatata_(?)].] further, as regards the question of direction of a _vena profunda_, one runs straight from one quarter of the earth to that quarter which is opposite, while another one runs in a curve, in which case it may happen that a vein proceeding from the east does not turn to the quarter opposite, which is the west, but twists itself and turns to the south or the north. [illustration b (veins in mountain): a--horizontal _vena dilatata_. b--inclined _vena dilatata_. c--curved _vena dilatata_.] similarly some _venae dilatatae_ are horizontal, some are inclined, and some are curved. [illustration a (veins in mountain)] also the veins which we call _profundae_ differ in the manner in which they descend into the depths of the earth; for some are vertical (a), some are inclined and sloping (b), others crooked (c). [illustration b (veins in mountain)] moreover, _venae profundae_ (b) differ much among themselves regarding the kind of locality through which they pass, for some extend along the slopes of mountains or hills (a-c) and do not descend down the sides. [illustration a (veins in mountain)] other _venae profundae_ (d, e, f) from the very summit of the mountain or hill descend the slope (a) to the hollow or valley (b), and they again ascend the slope or the side of the mountain or hill opposite (c). [illustration b (veins in mountain)] other _venae profundae_ (c, d) descend the mountain or hill (a) and extend out into the plain (b). [illustration a (veins in mountain): a--mountainous plain. b--_vena profunda_.] some veins run straight along on the plateaux, the hills, or plains. [illustration b (intersections of veins): a--principal vein. b--transverse vein. c--vein cutting principal one obliquely.] in the next place, _venae profundae_ differ not a little in the manner in which they intersect, since one may cross through a second transversely, or one may cross another one obliquely as if cutting it in two. [illustration (intersections of veins): a--principal vein. b--vein which cuts a obliquely. c--part carried away. d--that part which has been carried forward.] if a vein which cuts through another principal one obliquely be the harder of the two, it penetrates right through it, just as a wedge of beech or iron can be driven through soft wood by means of a tool. if it be softer, the principal vein either drags the soft one with it for a distance of three feet, or perhaps one, two, three, or several fathoms, or else throws it forward along the principal vein; but this latter happens very rarely. but that the vein which cuts the principal one is the same vein on both sides, is shown by its having the same character in its footwalls and hangingwalls. [illustration a (intersections of veins): a, b--two veins descend inclined and dip toward each other. c--junction. likewise two veins. d--indicates one descending vertically. e--marks the other descending inclined, which dips toward d. f--their junction.] sometimes _venae profundae_ join one with another, and from two or more outcropping veins[ ], one is formed; or from two which do not outcrop one is made, if they are not far distant from each other, and the one dips into the other, or if each dips toward the other, and they thus join when they have descended in depth. in exactly the same way, out of three or more veins, one may be formed in depth. [illustration b (intersections of veins)] however, such a junction of veins sometimes disunites and in this way it happens that the vein which was the right-hand vein becomes the left; and again, the one which was on the left becomes the right. furthermore, one vein may be split and divided into parts by some hard rock resembling a beak, or stringers in soft rock may sunder the vein and make two or more. these sometimes join together again and sometimes remain divided. [illustration (intersections of veins): a, b--veins dividing. c--the same joining.] whether a vein is separating from or uniting with another can be determined only from the seams in the rocks. for example, if a principal vein runs from the east to the west, the rock seams descend in depth likewise from the east toward the west, and the associated vein which joins with the principal vein, whether it runs from the south or the north, has its rock seams extending in the same way as its own, and they do not conform with the seams in the rock of the principal vein--which remain the same after the junction--unless the associated vein proceeds in the same direction as the principal vein. in that case we name the broader vein the principal one, and the narrower the associated vein. but if the principal vein splits, the rock seams which belong respectively to the parts, keep the same course when descending in depth as those of the principal vein. [illustration (intersections of veins): a, c--_vena dilatata_ crossing a _vena profunda_. b--_vena profunda_. d, e--_vena dilatata_ which junctions with a _vena profunda_. f--_vena profunda_. g--_vena dilatata_. h, i--its divided parts. k--_vena profunda_ which divides the _vena dilatata_.] but enough of _venae profundae_, their junctions and divisions. now we come to _venae dilatatae_. a _vena dilatata_ may either cross a _vena profunda_, or join with it, or it may be cut by a _vena profunda_, and be divided into parts. [illustration a (veins in mountain): a--the "beginning" (_origo_). b--the "end" (_finis_). c--the "head" (_caput_). d--the "tail" (_cauda_).] finally, a _vena profunda_ has a "beginning" (_origo_), an "end" (_finis_), a "head" (_caput_), and a "tail" (_cauda_). that part whence it takes its rise is said to be its "beginning," that in which it terminates the "end." its "head"[ ] is that part which emerges into daylight; its "tail" that part which is hidden in the earth. but miners have no need to seek the "beginning" of veins, as formerly the kings of egypt sought for the source of the nile, but it is enough for them to discover some other part of the vein and to recognise its direction, for seldom can either the "beginning" or the "end" be found. the direction in which the head of the vein comes into the light, or the direction toward which the tail extends, is indicated by its footwall and hangingwall. the latter is said to hang, and the former to lie. the vein rests on the footwall, and the hangingwall overhangs it; thus, when we descend a shaft, the part to which we turn the face is the footwall and seat of the vein, that to which we turn the back is the hangingwall. also in another way, the head accords with the footwall and the tail with the hangingwall, for if the footwall is toward the south, the vein extends its head into the light toward the south; and the hangingwall, because it is always opposite to the footwall, is then toward the north. consequently the vein extends its tail toward the north if it is an inclined _vena profunda_. similarly, we can determine with regard to east and west and the subordinate and their intermediate directions. a _vena profunda_ which descends into the earth may be either vertical, inclined, or crooked; the footwall of an inclined vein is easily distinguished from the hangingwall, but it is not so with a vertical vein; and again, the footwall of a crooked vein is inverted and changed into the hangingwall, and contrariwise the hangingwall is twisted into the footwall, but very many of these crooked veins may be turned back to vertical or inclined ones. [illustration b (veins in mountain): a--the "beginning." b--the "end." c, d--the "sides."] a _vena dilatata_ has only a "beginning" and an "end," and in the place of the "head" and "tail" it has two sides. [illustration (veins in mountain): a--the "beginning." b--the "end." c--the "head." d--the "tail." e--transverse vein.] a _vena cumulata_ has a "beginning," an "end," a "head," and a "tail," just as a _vena profunda_. moreover, a _vena cumulata_, and likewise a _vena dilatata_, are often cut through by a transverse _vena profunda_. [illustration a (fibra dilatata): a, b--veins. c--transverse stringer. d--oblique stringer. e--associated stringer. f--_fibra dilatata_.] stringers (_fibrae_)[ ], which are little veins, are classified into _fibrae transversae_, _fibrae obliquae_ which cut the vein obliquely, _fibrae sociae_, _fibrae dilatatae_, and _fibrae incumbentes_. the _fibra transversa_ crosses the vein; the _fibra obliqua_ crosses the vein obliquely; the _fibra socia_ joins with the vein itself; the _fibra dilatata_, like the _vena dilatata_, penetrates through it; but the _fibra dilatata_, as well as the _fibra profunda_, is usually found associated with a vein. [illustration b (fibra incumbens): a--vein. b--_fibra incumbens_ from the surface of the hangingwall. c--same from the footwall.] the _fibra incumbens_ does not descend as deeply into the earth as the other stringers, but lies on the vein, as it were, from the surface to the hangingwall or footwall, from which it is named _subdialis_.[ ] in truth, as to direction, junctions, and divisions, the stringers are not different from the veins. [illustration (seams in the rocks): a--seams which proceed from the east. b--the inverse.] lastly, the seams, which are the very finest stringers (_fibrae_), divide the rock, and occur sometimes frequently, sometimes rarely. from whatever direction the vein comes, its seams always turn their heads toward the light in the same direction. but, while the seams usually run from one point of the compass to another immediately opposite it, as for instance, from east to west, if hard stringers divert them, it may happen that these very seams, which before were running from east to west, then contrariwise proceed from west to east, and the direction of the rocks is thus inverted. in such a case, the direction of the veins is judged, not by the direction of the seams which occur rarely, but by those which constantly recur. [illustration (veins in mountain): a--solid vein. b--solid stringer. c--cavernous vein. d--cavernous stringer. e--barren vein. f--barren stringer.] both veins or stringers may be solid or drusy, or barren of minerals, or pervious to water. solid veins contain no water and very little air. the drusy veins rarely contain water; they often contain air. those which are barren of minerals often carry water. solid veins and stringers consist sometimes of hard materials, sometimes of soft, and sometimes of a kind of medium between the two. but to return to veins. a great number of miners consider[ ] that the best veins in depth are those which run from the vi or vii direction of the east to the vi or vii direction of the west, through a mountain slope which inclines to the north; and whose hangingwalls are in the south, and whose footwalls are in the north, and which have their heads rising to the north, as explained before, always like the footwall, and finally, whose rock seams turn their heads to the east. and the veins which are the next best are those which, on the contrary, extend from the vi or vii direction of the west to the vi or vii direction of the east, through the slope of a mountain which similarly inclines to the north, whose hangingwalls are also in the south, whose footwalls are in the north, and whose heads rise toward the north; and lastly, whose rock seams raise their heads toward the west. in the third place, they recommend those veins which extend from xii north to xii south, through the slope of a mountain which faces east; whose hangingwalls are in the west, whose footwalls are in the east; whose heads rise toward the east; and whose rock seams raise their heads toward the north. therefore they devote all their energies to those veins, and give very little or nothing to those whose heads, or the heads of whose rock seams rise toward the south or west. for although they say these veins sometimes show bright specks of pure metal adhering to the stones, or they come upon lumps of metal, yet these are so few and far between that despite them it is not worth the trouble to excavate such veins; and miners who persevere in digging in the hope of coming upon a quantity of metal, always lose their time and trouble. and they say that from veins of this kind, since the sun's rays draw out the metallic material, very little metal is gained. but in this matter the actual experience of the miners who thus judge of the veins does not always agree with their opinions, nor is their reasoning sound; since indeed the veins which run from east to west through the slope of a mountain which inclines to the south, whose heads rise likewise to the south, are not less charged with metals, than those to which miners are wont to accord the first place in productiveness; as in recent years has been proved by the st. lorentz vein at abertham, which our countrymen call gottsgaab, for they have dug out of it a large quantity of pure silver; and lately a vein in annaberg, called by the name of himmelsch hoz[ ], has made it plain by the production of much silver that veins which extend from the north to the south, with their heads rising toward the west, are no less rich in metals than those whose heads rise toward the east. it may be denied that the heat of the sun draws the metallic material out of these veins; for though it draws up vapours from the surface of the ground, the rays of the sun do not penetrate right down to the depths; because the air of a tunnel which is covered and enveloped by solid earth to the depth of only two fathoms is cold in summer, for the intermediate earth holds in check the force of the sun. having observed this fact, the inhabitants and dwellers of very hot regions lie down by day in caves which protect them from the excessive ardour of the sun. therefore it is unlikely that the sun draws out from within the earth the metallic bodies. indeed, it cannot even dry the moisture of many places abounding in veins, because they are protected and shaded by the trees. furthermore, certain miners, out of all the different kinds of metallic veins, choose those which i have described, and others, on the contrary, reject copper mines which are of this sort, so that there seems to be no reason in this. for what can be the reason if the sun draws no copper from copper veins, that it draws silver from silver veins, and gold from gold veins? moreover, some miners, of whose number was calbus[ ], distinguish between the gold-bearing rivers and streams. a river, they say, or a stream, is most productive of fine and coarse grains of gold when it comes from the east and flows to the west, and when it washes against the foot of mountains which are situated in the north, and when it has a level plain toward the south or west. in the second place, they esteem a river or a stream which flows in the opposite course from the west toward the east, and which has the mountains to the north and the level plain to the south. in the third place, they esteem the river or the stream which flows from the north to the south and washes the base of the mountains which are situated in the east. but they say that the river or stream is least productive of gold which flows in a contrary direction from the south to the north, and washes the base of mountains which are situated in the west. lastly, of the streams or rivers which flow from the rising sun toward the setting sun, or which flow from the northern parts to the southern parts, they favour those which approach the nearest to the lauded ones, and say they are more productive of gold, and the further they depart from them the less productive they are. such are the opinions held about rivers and streams. now, since gold is not generated in the rivers and streams, as we have maintained against albertus[ ] in the book entitled "_de subterraneorum ortu et causis_," book v, but is torn away from the veins and stringers and settled in the sands of torrents and water-courses, in whatever direction the rivers or streams flow, therefore it is reasonable to expect to find gold therein; which is not opposed by experience. nevertheless, we do not deny that gold is generated in veins and stringers which lie under the beds of rivers or streams, as in other places. end of book iii. footnotes: [ ] modern nomenclature in the description of ore-deposits is so impregnated with modern views of their origin, that we have considered it desirable in many instances to adopt the latin terms used by the author, for we believe this method will allow the reader greater freedom of judgment as to the author's views. the latin names retained are usually expressive even to the non-latin student. in a general way, a _vena profunda_ is a fissure vein, a _vena dilatata_ is a bedded deposit, and a _vena cumulata_ an impregnation, or a replacement or a _stockwerk_. the _canales_, as will appear from the following footnote, were ore channels. "the seams of the rocks" (_commissurae saxorum_) are very puzzling. the author states, as appears in the following note, that they are of two kinds,--contemporaneous with the formation of the rocks, and also of the nature of veinlets. however, as to their supposed relation to the strike of veins, we can offer no explanation. there are passages in this chapter where if the word "ore-shoot" were introduced for "seams in the rocks" the text would be intelligible. that is, it is possible to conceive the view that the determination of whether an east-west vein ran east or ran west was dependent on the dip of the ore-shoot along the strike. this view, however, is utterly impossible to reconcile with the description and illustration of _commissurae saxorum_ given on page , where they are defined as the finest stringers. the following passage from the _nützliche bergbüchlin_ (see appendix), reads very much as though the dip of ore-shoots was understood at this time in relation to the direction of veins. "every vein (_gang_) has two (outcrops) _ausgehen_, one of the _ausgehen_ is toward daylight along the whole length of the vein, which is called the _ausgehen_ of the whole vein. the other _ausgehen_ is contrary to or toward the strike (_streichen_) of the vein, according to its rock (_gestein_), that is called the _gesteins ausgehen_; for instance, every vein that has its strike from east to west has its _gesteins ausgehen_ to the east, and _vice-versa_." agricola's classification of ore-deposits, after the general distinction between alluvial and _in situ_ deposits, is based entirely upon form, as will be seen in the quotation below relating to the origin of _canales_. the german equivalents in the glossary are as follows:-- fissure vein (_vena profunda_) _gang._ bedded deposit (_vena dilatata_) _schwebender gang oder fletze._ stockwerk or impregnation (_vena cumulata_) _geschute oder stock._ stringer (_fibra_) _klufft._ seams or joints (_commissurae saxorum_) _absetzen des gesteins._ it is interesting to note that in _de natura fossilium_ he describes coal and salt, and later in _de re metallica_ he describes the mannsfeld copper schists, as all being _venae dilatatae_. this nomenclature and classification is not original with agricola. pliny (xxxiii, ) uses the term _vena_ with no explanations, and while agricola coined the latin terms for various kinds of veins, they are his transliteration of german terms already in use. the _nützliche bergbüchlin_ gives this same classification. historical note on the theory of ore deposits. prior to agricola there were three schools of explanation of the phenomena of ore deposits, the orthodox followers of the genesis, the greek philosophers, and the alchemists. the geology of the genesis--the contemporaneous formation of everything--needs no comment other than that for anyone to have proposed an alternative to the dogma of the orthodox during the middle ages, required much independence of mind. of the greek views--which are meagre enough--that of the peripatetics greatly dominated thought on natural phenomena down to the th century. aristotle's views may be summarized: the elements are earth, water, air, and fire; they are transmutable and never found pure, and are endowed with certain fundamental properties which acted as an "efficient" force upon the material cause--the elements. these properties were dryness and dampness and heat and cold, the latter being active, the former passive. further, the elements were possessed of weight and lightness, for instance earth was absolutely heavy, fire absolutely light. the active and passive properties existed in binary combinations, one of which is characteristic, _i.e._, "earth" is cold and dry, water damp and cold, fire hot and dry, air hot and wet; transmutation took place, for instance, by removing the cold from water, when air resulted (really steam), and by removing the dampness from water, when "earth" resulted (really any dissolved substance). the transmutation of the elements in the earth (meaning the globe) produces two "exhalations," the one fiery (probably meaning gases), the other damp (probably meaning steam). the former produces stones, the latter the metals. theophrastus (on stones, i to vii.) elaborates the views of aristotle on the origin of stones, metals, etc.: "of things formed in the earth some have their origin from water, others from earth. water is the basis of metals, silver, gold, and the rest; 'earth' of stones, as well the more precious as the common.... all these are formed by solidification of matter pure and equal in its constituent parts, which has been brought together in that state by mere afflux or by means of some kind of percolation, or separated.... the solidification is in some of these substances due to heat and in others to cold." (based on hill's trans., pp. - ). that is, the metals inasmuch as they become liquid when heated must be in a large part water, and, like water, they solidify with cold. therefore, the "metals are cold and damp." stones, on the other hand, solidify with heat and do not liquefy, therefore, they are "dry and hot" and partake largely of "earth." this "earth" was something indefinite, but purer and more pristine than common clay. in discussing the ancient beliefs with regard to the origin of deposits, we must not overlook the import of the use of the word "vein" (_vena_) by various ancient authors including pliny (xxxiii, ), although he offers no explanation of the term. during the middle ages there arose the horde of alchemists and astrologers, a review of the development of whose muddled views is but barren reading. in the main they held more or less to the peripatetic view, with additions of their own. geber ( th (?) century, see appendix b) propounded the conception that all metals were composed of varying proportions of "spiritual" sulphur and quicksilver, and to these albertus magnus added salt. the astrologers contributed the idea that the immediate cause of the metals were the various planets. the only work devoted to description of ore-deposits prior to agricola was the _bergbüchlin_ (about , see appendix b), and this little book exhibits the absolute apogee of muddled thought derived from the peripatetics, the alchemists, and the astrologers. we believe it is of interest to reproduce the following statement, if for no other reason than to indicate the great advance in thought shown by agricola. "the first chapter or first part; on the common origin of ore, whether silver, gold, tin, copper, iron, or lead ore, in which they all appear together, and are called by the common name of metallic ore. it must be noticed that for the washing or smelting of metallic ore, there must be the one who works and the thing that is worked upon, or the material upon which the work is expended. the general worker (efficient force) on the ore and on all things that are born, is the heavens, its movement, its light and influences, as the philosophers say. the influence of the heavens is multiplied by the movement of the firmaments and the movements of the seven planets. therefore, every metallic ore receives a special influence from its own particular planet, due to the properties of the planet and of the ore, also due to properties of heat, cold, dampness, and dryness. thus gold is of the sun or its influence, silver of the moon, tin of jupiter, copper of venus, iron of mars, lead of saturn, and quicksilver of mercury. therefore, metals are often called by these names by hermits and other philosophers. thus gold is called the sun, in latin _sol_, silver is called the moon, in latin _luna_, as is clearly stated in the special chapters on each metal. thus briefly have we spoken of the 'common worker' of metal and ore. but the thing worked upon, or the common material of all metals, according to the opinion of the learned, is sulphur and quicksilver, which through the movement and influence of the heavens must have become united and hardened into one metallic body or one ore. certain others hold that through the movement and the influence of the heavens, vapours or _braden_, called mineral exhalations, are drawn up from the depths of the earth, from sulphur and quicksilver, and the rising fumes pass into the veins and stringers and are united through the effect of the planets and made into ore. certain others hold that metal is not formed from quicksilver, because in many places metallic ore is found and no quicksilver. but instead of quicksilver they maintain a damp and cold and slimy material is set up on all sulphur which is drawn out from the earth, like your perspiration, and from that mixed with sulphur all metals are formed. now each of these opinions is correct according to a good understanding and right interpretation; the ore or metal is formed from the fattiness of the earth as the material of the first degree (primary element), also the vapours or _braden_ on the one part and the materials on the other part, both of which are called quicksilver. likewise in the mingling or union of the quicksilver and the sulphur in the ore, the sulphur is counted the male and quicksilver the female, as in the bearing or conception of a child. also the sulphur is a special worker in ore or metal. "the second chapter or part deals with the general capacity of the mountain. although the influence of the heavens and the fitness of the material are necessary to the formation of ore or metal, yet these are not enough thereto. but there must be adaptability of the natural vessel in which the ore is formed, such are the veins, namely _steinendegange_, _flachgange_, _schargange_, _creutzgange_, or as these may be termed in provincial names. also the mineral force must have easy access to the natural vessel such as through the _kluffte_ (stringers), namely _hengkluft_, _querklufte_, _flachekluffte_, _creutzklufft_, and other occasional _flotzwerk_, according to their various local names. also there must be a suitable place in the mountain which the veins and stringers can traverse." agricola's views on the origin of ore deposits. agricola rejected absolutely the biblical view which, he says, was the opinion of the vulgar; further, he repudiates the alchemistic and astrological view with great vigour. there can be no doubt, however, that he was greatly influenced by the peripatetic philosophy. he accepted absolutely the four elements--earth, fire, water, and air, and their "binary" properties, and the theory that every substance had a material cause operated upon by an efficient force. beyond this he did not go, and a large portion of _de ortu et causis_ is devoted to disproof of the origin of metals and stones from the peripatetic "exhalations." no one should conclude that agricola's theories are set out with the clarity of darwin or lyell. however, the matter is of such importance in the history of the theory of ore-deposits, and has been either so ignored or so coloured by the preconceptions of narrators, that we consider it justifiable to devote the space necessary to a reproduction of his own statements in _de ortu et causis_ and other works. before doing so we believe it will be of service to readers to summarize these views, and in giving quotations from the author's other works, to group them under special headings, following the outline of his theory given below. his theory was:-- ( ) openings in the earth (_canales_) were formed by the erosion of subterranean waters. ( ) these ground waters were due (_a_) to the infiltration of the surface waters, rain, river, and sea water; (_b_) to the condensation of steam (_halitus_) arising from the penetration of the surface waters to greater depths,--the production of this _halitus_ being due to subterranean heat, which in his view was in turn due in the main to burning bitumen (a comprehensive genera which embraced coal). ( ) the filling of these _canales_ is composed of "earth," "solidified juices," "stone," metals, and "compounds," all deposited from water and "juices" circulating in the _canales_. (see also note , page ). "earth" comprises clay, mud, ochre, marl, and "peculiar earths" generally. the origin of these "earths" was from rocks, due to erosion, transportation, and deposition by water. "solidified juices" (_succi concreti_) comprised salt, soda, vitriol, bitumen, etc., being generally those substances which he conceived were soluble in and deposited from water. "stones" comprised precious, semi-precious, and unusual stones, such as quartz, fluor-spar, etc., as distinguished from country rock; the origin of these he attributed in minor proportion to transportation of fragments of rock, but in the main to deposits from ordinary mineral juice and from "stone juice" (_succus lapidescens_). metals comprised the seven traditional metals; the "compounds" comprised the metallic minerals; and both were due to deposition from juices, the compounds being due to a mixture of juices. the "juices" play the most important part in agricola's theory. each substance had its own particular juice, and in his theory every substance had a material and an efficient cause, the first being the juice, the second being heat or cold. owing to the latter the juices fell into two categories--those solidified by heat (_i.e._, by evaporation, such as salt), and those solidified by cold, (_i.e._, because metals melt and flow by heat, therefore their solidification was due to cold, and the juice underwent similar treatment). as to the origin of these juices, some were generated by the solution of their own particular substance, but in the main their origin was due to the combination of "dry things," such as "earth," with water, the mixture being heated, and the resultant metals depended upon the proportions of "earth" and water. in some cases we have been inclined to translate _succus_ (juice) as "solution," but in other cases it embraced substances to which this would not apply, and we feared implying in the text a chemical understanding not warranted prior to the atomic theory. in order to distinguish between earths, (clays, etc.,) the peripatetic "earth" (a pure element) and the earth (the globe) we have given the two former in quotation marks. there is no doubt some confusion between earth (clays, etc.) and the peripatetic "earth," as the latter was a pure substance not found in its pristine form in nature; it is, however, difficult to distinguish between the two. origin of canales (_de ortu_, p. ). "i now come to the _canales_ in the earth. these are veins, veinlets, and what are called 'seams in the rocks.' these serve as vessels or receptacles for the material from which minerals (_res fossiles_) are formed. the term _vena_ is most frequently given to what is contained in the _canales_, but likewise the same name is applied to the _canales_ themselves. the term vein is borrowed from that used for animals, for just as their veins are distributed through all parts of the body, and just as by means of the veins blood is diffused from the liver throughout the whole body, so also the veins traverse the whole globe, and more particularly the mountainous districts; and water runs and flows through them. with regard to veinlets or stringers and 'seams in the rocks,' which are the thinnest stringers, the following is the mode of their arrangement. veins in the earth, just like the veins of an animal, have certain veinlets of their own, but in a contrary way. for the larger veins of animals pour blood into the veinlets, while in the earth the humours are usually poured from the veinlets into the larger veins, and rarely flow from the larger into the smaller ones. as for the seams in the rocks (_commissurae saxorum_) we consider that they are produced by two methods: by the first, which is peculiar to themselves, they are formed at the same time as the rocks, for the heat bakes the refractory material into stone and the non-refractory material similarly heated exhales its humours and is made into 'earth,' generally friable. the other method is common also to veins and veinlets, when water is collected into one place it softens the rock by its liquid nature, and by its weight and pressure breaks and divides it. now, if the rock is hard, it makes seams in the rocks and veinlets, and if it is not too hard it makes veins. however, if the rocks are not hard, seams and veinlets are created as well as veins. if these do not carry a very large quantity of water, or if they are pressed by a great volume of it, they soon discharge themselves into the nearest veins. the following appears to be the reason why some veinlets or stringers and veins are _profundae_ and others _dilatatae_. the force of the water crushes and splits the brittle rocks; and when they are broken and split, it forces its way through them and passes on, at one time in a downward direction, making small and large _venae profundae_, at another time in a lateral direction, in which way _venae dilatatae_ are formed. now since in each class there are found some which are straight, some inclined, and some crooked, it should be explained that the water makes the _vena profunda_ straight when it runs straight downward, inclined when it runs in an inclined direction; and that it makes a _vena dilatata_ straight when it runs horizontally to the right or left, and in a similar way inclined when it runs in a sloping direction. stringers and large veins of the _profunda_ sort, extending for considerable lengths, become crooked from two causes. in one case when narrow veins are intersected by wide ones, then the latter bend or drag the former a little. in the other case, when the water runs against very hard rock, being unable to break through, it goes around the nearest way, and the stringers and veins are formed bent and crooked. this last is also the reason we sometimes see crooked small and large _venae dilatatae_, not unlike the gentle rise and fall of flowing water. next, _venae profundae_ are wide, either because of abundant water or because the rock is fragile. on the other hand, they are narrow, either because but little water flows and trickles through them, or because the rock is very hard. the _venae dilatatae_, too, for the same reasons, are either thin or thick. there are other differences, too, in stringers and veins, which i will explain in my work _de re metallica_.... there is also a third kind of vein which, as it cannot be described as a wide _vena profunda_, nor as a thick _vena dilatata_, we will call a _vena cumulata_. these are nothing else than places where some species of mineral is accumulated; sometimes exceeding in depth and also in length and breadth feet; sometimes, or rather generally, not so deep nor so long, nor so wide. these are created when water has broken away the rock for such a length, breadth, and thickness, and has flung aside and ejected the stones and sand from the great cavern which is thus made; and afterward when the mouth is obstructed and closed up, the whole cavern is filled with material from which there is in time produced some one or more minerals. now i have stated when discoursing on the origin of subterranean humours, that water erodes away substances inside the earth, just as it does those on the surface, and least of all does it shun minerals; for which reason we may daily see veinlets and veins sometimes filled with air and water, but void and empty of mining products, and sometimes full of these same materials. even those which are empty of minerals become finally obstructed, and when the rock is broken through at some other point the water gushes out. it is certain that old springs are closed up in some way and new ones opened in others. in the same manner, but much more easily and quickly than in the solid rock, water produces stringers and veins in surface material, whether it be in plains, hills, or mountains. of this kind are the stringers in the banks of rivers which produce gold, and the veins which produce peculiar earth. so in this manner in the earth are made _canales_ which bear minerals." origin of ground waters. (_de ortu_ p. ). "... besides rain there is another kind of water by which the interior of the earth is soaked, so that being heated it can continually give off _halitus_, from which arises a great and abundant force of waters." in description of the _modus operandi_ of _halitum_, he says (p. ): "... _halitus_ rises to the upper parts of the _canales_, where the congealing cold turns it into water, which by its gravity and weight again runs down to the lowest parts and increases the flow of water if there is any. if any finds its way through a _canales dilatata_ the same thing happens, but it is carried a long way from its place of origin. the first phase of distillation teaches us how this water is produced, for when that which is put into the ampulla is warmed it evaporates (_expirare_), and this _halitus_ rising into the operculum is converted by cold into water, which drips through the spout. in this way water is being continually created underground." (_de ortu_, p. ): "and so we know from all this that of the waters which are under the earth, some are collected from rain, some arise from _halitus_ (steam), some from river-water, some from sea-water; and we know that the _halitum_ is produced within the earth partly from rain-water, partly from river-water, and partly from sea-water." it would require too much space to set out agricola's views upon the origin of the subterranean heat which produced this steam. it is an involved theory embracing clashing winds, burning bitumen, coal, etc., and is fully set out in the latter part of book ii, _de ortu et causis_. origin of gangue minerals. it is necessary to bear in mind that agricola divided minerals (_res fossiles_--"things dug up," see note , p. ) into "earths," "solidified juices," "stones," "metals," and "compounds;" and, further, to bear in mind that in his conception of the origin of things generally, he was a disciple of the peripatetic logic of a "material substance" and an "efficient force," as mentioned above. as to the origin of "earths," he says (_de ortu_, p. ): "pure and simple 'earth' originates in the _canales_ in the following way: rain water, which is absorbed by the surface of the earth, first of all penetrates and passes into the inner parts of the earth and mixes with it; next, it is collected from all sides into stringers and veins, where it, and sometimes water of other origin, erodes the 'earth' away,--a great quantity of it if the stringers and veins are in 'earth,' a small quantity if they are in rock. the softer the rock is, the more the water wears away particles by its continual movement. to this class of rock belongs limestone, from which we see chalk, clay, and marl, and other unctuous 'earths' made; also sandstone, from which are made those barren 'earths' which we may see in ravines and on bare rocks. for the rain softens limestone or sandstone and carries particles away with it, and the sediment collects together and forms mud, which afterward solidifies into some kind of 'earth.' in a similar way under the ground the power of water softens the rock and dissolves the coarser fragments of stone. this is clearly shown by the following circumstance, that frequently the powder of rock or marble is found in a soft state and as if partly dissolved. now, the water carries this mixture into the course of some underground _canalis_, or dragging it into narrow places, filters away. and in each case the water flows away and a pure and uniform material is left from which 'earth' is made.... particles of rock, however, are only by force of long time so softened by water as to become similar to particles of 'earth.' it is possible to see 'earth' being made in this way in underground _canales_ in the earth, when drifts or tunnels are driven into the mountains, or when shafts are sunk, for then the _canales_ are laid bare; also it can be seen above ground in ravines, as i have said, or otherwise disclosed. for in both cases it is clear to the eye that they are made out of the 'earth' or rocks, which are often of the same colour. and in just the same way they are made in the springs which the veins discharge. since all those things which we see with our eyes and which are perceived with our senses, are more clearly understood than if they were learnt by means of reasoning, we deem it sufficient to explain by this argument our view of the origin of 'earth.' in the manner which i have described, 'earths' originate in veins and veinlets, seams in the rocks, springs, ravines, and other openings, therefore all 'earths' are made in this way. as to those that are found in underground _canales_ which do not appear to have been derived from the earth or rock adjoining, these have undoubtedly been carried by the water for a greater distance from their place of origin; which may be made clear to anyone who seeks their source." on the origin of solidified juices he states (_de ortu_, p. ): "i will now speak of solidified juices (_succi concreti_). i give this name to those minerals which are without difficulty resolved into liquids (_humore_). some stones and metals, even though they are themselves composed of juices, have been compressed so solidly by the cold that they can only be dissolved with difficulty or not at all.... for juices, as i said above, are either made when dry substances immersed in moisture are cooked by heat, or else they are made when water flows over 'earth,' or when the surrounding moisture corrodes metallic material; or else they are forced out of the ground by the power of heat alone. therefore, solidified juices originate from liquid juices, which either heat or cold have condensed. but that which heat has dried, fire reduces to dust, and moisture dissolves. not only does warm or cold water dissolve certain solidified juices, but also humid air; and a juice which the cold has condensed is liquefied by fire and warm water. a salty juice is condensed into salt; a bitter one into soda; an astringent and sharp one into alum or into vitriol. skilled workmen in a similar way to nature, evaporate water which contains juices of this kind until it is condensed; from salty ones they make salt, from aluminous ones alum, from one which contains vitriol they make vitriol. these workmen imitate nature in condensing liquid juices with heat, but they cannot imitate nature in condensing them by cold. from an astringent juice not only is alum made and vitriol, but also _sory_, _chalcitis_, and _misy_, which appears to be the 'flower' of vitriol, just as _melanteria_ is of _sory_. (see note on p. for these minerals.) when humour corrodes pyrites so that it is friable, an astringent juice of this kind is obtained." on the origin of stones (_de ortu_, p. ), he states: "it is now necessary to review in a few words what i have said as to all of the material from which stones are made; there is first of all mud; next juice which is solidified by severe cold; then fragments of rock; afterward stone juice (_succus lapidescens_), which also turns to stone when it comes out into the air; and lastly, everything which has pores capable of receiving a stony juice." as to an "efficient force," he states (p. ): "but it is now necessary that i should explain my own view, omitting the first and antecedent causes. thus the immediate causes are heat and cold; next in some way a stony juice. for we know that stones which water has dissolved, are solidified when dried by heat; and on the contrary, we know that stones which melt by fire, such as quartz, solidify by cold. for solidification and the conditions which are opposite thereto, namely, dissolving and liquefying, spring from causes which are the opposite to each other. heat, driving the water (_humorem_) out of a substance, makes it hard; and cold, by withdrawing the air, solidifies the same stone firmly. but if a stony juice, either alone or mixed with water, finds its way into the pores either of plants or animals ... it creates stones.... if stony juice is obtained in certain stony places and flows through the veins, for this reason certain springs, brooks, streams, and lakes, have the power of turning things to stone." on the origin of metals, he says (_de ortu_, p. ): "having now refuted the opinions of others, i must explain what it really is from which metals are produced. the best proof that there is water in their materials is the fact that they flow when melted, whereas they are again solidified by the cold of air or water. this, however, must be understood in the sense that there is more water in them and less 'earth'; for it is not simply water that is their substance but water mixed with 'earth.' and such a proportion of 'earth' is in the mixture as may obscure the transparency of the water, but not remove the brilliance which is frequently in unpolished things. again, the purer the mixture, the more precious the metal which is made from it, and the greater its resistance to fire. but what proportion of 'earth' is in each liquid from which a metal is made no mortal can ever ascertain, or still less explain, but the one god has known it, who has given certain sure and fixed laws to nature for mixing and blending things together. it is a juice (_succus_) then, from which metals are formed; and this juice is created by various operations. of these operations the first is a flow of water which softens the 'earth' or carries the 'earth' along with it, thus there is a mixture of 'earth' and water, then the power of heat works upon the mixtures so as to produce that kind of a juice. we have spoken of the substance of metals; we must now speak of their efficient cause.... (p. ): we do not deny the statement of albertus magnus that the mixture of 'earth' and water is baked by subterranean heat to a certain denseness, but it is our opinion that the juice so obtained is afterward solidified by cold so as to become a metal.... we grant, indeed, that heat is the efficient cause of a good mixture of elements, and also cooks this same mixture into a juice, but until this juice is solidified by cold it is not a metal.... (p. ): this view of aristotle is the true one. for metals melt through the heat and somehow become softened; but those which have become softened through heat are again solidified by the influence of cold, and, on the contrary, those which become softened by moisture are solidified by heat." on the origin of compounds, he states (_de ortu_, p. ): "there now remain for our consideration the compound minerals (_mistae_), that is to say, minerals which contain either solidified juice (_succus concretus_) and 'stone,' or else metal or metals and 'stone,' or else metal-coloured 'earth,' of which two or more have so grown together by the action of cold that one body has been created. by this sign they are distinguished from mixed minerals (_composita_), for the latter have not one body. for example, pyrites, galena, and ruby silver are reckoned in the category of compound minerals, whereas we say that metallic 'earths' or stony 'earths' or 'earths' mingled with juices, are mixed minerals; or similarly, stones in which metal or solidified juices adhere, or which contain 'earth.' but of both these classes i will treat more fully in my book _de natura fossilium_. i will now discuss their origin in a few words. a compound mineral is produced when either a juice from which some metal is obtained, or a _humour_ and some other juice from which stone is obtained, are solidified by cold, or when two or more juices of different metals mixed with the juice from which stone is made, are condensed by the same cold, or when a metallic juice is mixed with 'earth' whose whole mass is stained with its colour, and in this way they form one body. to the first class belongs _galena_, composed of lead juice and of that material which forms the substance of opaque stone. similarly, transparent ruby silver is made out of silver juice and the juice which forms the substance of transparent stone; when it is smelted into pure silver, since from it is separated the transparent juice, it is no longer transparent. then too, there is pyrites, or _lapis fissilis_, from which sulphur is melted. to the second kind belongs that kind of pyrites which contains not only copper and stone, but sometimes copper, silver, and stone; sometimes copper, silver, gold, and stone; sometimes silver, lead, tin, copper and silver glance. that compound minerals consist of stone and metal is sufficiently proved by their hardness; that some are made of 'earth' and metal is proved from brass, which is composed of copper and calamine; and also proved from white brass, which is coloured by artificial white arsenic. sometimes the heat bakes some of them to such an extent that they appear to have flowed out of blazing furnaces, which we may see in the case of _cadmia_ and pyrites. a metallic substance is produced out of 'earth' when a metallic juice impregnating the 'earth' solidifies with cold, the 'earth' not being changed. a stony substance is produced when viscous and non-viscous 'earth' are accumulated in one place and baked by heat; for then the viscous part turns into stone and the non-viscous is only dried up." the origin of juices. the portion of agricola's theory surrounding this subject is by no means easy to follow in detail, especially as it is difficult to adjust one's point of view to the peripatetic elements, fire, water, earth, and air, instead of to those of the atomic theory which so dominates our every modern conception. that agricola's 'juice' was in most cases a solution is indicated by the statement (_de ortu_, p. ): "nor is juice anything but water, which on the other hand has absorbed 'earth' or has corroded or touched metal and somehow become heated." that he realized the difference between mechanical suspension and solution is evident from (_de ortu_, p. ): "a stony juice differs from water which has abraded something from rock, either because it has more of that which deposits, or because heat, by cooking water of that kind, has thickened it, or because there is something in it which has powerful astringent properties." much of the author's notion of juices has already been given in the quotations regarding various minerals, but his most general statement on the subject is as follows:--(_de ortu_, p. ): "juices, however, are distinguished from water by their density (_crassitudo_), and are generated in various ways--either when dry things are soaked with moisture and the mixture is heated, in which way by far the greatest part of juices arise, not only inside the earth, but outside it; or when water running over the earth is made rather dense, in which way, for the most part the juice becomes salty and bitter; or when the moisture stands upon metal, especially copper, and corrodes it, and in this way is produced the juice from which chrysocolla originates. similarly, when the moisture corrodes friable cupriferous pyrites an acrid juice is made from which is produced vitriol and sometimes alum; or, finally, juices are pressed out by the very force of the heat from the earth. if the force is great the juice flows like pitch from burning pine ... in this way we know a kind of bitumen is made in the earth. in the same way different kinds of moisture are generated in living bodies, so also the earth produces waters differing in quality, and in the same way juices." conclusion. if we strip his theory of the necessary influence of the state of knowledge of his time, and of his own deep classical learning, we find two propositions original with agricola, which still to-day are fundamentals: ( ) that ore channels were of origin subsequent to their containing rocks; ( ) that ores were deposited from solutions circulating in these openings. a scientist's work must be judged by the advancement he gave to his science, and with this gauge one can say unhesitatingly that the theory which we have set out above represents a much greater step from what had gone before than that of almost any single observer since. moreover, apart from any tangible proposition laid down, the deduction of these views from actual observation instead of from fruitless speculation was a contribution to the very foundation of natural science. agricola was wrong in attributing the creation of ore channels to erosion alone, and it was not until von oppel (_anleitung zur markscheidekunst_, dresden, and other essays), two centuries after agricola, that the positive proposition that ore channels were due to fissuring was brought forward. von oppel, however, in neglecting channels due to erosion (and in this term we include solution) was not altogether sound. nor was it until late in the th century that the filling of ore channels by deposition from solutions was generally accepted. in the meantime, agricola's successors in the study of ore deposits exhibited positive retrogression from the true fundamentals advocated by him. gesner, utman, meier, lohneys, barba, rössler, becher, stahl, henckel, and zimmerman, all fail to grasp the double essentials. other writers of this period often enough merely quote agricola, some not even acknowledging the source, as, for instance, pryce (_mineralogia cornubiensis_, london, ) and williams (natural history of the mineral kingdom, london, ). after von oppel, the two fundamental principles mentioned were generally accepted, but then arose the complicated and acrimonious discussion of the origin of solutions, and nothing in agricola's view was so absurd as werner's contention (_neue theorie von der entstehung der gänge_, freiberg, ) of the universal chemical deluge which penetrated fissures open at the surface. while it is not the purpose of these notes to pursue the history of these subjects subsequent to the author's time, it is due to him and to the current beliefs as to the history of the theory of ore deposits, to call the attention of students to the perverse representation of agricola's views by werner (op. cit.) upon which most writers have apparently relied. why this author should be (as, for instance, by posepny, amer. inst. mining engineers, ) so generally considered the father of our modern theory, can only be explained by a general lack of knowledge of the work of previous writers on ore deposition. not one of the propositions original with werner still holds good, while his rejection of the origin of solutions within the earth itself halted the march of advance in thought on these subjects for half a century. it is our hope to discuss exhaustively at some future time the development of the history of this, one of the most far-reaching of geologic hypotheses. [ ] the latin _vena_, "vein," is also used by the author for ore; hence this descriptive warning as to its intended double use. [ ] the endeavour to discover the origin of the compass with the chinese, arabs, or other orientals having now generally ceased, together with the idea that the knowledge of the lodestone involved any acquaintance with the compass, it is permissible to take a rational view of the subject. the lodestone was well known even before plato and aristotle, and is described by theophrastus (see note , p. .) the first authentic and specific mention of the compass appears to be by alexander neckam (an englishman who died in ), in his works _de utensilibus_ and _de naturis rerum_. the first tangible description of the instrument was in a letter to petrus peregrinus de maricourt, written in , a translation of which was published by sir sylvanus thompson (london, ). his circle was divided into four quadrants and these quarters divided into degrees each. the first mention of a compass in connection with mines so far as we know is in the _nützlich bergbüchlin_, a review of which will be found in appendix b. this book, which dates from , gives a compass much like the one described above by agricola. it is divided in like manner into two halves of divisions each. the four cardinal points being marked _mitternacht_, _morgen_, _mittag_, and _abend_. thus the directions read were referred to as ii. after midnight, etc. according to joseph carne (trans. roy. geol. socy. of cornwall, vol. ii, ), the cornish miners formerly referred to north-south veins as o'clock veins; south-east north-west veins as o'clock veins, etc. [ ] _crudariis._ pliny (xxxiii., ), says:--"_argenti vena in summo reperta crudaria appellatur._" "silver veins discovered at the surface are called _crudaria._" the german translator of agricola uses the term _sylber gang_--silver vein, obviously misunderstanding the author's meaning. [ ] it might be considered that the term "outcrop" could be used for "head," but it will be noticed that a _vena dilatata_ would thus be stated to have no outcrop. [ ] it is possible that "veinlets" would be preferred by purists, but the word "stringer" has become fixed in the nomenclature of miners and we have adopted it. the old english term was "stringe," and appears in edward manlove's "rhymed chronicle," london, ; pryce's, _mineralogia cornubiensis_, london, , pp. and ; mawe's "mineralogy of devonshire," london, , p. , etc., etc. [ ] _subdialis._ "in the open air." the glossary gives the meaning as _ein tag klufft oder tag gehenge_--a surface stringer. [ ] the following from chapter iv of the _nützlich bergbüchlin_ (see appendix b) may indicate the source of the theory which agricola here discards:--"as to those veins which are most profitable to work, it must be remarked that the most suitable location for the vein is on the slope of the mountain facing south, so its strike is from vii or vi east to vi or vii west. according to the above-mentioned directions, the outcrop of the whole vein should face north, its _gesteins ausgang_ toward the east, its hangingwall toward the south, and its footwall toward the north, for in such mountains and veins the influence of the planets is conveniently received to prepare the matter out of which the silver is to be made or formed.... the other strikes of veins from between east and south to the region between west and north are esteemed more or less valuable, according to whether they are nearer or further away from the above-mentioned strikes, but with the same hangingwall, footwall, and outcrops. but the veins having their strike from north to south, their hangingwall toward the west, their footwall and their outcrops toward the east, are better to work than veins which extend from south to north, whose hangingwalls are toward the east, and footwalls and outcrops toward the west. although the latter veins sometimes yield solid and good silver ore, still it is not sure and certain, because the whole mineral force is completely scattered and dispersed through the outcrop, etc." [ ] the names in the latin are given as _donum divinum_--"god's gift," and _coelestis exercitus_--"heavenly host." the names given in the text are from the german translation. the former of these mines was located in the valley of joachim, where agricola spent many years as the town physician at joachimsthal. it is of further interest, as agricola obtained an income from it as a shareholder. he gives the history of the mine (_de veteribus et novis metallis_, book i.), as follows:--"the mines at abertham were discovered, partly by chance, partly by science. in the eleventh year of charles v. ( ), on the th of february, a poor miner, but one skilled in the art of mining, dwelt in the middle of the forest in a solitary hut, and there tended the cattle of his employer. while digging a little trench in which to store milk, he opened a vein. at once he washed some in a bowl and saw particles of the purest silver settled at the bottom. overcome with joy he informed his employer, and went to the _bergmeister_ and petitioned that official to give him a head mining lease, which in the language of our people he called _gottsgaab_. then he proceeded to dig the vein, and found more fragments of silver, and the miners were inspired with great hopes as to the richness of the vein. although such hopes were not frustrated, still a whole year was spent before they received any profits from the mine; whereby many became discouraged and did not persevere in paying expenses, but sold their shares in the mine; and for this reason, when at last an abundance of silver was being drawn out, a great change had taken place in the ownership of the mine; nay, even the first finder of the vein was not in possession of any share in it, and had spent nearly all the money which he had obtained from the selling of his shares. then this mine yielded such a quantity of pure silver as no other mine that has existed within our own or our fathers' memories, with the exception of the st. george at schneeberg. we, as a shareholder, through the goodness of god, have enjoyed the proceeds of this 'god's gift' since the very time when the mine began first to bestow such riches." later on in the same book he gives the following further information with regard to these mines:--"now if all the individual mines which have proved fruitful in our own times are weighed in the balance, the one at annaberg, which is known as the _himmelsch hoz_, surpasses all others. for the value of the silver which has been dug out has been estimated at , rhenish gulden. next to this comes the lead mine in joachimsthal, whose name is the _sternen_, from which as much silver has been dug as would be equivalent to , rhenish gulden; from the gottsgaab at abertham, explained before, the equivalent of , . but far before all others within our fathers' memory stands the st. george of schneeberg, whose silver has been estimated as being equal to two million rhenish gulden." a rhenish gulden was about . shillings, or, say, $ . . however, the ratio value of silver to gold at this period was about . to one, or in other words an ounce of silver was worth about a gulden, so that, for purposes of rough calculation, one might say that the silver product mentioned in gulden is practically of the same number of ounces of silver. moreover, it must be remembered that the purchasing power of money was vastly greater then. [ ] the following passage occurs in the _nützlich bergbüchlin_ (chap. v.), which is interesting on account of the great similarity to agricola's quotation:--"the best position of the stream is when it has a cliff beside it on the north and level ground on the south, but its current should be from east to west--that is the most suitable. the next best after this is from west to east, with the same position of the rocks as already stated. the third in order is when the stream flows from north to south with rocks toward the east, but the worst flow of water for the preparation of gold is from south to north if a rock or hill rises toward the west." calbus was probably the author of this booklet. [ ] albertus magnus. book iv. the third book has explained the various and manifold varieties of veins and stringers. this fourth book will deal with mining areas and the method of delimiting them, and will then pass on to the officials who are connected with mining affairs[ ]. now the miner, if the vein he has uncovered is to his liking, first of all goes to the _bergmeister_ to request to be granted a right to mine, this official's special function and office being to adjudicate in respect of the mines. and so to the first man who has discovered the vein the _bergmeister_ awards the head meer, and to others the remaining meers, in the order in which each makes his application. the size of a meer is measured by fathoms, which for miners are reckoned at six feet each. the length, in fact, is that of a man's extended arms and hands measured across his chest; but different peoples assign to it different lengths, for among the greeks, who called it an [greek: orguia], it was six feet, among the romans five feet. so this measure which is used by miners seems to have come down to the germans in accordance with the greek mode of reckoning. a miner's foot approaches very nearly to the length of a greek foot, for it exceeds it by only three-quarters of a greek digit, but like that of the romans it is divided into twelve _unciae_[ ]. [illustration a (square with lengths and area): shape of a square meer.] now square fathoms are reckoned in units of one, two, three, or more "measures", and a "measure" is seven fathoms each way. mining meers are for the most part either square or elongated; in square meers all the sides are of equal length, therefore the numbers of fathoms on the two sides multiplied together produce the total in square fathoms. thus, if the shape of a "measure" is seven fathoms on every side, this number multiplied by itself makes forty-nine square fathoms. [illustration b (rectangle with lengths and area): shape of a long meer or double measure.] the sides of a long meer are of equal length, and similarly its ends are equal; therefore, if the number of fathoms in one of the long sides be multiplied by the number of fathoms in one of the ends, the total produced by the multiplication is the total number of square fathoms in the long meer. for example, the double measure is fourteen fathoms long and seven broad, which two numbers multiplied together make ninety-eight square fathoms. [illustration c (rectangle with lengths and area): shape of a head meer.] since meers vary in shape according to the different varieties of veins it is necessary for me to go more into detail concerning them and their measurements. if the vein is a _vena profunda_, the head meer is composed of three double measures, therefore it is forty-two fathoms in length and seven in width, which numbers multiplied together give two hundred and ninety-four square fathoms, and by these limits the _bergmeister_ bounds the owner's rights in a head-meer. [illustration a (rectangle with lengths and area): shape of a meer.] the area of every other meer consists of two double measures, on whichever side of the head meer it lies, or whatever its number in order may be, that is to say, whether next to the head meer, or second, third, or any later number. therefore, it is twenty-eight fathoms long and seven wide, so multiplying the length by the width we get one hundred and ninety-six square fathoms, which is the extent of the meer, and by these boundaries the _bergmeister_ defines the right of the owner or company over each mine. now we call that part of the vein which is first discovered and mined, the head-meer, because all the other meers run from it, just as the nerves from the head. the _bergmeister_ begins his measurements from it, and the reason why he apportions a larger area to the head-meer than to the others, is that he may give a suitable reward to the one who first found the vein and may encourage others to search for veins. since meers often reach to a torrent, or river, or stream, if the last meer cannot be completed it is called a fraction[ ]. if it is the size of a double measure, the _bergmeister_ grants the right of mining it to him who makes the first application, but if it is the size of a single measure or a little over, he divides it between the nearest meers on either side of it. it is the custom among miners that the first meer beyond a stream on that part of the vein on the opposite side is a new head-meer, and they call it the "opposite,"[ ] while the other meers beyond are only ordinary meers. formerly every head-meer was composed of three double measures and one single one, that is, it was forty-nine fathoms long and seven wide, and so if we multiply these two together we have three hundred and forty-three square fathoms, which total gives us the area of an ancient head-meer. [illustration b (rectangle with lengths and area): shape of an ancient head-meer.] every ancient meer was formed of a single measure, that is to say, it was seven fathoms in length and width, and was therefore square. in memory of which miners even now call the width of every meer which is located on a _vena profunda_ a "square"[ ]. the following was formerly the usual method of delimiting a vein: as soon as the miner found metal, he gave information to the _bergmeister_ and the tithe-gatherer, who either proceeded personally from the town to the mountains, or sent thither men of good repute, at least two in number, to inspect the metal-bearing vein. thereupon, if they thought it of sufficient importance to survey, the _bergmeister_ again having gone forth on an appointed day, thus questioned him who first found the vein, concerning the vein and the diggings: "which is your vein?" "which digging carried metal?" then the discoverer, pointing his finger to his vein and diggings, indicated them, and next the _bergmeister_ ordered him to approach the windlass and place two fingers of his right hand upon his head, and swear this oath in a clear voice: "i swear by god and all the saints, and i call them all to witness, that this is my vein; and moreover if it is not mine, may neither this my head nor these my hands henceforth perform their functions." then the _bergmeister_, having started from the centre of the windlass, proceeded to measure the vein with a cord, and to give the measured portion to the discoverer,--in the first instance a half and then three full measures; afterward one to the king or prince, another to his consort, a third to the master of the horse, a fourth to the cup-bearer, a fifth to the groom of the chamber, a sixth to himself. then, starting from the other side of the windlass, he proceeded to measure the vein in a similar manner. thus the discoverer of the vein obtained the head-meer, that is, seven single measures; but the king or ruler, his consort, the leading dignitaries, and lastly, the _bergmeister_, obtained two measures each, or two ancient meers. this is the reason there are to be found at freiberg in meissen so many shafts with so many intercommunications on a single vein--which are to a great extent destroyed by age. if, however, the _bergmeister_ had already fixed the boundaries of the meers on one side of the shaft for the benefit of some other discoverer, then for those dignitaries i have just mentioned, as many meers as he was unable to award on that side he duplicated on the other. but if on both sides of the shaft he had already defined the boundaries of meers, he proceeded to measure out only that part of the vein which remained free, and thus it sometimes happened that some of those persons i have mentioned obtained no meer at all. to-day, though that old-established custom is observed, the method of allotting the vein and granting title has been changed. as i have explained above, the head-meer consists of three double measures, and each other meer of two measures, and the _bergmeister_ grants one each of the meers to him who makes the first application. the king or prince, since all metal is taxed, is himself content with that, which is usually one-tenth. of the width of every meer, whether old or new, one-half lies on the footwall side of a _vena profunda_ and one half on the hangingwall side. if the vein descends vertically into the earth, the boundaries similarly descend vertically; but if the vein inclines, the boundaries likewise will be inclined. the owner always holds the mining right for the width of the meer, however far the vein descends into the depth of the earth.[ ] further, the _bergmeister_, on application being made to him, grants to one owner or company a right over not only the head meer, or another meer, but also the head meer and the next meer or two adjoining meers. so much for the shape of meers and their dimensions in the case of a _vena profunda_. i now come to the case of _venae dilatatae_. the boundaries of the areas on such veins are not all measured by one method. for in some places the _bergmeister_ gives them shapes similar to the shapes of the meers on _venae profundae_, in which case the head-meer is composed of three double measures, and the area of every other mine of two measures, as i have explained more fully above. in this case, however, he measures the meers with a cord, not only forward and backward from the ends of the head-meer, as he is wont to do in the case where the owner of a _vena profunda_ has a meer granted him, but also from the sides. in this way meers are marked out when a torrent or some other force of nature has laid open a _vena dilatata_ in a valley, so that it appears either on the slope of a mountain or hill or on a plain. elsewhere the _bergmeister_ doubles the width of the head-meer and it is made fourteen fathoms wide, while the width of each of the other meers remains single, that is seven fathoms, but the length is not defined by boundaries. in some places the head-meer consists of three double measures, but has a width of fourteen fathoms and a length of twenty-one. [illustration a (rectangle with lengths): shape of a head-meer.] [illustration b (square with lengths): shape of every other meer.] in the same way, every other meer is composed of two measures, doubled in the same fashion, so that it is fourteen fathoms in width and of the same length. elsewhere every meer, whether a head-meer or other meer, comprises forty-two fathoms in width and as many in length. in other places the _bergmeister_ gives the owner or company all of some locality defined by rivers or little valleys as boundaries. but the boundaries of every such area of whatsoever shape it be, descend vertically into the earth; so the owner of that area has a right over that part of any _vena dilatata_ which lies beneath the first one, just as the owner of the meer on a _vena profunda_ has a right over so great a part of all other _venae profundae_ as lies within the boundaries of his meer; for just as wherever one _vena profunda_ is found, another is found not far away, so wherever one _vena dilatata_ is found, others are found beneath it. finally, the _bergmeister_ divides _vena cumulata_ areas in different ways, for in some localities the head-meer is composed of three measures, doubled in such a way that it is fourteen fathoms wide and twenty-one long; and every other meer consists of two measures doubled, and is square, that is, fourteen fathoms wide and as many long. in some places the head-meer is composed of three single measures, and its width is seven fathoms and its length twenty-one, which two numbers multiplied together make one hundred and forty-seven square fathoms. [illustration (rectangle with lengths and area): shape of a head-meer.] each other meer consists of one double measure. in some places the head-meer is given the shape of a double measure, and every other meer that of a single measure. lastly, in other places the owner or a company is given a right over some complete specified locality bounded by little streams, valleys, or other limits. furthermore, all meers on _venae cumulatae_, as in the case of _dilatatae_, descend vertically into the depths of the earth, and each meer has the boundaries so determined as to prevent disputes arising between the owners of neighbouring mines. the boundary marks in use among miners formerly consisted only of stones, and from this their name was derived, for now the marks of a boundary are called "boundary stones." to-day a row of posts, made either of oak or pine, and strengthened at the top with iron rings to prevent them from being damaged, is fixed beside the boundary stones to make them more conspicuous. by this method in former times the boundaries of the fields were marked by stones or posts, not only as written of in the book "_de limitibus agrorum_,"[ ] but also as testified to by the songs of the poets. such then is the shape of the meers, varying in accordance with the different kinds of veins. now tunnels are of two sorts, one kind having no right of property, the other kind having some limited right. for when a miner in some particular locality is unable to open a vein on account of a great quantity of water, he runs a wide ditch, open at the top and three feet deep, starting on the slope and running up to the place where the vein is found. through it the water flows off, so that the place is made dry and fit for digging. but if it is not sufficiently dried by this open ditch, or if a shaft which he has now for the first time begun to sink is suffering from overmuch water, he goes to the _bergmeister_ and asks that official to give him the right for a tunnel. having obtained leave, he drives the tunnel, and into its drains all the water is diverted, so that the place or shaft is made fit for digging. if it is not seven fathoms from the surface of the earth to the bottom of this kind of tunnel, the owner possesses no rights except this one: namely, that the owners of the mines, from whose leases the owner of the tunnel extracts gold or silver, themselves pay him the sum he expends within their meer in driving the tunnel through it. to a depth or height of three and a half fathoms above and below the mouth of the tunnel, no one is allowed to begin another tunnel. the reason for this is that this kind of a tunnel is liable to be changed into the other kind which has a complete right of property, when it drains the meers to a depth of seven fathoms, or to ten, according as the old custom in each place acquires the force of law. in such case this second kind of tunnel has the following right; in the first place, whatever metal the owner, or company owning it, finds in any meer through which it is driven, all belongs to the tunnel owner within a height or depth of one and a quarter fathoms. in the years which are not long passed, the owner of a tunnel possessed all the metal which a miner standing at the bottom of the tunnel touched with a bar, whose handle did not exceed the customary length; but nowadays a certain prescribed height and width is allowed to the owner of the tunnel, lest the owners of the mines be damaged, if the length of the bar be longer than usual. further, every metal-yielding mine which is drained and supplied with ventilation by a tunnel, is taxed in the proportion of one-ninth for the benefit of the owner of the tunnel. but if several tunnels of this kind are driven through one mining area which is yielding metals, and all drain it and supply it with ventilation, then of the metal which is dug out from above the bottom of each tunnel, one-ninth is given to the owner of that tunnel; of that which is dug out below the bottom of each tunnel, one-ninth is in each case given to the owner of the tunnel which follows next in order below. but if the lower tunnel does not yet drain the shaft of that meer nor supply it with ventilation, then of the metal which is dug out below the bottom of the higher tunnel, one-ninth part is given to the owner of such upper tunnel. moreover, no one tunnel deprives another of its right to one-ninth part, unless it be a lower one, from the bottom of which to the bottom of the one above must not be less than seven or ten fathoms, according as the king or prince has decreed. further, of all the money which the owner of the tunnel has spent on his tunnel while driving it through a meer, the owner of that meer pays one-fourth part. if he does not do so he is not allowed to make use of the drains. finally, with regard to whatever veins are discovered by the owner at whose expense the tunnel is driven, the right of which has not been already awarded to anyone, on the application of such owner the _bergmeister_ grants him a right of a head-meer, or of a head-meer together with the next meer. ancient custom gives the right for a tunnel to be driven in any direction for an unlimited length. further, to-day he who commences a tunnel is given, on his application, not only the right over the tunnel, but even the head and sometimes the next meer also. in former days the owner of the tunnel obtained only so much ground as an arrow shot from the bow might cover, and he was allowed to pasture cattle therein. in a case where the shafts of several meers on some vein could not be worked on account of the great quantity of water, ancient custom also allowed the _bergmeister_ to grant the right of a large meer to anyone who would drive a tunnel. when, however, he had driven a tunnel as far as the old shafts and had found metal, he used to return to the _bergmeister_ and request him to bound and mark off the extent of his right to a meer. thereupon, the _bergmeister_, together with a certain number of citizens of the town--in whose place jurors have now succeeded--used to proceed to the mountain and mark off with boundary stones a large meer, which consisted of seven double measures, that is to say, it was ninety-eight fathoms long and seven wide, which two numbers multiplied together make six hundred and eighty-six square fathoms. [illustration (rectangle with lengths and area): large area.] but each of these early customs has been changed, and we now employ the new method. i have spoken of tunnels; i will now speak about the division of ownership in mines and tunnels. one owner is allowed to possess and to work one, two, three, or more whole meers, or similarly one or more separate tunnels, provided he conforms to the decrees of the laws relating to metals, and to the orders of the _bergmeister_. and because he alone provides the expenditure of money on the mines, if they yield metal he alone obtains the product from them. but when large and frequent expenditures are necessary in mining, he to whom the _bergmeister_ first gave the right often admits others to share with him, and they join with him in forming a company, and they each lay out a part of the expense and share with him the profit or loss of the mine. but the title of the mines or tunnels remains undivided, although for the purpose of dividing the expense and profit it may be said each mine or tunnel is divided into parts[ ]. this division is made in various ways. a mine, and the same thing must be understood with regard to a tunnel, may be divided into two halves, that is into two similar portions, by which method two owners spend an equal amount on it and draw an equal profit from it, for each possesses one half. sometimes it is divided into four shares, by which compact four persons can be owners, so that each possesses one-fourth, or also two persons, so that one possesses three-fourths, and the other only one-fourth; or three owners, so that the first has two-fourths, and the second and third one-fourth each. sometimes it is divided into eight shares, by which plan there may be eight owners, so that each is possessor of one-eighth; sometimes there are two owners, so that one has five-sixths[ ] together with one twenty-fourth, and the other one-eighth; or there may be three owners, in which one has three-quarters and the second and third each one-eighth; or it may be divided so that one owner has seven-twelfths, together with one twenty-fourth, a second owner has one-quarter, and a third owner has one-eighth; or so that the first has one-half, the second one-third and one twenty-fourth, and the third one-eighth; or so that the first has one-half, as before, and the second and third each one-quarter; or so that the first and second each have one-third and one twenty-fourth, and the third one-quarter; and in the same way the divisions may be adjusted in all the other proportions. the different ways of dividing the shares originate from the different proportions of ownership. sometimes a mine is divided into sixteen parts, each of which is a twenty-fourth and a forty-eighth; or it may be divided into thirty-two parts, each of which is a forty-eighth and half a seventy-second and a two hundred and eighty-eighth; or into sixty-four parts of which each share is one seventy-second and one five hundred and seventy-sixth; or finally, into one hundred and twenty-eight parts, any one of which is half a seventy-second and half of one five hundred and seventy-sixth. now an iron mine either remains undivided or is divided into two, four, or occasionally more shares, which depends on the excellence of the veins. but a lead, bismuth, or tin mine, and likewise one of copper or even quicksilver, is also divided into eight shares, or into sixteen or thirty-two, and less commonly into sixty-four. the number of the divisions of the silver mines at freiberg in meissen did not formerly progress beyond this; but within the memory of our fathers, miners have divided a silver mine, and similarly the tunnel at schneeberg, first of all into one hundred and twenty-eight shares, of which one hundred and twenty-six are the property of private owners in the mines or tunnels, one belongs to the state and one to the church; while in joachimsthal only one hundred and twenty-two shares of the mines or tunnels are the property of private owners, four are proprietary shares, and the state and church each have one in the same way. to these there has lately been added in some places one share for the most needy of the population, which makes one hundred and twenty-nine shares. it is only the private owners of mines who pay contributions. a proprietary holder, though he holds as many as four shares such as i have described, does not pay contributions, but gratuitiously supplies the owners of the mines with sufficient wood from his forests for timbering, machinery, buildings, and smelting; nor do those belonging to the state, church, and the poor pay contributions, but the proceeds are used to build or repair public works and sacred buildings, and to support the most needy with the profits which they draw from the mines. furthermore, in our state, the one hundred and twenty-eighth share has begun to be divided into two, four, or eight parts, or even into three, six, twelve, or smaller parts. this is done when one mine is created out of two, for then the owner who formerly possessed one-half becomes owner of one-fourth; he who possessed one-fourth, of one-eighth; he who possessed one-third, of one-sixth; he who possessed one-sixth, of one-twelfth. since our countrymen call a mine a _symposium_, that is, a drinking bout, we are accustomed to call the money which the owners subscribe a _symbolum_, or a contribution[ ]. for, just as those who go to a banquet (_symposium_) give contributions (_symbola_), so those who purpose making large profits from mining are accustomed to contribute toward the expenditure. however, the manager of the mine assesses the contributions of the owners annually, or for the most part quarterly, and as often he renders an account of receipts and expenses. at freiberg in meissen the old practice was for the manager to exact a contribution from the owners every week, and every week to distribute among them the profits of the mines, but this practice during almost the last fifteen years has been so far changed that contribution and distribution are made four[ ] times each year. large or small contributions are imposed according to the number of workmen which the mine or tunnel requires; as a result, those who possess many shares provide many contributions. four times a year the owners contribute to the cost, and four times during the year the profits of the mines are distributed among them; these are sometimes large, sometimes small, according as there is more or less gold or silver or other metal dug out. indeed, from the st. george mine in schneeberg the miners extracted so much silver in a quarter of a year that silver cakes, which were worth , rhenish guldens, were distributed to each one hundred and twenty-eighth share. from the annaberg mine which is known as the himmelisch höz, they had a dole of eight hundred thaler; from a mine in joachimsthal which is named the sternen, three hundred thaler; from the head mine at abertham, which is called st. lorentz, two hundred and twenty-five thaler[ ]. the more shares of which any individual is owner the more profits he takes. i will now explain how the owners may lose or obtain the right over a mine, or a tunnel, or a share. formerly, if anyone was able to prove by witnesses that the owners had failed to send miners for three continuous shifts[ ], the _bergmeister_ deprived them of their right over the mine, and gave the right over it to the informer, if he desired it. but although miners preserve this custom to-day, still mining share owners who have paid their contributions do not lose their right over their mines against their will. formerly, if water which had not been drawn off from the higher shaft of some mine percolated through a vein or stringer into the shaft of another mine and impeded their work, then the owners of the mine which suffered the damage went to the _bergmeister_ and complained of the loss, and he sent to the shafts two jurors. if they found that matters were as claimed, the right over the mine which caused the injury was given to the owners who suffered the injury. but this custom in certain places has been changed, for the _bergmeister_, if he finds this condition of things proved in the case of two shafts, orders the owners of the shaft which causes the injury to contribute part of the expense to the owners of the shaft which receives the injury; if they fail to do so, he then deprives them of their right over their mine; on the other hand, if the owners send men to the workings to dig and draw off the water from the shafts, they keep their right over their mine. formerly owners used to obtain a right over any tunnel, firstly, if in its bottom they made drains and cleansed them of mud and sand so that the water might flow out without any hindrance, and restored those drains which had been damaged; secondly, if they provided shafts or openings to supply the miners with air, and restored those which had fallen in; and finally, if three miners were employed continuously in driving the tunnel. but the principal reason for losing the title to a tunnel was that for a period of eight days no miner was employed upon it; therefore, when anyone was able to prove by witnesses that the owners of a tunnel had not done these things, he brought his accusation before the _bergmeister_, who, after going out from the town to the tunnel and inspecting the drains and the ventilating machines and everything else, and finding the charge to be true, placed the witness under oath, and asked him: "whose tunnel is this at the present time?" the witness would reply: "the king's" or "the prince's." thereupon the _bergmeister_ gave the right over the tunnel to the first applicant. this was the severe rule under which the owners at one time lost their rights over a tunnel; but its severity is now considerably mitigated, for the owners do not now forthwith lose their right over a tunnel through not having cleaned out the drains and restored the shafts or ventilation holes which have suffered damage; but the _bergmeister_ orders the tunnel manager to do it, and if he does not obey, the authorities fine the tunnel. also it is sufficient for one miner to be engaged in driving the tunnel. moreover, if the owner of a tunnel sets boundaries at a fixed spot in the rocks and stops driving the tunnel, he may obtain a right over it so far as he has gone, provided the drains are cleaned out and ventilation holes are kept in repair. but any other owner is allowed to start from the established mark and drive the tunnel further, if he pays the former owners of the tunnel as much money every three months as the _bergmeister_ decides ought to be paid. there remain for discussion, the shares in the mines and tunnels. formerly if anybody conveyed these shares to anyone else, and the latter had once paid his contribution, the seller[ ] was bound to stand by his bargain, and this custom to-day has the force of law. but if the seller denied that the contribution had been paid, while the buyer of the shares declared that he could prove by witnesses that he had paid his contribution to the other proprietors, and a case arose for trial, then the evidence of the other proprietors carried more weight than the oath of the seller. to-day the buyer of the shares proves that he has paid his contribution by a document which the mine or tunnel manager always gives each one; if the buyer has contributed no money there is no obligation on the seller to keep his bargain. formerly, as i have said above, the proprietors used to contribute money weekly, but now contributions are paid four times each year. to-day, if for the space of a month anyone does not take proceedings against the seller of the shares for the contribution, the right of taking proceedings is lost. but when the clerk has already entered on the register the shares which had been conveyed or bought, none of the owners loses his right over the share unless the money is not contributed which the manager of the mine or tunnel has demanded from the owner or his agent. formerly, if on the application of the manager the owner or his agent did not pay, the matter was referred to the _bergmeister_, who ordered the owner or his agent to make his contribution; then if he failed to contribute for three successive weeks, the _bergmeister_ gave the right to his shares to the first applicant. to-day this custom is unchanged, for if owners fail for the space of a month to pay the contributions which the manager of the mine has imposed on them, on a stated day their names are proclaimed aloud and struck off the list of owners, in the presence of the _bergmeister_, the jurors, the mining clerk, and the share clerk, and each of such shares is entered on the proscribed list. if, however, on the third, or at latest the fourth day, they pay their contributions to the manager of the mine or tunnel, and pay the money which is due from them to the share clerk, he removes their shares from the proscribed list. they are not thereupon restored to their former position unless the other owners consent; in which respect the custom now in use differs from the old practice, for to-day if the owners of shares constituting anything over half the mine consent to the restoration of those who have been proscribed, the others are obliged to consent whether they wish to or not. formerly, unless such restoration had been sanctioned by the approval of the owners of one hundred shares, those who had been proscribed were not restored to their former position. the procedure in suits relating to shares was formerly as follows: he who instituted a suit and took legal proceedings against another in respect of the shares, used to make a formal charge against the accused possessor before the _bergmeister_. this was done either at his house or in some public place or at the mines, once each day for three days if the shares belonged to an old mine, and three times in eight days if they belonged to a head-meer. but if he could not find the possessor of the shares in these places, it was valid and effectual to make the accusation against him at the house of the _bergmeister_. when, however, he made the charge for the third time, he used to bring with him a notary, whom the _bergmeister_ would interrogate: "have i earned the fee?" and who would respond: "you have earned it"; thereupon the _bergmeister_ would give the right over the shares to him who made the accusation, and the accuser in turn would pay down the customary fee to the _bergmeister_. after these proceedings, if the man whom the _bergmeister_ had deprived of his shares dwelt in the city, one of the proprietors of the mine or of the head-mine was sent to him to acquaint him with the facts, but if he dwelt elsewhere proclamation was made in some public place, or at the mine, openly and in a loud voice in the hearing of numbers of miners. nowadays a date is defined for the one who is answerable for the debt of shares or money, and information is given the accused by an official if he is near at hand, or if he is absent, a letter is sent him; nor is the right over his shares taken from anyone for the space of one and a half months. so much for these matters. now, before i deal with the methods which must be employed in working, i will speak of the duties of the mining prefect, the _bergmeister_, the jurors, the mining clerk, the share clerk, the manager of the mine or tunnel, the foreman of the mine or tunnel, and the workmen. to the mining prefect, whom the king or prince appoints as his deputy, all men of all races, ages, and rank, give obedience and submission. he governs and regulates everything at his discretion, ordering those things which are useful and advantageous in mining operations, and prohibiting those which are to the contrary. he levies penalties and punishes offenders; he arranges disputes which the _bergmeister_ has been unable to settle, and if even he cannot arrange them, he allows the owners who are at variance over some point to proceed to litigation; he even lays down the law, gives orders as a magistrate, or bids them leave their rights in abeyance, and he determines the pay of persons who hold any post or office. he is present in person when the mine managers present their quarterly accounts of profits and expenses, and generally represents the king or prince and upholds his dignity. the athenians in this way set thucydides, the famous historian, over the mines of thasos[ ]. next in power to the mining prefect comes the _bergmeister_, since he has jurisdiction over all who are connected with mines, with a few exceptions, which are the tithe gatherer, the cashier, the silver refiner, the master of the mint, and the coiners themselves. fraudulent, negligent, or dissolute men he either throws into prison, or deprives of promotion, or fines; of these fines, part is given as a tribute to those in power. when the mine owners have a dispute over boundaries he arbitrates it; or if he cannot settle the dispute, he pronounces judgment jointly with the jurors; from them, however, an appeal lies to the mining prefect. he transcribes his decrees in a book and sets up the records in public. it is also his duty to grant the right over the mines to those who apply, and to confirm their rights; he also must measure the mines, and fix their boundaries, and see that the mine workings are not allowed to become dangerous. some of these duties he observes on fixed days; for on wednesday in the presence of the jurors he confirms the rights over the mines which he has granted, settles disputes about boundaries, and pronounces judgments. on mondays, tuesdays, thursdays, and fridays, he rides up to the mines, and dismounting at some of them explains what is required to be done, or considers the boundaries which are under controversy. on saturday all the mine managers and mine foremen render an account of the money which they have spent on the mines during the preceding week, and the mining clerk transcribes this account into the register of expenses. formerly, for one principality there was one _bergmeister_, who used to create all the judges and exercise jurisdiction and control over them; for every mine had its own judge, just as to-day each locality has a _bergmeister_ in his place, the name alone being changed. to this ancient _bergmeister_, who used to dwell at freiberg in meissen, disputes were referred; hence right up to the present time the one at freiberg still has the power of pronouncing judgment when mine owners who are engaged in disputes among themselves appeal to him. the old _bergmeister_ could try everything which was presented to him in any mine whatsoever; whereas the judge could only try the things which were done in his own district, in the same way that every modern _bergmeister_ can. to each _bergmeister_ is attached a clerk, who writes out a schedule signifying to the applicant for a right over a mine, the day and hour on which the right is granted, the name of the applicant, and the location of the mine. he also affixes at the entrance to the mine, quarterly, at the appointed time, a sheet of paper on which is shown how much contribution must be paid to the manager of the mine. these notices are prepared jointly with the mining clerk, and in common they receive the fee rendered by the foremen of the separate mines. i now come to the jurors, who are men experienced in mining matters and of good repute. their number is greater or less as there are few or more mines; thus if there are ten mines there will be five pairs of jurors, like a _decemviral college_[ ]. into however many divisions the total number of mines has been divided, so many divisions has the body of jurors; each pair of jurors usually visits some of the mines whose administration is under their supervision on every day that workmen are employed; it is usually so arranged that they visit all the mines in the space of fourteen days. they inspect and consider all details, and deliberate and consult with the mine foreman on matters relating to the underground workings, machinery, timbering, and everything else. they also jointly with the mine foreman from time to time make the price per fathom to the workmen for mining the ore, fixing it at a high or low price, according to whether the rock is hard or soft; if, however, the contractors find that an unforeseen and unexpected hardness occurs, and for that reason have difficulty and delay in carrying out their work, the jurors allow them something in excess of the price fixed; while if there is a softness by reason of water, and the work is done more easily and quickly, they deduct something from the price. further, if the jurors discover manifest negligence or fraud on the part of any foreman or workman, they first admonish or reprimand him as to his duties and obligations, and if he does not become more diligent and improve, the matter is reported to the _bergmeister_, who by right of his authority deprives such persons of their functions and office, or, if they have committed a crime, throws them into prison. lastly, because the jurors have been given to the _bergmeister_ as councillors and advisors, in their absence he does not confirm the right over any mine, nor measure the mines, nor fix their boundaries, nor settle disputes about boundaries, nor pronounce judgment, nor, finally, does he without them listen to any account of profits and expenditure. now the mining clerk enters each mine in his books, the new mines in one book, the old mines which have been re-opened in another. this is done in the following way: first is written the name of the man who has applied for the right over the mine, then the day and hour on which he made his application, then the vein and the locality in which it is situated, next the conditions on which the right has been given, and lastly, the day on which the _bergmeister_ confirmed it. a document containing all these particulars is also given to the person whose right over a mine has been confirmed. the mining clerk also sets down in another book the names of the owners of each mine over which the right has been confirmed; in another any intermission of work permitted to any person for certain reasons by the _bergmeister_; in another the money which one mine supplies to another for drawing off water or making machinery; and in another the decisions of the _bergmeister_ and the jurors, and the disputes settled by them as honorary arbitrators. all these matters he enters in the books on wednesday of every week; if holidays fall on that day he does it on the following thursday. every saturday he enters in another book the total expenses of the preceding week, the account of which the mine manager has rendered; but the total quarterly expenses of each mine manager, he enters in a special book at his own convenience. he enters similarly in another book a list of owners who have been proscribed. lastly, that no one may be able to bring a charge of falsification against him, all these books are enclosed in a chest with two locks, the key of one of which is kept by the mining clerk, and of the other by the _bergmeister_. the share clerk enters in a book the owners of each mine whom the first finder of the vein names to him, and from time to time replaces the names of the sellers with those of the buyers of the shares. it sometimes happens that twenty or more owners come into the possession of some particular share. unless, however, the seller is present, or has sent a letter to the mining clerk with his seal, or better still with the seal of the mayor of the town where he dwells, his name is not replaced by that of anyone else; for if the share clerk is not sufficiently cautious, the law requires him to restore the late owner wholly to his former position. he writes out a fresh document, and in this way gives proof of possession. four times a year, when the accounts of the quarterly expenditure are rendered, he names the new proprietors to the manager of each mine, that the manager may know from whom he should demand contributions and among whom to distribute the profits of the mines. for this work the mine manager pays the clerk a fixed fee. i will now speak of the duties of the mine manager. in the case of the owners of every mine which is not yielding metal, the manager announces to the proprietors their contributions in a document which is affixed to the doors of the town hall, such contributions being large or small, according as the _bergmeister_ and two jurors determine. if anyone fails to pay these contributions for the space of a month, the manager removes their names from the list of owners, and makes their shares the common property of the other proprietors. and so, whomsoever the mine manager names as not having paid his contribution, that same man the mining clerk designates in writing, and so also does the share clerk. of the contribution, the mine manager applies part to the payment of the foreman and workmen, and lays by a part to purchase at the lowest price the necessary things for the mine, such as iron tools, nails, firewood, planks, buckets, drawing-ropes, or grease. but in the case of a mine which is yielding metal, the tithe-gatherer pays the mine manager week by week as much money as suffices to discharge the workmen's wages and to provide the necessary implements for mining. the mine manager of each mine also, in the presence of its foreman, on saturday in each week renders an account of his expenses to the _bergmeister_ and the jurors, he renders an account of his receipts, whether the money has been contributed by the owners or taken from the tithe-gatherer; and of his quarterly expenditure in the same way to them and to the mining prefect and to the mining clerk, four times a year at the appointed time; for just as there are four seasons of the year, namely, spring, summer, autumn, and winter, so there are fourfold accounts of profits and expenses. in the beginning of the first month of each quarter an account is rendered of the money which the manager has spent on the mine during the previous quarter, then of the profit which he has taken from it during the same period; for example, the account which is rendered at the beginning of spring is an account of all the profits and expenses of each separate week of winter, which have been entered by the mining clerk in the book of accounts. if the manager has spent the money of the proprietors advantageously in the mine and has faithfully looked after it, everyone praises him as a diligent and honest man; if through ignorance in these matters he has caused loss, he is generally deprived of his office; if by his carelessness and negligence the owners have suffered loss, the _bergmeister_ compels him to make good the loss; and finally, if he has been guilty of fraud or theft, he is punished with fine, prison, or death. further, it is the business of the manager to see that the foreman of the mine is present at the beginning and end of the shifts, that he digs the ore in an advantageous manner, and makes the required timbering, machines, and drains. the manager also makes the deductions from the pay of the workmen whom the foreman has noted as negligent. next, if the mine is rich in metal, the manager must see that its ore-house is closed on those days on which no work is performed; and if it is a rich vein of gold or silver, he sees that the miners promptly transfer the output from the shaft or tunnel into a chest or into the strong room next to the house where the foreman dwells, that no opportunity for theft may be given to dishonest persons. this duty he shares in common with the foreman, but the one which follows is peculiarly his own. when ore is smelted he is present in person, and watches that the smelting is performed carefully and advantageously. if from it gold or silver is melted out, when it is melted in the cupellation furnace he enters the weight of it in his books and carries it to the tithe-gatherer, who similarly writes a note of its weight in his books; it is then conveyed to the refiner. when it has been brought back, both the tithe-gatherer and manager again enter its weight in their books. why again? because he looks after the goods of the owners just as if they were his own. now the laws which relate to mining permit a manager to have charge of more than one mine, but in the case of mines yielding gold or silver, to have charge of only two. if, however, several mines following the head-mine begin to produce metal, he remains in charge of these others until he is freed from the duty of looking after them by the _bergmeister_. last of all, the manager, the _bergmeister_, and the two jurors, in agreement with the owners, settle the remuneration for the labourers. enough of the duties and occupation of the manager. i will now leave the manager, and discuss him who controls the workmen of the mine, who is therefore called the foreman, although some call him the watchman. it is he who distributes the work among the labourers, and sees diligently that each faithfully and usefully performs his duties. he also discharges workmen on account of incompetence, or negligence, and supplies others in their places if the two jurors and manager give their consent. he must be skilful in working wood, that he may timber shafts, place posts, and make underground structures capable of supporting an undermined mountain, lest the rocks from the hangingwall of the veins, not being supported, become detached from the mass of the mountain and overwhelm the workmen with destruction. he must be able to make and lay out the drains in the tunnels, into which the water from the veins, stringers, and seams in the rocks may collect, that it may be properly guided and can flow away. further, he must be able to recognize veins and stringers, so as to sink shafts to the best advantage, and must be able to discern one kind of material which is mined from another, or to train his subordinates that they may separate the materials correctly. he must also be well acquainted with all methods of washing, so as to teach the washers how the metalliferous earth or sand is washed. he supplies the miners with iron tools when they are about to start to work in the mines, and apportions a certain weight of oil for their lamps, and trains them to dig to the best advantage, and sees that they work faithfully. when their shift is finished, he takes back the oil which has been left. on account of his numerous and important duties and labours, only one mine is entrusted to one foreman, nay, rather sometimes two or three foremen are set over one mine. since i have mentioned the shifts, i will briefly explain how these are carried on. the twenty-four hours of a day and night are divided into three shifts, and each shift consists of seven hours. the three remaining hours are intermediate between the shifts, and form an interval during which the workmen enter and leave the mines. the first shift begins at the fourth hour in the morning and lasts till the eleventh hour; the second begins at the twelfth and is finished at the seventh; these two are day shifts in the morning and afternoon. the third is the night shift, and commences at the eighth hour in the evening and finishes at the third in the morning. the _bergmeister_ does not allow this third shift to be imposed upon the workmen unless necessity demands it. in that case, whether they draw water from the shafts or mine the ore, they keep their vigil by the night lamps, and to prevent themselves falling asleep from the late hours or from fatigue, they lighten their long and arduous labours by singing, which is neither wholly untrained nor unpleasing. in some places one miner is not allowed to undertake two shifts in succession, because it often happens that he either falls asleep in the mine, overcome by exhaustion from too much labour, or arrives too late for his shift, or leaves sooner than he ought. elsewhere he is allowed to do so, because he cannot subsist on the pay of one shift, especially if provisions grow dearer. the _bergmeister_ does not, however, forbid an extraordinary shift when he concedes only one ordinary shift. when it is time to go to work the sound of a great bell, which the foreigners call a "campana," gives the workmen warning, and when this is heard they run hither and thither through the streets toward the mines. similarly, the same sound of the bell warns the foreman that a shift has just been finished; therefore as soon as he hears it, he stamps on the woodwork of the shaft and signals the workmen to come out. thereupon, the nearest as soon as they hear the signal, strike the rocks with their hammers, and the sound reaches those who are furthest away. moreover, the lamps show that the shift has come to an end when the oil becomes almost consumed and fails them. the labourers do not work on saturdays, but buy those things which are necessary to life, nor do they usually work on sundays or annual festivals, but on these occasions devote the shift to holy things. however, the workmen do not rest and do nothing if necessity demands their labour; for sometimes a rush of water compels them to work, sometimes an impending fall, sometimes something else, and at such times it is not considered irreligious to work on holidays. moreover, all workmen of this class are strong and used to toil from birth. the chief kinds of workmen are miners, shovellers, windlass men, carriers, sorters, washers, and smelters, as to whose duties i will speak in the following books, in their proper place. at present it is enough to add this one fact, that if the workmen have been reported by the foreman for negligence, the _bergmeister_, or even the foreman himself, jointly with the manager, dismisses them from their work on saturday, or deprives them of part of their pay; or if for fraud, throws them into prison. however, the owners of works in which the metals are smelted, and the master of the smelter, look after their own men. as to the government and duties of miners, i have now said enough; i will explain them more fully in another work entitled _de jure et legibus metallicis_[ ]. end of book iv. footnotes: [ ] the nomenclature in this chapter has given unusual difficulty, because the organisation of mines, either past or present, in english-speaking countries provides no exact equivalents for many of these offices and for many of the legal terms. the latin terms in the text were, of course, coined by the author, and have no historical basis to warrant their adoption, while the introduction of the original german terms is open to much objection, as they are not only largely obsolete, but also in the main would convey no meaning to the majority of readers. we have, therefore, reached a series of compromises, and in the main give the nearest english equivalent. of much interest in this connection is a curious exotic survival in mining law to be found in the high peak of derbyshire. we believe (see note on p. ) that the law of this district was of saxon importation, for in it are not only many terms of german origin, but the character of the law is foreign to the older english districts and shows its near kinship to that of saxony. it is therefore of interest in connection with the nomenclature to be adopted in this book, as it furnishes about the only english precedents in many cases. the head of the administration in the peak was the steward, who was the chief judicial officer, with functions somewhat similar to the _berghauptmann_. however, the term steward has come to have so much less significance that we have adopted a literal rendering of the latin. under the steward was the barmaster, barghmaster, or barmar, as he was variously called, and his duties were similar to those of the _bergmeister_. the english term would seem to be a corruption of the german, and as the latter has come to be so well understood by the english-speaking mining class, we have in this case adopted the german. the barmaster acted always by the consent and with the approval of a jury of from to members. in this instance the english had functions much like a modern jury, while the _geschwornen_ of saxony had much more widely extended powers. the german _geschwornen_ were in the main inspectors; despite this, however, we have not felt justified in adopting any other than the literal english for the latin and german terms. we have vacillated a great deal over the term _praefectus fodinae_, the german _steiger_ having, like the cornish "captain," in these days degenerated into a foreman, whereas the duties as described were not only those of the modern superintendent or manager, but also those of treasurer of the company, for he made the calls on shares and paid the dividends. the term purser has been used for centuries in english mining for the accountant or cashier, but his functions were limited to paying dividends, wages, etc., therefore we have considered it better not to adopt the latter term, and have compromised upon the term superintendent or manager, although it has a distinctly modern flavor. the word for _area_ has also caused much hesitation, and the "meer" has finally been adopted with some doubt. the title described by agricola has a very close equivalent in the meer of old derbyshire. as will be seen later, the mines of saxony were regal property, and were held subject to two essential conditions, _i.e._, payment of a tithe, and continuous operation. this form of title thus approximates more closely to the "lease" of australia than to the old cornish _sett_, or the american _claim_. the _fundgrube_ of saxony and agricola's equivalent, the _area capitis_--head lease--we have rendered literally as "head meer," although in some ways "founders' meer" might be better, for, in derbyshire, this was called the "finder's" or founder's meer, and was awarded under similar circumstances. it has also an analogy in australian law in the "reward" leases. the term "measure" has the merit of being a literal rendering of the latin, and also of being the identical term in the same use in the high peak. the following table of the principal terms gives the originals of the latin text, their german equivalents according in the glossary and other sources, and those adopted in the translation:-- agricola. german glossary. term adopted. _praefectus metallorum_ _bergamptmann_ mining prefect. _magister metallicorum_ _bergmeister_ bergmeister. _scriba magister _bergmeister's schreiber_ bergmeister's clerk. metallicorum_ _jurati_ _geschwornen_ jurates or jurors. _publicus signator_ _gemeiner sigler_ notary. _decumanus_ _zehender_ tithe gatherer. _distributor_ _aussteiler_ cashier. _scriba partium_ _gegenschreiber_ share clerk. _scriba fodinarum_ _bergschreiber_ mining clerk. _praefectus fodinae_ } _steiger_ { manager of the mine. _praefectus cuniculi_ } { manager of the tunnel. _praeses fodinae_ } _schichtmeister_ { foreman of the mine. _praeses cuniculi_ } { foreman of the tunnel. _fossores_ _berghauer_ miners or diggers. _ingestores_ _berganschlagen_ shovellers. _vectarii_ _hespeler_ lever workers (windlass men). _discretores_ _ertzpucher_ sorters. _lotores_ _wescher und seiffner_ washers, buddlers, sifters, etc. _excoctores_ _schmeltzer_ smelters. _purgator argenti_ _silber brenner_ silver refiner. _magister monetariorum_ _müntzmeister_ master of the mint. _monetarius_ _müntzer_ coiner. _area fodinarum_ _masse_ meer. _area capitis fodinarum_ _fundgrube_ head meer. _demensum_ _lehen_ measure. [ ] the following are the equivalents of the measures mentioned in this book. it is not always certain which "foot" or "fathom" agricola actually had in mind although they were probably the german. greek-- _dactylos_ = . inches = _pous_ = . inches = _orguia_ = . inches. roman-- _uncia_ = . " = _pes_ = . " = _passus_ = . " german-- _zoll_ = . " = _werckschuh_ = . " = _lachter_ = . " english-- inch = . " = foot = . " = fathom = . " the discrepancies are due to variations in authorities and to decimals dropped. the _werckschuh_ taken is the chemnitz foot deduced from agricola's statement in his _de mensuris et ponderibus_, basel, , p. . for further notes see appendix c. [ ] _subcisivum_--"remainder." german glossary, _ueberschar_. the term used in mendip and derbyshire was _primgap_ or _primegap_. it did not, however, in this case belong to adjacent mines, but to the landlord. [ ] _adversum_. glossary, _gegendrumb_. the _bergwerk lexicon_, chemnitz, , gives _gegendrom_ or _gegentramm_, and defines it as the _masse_ or lease next beyond a stream. [ ] _quadratum_. glossary, _vierung_. the _vierung_ in old saxon title meant a definite zone on either side of the vein, - / _lachter_ (_lachter_ = ft. . inches) into the hangingwall and the same into the footwall, the length of one _vierung_ being _lachter_ along the strike. it must be borne in mind that the form of rights here referred to entitled the miner to follow his vein, carrying the side line with him in depth the same distance from the vein, in much the same way as with the apex law of the united states. from this definition as given in the _bergwerk lexicon_, p. , it would appear that the vein itself was not included in the measurements, but that they started from the walls. [ ] historical note on the development of mining law.--there is no branch of the law of property, of which the development is more interesting and illuminating from a social point of view than that relating to minerals. unlike the land, the minerals have ever been regarded as a sort of fortuitous property, for the title of which there have been four principal claimants--that is, the overlord, as represented by the king, prince, bishop, or what not; the community or the state, as distinguished from the ruler; the landowner; and the mine operator, to which class belongs the discoverer. the one of these that possessed the dominant right reflects vividly the social state and sentiment of the period. the divine right of kings; the measure of freedom of their subjects; the tyranny of the land-owning class; the rights of the community as opposed to its individual members; the rise of individualism; and finally, the modern return to more communal view, have all been reflected promptly in the mineral title. of these parties the claims of the overlord have been limited only by the resistance of his subjects; those of the state limited by the landlord; those of the landlord by the sovereign or by the state; while the miner, ever in a minority in influence as well as in numbers, has been buffeted from pillar to post, his only protection being the fact that all other parties depended upon his exertion and skill. the conception as to which of these classes had a right in the title have been by no means the same in different places at the same time, and in all it varies with different periods; but the whole range of legislation indicates the encroachment of one factor in the community over another, so that their relative rights have been the cause of never-ending contention, ever since a record of civil and economic contentions began. in modern times, practically over the whole world, the state has in effect taken the rights from the overlord, but his claims did not cease until his claims over the bodies of his subjects also ceased. however, he still remains in many places with his picture on the coinage. the landlord has passed through many vicissitudes; his complete right to minerals was practically never admitted until the doctrine of _laissez-faire_ had become a matter of faith, and this just in time to vest him with most of the coal and iron deposits in the world; this, no doubt, being also partially due to the little regard in which such deposits were generally held at that time, and therefore to the little opposition to his ever-ready pretentions. their numbers, however, and their prominence in the support of the political powers _de jure_ have usually obtained them some recognition. in the rise of individualism, the apogee of the _laissez-faire_ fetish came about the time of the foundation of the united states, and hence the relaxation in the claims of the state in that country and the corresponding position attained by the landlord and miner. the discoverer and the operator--that is, the miner himself--has, however, had to be reckoned with by all three of the other claimants, because they have almost universally sought to escape the risks of mining, to obtain the most skilful operation, and to stimulate the productivity of the mines; thereupon the miner has secured at least partial consideration. this stands out in all times and all places, and while the miner has had to take the risks of his fortuitous calling, the overlord, state, or landlord have all made for complacent safety by demanding some kind of a tithe on his exertions. moreover, there has often been a low cunning displayed by these powers in giving something extra to the first discoverer. in these relations of the powers to the mine operator, from the very first we find definite records of the imposition of certain conditions with extraordinary persistence--so fixed a notion that even the united states did not quite escape it. this condition was, no doubt, designed as a stimulus to productive activity, and was the requirement that the miner should continuously employ himself digging in the piece of ground allotted to him. the greeks, romans, mediæval germans, old and modern englishmen, modern australians, all require the miner to keep continuously labouring at his mines, or lose his title. the american, as his inauguration of government happened when things were easier for individuals, allows him a vacation of months in the year for a few years, and finally a holiday altogether. there are other points where the overlord, the state, or the landlord have always considered that they had a right to interfere, principally as to the way the miner does his work, lest he should miss, or cause to be missed, some of the mineral; so he has usually been under pains and penalties as to his methods--these quite apart from the very proper protection to human life, which is purely a modern invention, largely of the miner himself. somebody has had to keep peace and settle disputes among the usually turbulent miners (for what other sort of operators would undertake the hazards and handicaps?), and therefore special officials and codes, or courts, for his benefit are of the oldest and most persistent of institutions. between the overlord and the landowner the fundamental conflict of view as to their respective rights has found its interpretation in the form of the mineral title. the overlord claimed the metals as distinguished from the land, while the landowner claimed all beneath his soil. therefore, we find two forms of title--that in which the miner could follow the ore regardless of the surface (the "apex" conception), and that in which the boundaries were vertical from the land surface. lest the americans think that the apex law was a sin original to themselves, we may mention that it was made use of in europe a few centuries before agricola, who will be found to set it out with great precision. from these points of view, more philosophical than legal, we present a few notes on various ancient laws of mines, though space forbids a discussion of a tithe of the amount it deserves at some experienced hand. of the ancient egyptian, lydian, assyrian, persian, indian, and chinese laws as to mines we have no record, but they were of great simplicity, for the bodies as well as the property of subjects were at the abject disposition of the overlord. we are informed on countless occasions of emperors, kings, and princes of various degree among these races, owning and operating mines with convicts, soldiers, or other slaves, so we may take it for certain that continuous labour was enforced, and that the boundaries, inspection, and landlords did not cause much anxiety. however, herein lies the root of regalian right. our first glimpse of a serious right of the subject to mines is among some of the greek states, as could be expected from their form of government. with republican ideals, a rich mining district at mount laurion, an enterprising and contentious people, it would be surprising indeed if athenian literature was void on the subject. while we know that the active operation of these mines extended over some years, from to b.c., the period of most literary reference was from to b.c. our information on the subject is from two of demosthenes' orations--one against pantaenetus, the other against phaenippus--the first mining lawsuit in which the address of counsel is extant. there is also available some information in xenophon's essay upon the revenues, aristotle's constitution of athens, lycurgus' prosecution of diphilos, the tablets of the poletae, and many incidental references and inscriptions of minor order. the minerals were the property of the state, a conception apparently inherited from the older civilizations. leases for exploitation were granted to individuals for terms of three to ten years, depending upon whether the mines had been previously worked, thus a special advantage was conferred upon the pioneer. the leases did not carry surface rights, but the boundaries at mt. laurion were vertical, as necessarily must be the case everywhere in horizontal deposits. what they were elsewhere we do not know. the landlord apparently got nothing. the miner must continuously operate his mine, and was required to pay a large tribute to the state, either in the initial purchase of his lease or in annual rent. there were elaborate regulations as to interference and encroachment, and proper support of the workings. diphilos was condemned to death and his fortune confiscated for robbing pillars. the mines were worked with slaves. the romans were most intensive miners and searchers after metallic wealth already mined. the latter was obviously the objective of most roman conquest, and those nations rich in these commodities, at that time necessarily possessed their own mines. thus a map showing the extensions of empire coincides in an extraordinary manner with the metal distribution of europe, asia, and north africa. further, the great indentations into the periphery of the imperial map, though many were rich from an agricultural point of view, had no lure to the roman because they had no mineral wealth. on the roman law of mines the student is faced with many perplexities. with the conquest of the older states, the plunderers took over the mines and worked them, either by leases from the state to public companies or to individuals; or even in some cases worked them directly by the state. there was thus maintained the concept of state ownership of the minerals which, although apparently never very specifically defined, yet formed a basis of support to the contention of regalian rights in europe later on. parallel with this system, mines were discovered and worked by individuals under tithe to the state, and in pliny (xxxiv, ) there is reference to the miners in britain limiting their own output. individual mining appears to have increased with any relaxation of central authority, as for instance under augustus. it appears, as a rule, that the mines were held on terminable leases, and that the state did at times resume them; the labour was mostly slaves. as to the detailed conditions under which the mine operator held his title, we know less than of the greeks--in fact, practically nothing other than that he paid a tithe. the romans maintained in each mining district an official--the _procurator metallorum_--who not only had general charge of the leasing of the mines on behalf of the state, but was usually the magistrate of the district. a bronze tablet found near aljustrel, in portugal, in , generally known as the aljustrel tablet, appears to be the third of a series setting out the regulations of the mining district. it refers mostly to the regulation of public auctions, the baths, barbers, and tradesmen; but one clause (vii.) is devoted to the regulation of those who work dumps of scoria, etc., and provides for payment to the administrator of the mines of a _capitation_ on the slaves employed. it does not, however, so far as we can determine, throw any light upon the actual regulations for working the mines. (those interested will find ample detail in jacques flach, "_la table de bronze d'aljustrel: nouvelle revue historique de droit francais et etranger_," , p. ; _estacio da veiga, memorias da acad. real das ciencias de lisbon, nova scrie, tome v, part ii_, lisbon, .) despite the systematic law of property evolved by the romans, the codes contain but small reference to mines, and this in itself is indirect evidence of the concept that they were the property of the state. any general freedom of the metals would have given rise to a more extensive body of law. there are, of course, the well-known sections in the justinian and theodosian codes, but the former in the main bears on the collection of the tithe and the stimulation of mining by ordering migrant miners to return to their own hearths. there is also some intangible prohibition of mining near edifices. there is in the theodosian code evident extension of individual right to mine or quarry, and this "freeing" of the mines was later considerably extended. the empire was, however, then on the decline; and no doubt it was hoped to stimulate the taxable commodities. there is nothing very tangible as to the position of the landlord with regard to minerals found on his property; the metals were probably of insufficient frequency on the land of italian landlords to matter much, and the attitude toward subject races was not usually such as to require an extensive body of law. in the chaos of the middle ages, europe was governed by hundreds of potentates, great and small, who were unanimous on one point, and this that the minerals were their property. in the bickerings among themselves, the stronger did not hesitate to interpret the roman law in affirming regalian rights as an excuse to dispossess the weaker. the rights to the mines form no small part of the differences between these potentates and the more important of their subjects; and with the gradual accretion of power into a few hands, we find only the most powerful of vassals able to resist such encroachment. however, as to what position the landlord or miner held in these rights, we have little indication until about the beginning of the th century, after which there appear several well-known charters, which as time went on were elaborated into practical codes of mining law. the earliest of these charters are those of the bishop of trent, ; that of the harz miners, ; of the town of iglau in . many such in connection with other districts appear throughout the th, th, and th centuries. (references to the most important of such charters may be found in sternberg, _umrisse der geschichte des bergbaues_, prague, ; eisenhart, _de regali metalli fodinarium_, helmestadt, ; gmelin, _beyträge zur geschichte des teutschen bergbaus_, halle, ; inama-sternegg, _deutsche wirthschaftsgeschichte_, leipzig, - ; transactions, royal geol. soc. cornwall vi, ; lewis, the stannaries, new york, .) by this time a number of mining communities had grown up, and the charters in the main are a confirmation to them of certain privileges; they contain, nevertheless, rigorous reservation of the regalian right. the landlord, where present, was usually granted some interest in the mine, but had to yield to the miner free entry. the miner was simply a sort of tributer to the crown, loaded with an obligation when upon private lands to pay a further portion of his profits to the landlord. he held tenure only during strenuous operation. however, it being necessary to attract skilled men, they were granted many civil privileges not general to the people; and from many of the principal mining towns "free cities" were created, possessing a measure of self-government. there appear in the iglau charter of the first symptoms of the "apex" form of title, this being the logical development of the conception that the minerals were of quite distinct ownership from the land. the law, as outlined by agricola, is much the same as set out in the iglavian charter of three centuries before, and we must believe that such fully developed conceptions as that charter conveys were but the confirmation of customs developed over generations. in france the landlord managed to maintain a stronger position _vis-à-vis_ with the crown, despite much assertion of its rights; and as a result, while the landlord admitted the right to a tithe for the crown, he maintained the actual possession, and the boundaries were defined with the land. in england the law varied with special mining communities, such as cornwall, devon, the forest of dean, the forest of mendip, alston moor, and the high peak, and they exhibit a curious complex of individual growth, of profound interest to the student of the growth of institutions. these communities were of very ancient origin, some of them at least pre-roman; but we are, except for the reference in pliny, practically without any idea of their legal doings until after the norman occupation ( a.d.). the genius of these conquerors for systematic government soon led them to inquire into the doings of these communities, and while gradually systematising their customs into law, they lost no occasion to assert the regalian right to the minerals. in the two centuries subsequent to their advent there are on record numerous inquisitions, with the recognition and confirmation of "the customs and liberties which had existed from time immemorial," always with the reservation to the crown of some sort of royalty. except for the high peak in derbyshire, the period and origin of these "customs and liberties" are beyond finding out, as there is practically no record of english history between the roman withdrawal and the norman occupation. there may have been "liberties" under the romans, but there is not a shred of evidence on the subject, and our own belief is that the forms of self-government which sprang up were the result of the roman evacuation. the miner had little to complain of in the norman treatment in these matters; but between the crown and the landlord as represented by the barons, lords of the manor, etc., there were wide differences of opinion on the regalian rights, for in the extreme interpretation of the crown it tended greatly to curtail the landlord's position in the matter, and the success of the crown on this subject was by no means universal. in fact, a considerable portion of english legal history of mines is but the outcropping of this conflict, and one of the concessions wrung from king john at runnymede in was his abandonment of a portion of such claims. the mining communities of cornwall and devon were early in the th century definitely chartered into corporations--"the stannaries"--possessing definite legislative and executive functions, judicial powers, and practical self-government; but they were required to make payment of the tithe in the shape of "coinage" on the tin. such recognition, while but a ratification of prior custom, was not obtained without struggle, for the norman kings early asserted wide rights over the mines. tangible record of mining in these parts, from a legal point of view, practically begins with a report by william de wrotham in upon his arrangements regarding the coinage. a charter of king john in , while granting free right of entry to the miners, thus usurped the rights of the landlords--a claim which he was compelled by the barons to moderate; the crown, as above mentioned did maintain its right to a royalty, but the landlord held the minerals. it is not, however, until the time of richard carew's "survey of cornwall" (london, ) that we obtain much insight into details of miners' title, and the customs there set out were maintained in broad principle down to the th century. at carew's time the miner was allowed to prospect freely upon "common" or wastrel lands (since mostly usurped by landlords), and upon mineral discovery marked his boundaries, within which he was entitled to the vertical contents. even upon such lands, however, he must acknowledge the right of the lord of the manor to a participation in the mine. upon "enclosed" lands he had no right of entry without the consent of the landlord; in fact, the minerals belonged to the land as they do to-day except where voluntarily relinquished. in either case he was compelled to "renew his bounds" once a year, and to operate more or less continuously to maintain the right once obtained. there thus existed a "labour condition" of variable character, usually imposed more or less vigorously in the bargains with landlords. the regulations in devonshire differed in the important particular that the miner had right of entry to private lands, although he was not relieved of the necessity to give a participation of some sort to the landlord. the forests of dean, mendip, and other old mining communities possessed a measure of self-government, which do not display any features in their law fundamentally different from those of cornwall and devon. the high peak lead mines of derbyshire, however, exhibit one of the most profoundly interesting of these mining communities. as well as having distinctively saxon names for some of the mines, the customs there are of undoubted saxon origin, and as such their ratification by the normans caused the survival of one of the few saxon institutions in england--a fact which, we believe, has been hitherto overlooked by historians. beginning with inquisitions by edward i. in , there is in the record office a wealth of information, the bare titles of which form too extensive a list to set out here. (of published works, the most important are edward manlove's "the liberties and customs of the lead mines within the wapentake of wirksworth," london, , generally referred to as the "rhymed chronicle"; thomas houghton, "rara avis in terra," london, ; william hardy, "the miner's guide," sheffield, ; thomas tapping, "high peak mineral customs," london, .) the miners in this district were presided over by a "barmaster," "barghmaster," or "barmar," as he was variously spelled, all being a corruption of the german bergmeister, with precisely the same functions as to the allotment of title, settlement of disputes, etc., as his saxon progenitor had, and, like him, he was advised by a jury. the miners had entry to all lands except churchyards (this regulation waived upon death), and a few similar exceptions, and was subject to royalty to the crown and the landlord. the discoverer was entitled to a finder's "meer" of extra size, and his title was to the vein within the end lines, _i.e._, the "apex" law. this title was held subject to rigorous labour conditions, amounting to forfeiture for failure to operate the mine for a period of nine weeks. space does not permit of the elaboration of the details of this subject, which we hope to pursue elsewhere in its many historical bearings. among these we may mention that if the american "apex law" is of english descent, it must be laid to the door of derbyshire, and not of cornwall, as is generally done. our own belief, however, is that the american "apex" conception came straight from germany. it is not our purpose to follow these inquiries into mining law beyond the th century, but we may point out that with the growth of the sentiment of individualism the miners and landlords obtained steadily wider and wider rights at the cost of the state, until well within the th century. the growth of stronger communal sentiment since the middle of the last century has already found its manifestation in the legislation with regard to mines, for the laws of south africa, australia, and england, and the agitation in the united states are all toward greater restrictions on the mineral ownership in favour of the state. [ ] ?_de limitibus et de re agraria_ of sextus julius frontinus (about - a.d.) [ ] such a form of ownership is very old. apparently upon the instigation of xenophon (see note , p. ) the greeks formed companies to work the mines of laurion, further information as to which is given in note , p. . pliny (note , p. ) mentions the company working the quicksilver mines in spain. in fact, company organization was very common among the romans, who speculated largely in the shares, especially in those companies which farmed the taxes of the provinces, or leased public lands, or took military and civil contracts. [ ] the latin text gives one-sixth, obviously an error. [ ] a _symposium_ is a banquet, and a _symbola_ is a contribution of money to a banquet. this sentence is probably a play on the old german _zeche_, mine, this being also a term for a drinking bout. [ ] in the latin text this is "three"--obviously an error. [ ] see note , p. , for further information with regard to these mines. the rhenish gulden was about . shillings, or $ . . silver was worth about this amount per troy ounce at this period, so that roughly, silver of a value of , gulden would be about , troy ounces. the saxon thaler was worth about . shillings or about $ . . the thaler, therefore, represented about . troy ounces of silver, so that thalers were about troy ounces, and thalers about troy ounces. [ ] _opera continens_. the glossary gives _schicht_,--the origin of the english "shift." [ ] the terms in the latin text are _donator_, a giver of a gift, and _donatus_, a receiver. it appears to us, however, that some consideration passed, and we have, therefore, used "seller" and "buyer." [ ] see note , p. . [ ] _decemviri_--"the ten men." the original _decemviri_ were a body appointed by the romans in b.c., principally to codify the law. such commissions were afterward instituted for other purposes, but the analogy of the above paragraph is a little remote. [ ] this work was apparently never published; see appendix a. book v. in the last book i have explained the methods of delimiting the meers along each kind of vein, and the duties of mine officials. in this book[ ] i will in like manner explain the principles of underground mining and the art of surveying. first then, i will proceed to deal with those matters which pertain to the former heading, since both the subject and methodical arrangement require it. and so i will describe first of all the digging of shafts, tunnels, and drifts on _venae profundae_; next i will discuss the good indications shown by _canales_[ ], by the materials which are dug out, and by the rocks; then i will speak of the tools by which veins and rocks are broken down and excavated; the method by which fire shatters the hard veins; and further, of the machines with which water is drawn from the shafts and air is forced into deep shafts and long tunnels, for digging is impeded by the inrush of the former or the failure of the latter; next i will deal with the two kinds of shafts, and with the making of them and of tunnels; and finally, i will describe the method of mining _venae dilatatae_, _venae cumulatae_, and stringers. now when a miner discovers a _vena profunda_ he begins sinking a shaft and above it sets up a windlass, and builds a shed over the shaft to prevent the rain from falling in, lest the men who turn the windlass be numbed by the cold or troubled by the rain. the windlass men also place their barrows in it, and the miners store their iron tools and other implements therein. next to the shaft-house another house is built, where the mine foreman and the other workmen dwell, and in which are stored the ore and other things which are dug out. although some persons build only one house, yet because sometimes boys and other living things fall into the shafts, most miners deliberately place one house apart from the other, or at least separate them by a wall. [illustration (shafts): three vertical shafts, of which the first, a, does not reach the tunnel; the second, b, reaches the tunnel; to the third, c, the tunnel has not yet been driven. d--tunnel.] [illustration (shafts): three inclined shafts, of which a does not yet reach the tunnel; b reaches the tunnel; to the third, c, the tunnel has not yet been driven. d--tunnel.] now a shaft is dug, usually two fathoms long, two-thirds of a fathom wide, and thirteen fathoms deep; but for the purpose of connecting with a tunnel which has already been driven in a hill, a shaft may be sunk to a depth of only eight fathoms, at other times to fourteen, more or less[ ]. a shaft may be made vertical or inclined, according as the vein which the miners follow in the course of digging is vertical or inclined. a tunnel is a subterranean ditch driven lengthwise, and is nearly twice as high as it is broad, and wide enough that workmen and others may be able to pass and carry their loads. it is usually one and a quarter fathoms high, while its width is about three and three-quarters feet. usually two workmen are required to drive it, one of whom digs out the upper and the other the lower part, and the one goes forward, while the other follows closely after. each sits upon small boards fixed securely from the footwall to the hangingwall, or if the vein is a soft one, sometimes on a wedge-shaped plank fixed on to the vein itself. miners sink more inclined shafts than vertical, and some of each kind do not reach to tunnels, while some connect with them. but as for some shafts, though they have already been sunk to the required depth, the tunnel which is to pierce the mountain may not yet have been driven far enough to connect with them. [illustration (shafts): a--shaft. b, c--drift. d--another shaft. e--tunnel. f--mouth of tunnel.] it is advantageous if a shaft connects with a tunnel, for then the miners and other workmen carry on more easily the work they have undertaken; but if the shaft is not so deep, it is usual to drift from one or both sides of it. from these openings the owner or foreman becomes acquainted with the veins and stringers that unite with the principal vein, or cut across it, or divide it obliquely; however, my discourse is now concerned mainly with _vena profunda_, but most of all with the metallic material which it contains. excavations of this kind were called by the greeks [greek: kryptai] for, extending along after the manner of a tunnel, they are entirely hidden within the ground. this kind of an opening, however, differs from a tunnel in that it is dark throughout its length, whereas a tunnel has a mouth open to daylight. i have spoken of shafts, tunnels, and drifts. i will now speak of the indications given by the _canales_, by the materials which are dug out, and by the rocks. these indications, as also many others which i will explain, are to a great extent identical in _venae dilatatae_ and _venae cumulatae_ with _venae profundae_. when a stringer junctions with a main vein and causes a swelling, a shaft should be sunk at the junction. but when we find the stringer intersecting the main vein crosswise or obliquely, if it descends vertically down to the depths of the earth, a second shaft should be sunk to the point where the stringer cuts the main vein; but if the stringer cuts it obliquely the shaft should be two or three fathoms back, in order that the junction may be pierced lower down. at such junctions lies the best hope of finding the ore for the sake of which we explore the ground, and if ore has already been found, it is usually found in much greater abundance at that spot. again, if several stringers descend into the earth, the miner, in order to pierce through the point of contact, should sink the shaft in the midst of these stringers, or else calculate on the most prominent one. since an inclined vein often lies near a vertical vein, it is advisable to sink a shaft at the spot where a stringer or cross-vein cuts them both; or where a _vena dilatata_ or a stringer _dilatata_ passes through, for minerals are usually found there. in the same way we have a good prospect of finding metal at the point where an inclined vein joins a vertical one; this is why miners cross-cut the hangingwall or footwall of a main vein, and in these openings seek for a vein which may junction with the principal vein a few fathoms below. nay, further, these same miners, if no stringer or cross-vein intersects the main vein so that they can follow it in their workings, even cross-cut through the solid rock of the hangingwall or footwall. these cross-cuts are likewise called "[greek: kryptai]," whether the beginning of the opening which has to be undertaken is made from a tunnel or from a drift. miners have some hope when only a cross vein cuts a main vein. further, if a vein which cuts the main vein obliquely does not appear anywhere beyond it, it is advisable to dig into that side of the main vein toward which the oblique vein inclines, whether the right or left side, that we may ascertain if the main vein has absorbed it; if after cross-cutting six fathoms it is not found, it is advisable to dig on the other side of the main vein, that we may know for certain whether it has carried it forward. the owners of a main vein can often dig no less profitably on that side where the vein which cuts the main vein again appears, than where it first cuts it; the owners of the intersecting vein, when that is found again, recover their title, which had in a measure been lost. the common miners look favourably upon the stringers which come from the north and join the main vein; on the other hand, they look unfavourably upon those which come from the south, and say that these do much harm to the main vein, while the former improve it. but i think that miners should not neglect either of them: as i showed in book iii, experience does not confirm those who hold this opinion about veins, so now again i could furnish examples of each kind of stringers rejected by the common miners which have proved good, but i know this could be of little or no benefit to posterity. if the miners find no stringers or veins in the hangingwall or footwall of the main vein, and if they do not find much ore, it is not worth while to undertake the labour of sinking another shaft. nor ought a shaft to be sunk where a vein is divided into two or three parts, unless the indications are satisfactory that those parts may be united and joined together a little later. further, it is a bad indication for a vein rich in mineral to bend and turn hither and thither, for unless it goes down again into the ground vertically or inclined, as it first began, it produces no more metal; and even though it does go down again, it often continues barren. stringers which in their outcrops bear metals, often disappoint miners, no metal being found in depth. further, inverted seams in the rocks are counted among the bad indications. the miners hew out the whole of solid veins when they show clear evidence of being of good quality; similarly they hew out the drusy[ ] veins, especially if the cavities are plainly seen to have formerly borne metal, or if the cavities are few and small. they do not dig barren veins through which water flows, if there are no metallic particles showing; occasionally, however, they dig even barren veins which are free from water, because of the pyrites which is devoid of all metal, or because of a fine black soft substance which is like wool. they dig stringers which are rich in metal, or sometimes, for the purpose of searching for the vein, those that are devoid of ore which lie near the hangingwall or footwall of the main vein. this then, generally speaking, is the mode of dealing with stringers and veins. let us now consider the metallic material which is found in the _canales_ of _venae profundae_, _venae dilatatae_, and _venae cumulatae_, being in all these either cohesive and continuous, or scattered and dispersed among them, or swelling out in bellying shapes, or found in veins or stringers which originate from the main vein and ramify like branches; but these latter veins and stringers are very short, for after a little space they do not appear again. if we come across a small quantity of metallic material it is an indication; but if a large quantity, it is not an "indication," but the very thing for which we explore the earth. as soon as a miner who searches for veins discovers pure metal or minerals, or rich metallic material, or a great abundance of material which is poor in metal, let him sink a shaft on the spot without any delay. if the material appears more abundant or of better quality on the one side, he will incline his digging in that direction. gold, silver, copper, and quicksilver are often found native[ ]; less often iron and bismuth; almost never tin and lead. nevertheless tin-stone is not far removed from the pure white tin which is melted out of them, and galena, from which lead is obtained, differs little from that metal itself. now we may classify gold ores. next after native gold, we come to the _rudis_[ ], of yellowish green, yellow, purple, black, or outside red and inside gold colour. these must be reckoned as the richest ores, because the gold exceeds the stone or earth in weight. next come all gold ores of which each one hundred _librae_ contains more than three _unciae_ of gold[ ]; for although but a small proportion of gold is found in the earth or stone, yet it equals in value other metals of greater weight.[ ] all other gold ores are considered poor, because the earth or stone too far outweighs the gold. a vein which contains a larger proportion of silver than of gold is rarely found to be a rich one. earth, whether it be dry or wet, rarely abounds in gold; but in dry earth there is more often found a greater quantity of gold, especially if it has the appearance of having been melted in a furnace, and if it is not lacking in scales resembling mica. the solidified juices, azure, chrysocolla, orpiment, and realgar, also frequently contain gold. likewise native or _rudis_ gold is found sometimes in large, and sometimes in small quantities in quartz, schist, marble, and also in stone which easily melts in fire of the second degree, and which is sometimes so porous that it seems completely decomposed. lastly, gold is found in pyrites, though rarely in large quantities. when considering silver ores other than native silver, those ores are classified as rich, of which each one hundred _librae_ contains more than three _librae_ of silver. this quality comprises _rudis_ silver, whether silver glance or ruby silver, or whether white, or black, or grey, or purple, or yellow, or liver-coloured, or any other. sometimes quartz, schist, or marble is of this quality also, if much native or _rudis_ silver adheres to it. but that ore is considered of poor quality if three _librae_ of silver at the utmost are found in each one hundred _librae_ of it[ ]. silver ore usually contains a greater quantity than this, because nature bestows quantity in place of quality; such ore is mixed with all kinds of earth and stone compounds, except the various kinds of _rudis_ silver; especially with pyrites, _cadmia metallica fossilis_, galena, _stibium_, and others. as regards other kinds of metal, although some rich ores are found, still, unless the veins contain a large quantity of ore, it is very rarely worth while to dig them. the indians and some other races do search for gems in veins hidden deep in the earth, but more often they are noticed from their clearness, or rather their brilliancy, when metals are mined. when they outcrop, we follow veins of marble by mining in the same way as is done with rock or building-stones when we come upon them. but gems, properly so called, though they sometimes have veins of their own, are still for the most part found in mines and rock quarries, as the lodestone in iron mines, the emery in silver mines, the _lapis judaicus_, _trochites_, and the like in stone quarries where the diggers, at the bidding of the owners, usually collect them from the seams in the rocks.[ ] nor does the miner neglect the digging of "extraordinary earths,"[ ] whether they are found in gold mines, silver mines, or other mines; nor do other miners neglect them if they are found in stone quarries, or in their own veins; their value is usually indicated by their taste. nor, lastly, does the miner fail to give attention to the solidified juices which are found in metallic veins, as well as in their own veins, from which he collects and gathers them. but i will say no more on these matters, because i have explained more fully all the metals and mineral substances in the books "_de natura fossilium_." but i will return to the indications. if we come upon earth which is like lute, in which there are particles of any sort of metal, native or _rudis_, the best possible indication of a vein is given to miners, for the metallic material from which the particles have become detached is necessarily close by. but if this kind of earth is found absolutely devoid of all metallic material, but fatty, and of white, green, blue, and similar colours, they must not abandon the work that has been started. miners have other indications in the veins and stringers, which i have described already, and in the rocks, about which i will speak a little later. if the miner comes across other dry earths which contain native or _rudis_ metal, that is a good indication; if he comes across yellow, red, black, or some other "extraordinary" earth, though it is devoid of mineral, it is not a bad indication. chrysocolla, or azure, or verdigris, or orpiment, or realgar, when they are found, are counted among the good indications. further, where underground springs throw up metal we ought to continue the digging we have begun, for this points to the particles having been detached from the main mass like a fragment from a body. in the same way the thin scales of any metal adhering to stone or rock are counted among the good indications. next, if the veins which are composed partly of quartz, partly of clayey or dry earth, descend one and all into the depths of the earth together, with their stringers, there is good hope of metal being found; but if the stringers afterward do not appear, or little metallic material is met with, the digging should not be given up until there is nothing remaining. dark or black or horn or liver-coloured quartz is usually a good sign; white is sometimes good, sometimes no sign at all. but calc-spar, showing itself in a _vena profunda_, if it disappears a little lower down is not a good indication; for it did not belong to the vein proper, but to some stringer. those kinds of stone which easily melt in fire, especially if they are translucent (fluorspar?), must be counted among the medium indications, for if other good indications are present they are good, but if no good indications are present, they give no useful significance. in the same way we ought to form our judgment with regard to gems. veins which at the hangingwall and footwall have horn-coloured quartz or marble, but in the middle clayey earth, give some hope; likewise those give hope in which the hangingwall or footwall shows iron-rust coloured earth, and in the middle greasy and sticky earth; also there is hope for those which have at the hanging or footwall that kind of earth which we call "soldiers' earth," and in the middle black earth or earth which looks as if burnt. the special indication of gold is orpiment; of silver is bismuth and _stibium_; of copper is verdigris, _melanteria_, _sory_, _chalcitis_, _misy_, and vitriol; of tin is the large pure black stones of which the tin itself is made, and a material they dig up resembling litharge; of iron, iron rust. gold and copper are equally indicated by chrysocolla and azure; silver and lead, by the lead. but, though miners rightly call bismuth "the roof of silver," and though copper pyrites is the common parent of vitriol and _melanteria_, still these sometimes have their own peculiar minerals, just as have orpiment and _stibium_. now, just as certain vein materials give miners a favourable indication, so also do the rocks through which the _canales_ of the veins wind their way, for sand discovered in a mine is reckoned among the good indications, especially if it is very fine. in the same way schist, when it is of a bluish or blackish colour, and also limestone, of whatever colour it may be, is a good sign for a silver vein. there is a rock of another kind that is a good sign; in it are scattered tiny black stones from which tin is smelted; especially when the whole space between the veins is composed of this kind of rock. very often indeed, this good kind of rock in conjunction with valuable stringers contains within its folds the _canales_ of mineral bearing veins: if it descends vertically into the earth, the benefit belongs to that mine in which it is seen first of all; if inclined, it benefits the other neighbouring mines[ ]. as a result the miner who is not ignorant of geometry can calculate from the other mines the depth at which the _canales_ of a vein bearing rich metal will wind its way through the rock into his mine. so much for these matters. i now come to the mode of working, which is varied and complex, for in some places they dig crumbling ore, in others hard ore, in others a harder ore, and in others the hardest kind of ore. in the same way, in some places the hangingwall rock is soft and fragile, in others hard, in others harder, and in still others of the hardest sort. i call that ore "crumbling" which is composed of earth, and of soft solidified juices; that ore "hard" which is composed of metallic minerals and moderately hard stones, such as for the most part are those which easily melt in a fire of the first and second orders, like lead and similar materials. i call that ore "harder" when with those i have already mentioned are combined various sorts of quartz, or stones which easily melt in fire of the third degree, or pyrites, or _cadmia_, or very hard marble. i call that ore hardest, which is composed throughout the whole vein of these hard stones and compounds. the hanging or footwalls of a vein are hard, when composed of rock in which there are few stringers or seams; harder, in which they are fewer; hardest, in which they are fewest or none at all. when these are absent, the rock is quite devoid of water which softens it. but the hardest rock of the hanging or footwall, however, is seldom as hard as the harder class of ore. miners dig out crumbling ore with the pick alone. when the metal has not yet shown itself, they do not discriminate between the hangingwall and the veins; when it has once been found, they work with the utmost care. for first of all they tear away the hangingwall rock separately from the vein, afterward with a pick they dislodge the crumbling vein from the footwall into a dish placed underneath to prevent any of the metal from falling to the ground. they break a hard vein loose from the footwall by blows with a hammer upon the first kind of iron tool[ ], all of which are designated by appropriate names, and with the same tools they hew away the hard hangingwall rock. they hew out the hangingwall rock in advance more frequently, the rock of the footwall more rarely; and indeed, when the rock of the footwall resists iron tools, the rock of the hangingwall certainly cannot be broken unless it is allowable to shatter it by fire. with regard to the harder veins which are tractable to iron tools, and likewise with regard to the harder and hardest kind of hangingwall rock, they generally attack them with more powerful iron tools, in fact, with the fourth kind of iron tool, which are called by their appropriate names; but if these are not ready to hand, they use two or three iron tools of the first kind together. as for the hardest kind of metal-bearing vein, which in a measure resists iron tools, if the owners of the neighbouring mines give them permission, they break it with fires. but if these owners refuse them permission, then first of all they hew out the rock of the hangingwall, or of the footwall if it be less hard; then they place timbers set in hitches in the hanging or footwall, a little above the vein, and from the front and upper part, where the vein is seen to be seamed with small cracks, they drive into one of the little cracks one of the iron tools which i have mentioned; then in each fracture they place four thin iron blocks, and in order to hold them more firmly, if necessary, they place as many thin iron plates back to back; next they place thinner iron plates between each two iron blocks, and strike and drive them by turns with hammers, whereby the vein rings with a shrill sound; and the moment when it begins to be detached from the hangingwall or footwall rock, a tearing sound is heard. as soon as this grows distinct the miners hastily flee away; then a great crash is heard as the vein is broken and torn, and falls down. by this method they throw down a portion of a vein weighing a hundred pounds more or less. but if the miners by any other method hew the hardest kind of vein which is rich in metal, there remain certain cone-shaped portions which can be cut out afterward only with difficulty. as for this knob of hard ore, if it is devoid of metal, or if they are not allowed to apply fire to it, they proceed round it by digging to the right or left, because it cannot be broken into by iron wedges without great expense. meantime, while the workmen are carrying out the task they have undertaken, the depths of the earth often resound with sweet singing, whereby they lighten a toil which is of the severest kind and full of the greatest dangers. as i have just said, fire shatters the hardest rocks, but the method of its application is not simple[ ]. for if a vein held in the rocks cannot be hewn out because of the hardness or other difficulty, and the drift or tunnel is low, a heap of dried logs is placed against the rock and fired; if the drift or tunnel is high, two heaps are necessary, of which one is placed above the other, and both burn until the fire has consumed them. this force does not generally soften a large portion of the vein, but only some of the surface. when the rock in the hanging or footwall can be worked by the iron tools and the vein is so hard that it is not tractable to the same tools, then the walls are hollowed out; if this be in the end of the drift or tunnel or above or below, the vein is then broken by fire, but not by the same method; for if the hollow is wide, as many logs are piled into it as possible, but if narrow, only a few. by the one method the greater fire separates the vein more completely from the footwall or sometimes from the hangingwall, and by the other, the smaller fire breaks away less of the vein from the rock, because in that case the fire is confined and kept in check by portions of the rock which surround the wood held in such a narrow excavation. further, if the excavation is low, only one pile of logs is placed in it, if high, there are two, one placed above the other, by which plan the lower bundle being kindled sets alight the upper one; and the fire being driven by the draught into the vein, separates it from the rock which, however hard it may be, often becomes so softened as to be the most easily breakable of all. applying this principle, hannibal, the carthaginian general, imitating the spanish miners, overcame the hardness of the alps by the use of vinegar and fire. even if a vein is a very wide one, as tin veins usually are, miners excavate into the small streaks, and into those hollows they put dry wood and place amongst them at frequent intervals sticks, all sides of which are shaved down fan-shaped, which easily take light, and when once they have taken fire communicate it to the other bundles of wood, which easily ignite. [illustration (fire-setting): a--kindled logs. b--sticks shaved down fan-shaped. c--tunnel.] while the heated veins and rock are giving forth a foetid vapour and the shafts or tunnels are emitting fumes, the miners and other workmen do not go down in the mines lest the stench affect their health or actually kill them, as i will explain in greater detail when i come to speak of the evils which affect miners. the _bergmeister_, in order to prevent workmen from being suffocated, gives no one permission to break veins or rock by fire in shafts or tunnels where it is possible for the poisonous vapour and smoke to permeate the veins or stringers and pass through into the neighbouring mines, which have no hard veins or rock. as for that part of a vein or the surface of the rock which the fire has separated from the remaining mass, if it is overhead, the miners dislodge it with a crowbar, or if it still has some degree of hardness, they thrust a smaller crowbar into the cracks and so break it down, but if it is on the sides they break it with hammers. thus broken off, the rock tumbles down; or if it still remains, they break it off with picks. rock and earth on the one hand, and metal and ore on the other, are filled into buckets separately and drawn up to the open air or to the nearest tunnel. if the shaft is not deep, the buckets are drawn up by a machine turned by men; if it is deep, they are drawn by machines turned by horses. it often happens that a rush of water or sometimes stagnant air hinders the mining; for this reason miners pay the greatest attention to these matters, just as much as to digging, or they should do so. the water of the veins and stringers and especially of vacant workings, must be drained out through the shafts and tunnels. air, indeed, becomes stagnant both in tunnels and in shafts; in a deep shaft, if it be by itself, this occurs if it is neither reached by a tunnel nor connected by a drift with another shaft; this occurs in a tunnel if it has been driven too far into a mountain and no shaft has yet been sunk deep enough to meet it; in neither case can the air move or circulate. for this reason the vapours become heavy and resemble mist, and they smell of mouldiness, like a vault or some underground chamber which has been completely closed for many years. this suffices to prevent miners from continuing their work for long in these places, even if the mine is full of silver or gold, or if they do continue, they cannot breathe freely and they have headaches; this more often happens if they work in these places in great numbers, and bring many lamps, which then supply them with a feeble light, because the foul air from both lamps and men make the vapours still more heavy. a small quantity of water is drawn from the shafts by machines of different kinds which men turn or work. if so great a quantity has flowed into one shaft as greatly to impede mining, another shaft is sunk some fathoms distant from the first, and thus in one of them work and labour are carried on without hindrance, and the water is drained into the other, which is sunk lower than the level of the water in the first one; then by these machines or by those worked by horses, the water is drawn up into the drain and flows out of the shaft-house or the mouth of the nearest tunnel. but when into the shaft of one mine, which is sunk more deeply, there flows all the water of all the neighbouring mines, not only from that vein in which the shaft is sunk, but also from other veins, then it becomes necessary for a large sump to be made to collect the water; from this sump the water is drained by machines which draw it through pipes, or by ox-hides, about which i will say more in the next book. the water which pours into the tunnels from the veins and stringers and seams in the rocks is carried away in the drains. air is driven into the extremities of deep shafts and long tunnels by powerful blowing machines, as i will explain in the following book, which will deal with these machines also. the outer air flows spontaneously into the caverns of the earth, and when it can pass through them comes out again. this, however, comes about in different ways, for in spring and summer it flows into the deeper shafts, traverses the tunnels or drifts, and finds its way out of the shallower shafts; similarly at the same season it pours into the lowest tunnel and, meeting a shaft in its course, turns aside to a higher tunnel and passes out therefrom; but in autumn and winter, on the other hand, it enters the upper tunnel or shaft and comes out at the deeper ones. this change in the flow of air currents occurs in temperate regions at the beginning of spring and the end of autumn, but in cold regions at the end of spring and the beginning of autumn. but at each period, before the air regularly assumes its own accustomed course, generally for a space of fourteen days it undergoes frequent variations, now blowing into an upper shaft or tunnel, now into a lower one. but enough of this, let us now proceed to what remains. there are two kinds of shafts, one of the depth already described, of which kind there are usually several in one mine; especially if the mine is entered by a tunnel and is metal-bearing. for when the first tunnel is connected with the first shaft, two new shafts are sunk; or if the inrush of water hinders sinking, sometimes three are sunk; so that one may take the place of a sump and the work of sinking which has been begun may be continued by means of the remaining two shafts; the same is done in the case of the second tunnel and the third, or even the fourth, if so many are driven into a mountain. the second kind of shaft is very deep, sometimes as much as sixty, eighty, or one hundred fathoms. these shafts continue vertically toward the depths of the earth, and by means of a hauling-rope the broken rock and metalliferous ores are drawn out of the mine; for which reason miners call them vertical shafts. over these shafts are erected machines by which water is extracted; when they are above ground the machines are usually worked by horses, but when they are in tunnels, other kinds are used which are turned by water-power. such are the shafts which are sunk when a vein is rich in metal. now shafts, of whatever kind they may be, are supported in various ways. if the vein is hard, and also the hanging and footwall rock, the shaft does not require much timbering, but timbers are placed at intervals, one end of each of which is fixed in a hitch cut into the rock of the hangingwall and the other fixed into a hitch cut in the footwall. to these timbers are fixed small timbers along the footwall, to which are fastened the lagging and ladders. the lagging is also fixed to the timbers, both to those which screen off the shaft on the ends from the vein, and to those which screen off the rest of the shaft from that part in which the ladders are placed. the lagging on the sides of the shaft confine the vein, so as to prevent fragments of it which have become loosened by water from dropping into the shaft and terrifying, or injuring, or knocking off the miners and other workmen who are going up or down the ladders from one part of the mine to another. for the same reason, the lagging between the ladders and the haulage-way on the other hand, confine and shut off from the ladders the fragments of rock which fall from the buckets or baskets while they are being drawn up; moreover, they make the arduous and difficult descent and ascent to appear less terrible, and in fact to be less dangerous. [illustration (timbering shafts): a--wall plates. b--dividers. c--long end posts. d--end plates.] if a vein is soft and the rock of the hanging and footwalls is weak, a closer structure is necessary; for this purpose timbers are joined together, in rectangular shapes and placed one after the other without a break. these are arranged on two different systems; for either the square ends of the timbers, which reach from the hangingwall to the footwall, are fixed into corresponding square holes in the timbers which lie along the hanging or footwall, or the upper part of the end of one and the lower part of the end of the other are cut out and one laid on the other. the great weight of these joined timbers is sustained by stout beams placed at intervals, which are deeply set into hitches in the footwall and hangingwall, but are inclined. in order that these joined timbers may remain stationary, wooden wedges or poles cut from trees are driven in between the timbers and the vein and the hangingwall and the footwall; and the space which remains empty is filled with loose dirt. if the hanging and footwall rock is sometimes hard and sometimes soft, and the vein likewise, solid joined timbers are not used, but timbers are placed at intervals; and where the rock is soft and the vein crumbling, carpenters put in lagging between them and the wall rocks, and behind these they fill with loose dirt; by this means they fill up the void. when a very deep shaft, whether vertical or inclined, is supported by joined timbers, then, since they are sometimes of bad material and a fall is threatened, for the sake of greater firmness three or four pairs of strong end posts are placed between these, one pair on the hangingwall side, the other on the footwall side. to prevent them from falling out of position and to make them firm and substantial, they are supported by frequent end plates, and in order that these may be more securely fixed they are mortised into the posts. further, in whatever way the shaft may be timbered, dividers are placed upon the wall plates, and to these is fixed lagging, and this marks off and separates the ladder-way from the remaining part of the shaft. if a vertical shaft is a very deep one, planks are laid upon the timbers by the side of the ladders and fixed on to the timbers, in order that the men who are going up or down may sit or stand upon them and rest when they are tired. to prevent danger to the shovellers from rocks which, after being drawn up from so deep a shaft fall down again, a little above the bottom of the shaft small rough sticks are placed close together on the timbers, in such a way as to cover the whole space of the shaft except the ladder-way. a hole, however, is left in this structure near the footwall, which is kept open so that there may be one opening to the shaft from the bottom, that the buckets full of the materials which have been dug out may be drawn from the shaft through it by machines, and may be returned to the same place again empty; and so the shovellers and other workmen, as it were hiding beneath this structure, remain perfectly safe in the shaft. [illustration (timbering tunnels): a--posts. b--caps. c--sills. d--doors. e--lagging. f--drains.] in mines on one vein there are driven one, two, or sometimes three or more tunnels, always one above the other. if the vein is solid and hard, and likewise the hanging and footwall rock, no part of the tunnel needs support, beyond that which is required at the mouth, because at that spot there is not yet solid rock; if the vein is soft, and the hanging and footwall rock are likewise soft, the tunnel requires frequent strong timbering, which is provided in the following way. first, two dressed posts are erected and set into the tunnel floor, which is dug out a little; these are of medium thickness, and high enough that their ends, which are cut square, almost touch the top of the tunnel; then upon them is placed a smaller dressed cap, which is mortised into the heads of the posts; at the bottom, other small timbers, whose ends are similarly squared, are mortised into the posts. at each interval of one and a half fathoms, one of these sets is erected; each one of these the miners call a "little doorway," because it opens a certain amount of passage way; and indeed, when necessity requires it, doors are fixed to the timbers of each little doorway so that it can be closed. then lagging of planks or of poles is placed upon the caps lengthwise, so as to reach from one set of timbers to another, and is laid along the sides, in case some portion of the body of the mountain may fall, and by its bulk impede passage or crush persons coming in or out. moreover, to make the timbers remain stationary, wooden pegs are driven between them and the sides of the tunnel. lastly, if rock or earth are carried out in wheelbarrows, planks joined together are laid upon the sills; if the rock is hauled out in trucks, then two timbers three-quarters of a foot thick and wide are laid on the sills, and, where they join, these are usually hollowed out so that in the hollow, as in a road, the iron pin of the truck may be pushed along; indeed, because of this pin in the groove, the truck does not leave the worn track to the left or right. beneath the sills are the drains through which the water flows away. miners timber drifts in the same way as tunnels. these do not, however, require sill-pieces, or drains; for the broken rock is not hauled very far, nor does the water have far to flow. if the vein above is metal-bearing, as it sometimes is for a distance of several fathoms, then from the upper part of tunnels or even drifts that have already been driven, other drifts are driven again and again until that part of the vein is reached which does not yield metal. the timbering of these openings is done as follows: stulls are set at intervals into hitches in the hanging and footwall, and upon them smooth poles are laid continuously; and that they may be able to bear the weight, the stulls are generally a foot and a half thick. after the ore has been taken out and the mining of the vein is being done elsewhere, the rock then broken, especially if it cannot be taken away without great difficulty, is thrown into these openings among the timber, and the carriers of the ore are saved toil, and the owners save half the expense. this then, generally speaking, is the method by which everything relating to the timbering of shafts, tunnels, and drifts is carried out. all that i have hitherto written is in part peculiar to _venae profundae_, and in part common to all kinds of veins; of what follows, part is specially applicable to _venae dilatatae_, part to _venae cumulatae_. but first i will describe how _venae dilatatae_ should be mined. where torrents, rivers, or streams have by inundations washed away part of the slope of a mountain or a hill, and have disclosed a _vena dilatata_, a tunnel should be driven first straight and narrow, and then wider, for nearly all the vein should be hewn away; and when this tunnel has been driven further, a shaft which supplies air should be sunk in the mountain or hill, and through it from time to time the ore, earth, and rock can be drawn up at less expense than if they be drawn out through the very great length of the tunnel; and even in those places to which the tunnel does not yet reach, miners dig shafts in order to open a _vena dilatata_ which they conjecture must lie beneath the soil. in this way, when the upper layers are removed, they dig through rock sometimes of one kind and colour, sometimes of one kind but different colours, sometimes of different kinds but of one colour, and, lastly, of different kinds and different colours. the thickness of rock, both of each single stratum and of all combined, is uncertain, for the whole of the strata are in some places twenty fathoms deep, in others more than fifty; individual strata are in some places half a foot thick; in others, one, two, or more feet; in others, one, two, three, or more fathoms. for example, in those districts which lie at the foot of the harz mountains, there are many different coloured strata, covering a copper _vena dilatata_. when the soil has been stripped, first of all is disclosed a stratum which is red, but of a dull shade and of a thickness of twenty, thirty, or five and thirty fathoms. then there is another stratum, also red, but of a light shade, which has usually a thickness of about two fathoms. beneath this is a stratum of ash-coloured clay nearly a fathom thick, which, although it is not metalliferous, is reckoned a vein. then follows a third stratum, which is ashy, and about three fathoms thick. beneath this lies a vein of ashes to the thickness of five fathoms, and these ashes are mixed with rock of the same colour. joined to the last, and underneath, comes a stratum, the fourth in number, dark in colour and a foot thick. under this comes the fifth stratum, of a pale or yellowish colour, two feet thick; underneath which is the sixth stratum, likewise dark, but rough and three feet thick. afterward occurs the seventh stratum, likewise of dark colour, but still darker than the last, and two feet thick. this is followed by an eighth stratum, ashy, rough, and a foot thick. this kind, as also the others, is sometimes distinguished by stringers of the stone which easily melts in fire of the second order. beneath this is another ashy rock, light in weight, and five feet thick. next to this comes a lighter ash-coloured one, a foot thick; beneath this lies the eleventh stratum, which is dark and very much like the seventh, and two feet thick. below the last is a twelfth stratum of a whitish colour and soft, also two feet thick; the weight of this rests on a thirteenth stratum, ashy and one foot thick, whose weight is in turn supported by a fourteenth stratum, which is blackish and half a foot thick. there follows this, another stratum of black colour, likewise half a foot thick, which is again followed by a sixteenth stratum still blacker in colour, whose thickness is also the same. beneath this, and last of all, lies the cupriferous stratum, black coloured and schistose, in which there sometimes glitter scales of gold-coloured pyrites in the very thin sheets, which, as i said elsewhere, often take the forms of various living things.[ ] the miners mine out a _vena dilatata_ laterally and longitudinally by driving a low tunnel in it, and if the nature of the work and place permit, they sink also a shaft in order to discover whether there is a second vein beneath the first one; for sometimes beneath it there are two, three, or more similar metal-bearing veins, and these are excavated in the same way laterally and longitudinally. they generally mine _venae dilatatae_ lying down; and to avoid wearing away their clothes and injuring their left shoulders they usually bind on themselves small wooden cradles. for this reason, this particular class of miners, in order to use their iron tools, are obliged to bend their necks to the left, not infrequently having them twisted. now these veins also sometimes divide, and where these parts re-unite, ore of a richer and a better quality is generally found; the same thing occurs where the stringers, of which they are not altogether devoid, join with them, or cut them crosswise, or divide them obliquely. to prevent a mountain or hill, which has in this way been undermined, from subsiding by its weight, either some natural pillars and arches are left, on which the pressure rests as on a foundation, or timbering is done for support. moreover, the materials which are dug out and which are devoid of metal are removed in bowls, and are thrown back, thus once more filling the caverns. next, as to _venae cumulatae_. these are dug by a somewhat different method, for when one of these shows some metal at the top of the ground, first of all one shaft is sunk; then, if it is worth while, around this one many shafts are sunk and tunnels are driven into the mountain. if a torrent or spring has torn fragments of metal from such a vein, a tunnel is first driven into the mountain or hill for the purpose of searching for the ore; then when it is found, a vertical shaft is sunk in it. since the whole mountain, or more especially the whole hill, is undermined, seeing that the whole of it is composed of ore, it is necessary to leave the natural pillars and arches, or the place is timbered. but sometimes when a vein is very hard it is broken by fire, whereby it happens that the soft pillars break up, or the timbers are burnt away, and the mountain by its great weight sinks into itself, and then the shaft buildings are swallowed up in the great subsidence. therefore, about a _vena cumulata_ it is advisable to sink some shafts which are not subject to this kind of ruin, through which the materials that are excavated may be carried out, not only while the pillars and underpinnings still remain whole and solid, but also after the supports have been destroyed by fire and have fallen. since ore which has thus fallen must necessarily be broken by fire, new shafts through which the smoke can escape must be sunk in the abyss. at those places where stringers intersect, richer ore is generally obtained from the mine; these stringers, in the case of tin mines, sometimes have in them black stones the size of a walnut. if such a vein is found in a plain, as not infrequently happens in the case of iron, many shafts are sunk, because they cannot be sunk very deep. the work is carried on by this method because the miners cannot drive a tunnel into a level plain of this kind. there remain the stringers in which gold alone is sometimes found, in the vicinity of rivers and streams, or in swamps. if upon the soil being removed, many of these are found, composed of earth somewhat baked and burnt, as may sometimes be seen in clay pits, there is some hope that gold may be obtained from them, especially if several join together. but the very point of junction must be pierced, and the length and width searched for ore, and in these places very deep shafts cannot be sunk. i have completed one part of this book, and now come to the other, in which i will deal with the art of surveying. miners measure the solid mass of the mountains in order that the owners may lay out their plans, and that their workmen may not encroach on other people's possessions. the surveyor either measures the interval not yet wholly dug through, which lies between the mouth of a tunnel and a shaft to be sunk to that depth, or between the mouth of a shaft and the tunnel to be driven to that spot which lies under the shaft, or between both, if the tunnel is neither so long as to reach to the shaft, nor the shaft so deep as to reach to the tunnel; and thus on both sides work is still to be done. or in some cases, within the tunnels and drifts, are to be fixed the boundaries of the meers, just as the _bergmeister_ has determined the boundaries of the same meers above ground.[ ] each method of surveying depends on the measuring of triangles. a small triangle should be laid out, and from it calculations must be made regarding a larger one. most particular care must be taken that we do not deviate at all from a correct measuring; for if, at the beginning, we are drawn by carelessness into a slight error, this at the end will produce great errors. now these triangles are of many shapes, since shafts differ among themselves and are not all sunk by one and the same method into the depths of the earth, nor do the slopes of all mountains come down to the valley or plain in the same manner. for if a shaft is vertical, there is a triangle with a right angle, which the greeks call [greek: orthogônion] and this, according to the inequalities of the mountain slope, has either two equal sides or three unequal sides. the greeks call the former [greek: trigônon isoskeles] the latter [greek: skalênon] for a right angle triangle cannot have three equal sides. if a shaft is inclined and sunk in the same vein in which the tunnel is driven, a triangle is likewise made with a right angle, and this again, according to the various inequalities of the mountain slope, has either two equal or three unequal sides. but if a shaft is inclined and is sunk in one vein, and a tunnel is driven in another vein, then a triangle comes into existence which has either an obtuse angle or all acute angles. the former the greeks call [greek: amblygônion], the latter [greek: oxygônion]. that triangle which has an obtuse angle cannot have three equal sides, but in accordance with the different mountain slopes has either two equal sides or three unequal sides. that triangle which has all acute angles in accordance with the different mountain slopes has either three equal sides, which the greeks call [greek: trigônon isopleuron] or two equal sides or three unequal sides. the surveyor, as i said, employs his art when the owners of the mines desire to know how many fathoms of the intervening ground require to be dug; when a tunnel is being driven toward a shaft and does not yet reach it; or when the shaft has not yet been sunk to the depth of the bottom of the tunnel which is under it; or when neither the tunnel reaches to that point, nor has the shaft been sunk to it. it is of importance that miners should know how many fathoms remain from the tunnel to the shaft, or from the shaft to the tunnel, in order to calculate the expenditure; and in order that the owners of a metal-bearing mine may hasten the sinking of a shaft and the excavation of the metal, before the tunnel reaches that point and the tunnel owners excavate part of the metal by any right of their own; and on the other hand, it is important that the owners of a tunnel may similarly hasten their driving before a shaft can be sunk to the depth of a tunnel, so that they may excavate the metal to which they will have a right. [illustration (surveying): a--upright forked posts. b--pole over the posts. c--shaft. d--first cord. e--weight of first cord. f--second cord. g--same fixed ground. h--head of first cord. i--mouth of tunnel. k--third cord. l--weight of third cord. m--first side minor triangle. n--second side minor triangle. o--third side minor triangle. p--the minor triangle.] the surveyor, first of all, if the beams of the shaft-house do not give him the opportunity, sets a pair of forked posts by the sides of the shaft in such a manner that a pole may be laid across them. next, from the pole he lets down into the shaft a cord with a weight attached to it. then he stretches a second cord, attached to the upper end of the first cord, right down along the slope of the mountain to the bottom of the mouth of the tunnel, and fixes it to the ground. next, from the same pole not far from the first cord, he lets down a third cord, similarly weighted, so that it may intersect the second cord, which descends obliquely. then, starting from that point where the third cord cuts the second cord which descends obliquely to the mouth of the tunnel, he measures the second cord upward to where it reaches the end of the first cord, and makes a note of this first side of the minor triangle[ ]. afterward, starting again from that point where the third cord intersects the second cord, he measures the straight space which lies between that point and the opposite point on the first cord, and in that way forms the minor triangle, and he notes this second side of the minor triangle in the same way as before. then, if it is necessary, from the angle formed by the first cord and the second side of the minor triangle, he measures upward to the end of the first cord and also makes a note of this third side of the minor triangle. the third side of the minor triangle, if the shaft is vertical or inclined and is sunk on the same vein in which the tunnel is driven, will necessarily be the same length as the third cord above the point where it intersects the second cord; and so, as often as the first side of the minor triangle is contained in the length of the whole cord which descends obliquely, so many times the length of the second side of the minor triangle indicates the distance between the mouth of the tunnel and the point to which the shaft must be sunk; and similarly, so many times the length of the third side of the minor triangle gives the distance between the mouth of the shaft and the bottom of the tunnel. when there is a level bench on the mountain slope, the surveyor first measures across this with a measuring-rod; then at the edges of this bench he sets up forked posts, and applies the principle of the triangle to the two sloping parts of the mountain; and to the fathoms which are the length of that part of the tunnel determined by the triangles, he adds the number of fathoms which are the width of the bench. but if sometimes the mountain side stands up, so that a cord cannot run down from the shaft to the mouth of the tunnel, or, on the other hand, cannot run up from the mouth of the tunnel to the shaft, and, therefore, one cannot connect them in a straight line, the surveyor, in order to fix an accurate triangle, measures the mountain; and going downward he substitutes for the first part of the cord a pole one fathom long, and for the second part a pole half a fathom long. going upward, on the contrary, for the first part of the cord he substitutes a pole half a fathom long, and for the next part, one a whole fathom long; then where he requires to fix his triangle he adds a straight line to these angles. [illustration (surveying triangle): a triangle having a right angle and two equal sides.] to make this system of measuring clear and more explicit, i will proceed by describing each separate kind of triangle. when a shaft is vertical or inclined, and is sunk in the same vein on which the tunnel is driven, there is created, as i said, a triangle containing a right angle. now if the minor triangle has the two sides equal, which, in accordance with the numbering used by surveyors, are the second and third sides, then the second and third sides of the major triangle will be equal; and so also the intervening distances will be equal which lie between the mouth of the tunnel and the bottom of the shaft, and which lie between the mouth of the shaft and the bottom of the tunnel. for example, if the first side of the minor triangle is seven feet long and the second and likewise the third sides are five feet, and the length shown by the cord for the side of the major triangle is times seven feet, that is fathoms and five feet, then the intervening space, of course, whether the whole of it has been already driven through or has yet to be driven, will be one hundred times five feet, which makes eighty-three fathoms and two feet. anyone with this example of proportions will be able to construct the major and minor triangles in the same way as i have done, if there be the necessary upright posts and cross-beams. when a shaft is vertical the triangle is absolutely upright; when it is inclined and is sunk on the same vein in which the tunnel is driven, it is inclined toward one side. therefore, if a tunnel has been driven into the mountain for sixty fathoms, there remains a space of ground to be penetrated twenty-three fathoms and two feet long; for five feet of the second side of the major triangle, which lies above the mouth of the shaft and corresponds with the first side of the minor triangle, must not be added. therefore, if the shaft has been sunk in the middle of the head meer, a tunnel sixty fathoms long will reach to the boundary of the meer only when the tunnel has been extended a further two fathoms and two feet; but if the shaft is located in the middle of an ordinary meer, then the boundary will be reached when the tunnel has been driven a further length of nine fathoms and two feet. since a tunnel, for every one hundred fathoms of length, rises in grade one fathom, or at all events, ought to rise as it proceeds toward the shaft, one more fathom must always be taken from the depth allowed to the shaft, and one added to the length allowed to the tunnel. proportionately, because a tunnel fifty fathoms long is raised half a fathom, this amount must be taken from the depth of the shaft and added to the length of the tunnel. in the same way if a tunnel is one hundred or fifty fathoms shorter or longer, the same proportion also must be taken from the depth of the one and added to the length of the other. for this reason, in the case mentioned above, half a fathom and a little more must be added to the distance to be driven through, so that there remain twenty-three fathoms, five feet, two palms, one and a half digits and a fifth of a digit; that is, if even the minutest proportions are carried out; and surveyors do not neglect these without good cause. similarly, if the shaft is seventy fathoms deep, in order that it may reach to the bottom of the tunnel, it still must be sunk a further depth of thirteen fathoms and two feet, or rather twelve fathoms and a half, one foot, two digits, and four-fifths of half a digit. and in this instance five feet must be deducted from the reckoning, because these five feet complete the third side of the minor triangle, which is above the mouth of the shaft, and from its depth there must be deducted half a fathom, two palms, one and a half digits and the fifth part of half a digit. but if the tunnel has been driven to a point where it is under the shaft, then to reach the roof of the tunnel the shaft must still be sunk a depth of eleven fathoms, two and a half feet, one palm, two digits, and four-fifths of half a digit. [illustration (surveying triangle): a triangle having a right angle and three unequal sides.] if a minor triangle is produced of the kind having three unequal sides, then the sides of the greater triangle cannot be equal; that is, if the first side of the minor triangle is eight feet long, the second six feet long, and the third five feet long, and the cord along the side of the greater triangle, not to go too far from the example just given, is one hundred and one times eight feet, that is, one hundred and thirty-four fathoms and four feet, the distance which lies between the mouth of the tunnel and the bottom of the shaft will occupy one hundred times six feet in length, that is, one hundred fathoms. the distance between the mouth of the shaft and the bottom of the tunnel is one hundred times five feet, that is, eighty-three fathoms and two feet. and so, if the tunnel is eighty-five fathoms long, the remainder to be driven into the mountain is fifteen fathoms long, and here, too, a correction in measurement must be taken from the depth of the shaft and added to the length of the tunnel; what this is precisely, i will pursue no further, since everyone having a small knowledge of arithmetic can work it out. if the shaft is sixty-seven fathoms deep, in order that it may reach the bottom of the tunnel, the further distance required to be sunk amounts to sixteen fathoms and two feet. [illustration a (surveying triangle): triangle having an obtuse angle and two equal sides.] the surveyor employs this same method in measuring the mountain, whether the shaft and tunnel are on one and the same vein, whether the vein is vertical or inclined, or whether the shaft is on the principal vein and the tunnel on a transverse vein descending vertically to the depths of the earth; in the latter case the excavation is to be made where the transverse vein cuts the vertical vein. if the principal vein descends on an incline and the cross-vein descends vertically, then a minor triangle is created having one obtuse angle or all three angles acute. if the minor triangle has one angle obtuse and the two sides which are the second and third are equal, then the second and third sides of the major triangle will be equal, so that if the first side of the minor triangle is nine feet, the second, and likewise the third, will be five feet. then the first side of the major triangle will be one hundred and one times nine feet, or one hundred and fifty-one and one-half fathoms, and each of the other sides of the major triangle will be one hundred times five feet, that is, eighty-three fathoms and two feet. but when the first shaft is inclined, generally speaking, it is not deep; but there are usually several, all inclined, and one always following the other. therefore, if a tunnel is seventy-seven fathoms long, it will reach to the middle of the bottom of a shaft when six fathoms and two feet further have been sunk. but if all such inclined shafts are seventy-six fathoms deep, in order that the last one may reach the bottom of the tunnel, a depth of seven fathoms and two feet remains to be sunk. [illustration b (surveying triangle): triangle having an obtuse angle and three unequal sides.] if a minor triangle is made which has an obtuse angle and three unequal sides, then again the sides of the large triangle cannot be equal. for example, if the first side of the minor triangle is six feet long, the second three feet, and the third four feet, and the cord along the side of the greater triangle one hundred and one times six feet, that is, one hundred and one fathoms, the distance between the mouth of the tunnel and the bottom of the last shaft will be a length one hundred times three feet, or fifty fathoms; but the depth that lies between the mouth of the first shaft and the bottom of the tunnel is one hundred times four feet, or sixty-six fathoms and four feet. therefore, if a tunnel is forty-four fathoms long, the remaining distance to be driven is six fathoms. if the shafts are fifty-eight fathoms deep, the newest will touch the bottom of the tunnel when eight fathoms and four feet have been sunk. [illustration a (surveying triangle): a triangle having all its angles acute and its three sides equal.] if a minor triangle is produced which has all its angles acute and its three sides equal, then necessarily the second and third sides of the minor triangle will be equal, and likewise the sides of the major triangle frequently referred to will be equal. thus if each side of the minor triangle is six feet long, and the cord measurement for the side of the major triangle is one hundred and one times six feet, that is, one hundred and one fathoms, then both the distances to be dug will be one hundred fathoms. and thus if the tunnel is ninety fathoms long, it will reach the middle of the bottom of the last shaft when ten fathoms further have been driven. if the shafts are ninety-five fathoms deep, the last will reach the bottom of the tunnel when it is sunk a further depth of five fathoms. [illustration b (surveying triangle): triangle having all its angles acute and two sides equal, a, b, unequal side c.] if a triangle is made which has all its angles acute, but only two sides equal, namely, the first and third, then the second and third sides are not equal; therefore the distances to be dug cannot be equal. for example, if the first side of the minor triangle is six feet long, and the second is four feet, and the third is six feet, and the cord measurement for the side of the major triangle is one hundred and one times six feet, that is, one hundred and one fathoms, then the distance between the mouth of the tunnel and the bottom of the last shaft will be sixty-six fathoms and four feet. but the distance from the mouth of the first shaft to the bottom of the tunnel is one hundred fathoms. so if the tunnel is sixty fathoms long, the remaining distance to be driven into the mountain is six fathoms and four feet. if the shaft is ninety-seven fathoms deep, the last one will reach the bottom of the tunnel when a further depth of three fathoms has been sunk. [illustration (surveying triangle): a triangle having all its angles acute and its three sides unequal.] if a minor triangle is produced which has all its angles acute, but its three sides unequal, then again the distances to be dug cannot be equal. for example, if the first side of the minor triangle is seven feet long, the second side is four feet, and the third side is six feet, and the cord measurement for the side of the major triangle is one hundred and one times seven feet or one hundred and seventeen fathoms and four feet, the distance between the mouth of the tunnel and the bottom of the last shaft will be four hundred feet or sixty-six fathoms, and the depth between the mouth of the first shaft and the bottom of the tunnel will be one hundred fathoms. therefore, if a tunnel is fifty fathoms long, it will reach the middle of the bottom of the newest shaft when it has been driven sixteen fathoms and four feet further. but if the shafts are then ninety-two fathoms deep, the last shaft will reach the bottom of the tunnel when it has been sunk a further eight fathoms. this is the method of the surveyor in measuring the mountain, if the principal vein descends inclined into the depths of the earth or the transverse vein is vertical. but if they are both inclined, the surveyor uses the same method, or he measures the slope of the mountain separately from the slope of the shaft. next, if a transverse vein in which a tunnel is driven does not cut the principal vein in that spot where the shaft is sunk, then it is necessary for the starting point of the survey to be in the other shaft in which the transverse vein cuts the principal vein. but if there be no shaft on that spot where the outcrop of the transverse vein cuts the outcrop of the principal vein, then the surface of the ground which lies between the shafts must be measured, or that between the shaft and the place where the outcrop of the one vein intersects the outcrop of the other. [illustration (hemicycle): a--waxed semicircle of the hemicycle. b--semicircular lines. c--straight lines. d--line measuring the half. e--line measuring the whole. f--tongue.] [illustration a (surveying rods): a--lines of the rod which separate minor spaces. b--lines of the rod which separate major spaces.] some surveyors, although they use three cords, nevertheless ascertain only the length of a tunnel by that method of measuring, and determine the depth of a shaft by another method; that is, by the method by which cords are re-stretched on a level part of the mountain or in a valley, or in flat fields, and are measured again. some, however, do not employ this method in surveying the depth of a shaft and the length of a tunnel, but use only two cords, a graduated hemicycle[ ] and a rod half a fathom long. they suspend in the shaft one cord, fastened from the upper pole and weighted, just as the others do. fastened to the upper end of this cord, they stretch another right down the slope of the mountain to the bottom of the mouth of the tunnel and fix it to the ground. then to the upper part of this second cord they apply on its lower side the broad part of a hemicycle. this consists of half a circle, the outer margin of which is covered with wax, and within this are six semi-circular lines. from the waxed margin through the first semi-circular line, and reaching to the second, there proceed straight lines converging toward the centre of the hemicycle; these mark the middles of intervening spaces lying between other straight lines which extend to the fourth semi-circular line. but all lines whatsoever, from the waxed margin up to the fourth line, whether they go beyond it or not, correspond with the graduated lines which mark the minor spaces of a rod. those which go beyond the fourth line correspond with the lines marking the major spaces on the rod, and those which proceed further, mark the middle of the intervening space which lies between the others. the straight lines, which run from the fifth to the sixth semi-circular line, show nothing further. nor does the line which measures the half, show anything when it has already passed from the sixth straight line to the base of the hemicycle. when the hemicycle is applied to the cord, if its tongue indicates the sixth straight line which lies between the second and third semi-circular lines, the surveyor counts on the rod six lines which separate the minor spaces, and if the length of this portion of the rod be taken from the second cord, as many times as the cord itself is half-fathoms long, the remaining length of cord shows the distance the tunnel must be driven to reach under the shaft. but if he sees that the tongue has gone so far that it marks the sixth line between the fourth and fifth semi-circular lines, he counts six lines which separate the major spaces on the rod; and this entire space is deducted from the length of the second cord, as many times as the number of whole fathoms which the cord contains; and then, in like manner, the remaining length of cord shows us the distance the tunnel must be driven to reach under the shaft.[ ] [illustration (surveying triangle): stretched cords: a--first cord. b--second cord. c--third cord. d--triangle.] both these surveyors, as well as the others, in the first place make use of the haulage rope. these they measure by means of others made of linden bark, because the latter do not stretch at all, while the former become very slack. these cords they stretch on the surveyor's field, the first one to represent the parts of mountain slopes which descend obliquely. then the second cord, which represents the length of the tunnel to be driven to reach the shaft, they place straight, in such a direction that one end of it can touch the lower end of the first cord; then they similarly lay the third cord straight, and in such a direction that its upper end may touch the upper end of the first cord, and its lower end the other extremity of the second cord, and thus a triangle is formed. this third cord is measured by the instrument with the index, to determine its relation to the perpendicular; and the length of this cord shows the depth of the shaft. [illustration (surveying triangles): stretched cords: a--first. b--second. b--third. c--fourth. c--fifth. d--quadrangle.] some surveyors, to make their system of measuring the depth of a shaft more certain, use five stretched cords: the first one descending obliquely; two, that is to say the second and third, for ascertaining the length of the tunnel; two for the depth of the shaft; in which way they form a quadrangle divided into two equal triangles, and this tends to greater accuracy. these systems of measuring the depth of a shaft and the length of a tunnel, are accurate when the vein and also the shaft or shafts go down to the tunnel vertically or inclined, in an uninterrupted course. the same is true when a tunnel runs straight on to a shaft. but when each of them bends now in this, now in that direction, if they have not been completely driven and sunk, no living man is clever enough to judge how far they are deflected from a straight course. but if the whole of either one of the two has been excavated its full distance, then we can estimate more easily the length of one, or the depth of the other; and so the location of the tunnel, which is below a newly-started shaft, is determined by a method of surveying which i will describe. first of all a tripod is fixed at the mouth of the tunnel, and likewise at the mouth of the shaft which has been started, or at the place where the shaft will be started. the tripod is made of three stakes fixed to the ground, a small rectangular board being placed upon the stakes and fixed to them, and on this is set a compass. then from the lower tripod a weighted cord is let down perpendicularly to the earth, close to which cord a stake is fixed in the ground. to this stake another cord is tied and drawn straight into the tunnel to a point as far as it can go without being bent by the hangingwall or the footwall of the vein. next, from the cord which hangs from the lower tripod, a third cord likewise fixed is brought straight up the sloping side of the mountain to the stake of the upper tripod, and fastened to it. in order that the measuring of the depth of the shaft may be more certain, the third cord should touch one and the same side of the cord hanging from the lower tripod which is touched by the second cord--the one which is drawn into the tunnel. all this having been correctly carried out, the surveyor, when at length the cord which has been drawn straight into the tunnel is about to be bent by the hangingwall or footwall, places a plank in the bottom of the tunnel and on it sets the orbis, an instrument which has an indicator peculiar to itself. this instrument, although it also has waxed circles, differs from the other, which i have described in the third book. but by both these instruments, as well as by a rule and a square, he determines whether the stretched cords reach straight to the extreme end of the tunnel, or whether they sometimes reach straight, and are sometimes bent by the footwall or hangingwall. each instrument is divided into parts, but the compass into twenty-four parts, the orbis into sixteen parts; for first of all it is divided into four principal parts, and then each of these is again divided into four. both have waxed circles, but the compass has seven circles, and the orbis only five circles. these waxed circles the surveyor marks, whichever instrument he uses, and by the succession of these same marks he notes any change in the direction in which the cord extends. the orbis has an opening running from its outer edge as far as the centre, into which opening he puts an iron screw, to which he binds the second cord, and by screwing it into the plank, fixes it so that the orbis may be immovable. he takes care to prevent the second cord, and afterward the others which are put up, from being pulled off the screw, by employing a heavy iron, into an opening of which he fixes the head of the screw. in the case of the compass, since it has no opening, he merely places it by the side of the screw. that the instrument does not incline forward or backward, and in that way the measurement become a greater length than it should be, he sets upon the instrument a standing plummet level, the tongue of which, if the instrument is level, indicates no numbers, but the point from which the numbers start. [illustration (compass): compass. a, b, c, d, e, f, g are the seven waxed circles.] [illustration a (orbis): a, b, c, d, e--five waxed circles of the _orbis_. f--opening of same. g--screw. h--perforated iron.] [illustration (miner using level): a--standing plummet level. b--tongue. c--level and tongue.] when the surveyor has carefully observed each separate angle of the tunnel and has measured such parts as he ought to measure, then he lays them out in the same way on the surveyor's field[ ] in the open air, and again no less carefully observes each separate angle and measures them. first of all, to each angle, according as the calculation of his triangle and his art require it, he lays out a straight cord as a line. then he stretches a cord at such an angle as represents the slope of the mountain, so that its lower end may reach the end of the straight cord; then he stretches a third cord similarly straight and at such an angle, that with its upper end it may reach the upper end of the second cord, and with its lower end the last end of the first cord. the length of the third cord shows the depth of the shaft, as i said before, and at the same time that point on the tunnel to which the shaft will reach when it has been sunk. if one or more shafts reach the tunnel through intermediate drifts and shafts, the surveyor, starting from the nearest which is open to the air, measures in a shorter time the depth of the shaft which requires to be sunk, than if he starts from the mouth of the tunnel. first of all he measures that space on the surface which lies between the shaft which has been sunk and the one which requires to be sunk. then he measures the incline of all the shafts which it is necessary to measure, and the length of all the drifts with which they are in any way connected to the tunnel. lastly, he measures part of the tunnel; and when all this is properly done, he demonstrates the depth of the shaft and the point in the tunnel to which the shaft will reach. but sometimes a very deep straight shaft requires to be sunk at the same place where there is a previous inclined shaft, and to the same depth, in order that loads may be raised and drawn straight up by machines. those machines on the surface are turned by horses; those inside the earth, by the same means, and also by water-power. and so, if it becomes necessary to sink such a shaft, the surveyor first of all fixes an iron screw in the upper part of the old shaft, and from the screw he lets down a cord as far as the first angle, where again he fixes a screw, and again lets down the cord as far as the second angle; this he repeats again and again until the cord reaches to the bottom of the shaft. then to each angle of the cord he applies a hemicycle, and marks the waxed semi-circle according to the lines which the tongue indicates, and designates it by a number, in case it should be moved; then he measures the separate parts of the cord with another cord made of linden bark. afterward, when he has come back out of the shaft, he goes away and transfers the markings from the waxed semi-circle of the hemicycle to an orbis similarly waxed. lastly, the cords are stretched on the surveyor's field, and he measures the angles, as the system of measuring by triangles requires, and ascertains which part of the footwall and which part of the hangingwall rock must be cut away in order that the shaft may descend straight. but if the surveyor is required to show the owners of the mine, the spot in a drift or a tunnel in which a shaft needs to be raised from the bottom upward, that it should cut through more quickly, he begins measuring from the bottom of the drift or tunnel, at a point beyond the spot at which the bottom of the shaft will arrive, when it has been sunk. when he has measured the part of the drift or tunnel up to the first shaft which connects with an upper drift, he measures the incline of this shaft by applying a hemicycle or orbis to the cord. then in a like manner he measures the upper drift and the incline shaft which is sunk therein toward which a raise is being dug, then again all the cords are stretched in the surveyor's field, the last cord in such a way that it reaches the first, and then he measures them. from this measurement is known in what part of the drift or tunnel the raise should be made, and how many fathoms of vein remain to be broken through in order that the shaft may be connected. i have described the first reason for surveying; i will now describe another. when one vein comes near another, and their owners are different persons who have late come into possession, whether they drive a tunnel or a drift, or sink a shaft, they may encroach, or seem to encroach, without any lawful right, upon the boundaries of the older owners, for which reason the latter very often seek redress, or take legal proceedings. the surveyor either himself settles the dispute between the owners, or by his art gives evidence to the judges for making their decision, that one shall not encroach on the mine of the other. thus, first of all he measures the mines of each party with a basket rope and cords of linden bark; and having applied to the cords an orbis or a compass, he notes the directions in which they extend. then he stretches the cords on the surveyor's field; and starting from that point whose owners are in possession of the old meer toward the other, whether it is in the hanging or footwall of the vein, he stretches a cross-cord in a straight line, according to the sixth division of the compass, that is, at a right angle to the vein, for a distance of three and a half fathoms, and assigns to the older owners that which belongs to them. but if both ends of one vein are being dug out in two tunnels, or drifts from opposite directions, the surveyor first of all considers the lower tunnel or drift and afterward the upper one, and judges how much each of them has risen little by little. on each side strong men take in their hands a stretched cord and hold it so that there is no point where it is not strained tight; on each side the surveyor supports the cord with a rod half a fathom long, and stays the rod at the end with a short stick as often as he thinks it necessary. but some fasten cords to the rods to make them steadier. the surveyor attaches a suspended plummet level to the middle of the cord to enable him to calculate more accurately on both sides, and from this he ascertains whether one tunnel has risen more than another, or in like manner one drift more than another. afterward he measures the incline of the shafts on both sides, so that he can estimate their position on each side. then he easily sees how many fathoms remain in the space which must be broken through. but the grade of each tunnel, as i said, should rise one fathom in the distance of one hundred fathoms. [illustration (plummet cord and weight): indicator of a suspended plummet level.] [illustration (compass): a--needle of the instrument. b--its tongue. c, d, e--holes in the tongue.] the swiss surveyors, when they wish to measure tunnels driven into the highest mountains, also use a rod half a fathom long, but composed of three parts, which screw together, so that they may be shortened. they use a cord made of linden bark to which are fastened slips of paper showing the number of fathoms. they also employ an instrument peculiar to them, which has a needle; but in place of the waxed circles they carry in their hands a chart on which they inscribe the readings of the instrument. the instrument is placed on the back part of the rod so that the tongue, and the extended cord which runs through the three holes in the tongue, demonstrates the direction, and they note the number of fathoms. the tongue shows whether the cord inclines forward or backward. the tongue does not hang, as in the case of the suspended plummet level, but is fixed to the instrument in a half-lying position. they measure the tunnels for the purpose of knowing how many fathoms they have been increased in elevation; how many fathoms the lower is distant from the upper one; how many fathoms of interval is not yet pierced between the miners who on opposite sides are digging on the same vein, or cross-stringers, or two veins which are approaching one another. but i return to our mines. if the surveyor desires to fix the boundaries of the meer within the tunnels or drifts, and mark to them with a sign cut in the rock, in the same way that the _bergmeister_ has marked these boundaries above ground, he first of all ascertains, by measuring in the manner which i have explained above, which part of the tunnel or drift lies beneath the surface boundary mark, stretching the cords along the drifts to a point beyond that spot in the rock where he judges the mark should be cut. then, after the same cords have been laid out on the surveyor's field, he starts from that upper cord at a point which shows the boundary mark, and stretches another cross-cord straight downward according to the sixth division of the compass--that is at a right angle. then that part of the lowest cord which lies beyond the part to which the cross-cord runs being removed, it shows at what point the boundary mark should be cut into the rock of the tunnel or drift. the cutting is made in the presence of the two jurors and the manager and the foreman of each mine. for as the _bergmeister_ in the presence of these same persons sets the boundary stones on the surface, so the surveyor cuts in the rock a sign which for this reason is called the boundary rock. if he fixes the boundary mark of a meer in which a shaft has recently begun to be sunk on a vein, first of all he measures and notes the incline of that shaft by the compass or by another way with the applied cords; then he measures all the drifts up to that one in whose rock the boundary mark has to be cut. of these drifts he measures each angle; then the cords, being laid out on the surveyor's field, in a similar way he stretches a cross-cord, as i said, and cuts the sign on the rock. but if the underground boundary rock has to be cut in a drift which lies beneath the first drift, the surveyor starts from the mark in the first drift, notes the different angles, one by one, takes his measurements, and in the lower drift stretches a cord beyond that place where he judges the mark ought to be cut; and then, as i said before, lays out the cords on the surveyor's field. even if a vein runs differently in the lower drift from the upper one, in which the first boundary mark has been cut in the rock, still, in the lower drift the mark must be cut in the rock vertically beneath. for if he cuts the lower mark obliquely from the upper one some part of the possession of one mine is taken away to its detriment, and given to the other. moreover, if it happens that the underground boundary mark requires to be cut in an angle, the surveyor, starting from that angle, measures one fathom toward the front of the mine and another fathom toward the back, and from these measurements forms a triangle, and dividing its middle by a cross-cord, makes his cutting for the boundary mark. lastly, the surveyor sometimes, in order to make more certain, finds the boundary of the meers in those places where many old boundary marks are cut in the rock. then, starting from a stake fixed on the surface, he first of all measures to the nearest mine; then he measures one shaft after another; then he fixes a stake on the surveyors' field, and making a beginning from it stretches the same cords in the same way and measures them, and again fixes in the ground a stake which for him will signify the end of his measuring. afterward he again measures underground from that spot at which he left off, as many shafts and drifts as he can remember. then he returns to the surveyor's field, and starting again from the second stake, makes his measurements; and he does this as far as the drift in which the boundary mark must be cut in the rock. finally, commencing from the stake first fixed in the ground, he stretches a cross-cord in a straight line to the last stake, and this shows the length of the lowest drift. the point where they touch, he judges to be the place where the underground boundary mark should be cut. end of book v. footnotes: [ ] it has been suggested that we should adopt throughout this volume the mechanical and mining terms used in english mines at agricola's time. we believe, however, that but a little inquiry would illustrate the undesirability of this course as a whole. where there is choice in modern miner's nomenclature between an old and a modern term, we have leaned toward age, if it be a term generally understood. but except where the subject described has itself become obsolete, we have revived no obsolete terms. in substantiation of this view, we append a few examples of terms which served the english miner well for centuries, some of which are still extant in some local communities, yet we believe they would carry as little meaning to the average reader as would the reproduction of the latin terms coined by agricola. rake = a perpendicular vein. woughs = walls of the vein. shakes = cracks in the walls. flookan = gouge. bryle = outcrop. hade = incline or underlay of the vein. dawling = impoverishment of the vein. rither = a "horse" in a vein. twitches = "pinching" of a vein. slough = drainage tunnel. sole = lowest drift. stool = face of a drift or stope. winds } turn } = winze. dippas} grove = shaft. dutins = set of timber. stemple = post or stull. laths = lagging. as examples of the author's coinage and adaptations of terms in this book we may cite:-- _fossa latens_ = drift. _fossa latens transversa_ = crosscut. _tectum_ = hangingwall. _fundamentum_ = footwall. _tigna per intervalla posita_ = wall plate. _arbores dissectae_ = lagging. _formae_ = hitches. we have adopted the term "tunnel" for openings by way of outlet to the mine. the word in this narrow sense is as old as "adit," a term less expressive and not so generally used in the english-speaking mining world. we have for the same reason adopted the word "drift" instead of the term "level" so generally used in america, because that term always leads to confusion in discussion of mine surveys. we may mention, however, that the term "level" is a heritage from the derbyshire mines, and is of an equally respectable age as "drift." [ ] see note on p. - . the _canales_, as here used, were the openings in the earth, in which minerals were deposited. [ ] this statement, as will appear by the description later on, refers to the depth of winzes or to the distance between drifts, that is "the lift." we have not, however, been justified in using the term "winze," because some of these were openings to the surface. as showing the considerable depth of shafts in agricola's time, we may quote the following from _bermannus_ (p. ): "the depths of our shafts forced us to invent hauling machines suitable for them. there are some of them larger and more ingenious than this one, for use in deep shafts, as, for instance, those in my native town of geyer, but more especially at schneeberg, where the shaft of the mine from which so much treasure was taken in our memory has reached the depth of about fathoms (feet?), wherefore the necessity of this kind of machinery. _naevius_: what an enormous depth! have you reached the inferno? _bermannus_: oh, at kuttenberg there are shafts more than fathoms (feet?) deep. _naevius_: and not yet reached the kingdom of pluto?" it is impossible to accept these as fathoms, as this would in the last case represent , feet vertically. the expression used, however, for fathoms is _passus_, presumably the roman measure equal to . inches. [ ] _cavernos_. the glossary gives _drusen_, our word _drusy_ having had this origin. [ ] _purum_,--"pure." _interpretatio_ gives the german as _gedigen_,--"native." [ ] _rudis_,--"crude." by this expression the author really means ores very rich in any designated metal. in many cases it serves to indicate the minerals of a given metal, as distinguished from the metal itself. our system of mineralogy obviously does not afford an acceptable equivalent. agricola (_de nat. foss._, p. ) says: "i find it necessary to call each genus (of the metallic minerals) by the name of its own metal, and to this i add a word which differentiates it from the pure (_puro_) metal, whether the latter has been mined or smelted; so i speak of _rudis_ gold, silver, quicksilver, copper, tin, bismuth, lead, or iron. this is not because i am unaware that varro called silver _rudis_ which had not yet been refined and stamped, but because a word which will distinguish the one from the other is not to be found." [ ] the reasons for retaining the latin weights are given in the appendix on weights and measures. a _centumpondium_ weighs . lbs. avoirdupois, an _uncia_ . troy grains, therefore, this value is equal to ounces pennyweights per short ton. [ ] agricola mentions many minerals in _de re metallica_, but without such description as would make possible a hazard at their identity. from his _de natura fossilium_, however, and from other mineralogies of the th century, some can be fully identified and others surmised. while we consider it desirable to set out the probable composition of these minerals, on account of the space required, the reasons upon which our opinion has been based cannot be given in detail, as that would require extensive quotations. in a general way, we have throughout the text studiously evaded the use of modern mineralogical terms--unless the term used to-day is of agricola's age--and have adopted either old english terms of pre-chemistry times or more loose terms used by common miners. obviously modern mineralogic terms imply a precision of knowledge not existing at that period. it must not be assumed that the following is by any means a complete list of the minerals described by agricola, but they include most of those referred to in this chapter. his system of mineralogy we have set out in note , p. , and it requires no further comment here. the grouping given below is simply for convenience and does not follow agricola's method. where possible, we tabulate in columns the latin term used in _de re metallica_; the german equivalent given by the author in either the _interpretatio_ or the glossary; our view of the probable modern equivalent based on investigation of his other works and other ancient mineralogies, and lastly the terms we have adopted in the text. the german spelling is that given in the original. as an indication of agricola's position as a mineralogist, we mark with an asterisk the minerals which were first specifically described by him. we also give some notes on matters of importance bearing on the nomenclature used in _de re metallica_. historical notes on the chief metals will be found elsewhere, generally with the discussion of smelting methods. we should not omit to express our indebtedness to dana's great "system of mineralogy," in the matter of correlation of many old and modern minerals. gold minerals. agricola apparently believed that there were various gold minerals, green, yellow, purple, black, etc. there is nothing, however, in his works that permits of any attempt to identify them, and his classification seems to rest on gangue colours. silver minerals. _argentum purum in _gedigen silber_ -- *native silver venis reperitur_ _argentum rude_ _gedigen silber -- _rudis_ silver, or ertz_ pure silver minerals _argentum rude _glas ertz_ argentite *silver glance plumbei coloris_ (ag_{ }s) _argentum rude _rot gold ertz_ pyrargyrite *red silver rubrum_ (ag_{ }sbs_{ }) _argentum rude _durchsichtig proustite *ruby silver rubrum rod gulden (ag_{ }ass_{ }) translucidum_ ertz_ _argentum rude _weis rod gulden -- white silver album_ ertz: dan es ist frisch wie offtmals rod gulden ertz pfleget zusein_ _argentum rude _gedigen part bromyrite liver-coloured jecoris leberfarbig (ag br) silver colore_ ertz_ _argentum rude _gedigen -- yellow silver luteum_ geelertz_ _argentum rude _gedigen graw } { *grey silver cineraceum_ ertz_ } part cerargurite { } (ag cl) (horn { _argentum rude _gedigen } silver) part { *black silver nigrum_ schwartz ertz_ } stephanite { } (ag_{ }sbs_{ }) { _argentum rude _gedigen braun } { *purple silver purpureum_ ertz_ } { the last six may be in part also alteration products from all silver minerals. the reasons for indefiniteness in determination usually lie in the failure of ancient authors to give sufficient or characteristic descriptions. in many cases agricola is sufficiently definite as to assure certainty, as the following description of what we consider to be silver glance, from _de natura fossilium_ (p. ), will indicate: "lead-coloured _rudis_ silver is called by the germans from the word glass (_glasertz_), not from lead. indeed, it has the colour of the latter or of galena (_plumbago_), but not of glass, nor is it transparent like glass, which one might indeed expect had the name been correctly derived. this mineral is occasionally so like galena in colour, although it is darker, that one who is not experienced in minerals is unable to distinguish between the two at sight, but in substance they differ greatly from one another. nature has made this kind of silver out of a little earth and much silver. whereas galena consists of stone and lead containing some silver. but the distinction between them can be easily determined, for galena may be ground to powder in a mortar with a pestle, but this treatment flattens out this kind of _rudis_ silver. also galena, when struck by a mallet or bitten or hacked with a knife, splits and breaks to pieces; whereas this silver is malleable under the hammer, may be dented by the teeth, and cut with a knife." copper minerals. _aes purum _gedigen kupfer_ native copper native copper fossile_ _aes rude _kupferglas ertz_ chalcocite *copper glance plumbei (cu_{ }s) coloris_ _chalcitis_ _rodt atrament_ a decomposed _chalcitis_ (see copper or notes on p. ) iron sulphide _pyrites aurei } _geelkis oder { part chalcopyrite copper pyrites colore_ } kupferkis_ { (cu fe s) part } { bornite _pyrites aerosus_ } { (cu_{ }fes_{ }) _caeruleum_ _berglasur_ azurite azure _chrysocolla_ _berggrün und { part chrysocolla chrysocolla (see schifergrün_ { part malachite note , p. ) _molochites_ _molochit_ malachite malachite _lapis aerarius_ _kupfer ertz_ -- copper ore _aes caldarium } _lebeter kupfer_ { when used for rubrum fuscum_ } { an ore, is *ruby copper ore or } { probably _aes sui coloris_ } _rotkupfer_ { cuprite _aes nigrum_ _schwartz kupfer_ probably cuo from *black copper oxidation of other minerals in addition to the above the author uses the following, which were in the main artificial products: _aerugo_ _grünspan oder verdigris verdigris spanschgrün_ _aes luteum_ _gelfarkupfer_ } impure blister { unrefined copper } copper { (see note , } { p. ) _aes caldarium_ _lebeterkupfer_ } { _aeris flos_ _kupferbraun_ } cupric oxide { copper flower } scales { } { _aeris squama_ _kupferhammer- } { copper scale (see schlag_ } { note , p. ) _atramentum _blaw kupfer chalcanthite native blue sutorium wasser_ vitriol (see caeruleum_ or note on p. ) _chalcanthum_ blue and green copper minerals were distinguished by all the ancient mineralogists. theophrastus, dioscorides, pliny, etc., all give sufficient detail to identify their _cyanus_ and _caeruleum_ partly with modern azurite, and their _chrysocolla_ partly with the modern mineral of the same name. however, these terms were also used for vegetable pigments, as well as for the pigments made from the minerals. the greek origin of _chrysocolla_ (_chrysos_, gold and _kolla_, solder) may be blamed with another and distinct line of confusion, in that this term has been applied to soldering materials, from greek down to modern times, some of the ancient mineralogists even asserting that the copper mineral _chrysocolla_ was used for this purpose. agricola uses _chrysocolla_ for borax, but is careful to state in every case (see note xx., p. x): "_chrysocolla_ made from _nitrum_," or "_chrysocolla_ which the moors call borax." dioscorides and pliny mention substances which were evidently copper sulphides, but no description occurs prior to agricola that permits a hazard as to different species. lead minerals. _plumbarius lapis_ _glantz_ galena galena _galena_ _glantz und galena galena pleiertz_ _plumbum nigrum } _pleiertz oder cerussite yellow lead ore lutei coloris_ } pleischweis_ (pbco_{ }) } _plumbago } metallica_ } _cerussa_ _pleiweis_ artificial white-lead (see white-lead note , p. ) _ochra facticia_ _pleigeel_ massicot (pb o) *lead-ochre (see or _ochra note , p. ) plumbaria_ _molybdaena_ } _herdplei_ part litharge hearth-lead (see } note , p. ) _plumbago } fornacis_ } _spuma argenti_ } _glett_ litharge litharge (see note } on p. ) _lithargyrum_ } _minium _menning_ minium red-lead (see note secundarium_ (pb_{ }o_{ }) , p. ) so far as we can determine, all of these except the first three were believed by agricola to be artificial products. of the first three, galena is certain enough, but while he obviously was familiar with the alteration lead products, his descriptions are inadequate and much confused with the artificial oxides. great confusion arises in the ancient mineralogies over the terms _molybdaena_, _plumbago_, _plumbum_, _galena_, and _spuma argenti_, all of which, from roman mineralogists down to a century after agricola, were used for lead in some form. further discussion of such confusion will be found in note , p. . agricola in _bermannus_ and _de natura fossilium_, devotes pages to endeavouring to reconcile the ancient usages of these terms, and all the confusion existing in agricola's time was thrice confounded when the names _molybdaena_ and _plumbago_ were assigned to non-lead minerals. tin. agricola knew only one tin mineral: _lapilli nigri ex quibus conflatur plumbum candidum_, _i.e._, "little black stones from which tin is smelted," and he gives the german equivalent as _zwitter_, "tin-stone." he describes them as being of different colours, but probably due to external causes. antimony. (_interpretatio_,--_spiesglas_.) the _stibi_ or _stibium_ of agricola was no doubt the sulphide, and he follows dioscorides in dividing it into male and female species. this distinction, however, is impossible to apply from the inadequate descriptions given. the mineral and metal known to agricola and his predecessors was almost always the sulphide, and we have not felt justified in using the term antimony alone, as that implies the refined product, therefore, we have adopted either the latin term or the old english term "grey antimony." the smelted antimony of commerce sold under the latter term was the sulphide. for further notes see p. . bismuth*. _plumbum cinereum_ (_interpretatio_,--_bismut_). agricola states that this mineral occasionally occurs native, "but more often as a mineral of another colour" (_de nat. fos._, p. ), and he also describes its commonest form as black or grey. this, considering his localities, would indicate the sulphide, although he assigns no special name to it. although bismuth is mentioned before agricola in the _nützliche bergbüchlin_, he was the first to describe it (see p. ). quicksilver. apart from native quicksilver, agricola adequately describes cinnabar only. the term used by him for the mineral is _minium nativum_ (_interpretatio_,--_bergzinober_ or _cinnabaris_). he makes the curious statement _(de nat. fos._ p. ) that _rudis_ quicksilver also occurs liver-coloured and blackish,--probably gangue colours. (see p. ). arsenical minerals. metallic arsenic was unknown, although it has been maintained that a substance mentioned by albertus magnus (_de rebus metallicis_) was the metallic form. agricola, who was familiar with all albertus's writings, makes no mention of it, and it appears to us that the statement of albertus referred only to the oxide from sublimation. our word "arsenic" obviously takes root in the greek for orpiment, which was also used by pliny (xxxiv, ) as _arrhenicum_, and later was modified to _arsenicum_ by the alchemists, who applied it to the oxide. agricola gives the following in _bermannus_ (p. ), who has been previously discussing realgar and orpiment:--"_ancon_: avicenna also has a white variety. _bermannus_: i cannot at all believe in a mineral of a white colour; perhaps he was thinking of an artificial product; there are two which the alchemists make, one yellow and the other white, and they are accounted the most powerful poisons to-day, and are called only by the name _arsenicum_." in _de natura fossilium_ (p. ) is described the making of "the white variety" by sublimating orpiment, and also it is noted that realgar can be made from orpiment by heating the latter for five hours in a sealed crucible. in _de re metallica_ (book x.), he refers to _auripigmentum facticum_, and no doubt means the realgar made from orpiment. the four minerals of arsenic base mentioned by agricola were:-- _auripigmentum_ _operment_ orpiment orpiment (as_{ }s_{ }) _sandaraca_ _rosgeel_ realgar (as s) realgar _arsenicum_ _arsenik_ artificial white arsenic arsenical oxide _lapis subrutilus _mistpuckel_ arsenopyrite *mispickel atque ... (fe as s) splendens_ we are somewhat uncertain as to the identification of the last. the yellow and red sulphides, however, were well known to the ancients, and are described by aristotle, theophrastus ( and ), dioscorides (v, ), pliny (xxxiii, , etc.); and strabo (xii, , ) mentions a mine of them near pompeiopolis, where, because of its poisonous character none but slaves were employed. the ancients believed that the yellow sulphide contained gold--hence the name _auripigmentum_, and pliny describes the attempt of the emperor caligula to extract the gold from it, and states that he did obtain a small amount, but unprofitably. so late a mineralogist as hill ( ) held this view, which seemed to be general. both realgar and orpiment were important for pigments, medicinal purposes, and poisons among the ancients. in addition to the above, some arsenic-cobalt minerals are included under _cadmia_. iron minerals. _ferrum purum_ _gedigen eisen_ native iron *native iron _terra ferria_ _eisen ertz_ } various soft and } ironstone } hard iron } _ferri vena_ _eisen ertz_ } ores, probably } } mostly hematite} _galenae genus _eisen glantz_ } } tertium omnis } } metalli } } inanissimi_ } } } } _schistos_ _glasköpfe oder } } blütstein_ } } } } _ferri vena _leber ertz_ } } jecoris colore_ } } _ferrugo_ _rüst_ part limonite iron rust _magnes_ _siegelstein magnetite lodestone oder magnet_ _ochra nativa_ _berg geel_ limonite yellow ochre or ironstone _haematites_ _blüt stein_ { part hematite bloodstone or { part jasper ironstone _schistos_ _glas köpfe_ part limonite ironstone _pyrites_ _kis_ pyrites pyrites _pyrites argenti _wasser oder marcasite *white iron coloris_ weisser kis_ pyrites _misy_ _gel atrament_ part copiapite _misy_ (see note on p. ) _sory_ _graw und partly a _sory_ (see note schwartz decomposed iron on p. ) atrament_ pyrite _melanteria_ _schwartz und melanterite _melanteria_ (see grau atrament_ (native vitriol) note on p. ) the classification of iron ores on the basis of exterior characteristics, chiefly hardness and brilliancy, does not justify a more narrow rendering than "ironstone." agricola (_de nat. fos._, book v.) gives elaborate descriptions of various iron ores, but the descriptions under any special name would cover many actual minerals. the subject of pyrites is a most confused one; the term originates from the greek word for fire, and referred in greek and roman times to almost any stone that would strike sparks. by agricola it was a generic term in somewhat the same sense that it is still used in mineralogy, as, for instance, iron pyrite, copper pyrite, etc. so much was this the case later on, that henckel, the leading mineralogist of the th century, entitled his large volume _pyritologia_, and in it embraces practically all the sulphide minerals then known. the term _marcasite_, of mediæval arabic origin, seems to have had some vogue prior and subsequent to agricola. he, however, puts it on one side as merely a synonym for pyrite, nor can it be satisfactorily defined in much better terms. agricola apparently did not recognise the iron base of pyrites, for he says (_de nat. fos._, p. ): "sometimes, however, pyrites do not contain any gold, silver, copper, or lead, and yet it is not a pure stone, but a compound, and consists of stone and a substance which is somewhat metallic, which is a species of its own." many varieties were known to him and described, partly by their other metal association, but chiefly by their colour. cadmia. the minerals embraced under this term by the old mineralogists form one of the most difficult chapters in the history of mineralogy. these complexities reached their height with agricola, for at this time various new minerals classed under this heading had come under debate. all these minerals were later found to be forms of zinc, cobalt, or arsenic, and some of these minerals were in use long prior to agricola. from greek and roman times down to long after agricola, brass was made by cementing zinc ore with copper. aristotle and strabo mention an earth used to colour copper, but give no details. it is difficult to say what zinc mineral the _cadmium_ of dioscorides (v, ) and pliny (xxxiv, ), really was. it was possibly only furnace calamine, or perhaps blende for it was associated with copper. they amply describe _cadmia_ produced in copper furnaces, and _pompholyx_ (zinc oxide). it was apparently not until theophilus ( ) that the term _calamina_ appears for that mineral. precisely when the term "zinc," and a knowledge of the metal, first appeared in europe is a matter of some doubt; it has been attributed to paracelsus, a contemporary of agricola (see note on p. ), but we do not believe that author's work in question was printed until long after. the quotations from agricola given below, in which _zincum_ is mentioned in an obscure way, do not appear in the first editions of these works, but only in the revised edition of . in other words, agricola himself only learned of a substance under this name a short period before his death in . the metal was imported into europe from china prior to this time. he however does describe actual metallic zinc under the term _conterfei_, and mentions its occurrence in the cracks of furnace walls. (see also notes on p. ). the word cobalt (german _kobelt_) is from the greek word _cobalos_, "mime," and its german form was the term for gnomes and goblins. it appears that the german miners, finding a material (agricola's "corrosive material") which injured their hands and feet, connected it with the goblins, or used the term as an epithet, and finally it became established for certain minerals (see note , p. , on this subject). the first written appearance of the term in connection with minerals, appears in agricola's _bermannus_ ( ). the first practical use of cobalt was in the form of _zaffre_ or cobalt blue. there seems to be no mention of the substance by the greek or roman writers, although analyses of old colourings show some traces of cobalt, but whether accidental or not is undetermined. the first mention we know of, was by biringuccio in (_de la pirotechnia_, book ii, chap. ix.), who did not connect it with the minerals then called _cobalt_ or _cadmia_. "_zaffera_ is another mineral substance, like a metal of middle weight, which will not melt alone, but accompanied by vitreous substances it melts into an azure colour so that those who colour glass, or paint vases or glazed earthenware, make use of it. not only does it serve for the above-mentioned operations, but if one uses too great a quantity of it, it will be black and all other colours, according to the quantity used." agricola, although he does not use the word _zaffre_, does refer to a substance of this kind, and in any event also missed the relation between _zaffre_ and cobalt, as he seems to think (_de nat. fos._, p. ) that _zaffre_ came from bismuth, a belief that existed until long after his time. the cobalt of the erzgebirge was of course, intimately associated with this mineral. he says, "the slag of bismuth, mixed together with metalliferous substances, which when melted make a kind of glass, will tint glass and earthenware vessels blue." _zaffre_ is the roasted mineral ground with sand, while _smalt_, a term used more frequently, is the fused mixture with sand. the following are the substances mentioned by agricola, which, we believe, relate to cobalt and zinc minerals, some of them arsenical compounds. other arsenical minerals we give above. _cadmia fossilis_ _calmei_; _lapis calamine calamine calaminaris_ _cadmia metallica_ _kobelt_ part cobalt *_cadmia metallica_ _cadmia fornacis_ _mitlere und furnace furnace accretions obere accretions or offenbrüche_ furnace calamine _bituminosa _kobelt des (mannsfeld copper _bituminosa cadmia_ cadmia_ bergwacht_ schists) (see note , p. ) _galena inanis_ _blende_ sphalerite* *blende (zn s) _cobaltum -- smallite* } _cadmia metallica_ cineraceum_ (coas_{ }) } } _cobaltum nigrum_ -- abolite* } } _cobaltum ferri -- cobaltite } colore_ (coass) } _zincum_ _zinck_ zinc zinc _liquor candidus _conterfei_ zinc see note , p. ex fornace ... etc._ _atramentum -- goslarite *native white sutorium, (zn so_{ }) vitriol candidum, potissimum reperitur goselariae_ _spodos _geeler zechen } either natural { grey _spodos_ subterranea rauch_ } or artificial { cinerea_ } zinc oxides, { } no doubt { _spodos _schwartzer } containing { black _spodos_ subterranea zechen rauch, } arsenical { nigra_ auff dem } oxides { altenberge } { nennet man in } { kis_ } { } { _spodos _grauer zechen } { green _spodos_ subterranea rauch_ } { viridis_ } { } { _pompholyx_ _hüttenrauch_ } { _pompholyx_ (see } { note , p. ) as seen from the following quotations from agricola, on _cadmia_ and cobalt, there was infinite confusion as to the zinc, cobalt, and arsenic minerals; nor do we think any good purpose is served by adding to the already lengthy discussion of these passages, the obscurity of which is natural to the state of knowledge; but we reproduce them as giving a fairly clear idea of the amount of confusion then existing. it is, however, desirable to bear in mind that the mines familiar to agricola abounded in complex mixtures of cobalt, nickel, arsenic, bismuth, zinc, and antimony. agricola frequently mentions the garlic odour from _cadmia metallica_, which, together with the corrosive qualities mentioned below, would obviously be due to arsenic. _bermannus_ (p. ). "this kind of pyrites miners call _cobaltum_, if it be allowed to me to use our german name. the greeks call it _cadmia_. the juices, however, out of which pyrites and silver are formed, appear to solidify into one body, and thus is produced what they call _cobaltum_. there are some who consider this the same as pyrites, because it is almost the same. there are some who distinguish it as a species, which pleases me, for it has the distinctive property of being extremely corrosive, so that it consumes the hands and feet of the workmen, unless they are well protected, which i do not believe that pyrites can do. three kinds are found, and distinguished more by the colour than by other properties; they are black (abolite?), grey (smallite?), and iron colour (cobalt glance?). moreover, it contains more silver than does pyrites...." _bermannus_ (p. ). "it (a sort of pyrites) is so like the colour of galena that not without cause might anybody have doubt in deciding whether it be pyrites or galena.... perhaps this kind is neither pyrites nor galena, but has a genus of its own. for it has not the colour of pyrites, nor the hardness. it is almost the colour of galena, but of entirely different components. from it there is made gold and silver, and a great quantity is dug out from reichenstein which is in silesia, as was lately reported to me. much more is found at raurici, which they call _zincum_; which species differs from pyrites, for the latter contains more silver than gold, the former only gold, or hardly any silver." (_de natura fossilium_, p. ). "_cadmia fossilis_ has an odour like garlic" ... (p. ). "we now proceed with _cadmia_, not the _cadmia fornacis_ (furnace accretions) of which i spoke in the last book, nor the _cadmia fossilis_ (calamine) devoid of metal, which is used to colour copper, whose nature i explained in book v, but the metallic mineral (_fossilis metallica_), which pliny states to be an ore from which copper is made. the ancients have left no record that another metal could be smelted from it. yet it is a fact that not only copper but also silver may be smelted from it, and indeed occasionally both copper and silver together. sometimes, as is the case with pyrites, it is entirely devoid of metal. it is frequently found in copper mines, but more frequently still in silver mines. and there are likewise veins of _cadmia_ itself.... there are several species of the _cadmia fossilis_ just as there were of _cadmia fornacum_. for one kind has the form of grapes and another of broken tiles, a third seems to consist of layers. but the _cadmia fossilis_ has much stronger properties than that which is produced in the furnaces. indeed, it often possesses such highly corrosive power that it corrodes the hands and feet of the miners. it, therefore, differs from pyrites in colour and properties. for pyrites, if it does not contain vitriol, is generally either of a gold or silver colour, rarely of any other. _cadmia_ is either black or brown or grey, or else reddish like copper when melted in the furnace.... for this _cadmia_ is put in a suitable vessel, in the same way as quicksilver, so that the heat of the fire will cause it to sublimate, and from it is made a black or brown or grey body which the alchemists call 'sublimated _cadmia_' (_cadmiam sublimatam_). this possesses corrosive properties of the highest degree. cognate with _cadmia_ and pyrites is a compound which the noricians and rhetians call _zincum_. this contains gold and silver, and is either red or white. it is likewise found in the sudetian mountains, and is devoid of those metals.... with this _cadmia_ is naturally related mineral _spodos_, known to the moor serapion, but unknown to the greeks; and also _pompholyx_--for both are produced by fire where the miners, breaking the hard rocks in drifts, tunnels, and shafts, burn the _cadmia_ or pyrites or galena or other similar minerals. from _cadmia_ is made black, brown, and grey _spodos_; from pyrites, white _pompholyx_ and _spodos_; from galena is made yellow or grey _spodos_. but _pompholyx_ produced from copper stone (_lapide aeroso_) after some time becomes green. the black _spodos_, similar to soot, is found at altenberg in meissen. the white _pompholyx_, like wool which floats in the air in summer, is found in hildesheim in the seams in the rocks of almost all quarries except in the sandstone. but the grey and the brown and the yellow _pompholyx_ are found in those silver mines where the miners break up the rocks by fire. all consist of very fine particles which are very light, but the lightest of all is white _pompholyx_." quartz minerals. _quarzum_ ("which _quertz oder quartz quartz (see note latins call kiselstein_ , p. ) _silex_") _silex_ _hornstein oder flinty or jaspery hornstone feurstein_ quartz _crystallum_ _crystal_ clear crystals crystal _achates_ _achat_ agate agate _sarda_ _carneol_ carnelian carnelian _jaspis_ _jaspis_ part coloured _jaspis_ quartz, part jade _murrhina_ _chalcedonius_ chalcedony chalcedony _coticula_ _goldstein_ a black silicious touchstone (see stone note , p. ) _amethystus_ _amethyst_ amethyst amethyst lime minerals. _lapis } _gips_ gypsum gypsum specularis_ } } _gypsum_ } _marmor_ _marmelstein_ marble marble _marmor _alabaster_ alabaster alabaster alabastrites_ _marmor glarea_ -- calcite (?) calc spar(?) _saxum calcis_ _kalchstein_ limestone limestone _marga_ _mergel_ marl marl _tophus_ _toffstein oder sintry _tophus_ (see note topstein_ limestones, , p. ) stalagmites, etc. miscellaneous. _amiantus_ _federwis, pliant usually asbestos asbestos salamanderhar_ _magnetis_ _silberweis oder } mica *mica katzensilber_ } } _bracteolae -- } magnetidi simile_ } } _mica_ _katzensilber } oder glimmer_ } _silex ex eo ictu -- feldspar *feldspar ferri facile ignis elicitur.... excubus figuris_ _medulla saxorum_ _steinmarck_ kaolinite porcelain clay _fluores (lapides _flusse_ fluorspar *fluorspar gemmarum simili)_ (see note , p. ) _marmor in _spat_ barite *heavy spar metallis repertum_ apart from the above, many other minerals are mentioned in other chapters, and some information is given with regard to them in the footnotes. [ ] three _librae_ of silver per _centumpondium_ would be equal to ounces per short ton. [ ] as stated in note on p. , agricola divided "stones so called" into four kinds; the first, common stones in which he included lodestone and jasper or bloodstone; the second embraced gems; the third were decorative stones, such as marble, porphyry, etc.; the fourth were rocks, such as sandstone and limestone. lodestone. (_magnes_; _interpretatio_ gives _siegelstein oder magnet_). the lodestone was well-known to the ancients under various names--_magnes_, _magnetis_, _heraclion_, and _sideritis_. a review of the ancient opinions as to its miraculous properties would require more space than can be afforded. it is mentioned by many greek writers, including hippocrates ( - b.c.) and aristotle; while theophrastus ( ), dioscorides (v, ), and pliny (xxxiv, , xxxvi, ) describe it at length. the ancients also maintained the existence of a stone, _theamedes_, having repellant properties, and the two were supposed to exist at times in the same stone. emery. (_smiris_; _interpretatio_ gives _smirgel_). agricola (_de natura fossilium_, p. ) says: "the ring-makers polish and clean their hard gems with _smiris_. the glaziers use it to cut their glass into sheets. it is found in the silver mines of annaberg in meissen and elsewhere." stones used for polishing gems are noted by the ancient authors, and dana (syst. of mineralogy, p. ) considers the stone of armenia, of theophrastus ( ), to be emery, although it could quite well be any hard stone, such as novaculite--which is found in armenia. dioscorides (v, ) describes a stone with which the engravers polish gems. lapis judaicus. (_interpretatio_ gives _jüden stein_). this was undoubtedly a fossil, possibly a _pentremites_. agricola (_de natura fossilium_, p. ) says: "it is shaped like an acorn, from the obtuse end to the point proceed raised lines, all equidistant, etc." many fossils were included among the semi-precious stones by the ancients. pliny (xxxvii, , , ) describes many such stones, among them the _balanites_, _phoenicitis_ and the _pyren_, which resemble the above. trochitis. (_interpretatio_ gives _spangen oder rederstein_). this was also a fossil, probably crinoid stems. agricola (_de natura fossilium_, p. ) describes it: "_trochites_ is so called from a wheel, and is related to _lapis judaicus_. nature has indeed given it the shape of a drum (_tympanum_). the round part is smooth, but on both ends as it were there is a module from which on all sides there extend radii to the outer edge, which corresponds with the radii. these radii are so much raised that it is fluted. the size of these _trochites_ varies greatly, for the smallest is so little that the largest is ten times as big, and the largest are a digit in length by a third of a digit in thickness ... when immersed in vinegar they make bubbles." [ ] the "extraordinary earths" of agricola were such substances as ochres, tripoli, fullers earth, potters' clay, clay used for medicinal purposes, etc., etc. [ ] presumably the ore-body dips into a neighbouring property. [ ] the various kinds of iron tools are described in great detail in book vi. [ ] fire-setting as an aid to breaking rock is of very ancient origin, and moreover it persisted in certain german and norwegian mines down to the end of the th century-- years after the first application of explosives to mining. the first specific reference to fire-setting in mining is by agatharchides ( nd century b.c.) whose works are not extant, but who is quoted by both diodorus siculus and photius, for which statement see note , p. . pliny (xxxiii, ) says: "occasionally a kind of silex is met with, which must be broken with fire and vinegar, or as the tunnels are filled with suffocating fumes and smoke, they frequently use bruising machines, carrying _librae_ of iron." this combination of fire and vinegar he again refers to (xxiii, ), where he dilates in the same sentence on the usefulness of vinegar for breaking rock and for salad dressing. this myth about breaking rocks with fire and vinegar is of more than usual interest, and its origin seems to be in the legend that hannibal thus broke through the alps. livy ( b.c., a.d.) seems to be the first to produce this myth in writing; and, in any event, by pliny's time ( - a.d.) it had become an established method--in literature. livy (xxi, ) says, in connection with hannibal's crossing of the alps: "they set fire to it (the timber) when a wind had arisen suitable to excite the fire, then when the rock was hot it was crumbled by pouring on vinegar (_infuso aceto_). in this manner the cliff heated by the fire was broken by iron tools, and the declivities eased by turnings, so that not only the beasts of burden but also the elephants could be led down." hannibal crossed the alps in b.c. and livy's account was written years later, by which time hannibal's memory among the romans was generally surrounded by herculean fables. be this as it may, by pliny's time the vinegar was generally accepted, and has been ceaselessly debated ever since. nor has the myth ceased to grow, despite the remarks of gibbon, lavalette, and others. a recent historian (hennebert, _histoire d' annibal_ ii, p. ) of that famous engineer and soldier, soberly sets out to prove that inasmuch as literal acceptance of ordinary vinegar is impossible, the phoenicians must have possessed some mysterious high explosive. a still more recent biographer swallows this argument _in toto_. (morris, "hannibal," london, , p. ). a study of the commentators of this passage, although it would fill a volume with sterile words, would disclose one generalization: that the real scholars have passed over the passage with the comment that it is either a corruption or an old woman's tale, but that hosts of soldiers who set about the biography of famous generals and campaigns, almost to a man take the passage seriously, and seriously explain it by way of the rock being limestone, or snow, or by the use of explosives, or other foolishness. it has been proposed, although there are grammatical objections, that the text is slightly corrupt and read _infosso acuto_, instead of _infuso aceto_, in which case all becomes easy from a mining point of view. if so, however, it must be assumed that the corruption occurred during the years between livy and pliny. by the use of fire-setting in recent times at königsberg (arthur l. collins, "fire-setting," federated inst. of mining engineers, vol. v, p. ) an advance of from to feet per month in headings was accomplished, and on the score of economy survived the use of gunpowder, but has now been abandoned in favour of dynamite. we may mention that the use of gunpowder for blasting was first introduced at schemnitz by caspar weindle, in , but apparently was not introduced into english mines for nearly years afterward, as the late th century english writers continue to describe fire-setting. [ ] the strata here enumerated are given in the glossary of _de re metallica_ as follows:-- _corium terrae_ _die erd oder leim._ _saxum rubrum_ _rot gebirge._ _alterum item rubrum_ _roterkle._ _argilla cinerea_ _thone._ _tertium saxum_ _gerhulle._ _cineris vena_ _asche._ _quartum saxum_ _gniest._ _quintum saxum_ _schwehlen._ _sextum saxum_ _oberrauchstein._ _septimum saxum_ _zechstein._ _octavum saxum_ _underrauchstein._ _nonum saxum_ _blitterstein._ _decimum saxum_ _oberschuelen._ _undecimum saxum_ _mittelstein._ _duodecimum saxum_ _underschuelen._ _decimumtertium saxum_ _dach._ _decimumquartum saxum_ _norweg._ _decimumquintum saxum_ _lotwerg._ _decimumsextum saxum_ _kamme._ _lapis aerosus fissilis_ _schifer._ the description is no doubt that of the mannsfeld cupriferous slates. it is of some additional interest as the first attempt at stratigraphic distinctions, although this must not be taken too literally, for we have rendered the different numbered "_saxum_" in this connection as "stratum." the german terms given by agricola above, can many of them be identified in the miners' terms to-day for the various strata at mannsfeld. over the _kupferschiefer_ the names to-day are _kammschale_, _dach_, _faule_, _zechstein_, _rauchwacke_, _rauchstein_, _asche_. the relative thickness of these beds is much the same as given by agricola. the stringers in the th stratum of stone, which fuse in the fire of the second order, were possibly calcite. the _rauchstein_ of the modern section is distinguished by stringers of calcite, which give it at times a brecciated appearance. [ ] the history of surveying and surveying instruments, and in a subsidiary way their application to mine work, is a subject upon which there exists a most extensive literature. however, that portion of such history which relates to the period prior to agricola represents a much less proportion of the whole than do the citations to this chapter in _de re metallica_, which is the first comprehensive discussion of the mining application. the history of such instruments is too extensive to be entered upon in a footnote, but there are some fundamental considerations which, if they had been present in the minds of historical students of this subject, would have considerably abridged the literature on it. first, there can be no doubt that measuring cords or rods and boundary stones existed almost from the first division of land. there is, therefore, no need to try to discover their origins. second, the history of surveying and surveying instruments really begins with the invention of instruments for taking levels, or for the determination of angles with a view to geometrical calculation. the meagre facts bearing upon this subject do not warrant the endless expansion they have received by argument as to what was probable, in order to accomplish assumed methods of construction among the ancients. for instance, the argument that in carrying the grand canal over watersheds with necessary reservoir supply, the chinese must have had accurate levelling and surveying instruments before the christian era, and must have conceived in advance a completed work, does not hold water when any investigation will demonstrate that the canal grew by slow accretion from the lateral river systems, until it joined almost by accident. much the same may be said about the preconception of engineering results in several other ancient works. there can be no certainty as to who first invented instruments of the order mentioned above; for instance, the invention of the dioptra has been ascribed to hero, _vide_ his work on the _dioptra_. he has been assumed to have lived in the st or nd century b.c. recent investigations, however, have shown that he lived about a.d. (sir thomas heath, encyc. brit. th ed., xiii, ). as this instrument is mentioned by vitruvius ( - b.c.) the myth that hero was the inventor must also disappear. incidentally vitruvius (viii, ) describes a levelling instrument called a _chorobates_, which was a frame levelled either by a groove of water or by plumb strings. be the inventor of the _dioptra_ who he may, hero's work on that subject contains the first suggestion of mine surveys in the problems (xiii, xiv, xv, xvi), where geometrical methods are elucidated for determining the depths required for the connection of shafts and tunnels. on the compass we give further notes on p. . it was probably an evolution of the th century. as to the application of angle- and level-determining instruments to underground surveys, so far as we know there is no reference prior to agricola, except that of hero. mr. bennett brough (cantor lecture, london, ) points out that the _nützliche bergbüchlin_ (see appendix) describes a mine compass, but there is not the slightest reference to its use for anything but surface direction of veins. although map-making of a primitive sort requires no instruments, except legs, the oldest map in the world possesses unusual interest because it happens to be a map of a mining region. this well-known turin papyrus dates from seti i. (about b.c.), and it represents certain gold mines between the nile and the red sea. the best discussion is by chabas (_inscriptions des mines d'or_, chalons-sur-saone, paris, , p. - ). fragments of another papyrus, in the turin museum, are considered by lieblein (_deux papyras hiératiques_, christiania, ) also to represent a mine of the time of rameses i. if so, this one dates from about b.c. as to an actual map of underground workings (disregarding illustrations) we know of none until after agricola's time. at his time maps were not made, as will be gathered from the text. [ ] for greater clarity we have in a few places interpolated the terms "major" and "minor" triangles. [ ] the names of the instruments here described in the original text, their german equivalents in the glossary, and the terms adopted in translation are given below:-- latin text. glossary. terms adopted. _funiculus_ -- cord _pertica_ _stab_ rod _hemicyclium_ _donlege bretlein_ hemicycle _tripus_ _stul_ tripod _instrumentum cui _compass_ compass index_ _orbis_ _scheube_ orbis _libra stativa_ _auffsafz_ standing plummet level _libra pensilis_ _wage_ suspended plummet level _instrumentum cui _der schiner swiss compass index alpinum_ compass_ [ ] it is interesting to note that the ratio of any length so obtained, to the whole length of the staff, is practically equal to the cosine of the angle represented by the corresponding gradation on the hemicycle; the gradations on the rod forming a fairly accurate table of cosines. [ ] it must be understood that instead of "plotting" a survey on a reduced scale on paper, as modern surveyors do, the whole survey was reproduced in full scale on the "surveyor's field." book vi. digging of veins i have written of, and the timbering of shafts, tunnels, drifts, and other excavations, and the art of surveying. i will now speak first of all, of the iron tools with which veins and rocks are broken, then of the buckets into which the lumps of earth, rock, metal, and other excavated materials are thrown, in order that they may be drawn, conveyed, or carried out. also, i will speak of the water vessels and drains, then of the machines of different kinds,[ ] and lastly of the maladies of miners. and while all these matters are being described accurately, many methods of work will be explained. [illustration (iron tools): a--first "iron tool." b--second. c--third. d--fourth.[ ] e--wedge. f--iron block. g--iron plate. h--wooden handle. i--handle inserted in first tool.] there are certain iron tools which the miners designate by names of their own, and besides these, there are wedges, iron blocks, iron plates, hammers, crowbars, pikes, picks, hoes, and shovels. of those which are especially referred to as "iron tools" there are four varieties, which are different from one another in length or thickness, but not in shape, for the upper end of all of them is broad and square, so that it can be struck by the hammer. the lower end is pointed so as to split the hard rocks and veins with its point. all of these have eyes except the fourth. the first, which is in daily use among miners, is three-quarters of a foot long, a digit and a half wide, and a digit thick. the second is of the same width as the first, and the same thickness, but one and one half feet long, and is used to shatter the hardest veins in such a way that they crack open. the third is the same length as the second, but is a little wider and thicker; with this one they dig the bottoms of those shafts which slowly accumulate water. the fourth is nearly three palms and one digit long, two digits thick, and in the upper end it is three digits wide, in the middle it is one palm wide, and at the lower end it is pointed like the others; with this they cut out the harder veins. the eye in the first tool is one palm distant from the upper end, in the second and third it is seven digits distant; each swells out around the eye on both sides, and into it they fit a wooden handle, which they hold with one hand, while they strike the iron tool with a hammer, after placing it against the rock. these tools are made larger or smaller as necessary. the smiths, as far as possible, sharpen again all that become dull. a wedge is usually three palms and two digits long and six digits wide; at the upper end, for a distance of a palm, it is three digits thick, and beyond that point it becomes thinner by degrees, until finally it is quite sharp. the iron block is six digits in length and width; at the upper end it is two digits thick, and at the bottom a digit and a half. the iron plate is the same length and width as the iron block, but it is very thin. all of these, as i explained in the last book, are used when the hardest kind of veins are hewn out. wedges, blocks, and plates, are likewise made larger or smaller. [illustration (hammers): a--smallest of the smaller hammers. b--intermediate. c--largest. d--small kind of the larger hammer. e--large kind. f--wooden handle. g--handle fixed in the smallest hammer.] hammers are of two kinds, the smaller ones the miners hold in one hand, and the larger ones they hold with both hands. the former, because of their size and use, are of three sorts. with the smallest, that is to say, the lightest, they strike the second "iron tool;" with the intermediate one the first "iron tool;" and with the largest the third "iron tool"; this one is two digits wide and thick. of the larger sort of hammers there are two kinds; with the smaller they strike the fourth "iron tool;" with the larger they drive the wedges into the cracks; the former are three, and the latter five digits wide and thick, and a foot long. all swell out in their middle, in which there is an eye for a handle, but in most cases the handles are somewhat light, in order that the workmen may be able to strike more powerful blows by the hammer's full weight being thus concentrated. [illustration a (crowbars): a--round crowbar. b--flat crowbar. c--pike.] the iron crowbars are likewise of two kinds, and each kind is pointed at one end. one is rounded, and with this they pierce to a shaft full of water when a tunnel reaches to it; the other is flat, and with this they knock out of the stopes on to the floor, the rocks which have been softened by the fire, and which cannot be dislodged by the pike. a miner's pike, like a sailor's, is a long rod having an iron head. [illustration b (picks): a--pick. b--hoe. c--shovel.] the miner's pick differs from a peasant's pick in that the latter is wide at the bottom and sharp, but the former is pointed. it is used to dig out ore which is not hard, such as earth. likewise a hoe and shovel are in no way different from the common articles, with the one they scrape up earth and sand, with the other they throw it into vessels. now earth, rock, mineral substances and other things dug out with the pick or hewn out with the "iron tools" are hauled out of the shaft in buckets, or baskets, or hide buckets; they are drawn out of tunnels in wheelbarrows or open trucks, and from both they are sometimes carried in trays. [illustration a (buckets for hoisting ore)] [illustration b (buckets for hoisting ore): a--small bucket. b--large bucket. c--staves. d--iron hoops. e--iron straps. f--iron straps on the bottom. g--hafts. h--iron bale. i--hook of drawing-rope. k--basket. l--hide bucket or sack.] buckets are of two kinds, which differ in size, but not in material or shape. the smaller for the most part hold only about one _metreta_; the larger are generally capable of carrying one-sixth of a _congius_; neither is of unchangeable capacity, but they often vary.[ ] each is made of staves circled with hoops, one of which binds the top and the other the bottom. the hoops are sometimes made of hazel and oak, but these are easily broken by dashing against the shaft, while those made of iron are more durable. in the larger buckets the staves are thicker and wider, as also are both hoops, and in order that the buckets may be more firm and strong, they have eight iron straps, somewhat broad, four of which run from the upper hoop downwards, and four from the lower hoop upwards, as if to meet each other. the bottom of each bucket, both inside and outside, is furnished with two or three straps of iron, which run from one side of the lower hoop to the other, but the straps which are on the outside are fixed crosswise. each bucket has two iron hafts which project above the edge, and it has an iron semi-circular bale whose lower ends are fixed directly into the hafts, that the bucket may be handled more easily. each kind of bucket is much deeper than it is wide, and each is wider at the top, in order that the material which is dug out may be the more easily poured in and poured out again. into the smaller buckets strong boys, and into larger ones men, fill earth from the bottom of the shaft with hoes; or the other material dug up is shovelled into them or filled in with their hands, for which reason these men are called "shovellers.[ ]" afterward they fix the hook of the drawing-rope into the bale; then the buckets are drawn up by machines--the smaller ones, because of their lighter weight, by machines turned by men, and the larger ones, being heavier, by the machines turned by horses. some, in place of these buckets, substitute baskets which hold just as much, or even more, since they are lighter than the buckets; some use sacks made of ox-hide instead of buckets, and the drawing-rope hook is fastened to their iron bale, usually three of these filled with excavated material are drawn up at the same time as three are being lowered and three are being filled by boys. the latter are generally used at schneeberg and the former at freiberg. [illustration (wheelbarrows): a--small wheelbarrow. b--long planks thereof. c--end-boards. d--small wheel. e--larger barrow. f--front end-board thereof.] that which we call a _cisium_[ ] is a vehicle with one wheel, not with two, such as horses draw. when filled with excavated material it is pushed by a workman out of tunnels or sheds. it is made as follows: two planks are chosen about five feet long, one foot wide, and two digits thick; of each of these the lower side is cut away at the front for a length of one foot, and at the back for a length of two feet, while the middle is left whole. then in the front parts are bored circular holes, in order that the ends of an axle may revolve in them. the intermediate parts of the planks are perforated twice near the bottom, so as to receive the heads of two little cleats on which the planks are fixed; and they are also perforated in the middle, so as to receive the heads of two end-boards, while keys fixed in these projecting heads strengthen the whole structure. the handles are made out of the extreme ends of the long planks, and they turn downward at the ends that they may be grasped more firmly in the hands. the small wheel, of which there is only one, neither has a nave nor does it revolve around the axle, but turns around with it. from the felloe, which the greeks called [greek: apsides], two transverse spokes fixed into it pass through the middle of the axle toward the opposite felloe; the axle is square, with the exception of the ends, each of which is rounded so as to turn in the opening. a workman draws out this barrow full of earth and rock and draws it back empty. miners also have another wheelbarrow, larger than this one, which they use when they wash earth mixed with tin-stone on to which a stream has been turned. the front end-board of this one is deeper, in order that the earth which has been thrown into it may not fall out. [illustration (trucks): a--rectangular iron bands on truck. b--its iron straps. c--iron axle. d--wooden rollers. e--small iron keys. f--large blunt iron pin. g--same truck upside down.] the open truck has a capacity half as large again as a wheelbarrow; it is about four feet long and about two and a half feet wide and deep; and since its shape is rectangular, it is bound together with three rectangular iron bands, and besides these there are iron straps on all sides. two small iron axles are fixed to the bottom, around the ends of which wooden rollers revolve on either side; in order that the rollers shall not fall off the immovable axles, there are small iron keys. a large blunt pin fixed to the bottom of the truck runs in a groove of a plank in such a way that the truck does not leave the beaten track. holding the back part with his hands, the carrier pushes out the truck laden with excavated material, and pushes it back again empty. some people call it a "dog"[ ], because when it moves it makes a noise which seems to them not unlike the bark of a dog. this truck is used when they draw loads out of the longest tunnels, both because it is moved more easily and because a heavier load can be placed in it. [illustration (batea): a--small batea. b--rope. c--large batea.] bateas[ ] are hollowed out of a single block of wood; the smaller kind are generally two feet long and one foot wide. when they have been filled with ore, especially when but little is dug from the shafts and tunnels, men either carry them out on their shoulders, or bear them away hung from their necks. pliny[ ] is our authority that among the ancients everything which was mined was carried out on men's shoulders, but in truth this method of carrying forth burdens is onerous, since it causes great fatigue to a great number of men, and involves a large expenditure for labour; for this reason it has been rejected and abandoned in our day. the length of the larger batea is as much as three feet, the width up to a foot and a palm. in these bateas the metallic earth is washed for the purpose of testing it. [illustration a (buckets for hoisting water): a--smaller water-bucket. b--larger water-bucket. c--dipper.] water-vessels differ both in the use to which they are put and in the material of which they are made; some draw the water from the shafts and pour it into other things, as dippers; while some of the vessels filled with water are drawn out by machines, as buckets and bags; some are made of wood, as the dippers and buckets, and others of hides, as the bags. the water-buckets, just like the buckets which are filled with dry material, are of two kinds, the smaller and the larger, but these are unlike the other buckets at the top, as in this case they are narrower, in order that the water may not be spilled by being bumped against the timbers when they are being drawn out of the shafts, especially those considerably inclined. the water is poured into these buckets by dippers, which are small wooden buckets, but unlike the water-buckets, they are neither narrow at the top nor bound with iron hoops, but with hazel,--because there is no necessity for either. the smaller buckets are drawn up by machines turned by men, the larger ones by those turned by horses. [illustration b (bags for hoisting water): a--water-bag which takes in water by itself. b--water-bag into which water pours when it is pushed with a shovel.] our people give the name of water-bags to those very large skins for carrying water which are made of two, or two and a half, ox-hides. when these water-bags have undergone much wear and use, first the hair comes off them and they become bald and shining; after this they become torn. if the tear is but a small one, a piece of smooth notched stick is put into the broken part, and the broken bag is bound into its notches on either side and sewn together; but if it is a large one, they mend it with a piece of ox-hide. the water-bags are fixed to the hook of a drawing-chain and let down and dipped into the water, and as soon as they are filled they are drawn up by the largest machine. they are of two kinds; the one kind take in the water by themselves; the water pours into the other kind when it is pushed in a certain way by a wooden shovel. [illustration (trough): a--trough. b--hopper.] when the water has been drawn out from the shafts, it is run off in troughs, or into a hopper, through which it runs into the trough. likewise the water which flows along the sides of the tunnels is carried off in drains. these are composed of two hollowed beams joined firmly together, so as to hold the water which flows through them, and they are covered by planks all along their course, from the mouth of the tunnel right up to the extreme end of it, to prevent earth or rock falling into them and obstructing the flow of the water. if much mud gradually settles in them the planks are raised and the drains are cleaned out, for they would otherwise become stopped up and obstructed by this accident. with regard to the trough lying above ground, which miners place under the hoppers which are close by the shaft houses, these are usually hollowed out of single trees. hoppers are generally made of four planks, so cut on the lower side and joined together that the top part of the hopper is broader and the bottom part narrower. i have sufficiently indicated the nature of the miners' iron tools and their vessels. i will now explain their machines, which are of three kinds, that is, hauling machines, ventilating machines, and ladders. by means of the hauling machines loads are drawn out of the shafts; the ventilating machines receive the air through their mouths and blow it into shafts or tunnels, for if this is not done, diggers cannot carry on their labour without great difficulty in breathing; by the steps of the ladders the miners go down into the shafts and come up again. [illustration (windlass): a--timber placed in front of the shaft. b--timber placed at the back of the shaft. c--pointed stakes. d--cross-timbers. e--posts or thick planks. f--iron sockets. g--barrel. h--ends of barrel. i--pieces of wood. k--handle. l--drawing-rope. m--its hook. n--bucket. o--bale of the bucket.] hauling machines are of varied and diverse forms, some of them being made with great skill, and if i am not mistaken, they were unknown to the ancients. they have been invented in order that water may be drawn from the depths of the earth to which no tunnels reach, and also the excavated material from shafts which are likewise not connected with a tunnel, or if so, only with very long ones. since shafts are not all of the same depth, there is a great variety among these hauling machines. of those by which dry loads are drawn out of the shafts, five sorts are in the most common use, of which i will now describe the first. two timbers a little longer than the shaft are placed beside it, the one in the front of the shaft, the other at the back. their extreme ends have holes through which stakes, pointed at the bottom like wedges, are driven deeply into the ground, so that the timbers may remain stationary. into these timbers are mortised the ends of two cross-timbers, one laid on the right end of the shaft, while the other is far enough from the left end that between it and that end there remains suitable space for placing the ladders. in the middle of the cross-timbers, posts are fixed and secured with iron keys. in hollows at the top of these posts thick iron sockets hold the ends of the barrel, of which each end projects beyond the hollow of the post, and is mortised into the end of another piece of wood a foot and a half long, a palm wide and three digits thick; the other end of these pieces of wood is seven digits wide, and into each of them is fixed a round handle, likewise a foot and a half long. a winding-rope is wound around the barrel and fastened to it at the middle part. the loop at each end of the rope has an iron hook which is engaged in the bale of a bucket, and so when the windlass revolves by being turned by the cranks, a loaded bucket is always being drawn out of the shaft and an empty one is being sent down into it. two robust men turn the windlass, each having a wheelbarrow near him, into which he unloads the bucket which is drawn up nearest to him; two buckets generally fill a wheelbarrow; therefore when four buckets have been drawn up, each man runs his own wheelbarrow out of the shed and empties it. thus it happens that if shafts are dug deep, a hillock rises around the shed of the windlass. if a vein is not metal-bearing, they pour out the earth and rock without discriminating; whereas if it is metal-bearing, they preserve these materials, which they unload separately and crush and wash. when they draw up buckets of water they empty the water through the hopper into a trough, through which it flows away. [illustration (windlass): a--barrel. b--straight levers. c--usual crank. d--spokes of wheel. e--rim of the same wheel.] the next kind of machine, which miners employ when the shaft is deeper, differs from the first in that it possesses a wheel as well as cranks. this windlass, if the load is not being drawn up from a great depth, is turned by one windlass man, the wheel taking the place of the other man. but if the depth is greater, then the windlass is turned by three men, the wheel being substituted for a fourth, because the barrel having been once set in motion, the rapid revolutions of the wheel help, and it can be turned more easily. sometimes masses of lead are hung on to this wheel, or are fastened to the spokes, in order that when it is turned they depress the spokes by their weight and increase the motion; some persons for the same reason fasten into the barrel two, three, or four iron rods, and weight their ends with lumps of lead. the windlass wheel differs from the wheel of a carriage and from the one which is turned by water power, for it lacks the buckets of a water-wheel and it lacks the nave of a carriage wheel. in the place of the nave it has a thick barrel, in which are mortised the lower ends of the spokes, just as their upper ends are mortised into the rim. when three windlass men turn this machine, four straight levers are fixed to the one end of the barrel, and to the other the crank which is usual in mines, and which is composed of two limbs, of which the rounded horizontal one is grasped by the hands; the rectangular limb, which is at right angles to the horizontal one, has mortised in its lower end the round handle, and in the upper end the end of the barrel. this crank is worked by one man, the levers by two men, of whom one pulls while the other pushes; all windlass workers, whatsoever kind of a machine they may turn, are necessarily robust that they can sustain such great toil. [illustration (tread whim): a--upright axle. b--block. c--roof beam. d--wheel. e--toothed-drum. f--horizontal axle. g--drum composed of rundles. h--drawing rope. i--pole. k--upright posts. l--cleats on the wheel.] the third kind of machine is less fatiguing for the workman, while it raises larger loads; even though it is slower, like all other machines which have drums, yet it reaches greater depths, even to a depth of feet. it consists of an upright axle with iron journals at its extremities, which turn in two iron sockets, the lower of which is fixed in a block set in the ground and the upper one in the roof beam. this axle has at its lower end a wheel made of thick planks joined firmly together, and at its upper end a toothed drum; this toothed drum turns another drum made of rundles, which is on a horizontal axle. a winding-rope is wound around this latter axle, which turns in iron bearings set in the beams. so that they may not fall, the two workmen grasp with their hands a pole fixed to two upright posts, and then pushing the cleats of the lower wheel backward with their feet, they revolve the machine; as often as they have drawn up and emptied one bucket full of excavated material, they turn the machine in the opposite direction and draw out another. [illustration (horse whim): a--upright beams. b--sills laid flat upon the ground. c--posts. d--area. e--sill set at the bottom of the hole. f--axle. g--double cross-beams. h--drum. i--winding-ropes. k--bucket. l--small pieces of wood hanging from double cross-beams. m--short wooden block. n--chain. o--pole bar. p--grappling hook. (some members mentioned in the text are not shown).] the fourth machine raises burdens once and a half as large again as the two machines first explained. when it is made, sixteen beams are erected each forty feet long, one foot thick and one foot wide, joined at the top with clamps and widely separated at the bottom. the lower ends of all of them are mortised into separate sills laid flat upon the ground; these sills are five feet long, a foot and a half wide, and a foot thick. each beam is also connected with its sill by a post, whose upper end is mortised into the beam and its lower end mortised into the sill; these posts are four feet long, one foot thick, and one foot wide. thus a circular area is made, the diameter of which is fifty feet; in the middle of this area a hole is sunk to a depth of ten feet, and rammed down tight, and in order to give it sufficient firmness, it is strengthened with contiguous small timbers, through which pins are driven, for by them the earth around the hole is held so that it cannot fall in. in the bottom of the hole is planted a sill, three or four feet long and a foot and a half thick and wide; in order that it may remain fixed, it is set into the small timbers; in the middle of it is a steel socket in which the pivot of the axle turns. in like manner a timber is mortised into two of the large beams, at the top beneath the clamps; this has an iron bearing in which the other iron journal of the axle revolves. every axle used in mining, to speak of them once for all, has two iron journals, rounded off on all sides, one fixed with keys in the centre of each end. that part of this journal which is fixed to the end of the axle is as broad as the end itself and a digit thick; that which projects beyond the axle is round and a palm thick, or thicker if necessity requires; the ends of each miner's axle are encircled and bound by an iron band to hold the journal more securely. the axle of this machine, except at the ends, is square, and is forty feet long, a foot and a half thick and wide. mortised and clamped into the axle above the lower end are the ends of four inclined beams; their outer ends support two double cross-beams similarly mortised into them; the inclined beams are eighteen feet long, three palms thick, and five wide. the two cross-beams are fixed to the axle and held together by wooden keys so that they will not separate, and they are twenty-four feet long. next, there is a drum which is made of three wheels, of which the middle one is seven feet distant from the upper one and from the lower one; the wheels have four spokes which are supported by the same number of inclined braces, the lower ends of which are joined together round the axle by a clamp; one end of each spoke is mortised into the axle and the other into the rim. there are rundles all round the wheels, reaching from the rim of the lowest one to the rim of the middle one, and likewise from the rim of the middle wheel to the rim of the top one; around these rundles are wound the drawing-ropes, one between the lowest wheel and the middle one, the other between the middle and top wheels. the whole of this construction is shaped like a cone, and is covered with a shingle roof, with the exception of that square part which faces the shaft. then cross-beams, mortised at both ends, connect a double row of upright posts; all of these are eighteen feet long, but the posts are one foot thick and one foot wide, and the cross-beams are three palms thick and wide. there are sixteen posts and eight cross-beams, and upon these cross-beams are laid two timbers a foot wide and three palms thick, hollowed out to a width of half a foot and to a depth of five digits; the one is laid upon the upper cross-beams and the other upon the lower; each is long enough to reach nearly from the drum of the whim to the shaft. near the same drum each timber has a small round wooden roller six digits thick, whose ends are covered with iron bands and revolve in iron rings. each timber also has a wooden pulley, which together with its iron axle revolves in holes in the timber. these pulleys are hollowed out all round, in order that the drawing-rope may not slip out of them, and thus each rope is drawn tight and turns over its own roller and its own pulley. the iron hook of each rope is engaged with the bale of the bucket. further, with regard to the double cross-beams which are mortised to the lower part of the main axle, to each end of them there is mortised a small piece of wood four feet long. these appear to hang from the double cross-beams, and a short wooden block is fixed to the lower part of them, on which a driver sits. each of these blocks has an iron clavis which holds a chain, and that in turn a pole-bar. in this way it is possible for two horses to draw this whim, now this way and now that; turn by turn one bucket is drawn out of the shaft full and another is let down into it empty; if, indeed, the shaft is very deep four horses turn the whim. when a bucket has been drawn up, whether filled with dry or wet materials, it must be emptied, and a workman inserts a grappling hook and overturns it; this hook hangs on a chain made of three or four links, fixed to a timber. [illustration (horse whim): a--toothed drum which is on the upright axle. b--horizontal axle. c--drum which is made of rundles. d--wheel near it. e--drum made of hubs. f--brake. g--oscillating beam. h--short beam. i--hook.] the fifth machine is partly like the whim, and partly like the third rag and chain pump, which draws water by balls when turned by horse power, as i will explain a little later. like this pump, it is turned by horse power and has two axles, namely, an upright one--about whose lower end, which descends into an underground chamber, there is a toothed drum--and a horizontal one, around which there is a drum made of rundles. it has indeed two drums around its horizontal axle, similar to those of the big machine, but smaller, because it draws buckets from a shaft almost two hundred and forty feet deep. one drum is made of hubs to which cleats are fixed, and the other is made of rundles; and near the latter is a wheel two feet deep, measured on all sides around the axle, and one foot wide; and against this impinges a brake,[ ] which holds the whim when occasion demands that it be stopped. this is necessary when the hide buckets are emptied after being drawn up full of rock fragments or earth, or as often as water is poured out of buckets similarly drawn up; for this machine not only raises dry loads, but also wet ones, just like the other four machines which i have already described. by this also, timbers fastened on to its winding-chain are let down into a shaft. the brake is made of a piece of wood one foot thick and half a foot long, projecting from a timber that is suspended by a chain from one end of a beam which oscillates on an iron pin, this in turn being supported in the claws of an upright post; and from the other end of this oscillating beam a long timber is suspended by a chain, and from this long timber again a short beam is suspended. a workman sits on the short beam when the machine needs to be stopped, and lowers it; he then inserts a plank or small stick so that the two timbers are held down and cannot be raised. in this way the brake is raised, and seizing the drum, presses it so tightly that sparks often fly from it; the suspended timber to which the short beam is attached, has several holes in which the chain is fixed, so that it may be raised as much as is convenient. above this wheel there are boards to prevent the water from dripping down and wetting it, for if it becomes wet the brake will not grip the machine so well. near the other drum is a pin from which hangs a chain, in the last link of which there is an iron hook three feet long; a ring is fixed to the bottom of the bucket, and this hook, being inserted into it, holds the bucket back so that the water may be poured out or the fragments of rock emptied. [illustration (sleigh for ore): a--sledge with box placed on it. b--sledge with sacks placed on it. c--stick. d--dogs with pack-saddles. e--pigskin sacks tied to a rope.] the miners either carry, draw, or roll down the mountains the ore which is hauled out of the shafts by these five machines or taken out of the tunnels. in the winter time our people place a box on a sledge and draw it down the low mountains with a horse; and in this season they also fill sacks made of hide and load them on dogs, or place two or three of them on a small sledge which is higher in the fore part and lower at the back. sitting on these sacks, not without risk of his life, the bold driver guides the sledge as it rushes down the mountain into the valleys with a stick, which he carries in his hand; when it is rushing down too quickly he arrests it with the stick, or with the same stick brings it back to the track when it is turning aside from its proper course. some of the noricians[ ] collect ore during the winter into sacks made of bristly pigskins, and drag them down from the highest mountains, which neither horses, mules nor asses can climb. strong dogs, that are trained to bear pack saddles, carry these sacks when empty into the mountains. when they are filled with ore, bound with thongs, and fastened to a rope, a man, winding the rope round his arm or breast, drags them down through the snow to a place where horses, mules, or asses bearing pack-saddles can climb. there the ore is removed from the pigskin sacks and put into other sacks made of double or triple twilled linen thread, and these placed on the pack-saddles of the beasts are borne down to the works where the ores are washed or smelted. if, indeed, the horses, mules, or asses are able to climb the mountains, linen sacks filled with ore are placed on their saddles, and they carry these down the narrow mountain paths, which are passable neither by wagons nor sledges, into the valleys lying below the steeper portions of the mountains. but on the declivity of cliffs which beasts cannot climb, are placed long open boxes made of planks, with transverse cleats to hold them together; into these boxes is thrown the ore which has been brought in wheelbarrows, and when it has run down to the level it is gathered into sacks, and the beasts either carry it away on their backs or drag it away after it has been thrown into sledges or wagons. when the drivers bring ore down steep mountain slopes they use two-wheeled carts, and they drag behind them on the ground the trunks of two trees, for these by their weight hold back the heavily-laden carts, which contain ore in their boxes, and check their descent, and but for these the driver would often be obliged to bind chains to the wheels. when these men bring down ore from mountains which do not have such declivities, they use wagons whose beds are twice as long as those of the carts. the planks of these are so put together that, when the ore is unloaded by the drivers, they can be raised and taken apart, for they are only held together by bars. the drivers employed by the owners of the ore bring down thirty or sixty wagon-loads, and the master of the works marks on a stick the number of loads for each driver. but some ore, especially tin, after being taken from the mines, is divided into eight parts, or into nine, if the owners of the mine give "ninth parts" to the owners of the tunnel. this is occasionally done by measuring with a bucket, but more frequently planks are put together on a spot where, with the addition of the level ground as a base, it forms a hollow box. each owner provides for removing, washing, and smelting that portion which has fallen to him. (illustration p. ). [illustration (wagons for hauling ore): a--horses with pack-saddles. b--long box placed on the slope of the cliff. c--cleats thereof. d--wheelbarrow. e--two-wheeled cart. f--trunks of trees. g--wagon. h--ore being unloaded from the wagon. i--bars. k--master of the works marking the number of carts on a stick. l--boxes into which are thrown the ore which has to be divided.] into the buckets, drawn by these five machines, the boys or men throw the earth and broken rock with shovels, or they fill them with their hands; hence they get their name of shovellers. as i have said, the same machines raise not only dry loads, but also wet ones, or water; but before i explain the varied and diverse kinds of machines by which miners are wont to draw water alone, i will explain how heavy bodies, such as axles, iron chains, pipes, and heavy timbers, should be lowered into deep vertical shafts. a windlass is erected whose barrel has on each end four straight levers; it is fixed into upright beams and around it is wound a rope, one end of which is fastened to the barrel and the other to those heavy bodies which are slowly lowered down by workmen; and if these halt at any part of the shaft they are drawn up a little way. when these bodies are very heavy, then behind this windlass another is erected just like it, that their combined strength may be equal to the load, and that it may be lowered slowly. sometimes for the same reason, a pulley is fastened with cords to the roof-beam, and the rope descends and ascends over it. [illustration (windlass): a--windlass. b--straight levers. c--upright beams. d--rope. e--pulley. f--timbers to be lowered.] water is either hoisted or pumped out of shafts. it is hoisted up after being poured into buckets or water-bags; the water-bags are generally brought up by a machine whose water-wheels have double paddles, while the buckets are brought up by the five machines already described, although in certain localities the fourth machine also hauls up water-bags of moderate size. water is drawn up also by chains of dippers, or by suction pumps, or by "rag and chain" pumps.[ ] when there is but a small quantity, it is either brought up in buckets or drawn up by chains of dippers or suction pumps, and when there is much water it is either drawn up in hide bags or by rag and chain pumps. [illustration (chain pumps): a--iron frame. b--lowest axle. c--fly-wheel. d--smaller drum made of rundles. e--second axle. f--smaller toothed wheel. g--larger drum made of rundles. h--upper axle. i--larger toothed wheel. k--bearings. l--pillow. m--framework. n--oak timber. o--support of iron bearing. p--roller. q--upper drum. r--clamps. s--chain. t--links. v--dippers. x--crank. y--lower drum or balance weight.] first of all, i will describe the machines which draw water by chains of dippers, of which there are three kinds. for the first, a frame is made entirely of iron bars; it is two and a half feet high, likewise two and a half feet long, and in addition one-sixth and one-quarter of a digit long, one-fourth and one-twenty-fourth of a foot wide. in it there are three little horizontal iron axles, which revolve in bearings or wide pillows of steel, and also four iron wheels, of which two are made with rundles and the same number are toothed. outside the frame, around the lowest axle, is a wooden fly-wheel, so that it can be more readily turned, and inside the frame is a smaller drum which is made of eight rundles, one-sixth and one twenty-fourth of a foot long. around the second axle, which does not project beyond the frame, and is therefore only two and a half feet and one-twelfth and one-third part of a digit long, there is on the one side, a smaller toothed wheel, which has forty-eight teeth, and on the other side a larger drum, which is surrounded by twelve rundles one-quarter of a foot long. around the third axle, which is one inch and one-third thick, is a larger toothed wheel projecting one foot from the axle in all directions, which has seventy-two teeth. the teeth of each wheel are fixed in with screws, whose threads are screwed into threads in the wheel, so that those teeth which are broken can be replaced by others; both the teeth and rundles are steel. the upper axle projects beyond the frame, and is so skilfully mortised into the body of another axle that it has the appearance of being one; this axle proceeds through a frame made of beams which stands around the shaft, into an iron fork set in a stout oak timber, and turns on a roller made of pure steel. around this axle is a drum of the kind possessed by those machines which draw water by rag and chain; this drum has triple curved iron clamps, to which the links of an iron chain hook themselves, so that a great weight cannot tear them away. these links are not whole like the links of other chains, but each one being curved in the upper part on each side catches the one which comes next, whereby it presents the appearance of a double chain. at the point where one catches the other, dippers made of iron or brass plates and holding half a _congius_[ ] are bound to them with thongs; thus, if there are one hundred links there will be the same number of dippers pouring out water. when the shafts are inclined, the mouths of the dippers project and are covered on the top that they may not spill out the water, but when the shafts are vertical the dippers do not require a cover. by fitting the end of the lowest small axle into the crank, the man who works the crank turns the axle, and at the same time the drum whose rundles turn the toothed wheel of the second axle; by this wheel is driven the one that is made of rundles, which again turns the toothed wheel of the upper small axle and thus the drum to which the clamps are fixed. in this way the chain, together with the empty dippers, is slowly let down, close to the footwall side of the vein, into the sump to the bottom of the balance drum, which turns on a little iron axle, both ends of which are set in a thick iron bearing. the chain is rolled round the drum and the dippers fill with water; the chain being drawn up close to the hangingwall side, carries the dippers filled with water above the drum of the upper axle. thus there are always three of the dippers inverted and pouring water into a lip, from which it flows away into the drain of the tunnel. this machine is less useful, because it cannot be constructed without great expense, and it carries off but little water and is somewhat slow, as also are other machines which possess a great number of drums. [illustration (chain pumps): a--wheel which is turned by treading. b--axle. c--double chain. d--link of double chain. e--dippers. f--simple clamps. g--clamp with triple curves.] the next machine of this kind, described in a few words by vitruvius,[ ] more rapidly brings up dippers, holding a _congius_; for this reason, it is more useful than the first one for drawing water out of shafts, into which much water is continually flowing. this machine has no iron frame nor drums, but has around its axle a wooden wheel which is turned by treading; the axle, since it has no drum, does not last very long. in other respects this pump resembles the first kind, except that it differs from it by having a double chain. clamps should be fixed to the axle of this machine, just as to the drum of the other one; some of these are made simple and others with triple curves, but each kind has four barbs. [illustration (chain pumps): a--wheel whose paddles are turned by the force of the stream. b--axle. c--drum of axle, to which clamps are fixed. d--chain. e--link. f--dippers. g--balance drum.] the third machine, which far excels the two just described, is made when a running stream can be diverted to a mine; the impetus of the stream striking the paddles revolves a water-wheel in place of the wheel turned by treading. with regard to the axle, it is like the second machine, but the drum which is round the axle, the chain, and the balance drum, are like the first machine. it has much more capacious dippers than even the second machine, but since the dippers are frequently broken, miners rarely use these machines; for they prefer to lift out small quantities of water by the first five machines or to draw it up by suction pumps, or, if there is much water, to drain it by the rag and chain pump or to bring it up in water-bags. [illustration (suction pumps): a--sump. b--pipes. c--flooring. d--trunk. e--perforations of trunk. f--valve. g--spout. h--piston-rod. i--hand-bar of piston. k--shoe. l--disc with round openings. m--disc with oval openings. n--cover. o--this man is boring logs and making them into pipes. p--borer with auger. q--wider borer.] enough, then, of the first sort of pumps. i will now explain the other, that is the pump which draws, by means of pistons, water which has been raised by suction. of these there are seven varieties, which though they differ from one another in structure, nevertheless confer the same benefits upon miners, though some to a greater degree than others. the first pump is made as follows. over the sump is placed a flooring, through which a pipe--or two lengths of pipe, one of which is joined into the other--are let down to the bottom of the sump; they are fastened with pointed iron clamps driven in straight on both sides, so that the pipes may remain fixed. the lower end of the lower pipe is enclosed in a trunk two feet deep; this trunk, hollow like the pipe, stands at the bottom of the sump, but the lower opening of it is blocked with a round piece of wood; the trunk has perforations round about, through which water flows into it. if there is one length of pipe, then in the upper part of the trunk which has been hollowed out there is enclosed a box of iron, copper, or brass, one palm deep, but without a bottom, and a rounded valve so tightly closes it that the water, which has been drawn up by suction, cannot run back; but if there are two lengths of pipe, the box is enclosed in the lower pipe at the point of junction. an opening or a spout in the upper pipe reaches to the drain of the tunnel. thus the workman, eager at his labour, standing on the flooring boards, pushes the piston down into the pipe and draws it out again. at the top of the piston-rod is a hand-bar and the bottom is fixed in a shoe; this is the name given to the leather covering, which is almost cone-shaped, for it is so stitched that it is tight at the lower end, where it is fixed to the piston-rod which it surrounds, but in the upper end where it draws the water it is wide open. or else an iron disc one digit thick is used, or one of wood six digits thick, each of which is far superior to the shoe. the disc is fixed by an iron key which penetrates through the bottom of the piston-rod, or it is screwed on to the rod; it is round, with its upper part protected by a cover, and has five or six openings, either round or oval, which taken together present a star-like appearance; the disc has the same diameter as the inside of the pipe, so that it can be just drawn up and down in it. when the workman draws the piston up, the water which has passed in at the openings of the disc, whose cover is then closed, is raised to the hole or little spout, through which it flows away; then the valve of the box opens, and the water which has passed into the trunk is drawn up by the suction and rises into the pipe; but when the workman pushes down the piston, the valve closes and allows the disc again to draw in the water. [illustration (suction pumps): a--erect timber. b--axle. c--sweep which turns about the axle. d--piston rod. e--cross-bar. f--ring with which two pipes are generally joined.] the piston of the second pump is more easily moved up and down. when this pump is made, two beams are placed over the sump, one near the right side of it, and the other near the left. to one beam a pipe is fixed with iron clamps; to the other is fixed either the forked branch of a tree or a timber cut out at the top in the shape of a fork, and through the prongs of the fork a round hole is bored. through a wide round hole in the middle of a sweep passes an iron axle, so fastened in the holes in the fork that it remains fixed, and the sweep turns on this axle. in one end of the sweep the upper end of a piston-rod is fastened with an iron key; at the other end a cross-bar is also fixed, to the extreme ends of which are handles to enable it to be held more firmly in the hands. and so when the workman pulls the cross-bar upward, he forces the piston into the pipe; when he pushes it down again he draws the piston out of the pipe; and thus the piston carries up the water which has been drawn in at the openings of the disc, and the water flows away through the spout into the drains. this pump, like the next one, is identical with the first in all that relates to the piston, disc, trunk, box, and valve. [illustration (suction pumps): a--posts. b--axle. c--wooden bars. d--piston rod. e--short piece of wood. f--drain. g--this man is diverting the water which is flowing out of the drain, to prevent it from flowing into the trenches which are being dug.] the third pump is not unlike the one just described, but in place of one upright, posts are erected with holes at the top, and in these holes the ends of an axle revolve. to the middle of this axle are fixed two wooden bars, to the end of one of which is fixed the piston, and to the end of the other a heavy piece of wood, but short, so that it can pass between the two posts and may move backward and forward. when the workman pushes this piece of wood, the piston is drawn out of the pipe; when it returns by its own weight, the piston is pushed in. in this way, the water which the pipe contains is drawn through the openings in the disc and emptied by the piston through the spout into the drain. there are some who place a hand-bar underneath in place of the short piece of wood. this pump, as also the last before described, is less generally used among miners than the others. [illustration (duplex suction pumps): a--box. b--lower part of box. c--upper part of same. d--clamps. e--pipes below the box. f--column pipe fixed above the box. g--iron axle. h--piston-rods. i--washers to protect the bearings. k--leathers. l--eyes in the axle. m--rods whose ends are weighted with lumps of lead. n--crank. (_this plate is unlettered in the first edition but corrected in those later._)] the fourth kind is not a simple pump but a duplex one. it is made as follows. a rectangular block of beechwood, five feet long, two and a half feet wide, and one and a half feet thick, is cut in two and hollowed out wide and deep enough so that an iron axle with cranks can revolve in it. the axle is placed between the two halves of this box, and the first part of the axle, which is in contact with the wood, is round and the straight end forms a journal. then the axle is bent down the depth of a foot and again bent so as to continue straight, and at this point a round piston-rod hangs from it; next it is bent up as far as it was bent down; then it continues a little way straight again, and then it is bent up a foot and again continues straight, at which point a second round piston-rod is hung from it; afterward it is bent down the same distance as it was bent up the last time; the other end of it, which also acts as a journal, is straight. this part which protrudes through the wood is protected by two iron washers in the shape of discs, to which are fastened two leather washers of the same shape and size, in order to prevent the water which is drawn into the box from gushing out. these discs are around the axle; one of them is inside the box and the other outside. beyond this, the end of the axle is square and has two eyes, in which are fixed two iron rods, and to their ends are weighted lumps of lead, so that the axle may have a greater propensity to revolve; this axle can easily be turned when its end has been mortised in a crank. the upper part of the box is the shallower one, and the lower part the deeper; the upper part is bored out once straight down through the middle, the diameter of the opening being the same as the outside diameter of the column pipe; the lower box has, side by side, two apertures also bored straight down; these are for two pipes, the space of whose openings therefore is twice as great as that of the upper part; this lower part of the box is placed upon the two pipes, which are fitted into it at their upper ends, and the lower ends of these pipes penetrate into trunks which stand in the sump. these trunks have perforations through which the water flows into them. the iron axle is placed in the inside of the box, then the two iron piston-rods which hang from it are let down through the two pipes to the depth of a foot. each piston has a screw at its lower end which holds a thick iron plate, shaped like a disc and full of openings, covered with a leather, and similarly to the other pump it has a round valve in a little box. then the upper part of the box is placed upon the lower one and properly fitted to it on every side, and where they join they are bound by wide thick iron plates, and held with small wide iron wedges, which are driven in and are fastened with clamps. the first length of column pipe is fixed into the upper part of the box, and another length of pipe extends it, and a third again extends this one, and so on, another extending on another, until the uppermost one reaches the drain of the tunnel. when the crank worker turns the axle, the pistons in turn draw the water through their discs; since this is done quickly, and since the area of openings of the two pipes over which the box is set, is twice as large as the opening of the column pipe which rises from the box, and since the pistons do not lift the water far up, the impetus of the water from the lower pipes forces it to rise and flow out of the column pipe into the drain of the tunnel. since a wooden box frequently cracks open, it is better to make it of lead or copper or brass. [illustration (suction pumps): a--tappets of piston-rods. b--cams of the barrel. c--square upper parts of piston-rods. d--lower rounded parts of piston-rods. e--cross-beams. f--pipes. g--apertures of pipes. h--trough. (fifth kind of pump--see p. ).] the fifth kind of pump is still less simple, for it is composed of two or three pumps whose pistons are raised by a machine turned by men, for each piston-rod has a tappet which is raised, each in succession, by two cams on a barrel; two or four strong men turn it. when the pistons descend into the pipes their discs draw the water; when they are raised these force the water out through the pipes. the upper part of each of these piston-rods, which is half a foot square, is held in a slot in a cross-beam; the lower part, which drops down into the pipes, is made of another piece of wood and is round. each of these three pumps is composed of two lengths of pipe fixed to the shaft timbers. this machine draws the water higher, as much as twenty-four feet. if the diameter of the pipes is large, only two pumps are made; if smaller, three, so that by either method the volume of water is the same. this also must be understood regarding the other machines and their pipes. since these pumps are composed of two lengths of pipe, the little iron box having the iron valve which i described before, is not enclosed in a trunk, but is in the lower length of pipe, at that point where it joins the upper one; thus the rounded part of the piston-rod is only as long as the upper length of pipe; but i will presently explain this more clearly. [illustration (suction pumps): a--water-wheel. b--axle. c--trunk on which the lowest pipe stands. d--basket surrounding trunk. (sixth kind of pump--see p. .)] the sixth kind of pump would be just the same as the fifth were it not that it has an axle instead of a barrel, turned not by men but by a water-wheel, which is revolved by the force of water striking its buckets. since water-power far exceeds human strength, this machine draws water through its pipes by discs out of a shaft more than one hundred feet deep. the bottom of the lowest pipe, set in the sump, not only of this pump but also of the others, is generally enclosed in a basket made of wicker-work, to prevent wood shavings and other things being sucked in. (see p. .) [illustration (suction pumps): a--shaft. b--bottom pump. c--first tank. d--second pump. e--second tank. f--third pump. g--trough. h--the iron set in the axle. i--first pump rod. k--second pump rod. l--third pump rod. m--first piston rod. n--second piston rod. o--third piston rod. p--little axles. q--"claws."] the seventh kind of pump, invented ten years ago, which is the most ingenious, durable, and useful of all, can be made without much expense. it is composed of several pumps, which do not, like those last described, go down into the shaft together, but of which one is below the other, for if there are three, as is generally the case, the lower one lifts the water of the sump and pours it out into the first tank; the second pump lifts again from that tank into a second tank, and the third pump lifts it into the drain of the tunnel. a wheel fifteen feet high raises the piston-rods of all these pumps at the same time and causes them to drop together. the wheel is made to revolve by paddles, turned by the force of a stream which has been diverted to the mountain. the spokes of the water-wheel are mortised in an axle six feet long and one foot thick, each end of which is surrounded by an iron band, but in one end there is fixed an iron journal; to the other end is attached an iron like this journal in its posterior part, which is a digit thick and as wide as the end of the axle itself. then the iron extends horizontally, being rounded and about three digits in diameter, for the length of a foot, and serves as a journal; thence, it bends to a height of a foot in a curve, like the horn of the moon, after which it again extends straight out for one foot; thus it comes about that this last straight portion, as it revolves in an orbit becomes alternately a foot higher and a foot lower than the first straight part. from this round iron crank there hangs the first flat pump-rod, for the crank is fixed in a perforation in the upper end of this flat pump-rod just as the iron key of the first set of "claws" is fixed into the lower end. in order to prevent the pump-rod from slipping off it, as it could easily do, and that it may be taken off when necessary, its opening is wider than the corresponding part of the crank, and it is fastened on both sides by iron keys. to prevent friction, the ends of the pump-rods are protected by iron plates or intervening leathers. this first pump-rod is about twelve feet long, the other two are twenty-six feet, and each is a palm wide and three digits thick. the sides of each pump-rod are covered and protected by iron plates, which are held on by iron screws, so that a part which has received damage can be repaired. in the "claws" is set a small round axle, a foot and a half long and two palms thick. the ends are encircled by iron bands to prevent the iron journals which revolve in the iron bearings of the wood from slipping out of it.[ ] from this little axle the wooden "claws" extend two feet, with a width and thickness of six digits; they are three palms distant from each other, and both the inner and outer sides are covered with iron plates. two rounded iron keys two digits thick are immovably fixed into the claws. the one of these keys perforates the lower end of the first pump-rod, and the upper end of the second pump-rod which is held fast. the other key, which is likewise immovable, perforates the iron end of the first piston-rod, which is bent in a curve and is immovable. each such piston-rod is thirteen feet long and three digits thick, and descends into the first pipe of each pump to such depth that its disc nearly reaches the valve-box. when it descends into the pipe, the water, penetrating through the openings of the disc, raises the leather, and when the piston-rod is raised the water presses down the leather, and this supports its weight; then the valve closes the box as a door closes an entrance. the pipes are joined by two iron bands, one palm wide, one outside the other, but the inner one is sharp all round that it may fit into each pipe and hold them together. although at the present time pipes lack the inner band, still they have nipples by which they are joined together, for the lower end of the upper one holds the upper end of the lower one, each being hewn away for a length of seven digits, the former inside, the latter outside, so that the one can fit into the other. when the piston-rod descends into the first pipe, that valve which i have described is closed; when the piston-rod is raised, the valve is opened so that the water can run in through the perforations. each one of such pumps is composed of two lengths of pipe, each of which is twelve feet long, and the inside diameter is seven digits. the lower one is placed in the sump of the shaft, or in a tank, and its lower end is blocked by a round piece of wood, above which there are six perforations around the pipe through which the water flows into it. the upper part of the upper pipe has a notch one foot deep and a palm wide, through which the water flows away into a tank or trough. each tank is two feet long and one foot wide and deep. there is the same number of axles, "claws," and rods of each kind as there are pumps; if there are three pumps, there are only two tanks, because the sump of the shaft and the drain of the tunnel take the place of two. the following is the way this machine draws water from a shaft. the wheel being turned raises the first pump-rod, and the pump-rod raises the first "claw," and thus also the second pump-rod, and the first piston-rod; then the second pump-rod raises the second "claw," and thus the third pump-rod and the second piston-rod; then the third pump-rod raises the third "claw" and the third piston-rod, for there hangs no pump-rod from the iron key of these claws, for it can be of no use in the last pump. in turn, when the first pump-rod descends, each set of "claws" is lowered, each pump-rod and each piston-rod. and by this system, at the same time the water is lifted into the tanks and drained out of them; from the sump at the bottom of the shaft it is drained out, and it is poured into the trough of the tunnel. further, around the main axle there may be placed two water wheels, if the river supplies enough water to turn them, and from the back part of each round iron crank, one or two pump-rods can be hung, each of which can move the piston-rods of three pumps. lastly, it is necessary that the shafts from which the water is pumped out in pipes should be vertical, for as in the case of the hauling machines, all pumps which have pipes do not draw the water so high if the pipes are inclined in inclined shafts, as if they are placed vertically in vertical shafts. [illustration (suction pumps): a--water wheel of upper machine. b--its pump. c--its trough. d--wheel of lower machine. e--its pump. f--race.] if the river does not supply enough water-power to turn the last-described pump, which happens because of the nature of the locality or occurs during the summer season when there are daily droughts, a machine is built with a wheel so low and light that the water of ever so little a stream can turn it. this water, falling into a race, runs therefrom on to a second high and heavy wheel of a lower machine, whose pump lifts the water out of a deep shaft. since, however, the water of so small a stream cannot alone revolve the lower water-wheel, the axle of the latter is turned at the start with a crank worked by two men, but as soon as it has poured out into a pool the water which has been drawn up by the pumps, the upper wheel draws up this water by its own pump, and pours it into the race, from which it flows on to the lower water-wheel and strikes its buckets. so both this water from the mine, as well as the water of the stream, being turned down the races on to that subterranean wheel of the lower machine, turns it, and water is pumped out of the deeper part of the shaft by means of two or three pumps.[ ] [illustration (duplex suction pumps): a--upper axle. b--wheel whose buckets the force of the stream strikes. c--toothed drum. d--second axle. e--drum composed of rundles. f--curved round irons. g--rows of pumps.] if the stream supplies enough water straightway to turn a higher and heavier water-wheel, then a toothed drum is fixed to the other end of the axle, and this turns the drum made of rundles on another axle set below it. to each end of this lower axle there is fitted a crank of round iron curved like the horns of the moon, of the kind employed in machines of this description. this machine, since it has rows of pumps on each side, draws great quantities of water. [illustration (rag and chain pumps): a--wheel. b--axle. c--journals. d--pillows. e--drum. f--clamps. g--drawing-chain. h--timbers. i--balls. k--pipe. l--race of stream.] of the rag and chain pumps there are six kinds known to us, of which the first is made as follows: a cave is dug under the surface of earth or in a tunnel, and timbered on all sides by stout posts and planks, to prevent either the men from being crushed or the machine from being broken by its collapse. in this cave, thus timbered, is placed a water-wheel fitted to an angular axle. the iron journals of the axle revolve in iron pillows, which are held in timbers of sufficient strength. the wheel is generally twenty-four feet high, occasionally thirty, and in no way different from those which are made for grinding corn, except that it is a little narrower. the axle has on one side a drum with a groove in the middle of its circumference, to which are fixed many four-curved iron clamps. in these clamps catch the links of the chain, which is drawn through the pipes out of the sump, and which again falls, through a timbered opening, right down to the bottom into the sump to a balancing drum. there is an iron band around the small axle of the balancing drum, each journal of which revolves in an iron bearing fixed to a timber. the chain turning about this drum brings up the water by the balls through the pipes. each length of pipe is encircled and protected by five iron bands, a palm wide and a digit thick, placed at equal distances from each other; the first band on the pipe is shared in common with the preceding length of pipe into which it is fitted, the last band with the succeeding length of pipe which is fitted into it. each length of pipe, except the first, is bevelled on the outer circumference of the upper end to a distance of seven digits and for a depth of three digits, in order that it may be inserted into the length of pipe which goes before it; each, except the last, is reamed out on the inside of the lower end to a like distance, but to the depth of a palm, that it may be able to take the end of the pipe which follows. and each length of pipe is fixed with iron clamps to the timbers of the shaft, that it may remain stationary. through this continuous series of pipes, the water is drawn by the balls of the chain up out of the sump as far as the tunnel, where it flows but into the drains through an aperture in the highest pipe. the balls which lift the water are connected by the iron links of the chain, and are six feet distant from one another; they are made of the hair of a horse's tail sewn into a covering to prevent it from being pulled out by the iron clamps on the drum; the balls are of such size that one can be held in each hand. if this machine is set up on the surface of the earth, the stream which turns the water-wheel is led away through open-air ditches; if in a tunnel, the water is led away through the subterranean drains. the buckets of the water-wheel, when struck by the impact of the stream, move forward and turn the wheel, together with the drum, whereby the chain is wound up and the balls expel the water through the pipes. if the wheel of this machine is twenty-four feet in diameter, it draws water from a shaft two hundred and ten feet deep; if thirty feet in diameter, it will draw water from a shaft two hundred and forty feet deep. but such work requires a stream with greater water-power. the next pump has two drums, two rows of pipes and two drawing-chains whose balls lift out the water; otherwise they are like the last pump. this pump is usually built when an excessive amount of water flows into the sump. these two pumps are turned by water-power; indeed, water draws water. the following is the way of indicating the increase or decrease of the water in an underground sump, whether it is pumped by this rag and chain pump or by the first pump, or the third, or some other. from a beam which is as high above the shaft as the sump is deep, is hung a cord, to one end of which there is fastened a stone, the other end being attached to a plank. the plank is lowered down by an iron wire fastened to the other end; when the stone is at the mouth of the shaft the plank is right down the shaft in the sump, in which water it floats. this plank is so heavy that it can drag down the wire and its iron clasp and hook, together with the cord, and thus pull the stone upwards. thus, as the water decreases, the plank descends and the stone is raised; on the contrary, when the water increases the plank rises and the stone is lowered. when the stone nearly touches the beam, since this indicates that the water has been exhausted from the sump by the pump, the overseer in charge of the machine closes the water-race and stops the water-wheel; when the stone nearly touches the ground at the side of the shaft, this indicates that the sump is full of water which has again collected in it, because the water raises the plank and thus the stone drags back both the rope and the iron wire; then the overseer opens the water-race, whereupon the water of the stream again strikes the buckets of the water-wheel and turns the pump. as workmen generally cease from their labours on the yearly holidays, and sometimes on working days, and are thus not always near the pump, and as the pump, if necessary, must continue to draw water all the time, a bell rings aloud continuously, indicating that this pump, or any other kind, is uninjured and nothing is preventing its turning. the bell is hung by a cord from a small wooden axle held in the timbers which stand over the shaft, and a second long cord whose upper end is fastened to the small axle is lowered into the shaft; to the lower end of this cord is fastened a piece of wood; and as often as a cam on the main axle strikes it, so often does the bell ring and give forth a sound. [illustration (rag and chain pumps): a--upright axle. b--toothed wheel. c--teeth. d--horizontal axle. e--drum which is made of rundles. f--second drum. g--drawing-chain. h--the balls.] the third pump of this kind is employed by miners when no river capable of turning a water-wheel can be diverted, and it is made as follows. they first dig a chamber and erect strong timbers and planks to prevent the sides from falling in, which would overwhelm the pump and kill the men. the roof of the chamber is protected with contiguous timbers, so arranged that the horses which pull the machine can travel over it. next they again set up sixteen beams forty feet long and one foot wide and thick, joined by clamps at the top and spreading apart at the bottom, and they fit the lower end of each beam into a separate sill laid flat on the ground, and join these by a post; thus there is created a circular area of which the diameter is fifty feet. through an opening in the centre of this area there descends an upright square axle, forty-five feet long and a foot and a half wide and thick; its lower pivot revolves in a socket in a block laid flat on the ground in the chamber, and the upper pivot revolves in a bearing in a beam which is mortised into two beams at the summit beneath the clamps; the lower pivot is seventeen feet distant from either side of the chamber, _i.e._, from its front and rear. at the height of a foot above its lower end, the axle has a toothed wheel, the diameter of which is twenty-two feet. this wheel is composed of four spokes and eight rim pieces; the spokes are fifteen feet long and three-quarters of a foot wide and thick[ ]; one end of them is mortised in the axle, the other in the two rims where they are joined together. these rims are three-quarters of a foot thick and one foot wide, and from them there rise and project upright teeth three-quarters of a foot high, half a foot wide, and six digits thick. these teeth turn a second horizontal axle by means of a drum composed of twelve rundles, each three feet long and six digits wide and thick. this drum, being turned, causes the axle to revolve, and around this axle there is a drum having iron clamps with fourfold curves in which catch the links of a chain, which draws water through pipes by means of balls. the iron journals of this horizontal axle revolve on pillows which are set in the centre of timbers. above the roof of the chamber there are mortised into the upright axle the ends of two beams which rise obliquely; the upper ends of these beams support double cross-beams, likewise mortised to the axle. in the outer end of each cross-beam there is mortised a small wooden piece which appears to hang down; in this wooden piece there is similarly mortised at the lower end a short board; this has an iron key which engages a chain, and this chain again a pole-bar. this machine, which draws water from a shaft two hundred and forty feet deep, is worked by thirty-two horses; eight of them work for four hours, and then these rest for twelve hours, and the same number take their place. this kind of machine is employed at the foot of the harz[ ] mountains and in the neighbourhood. further, if necessity arises, several pumps of this kind are often built for the purpose of mining one vein, but arranged differently in different localities varying according to the depth. at schemnitz, in the carpathian mountains, there are three pumps, of which the lowest lifts water from the lowest sump to the first drains, through which it flows into the second sump; the intermediate one lifts from the second sump to the second drain, from which it flows into the third sump; and the upper one lifts it to the drains of the tunnel, through which it flows away. this system of three machines of this kind is turned by ninety-six horses; these horses go down to the machines by an inclined shaft, which slopes and twists like a screw and gradually descends. the lowest of these machines is set in a deep place, which is distant from the surface of the ground feet. [illustration (rag and chain pumps): a--axle. b--drum. c--drawing-chain. d--balls. e--clamps.] the fourth species of pump belongs to the same genera, and is made as follows. two timbers are erected, and in openings in them, the ends of a barrel revolve. two or four strong men turn the barrel, that is to say, one or two pull the cranks, and one or two push them, and in this way help the others; alternately another two or four men take their place. the barrel of this machine, just like the horizontal axle of the other machines, has a drum whose iron clamps catch the links of a drawing-chain. thus water is drawn through the pipes by the balls from a depth of forty-eight feet. human strength cannot draw water higher than this, because such very heavy labour exhausts not only men, but even horses; only water-power can drive continuously a drum of this kind. several pumps of this kind, as of the last, are often built for the purpose of mining on a single vein, but they are arranged differently for different positions and depths. [illustration (rag and chain pumps): a--axles. b--levers. c--toothed drum. d--drum made of rundles. e--drum in which iron clamps are fixed.] the fifth pump of this kind is partly like the third and partly like the fourth, because it is turned by strong men like the last, and like the third it has two axles and three drums, though each axle is horizontal. the journals of each axle are so fitted in the pillows of the beams that they cannot fly out; the lower axle has a crank at one end and a toothed drum at the other end; the upper axle has at one end a drum made of rundles, and at the other end, a drum to which are fixed iron clamps, in which the links of a chain catch in the same way as before, and from the same depth, draw water through pipes by means of balls. this revolving machine is turned by two pairs of men alternately, for one pair stands working while the other sits taking a rest; while they are engaged upon the task of turning, one pulls the crank and the other pushes, and the drums help to make the pump turn more easily. [illustration (rag and chain pumps): a--axles. b--wheel which is turned by treading. c--toothed wheel. d--drum made of rundles. e--drum to which are fixed iron clamps. f--second wheel. g--balls.] the sixth pump of this kind likewise has two axles. at one end of the lower axle is a wheel which is turned by two men treading, this is twenty-three feet high and four feet wide, so that one man may stand alongside the other. at the other end of this axle is a toothed wheel. the upper[ ] axle has two drums and one wheel; the first drum is made of rundles, and to the other there are fixed the iron clamps. the wheel is like the one on the second machine which is chiefly used for drawing earth and broken rock out of shafts. the treaders, to prevent themselves from falling, grasp in their hands poles which are fixed to the inner sides of the wheel. when they turn this wheel, the toothed drum being made to revolve, sets in motion the other drum which is made of rundles, by which means again the links of the chain catch to the cleats of the third drum and draw water through pipes by means of balls,--from a depth of sixty-six feet. [illustration (baling water): a--reservoir. b--race. c, d--levers. e, f--troughs under the water gates. g, h--double rows of buckets. i--axle. k--larger drum. l--drawing-chain. m--bag. n--hanging cage. o--man who directs the machine. p, q--men emptying bags.] but the largest machine of all those which draw water is the one which follows. first of all a reservoir is made in a timbered chamber; this reservoir is eighteen feet long and twelve feet wide and high. into this reservoir a stream is diverted through a water-race or through the tunnel; it has two entrances and the same number of gates. levers are fixed to the upper part of these gates, by which they can be raised and let down again, so that by one way the gates are opened and in the other way closed. beneath the openings are two plank troughs which carry the water flowing from the reservoir, and pour it on to the buckets of the water-wheel, the impact of which turns the wheel. the shorter trough carries the water, which strikes the buckets that turn the wheel toward the reservoir, and the longer trough carries the water which strikes those buckets that turn the wheel in the opposite direction. the casing or covering of the wheel is made of joined boards to which strips are affixed on the inner side. the wheel itself is thirty-six feet in diameter, and is mortised to an axle, and it has, as i have already said, two rows of buckets, of which one is set the opposite way to the other, so that the wheel may be turned toward the reservoir or in the opposite direction. the axle is square and is thirty-five feet long and two feet thick and wide. beyond the wheel, at a distance of six feet, the axle has four hubs, one foot wide and thick, each one of which is four feet distant from the next; to these hubs are fixed by iron nails as many pieces of wood as are necessary to cover the hubs, and, in order that the wood pieces may fit tight, they are broader on the outside and narrower on the inside; in this way a drum is made, around which is wound a chain to whose ends are hooked leather bags. the reason why a drum of this kind is made, is that the axle may be kept in good condition, because this drum when it becomes worn away by use can be repaired easily. further along the axle, not far from the end, is another drum one foot broad, projecting two feet on all sides around the axle. and to this, when occasion demands, a brake is applied forcibly and holds back the machine; this kind of brake i have explained before. near the axle, in place of a hopper, there is a floor with a considerable slope, having in front of the shaft a width of fifteen feet and the same at the back; at each side of it there is a stout post carrying an iron chain which has a large hook. five men operate this machine; one lets down the doors which close the reservoir gates, or by drawing down the levers, opens the water-races; this man, who is the director of this machine, stands in a hanging cage beside the reservoir. when one bag has been drawn out nearly as far as the sloping floor, he closes the water gate in order that the wheel may be stopped; when the bag has been emptied he opens the other water gate, in order that the other set of buckets may receive the water and drive the wheel in the opposite direction. if he cannot close the water-gate quickly enough, and the water continues to flow, he calls out to his comrade and bids him raise the brake upon the drum and stop the wheel. two men alternately empty the bags, one standing on that part of the floor which is in front of the shaft, and the other on that part which is at the back. when the bag has been nearly drawn up--of which fact a certain link of the chain gives warning--the man who stands on the one part of the floor, catches a large iron hook in one link of the chain, and pulls out all the subsequent part of the chain toward the floor, where the bag is emptied by the other man. the object of this hook is to prevent the chain, by its own weight, from pulling down the other empty bag, and thus pulling the whole chain from its axle and dropping it down the shaft. his comrade in the work, seeing that the bag filled with water has been nearly drawn out, calls to the director of the machine and bids him close the water of the tower so that there will be time to empty the bag; this being emptied, the director of the machine first of all slightly opens the other water-gate of the tower to allow the end of the chain, together with the empty bag, to be started into the shaft again, and then opens entirely the water-gates. when that part of the chain which has been pulled on to the floor has been wound up again, and has been let down over the shaft from the drum, he takes out the large hook which was fastened into a link of the chain. the fifth man stands in a sort of cross-cut beside the sump, that he may not be hurt, if it should happen that a link is broken and part of the chain or anything else should fall down; he guides the bag with a wooden shovel, and fills it with water if it fails to take in the water spontaneously. in these days, they sew an iron band into the top of each bag that it may constantly remain open, and when lowered into the sump may fill itself with water, and there is no need for a man to act as governor of the bags. further, in these days, of those men who stand on the floor the one empties the bags, and the other closes the gates of the reservoir and opens them again, and the same man usually fixes the large hook in the link of the chain. in this way, three men only are employed in working this machine; or even--since sometimes the one who empties the bag presses the brake which is raised against the other drum and thus stops the wheel--two men take upon themselves the whole labour. but enough of haulage machines; i will now speak of ventilating machines. if a shaft is very deep and no tunnel reaches to it, or no drift from another shaft connects with it, or when a tunnel is of great length and no shaft reaches to it, then the air does not replenish itself. in such a case it weighs heavily on the miners, causing them to breathe with difficulty, and sometimes they are even suffocated, and burning lamps are also extinguished. there is, therefore, a necessity for machines which the greeks call [greek: pneumatikai] and the latins _spiritales_--though they do not give forth any sound--which enable the miners to breathe easily and carry on their work. [illustration (windsails for ventilation): a--sills. b--pointed stakes. c--cross-beams. d--upright planks. e--hollows. f--winds. g--covering disc. h--shafts. i--machine without a covering.] these devices are of three genera. the first receives and diverts into the shaft the blowing of the wind, and this genus is divided into three species, of which the first is as follows. over the shaft--to which no tunnel connects--are placed three sills a little longer than the shaft, the first over the front, the second over the middle, and the third over the back of the shaft. their ends have openings, through which pegs, sharpened at the bottom, are driven deeply into the ground so as to hold them immovable, in the same way that the sills of the windlass are fixed. each of these sills is mortised into each of three cross-beams, of which one is at the right side of the shaft, the second at the left, and the third in the middle. to the second sill and the second cross-beam--each of which is placed over the middle of the shaft--planks are fixed which are joined in such a manner that the one which precedes always fits into the groove of the one which follows. in this way four angles and the same number of intervening hollows are created, which collect the winds that blow from all directions. the planks are roofed above with a cover made in a circular shape, and are open below, in order that the wind may not be diverted upward and escape, but may be carried downward; and thereby the winds of necessity blow into the shafts through these four openings. however, there is no need to roof this kind of machine in those localities in which it can be so placed that the wind can blow down through its topmost part. [illustration (windsails for ventilation): a--projecting mouth of conduit. b--planks fixed to the mouth of the conduit which does not project.] the second machine of this genus turns the blowing wind into a shaft through a long box-shaped conduit, which is made of as many lengths of planks, joined together, as the depth of the shaft requires; the joints are smeared with fat, glutinous clay moistened with water. the mouth of this conduit either projects out of the shaft to a height of three or four feet, or it does not project; if it projects, it is shaped like a rectangular funnel, broader and wider at the top than the conduit itself, that it may the more easily gather the wind; if it does not project, it is not broader than the conduit, but planks are fixed to it away from the direction in which the wind is blowing, which catch the wind and force it into the conduit. [illustration (windsails for ventilation): a--wooden barrels. b--hoops. c--blow-holes. d--pipe. e--table. f--axle. g--opening in the bottom of the barrel. h--wing.] the third of this genus of machine is made of a pipe or pipes and a barrel. above the uppermost pipe there is erected a wooden barrel, four feet high and three feet in diameter, bound with wooden hoops; it has a square blow-hole always open, which catches the breezes and guides them down either by a pipe into a conduit or by many pipes into the shaft. to the top of the upper pipe is attached a circular table as thick as the bottom of the barrel, but of a little less diameter, so that the barrel may be turned around on it; the pipe projects out of the table and is fixed in a round opening in the centre of the bottom of the barrel. to the end of the pipe a perpendicular axle is fixed which runs through the centre of the barrel into a hole in the cover, in which it is fastened, in the same way as at the bottom. around this fixed axle and the table on the pipe, the movable barrel is easily turned by a zephyr, or much more by a wind, which govern the wing on it. this wing is made of thin boards and fixed to the upper part of the barrel on the side furthest away from the blow-hole; this, as i have said, is square and always open. the wind, from whatever quarter of the world it blows, drives the wing straight toward the opposite direction, in which way the barrel turns the blow-hole towards the wind itself; the blow-hole receives the wind, and it is guided down into the shaft by means of the conduit or pipes. [illustration (ventilation fans): a--drum. b--box-shaped casing. c--blow-hole. d--second hole. e--conduit. f--axle. g--lever of axle. h--rods.] the second genus of blowing machine is made with fans, and is likewise varied and of many forms, for the fans are either fitted to a windlass barrel or to an axle. if to an axle, they are either contained in a hollow drum, which is made of two wheels and a number of boards joining them together, or else in a box-shaped casing. the drum is stationary and closed on the sides, except for round holes of such size that the axle may turn in them; it has two square blow-holes, of which the upper one receives the air, while the lower one empties into the conduit through which the air is led down the shaft. the ends of the axle, which project on each side of the drum, are supported by forked posts or hollowed beams plated with thick iron; one end of the axle has a crank, while in the other end are fixed four rods with thick heavy ends, so that they weight the axle, and when turned, make it prone to motion as it revolves. and so, when the workman turns the axle by the crank, the fans, the description of which i will give a little later, draw in the air by the blow-hole, and force it through the other blow-hole which leads to the conduit, and through this conduit the air penetrates into the shaft. [illustration (ventilation fans): a--box-shaped casing placed on the ground. b--its blow-hole. c--its axle with fans. d--crank of the axle. e--rods of same. f--casing set on timbers. g--sails which the axle has outside the casing.] the one with the box-shaped casing is furnished with just the same things as the drum, but the drum is far superior to the box; for the fans so fill the drum that they almost touch it on every side, and drive into the conduit all the air that has been accumulated; but they cannot thus fill the box-shaped casing, on account of its angles, into which the air partly retreats; therefore it cannot be as useful as the drum. the kind with a box-shaped casing is not only placed on the ground, but is also set up on timbers like a windmill, and its axle, in place of a crank, has four sails outside, like the sails of a windmill. when these are struck by the wind they turn the axle, and in this way its fans--which are placed within the casing--drive the air through the blow-hole and the conduit into the shaft. although this machine has no need of men whom it is necessary to pay to work the crank, still when the sky is devoid of wind, as it often is, the machine does not turn, and it is therefore less suitable than the others for ventilating a shaft. [illustration (ventilation fans): a--hollow drum. b--its blow-hole. c--axle with fans. d--drum which is made of rundles. e--lower axle. f--its toothed wheel. g--water wheel.] in the kind where the fans are fixed to an axle, there is generally a hollow stationary drum at one end of the axle, and on the other end is fixed a drum made of rundles. this rundle drum is turned by the toothed wheel of a lower axle, which is itself turned by a wheel whose buckets receive the impetus of water. if the locality supplies an abundance of water this machine is most useful, because to turn the crank does not need men who require pay, and because it forces air without cessation through the conduit into the shaft. [illustration (ventilation fans): a--first kind of fan. b--second kind of fan. c--third kind of fan. d--quadrangular part of axle. e--round part of same. f--crank.] of the fans which are fixed on to an axle contained in a drum or box, there are three sorts. the first sort is made of thin boards of such length and width as the height and width of the drum or box require; the second sort is made of boards of the same width, but shorter, to which are bound long thin blades of poplar or some other flexible wood; the third sort has boards like the last, to which are bound double and triple rows of goose feathers. this last is less used than the second, which in turn is less used than the first. the boards of the fan are mortised into the quadrangular parts of the barrel axle. [illustration (bellows for mine ventilation): a--smaller part of shaft. b--square conduit. c--bellows. d--larger part of shaft.] blowing machines of the third genus, which are no less varied and of no fewer forms than those of the second genus, are made with bellows, for by its blasts the shafts and tunnels are not only furnished with air through conduits or pipes, but they can also be cleared by suction of their heavy and pestilential vapours. in the latter case, when the bellows is opened it draws the vapours from the conduits through its blow-hole and sucks these vapours into itself; in the former case, when it is compressed, it drives the air through its nozzle into the conduits or pipes. they are compressed either by a man, or by a horse or by water-power; if by a man, the lower board of a large bellows is fixed to the timbers above the conduit which projects out of the shaft, and so placed that when the blast is blown through the conduit, its nozzle is set in the conduit. when it is desired to suck out heavy or pestilential vapours, the blow-hole of the bellows is fitted all round the mouth of the conduit. fixed to the upper bellows board is a lever which couples with another running downward from a little axle, into which it is mortised so that it may remain immovable; the iron journals of this little axle revolve in openings of upright posts; and so when the workman pulls down the lever the upper board of the bellows is raised, and at the same time the flap of the blow-hole is dragged open by the force of the wind. if the nozzle of the bellows is enclosed in the conduit it draws pure air into itself, but if its blow-hole is fitted all round the mouth of the conduit it exhausts the heavy and pestilential vapours out of the conduit and thus from the shaft, even if it is one hundred and twenty feet deep. a stone placed on the upper board of the bellows depresses it and then the flap of the blow-hole is closed. the bellows, by the first method, blows fresh air into the conduit through its nozzle, and by the second method blows out through the nozzle the heavy and pestilential vapours which have been collected. in this latter case fresh air enters through the larger part of the shaft, and the miners getting the benefit of it can sustain their toil. a certain smaller part of the shaft which forms a kind of estuary, requires to be partitioned off from the other larger part by uninterrupted lagging, which reaches from the top of the shaft to the bottom; through this part the long but narrow conduit reaches down nearly to the bottom of the shaft. [illustration (bellows for mine ventilation): a--tunnel. b--pipe. c--nozzle of double bellows.] when no shaft has been sunk to such depth as to meet a tunnel driven far into a mountain, these machines should be built in such a manner that the workman can move them about. close by the drains of the tunnel through which the water flows away, wooden pipes should be placed and joined tightly together in such a manner that they can hold the air; these should reach from the mouth of the tunnel to its furthest end. at the mouth of the tunnel the bellows should be so placed that through its nozzle it can blow its accumulated blasts into the pipes or the conduit; since one blast always drives forward another, they penetrate into the tunnel and change the air, whereby the miners are enabled to continue their work. [illustration (bellows for mine ventilation): a--machine first described. b--this workman, treading with his feet, is compressing the bellows. c--bellows without nozzles. d--hole by which heavy vapours or blasts are blown out. e--conduits. f--tunnel. g--second machine described. h--wooden wheel. i--its steps. k--bars. l--hole in same wheel. m--pole. n--third machine described. o--upright axle. p--its toothed drum. q--horizontal axle. r--its drum which is made of rundles.] if heavy vapours need to be drawn off from the tunnels, generally three double or triple bellows, without nozzles and closed in the forepart, are placed upon benches. a workman compresses them by treading with his feet, just as persons compress those bellows of the organs which give out varied and sweet sounds in churches. these heavy vapours are thus drawn along the air-pipes and through the blow-hole of the lower bellows board, and are expelled through the blow-hole of the upper bellows board into the open air, or into some shaft or drift. this blow-hole has a flap-valve, which the noxious blast opens, as often as it passes out. since one volume of air constantly rushes in to take the place of another which has been drawn out by the bellows, not only is the heavy air drawn out of a tunnel as great as , feet long, or even longer, but also the wholesome air is naturally drawn in through that part of the tunnel which is open outside the conduits. in this way the air is changed, and the miners are enabled to carry on the work they have begun. if machines of this kind had not been invented, it would be necessary for miners to drive two tunnels into a mountain, and continually, at every two hundred feet at most, to sink a shaft from the upper tunnel to the lower one, that the air passing into the one, and descending by the shafts into the other, would be kept fresh for the miners; this could not be done without great expense. there are two different machines for operating, by means of horses, the above described bellows. the first of these machines has on its axle a wooden wheel, the rim of which is covered all the way round by steps; a horse is kept continually within bars, like those within which horses are held to be shod with iron, and by treading these steps with its feet it turns the wheel, together with the axle; the cams on the axle press down the sweeps which compress the bellows. the way the instrument is made which raises the bellows again, and also the benches on which the bellows rest, i will explain more clearly in book ix. each bellows, if it draws heavy vapours out of a tunnel, blows them out of the hole in the upper board; if they are drawn out of a shaft, it blows them out through its nozzle. the wheel has a round hole, which is transfixed with a pole when the machine needs to be stopped. the second machine has two axles; the upright one is turned by a horse, and its toothed drum turns a drum made of rundles on a horizontal axle; in other respects this machine is like the last. here, also, the nozzles of the bellows placed in the conduits blow a blast into the shaft or tunnel. [illustration (ventilating with damp cloth): a--tunnel. b--linen cloth.] in the same way that this last machine can refresh the heavy air of a shaft or tunnel, so also could the old system of ventilating by the constant shaking of linen cloths, which pliny[ ] has explained; the air not only grows heavier with the depth of a shaft, of which fact he has made mention, but also with the length of a tunnel. [illustration (descent into mines): a--descending into the shaft by ladders. b--by sitting on a stick. c--by sitting on the dirt. d--descending by steps cut in the rock.] the climbing machines of miners are ladders, fixed to one side of the shaft, and these reach either to the tunnel or to the bottom of the shaft. i need not describe how they are made, because they are used everywhere, and need not so much skill in their construction as care in fixing them. however, miners go down into mines not only by the steps of ladders, but they are also lowered into them while sitting on a stick or a wicker basket, fastened to the rope of one of the three drawing machines which i described at first. further, when the shafts are much inclined, miners and other workmen sit in the dirt which surrounds their loins and slide down in the same way that boys do in winter-time when the water on some hillside has congealed with the cold, and to prevent themselves from falling, one arm is wound about a rope, the upper end of which is fastened to a beam at the mouth of the shaft, and the lower end to a stake fixed in the bottom of the shaft. in these three ways miners descend into the shafts. a fourth way may be mentioned which is employed when men and horses go down to the underground machines and come up again, that is by inclined shafts which are twisted like a screw and have steps cut in the rock, as i have already described. it remains for me to speak of the ailments and accidents of miners, and of the methods by which they can guard against these, for we should always devote more care to maintaining our health, that we may freely perform our bodily functions, than to making profits. of the illnesses, some affect the joints, others attack the lungs, some the eyes, and finally some are fatal to men. where water in shafts is abundant and very cold, it frequently injures the limbs, for cold is harmful to the sinews. to meet this, miners should make themselves sufficiently high boots of rawhide, which protect their legs from the cold water; the man who does not follow this advice will suffer much ill-health, especially when he reaches old age. on the other hand, some mines are so dry that they are entirely devoid of water, and this dryness causes the workmen even greater harm, for the dust which is stirred and beaten up by digging penetrates into the windpipe and lungs, and produces difficulty in breathing, and the disease which the greeks call [greek: asthma]. if the dust has corrosive qualities, it eats away the lungs, and implants consumption in the body; hence in the mines of the carpathian mountains women are found who have married seven husbands, all of whom this terrible consumption has carried off to a premature death. at altenberg in meissen there is found in the mines black _pompholyx_, which eats wounds and ulcers to the bone; this also corrodes iron, for which reason the keys of their sheds are made of wood. further, there is a certain kind of _cadmia_[ ] which eats away the feet of the workmen when they have become wet, and similarly their hands, and injures their lungs and eyes. therefore, for their digging they should make for themselves not only boots of rawhide, but gloves long enough to reach to the elbow, and they should fasten loose veils over their faces; the dust will then neither be drawn through these into their windpipes and lungs, nor will it fly into their eyes. not dissimilarly, among the romans[ ] the makers of vermilion took precautions against breathing its fatal dust. stagnant air, both that which remains in a shaft and that which remains in a tunnel, produces a difficulty in breathing; the remedies for this evil are the ventilating machines which i have explained above. there is another illness even more destructive, which soon brings death to men who work in those shafts or levels or tunnels in which the hard rock is broken by fire. here the air is infected with poison, since large and small veins and seams in the rocks exhale some subtle poison from the minerals, which is driven out by the fire, and this poison itself is raised with the smoke not unlike _pompholyx_,[ ] which clings to the upper part of the walls in the works in which ore is smelted. if this poison cannot escape from the ground, but falls down into the pools and floats on their surface, it often causes danger, for if at any time the water is disturbed through a stone or anything else, these fumes rise again from the pools and thus overcome the men, by being drawn in with their breath; this is even much worse if the fumes of the fire have not yet all escaped. the bodies of living creatures who are infected with this poison generally swell immediately and lose all movement and feeling, and they die without pain; men even in the act of climbing from the shafts by the steps of ladders fall back into the shafts when the poison overtakes them, because their hands do not perform their office, and seem to them to be round and spherical, and likewise their feet. if by good fortune the injured ones escape these evils, for a little while they are pale and look like dead men. at such times, no one should descend into the mine or into the neighbouring mines, or if he is in them he should come out quickly. prudent and skilled miners burn the piles of wood on friday, towards evening, and they do not descend into the shafts nor enter the tunnels again before monday, and in the meantime the poisonous fumes pass away. there are also times when a reckoning has to be made with orcus,[ ] for some metalliferous localities, though such are rare, spontaneously produce poison and exhale pestilential vapour, as is also the case with some openings in the ore, though these more often contain the noxious fumes. in the towns of the plains of bohemia there are some caverns which, at certain seasons of the year, emit pungent vapours which put out lights and kill the miners if they linger too long in them. pliny, too, has left a record that when wells are sunk, the sulphurous or aluminous vapours which arise kill the well-diggers, and it is a test of this danger if a burning lamp which has been let down is extinguished. in such cases a second well is dug to the right or left, as an air-shaft, which draws off these noxious vapours. on the plains they construct bellows which draw up these noxious vapours and remedy this evil; these i have described before. further, sometimes workmen slipping from the ladders into the shafts break their arms, legs, or necks, or fall into the sumps and are drowned; often, indeed, the negligence of the foreman is to blame, for it is his special work both to fix the ladders so firmly to the timbers that they cannot break away, and to cover so securely with planks the sumps at the bottom of the shafts, that the planks cannot be moved nor the men fall into the water; wherefore the foreman must carefully execute his own work. moreover, he must not set the entrance of the shaft-house toward the north wind, lest in winter the ladders freeze with cold, for when this happens the men's hands become stiff and slippery with cold, and cannot perform their office of holding. the men, too, must be careful that, even if none of these things happen, they do not fall through their own carelessness. mountains, too, slide down and men are crushed in their fall and perish. in fact, when in olden days rammelsberg, in goslar, sank down, so many men were crushed in the ruins that in one day, the records tell us, about women were robbed of their husbands. and eleven years ago, part of the mountain of altenberg, which had been excavated, became loose and sank, and suddenly crushed six miners; it also swallowed up a hut and one mother and her little boy. but this generally occurs in those mountains which contain _venae cumulatae_. therefore, miners should leave numerous arches under the mountains which need support, or provide underpinning. falling pieces of rock also injure their limbs, and to prevent this from happening, miners should protect the shafts, tunnels, and drifts. the venomous ant which exists in sardinia is not found in our mines. this animal is, as solinus[ ] writes, very small and like a spider in shape; it is called _solifuga_, because it shuns (_fugit_) the light (_solem_). it is very common in silver mines; it creeps unobserved and brings destruction upon those who imprudently sit on it. but, as the same writer tells us, springs of warm and salubrious waters gush out in certain places, which neutralise the venom inserted by the ants. in some of our mines, however, though in very few, there are other pernicious pests. these are demons of ferocious aspect, about which i have spoken in my book _de animantibus subterraneis_. demons of this kind are expelled and put to flight by prayer and fasting.[ ] some of these evils, as well as certain other things, are the reason why pits are occasionally abandoned. but the first and principal cause is that they do not yield metal, or if, for some fathoms, they do bear metal they become barren in depth. the second cause is the quantity of water which flows in; sometimes the miners can neither divert this water into the tunnels, since tunnels cannot be driven so far into the mountains, or they cannot draw it out with machines because the shafts are too deep; or if they could draw it out with machines, they do not use them, the reason undoubtedly being that the expenditure is greater than the profits of a moderately poor vein. the third cause is the noxious air, which the owners sometimes cannot overcome either by skill or expenditure, for which reason the digging is sometimes abandoned, not only of shafts, but also of tunnels. the fourth cause is the poison produced in particular places, if it is not in our power either completely to remove it or to moderate its effects. this is the reason why the caverns in the plain known as laurentius[ ] used not to be worked, though they were not deficient in silver. the fifth cause are the fierce and murderous demons, for if they cannot be expelled, no one escapes from them. the sixth cause is that the underpinnings become loosened and collapse, and a fall of the mountain usually follows; the underpinnings are then only restored when the vein is very rich in metal. the seventh cause is military operations. shafts and tunnels should not be re-opened unless we are quite certain of the reasons why the miners have deserted them, because we ought not to believe that our ancestors were so indolent and spiritless as to desert mines which could have been carried on with profit. indeed, in our own days, not a few miners, persuaded by old women's tales, have re-opened deserted shafts and lost their time and trouble. therefore, to prevent future generations from being led to act in such a way, it is advisable to set down in writing the reason why the digging of each shaft or tunnel has been abandoned, just as it is agreed was once done at freiberg, when the shafts were deserted on account of the great inrush of water. end of book vi. footnotes: [ ] this book is devoted in the main to winding, ventilating, and pumping machinery. their mechanical principles are very old. the block and pulley, the windlass, the use of water-wheels, the transmission of power through shafts and gear-wheels, chain-pumps, piston-pumps with valves, were all known to the greeks and romans, and possibly earlier. machines involving these principles were described by ctesibius, an alexandrian of b.c., by archimedes ( - b.c.), and by vitruvius ( st century b.c.) as to how far these machines were applied to mining by the ancients we have but little evidence, and this largely in connection with handling water. diodorus siculus ( st century b.c.) referring to the spanish mines, says (book v.): "sometimes at great depths they meet great rivers underground, but by art give check to the violence of the streams, for by cutting trenches they divert the current, and being sure to gain what they aim at when they have begun, they never leave off till they have finished it. and they admirably pump out the water with those instruments called egyptian pumps, invented by archimedes, the syracusan, when he was in egypt. by these, with constant pumping by turns they throw up the water to the mouth of the pit and thus drain the mine; for this engine is so ingeniously contrived that a vast quantity of water is strangely and with little labour cast out." strabo ( b.c.- a.d., iii., , ), also referring to spanish mines, quoting from posidonius (about b.c.), says: "he compares with these (the athenians) the activity and diligence of the turdetani, who are in the habit of cutting tortuous and deep tunnels, and draining the streams which they frequently encounter by means of egyptian screws." (hamilton's tran., vol. i., p. ). the "egyptian screw" was archimedes' screw, and was thus called because much used by the egyptians for irrigation. pliny (xxxiii., ) also says, in speaking of the spanish silver-lead mines: "the mountain has been excavated for a distance of , paces, and along this distance there are water-carriers standing by torch-light night and day steadily baling the water (thus) making quite a river." the re-opening of the mines at rio tinto in the middle of the th century disclosed old roman stopes, in which were found several water-wheels. these were about feet in diameter, lifting the water by the reverse arrangement to an overshot water-wheel. a wooden archimedian screw was also found in the neighbourhood. (nash, the rio tinto mine, its history and romance, london, ). until early in the th century, water formed the limiting factor in the depth of mines. to the great devotion to this water problem we owe the invention of the steam engine. in newcomen--no doubt inspired by savery's unsuccessful attempt--invented his engine, and installed the first one on a colliery at wolverhampton, in staffordshire. with its success, a new era was opened to the miner, to be yet further extended by watt's improvements sixty years later. it should be a matter of satisfaction to mining engineers that not only was the steam engine the handiwork of their profession, but that another mining engineer, stephenson, in his effort to further the advance of his calling, invented the locomotive. [ ] while these particular tools serve the same purpose as the "gad" and the "moil," the latter are not fitted with handles, and we have, therefore, not felt justified in adopting these terms, but have given a literal rendering of the latin. the latin and old german terms for these tools were:-- first iron tool = _ferramentum primum_ = _bergeisen_. second " = " _secundum_ = _rutzeisen_. third " = " _tertium_ = _sumpffeisen_. fourth " = " _quartum_ = _fimmel_. wedge = _cuneus_ = _keil_. iron block = _lamina_ = _plôtz_. iron plate = _bractea_ = _feder_. the german words obviously had local value and do not bear translation literally. [ ] one _metreta_, a greek measure, equalled about nine english gallons, and a _congius_ contained about six pints. [ ] _ingestores_. this is a case of agricola coining a name for workmen from the work, the term being derived from _ingero_, to pour or to throw in, used in the previous clause--hence the "reason." see p. xxxi. [ ] _cisium_. a two-wheeled cart. in the preface agricola gives this as an example of his intended adaptations. see p. xxxi. [ ] _canis_. the germans in agricola's time called a truck a _hundt_--a hound. [ ] _alveus_,--"tray." the spanish term _batea_ has been so generally adopted into the mining vocabulary for a wooden bowl for these purposes, that we introduce it here. [ ] pliny (xxxiii., ). "the fragments are carried on workmen's shoulders; night and day each passes the material to his neighbour, only the last of them seeing the daylight." [ ] _harpago_,--a "grapple" or "hook." [ ] ancient noricum covered the region of modern tyrol, with parts of bavaria, salzburg, etc. [ ] _machina quae pilis aquas haurit_. "machine which draws water with balls." this apparatus is identical with the cornish "rag and chain pump" of the same period, and we have therefore adopted that term. [ ] a _congius_ contained about six pints. [ ] vitruvius (x., ). "but if the water is to be supplied to still higher places, a double chain of iron is made to revolve on the axis of the wheel, long enough to reach to the lower level. this is furnished with brazen buckets, each holding about a _congius_. then by turning the wheel, the chain also turns upon the axis and brings the buckets to the top thereof, on passing which they are inverted and pour into the conduits the water they have raised." [ ] this description certainly does not correspond in every particular with the illustration. [ ] there is a certain deficiency in the hydraulics of this machine. [ ] the dimensions given in this description for the various members do not tally. [ ] _melibocian_,--the harz. [ ] in the original text this is given as "lower," and appears to be an error. [ ] pliny (xxxi, ). "in deep wells, the occurrence of _sulphurata_ or _aluminosa_ vapor is fatal to the diggers. the presence of this peril is shown if a lighted lamp let down into the well is extinguished. if so, other wells are sunk to the right and left, which carry off these noxious gases. apart from these evils, the air itself becomes noxious with depth, which can be remedied by constantly shaking linen cloths, thus setting the air in motion." [ ] this is given in the german translation as _kobelt_. the _kobelt_ (or _cobaltum_ of agricola) was probably arsenical-cobalt, a mineral common in the saxon mines. the origin of the application of the word cobalt to a mineral appears to lie in the german word for the gnomes and goblins (_kobelts_) so universal to saxon miners' imaginations,--this word in turn probably being derived from the greek _cobali_ (mimes). the suffering described above seems to have been associated with the malevolence of demons, and later the word for these demons was attached to this disagreeable ore. a quaint series of mining "sermons," by johann mathesius, entitled _sarepta oder bergpostill_, nürnberg, , contains the following passage (p. ) which bears out this view. we retain the original and varied spelling of cobalt and also add another view of mathesius, involving an experience of solomon and hiram of tyre with some mines containing cobalt. "sometimes, however, from dry hard veins a certain black, greenish, grey or ash-coloured earth is dug out, often containing good ore, and this mineral being burnt gives strong fumes and is extracted like 'tutty.' it is called _cadmia fossilis_. you miners call it _cobelt_. germans call the black devil and the old devil's furies, old and black _cobel_, who injure people and their cattle with their witchcrafts. now the devil is a wicked, malicious spirit, who shoots his poisoned darts into the hearts of men, as sorcerers and witches shoot at the limbs of cattle and men, and work much evil and mischief with _cobalt_ or _hipomane_ or horses' poison. after quicksilver and _rotgültigen_ ore, are _cobalt_ and _wismuth_ fumes; these are the most poisonous of the metals, and with them one can kill flies, mice, cattle, birds, and men. so, fresh _cobalt_ and _kisswasser_ (vitriol?) devour the hands and feet of miners, and the dust and fumes of _cobalt_ kill many mining people and workpeople who do much work among the fumes of the smelters. whether or not the devil and his hellish crew gave their name to _cobelt_, or _kobelt_, nevertheless, _cobelt_ is a poisonous and injurious metal even if it contains silver. i find in i. kings , the word _cabul_. when solomon presented twenty towns in galilee to the king of tyre, hiram visited them first, and would not have them, and said the land was well named _cabul_ as joshua had christened it. it is certain from joshua that these twenty towns lay in the kingdom of aser, not far from our _sarepta_, and that there had been iron and copper mines there, as moses says in another place. inasmuch, then, as these twenty places were mining towns, and _cobelt_ is a metal, it appears quite likely that the mineral took its name from the land of cabul. history and circumstances bear out the theory that hiram was an excellent and experienced miner, who obtained much gold from ophir, with which he honoured solomon. therefore, the great king wished to show his gratitude to his good neighbour by honouring a miner with mining towns. but because the king of tyre was skilled in mines, he first inspected the new mines, and saw that they only produced poor metal and much wild _cobelt_ ore, therefore he preferred to find his gold by digging the gold and silver in india rather than by getting it by the _cobelt_ veins and ore. for truly, _cobelt_ ores are injurious, and are usually so embedded in other ore that they rob them in the fire and consume (_madtet und frist_) much lead before the silver is extracted, and when this happens it is especially _speysig_. therefore hiram made a good reckoning as to the mines and would not undertake all the expense of working and smelting, and so returned solomon the twenty towns." [ ] pliny (xxxiii, ). "those employed in the works preparing vermilion, cover their faces with a bladder-skin, that they may not inhale the pernicious powder, yet they can see through the skin." [ ] _pompholyx_ was a furnace deposit, usually mostly zinc oxide, but often containing arsenical oxide, and to this latter quality this reference probably applies. the symptoms mentioned later in the text amply indicate arsenical poisoning, of which a sort of spherical effect on the hands is characteristic. see also note on p. for discussion of "corrosive" _cadmia_; further information on _pompholyx_ is given in note , p. . [ ] orcus, the god of the infernal regions,--otherwise pluto. [ ] caius julius solinus was an unreliable roman grammarian of the rd century. there is much difference of opinion as to the precise animal meant by _solifuga_. the word is variously spelled _solipugus, solpugus, solipuga, solipunga_, etc., and is mentioned by pliny (viii., ), and other ancient authors all apparently meaning a venomous insect, either an ant or a spider. the term in later times indicated a scorpion. [ ] the presence of demons or gnomes in the mines was so general a belief that agricola fully accepted it. this is more remarkable, in view of our author's very general scepticism regarding the supernatural. he, however, does not classify them all as bad--some being distinctly helpful. the description of gnomes of kindly intent, which is contained in the last paragraph in _de animantibus_ is of interest:-- "then there are the gentle kind which the germans as well as the greeks call cobalos, because they mimic men. they appear to laugh with glee and pretend to do much, but really do nothing. they are called little miners, because of their dwarfish stature, which is about two feet. they are venerable looking and are clothed like miners in a filleted garment with a leather apron about their loins. this kind does not often trouble the miners, but they idle about in the shafts and tunnels and really do nothing, although they pretend to be busy in all kinds of labour, sometimes digging ore, and sometimes putting into buckets that which has been dug. sometimes they throw pebbles at the workmen, but they rarely injure them unless the workmen first ridicule or curse them. they are not very dissimilar to goblins, which occasionally appear to men when they go to or from their day's work, or when they attend their cattle. because they generally appear benign to men, the germans call them _guteli_. those called _trulli_, which take the form of women as well as men, actually enter the service of some people, especially the _suions_. the mining gnomes are especially active in the workings where metal has already been found, or where there are hopes of discovering it, because of which they do not discourage the miners, but on the contrary stimulate them and cause them to labour more vigorously." the german miners were not alone in such beliefs, for miners generally accepted them--even to-day the faith in "knockers" has not entirely disappeared from cornwall. neither the sea nor the forest so lends itself to the substantiation of the supernatural as does the mine. the dead darkness, in which the miners' lamps serve only to distort every shape, the uncanny noises of restless rocks whose support has been undermined, the approach of danger and death without warning, the sudden vanishing or discovery of good fortune, all yield a thousand corroborations to minds long steeped in ignorance and prepared for the miraculous through religious teaching. [ ] the plains of laurentius extend from the mouth of the tiber southward--say twenty miles south of rome. what agricola's authority was for silver mines in this region we cannot discover. this may, however, refer to the lead-silver district of the attic peninsula, laurion being sometimes latinized as _laurium_ or _laurius_. book vii. since the sixth book has described the iron tools, the vessels and the machines used in mines, this book will describe the methods of assaying[ ] ores; because it is desirable to first test them in order that the material mined may be advantageously smelted, or that the dross may be purged away and the metal made pure. although writers have mentioned such tests, yet none of them have set down the directions for performing them, wherefore it is no wonder that those who come later have written nothing on the subject. by tests of this kind miners can determine with certainty whether ores contain any metal in them or not; or if it has already been indicated that the ore contains one or more metals, the tests show whether it is much or little; the miners also ascertain by such tests the method by which the metal can be separated from that part of the ore devoid of it; and further, by these tests, they determine that part in which there is much metal from that part in which there is little. unless these tests have been carefully applied before the metals are melted out, the ore cannot be smelted without great loss to the owners, for the parts which do not easily melt in the fire carry the metals off with them or consume them. in the last case, they pass off with the fumes; in the other case they are mixed with the slag and furnace accretions, and in such event the owners lose the labour which they have spent in preparing the furnaces and the crucibles, and further, it is necessary for them to incur fresh expenditure for fluxes and other things. metals, when they have been melted out, are usually assayed in order that we may ascertain what proportion of silver is in a _centumpondium_ of copper or lead, or what quantity of gold is in one _libra_ of silver; and, on the other hand, what proportion of copper or lead is contained in a _centumpondium_ of silver, or what quantity of silver is contained in one _libra_ of gold. and from this we can calculate whether it will be worth while to separate the precious metals from the base metals, or not. further, a test of this kind shows whether coins are good or are debased; and readily detects silver, if the coiners have mixed more than is lawful with the gold; or copper, if the coiners have alloyed with the gold or silver more of it than is allowable. i will explain all these methods with the utmost care that i can. the method of assaying ore used by mining people, differs from smelting only by the small amount of material used. inasmuch as, by smelting a small quantity, they learn whether the smelting of a large quantity will compensate them for their expenditure; hence, if they are not particular to employ assays, they may, as i have already said, sometimes smelt the metal from the ore with a loss or sometimes without any profit; for they can assay the ore at a very small expense, and smelt it only at a great expense. both processes, however, are carried out in the same way, for just as we assay ore in a little furnace, so do we smelt it in the large furnace. also in both cases charcoal and not wood is burned. moreover, in the crucible when metals are tested, be they gold, silver, copper, or lead, they are mixed in precisely the same way as they are mixed in the blast furnace when they are smelted. further, those who assay ores with fire, either pour out the metal in a liquid state, or, when it has cooled, break the crucible and clean the metal from slag; and in the same way the smelter, as soon as the metal flows from the furnace into the forehearth, pours in cold water and takes the slag from the metal with a hooked bar. finally, in the same way that gold and silver are separated from lead in a cupel, so also are they separated in the cupellation furnace. it is necessary that the assayer who is testing ore or metals should be prepared and instructed in all things necessary in assaying, and that he should close the doors of the room in which the assay furnace stands, lest anyone coming at an inopportune moment might disturb his thoughts when they are intent on the work. it is also necessary for him to place his balances in a case, so that when he weighs the little buttons of metal the scales may not be agitated by a draught of air, for that is a hindrance to his work. [illustration a (muffle furnace): round assay furnace.] [illustration b (muffle furnace): rectangular assay furnace.] [illustration (muffle assay furnace): a--openings in the plate. b--part of plate which projects beyond the furnace.] now i will describe the different things which are necessary in assaying, beginning with the assay furnace, of which one differs from another in shape, material, and the place in which it is set. in shape, they may be round or rectangular, the latter shape being more suited to assaying ores. the materials of the assay furnaces differ, in that one is made of bricks, another of iron, and certain ones of clay. the one of bricks is built on a chimney-hearth which is three and a half feet high; the iron one is placed in the same position, and also the one of clay. the brick one is a cubit high, a foot wide on the inside, and one foot two digits long; at a point five digits above the hearth--which is usually the thickness of an unbaked[ ] brick--an iron plate is laid, and smeared over with lute on the upper side to prevent it from being injured by the fire; in front of the furnace above the plate is a mouth a palm high, five digits wide, and rounded at the top. the iron plate has three openings which are one digit wide and three digits long, one is at each side and the third at the back; through them sometimes the ash falls from the burning charcoal, and sometimes the draught blows through the chamber which is below the iron plate, and stimulates the fire. for this reason this furnace when used by metallurgists is named from assaying, but when used by the alchemists it is named from the wind[ ]. the part of the iron plate which projects from the furnace is generally three-quarters of a palm long and a palm wide; small pieces of charcoal, after being laid thereon, can be placed quickly in the furnace through its mouth with a pair of tongs, or again, if necessary, can be taken out of the furnace and laid there. the iron assay furnace is made of four iron bars a foot and a half high; which at the bottom are bent outward and broadened a short distance to enable them to stand more firmly; the front part of the furnace is made from two of these bars, and the back part from two of them; to these bars on both sides are joined and welded three iron cross-bars, the first at a height of a palm from the bottom, the second at a height of a foot, and the third at the top. the upright bars are perforated at that point where the side cross-bars are joined to them, in order that three similar iron bars on the remaining sides can be engaged in them; thus there are twelve cross-bars, which make three stages at unequal intervals. at the lower stage, the upright bars are distant from each other one foot and five digits; and at the middle stage the front is distant from the back three palms and one digit, and the sides are distant from each other three palms and as many digits; at the highest stage from the front to the back there is a distance of two palms, and between the sides three palms, so that in this way the furnace becomes narrower at the top. furthermore, an iron rod, bent to the shape of the mouth, is set into the lowest bar of the front; this mouth, just like that of the brick furnace, is a palm high and five digits wide. then the front cross-bar of the lower stage is perforated on each side of the mouth, and likewise the back one; through these perforations there pass two iron rods, thus making altogether four bars in the lower stage, and these support an iron plate smeared with lute; part of this plate also projects outside the furnace. the outside of the furnace from the lower stage to the upper, is covered with iron plates, which are bound to the bars by iron wires, and smeared with lute to enable them to bear the heat of the fire as long as possible. as for the clay furnace, it must be made of fat, thick clay, medium so far as relates to its softness or hardness. this furnace has exactly the same height as the iron one, and its base is made of two earthenware tiles, one foot and three palms long and one foot and one palm wide. each side of the fore part of both tiles is gradually cut away for the length of a palm, so that they are half a foot and a digit wide, which part projects from the furnace; the tiles are about a digit and a half thick. the walls are similarly of clay, and are set on the lower tiles at a distance of a digit from the edge, and support the upper tiles; the walls are three digits high and have four openings, each of which is about three digits high; those of the back part and of each side are five digits wide, and of the front, a palm and a half wide, to enable the freshly made cupels to be conveniently placed on the hearth, when it has been thoroughly warmed, that they may be dried there. both tiles are bound on the outer edge with iron wire, pressed into them, so that they will be less easily broken; and the tiles, not unlike the iron bed-plate, have three openings three digits long and a digit wide, in order that when the upper one on account of the heat of the fire or for some other reason has become damaged, the lower one may be exchanged and take its place. through these holes, the ashes from the burning charcoal, as i have stated, fall down, and air blows into the furnace after passing through the openings in the walls of the chamber. the furnace is rectangular, and inside at the lower part it is three palms and one digit wide and three palms and as many digits long. at the upper part it is two palms and three digits wide, so that it also grows narrower; it is one foot high; in the middle of the back it is cut out at the bottom in the shape of a semicircle, of half a digit radius. not unlike the furnace before described, it has in its forepart a mouth which is rounded at the top, one palm high and a palm and a digit wide. its door is also made of clay, and this has a window and a handle; even the lid of the furnace which is made of clay has its own handle, fastened on with iron wire. the outer parts and sides of this furnace are bound with iron wires, which are usually pressed in, in the shape of triangles. the brick furnaces must remain stationary; the clay and iron ones can be carried from one place to another. those of brick can be prepared more quickly, while those of iron are more lasting, and those of clay are more suitable. assayers also make temporary furnaces in another way; they stand three bricks on a hearth, one on each side and a third one at the back, the forepart lies open to the draught, and on these bricks is placed an iron plate, upon which they again stand three bricks, which hold and retain the charcoal. the setting of one furnace differs from another, in that some are placed higher and others lower; that one is placed higher, in which the man who is assaying the ore or metals introduces the scorifier through the mouth with the tongs; that one is placed lower, into which he introduces the crucible through its open top. [illustration (crucible assay furnace): a--iron hoop. b--double bellows. c--its nozzle. d--lever.] in some cases the assayer uses an iron hoop[ ] in place of a furnace; this is placed upon the hearth of a chimney, the lower edge being daubed with lute to prevent the blast of the bellows from escaping under it. if the blast is given slowly, the ore will be smelted and the copper will melt in the triangular crucible, which is placed in it and taken away again with the tongs. the hoop is two palms high and half a digit thick; its diameter is generally one foot and one palm, and where the blast from the bellows enters into it, it is notched out. the bellows is a double one, such as goldworkers use, and sometimes smiths. in the middle of the bellows there is a board in which there is an air-hole, five digits wide and seven long, covered by a little flap which is fastened over the air-hole on the lower side of the board; this flap is of equal length and width. the bellows, without its head, is three feet long, and at the back is one foot and one palm wide and somewhat rounded, and it is three palms wide at the head; the head itself is three palms long and two palms and a digit wide at the part where it joins the boards, then it gradually becomes narrower. the nozzle, of which there is only one, is one foot and two digits long; this nozzle, and one-half of the head in which the nozzle is fixed, are placed in an opening of the wall, this being one foot and one palm thick; it reaches only to the iron hoop on the hearth, for it does not project beyond the wall. the hide of the bellows is fixed to the bellows-boards with its own peculiar kind of iron nails. it joins both bellows-boards to the head, and over it there are cross strips of hide fixed to the bellows-boards with broad-headed nails, and similarly fixed to the head. the middle board of the bellows rests on an iron bar, to which it is fastened with iron nails clinched on both ends, so that it cannot move; the iron bar is fixed between two upright posts, through which it penetrates. higher up on these upright posts there is a wooden axle, with iron journals which revolve in the holes in the posts. in the middle of this axle there is mortised a lever, fixed with iron nails to prevent it from flying out; the lever is five and a half feet long, and its posterior end is engaged in the iron ring of an iron rod which reaches to the "tail" of the lowest bellows-board, and there engages another similar ring. and so when the workman pulls down the lever, the lower part of the bellows is raised and drives the wind into the nozzle; then the wind, penetrating through the hole in the middle bellows-board, which is called the air-hole, lifts up the upper part of the bellows, upon whose upper board is a piece of lead, heavy enough to press down that part of the bellows again, and this being pressed down blows a blast through the nozzle. this is the principle of the double bellows, which is peculiar to the iron hoop where are placed the triangular crucibles in which copper ore is smelted and copper is melted. [illustration (muffles): a--broad little windows of muffle. b--narrow ones. c--openings in the back thereof.] i have spoken of the furnaces and the iron hoop; i will now speak of the muffles and the crucibles. the muffle is made of clay, in the shape of an inverted gutter tile; it covers the scorifiers, lest coal dust fall into them and interfere with the assay. it is a palm and a half broad, and the height, which corresponds with the mouth of the furnace, is generally a palm, and it is nearly as long as the furnace; only at the front end does it touch the mouth of the furnace, everywhere else on the sides and at the back there is a space of three digits, to allow the charcoal to lie in the open space between it and the furnace. the muffle is as thick as a fairly thick earthen jar; its upper part is entire; the back has two little windows, and each side has two or three or even four, through which the heat passes into the scorifiers and melts the ore. in place of little windows, some muffles have small holes, ten in the back and more on each side. moreover, in the back below the little windows, or small holes, there are cut away three semi-circular notches half a digit high, and on each side there are four. the back of the muffle is generally a little lower than the front. [illustration (containers): a--scorifier. b--triangular crucible. c--cupel.] the crucibles differ in the materials from which they are made, because they are made of either clay or ashes; and those of clay, which we also call "earthen," differ in shape and size. some are made in the shape of a moderately thick salver (scorifiers), three digits wide, and of a capacity of an _uncia_ measure; in these the ore mixed with fluxes is melted, and they are used by those who assay gold or silver ore. some are triangular and much thicker and more capacious, holding five, or six, or even more _unciae_; in these copper is melted, so that it can be poured out, expanded, and tested with fire, and in these copper ore is usually melted. the cupels are made of ashes; like the preceding scorifiers they are tray-shaped, and their lower part is very thick but their capacity is less. in these lead is separated from silver, and by them assays are concluded. inasmuch as the assayers themselves make the cupels, something must be said about the material from which they are made, and the method of making them. some make them out of all kinds of ordinary ashes; these are not good, because ashes of this kind contain a certain amount of fat, whereby such cupels are easily broken when they are hot. others make them likewise out of any kind of ashes which have been previously leached; of this kind are the ashes into which warm water has been infused for the purpose of making lye. these ashes, after being dried in the sun or a furnace, are sifted in a hair sieve; and although warm water washes away the fat from the ashes, still the cupels which are made from such ashes are not very good because they often contain charcoal dust, sand, and pebbles. some make them in the same way out of any kind of ashes, but first of all pour water into the ashes and remove the scum which floats thereon; then, after it has become clear, they pour away the water, and dry the ashes; they then sift them and make the cupels from them. these, indeed, are good, but not of the best quality, because ashes of this kind are also not devoid of small pebbles and sand. to enable cupels of the best quality to be made, all the impurities must be removed from the ashes. these impurities are of two kinds; the one sort light, to which class belong charcoal dust and fatty material and other things which float in water, the other sort heavy, such as small stones, fine sand, and any other materials which settle in the bottom of a vessel. therefore, first of all, water should be poured into the ashes and the light impurities removed; then the ashes should be kneaded with the hands, so that they will become properly mixed with the water. when the water has become muddy and turbid, it should be poured into a second vessel. in this way the small stones and fine sand, or any other heavy substance which may be there, remain in the first vessel, and should be thrown away. when all the ashes have settled in this second vessel, which will be shown if the water has become clear and does not taste of the flavour of lye, the water should be thrown away, and the ashes which have settled in the vessel should be dried in the sun or in a furnace. this material is suitable for the cupels, especially if it is the ash of beech wood or other wood which has a small annual growth; those ashes made from twigs and limbs of vines, which have rapid annual growth, are not so good, for the cupels made from them, since they are not sufficiently dry, frequently crack and break in the fire and absorb the metals. if ashes of beech or similar wood are not to be had, the assayer makes little balls of such ashes as he can get, after they have been cleared of impurities in the manner before described, and puts them in a baker's or potter's oven to burn, and from these the cupels are made, because the fire consumes whatever fat or damp there may be. as to all kinds of ashes, the older they are the better, for it is necessary that they should have the greatest possible dryness. for this reason ashes obtained from burned bones, especially from the bones of the heads of animals, are the most suitable for cupels, as are also those ashes obtained from the horns of deer and the spines of fishes. lastly, some take the ashes which are obtained from burnt scrapings of leather, when the tanners scrape the hides to clear them from hair. some prefer to use compounds, that one being recommended which has one and a half parts of ashes from the bones of animals or the spines of fishes, and one part of beech ashes, and half a part of ashes of burnt hide scrapings. from this mixture good cupels are made, though far better ones are obtained from equal portions of ashes of burnt hide scrapings, ashes of the bones of heads of sheep and calves, and ashes of deer horns. but the best of all are produced from deer horns alone, burnt to powder; this kind, by reason of its extreme dryness, absorbs metals least of all. assayers of our own day, however, generally make the cupels from beech ashes. these ashes, after being prepared in the manner just described, are first of all sprinkled with beer or water, to make them stick together, and are then ground in a small mortar. they are ground again after being mixed with the ashes obtained from the skulls of beasts or from the spines of fishes; the more the ashes are ground the better they are. some rub bricks and sprinkle the dust so obtained, after sifting it, into the beech ashes, for dust of this kind does not allow the hearth-lead to absorb the gold or silver by eating away the cupels. others, to guard against the same thing, moisten the cupels with white of egg after they have been made, and when they have been dried in the sun, again crush them; especially if they want to assay in it an ore of copper which contains iron. some moisten the ashes again and again with cow's milk, and dry them, and grind them in a small mortar, and then mould the cupels. in the works in which silver is separated from copper, they make cupels from two parts of the ashes of the crucible of the cupellation furnace, for these ashes are very dry, and from one part of bone-ash. cupels which have been made in these ways also need to be placed in the sun or in a furnace; afterward, in whatever way they have been made, they must be kept a long time in dry places, for the older they are, the dryer and better they are. [illustration (cupel moulds and pestles): a--little mould. b--inverted mould. c--pestle. d--its knob. e--second pestle.] not only potters, but also the assayers themselves, make scorifiers and triangular crucibles. they make them out of fatty clay, which is dry[ ], and neither hard nor soft. with this clay they mix the dust of old broken crucibles, or of burnt and worn bricks; then they knead with a pestle the clay thus mixed with dust, and then dry it. as to these crucibles, the older they are, the dryer and better they are. the moulds in which the cupels are moulded are of two kinds, that is, a smaller size and a larger size. in the smaller ones are made the cupels in which silver or gold is purged from the lead which has absorbed it; in the larger ones are made cupels in which silver is separated from copper and lead. both moulds are made out of brass and have no bottom, in order that the cupels can be taken out of them whole. the pestles also are of two kinds, smaller and larger, each likewise of brass, and from the lower end of them there projects a round knob, and this alone is pressed into the mould and makes the hollow part of the cupel. the part which is next to the knob corresponds to the upper part of the mould. so much for these matters. i will now speak of the preparation of the ore for assaying. it is prepared by roasting, burning, crushing, and washing. it is necessary to take a fixed weight of ore in order that one may determine how great a portion of it these preparations consume. the hard stone containing the metal is burned in order that, when its hardness has been overcome, it can be crushed and washed; indeed, the very hardest kind, before it is burned, is sprinkled with vinegar, in order that it may more rapidly soften in the fire. the soft stone should be broken with a hammer, crushed in a mortar and reduced to powder; then it should be washed and then dried again. if earth is mixed with the mineral, it is washed in a basin, and that which settles is assayed in the fire after it is dried. all mining products which are washed must again be dried. but ore which is rich in metal is neither burned nor crushed nor washed, but is roasted, lest that method of preparation should lose some of the metal. when the fires have been kindled, this kind of ore is roasted in an enclosed pot, which is stopped up with lute. a less valuable ore is even burned on a hearth, being placed upon the charcoal; for we do not make a great expenditure upon metals, if they are not worth it. however, i will go into fuller details as to all these methods of preparing ore, both a little later, and in the following book. for the present, i have decided to explain those things which mining people usually call fluxes[ ] because they are added to ores, not only for assaying, but also for smelting. great power is discovered in all these fluxes, but we do not see the same effects produced in every case; and some are of a very complicated nature. for when they have been mixed with the ore and are melted in either the assay or the smelting furnace, some of them, because they melt easily, to some extent melt the ore; others, because they either make the ore very hot or penetrate into it, greatly assist the fire in separating the impurities from the metals, and they also mix the fused part with the lead, or they partly protect from the fire the ore whose metal contents would be either consumed in the fire, or carried up with the fumes and fly out of the furnace; some fluxes absorb the metals. to the first order belongs lead, whether it be reduced to little granules or resolved into ash by fire, or red-lead[ ], or ochre made from lead[ ], or litharge, or hearth-lead, or galena; also copper, the same either roasted or in leaves or filings[ ]; also the slags of gold, silver, copper, and lead; also soda[ ], its slags, saltpetre, burned alum, vitriol, _sal tostus_, and melted salt[ ]; stones which easily melt in hot furnaces, the sand which is made from them[ ]; soft _tophus_[ ], and a certain white schist[ ]. but lead, its ashes, red-lead, ochre, and litharge, are more efficacious for ores which melt easily; hearth-lead for those which melt with difficulty; and galena for those which melt with greater difficulty. to the second order belong iron filings, their slag, _sal artificiosus_, argol, dried lees of vinegar[ ], and the lees of the _aqua_ which separates gold from silver[ ]; these lees and _sal artificiosus_ have the power of penetrating into ore, the argol to a considerable degree, the lees of vinegar to a greater degree, but most of all those of the _aqua_ which separates gold from silver; filings and slags of iron, since they melt more slowly, have the power of heating the ore. to the third order belong pyrites, the cakes which are melted from them, soda, its slags, salt, iron, iron scales, iron filings, iron slags, vitriol, the sand which is resolved from stones which easily melt in the fire, and _tophus_; but first of all are pyrites and the cakes which are melted from it, for they absorb the metals of the ore and guard them from the fire which consumes them. to the fourth order belong lead and copper, and their relations. and so with regard to fluxes, it is manifest that some are natural, others fall in the category of slags, and the rest are purged from slag. when we assay ores, we can without great expense add to them a small portion of any sort of flux, but when we smelt them we cannot add a large portion without great expense. we must, therefore, consider how great the cost is, to avoid incurring a greater expense on smelting an ore than the profit we make out of the metals which it yields. the colour of the fumes which the ore emits after being placed on a hot shovel or an iron plate, indicates what flux is needed in addition to the lead, for the purpose of either assaying or smelting. if the fumes have a purple tint, it is best of all, and the ore does not generally require any flux whatever. if the fumes are blue, there should be added cakes melted out of pyrites or other cupriferous rock; if yellow, litharge and sulphur should be added; if red, glass-galls[ ] and salt; if green, then cakes melted from cupriferous stones, litharge, and glass-galls; if the fumes are black, melted salt or iron slag, litharge and white lime rock. if they are white, sulphur and iron which is eaten with rust; if they are white with green patches, iron slag and sand obtained from stones which easily melt; if the middle part of the fumes are yellow and thick, but the outer parts green, the same sand and iron slag. the colour of the fumes not only gives us information as to the proper remedies which should be applied to each ore, but also more or less indication as to the solidified juices which are mixed with it, and which give forth such fumes. generally, blue fumes signify that the ore contains azure yellow, orpiment; red, realgar; green, chrysocolla; black, black bitumen; white, tin[ ]; white with green patches, the same mixed with chrysocolla; the middle part yellow and other parts green show that it contains sulphur. earth, however, and other things dug up which contain metals, sometimes emit similarly coloured fumes. if the ore contains any _stibium_, then iron slag is added to it; if pyrites, then are added cakes melted from a cupriferous stone and sand made from stones which easily melt. if the ore contains iron, then pyrites and sulphur are added; for just as iron slag is the flux for an ore mixed with sulphur, so on the contrary, to a gold or silver ore containing iron, from which they are not easily separated, is added sulphur and sand made from stones which easily melt. _sal artificiosus_[ ] suitable for use in assaying ore is made in many ways. by the first method, equal portions of argol, lees of vinegar, and urine, are all boiled down together till turned into salt. the second method is from equal portions of the ashes which wool-dyers use, of lime, of argol purified, and of melted salt; one _libra_ of each of these ingredients is thrown into twenty _librae_ of urine; then all are boiled down to one-third and strained, and afterward there is added to what remains one _libra_ and four _unciae_ of unmelted salt, eight pounds of lye being at the same time poured into the pots, with litharge smeared around on the inside, and the whole is boiled till the salt becomes thoroughly dry. the third method follows. unmelted salt, and iron which is eaten with rust, are put into a vessel, and after urine has been poured in, it is covered with a lid and put in a warm place for thirty days; then the iron is washed in the urine and taken out, and the residue is boiled until it is turned into salt. in the fourth method by which _sal artificiosus_ is prepared, the lye made from equal portions of lime and the ashes which wool-dyers use, together with equal portions of salt, soap, white argol, and saltpetre, are boiled until in the end the mixture evaporates and becomes salt. this salt is mixed with the concentrates from washing, to melt them. saltpetre is prepared in the following manner, in order that it may be suitable for use in assaying ore. it is placed in a pot which is smeared on the inside with litharge, and lye made of quicklime is repeatedly poured over it, and it is heated until the fire consumes it. wherefore the saltpetre does not kindle with the fire, since it has absorbed the lime which preserves it, and thus it is prepared[ ]. the following compositions[ ] are recommended to smelt all ores which the heat of fire breaks up or melts only with difficulty. of these, one is made from stones of the third order, which easily melt when thrown into hot furnaces. they are crushed into pure white powder, and with half an _uncia_ of this powder there are mixed two _unciae_ of yellow litharge, likewise crushed. this mixture is put into a scorifier large enough to hold it, and placed under the muffle of a hot furnace; when the charge flows like water, which occurs after half an hour, it is taken out of the furnace and poured on to a stone, and when it has hardened it has the appearance of glass, and this is likewise crushed. this powder is sprinkled over any metalliferous ore which does not easily melt when we are assaying it, and it causes the slag to exude. others, in place of litharge, substitute lead ash,[ ] which is made in the following way: sulphur is thrown into lead which has been melted in a crucible, and it soon becomes covered with a sort of scum; when this is removed, sulphur is again thrown in, and the skin which forms is again taken off; this is frequently repeated, in fact until all the lead is turned into powder. there is a powerful flux compound which is made from one _uncia_ each of prepared saltpetre, melted salt, glass-gall, and argol, and one-third of an _uncia_ of litharge and a _bes_ of glass ground to powder; this flux, being added to an equal weight of ore, liquefies it. a more powerful flux is made by placing together in a pot, smeared on the inside with litharge, equal portions of white argol, common salt, and prepared saltpetre, and these are heated until a white powder is obtained from them, and this is mixed with as much litharge; one part of this compound is mixed with two parts of the ore which is to be assayed. a still more powerful flux than this is made out of ashes of black lead, saltpetre, orpiment, _stibium_, and dried lees of the _aqua_ with which gold workers separate gold from silver. the ashes of lead[ ] are made from one pound of lead and one pound of sulphur; the lead is flattened out into sheets by pounding with a hammer, and placed alternately with sulphur in a crucible or pot, and they are heated together until the fire consumes the sulphur and the lead turns to ashes. one _libra_ of crushed saltpetre is mixed with one _libra_ of orpiment similarly ground to powder, and the two are cooked in an iron pan until they liquefy; they are then poured out, and after cooling are again ground to powder. a _libra_ of _stibium_ and a _bes_ of the dried lees (_of what?_) are placed alternately in a crucible and heated to the point at which they form a button, which is similarly reduced to powder. a _bes_ of this powder and one _libra_ of the ashes of lead, as well as a _libra_ of powder made out of the saltpetre and orpiment, are mixed together and a powder is made from them, one part of which added to two parts of ore liquefies it and cleanses it of dross. but the most powerful flux is one which has two _drachmae_ of sulphur and as much glass-galls, and half an _uncia_ of each of the following,--_stibium_, salt obtained from boiled urine, melted common salt, prepared saltpetre, litharge, vitriol, argol, salt obtained from ashes of musk ivy, dried lees of the _aqua_ by which gold-workers separate gold from silver, alum reduced by fire to powder, and one _uncia_ of camphor[ ] combined with sulphur and ground into powder. a half or whole portion of this mixture, as the necessity of the case requires, is mixed with one portion of the ore and two portions of lead, and put in a scorifier; it is sprinkled with powder of crushed venetian glass, and when the mixture has been heated for an hour and a half or two hours, a button will settle in the bottom of the scorifier, and from it the lead is soon separated. there is also a flux which separates sulphur, orpiment and realgar from metalliferous ore. this flux is composed of equal portions of iron slag, white _tophus_, and salt. after these juices have been secreted, the ores themselves are melted, with argol added to them. there is one flux which preserves _stibium_ from the fire, that the fire may not consume it, and which preserves the metals from the _stibium_; and this is composed of equal portions of sulphur, prepared saltpetre, melted salt, and vitriol, heated together in lye until no odour emanates from the sulphur, which occurs after a space of three or four hours.[ ] it is also worth while to substitute certain other mixtures. take two portions of ore properly prepared, one portion of iron filings, and likewise one portion of salt, and mix; then put them into a scorifier and place them in a muffle furnace; when they are reduced by the fire and run together, a button will settle in the bottom of the scorifier. or else take equal portions of ore and of lead ochre, and mix with them a small quantity of iron filings, and put them into a scorifier, then scatter iron filings over the mixture. or else take ore which has been ground to powder and sprinkle it in a crucible, and then sprinkle over it an equal quantity of salt that has been three or four times moistened with urine and dried; then, again and again alternately, powdered ore and salt; next, after the crucible has been covered with a lid and sealed, it is placed upon burning charcoal. or else take one portion of ore, one portion of minute lead granules, half a portion of venetian glass, and the same quantity of glass-galls. or else take one portion of ore, one portion of lead granules, half a portion of salt, one-fourth of a portion of argol, and the same quantity of lees of the _aqua_ which separates gold from silver. or else take equal portions of prepared ore and a powder in which there are equal portions of very minute lead granules, melted salt, _stibium_ and iron slag. or else take equal portions of gold ore, vitriol, argol, and of salt. so much for the fluxes. in the assay furnace, when it has been prepared in the way in which i have described, is first placed a muffle. then selected pieces of live charcoals are laid on it, for, from pieces of inferior quality, a great quantity of ash collects around the muffle and hinders the action of the fire. then the scorifiers are placed under the muffle with tongs, and glowing coals are placed under the fore part of the muffle to warm the scorifiers more quickly; and when the lead or ore is to be placed in the scorifiers, they are taken out again with the tongs. when the scorifiers glow in the heat, first of all the ash or small charcoals, if any have fallen into them, should be blown away with an iron pipe two feet long and a digit in diameter; this same thing must be done if ash or small coal has fallen into the cupels. next, put in a small ball of lead with the tongs, and when this lead has begun to be turned into fumes and consumed, add to it the prepared ore wrapped in paper. it is preferable that the assayer should wrap it in paper, and in this way put it in the scorifier, than that he should drop it in with a copper ladle; for when the scorifiers are small, if he uses a ladle he frequently spills some part of the ore. when the paper is burnt, he stirs the ore with a small charcoal held in the tongs, so that the lead may absorb the metal which is mixed in the ore; when this mixture has taken place, the slag partly adheres by its circumference to the scorifier and makes a kind of black ring, and partly floats on the lead in which is mixed the gold or silver; then the slag must be removed from it. the lead used must be entirely free from every trace of silver, as is that which is known as _villacense_.[ ] but if this kind is not obtainable, the lead must be assayed separately, to determine with certainty that proportion of silver it contains, so that it may be deducted from the calculation of the ore, and the result be exact; for unless such lead be used, the assay will be false and misleading. the lead balls are made with a pair of iron tongs, about one foot long; its iron claws are so formed that when pressed together they are egg-shaped; each claw contains a hollow cup, and when the claws are closed there extends upward from the cup a passage, so there are two openings, one of which leads to each hollow cup. and so when the molten lead is poured in through the openings, it flows down into the hollow cup, and two balls are formed by one pouring. in this place i ought not to omit mention of another method of assaying employed by some assayers. they first of all place prepared ore in the scorifiers and heat it, and afterward they add the lead. of this method i cannot approve, for in this way the ore frequently becomes cemented, and for this reason it does not stir easily afterward, and is very slow in mixing with the lead. [illustration a (tongs): a--claws of the tongs. b--iron, giving form of an egg. c--opening.] if the whole space of the furnace covered by the muffle is not filled with scorifiers, cupels are put in the empty space, in order that they may become warmed in the meantime. sometimes, however, it is filled with scorifiers, when we are assaying many different ores, or many portions of one ore at the same time. although the cupels are usually dried in one hour, yet smaller ones are done more quickly, and the larger ones more slowly. unless the cupels are heated before the metal mixed with lead is placed in them, they frequently break, and the lead always sputters and sometimes leaps out of them; if the cupel is broken or the lead leaps out of it, it is necessary to assay another portion of ore; but if the lead only sputters, then the cupels should be covered with broad thin pieces of glowing charcoal, and when the lead strikes these, it falls back again, and thus the mixture is slowly exhaled. further, if in the cupellation the lead which is in the mixture is not consumed, but remains fixed and set, and is covered by a kind of skin, this is a sign that it has not been heated by a sufficiently hot fire; put into the mixture, therefore, a dry pine stick, or a twig of a similar tree, and hold it in the hand in order that it can be drawn away when it has been heated. then take care that the heat is sufficient and equal; if the heat has not passed all round the charge, as it should when everything is done rightly, but causes it to have a lengthened shape, so that it appears to have a tail, this is a sign that the heat is deficient where the tail lies. then in order that the cupel may be equally heated by the fire, turn it around with a small iron hook, whose handle is likewise made of iron and is a foot and a half long. [illustration b (hook): small iron hook.] next, if the mixture has not enough lead, add as much of it as is required with the iron tongs, or with the brass ladle to which is fastened a very long handle. in order that the charge may not be cooled, warm the lead beforehand. but it is better at first to add as much lead as is required to the ore which needs melting, rather than afterward when the melting has been half finished, that the whole quantity may not vanish in fumes, but part of it remain fast. when the heat of the fire has nearly consumed the lead, then is the time when the gold and silver gleam in their varied colours, and when all the lead has been consumed the gold or silver settles in the cupel. then as soon as possible remove the cupel out of the furnace, and take the button out of it while it is still warm, in order that it does not adhere to the ashes. this generally happens if the button is already cold when it is taken out. if the ashes do adhere to it, do not scrape it with a knife, lest some of it be lost and the assay be erroneous, but squeeze it with the iron tongs, so that the ashes drop off through the pressure. finally, it is of advantage to make two or three assays of the same ore at the same time, in order that if by chance one is not successful, the second, or in any event the third, may be certain. [illustration (shield for muffle furnace): a--handle of tablet. b--its crack.] while the assayer is assaying the ore, in order to prevent the great heat of the fire from injuring his eyes, it will be useful for him always to have ready a thin wooden tablet, two palms wide, with a handle by which it may be held, and with a slit down the middle in order that he may look through it as through a crack, since it is necessary for him to look frequently within and carefully to consider everything. now the lead which has absorbed the silver from a metallic ore is consumed in the cupel by the heat in the space of three quarters of an hour. when the assays are completed the muffle is taken out of the furnace, and the ashes removed with an iron shovel, not only from the brick and iron furnaces, but also from the earthen one, so that the furnace need not be removed from its foundation. from ore placed in the triangular crucible a button is melted out, from which metal is afterward made. first of all, glowing charcoal is put into the iron hoop, then is put in the triangular crucible, which contains the ore together with those things which can liquefy it and purge it of its dross; then the fire is blown with the double bellows, and the ore is heated until the button settles in the bottom of the crucible. we have explained that there are two methods of assaying ore,--one, by which the lead is mixed with ore in the scorifier and afterward again separated from it in the cupel; the other, by which it is first melted in the triangular earthen crucible and afterward mixed with lead in the scorifier, and later separated from it in the cupel. now let us consider which is more suitable for each ore, or, if neither is suitable, by what other method in one way or another we can assay it. we justly begin with a gold ore, which we assay by both methods, for if it is rich and seems not to be strongly resistant to fire, but to liquefy easily, one _centumpondium_ of it (known to us as the lesser weights),[ ] together with one and a half, or two _unciae_ of lead of the larger weights, are mixed together and placed in the scorifier, and the two are heated in the fire until they are well mixed. but since such an ore sometimes resists melting, add a little salt to it, either _sal torrefactus_ or _sal artificiosus_, for this will subdue it, and prevent the alloy from collecting much dross; stir it frequently with an iron rod, in order that the lead may flow around the gold on every side, and absorb it and cast out the waste. when this has been done, take out the alloy and cleanse it of slag; then place it in the cupel and heat it until it exhales all the lead, and a bead of gold settles in the bottom. if the gold ore is seen not to be easily melted in the fire, roast it and extinguish it with brine. do this again and again, for the more often you roast it and extinguish it, the more easily the ore can be crushed fine, and the more quickly does it melt in the fire and give up whatever dross it possesses. mix one part of this ore, when it has been roasted, crushed, and washed, with three parts of some powder compound which melts ore, and six parts of lead. put the charge into the triangular crucible, place it in the iron hoop to which the double bellows reaches, and heat first in a slow fire, and afterward gradually in a fiercer fire, till it melts and flows like water. if the ore does not melt, add to it a little more of these fluxes, mixed with an equal portion of yellow litharge, and stir it with a hot iron rod until it all melts. then take the crucible out of the hoop, shake off the button when it has cooled, and when it has been cleansed, melt first in the scorifier and afterward in the cupel. finally, rub the gold which has settled in the bottom of the cupel, after it has been taken out and cooled, on the touchstone, in order to find out what proportion of silver it contains. another method is to put a _centumpondium_ (of the lesser weights) of gold ore into the triangular crucible, and add to it a _drachma_ (of the larger weights) of glass-galls. if it resists melting, add half a _drachma_ of roasted argol, and if even then it resists, add the same quantity of roasted lees of vinegar, or lees of the _aqua_ which separates gold from silver, and the button will settle in the bottom of the crucible. melt this button again in the scorifier and a third time in the cupel. we determine in the following way, before it is melted in the muffle furnace, whether pyrites contains gold in it or not: if, after being three times roasted and three times quenched in sharp vinegar, it has not broken nor changed its colour, there is gold in it. the vinegar by which it is quenched should be mixed with salt that is put in it, and frequently stirred and dissolved for three days. nor is pyrites devoid of gold, when, after being roasted and then rubbed on the touchstone, it colours the touchstone in the same way that it coloured it when rubbed in its crude state. nor is gold lacking in that, whose concentrates from washing, when heated in the fire, easily melt, giving forth little smell and remaining bright; such concentrates are heated in the fire in a hollowed piece of charcoal covered over with another charcoal. we also assay gold ore without fire, but more often its sand or the concentrates which have been made by washing, or the dust gathered up by some other means. a little of it is slightly moistened with water and heated until it begins to exhale an odour, and then to one portion of ore are placed two portions of quicksilver[ ] in a wooden dish as deep as a basin. they are mixed together with a little brine, and are then ground with a wooden pestle for the space of two hours, until the mixture becomes of the thickness of dough, and the quicksilver can no longer be distinguished from the concentrates made by the washing, nor the concentrates from the quicksilver. warm, or at least tepid, water is poured into the dish and the material is washed until the water runs out clear. afterward cold water is poured into the same dish, and soon the quicksilver, which has absorbed all the gold, runs together into a separate place away from the rest of the concentrates made by washing. the quicksilver is afterward separated from the gold by means of a pot covered with soft leather, or with canvas made of woven threads of cotton; the amalgam is poured into the middle of the cloth or leather, which sags about one hand's breadth; next, the leather is folded over and tied with a waxed string, and the dish catches the quicksilver which is squeezed through it. as for the gold which remains in the leather, it is placed in a scorifier and purified by being placed near glowing coals. others do not wash away the dirt with warm water, but with strong lye and vinegar, for they pour these liquids into the pot, and also throw into it the quicksilver mixed with the concentrates made by washing. then they set the pot in a warm place, and after twenty-four hours pour out the liquids with the dirt, and separate the quicksilver from the gold in the manner which i have described. then they pour urine into a jar set in the ground, and in the jar place a pot with holes in the bottom, and in the pot they place the gold; then the lid is put on and cemented, and it is joined with the jar; they afterward heat it till the pot glows red. after it has cooled, if there is copper in the gold they melt it with lead in a cupel, that the copper may be separated from it; but if there is silver in the gold they separate them by means of the _aqua_ which has the power of parting these two metals. there are some who, when they separate gold from quicksilver, do not pour the amalgam into a leather, but put it into a gourd-shaped earthen vessel, which they place in the furnace and heat gradually over burning charcoal; next, with an iron plate, they cover the opening of the operculum, which exudes vapour, and as soon as it has ceased to exude, they smear it with lute and heat it for a short time; then they remove the operculum from the pot, and wipe off the quicksilver which adheres to it with a hare's foot, and preserve it for future use. by the latter method, a greater quantity of quicksilver is lost, and by the former method, a smaller quantity. if an ore is rich in silver, as is _rudis_ silver[ ], frequently silver glance, or rarely ruby silver, gray silver, black silver, brown silver, or yellow silver, as soon as it is cleansed and heated, a _centumpondium_ (of the lesser weights) of it is placed in an _uncia_ of molten lead in a cupel, and is heated until the lead exhales. but if the ore is of poor or moderate quality, it must first be dried, then crushed, and then to a _centumpondium_ (of the lesser weights) an _uncia_ of lead is added, and it is heated in the scorifier until it melts. if it is not soon melted by the fire, it should be sprinkled with a little powder of the first order of fluxes, and if then it does not melt, more is added little by little until it melts and exudes its slag; that this result may be reached sooner, the powder which has been sprinkled over it should be stirred in with an iron rod. when the scorifier has been taken out of the assay furnace, the alloy should be poured into a hole in a baked brick; and when it has cooled and been cleansed of the slag, it should be placed in a cupel and heated until it exhales all its lead; the weight of silver which remains in the cupel indicates what proportion of silver is contained in the ore. we assay copper ore without lead, for if it is melted with it, the copper usually exhales and is lost. therefore, a certain weight of such an ore is first roasted in a hot fire for about six or eight hours; next, when it has cooled, it is crushed and washed; then the concentrates made by washing are again roasted, crushed, washed, dried, and weighed. the portion which it has lost whilst it is being roasted and washed is taken into account, and these concentrates by washing represent the cake which will be melted out of the copper ore. place three _centumpondia_ (lesser weights) of this, mixed with three _centumpondia_ (lesser weights) each of copper scales[ ], saltpetre, and venetian glass, mixed, into the triangular crucible, and place it in the iron hoop which is set on the hearth in front of the double bellows. cover the crucible with charcoal in such a way that nothing may fall into the ore which is to be melted, and so that it may melt more quickly. at first blow a gentle blast with the bellows in order that the ore may be heated gradually in the fire; then blow strongly till it melts, and the fire consumes that which has been added to it, and the ore itself exudes whatever slag it possesses. next, cool the crucible which has been taken out, and when this is broken you will find the copper; weigh this, in order to ascertain how great a portion of the ore the fire has consumed. some ore is only once roasted, crushed, and washed; and of this kind of concentrates, three _centumpondia_ (lesser weights) are taken with one _centumpondium_ each of common salt, argol and glass-galls. heat them in the triangular crucible, and when the mixture has cooled a button of pure copper will be found, if the ore is rich in this metal. if, however, it is less rich, a stony lump results, with which the copper is intermixed; this lump is again roasted, crushed, and, after adding stones which easily melt and saltpetre, it is again melted in another crucible, and there settles in the bottom of the crucible a button of pure copper. if you wish to know what proportion of silver is in this copper button, melt it in a cupel after adding lead. with regard to this test i will speak later. those who wish to know quickly what portion of silver the copper ore contains, roast the ore, crush and wash it, then mix a little yellow litharge with one _centumpondium_ (lesser weights) of the concentrates, and put the mixture into a scorifier, which they place under the muffle in a hot furnace for the space of half an hour. when the slag exudes, by reason of the melting force which is in the litharge, they take the scorifier out; when it has cooled, they cleanse it of slag and again crush it, and with one _centumpondium_ of it they mix one and a half _unciae_ of lead granules. they then put it into another scorifier, which they place under the muffle in a hot furnace, adding to the mixture a little of the powder of some one of the fluxes which cause ore to melt; when it has melted they take it out, and after it has cooled, cleanse it of slag; lastly, they heat it in the cupel till it has exhaled all of the lead, and only silver remains. lead ore may be assayed by this method: crush half an _uncia_ of pure lead-stone and the same quantity of the _chrysocolla_ which they call borax, mix them together, place them in a crucible, and put a glowing coal in the middle of it. as soon as the borax crackles and the lead-stone melts, which soon occurs, remove the coal from the crucible, and the lead will settle to the bottom of it; weigh it out, and take account of that portion of it which the fire has consumed. if you also wish to know what portion of silver is contained in the lead, melt the lead in the cupel until all of it exhales. another way is to roast the lead ore, of whatsoever quality it be, wash it, and put into the crucible one _centumpondium_ of the concentrates, together with three _centumpondia_ of the powdered compound which melts ore, mixed together, and place it in the iron hoop that it may melt; when it has cooled, cleanse it of its slag, and complete the test as i have already said. another way is to take two _unciae_ of prepared ore, five _drachmae_ of roasted copper, one _uncia_ of glass, or glass-galls reduced to powder, a _semi-uncia_ of salt, and mix them. put the mixture into the triangular crucible, and heat it over a gentle fire to prevent it from breaking; when the mixture has melted, blow the fire vigorously with the bellows; then take the crucible off the live coals and let it cool in the open air; do not pour water on it, lest the lead button being acted upon by the excessive cold should become mixed with the slag, and the assay in this way be erroneous. when the crucible has cooled, you will find in the bottom of it the lead button. another way is to take two _unciae_ of ore, a _semi-uncia_ of litharge, two _drachmae_ of venetian glass and a _semi-uncia_ of saltpetre. if there is difficulty in melting the ore, add to it iron filings, which, since they increase the heat, easily separate the waste from lead and other metals. by the last way, lead ore properly prepared is placed in the crucible, and there is added to it only the sand made from stones which easily melt, or iron filings, and then the assay is completed as formerly. you can assay tin ore by the following method. first roast it, then crush, and afterward wash it; the concentrates are again roasted, crushed, and washed. mix one and a half _centumpondia_ of this with one _centumpondium_ of the _chrysocolla_ which they call borax; from the mixture, when it has been moistened with water, make a lump. afterwards, perforate a large round piece of charcoal, making this opening a palm deep, three digits wide on the upper side and narrower on the lower side; when the charcoal is put in its place the latter should be on the bottom and the former uppermost. let it be placed in a crucible, and let glowing coal be put round it on all sides; when the perforated piece of coal begins to burn, the lump is placed in the upper part of the opening, and it is covered with a wide piece of glowing coal, and after many pieces of coal have been put round it, a hot fire is blown up with the bellows, until all the tin has run out of the lower opening of the charcoal into the crucible. another way is to take a large piece of charcoal, hollow it out, and smear it with lute, that the ore may not leap out when white hot. next, make a small hole through the middle of it, then fill up the large opening with small charcoal, and put the ore upon this; put fire in the small hole and blow the fire with the nozzle of a hand bellows; place the piece of charcoal in a small crucible, smeared with lute, in which, when the melting is finished, you will find a button of tin. in assaying bismuth ore, place pieces of ore in the scorifier, and put it under the muffle in a hot furnace; as soon as they are heated, they drip with bismuth, which runs together into a button. quicksilver ore is usually tested by mixing one part of broken ore with three-parts of charcoal dust and a handful of salt. put the mixture into a crucible or a pot or a jar, cover it with a lid, seal it with lute, place it on glowing charcoal, and as soon as a burnt cinnabar colour shows in it, take out the vessel; for if you continue the heat too long the mixture exhales the quicksilver with the fumes. the quicksilver itself, when it has become cool, is found in the bottom of the crucible or other vessel. another way is to place broken ore in a gourd-shaped earthen vessel, put it in the assay furnace, and cover with an operculum which has a long spout; under the spout, put an ampulla to receive the quicksilver which distills. cold water should be poured into the ampulla, so that the quicksilver which has been heated by the fire may be continuously cooled and gathered together, for the quicksilver is borne over by the force of the fire, and flows down through the spout of the operculum into the ampulla. we also assay quicksilver ore in the very same way in which we smelt it. this i will explain in its proper place. lastly, we assay iron ore in the forge of a blacksmith. such ore is burned, crushed, washed, and dried; a magnet is laid over the concentrates, and the particles of iron are attracted to it; these are wiped off with a brush, and are caught in a crucible, the magnet being continually passed over the concentrates and the particles wiped off, so long as there remain any particles which the magnet can attract to it. these particles are heated in the crucible with saltpetre until they melt, and an iron button is melted out of them. if the magnet easily and quickly attracts the particles to it, we infer that the ore is rich in iron; if slowly, that it is poor; if it appears actually to repel the ore, then it contains little or no iron. this is enough for the assaying of ores. i will now speak of the assaying of the metal alloys. this is done both by coiners and merchants who buy and sell metal, and by miners, but most of all by the owners and mine masters, and by the owners and masters of the works in which the metals are smelted, or in which one metal is parted from another. first i will describe the way assays are usually made to ascertain what portion of precious metal is contained in base metal. gold and silver are now reckoned as precious metals and all the others as base metals. once upon a time the base metals were burned up, in order that the precious metals should be left pure; the ancients even discovered by such burning what portion of gold was contained in silver, and in this way all the silver was consumed, which was no small loss. however, the famous mathematician, archimedes[ ], to gratify king hiero, invented a method of testing the silver, which was not very rapid, and was more accurate for testing a large mass than a small one. this i will explain in my commentaries. the alchemists have shown us a way of separating silver from gold by which neither of them is lost[ ]. gold which contains silver,[ ] or silver which contains gold, is first rubbed on the touchstone. then a needle in which there is a similar amount of gold or silver is rubbed on the same touchstone, and from the lines which are produced in this way, is perceived what portion of silver there is in the gold, or what portion of gold there is in the silver. next there is added to the silver which is in the gold, enough silver to make it three times as much as the gold. then lead is placed in a cupel and melted; a little later, a small amount of copper is put in it, in fact, half an _uncia_ of it, or half an _uncia_ and a _sicilicus_ (of the smaller weights) if the gold or silver does not contain any copper. the cupel, when the lead and copper are wanting, attracts the particles of gold and silver, and absorbs them. finally, one-third of a _libra_ of the gold, and one _libra_[ ] of the silver must be placed together in the same cupel and melted; for if the gold and silver were first placed in the cupel and melted, as i have already said, it absorbs particles of them, and the gold, when separated from the silver, will not be found pure. these metals are heated until the lead and the copper are consumed, and again, the same weight of each is melted in the same manner in another cupel. the buttons are pounded with a hammer and flattened out, and each little leaf is shaped in the form of a tube, and each is put into a small glass ampulla. over these there is poured one _uncia_ and one _drachma_ (of the large weight) of the third quality _aqua valens_, which i will describe in the tenth book. this is heated over a slow fire, and small bubbles, resembling pearls in shape, will be seen to adhere to the tubes. the redder the _aqua_ appears, the better it is judged to be; when the redness has vanished, small white bubbles are seen to be resting on the tubes, resembling pearls not only in shape, but also in colour. after a short time the _aqua_ is poured off and other is poured on; when this has again raised six or eight small white bubbles, it is poured off and the tubes are taken out and washed four or five times with spring water; or if they are heated with the same water, when it is boiling, they will shine more brilliantly. then they are placed in a saucer, which is held in the hand and gradually dried by the gentle heat of the fire; afterward the saucer is placed over glowing charcoal and covered with a charcoal, and a moderate blast is blown upon it with the mouth and then a blue flame will be emitted. in the end the tubes are weighed, and if their weights prove equal, he who has undertaken this work has not laboured in vain. lastly, both are placed in another balance-pan and weighed; of each tube four grains must not be counted, on account of the silver which remains in the gold and cannot be separated from it. from the weight of the tubes we learn the weight both of the gold and of the silver which is in the button. if some assayer has omitted to add so much silver to the gold as to make it three times the quantity, but only double, or two and a half times as much, he will require the stronger quality of _aqua_ which separates gold from silver, such as the fourth quality. whether the _aqua_ which he employs for gold and silver is suitable for the purpose, or whether it is more or less strong than is right, is recognised by its effect. that of medium strength raises the little bubbles on the tubes and is found to colour the ampulla and the operculum a strong red; the weaker one is found to colour them a light red, and the stronger one to break the tubes. to pure silver in which there is some portion of gold, nothing should be added when they are being heated in the cupel prior to their being parted, except a _bes_ of lead and one-fourth or one-third its amount of copper of the lesser weights. if the silver contains in itself a certain amount of copper, let it be weighed, both after it has been melted with the lead, and after the gold has been parted from it; by the former we learn how much copper is in it, by the latter how much gold. base metals are burnt up even to-day for the purpose of assay, because to lose so little of the metal is small loss, but from a large mass of base metal, the precious metal is always extracted, as i will explain in books x. and xi. we assay an alloy of copper and silver in the following way. from a few cakes of copper the assayer cuts out portions, small samples from small cakes, medium samples from medium cakes, and large samples from large cakes; the small ones are equal in size to half a hazel nut, the large ones do not exceed the size of half a chestnut, and those of medium size come between the two. he cuts out the samples from the middle of the bottom of each cake. he places the samples in a new, clean, triangular crucible and fixes to them pieces of paper upon which are written the weight of the cakes of copper, of whatever size they may be; for example, he writes, "these samples have been cut from copper which weighs twenty _centumpondia_." when he wishes to know how much silver one _centumpondium_ of copper of this kind has in it, first of all he throws glowing coals into the iron hoop, then adds charcoal to it. when the fire has become hot, the paper is taken out of the crucible and put aside, he then sets that crucible on the fire and gradually heats it for a quarter of an hour until it becomes red hot. then he stimulates the fire by blowing with a blast from the double bellows for half an hour, because copper which is devoid of lead requires this time to become hot and to melt; copper not devoid of lead melts quicker. when he has blown the bellows for about the space of time stated, he removes the glowing charcoal with the tongs, and stirs the copper with a splinter of wood, which he grasps with the tongs. if it does not stir easily, it is a sign that the copper is not wholly liquefied; if he finds this is the case, he again places a large piece of charcoal in the crucible, and replaces the glowing charcoal which had been removed, and again blows the bellows for a short time. when all the copper has melted he stops using the bellows, for if he were to continue to use them, the fire would consume part of the copper, and then that which remained would be richer than the cake from which it had been cut; this is no small mistake. therefore, as soon as the copper has become sufficiently liquefied, he pours it out into a little iron mould, which may be large or small, according as more or less copper is melted in the crucible for the purpose of the assay. the mould has a handle, likewise made of iron, by which it is held when the copper is poured in, after which, he plunges it into a tub of water placed near at hand, that the copper may be cooled. then he again dries the copper by the fire, and cuts off its point with an iron wedge; the portion nearest the point he hammers on an anvil and makes into a leaf, which he cuts into pieces. [illustration (copper mould for assaying): a--iron mould. b--its handle.] others stir the molten copper with a stick of linden tree charcoal, and then pour it over a bundle of new clean birch twigs, beneath which is placed a wooden tub of sufficient size and full of water, and in this manner the copper is broken up into little granules as small as hemp seeds. others employ straw in place of twigs. others place a broad stone in a tub and pour in enough water to cover the stone, then they run out the molten copper from the crucible on to the stone, from which the minute granules roll off; others pour the molten copper into water and stir it until it is resolved into granules. the fire does not easily melt the copper in the cupel unless it has been poured and a thin leaf made of it, or unless it has been resolved into granules or made into filings; and if it does not melt, all the labour has been undertaken in vain. in order that they may be accurately weighed out, silver and lead are resolved into granules in the same manner as copper. but to return to the assay of copper. when the copper has been prepared by these methods, if it is free of lead and iron, and rich in silver, to each _centumpondium_ (lesser weights) add one and a half _unciae_ of lead (larger weights). if, however, the copper contains some lead, add one _uncia_ of lead; if it contains iron, add two _unciae_. first put the lead into a cupel, and after it begins to smoke, add the copper; the fire generally consumes the copper, together with the lead, in about one hour and a quarter. when this is done, the silver will be found in the bottom of the cupel. the fire consumes both of those metals more quickly if they are heated in that furnace which draws in air. it is better to cover the upper half of it with a lid, and not only to put on the muffle door, but also to close the window of the muffle door with a piece of charcoal, or with a piece of brick. if the copper be such that the silver can only be separated from it with difficulty, then before it is tested with fire in the cupel, lead should first be put into the scorifier, and then the copper should be added with a moderate quantity of melted salt, both that the lead may absorb the copper and that the copper may be cleansed of the dross which abounds in it. tin which contains silver should not at the beginning of the assay be placed in a cupel, lest the silver, as often happens, be consumed and converted into fumes, together with the tin. as soon as the lead[ ] has begun to fume in the scorifier, then add that[ ] to it. in this way the lead will take the silver and the tin will boil and turn into ashes, which may be removed with a wooden splinter. the same thing occurs if any alloy is melted in which there is tin. when the lead has absorbed the silver which was in the tin, then, and not till then, it is heated in the cupel. first place the lead with which the silver is mixed, in an iron pan, and stand it on a hot furnace and let it melt; afterward pour this lead into a small iron mould, and then beat it out with a hammer on an anvil and make it into leaves in the same way as the copper. lastly, place it in the cupel, which assay can be carried out in the space of half an hour. a great heat is harmful to it, for which reason there is no necessity either to cover the half of the furnace with a lid or to close up its mouth. the minted metal alloys, which are known as money, are assayed in the following way. the smaller silver coins which have been picked out from the bottom and top and sides of a heap are first carefully cleansed; then, after they have been melted in the triangular crucible, they are either resolved into granules, or made into thin leaves. as for the large coins which weigh a _drachma_, a _sicilicus_, half an _uncia_, or an _uncia_, beat them into leaves. then take a _bes_ of the granules, or an equal weight of the leaves, and likewise take another _bes_ in the same way. wrap each sample separately in paper, and afterwards place two small pieces of lead in two cupels which have first been heated. the more precious the money is, the smaller portion of lead do we require for the assay, the more base, the larger is the portion required; for if a _bes_ of silver is said to contain only half an _uncia_ or one _uncia_ of copper, we add to the _bes_ of granules half an _uncia_ of lead. if it is composed of equal parts of silver and copper, we add an _uncia_ of lead, but if in a _bes_ of copper there is only half an _uncia_ or one _uncia_ of silver, we add an _uncia_ and a half of lead. as soon as the lead has begun to fume, put into each cupel one of the papers in which is wrapped the sample of silver alloyed with copper, and close the mouth of the muffle with charcoal. heat them with a gentle fire until all the lead and copper are consumed, for a hot fire by its heat forces the silver, combined with a certain portion of lead, into the cupel, in which way the assay is rendered erroneous. then take the beads out of the cupel and clean them of dross. if neither depresses the pan of the balance in which it is placed, but their weight is equal, the assay has been free from error; but if one bead depresses its pan, then there is an error, for which reason the assay must be repeated. if the _bes_ of coin contains but seven _unciae_ of pure silver it is because the king, or prince, or the state who coins the money, has taken one _uncia_, which he keeps partly for profit and partly for the expense of coining, he having added copper to the silver. of all these matters i have written extensively in my book _de precio metallorum et monetis_. we assay gold coins in various ways. if there is copper mixed with the gold, we melt them by fire in the same way as silver coins; if there is silver mixed with the gold, they are separated by the strongest _aqua valens_; if there is copper and silver mixed with the gold, then in the first place, after the addition of lead, they are heated in the cupel until the fire consumes the copper and the lead, and afterward the gold is parted from the silver. it remains to speak of the touchstone[ ] with which gold and silver are tested, and which was also used by the ancients. for although the assay made by fire is more certain, still, since we often have no furnace, nor muffle, nor crucibles, or some delay must be occasioned in using them, we can always rub gold or silver on the touchstone, which we can have in readiness. further, when gold coins are assayed in the fire, of what use are they afterward? a touchstone must be selected which is thoroughly black and free of sulphur, for the blacker it is and the more devoid of sulphur, the better it generally is; i have written elsewhere of its nature[ ]. first the gold is rubbed on the touchstone, whether it contains silver or whether it is obtained from the mines or from the smelting; silver also is rubbed in the same way. then one of the needles, that we judge by its colour to be of similar composition, is rubbed on the touchstone; if this proves too pale, another needle which has a stronger colour is rubbed on the touchstone; and if this proves too deep in colour, a third which has a little paler colour is used. for this will show us how great a proportion of silver or copper, or silver and copper together, is in the gold, or else how great a proportion of copper is in silver. these needles are of four kinds.[ ] the first kind are made of gold and silver, the second of gold and copper, the third of gold, silver, and copper, and the fourth of silver and copper. the first three kinds of needles are used principally for testing gold, and the fourth for silver. needles of this kind are prepared in the following ways. the lesser weights correspond proportionately to the larger weights, and both of them are used, not only by mining people, but by coiners also. the needles are made in accordance with the lesser weights, and each set corresponds to a _bes_, which, in our own vocabulary, is called a _mark_. the _bes_, which is employed by those who coin gold, is divided into twenty-four double _sextulae_, which are now called after the greek name _ceratia_; and each double _sextula_ is divided into four _semi-sextulae_, which are called _granas_; and each _semi-sextula_ is divided into three units of four _siliquae_ each, of which each unit is called a _grenlin_. if we made the needles to be each four _siliquae_, there would be two hundred and eighty-eight in a _bes_, but if each were made to be a _semi-sextula_ or a double _scripula_, then there would be ninety-six in a _bes_. by these two methods too many needles would be made, and the majority of them, by reason of the small difference in the proportion of the gold, would indicate nothing, therefore it is advisable to make them each of a double _sextula_; in this way twenty-four needles are made, of which the first is made of twenty-three _duellae_ of silver and one of gold. fannius is our authority that the ancients called the double _sextula_ a _duella_. when a bar of silver is rubbed on the touchstone and colours it just as this needle does, it contains one _duella_ of gold. in this manner we determine by the other needles what proportion of gold there is, or when the gold exceeds the silver in weight, what proportion of silver. [illustration (touch-needles)] the needles are made[ ]:-- the st needle of _duellae_ of silver and _duella_ of gold. " nd " " " _duellae_ of gold. " rd " " " " " " th " " " " " " th " " " " " " th " " " " " " th " " " " " " th " " " " " " th " " " " " " th " " " " " " th " " " " " " th " " " " " " th " " " " " " th " " " " " " th " " " " " " th " " " " " " th " " " " " " th " " " " " " th " " " " " " th " " " " " " st " " " " " " nd " " " " " " rd " " " " " " th " pure gold by the first eleven needles, when they are rubbed on the touchstone, we test what proportion of gold a bar of silver contains, and with the remaining thirteen we test what proportion of silver is in a bar of gold; and also what proportion of either may be in money. since some gold coins are composed of gold and copper, thirteen needles of another kind are made as follows:-- the st of _duellae_ of gold and _duellae_ of copper. " nd " " " " " " rd " " " " " " th " " " " " " th " " " " " " th " " " " " " th " " " " " " th " " " " " " th " " " " " " th " " " " " " th " " " " " " th " " " " " " th " pure gold. these needles are not much used, because gold coins of that kind are somewhat rare; the ones chiefly used are those in which there is much copper. needles of the third kind, which are composed of gold, silver, and copper, are more largely used, because such gold coins are common. but since with the gold there are mixed equal or unequal portions of silver and copper, two sorts of needles are made. if the proportion of silver and copper is equal, the needles are as follows:-- gold. silver. copper. the st of _duellae_ _duellae_ _sextula_ _duellae_ _sextula_ " nd " " " " " " " rd " " " " " th " " " " " " " th " " " " " th " " " " " " " th " " " " " th " " " " " " " th " " " " " th " " " " " " " th " " " " " th " " " " th " pure gold. some make twenty-five needles, in order to be able to detect the two _scripula_ of silver or copper which are in a _bes_ of gold. of these needles, the first is composed of twelve _duellae_ of gold and six of silver, and the same number of copper. the second, of twelve _duellae_ and one _sextula_ of gold and five _duellae_ and one and a half _sextulae_ of silver, and the same number of _duellae_ and one and a half _sextulae_ of copper. the remaining needles are made in the same proportion. pliny is our authority that the romans could tell to within one _scripulum_ how much gold was in any given alloy, and how much silver or copper. needles may be made in either of two ways, namely, in the ways of which i have spoken, and in the ways of which i am now about to speak. if unequal portions of silver and copper have been mixed with the gold, thirty-seven needles are made in the following way:-- gold. silver. copper. _duellae_. _duellae_ _duellae_ _sextulae_ _sextulae_ _siliquae_. _siliquae_. the st of " nd " " rd " " th " / / " th " / " th " / " th " " th " / " th " - / " th " - / / " th " " th " / - / " th " " th " / " th " / " th " / - / " th " / " th " - / " th " " th " " st " " nd " - / / " rd " / " th " - / " th " " th " / " th " / " th " / - / " th " " th " - / / " st " " nd " / " rd " - / " th " - / / " th " / " th " / " th " pure gold. since it is rarely found that gold, which has been coined, does not amount to at least fifteen _duellae_ gold in a _bes_, some make only twenty-eight needles, and some make them different from those already described, inasmuch as the alloy of gold with silver and copper is sometimes differently proportioned. these needles are made:-- gold. silver. copper. _duellae_. _duellae_ _duellae_ _sextulae_ _sextulae_ _siliquae_. _siliquae_. the st of / " nd " - / " rd " / - / " th " / - / " th " / " th " - / " th " / " th " - / " th " / " th " " th " " th " " th " - / " th " / " th " - / " th " " th " " th " " th " / " th " - / " st " / " nd " / " rd " " th " / " th " - / " th " - / / " th " / " th " pure gold next follows the fourth kind of needles, by which we test silver coins which contain copper, or copper coins which contain silver. the _bes_ by which we weigh the silver is divided in two different ways. it is either divided twelve times, into units of five _drachmae_ and one _scripulum_ each, which the ordinary people call _nummi_[ ]; each of these units we again divide into twenty-four units of four _siliquae_ each, which the same ordinary people call a _grenlin_; or else the _bes_ is divided into sixteen _semunciae_ which are called _loths_, each of which is again divided into eighteen units of four _siliquae_ each, which they call _grenlin_. or else the _bes_ is divided into sixteen _semunciae_, of which each is divided into four _drachmae_, and each _drachma_ into four _pfennige_. needles are made in accordance with each method of dividing the _bes_. according to the first method, to the number of twenty-four half _nummi_; according to the second method, to the number of thirty-one half _semunciae_, that is to say a _sicilicus_; for if the needles were made to the number of the smaller weights, the number of needles would again be too large, and not a few of them, by reason of the small difference in proportion of silver or copper, would have no significance. we test both bars and coined money composed of silver and copper by both scales. the one is as follows: the first needle is made of twenty-three parts of copper and one part silver; whereby, whatsoever bar or coin, when rubbed on the touchstone, colours it just as this needle does, in that bar or money there is one twenty-fourth part of silver, and so also, in accordance with the proportion of silver, is known the remaining proportion of the copper. the st needle is made of parts of copper and of silver. " nd " " " " " " rd " " " " " " th " " " " " " th " " " " " " th " " " " " " th " " " " " " th " " " " " " th " " " " " " th " " " " " " th " " " " " " th " " " " " " th " " " " " " th " " " " " " th " " " " " " th " " " " " " th " " " " " " th " " " " " " th " " " " " " th " " " " " " st " " " " " " nd " " " " " " rd " " " " " " th of pure silver. the other method of making needles is as follows:-- copper. silver. _semunciae_ _sicilici._ _semunciae_ _sicilici._ the st is of " nd " " " rd " " " th " " " th " " " th " " " th " " " th " " " th " " " th " " " th " " " th " " " th " " " th " " " th " " " th " " " th " " " th " " " th " " " th " " " st " " " nd " " " rd " " " th " " " th " " " th " " " th " " " th " " " th " " " th " " " st of pure silver. so much for this. perhaps i have used more words than those most highly skilled in the art may require, but it is necessary for the understanding of these matters. i will now speak of the weights, of which i have frequently made mention. among mining people these are of two kinds, that is, the greater weights and the lesser weights. the _centumpondium_ is the first and largest weight, and of course consists of one hundred _librae_, and for that reason is called a hundred weight. the various weights are:-- st = _librae_ = _centumpondium_. nd = " rd = " th = " th = " th = " th = " th = _libra_. this _libra_ consists of sixteen _unciae_, and the half part of the _libra_ is the _selibra_, which our people call a _mark_, and consists of eight _unciae_, or, as they divide it, of sixteen _semunciae_:-- th = _unciae_. th = _semunciae_. th = " th = " th = _semuncia_. th = _sicilicus_. th = _drachma_. th = _dimidi-drachma_. [illustration (weights for assay balances)] the above is how the "greater" weights are divided. the "lesser" weights are made of silver or brass or copper. of these, the first and largest generally weighs one _drachma_, for it is necessary for us to weigh, not only ore, but also metals to be assayed, and smaller quantities of lead. the first of these weights is called a _centumpondium_ and the number of _librae_ in it corresponds to the larger scale, being likewise one hundred[ ]. the st is called _centumpondium_. " nd " _librae_. " rd " " " th " " " th " " " th " " " th " " " th " " " th " _selibra_. " th " _semunciae_. " th " " " th " " " th " " " th " _sicilicus_. the fourteenth is the last, for the proportionate weights which correspond with a _drachma_ and half a _drachma_ are not used. on all these weights of the lesser scale, are written the numbers of _librae_ and of _semunciae_. some copper assayers divide both the lesser and greater scale weights into divisions of a different scale. their largest weight of the greater scale weighs one hundred and twelve _librae_, which is the first unit of measurement. st = _librae_. nd = " rd = " th = " th = " th = " th = " th = " th = _selibra_ or sixteen _semunciae_. th = _semunciae_. th = " th = " th = " as for the _selibra_ of the lesser weights, which our people, as i have often said, call a _mark_, and the romans call a _bes_, coiners who coin gold, divide it just like the greater weights scale, into twenty-four units of two _sextulae_ each, and each unit of two _sextulae_ is divided into four _semi-sextulae_ and each _semi-sextula_ into three units of four _siliquae_ each. some also divide the separate units of four _siliquae_ into four individual _siliquae_, but most, omitting the _semi-sextulae_, then divide the double _sextula_ into twelve units of four _siliquae_ each, and do not divide these into four individual _siliquae_. thus the first and greatest unit of measurement, which is the _bes_, weighs twenty-four double _sextulae_. the nd = double _sextulae_. " rd = " " " th = " " " th = " " " th = " " " th = _semi-sextulae_ or four _semi-sextulae_. " th = _semi-sextula_ or units of _siliquae_ each. " th = units of four _siliquae_ each. " th = " " " coiners who mint silver also divide the _bes_ of the lesser weights in the same way as the greater weights; our people, indeed, divide it into sixteen _semunciae_, and the _semuncia_ into eighteen units of four _siliquae_ each. there are ten weights which are placed in the other pan of the balance, when they weigh the silver which remains from the copper that has been consumed, when they assay the alloy with fire. the st = _semunciae_ = _bes_. " nd = " " rd = " " th = " " th = " or units of _siliquae_ each. " th = units of _siliquae_ each. " th = " " " th = " " " th = " " " th = " " the coiners of nuremberg who mint silver, divide the _bes_ into sixteen _semunciae_, but divide the _semuncia_ into four _drachmae_, and the _drachma_ into four _pfennige_. they employ nine weights. the st = _semunciae_. " nd = " " rd = " " th = " " th = " for they divide the _bes_ in the same way as our own people, but since they divide the _semuncia_ into four _drachmae_, the th weight = _drachmae_. " th " = _drachma_ or _pfennige_. " th " = _pfennige_. " th " = _pfennig_. the men of cologne and antwerp[ ] divide the _bes_ into twelve units of five _drachmae_ and one _scripulum_, which weights they call _nummi_. each of these they again divide into twenty-four units of four _siliquae_ each, which they call _grenlins_. they have ten weights, of which the st = _nummi_ = _bes_. " nd = " " rd = " " th = " " th = " = units of _siliquae_ each. " th = units of _siliquae_ each. " th = " " " th = " " " th = " " " th = " " and so with them, just as with our own people, the _mark_ is divided into two hundred and eighty-eight _grenlins_, and by the people of nuremberg it is divided into two hundred and fifty-six _pfennige_. lastly, the venetians divide the _bes_ into eight _unciae_. the _uncia_ into four _sicilici_, the _sicilicus_ into thirty-six _siliquae_. they make twelve weights, which they use whenever they wish to assay alloys of silver and copper. of these the st = _unciae_ = _bes_. " nd = " " rd = " " th = " or _sicilici_. " th = _sicilici_. " th = _sicilicus_. " th = _siliquae_. " th = " " th = " " th = " " th = " " th = " since the venetians divide the _bes_ into eleven hundred and fifty-two _siliquae_, or two hundred and eighty-eight units of _siliquae_ each, into which number our people also divide the _bes_, they thus make the same number of _siliquae_, and both agree, even though the venetians divide the _bes_ into smaller divisions. this, then, is the system of weights, both of the greater and the lesser kinds, which metallurgists employ, and likewise the system of the lesser weights which coiners and merchants employ, when they are assaying metals and coined money. the _bes_ of the larger weight with which they provide themselves when they weigh large masses of these things, i have explained in my work _de mensuris et ponderibus_, and in another book, _de precio metallorum et monetis_. [illustration (balances): a--first small balance. b--second. c--third, placed in a case.] there are three small balances by which we weigh ore, metals, and fluxes. the first, by which we weigh lead and fluxes, is the largest among these smaller balances, and when eight _unciae_ (of the greater weights) are placed in one of its pans, and the same number in the other, it sustains no damage. the second is more delicate, and by this we weigh the ore or the metal, which is to be assayed; this is well able to carry one _centumpondium_ of the lesser weights in one pan, and in the other, ore or metal as heavy as that weight. the third is the most delicate, and by this we weigh the beads of gold or silver, which, when the assay is completed, settle in the bottom of the cupel. but if anyone weighs lead in the second balance, or an ore in the third, he will do them much injury. whatsoever small amount of metal is obtained from a _centumpondium_ of the lesser weights of ore or metal alloy, the same greater weight of metal is smelted from a _centumpondium_ of the greater weight of ore or metal alloy. end of book vii. footnotes: [ ] we have but little record of anything which could be called "assaying" among the greeks and romans. the fact, however, that they made constant use of the touchstone (see note , p. ) is sufficient proof that they were able to test the purity of gold and silver. the description of the touchstone by theophrastus contains several references to "trial" by fire (see note , p. ). they were adepts at metal working, and were therefore familiar with melting metals on a small scale, with the smelting of silver, lead, copper, and tin ores (see note , p. ) and with the parting of silver and lead by cupellation. consequently, it would not require much of an imaginative flight to conclude that there existed some system of tests of ore and metal values by fire. apart from the statement of theophrastus referred to, the first references made to anything which might fill the _rôle_ of assaying are from the alchemists, particularly geber (prior to ), for they describe methods of solution, precipitation, distillation, fusing in crucibles, cupellation, and of the parting of gold and silver by acid and by sulphur, antimony, or cementation. however, they were not bent on determining quantitative values, which is the fundamental object of the assayer's art, and all their discussion is shrouded in an obscure cloak of gibberish and attempted mysticism. nevertheless, therein lies the foundation of many cardinal assay methods, and even of chemistry itself. the first explicit records of assaying are the anonymous booklets published in german early in the th century under the title _probierbüchlein_. therein the art is disclosed well advanced toward maturity, so far as concerns gold and silver, with some notes on lead and copper. we refer the reader to appendix b for fuller discussion of these books, but we may repeat here that they are a collection of disconnected recipes lacking in arrangement, the items often repeated, and all apparently the inheritance of wisdom passed from father to son over many generations. it is obviously intended as a sort of reminder to those already skilled in the art, and would be hopeless to a novice. apart from some notes in biringuccio (book iii, chaps. and ) on assaying gold and silver, there is nothing else prior to _de re metallica_. agricola was familiar with these works and includes their material in this chapter. the very great advance which his account represents can only be appreciated by comparison, but the exhaustive publication of other works is foreign to the purpose of these notes. agricola introduces system into the arrangement of his materials, describes implements, and gives a hundred details which are wholly omitted from the previous works, all in a manner which would enable a beginner to learn the art. furthermore, the assaying of lead, copper, tin, quicksilver, iron, and bismuth, is almost wholly new, together with the whole of the argument and explanations. we would call the attention of students of the history of chemistry to the general oversight of these early th century attempts at analytical chemistry, for in them lie the foundations of that science. the statement sometimes made that agricola was the first assayer, is false if for no other reason than that science does not develop with such strides at any one human hand. he can, however, fairly be accounted as the author of the first proper text-book upon assaying. those familiar with the art will be astonished at the small progress made since his time, for in his pages appear most of the reagents and most of the critical operations in the dry analyses of gold, silver, lead, copper, tin, bismuth, quicksilver, and iron of to-day. further, there will be recognised many of the "kinks" of the art used even yet, such as the method of granulation, duplicate assays, the "assay ton" method of weights, the use of test lead, the introduction of charges in leaf lead, and even the use of beer instead of water to damp bone-ash. the following table is given of the substances mentioned requiring some comment, and the terms adopted in this book, with notes for convenience in reference. the german terms are either from agricola's glossary of _de re metallica_, his _interpretatio_, or the german translation. we have retained the original german spelling. the fifth column refers to the page where more ample notes are given:-- terms latin. german. remarks. further adopted. notes. alum _alumen_ _alaun_ either potassium p. or ammonia alum ampulla _ampulla_ _kolb_ a distillation jar antimony _stibium_ _spiesglas_ practically always p. antimony sulphide _aqua valens_ _aqua valens_ _scheidewasser_ mostly nitric acid p. or _aqua_ argol _feces vini _die crude tartar p. siccae_ weinheffen_ ash of lead _nigrum artificial lead p. plumbum sulphide cinereum_ ash of musk ivy _sal ex _salalkali_ mostly potash p. (salt made anthyllidis from) cinere factus_ ashes which _cineres quo mostly potash p. wool-dyers use infectores lanarum utuntur_ assay _venas experiri_ _probiren_ assay furnace _fornacula_ _probir ofen_ "little" furnace azure _caeruleum_ _lasur_ partly copper p. carbonate (azurite) partly silicate bismuth _plumbum _wismut_ _bismuth_ p. cinereum_ bitumen _bitumen_ _bergwachs_ p. blast furnace _prima fornax_ _schmeltzofen_ borax _chrysocolla ex _borras; tincar_ p. nitro confecta; chrysocolla quam boracem nominant_ burned alum _alumen coctum_ _gesottener probably p. alaun_ dehydrated alum _cadmia_ ( ) furnace p. (see note accretions ( ) , p. ) calamine ( ) zinc blende ( ) cobalt arsenical sulphides camphor _camphora_ _campffer_ p. chrysocolla called borax (see borax) chrysocolla _chrysocolla_ _berggrün und partly p. (copper schifergrün_ chrysocolla, mineral) partly malachite copper filings _aeris scobs _kupferfeilich_ apparently finely p. elimata_ divided copper metal copper flowers _aeris flos_ _kupferbraun_ cupric oxide p. copper scales _aeris squamae_ _kupfer probably cupric hammerschlag oxide oder kessel braun_ copper minerals (see note , p. ) crucible _catillus _dreieckicht- see illustration p. (triangular) triangularis_ schirbe_ cupel _catillus _capelle_ cinereus_ cupellation _secunda _treibherd_ furnace fornax_ flux _additamentum_ _zusetze_ p. furnace _cadmia _mitlere und accretions fornacum_ obere offenbrüche_ galena _lapis _glantz_ lead sulphide p. plumbarius_ glass-gall _recrementum _glassgallen_ skimmings from p. vitri_ glass melting grey antimony or _stibi_ or _spiesglas_ antimony sulphide, p. stibium _stibium_ stibnite hearth-lead _molybdaena_ _herdplei_ the saturated p. furnace bottoms from cupellation hoop (iron) _circulus _ring_ a forge for p. ferreus_ crucibles iron filings _ferri scobs _eisen feilich_ metallic iron elimata_ iron scales _squamae ferri_ _eisen partly iron oxide hammerschlag_ iron slag _recrementum _sinder_ ferri_ lead ash _cinis plumbi _pleiasche_ artificial lead p. nigri_ sulphide lead granules _globuli _gekornt plei_ granulated lead plumbei_ lead ochre _ochra _pleigeel_ modern massicot p. plumbaria_ (pbo) lees of _aqua_ _feces aquarum _scheidewasser uncertain p. which separates quae aurum ab heffe_ gold from argento silver secernunt_ dried lees of _siccae feces _heffe des argol p. vinegar aceti_ essigs_ dried lees of _feces vini _wein heffen_ argol p. wine siccae_ limestone _saxum calcis_ _kalchstein_ litharge _spuma argenti_ _glette_ lye _lixivium_ _lauge durch mostly potash p. asschen gemacht_ muffle _tegula_ _muffel_ latin, literally "roof-tile" operculum _operculum_ _helm oder helmet or cover alembick_ for a distillation jar orpiment _auripigmentum_ _operment_ yellow sulphide p. of arsenic (as_{ }s_{ }) pyrites _pyrites_ _kis_ rather a genus p. of sulphides, than iron pyrite in particular pyrites (cakes _panes ex _stein_ iron or copper p. from) pyrite matte conflati_ realgar _sandaraca_ _rosgeel_ red sulphide of p. arsenic (ass) red lead _minium_ _menning_ pb_{ }o_{ } p. roasted copper _aes ustum_ _gebrandt artificial p. kupffer_ copper sulphide (?) salt _sal_ _saltz_ nacl p. salt (rock) _sal fossilis_ _berg saltz_ nacl p. _sal _sal a stock flux? p. artificiosus_ artificiosus_ sal ammoniac _sal _salarmoniac_ nh_{ }cl p. ammoniacus_ saltpetre _halinitrum_ _salpeter_ kno_{ } p. salt (refined) _sal facticius nacl purgatus_ _sal tostus_ _sal tostus_ _geröst saltz_ apparently p. simply heated or melted common salt _sal _sal _geröst saltz_ p. torrefactus_ torrefactus_ salt (melted) _sal _geflossen melted salt or p. liquefactus_ saltz_ salt glass scorifier _catillus _scherbe_ fictilis_ schist _saxum fissile_ _schifer_ silver minerals (see note , p. ) slag _recrementum_ _schlacken_ soda _nitrum_ mostly soda from p. egypt, na_{ }co_{ } stones which _lapides qui _flüs_ quartz and p. easily melt facile igni fluorspar liquescunt_ sulphur _sulfur_ _schwefel_ p. _tophus_ _tophus_ _topstein_ marl(?) p. touchstone _coticula_ _goldstein_ venetian glass _venetianum vitrum_ verdigris _aerugo _grünspan_ copper p. oder sub-acetate spanschgrün_ vitriol _atramentum _kupferwasser_ mostly feso_{ } p. sutorium_ white schist _saxum fissile _weisser p. album_ schifer_ weights (see appendix). [ ] _crudorum_,--unbaked? [ ] this reference is not very clear. apparently the names refer to the german terms _probier ofen_ and _windt ofen_. [ ] _circulus_. this term does not offer a very satisfactory equivalent, as such a furnace has no distinctive name in english. it is obviously a sort of forge for fusing in crucibles. [ ] _spissa_,--"dry." this term is used in contra-distinction to _pingue_, unctuous or "fatty." [ ] _additamenta_,--"additions." hence the play on words. we have adopted "flux" because the old english equivalent for all these materials was "flux," although in modern nomenclature the term is generally restricted to those substances which, by chemical combination in the furnace, lower the melting point of some of the charge. the "additions" of agricola, therefore, include reducing, oxidizing, sulphurizing, desulphurizing, and collecting agents as well as fluxes. a critical examination of the fluxes mentioned in the next four pages gives point to the author's assertion that "some are of a very complicated nature." however, anyone of experience with home-taught assayers has come in contact with equally extraordinary combinations. the four orders of "additions" enumerated are quite impossible to reconcile from a modern metallurgical point of view. [ ] _minium secundarium_. (_interpretatio_,--_menning_. pb_{ }o_{ }). agricola derived his latin term from pliny. there is great confusion in the ancient writers on the use of the word _minium_, for prior to the middle ages it was usually applied to vermilion derived from cinnabar. vermilion was much adulterated with red-lead, even in roman times, and finally in later centuries the name came to be appropriated to the lead product. theophrastus ( ) mentions a substitute for vermilion, but, in spite of commentators, there is no evidence that it was red-lead. the first to describe the manufacture of real red-lead was apparently vitruvius (vii, ), who calls it _sandaraca_ (this name was usually applied to red arsenical sulphide), and says: "white-lead is heated in a furnace and by the force of the fire becomes red lead. this invention was the result of observation in the case of an accidental fire, and by the process a much better material is obtained than from the mines." he describes _minium_ as the product from cinnabar. dioscorides (v, ), after discussing white-lead, says it may be burned until it becomes the colour of _sandaracha_, and is called _sandyx_. he also states (v, ) that those are deceived who consider cinnabar to be the same as _minium_, for _minium_ is made in spain out of stone mixed with silver sands. therefore he is not in agreement with vitruvius and pliny on the use of the term. pliny (xxxiii, ) says: "these barren stones (apparently lead ores barren of silver) may be recognised by their colour; it is only in the furnace that they turn red. after being roasted it is pulverized and is _minium secundarium_. it is known to few and is very inferior to the natural kind made from those sands we have mentioned (_cinnabar_). it is with this that the genuine _minium_ is adulterated in the works of the company." this proprietary company who held a monopoly of the spanish quicksilver mines, "had many methods of adulterating it (_minium_)--a source of great plunder to the company." pliny also describes the making of red lead from white. [ ] _ochra plumbaria_. (_interpretatio_,--_pleigeel_; modern german,--_bleigelb_). the german term indicates that this "lead ochre," a form of pbo, is what in the english trade is known as _massicot_, or _masticot_. this material can be a partial product from almost any cupellation where oxidation takes place below the melting point of the oxide. it may have been known to the ancients among the various species into which they divided litharge, but there is no valid reason for assigning to it any special one of their terms, so far as we can see. [ ] there are four forms of copper named as re-agents by agricola: copper filings _aeris scobs elimata._ copper scales _aeris squamae._ copper flowers _aeris flos._ roasted copper _aes ustum._ the first of these was no doubt finely divided copper metal; the second, third, and fourth were probably all cupric oxide. according to agricola (_de nat. fos._, p. ), the scales were the result of hammering the metal; the flowers came off the metal when hot bars were quenched in water, and a third kind were obtained from calcining the metal. "both flowers (_flos_) and hammer-scales (_squama_) have the same properties as _crematum_ copper.... the particles of flower copper are finer than scales or _crematum_ copper." if we assume that the verb _uro_ used in _de re metallica_ is of the same import as _cremo_ in the _de natura fossilium_, we can accept this material as being merely cupric oxide, but the _aes ustum_ of pliny--agricola's usual source of technical nomenclature--is probably an artificial sulphide. dioscorides (v, ), who is apparently the source of pliny's information, says:--"of _chalcos cecaumenos_, the best is red, and pulverized resembles the colour of cinnabar; if it turns black, it is over-burnt. it is made from broken ship nails put into a rough earthen pot, with alternate layers of equal parts of sulphur and salt. the opening should be smeared with potter's clay and the pot put in the furnace until it is thoroughly heated," etc. pliny (xxxiv, ) states: "moreover cyprian copper is roasted in crude earthen pots with an equal amount of sulphur; the apertures of the pots are well luted, and they are kept in the furnace until the pot is thoroughly heated. some add salt, others use _alumen_ instead of sulphur, others add nothing, but only sprinkle it with vinegar." [ ] the reader is referred to note , p. , for more ample discussion of the alkalis. agricola gives in this chapter four substances of that character: soda (_nitrum_). lye. "ashes which wool-dyers use." "salt made from the ashes of musk ivy." the last three are certainly potash, probably impure. while the first might be either potash or soda, the fact that the last three are mentioned separately, together with other evidence, convinces us that by the first is intended the _nitrum_ so generally imported into europe from egypt during the middle ages. this imported salt was certainly the natural bicarbonate, and we have, therefore, used the term "soda." [ ] in this chapter are mentioned seven kinds of common salt: salt _sal._ rock salt _sal fossilis._ "made" salt _sal facticius._ refined salt _sal purgatius._ melted salt _sal liquefactus._ and in addition _sal tostus_ and _sal torrefactus_. _sal facticius_ is used in distinction from rock-salt. the melted salt would apparently be salt-glass. what form the _sal tostus_ and _sal torrefactus_ could have we cannot say, however, but they were possibly some form of heated salt; they may have been combinations after the order of _sal artificiosus_ (see p. ). [ ] "stones which easily melt in hot furnaces and sand which is made from them" (_lapides qui in ardentibus fornacibus facile liquescunt arenae ab eis resolutae_). these were probably quartz in this instance, although fluorspar is also included in this same genus. for fuller discussion see note on p. . [ ] _tophus_. (_interpretatio_, _toffstein oder topstein_). according to dana (syst. of min., p. ), the german _topfstein_ was english potstone or soapstone, a magnesian silicate. it is scarcely possible, however, that this is what agricola meant by this term, for such a substance would be highly infusible. agricola has a good deal to say about this mineral in _de natura fossilium_ (p. and ), and from these descriptions it would seem to be a tufaceous limestone of various sorts, embracing some marls, stalagmites, calcareous sinter, etc. he states: "generally fire does not melt it, but makes it harder and breaks it into powder. tophus is said to be a stone found in caverns, made from the dripping of stone juice solidified by cold ... sometimes it is found containing many shells, and likewise the impressions of alder leaves; our people make lime by burning it." pliny, upon whom agricola depends largely for his nomenclature, mentions such a substance (xxxvi, ): "among the multitude of stones there is _tophus_. it is unsuitable for buildings, because it is perishable and soft. still, however, there are some places which have no other, as carthage, in africa. it is eaten away by the emanations from the sea, crumbled to dust by the wind, and washed away by the rain." in fact, _tophus_ was a wide genus among the older mineralogists, wallerius (_meditationes physico-chemicae de origine mundi_, stockholm, , p. ), for instance, gives varieties. for the purposes for which it is used we believe it was always limestone of some form. [ ] _saxum fissile album._ (_the interpretatio_ gives the german as _schifer_). agricola mentions it in _bermannus_ ( ), in _de natura fossilium_ (p. ), but nothing definite can be derived from these references. it appears to us from its use to have been either a quartzite or a fissile limestone. [ ] argol (_feces vini siccae_,--"dried lees of wine." germ. trans. gives _die wein heffen_, although the usual german term of the period was _weinstein_). the lees of wine were the crude tartar or argols of commerce and modern assayers. the argols of white wine are white, while they are red from red wine. the white argol which agricola so often specifies would have no special excellence, unless it may be that it is less easily adulterated. agricola (_de nat. fos._, p. ) uses the expression "_fex vini sicca_ called _tartarum_"--one of the earliest appearances of the latter term in this connection. the use of argol is very old, for dioscorides ( st century a.d.) not only describes argol, but also its reduction to impure potash. he says (v, ): "the lees (_tryx_) are to be selected from old italian wine; if not, from other similar wine. lees of vinegar are much stronger. they are carefully dried and then burnt. there are some who burn them in a new earthen pot on a large fire until they are thoroughly incinerated. others place a quantity of the lees on live coals and pursue the same method. the test as to whether it is completely burned, is that it becomes white or blue, and seems to burn the tongue when touched. the method of burning lees of vinegar is the same.... it should be used fresh, as it quickly grows stale; it should be placed in a vessel in a secluded place." pliny (xxiii, ) says: "following these, come the lees of these various liquids. the lees of wine (_vini faecibus_) are so powerful as to be fatal to persons on descending into the vats. the test for this is to let down a lamp, which, if extinguished, indicates the peril.... their virtues are greatly increased by the action of fire." matthioli, commenting on this passage from dioscorides in , makes the following remark (p. ): "the precipitate of the wine which settles in the casks of the winery forms stone-like crusts, and is called by the works-people by the name _tartarum_." it will be seen above that these lees were rendered stronger by the action of fire, in which case the tartar was reduced to potassium carbonate. the _weinstein_ of the old german metallurgists was often the material lixiviated from the incinerated tartar. dried lees of vinegar (_siccae feces aceti_; _interpretatio_, _die heffe des essigs_). this would also be crude tartar. pliny (xxiii, ) says: "the lees of vinegar (_faex aceti_); owing to the more acrid material are more aggravating in their effects.... when combined with _melanthium_ it heals the bites of dogs and crocodiles." [ ] dried lees of _aqua_ which separates gold and silver. (_siccae feces aquarum quae aurum ab argento secernunt_. german translation, _der scheidwasser heffe_). there is no pointed description in agricola's works, or in any other that we can find, as to what this material was. the "separating _aqua_" was undoubtedly nitric acid (see p. , book x). there are two precipitates possible, both referred to as _feces_,--the first, a precipitate of silver chloride from clarifying the _aqua valens_, and the second, the residues left in making the acid by distillation. it is difficult to believe that silver chloride was the _feces_ referred to in the text, because such a precipitate would be obviously misleading when used as a flux through the addition of silver to the assays, too expensive, and of no merit for this purpose. therefore one is driven to the conclusion that the _feces_ must have been the residues left in the retorts when nitric acid was prepared. it would have been more in keeping with his usual mode of expression, however, to have referred to this material as a _residuus_. the materials used for making acid varied greatly, so there is no telling what such a _feces_ contained. a list of possibilities is given in note , p. . in the main, the residue would be undigested vitriol, alum, saltpetre, salt, etc., together with potassium, iron, and alum sulphates. the _probierbüchlin_ (p. ) also gives this re-agent under the term _toden kopff das ist schlam oder feces auss dem scheydwasser_. [ ] _recrementum vitri_. (_interpretatio_, _glassgallen_). formerly, when more impure materials were employed than nowadays, the surface of the mass in the first melting of glass materials was covered with salts, mostly potassium and sodium sulphates and chlorides which escaped perfect vitrification. this "slag" or "_glassgallen_" of agricola was also termed _sandiver_. [ ] the whole of this expression is "_candidus, candido_." it is by no means certain that this is tin, for usually tin is given as _plumbum candidum_. [ ] _sal artificiosus_. these are a sort of stock fluxes. such mixtures are common in all old assay books, from the _probierbüchlin_ to later than john cramer in (whose latin lectures on assaying were published in english under the title of "elements of the art of assaying metals," london, ). cramer observes (p. ) that: "artificers compose a great many fluxes with the above-mentioned salts and with the reductive ones; nay, some use as many different fluxes as there are different ores and metals; all which, however, we think needless to describe. it is better to have explained a few of the simpler ones, which serve for all the others, and are very easily prepared, than to tire the reader with confused compositions: and this chiefly because unskilled artificers sometimes attempt to obtain with many ingredients of the same nature heaped up beyond measure, and with much labour, though not more properly and more securely, what might have been easily effected, with one only and the same ingredient, thus increasing the number, not at all the virtue of the things employed. nevertheless, if anyone loves variety, he may, according to the proportions and cautions above prescribed, at his will chuse among the simpler kinds such as will best suit his purpose, and compose a variety of fluxes with them." [ ] this operation apparently results in a coating to prevent the deflagration of the saltpetre--in fact, it might be permitted to translate _inflammatur_ "deflagrate," instead of kindle. [ ] the results which would follow from the use of these "fluxes" would obviously depend upon the ore treated. they can all conceivably be successful. of these, the first is the lead-glass of the german assayers--a flux much emphasized by all old authorities, including lohneys, ercker and cramner, and used even yet. the "powerful flux" would be a reducing, desulphurizing, and an acid flux. the "more powerful" would be a basic flux in which the reducing action of the argols would be largely neutralised by the nitre. the "still more powerful" would be a strongly sulphurizing basic flux, while the "most powerful" would be a still more sulphurizing flux, but it is badly mixed as to its oxidation and basic properties. (see also note on _sal artificiosus_). [ ] lead ash (_cinis plumbi_. glossary, _pleyasch_).--this was obviously, from the method of making, an artificial lead sulphide. [ ] ashes of lead (_nigri plumbi cinis_). this, as well as lead ash, was also an artificial lead sulphide. such substances were highly valued by the ancients for medicinal purposes. dioscorides (v, ) says: "burned lead (_molybdos cecaumenos_) is made in this way: sprinkle sulphur over some very thinnest lead plates and put them into a new earthen pot, add other layers, putting sulphur between each layer until the pot is full; set it alight and stir the melted lead with an iron rod until it is entirely reduced to ashes and until none of the lead remains unburned. then take it off, first stopping up your nose, because the fumes of burnt lead are very injurious. or burn the lead filings in a pot with sulphur as aforesaid." pliny (xxxiv., ) gives much the same directions. [ ] camphor (_camphora_). this was no doubt the well-known gum. agricola, however, believed that camphor (_de nat. fossilium_, p. ) was a species of bitumen, and he devotes considerable trouble to the refutation of the statements by the arabic authors that it was a gum. in any event, it would be a useful reducing agent. [ ] inasmuch as orpiment and realgar are both arsenical sulphides, the use of iron "slag," if it contains enough iron, would certainly matte the sulphur and arsenic. sulphur and arsenic are the "juices" referred to (see note , p. ). it is difficult to see the object of preserving the antimony with such a sulphurizing "addition," unless it was desired to secure a regulus of antimony alone from a given antimonial ore. [ ] the lead free from silver, called _villacense_, was probably from bleyberg, not far from villach in upper austria, this locality having been for centuries celebrated for its pure lead. these mines were worked prior to, and long after, agricola's time. [ ] this method of proportionate weights for assay charges is simpler than the modern english "assay ton," both because of the use of units in the standard of weight (the _centumpondium_), and because of the lack of complication between the avoirdupois and troy scales. for instance, an ore containing a _libra_ of silver to the _centumpondium_ would contain / th part, and the same ratio would obtain, no matter what the actual weight of a _centumpondium_ of the "lesser weight" might be. to follow the matter still further, an _uncia_ being / , of a _centumpondium_, if the ore ran one "_uncia_ of the lesser weight" to the "_centumpondium_ of the lesser weight," it would also run one actual _uncia_ to the actual _centumpondium_; it being a matter of indifference what might be the actual weight of the _centumpondium_ upon which the scale of lesser weights is based. in fact agricola's statement (p. ) indicates that it weighed an actual _drachma_. we have, in some places, interpolated the expressions "lesser" and "greater" weights for clarity. this is not the first mention of this scheme of lesser weights, as it appears in the _probierbüchlein_ ( ? see appendix b) and biringuccio ( ). for a more complete discussion of weights and measures see appendix c. for convenience, we repeat here the roman scale, although, as will be seen in the appendix, agricola used the latin terms in many places merely as nomenclature equivalents of the old german scale. ozs. dwts. troy gr. grains. per short ton. _siliqua_ . per _centumpondium_ _siliquae_ = _scripulum_ . " " _scripula_ = _sextula_ . " " _sextulae_ = _uncia_ . " " _unciae_ = _libra_ . " " _librae_ = _centumpondium_ . however agricola may occasionally use _unciae_ = _libra_ . (?) _librae_ = _centumpondium_ . (?) also oz. dwts. gr. per short ton. _scripulum_ . per _centumpondium_ _scripula_ = _drachma_ . " " _drachmae_ = _sicilicus_ . " " _sicilici_ = _uncia_ . " " _unciae_ = _bes_ . " " [ ] the amalgamation of gold ores is fully discussed in note , p. . [ ] for discussion of the silver ores, see note , p. . _rudis_ silver was a fairly pure silver mineral, the various coloured silvers were partly horn-silver and partly alteration products. [ ] it is difficult to see why copper scales (_squamae aeris_--copper oxide?) are added, unless it be to collect a small ratio of copper in the ore. this additional copper is not mentioned again, however. the whole of this statement is very confused. [ ] this old story runs that hiero, king of syracuse, asked archimedes to tell him whether a crown made for him was pure gold or whether it contained some proportion of silver. archimedes is said to have puzzled over it until he noticed the increase in water-level upon entering his bath. whereupon he determined the matter by immersing bars of pure gold and pure silver, and thus determining the relative specific weights. the best ancient account of this affair is to be found in vitruvius, ix, preface. the story does not seem very probable, seeing that theophrastus, who died the year archimedes was born, described the touchstone in detail, and that it was of common knowledge among the greeks before (see note ). in any event, there is not sufficient evidence in this story on which to build the conclusion of meyer (hist. of chemistry, p. ) and others, that, inasmuch as archimedes was unable to solve the problem until his discovery of specific weights, therefore the ancients could not part gold and silver. the probability that he did not want to injure the king's jewellery would show sufficient reason for his not parting these metals. it seems probable that the ancients did part gold and silver by cementation. (see note on p. ). [ ] the alchemists (with whose works agricola was familiar--_vide_ preface) were the inventors of nitric acid separation. (see note on p. ). [ ] parting gold and silver by nitric acid is more exhaustively discussed in book x. and note , p. . [ ] the lesser weights, probably. [ ] lead and tin seem badly mixed in this paragraph. [ ] it is not clear what is added. [ ] historical note on touchstone. (_coticula_. _interpretatio_,--_goldstein_). theophrastus is, we believe, the first to describe the touchstone, although it was generally known to the greeks, as is evidenced by the metaphors of many of the poets,--pindar, theognis, euripides, etc. the general knowledge of the constituents of alloys which is implied, raises the question as to whether the greeks did not know a great deal more about parting metals, than has been attributed to them. theophrastus says ( - ): "the nature of the stone which tries gold is also very wonderful, as it seems to have the same power with fire; which is also a test of that metal. some people have for this reason questioned the truth of this power in the stone, but their doubts are ill-founded, for this trial is not of the same nature or made in the same manner as the other. the trial by fire is by the colour and by the quantity lost by it; but that by the stone is made only by rubbing the metal on it; the stone seeming to have the power to receive separately the distinct particles of different metals. it is said also that there is a much better kind of this stone now found out, than that which was formerly used; insomuch that it now serves not only for the trial of refined gold, but also of copper or silver coloured with gold; and shows how much of the adulterating matter by weight is mixed with gold; this has signs which it yields from the smallest weight of the adulterating matter, which is a grain, from thence a colybus, and thence a quadrans or semi-obolus, by which it is easy to distinguish if, and in what degree, that metal is adulterated. all these stones are found in the river tmolus; their texture is smooth and like that of pebbles; their figure broad, not round; and their bigness twice that of the common larger sort of pebbles. in their use in the trial of metals there is a difference in power between their upper surface, which has lain toward the sun, and their under, which has been to the earth; the upper performing its office the more nicely; and this is consonant to reason, as the upper part is dryer; for the humidity of the other surface hinders its receiving so well the particles of metals; for the same reason also it does not perform its office as well in hot weather as in colder, for in the hot it emits a kind of humidity out of its substance, which runs all over it. this hinders the metalline particles from adhering perfectly, and makes mistakes in the trials. this exudation of a humid matter is also common to many other stones, among others, to those of which statues are made; and this has been looked on as peculiar to the statue." (based on hill's trans.) this humid "exudation of fine-grained stones in summer" would not sound abnormal if it were called condensation. pliny (xxxiii, ) says: "the mention of gold and silver should be accompanied by that of the stone called _coticula_. formerly, according to theophrastus, it was only to be found in the river tmolus but now found in many parts, it was found in small pieces never over four inches long by two broad. that side which lay toward the sun is better than that toward the ground. those experienced with the _coticula_ when they rub ore (_vena_) with it, can at once say how much gold it contains, how much silver or copper. this method is so accurate that they do not mistake it to a scruple." this purported use for determining values of _ore_ is of about pliny's average accuracy. the first detailed account of touch-needles and their manner of making, which we have been able to find, is that of the _probierbüchlein_ ( ? see appendix) where many of the tables given by agricola may be found. [ ] _de natura fossilium_ (p. ) and _de ortu et causis subterraneorum_ (p. ). the author does not add any material mineralogical information to the quotations from theophrastus and pliny given above. [ ] in these tables agricola has simply adopted roman names as equivalents of the old german weights, but as they did not always approximate in proportions, he coined terms such as "units of _siliquae_," etc. it might seem more desirable to have introduced the german terms into this text, but while it would apply in this instance, as we have discussed on p. , the actual values of the roman weights are very different from the german, and as elsewhere in the book actual roman weights are applied, we have considered it better to use the latin terms consistently throughout. further, the obsolete german would be to most readers but little improvement upon the latin. for convenience of readers we set out the various scales as used by agricola, together with the german:-- roman scale. old german scale. _siliquae_ = _scripulum_ _grenlin_ = _gran_ _scripula_ = _sextula_ _gran_ = _krat_ _sextulae_ = _duella_ _kratt_ = _mark_ _duellae_ = _bes_ or _grenlin_ = "_nummus_" "_nummi_" = _mark_ also the following scales are applied to fineness by agricola:-- _scripula_ = _drachma_ _pfennige_ = _quintlein_ _drachmae_ = _sicilicus_ _quintlein_ = _loth_ _sicilici_ = _semuncia_ _loth_ = _mark_ _semunciae_ = _bes_ the term "_nummus_," a coin, given above and in the text, appears in the german translation as _pfennig_ as applied to both german scales, but as they are of different values, we have left agricola's adaptation in one scale to avoid confusion. the latin terms adopted by agricola are given below, together with the german:-- number in one value in roman term. german term. mark or bes. _siliquae_. _siliqua_ "unit of _siliquae_" _grenlin_ _pfennig_ -- _scripulum_ _scruple_ (?) _semi-sextula_ _gran_ _drachma_ _quintlein_ _sextula_ _halb krat_ _sicilicus_ _halb loth_ _duella_ _krat_ _semuncia_ _loth_ "_unit of drachmae "_nummus_" & scripulum_" _uncia_ _untzen_ _bes_ _mark_ while the proportions in a _bes_ or _mark_ are the same in both scales, the actual weight values are vastly different--for instance, the _mark_ contained about . , and the _bes_ troy grains. agricola also uses: _selibra_ _halb-pfundt_ _libra_ _pfundt_ _centumpondium_ _centner_. as the roman _libra_ contains _unciae_ and the german _pfundt_ _untzen_, the actual weights of these latter quantities are still further apart--the former and the latter troy grains. [ ] there are no tables in the latin text, the whole having been written out _in extenso_, but they have now been arranged as above, as being in a much more convenient and expressive form. [ ] see note above. [ ] see note , p. , for discussion of this "assay ton" arrangement. [ ] _agrippinenses_ and _antuerpiani_. book viii. questions of assaying were explained in the last book, and i have now come to a greater task, that is, to the description of how we extract the metals. first of all i will explain the method of preparing the ore[ ]; for since nature usually creates metals in an impure state, mixed with earth, stones, and solidified juices, it is necessary to separate most of these impurities from the ores as far as can be, before they are smelted, and therefore i will now describe the methods by which the ores are sorted, broken with hammers, burnt, crushed with stamps, ground into powder, sifted, washed, roasted, and calcined[ ]. i will start at the beginning with the first sort of work. experienced miners, when they dig the ore, sort the metalliferous material from earth, stones, and solidified juices before it is taken from the shafts and tunnels, and they put the valuable metal in trays and the waste into buckets. but if some miner who is inexperienced in mining matters has omitted to do this, or even if some experienced miner, compelled by some unavoidable necessity, has been unable to do so, as soon as the material which has been dug out has been removed from the mine, all of it should be examined, and that part of the ore which is rich in metal sorted from that part of it which is devoid of metal, whether such part be earth, or solidified juices, or stones. to smelt waste together with an ore involves a loss, for some expenditure is thrown away, seeing that out of earth and stones only empty and useless slags are melted out, and further, the solidified juices also impede the smelting of the metals and cause loss. the rock which lies contiguous to rich ore should also be broken into small pieces, crushed, and washed, lest any of the mineral should be lost. when, either through ignorance or carelessness, the miners while excavating have mixed the ore with earth or broken rock, the work of sorting the crude metal or the best ore is done not only by men, but also by boys and women. they throw the mixed material upon a long table, beside which they sit for almost the whole day, and they sort out the ore; when it has been sorted out, they collect it in trays, and when collected they throw it into tubs, which are carried to the works in which the ores are smelted. [illustration (sorting ore): a--long table. b--tray. c--tub.] [illustration (cutting metal): a--masses of metal. b--hammer. c--chisel. d--tree stumps. e--iron tool similar to a pair of shears.] the metal which is dug out in a pure or crude state, to which class belong native silver, silver glance, and gray silver, is placed on a stone by the mine foreman and flattened out by pounding with heavy square hammers. these masses, when they have been thus flattened out like plates, are placed either on the stump of a tree, and cut into pieces by pounding an iron chisel into them with a hammer, or else they are cut with an iron tool similar to a pair of shears. one blade of these shears is three feet long, and is firmly fixed in a stump, and the other blade which cuts the metal is six feet long. these pieces of metal are afterward heated in iron basins and smelted in the cupellation furnace by the smelters. [illustration (spalling ore): a--tables. b--upright planks. c--hammer. d--quadrangular hammer. e--deeper vessel. f--shallower vessel. g--iron rod.] although the miners, in the shafts or tunnels, have sorted over the material which they mine, still the ore which has been broken down and carried out must be broken into pieces by a hammer or minutely crushed, so that the more valuable and better parts can be distinguished from the inferior and worthless portions. this is of the greatest importance in smelting ore, for if the ore is smelted without this separation, the valuable part frequently receives great damage before the worthless part melts in the fire, or else the one consumes the other; this latter difficulty can, however, be partly avoided by the exercise of care and partly by the use of fluxes. now, if a vein is of poor quality, the better portions which have been broken down and carried out should be thrown together in one place, and the inferior portion and the rock thrown away. the sorters place a hard broad stone on a table; the tables are generally four feet square and made of joined planks, and to the edge of the sides and back are fixed upright planks, which rise about a foot from the table; the front, where the sorter sits, is left open. the lumps of ore, rich in gold or silver, are put by the sorters on the stone and broken up with a broad, but not thick, hammer; they either break them into pieces and throw them into one vessel, or they break and sort--whence they get their name--the more precious from the worthless, throwing and collecting them separately into different vessels. other men crush the lumps of ore less rich in gold or silver, which have likewise been put on the stone, with a broad thick hammer, and when it has been well crushed, they collect it and throw it into one vessel. there are two kinds of vessels; one is deeper, and a little wider in the centre than at the top or bottom; the other is not so deep though it is broader at the bottom, and becomes gradually a little narrower toward the top. the latter vessel is covered with a lid, while the former is not covered; an iron rod through the handles, bent over on either end, is grasped in the hand when the vessel is carried. but, above all, it behooves the sorters to be assiduous in their labours. [illustration (spalling ore): a--pyrites. b--leggings. c--gloves. d--hammer.] by another method of breaking ore with hammers, large hard fragments of ore are broken before they are burned. the legs of the workmen--at all events of those who crush pyrites in this manner with large hammers in goslar--are protected with coverings resembling leggings, and their hands are protected with long gloves, to prevent them from being injured by the chips which fly away from the fragments. [illustration (spalling ore): a--area paved with stones. b--broken ore. c--area covered with broken ore. d--iron tool. e--its handle. f--broom. g--short strake. h--wooden hoe.] in that district of greater germany which is called westphalia and in that district of lower germany which is named eifel, the broken ore which has been burned, is thrown by the workmen into a round area paved with the hardest stones, and the fragments are pounded up with iron tools, which are very much like hammers in shape and are used like threshing sledges. this tool is a foot long, a palm wide, and a digit thick, and has an opening in the middle just as hammers have, in which is fixed a wooden handle of no great thickness, but up to three and a half feet long, in order that the workmen can pound the ore with greater force by reason of its weight falling from a greater height. they strike and pound with the broad side of the tool, in the same way as corn is pounded out on a threshing floor with the threshing sledges, although the latter are made of wood and are smooth and fixed to poles. when the ore has been broken into small pieces, they sweep it together with brooms and remove it to the works, where it is washed in a short strake, at the head of which stands the washer, who draws the water upward with a wooden hoe. the water running down again, carries all the light particles into a trough placed underneath. i shall deal more fully with this method of washing a little later. ore is burned for two reasons; either that from being hard, it may become soft and more easily broken and more readily crushed with a hammer or stamps, and then can be smelted; or that the fatty things, that is to say, sulphur, bitumen, orpiment, or realgar[ ] may be consumed. sulphur is frequently found in metallic ores, and, generally speaking, is more harmful to the metals, except gold, than are the other things. it is most harmful of all to iron, and less to tin than to bismuth, lead, silver, or copper. since very rarely gold is found in which there is not some silver, even gold ores containing sulphur ought to be roasted before they are smelted, because, in a very vigorous furnace fire, sulphur resolves metal into ashes and makes slag of it. bitumen acts in the same way, in fact sometimes it consumes silver, which we may see in bituminous _cadmia_[ ]. [illustration (stall roasting ore): a--area. b--wood. c--ore. d--cone-shaped piles. e--canal.] i now come to the methods of roasting, and first of all to that one which is common to all ores. the earth is dug out to the required extent, and thus is made a quadrangular area of fair size, open at the front, and above this, firewood is laid close together, and on it other wood is laid transversely, likewise close together, for which reason our countrymen call this pile of wood a crate; this is repeated until the pile attains a height of one or two cubits. then there is placed upon it a quantity of ore that has been broken into small pieces with a hammer; first the largest of these pieces, next those of medium size, and lastly the smallest, and thus is built up a gently sloping cone. to prevent it from becoming scattered, fine sand of the same ore is soaked with water and smeared over it and beaten on with shovels; some workers, if they cannot obtain such fine sand, cover the pile with charcoal-dust, just as do charcoal-burners. but at goslar, the pile, when it has been built up in the form of a cone, is smeared with _atramentum sutorium rubrum_[ ], which is made by the leaching of roasted pyrites soaked with water. in some districts the ore is roasted once, in others twice, in others three times, as its hardness may require. at goslar, when pyrites is roasted for the third time, that which is placed on the top of the pyre exudes a certain greenish, dry, rough, thin substance, as i have elsewhere written[ ]; this is no more easily burned by the fire than is asbestos. very often also, water is put on to the ore which has been roasted, while it is still hot, in order to make it softer and more easily broken; for after fire has dried up the moisture in the ore, it breaks up more easily while it is still hot, of which fact burnt limestone affords the best example. [illustration (heap roasting ore): a--lighted pyre. b--pyre which is being constructed. c--ore. d--wood. e--pile of the same wood.] by digging out the earth they make the areas much larger, and square; walls should be built along the sides and back to hold the heat of the fire more effectively, and the front should be left open. in these compartments tin ore is roasted in the following manner. first of all wood about twelve feet long should be laid in the area in four layers, alternately straight and transverse. then the larger pieces of ore should be laid upon them, and on these again the smaller ones, which should also be placed around the sides; the fine sand of the same ore should also be spread over the pile and pounded with shovels, to prevent the pile from falling before it has been roasted; the wood should then be fired. [illustration (stall roasting ore): a--burning pyre which is composed of lead ore with wood placed above it. b--workman throwing ore into another area. c--oven-shaped furnace. d--openings through which the smoke escapes.] lead ore, if roasting is necessary, should be piled in an area just like the last, but sloping, and the wood should be placed over it. a tree trunk should be laid right across the front of the ore to prevent it from falling out. the ore, being roasted in this way, becomes partly melted and resembles slag. thuringian pyrites, in which there is gold, sulphur, and vitriol, after the last particle of vitriol has been obtained by heating it in water, is thrown into a furnace, in which logs are placed. this furnace is very similar to an oven in shape, in order that when the ore is roasted the valuable contents may not fly away with the smoke, but may adhere to the roof of the furnace. in this way sulphur very often hangs like icicles from the two openings of the roof through which the smoke escapes. [illustration (hearths for roasting): a--iron plates full of holes. b--walls. c--plate on which ore is placed. d--burning charcoal placed on the ore. e--pots. f--furnace. g--middle part of upper chamber. h--the other two compartments. i--divisions of the lower chamber. k--middle wall. l--pots which are filled with ore. m--lids of same pots. n--grating.] if pyrites or _cadmia_, or any other ore containing metal, possesses a good deal of sulphur or bitumen, it should be so roasted that neither is lost. for this purpose it is thrown on an iron plate full of holes, and roasted with charcoal placed on top; three walls support this plate, two on the sides and the third at the back. beneath the plate are placed pots containing water, into which the sulphurous or bituminous vapour descends, and in the water the fat accumulates and floats on the top. if it is sulphur, it is generally of a yellow colour; if bitumen, it is black like pitch. if these were not drawn out they would do much harm to the metal, when the ore is being smelted. when they have thus been separated they prove of some service to man, especially the sulphurous kind. from the vapour which is carried down, not into the water, but into the ground, there is created a sulphurous or a bituminous substance resembling _pompholyx_[ ], and so light that it can be blown away with a breath. some employ a vaulted furnace, open at the front and divided into two chambers. a wall built in the middle of the furnace divides the lower chamber into two equal parts, in which are set pots containing water, as above described. the upper chamber is again divided into three parts, the middle one of which is always open, for in it the wood is placed, and it is not broader than the middle wall, of which it forms the topmost portion. the other two compartments have iron doors which are closed, and which, together with the roof, keep in the heat when the wood is lighted. in these upper compartments are iron bars which take the place of a floor, and on these are arranged pots without bottoms, having in place of a bottom, a grating made of iron wire, fixed to each, through the openings of which the sulphurous or bituminous vapours roasted from the ore run into the lower pots. each of the upper pots holds a hundred pounds of ore; when they are filled they are covered with lids and smeared with lute. [illustration (heap roasting): a--heap of cupriferous stones. b--kindled heap. c--stones being taken to the beds of faggots.] in eisleben and the neighbourhood, when they roast the schistose stone from which copper is smelted, and which is not free from bitumen, they do not use piles of logs, but bundles of faggots. at one time, they used to pile this kind of stone, when extracted from the pit, on bundles of faggots and roast it by firing the faggots; nowadays, they first of all carry these same stones to a heap, where they are left to lie for some time in such a way as to allow the air and rain to soften them. then they make a bed of faggot bundles near the heap, and carry the nearest stones to this bed; afterward they again place bundles of faggots in the empty place from which the first stones have been removed, and pile over this extended bed, the stones which lay nearest to the first lot; and they do this right up to the end, until all the stones have been piled mound-shape on a bed of faggots. finally they fire the faggots, not, however, on the side where the wind is blowing, but on the opposite side, lest the fire blown up by the force of the wind should consume the faggots before the stones are roasted and made soft; by this method the stones which are adjacent to the faggots take fire and communicate it to the next ones, and these again to the adjoining ones, and in this way the heap very often burns continuously for thirty days or more. this schist rock when rich in copper, as i have said elsewhere, exudes a substance of a nature similar to asbestos. [illustration (stamp-mill): a--mortar. b--upright posts. c--cross-beams. d--stamps. e--their heads. f--axle (cam-shaft). g--tooth of the stamp (tappet). h--teeth of axle (cams).] ore is crushed with iron-shod stamps, in order that the metal may be separated from the stone and the hangingwall rock.[ ] the machines which miners use for this purpose are of four kinds, and are made by the following method. a block of oak timber six feet long, two feet and a palm square, is laid on the ground. in the middle of this is fixed a mortar-box, two feet and six digits long, one foot and six digits deep; the front, which might be called a mouth, lies open; the bottom is covered with a plate of iron, a palm thick and two palms and as many digits wide, each end of which is wedged into the timber with broad wedges, and the front and back part of it are fixed to the timber with iron nails. to the sides of the mortar above the block are fixed two upright posts, whose upper ends are somewhat cut back and are mortised to the timbers of the building. two and a half feet above the mortar are placed two cross-beams joined together, one in front and one in the back, the ends of which are mortised into the upright posts already mentioned. through each mortise is bored a hole, into which is driven an iron clavis; one end of the clavis has two horns, and the other end is perforated in order that a wedge driven through, binds the beams more firmly; one horn of the clavis turns up and the other down. three and a half feet above the cross-beams, two other cross-beams of the same kind are again joined in a similar manner; these cross-beams have square openings, in which the iron-shod stamps are inserted. the stamps are not far distant from each other, and fit closely in the cross-beams. each stamp has a tappet at the back, which requires to be daubed with grease on the lower side that it can be raised more easily. for each stamp there are on a cam-shaft, two cams, rounded on the outer end, which alternately raise the stamp, in order that, by its dropping into the mortar, it may with its iron head pound and crush the rock which has been thrown under it. to the cam-shaft is fixed a water-wheel whose buckets are turned by water-power. instead of doors, the mouth of the mortar has a board, which is fitted into notches cut out of the front of the block. this board can be raised, in order that when the mouth is open, the workmen can remove with a shovel the fine sand, and likewise the coarse sand and broken rock, into which the rocks have been crushed; this board can be lowered, so that the mouth thus being closed, the fresh rock thrown in may be crushed with the iron-shod stamps. if an oak block is not available, two timbers are placed on the ground and joined together with iron clamps, each of the timbers being six feet long, a foot wide, and a foot and a half thick. such depth as should be allowed to the mortar, is obtained by cutting out the first beam to a width of three-quarters of a foot and to a length of two and a third and one twenty-fourth of a foot. in the bottom of the part thus dug out, there should be laid a very hard rock, a foot thick and three-quarters of a foot wide; about it, if any space remains, earth or sand should be filled in and pounded. on the front, this bed rock is covered with a plank; this rock when it has been broken, should be taken away and replaced by another. a smaller mortar having room for only three stamps may also be made in the same manner. [illustration (stamps): a--stamp. b--stem cut out in lower part. c--shoe. d--the other shoe, barbed and grooved. e--quadrangular iron band. f--wedge. g--tappet. h--angular cam-shaft. i--cams. k--pair of compasses.] the stamp-stems are made of small square timbers nine feet long and half a foot wide each way. the iron head of each is made in the following way; the lower part of the head is three palms long and the upper part the same length. the lower part is a palm square in the middle for two palms, then below this, for a length of two digits it gradually spreads until it becomes five digits square; above the middle part, for a length of two digits, it again gradually swells out until it becomes a palm and a half square. higher up, where the head of the shoe is enclosed in the stem, it is bored through and similarly the stem itself is pierced, and through the opening of each, there passes a broad iron wedge, which prevents the head falling off the stem. to prevent the stamp head from becoming broken by the constant striking of fragments of ore or rocks, there is placed around it a quadrangular iron band a digit thick, seven digits wide, and six digits deep. those who use three stamps, as is common, make them much larger, and they are made square and three palms broad each way; then the iron shoe of each has a total length of two feet and a palm; at the lower end, it is hexagonal, and at that point it is seven digits wide and thick. the lower part of it which projects beyond the stem is one foot and two palms long; the upper part, which is enclosed in the stem, is three palms long; the lower part is a palm wide and thick; then gradually the upper part becomes narrower and thinner, so that at the top it is three digits and a half wide and two thick. it is bored through at the place where the angles have been somewhat cut away; the hole is three digits long and one wide, and is one digit's distance from the top. there are some who make that part of the head which is enclosed in the stem, barbed and grooved, in order that when the hooks have been fixed into the stem and wedges fitted to the grooves, it may remain tightly fixed, especially when it is also held with two quadrangular iron bands. some divide the cam-shaft with a compass into six sides, others into nine; it is better for it to be divided into twelve sides, in order that successively one side may contain a cam and the next be without one. [illustration (stamp-mill): a--box. although the upper part is not open, it is shown open here, that the wheel may be seen. b--wheel. c--cam-shaft. d--stamps.] the water-wheel is entirely enclosed under a quadrangular box, in case either the deep snows or ice in winter, or storms, may impede its running and its turning around. the joints in the planks are stopped all around with moss. the cover, however, has one opening, through which there passes a race bringing down water which, dropping on the buckets of the wheel, turns it round, and flows out again in the lower race under the box. the spokes of the water-wheel are not infrequently mortised into the middle of the cam-shaft; in this case the cams on both sides raise the stamps, which either both crush dry or wet ore, or else the one set crushes dry ore and the other set wet ore, just as circumstances require the one or the other; further, when the one set is raised and the iron clavises in them are fixed into openings in the first cross-beam, the other set alone crushes the ore. [illustration (handling stamped material): a--box laid flat on the ground. b--its bottom which is made of iron wire. c--box inverted. d--iron rods. e--box suspended from a beam, the inside being visible. f--box suspended from a beam, the outside being visible.] broken rock or stones, or the coarse or fine sand, are removed from the mortar of this machine and heaped up, as is also done with the same materials when raked out of the dump near the mine. they are thrown by a workman into a box, which is open on the top and the front, and is three feet long and nearly a foot and a half wide. its sides are sloping and made of planks, but its bottom is made of iron wire netting, and fastened with wire to two iron rods, which are fixed to the two side planks. this bottom has openings, through which broken rock of the size of a hazel nut cannot pass; the pieces which are too large to pass through are removed by the workman, who again places them under stamps, while those which have passed through, together with the coarse and fine sand, he collects in a large vessel and keeps for the washing. when he is performing his laborious task he suspends the box from a beam by two ropes. this box may rightly be called a quadrangular sieve, as may also that kind which follows. [illustration (sifting ore): a--sieve. b--small planks. c--post. d--bottom of sieve. e--open box. f--small cross-beam. g--upright posts.] some employ a sieve shaped like a wooden bucket, bound with two iron hoops; its bottom, like that of the box, is made of iron wire netting. they place this on two small cross-planks fixed upon a post set in the ground. some do not fix the post in the ground, but stand it on the ground until there arises a heap of the material which has passed through the sieve, and in this the post is fixed. with an iron shovel the workman throws into this sieve broken rock, small stones, coarse and fine sand raked out of the dump; holding the handles of the sieve in his hands, he agitates it up and down in order that by this movement the dust, fine and coarse sand, small stones, and fine broken rock may fall through the bottom. others do not use a sieve, but an open box, whose bottom is likewise covered with wire netting; this they fix on a small cross-beam fastened to two upright beams and tilt it backward and forward. [illustration (sifting ore): a--box. b--bale. c--rope. d--beam. e--handles. f--five-toothed rake. g--sieve. h--its handles. i--pole. k--rope. l--timber.] some use a sieve made of copper, having square copper handles on both sides, and through these handles runs a pole, of which one end projects three-quarters of a foot beyond one handle; the workman then places that end in a rope which is suspended from a beam, and rapidly shakes the pole alternately backward and forward. by this movement the small particles fall through the bottom of the sieve. in order that the end of the pole may be easily placed in the rope, a stick, two palms long, holds open the lower part of the rope as it hangs double, each end of the rope being tied to the beam; part of the rope, however, hangs beyond the stick to a length of half a foot. a large box is also used for this purpose, of which the bottom is either made of a plank full of holes or of iron netting, as are the other boxes. an iron bale is fastened from the middle of the planks which form its sides; to this bale is fastened a rope which is suspended from a wooden beam, in order that the box may be moved or tilted in any direction. there are two handles on each end, not unlike the handles of a wheelbarrow; these are held by two workmen, who shake the box to and fro. this box is the one principally used by the germans who dwell in the carpathian mountains. the smaller particles are separated from the larger ones by means of three boxes and two sieves, in order that those which pass through each, being of equal size, may be washed together; for the bottoms of both the boxes and sieves have openings which do not let through broken rock of the size of a hazel nut. as for the dry remnants in the bottoms of the sieves, if they contain any metal the miners put them under the stamps. the larger pieces of broken rock are not separated from the smaller by this method until the men and boys, with five-toothed rakes, have separated them from the rock fragments, the little stones, the coarse and the fine sand and earth, which have been thrown on to the dumps. [illustration (sifting ore): a--workman carrying broken rock in a barrow. b--first chute. c--first box. d--its handles. e--its bales. f--rope. g--beam. h--post. i--second chute. k--second box. l--third chute. m--third box. n--first table. o--first sieve. p--first tub. q--second table. r--second sieve. s--second tub. t--third table. v--third sieve. x--third tub. y--plugs.] at neusohl, in the carpathians, there are mines where the veins of copper lie in the ridges and peaks of the mountains, and in order to save expense being incurred by a long and difficult transport, along a rough and sometimes very precipitous road, one workman sorts over the dumps which have been thrown out from the mines, and another carries in a wheelbarrow the earth, fine and coarse sand, little stones, broken rock, and even the poorer ore, and overturns the barrow into a long open chute fixed to a steep rock. this chute is held apart by small cleats, and the material slides down a distance of about one hundred and fifty feet into a short box, whose bottom is made of a thick copper plate, full of holes. this box has two handles by which it is shaken to and fro, and at the top there are two bales made of hazel sticks, in which is fixed the iron hook of a rope hung from the branch of a tree or from a wooden beam which projects from an upright post. from time to time a sifter pulls this box and thrusts it violently against the tree or post, by which means the small particles passing through its holes descend down another chute into another short box, in whose bottom there are smaller holes. a second sifter, in like manner, thrusts this box violently against a tree or post, and a second time the smaller particles are received into a third chute, and slide down into a third box, whose bottom has still smaller holes. a third sifter, in like manner, thrusts this box violently against a tree or post, and for the third time the tiny particles fall through the holes upon a table. while the workman is bringing in the barrow, another load which has been sorted from the dump, each sifter withdraws the hooks from his bale and carries away his own box and overturns it, heaping up the broken rock or sand which remains in the bottom of it. as for the tiny particles which have slid down upon the table, the first washer--for there are as many washers as sifters--sweeps them off and in a tub nearly full of water, washes them through a sieve whose holes are smaller than the holes of the third box. when this tub has been filled with the material which has passed through the sieve, he draws out the plug to let the water run away; then he removes with a shovel that which has settled in the tub and throws it upon the table of a second washer, who washes it in a sieve with smaller holes. the sediment which has this time settled in his tub, he takes out and throws on the table of a third washer, who washes it in a sieve with the smallest holes. the copper concentrates which have settled in the last tub are taken out and smelted; the sediment which each washer has removed with a limp is washed on a canvas strake. the sifters at altenberg, in the tin mines of the mountains bordering on bohemia, use such boxes as i have described, hung from wooden beams. these, however, are a little larger and open in the front, through which opening the broken rock which has not gone through the sieve can be shaken out immediately by thrusting the sieve against its post. [illustration (sifting ore): a--sieve. b--its handles. c--tub. d--bottom of sieve made of iron wires. e--hoop. f--rods. g--hoops. h--woman shaking the sieve. i--boy supplying it with material which requires washing. k--man with shovel removing from the tub the material which has passed through the sieve.] if the ore is rich in metal, the earth, the fine and coarse sand, and the pieces of rock which have been broken from the hangingwall, are dug out of the dump with a spade or rake and, with a shovel, are thrown into a large sieve or basket, and washed in a tub nearly full of water. the sieve is generally a cubit broad and half a foot deep; its bottom has holes of such size that the larger pieces of broken rock cannot pass through them, for this material rests upon the straight and cross iron wires, which at their points of contact are bound by small iron clips. the sieve is held together by an iron band and by two cross-rods likewise of iron; the rest of the sieve is made of staves in the shape of a little tub, and is bound with two iron hoops; some, however, bind it with hoops of hazel or oak, but in that case they use three of them. on each side it has handles, which are held in the hands by whoever washes the metalliferous material. into this sieve a boy throws the material to be washed, and a woman shakes it up and down, turning it alternately to the right and to the left, and in this way passes through it the smaller pieces of earth, sand, and broken rock. the larger pieces remain in the sieve, and these are taken out, placed in a heap and put under the stamps. the mud, together with fine sand, coarse sand, and broken rock, which remain after the water has been drawn out of the tub, is removed by an iron shovel and washed in the sluice, about which i will speak a little later. [illustration (sifting ore): a--basket. b--its handles. c--dish. d--its back part. e--its front part. f--handles of same.] the bohemians use a basket a foot and a half broad and half a foot deep, bound together by osiers. it has two handles by which it is grasped, when they move it about and shake it in the tub or in a small pool nearly full of water. all that passes through it into the tub or pool they take out and wash in a bowl, which is higher in the back part and lower and flat in the front; it is grasped by the two handles and shaken in the water, the lighter particles flowing away, and the heavier and mineral portion sinking to the bottom. [illustration (mills for grinding ore): a--axle. b--water-wheel. c--toothed drum. d--drum made of rundles. e--iron axle. f--millstone. g--hopper. h--round wooden plate. i--trough.] gold ore, after being broken with hammers or crushed by the stamps, and even tin ore, is further milled to powder. the upper millstone, which is turned by water-power, is made in the following way. an axle is rounded to compass measure, or is made angular, and its iron pinions turn in iron sockets which are held in beams. the axle is turned by a water-wheel, the buckets of which are fixed to the rim and are struck by the force of a stream. into the axle is mortised a toothed drum, whose teeth are fixed in the side of the rim. these teeth turn a second drum of rundles, which are made of very hard material. this drum surrounds an iron axle which has a pinion at the bottom and revolves in an iron cup in a timber. at the top of the iron axle is an iron tongue, dove-tailed into the millstone, and so when the teeth of the one drum turn the rundles of the other, the millstone is made to turn round. an overhanging machine supplies it with ore through a hopper, and the ore, being ground to powder, is discharged from a round wooden plate into a trough and flowing away through it accumulates on the floor; from there the ore is carried away and reserved for washing. since this method of grinding requires the millstone to be now raised and now lowered, the timber in whose socket the iron of the pinion axle revolves, rests upon two beams, which can be raised and lowered. [illustration (mills for grinding ore): a--first mill. b--wheel turned by goats. c--second mill. d--disc of upright axle. e--its toothed drum. f--third mill. g--shape of lower millstone. h--small upright axle of the same. i--its opening. k--lever of the upper millstone. l--its opening.] there are three mills in use in milling gold ores, especially for quartz[ ] which is not lacking in metal. they are not all turned by water-power, but some by the strength of men, and two of them even by the power of beasts of burden. the first revolving one differs from the next only in its driving wheel, which is closed in and turned by men treading it, or by horses, which are placed inside, or by asses, or even by strong goats; the eyes of these beasts are covered by linen bands. the second mill, both when pushed and turned round, differs from the two above by having an upright axle in the place of the horizontal one; this axle has at its lower end a disc, which two workmen turn by treading back its cleats with their feet, though frequently one man sustains all the labour; or sometimes there projects from the axle a pole which is turned by a horse or an ass, for which reason it is called an _asinaria_. the toothed drum which is at the upper end of the axle turns the drum which is made of rundles, and together with it the millstone. the third mill is turned round and round, and not pushed by hand; but between this and the others there is a great distinction, for the lower millstone is so shaped at the top that it can hold within it the upper millstone, which revolves around an iron axle; this axle is fastened in the centre of the lower stone and passes through the upper stone. a workman, by grasping in his hand an upright iron bar placed in the upper millstone, moves it round. the middle of the upper millstone is bored through, and the ore, being thrown into this opening, falls down upon the lower millstone and is there ground to powder, which gradually runs out through its opening; it is washed by various methods before it is mixed with quicksilver, which i will explain presently. [illustration (stamp-mill): a--water-wheel. b--axle. c--stamp. d--hopper in the upper millstone. e--opening passing through the centre. f--lower millstone. g--its round depression. h--its outlet. i--iron axle. k--its crosspiece. l--beam. m--drum of rundles on the iron axle. n--toothed drum of main axle. o--tubs. p--the small planks. q--small upright axles. r--enlarged part of one. s--their paddles. t--their drums which are made of rundles. v--small horizontal axle set into the end of the main axle. x--its toothed drums. y--three sluices. z--their small axles. aa--spokes. bb--paddles.] some people build a machine which at one and the same time can crush, grind, cleanse, and wash the gold ore, and mix the gold with quicksilver. this machine has one water-wheel, which is turned by a stream striking its buckets; the main axle on one side of the water-wheel has long cams, which raise the stamps that crush the dry ore. then the crushed ore is thrown into the hopper of the upper millstone, and gradually falling through the opening, is ground to powder. the lower millstone is square, but has a round depression in which the round, upper millstone turns, and it has an outlet from which the powder falls into the first tub. a vertical iron axle is dove-tailed into a cross-piece, which is in turn fixed into the upper millstone; the upper pinion of this axle is held in a bearing fixed in a beam; the drum of the vertical axle is made of rundles, and is turned by the toothed drum on the main axle, and thus turns the millstone. the powder falls continually into the first tub, together with water, and from there runs into a second tub which is set lower down, and out of the second into a third, which is the lowest; from the third, it generally flows into a small trough hewn out of a tree trunk. quicksilver[ ] is placed in each tub, across which is fixed a small plank, and through a hole in the middle of each plank there passes a small upright axle, which is enlarged above the plank to prevent it from dropping into the tub lower than it should. at the lower end of the axle three sets of paddles intersect, each made from two little boards fixed to the axle opposite each other. the upper end of this axle has a pinion held by a bearing set in a beam, and around each of these axles is a small drum made of rundles, each of which is turned by a small toothed drum on a horizontal axle, one end of which is mortised into the large horizontal axle, and the other end is held in a hollow covered with thick iron plates in a beam. thus the paddles, of which there are three sets in each tub, turn round, and agitating the powder, thoroughly mix it with water and separate the minute particles of gold from it, and these are attracted by the quicksilver and purified. the water carries away the waste. the quicksilver is poured into a bag made of leather or cloth woven from cotton, and when this bag is squeezed, as i have described elsewhere, the quicksilver drips through it into a jar placed underneath. the pure gold[ ] remains in the bag. some people substitute three broad sluices for the tubs, each of which has an angular axle on which are set six narrow spokes, and to them are fixed the same number of broad paddles; the water that is poured in strikes these paddles and turns them round, and they agitate the powder which is mixed with the water and separate the metal from it. if the powder which is being treated contains gold particles, the first method of washing is far superior, because the quicksilver in the tubs immediately attracts the gold; if it is powder in which are the small black stones from which tin is smelted, this latter method is not to be despised. it is very advantageous to place interlaced fir boughs in the sluices in which such tin-stuff is washed, after it has run through the launders from the mills, because the fine tin-stone is either held back by the twigs, or if the current carries them along they fall away from the water and settle down. seven methods of washing are in common use for the ores of many metals; for they are washed either in a simple buddle, or in a divided buddle, or in an ordinary strake, or in a large tank, or in a short strake, or in a canvas strake, or in a jigging sieve. other methods of washing are either peculiar to some particular metal, or are combined with the method of crushing wet ore by stamps. [illustration (buddles): a--head of buddle. b--pipe. c--buddle. d--board. e--transverse buddle. f--shovel. g--scrubber.] a simple buddle is made in the following way. in the first place, the head is higher than the rest of the buddle, and is three feet long and a foot and a half broad; this head is made of planks laid upon a timber and fastened, and on both sides, side-boards are set up so as to hold the water, which flows in through a pipe or trough, so that it shall fall straight down. the middle of the head is somewhat depressed in order that the broken rock and the larger metallic particles may settle into it. the buddle is sunk into the earth to a depth of three-quarters of a foot below the head, and is twelve feet long and a foot and a half wide and deep; the bottom and each side are lined with planks to prevent the earth, when it is softened by the water, from falling in or from absorbing the metallic particles. the lower end of the buddle is obstructed by a board, which is not as high as the sides. to this straight buddle there is joined a second transverse buddle, six feet long and a foot and a half wide and deep, similarly lined with planks; at the lower end it is closed up with a board, also lower than the sides of the buddle so that the water can flow away; this water falls into a launder and is carried outside the building. in this simple buddle is washed the metallic material which has passed on to the floor of the works through the five large sieves. when this has been gathered into a heap, the washer throws it into the head of the buddle, and water is poured upon it through the pipe or small trough, and the portion which sinks and settles in the middle of the head compartment he stirs with a wooden scrubber,--this is what we will henceforth call the implement made of a stick to which is fixed a piece of wood a foot long and a palm broad. the water is made turbid by this stirring, and carries the mud and sand and small particles of metal into the buddle below. together with the broken rock, the larger metallic particles remain in the head compartment, and when these have been removed, boys throw them upon the platform of a washing tank or the short strake, and separate them from the broken rock. when the buddle is full of mud and sand, the washer closes the pipe through which the water flows into the head; very soon the water which remains in the buddle flows away, and when this has taken place, he removes with a shovel the mud and sand which are mixed with minute particles of metal, and washes them on a canvas strake. sometimes before the buddles have been filled full, the boys throw the material into a bowl and carry it to the strakes and wash it. pulverized ore is washed in the head of this kind of a buddle; but usually when tin-stone is washed in it, interlacing fir boughs are put into the buddle, in the same manner as in the sluice when wet ore is crushed with stamps. the larger tin-stone particles, which sink in the upper part of the buddle, are washed separately in a strake; those particles which are of medium size, and settle in the middle part, are washed separately in the same way; and the mud mixed with minute particles of tin-stone, which has settled in the lowest part of the buddle below the fir boughs, is washed separately on the canvas strakes. [illustration (buddles): a--pipe. b--cross launder. c--small troughs. d--head of the buddle. e--wooden scrubber. f--dividing boards. g--short strake.] the divided buddle differs from the last one by having several cross-boards, which, being placed inside it, divide it off like steps; if the buddle is twelve feet long, four of them are placed within; if nine feet long, three. the nearer each one is to the head, the greater is its height; the further from the head, the lower it is; and so when the highest is a foot and a palm high, the second is usually a foot and three digits high, the third a foot and two digits, and the lowest a foot and one digit. in this buddle is generally washed that metalliferous material which has been sifted through the large sieve into the tub containing water. this material is continuously thrown with an iron shovel into the head of the buddle, and the water which has been let in is stirred up by a wooden scrubber, until the buddle is full, then the cross-boards are taken out by the washer, and the water is drained off; next the metalliferous material which has settled in the compartments is again washed, either on a short strake or on the canvas strakes or in the jigging sieves. since a short strake is often united with the upper part of this buddle, a pipe in the first place carries the water into a cross launder, from which it flows down through one little launder into the buddle, and through another into the short strake. [illustration (washing material): a--head. b--strake. c--trowel. d--scrubber. e--canvas. f--rod by which the canvas is made smooth.] an ordinary strake, so far as the planks are concerned, is not unlike the last two. the head of this, as of the others, is first made of earth stamped down, then covered with planks; and where it is necessary, earth is thrown in and beaten down a second time, so that no crevice may remain through which water carrying the particles of metal can escape. the water ought to fall straight down into the strake, which has a length of eight feet and a breadth of a foot and a half; it is connected with a transverse launder, which then extends to a settling pit outside the building. a boy with a shovel or a ladle takes the impure concentrates or impure tin-stone from a heap, and throws them into the head of the strake or spreads them over it. a washer with a wooden scrubber then agitates them in the strake, whereby the mud mixed with water flows away into the transverse launder, and the concentrates or the tin-stone settle on the strake. since sometimes the concentrates or fine tin-stone flow down together with the mud into the transverse launder, a second washer closes it, after a distance of about six feet, with a cross-board and frequently stirs the mud with a shovel, in order that when mixed with water it may flow out into the settling-pit; and there remains in the launder only the concentrates or tin-stone. the tin-stuff of schlackenwald and erbisdorff is washed in this kind of a strake once or twice; those of altenberg three or four times; those of geyer often seven times; for in the ore at schlackenwald and erbisdorff the tin-stone particles are of a fair size, and are crushed with stamps; at altenberg they are of much smaller size, and in the broken ore at geyer only a few particles of tin-stone can be seen occasionally. this method of washing was first devised by the miners who treated tin ore, whence it passed on from the works of the tin workers to those of the silver workers and others; this system is even more reliable than washing in jigging-sieves. near this ordinary strake there is generally a canvas strake. [illustration (washing material): a--upper cross launder. b--small launders. c--heads of strakes. d--strakes. e--lower transverse launder. f--settling pit. g--socket in the sill. h--halved iron rings fixed to beam. i--pole. k--its little scrubber. l--second small scrubber.] in modern times two ordinary strakes, similarly made, are generally joined together; the head of one is three feet distant from that of the other, while the bodies are four feet distant from each other, and there is only one cross launder under the two strakes. one boy shovels, from the heap into the head of each, the concentrates or tin-stone mixed with mud. there are two washers, one of whom sits at the right side of one strake, and the other at the left of the other strake, and each pursues his task, using the following sort of implement. under each strake is a sill, from a socket in which a round pole rises, and is held by half an iron ring in a beam of the building, so that it may revolve; this pole is nine feet long and a palm thick. penetrating the pole is a small round piece of wood, three palms long and as many digits thick, to which is affixed a small board two feet long and five digits wide, in an opening of which one end of a small axle revolves, and to this axle is fixed the handle of a little scrubber. the other end of this axle turns in an opening of a second board, which is likewise fixed to a small round piece of wood; this round piece, like the first one, is three palms long and as many digits thick, and is used by the washer as a handle. the little scrubber is made of a stick three feet long, to the end of which is fixed a small tablet of wood a foot long, six digits broad, and a digit and a half thick. the washer constantly moves the handle of this implement with one hand; in this way the little scrubber stirs the concentrates or the fine tin-stone mixed with mud in the head of the strake, and the mud, on being stirred, flows on to the strake. in the other hand he holds a second little scrubber, which has a handle of half the length, and with this he ceaselessly stirs the concentrates or tin-stone which have settled in the upper part of the strake; in this way the mud and water flow down into the transverse launder, and from it into the settling-pit which is outside the building. [illustration (washing material): a--trough. b--platform. c--wooden scrubber.] before the short strake and the jigging-sieve had been invented, metalliferous ores, especially tin, were crushed dry with stamps and washed in a large trough hollowed out of one or two tree trunks; and at the head of this trough was a platform, on which the ore was thrown after being completely crushed. the washer pulled it down into the trough with a wooden scrubber which had a long handle, and when the water had been let into the trough, he stirred the ore with the same scrubber. [illustration (washing material): a--short strake. b--small launder. c--transverse launder. d--wooden scrubber.] the short strake is narrow in the upper part where the water flows down into it through the little launder; in fact it is only two feet wide; at the lower end it is wider, being three feet and as many palms. at the sides, which are six feet long, are fixed boards two palms high. in other respects the head resembles the head of the simple buddle, except that it is not depressed in the middle. beneath is a cross launder closed by a low board. in this short strake not only is ore agitated and washed with a wooden scrubber, but boys also separate the concentrates from the broken rock in them and collect them in tubs. the short strake is now rarely employed by miners, owing to the carelessness of the boys, which has been frequently detected; for this reason, the jigging-sieve has taken its place. the mud which settles in the launder, if the ore is rich, is taken up and washed in a jigging-sieve or on a canvas strake. [illustration (washing material): a--beams. b--canvas. c--head of strake. d--small launder. e--settling pit or tank. f--wooden scrubber. g--tubs.] a canvas strake is made in the following way. two beams, eighteen feet long and half a foot broad and three palms thick, are placed on a slope; one half of each of these beams is partially cut away lengthwise, to allow the ends of planks to be fastened in them, for the bottom is covered by planks three feet long, set crosswise and laid close together. one half of each supporting beam is left intact and rises a palm above the planks, in order that the water that is running down may not escape at the sides, but shall flow straight down. the head of the strake is higher than the rest of the body, and slopes so as to enable the water to flow away. the whole strake is covered by six stretched pieces of canvas, smoothed with a stick. the first of them occupies the lowest division, and the second is so laid as to slightly overlap it; on the second division, the third is similarly laid, and so on, one on the other. if they are laid in the opposite way, the water flowing down carries the concentrates or particles of tin-stone under the canvas, and a useless task is attempted. boys or men throw the concentrates or tin-stuff mixed with mud into the head of the strake, after the canvas has been thus stretched, and having opened the small launder they let the water flow in; then they stir the concentrates or tin-stone with a wooden scrubber till the water carries them all on to the canvas; next they gently sweep the linen with the wooden scrubber until the mud flows into the settling-pit or into the transverse launder. as soon as there is little or no mud on the canvas, but only concentrates or tin-stone, they carry the canvas away and wash it in a tub placed close by. the tin-stone settles in the tub, and the men return immediately to the same task. finally, they pour the water out of the tub, and collect the concentrates or tin-stone. however, if either concentrates or tin-stone have washed down from the canvas and settled in the settling-pit or in the transverse launder, they wash the mud again. [illustration (collecting concentrates): a--canvas strake. b--man dashing water on the canvas. c--bucket. d--bucket of another kind. e--man removing concentrates or tin-stone from the trough.] some neither remove the canvas nor wash it in the tubs, but place over it on each edge narrow strips, of no great thickness, and fix them to the beams with nails. they agitate the metalliferous material with wooden scrubbers and wash it in a similar way. as soon as little or no mud remains on the canvas, but only concentrates or fine tin-stone, they lift one beam so that the whole strake rests on the other, and dash it with water, which has been drawn with buckets out of the small tank, and in this way all the sediment which clings to the canvas falls into the trough placed underneath. this trough is hewn out of a tree and placed in a ditch dug in the ground; the interior of the trough is a foot wide at the top, but narrower in the bottom, because it is rounded out. in the middle of this trough they put a cross-board, in order that the fairly large particles of concentrates or fairly large-sized tin-stone may remain in the forepart into which they have fallen, and the fine concentrates or fine tin-stone in the lower part, for the water flows from one into the other, and at last flows down through an opening into the pit. as for the fairly large-sized concentrates or tin-stone which have been removed from the trough, they are washed again on the ordinary strake. the fine concentrates and fine tin-stone are washed again on this canvas strake. by this method, the canvas lasts longer because it remains fixed, and nearly double the work is done by one washer as quickly as can be done by two washers by the other method. [illustration (jigging sieve): a--fine sieves. b--limp. c--finer sieve. d--finest sieve.] the jigging sieve has recently come into use by miners. the metalliferous material is thrown into it and sifted in a tub nearly full of water. the sieve is shaken up and down, and by this movement all the material below the size of a pea passes through into the tub, and the rest remains on the bottom of the sieve. this residue is of two kinds, the metallic particles, which occupy the lower place, and the particles of rock and earth, which take the higher place, because the heavy substance always settles, and the light is borne upward by the force of the water. this light material is taken away with a limp, which is a thin tablet of wood almost semicircular in shape, three-quarters of a foot long, and half a foot wide. before the lighter portion is taken away the contents of the sieve are generally divided crosswise with a limp, to enable the water to penetrate into it more quickly. afterward fresh material is again thrown into the sieve and shaken up and down, and when a great quantity of metallic particles have settled in the sieve, they are taken out and put into a tray close by. but since there fall into the tub with the mud, not only particles of gold or silver, but also of sand, pyrites, _cadmia_, galena, quartz, and other substances, and since the water cannot separate these from the metallic particles because they are all heavy, this muddy mixture is washed a second time, and the part which is useless is thrown away. to prevent the sieve passing this sand again too quickly, the washer lays small stones or gravel in the bottom of the sieve. however, if the sieve is not shaken straight up and down, but is tilted to one side, the small stones or broken ore move from one part to another, and the metallic material again falls into the tub, and the operation is frustrated. the miners of our country have made an even finer sieve, which does not fail even with unskilled washers; in washing with this sieve they have no need for the bottom to be strewn with small stones. by this method the mud settles in the tub with the very fine metallic particles, and the larger sizes of metal remain in the sieve and are covered with the valueless sand, and this is taken away with a limp. the concentrates which have been collected are smelted together with other things. the mud mixed with the very fine metallic particles is washed for a third time and in the finest sieve, whose bottom is woven of hair. if the ore is rich in metal, all the material which has been removed by the limp is washed on the canvas strakes, or if the ore is poor it is thrown away. i have explained the methods of washing which are used in common for the ores of many metals. i now come to another method of crushing ore, for i ought to speak of this before describing those methods of washing which are peculiar to ores of particular metals. [illustration (stamp-mill): a--mortar. b--open end of mortar. c--slab of rock. d--iron sole plates. e--screen. f--launder. g--wooden shovel. h--settling pit. i--iron shovel. k--heap of material which has settled. l--ore which requires crushing. m--small launder.] in the year , george, the illustrious duke of saxony[ ], gave the overlordship of all the dumps ejected from the mines in meissen to the noble and wise sigismund maltitz, father of john, bishop of meissen. rejecting the dry stamps, the large sieve, and the stone mills of dippoldswalde and altenberg, in which places are dug the small black stones from which tin is smelted, he invented a machine which could crush the ore wet under iron-shod stamps. that is called "wet ore" which is softened by water which flows into the mortar box, and they are sometimes called "wet stamps" because they are drenched by the same water; and on the other hand, the other kinds are called "dry stamps" or "dry ore," because no water is used to soften the ore when the stamps are crushing. but to return to our subject. this machine is not dissimilar to the one which crushes the ore with dry iron-shod stamps, but the heads of the wet stamps are larger by half than the heads of the others. the mortar-box, which is made of oak or beech timber, is set up in the space between the upright posts; it does not open in front, but at one end, and it is three feet long, three-quarters of a foot wide, and one foot and six digits deep. if it has no bottom, it is set up in the same way over a slab of hard, smooth rock placed in the ground, which has been dug down a little. the joints are stopped up all round with moss or cloth rags. if the mortar has a bottom, then an iron sole-plate, three feet long, three-quarters of a foot wide, and a palm thick, is placed in it. in the opening in the end of the mortar there is fixed an iron plate full of holes, in such a way that there is a space of two digits between it and the shoe of the nearest stamp, and the same distance between this screen and the upright post, in an opening through which runs a small but fairly long launder. the crushed particles of silver ore flow through this launder with the water into a settling-pit, while the material which settles in the launder is removed with an iron shovel to the nearest planked floor; that material which has settled in the pit is removed with an iron shovel on to another floor. most people make two launders, in order that while the workman empties one of them of the accumulation which has settled in it, a fresh deposit may be settling in the other. the water flows in through a small launder at the other end of the mortar that is near the water-wheel which turns the machine. the workman throws the ore to be crushed into the mortar in such a way that the pieces, when they are thrown in among the stamps, do not impede the work. by this method a silver or gold ore is crushed very fine by the stamps. [illustration (buddle): a--launder reaching to the screen. b--transverse trough. c--spouts. d--large buddles. e--shovel. f--interwoven twigs. g--boards closing the buddles. h--cross trough.] when tin ore is crushed by this kind of iron-shod stamps, as soon as crushing begins, the launder which extends from the screen discharges the water carrying the fine tin-stone and fine sand into a transverse trough, from which the water flows down through the spouts, which pierce the side of the trough, into the one or other of the large buddles set underneath. the reason why there are two is that, while the washer empties the one which is filled with fine tin-stone and sand, the material may flow into the other. each buddle is twelve feet long, one cubit deep, and a foot and a half broad. the tin-stone which settles in the upper part of the buddles is called the large size; these are frequently stirred with a shovel, in order that the medium sized particles of tin-stone, and the mud mixed with the very fine particles of the stones may flow away. the particles of medium size generally settle in the middle part of the buddle, where they are arrested by interwoven fir twigs. the mud which flows down with the water settles between the twigs and the board which closes the lower end of the buddle. the tin-stone of large size is removed separately from the buddle with a shovel; those of medium size are also removed separately, and likewise the mud is removed separately, for they are separately washed on the canvas strakes and on the ordinary strake, and separately roasted and smelted. the tin-stone which has settled in the middle part of the buddle, is also always washed separately on the canvas strakes; but if the particles are nearly equal in size to those which have settled in the upper part of the buddle, they are washed with them in the ordinary strake and are roasted and smelted with them. however, the mud is never washed with the others, either on the canvas strakes or on the ordinary strake, but separately, and the fine tin-stone which is obtained from it is roasted and smelted separately. the two large buddles discharge into a cross trough, and it again empties through a launder into a settling-pit which is outside the building. this method of washing has lately undergone a considerable change; for the launder which carries the water, mixed with the crushed tin-stone and fine sand which flow from the openings of the screen, does not reach to a transverse trough which is inside the same room, but runs straight through a partition into a small settling-pit. a boy draws a three-toothed rake through the material which has settled in the portion of the launder outside the room, by which means the larger sized particles of tin-stone settle at the bottom, and these the washer takes out with the wooden shovel and carries into the room; this material is thrown into an ordinary strake and swept with a wooden scrubber and washed. as for those tin-stone particles which the water carries off from the strake, after they have been brought back on to the strake, he washes them again until they are clean. [illustration (buddle): a--first launder. b--three-toothed rake. c--small settling pit. d--large buddle. e--buddle resembling the simple buddle. f--small roller. g--boards. h--their holes. i--shovel. k--building. l--stove. (this picture does not entirely agree with the text).] the remaining tin-stone, mixed with sand, flows into the small settling-pit which is within the building, and this discharges into two large buddles. the tin-stone of moderate size, mixed with those of fairly large size, settle in the upper part, and the small size in the lower part; but both are impure, and for this reason they are taken out separately and the former is washed twice, first in a buddle like the simple buddle, and afterward on an ordinary strake. likewise the latter is washed twice, first on a canvas strake and afterward on an ordinary strake. this buddle, which is like the simple buddle, differs from it in the head, the whole of which in this case is sloping, while in the case of the other it is depressed in the centre. in order that the boy may be able to rest the shovel with which he cleanses the tin-stone, this sluice has a small wooden roller which turns in holes in two thick boards fixed to the sides of the buddle; if he did not do this, he would become over-exhausted by his task, for he spends whole days standing over these labours. the large buddle, the one like the simple buddle, the ordinary strake, and the canvas strakes, are erected within a special building. in this building there is a stove that gives out heat through the earthen tiles or iron plates of which it is composed, in order that the washers can pursue their labours even in winter, if the rivers are not completely frozen over. [illustration (workroom with settling-pit): a--launder from the screen of the mortar-box. b--three-toothed rake. c--small settling-pit. d--canvas. e--strakes. f--brooms.] on the canvas strakes are washed the very fine tin-stone mixed with mud which has settled in the lower end of the large buddle, as well as in the lower end of the simple buddle and of the ordinary strake. the canvas is cleaned in a trough hewn out of one tree trunk and partitioned off with two boards, so that three compartments are made. the first and second pieces of canvas are washed in the first compartment, the third and fourth in the second compartment, the fifth and sixth in the third compartment. since among the very fine tin-stone there are usually some grains of stone, rock, or marble, the master cleanses them on the ordinary strake, lightly brushing the top of the material with a broom, the twigs of which do not all run the same way, but some straight and some crosswise. in this way the water carries off these impurities from the strake into the settling-pit because they are lighter, and leaves the tin-stone on the table because it is heavier. below all buddles or strakes, both inside and outside the building, there are placed either settling-pits or cross-troughs into which they discharge, in order that the water may carry on down into the stream but very few of the most minute particles of tin-stone. the large settling-pit which is outside the building is generally made of joined flooring, and is eight feet in length, breadth and depth. when a large quantity of mud, mixed with very fine tin-stone, has settled in it, first of all the water is let out by withdrawing a plug, then the mud which is taken out is washed outside the house on the canvas strakes, and afterward the concentrates are washed on the strake which is inside the building. by these methods the very finest tin-stone is made clean. [illustration (streaming for tin): a--river. b--weir. c--gate. d--area. e--meadow. f--fence. g--ditch.] the mud mixed with the very fine tin-stone, which has neither settled in the large settling-pit nor in the transverse launder which is outside the room and below the canvas strakes, flows away and settles in the bed of the stream or river. in order to recover even a portion of the fine tin-stone, many miners erect weirs in the bed of the stream or river, very much like those that are made above the mills, to deflect the current into the races through which it flows to the water-wheels. at one side of each weir there is an area dug out to a depth of five or six or seven feet, and if the nature of the place will permit, extending in every direction more than sixty feet. thus, when the water of the river or stream in autumn and winter inundates the land, the gates of the weir are closed, by which means the current carries the mud mixed with fine tin-stone into the area. in spring and summer this mud is washed on the canvas strakes or on the ordinary strake, and even the finest black-tin is collected. within a distance of four thousand fathoms along the bed of the stream or river below the buildings in which the tin-stuff is washed, the miners do not make such weirs, but put inclined fences in the meadows, and in front of each fence they dig a ditch of the same length, so that the mud mixed with the fine tin-stone, carried along by the stream or river when in flood, may settle in the ditch and cling to the fence. when this mud is collected, it is likewise washed on canvas strakes and on the ordinary strake, in order that the fine tin-stone may be separated from it. indeed we may see many such areas and fences collecting mud of this kind in meissen below altenberg in the river moglitz,--which is always of a reddish colour when the rock containing the black tin is being crushed under the stamps. [illustration (stamp-mill): a--first machine. b--its stamps. c--its mortar-box. d--second machine. e--its stamps. f--its mortar-box. g--third machine. h--its stamps. i--its mortar-box. k--fourth machine. l--its stamps. m--its mortar-box.] but to return to the stamping machines. some usually set up four machines of this kind in one place, that is to say, two above and the same number below. by this plan it is necessary that the current which has been diverted should fall down from a greater height upon the upper water-wheels, because these turn axles whose cams raise heavier stamps. the stamp-stems of the upper machines should be nearly twice as long as the stems of the lower ones, because all the mortar-boxes are placed on the same level. these stamps have their tappets near their upper ends, not as in the case of the lower stamps, which are placed just above the bottom. the water flowing down from the two upper water-wheels is caught in two broad races, from which it falls on to the two lower water-wheels. since all these machines have the stamps very close together, the stems should be somewhat cut away, to prevent the iron shoes from rubbing each other at the point where they are set into the stems. where so many machines cannot be constructed, by reason of the narrowness of the valley, the mountain is excavated and levelled in two places, one of which is higher than the other, and in this case two machines are constructed and generally placed in one building. a broad race receives in the same way the water which flows down from the upper water-wheel, and similarly lets it fall on the lower water-wheel. the mortar-boxes are not then placed on one level, but each on the level which is appropriate to its own machine, and for this reason, two workmen are then required to throw ore into the mortar-boxes. when no stream can be diverted which will fall from a higher place upon the top of the water-wheel, one is diverted which will turn the foot of the wheel; a great quantity of water from the stream is collected in one pool capable of holding it, and from this place, when the gates are raised, the water is discharged against the wheel which turns in the race. the buckets of a water-wheel of this kind are deeper and bent back, projecting upward; those of the former are shallower and bent forward, inclining downward. [illustration (stamp-mill): a--stamps. b--mortar. c--plates full of holes. d--transverse launder. e--planks full of cup-like depressions. f--spout. g--bowl into which the concentrates fall. h--canvas strake. i--bowls shaped like a small boat. k--settling-pit under the canvas strake.] further, in the julian and rhaetian alps[ ] and in the carpathian mountains, gold or even silver ore is now put under stamps, which are sometimes placed more than twenty in a row, and crushed wet in a long mortar-box. the mortar has two plates full of holes through which the ore, after being crushed, flows out with the water into the transverse launder placed underneath, and from there it is carried down by two spouts into the heads of the canvas strakes. each head is made of a thick broad plank, which can be raised and set upright, and to which on each side are fixed pieces projecting upward. in this plank there are many cup-like depressions equal in size and similar in shape, in each of which an egg could be placed. right down in these depressions are small crevices which can retain the concentrates of gold or silver, and when the hollows are nearly filled with these materials, the plank is raised on one side so that the concentrates will fall into a large bowl. the cup-like depressions are washed out by dashing them with water. these concentrates are washed separately in different bowls from those which have settled on the canvas. this bowl is smooth and two digits wide and deep, being in shape very similar to a small boat; it is broad in the fore part, narrow in the back, and in the middle of it there is a cross groove, in which the particles of pure gold or silver settle, while the grains of sand, since they are lighter, flow out of it. in some parts of moravia, gold ore, which consists of quartz mixed with gold, is placed under the stamps and crushed wet. when crushed fine it flows out through a launder into a trough, is there stirred by a wooden scrubber, and the minute particles of gold which settle in the upper end of the trough are washed in a black bowl. so far i have spoken of machines which crush wet ore with iron-shod stamps. i will now explain the methods of washing which are in a measure peculiar to the ore of certain metals, beginning with gold. the ore which contains particles of this metal, and the sand of streams and rivers which contains grains of it, are washed in frames or bowls; the sands especially are also washed in troughs. more than one method is employed for washing on frames, for these frames either pass or retain the particles or concentrates of gold; they pass them if they have holes, and retain them if they have no holes. but either the frame itself has holes, or a box is substituted for it; if the frame itself is perforated it passes the particles or concentrates of gold into a trough; if the box has them, it passes the gold material into the long sluice. i will first speak of these two methods of washing. the frame is made of two planks joined together, and is twelve feet long and three feet wide, and is full of holes large enough for a pea to pass. to prevent the ore or sand with which the gold is mixed from falling out at the sides, small projecting edge-boards are fixed to it. this frame is set upon two stools, the first of which is higher than the second, in order that the gravel and small stones can roll down it. the washer throws the ore or sand into the head of the frame, which is higher, and opening the small launder, lets the water into it, and then agitates it with a wooden scrubber. in this way, the gravel and small stones roll down the frame on to the ground, while the particles or concentrates of gold, together with the sand, pass through the holes into the trough which is placed under the frame, and after being collected are washed in the bowl. [illustration (frames for washing ore or alluvial): a--head of frame. b--frame. c--holes. d--edge-boards. e--stools. f--scrubber. g--trough. h--launder. i--bowl.] [illustration (frames for washing ore or alluvial): a--sluice. b--box. c--bottom of inverted box. d--open part of it. e--iron hoe. f--riffles. g--small launder. h--bowl with which settlings are taken away. i--black bowl in which they are washed.] a box which has a bottom made of a plate full of holes, is placed over the upper end of a sluice, which is fairly long but of moderate width. the gold material to be washed is thrown into this box, and a great quantity of water is let in. the lumps, if ore is being washed, are mashed with an iron shovel. the fine portions fall through the bottom of the box into the sluice, but the coarse pieces remain in the box, and these are removed with a scraper through an opening which is nearly in the middle of one side. since a large amount of water is necessarily let into the box, in order to prevent it from sweeping away any particles of gold which have fallen into the sluice, the sluice is divided off by ten, or if it is as long again, by fifteen riffles. these riffles are placed equidistant from one another, and each is higher than the one next toward the lower end of the sluice. the little compartments which are thus made are filled with the material and the water which flows through the box; as soon as these compartments are full and the water has begun to flow over clear, the little launder through which this water enters into the box is closed, and the water is turned in another direction. then the lowest riffle is removed from the sluice, and the sediment which has accumulated flows out with the water and is caught in a bowl. the riffles are removed one by one and the sediment from each is taken into a separate bowl, and each is separately washed and cleansed in a bowl. the larger particles of gold concentrates settle in the higher compartments, the smaller size, in the lower compartments. this bowl is shallow and smooth, and smeared with oil or some other slippery substance, so that the tiny particles of gold may not cling to it, and it is painted black, that the gold may be more easily discernible; on the exterior, on both sides and in the middle, it is slightly hollowed out in order that it may be grasped and held firmly in the hands when shaken. by this method the particles or concentrates of gold settle in the back part of the bowl; for if the back part of the bowl is tapped or shaken with one hand, as is usual, the contents move toward the fore part. in this way the moravians, especially, wash gold ore. the gold particles are also caught on frames which are either bare or covered. if bare, the particles are caught in pockets; if covered, they cling to the coverings. pockets are made in various ways, either with iron wire or small cross-boards fixed to the frame, or by holes which are sunk into the sluice itself or into its head, but which do not quite go through. these holes are round or square, or are grooves running crosswise. the frames are either covered with skins, pieces of cloth, or turf, which i will deal with one by one in turn. [illustration (frames for washing ore or alluvial): a--plank. b--side-boards. c--iron wire. d--handles.] in order to prevent the sand which contains the particles of gold from spilling out, the washer fixes side-boards to the edges of a plank which is six feet long and one and a quarter wide. he then lays crosswise many iron wires a digit apart, and where they join he fixes them to the bottom plank with iron nails. then he makes the head of the frame higher, and into this he throws the sand which needs washing, and taking in his hands the handles which are at the head of the frame, he draws it backward and forward several times in the river or stream. in this way the small stones and gravel flow down along the frame, and the sand mixed with particles of gold remains in the pockets between the strips. when the contents of the pockets have been shaken out and collected in one place, he washes them in a bowl and thus cleans the gold dust. [illustration (frames for washing ore or alluvial): a--head of the sluice. b--riffles. c--wooden scrubber. d--pointed stick. e--dish. f--its cup-like depression. g--grooved dish.] other people, among whom are the lusitanians[ ], fix to the sides of a sluice, which is about six feet long and a foot and a half broad, many cross-strips or riffles, which project backward and are a digit apart. the washer or his wife lets the water into the head of the sluice, where he throws the sand which contains the particles of gold. as it flows down he agitates it with a wooden scrubber, which he moves transversely to the riffles. he constantly removes with a pointed wooden stick the sediment which settles in the pockets between the riffles, and in this way the particles of gold settle in them, while the sand and other valueless materials are carried by the water into a tub placed below the sluice. he removes the particles of metal with a small wooden shovel into a wooden bowl. this bowl does not exceed a foot and a quarter in breadth, and by moving it up and down in the stream he cleanses the gold dust, for the remaining sand flows out of the dish, and the gold dust settles in the middle of it, where there is a cup-like depression. some make use of a bowl which is grooved inside like a shell, but with a smooth lip where the water flows out. this smooth place, however, is narrower where the grooves run into it, and broader where the water flows out. [illustration (frames for washing ore or alluvial): a--head of the sluice. b--side-boards. c--lower end of the sluice. d--pockets. e--grooves. f--stools. g--shovel. h--tub set below. i--launder.] the cup-like pockets and grooves are cut or burned at the same time into the bottom of the sluice; the bottom is composed of three planks ten feet long, and is about four feet wide; but the lower end, through which the water is discharged, is narrower. this sluice, which likewise has side-boards fixed to its edges, is full of rounded pockets and of grooves which lead to them, there being two grooves to one pocket, in order that the water mixed with sand may flow into each pocket through the upper groove, and that after the sand has partly settled, the water may again flow out through the lower groove. the sluice is set in the river or stream or on the bank, and placed on two stools, of which the first is higher than the second in order that the gravel and small stones may roll down the sluice. the washer throws sand into the head with a shovel, and opening the launder, lets in the water, which carries the particles of metal with a little sand down into the pockets, while the gravel and small stones with the rest of the sand falls into a tub placed below the sluice. as soon as the pockets are filled, he brushes out the concentrates and washes them in a bowl. he washes again and again through this sluice. [illustration (frames for washing ore or alluvial): a--cross grooves. b--tub set under the sluice. c--another tub.] some people cut a number of cross-grooves, one palm distant from each other, in a sluice similarly composed of three planks eight feet long. the upper edge of these grooves is sloping, that the particles of gold may slip into them when the washer stirs the sand with a wooden shovel; but their lower edge is vertical so that the gold particles may thus be unable to slide out of them. as soon as these grooves are full of gold particles mixed with fine sand, the sluice is removed from the stools and raised up on its head. the head in this case is nothing but the upper end of the planks of which the sluice is composed. in this way the metallic particles, being turned over backward, fall into another tub, for the small stones and gravel have rolled down the sluice. some people place large bowls under the sluice instead of tubs, and as in the other cases, the unclean concentrates are washed in the small bowl. [illustration (frames for washing ore or alluvial): a--sluice covered with canvas. b--its head full of pockets and grooves. c--head removed and washed in a tub. d--sluice which has square pockets. e--sluice to whose planks small shavings cling. f--broom. g--skins of oxen. h--wooden scrubber.] the thuringians cut rounded pockets, a digit in diameter and depth, in the head of the sluice, and at the same time they cut grooves reaching from one to another. the sluice itself they cover with canvas. the sand which is to be washed, is thrown into the head and stirred with a wooden scrubber; in this way the water carries the light particles of gold on to the canvas, and the heavy ones sink in the pockets, and when these hollows are full, the head is removed and turned over a tub, and the concentrates are collected and washed in a bowl. some people make use of a sluice which has square pockets with short vertical recesses which hold the particles of gold. other workers use a sluice made of planks, which are rough by reason of the very small shavings which still cling to them; these sluices are used instead of those with coverings, of which this sluice is bare, and when the sand is washed, the particles of gold cling no less to these shavings than to canvas, or skins, or cloths, or turf. the washer sweeps the sluice upward with a broom, and when he has washed as much of the sand as he wishes, he lets a more abundant supply of water into the sluice again to wash out the concentrates, which he collects in a tub set below the sluice, and then washes again in a bowl. just as thuringians cover the sluice with canvas, so some people cover it with the skins of oxen or horses. they push the auriferous sand upward with a wooden scrubber, and by this system the light material flows away with the water, while the particles of gold settle among the hairs; the skins are afterward washed in a tub; and the concentrates are collected in a bowl. [illustration (washing material in spring): a--spring. b--skin. c--argonauts.] the colchians[ ] placed the skins of animals in the pools of springs; and since many particles of gold had clung to them when they were removed, poets invented the "golden fleece" of the colchians. in like manner, it can be contrived by the methods of miners that skins should take up, not only particles of gold, but also of silver and gems. [illustration (frames for washing ore or alluvial): a--head of frame. b--frame. c--cloth. d--small launder. e--tub set below the frame. f--tub in which cloth is washed.] many people cover the frame with a green cloth as long and wide as the frame itself, and fasten it with iron nails in such a way that they can easily draw them out and remove the cloth. when the cloth appears to be golden because of the particles which adhere to it, it is washed in a special tub and the particles are collected in a bowl. the remainder which has run down into the tub is again washed on the frame. [illustration (frames for washing ore or alluvial): a--cloth full of small knots, spread out. b--small knots more conspicuously shown. c--tub in which cloth is washed.] some people, in place of a green cloth, use a cloth of tightly woven horsehair, which has a rough knotty surface. since these knots stand out and the cloth is rough, even the very small particles of gold adhere to it; these cloths are likewise washed in a tub with water. [illustration (frames for washing ore or alluvial): a--head of frame. b--small launder through which water flows into head of frame. c--pieces of turf. d--trough placed under frame. e--tub in which pieces of turf are washed.] some people construct a frame not unlike the one covered with canvas, but shorter. in place of the canvas they set pieces of turf in rows. they wash the sand, which has been thrown into the head of the frame, by letting in water. in this way the particles of gold settle in the turf, the mud and sand, together with the water, are carried down into the settling-pit or trough below, which is opened when the work is finished. after all the water has passed out of the settling-pit, the sand and mud are carried away and washed over again in the same manner. the particles which have clung to the turf are afterward washed down into the settling-pit or trough by a stronger current of the water, which is let into the frame through a small launder. the concentrates are finally collected and washed in a bowl. pliny was not ignorant of this method of washing gold. "the ulex," he says, "after being dried, is burnt, and its ashes are washed over a grassy turf, that the gold may settle on it." [illustration (trays for washing alluvial): a--tray. b--bowl-like depression. c--handles.] sand mixed with particles of gold is also washed in a tray, or in a trough or bowl. the tray is open at the further end, is either hewn out of a squared trunk of a tree or made out of a thick plank to which side-boards are fixed, and is three feet long, a foot and a half wide, and three digits deep. the bottom is hollowed out into the shape of an elongated bowl whose narrow end is turned toward the head, and it has two long handles, by which it is drawn backward and forward in the river. in this way the fine sand is washed, whether it contains particles of gold or the little black stones from which tin is made. [illustration (trough for washing alluvial): a--trough. b--its open end. c--end that may be closed. d--stream. e--hoe. f--end-board. g--bag.] the italians who come to the german mountains seeking gold, in order to wash the river sand which contains gold-dust and garnets,[ ] use a fairly long shallow trough hewn out of a tree, rounded within and without, open at one end and closed at the other, which they turn in the bed of the stream in such a way that the water does not dash into it, but flows in gently. they stir the sand, which they throw into it, with a wooden hoe, also rounded. to prevent the particles of gold or garnets from running out with the light sand, they close the end with a board similarly rounded, but lower than the sides of the trough. the concentrates of gold or garnets which, with a small quantity of heavy sand, have settled in the trough, they wash in a bowl and collect in bags and carry away with them. [illustration (bowls for alluvial washing): a--large bowl. b--ropes. c--beam. d--other large bowl which coiners use. e--small bowl.] some people wash this kind of sand in a large bowl which can easily be shaken, the bowl being suspended by two ropes from a beam in a building. the sand is thrown into it, water is poured in, then the bowl is shaken, and the muddy water is poured out and clear water is again poured in, this being done again and again. in this way, the gold particles settle in the back part of the bowl because they are heavy, and the sand in the front part because it is light; the latter is thrown away, the former kept for smelting. the one who does the washing then returns immediately to his task. this method of washing is rarely used by miners, but frequently by coiners and goldsmiths when they wash gold, silver, or copper. the bowl they employ has only three handles, one of which they grasp in their hands when they shake the bowl, and in the other two is fastened a rope by which the bowl is hung from a beam, or from a cross-piece which is upheld by the forks of two upright posts fixed in the ground. miners frequently wash ore in a small bowl to test it. this bowl, when shaken, is held in one hand and thumped with the other hand. in other respects this method of washing does not differ from the last. [illustration (ground sluicing): a--stream. b--ditch. c--mattock. d--pieces of turf. e--seven-pronged fork. f--iron shovel. g--trough. h--another trough below it. i--small wooden trowel.] i have spoken of the various methods of washing sand which contains grains of gold; i will now speak of the methods of washing the material in which are mixed the small black stones from which tin is made[ ]. eight such methods are in use, and of these two have been invented lately. such metalliferous material is usually found torn away from veins and stringers and scattered far and wide by the impetus of water, although sometimes _venae dilatatae_ are composed of it. the miners dig out the latter material with a broad mattock, while they dig the former with a pick. but they dig out the little stones, which are not rare in this kind of ore, with an instrument like the bill of a duck. in districts which contain this material, if there is an abundant supply of water, and if there are valleys or gentle slopes and hollows, so that rivers can be diverted into them, the washers in summer-time first of all dig a long ditch sloping so that the water will run through it rapidly. into the ditch is thrown the metallic material, together with the surface material, which is six feet thick, more or less, and often contains moss, roots of plants, shrubs, trees, and earth; they are all thrown in with a broad mattock, and the water flows through the ditch. the sand and tin-stone, as they are heavy, sink to the bottom of the ditch, while the moss and roots, as they are light, are carried away by the water which flows through the ditch. the bottom of the ditch is obstructed with turf and stones in order to prevent the water from carrying away the tin-stone at the same time. the washers, whose feet are covered with high boots made of hide, though not of rawhide, themselves stand in the ditch and throw out of it the roots of the trees, shrubs, and grass with seven-pronged wooden forks, and push back the tin-stone toward the head of the ditch. after four weeks, in which they have devoted much work and labour, they raise the tin-stone in the following way; the sand with which it is mixed is repeatedly lifted from the ditch with an iron shovel and agitated hither and thither in the water, until the sand flows away and only the tin-stone remains on the shovel. the tin-stone is all collected together and washed again in a trough by pushing it up and turning it over with a wooden trowel, in order that the remaining sand may separate from it. afterward they return to their task, which they continue until the metalliferous material is exhausted, or until the water can no longer be diverted into the ditches. [illustration (sluicing tin): a--trough. b--wooden shovel. c--tub. d--launder. e--wooden trowel. f--transverse trough. g--plug. h--falling water. i--ditch. k--barrow conveying material to be washed. l--pick like the beak of a duck with which the miner digs out the material from which the small stones are obtained.] the trough which i mentioned is hewn out of the trunk of a tree and the interior is five feet long, three-quarters of a foot deep, and six digits wide. it is placed on an incline and under it is put a tub which contains interwoven fir twigs, or else another trough is put under it, the interior of which is three feet long and one foot wide and deep; the fine tin-stone, which has run out with the water, settles in the bottom. some people, in place of a trough, put a square launder underneath, and in like manner they wash the tin-stone in this by agitating it up and down and turning it over with a small wooden trowel. a transverse trough is put under the launder, which is either open on one end and drains off into a tub or settling-pit, or else is closed and perforated through the bottom; in this case, it drains into a ditch beneath, where the water falls when the plug has been partly removed. the nature of this ditch i will now describe. [illustration (sluicing tin): a--launder. b--interlacing fir twigs. c--logs; three on one side, for the fourth cannot be seen because the ditch is so full with material now being washed. d--logs at the head of the ditch. e--barrow. f--seven-pronged fork. g--hoe.] if the locality does not supply an abundance of water, the washers dig a ditch thirty or thirty-six feet long, and cover the bottom, the full length, with logs joined together and hewn on the side which lies flat on the ground. on each side of the ditch, and at its head also, they place four logs, one above the other, all hewn smooth on the inside. but since the logs are laid obliquely along the sides, the upper end of the ditch is made four feet wide and the tail end, two feet. the water has a high drop from a launder and first of all it falls into interlaced fir twigs, in order that it shall fall straight down for the most part in an unbroken stream and thus break up the lumps by its weight. some do not place these twigs under the end of the launder, but put a plug in its mouth, which, since it does not entirely close the launder, nor altogether prevent the discharge from it, nor yet allow the water to spout far afield, makes it drop straight down. the workman brings in a wheelbarrow the material to be washed, and throws it into the ditch. the washer standing in the upper end of the ditch breaks the lumps with a seven-pronged fork, and throws out the roots of trees, shrubs, and grass with the same instrument, and thereby the small black stones settle down. when a large quantity of the tin-stone has accumulated, which generally happens when the washer has spent a day at this work, to prevent it from being washed away he places it upon the bank, and other material having been again thrown into the upper end of the ditch, he continues the task of washing. a boy stands at the lower end of the ditch, and with a thin pointed hoe stirs up the sediment which has settled at the lower end, to prevent the washed tin-stone from being carried further, which occurs when the sediment has accumulated to such an extent that the fir branches at the outlet of the ditch are covered. [illustration (sifting ore): a--strakes. b--tank. c--launder. d--plug. e--wooden shovel. f--wooden mallet. g--wooden shovel with short handle. h--the plug in the strake. i--tank placed under the plug.] the third method of washing materials of this kind follows. two strakes are made, each of which is twelve feet long and a foot and a half wide and deep. a tank is set at their head, into which the water flows through a little launder. a boy throws the ore into one strake; if it is of poor quality he puts in a large amount of it, if it is rich he puts in less. the water is let in by removing the plug, the ore is stirred with a wooden shovel, and in this way the tin-stone, mixed with the heavier material, settles in the bottom of the strake, and the water carries the light material into the launder, through which it flows on to a canvas strake. the very fine tin-stone, carried by the water, settles on to the canvas and is cleansed. a low cross-board is placed in the strake near the head, in order that the largest sized tin-stone may settle there. as soon as the strake is filled with the material which has been washed, he closes the mouth of the tank and continues washing in the other strake, and then the plug is withdrawn and the water and tin-stone flow down into a tank below. then he pounds the sides of the loaded strake with a wooden mallet, in order that the tin-stone clinging to the sides may fall off; all that has settled in it, he throws out with a wooden shovel which has a short handle. silver slags which have been crushed under the stamps, also fragments of silver-lead alloy and of cakes melted from pyrites, are washed in a strake of this kind. [illustration (sifting ore): a--sieve. b--tub. c--water flowing out of the bottom of it. d--strake. e--three-toothed rake. f--wooden scrubber.] material of this kind is also washed while wet, in a sieve whose bottom is made of woven iron wire, and this is the fourth method of washing. the sieve is immersed in the water which is contained in a tub, and is violently shaken. the bottom of this tub has an opening of such size that as much water, together with tailings from the sieve, can flow continuously out of it as water flows into it. the material which settles in the strake, a boy either digs over with a three-toothed iron rake or sweeps with a wooden scrubber; in this way the water carries off a great part of both sand and mud. the tin-stone or metalliferous concentrates settle in the strake and are afterward washed in another strake. [illustration (sluicing tin): a--box. b--perforated plate. c--trough. d--cross-boards. e--pool. f--launder. g--shovel. h--rake.] these are ancient methods of washing material which contains tin-stone; there follow two modern methods. if the tin-stone mixed with earth or sand is found on the slopes of mountains or hills, or in the level fields which are either devoid of streams or into which a stream cannot be diverted, miners have lately begun to employ the following method of washing, even in the winter months. an open box is constructed of planks, about six feet long, three feet wide, and two feet and one palm deep. at the upper end on the inside, an iron plate three feet long and wide is fixed, at a depth of one foot and a half from the top; this plate is very full of holes, through which tin-stone about the size of a pea can fall. a trough hewn from a tree is placed under the box, and this trough is about twenty-four feet long and three-quarters of a foot wide and deep; very often three cross-boards are placed in it, dividing it off into compartments, each one of which is lower than the next. the turbid waters discharge into a settling-pit. the metalliferous material is sometimes found not very deep beneath the surface of the earth, but sometimes so deep that it is necessary to drive tunnels and sink shafts. it is transported to the washing-box in wheelbarrows, and when the washers are about to begin they lay a small launder, through which there flows on to the iron plate so much water as is necessary for this washing. next, a boy throws the metalliferous material on to the iron plate with an iron shovel and breaks the small lumps, stirring them this way and that with the same implement. then the water and sand penetrating the holes of the plate, fall into the box, while all the coarse gravel remains on the plate, and this he throws into a wheelbarrow with the same shovel. meantime, a younger boy continually stirs the sand under the plate with a wooden scrubber nearly as wide as the box, and drives it to the upper end of the box; the lighter material, as well as a small amount of tin-stone, is carried by the water down into the underlying trough. the boys carry on this labour without intermission until they have filled four wheelbarrows with the coarse and worthless residues, which they carry off and throw away, or three wheelbarrows if the material is rich in black tin. then the foreman has the plank removed which was in front of the iron plate, and on which the boy stood. the sand, mixed with the tin-stone, is frequently pushed backward and forward with a scrubber, and the same sand, because it is lighter, takes the upper place, and is removed as soon as it appears; that which takes the lower place is turned over with a spade, in order that any that is light can flow away; when all the tin-stone is heaped together, he shovels it out of the box and carries it away. while the foreman does this, one boy with an iron hoe stirs the sand mixed with fine tin-stone, which has run out of the box and has settled in the trough and pushes it back to the uppermost part of the trough, and this material, since it contains a very great amount of tin-stone, is thrown on to the plate and washed again. the material which has settled in the lowest part of the trough is taken out separately and piled in a heap, and is washed on the ordinary strake; that which has settled in the pool is washed on the canvas strake. in the summer-time this fruitful labour is repeated more often, in fact ten or eleven times. the tin-stone which the foreman removes from the box, is afterward washed in a jigging sieve, and lastly in a tub, where at length all the sand is separated out. finally, any material in which are mixed particles of other metals, can be washed by all these methods, whether it has been disintegrated from veins or stringers, or whether it originated from _venae dilatatae_, or from streams and rivers. [illustration (ground sluicing): a--launder. b--cross trough. c--two spouts. d--boxes. e--plate. f--grating. g--shovels. h--second cross trough. i--strake. k--wooden scrubber. l--third cross trough. m--launder. n--three-toothed rake.] the sixth method of washing material of this kind is even more modern and more useful than the last. two boxes are constructed, into each of which water flows through spouts from a cross trough into which it has been discharged through a pipe or launder. when the material has been agitated and broken up with iron shovels by two boys, part of it runs down and falls through the iron plates full of holes, or through the iron grating, and flows out of the box over a sloping surface into another cross trough, and from this into a strake seven feet long and two and a half feet wide. then the foreman again stirs it with a wooden scrubber that it may become clean. as for the material which has flowed down with the water and settled in the third cross trough, or in the launder which leads from it, a third boy rakes it with a two-toothed rake; in this way the fine tin-stone settles down and the water carries off the valueless sand into the creek. this method of washing is most advantageous, for four men can do the work of washing in two boxes, while the last method, if doubled, requires six men, for it requires two boys to throw the material to be washed on to the plate and to stir it with iron shovels; two more are required with wooden scrubbers to keep stirring the sand, mixed with the tin-stone, under the plate, and to push it toward the upper end of the box; further, two foremen are required to clean the tin-stone in the way i have described. in the place of a plate full of holes, they now fix in the boxes a grating made of iron wire as thick as the stalks of rye; that these may not be depressed by the weight and become bent, three iron bars support them, being laid crosswise underneath. to prevent the grating from being broken by the iron shovels with which the material is stirred in washing, five or six iron rods are placed on top in cross lines, and are fixed to the box so that the shovels may rub them instead of the grating; for this reason the grating lasts longer than the plates, because it remains intact, while the rods, when worn by rubbing, can easily be replaced by others. [illustration (ground sluicing): a--pits. b--torrent. c--seven-pronged fork. d--shovel.] miners use the seventh method of washing when there is no stream of water in the part of the mountain which contains the black tin, or particles of gold, or of other metals. in this case they frequently dig more than fifty ditches on the slope below, or make the same number of pits, six feet long, three feet wide, and three-quarters of a foot deep, not any great distance from each other. at the season when a torrent rises from storms of great violence or long duration, and rushes down the mountain, some of the miners dig the metalliferous material in the woods with broad hoes and drag it to the torrent. other miners divert the torrent into the ditches or pits, and others throw the roots of trees, shrubs, and grass out of the ditches or pits with seven-pronged wooden forks. when the torrent has run down, they remove with shovels the uncleansed tin-stone or particles of metal which have settled in the ditches or pits, and cleanse it. [illustration (ground sluicing): a--gully. b--ditch. c--torrent. d--sluice box employed by the lusitanians.] the eighth method is also employed in the regions which the lusitanians hold in their power and sway, and is not dissimilar to the last. they drive a great number of deep ditches in rows in the gullies, slopes, and hollows of the mountains. into these ditches the water, whether flowing down from snow melted by the heat of the sun or from rain, collects and carries together with earth and sand, sometimes tin-stone, or, in the case of the lusitanians, the particles of gold loosened from veins and stringers. as soon as the waters of the torrent have all run away, the miners throw the material out of the ditches with iron shovels, and wash it in a common sluice box. [illustration (trough for washing alluvial): a--trough. b--launder. c--hoe. d--sieve.] the poles wash the impure lead from _venae dilatatae_ in a trough ten feet long, three feet wide, and one and one-quarter feet deep. it is mixed with moist earth and is covered by a wet and sandy clay, and so first of all the clay, and afterward the ore, is dug out. the ore is carried to a stream or river, and thrown into a trough into which water is admitted by a little launder, and the washer standing at the lower end of the trough drags the ore out with a narrow and nearly pointed hoe, whose wooden handle is nearly ten feet long. it is washed over again once or twice in the same way and thus made pure. afterward when it has been dried in the sun they throw it into a copper sieve, and separate the very small pieces which pass through the sieve from the larger ones; of these the former are smelted in a faggot pile and the latter in the furnace. of such a number then are the methods of washing. [illustration (tin burning furnace): a--furnace. b--its mouth. c--poker. d--rake with two teeth. e--hoe.] one method of burning is principally employed, and two of roasting. the black tin is burned by a hot fire in a furnace similar to an oven[ ]; it is burned if it is a dark-blue colour, or if pyrites and the stone from which iron is made are mixed with it, for the dark blue colour if not burnt, consumes the tin. if pyrites and the other stone are not volatilised into fumes in a furnace of this kind, the tin which is made from the tin-stone is impure. the tin-stone is thrown either into the back part of the furnace, or into one side of it; but in the former case the wood is placed in front, in the latter case alongside, in such a manner, however, that neither firebrands nor coals may fall upon the tin-stone itself or touch it. the fuel is manipulated by a poker made of wood. the tin-stone is now stirred with a rake with two teeth, and now again levelled down with a hoe, both of which are made of iron. the very fine tin-stone requires to be burned less than that of moderate size, and this again less than that of the largest size. while the tin-stone is being thus burned, it frequently happens that some of the material runs together. the burned tin-stone should then be washed again on the strake, for in this way the material which has been run together is carried away by the water into the cross-trough, where it is gathered up and worked over, and again washed on the strake. by this method the metal is separated from that which is devoid of metal. [illustration (stall roasting matte): a--pits. b--wood. c--cakes. d--launder.] cakes from pyrites, or _cadmia_, or cupriferous stones, are roasted in quadrangular pits, of which the front and top are open, and these pits are generally twelve feet long, eight feet wide, and three feet deep. the cakes of melted pyrites are usually roasted twice over, and those of _cadmia_ once. these latter are first rolled in mud moistened with vinegar, to prevent the fire from consuming too much of the copper with the bitumen, or sulphur, or orpiment, or realgar. the cakes of pyrites are first roasted in a slow fire and afterward in a fierce one, and in both cases, during the whole following night, water is let in, in order that, if there is in the cakes any alum or vitriol or saltpetre capable of injuring the metals, although it rarely does injure them, the water may remove it and make the cakes soft. the solidified juices are nearly all harmful to the metal, when cakes or ore of this kind are smelted. the cakes which are to be roasted are placed on wood piled up in the form of a crate, and this pile is fired[ ]. [illustration (matte roasting): a--cakes. b--bundles of faggots. c--furnaces.] the cakes which are made of copper smelted from schist are first thrown upon the ground and broken, and then placed in the furnace on bundles of faggots, and these are lighted. these cakes are generally roasted seven times and occasionally nine times. while this is being done, if they are bituminous, then the bitumen burns and can be smelled. these furnaces have a structure like the structure of the furnaces in which ore is smelted, except that they are open in front; they are six feet high and four feet wide. as for this kind of furnace, three of them are required for one of those in which the cakes are melted. first of all they are roasted in the first furnace, then when they are cooled, they are transferred into the second furnace and again roasted; later they are carried to the third, and afterward back to the first, and this order is preserved until they have been roasted seven or nine times. end of book viii. footnotes: [ ] as would be expected, practically all the technical terms used by agricola in this chapter are adaptations. the latin terms, _canalis_, _area_, _lacus_, _vasa_, _cribrum_, and _fossa_, have had to be pressed into service for many different devices, largely by extemporised combinations. where the devices described have become obsolete, we have adopted the nomenclature of the old works on cornish methods. the following examples may be of interest:-- simple buddle = _canalis simplex_ divided buddle = _canalis tabellis distinctus_ ordinary strake = _canalis devexus_ short strake = _area curta_ canvas strake = _area linteis extensis contecta_ limp = _radius_. the strake (or streke) when applied to alluvial tin, would have been termed a "tye" in some parts of cornwall, and the "short strake" a "gounce." in the case of the stamp mill, inasmuch as almost every mechanical part has its counterpart in a modern mill, we have considered the reader will have less difficulty if the modern designations are used instead of the old cornish. the following are the essential terms in modern, old cornish, and latin:-- stamp stamper _pilum_ stamp-stem lifter _pilum_ shoes stamp-heads _capita_ mortar-box box _capsa_ cam-shaft barrell _axis_ cams caps _dentes_ tappets tongues _pili dentes_ screen crate _laminae foraminum plenae_ settling pit catchers _lacus_ jigging sieve dilleugher _cribrum angustum_ [ ] agricola uses four latin verbs in connection with heat operations at temperatures under the melting point: _calefacio_, _uro_, _torreo_, and _cremo_. the first he always uses in the sense of "to warm" or "to heat," but the last three he uses indiscriminately in much the same way as the english verbs burn, roast, and calcine are used; but in general he uses the latin verbs in the order given to indicate degrees of heat. we have used the english verbs in their technical sense as indicated by the context. it is very difficult to say when roasting began as a distinct and separate metallurgical step in sulphide ore treatment. the greeks and romans worked both lead and copper sulphides (see note on p. , and note on p. ), but neither in the remains of old works nor in their literature is there anything from which satisfactory details of such a step can be obtained. the ancients, of course, understood lime-burning, and calcined several salts to purify them or to render them more caustic. practically the only specific mention is by pliny regarding lead ores (see p. ). even the statement of theophilus ( - , a.d.), may refer simply to rendering ore more fragile, for he says (p. ) in regard to copper ore: "this stone dug up in abundance is placed upon a pile and burned (_comburitur_) after the manner of lime. nor does it change colour, but loses its hardness and can be broken up, and afterward it is smelted." the _probierbüchlein_ casually mentions roasting prior to assaying, and biringuccio (iii, ) mentions incidentally that "dry and ill-disposed ores before everything must be roasted in an open oven so that the air can get in." he gives no further information; and therefore this account of agricola's becomes practically the first. apparently roasting, as a preliminary to the treatment of copper sulphides, did not come into use in england until some time later than agricola, for in col. grant francis' "smelting of copper in the swansea district" (london, , p. ), a report is set of the "doeinges of jochim ganse"--an imported german--at the "mynes by keswicke in cumberland, a.d., ," wherein the delinquencies of the then current practice are described: "thei never coulde, nether yet can make (copper) under xxii. tymes passinge thro the fire, and xxii. weekes doeing thereof ane sometyme more. but now the nature of these ix. hurtfull humors abovesaid being discovered and opened by jochim's way of doeing, we can, by his order of workeinge, so correct theim, that parte of theim beinge by nature hurtfull to the copper in wasteinge of it, ar by arte maide freindes, and be not onely an encrease to the copper, but further it in smeltinge; and the rest of the other evill humors shalbe so corrected, and their humors so taken from them, that by once rosteinge and once smeltinge the ure (which shalbe done in the space of three dayes), the same copper ure shall yeeld us black copper." jochim proposed by 'rostynge' to be rid of "sulphur, arsineque, and antimony." [ ] _orpiment_ and _realgar_ are the red and yellow arsenical sulphides. (see note on p. ). [ ] _cadmia bituminosa_. the description of this substance by agricola, given below, indicates that it was his term for the complex copper-zinc-arsenic-cobalt minerals found in the well-known, highly bituminous, copper schists at mannsfeld. the later mineralogists, wallerius (_mineralogia_, stockholm, ), valmont de bomare (_mineralogie_, paris, ), and others assume agricola's _cadmia bituminosa_ to be "black arsenic" or "arsenic noir," but we see no reason for this assumption. agricola's statement (_de nat. foss._, p. ) is "... the schistose stone dug up at the foot of the melibocus mountains, or as they are now called the harz (_hercynium_), near eisleben, mannsfeld, and near hettstedt, is similar to _spinos_ (a bituminous substance described by theophrastus), if not identical with it. this is black, bituminous, and cupriferous, and when first extracted from the mine it is thrown out into an open space and heaped up in a mound. then the lower part of the mound is surrounded by faggots, on to which are likewise thrown stones of the same kind. then the faggots are kindled and the fire soon spreads to the stones placed upon them; by these the fire is communicated to the next, which thus spreads to the whole heap. this easy reception of fire is a characteristic which bitumen possesses in common with sulphur. yet the small, pure and black bituminous ore is distinguished from the stones as follows: when they burn they emit the kind of odour which is usually given off by burning bituminous coal, and besides, if while they are burning a small shower of rain should fall, they burn more brightly and soften more quickly. indeed, when the wind carries the fumes so that they descend into nearby standing waters, there can be seen floating in it something like a bituminous liquid, either black, or brown, or purple, which is sufficient to indicate that those stones were bituminous. and that genus of stones has been recently found in the harz in layers, having occasionally gold-coloured specks of pyrites adhering to them, representing various flat sea-fish or pike or perch or birds, and poultry cocks, and sometimes salamanders." [ ] _atramentum sutorium rubrum_. literally, this would be red vitriol. the german translation gives _rot kupferwasser_, also red vitriol. we must confess that we cannot make this substance out, nor can we find it mentioned in the other works of agricola. it may be the residue from leaching roasted pyrites for vitriol, which would be reddish oxide of iron. [ ] the statement "elsewhere" does not convey very much more information. it is (_de nat. fos._, p. ): "when goslar pyrites and eisleben (copper) schists are placed on the pyre and roasted for the third time, they both exude a certain substance which is of a greenish colour, dry, rough, and fibrous (_tenue_). this substance, like asbestos, is not consumed by the fire. the schists exude it more plentifully than the pyrites." the _interpretatio_ gives _federwis_, as the german equivalent of _amiantus_ (asbestos). this term was used for the feathery alum efflorescence on aluminous slates. [ ] bearing in mind that bituminous cadmia contained arsenical-cobalt minerals, this substance "resembling _pompholyx_" would probably be arsenic oxide. in _de natura fossilium_ (p. ). agricola discusses the _pompholyx_ from _cadmia_ at length and pronounces it to be of remarkably "corrosive" quality. (see also note on p. .) [ ] historical note on crushing and concentration of ores. there can be no question that the first step in the metallurgy of ores was direct smelting, and that this antedates human records. the obvious advantages of reducing the bulk of the material to be smelted by the elimination of barren portions of the ore, must have appealed to metallurgists at a very early date. logically, therefore, we should find the second step in metallurgy to be concentration in some form. the question of crushing is so much involved with concentration that we have not endeavoured to keep them separate. the earliest indication of these processes appears to be certain inscriptions on monuments of the iv dynasty ( , b.c.?) depicting gold washing (wilkinson, the ancient egyptians, london, , ii, p. ). certain stelae of the xii dynasty ( , b.c.) in the british museum ( bay and bay ) refer to gold washing in the sudan, and one of them appears to indicate the working of gold ore as distinguished from alluvial. the first written description of the egyptian methods--and probably that reflecting the most ancient technology of crushing and concentration--is that of agatharchides, a greek geographer of the second century b.c. this work is lost, but the passage in question is quoted by diodorus siculus ( st century b.c.) and by photius (died a.d.). we give booth's translation of diodorus (london, , p. ), slightly amended: "in the confines of egypt and the neighbouring countries of arabia and ethiopia there is a place full of rich gold mines, out of which with much cost and pains of many labourers gold is dug. the soil here is naturally black, but in the body of the earth run many white veins, shining like white marble, surpassing in lustre all other bright things. out of these laborious mines, those appointed overseers cause the gold to be dug up by the labour of a vast multitude of people. for the kings of egypt condemn to these mines notorious criminals, captives taken in war, persons sometimes falsely accused, or against whom the king is incens'd; and not only they themselves, but sometimes all their kindred and relations together with them, are sent to work here, both to punish them, and by their labour to advance the profit and gain of the kings. there are infinite numbers upon these accounts thrust down into these mines, all bound in fetters, where they work continually, without being admitted any rest night or day, and so strictly guarded that there is no possibility or way left to make an escape. for they set over them barbarians, soldiers of various and strange languages, so that it is not possible to corrupt any of the guard by discoursing one with another, or by the gaining insinuations of familiar converse. the earth which is hardest and full of gold they soften by putting fire under it, and then work it out with their hands. the rocks thus soften'd and made more pliant and yielding, several thousands of profligate wretches break in pieces with hammers and pickaxes. there is one artist that is the overseer of the whole work, who marks out the stone, and shows the labourers the way and manner how he would have it done. those that are the strongest amongst them that are appointed to this slavery, provided with sharp iron pickaxes, cleave the marble-shining rock by mere force and strength, and not by arts or sleight-of-hand. they undermine not the rock in a direct line, but follow the bright shining vein of the mine. they carry lamps fastened to their foreheads to give them light, being otherwise in perfect darkness in the various windings and turnings wrought in the mine; and having their bodies appearing sometimes of one colour and sometimes of another (according to the nature of the mine where they work) they throw the lumps and pieces of the stone cut out of the rock upon the floor. and thus they are employed continually without intermission, at the very nod of the overseer, who lashes them severely besides. and there are little boys who penetrate through the galleries into the cavities and with great labour and toil gather up the lumps and pieces hewed out of the rock as they are cast upon the ground, and carry them forth and lay them upon the bank. those that are over thirty years of age take a piece of the rock of such a certain quantity, and pound it in a stone mortar with iron pestles till it be as small as a vetch; then those little stones so pounded are taken from them by women and older men, who cast them into mills that stand together there near at hand in a long row, and two or three of them being employed at one mill they grind a certain measure given to them at a time, until it is as small as fine meal. no care at all is taken of the bodies of these poor creatures, so that they have not a rag so much as to cover their nakedness, and no man that sees them can choose but commiserate their sad and deplorable condition. for though they are sick, maimed, or lame, no rest nor intermission in the least is allowed them; neither the weakness of old age, nor women's infirmities are any plea to excuse them; but all are driven to their work with blows and cudgelling, till at length, overborne with the intolerable weight of their misery, they drop down dead in the midst of their insufferable labours; so that these miserable creatures always expect the future to be more terrible than even the present, and therefore long for death as far more desirable than life. "at length the masters of the work take the stone thus ground to powder, and carry it away in order to perfect it. they spread the mineral so ground upon a broad board, somewhat sloping, and pouring water upon it, rub it and cleanse it; and so all the earthy and drossy part being separated from the rest by the water, it runs off the board, and the gold by reason of its weight remains behind. then washing it several times again, they first rub it lightly with their hands; afterward they draw off any earthy and drossy matter with slender sponges gently applied to the powdered dust, till it be clean, pure gold. at last other workmen take it away by weight and measure, and these put it into earthen pots, and according to the quantity of the gold in every pot they mix with it some lead, grains of salt, a little tin and barley bran. then, covering every pot close, and carefully daubing them over with clay, they put them in a furnace, where they abide five days and nights together; then after a convenient time that they have stood to cool, nothing of the other matter is to be found in the pots but only pure, refined gold, some little thing diminished in the weight. and thus gold is prepared in the borders of egypt, and perfected and completed with so many and so great toils and vexations. and, therefore, i cannot but conclude that nature itself teaches us, that as gold is got with labour and toil, so it is kept with difficulty; it creates everywhere the greatest cares; and the use of it is mixed both with pleasure and sorrow." the remains at mt. laurion show many of the ancient mills and concentration works of the greeks, but we cannot be absolutely certain at what period in the history of these mines crushing and concentration were introduced. while the mines were worked with great activity prior to b.c. (see note , p. ), it was quite feasible for the ancient miner to have smelted these argentiferous lead ores direct. however, at some period prior to the decadence of the mines in the rd century b.c., there was in use an extensive system of milling and concentration. for the following details we are indebted mostly to edouard ardaillon (_les mines du laurion dans l'antiquité_, chap. iv.). the ore was first hand-picked (in one portion of these rejects was estimated at , , tons) and afterward it was apparently crushed in stone mortars some to inches in diameter, and thence passed to the mills. these mills, which crushed dry, were of the upper and lower millstone order, like the old-fashioned flour mills, and were turned by hand. the stones were capable of adjustment in such a way as to yield different sizes. the sand was sifted and the oversize returned to the mills. from the mills it was taken to washing plants, which consisted essentially of an inclined area, below which a canal, sometimes with riffles, led through a series of basins, ultimately returning the water again to near the head of the area. these washing areas, constructed with great care, were made of stone cemented over smoothly, and were so efficiently done as to remain still intact. in washing, a workman brushed upward the pulp placed on the inclined upper portion of the area, thus concentrating there a considerable proportion of the galena; what escaped had an opportunity to settle in the sequence of basins, somewhat on the order of the buddle. a quotation by strabo (iii, , ) from the lost work of polybius ( - b.c.) also indicates concentration of lead-silver ores in spain previous to the christian era: "polybius speaking of the silver mines of new carthage, tells us that they are extremely large, distant from the city about stadia, and occupy a circuit of stadia, that there are , men regularly engaged in them, and that they yield daily to the roman people (a revenue of) , drachmae. the rest of the process i pass over, as it is too long, but as for the silver ore collected, he tells us that it is broken up, and sifted through sieves over water; that what remains is to be again broken, and the water having been strained off, it is to be sifted and broken a third time. the dregs which remain after the fifth time are to be melted, and the lead being poured off, the silver is obtained pure. these silver mines still exist; however, they are no longer the property of the state, neither these nor those elsewhere, but are possessed by private individuals. the gold mines, on the contrary, nearly all belong to the state. both at castlon and other places there are singular lead mines worked. they contain a small proportion of silver, but not sufficient to pay for the expense of refining." (hamilton's translation, vol. i., p. ). while pliny gives considerable information on vein mining and on alluvial washing, the following obscure passage (xxxiii, ) appears to be the only reference to concentration of ores: "that which is dug out is crushed, washed, roasted, and ground to powder. this powder is called _apitascudes_, while the silver (lead?) which becomes disengaged in the furnace is called _sudor_ (sweat). that which is ejected from the chimney is called _scoria_ as with other metals. in the case of gold this _scoria_ is crushed and melted again." it is evident enough from these quotations that the ancients by "washing" and "sifting," grasped the practical effect of differences in specific gravity of the various components of an ore. such processes are barely mentioned by other mediæval authors, such as theophilus, biringuccio, etc., and thus the account in this chapter is the first tangible technical description. lead mining has been in active progress in derbyshire since the th century, and concentration was done on an inclined board until the th century, when william humphrey (see below) introduced the jigging sieve. some further notes on this industry will be found in note , p. . however, the buddle and strake which appear at that time, are but modest improvements over the board described by agatharchides in the quotation above. the ancient crushing appliances, as indicated by the ancient authors and by the greek and roman remains scattered over europe, were hand-mortars and mill-stones of the same order as those with which they ground flour. the stamp-mill, the next advance over grinding in mill-stones, seems to have been invented some time late in the th or early in the th centuries, but who invented it is unknown. beckmann (hist. of inventions, ii, p. ) says: "in the year the process of sifting and wet-stamping was established at joachimsthal by paul grommestetter, a native of schwarz, named on that account the schwarzer, whom melzer praises as an ingenious and active washer; and we are told that he had before introduced the same improvements at schneeberg. soon after, that is in , a large stamping-work was erected at joachimsthal, and the process of washing was begun. a considerable saving was thus made, as a great many metallic particles were before left in the washed sand, which was either thrown away or used as mortar for building. in the year , hans pörtner employed at schlackenwalde the wet method of stamping, whereas before that period the ore there was ground. in the harz this invention was introduced at wildenmann by peter philip, who was assay-master there soon after the works at the upper harz were resumed by duke henry the younger, about the year . this we learn from the papers of herdan hacke or haecke, who was preacher at wildenmann in ." in view of the great amount of direct and indirect reference to tin mining in cornwall, covering four centuries prior to agricola, it would be natural to expect some statement bearing upon the treatment of ore. curiously enough, while alluvial washing and smelting of the black-tin are often referred to, there is nothing that we have been able to find, prior to richard carew's "survey of cornwall" (london, , p. ) which gives any tangible evidence on the technical phases of ore-dressing. in any event, an inspection of charters, tax-rolls, stannary court proceedings, etc., prior to that date gives the impression that vein mining was a very minor portion of the source of production. although carew's work dates years after agricola, his description is of interest: "as much almost dooth it exceede credite, that the tynne, for and in so small quantitie digged up with so great toyle, and passing afterwards thorow the managing of so many hands, ere it comes to sale, should be any way able to acquite the cost: for being once brought above ground in the stone, it is first broken in peeces with hammers; and then carryed, either in waynes, or on horses' backs, to a stamping mill, where three, and in some places sixe great logges of timber, bounde at the ends with yron, and lifted up and downe by a wheele, driven with the water, doe break it smaller. if the stones be over-moyst, they are dried by the fire in an yron cradle or grate. from the stamping mill, it passeth to the crazing mill, which betweene two grinding stones, turned also with a water-wheel, bruseth the same to a find sand; howbeit, of late times they mostly use wet stampers, and so have no need of the crazing mills for their best stuffe, but only for the crust of their tayles. the streame, after it hath forsaken the mill, is made to fall by certayne degrees, one somewhat distant from another; upon each of which, at every discent, lyeth a greene turfe, three or foure foote square, and one foote thick. on this the tinner layeth a certayne portion of the sandie tinne, and with his shovel softly tosseth the same to and fro, that, through this stirring, the water which runneth over it may wash away the light earth from the tinne, which of a heavier substance lyeth fast on the turfe. having so clensed one portion, he setteth the same aside, and beginneth with another, until his labour take end with his taske. the best of those turfes (for all sorts serve not) are fetched about two miles to the eastwards of s. michael's mount, where at low water they cast aside the sand, and dig them up; they are full of rootes of trees, and on some of them nuts have been found, which confirmeth my former assertion of the sea's intrusion. after it is thus washed, they put the remnant into a wooden dish, broad, flat, and round, being about two foote over, and having two handles fastened at the sides, by which they softly shogge the same to and fro in the water betweene their legges, as they sit over it, untill whatsoever of the earthie substance that was yet left be flitted away. some of later time, with a sleighter invention, and lighter labour, doe cause certayne boyes to stir it up and down with their feete, which worketh the same effect; the residue, after this often clensing, they call blacke tynne." it will be noticed that the "wet stampers" and the buddle--worked with "boyes feete"--are "innovations of late times." and the interesting question arises as to whether cornwall did not derive the stamp-mill, buddle, and strake, from the germans. the first adequate detailed description of cornish appliances is that of pryce (_mineralogia cornubiensis_, london, ) where the apparatus is identical with that described by agricola years before. the word "stamper" of cornwall is of german origin, from _stampfer_, or, as it is often written in old german works, _stamper_. however, the pursuit of the subject through etymology ends here, for no derivatives in german can be found for buddle, tye, strake, or other collateral terms. the first tangible evidence of german influence is to be found in carew who, continuing after the above quotation, states: "but sithence i gathered stickes to the building of this poore nest, sir francis godolphin (whose kind helpe hath much advanced this my playing labour) entertained a dutch mynerall man, and taking light from his experience, but building thereon farre more profitable conclusions of his owne invention, hath practised a more saving way in these matters, and besides, made tynne with good profit of that refuse which tynners rejected as nothing worth." beyond this quotation we can find no direct evidence of the influence of "dutch mynerall men" in cornish tin mining at this time. there can be no doubt, however, that in copper mining in cornwall and elsewhere in england, the "dutch mynerall men" did play a large part in the latter part of the th century. pettus (_fodinæ regales_, london, , p. ) states that "about the third year of queen elizabeth ( ) she by the advice of her council sent over for some germans experienced in mines, and being supplied, she, on the tenth of october, in the sixth of her reign, granted the mines of eight counties ... to houghsetter, a german whose name and family still continue in cardiganshire." elizabeth granted large mining rights to various germans, and the opening paragraphs of two out of several charters may be quoted in point. this grant is dated , and in part reads: "elizabeth, by the grace of god, queen of england, france, and ireland, defender of the faith, &c. to all men to whom these letters patents shall come, greeting. where heretofore we have granted privileges to cornelius de voz, for the mining and digging in our realm of england, for allom and copperas, and for divers ewers of metals that were to be found in digging for the said allom and copperas, incidently and consequently without fraud or guile, as by the same our privilege may appear. and where we also moved, by credible report to us made, of one daniel houghsetter, a german born, and of his skill and knowledge of and in all manner of mines, of metals and minerals, have given and granted privilege to thomas thurland, clerk, one of our chaplains, and master of the hospital of savoy, and to the same daniel, for digging and mining for all manner of ewers of gold, silver, copper, and quicksilver, within our counties of york, lancaster, cumberland, westmorland, cornwall, devon, gloucester, and worcester, and within our principality of wales; and with the same further to deal, as by our said privilege thereof granted and made to the said thomas thurland and daniel houghsetter may appear. _and_ we now being minded that the said commodities, and all other treasures of the earth, in all other places of our realm of england...." on the same date another grant reads: "elizabeth, by the grace of god, queen of england, france, and ireland, defender of the faith, &c. to all men to whom these our letters patents shall come, greeting. where we have received credible information that our faithful and well-beloved subject william humfrey, saymaster of our mint within our tower of london, by his great endeavour, labour, and charge, hath brought into this our realm of england one christopher shutz, an almain, born at _st. annen berg_, under the obedience of the electer of saxony; a workman as it is reported, of great cunning, knowledge, and experience, as well in the finding of the calamin stone, call'd in latin, _lapis calaminaris_, and in the right and proper use and commodity thereof, for the composition of the mix'd metal commonly call'd _latten_, etc." col. grant-francis, in his most valuable collection (smelting of copper in the swansea district, london, ) has published a collection of correspondence relating to early mining and smelting operations in great britain. and among them (p. ., etc.) are letters in the years - from william carnsewe and others to thomas smyth, with regard to the first smelter erected at neath, which was based upon copper mines in cornwall. he mentions "mr. weston's (a partner) provydence in bringynge hys dutch myners hether to aplye such businys in this countrye ys more to be commendyd than his ignorance of our countrymen's actyvytyes in suche matters." the principal "dutche mineral master" referred to was one ulrick frosse, who had charge of the mine at perin sands in cornwall, and subsequently of the smelter at neath. further on is given (p. ) a report by jochim gaunse upon the smelting of copper ores at keswick in cumberland in , referred to in note , p. . the daniel hochstetter mentioned in the charter above, together with other german and english gentlemen, formed the "company of mines royal" and among the properties worked were those with which gaunse's report is concerned. there is in the record office, london (exchequer k.r. com. derby . eliz.) the record of an interesting inquisition into derbyshire methods in which a then recent great improvement was the jigging sieve, the introduction of which was due to william humphrey (mentioned above). it is possible that he learned of it from the german with whom he was associated. much more evidence of the activity of the germans in english mining at this period can be adduced. on the other hand, cornwall has laid claims to having taught the art of tin mining and metallurgy to the germans. matthew paris, a benedictine monk, by birth an englishman, who died in , relates (_historia major angliae_, london, ) that a cornishman who fled to germany on account of a murder, first discovered tin there in , and that in consequence the price of tin fell greatly. this statement is recalled with great persistence by many writers on cornwall. (camden, _britannia_, london, ; borlase, natural history of cornwall, oxford, ; pryce, _mineralogia cornubiensis_, london, , p. , and others). [ ] _lapidibus liquescentibus_. (see note , p. ). [ ] historical note on amalgamation. the recovery of gold by the use of mercury possibly dates from roman times, but the application of the process to silver does not seem to go back prior to the th century. quicksilver was well-known to the greeks, and is described by theophrastus ( ) and others (see note , p. , on quicksilver). however, the greeks made no mention of its use for amalgamation, and, in fact, dioscorides (v, ) says "it is kept in vessels of glass, lead, tin or silver; if kept in vessels of any other kind it consumes them and flows away." it was used by them for medicinal purposes. the romans amalgamated gold with mercury, but whether they took advantage of the principle to recover gold from ores we do not know. vitruvius (vii, ) makes the following statement:--"if quicksilver be placed in a vessel and a stone of a hundred pounds' weight be placed on it, it will swim at the top, and will, notwithstanding its weight, be incapable of pressing the liquid so as to break or separate it. if this be taken out, and only a single scruple of gold be put in, that will not swim, but immediately descend to the bottom. this is a proof that the gravity of a body does not depend on its weight, but on its nature. quicksilver is used for many purposes; without it, neither silver nor brass can be properly gilt. when gold is embroidered on a garment which is worn out and no longer fit for use, the cloth is burnt over the fire in earthen pots; the ashes are thrown into water and quicksilver added to them; this collects all the particles of gold and unites with them. the water is then poured off and the residuum placed in a cloth, which, when squeezed with the hands, suffers the liquid quicksilver to pass through the pores of the cloth, but retains the gold in a mass within it." (gwilt's trans., p. ). pliny is rather more explicit (xxxiii, ): "all floats on it (quicksilver) except gold. this it draws into itself, and on that account is the best means of purifying; for, on being repeatedly agitated in earthen pots it casts out the other things and the impurities. these things being rejected, in order that it may give up the gold, it is squeezed in prepared skins, through which, exuding like perspiration, it leaves the gold pure." it may be noted particularly that both these authors state that gold is the only substance that does not float, and, moreover, nowhere do we find any reference to silver combining with mercury, although beckmann (hist. of inventions, vol. i, p. ) not only states that the above passage from pliny refers to silver, but in further error, attributes the origin of silver amalgamation of ores to the spaniards in the indies. the alchemists of the middle ages were well aware that silver would amalgamate with mercury. there is, however, difficulty in any conclusion that it was applied by them to separating silver or gold from ore. the involved gibberish in which most of their utterances was couched, obscures most of their reactions in any event. the school of geber (appendix b) held that all metals were a compound of "spiritual" mercury and sulphur, and they clearly amalgamated silver with mercury, and separated them by distillation. the _probierbüchlein_ ( ?) describes a method of recovering silver from the cement used in parting gold and silver, by mixing the cement (silver chlorides) with quicksilver. agricola nowhere in this work mentions the treatment of silver ores by amalgamation, although he was familiar with biringuccio (_de la pirotechnia_), as he himself mentions in the preface. this work, published at least ten years before _de re metallica_, contains the first comprehensive account of silver amalgamation. there is more than usual interest in the description, because, not only did it precede _de re metallica_, but it is also a specific explanation of the fundamental essentials of the patio process long before the date when the spaniards could possibly have invented that process in mexico. we quote mr. a. dick's translation from percy (metallurgy of silver and gold, p. ): "he was certainly endowed with much useful and ingenious thought who invented the short method of extracting metal from the sweepings produced by those arts which have to do with gold and silver, every substance left in the refuse by smelters, and also the substance from certain ores themselves, without the labour of fusing, but by the sole means and virtue of mercury. to effect this, a large basin is first constructed of stone or timber and walled, into which is fitted a millstone made to turn like that of a mill. into the hollow of this basin is placed matter containing gold (_della materia vra che tiene oro_), well ground in a mortar and afterward washed and dried; and, with the above-mentioned millstone, it is ground while being moistened with vinegar, or water, in which has been dissolved corrosive sublimate (_solimato_), verdigris (_verde rame_), and common salt. over these materials is then put as much mercury as will cover them; they are then stirred for an hour or two, by turning the millstone, either by hand, or horse-power, according to the plan adopted, bearing in mind that the more the mercury and the materials are bruised together by the millstone, the more the mercury may be trusted to have taken up the substance which the materials contain. the mercury, in this condition, can then be separated from the earthy matter by a sieve, or by washing, and thus you will recover the auriferous mercury (_el vro mercurio_). after this, by driving off the mercury by means of a flask (_i.e._, by heating in a retort or an alembic), or by passing it through a bag, there will remain, at the bottom, the gold, silver, or copper, or whatever metal was placed in the basin under the millstone to be ground. having been desirous of knowing this secret, i gave to him who taught it to me a ring with a diamond worth ducats; he also required me to give him the eighth part of any profit i might make by using it. this i wished to tell you, not that you should return the ducats to me for teaching you the secret, but in order that you should esteem it all the more and hold it dear." in another part of the treatise biringuccio states that washed (concentrated) ores may be ultimately reduced either by lead or mercury. concerning these silver concentrates he writes: "afterward drenching them with vinegar in which has been put green copper (_i.e._, verdigris); or drenching them with water in which has been dissolved vitriol and green copper...." he next describes how this material should be ground with mercury. the question as to who was the inventor of silver amalgamation will probably never be cleared up. according to ulloa (_relacion historica del viage a la america meridional_, madrid, ) dom pedro fernandes de velasco discovered the process in mexico in . the earliest technical account is that of father joseph de acosta (_historia natural y moral de las indias_, seville, , english trans. edward grimston, london, , re-published by the hakluyt society, ). acosta was born in , and spent the years to in peru, and in mexico. it may be noted that potosi was discovered in . he states that refining silver with mercury was introduced at potosi by pedro fernandes de velasco from mexico in , and states (grimston's trans., vol. i, p. ): "... they put the powder of the metall into the vessels upon furnaces, whereas they anoint it and mortifie it with brine, putting to every fiftie quintalles of powder five quintalles of salt. and this they do for that the salt separates the earth and filth, to the end the quicksilver may the more easily draw the silver unto it. after, they put quicksilver into a piece of holland and presse it out upon the metall, which goes forth like a dewe, alwaies turning and stirring the metall, to the end it may be well incorporate. before the invention of these furnaces of fire, they did often mingle their metall with quicksilver in great troughes, letting it settle some daies, and did then mix it and stirre it againe, until they thought all the quicksilver were well incorporate with the silver, the which continued twentie daies and more, and at least nine daies." frequent mention of the different methods of silver amalgamation is made by the spanish writers subsequent to this time, the best account being that of alonso barba, a priest. barba was a native of lepe, in andalusia, and followed his calling at various places in peru from about to about , and at one time held the curacy of st. bernard at potosi. in he published at madrid his _arte de los metales_, etc., in five books. the first two books of this work were translated into english by the earl of sandwich, and published in london in , under the title "the first book of the art of metals." this translation is equally wretched with those in french and german, as might be expected from the translators' total lack of technical understanding. among the methods of silver amalgamation described by barba is one which, upon later "discovery" at virginia city, is now known as the "washoe process." none of the spanish writers, so far as we know, make reference to biringuccio's account, and the question arises whether the patio process was an importation from europe or whether it was re-invented in mexico. while there is no direct evidence on the point, the presumption is in favour of the former. the general introduction of the amalgamation of silver ores into central europe seems to have been very slow, and over years elapsed after its adoption in peru and mexico before it received serious attention by the german metallurgists. ignaz elder v. born was the first to establish the process effectually in europe, he having in erected a "quick-mill" at glasshutte, near shemnitz. he published an elaborate account of a process which he claimed as his own, under the title _ueber das anquicken der gold und silberhältigen erze_, vienna, . the only thing new in his process seems to have been mechanical agitation. according to born, a spaniard named don juan de corduba, in the year , applied to the court at vienna offering to extract silver from ores with mercury. various tests were carried out under the celebrated lazarus erckern, and although it appears that some vitriol and salt were used, the trials apparently failed, for erckern concluded his report with the advice: "that their lordships should not suffer any more expense to be thrown away upon this experiment." born's work was translated into english by r. e. raspe, under the title--"baron inigo born's new process of amalgamation, etc.," london, . some interest attaches to raspe, in that he was not only the author of "baron munchausen," but was also the villain in scott's "antiquary." raspe was a german professor at cassel, who fled to england to avoid arrest for theft. he worked at various mines in cornwall, and in involved sir john sinclair in a fruitless mine, but disappeared before that was known. the incident was finally used by sir walter scott in this novel. [ ] _aurum in ea remanet purum_. this same error of assuming squeezed amalgam to be pure gold occurs in pliny; see previous footnote. [ ] george, duke of saxony, surnamed "the bearded," was born , and died . he was chiefly known for his bitter opposition to the reformation. [ ] the julian alps are a section east of the carnic alps and lie north of trieste. the term rhaetian alps is applied to that section along the swiss italian boundary, about north of lake como. [ ] ancient lusitania comprised portugal and some neighbouring portions of spain. [ ] colchis, the traditional land of the golden fleece, lay between the caucasus on the north, armenia on the south, and the black sea on the west. if agricola's account of the metallurgical purpose of the fleece is correct, then jason must have had real cause for complaint as to the tangible results of his expedition. the fact that we hear nothing of the fleece after the day it was taken from the dragon would thus support agricola's theory. tons of ink have been expended during the past thirty centuries in explanations of what the fleece really was. these explanations range through the supernatural and metallurgical, but more recent writers have endeavoured to construct the journey of the argonauts into an epic of the development of the greek trade in gold with the euxine. we will not attempt to traverse them from a metallurgical point of view further than to maintain that agricola's explanation is as probable and equally as ingenious as any other, although strabo (xi, , .) gives much the same view long before. alluvial mining--gold washing--being as old as the first glimmer of civilization, it is referred to, directly or indirectly, by a great majority of ancient writers, poets, historians, geographers, and naturalists. early egyptian inscriptions often refer to this industry, but from the point of view of technical methods the description by pliny is practically the only one of interest, and in pliny's chapter on the subject, alluvial is badly confused with vein mining. this passage (xxxiii, ) is as follows: "gold is found in the world in three ways, to say nothing of that found in india by the ants, and in scythia by the griffins. the first is as gold dust found in streams, as, for instance, in the tagus in spain, in the padus in italy, in the hebrus in thracia, in the pactolus in asia, and in the ganges in india; indeed, there is no gold found more perfect than this, as the current polishes it thoroughly by attrition.... others by equal labour and greater expense bring rivers from the mountain heights, often a hundred miles, for the purpose of washing this debris. the ditches thus made are called _corrugi_, from our word _corrivatio_, i suppose; and these entail a thousand fresh labours. the fall must be steep, that the water may rush down from very high places, rather than flow gently. the ditches across the valleys are joined by aqueducts, and in other places, impassable rocks have to be cut away and forced to make room for troughs of hollowed-out logs. those who cut the rocks are suspended by ropes, so that to those who watch them from a distance, the workmen seem not so much beasts as birds. hanging thus, they take the levels and trace the lines which the ditch is to take; and thus, where there is no place for man's footstep, streams are dragged by men. the water is vitiated for washing if the current of the stream carries mud with it. this kind of earth is called _urium_, hence these ditches are laid out to carry the water over beds of pebbles to avoid this _urium_. when they have reached the head of the fall, at the top of the mountain, reservoirs are excavated a couple of hundred feet long and wide, and about ten feet deep. in these reservoirs there are generally five gates left, about three feet square, so that when the reservoir is full, the gates are opened, and the torrent bursts forth with such violence that the rocks are hurled along. when they have reached the plain there is yet more labour. trenches called _agogae_ are dug for the flow of the water. the bottoms of these are spread at regular intervals with _ulex_ to catch the gold. this _ulex_ is similar to rosemary, rough and prickly. the sides, too, are closed in with planks and are suspended when crossing precipitous spots. the earth is carried to the sea and thus the shattered mountain is washed away and scattered; and this deposition of the earth in the sea has extended the shore of spain.... the gold procured from _arrugiae_ does not require to be melted, but is already pure gold. it is found in lumps, in shafts as well, sometimes even exceeding ten _librae_ in weight. these lumps are called _palagae_ and _palacurnae_, while the small grains are called _baluce_. the ulex is dried and burnt and the ashes are washed on a bed of grassy turf in order that the gold may settle thereon." [ ] _carbunculus carchedonius_--carthaginian carbuncle. the german is given by agricola in the _interpretatio_ as _granat_, _i.e._, garnet. [ ] as the concentration of crushed tin ore has been exhaustively treated of already, the descriptions from here on probably refer entirely to alluvial tin. [ ] from a metallurgical point of view all of these operations are roasting. even to-day, however, the expression "burning" tin is in use in some parts of cornwall, and in former times it was general. [ ] there can be no doubt that these are mattes, as will develop in book ix. the german term in the glossary for _panes ex pyrite_ is _stein_, the same as the modern german for matte. orpiment and realgar are the yellow and red arsenical sulphides. the _cadmia_ was no doubt the cobalt-arsenic minerals (see note on p. ). the "solidified juices" were generally anything that could be expelled short of smelting, _i.e._, roasted off or leached out, as shown in note , p. ; they embrace the sulphates, salts, sulphur, bitumen, and arsenical sulphides, etc. for further information on leaching out the sulphates, alum, etc., see note , p. . book ix.[ ] since i have written of the varied work of preparing the ores, i will now write of the various methods of smelting them. although those who burn, roast and calcine[ ] the ore, take from it something which is mixed or combined with the metals; and those who crush it with stamps take away much; and those who wash, screen and sort it, take away still more; yet they cannot remove all which conceals the metal from the eye and renders it crude and unformed. wherefore smelting is necessary, for by this means earths, solidified juices, and stones are separated from the metals so that they obtain their proper colour and become pure, and may be of great use to mankind in many ways. when the ore is smelted, those things which were mixed with the metal before it was melted are driven forth, because the metal is perfected by fire in this manner. since metalliferous ores differ greatly amongst themselves, first as to the metals which they contain, then as to the quantity of the metal which is in them, and then by the fact that some are rapidly melted by fire and others slowly, there are, therefore, many methods of smelting. constant practice has taught the smelters by which of these methods they can obtain the most metal from any one ore. moreover, while sometimes there are many methods of smelting the same ore, by which an equal weight of metal is melted out, yet one is done at a greater cost and labour than the others. ore is either melted with a furnace or without one; if smelted with a furnace the tap-hole is either temporarily closed or always open, and if smelted without a furnace, it is done either in pots or in trenches. but in order to make this matter clearer, i will describe each in detail, beginning with the buildings and the furnaces. a wall which will be called the "second wall" is constructed of brick or stone, two feet and as many palms thick, in order that it may be strong enough to bear the weight. it is built fifteen feet high, and its length depends on the number of furnaces which are put in the works; there are usually six furnaces, rarely more, and often less. there are three furnace walls, a back one which is against the "second" wall, and two side ones, of which i will speak later. these should be made of natural stone, as this is more serviceable than burnt bricks, because bricks soon become defective and crumble away, when the smelter or his deputy chips off the accretions which adhere to the walls when the ore is smelted. natural stone resists injury by the fire and lasts a long time, especially that which is soft and devoid of cracks; but, on the contrary, that which is hard and has many cracks is burst asunder by the fire and destroyed. for this reason, furnaces which are made of the latter are easily weakened by the fire, and when the accretions are chipped off they crumble to pieces. the front furnace wall should be made of brick, and there should be in the lower part a mouth three palms wide and one and a half feet high, when the hearth is completed. a hole slanting upward, three palms long, is made through the back furnace wall, at the height of a cubit, before the hearth has been prepared; through this hole and a hole one foot long in the "second" wall--as the back of this wall has an arch--is inserted a pipe of iron or bronze, in which are fixed the nozzles of the bellows. the whole of the front furnace wall is not more than five feet high, so that the ore may be conveniently put into the furnace, together with those things which the master needs for his work of smelting. both the side walls of the furnace are six feet high, and the back one seven feet, and they are three palms thick. the interior of the furnace is five palms wide, six palms and a digit long, the width being measured by the space which lies between the two side walls, and the length by the space between the front and the back walls; however, the upper part of the furnace widens out somewhat. [illustration (blast furnaces): a--furnaces. b--forehearths.] there are two doors in the second wall if there are six furnaces, one of the doors being between the second and third furnaces and the other between the fourth and fifth furnaces. they are a cubit wide and six feet high, in order that the smelters may not have mishaps in coming and going. it is necessary to have a door to the right of the first furnace, and similarly one to the left of the last, whether the wall is longer or not. the second wall is carried further when the rooms for the cupellation furnaces, or any other building, adjoin the rooms for the blast furnaces, these buildings being only divided by a partition. the smelter, and the ones who attend to the first and the last furnaces, if they wish to look at the bellows or to do anything else, go out through the doors at the end of the wall, and the other people go through the other doors, which are the common ones. the furnaces are placed at a distance of six feet from one another, in order that the smelters and their assistants may more easily sustain the fierceness of the heat. inasmuch as the interior of each furnace is five palms wide and each is six feet distant from the other, and inasmuch as there is a space of four feet three palms at the right side of the first furnace and as much at the left side of the last furnace, and there are to be six furnaces in one building, then it is necessary to make the second wall fifty-two feet long; because the total of the widths of all of the furnaces is seven and a half feet, the total of the spaces between the furnaces is thirty feet, the space on the outer sides of the first and last furnaces is nine feet and two palms, and the thickness of the two transverse walls is five feet, which make a total measurement of fifty-two feet.[ ] outside each furnace hearth there is a small pit full of powder which is compressed by ramming, and in this manner is made the forehearth which receives the metal flowing from the furnaces. of this i will speak later. [illustration (blast furnaces): a--furnaces. b--forehearth. c--door. d--water tank. e--stone which covers it. f--material of the vent walls. g--stone which covers it. h--pipe exhaling the vapour.] buried about a cubit under the forehearth and the hearth of the furnace is a transverse water-tank, three feet long, three palms wide and a cubit deep. it is made of stone or brick, with a stone cover, for if it were not covered, the heat would draw the moisture from below and the vapour might be blown into the hearth of the furnace as well as into the forehearth, and would dampen the blast. the moisture would vitiate the blast, and part of the metal would be absorbed and part would be mixed with the slags, and in this manner the melting would be greatly damaged. from each water-tank is built a walled vent, to the same depth as the tank, but six digits wide; this vent slopes upward, and sooner or later penetrates through to the other side of the wall, against which the furnace is built. at the end of this vent there is an opening where the steam, into which the water has been converted, is exhausted through a copper or iron tube or pipe. this method of making the tank and the vent is much the best. another kind has a similar vent but a different tank, for it does not lie transversely under the forehearth, but lengthwise; it is two feet and a palm long, and a foot and three palms wide, and a foot and a palm deep. this method of making tanks is not condemned by us, as is the construction of those tanks without a vent; the latter, which have no opening into the air through which the vapour may discharge freely, are indeed to be condemned. [illustration (bellows for blast furnaces)] fifteen feet behind the second wall is constructed the first wall, thirteen feet high. in both of these are fixed roof beams[ ], which are a foot wide and thick, and nineteen feet and a palm long; these are placed three feet distant from one another. as the second wall is two feet higher than the first wall, recesses are cut in the back of it two feet high, one foot wide, and a palm deep, and in these recesses, as it were in mortises, are placed one end of each of the beams. into these ends are mortised the bottoms of just as many posts; these posts are twenty-four feet high, three palms wide and thick, and from the tops of the posts the same number of rafters stretch downward to the ends of the beams superimposed on the first wall; the upper ends of the rafters are mortised into the posts and the lower ends are mortised into the ends of the beams laid on the first wall; the rafters support the roof, which consists of burnt tiles. each separate rafter is propped up by a separate timber, which is a cross-beam, and is joined to its post. planks close together are affixed to the posts above the furnaces; these planks are about two digits thick and a palm wide, and they, together with the wicker work interposed between the timbers, are covered with lute so that there may be no risk of fire to the timbers and wicker-work. in this practical manner is constructed the back part of the works, which contains the bellows, their frames, the mechanism for compressing the bellows, and the instrument for distending them, of all of which i will speak hereafter. [illustration (plan of smelter building): the four long walls: a--first. b--second. c--third. d--fourth. the seven transverse walls: e--first. f--second. g--third. h--fourth. i--fifth. k--sixth. l--seventh, or middle.] in front of the furnaces is constructed the third long wall and likewise the fourth. both are nine feet high, but of the same length and thickness as the other two, the fourth being nine feet distant from the third; the third is twenty-one and a half feet from the second. at a distance of twelve feet from the second wall, four posts seven and a half feet high, a cubit wide and thick, are set upon rock laid underneath. into the tops of the posts the roof beam is mortised; this roof beam is two feet and as many palms longer than the distance between the second and the fifth transverse walls, in order that its ends may rest on the transverse walls. if there should not be so long a beam at hand, two are substituted for it. as the length of the long beam is as above, and as the posts are equidistant, it is necessary that the posts should be a distance of nine feet, one palm, two and two-fifths digits from each other, and the end ones this distance from the transverse walls. on this longitudinal beam and to the third and fourth walls are fixed twelve secondary beams twenty-four feet long, one foot wide, three palms thick, and distant from each other three feet, one palm, and two digits. in these secondary beams, where they rest on the longitudinal beams, are mortised the ends of the same number of rafters as there are posts which stand on the second wall. the ends of the rafters do not reach to the tops of the posts, but are two feet away from them, that through this opening, which is like the open part of a forge, the furnaces can emit their fumes. in order that the rafters should not fall down, they are supported partly by iron rods, which extend from each rafter to the opposite post, and partly supported by a few tie-beams, which in the same manner extend from some rafters to the posts opposite, and give them stability. to these tie-beams, as well as to the rafters which face the posts, a number of boards, about two digits thick and a palm wide, are fixed at a distance of a palm from each other, and are covered with lute so that they do not catch fire. in the secondary beams, where they are laid on the fourth wall, are mortised the lower ends of the same number of rafters as those in a set of rafters[ ] opposite them. from the third long wall these rafters are joined and tied to the ends of the opposite rafters, so that they may not slip, and besides they are strengthened with substructures which are made of cross and oblique timbers. the rafters support the roof. in this manner the front part of the building is made, and is divided into three parts; the first part is twelve feet wide and is under the hood, which consists of two walls, one vertical and one inclined. the second part is the same number of feet wide and is for the reception of the ore to be smelted, the fluxes, the charcoal, and other things which are needed by the smelter. the third part is nine feet wide and contains two separate rooms of equal size, in one of which is the assay furnace, while the other contains the metal to be melted in the cupellation furnaces. it is thus necessary that in the building there should be, besides the four long walls, seven transverse walls, of which the first is constructed from the upper end of the first long wall to the upper end of the second long wall; the second proceeds from the end of this to the end of the third long wall; the third likewise from this end of the last extends to the end of the fourth long wall; the fourth leads from the lower end of the first long wall to the lower end of the second long wall; the fifth extends from the end of this to the end of the third long wall; the sixth extends from this last end to the end of the fourth long wall; the seventh divides into two parts the space between the third and fourth long walls. to return to the back part of the building, in which, as i said, are the bellows[ ], their frames, the machinery for compressing them, and the instrument for distending them. each bellows consists of a body and a head. the body is composed of two "boards," two bows, and two hides. the upper board is a palm thick, five feet and three palms long, and two and a half feet wide at the back part, where each of the sides is a little curved, and it is a cubit wide at the front part near the head. the whole of the body of the bellows tapers toward the head. that which we now call the "board" consists of two pieces of pine, joined and glued together, and of two strips of linden wood which bind the edges of the board, these being seven digits wide at the back, and in front near the head of the bellows one and a half digits wide. these strips are glued to the boards, so that there shall be less damage from the iron nails driven through the hide. there are some people who do not surround the boards with strips, but use boards only, which are very thick. the upper board has an aperture and a handle; the aperture is in the middle of the board and is one foot three palms distant from where the board joins the head of the bellows, and is six digits long and four wide. the lid for this aperture is two palms and a digit long and wide, and three digits thick; toward the back of the lid is a little notch cut into the surface so that it may be caught by the hand; a groove is cut out of the top of the front and sides, so that it may engage in mouldings a palm wide and three digits thick, which are also cut out in a similar manner under the edges. now, when the lid is drawn forward the hole is closed, and when drawn back it is opened; the smelter opens the aperture a little so that the air may escape from the bellows through it, if he fears the hides might be burst when the bellows are too vigorously and quickly inflated; he, however, closes the aperture if the hides are ruptured and the air escapes. others perforate the upper board with two or three round holes in the same place as the rectangular one, and they insert plugs in them which they draw out when it is necessary. the wooden handle is seven palms long, or even longer, in order that it may extend outside; one-half of this handle, two palms wide and one thick, is glued to the end of the board and fastened with pegs covered with glue; the other half projects beyond the board, and is rounded and seven digits thick. besides this, to the handle and to the board is fixed a cleat two feet long, as many palms wide and one palm thick, and to the under side of the same board, at a distance of three palms from the end, is fixed another cleat two feet long, in order that the board may sustain the force of distension and compression; these two cleats are glued to the board, and are fastened to it with pegs covered with glue. the lower bellows-board, like the upper, is made of two pieces of pine and of two strips of linden wood, all glued together; it is of the same width and thickness as the upper board, but is a cubit longer, this extension being part of the head of which i have more to say a little later. this lower bellows-board has an air-hole and an iron ring. the air-hole is about a cubit distant from the posterior end, and it is midway between the sides of the bellows-board, and is a foot long and three palms wide; it is divided into equal parts by a small rib which forms part of the board, and is not cut from it; this rib is a palm long and one-third of a digit wide. the flap of the air-hole is a foot and three digits long, three palms and as many digits wide; it is a thin board covered with goat skin, the hairy part of which is turned toward the ground. there is fixed to one end of the flap, with small iron nails, one-half of a doubled piece of leather a palm wide and as long as the flap is wide; the other half of the leather, which is behind the flap, is twice perforated, as is also the bellows-board, and these perforations are seven digits apart. passing through these a string is tied on the under side of the board; and thus the flap when tied to the board does not fall away. in this manner are made the flap and the air-hole, so when the bellows are distended the flap opens, when compressed it closes. at a distance of about a foot beyond the air-hole a slightly elliptical iron ring, two palms long and one wide, is fastened by means of an iron staple to the under part of the bellows-board; it is at a distance of three palms from the back of the bellows. in order that the lower bellows-board may remain stationary, a wooden bolt is driven into the ring, after it penetrates through the hole in the transverse supporting plank which forms part of the frame for the bellows. there are some who dispense with the ring and fasten the bellows-board to the frame with two iron screws something like nails. the bows are placed between the two boards and are of the same length as the upper board. they are both made of four pieces of linden wood three digits thick, of which the two long ones are seven digits wide at the back and two and a half at the front; the third piece, which is at the back, is two palms wide. the ends of the bows are a little more than a digit thick, and are mortised to the long pieces, and both having been bored through, wooden pegs covered with glue are fixed in the holes; they are thus joined and glued to the long pieces. each of the ends is bowed (_arcuatur_) to meet the end of the long part of the bow, whence its name "bow" originated. the fourth piece keeps the ends of the bow distended, and is placed a cubit distant from the head of the bellows; the ends of this piece are mortised into the ends of the bow and are joined and glued to them; its length without the tenons is a foot, and its width a palm and two digits. there are, besides, two other very small pieces glued to the head of the bellows and to the lower board, and fastened to them by wooden pegs covered with glue, and they are three palms and two digits long, one palm high, and a digit thick, one half being slightly cut away. these pieces keep the ends of the bow away from the hole in the bellows-head, for if they were not there, the ends, forced inward by the great and frequent movement, would be broken. the leather is of ox-hide or horse-hide, but that of the ox is far preferable to that of the horse. each of these hides, for there are two, is three and a half feet wide where they are joined at the back part of the bellows. a long leathern thong is laid along each of the bellows-boards and each of the bows, and fastened by t-shaped iron nails five digits long; each of the horns of the nails is two and a half digits long and half a digit wide. the hide is attached to the bellows-boards by means of these nails, so that a horn of one nail almost touches the horn of the next; but it is different with the bows, for the hide is fastened to the back piece of the bow by only two nails, and to the two long pieces by four nails. in this practical manner they put ten nails in one bow and the same number in the other. sometimes when the smelter is afraid that the vigorous motion of the bellows may pull or tear the hide from the bows, he also fastens it with little strips of pine by means of another kind of nail, but these strips cannot be fastened to the back pieces of the bow, because these are somewhat bent. some people do not fix the hide to the bellows-boards and bows by iron nails, but by iron screws, screwed at the same time through strips laid over the hide. this method of fastening the hide is less used than the other, although there is no doubt that it surpasses it in excellence. lastly, the head of the bellows, like the rest of the body, consists of two boards, and of a nozzle besides. the upper board is one cubit long, one and a half palms thick. the lower board is part of the whole of the lower bellows-board; it is of the same length as the upper piece, but a palm and a digit thick. from these two glued together is made the head, into which, when it has been perforated, the nozzle is fixed. the back part of the head, where it is attached to the rest of the bellows-body, is a cubit wide, but three palms forward it becomes two digits narrower. afterward it is somewhat cut away so that the front end may be rounded, until it is two palms and as many digits in diameter, at which point it is bound with an iron ring three digits wide. the nozzle is a pipe made of a thin plate of iron; the diameter in front is three digits, while at the back, where it is encased in the head of the bellows, it is a palm high and two palms wide. it thus gradually widens out, especially at the back, in order that a copious wind can penetrate into it; the whole nozzle is three feet long. [illustration (bellows for blast furnaces): a--upper bellows-board. b--lower bellows-board. c--the two pieces of wood of which each consists. d--posterior arched part of each. e--tapered front part of each. f--pieces of linden wood. g--aperture in the upper board. h--lid. i--little mouldings of wood. k--handle. l--cleat on the outside. the cleat inside i am not able to depict. m--interior of the lower bellows-board. n--part of the head. o--air-hole. p--supporting bar. q--flap. r--hide. s--thong. t--exterior of the lower board. v--staple. x--ring. y--bow. z--its long pieces. aa--back piece of the bow. bb--the bowed ends. cc--crossbar distending the bow. dd--the two little pieces. ee--hide. ff--nail. gg--horn of the nail. hh--a screw. ii--long thong. kk--head. ll--its lower board. mm--its upper board. nn--nozzle. oo--the whole of the lower bellows-board. pp--the two exterior plates of the head hinges. qq--their curved piece. rr--middle plate of the head. ss--the two outer plates of the upper bellows-board. tt--its middle plate. vv--little axle. xx--whole bellows.] the upper bellows-board is joined to the head of the bellows in the following way. an iron plate[ ], a palm wide and one and a half palms long, is first fastened to the head at a distance of three digits from the end; from this plate there projects a piece three digits long and two wide, curved in a small circle. the other side has a similar plate. then in the same part of the upper board are fixed two other iron plates, distant two digits from the edge, each of which are six digits wide and seven long; in each of these plates the middle part is cut away for a little more than three digits in length and for two in depth, so that the curved part of the plates on the head corresponding to them may fit into this cut out part. from both sides of each plate there project pieces, three digits long and two digits wide, similarly curved into small circles. a little iron pin is passed through these curved pieces of the plates, like a little axle, so that the upper board of the bellows may turn upon it. the little axle is six digits long and a little more than a digit thick, and a small groove is cut out of the upper board, where the plates are fastened to it, in such a manner that the little axle when fixed to the plates may not fall out. both plates fastened to the bellows-board are affixed by four iron nails, of which the heads are on the inner part of the board, whereas the points, clinched at the top, are transformed into heads, so to speak. each of the other plates is fastened to the head of the bellows by means of a nail with a wide head, and by two other nails of which the heads are on the edge of the bellows-head. midway between the two plates on the bellows-board there remains a space two palms wide, which is covered by an iron plate fastened to the board by little nails; and another plate corresponding to this is fastened to the head between the other two plates; they are two palms and the same number of digits wide. the hide is common to the head as to all the other parts of the body; the plates are covered with it, as well as the front part of the upper bellows-board, and both the bows and the back of the head of the bellows, so that the wind may not escape from that part of the bellows. it is three palms and as many digits wide, and long enough to extend from one of the sides of the lower board over the back of the upper; it is fastened by many t-headed nails on one side to the upper board, and on the other side to the head of the bellows, and both ends are fastened to the lower bellows-board. in the above manner the bellows is made. as two are required for each furnace, it is necessary to have twelve bellows, if there are to be six furnaces in one works. [illustration (bellows for blast furnaces): a--front sill. b--back sill. c--front posts. d--their slots. e--beam imposed upon them. f--higher posts. g--their slots. h--beam imposed upon them. i--timber joined in the mortises of the posts. k--planks. l--transverse supporting planks. m--the holes in them. n--pipe. o--its front end. p--its rear end.] now it is time to describe their framework. first, two sills a little shorter than the furnace wall are placed on the ground. the front one of these is three palms wide and thick, and the back one three palms and two digits. the front one is two feet distant from the back wall of the furnace, and the back one is six feet three palms distant from the front one. they are set into the earth, that they may remain firm; there are some who accomplish this by means of pegs which, through several holes, penetrate deeply into the ground. then twelve short posts are erected, whose lower ends are mortised into the sill that is near the back of the furnace wall; these posts are two feet high, exclusive of the tenons, and are three palms and the same number of digits wide, and two palms thick. a slot one and a half palms wide is cut through them, beginning two palms from the bottom and extending for a height of three palms. all the posts are not placed at the same intervals, the first being at a distance of three feet five digits from the second, and likewise the third from the fourth, but the second is two feet one palm and three digits from the third; the intervals between the other posts are arranged in the same manner, equal and unequal, of which each four pertain to two furnaces. the upper ends of these posts are mortised into a transverse beam which is twelve feet, two palms, and three digits long, and projects five digits beyond the first post and to the same distance beyond the fourth; it is two palms and the same number of digits wide, and two palms thick. since each separate transverse beam supports four bellows, it is necessary to have three of them. behind the twelve short posts the same number of higher posts are erected, of which each has the middle part of the lower end cut out, so that its two resulting lower ends are mortised into the back sill; these posts, exclusive of the tenons, are twelve feet and two palms high, and are five palms wide and two palms thick. they are cut out from the bottom upward, the slot being four feet and five digits high and six digits wide. the upper ends of these posts are mortised into a long beam imposed upon them; this long beam is placed close under the timbers which extend from the wall at the back of the furnace to the first long wall; the beam is three palms wide and two palms thick, and forty-three feet long. if such a long one is not at hand, two or three may be substituted for it, which when joined together make up that length. these higher posts are not placed at equal distances, but the first is at a distance of two feet three palms one digit from the second, and the third is at the same distance from the fourth; while the second is at a distance of one foot three palms and the same number of digits from the third, and in the same manner the rest of the posts are arranged at equal and unequal intervals. moreover, there is in every post, where it faces the shorter post, a mortise at a foot and a digit above the slot; in these mortises of the four posts is tenoned a timber which itself has four mortises. tenons are enclosed in mortises in order that they may be better joined, and they are transfixed with wooden pins. this timber is thirteen feet three palms one digit long, and it projects beyond the first post a distance of two palms and two digits, and to the same number of palms and digits beyond the fourth post. it is two palms and as many digits wide, and also two palms thick. as there are twelve posts it is necessary to have three timbers of this kind. on each of these timbers, and on each of the cross-beams which are laid upon the shorter posts, are placed four planks, each nine feet long, two palms three digits wide, and two palms one digit thick. the first plank is five feet one palm one digit distant from the second, at the front as well as at the back, for each separate plank is placed outside of the posts. the third is at the same distance from the fourth, but the second is one foot and three digits distant from the third. in the same manner the rest of the eight planks are arranged at intervals, the fifth from the sixth and the seventh from the eighth are at the same distances as the first from the second and the third from the fourth; the sixth is at the same distance from the seventh as the second from the third. two planks support one transverse plank six feet long, one foot wide, one palm thick, placed at a distance of three feet and two palms from the back posts. when there are six of these supporting planks, on each separate one are placed two bellows; the lower bellows-boards project a palm beyond them. from each of the bellows-boards an iron ring descends through a hole in its supporting plank, and a wooden peg is driven into the ring, so that the bellows-board may remain stationary, as i stated above. the two bellows communicate, each by its own plank, to the back of a copper pipe in which are set both of the nozzles, and their ends are tightly fastened in it. the pipe is made of a rolled copper or iron plate, a foot and two palms and the same number of digits long; the plate is half a digit thick, but a digit thick at the back. the interior of the pipe is three digits wide, and two and a half digits high in the front, for it is not absolutely round; and at the back it is a foot and two palms and three digits in diameter. the plate from which the pipe is made is not entirely joined up, but at the front there is left a crack half a digit wide, increasing at the back to three digits. this pipe is placed in the hole in the furnace, which, as i said, was in the middle of the wall and the arch. the nozzles of the bellows, placed in this pipe, are a distance of five digits from its front end. [illustration (bellows for blast furnaces): a--lever which when depressed by means of a cam compresses the bellows. b--slots through the posts. c--bar. d--iron implement with a rectangular link. e--iron instrument with round ring. f--handle of bellows. g--upper post. h--upper lever. i--box with equal sides. k--box narrow at the bottom. l--pegs driven into the upper lever.] the levers are of the same number as the bellows, and when depressed by the cams of the long axle they compress the bellows. these levers are eight feet three palms long, one palm wide and thick, and the ends are inserted in the slots of the posts; they project beyond the front posts to a distance of two palms, and the same distance beyond the back posts in order that each may have its end depressed by its two cams on the axle. the cams not only penetrate into the slots of the back posts, but project three digits beyond them. an iron pin is set in round holes made through both sides of the slot of each front post, at three palms and as many digits from the bottom; the pin penetrates the lever, which turns about it when depressed or raised. the back of the lever for the length of a cubit is a palm and a digit wider than the rest, and is perforated; in this hole is engaged a bar six feet and two palms long, three digits wide, and about one and one-half digits thick; it is somewhat hooked at the upper end, and approaches the handle of the bellows. under the lever there is a nail, which penetrates through a hole in the bar, so that the lever and bar may move together. the bar is perforated in the upper end at a distance of six digits from the top; this hole is two palms long and a digit wide, and in it is engaged the hook of an iron implement which is a digit thick. at the upper part this implement has either a round or square opening, like a link, and at the lower end is hooked; the link is two digits high and wide and the hook is three digits long; the middle part between the link and the hook is three palms and two digits long. the link of this implement engages either the handle of the bellows, or else a large ring which does engage it. this iron ring is a digit thick, two palms wide on the inside of the upper part, and two digits in the lower part, and this iron ring, not unlike the first one, engages the handle of the bellows. the iron ring either has its narrower part turned upward, and in it is engaged the ring of another iron implement, similar to the first, whose hook, extending upward, grips the rope fastened to the iron ring holding the end of the second lever, of which i will speak presently; or else the iron ring grips this lever, and then in its hook is engaged the ring of the other implement whose ring engages the handle of the bellows, and in this case the rope is dispensed with. resting on beams fixed in the two walls is a longitudinal beam, at a distance of four and a half feet from the back posts; it is two palms wide, one and a half palms thick. there are mortised into this longitudinal beam the lower ends of upper posts three palms wide and two thick, which are six feet two palms high, exclusive of their tenons. the upper ends of these posts are mortised into an upper longitudinal beam, which lies close under the rafters of the building; this upper longitudinal beam is two palms wide and one thick. the upper posts have a slot cut out upward from a point two feet from the bottom, and the slot is two feet high and six digits wide. through these upper posts a round hole is bored from one side to the other at a point three feet one palm from the bottom, and a small iron axle penetrates through the hole and is fastened there. around this small iron axle turns the second lever when it is depressed and raised. this lever is eight feet long, and its other end is three digits wider than the rest of the lever; at this widest point is a hole two digits wide and three high, in which is fixed an iron ring, to which is tied the rope i have mentioned; it is five palms long, its upper loop is two palms and as many digits wide, and the lower one is one palm one digit wide. this half of the second lever, the end of which i have just mentioned, is three palms high and one wide; it projects three feet beyond the slot of the post on which it turns; the other end, which faces the back wall of the furnaces, is one foot and a palm high and a foot wide. on this part of the lever stands and is fixed a box three and a half feet long, one foot and one palm wide, and half a foot deep; but these measurements vary; sometimes the bottom of this box is narrower, sometimes equal in width to the top. in either case, it is filled with stones and earth to make it heavy, but the smelters have to be on their guard and make provision against the stones falling out, owing to the constant motion; this is prevented by means of an iron band which is placed over the top, both ends being wedge-shaped and driven into the lever so that the stones can be held in. some people, in place of the box, drive four or more pegs into the lever and put mud between them, the required amount being added to the weight or taken away from it. there remains to be considered the method of using this machine. the lower lever, being depressed by the cams, compresses the bellows, and the compression drives the air through the nozzle. then the weight of the box on the other end of the upper lever raises the upper bellows-board, and the air is drawn in, entering through the air-hole. [illustration (bellows for blast furnaces): a--axle. b--water-wheel. c--drum composed of rundles. d--other axle. e--toothed wheel. f--its spokes. g--its segments. h--its teeth. i--cams of the axle.] the machine whose cams depress the lower lever is made as follows. first there is an axle, on whose end outside the building is a water-wheel; at the other end, which is inside the building, is a drum made of rundles. this drum is composed of two double hubs, a foot apart, which are five digits thick, the radius all round being a foot and two digits; but they are double, because each hub is composed of two discs, equally thick, fastened together with wooden pegs glued in. these hubs are sometimes covered above and around by iron plates. the rundles are thirty in number, a foot and two palms and the same number of digits long, with each end fastened into a hub; they are rounded, three digits in diameter, and the same number of digits apart. in this practical manner is made the drum composed of rundles. there is a toothed wheel, two palms and a digit thick, on the end of another axle; this wheel is composed of a double disc[ ]. the inner disc is composed of four segments a palm thick, everywhere two palms and a digit wide. the outer disc, like the inner, is made of four segments, and is a palm and a digit thick; it is not equally wide, but where the head of the spokes are inserted it is a foot and a palm and digit wide, while on each side of the spokes it becomes a little narrower, until the narrowest part is only two palms and the same number of digits wide. the outer segments are joined to the inner ones in such a manner that, on the one hand, an outer segment ends in the middle of an inner one, and, on the other hand, the ends of the inner segments are joined in the middle of the outer ones; there is no doubt that by this kind of joining the wheel is made stronger. the outer segments are fastened to the inner by means of a large number of wooden pegs. each segment, measured over its round back, is four feet and three palms long. there are four spokes, each two palms wide and a palm and a digit thick; their length, excluding the tenons, being two feet and three digits. one end of the spoke is mortised into the axle, where it is firmly fastened with pegs; the wide part of the other end, in the shape of a triangle, is mortised into the outer segment opposite it, keeping the shape of the same as far as the segment ascends. they also are joined together with wooden pegs glued in, and these pegs are driven into the spokes under the inner disc. the parts of the spokes in the shape of the triangle are on the inside; the outer part is simple. this triangle has two sides equal, the erect ones as is evident, which are a palm long; the lower side is not of the same length, but is five digits long, and a mortise of the same shape is cut out of the segments. the wheel has sixty teeth, since it is necessary that the rundle drum should revolve twice while the toothed wheel revolves once. the teeth are a foot long, and project one palm from the inner disc of the wheel, and three digits from the outer disc; they are a palm wide and two and a half digits thick, and it is necessary that they should be three digits apart, as were the rundles. the axle should have a thickness in proportion to the spokes and the segments. as it has two cams to depress each of the levers, it is necessary that it should have twenty-four cams, which project beyond it a foot and a palm and a digit. the cams are of almost semicircular shape, of which the widest part is three palms and a digit wide, and they are a palm thick; they are distributed according to the four sides of the axle, on the upper, the lower and the two lateral sides. the axle has twelve holes, of which the first penetrates through from the upper side to the lower, the second from one lateral side to the other; the first hole is four feet two palms distant from the second; each alternate one of these holes is made in the same direction, and they are arranged at equal intervals. each single cam must be opposite another; the first is inserted into the upper part of the first hole, the second into the lower part of the same hole, and so fixed by pegs that they do not fall out; the third cam is inserted into that part of the second hole which is on the right side, and the fourth into that part on the left. in like manner all the cams are inserted into the consecutive holes, for which reason it happens that the cams depress the levers of the bellows in rotation. finally we must not omit to state that this is only one of many such axles having cams and a water-wheel. i have arrived thus far with many words, and yet it is not unreasonable that i have in this place pursued the subject minutely, since the smelting of all the metals, to which i am about to proceed, could not be undertaken without it. the ores of gold, silver, copper, and lead, are smelted in a furnace by four different methods. the first method is for the rich ores of gold or silver, the second for the mediocre ores, the third for the poor ores, and the fourth method is for those ores which contain copper or lead, whether they contain precious metals or are wanting in them. the smelting of the first ores is performed in the furnace of which the tap-hole is intermittently closed; the other three ores are melted in furnaces of which the tap-holes are always open. [illustration (stamp-mill): a--charcoal. b--mortar-box. c--stamps.] first, i will speak of the manner in which the furnaces are prepared for the smelting of the ores, and of the first method of smelting. the powder from which the hearth and forehearth should be made is composed of charcoal and earth (clay?). the charcoal is crushed by the stamps in a mortar-box, the front of which is closed by a board at the top, while the charcoal, crushed to powder, is removed through the open part below; the stamps are not shod with iron, but are made entirely of wood, although at the lower part they are bound round at the wide part by an iron band. [illustration (clay washing): a--tub. b--sieve. c--rods. d--bench-frame.] the powder into which the charcoal is crushed is thrown on to a sieve whose bottom consists of interwoven withes of wood. the sieve is drawn backward and forward over two wooden or iron rods placed in a triangular position on a tub, or over a bench-frame set on the floor of the building; the powder which falls into the tub or on to the floor is of suitable size, but the pieces of small charcoal which remain in the sieve are emptied out and thrown back under the stamps. [illustration (clay washing): a--screen. b--poles. c--shovel. d--two-wheeled cart. e--hand-sieve. f--narrow boards. g--box. h--covered pit.] when the earth is dug up it is first exposed to the sun that it may dry. later on it is thrown with a shovel on to a screen--set up obliquely and supported by poles,--made of thick, loosely woven hazel withes, and in this way the fine earth and its small lumps pass through the holes of the screen, but the clods and stones do not pass through, but run down to the ground. the earth which passes through the screen is conveyed in a two-wheeled cart to the works and there sifted. this sieve, which is not dissimilar to the one described above, is drawn backward and forward upon narrow boards of equal length placed over a long box; the powder which falls through the sieve into the box is suitable for the mixture; the lumps that remain in the sieve are thrown away by some people, but by others they are placed under the stamps. this powdered earth is mixed with powdered charcoal, moistened, and thrown into a pit, and in order that it may remain good for a long time, the pit is covered up with boards so that the mixture may not become contaminated. [illustration (implements for furnace work): a--furnace. b--ladder. c--board fixed to it. d--hoe. e--five-toothed rake. f--wooden spatula. g--broom. h--rammer. i--rammer, same diameter. k--two wooden spatulas. l--curved blade. m--bronze rammer. n--another bronze rammer. o--wide spatula. p--rod. q--wicker basket. r--two buckets of leather in which water is carried for putting out a conflagration, should the _officina_ catch fire. s--brass pump with which the water is squirted out. t--two hooks. v--rake. x--workman beating the clay with an iron implement.] they take two parts of pulverised charcoal and one part of powdered earth, and mix them well together with a rake; the mixture is moistened by pouring water over it so that it may easily be made into shapes resembling snowballs; if the powder be light it is moistened with more water, if heavy with less. the interior of the new furnace is lined with lute, so that the cracks in the walls, if there are any, may be filled up, but especially in order to preserve the rock from injury by fire. in old furnaces in which ore has been melted, as soon as the rocks have cooled the assistant chips away, with a spatula, the accretions which adhere to the walls, and then breaks them up with an iron hoe or a rake with five teeth. the cracks of the furnace are first filled in with fragments of rock or brick, which he does by passing his hand into the furnace through its mouth, or else, having placed a ladder against it, he mounts by the rungs to the upper open part of the furnace. to the upper part of the ladder a board is fastened that he may lean and recline against it. then standing on the same ladder, with a wooden spatula, he smears the furnace walls over with lute; this spatula is four feet long, a digit thick, and for a foot upward from the bottom it is a palm wide, or even wider, generally two and a half digits. he spreads the lute equally over the inner walls of the furnace. the mouth of the copper pipe[ ] should not protrude from the lute, lest sows[ ] form round about it and thus impede the melting, for the furnace bellows could not force a blast through them. then the same assistant throws a little powdered charcoal into the pit of the forehearth and sprinkles it with pulverised earth. afterward, with a bucket he pours water into it and sweeps this all over the forehearth pit, and with the broom drives the turbid water into the furnace hearth and likewise sweeps it out. next he throws the mixed and moistened powder into the furnace, and then a second time mounting the steps of the ladder, he introduces the rammer into the furnace and pounds the powder so that the hearth is made solid. the rammer is rounded and three palms long; at the bottom it is five digits in diameter, at the top three and a half, therefore it is made in the form of a truncated cone; the handle of the rammer is round and five feet long and two and a half digits thick; the upper part of the rammer, where the handle is inserted, is bound with an iron band two digits wide. there are some who, instead, use two rounded rammers three and a half digits in diameter, the same at the bottom as at the top. some people prefer two wooden spatulas, or a rammer spatula. in a similar manner, mixed and moistened powder is thrown and pounded with a rammer in the forehearth pit, which is outside the furnace. when this is nearly completed, powder is again put in, and pushed with the rammer up toward the protruding copper pipe, so that from a point a digit under the mouth of the copper pipe the hearth slopes down into the crucible of the forehearth,[ ] and the metal can run down. the same is repeated until the forehearth pit is full, then afterward this is hollowed out with a curved blade; this blade is of iron, two palms and as many digits long, three digits wide, blunt at the top and sharp at the bottom. the crucible of the forehearth must be round, a foot in diameter and two palms deep if it has to contain a _centumpondium_ of lead, or if only seventy _librae_, then three palms in diameter and two palms deep like the other. when the forehearth has been hollowed out it is pounded with a round bronze rammer. this is five digits high and the same in diameter, having a curved round handle one and a half digits thick; or else another bronze rammer is used, which is fashioned in the shape of a cone, truncated at the top, on which is imposed another cut away at the bottom, so that the middle part of the rammer may be grasped by the hand; this is six digits high, and five digits in diameter at the lower end and four at the top. some use in its place a wooden spatula two and a half palms wide at the lower end and one palm thick. the assistant, having prepared the forehearth, returns to the furnace and besmears both sides as well as the top of the mouth with simple lute. in the lower part of the mouth he places lute that has been dipped in charcoal dust, to guard against the risk of the lute attracting to itself the powder of the hearth and vitiating it. next he lays in the mouth of the furnace a straight round rod three quarters of a foot long and three digits in diameter. afterward he places a piece of charcoal on the lute, of the same length and width as the mouth, so that it is entirely closed up; if there be not at hand one piece of charcoal so large, he takes two instead. when the mouth is thus closed up, he throws into the furnace a wicker basket full of charcoal, and in order that the piece of charcoal with which the mouth of the furnace is closed should not then fall out, the master holds it in with his hand. the pieces of charcoal which are thrown into the furnace should be of medium size, for if they are large they impede the blast of the bellows and prevent it from blowing through the tap-hole of the furnace into the forehearth to heat it. then the master covers over the charcoal, placed at the mouth of the furnace, with lute and extracts the wooden rod, and thus the furnace is prepared. afterward the assistant throws four or five larger baskets full of charcoal into the furnace, filling it right up; he also throws a little charcoal into the forehearth, and places glowing coals upon it in order that it may be kindled, but in order that the flames of this fire should not enter through the tap-hole of the furnace and fire the charcoal inside, he covers the tap-hole with lute or closes it with fragments of pottery. some do not warm the forehearth the same evening, but place large charcoals round the edge of it, one leaning on the other; those who follow the first method sweep out the forehearth in the morning, and clean out the little pieces of charcoal and cinders, while those who follow the latter method take, early in the morning, burning firebrands, which have been prepared by the watchman of the works, and place them on the charcoal. at the fourth hour the master begins his work. he first inserts a small piece of glowing coal into the furnace, through the bronze nozzle-pipe of the bellows, and blows up the fire with the bellows; thus within the space of half an hour the forehearth, as well as the hearth, becomes warmed, and of course more quickly if on the preceding day ores have been smelted in the same furnace, but if not then it warms more slowly. if the hearth and forehearth are not warmed before the ore to be smelted is thrown in, the furnace is injured and the metals lost; or if the powder from which both are made is damp in summer or frozen in winter, they will be cracked, and, giving out a sound like thunder, they will blow out the metals and other substances with great peril to the workmen. after the furnace has been warmed, the master throws in slags, and these, when melted, flow out through the tap-hole into the forehearth. then he closes up the tap-hole at once with mixed lute and charcoal dust; this plug he fastens with his hand to a round wooden rammer that is five digits thick, two palms high, with a handle three feet long. the smelter extracts the slags from the forehearth with a hooked bar; if the ore to be smelted is rich in gold or silver he puts into the forehearth a _centumpondium_ of lead, or half as much if the ore is poor, because the former requires much lead, the latter little; he immediately throws burning firebrands on to the lead so that it melts. afterward he performs everything according to the usual manner and order, whereby he first throws into the furnace as many cakes melted from pyrites[ ], as he requires to smelt the ore; then he puts in two wicker baskets full of ore with litharge and hearth-lead[ ], and stones which fuse easily by fire of the second order, all mixed together; then one wicker basket full of charcoal, and lastly the slags. the furnace now being filled with all the things i have mentioned, the ore is slowly smelted; he does not put too much of it against the back wall of the furnace, lest sows should form around the nozzles of the bellows and the blast be impeded and the fire burn less fiercely. this, indeed, is the custom of many most excellent smelters, who know how to govern the four elements[ ]. they combine in right proportion the ores, which are part earth, placing no more than is suitable in the furnaces; they pour in the needful quantity of water; they moderate with skill the air from the bellows; they throw the ore into that part of the fire which burns fiercely. the master sprinkles water into each part of the furnace to dampen the charcoal slightly, so that the minute parts of ore may adhere to it, which otherwise the blast of the bellows and the force of the fire would agitate and blow away with the fumes. but as the nature of the ores to be smelted varies, the smelters have to arrange the hearth now high, now low, and to place the pipe in which the nozzles of the bellows are inserted sometimes on a great and sometimes at a slight angle, so that the blast of the bellows may blow into the furnace in either a mild or a vigorous manner. for those ores which heat and fuse easily, a low hearth is necessary for the work of the smelters, and the pipe must be placed at a gentle angle to produce a mild blast from the bellows. on the contrary, those ores that heat and fuse slowly must have a high hearth, and the pipe must be placed at a steep incline in order to blow a strong blast of the bellows, and it is necessary, for this kind of ore, to have a very hot furnace in which slags, or cakes melted from pyrites, or stones which melt easily in the fire[ ], are first melted, so that the ore should not settle in the hearth of the furnace and obstruct and choke up the tap-hole, as the minute metallic particles that have been washed from the ores are wont to do. large bellows have wide nozzles, for if they were narrow the copious and strong blast would be too much compressed and too acutely blown into the furnace, and then the melted material would be chilled, and would form sows around the nozzle, and thus obstruct the opening into the furnace, which would cause great damage to the proprietors' property. if the ores agglomerate and do not fuse, the smelter, mounting on the ladder placed against the side of the furnace, divides the charge with a pointed or hooked bar, which he also pushes down into the pipe in which the nozzle of the bellows is placed, and by a downward movement dislodges the ore and the sows from around it. after a quarter of an hour, when the lead which the assistant has placed in the forehearth is melted, the master opens the tap-hole of the furnace with a tapping-bar. this bar is made of iron, is three and a half feet long, the forward end pointed and a little curved, and the back end hollow so that into it may be inserted a wooden handle, which is three feet long and thick enough to be well grasped by the hand. the slag first flows from the furnace into the forehearth, and in it are stones mixed with metal or with the metal adhering to them partly altered, the slag also containing earth and solidified juices. after this the material from the melted pyrites flows out, and then the molten lead contained in the forehearth absorbs the gold and silver. when that which has run out has stood for some time in the forehearth, in order to be able to separate one from the other, the master first either skims off the slags with the hooked bar or else lifts them off with an iron fork; the slags, as they are very light, float on the top. he next draws off the cakes of melted pyrites, which as they are of medium weight hold the middle place; he leaves in the forehearth the alloy of gold or silver with the lead, for these being the heaviest, sink to the bottom. as, however, there is a difference in slags, the uppermost containing little metal, the middle more, and the lowest much, he puts these away separately, each in its own place, in order that to each heap, when it is re-smelted, he may add the proper fluxes, and can put in as much lead as is demanded for the metal in the slag; when the slag is re-melted, if it emits much odour, there is some metal in it; if it emits no odour, then it contains none. he puts the cakes of melted pyrites away separately, as they were nearest in the forehearth to the metal, and contain a little more of it than the slags; from all these cakes a conical mound is built up, by always placing the widest of them at the bottom. the hooked bar has a hook on the end, hence its name; otherwise it is similar to other bars. [illustration (blast furnaces): a, b, c--three furnaces. at the first stands the smelter, who with a ladle pours the alloy out of the forehearth into the moulds. d--forehearth. e--ladle. f--moulds. g--round wooden rammer. h--tapping-bar. at the second furnace stands the smelter, who opens the tap-hole with his tapping-bar. the assistant, standing on steps placed against the third furnace which has been broken open, chips off the accretions. i--steps. k--spatula. l--the other hooked bar. m--mine captain carrying a cake, in which he has stuck the pick, to the scales to be weighed. n--another mine captain opens a chest in which his things are kept.] afterward the master closes up the tap-hole and fills the furnace with the same materials i described above, and again, the ores having been melted, he opens the tap-hole, and with a hooked bar extracts the slags and the cakes melted from pyrites, which have run down into the forehearth. he repeats the same operation until a certain and definite part of the ore has been smelted, and the day's work is at an end; if the ore was rich the work is finished in eight hours; if poor, it takes a longer time. but if the ore was so rich as to be smelted in less than eight hours, another operation is in the meanwhile combined with the first, and both are performed in the space of ten hours. when all the ore has been smelted, he throws into the furnace a basket full of litharge or hearth-lead, so that the metal which has remained in the accretions may run out with these when melted. when he has finally drawn out of the forehearth the slags and the cakes melted from pyrites, he takes out, with a ladle, the lead alloyed with gold or silver and pours it into little iron or copper pans, three palms wide and as many digits deep, but first lined on the inside with lute and dried by warming, lest the glowing molten substances should break through. the iron ladle is two palms wide, and in other respects it is similar to the others, all of which have a sufficiently long iron shaft, so that the fire should not burn the wooden part of the handle. when the alloy has been poured out of the forehearth, the smelter foreman and the mine captain weigh the cakes. then the master breaks out the whole of the mouth of the furnace with a crowbar, and with that other hooked bar, the rabble and the five-toothed rake, he extracts the accretions and the charcoal. this crowbar is not unlike the other hooked one, but larger and wider; the handle of the rabble is six feet long and is half of iron and half of wood. the furnace having cooled, the master chips off the accretions clinging to the walls with a rectangular spatula six digits long, a palm broad, and sharp on the front edge; it has a round handle four feet long, half of it being of iron and half of wood. this is the first method of smelting ores. because they generally consist of unequal constituents, some of which melt rapidly and others slowly, the ores rich in gold and silver cannot be smelted as rapidly or as easily by the other methods as they can by the first method, for three important reasons. the first reason is that, as often as the closed tap-hole of the furnace is opened with a tapping-bar, so often can the smelter observe whether the ore is melting too quickly or too slowly, or whether it is flaming in scattered bits, and not uniting in one mass; in the first case the ore is smelting too slowly and not without great expense; in the second case the metal mixes with the slag which flows out of the furnace into the forehearth, wherefore there is the expense of melting it again; in the third case, the metal is consumed by the violence of the fire. each of these evils has its remedy; if the ore melts slowly or does not come together, it is necessary to add some amount of fluxes which melt the ore; or if they melt too readily, to decrease the amount. the second reason is that each time that the furnace is opened with a tapping-bar, it flows out into the forehearth, and the smelter is able to test the alloy of gold and lead or of silver with lead, which is called _stannum_.[ ] when the tap-hole is opened the second or third time, this test shows us whether the alloy of gold or silver has become richer, or whether the lead is too debilitated and wanting in strength to absorb any more gold or silver. if it has become richer, some portion of lead added to it should renew its strength; if it has not become richer, it is poured out of the forehearth that it may be replaced with fresh lead. the third reason is that if the tap-hole of the furnace is always open when the ore and other things are being smelted, the fluxes, which are easily melted, run out of the furnace before the rich gold and silver ores, for these are sometimes of a kind that oppose and resist melting by the fire for a longer period. it follows in this case, that some part of the ore is either consumed or is mixed with the accretions, and as a result little lumps of ore not yet melted are now and then found in the accretions. therefore when these ores are being smelted, the tap-hole of the furnace should be closed for a time, as it is necessary to heat and mix the ore and the fluxes at the same time; since the fluxes fuse more rapidly than the ore, when the molten fluxes are held in the furnace, they thus melt the ore which does not readily fuse or mix with the lead. the lead absorbs the gold or silver, just as tin or lead when melted in the forehearth absorbs the other unmelted metal which has been thrown into it. but if the molten matter is poured upon that which is not molten, it runs off on all sides and consequently does not melt it. it follows from all this that ores rich in gold or silver, when put into a furnace with its tap-hole always open, cannot for that reason be smelted so successfully as in one where the tap-hole is closed for a time, so that during this time the ore may be melted by the molten fluxes. afterward, when the tap-hole has been opened, they flow into the forehearth and mix there with the molten lead. this method of smelting the ores is used by us and by the bohemians. [illustration (blast furnaces): a, b--two furnaces. c--forehearths. d--dipping-pot. the smelter standing by the first furnace draws off the slags with a hooked bar. e--hooked bar. f--slags. g--the assistant drawing a bucket of water which he pours over the glowing slags to quench them. h--basket made of twigs of wood intertwined. i--rabble. k--ore to be smelted. l--the master stands at the other furnace and prepares the forehearth by ramming it with two rammers. m--crowbar.] the three remaining methods of smelting ores are similar to each other in that the tap-holes of the furnaces always remain open, so that the molten metals may continually run out. they differ greatly from each other, however, for the tap-hole of the first of this kind is deeper in the furnace and narrower than that of the third, and besides it is invisible and concealed. it easily discharges into the forehearth, which is one and a half feet higher than the floor of the building, in order that below it to the left a dipping-pot can be made. when the forehearth is nearly full of the slags, which well up from the invisible tap-hole of the furnace, they are skimmed off from the top with a hooked bar; then the alloy of gold or silver with lead and the melted pyrites, being uncovered, flow into the dipping-pot, and the latter are made into cakes; these cakes are broken and thrown back into the furnace so that all their metal may be smelted out. the alloy is poured into little iron moulds. the smelter, besides lead and cognate things, uses fluxes which combine with the ore, of which i gave a sufficient account in book vii. the metals which are melted from ores that fuse readily in the fire, are profitable because they are smelted in a short time, while those which are difficult to fuse are not as profitable, because they take a long time. when fluxes remain in the furnace and do not melt, they are not suitable; for this reason, accretions and slags are the most convenient for smelting, because they melt quickly. it is necessary to have an industrious and experienced smelter, who in the first place takes care not to put into the furnace more ores mixed with fluxes than it can accommodate. the powder out of which this furnace hearth and the adjoining forehearth and the dipping-pot are usually made, consists mostly of equal proportions of charcoal dust and of earth, or of equal parts of the same and of ashes. when the hearth of the furnace is prepared, a rod that will reach to the forehearth is put into it, higher up if the ore to be smelted readily fuses, and lower down if it fuses with difficulty. when the dipping-pot and forehearth are finished, the rod is drawn out of the furnace so that the tap-hole is open, and through it the molten material flows continuously into the forehearth, which should be very near the furnace in order that it may keep very hot and the alloy thus be made purer. if the ore to be smelted does not melt easily, the hearth of the furnace must not be made too sloping, lest the molten fluxes should run down into the forehearth before the ore is smelted, and the metal thus remain in the accretions on the sides of the furnace. the smelter must not ram the hearth so much that it becomes too hard, nor make the mistake of ramming the lower part of the mouth to make it hard, for it could not breathe[ ], nor could the molten matter flow freely out of the furnace. the ore which does not readily melt is thrown as much as possible to the back of the furnace, and toward that part where the fire burns very fiercely, so that it may be smelted longer. in this way the smelter may direct it whither he wills. only when it glows at the part near the bellows' nozzle does it signify that all the ore is smelted which has been thrown to the side of the furnace in which the nozzles are placed. if the ore is easily melted, one or two wicker baskets full are thrown into the front part of the furnace so that the fire, being driven back by it, may also smelt the ore and the sows that form round about the nozzles of the bellows. this process of smelting is very ancient among the tyrolese[ ], but not so old among the bohemians. [illustration (blast furnaces): a, b--two furnaces. c--forehearth. d--dipping-pots. the master stands at the one furnace and draws away the slags with an iron fork. e--iron fork. f--wooden hoe with which the cakes of melted pyrites are drawn out. g--the forehearth crucible: one-half inside is to be seen open in the other furnace. h--the half outside the furnace. i--the assistant prepares the forehearth, which is separated from the furnace that it may be seen. k--bar. l--wooden rammer. m--ladder. n--ladle.] the second method of smelting ores stands in a measure midway between that one performed in a furnace of which the tap-hole is closed intermittently, and the first of the methods performed in a furnace where the tap-hole is always open. in this manner are smelted the ores of gold and silver that are neither very rich nor very poor, but mediocre, which fuse easily and are readily absorbed by the lead. it was found that in this way a large quantity of ore could be smelted at one operation without much labour or great expense, and could thus be alloyed with lead. this furnace has two crucibles, one of which is half inside the furnace and half outside, so that the lead being put into this crucible, the part of the lead which is in the furnace absorbs the metals of the ores which easily fuse; the other crucible is lower, and the alloy and the molten pyrites run into it. those who make use of this method of smelting, tap the alloy of gold or silver with lead from the upper crucible once or twice if need be, and throw in other lead or litharge, and each absorbs that flux which is nearest. this method of smelting is in use in styria[ ]. [illustration (furnaces): a, b--two furnaces. c--tap-holes of furnaces. d--forehearths. e--their tap-holes. f--dipping-pots. g--at the one furnace stands the smelter carrying a wicker basket full of charcoal. at the other furnace stands a smelter who with the third hooked bar breaks away the material which has frozen the tap-hole of the furnace. h--hooked bar. i--heap of charcoal. k--barrow on which is a box made of wicker work in which the coals are measured. l--iron spade.] the furnace in the third method of smelting ores has the tap-hole likewise open, but the furnace is higher and wider than the others, and its bellows are larger; for these reasons a larger charge of the ore can be thrown into it. when the mines yield a great abundance of ore for the smelter, they smelt in the same furnace continuously for three days and three nights, providing there be no defect either in the hearth or in the forehearth. in this kind of a furnace almost every kind of accretion will be found. the forehearth of the furnace is not unlike the forehearth of the first furnace of all, except that it has a tap-hole. however, because large charges of ore are smelted uninterruptedly, and the melted material runs out and the slags are skimmed off, there is need for a second forehearth crucible, into which the molten material runs through an opened tap-hole when the first is full. when a smelter has spent twelve hours' labour on this work, another always takes his place. the ores of copper and lead and the poorest ores of gold and silver are smelted by this method, because they cannot be smelted by the other three methods on account of the greater expense occasioned. yet by this method a _centumpondium_ of ore containing only one or two _drachmae_ of gold, or only a half to one _uncia_, of silver,[ ] can be smelted; because there is a large amount of ore in each charge, smelting is continuous, and without expensive fluxes such as lead, litharge, and hearth-lead. in this method of smelting we must use only cupriferous pyrites which easily melt in the fire, in truth the cakes melted out from this, if they no longer absorb much gold or silver, are replenished again from crude pyrites alone. if from this poor ore, with melted pyrites alone, material for cakes cannot be made, there are added other fluxes which have not previously been melted. these fluxes are, namely, lead ore, stones easily fused by fire of the second order and sand made from them, limestone, _tophus_, white schist, and iron stone[ ]. although this method of smelting ores is rough and might not seem to be of great use, yet it is clever and useful; for a great weight of ores, in which the gold, silver, or copper are in small quantities, may be reduced into a few cakes containing all the metal. if on being first melted they are too crude to be suitable for the second melting, in which the lead absorbs the precious metals that are in the cakes, or in which the copper is melted out of them, yet they can be made suitable if they are repeatedly roasted, sometimes as often as seven or eight times, as i have explained in the last book. smelters of this kind are so clever and expert, that in smelting they take out all the gold and silver which the assayer in assaying the ores has stated to be contained in them, because if during the first operation, when he makes the cakes, there is a _drachma_ of gold or half an _uncia_ of silver lost from the ores, the smelter obtains it from the slags by the second smelting. this method of smelting ores is old and very common to most of those who use other methods. [illustration (lead smelting furnaces): a--furnace of the carni. b--low wall. c--wood. d--ore dripping lead. e--large crucible. f--moulds. g--ladle. h--slabs of lead. i--rectangular hole at the back of the furnace. k--saxon furnace. l--opening in the back of the furnace. m--wood. n--upper crucible. o--dipping-pot. p--westphalian method of melting. q--heaps of charcoal. r--straw. s--wide slabs. t--crucibles. v--polish hearth.] although lead ores are usually smelted in the third furnace--whose tap-hole is always open,--yet not a few people melt them in special furnaces by a method which i will briefly explain. the _carni_[ ] first burn such lead ores, and afterward break and crush them with large round mallets. between the two low walls of a hearth, which is inside a furnace made of and vaulted with a rock that resists injury by the fire and does not burn into chalk, they place green wood with a layer of dry wood on the top of it; then they throw the ore on to this, and when the wood is kindled the lead drips down and runs on to the underlying sloping hearth[ ]. this hearth is made of pulverised charcoal and earth, as is also a large crucible, one-half of which lies under the furnace and the other half outside it, into which runs the lead. the smelter, having first skimmed off the slags and other things with a hoe, pours the lead with a ladle into moulds, taking out the cakes after they have cooled. at the back of the furnace is a rectangular hole, so that the fire may be allowed more draught, and so that the smelter can crawl through it into the furnace if necessity demands. the saxons who inhabit gittelde, when smelting lead ore in a furnace not unlike a baking oven, put the wood in through a hole at the back of the furnace, and when it begins to burn vigorously the lead trickles out of the ore into a forehearth. when this is full, the smelting being accomplished, the tap-hole is opened with a bar, and in this way the lead, together with the slags, runs into the dipping-pots below. afterward the cakes of lead, when they are cold, are taken from the moulds. in westphalia they heap up ten wagon-loads of charcoal on some hillside which adjoins a level place, and the top of the heap being made flat, straw is thrown upon it to the thickness of three or four digits. on the top of this is laid as much pure lead ore as the heap can bear; then the charcoal is kindled, and when the wind blows, it fans the fire so that the ore is smelted. in this wise the lead, trickling down from the heap, flows on to the level and forms broad thin slabs. a few hundred pounds of lead ore are kept at hand, which, if things go well, are scattered over the heap. these broad slabs are impure and are laid upon dry wood which in turn is placed on green wood laid over a large crucible, and the former having been kindled, the lead is re-melted. the poles use a hearth of bricks four feet high, sloping on both sides and plastered with lute. on the upper level part of the hearth large pieces of wood are piled, and on these is placed small wood with lute put in between; over the top are laid wood shavings, and upon these again pure lead ore covered with large pieces of wood. when these are kindled, the ore melts and runs down on to the lower layer of wood; and when this is consumed by the fire, the metal is collected. if necessity demand, it is melted over and over again in the same manner, but it is finally melted by means of wood laid over the large crucible, the slabs of lead being placed upon it. the concentrates from washing are smelted together with slags (fluxes?) in a third furnace, of which the tap-hole is always open. [illustration (blast furnaces): a--furnaces. b--vaulted roof. c--columns. d--dust-chamber. e--opening. f--chimney. g--window. h--door. i--chute.] it is worth while to build vaulted dust-chambers over the furnaces, especially over those in which the precious ores are to be smelted, in order that the thicker part of the fumes, in which metals are not wanting, may be caught and saved. in this way two or more furnaces are combined under the same vaulted ceiling, which is supported by the wall, against which the furnaces are built, and by four columns. under this the smelters of the ore perform their work. there are two openings through which the fumes rise from the furnaces into the wide vaulted chamber, and the wider this is the more fumes it collects; in the middle of this chamber over the arch is an opening three palms high and two wide. this catches the fumes of both furnaces, which have risen up from both sides of the vaulted chamber to its arch, and have fallen again because they could not force their way out; and they thus pass out through the opening mentioned, into the chimney which the greeks call [greek: kapnodochê], the name being taken from the object. the chimney has thin iron plates fastened into the walls, to which the thinner metallic substances adhere when ascending with the fumes. the thicker metallic substances, or _cadmia_,[ ] adhere to the vaulted chamber, and often harden into stalactites. on one side of the chamber is a window in which are set panes of glass, so that the light may be transmitted, but the fumes kept in; on the other side is a door, which is kept entirely closed while the ores are being smelted in the furnaces, so that none of the fumes may escape. it is opened in order that the workman, passing through it, may be enabled to enter the chamber and remove the soot and _pompholyx_[ ] and chip off the _cadmia_; this sweeping is done twice a year. the soot mixed with _pompholyx_ and the _cadmia_, being chipped off, is thrown down through a long chute made of four boards joined in the shape of a rectangle, that they should not fly away. they fall on to the floor, and are sprinkled with salt water, and are again smelted with ore and litharge, and become an emolument to the proprietors. such chambers, which catch the metallic substances that rise with the fumes, are profitable for all metalliferous ores; but especially for the minute metallic particles collected by washing crushed ores and rock, because these usually fly out with the fire of the furnaces. i have explained the four general methods of smelting ores; now i will state how the ores of each metal are smelted, or how the metal is obtained from the ore. i will begin with gold. its sand, the concentrates from washing, or the gold dust collected in any other manner, should very often not be smelted, but should be mixed with quicksilver and washed with tepid water, so that all the impurities may be eliminated. this method i explained in book vii. or they are placed in the _aqua_ which separates gold from silver, for this also separates its impurities. in this method we see the gold sink in the glass ampulla, and after all the _aqua_ has been drained from the particles, it frequently remains as a gold-coloured residue at the bottom; this powder, when it has been moistened with oil made from argol[ ], is then dried and placed in a crucible, where it is melted with borax or with saltpetre and salt; or the same very fine dust is thrown into molten silver, which absorbs it, and from this it is again parted by _aqua valens_[ ]. it is necessary to smelt gold ore either outside the blast furnace in a crucible, or inside the blast furnace; in the former case a small charge of ore is used, in the latter a large charge of it. _rudis_ gold, of whatever colour it is, is crushed with a _libra_ each of sulphur and salt, a third of a _libra_ of copper, and a quarter of a _libra_ of argol; they should be melted in a crucible on a slow fire for three hours, then the alloy is put into molten silver that it may melt more rapidly. or a _libra_ of the same crude gold, crushed up, is mixed together with half a _libra_ of _stibium_ likewise crushed, and put into a crucible with half an _uncia_ of copper filings, and heated until they melt, then a sixth part of granulated lead is thrown into the same crucible. as soon as the mixture emits an odour, iron-filings are added to it, or if these are not at hand, iron hammer-scales, for both of these break the strength of the _stibium_. when the fire consumes it, not alone with it is some strength of the _stibium_ consumed, but some particles of gold and also of silver, if it be mixed with the gold[ ]. when the button has been taken out of the crucible and cooled, it is melted in a cupel, first until the antimony is exhaled, and thereafter until the lead is separated from it. crushed pyrites which contains gold is smelted in the same way; it and the _stibium_ should be of equal weight and in truth the gold may be made from them in a number of different ways[ ]. one part of crushed material is mixed with six parts of copper, one part of sulphur, half a part of salt, and they are all placed in a pot and over them is poured wine distilled by heating liquid argol in an ampulla. the pot is covered and smeared over with lute and is put in a hot place, so that the mixture moistened with wine may dry for the space of six days, then it is heated for three hours over a gentle fire that it may combine more rapidly with the lead. finally it is put into a cupel and the gold is separated from the lead[ ]. or else one _libra_ of the concentrates from washing pyrites, or other stones to which gold adheres, is mixed with half a _libra_ of salt, half a _libra_ of argol, a third of a _libra_ of glass-galls, a sixth of a _libra_ of gold or silver slags, and a _sicilicus_ of copper. the crucible into which these are put, after it has been covered with a lid, is sealed with lute and placed in a small furnace that is provided with small holes through which the air is drawn in, and then it is heated until it turns red and the substances put in have alloyed; this should take place within four or five hours. the alloy having cooled, it is again crushed to powder and a pound of litharge is added to it; then it is heated again in another crucible until it melts. the button is taken out, purged of slag, and placed in a cupel, where the gold is separated from the lead. or to a _libra_ of the powder prepared from such metalliferous concentrates, is added a _libra_ each of salt, of saltpetre, of argol, and of glass-galls, and it is heated until it melts. when cooled and crushed, it is washed, then to it is added a _libra_ of silver, a third of copper filings, a sixth of litharge, and it is likewise heated again until it melts. after the button has been purged of slag, it is put into the cupel, and the gold and silver are separated from the lead; the gold is parted from the silver with _aqua valens_. or else a _libra_ of the powder prepared from such metalliferous concentrates, a quarter of a _libra_ of copper filings, and two _librae_ of that second powder[ ] which fuses ores, are heated until they melt. the mixture when cooled is again reduced to powder, roasted and washed, and in this manner a blue powder is obtained. of this, and silver, and that second powder which fuses ores, a _libra_ each are taken, together with three _librae_ of lead, and a quarter of a _libra_ of copper, and they are heated together until they melt; then the button is treated as before. or else a _libra_ of the powder prepared from such metalliferous concentrates, half a _libra_ of saltpetre, and a quarter of a _libra_ of salt are heated until they melt. the alloy when cooled is again crushed to powder, one _libra_ of which is absorbed by four pounds of molten silver. or else a _libra_ of the powder made from that kind of concentrates, together with a _libra_ of sulphur, a _libra_ and a half of salt, a third of a _libra_ of salt made from argol, and a third of a _libra_ of copper resolved into powder with sulphur, are heated until they melt. afterward the lead is re-melted, and the gold is separated from the other metals. or else a _libra_ of the powder of this kind of concentrates, together with two _librae_ of salt, half a _libra_ of sulphur, and one _libra_ of litharge, are heated, and from these the gold is melted out. by these and similar methods concentrates containing gold, if there be a small quantity of them or if they are very rich, can be smelted outside the blast furnace. if there be much of them and they are poor, then they are smelted in the blast furnace, especially the ore which is not crushed to powder, and particularly when the gold mines yield an abundance of it[ ]. the gold concentrates mixed with litharge and hearth-lead, to which are added iron-scales, are smelted in the blast furnace whose tap-hole is intermittently closed, or else in the first or the second furnaces in which the tap-hole is always open. in this manner an alloy of gold and lead is obtained which is put into the cupellation furnace. two parts of roasted pyrites or _cadmia_ which contain gold, are put with one part of unroasted, and are smelted together in the third furnace whose tap-hole is always open, and are made into cakes. when these cakes have been repeatedly roasted, they are re-smelted in the furnace whose tap-hole is temporarily closed, or in one of the two others whose tap-holes are always open. in this manner the lead absorbs the gold, whether pure or argentiferous or cupriferous, and the alloy is taken to the cupellation furnace. pyrites, or other gold ore which is mixed with much material that is consumed by fire and flies out of the furnace, is melted with stone from which iron is melted, if this is at hand. six parts of such pyrites, or of gold ore reduced to powder and sifted, four of stone from which iron is made, likewise crushed, and three of slaked lime, are mixed together and moistened with water; to these are added two and a half parts of the cakes which contain some copper, together with one and a half parts of slag. a basketful of fragments of the cakes is thrown into the furnace, then the mixture of other things, and then the slag. now when the middle part of the forehearth is filled with the molten material which runs down from the furnace, the slags are first skimmed off, and then the cakes made of pyrites; afterward the alloy of copper, gold and silver, which settles at the bottom, is taken out. the cakes are gently roasted and re-smelted with lead, and made into cakes, which are carried to other works. the alloy of copper, gold, and silver is not roasted, but is re-melted again in a crucible with an equal portion of lead. cakes are also made much richer in copper and gold than those i spoke of. in order that the alloy of gold and silver may be made richer, to eighteen _librae_ of it are added forty-eight _librae_ of crude ore, three _librae_ of the stone from which iron is made, and three-quarters of a _libra_ of the cakes made from pyrites, and mixed with lead, all are heated together in the crucible until they melt. when the slag and the cakes melted from pyrites have been skimmed off, the alloy is carried to other furnaces. there now follows silver, of which the native silver or the lumps of _rudis_ silver[ ] obtained from the mines are not smelted in the blast furnaces, but in small iron pans, of which i will speak at the proper place; these lumps are heated and thrown into molten silver-lead alloy in the cupellation furnace when the silver is being separated from the lead, and refined. the tiny flakes or tiny lumps of silver adhering to stones or marble or rocks, or again the same little lumps mixed with earth, or silver not pure enough, should be smelted in the furnace of which the tap-hole is only closed for a short time, together with cakes melted from pyrites, with silver slags, and with stones which easily fuse in fire of the second order. in order that particles of silver should not fly away[ ] from the lumps of ore consisting of minute threads of pure silver and twigs of native silver, they are enclosed in a pot, and are placed in the same furnace where the rest of the silver ores are being smelted. some people smelt lumps of native silver not sufficiently pure, in pots or triangular crucibles, whose lids are sealed with lute. they do not place these pots in the blast furnace, but arrange them in the assay furnace into which the draught of the air blows through small holes. to one part of the native silver they add three parts of powdered litharge, as many parts of hearth-lead, half a part of galena[ ], and a small quantity of salt and iron-scales. the alloy which settles at the bottom of the other substances in the pot is carried to the cupellation furnace, and the slags are re-melted with the other silver slags. they crush under the stamps and wash the pots or crucibles to which silver-lead alloy or slags adhere, and having collected the concentrates they smelt them together with the slags. this method of smelting _rudis_ silver, if there is a small quantity of it, is the best, because the smallest portion of silver does not fly out of the pot or the crucible, and get lost. if bismuth ore or antimony ore or lead ore[ ] contains silver, it is smelted with the other ores of silver; likewise galena or pyrites, if there is a small amount of it. if there be much galena, whether it contain a large or a small amount of silver, it is smelted separately from the others; which process i will explain a little further on. because lead and copper ores and their metals have much in common with silver ores, it is fitting that i should say a great deal concerning them, both now and later on. also in the same manner, pyrites are smelted separately if there be much of them. to three parts of roasted lead or copper ore and one part of crude ore, are added concentrates if they were made by washing the same ore, together with slags, and all are put in the third furnace whose tap-hole is always open. cakes are made from this charge, which, when they have been quenched with water, are roasted. of these roasted cakes generally four parts are again mixed with one part of crude pyrites and re-melted in the same furnace. cakes are again made from this charge, and if there is a large amount of copper in these cakes, copper is made immediately after they have been roasted and re-melted; if there is little copper in the cakes they are also roasted, but they are re-smelted with a little soft slag. in this method the molten lead in the forehearth absorbs the silver. from the pyritic material which floats on the top of the forehearth are made cakes for the third time, and from them when they have been roasted and re-smelted is made copper. similarly, three parts of roasted _cadmia_[ ] in which there is silver, are mixed with one part of crude pyrites, together with slag, and this charge is smelted and cakes are made from it; these cakes having been roasted are re-smelted in the same furnace. by this method the lead contained in the forehearth absorbs the silver, and the silver-lead is taken to the cupellation furnace. crude quartz and stones which easily fuse in fire of the third order, together with other ores in which there is a small amount of silver, ought to be mixed with crude roasted pyrites or _cadmia_, because the roasted cakes of pyrites or _cadmia_ cannot be profitably smelted separately. in a similar manner earths which contain little silver are mixed with the same; but if pyrites and _cadmia_ are not available to the smelter, he smelts such silver ores and earths with litharge, hearth-lead, slags, and stones which easily melt in the fire. the concentrates[ ] originating from the washing of _rudis_ silver, after first being roasted[ ] until they melt, are smelted with mixed litharge and hearth-lead, or else, after being moistened with water, they are smelted with cakes made from pyrites and _cadmia_. by neither of these methods do (the concentrates) fall back in the furnace, or fly out of it, driven by the blast of the bellows and the agitation of the fire. if the concentrates originated from galena they are smelted with it after having been roasted; and if from pyrites, then with pyrites. pure copper ore, whether it is its own colour or is tinged with chrysocolla or azure, and copper glance, or grey or black _rudis_ copper, is smelted in a furnace of which the tap-hole is closed for a very short time, or else is always open[ ]. if there is a large amount of silver in the ore it is run into the forehearth, and the greater part of the silver is absorbed by the molten lead, and the remainder is sold with the copper to the proprietor of the works in which silver is parted from copper[ ]. if there is a small amount of silver in the ore, no lead is put into the forehearth to absorb the silver, and the above-mentioned proprietors buy it in with the copper; if there be no silver, copper is made direct. if such copper ore contains some minerals which do not easily melt, as pyrites or _cadmia metallica fossilis_[ ], or stone from which iron is melted, then crude pyrites which easily fuse are added to it, together with slag. from this charge, when smelted, they make cakes; and from these, when they have been roasted as much as is necessary and re-smelted, the copper is made. but if there be some silver in the cakes, for which an outlay of lead has to be made, then it is first run into the forehearth, and the molten lead absorbs the silver. indeed, _rudis_ copper ore of inferior quality, whether ash-coloured or purple, blackish and occasionally in parts blue, is smelted in the first furnace whose tap-hole is always open. this is the method of the tyrolese. to as much _rudis_ copper ore as will fill eighteen vessels, each of which holds almost as much as seven roman _moduli_[ ], the first smelter--for there are three--adds three cartloads of lead slags, one cartload of schist, one fifth of a _centumpondium_ of stones which easily fuse in the fire, besides a small quantity of concentrates collected from copper slag and accretions, all of which he smelts for the space of twelve hours, and from which he makes six _centumpondia_ of primary cakes and one-half of a _centumpondium_ of alloy. one half of the latter consists of copper and silver, and it settles to the bottom of the forehearth. in every _centumpondium_ of the cakes there is half a _libra_ of silver and sometimes half an _uncia_ besides; in the half of a _centumpondium_ of the alloy there is a _bes_ or three-quarters of silver. in this way every week, if the work is for six days, thirty-six _centumpondia_ of cakes are made and three _centumpondia_ of alloy, in all of which there is often almost twenty-four _librae_ of silver. the second smelter separates from the primary cakes the greater part of the silver by absorbing it in lead. to eighteen _centumpondia_ of cakes made from crude copper ore, he adds twelve _centumpondia_ of hearth-lead and litharge, three _centumpondia_ of stones from which lead is smelted, five _centumpondia_ of hard cakes rich in silver, and two _centumpondia_ of exhausted liquation cakes[ ]; he adds besides, some of the slags resulting from smelting crude copper, together with a small quantity of concentrates made from accretions, all of which he melts for the space of twelve hours, and makes eighteen _centumpondia_ of secondary cakes, and twelve _centumpondia_ of copper-lead-silver alloy; in each _centumpondium_ of the latter there is half a _libra_ of silver. after he has taken off the cakes with a hooked bar, he pours the alloy out into copper or iron moulds; by this method they make four cakes of alloy, which are carried to the works in which silver is parted from copper. on the following day, the same smelter, taking eighteen _centumpondia_ of the secondary cakes, again adds twelve _centumpondia_ of hearth-lead and litharge, three _centumpondia_ of stones from which lead is smelted, five _centumpondia_ of hard cakes rich in silver, together with slags from the smelting of the primary cakes, and with concentrates washed from the accretions which are usually made at that time. this charge is likewise smelted for the space of twelve hours, and he makes as many as thirteen _centumpondia_ of tertiary cakes and eleven _centumpondia_ of copper-lead-silver alloy, each _centumpondium_ of which contains one-third of a _libra_ and half an _uncia_ of silver. when he has skimmed off the tertiary cakes with a hooked bar, the alloy is poured into copper moulds, and by this method four cakes of alloy are made, which, like the preceding four cakes of alloy, are carried to the works in which silver is parted from copper. by this method the second smelter makes primary cakes on alternate days and secondary cakes on the intermediate days. the third smelter takes eleven cartloads of the tertiary cakes and adds to them three cartloads of hard cakes poor in silver, together with the slag from smelting the secondary cakes, and the concentrates from the accretions which are usually made at that time. from this charge when smelted, he makes twenty _centumpondia_ of quaternary cakes, which are called "hard cakes," and also fifteen _centumpondia_ of those "hard cakes rich in silver," each _centumpondium_ of which contains a third of a _libra_ of silver. these latter cakes the second smelter, as i said before, adds to the primary and secondary cakes when he re-melts them. in the same way, from eleven cartloads of quaternary cakes thrice roasted, he makes the "final" cakes, of which one _centumpondium_ contains only half an _uncia_ of silver. in this operation he also makes fifteen _centumpondia_ of "hard cakes poor in silver," in each _centumpondium_ of which is a sixth of a _libra_ of silver. these hard cakes the third smelter, as i have said, adds to the tertiary cakes when he re-smelts them, while from the "final" cakes, thrice roasted and re-smelted, is made black copper[ ]. the _rudis_ copper from which pure copper is made, if it contains little silver or if it does not easily melt, is first smelted in the third furnace of which the tap-hole is always open; and from this are made cakes, which after being seven times roasted are re-smelted, and from these copper is melted out; the cakes of copper are carried to a furnace of another kind, in which they are melted for the third time, in order that in the copper "bottoms" there may be more silver, while in the "tops" there may be less, which process is explained in book xi. pyrites, when they contain not only copper, but also silver, are smelted in the manner i described when i treated of ores of silver. but if they are poor in silver, and if the copper which is melted out of them cannot easily be treated, they are smelted according to the method which i last explained. finally, the copper schists containing bitumen or sulphur are roasted, and then smelted with stones which easily fuse in a fire of the second order, and are made into cakes, on the top of which the slags float. from these cakes, usually roasted seven times and re-melted, are melted out slags and two kinds of cakes; one kind is of copper and occupies the bottom of the crucible, and these are sold to the proprietors of the works in which silver is parted from copper; the other kind of cakes are usually re-melted with primary cakes. if the schist contains but a small amount of copper, it is burned, crushed under the stamps, washed and sieved, and the concentrates obtained from it are melted down; from this are made cakes from which, when roasted, copper is made. if either chrysocolla or azure, or yellow or black earth containing copper and silver, adheres to the schist, it is not washed, but is crushed and smelted with stones which easily fuse in fire of the second order. lead ore, whether it be _molybdaena_[ ], pyrites, (galena?) or stone from which it is melted, is often smelted in a special furnace, of which i have spoken above, but no less often in the third furnace of which the tap-hole is always open. the hearth and forehearth are made from powder containing a small portion of iron hammer-scales; iron slag forms the principal flux for such ores; both of these the expert smelters consider useful and to the owner's advantage, because it is the nature of iron to attract lead. if it is _molybdaena_ or the stone from which lead is smelted, then the lead runs down from the furnace into the forehearth, and when the slags have been skimmed off, the lead is poured out with a ladle. if pyrites are smelted, the first to flow from the furnace into the forehearth, as may be seen at goslar, is a white molten substance, injurious and noxious to silver, for it consumes it. for this reason the slags which float on the top having been skimmed off, this substance is poured out; or if it hardens, then it is taken out with a hooked bar; and the walls of the furnace exude the same substance[ ]. then the _stannum_ runs out of the furnace into the forehearth; this is an alloy of lead and silver. from the silver-lead alloy they first skim off the slags, not rarely white, as some pyrites[ ] are, and afterward they skim off the cakes of pyrites, if there are any. in these cakes there is usually some copper; but since there is usually but a very small quantity, and as the forest charcoal is not abundant, no copper is made from them. from the silver-lead poured into iron moulds they likewise make cakes; when these cakes have been melted in the cupellation furnace, the silver is parted from the lead, because part of the lead is transformed into litharge and part into hearth-lead, from which in the blast furnace on re-melting they make de-silverized lead, for in this lead each _centumpondium_ contains only a _drachma_ of silver, when before the silver was parted from it each _centumpondium_ contained more or less than three _unciae_ of silver[ ]. the little black stones[ ] and others from which tin is made, are smelted in their own kind of furnace, which should be narrower than the other furnaces, that there may be only the small fire which is necessary for this ore. these furnaces are higher, that the height may compensate for the narrowness and make them of almost the same capacity as the other furnaces. at the top, in front, they are closed and on the other side they are open, where there are steps, because they cannot have the steps in front on account of the forehearth; the smelters ascend by these steps to put the tin-stone into the furnace. the hearth of the furnace is not made of powdered earth and charcoal, but on the floor of the works are placed sandstones which are not too hard; these are set on a slight slope, and are two and three-quarters feet long, the same number of feet wide, and two feet thick, for the thicker they are the longer they last in the fire. around them is constructed a rectangular furnace eight or nine feet high, of broad sandstones, or of those common substances which by nature are composed of diverse materials[ ]. on the inside the furnace is everywhere evenly covered with lute. the upper part of the interior is two feet long and one foot wide, but below it is not so long and wide. above it are two hood-walls, between which the fumes ascend from the furnace into the dust chamber, and through this they escape by a narrow opening in the roof. the sandstones are sloped at the bed of the furnace, so that the tin melted from the tin-stone may flow through the tap-hole of the furnace into the forehearth.[ ] as there is no need for the smelters to have a fierce fire, it is not necessary to place the nozzles of the bellows in bronze or iron pipes, but only through a hole in the furnace wall. they place the bellows higher at the back so that the blast from the nozzles may blow straight toward the tap-hole of the furnace. that it may not be too fierce, the nozzles are wide, for if the fire were fiercer, tin could not be melted out from the tin-stone, as it would be consumed and turned into ashes. near the steps is a hollowed stone, in which is placed the tin-stone to be smelted; as often as the smelter throws into the furnace an iron shovel-ful of this tin-stone, he puts on charcoal that was first put into a vat and washed with water to be cleansed from the grit and small stones which adhere to it, lest they melt at the same time as the tin-stone and obstruct the tap-hole and impede the flow of tin from the furnace. the tap-hole of the furnace is always open; in front of it is a forehearth a little more than half a foot deep, three-quarters of two feet long and one foot wide; this is lined with lute, and the tin from the tap-hole flows into it. on one side of the forehearth is a low wall, three-quarters of a foot wider and one foot longer than the forehearth, on which lies charcoal powder. on the other side the floor of the building slopes, so that the slags may conveniently run down and be carried away. as soon as the tin begins to run from the tap-hole of the furnace into the forehearth, the smelter scrapes down some of the powdered charcoal into it from the wall, so that the slags may be separated from the hot metal, and so that it may be covered, lest any part of it, being very hot, should fly away with the fumes. if after the slag has been skimmed off, the powder does not cover up the whole of the tin, the smelter draws a little more charcoal off the wall with a scraper. after he has opened the tap-hole of the forehearth with a tapping-bar, in order that the tin can flow into the tapping-pot, likewise smeared with lute, he again closes the tap-hole with pure lute or lute mixed with powdered charcoal. the smelter, if he be diligent and experienced, has brooms at hand with which he sweeps down the walls above the furnace; to these walls and to the dust chamber minute tin-stones sometimes adhere with part of the fumes. if he be not sufficiently experienced in these matters and has melted at the same time all of the tin-stone,--which is commonly of three sizes, large, medium, and very small,--not a little waste of the proprietor's tin results; because, before the large or the medium sizes have melted, the small have either been burnt up in the furnace, or else, flying up from it, they not only adhere to the walls but also fall in the dust chamber. the owner of the works has the sweepings by right from the owner of the ore. for the above reasons the most experienced smelter melts them down separately; indeed, he melts the very small size in a wider furnace, the medium in a medium-sized furnace, and the largest size in the narrowest furnace. when he melts down the small size he uses a gentle blast from the bellows, with the medium-sized a moderate one, with the large size a violent blast; and when he smelts the first size he needs a slow fire, for the second a medium one, and for the third a fierce one; yet he uses a much less fierce fire than when he smelts the ores of gold, silver, or copper. when the workmen have spent three consecutive days and nights in this work, as is usual, they have finished their labours; in this time they are able to melt out a large weight of small sized tin-stone which melts quickly, but less of the large ones which melt slowly, and a moderate quantity of the medium-sized which holds the middle course. those who do not smelt the tin-stone in furnaces made sometimes wide, sometimes medium, or sometimes narrow, in order that great loss should not be occasioned, throw in first the smallest size, then the medium, then the large size, and finally those which are not quite pure; and the blast of the bellows is altered as required. in order that the tin-stone thrown into the furnace should not roll off from the large charcoal into the forehearth before the tin is melted out of it, the smelter uses small charcoal; first some of this moistened with water is placed in the furnace, and then he frequently repeats this succession of charcoal and tin-stone. the tin-stone, collected from material which during the summer was washed in a ditch through which a stream was diverted, and during the winter was screened on a perforated iron plate, is smelted in a furnace a palm wider than that in which the fine tin-stone dug out of the earth is smelted. for the smelting of these, a more vigorous blast of the bellows and a fiercer fire is needed than for the smelting of the large tin-stone. whichever kind of tin-stone is being smelted, if the tin first flows from the furnace, much of it is made, and if slags first flow from the furnace, then only a little. it happens that the tin-stone is mixed with the slags when it is either less pure or ferruginous--that is, not enough roasted--and is imperfect when put into the furnace, or when it has been put in in a larger quantity than was necessary; then, although it may be pure and melt easily, the ore either runs out of the furnace at the same time, mixed with the slags, or else it settles so firmly at the bottom of the furnace that the operation of smelting being necessarily interrupted, the furnace freezes up. [illustration (tin smelting furnaces): a--furnace. b--its tap-hole. c--forehearth. d--its tap-hole. e--slags. f--scraper. g--dipping-pot. h--walls of the chimney. i--broom. k--copper plate. l--latticework bars. m--iron seal or die. n--hammer.] the tap-hole of the forehearth is opened and the tin is diverted into the dipping-pot, and as often as the slags flow down the sloping floor of the building they are skimmed off with a rabble; as soon as the tin has run out of the forehearth, the tap-hole is again closed up with lute mixed with powdered charcoal. glowing coals are put in the dipping-pot so that the tin, after it has run out, should not get chilled. if the metal is so impure that nothing can be made from it, the material which has run out is made into cakes to be re-smelted in the hearth, of which i shall have something to say later; if the metal is pure, it is poured immediately upon thick copper plates, at first in straight lines and then transversely over these to make a lattice. each of these lattice bars is impressed with an iron die; if the tin was melted out of ore excavated from mines, then one stamp only, namely, that of the magistrate, is usually imprinted, but if it is made from tin-stone collected on the ground after washing, then it is impressed with two seals, one the magistrate's and the other a fork which the washers use. generally, three of this kind of lattice bars are beaten and amalgamated into one mass with a wooden mallet. the slags that are skimmed off are afterward thrown with an iron shovel into a small trough hollowed from a tree, and are cleansed from charcoal by agitation; when taken out they are broken up with a square iron mallet, and then they are re-melted with the fine tin-stone next smelted. there are some who crush the slags three times under wet stamps and re-melt them three times; if a large quantity of this be smelted while still wet, little tin is melted from it, because the slag, soon melted again, flows from the furnace into the forehearth. under the wet stamps are also crushed the lute and broken rock with which such furnaces are lined, and also the accretions, which often contain fine tin-stone, either not melted or half-melted, and also prills of tin. the tin-stone not yet melted runs out through the screen into a trough, and is washed in the same way as tin-stone, while the partly melted and the prills of tin are taken from the mortar-box and washed in the sieve on which not very minute particles remain, and thence to the canvas strake. the soot which adheres to that part of the chimney which emits the smoke, also often contains very fine tin-stone which flies from the furnace with the fumes, and this is washed in the strake which i have just mentioned, and in other sluices. the prills of tin and the partly melted tin-stone that are contained in the lute and broken rock with which the furnace is lined, and in the remnants of the tin from the forehearth and the dipping-pot, are smelted together with the tin-stone. when tin-stone has been smelted for three days and as many nights in a furnace prepared as i have said above, some little particles of the rock from which the furnace is constructed become loosened by the fire and fall down; and then the bellows being taken away, the furnace is broken through at the back, and the accretions are first chipped off with hammers, and afterward the whole of the interior of the furnace is re-fitted with the prepared sandstone, and again evenly lined with lute. the sandstone placed on the bed of the furnace, if it has become faulty, is taken out, and another is laid down in its place; those rocks which are too large the smelter chips off and fits with a sharp pick. [illustration (tin smelting furnaces): a--furnaces. b--forehearths. c--their tap-holes. d--dipping-pots. e--pillars. f--dust-chamber. g--window. h--chimneys. i--tub in which the coals are washed.] some build two furnaces against the wall just like those i have described, and above them build a vaulted ceiling supported by the wall and by four pillars. through holes in the vaulted ceiling the fumes from the furnaces ascend into a dust chamber, similar to the one described before, except that there is a window on each side and there is no door. the smelters, when they have to clear away the flue-dust, mount by the steps at the side of the furnaces, and climb by ladders into the dust chamber through the apertures in the vaulted ceilings over the furnaces. they then remove the flue-dust from everywhere and collect it in baskets, which are passed from one to the other and emptied. this dust chamber differs from the other described, in the fact that the chimneys, of which it has two, are not dissimilar to those of a house; they receive the fumes which, being unable to escape through the upper part of the chamber, are turned back and re-ascend and release the tin; thus the tin set free by the fire and turned to ash, and the little tin-stones which fly up with the fumes, remain in the dust chamber or else adhere to copper plates in the chimney. [illustration (refining tin): a--hearths. b--dipping-pots. c--wood. d--cakes. e--ladle. f--copper plate. g--lattice-shaped bars. h--iron dies. i--wooden mallet. k--mass of tin bars. l--shovel.] if the tin is so impure that it cracks when struck with the hammer, it is not immediately made into lattice-like bars, but into the cakes which i have spoken of before, and these are refined by melting again on a hearth. this hearth consists of sandstones, which slope toward the centre and a little toward a dipping-pot; at their joints they are covered with lute. dry logs are arranged on each side, alternately upright and lengthwise, and more closely in the middle; on this wood are placed five or six cakes of tin which all together weigh about six _centumpondia_; the wood having been kindled, the tin drips down and flows continuously into the dipping-pot which is on the floor. the impure tin sinks to the bottom of this dipping-pot and the pure tin floats on the top; then both are ladled out by the master, who first takes out the pure tin, and by pouring it over thick plates of copper makes lattice-like bars. afterward he takes out the impure tin from which he makes cakes; he discriminates between them, when he ladles and pours, by the ease or difficulty of the flow. one _centumpondium_ of the lattice-like bars sells for more than a _centumpondium_ of cakes, for the price of the former exceeds the price of the latter by a gold coin[ ]. these lattice-like bars are lighter than the others, and when five of them are pounded and amalgamated with a wooden mallet, a mass is made which is stamped with an iron die. there are some who do not make a dipping-pot on the floor for the tin to run into, but in the hearth itself; out of this the master, having removed the charcoal, ladles the tin and pours it over the copper-plate. the dross which adheres to the wood and the charcoal, having been collected, is re-smelted in the furnace. [illustration (blast furnaces): a--furnace. b--bellows. c--iron disc. d--nozzle. e--wooden disc. f--blow-hole. g--handle. h--haft. i--hoops. k--masses of tin.] some of the lusitanians melt tin from tin-stone in small furnaces. they use round bellows made of leather, of which the fore end is a round iron disc and the rear end a disc of wood; in a hole in the former is fixed the nozzle, in the middle of the latter the blow-hole. above this is the handle or haft, which draws open the round bellows and lets in the air, or compresses it and drives the air out. between the discs are several iron hoops to which the leather is fastened, making such folds as are to be seen in paper lanterns that are folded together. since this kind of bellows does not give a vigorous blast, because they are drawn apart and compressed slowly, the smelter is not able during a whole day to smelt much more than half a _centumpondium_ of tin. [illustration (iron smelting furnaces): a--hearth. b--heap. c--slag-vent. d--iron mass. e--wooden mallets. f--hammer. g--anvil.] very good iron ore is smelted[ ] in a furnace almost like the cupellation furnace. the hearth is three and a half feet high, and five feet long and wide; in the centre of it is a crucible a foot deep and one and a half feet wide, but it may be deeper or shallower, wider or narrower, according to whether more or less ore is to be made into iron. a certain quantity of iron ore is given to the master, out of which he may smelt either much or little iron. he being about to expend his skill and labour on this matter, first throws charcoal into the crucible, and sprinkles over it an iron shovel-ful of crushed iron ore mixed with unslaked lime. then he repeatedly throws on charcoal and sprinkles it with ore, and continues this until he has slowly built up a heap; it melts when the charcoal has been kindled and the fire violently stimulated by the blast of the bellows, which are skilfully fixed in a pipe. he is able to complete this work sometimes in eight hours, sometimes in ten; and again sometimes in twelve. in order that the heat of the fire should not burn his face, he covers it entirely with a cap, in which, however, there are holes through which he may see and breathe. at the side of the hearth is a bar which he raises as often as is necessary, when the bellows blow too violent a blast, or when he adds more ore and charcoal. he also uses the bar to draw off the slags, or to open or close the gates of the sluice, through which the waters flow down on to the wheel which turns the axle that compresses the bellows. in this sensible way, iron is melted out and a mass weighing two or three _centumpondia_ may be made, providing the iron ore was rich. when this is done the master opens the slag-vent with the tapping-bar, and when all has run out he allows the iron mass to cool. afterward he and his assistant stir the iron with the bar, and then in order to chip off the slags which had until then adhered to it, and to condense and flatten it, they take it down from the furnace to the floor, and beat it with large wooden mallets having slender handles five feet long. thereupon it is immediately placed on the anvil, and repeatedly beaten by the large iron hammer that is raised by the cams of an axle turned by a water-wheel. not long afterward it is taken up with tongs and placed under the same hammer, and cut up with a sharp iron into four, five, or six pieces, according to whether it is large or small. these pieces, after they have been re-heated in the blacksmith's forge and again placed on the anvil, are shaped by the smith into square bars or into ploughshares or tyres, but mainly into bars. four, six, or eight of these bars weigh one-fifth of a _centumpondium_, and from these they make various implements. during the blows from the hammer by which it is shaped by the smith, a youth pours water with a ladle on to the glowing iron, and this is why the blows make such a loud sound that they may be heard a long distance from the works. the masses, if they remain and settle in the crucible of the furnace in which the iron is smelted, become hard iron which can only be hammered with difficulty, and from these they make the iron-shod heads for the stamps, and such-like very hard articles. [illustration (iron smelting furnaces): a--furnace. b--stairs. c--ore. d--charcoal.] but to iron ore which is cupriferous, or which when heated[ ] melts with difficulty, it is necessary for us to give a fiercer fire and more labour; because not only must we separate the parts of it in which there is metal from those in which there is no metal, and break it up by dry stamps, but we must also roast it, so that the other metals and noxious juices may be exhaled; and we must wash it, so that the lighter parts may be separated from it. such ores are smelted in a furnace similar to the blast furnace, but much wider and higher, so that it may hold a great quantity of ore and much charcoal; mounting the stairs at the side of the furnace, the smelters fill it partly with fragments of ore not larger than nuts, and partly with charcoal; and from this kind of ore once or twice smelted they make iron which is suitable for re-heating in the blacksmith's forge, after it is flattened out with the large iron hammer and cut into pieces with the sharp iron. [illustration (steel making furnaces): a--forge. b--bellows. c--tongs. d--hammer. e--cold stream.] by skill with fire and fluxes is made that kind of iron from which steel is made, which the greeks call [greek: stomôma]. iron should be selected which is easy to melt, is hard and malleable. now although iron may be smelted from ore which contains other metals, yet it is then either soft or brittle; such (iron) must be broken up into small pieces when it is hot, and then mixed with crushed stone which melts. then a crucible is made in the hearth of the smith's furnace, from the same moistened powder from which are made the forehearths in front of the furnaces in which ores of gold or silver are smelted; the width of this crucible is about one and a half feet and the depth one foot. the bellows are so placed that the blast may be blown through the nozzle into the middle of the crucible. then the whole of the crucible is filled with the best charcoal, and it is surrounded by fragments of rock to hold in place the pieces of iron and the superimposed charcoal. as soon as all the charcoal is kindled and the crucible is glowing, a blast is blown from the bellows and the master pours in gradually as much of the mixture of iron and flux as he wishes. into the middle of this, when it is melted, he puts four iron masses each weighing thirty pounds, and heats them for five or six hours in a fierce fire; he frequently stirs the melted iron with a bar, so that the small pores in each mass absorb the minute particles, and these particles by their own strength consume and expand the thick particles of the masses, which they render soft and similar to dough. afterward the master, aided by his assistant, takes out a mass with the tongs and places it on the anvil, where it is pounded by the hammer which is alternately raised and dropped by means of the water-wheel; then, without delay, while it is still hot, he throws it into water and tempers it; when it is tempered, he places it again on the anvil, and breaks it with a blow from the same hammer. then at once examining the fragments, he decides whether the iron in some part or other, or as a whole, appears to be dense and changed into steel; if so, he seizes one mass after another with the tongs, and taking them out he breaks them into pieces. afterward he heats the mixture up again, and adds a portion afresh to take the place of that which has been absorbed by the masses. this restores the energy of that which is left, and the pieces of the masses are again put back into the crucible and made purer. each of these, after having been heated, is seized with the tongs, put under the hammer and shaped into a bar. while they are still glowing, he at once throws them into the very coldest nearby running water, and in this manner, being suddenly condensed, they are changed into pure steel, which is much harder and whiter than iron. the ores of the other metals are not smelted in furnaces. quicksilver ores and also antimony are melted in pots, and bismuth in troughs. [illustration (quicksilver distillation furnaces): a--hearth. b--poles. c--hearth without fire in which the pots are placed. d--rocks. e--rows of pots. f--upper pots. g--lower pots.] i will first speak of quicksilver. this is collected when found in pools formed from the outpourings of the veins and stringers; it is cleansed with vinegar and salt, and then it is poured into canvas or soft leather, through which, when squeezed and compressed, the quicksilver runs out into a pot or pan. the ore of quicksilver is reduced in double or single pots. if in double pots, then the upper one is of a shape not very dissimilar to the glass ampullas used by doctors, but they taper downward toward the bottom, and the lower ones are little pots similar to those in which men and women make cheese, but both are larger than these; it is necessary to sink the lower pots up to the rims in earth, sand, or ashes. the ore, broken up into small pieces is put into the upper pots; these having been entirely closed up with moss, are placed upside down in the openings of the lower pots, where they are joined with lute, lest the quicksilver which takes refuge in them should be exhaled. there are some who, after the pots have been buried, do not fear to leave them uncemented, and who boast that they are able to produce no less weight of quicksilver than those who do cement them, but nevertheless cementing with lute is the greatest protection against exhalation. in this manner seven hundred pairs of pots are set together in the ground or on a hearth. they must be surrounded on all sides with a mixture consisting of crushed earth and charcoal, in such a way that the upper pots protrude to a height of a palm above it. on both sides of the hearth rocks are first laid, and upon them poles, across which the workmen place other poles transversely; these poles do not touch the pots, nevertheless the fire heats the quicksilver, which fleeing from the heat is forced to run down through the moss into the lower pots. if the ore is being reduced in the upper pots, it flees from them, wherever there is an exit, into the lower pots, but if the ore on the contrary is put in the lower pots the quicksilver rises into the upper pot or into the operculum, which, together with the gourd-shaped vessels, are cemented to the upper pots. the pots, lest they should become defective, are moulded from the best potters' clay, for if there are defects the quicksilver flies out in the fumes. if the fumes give out a very sweet odour it indicates that the quicksilver is being lost, and since this loosens the teeth, the smelters and others standing by, warned of the evil, turn their backs to the wind, which drives the fumes in the opposite direction; for this reason, the building should be open around the front and the sides, and exposed to the wind. if these pots are made of cast copper they last a long time in the fire. this process for reducing the ores of quicksilver is used by most people. in a similar manner the antimony ore,[ ] if free from other metals, is reduced in upper pots which are twice as large as the lower ones. their size, however, depends on the cakes, which have not the same weight everywhere; for in some places they are made to weigh six _librae_, in other places ten, and elsewhere twenty. when the smelter has concluded his operation, he extinguishes the fire with water, removes the lids from the pots, throws earth mixed with ash around and over them, and when they have cooled, takes out the cakes from the pots. [illustration (quicksilver distillation furnaces): a--pots. b--opercula. c--nozzles. d--gourd-shaped earthenware vessels.] other methods for reducing quicksilver are given below. big-bellied pots, having been placed in the upper rectangular open part of a furnace, are filled with the crushed ore. each of these pots is covered with a lid with a long nozzle--commonly called a _campana_--in the shape of a bell, and they are cemented. each of the small earthenware vessels shaped like a gourd receives two of these nozzles, and these are likewise cemented. dried wood having been placed in the lower part of the furnace and kindled, the ore is heated until all the quicksilver has risen into the operculum which is over the pot; it then flows from the nozzle and is caught in the earthenware gourd-shaped vessel. [illustration (quicksilver distillation furnaces): a--enclosed chamber. b--door. c--little windows. d--mouths through the walls. e--furnace in the enclosed chamber. f--pots.] others build a hollow vaulted chamber, of which the paved floor is made concave toward the centre. inside the thick walls of the chamber are the furnaces. the doors through which the wood is put are in the outer part of the same wall. they place the pots in the furnaces and fill them with crushed ore, then they cement the pots and the furnaces on all sides with lute, so that none of the vapour may escape from them, and there is no entrance to the furnaces except through their mouths. between the dome and the paved floor they arrange green trees, then they close the door and the little windows, and cover them on all sides with moss and lute, so that none of the quicksilver can exhale from the chamber. after the wood has been kindled the ore is heated, and exudes the quicksilver; whereupon, impatient with the heat, and liking the cold, it escapes to the leaves of the trees, which have a cooling power. when the operation is completed the smelter extinguishes the fire, and when all gets cool he opens the door and the windows, and collects the quicksilver, most of which, being heavy, falls of its own accord from the trees, and flows into the concave part of the floor; if all should not have fallen from the trees, they are shaken to make it fall. [illustration (quicksilver distillation furnaces): a--larger pot. b--smaller. c--tripod. d--tub in which the sand is washed.] the following is the fourth method of reducing ores of quicksilver. a larger pot standing on a tripod is filled with crushed ore, and over the ore is put sand or ashes to a thickness of two digits, and tamped; then in the mouth of this pot is inserted the mouth of another smaller pot and cemented with lute, lest the vapours are emitted. the ore heated by the fire exhales the quicksilver, which, penetrating through the sand or the ashes, takes refuge in the upper pot, where condensing into drops it falls back into the sand or the ashes, from which the quicksilver is washed and collected. [illustration (quicksilver distillation furnaces): a--pots. b--lids. c--stones. d--furnace.] the fifth method is not very unlike the fourth. in the place of these pots are set other pots, likewise of earthenware, having a narrow bottom and a wide mouth. these are nearly filled with crushed ore, which is likewise covered with ashes to a depth of two digits and tamped in. the pots are covered with lids a digit thick, and they are smeared over on the inside with liquid litharge, and on the lid are placed heavy stones. the pots are set on the furnace, and the ore is heated and similarly exhales quicksilver, which fleeing from the heat takes refuge in the lid; on congealing there, it falls back into the ashes, from which, when washed, the quicksilver is collected. by these five methods quicksilver may be made, and of these not one is to be despised or repudiated; nevertheless, if the mine supplies a great abundance of ore, the first is the most expeditious and practical, because a large quantity of ore can be reduced at the same time without great expense.[ ] [illustration (bismuth smelting): a--pit across which wood is placed. b--forehearth. c--ladle. d--iron mould. e--cakes. f--empty pot lined with stones in layers. g--troughs. h--pits dug at the foot of the troughs. i--small wood laid over the troughs. k--wind.] bismuth[ ] ore, free from every kind of silver, is smelted by various methods. first a small pit is dug in the dry ground; into this pulverised charcoal is thrown and tamped in, and then it is dried with burning charcoal. afterward, thick dry pieces of beech wood are placed over the pit, and the bismuth ore is thrown on it. as soon as the kindled wood burns, the heated ore drips with bismuth, which runs down into the pit, from which when cooled the cakes are removed. because pieces of burnt wood, or often charcoal and occasionally slag, drop into the bismuth which collects in the pit, and make it impure, it is put back into another kind of crucible to be melted, so that pure cakes may be made. there are some who, bearing these things in mind, dig a pit on a sloping place and below it put a forehearth, into which the bismuth continually flows, and thus remains clean; then they take it out with ladles and pour it into iron pans lined inside with lute, and make cakes of it. they cover such pits with flat stones, whose joints are besmeared with a lute of mixed dust and crushed charcoal, lest the joints should absorb the molten bismuth. another method is to put the ore in troughs made of fir-wood and placed on sloping ground; they place small firewood over it, kindling it when a gentle wind blows, and thus the ore is heated. in this manner the bismuth melts and runs down from the troughs into a pit below, while there remains slag, or stones, which are of a yellow colour, as is also the wood laid across the pit. these are also sold. [illustration (bismuth smelting): a--wood. b--bricks. c--pans. d--furnace. e--crucible. f--pipe. g--dipping-pot.] others reduce the ore in iron pans as next described. they lay small pieces of dry wood alternately straight and transversely upon bricks, one and a half feet apart, and set fire to it. near it they put small iron pans lined on the inside with lute, and full of broken ore; then when the wind blows the flame of the fierce fire over the pans, the bismuth drips out of the ore; wherefore, in order that it may run, the ore is stirred with the tongs; but when they decide that all the bismuth is exuded, they seize the pans with the tongs and remove them, and pour out the bismuth into empty pans, and by turning many into one they make cakes. others reduce the ore, when it is not mixed with _cadmia_,[ ] in a furnace similar to the iron furnace. in this case they make a pit and a crucible of crushed earth mixed with pulverised charcoal, and into it they put the broken ore, or the concentrates from washing, from which they make more bismuth. if they put in ore, they reduce it with charcoal and small dried wood mixed, and if concentrates, they use charcoal only; they blow both materials with a gentle blast from a bellows. from the crucible is a small pipe through which the molten bismuth runs down into a dipping-pot, and from this cakes are made. [illustration (bismuth smelting): a--hearth in which ore is melted. b--hearth on which lie drops of bismuth. c--tongs. d--basket. e--wind.] on a dump thrown up from the mines, other people construct a hearth exposed to the wind, a foot high, three feet wide, and four and a half feet long. it is held together by four boards, and the whole is thickly coated at the top with lute. on this hearth they first put small dried sticks of fir wood, then over them they throw broken ore; then they lay more wood over it, and when the wind blows they kindle it. in this manner the bismuth drips out of the ore, and afterward the ashes of the wood consumed by the fire and the charcoals are swept away. the drops of bismuth which fall down into the hearth are congealed by the cold, and they are taken away with the tongs and thrown into a basket. from the melted bismuth they make cakes in iron pans. [illustration (bismuth smelting): a--box. b--pivot. c--transverse wood beams. d--grate. e--its feet. f--burning wood. g--stick. h--pans in which the bismuth is melted. i--pans for moulds. k--cakes. l--fork. m--brush.] others again make a box eight feet long, four feet wide, and two feet high, which they fill almost full of sand and cover with bricks, thus making the hearth. the box has in the centre a wooden pivot, which turns in a hole in two beams laid transversely one upon the other; these beams are hard and thick, are sunk into the ground, both ends are perforated, and through these holes wedge-shaped pegs are driven, in order that the beams may remain fixed, and that the box may turn round, and may be turned toward the wind from whichever quarter of the sky in may blow. in such a hearth they put an iron grate, as long and wide as the box and three-quarters of a foot high; it has six feet, and there are so many transverse bars that they almost touch one another. on the grate they lay pine-wood and over it broken ore, and over this they again lay pine-wood. when it has been kindled the ore melts, out of which the bismuth drips down; since very little wood is burned, this is the most profitable method of smelting the bismuth. the bismuth drips through the grate on to the hearth, while the other things remain upon the grate with the charcoal. when the work is finished, the workman takes a stick from the hearth and overturns the grate, and the things which have been accumulated on it; with the brush he sweeps up the bismuth and collects it in a basket, and then he melts it in an iron pan and makes cakes. as soon as possible after it is cool, he turns the pans over, so that the cakes may fall out, using for this purpose a two-pronged fork of which one prong is again forked. and immediately afterward he returns to his labours. end of book ix. footnotes: [ ] the history of the fusion of ores and of metals is the history of individual processes, and such information as we have been able to discover upon the individual methods previous to agricola we give on the pages where such processes are discussed. in general the records of the beginnings of metallurgy are so nebular that, if one wishes to shirk the task, he can adopt the explanation of william pryce one hundred and fifty years ago: "it is very probable that the nature and use of metals were not revealed to adam in his state of innocence: the toil and labour necessary to procure and use those implements of the iron age could not be known, till they made part of the curse incurred by his fall: 'in the sweat of thy face shalt thou eat bread, till thou return unto the ground; in sorrow shalt thou eat of it all the days of thy life' (genesis). that they were very early discovered, however, is manifest from the mosaick account of tubal cain, who was the first instructor of every artificer in brass [_sic_] and iron" (_mineralogia cornubiensis_, p. ). it is conceivable that gold could be found in large enough pieces to have had general use in pre-historic times, without fusion; but copper, which was also in use, must have been smelted, and therefore we must assume a considerable development of human knowledge on the subject prior to any human record. such incidental mention as exists after record begins does not, of course, extend to the beginning of any particular branch of the art--in fact, special arts obviously existed long before such mention, and down to the complete survey of the state of the art by agricola our dates are necessarily "prior to" some first mention in literature, or "prior to" the known period of existing remains of metallurgical operations. the scant egyptian records, the scriptures, and the shoo king give a little insight prior to b.c. the more extensive greek literature of about the th to the rd centuries b.c., together with the remains of greek mines, furnish another datum point of view, and the roman and greek writers at the beginning of the christian era give a still larger view. after them our next step is to the monk theophilus and the alchemists, from the th to the th centuries. finally, the awakening of learning at the end of the th and the beginning of the th centuries, enables us for the first time to see practically all that was known. the wealth of literature which exists subsequent to this latter time makes history thereafter a matter of some precision, but it is not included in this undertaking. considering the great part that the metals have played in civilization, it is astonishing what a minute amount of information is available on metallurgy. either the ancient metallurgists were secretive as to their art, or the ancient authors despised such common things, or, as is equally probable, the very partial preservation of ancient literature, by painful transcription over a score of centuries, served only for those works of more general interest. in any event, if all the direct or indirect material on metallurgy prior to the th century were compiled, it would not fill pages such as these. it may be of service to give a tabular summary indicating approximately the time when evidence of particular operations appear on the historical horizon: gold washed from alluvial prior to recorded civilization copper reduced from ores by smelting prior to recorded civilization bitumen mined and used prior to recorded civilization tin reduced from ores by smelting prior to b.c. bronze made prior to b.c. iron reduced from ores by smelting prior to b.c. soda mined and used prior to b.c. gold reduced from ores by concentration prior to b.c. silver reduced from ores by smelting prior to b.c. lead reduced from ores by smelting prior to b.c. (perhaps prior to b.c.) silver parted from lead by cupellation prior to b.c. bellows used in furnaces prior to b.c. steel produced prior to b.c. base metals separated from ores by water prior to b.c. concentration gold refined by cupellation prior to b.c. sulphide ores smelted for lead prior to b.c. mercury reduced from ores by (?) prior to b.c. white-lead made with vinegar prior to b.c. touchstone known for determining gold and silver prior to b.c. fineness quicksilver reduced from ore by distillation prior to christian era silver parted from gold by cementation with salt prior to " " brass made by cementation of copper and calamine prior to " " zinc oxides obtained from furnace fumes by prior to " " construction of dust chambers antimony reduced from ores by smelting (accidental) prior to " " gold recovered by amalgamation prior to " " refining of copper by repeated fusion prior to " " sulphide ores smelted for copper prior to " " vitriol (blue and green) made prior to " " alum made prior to " " copper refined by oxidation and poling prior to a.d. gold parted from copper by cupelling with lead prior to a.d. gold parted from silver by fusion with sulphur prior to a.d. manufacture of nitric acid and _aqua regia_ prior to a.d. gold parted from silver by nitric acid prior to a.d. gold parted from silver with antimony sulphide prior to a.d. gold parted from copper with sulphur prior to a.d. silver parted from iron with antimony sulphide prior to a.d. first text book on assaying prior to a.d. silver recovered from ores by amalgamation prior to a.d. separation of silver from copper by liquation prior to a.d. cobalt and manganese used for pigments prior to a.d. roasting copper ores prior to smelting prior to a.d. stamp-mill used prior to a.d. bismuth reduced from ore prior to a.d. zinc reduced from ore (accidental) prior to a.d. further, we believe it desirable to sketch at the outset the development of metallurgical appliances as a whole, leaving the details to special footnotes; otherwise a comprehensive view of the development of such devices is difficult to grasp. we can outline the character of metallurgical appliances at various periods in a few words. it is possible to set up a description of the imaginary beginning of the "bronze age" prior to recorded civilization, starting with the savage who accidentally built a fire on top of some easily reducible ore, and discovered metal in the ashes, etc.; but as this method has been pursued times out of number to no particular purpose, we will confine ourselves to a summary of such facts as we can assemble. "founders' hoards" of the bronze age are scattered over western europe, and indicate that smelting was done in shallow pits with charcoal. with the egyptians we find occasional inscriptions showing small furnaces with forced draught, in early cases with a blow-pipe, but later--about b.c.--with bellows also. the crucible was apparently used by the egyptians in secondary melting, such remains at mt. sinai probably dating before b.c. with the advent of the prophets, and the first greek literature-- th to th century b.c.--we find frequent references to bellows. the remains of smelting appliances at mt. laurion ( - b.c.) do not indicate much advance over the primitive hearth; however, at this locality we do find evidence of the ability to separate minerals by specific gravity, by washing crushed ore over inclined surfaces with a sort of buddle attachment. stone grinding-mills were used to crush ore from the earliest times of mt. laurion down to the middle ages. about the beginning of the christian era the writings of diodorus, strabo, dioscorides, and pliny indicate considerable advance in appliances. strabo describes high stacks to carry off lead fumes; dioscorides explains a furnace with a dust-chamber to catch _pompholyx_ (zinc oxide); pliny refers to the upper and lower crucibles (a forehearth) and to the pillars and arches of the furnaces. from all of their descriptions we may conclude that the furnaces had then reached some size, and were, of course, equipped with bellows. at this time sulphide copper and lead ores were smelted; but as to fluxes, except lead for silver, and lead and soda for gold, we have practically no mention. charcoal was the universal fuel for smelting down to the th century. both dioscorides and pliny describe a distillation apparatus used to recover quicksilver. a formidable list of mineral products and metal alloys in use, indicate in themselves considerable apparatus, of the details of which we have no indication; in the main these products were lead sulphide, sulphate, and oxide (red-lead and litharge); zinc oxide; iron sulphide, oxide and sulphate; arsenic and antimony sulphides; mercury sulphide, sulphur, bitumen, soda, alum and potash; and of the alloys, bronze, brass, pewter, electrum and steel. from this period to the period of the awakening of learning our only light is an occasional gleam from theophilus and the alchemists. the former gave a more detailed description of metallurgical appliances than had been done before, but there is little vital change apparent from the apparatus of roman times. the alchemists gave a great stimulus to industrial chemistry in the discovery of the mineral acids, and described distillation apparatus of approximately modern form. the next period--the renaissance--is one in which our descriptions are for the first time satisfactory, and a discussion would be but a review of _de re metallica_. [ ] see footnote , p. , on verbs used for roasting. [ ] agricola has here either forgotten to take into account his three-palm-thick furnace walls, which will make the length of this long wall sixty-one feet, or else he has included this foot and a half in each case in the six-foot distance between the furnaces, so that the actual clear space is only four and a half feet between the furnace with four feet on the ends. [ ] the paucity of terms in latin for describing structural members, and the consequent repetition of "beam" (_trabs_), "timber" (_tignum_), "billet" (_tigillum_), "pole" (_asser_), with such modifications as small, large, and transverse, and with long explanatory clauses showing their location, renders the original very difficult to follow. we have, therefore, introduced such terms as "posts," "tie-beams," "sweeps," "levers," "rafters," "sills," "moulding," "braces," "cleats," "supports," etc., as the context demands. [ ] this set of rafters appears to start from the longitudinal beam. [ ] devices for creating an air current must be of very old invention, for it is impossible to conceive of anything but the crudest melting of a few simple ores without some forced draft. wilkinson (the ancient egyptians, ii, p. ) gives a copy of an illustration of a foot-bellows from a tomb of the time of thotmes iii. ( b.c.). the rest of the world therefore, probably obtained them from the egyptians. they are mentioned frequently in the bible, the most pointed reference to metallurgical purposes being jeremiah (vi, ): "the bellows are burned, the lead is consumed in the fire; the founder melteth in vain; for the wicked are not plucked away." strabo (vii, ) states that ephorus ascribed the invention of bellows to anacharsis--a thracian prince of about b.c. [ ] this whole arrangement could be summarized by the word "hinge." [ ] the rim of this wheel is obviously made of segments fixed in two layers; the "disc" meaning the aggregate of segments on either side of the wheel. [ ] it has not been considered necessary to introduce the modern term _twyer_ in these descriptions, as the literal rendering is sufficiently clear. [ ] _ferruminata_. these accretions are practically always near the hearth, and would correspond to english "sows," and therefore that term has been adopted. it will be noted that, like most modern metallurgists, agricola offers no method for treating them. pliny (xxxiv, ) describes a "sow," and uses the verb _ferruminare_ (to weld or solder): "some say that in the furnace there are certain masses of stone which become soldered together, and that the copper fuses around it, the mass not becoming liquid unless it is transferred to another furnace; it thus forms a sort of knot, as it were, of the metal." [ ] what are known in english as "crucible," "furnace well," "forehearth," "dipping-pot," "tapping-pot," "receiving-pot," etc., are in the text all _catinus_, _i.e._, crucible. for easier reading, however, we have assigned the names indicated in the context. [ ] _panes ex pyrite conflati_. while the term _matte_ would cover most cases where this expression appears, and in many cases would be more expressive to the modern reader, yet there are instances where the expression as it stands indicates its particular origin, and it has been, therefore, considered advisable to adhere to the literal rendering. [ ] _molybdaena_. see note , p. . it was the saturated furnace bottoms from cupellation. [ ] the four elements were earth, air, fire, and water. [ ] "stones which easily melt in the fire." nowhere in _de re metallica_ does the author explain these substances. however in the _interpretatio_ (p. ) he gives three genera or orders with their german equivalents, as follows:--"_lapides qui igni liquescunt primi generis,--schöne flüsse; secundi,--flüsse zum schmeltzen flock quertze; tertii,--quertze oder kiselstein."_ we confess our inability to make certain of most of the substances comprised in the first and second orders. we consider they were in part fluor-spar, and in any event the third order embraced varieties of quartz, flint, and silicious material generally. as the matter is of importance from a metallurgical point of view, we reproduce at some length agricola's own statements on the subject from _bermannus_ and _de natura fossilium_. in the latter (p. ) he states: "finally there now remain those stones which i call 'stones which easily melt in the fire,' because when thrown into hot furnaces they flow (_fluunt_). there are three orders (_genera_) of these. the first resembles the transparent gems; the second is not similar, and is generally not translucent; it is translucent in some part, and in rare instances altogether translucent. the first is sparingly found in silver and other mines; the second abounds in veins of its own. the third genus is the material from which glass is made, although it can also be made out of the other two. the stones of the first order are not only transparent, but are also resplendent, and have the colours of gems, for some resemble crystal, others emerald, heliotrope, lapis lazuli, amethyst, sapphire, ruby, _chrysolithus_, _morion_ (cairngorm?), and other gems, but they differ from them in hardness.... to the first genus belongs the _lapis alabandicus_ (modern albandite?), if indeed it was different from the alabandic carbuncle. it can be melted, according to pliny, in the fire, and fused for the preparation of glass. it is black, but verging upon purple. it comes from caria, near alabanda, and from miletus in the same province. the second order of stones does not show a great variety of colours, and seldom beautiful ones, for it is generally white, whitish, greyish, or yellowish. because these (stones) very readily melt in the fire, they are added to the ores from which the metals are smelted. the small stones found in veins, veinlets, and the spaces between the veins, of the highest peaks of the sudetic range (_suditorum montium_), belong partly to this genus and partly to the first. they differ in size, being large and small; and in shape, some being round or angular or pointed; in colour they are black or ash-grey, or yellow, or purple, or violet, or iron colour. all of these are lacking in metals. neither do the little stones contain any metals which are usually found in the streams where gold dust is collected by washing.... in the rivers where are collected the small stones from which tin is smelted, there are three genera of small stones to be found, all somewhat rounded and of very light weight, and devoid of all metals. the largest are black, both on the outside and inside, smooth and brilliant like a mirror; the medium-sized are either bluish black or ash-grey; the smallest are of a yellowish colour, somewhat like a silkworm. but because both the former and the latter stones are devoid of metals, and fly to pieces under the blows of the hammer, we classify them as sand or gravel. glass is made from the stones of the third order, and particularly from sand. for when this is thrown into the heated furnace it is melted by the fire.... this kind of stone is either found in its own veins, which are occasionally very wide, or else scattered through the mines. it is less hard than flint, on account of which no fire can be struck from it. it is not transparent, but it is of many colours--that is to say, white, yellowish, ash-grey, brown, black, green, blue, reddish or red. this genus of stones occurs here and there in mountainous regions, on banks of rivers, and in the fields. those which are black right through to the interior, and not merely on the surface, are more rare; and very frequently one coloured vein is intersected by another of a different colour--for instance, a white one by a red one; the green is often spotted with white, the ash-grey with black, the white with crimson. fragments of these stones are frequently found on the surface of the earth, and in the running water they become polished by rubbing against stones of their own or of another genus. in this way, likewise, fragments of rocks are not infrequently shaped into spherical forms.... this stone is put to many uses; the streets are paved with it, whatever its colour; the blue variety is added to the ash of pines for making those other ashes which are used by wool-dyers. the white variety is burned, ground, and sifted, and from this they make the sand out of which glass is made. the whiter the sand is, the more useful it is." perusal of the following from _bermannus_ (p. ) can leave little doubt as to the first or second order being in part fluor-spar. agricola derived the name _fluores_ from _fluo_ "to flow," and we in turn obtain "fluorite," or "fluorspar," from agricola. "_bermannus_.--these stones are similar to gems, but less hard. allow me to explain word for word. our miners call them _fluores_, not inappropriately to my mind, for by the heat of fire, like ice in the sun, they liquefy and flow away. they are of varied and bright colours. _naevius_.--theophrastus says of them that they are made by a conflux in the earth. these red _fluores_, to employ the words just used by you, are the ruby silver which you showed us before. _bermannus_.--at the first glance it appears so, although it is not infrequently translucent. _naevius_.--then they are rubies? _bermannus_.--not that either. _naevius_.--in what way, then, can they be distinguished from rubies? _bermannus_.--chiefly by this sign, that they glitter more feebly when translucent. those which are not translucent may be distinguished from rubies. moreover, _fluores_ of all kinds melt when they are subject to the first fire; rubies do not melt in fire. _naevius_.--you distinguish well. _bermannus_.--you see the other kind, of a paler purple colour? _naevius_.--they appear to be an inferior kind of amethyst, such as are found in many places in bohemia. _bermannus_.--indeed, they are not very dissimilar, therefore the common people who do not know amethysts well, set them in rings for gems, and they are easily sold. the third kind, as you see here, is white. _naevius_.--i should have thought it a crystal. _bermannus_.--a fourth is a yellow colour, a fifth ash colour, a sixth blackish. some are violet, some green, others gold-coloured. _anton_.--what is the use of _fluores_? _bermannus_.--they are wont to be made use of when metals are smelted, as they cause the material in the fire to be much more fluid, exactly like a kind of stone which we said is made from pyrites (matte); it is, indeed, made not far from here, at breitenbrunn, which is near schwarzenberg. moreover, from _fluores_ they can make colours which artists use." [ ] _stannum_. (_interpretatio_,--_werck_, modern _werk_). this term has been rendered throughout as "silver-lead" or "silver-lead alloy." it was the argentiferous lead suitable for cupellation. agricola, in using it in this sense, was no doubt following his interpretation of its use by pliny. further remarks upon this subject will be found in note , p. . [ ] _expirare_,--to exhale or blow out. [ ] _rhetos_. the ancient rhaetia comprised not only the greater part of tyrol, but also parts of switzerland and lombardy. the mining section was, however, in tyrol. [ ] _noricum_ was a region south of the danube, embracing not only modern styria, but also parts of austria, salzberg, and carinthia. [ ] one _drachma_ of gold to a _centumpondium_ would be (if we assume these were roman weights) ozs. dwt. troy per short ton. one-half _uncia_ of silver would be ozs. dwts. per short ton. [ ] for discussion of these fluxes see note page . [ ] _carni_. probably the people of modern austrian carniola, which lies south of styria and west of croatia. [ ] historical note on smelting lead and silver.--the history of lead and silver smelting is by no means a sequent array of exact facts. with one possible exception, lead does not appear upon the historical horizon until long after silver, and yet their metallurgy is so inextricably mixed that neither can be considered wholly by itself. as silver does not occur native in any such quantities as would have supplied the amounts possessed by the ancients, we must, therefore, assume its reduction by either ( ) intricate chemical processes, ( ) amalgamation, ( ) reduction with copper, ( ) reduction with lead. it is impossible to conceive of the first with the ancient knowledge of chemistry; the second (see note , p. ) does not appear to have been known until after roman times; in any event, quicksilver appears only at about b.c. the third was impossible, as the parting of silver from copper without lead involves metallurgy only possible during the last century. therefore, one is driven to the conclusion that the fourth case obtained, and that the lead must have been known practically contemporaneously with silver. there is a leaden figure exhibited in the british museum among the articles recovered from the temple of osiris at abydos, and considered to be of the archaic period--prior to b.c. the earliest known egyptian silver appears to be a necklace of beads, supposed to be of the xii. dynasty ( b.c.), which is described in the th memoir, egyptian exploration fund (london, , p. ). with this exception of the above-mentioned lead specimen, silver articles antedate positive evidence of lead by nearly a millennium, and if we assume lead as a necessary factor in silver production, we must conclude it was known long prior to any direct (except the above solitary possibility) evidence of lead itself. further, if we are to conclude its necessary association with silver, we must assume a knowledge of cupellation for the parting of the two metals. lead is mentioned in b.c. among the spoil captured by thotmes iii. leaden objects have frequently been found in egyptian tombs as early as rameses iii. ( b.c.). the statement is made by pulsifer (notes for a history of lead, new york , p. ) that egyptian pottery was glazed with lead. we have been unable to find any confirmation of this. it may be noted, incidentally, that lead is not included in the metals of the "tribute of yü" in the shoo king (the chinese classics, b.c.?), although silver is so included. after or b.c. evidences of the use of lead become frequent. moses (numbers xxxi, - ) directs the israelites with regard to their plunder from the midianites ( b.c.): "only the gold and the silver, the brass [_sic_], the iron, the tin, and the lead. everything that may abide the fire, ye shall make it go through the fire, and it shall be clean; nevertheless, it shall be purified with the water of separation, and all that abideth not the fire ye shall make go through the water." numerous other references occur in the scriptures (psalms xii, ; proverbs xvii, ; xxv, ; etc.), one of the most pointed from a metallurgical point of view being that of jeremiah ( b.c.), who says (vi, - ): "the bellows are burned, the lead is consumed of the fire; the founder melteth in vain; for the wicked are not plucked away. reprobate silver shall men call them because the lord hath rejected them." from the number of his metaphors in metallurgical terms we may well conclude that jeremiah was of considerable metallurgical experience, which may account for his critical tenor of mind. these biblical references all point to a knowledge of separating silver and lead. homer mentions lead (iliad xxiv, ), and it has been found in the remains of ancient troy and mycenae (h. schliemann, "troy and its remains," london, , and "mycenae," new york, ). both herodotus (i, ) and diodorus (ii, ) speak of the lead used to fix iron clamps in the stone bridge of nitocris ( b.c.) at babylon. our best evidence of ancient lead-silver metallurgy is the result of the studies at mt. laurion by edouard ardaillon (_mines du laurion dans l'antiquité_, paris, ). here the very extensive old workings and the slag heaps testify to the greatest activity. the re-opening of the mines in recent years by a french company has well demonstrated their technical character, and the frequent mention in greek history easily determines their date. these deposits of argentiferous galena were extensively worked before b.c. and while the evidence of concentration methods is ample, there is but little remaining of the ancient smelters. enough, however, remains to demonstrate that the galena was smelted in small furnaces at low heat, with forced draught, and that it was subsequently cupelled. in order to reduce the sulphides the ancient smelters apparently depended upon partial roasting in the furnace at a preliminary period in reduction, or else upon the ferruginous character of the ore, or upon both. see notes p. and p. . theognis ( th century b.c.) and hippocrates ( th century b.c.) are frequently referred to as mentioning the refining of gold with lead; an inspection of the passages fails to corroborate the importance which has been laid upon them. among literary evidences upon lead metallurgy of later date, theophrastus ( b.c.) describes the making of white-lead with lead plates and vinegar. diodorus siculus ( st century b.c.), in his well-known quotation from agatharchides ( nd century b.c.) with regard to gold mining and treatment in egypt, describes the refining of gold with lead. (see note , p. .) strabo ( b.c.- a.d.) says (iii, , ): "the furnaces for silver are constructed lofty in order that the vapour, which is dense and pestilent, may be raised and carried off." and again (iii, , ), in quoting from polybius ( - b.c.): "polybius, speaking of the silver mines of new carthage, tells us that they are extremely large, distant from the city about stadia, and occupy a circuit of stadia; that there are , men regularly engaged in them, and that they yield daily to the roman people (a revenue of) , drachmae. the rest of the process i pass over, as it is too long; but as for the silver ore collected, he tells us that it is broken up and sifted through sieves over water; that what remains is to be again broken, and the water having been strained off it is to be sifted and broken a third time. the dregs which remain after the fifth time are to be melted, and the lead being poured off, the silver is obtained pure. these silver mines still exist; however, they are no longer the property of the state, neither these nor those elsewhere, but are possessed by private individuals. the gold mines, on the contrary, nearly all belong to the state. both at castlon and other places there are singular lead mines worked. they contain a small proportion of silver, but not sufficient to pay for the expense of refining" (hamilton's trans.). dioscorides ( st century a.d.), among his medicines, describes several varieties of litharge, their origin, and the manner of making white-lead (see on pp. , ), but he gives no very tangible information on lead smelting. pliny, at the same period in speaking of silver, (xxxiii, ), says: "after this we speak of silver, the next folly. silver is only found in shafts, there being no indications like shining particles as in the case of gold. this earth is sometimes red, sometimes of an ashy colour. it is impossible to melt it except with lead ore (_vena plumbi_), called _galena_, which is generally found next to silver veins. and this the same agency of fire separates part into lead, which floats on the silver like oil on water." (we have transferred lead and silver in this last sentence, otherwise it means nothing.) also (xxxiv, ) he says: "there are two different sources of lead, it being smelted from its own ore, whence it comes without the admixture of any other substance, or else from an ore which contains it in common with silver. the metal, which flows liquid at the first melting in the furnace, is called _stannum_ that at the second melting is silver; that which remains in the furnace is _galena_, which is added to a third part of the ore. this being again melted, produces lead with a deduction of two-ninths." we have, despite some grammatical objections, rendered this passage quite differently from other translators, none of whom have apparently had any knowledge of metallurgy; and we will not, therefore, take the several pages of space necessary to refute their extraordinary and unnecessary hypotheses. from a metallurgical point of view, two facts must be kept in mind,--first, that _galena_ in this instance was the same substance as _molybdaena_, and they were both either a variety of litharge or of lead carbonates; second, that the _stannum_ of the ancients was silver-lead alloy. therefore, the metallurgy of this paragraph becomes a simple melting of an argentiferous lead ore, its subsequent cupellation, with a return of the litharge to the furnace. pliny goes into considerable detail as to varieties of litharge, for further notes upon which see p. . the romans were most active lead-silver miners, not only in spain, but also in britain. there are scores of lead pigs of the roman era in various english museums, many marked "_ex argent_." bruce (the roman wall, london, , p. ) describes some roman lead furnaces in cumberland where the draught was secured by driving a tapering tunnel into the hills. the roman lead slag ran high in metal, and formed a basis for quite an industry in england in the early th century (hunt, british mining, london, , p. , etc.). there is nothing in mediæval literature which carries us further with lead metallurgy than the knowledge displayed by pliny, until we arrive at agricola's period. the history of cupellation is specially dealt with in note on p. . [ ] _cadmia_. in the german translation this is given as _kobelt_. it would be of uncertain character, but no doubt partially furnace calamine. (see note on p. .) [ ] _pompholyx_. (_interpretatio_ gives the german as _weisser hütten rauch als ober dem garherde und ober dem kupfer ofen_). this was the impure protoxide of zinc deposited in the furnace outlets, and is modern "tutty." the ancient products, no doubt, contained arsenical oxides as well. it was well known to the ancients, and used extensively for medicinal purposes, they dividing it into two species--_pompholyx_ and _spodos_. the first adequate description is by dioscorides (v, ): "_pompholyx_ differs from _spodos_ in species, not in genus. for _spodos_ is blacker, and is often heavier, full of straws and hairs, like the refuse that is swept from the floors of copper smelters. but _pompholyx_ is fatty, unctuous, white and light enough to fly in the air. of this there are two kinds--the one inclines to sky blue and is unctuous; the other is exceedingly white, and is extremely light. white _pompholyx_ is made every time that the artificer, in the preparation and perfecting of copper (brass?) sprinkles powdered _cadmia_ upon it to make it more perfect, for the soot which rises being very fine becomes _pompholyx_. other _pompholyx_ is made, not only in working copper (brass?), but is also made from _cadmia_ by continually blowing with bellows. the manner of doing it is as follows:--the furnace is constructed in a two-storied building, and there is a medium-sized aperture opening to the upper chamber; the building wall nearest the furnace is pierced with a small opening to admit the nozzle of the bellows. the building must have a fair-sized door for the artificer to pass in and out. another small building must adjoin this, in which are the bellows and the man who works them. then the charcoal in the furnace is lighted, and the artificer continually throws broken bits of _cadmia_ from the place above the furnace, whilst his assistant, who is below, throws in charcoals, until all of the _cadmia_ inside is consumed. by this means the finest and lightest part of the stuff flies up with the smoke to the upper chamber, and adheres to the walls of the roof. the substance which is thus formed has at first the appearance of bubbles on water, afterward increasing in size, it looks like skeins of wool. the heaviest parts settle in the bottom, while some fall over and around the furnaces, and some lie on the floor of the building. this latter part is considered inferior, as it contains a lot of earth and becomes full of dirt." pliny (xxxiv, ) appears somewhat confused as to the difference between the two species: "that which is called _pompholyx_ and _spodos_ is found in the copper-smelting furnaces, the difference between them being that _pompholyx_ is separated by washing, while _spodos_ is not washed. some have called that which is white and very light _pompholyx_, and it is the soot of copper and _cadmia_; whereas _spodos_ is darker and heavier. it is scraped from the walls of the furnace, and is mixed with particles of metal, and sometimes with charcoal." (xxxiv, .) "the cyprian _spodos_ is the best. it is formed by fusing _cadmia_ with copper ore. this being the lightest part of the metal, it flies up in the fumes from the furnace, and adheres to the roof, being distinguished from the soot by its whiteness. that which is less white is immature from the furnace, and it is this which some call '_pompholyx_.'" agricola (_de natura fossilium_, p. ) traverses much the same ground as the authors previously quoted, and especially recommends the _pompholyx_ produced when making brass by melting alternate layers of copper and calamine (_cadmia fossilis_). [ ] _oleo, ex fece vini sicca confecto_. this oil, made from argol, is probably the same substance mentioned a few lines further on as "wine," distilled by heating argol in a retort. still further on, salt made from argol is mentioned. it must be borne in mind that this argol was crude tartrates from wine vats, and probably contained a good deal of organic matter. heating argol sufficiently would form potash, but that the distillation product could be anything effective it is difficult to see. [ ] _aqua valens_. no doubt mainly nitric acid, the preparation of which is explained at length in book x, p. . [ ] _quod cum ignis consumit non modo una cum eo, quae ipsius stibii vis est, aliqua auri particula, sed etiam argenti, si cum auro fuerit permistum, consumitur._ the meaning is by no means clear. on p. is set out the old method of parting silver from gold with antimony sulphide, of which this may be a variation. the silver combines with sulphur, and the reduced antimony forms an alloy with the gold. the added iron and copper would also combine with the sulphur from the antimony sulphide, and no doubt assist by increasing the amount of free collecting agent and by increasing the volume of the matte. (see note , p. .) [ ] there follow eight different methods of treating crude bullion or rich concentrates. in a general way three methods are involved,-- st, reduction with lead or antimony, and cupellation; nd, reduction with silver, and separation with nitric acid; rd, reduction with lead and silver, followed by cupellation and parting with nitric acid. the use of sulphur or antimony sulphide would tend to part out a certain amount of silver, and thus obtain fairly pure bullion upon cupellation. but the introduction of copper could only result deleteriously, except that it is usually accompanied by sulphur in some form, and would thus probably pass off harmlessly as a matte carrying silver. (see note below.) [ ] it is not very clear where this lead comes from. should it be antimony? the german translation gives this as "silver." [ ] these powders are described in book vii., p. . it is difficult to say which the second really is. there are numbers of such recipes in the _probierbüchlein_ (see appendix b), with which a portion of these are identical. [ ] a variety of methods are involved in this paragraph: st, crude gold ore is smelted direct; nd, gold concentrates are smelted in a lead bath with some addition of iron--which would simply matte off--the lead bullion being cupelled; rd, roasted and unroasted pyrites and _cadmia_ (probably blende, cobalt, arsenic, etc.) are melted into a matte; this matte is repeatedly roasted, and then re-melted in a lead bath; th, if the material "flies out of the furnace" it is briquetted with iron ore and lime, and the briquettes smelted with copper matte. three products result: (_a_) slag; (_b_) matte; (_c_) copper-gold-silver alloy. the matte is roasted, re-smelted with lead, and no doubt a button obtained, and further matte. the process from this point is not clear. it appears that the copper bullion is melted with lead, and normally this product would be taken to the liquation furnace, but from the text it would appear that the lead-copper bullion was melted again with iron ore and pyrites, in which case some of the copper would be turned into the matte, and the lead alloy would be richer in gold and silver. historical note on gold.--there is ample evidence of gold being used for ornamental purposes prior to any human record. the occurrence of large quantities of gold in native form, and the possibility of working it cold, did not necessitate any particular metallurgical ingenuity. the earliest indications of metallurgical work are, of course, among the egyptians, the method of washing being figured as early as the monuments of the iv dynasty (prior to b.c.). there are in the british museum two stelae of the xii dynasty ( b.c.) ( bay and bay ) relating to officers who had to do with gold mining in nubia, and upon one there are references to working what appears to be ore. if this be true, it is the earliest reference to this subject. the papyrus map ( b.c.) of a gold mine, in the turin museum (see note , p. ), probably refers to a quartz mine. of literary evidences there is frequent mention of refining gold and passing it through the fire in the books of moses, arts no doubt learned from the egyptians. as to working gold, ore as distinguished from alluvial, we have nothing very tangible, unless it be the stelae above, until the description of egyptian gold mining by agatharchides (see note , p. ). this geographer, of about the nd century b.c., describes very clearly indeed the mining, crushing, and concentration of ore and the refining of the concentrates in crucibles with lead, salt, and barley bran. we may mention in passing that theognis ( th century b.c.) is often quoted as mentioning the refining of gold with lead, but we do not believe that the passage in question ( ): "but having been put to the test and being rubbed beside (or against) lead as being refined gold, you will be fair," etc.; or much the same statement again ( ) will stand much metallurgical interpretation. in any event, the myriads of metaphorical references to fining and purity of gold in the earliest shreds of literature do not carry us much further than do those of shakespeare or milton. vitruvius and pliny mention the recovery or refining of gold with mercury (see note , p. on amalgamation); and it appears to us that gold was parted from silver by cementation with salt prior to the christian era. we first find mention of parting with sulphur in the th century, with nitric acid prior to the th century, by antimony sulphide prior to the th century, and by cementation with nitre by agricola. (see historical note on parting gold and silver, p. .) the first mention of parting gold from copper occurs in the early th century (see note , p. ). the first comprehensive description of gold metallurgy in all its branches is in _de re metallica_. [ ] _rudis_ silver comprised all fairly pure silver ores, such as silver sulphides, chlorides, arsenides, etc. this is more fully discussed in note , p. . [ ] _evolent_,--volatilize? [ ] _lapidis plumbarii facile liquescentis_. the german translation gives _glantz_, _i.e._, galena, and the _interpretatio_ also gives _glantz_ for _lapis plumbarius_. we are, however, uncertain whether this "easily melting" material is galena or some other lead ore. [ ] _molybdaena_ is usually hearth-lead in _de re metallica_, but the german translation in this instance uses _pleyertz_, lead ore. from the context it would not appear to mean hearth-lead--saturated bottoms of cupellation furnaces--for such material would not contain appreciable silver. agricola does confuse what are obviously lead carbonates with his other _molybdaena_ (see note , p. ). [ ] the term _cadmia_ is used in this paragraph without the usual definition. whether it was _cadmia fornacis_ (furnace accretions) or _cadmia metallica_ (cobalt-arsenic-blende mixture) is uncertain. we believe it to be the former. [ ] _ramentum si lotura ex argento rudi_. this expression is generally used by the author to indicate concentrates, but it is possible that in this sentence it means the tailings after washing rich silver minerals, because the treatment of the _rudis_ silver has been already discussed above. [ ] _ustum_. this might be rendered "burnt." in any event, it seems that the material is sintered. [ ] _aes purum sive proprius ei color insederit, sive chrysocolla vel caeruleo fuerit tinctum, et rude plumbei coloris, aut fusci, aut nigri._ there are six copper minerals mentioned in this sentence, and from our study of agricola's _de natura fossilium_ we hazard the following:--_proprius ei color insederit_,--"its own colour,"--probably cuprite or "ruby copper." _tinctum chrysocolla_--partly the modern mineral of that name and partly malachite. _tinctum caeruleo_, partly azurite and partly other blue copper minerals. _rude plumbei coloris_,--"lead coloured,"--was certainly chalcocite (copper glance). we are uncertain of _fusci aut nigri_, but they were probably alteration products. for further discussion see note on p. . [ ] historical note on copper smelting.--the discoverer of the reduction of copper by fusion, and his method, like the discoverer of tin and iron, will never be known, because he lived long before humanity began to make records of its discoveries and doings. moreover, as different races passed independently and at different times through the so-called "bronze age," there may have been several independent discoverers. upon the metallurgy of pre-historic man we have some evidence in the many "founders' hoards" or "smelters' hoards" of the bronze age which have been found, and they indicate a simple shallow pit in the ground into which the ore was placed, underlaid with charcoal. rude round copper cakes eight to ten inches in diameter resulted from the cooling of the metal in the bottom of the pit. analyses of such bronze age copper by professor gowland and others show a small percentage of sulphur, and this is possible only by smelting oxidized ores. copper objects appear in the pre-historic remains in egypt, are common throughout the first three dynasties, and bronze articles have been found as early as the iv dynasty (from to b.c., according to the authority adopted). the question of the origin of this bronze, whether from ores containing copper and tin or by alloying the two metals, is one of wide difference of opinion, and we further discuss the question in note , p. , under tin. it is also interesting to note that the crucible is the emblem of copper in the hieroglyphics. the earliest source of egyptian copper was probably the sinai peninsula, where there are reliefs as early as seneferu (about b.c.), indicating that he worked the copper mines. various other evidences exist of active copper mining prior to b.c. (petrie, researches in sinai, london, , p. , etc.). the finding of crucibles here would indicate some form of refining. our knowledge of egyptian copper metallurgy is limited to deductions from their products, to a few pictures of crude furnaces and bellows, and to the minor remains on the sinai peninsula; none of the pictures were, so far as we are aware, prior to b.c., but they indicate a considerable advance over the crude hearth, for they depict small furnaces with forced draught--first a blow-pipe, and in the xviii dynasty (about b.c.) the bellows appear. many copper articles have been found scattered over the eastern mediterranean and asia minor of pre-mycenaean age, some probably as early as b.c. this metal is mentioned in the "tribute of yü" in the shoo king ( b.c.?); but even less is known of early chinese metallurgy than of the egyptian. the remains of mycenaean, phoenician, babylonian, and assyrian civilizations, stretching over the period from to b.c., have yielded endless copper and bronze objects, the former of considerable purity, and the latter a fairly constant proportion of from % to % tin. the copper supply of the pre-roman world seems to have come largely, first from sinai, and later from cyprus, and from the latter comes our word copper, by way of the romans shortening _aes cyprium_ (cyprian copper) to _cuprum_. research in this island shows that it produced copper from b.c., and largely because of its copper it passed successively under the domination of the egyptians, assyrians, phoenicians, greeks, persians, and romans. the bronze objects found in cyprus show % to % of tin, although tin does not, so far as modern research goes, occur on that island. there can be no doubt that the greeks obtained their metallurgy from the egyptians, either direct or second-hand--possibly through mycenae or phoenicia. their metallurgical gods and the tradition of cadmus indicate this much. by way of literary evidences, the following lines from homer (iliad, xviii.) have interest as being the first preserved description in any language of a metallurgical work. hephaestus was much interrupted by thetis, who came to secure a shield for achilles, and whose general conversation we therefore largely omit. we adopt pope's translation:-- there the lame architect the goddess found obscure in smoke, his forges flaming round, while bathed in sweat from fire to fire he flew; and puffing loud the roaring bellows blew. * * * in moulds prepared, the glowing ore (metal?) he pours. * * * "vouchsafe, oh thetis! at our board to share the genial rites and hospitable fare; while i the labours of the forge forego, and bid the roaring bellows cease to blow." then from his anvil the lame artist rose; wide with distorted legs oblique he goes, and stills the bellows, and (in order laid) locks in their chests his instruments of trade; then with a sponge, the sooty workman dress'd his brawny arms embrown'd and hairy breast. * * * thus having said, the father of the fires to the black labours of his forge retires. soon as he bade them blow the bellows turn'd their iron mouths; and where the furnace burn'd resounding breathed: at once the blast expires, and twenty forges catch at once the fires; just as the god directs, now loud, now low, they raise a tempest, or they gently blow; in hissing flames huge silver bars are roll'd, and stubborn brass (copper?) and tin, and solid gold; before, deep fixed, the eternal anvils stand. the ponderous hammer loads his better hand; his left with tongs turns the vex'd metal round. and thick, strong strokes, the doubling vaults rebound then first he formed the immense and solid shield; even if we place the siege of troy at any of the various dates from to b.c., it does not follow that the epic received its final form for many centuries later, probably - b.c.; and the experience of the race in metallurgy at a much later period than troy may have been drawn upon to fill in details. it is possible to fill a volume with indirect allusion to metallurgical facts and to the origins of the art, from greek mythology, from greek poetry, from the works of the grammarians, and from the bible. but they are of no more technical value than the metaphors from our own tongue. greek literature in general is singularly lacking in metallurgical description of technical value, and it is not until dioscorides ( st century a.d.) that anything of much importance can be adduced. aristotle, however, does make an interesting reference to what may be brass (see note on p. ), and there can be no doubt that if we had the lost work of aristotle's successor, theophrastus ( - b.c.), on metals we should be in possession of the first adequate work on metallurgy. as it is, we find the green and blue copper minerals from cyprus mentioned in his "stones." and this is the first mention of any particular copper ore. he also mentions (xix.) pyrites "which melt," but whether it was a copper variety cannot be determined. theophrastus further describes the making of verdigris (see note , p. ). from dioscorides we get a good deal of light on copper treatment, but as his objective was to describe medicinal preparations, the information is very indirect. he states (v, ) that "pyrites is a stone from which copper is made." he mentions _chalcitis_ (copper sulphide, see note on, p. ); while his _misy_, _sory_, _melanteria_, _caeruleum_, and _chrysocolla_ were all oxidation copper or iron minerals. (see notes on p. .) in giving a method of securing _pompholyx_ (zinc oxide), "the soot flies up when the copper refiners sprinkle powdered _cadmia_ over the molten metal" (see note , p. ); he indirectly gives us the first definite indication of making brass, and further gives some details as to the furnaces there employed, which embraced bellows and dust chambers. in describing the making of flowers of copper (see note , p. ) he states that in refining copper, when the "molten metal flows through its tube into a receptacle, the workmen pour cold water on it, the copper spits and throws off the flowers." he gives the first description of vitriol (see note , p. ), and describes the pieces as "shaped like dice which stick together in bunches like grapes." altogether, from dioscorides we learn for the first time of copper made from sulphide ores, and of the recovery of zinc oxides from furnace fumes; and he gives us the first certain description of making brass, and finally the first notice of blue vitriol. the next author we have who gives any technical detail of copper work is pliny ( - a.d.), and while his statements carry us a little further than dioscorides, they are not as complete as the same number of words could have afforded had he ever had practical contact with the subject, and one is driven to the conclusion that he was not himself much of a metallurgist. pliny indicates that copper ores were obtained from veins by underground mining. he gives the same minerals as dioscorides, but is a good deal confused over _chrysocolla_ and _chalcitis_. he gives no description of the shapes of furnaces, but frequently mentions the bellows, and speaks of the _cadmia_ and _pompholyx_ which adhered to the walls and arches of the furnaces. he has nothing to say as to whether fluxes are used or not. as to fuel, he says (xxxiii, ) that "for smelting copper and iron pine wood is the best." the following (xxxiv, ) is of the greatest interest on the subject:--"cyprian copper is known as _coronarium_ and _regulare_; both are ductile.... in other mines are made that known as _regulare_ and _caldarium_. these differ, because the _caldarium_ is only melted, and is brittle to the hammer; whereas the _regulare_ is malleable or ductile. all cyprian copper is this latter kind. but in other mines with care the difference can be eliminated from _caldarium_, the impurities being carefully purged away by smelting with fire, it is made into _regulare_. among the remaining kinds of copper the best is that of campania, which is most esteemed for vessels and utensils. this kind is made in several ways. at capua it is melted with wood, not with charcoal, after which it is sprinkled with water and washed through an oak sieve. after it is melted a number of times spanish _plumbum argentum_ (probably pewter) is added to it in proportion of ten pounds of the lead to one hundred pounds of copper, and thereby it is made pliable and assumes that pleasing colour which in other kinds of copper is effected by oil and the sun. in many parts of the italian provinces they make a similar kind of metal; but there they add eight pounds of lead, and it is re-melted over charcoal because of the scarcity of wood. very different is the method carried on in gaul, particularly where the ore is smelted between red hot stones, for this burns the metal and renders it black and brittle. moreover, it is re-melted only a single time, whereas the oftener this operation is repeated the better the quality becomes. it is well to remark that all copper fuses best when the weather is intensely cold." the red hot stones in gaul were probably as much figments of imagination as was the assumption of one commentator that they were a reverberatory furnace. apart from the above, pliny says nothing very direct on refining copper. it is obvious that more than one melting was practised, but that anything was known of the nature of oxidation by a blast and reduction by poling is uncertain. we produce the three following statements in connection with some bye-products used for medicinal purposes, which at least indicate operations subsequent to the original melting. as to whether they represent this species of refining or not, we leave it to the metallurgical profession (xxxiv, ):--"the flowers of copper are used in medicine; they are made by fusing copper and moving it to another furnace, where the rapid blast separates it into a thousand particles, which are called flowers. these scales are also made when the copper cakes are cooled in water (xxxiv, ). _smega_ is prepared in the copper works; when the metal is melted and thoroughly smelted charcoal is added to it and gradually kindled; after this, being blown upon by a powerful bellows, it spits out, as it were, copper chaff (xxxiv, ). there is another product of these works easily distinguished from _smega_, which the greeks call _diphrygum_. this substance has three different origins.... a third way of making it is from the residues which fall to the bottom in copper furnaces. the difference between the different substances (in the furnace) is that the copper itself flows into a receiver; the slag makes its escape from the furnace; the flowers float on the top (of the copper?), and the _diphrygum_ remains behind. some say that in the furnace there are certain masses of stone which, being smelted, become soldered together, and that the copper fuses around it, the mass not becoming liquid unless it is transferred to another furnace. it thus forms a sort of knot, as it were, in the metal." pliny is a good deal confused over the copper alloys, failing to recognise _aurichalcum_ as the same product as that made by mixing _cadmia_ and molten copper. further, there is always the difficulty in translation arising from the fact that the latin _aes_ was indiscriminately copper, brass, and bronze. he does not, except in one instance (xxxiv., ), directly describe the mixture of _cadmia_ and copper. "next to livian (copper) this kind (_corduban_, from spain) most readily absorbs _cadmia_, and becomes almost as excellent as _aurichalcum_ for making _sesterces_." as to bronze, there is no very definite statement; but the _argentatium_ given in the quotation above from xxxiv, , is stated in xxxiv, , to be a mixture of tin and lead. the romans carried on most extensive copper mining in various parts of their empire; these activities extended from egypt through cyprus, central europe, the spanish peninsula, and britain. the activity of such works is abundantly evidenced in the mines, but very little remains upon the surface to indicate the equipment; thus, while mining methods are clear enough, the metallurgy receives little help from these sources. at rio tinto there still remain enormous slag heaps from the romans, and the phoenician miners before them. professor w. a. carlyle informs us that the ore worked must have been almost exclusively sulphides, as only negligible quantities of carbonates exist in the deposits; they probably mixed basic and siliceous ores. there is some evidence of roasting, and the slags run from . to . %. they must have run down mattes, but as to how they ultimately arrived at metallic copper there is no evidence to show. the special processes for separating other metals from copper by liquation and matting, or of refining by poling, etc., are none of them clearly indicated in records or remains until we reach the th century. here we find very adequate descriptions of copper smelting and refining by the monk theophilus (see appendix b). we reproduce two paragraphs of interest from hendrie's excellent translation (p. and ): "copper is engendered in the earth. when a vein of which is found, it is acquired with the greatest labour by digging and breaking. it is a stone of a green colour and most hard, and naturally mixed with lead. this stone, dug up in abundance, is placed upon a pile and burned after the manner of chalk, nor does it change colour, but yet loses its hardness, so that it can be broken up. then, being bruised small, it is placed in the furnace; coals and the bellows being applied, it is incessantly forged by day and night. this should be done carefully and with caution; that is, at first coals are placed in, then small pieces of stone are distributed over them, and again coals, and then stone anew, and it is thus arranged until it is sufficient for the size of the furnace. and when the stone has commenced to liquefy, the lead flows out through some small cavities, and the copper remains within. ( ) of the purification of copper. take an iron dish of the size you wish, and line it inside and out with clay strongly beaten and mixed, and it is carefully dried. then place it before a forge upon the coals, so that when the bellows act upon it the wind may issue partly within and partly above it, and not below it. and very small coals being placed round it, place copper in it equally, and add over it a heap of coals. when, by blowing a long time, this has become melted, uncover it and cast immediately fine ashes of coals over it, and stir it with a thin and dry piece of wood as if mixing it, and you will directly see the burnt lead adhere to these ashes like a glue. which being cast out again superpose coals, and blowing for a long time, as at first, again uncover it, and then do as you did before. you do this until at length, by cooking it, you can withdraw the lead entirely. then pour it over the mould which you have prepared for this, and you will thus prove if it be pure. hold it with pincers, glowing as it is, before it has become cold, and strike it with a large hammer strongly over the anvil, and if it be broken or split you must liquefy it anew as before." the next writer of importance was biringuccio, who was contemporaneous with agricola, but whose book precedes _de re metallica_ by years. that author (iii, ) is the first to describe particularly the furnace used in saxony and the roasting prior to smelting, and the first to mention fluxes in detail. he, however, describes nothing of matte smelting; in copper refining he gives the whole process of poling, but omits the pole. it is not until we reach _de re metallica_ that we find adequate descriptions of the copper minerals, roasting, matte smelting, liquation, and refining, with a wealth of detail which eliminates the necessity for a large amount of conjecture regarding technical methods of the time. [ ] _cadmia metallica fossilis_ (see note on p. ). this was undoubtedly the complex cobalt-arsenic-zinc minerals found in saxony. in the german translation, however, this is given as _kalmey_, calamine, which is unlikely from the association with pyrites. [ ] the roman _modius_ (_modulus_?) held about cubic inches, the english peck holding cubic inches. then, perhaps, his seven _moduli_ would be roughly, bushel pecks, and vessels full would be about bushels--say, roughly, , lbs. of ore. [ ] exhausted liquation cakes (_panes aerei fathiscentes_). this is the copper sponge resulting from the first liquation of lead, and still contains a considerable amount of lead. the liquation process is discussed in great detail in book xi. [ ] the method of this paragraph involves two main objectives--first, the gradual enrichment of matte to blister copper; and, second, the creation of large cakes of copper-lead-silver alloy of suitable size and ratio of metals for liquation. this latter process is described in detail in book xi. the following groupings show the circuit of the various products, the "lbs." being roman _librae_:-- charge. products. { crude ore , lbs. } primary matte ( ) lbs. { lead slags cartloads } st { schist cartload } silver-copper alloy (a) " { flux lbs. } { concentrates from } slags (b) { slags & accretions small quantity } { primary matte ( ) , lbs. } secondary matte ( ) , lbs. { hearth-lead & litharge , " } { lead ore " } silver-copper-lead nd { rich hard cakes (a_{ }) " } alloy (liquation { liquated cakes " } cakes) (a_{ }) , " { slags (b) } { concentrates from } slags (b_{ }) { accretions } { secondary matte ( ) , lbs. } tertiary matte ( ) , lbs. { hearth-lead & litharge , " } silver-copper-lead { lead ore " } alloy (liquation rd { rich hard cakes (a_{ }) " } cakes) (a_{ }) , " { slags (b_{ }) } slags (b_{ }) { concentrates from } { accretions } { tertiary matte ( ) cartloads } quaternary hard cakes { poor hard cakes (a_{ }) " } matte ( ) , lbs. th { slags (b_{ }) } rich hard cakes of { concentrates from } matte (a_{ }) , " { accretions } { roasted quartz } poor hard cakes of th { matte ( ) (three } matte (a_{ }) , lbs. { times roasted) cartloads } final cakes of matte ( ) th final matte three times roasted is smelted to blister copper. the following would be a rough approximation of the value of the various products:-- ( .) primary matte = ounces troy per short ton. ( .) secondary matte = " " " ( .) tertiary matte = " " " ( .) quaternary matte = indeterminate. a. copper-silver alloy = ounces troy per short ton. a_{ } copper-silver-lead alloy = " " " a_{ } " " " = " " " a_{ } rich hard cakes = " " " a_{ } poor hard cakes = indeterminate. final blister copper = ozs. troy per short ton. [ ] this expression is usually used for hearth-lead, but in this case the author is apparently confining himself to lead ore, and apparently refers to lead carbonates. the german translation gives _pleyschweiss_. the pyrites mentioned in this paragraph may mean galena, as pyrites was to agricola a sort of genera. [ ] (_excoquitur_) ... "_si verò pyrites, primò è fornace, ut goselariae videre licet, in catinum defluit liquor quidam candidus, argento inimicus et nocivus; id enim comburit: quo circa recrementis, quae supernatant, detractis effunditur: vel induratus conto uncinato extrahitur: eundem liquorem parietes fornacis exudant._" in the glossary the following statement appears: "_liquor candidus primo è fornace defluens cum goselariae excoquitur pyrites,--kobelt; quem parietes fornacis exudant,--conterfei._" in this latter statement agricola apparently recognised that there were two different substances, _i.e._, that the substance found in the furnace walls--_conterfei_--was not the same substance as that which first flowed from the furnace--_kobelt_. we are at no difficulty in recognizing _conterfei_ as metallic zinc; it was long known by that term, and this accidental occurrence is repeatedly mentioned by other authors after agricola. the substance which first flowed into the forehearth presents greater difficulties; it certainly was not zinc. in _de natura fossilium_ (p. ), agricola says that at goslar the lead has a certain white slag floating upon it, the "colour derived from the pyrites (_pyriten argenteum_) from which it was produced." _pyriten argenteum_ was either marcasite or mispickel, neither of which offers much suggestion; nor are we able to hazard an explanation of value. historical note on zinc. the history of zinc metallurgy falls into two distinct lines--first, that of the metal, and second, that of zinc ore, for the latter was known and used to make brass by cementation with copper and to yield oxides by sublimation for medicinal purposes, nearly , years before the metal became generally known and used in europe. there is some reason to believe that metallic zinc was known to the ancients, for bracelets made of it, found in the ruins of cameros (prior to b.c.), may have been of that age (raoul jagnaux, _traité de chimie générale_, , ii, ); and further, a passage in strabo ( b.c.- a.d.) is of much interest. he states: (xiii, , ) "there is found at andeira a stone which when burnt becomes iron. it is then put into a furnace, together with some kind of earth, when it distils a mock silver (_pseudargyrum_), or with the addition of copper it becomes the compound called _orichalcum_. there is found a mock silver near tismolu also." (hamilton's trans., ii, p. ). about the christian era the terms _orichalcum_ or _aurichalcum_ undoubtedly refer to brass, but whether these terms as used by earlier greek writers do not refer to bronze only, is a matter of considerable doubt. beyond these slight references we are without information until the th century. if the metal was known to the ancients it must have been locally, for by its greater adaptability to brass-making it would probably have supplanted the crude melting of copper with zinc minerals. it appears that the metal may have been known in the far east prior to such knowledge in europe; metallic zinc was imported in considerable quantities from the east as early as the th and th centuries under such terms as _tuteneque_, _tuttanego_, _calaëm_, and _spiauter_--the latter, of course, being the progenitor of our term spelter. the localities of eastern production have never been adequately investigated. w. hommel (engineering and mining journal, june , ) gives a very satisfactory review of the eastern literature upon the subject, and considers that the origin of manufacture was in india, although the most of the th and th century product came from china. the earliest certain description seems to be some recipes for manufacture quoted by praphulla chandra ray (a history of hindu chemistry, london, , p. ) dating from the th to the th centuries. there does not appear to be any satisfactory description of the chinese method until that of sir george staunton (journal asiatique paris, , p. .) we may add that spelter was produced in india by crude distillation of calamine in clay pots in the early part of the th century (brooke, jour. asiatic soc. of bengal, vol. xix, , p. ), and the remains of such smelting in rajputana are supposed to be very ancient. the discovery of zinc in europe seems to have been quite independent of the east, but precisely where and when is clouded with much uncertainty. the _marchasita aurea_ of albertus magnus has been called upon to serve as metallic zinc, but such belief requires a hypothesis based upon a great deal of assumption. further, the statement is frequently made that zinc is mentioned in basil valentine's triumphant chariot of antimony (the only one of the works attributed to this author which may date prior to the th century), but we have been unable to find any such reference. the first certain mention of metallic zinc is generally accredited to paracelsus ( - ), who states (_liber mineralium_ ii.): "moreover there is another metal generally unknown called _zinken_. it is of peculiar nature and origin; many other metals adulterate it. it can be melted, for it is generated from three fluid principles; it is not malleable. its colour is different from other metals and does not resemble others in its growth. its ultimate matter (_ultima materia_) is not to me yet fully known. it admits of no mixture and does not permit of the _fabricationes_ of other metals. it stands alone entirely to itself." we do not believe that this book was published until after agricola's works. agricola introduced the following statements into his revised edition of _bermannus_ (p. ), published in : "it (a variety of pyrites) is almost the colour of galena, but of entirely different components. from it there is made gold and silver, and a great quantity is dug in reichenstein, which is in silesia, as was recently reported to me. much more is found at raurici, which they call _zincum_, which species differs from pyrites, for the latter contains more silver than gold, the former only gold or hardly any silver." in _de natura fossilium_ (p. ): "for this _cadmia_ is put, in the same way as quicksilver, in a suitable vessel so that the heat of the fire will cause it to sublime, and from it is made a black or brown or grey body which the alchemists call _cadmia sublimata_. this possesses corrosive properties to the highest degree. cognate with this _cadmia_ and pyrites is a compound which the noricans and rhetians call _zincum_." we leave it to readers to decide how near this comes to metallic zinc; in any event, he apparently did not recognise his _conterfei_ from the furnaces as the same substance as the _zincum_ from silesia. the first correlation of these substances was apparently by lohneys, in , who says (_vom bergwerk_, p. - ): "when the people in the smelting works are smelting, there is made under the furnace and in the cracks in the walls among the badly plastered stones, a metal which is called _zinc_ or _counterfeht_, and when the wall is scraped it falls into a vessel placed to receive it. this metal greatly resembles tin, but it is harder and less malleable.... the alchemists have a great desire for this _zinc_ or bismuth." that this metal originated from blende or calamine was not recognised until long after, and libavis (_alchymia_, frankfort, ), in describing specimens which came from the east, did not so identify it, this office being performed by glauber, who says (_de prosperitate germanias_, amsterdam, ): "zink is a volatile mineral or half-ripe metal when it is extracted from its ore. it is more brilliant than tin and not so fusible or malleable ... it turns (copper) into brass, as does _lapis calaminaris_, for indeed this stone is nothing but infusible zinc, and this zinc might be called a fusible _lapis calaminaris_, inasmuch as both of them partake of the same nature.... it sublimates itself up into the cracks of the furnace, whereupon the smelters frequently break it out." the systematic distillation of zinc from calamine was not discovered in europe until the th century. henkel is generally accredited with the first statement to that effect. in a contribution published as an appendix to his other works, of which we have had access only to a french translation (_pyritologie_, paris, , p. ), he concludes that zinc is a half-metal of which the best ore is calamine, but believes it is always associated with lead, and mentions that an englishman lately arrived from bristol had seen it being obtained from calamine in his own country. he further mentions that it can be obtained by heating calamine and lead ore mixed with coal in a thick earthen vessel. the bristol works were apparently those of john champion, established about . the art of distillation was probably learned in the east. definite information as to the zinc minerals goes back to but a little before the christian era, unless we accept nebular references to _aurichalcum_ by the poets, or what is possibly zinc ore in the "earth" mentioned by aristotle (_de mirabilibus_, ): "men say that the copper of the mossynoeci is very brilliant and white, no tin being mixed with it; but there is a kind of earth there which is melted with it." this might quite well be an arsenical mineral. but whether we can accept the poets or aristotle or the remark of strabo given above, as sufficient evidence or not, there is no difficulty with the description of _cadmia_ and _pompholyx_ and _spodos_ of dioscorides ( st century), parts of which we reproduce in note , p. . his _cadmia_ is described as rising from the copper furnaces and clinging to the iron bars, but he continues: "_cadmia_ is also prepared by burning the stone called pyrites, which is found near mt. soloi in cyprus.... some say that _cadmia_ may also be found in stone quarries, but they are deceived by stones having a resemblance to _cadmia_." _pompholyx_ and _spodos_ are evidently furnace calamine. from reading the quotation given on p. , there can be no doubt that these materials, natural or artificial, were used to make brass, for he states (v, ): "white _pompholyx_ is made every time that the artificer in the working and perfecting of the copper sprinkles powdered _cadmia_ upon it to make it more perfect, the soot arising from this ... is _pompholyx_." pliny is confused between the mineral _cadmia_ and furnace _calamine_, and none of his statements are very direct on the subject of brass making. his most pointed statement is (xxxiv, ): "... next to livian (copper) this kind best absorbs _cadmia_, and is almost as good as _aurichalcum_ for making sesterces and double asses." as stated above, there can be little doubt that the _aurichalcum_ of the christian era was brass, and further, we do know of brass sesterces of this period. other roman writers of this and later periods refer to earth used with copper for making brass. apart from these evidences, however, there is the evidence of analyses of coins and objects, the earliest of which appears to be a large brass of the cassia family of b.c., analyzed by phillips, who found . % zinc (records of mining and metallurgy, london, , p. ). numerous analyses of coins and other objects dating during the following century corroborate the general use of brass. professor gowland (presidential address, inst. of metals, ) rightly considers the romans were the first to make brass, and at about the above period, for there appears to be no certainty of any earlier production. the first adequate technical description of brass making is in about a.d. being that of theophilus, who describes (hendrie's trans., p. ) calcining _calamina_ and mixing it with finely divided copper in glowing crucibles. the process was repeated by adding more calamine and copper until the pots were full of molten metal. this method is repeatedly described with minor variations by biringuccio, agricola (_de nat. fos._), and others, down to the th century. for discussion of the zinc minerals see note on p. . [ ] "_... non raro, ut nonnulli pyritae sunt, candida...._" this is apparently the unknown substance mentioned above. [ ] one _drachma_ is about ounces troy per short ton. three _unciae_ are about ounces dwts. troy per short ton. [ ] in this section, which treats of the metallurgy of _plumbum candidum_, "tin," the word _candidum_ is very often omitted in the latin, leaving only _plumbum_, which is confusing at times with lead. the black tin-stone, _lapilli nigri_ has been treated in a similar manner, _lapilli_ (small stones) constantly occurring alone in the latin. this has been rendered as "tin-stone" throughout, and the material prior to extraction of the _lapilli nigri_ has been rendered "tin-stuff," after the cornish. [ ] "_... ex saxis vilibus, quae natura de diversa materia composuit._" the glossary gives _grindstein_. granite (?). [ ] historical notes on tin metallurgy. the first appearance of tin lies in the ancient bronzes. and while much is written upon the "bronze age" by archæologists, we seriously doubt whether or not a large part of so-called bronze is not copper. in any event, this period varied with each race, and for instance, in britain may have been much later than egyptian historic times. the bronze articles of the iv dynasty (from to b.c. depending on the authority) place us on certain ground of antiquity. professor gowland (presidential address, inst. of metals, london, ) maintains that the early bronzes were the result of direct smelting of stanniferous copper ores, and while this may be partially true for western europe, the distribution and nature of the copper deposits do not warrant this assumption for the earlier scenes of human activity--asia minor, egypt, and india. further, the lumps of rough tin and also of copper found by borlase (tin mining in spain, past and present, london, , p. ) in cornwall, mixed with bronze celts under conditions certainly indicating the bronze age, is in itself of considerable evidence of independent melting. to our mind the vast majority of ancient bronzes must have been made from copper and tin mined and smelted independently. as to the source of supply of ancient tin, we are on clear ground only with the advent of the phoenicians, - b.c., who, as is well known, distributed to the ancient world a supply from spain and britain. what the source may have been prior to this time has been subject to much discussion, and while some slender threads indicate the east, we believe that a more local supply to egypt, etc., is not impossible. the discovery of large tin fields in central africa and the native-made tin ornaments in circulation among the negroes, made possible the entrance of the metal into egypt along the trade routes. further, we see no reason why alluvial tin may not have existed within easy reach and have become exhausted. how quickly such a source of metal supply can be forgotten and no evidence remain, is indicated by the seldom remembered alluvial gold supply from ireland. however, be these conjectures as they may, the east has long been the scene of tin production and of transportation activity. among the slender evidences that point in this direction is that the sanskrit term for tin is _kastira_, a term also employed by the chaldeans, and represented in arabic by _kasdir_, and it may have been the progenitor of the greek _cassiteros_. there can be no doubt that the phoenicians also traded with malacca, etc., but beyond these threads there is little to prove the pre-western source. the strained argument of beckmann (hist. of inventions, vol. ii., p. ) that the _cassiteros_ of homer and the _bedil_ of the hebrews was possibly not tin, and that tin was unknown at this time, falls to the ground in the face of the vast amount of tin which must have been in circulation to account for the bronze used over a period , years prior to those peoples. tin is early mentioned in the scriptures (numbers xxxi, ), being enumerated among the spoil of the midianites ( b.c.?), also ezekiel ( b.c., xxvii, ) speaks of tin from tarshish (the phoenician settlement on the coast of spain). according to homer tin played considerable part in vulcan's metallurgical stores. even approximately at what period the phoenicians began their distribution from spain and britain cannot be determined. they apparently established their settlements at gades (cadiz) in tarshish, beyond gibraltar, about b.c. the remains of tin mining in the spanish peninsula prior to the christian era indicate most extensive production by the phoenicians, but there is little evidence as to either mining or smelting methods. generally as to the technical methods of mining and smelting tin, we are practically without any satisfactory statement down to agricola. however, such scraps of information as are available are those in homer (see note on p. ), diodorus, and pliny. diodorus says (v, ) regarding tin in spain: "they dig it up, and melt it down in the same way as they do gold and silver;" and again, speaking of the tin in britain, he says: "these people make tin, which they dig up with a great deal of care and labour; being rocky, the metal is mixed with earth, out of which they melt the metal, and then refine it." pliny (xxxiv, ), in the well-known and much-disputed passage: "next to be considered are the characteristics of lead, which is of two kinds, black and white. the most valuable is the white; the greeks called it _cassiteros_, and there is a fabulous story of its being searched for and carried from the islands of atlantis in barks covered with hides. certainly it is obtained in lusitania and gallaecia on the surface of the earth from black-coloured sand. it is discovered by its great weight, and it is mixed with small pebbles in the dried beds of torrents. the miners wash these sands, and that which settles they heat in the furnace. it is also found in gold mines, which are called _alutiae_. a stream of water passing through detaches small black pebbles variegated with white spots, the weight of which is the same as gold. hence it is that they remain in the baskets of the gold collectors with the gold; afterward, they are separated in a _camillum_ and when melted become white lead." there is practically no reference to the methods of cornish tin-working over the whole period of , years that mining operations were carried on there prior to the norman occupation. from then until agricola's time, a period of some four centuries, there are occasional references in stannary court proceedings, charters, and such-like official documents which give little metallurgical insight. from a letter of william de wrotham, lord warden of the stannaries, in , setting out the regulations for the impost on tin, it is evident that the black tin was smelted once at the mines and that a second smelting or refining was carried out in specified towns under the observation of the crown officials. in many other official documents there are repeated references to the right to dig turfs and cut wood for smelting the tin. under note , p. , we give some further information on tin concentration, and the relation of cornish and german tin miners. biringuccio ( ) gives very little information on tin metallurgy, and we are brought to _de re metallica_ for the first clear exposition. as to the description on these pages it must be remembered that the tin-stone has been already roasted, thus removing some volatile impurities and oxidizing others, as described on page . the furnaces and the methods of working the tin, here described, are almost identical with those in use in saxony to-day. in general, since agricola's time tin has not seen the mechanical and metallurgical development of the other metals. the comparatively small quantities to be dealt with; the necessity of maintaining a strong reducing atmosphere, and consequently a mild cold blast; and the comparatively low temperature demanded, gave little impetus to other than crude appliances until very modern times. [ ] _aureo nummo_. german translation gives _reinschen gülden_, which was the equivalent of about $ . , or . shillings. the purchasing power of money was, however, several times as great as at present. [ ] in the following descriptions of iron-smelting, we have three processes described; the first being the direct reduction of malleable iron from ore, the second the transition stage then in progress from the direct to indirect method by way of cast-iron; and the third a method of making steel by cementation. the first method is that of primitive iron-workers of all times and all races, and requires little comment. a pasty mass was produced, which was subsequently hammered to make it exude the slag, the hammered mass being the ancient "bloom." the second process is of considerable interest, for it marks one of the earliest descriptions of working iron in "a furnace similar to a blast furnace, but much wider and higher." this original german _stückofen_ or high bloomery furnace was used for making "masses" of wrought-iron under essentially the same conditions as its progenitor the forge--only upon a larger scale. with high temperatures, however, such a furnace would, if desired, yield molten metal, and thus the step to cast-iron as a preliminary to wrought-iron became very easy and natural, in fact agricola mentions above that if the iron is left to settle in the furnace it becomes hard. the making of malleable iron by subsequent treatment of the cast-iron--the indirect method--originated in about agricola's time, and marks the beginning of one of those subtle economic currents destined to have the widest bearing upon civilization. it is to us uncertain whether he really understood the double treatment or not. in the above paragraph he says from ore "once or twice smelted they make iron," etc., and in _de natura fossilium_ (p. ) some reference is made to pouring melted iron, all of which would appear to be cast-iron. he does not, however, describe the th century method of converting cast into wrought iron by way of in effect roasting the pig iron to eliminate carbon by oxidation, with subsequent melting into a "ball" or "mass." it must be borne in mind that puddling for this purpose did not come into use until the end of the th century. a great deal of discussion has arisen as to where and at what time cast-iron was made systematically, but without satisfactory answer; in any event, it seems to have been in about the end of the th century, as cast cannon began to appear about that time. it is our impression that the whole of this discussion on iron in _de re metallica_ is an abstract from biringuccio, who wrote years earlier, as it is in so nearly identical terms. those interested will find a translation of biringuccio's statement with regard to steel in percy's metallurgy of iron and steel, london, , p. . historical note on iron smelting. the archæologists' division of the history of racial development into the stone, bronze, and iron ages, based upon objects found in tumuli, burial places, etc., would on the face of it indicate the prior discovery of copper metallurgy over iron, and it is generally so maintained by those scientists. the metallurgists have not hesitated to protest that while this distinction of "ages" may serve the archæologists, and no doubt represents the sequence in which the metal objects are found, yet it by no means follows that this was the order of their discovery or use, but that iron by its rapidity of oxidation has simply not been preserved. the arguments which may be advanced from our side are in the main these. iron ore is of more frequent occurrence than copper ores, and the necessary reduction of copper oxides (as most surface ores must have been) to fluid metal requires a temperature very much higher than does the reduction of iron oxides to wrought-iron blooms, which do not necessitate fusion. the comparatively greater simplicity of iron metallurgy under primitive conditions is well exemplified by the hill tribes of northern nigeria, where in village forges the negroes reduce iron sufficient for their needs, from hematite. copper alone would not be a very serviceable metal to primitive man, and he early made the advance to bronze; this latter metal requires three metallurgical operations, and presents immeasurably greater difficulties than iron. it is, as professor gowland has demonstrated (presidential address, inst. of metals, london, ) quite possible to make bronze from melting stanniferous copper ores, yet such combined occurrence at the surface is rare, and, so far as known, the copper sources from which asia minor and egypt obtained their supply do not contain tin. it seems to us, therefore, that in most cases the separate fusions of different ores and their subsequent re-melting were required to make bronze. the arguments advanced by the archæologists bear mostly upon the fact that, had iron been known, its superiority would have caused the primitive races to adopt it, and we should not find such an abundance of bronze tools. as to this, it may be said that bronze weapons and tools are plentiful enough in egyptian, mycenæan, and early greek remains, long after iron was demonstrably well known. there has been a good deal pronounced by etymologists on the history of iron and copper, for instance, by max müller, (lectures on the science of language, vol. ii, p. , london, ), and many others, but the amazing lack of metallurgical knowledge nullifies practically all their conclusions. the oldest egyptian texts extant, dating b.c., refer to iron, and there is in the british museum a piece of iron found in the pyramid of kephron ( b.c.) under conditions indicating its co-incident origin. there is exhibited also a fragment of oxidized iron lately found by professor petrie and placed as of the vi dynasty (b.c. ). despite this evidence of an early knowledge of iron, there is almost a total absence of egyptian iron objects for a long period subsequent to that time, which in a measure confirms the view of its disappearance rather than that of ignorance of it. many writers have assumed that the ancients must have had some superior art of hardening copper or bronze, because the cutting of the gigantic stonework of the time could not have been done with that alloy as we know it; no such hardening appears among the bronze tools found, and it seems to us that the argument is stronger that the oldest egyptian stoneworkers employed mostly iron tools, and that these have oxidized out of existence. the reasons for preferring copper alloys to iron for decorative objects were equally strong in ancient times as in the present day, and accounts sufficiently for these articles, and, therefore, iron would be devoted to more humble objects less likely to be preserved. further, the egyptians at a later date had some prejudices against iron for sacred purposes, and the media of preservation of most metal objects were not open to iron. we know practically nothing of very early egyptian metallurgy, but in the time of thotmes iii. ( b.c.) bellows were used upon the forge. of literary evidences the earliest is in the shoo king among the tribute of yü ( b.c.?). iron is frequently mentioned in the bible, but it is doubtful if any of the early references apply to steel. there is scarcely a greek or latin author who does not mention iron in some connection, and of the earliest, none are so suggestive from a metallurgical point of view as homer, by whom "laboured" mass (wrought-iron?) is often referred to. as, for instance, in the odyssey (i., ) pallas in the guise of mentes, says according to pope: "freighted with iron from my native land i steer my voyage to the brutian strand, to gain by commerce for the laboured mass a just proportion of refulgent brass." (brass is modern poetic licence for copper or bronze). also, in the odyssey (ix, ) when homer describes how ulysses plunged the stake into cyclop's eye, we have the first positive evidence of steel, although hard iron mentioned in the tribute of yü, above referred to, is sometimes given as steel: "and as when armourers temper in the ford the keen-edg'd pole-axe, or the shining sword, the red-hot metal hisses in the lake." no doubt early wrought-iron was made in the same manner as agricola describes. we are, however, not so clear as to the methods of making steel. under primitive methods of making wrought-iron it is quite possible to carburize the iron sufficiently to make steel direct from ore. the primitive method of india and japan was to enclose lumps of wrought-iron in sealed crucibles with charcoal and sawdust, and heat them over a long period. neither pliny nor any of the other authors of the period previous to the christian era give us much help on steel metallurgy, although certain obscure expressions of aristotle have been called upon (for instance, st. john v. day, prehistoric use of iron and steel, london, , p. ) to prove its manufacture by immersing wrought-iron in molten cast-iron. [ ] _quae vel aerosa est, vel cocta_. it is by no means certain that _cocta_, "cooked" is rightly translated, for the author has not hitherto used this expression for heated. this may be residues from roasting and leaching pyrites for vitriol, etc. [ ] agricola draws no sharp line of distinction between antimony the metal, and its sulphide. he uses the roman term _stibi_ or _stibium_ (_interpretatio_,--_spiesglas_) throughout this book, and evidently in most cases means the sulphide, but in others, particularly in parting gold and silver, metallic antimony would be reduced out. we have been in much doubt as to the term to introduce into the text, as the english "stibnite" carries too much precision of meaning. originally the "antimony" of trade was the sulphide. later, with the application of that term to the metal, the sulphide was termed "grey antimony," and we have either used _stibium_ for lack of better alternative, or adopted "grey antimony." the method described by agricola for treating antimony sulphide is still used in the harz, in bohemia, and elsewhere. the stibnite is liquated out at a low heat and drips from the upper to the lower pot. the resulting purified antimony sulphide is the modern commercial "crude antimony" or "grey antimony." historical note on the metallurgy of antimony. the egyptologists have adopted the term "antimony" for certain cosmetics found in egyptian tombs from a very early period. we have, however, failed to find any reliable analyses which warrant this assumption, and we believe that it is based on the knowledge that antimony was used as a base for eye ointments in greek and roman times, and not upon proper chemical investigation. it may be that the ideograph which is interpreted as antimony may really mean that substance, but we only protest that the chemist should have been called in long since. in st. jerome's translation of the bible, the cosmetic used by jezebel (ii. kings ix, ) and by the lady mentioned by ezekiel (xxiii, ), "who didst wash thyself and paintedst thine eyes" is specifically given as _stibio_. our modern translation carries no hint of the composition of the cosmetic, and whether some of the greek or hebrew mss. do furnish a basis for such translation we cannot say. the hebrew term for this mineral was _kohl_, which subsequently passed into "alcool" and "alkohol" in other languages, and appears in the spanish bible in the above passage in ezekiel as _alcoholaste_. the term _antimonium_ seems to have been first used in latin editions of geber published in the latter part of the th century. in any event, the metal is clearly mentioned by dioscorides ( st century), who calls it _stimmi_, and pliny, who termed it _stibium_, and they leave no doubt that it was used as a cosmetic for painting the eyebrows and dilating the eyes. dioscorides (v, ) says: "the best _stimmi_ is very brilliant and radiant. when broken it divides into layers with no part earthy or dirty; it is brittle. some call it _stimmi_, others _platyophthalmon_ (wide eyed); others _larbason_, others _gynaekeion_ (feminine).... it is roasted in a ball of dough with charcoal until it becomes a cinder.... it is also roasted by putting it on live charcoal and blowing it. if it is roasted too much it becomes lead." pliny states (xxxiii, and ): "in the same mines in which silver is found, properly speaking there is a stone froth. it is white and shining, not transparent; is called _stimmi_, or _stibi_, or _alabastrum_, and _larbasis_. there are two kinds of it, the male and the female. the most approved is the female, the male being more uneven, rougher, less heavy, not so radiant, and more gritty. the female kind is bright and friable, laminar and not globular. it is astringent and refrigerative, and its principal use is for the eyes.... it is burned in manure in a furnace, is quenched with milk, ground with rain water in a mortar, and while thus turbid it is poured into a copper vessel and purified with nitrum ... above all in roasting it care should be taken that it does not turn to lead." there can be little doubt from dioscorides' statement of its turning to lead that he had seen the metal antimony, although he thought it a species of lead. of further interest in connection with the ancient knowledge of the metal is the chaldean vase made of antimony described by berthelot (_comptes rendus_, , civ, ). it is possible that agricola knew the metal, although he gives no details as to de-sulphurizing it or for recovering the metal itself. in _de natura fossilium_ (p. ) he makes a statement which would indicate the metal, "_stibium_ when melted in the crucible and refined has as much right to be regarded as a metal as is accorded to lead by most writers. if when smelted a certain portion be added to tin, a printer's alloy is made from which type is cast that is used by those who print books." basil valentine, in his "triumphal chariot of antimony," gives a great deal that is new with regard to this metal, even if we can accredit the work with no earlier origin than its publication--about ; it seems possible however, that it was written late in the th century (see appendix b). he describes the preparation of the metal from the crude ore, both by roasting and reduction from the oxide with argol and saltpetre, and also by fusing with metallic iron. while the first description of these methods is usually attributed to valentine, it may be pointed out that in the _probierbüchlein_ ( ) as well as in agricola the separation of silver from iron by antimony sulphide implies the same reaction, and the separation of silver and gold with antimony sulphide, often attributed to valentine, is repeatedly set out in the _probierbüchlein_ and in _de re metallica_. biringuccio ( ) has nothing of importance to say as to the treatment of antimonial ores, but mentions it as an alloy for bell-metal, which would imply the metal. [ ] historical note on the metallurgy of quicksilver. the earliest mention of quicksilver appears to have been by aristotle (_meteorologica_ iv, , ), who speaks of it as fluid silver (_argyros chytos_). theophrastus ( ) states: "such is the production of quicksilver, which has its uses. this is obtained from cinnabar rubbed with vinegar in a brass mortar with a brass pestle." (hill's trans., p. ). theophrastus also ( ) mentions cinnabar from spain and elsewhere. dioscorides (v, ) appears to be the first to describe the recovery of quicksilver by distillation: "quicksilver (_hydrargyros_, _i.e._, liquid silver) is made from _ammion_, which is called _cinnabari_. an iron bowl containing _cinnabari_ is put into an earthen vessel and covered over with a cup-shaped lid smeared with clay. then it is set on a fire of coals and the soot which sticks to the cover when wiped off and cooled is quicksilver. quicksilver is also found in drops falling from the walls of the silver mines. some say there are quicksilver mines. it can be kept only in vessels of glass, lead, tin (?), or silver, for if put in vessels of any other substances it consumes them and flows through." pliny (xxxiii, ): "there has been discovered a way of extracting _hydrargyros_ from the inferior _minium_ as a substitute for quicksilver, as mentioned. there are two methods: either by pounding _minium_ and vinegar in a brass mortar with a brass pestle, or else by putting _minium_ into a flat earthen dish covered with a lid, well luted with potter's clay. this is set in an iron pan and a fire is then lighted under the pan, and continually blown by a bellows. the perspiration collects on the lid and is wiped off and is like silver in colour and as liquid as water." pliny is somewhat confused over the _minium_--or the text is corrupt, for this should be the genuine _minium_ of roman times. the methods of condensation on the leaves of branches placed in a chamber, of condensing in ashes placed over the mouth of the lower pot, and of distilling in a retort, are referred to by biringuccio (a.d. ), but with no detail. [ ] most of these methods depend upon simple liquation of native bismuth. the sulphides, oxides, etc., could not be obtained without fusing in a furnace with appropriate de-sulphurizing or reducing agents, to which agricola dimly refers. in _bermannus_ (p. ), he says: "_bermannus_.--i will show you another kind of mineral which is numbered amongst metals, but appears to me to have been unknown to the ancients; we call it _bisemutum_. _naevius_.--then in your opinion there are more kinds of metals than the seven commonly believed? _bermannus_.--more, i consider; for this which just now i said we called _bisemutum_, cannot correctly be called _plumbum candidum_ (tin) nor _nigrum_ (lead), but is different from both, and is a third one. _plumbum candidum_ is whiter and _plumbum nigrum_ is darker, as you see. _naevius_.--we see that this is of the colour of _galena_. _ancon_.--how then can _bisemutum_, as you call it, be distinguished from _galena_? _bermannus_.--easily; when you take it in your hands it stains them with black unless it is quite hard. the hard kind is not friable like _galena_, but can be cut. it is blacker than the kind of crude silver which we say is almost the colour of lead, and thus is different from both. indeed, it not rarely contains some silver. it generally shows that there is silver beneath the place where it is found, and because of this our miners are accustomed to call it the 'roof of silver.' they are wont to roast this mineral, and from the better part they make metal; from the poorer part they make a pigment of a kind not to be despised." this pigment was cobalt blue (see note on p. ), indicating a considerable confusion of these minerals. this quotation is the first description of bismuth, and the above text the first description of bismuth treatment. there is, however, bare mention of the mineral earlier, in the following single line from the _probierbüchlein_ (p. ): "jupiter (controls) the ores of tin and _wismundt_." and it is noted in the _nützliche bergbüchlein_ in association with silver (see appendix b). [ ] this _cadmia_ is given in the german translation as _kobelt_. it is probably the cobalt-arsenic-bismuth minerals common in saxony. a large portion of the world's supply of bismuth to-day comes from the cobalt treatment works near schneeberg. for further discussion of _cadmia_ see note on p. . book x. questions as to the methods of smelting ores and of obtaining metals i discussed in book ix. following this, i should explain in what manner the precious metals are parted from the base metals, or on the other hand the base metals from the precious[ ]. frequently two metals, occasionally more than two, are melted out of one ore, because in nature generally there is some amount of gold in silver and in copper, and some silver in gold, copper, lead, and iron; likewise some copper in gold, silver, lead, and iron, and some lead in silver; and lastly, some iron in copper[ ]. but i will begin with gold. gold is parted from silver, or likewise the latter from the former, whether it be mixed by nature or by art, by means of _aqua valens_[ ], and by powders which consist of almost the same things as this _aqua_. in order to preserve the sequence, i will first speak of the ingredients of which this _aqua_ is made, then of the method of making it, then of the manner in which gold is parted from silver or silver from gold. almost all these ingredients contain vitriol or alum, which, by themselves, but much more when joined with saltpetre, are powerful to part silver from gold. as to the other things that are added to them, they cannot individually by their own strength and nature separate those metals, but joined they are very powerful. since there are many combinations, i will set out a few. in the first, the use of which is common and general, there is one _libra_ of vitriol and as much salt, added to a third of a _libra_ of spring water. the second contains two _librae_ of vitriol, one of saltpetre, and as much spring or river water by weight as will pass away whilst the vitriol is being reduced to powder by the fire. the third consists of four _librae_ of vitriol, two and a half _librae_ of saltpetre, half a _libra_ of alum, and one and a half _librae_ of spring water. the fourth consists of two _librae_ of vitriol, as many _librae_ of saltpetre, one quarter of a _libra_ of alum, and three-quarters of a _libra_ of spring water. the fifth is composed of one _libra_ of saltpetre, three _librae_ of alum, half a _libra_ of brick dust, and three-quarters of a _libra_ of spring water. the sixth consists of four _librae_ of vitriol, three _librae_ of saltpetre, one of alum, one _libra_ likewise of stones which when thrown into a fierce furnace are easily liquefied by fire of the third order, and one and a half _librae_ of spring water. the seventh is made of two _librae_ of vitriol, one and a half _librae_ of saltpetre, half a _libra_ of alum, and one _libra_ of stones which when thrown into a glowing furnace are easily liquefied by fire of the third order, and five-sixths of a _libra_ of spring water. the eighth is made of two _librae_ of vitriol, the same number of _librae_ of saltpetre, one and a half _librae_ of alum, one _libra_ of the lees of the _aqua_ which parts gold from silver; and to each separate _libra_ a sixth of urine is poured over it. the ninth contains two _librae_ of powder of baked bricks, one _libra_ of vitriol, likewise one _libra_ of saltpetre, a handful of salt, and three-quarters of a _libra_ of spring water. only the tenth lacks vitriol and alum, but it contains three _librae_ of saltpetre, two _librae_ of stones which when thrown into a hot furnace are easily liquefied by fire of the third order, half a _libra_ each of verdigris[ ], of _stibium_, of iron scales and filings, and of asbestos[ ], and one and one-sixth _librae_ of spring water. all the vitriol from which the _aqua_ is usually made is first reduced to powder in the following way. it is thrown into an earthen crucible lined on the inside with litharge, and heated until it melts; then it is stirred with a copper wire, and after it has cooled it is pounded to powder. in the same manner saltpetre melted by the fire is pounded to powder when it has cooled. some indeed place alum upon an iron plate, roast it, and make it into powder. although all these _aquae_ cleanse gold concentrates or dust from impurities, yet there are certain compositions which possess singular power. the first of these consists of one _libra_ of verdigris and three-quarters of a _libra_ of vitriol. for each _libra_ there is poured over it one-sixth of a _libra_ of spring or river water, as to which, since this pertains to all these compounds, it is sufficient to have mentioned once for all. the second composition is made from one _libra_ of each of the following, artificial orpiment, vitriol, lime, alum, ash which the dyers of wool use, one quarter of a _libra_ of verdigris, and one and a half _unciae_ of _stibium_. the third consists of three _librae_ of vitriol, one of saltpetre, half a _libra_ of asbestos, and half a _libra_ of baked bricks. the fourth consists of one _libra_ of saltpetre, one _libra_ of alum, and half a _libra_ of sal-ammoniac.[ ] [illustration (nitric acid making): a--furnace. b--its round hole. c--air-holes. d--mouth of the furnace. e--draught opening under it. f--earthenware crucible. g--ampulla. h--operculum. i--its spout. k--other ampulla. l--basket in which this is usually placed lest it be broken.] the furnace in which _aqua valens_ is made[ ] is built of bricks, rectangular, two feet long and wide, and as many feet high and a half besides. it is covered with iron plates supported with iron rods; these plates are smeared on the top with lute, and they have in the centre a round hole, large enough to hold the earthen vessel in which the glass ampulla is placed, and on each side of the centre hole are two small round air-holes. the lower part of the furnace, in order to hold the burning charcoal, has iron plates at the height of a palm, likewise supported by iron rods. in the middle of the front there is the mouth, made for the purpose of putting the fire into the furnace; this mouth is half a foot high and wide, and rounded at the top, and under it is the draught opening. into the earthen vessel set over the hole is placed clean sand a digit deep, and in it the glass ampulla is set as deeply as it is smeared with lute. the lower quarter is smeared eight or ten times with nearly liquid lute, each time to the thickness of a blade, and each time it is dried again, until it has become as thick as the thumb; this kind of lute is well beaten with an iron rod, and is thoroughly mixed with hair or cotton thread, or with wool and salt, that it should not crackle. the many things of which the compounds are made must not fill the ampulla completely, lest when boiling they rise into the operculum. the operculum is likewise made of glass, and is closely joined to the ampulla with linen, cemented with wheat flour and white of egg moistened with water, and then lute free from salt is spread over that part of it. in a similar way the spout of the operculum is joined by linen covered with lute to another glass ampulla which receives the distilled _aqua_. a kind of thin iron nail or small wooden peg, a little thicker than a needle, is fixed in this joint, in order that when air seems necessary to the artificer distilling by this process he can pull it out; this is necessary when too much of the vapour has been driven into the upper part. the four air-holes which, as i have said, are on the top of the furnace beside the large hole on which the ampulla is placed, are likewise covered with lute. all this preparation having been accomplished in order, and the ingredients placed in the ampulla, they are gradually heated over burning charcoal until they begin to exhale vapour and the ampulla is seen to trickle with moisture. but when this, on account of the rising of the vapour, turns red, and the _aqua_ distils through the spout of the operculum, then one must work with the utmost care, lest the drops should fall at a quicker rate than one for every five movements of the clock or the striking of its bell, and not slower than one for every ten; for if it falls faster the glasses will be broken, and if it drops more slowly the work begun cannot be completed within the definite time, that is within the space of twenty-four hours. to prevent the first accident, part of the coals are extracted by means of an iron implement similar to pincers; and in order to prevent the second happening, small dry pieces of oak are placed upon the coals, and the substances in the ampulla are heated with a sharper fire, and the air-holes on the furnace are re-opened if need arise. as soon as the drops are being distilled, the glass ampulla which receives them is covered with a piece of linen moistened with water, in order that the powerful vapour which arises may be repelled. when the ingredients have been heated and the ampulla in which they were placed is whitened with moisture, it is heated by a fiercer fire until all the drops have been distilled[ ]. after the furnace has cooled, the _aqua_ is filtered and poured into a small glass ampulla, and into the same is put half a _drachma_ of silver[ ], which when dissolved makes the turbid _aqua_ clear. this is poured into the ampulla containing all the rest of the _aqua_, and as soon as the lees have sunk to the bottom the _aqua_ is poured off, removed, and reserved for use. gold is parted from silver by the following method[ ]. the alloy, with lead added to it, is first heated in a cupel until all the lead is exhaled, and eight ounces of the alloy contain only five _drachmae_ of copper or at most six, for if there is more copper in it, the silver separated from the gold soon unites with it again. such molten silver containing gold is formed into granules, being stirred by means of a rod split at the lower end, or else is poured into an iron mould, and when cooled is made into thin leaves. as the process of making granules from argentiferous gold demands greater care and diligence than making them from any other metals, i will now explain the method briefly. the alloy is first placed in a crucible, which is then covered with a lid and placed in another earthen crucible containing a few ashes. then they are placed in the furnace, and after they are surrounded by charcoal, the fire is blown by the blast of a bellows, and lest the charcoal fall away it is surrounded by stones or bricks. soon afterward charcoal is thrown over the upper crucible and covered with live coals; these again are covered with charcoal, so that the crucible is surrounded and covered on all sides with it. it is necessary to heat the crucibles with charcoal for the space of half an hour or a little longer, and to provide that there is no deficiency of charcoal, lest the alloy become chilled; after this the air is blown in through the nozzle of the bellows, that the gold may begin to melt. soon afterward it is turned round, and a test is quickly taken to see whether it be melted, and if it is melted, fluxes are thrown into it; it is advisable to cover up the crucible again closely that the contents may not be exhaled. the contents are heated together for as long as it would take to walk fifteen paces, and then the crucible is seized with tongs and the gold is emptied into an oblong vessel containing very cold water, by pouring it slowly from a height so that the granules will not be too big; in proportion as they are lighter, more fine and more irregular, the better they are, therefore the water is frequently stirred with a rod split into four parts from the lower end to the middle. the leaves are cut into small pieces, and they or the silver granules are put into a glass ampulla, and the _aqua_ is poured over them to a height of a digit above the silver. the ampulla is covered with a bladder or with waxed linen, lest the contents exhale. then it is heated until the silver is dissolved, the indication of which is the bubbling of the _aqua_. the gold remains in the bottom, of a blackish colour, and the silver mixed with the _aqua_ floats above. some pour the latter into a copper bowl and pour into it cold water, which immediately congeals the silver; this they take out and dry, having poured off the _aqua_[ ]. they heat the dried silver in an earthenware crucible until it melts, and when it is melted they pour it into an iron mould. the gold which remains in the ampulla they wash with warm water, filter, dry, and heat in a crucible with a little _chrysocolla_ which is called borax, and when it is melted they likewise pour it into an iron mould. some workers, into an ampulla which contains gold and silver and the _aqua_ which separates them, pour two or three times as much of this _aqua valens_ warmed, and into the same ampulla or into a dish into which all is poured, throw fine leaves of black lead and copper; by this means the gold adheres to the lead and the silver to the copper, and separately the lead from the gold, and separately the copper from the silver, are parted in a cupel. but no method is approved by us which loses the _aqua_ used to part gold from silver, for it might be used again[ ]. [illustration (parting precious metals with nitric acid): a--ampullae arranged in the vessels. b--an ampulla standing upright between iron rods. c--ampullae placed in the sand which is contained in a box, the spouts of which reach from the opercula into ampullae placed under them. d--ampullae likewise placed in sand which is contained in a box, of which the spouts from the opercula extend crosswise into ampullae placed under them. e--other ampullae receiving the distilled _aqua_ and likewise arranged in sand contained in the lower boxes. f--iron tripod, in which the ampulla is usually placed when there are not many particles of gold to be parted from the silver. g--vessel.] a glass ampulla, which bulges up inside at the bottom like a cone, is covered on the lower part of the outside with lute in the way explained above, and into it is put silver bullion weighing three and a half roman _librae_. the _aqua_ which parts the one from the other is poured into it, and the ampulla is placed in sand contained in an earthen vessel, or in a box, that it may be warmed with a gentle fire. lest the _aqua_ should be exhaled, the top of the ampulla is plastered on all sides with lute, and it is covered with a glass operculum, under whose spout is placed another ampulla which receives the distilled drops; this receiver is likewise arranged in a box containing sand. when the contents are heated it reddens, but when the redness no longer appears to increase, it is taken out of the vessel or box and shaken; by this motion the _aqua_ becomes heated again and grows red; if this is done two or three times before other _aqua_ is added to it, the operation is sooner concluded, and much less _aqua_ is consumed. when the first charge has all been distilled, as much silver as at first is again put into the ampulla, for if too much were put in at once, the gold would be parted from it with difficulty. then the second _aqua_ is poured in, but it is warmed in order that it and the ampulla may be of equal temperature, so that the latter may not be cracked by the cold; also if a cold wind blows on it, it is apt to crack. then the third _aqua_ is poured in, and also if circumstances require it, the fourth, that is to say more _aqua_ and again more is poured in until the gold assumes the colour of burned brick. the artificer keeps in hand two _aquae_, one of which is stronger than the other; the stronger is used at first, then the less strong, then at the last again the stronger. when the gold becomes of a reddish yellow colour, spring water is poured in and heated until it boils. the gold is washed four times and then heated in the crucible until it melts. the water with which it was washed is put back, for there is a little silver in it; for this reason it is poured into an ampulla and heated, and the drops first distilled are received by one ampulla, while those which come later, that is to say when the operculum begins to get red, fall into another. this latter _aqua_ is useful for testing the gold, the former for washing it; the former may also be poured over the ingredients from which the _aqua valens_ is made. the _aqua_ that was first distilled, which contains the silver, is poured into an ampulla wide at the base, the top of which is also smeared with lute and covered by an operculum, and is then boiled as before in order that it may be separated from the silver. if there be so much _aqua_ that (when boiled) it rises into the operculum, there is put into the ampulla one lozenge or two; these are made of soap, cut into small pieces and mixed together with powdered argol, and then heated in a pot over a gentle fire; or else the contents are stirred with a hazel twig split at the bottom, and in both cases the _aqua_ effervesces, and soon after again settles. when the powerful vapour appears, the _aqua_ gives off a kind of oil, and the operculum becomes red. but, lest the vapours should escape from the ampulla and the operculum in that part where their mouths communicate, they are entirely sealed all round. the _aqua_ is boiled continually over a fiercer fire, and enough charcoal must be put into the furnace so that the live coals touch the vessel. the ampulla is taken out as soon as all the _aqua_ has been distilled, and the silver, which is dried by the heat of the fire, alone remains in it; the silver is shaken out and put in an earthenware crucible, and heated until it melts. the molten glass is extracted with an iron rod curved at the lower end, and the silver is made into cakes. the glass extracted from the crucible is ground to powder, and to this are added litharge, argol, glass-galls, and saltpetre, and they are melted in an earthen crucible. the button that settles is transferred to the cupel and re-melted. if the silver was not sufficiently dried by the heat of the fire, that which is contained in the upper part of the ampulla will appear black; this when melted will be consumed. when the lute, which was smeared round the lower part of the ampulla, has been removed, it is placed in the crucible and is re-melted, until at last there is no more appearance of black[ ]. if to the first _aqua_ the other which contains silver is to be added, it must be poured in before the powerful vapours appear, and the _aqua_ gives off the oily substance, and the operculum becomes red; for he who pours in the _aqua_ after the vapour appears causes a loss, because the _aqua_ generally spurts out and the glass breaks. if the ampulla breaks when the gold is being parted from the silver or the silver from the _aqua_, the _aqua_ will be absorbed by the sand or the lute or the bricks, whereupon, without any delay, the red hot coals should be taken out of the furnace and the fire extinguished. the sand and bricks after being crushed should be thrown into a copper vessel, warm water should be poured over them, and they should be put aside for the space of twelve hours; afterward the water should be strained through a canvas, and the canvas, since it contains silver, should be dried by the heat of the sun or the fire, and then placed in an earthen crucible and heated until the silver melts, this being poured out into an iron mould. the strained water should be poured into an ampulla and separated from the silver, of which it contains a minute portion; the sand should be mixed with litharge, glass-galls, argol, saltpetre, and salt, and heated in an earthen crucible. the button which settles at the bottom should be transferred to a cupel, and should be re-melted, in order that the lead may be separated from the silver. the lute, with lead added, should be heated in an earthen crucible, then re-melted in a cupel. we also separate silver from gold by the same method when we assay them. for this purpose the alloy is first rubbed against a touchstone, in order to learn what proportion of silver there is in it; then as much silver as is necessary is added to the argentiferous gold, in a _bes_ of which there must be less than a _semi-uncia_ or a _semi-uncia_ and a _sicilicus_[ ] of copper. after lead has been added, it is melted in a cupel until the lead and the copper have exhaled, then the alloy of gold with silver is flattened out, and little tubes are made of the leaves; these are put into a glass ampulla, and strong _aqua_ is poured over them two or three times. the tubes after this are absolutely pure, with the exception of only a quarter of a _siliqua_, which is silver; for only this much silver remains in eight _unciae_ of gold[ ]. as great expense is incurred in parting the metals by the methods that i have explained, as night vigils are necessary when _aqua valens_ is made, and as generally much labour and great pains have to be expended on this matter, other methods for parting have been invented by clever men, which are less costly, less laborious, and in which there is less loss if through carelessness an error is made. there are three methods, the first performed with sulphur, the second with antimony, the third by means of some compound which consists of these or other ingredients. [illustration (parting precious metals with sulphur): a--pot. b--circular fire. c--crucibles. d--their lids. e--lid of the pot. f--furnace. g--iron rod.] in the first method,[ ] the silver containing some gold is melted in a crucible and made into granules. for every _libra_ of granules, there is taken a sixth of a _libra_ and a _sicilicus_ of sulphur (not exposed to the fire); this, when crushed, is sprinkled over the moistened granules, and then they are put into a new earthen pot of the capacity of four _sextarii_, or into several of them if there is an abundance of granules. the pot, having been filled, is covered with an earthen lid and smeared over, and placed within a circle of fire set one and a half feet distant from the pot on all sides, in order that the sulphur added to the silver should not be distilled when melted. the pot is opened, the black-coloured granules are taken out, and afterward thirty-three _librae_ of these granules are placed in an earthen crucible, if it has such capacity. for every _libra_ of silver granules, weighed before they were sprinkled with sulphur, there is weighed out also a sixth of a _libra_ and a _sicilicus_ of copper, if each _libra_ consists either of three-quarters of a _libra_ of silver and a quarter of a _libra_ of copper, or of three-quarters of a _libra_ and a _semi-uncia_ of silver and a sixth of a _libra_ and a _semi-uncia_ of copper. if, however, the silver contains five-sixths of a _libra_ of silver and a sixth of a _libra_ of copper, or five-sixths of a _libra_ and a _semi-uncia_ of silver and an _uncia_ and a half of copper, then there are weighed out a quarter of a _libra_ of copper granules. if a _libra_ contains eleven-twelfths of a _libra_ of silver and one _uncia_ of copper, or eleven-twelfths and a _semi-uncia_ of silver and a _semi-uncia_ of copper, then are weighed out a quarter of a _libra_ and a _semi-uncia_ and a _sicilicus_ of copper granules. lastly, if there is only pure silver, then as much as a third of a _libra_ and a _semi-uncia_ of copper granules are added. half of these copper granules are added soon afterward to the black-coloured silver granules. the crucible should be tightly covered and smeared over with lute, and placed in a furnace, into which the air is drawn through the draught-holes. as soon as the silver is melted, the crucible is opened, and there is placed in it a heaped ladleful more of granulated copper, and also a heaped ladleful of a powder which consists of equal parts of litharge, of granulated lead, of salt, and of glass-galls; then the crucible is again covered with the lid. when the copper granules are melted, more are put in, together with the powder, until all have been put in. a little of the regulus is taken from the crucible, but not from the gold lump which has settled at the bottom, and a _drachma_ of it is put into each of the cupels, which contain an _uncia_ of molten lead; there should be many of these cupels. in this way half a _drachma_ of silver is made. as soon as the lead and copper have been separated from the silver, a third of it is thrown into a glass ampulla, and _aqua valens_ is poured over it. by this method is shown whether the sulphur has parted all the gold from the silver, or not. if one wishes to know the size of the gold lump which has settled at the bottom of the crucible, an iron rod moistened with water is covered with chalk, and when the rod is dry it is pushed down straight into the crucible, and the rod remains bright to the height of the gold lump; the remaining part of the rod is coloured black by the regulus, which adheres to the rod if it is not quickly removed. if when the rod has been extracted the gold is observed to be satisfactorily parted from the silver, the regulus is poured out, the gold button is taken out of the crucible, and in some clean place the regulus is chipped off from it, although it usually flies apart. the lump itself is reduced to granules, and for every _libra_ of this gold they weigh out a quarter of a _libra_ each of crushed sulphur and of granular copper, and all are placed together in an earthen crucible, not into a pot. when they are melted, in order that the gold may more quickly settle at the bottom, the powder which i have mentioned is added. although minute particles of gold appear to scintillate in the regulus of copper and silver, yet if all that are in a _libra_ do not weigh as much as a single sesterce, then the sulphur has satisfactorily parted the gold from the silver; but if it should weigh a sesterce or more, then the regulus is thrown back again into the earthen crucible, and it is not advantageous to add sulphur, but only a little copper and powder, by which method a gold lump is again made to settle at the bottom; and this one is added to the other button which is not rich in gold. when gold is parted from sixty-six _librae_ of silver, the silver, copper, and sulphur regulus weighs one hundred and thirty-two _librae_. to separate the copper from the silver we require five hundred _librae_ of lead, more or less, with which the regulus is melted in the second furnace. in this manner litharge and hearth-lead are made, which are re-smelted in the first furnace. the cakes that are made from these are placed in the third furnace, so that the lead may be separated from the copper and used again, for it contains very little silver. the crucibles and their covers are crushed, washed, and the sediment is melted together with litharge and hearth-lead. those who wish to separate all the silver from the gold by this method leave one part of gold to three of silver, and then reduce the alloy to granules. then they place it in an ampulla, and by pouring _aqua valens_ over it, part the gold from the silver, which process i explained in book vii. if sulphur from the lye with which _sal artificiosus_ is made, is strong enough to float an egg thrown into it, and is boiled until it no longer emits fumes, and melts when placed upon glowing coals, then, if such sulphur is thrown into the melted silver, it parts the gold from it. [illustration (parting precious metals with antimony): a--furnace in which the air is drawn in through holes. b--goldsmith's forge. c--earthen crucibles. d--iron pots. e--block.] silver is also parted from gold by means of _stibium_[ ]. if in a _bes of_ gold there are seven, or six, or five double _sextulae_ of silver, then three parts of _stibium_ are added to one part of gold; but in order that the _stibium_ should not consume the gold, it is melted with copper in a red hot earthen crucible. if the gold contains some portion of copper, then to eight _unciae_ of _stibium_ a _sicilicus_ of copper is added; and if it contains no copper, then half an _uncia_, because copper must be added to _stibium_ in order to part gold from silver. the gold is first placed in a red hot earthen crucible, and when melted it swells, and a little _stibium_ is added to it lest it run over; in a short space of time, when this has melted, it likewise again swells, and when this occurs it is advisable to put in all the remainder of the _stibium_, and to cover the crucible with a lid, and then to heat the mixture for the time required to walk thirty-five paces. then it is at once poured out into an iron pot, wide at the top and narrow at the bottom, which was first heated and smeared over with tallow or wax, and set on an iron or wooden block. it is shaken violently, and by this agitation the gold lump settles to the bottom, and when the pot has cooled it is tapped loose, and is again melted four times in the same way. but each time a less weight of _stibium_ is added to the gold, until finally only twice as much _stibium_ is added as there is gold, or a little more; then the gold lump is melted in a cupel. the _stibium_ is melted again three or four times in an earthen crucible, and each time a gold lump settles, so that there are three or four gold lumps, and these are all melted together in a cupel. to two _librae_ and a half of such _stibium_ are added two _librae_ of argol and one _libra_ of glass-galls, and they are melted in an earthen crucible, where a lump likewise settles at the bottom; this lump is melted in the cupel. finally, the _stibium_ with a little lead added, is melted in the cupel, in which, after all the rest has been consumed by the fire, the silver alone remains. if the _stibium_ is not first melted in an earthen crucible with argol and glass-galls, before it is melted in the cupel, part of the silver is consumed, and is absorbed by the ash and powder of which the cupel is made. the crucible in which the gold and silver alloy are melted with _stibium_, and also the cupel, are placed in a furnace, which is usually of the kind in which the air is drawn in through holes; or else they are placed in a goldsmith's forge. just as _aqua valens_ poured over silver, from which the sulphur has parted the gold, shows us whether all has been separated or whether particles of gold remain in the silver; so do certain ingredients, if placed in the pot or crucible "alternately" with the gold, from which the silver has been parted by _stibium_, and heated, show us whether all have been separated or not. we use cements[ ] when, without _stibium_, we part silver or copper or both so ingeniously and admirably from gold. there are various cements. some consist of half a _libra_ of brick dust, a quarter of a _libra_ of salt, an _uncia_ of saltpetre, half an _uncia_ of sal-ammoniac, and half an _uncia_ of rock salt. the bricks or tiles from which the dust is made must be composed of fatty clays, free from sand, grit, and small stones, and must be moderately burnt and very old. another cement is made of a _bes_ of brick dust, a third of rock salt, an _uncia_ of saltpetre, and half an _uncia_ of refined salt. another cement is made of a _bes_ of brick dust, a quarter of refined salt, one and a half _unciae_ of saltpetre, an _uncia_ of sal-ammoniac, and half an _uncia_ of rock salt. another has one _libra_ of brick dust, and half a _libra_ of rock salt, to which some add a sixth of a _libra_ and a _sicilicus_ of vitriol. another is made of half a _libra_ of brick dust, a third of a _libra_ of rock salt, an _uncia_ and a half of vitriol, and one _uncia_ of saltpetre. another consists of a _bes_ of brick dust, a third of refined salt, a sixth of white vitriol[ ], half an _uncia_ of verdigris, and likewise half an _uncia_ of saltpetre. another is made of one and a third _librae_ of brick dust, a _bes_ of rock salt, a sixth of a _libra_ and half an _uncia_ of sal-ammoniac, a sixth and half an _uncia_ of vitriol, and a sixth of saltpetre. another contains a _libra_ of brick dust, a third of refined salt, and one and a half _unciae_ of vitriol. those ingredients above are peculiar to each cement, but what follows is common to all. each of the ingredients is first separately crushed to powder; the bricks are placed on a hard rock or marble, and crushed with an iron implement; the other things are crushed in a mortar with a pestle; each is separately passed through a sieve. then they are all mixed together, and are moistened with vinegar in which a little sal-ammoniac has been dissolved, if the cement does not contain any. but some workers, however, prefer to moisten the gold granules or gold-leaf instead. the cement should be placed, alternately with the gold, in new and clean pots in which no water has ever been poured. in the bottom the cement is levelled with an iron implement, and afterward the gold granules or leaves are placed one against the other, so that they may touch it on all sides; then, again, a handful of the cement, or more if the pots are large, is thrown in and levelled with an iron implement; the granules and leaves are laid over this in the same manner, and this is repeated until the pot is filled. then it is covered with a lid, and the place where they join is smeared over with artificial lute, and when this is dry the pots are placed in the furnace. [illustration (parting precious metals by cementation): a--furnace. b--pot. c--lid. d--air-holes.] the furnace has three chambers, the lowest of which is a foot high; into this lowest chamber the air penetrates through an opening, and into it the ashes fall from the burnt wood, which is supported by iron rods, arranged to form a grating. the middle chamber is two feet high, and the wood is pushed in through its mouth. the wood ought to be oak, holmoak, or turkey-oak, for from these the slow and lasting fire is made which is necessary for this operation. the upper chamber is open at the top so that the pots, for which it has the depth, may be put into it; the floor of this chamber consists of iron rods, so strong that they may bear the weight of the pots and the heat of the fire; they are sufficiently far apart that the fire may penetrate well and may heat the pots. the pots are narrow at the bottom, so that the fire entering into the space between them may heat them; at the top the pots are wide, so that they may touch and hold back the heat of the fire. the upper part of the furnace is closed in with bricks not very thick, or with tiles and lute, and two or three air-holes are left, through which the fumes and flames may escape. the gold granules or leaves and the cement, alternately placed in the pots, are heated by a gentle fire, gradually increasing for twenty-four hours, if the furnace was heated for two hours before the full pots were stood in it, and if this was not done, then for twenty-six hours. the fire should be increased in such a manner that the pieces of gold and the cement, in which is the potency to separate the silver and copper from the gold, may not melt, for in this case the labour and cost will be spent in vain; therefore, it is ample to have the fire hot enough that the pots always remain red. after so many hours all the burning wood should be drawn out of the furnace. then the refractory bricks or tiles are removed from the top of the furnace, and the glowing pots are taken out with the tongs. the lids are removed, and if there is time it is well to allow the gold to cool by itself, for then there is less loss; but if time cannot be spared for that operation, the pieces of gold are immediately placed separately into a wooden or bronze vessel of water and gradually quenched, lest the cement which absorbs the silver should exhale it. the pieces of gold, and the cement adhering to them, when cooled or quenched, are rolled with a little mallet so as to crush the lumps and free the gold from the cement. then they are sifted by a fine sieve, which is placed over a bronze vessel; in this manner the cement containing the silver or the copper or both, falls from the sieve into the bronze vessel, and the gold granules or leaves remain on it. the gold is placed in a vessel and again rolled with the little mallet, so that it may be cleansed from the cement which absorbs silver and copper. the particles of cement, which have dropped through the holes of the sieve into the bronze vessel, are washed in a bowl, over a wooden tub, being shaken about with the hands, so that the minute particles of gold which have fallen through the sieve may be separated. these are again washed in a little vessel, with warm water, and scrubbed with a piece of wood or a twig broom, that the moistened cement may be detached. afterward all the gold is again washed with warm water, and collected with a bristle brush, and should be washed in a copper full of holes, under which is placed a little vessel. then it is necessary to put the gold on an iron plate, under which is a vessel, and to wash it with warm water. finally, it is placed in a bowl, and, when dry, the granules or leaves are rubbed against a touchstone at the same time as a touch-needle, and considered carefully as to whether they be pure or alloyed. if they are not pure enough, the granules or the leaves, together with the cement which attracts silver and copper, are arranged alternately in layers in the same manner, and again heated; this is done as often as is necessary, but the last time it is heated as many hours as are required to cleanse the gold. some people add another cement to the granules or leaves. this cement lacks the ingredients of metalliferous origin, such as verdigris and vitriol, for if these are in the cement, the gold usually takes up a little of the base metal; or if it does not do this, it is stained by them. for this reason some very rightly never make use of cements containing these things, because brick dust and salt alone, especially rock salt, are able to extract all the silver and copper from the gold and to attract it to themselves. it is not necessary for coiners to make absolutely pure gold, but to heat it only until such a fineness is obtained as is needed for the gold money which they are coining. the gold is heated, and when it shows the necessary golden yellow colour and is wholly pure, it is melted and made into bars, in which case they are either prepared by the coiners with _chrysocolla_, which is called by the moors borax, or are prepared with salt of lye made from the ashes of ivy or of other salty herbs. the cement which has absorbed silver or copper, after water has been poured over it, is dried and crushed, and when mixed with hearth-lead and de-silverized lead, is smelted in the blast furnace. the alloy of silver and lead, or of silver and copper and lead, which flows out, is again melted in the cupellation furnace, in order that the lead and copper may be separated from the silver. the silver is finally thoroughly purified in the refining furnace, and in this practical manner there is no silver lost, or only a minute quantity. there are besides this, certain other cements[ ] which part gold from silver, composed of sulphur, _stibium_ and other ingredients. one of these compounds consists of half an _uncia_ of vitriol dried by the heat of the fire and reduced to powder, a sixth of refined salt, a third of _stibium_, half a _libra_ of prepared sulphur (not exposed to the fire), one _sicilicus_ of glass, likewise one _sicilicus_ of saltpetre, and a _drachma_ of sal-ammoniac.[ ] the sulphur is prepared as follows: it is first crushed to powder, then it is heated for six hours in sharp vinegar, and finally poured into a vessel and washed with warm water; then that which settles at the bottom of the vessel is dried. to refine the salt it is placed in river water and boiled, and again evaporated. the second compound contains one _libra_ of sulphur (not exposed to fire) and two _librae_ of refined salt. the third compound is made from one _libra_ of sulphur (not exposed to the fire), half a _libra_ of refined salt, a quarter of a _libra_ of sal-ammoniac, and one _uncia_ of red-lead. the fourth compound consists of one _libra_ each of refined salt, sulphur (not exposed to the fire) and argol, and half a _libra_ of _chrysocolla_ which the moors call borax. the fifth compound has equal proportions of sulphur (not exposed to the fire), sal-ammoniac, saltpetre, and verdigris. the silver which contains some portion of gold is first melted with lead in an earthen crucible, and they are heated together until the silver exhales the lead. if there was a _libra_ of silver, there must be six _drachmae_ of lead. then the silver is sprinkled with two _unciae_ of that powdered compound and is stirred; afterward it is poured into another crucible, first warmed and lined with tallow, and then violently shaken. the rest is performed according to the process i have already explained. gold may be parted without injury from silver goblets and from other gilt vessels and articles[ ], by means of a powder, which consists of one part of sal-ammoniac and half a part of sulphur. the gilt goblet or other article is smeared with oil, and the powder is dusted on; the article is seized in the hand, or with tongs, and is carried to the fire and sharply tapped, and by this means the gold falls into water in vessels placed underneath, while the goblet remains uninjured. gold is also parted from silver on gilt articles by means of quicksilver. this is poured into an earthen crucible, and so warmed by the fire that the finger can bear the heat when dipped into it; the silver-gilt objects are placed in it, and when the quicksilver adheres to them they are taken out and placed on a dish, into which, when cooled, the gold falls, together with the quicksilver. again and frequently the same silver-gilt object is placed in heated quicksilver, and the same process is continued until at last no more gold is visible on the object; then the object is placed in the fire, and the quicksilver which adheres to it is exhaled. then the artificer takes a hare's foot, and brushes up into a dish the quicksilver and the gold which have fallen together from the silver article, and puts them into a cloth made of woven cotton or into a soft leather; the quicksilver is squeezed through one or the other into another dish.[ ] the gold remains in the cloth or the leather, and when collected is placed in a piece of charcoal hollowed out, and is heated until it melts, and a little button is made from it. this button is heated with a little _stibium_ in an earthen crucible and poured out into another little vessel, by which method the gold settles at the bottom, and the _stibium_ is seen to be on the top; then the work is completed. finally, the gold button is put in a hollowed-out brick and placed in the fire, and by this method the gold is made pure. by means of the above methods gold is parted from silver and also silver from gold. now i will explain the methods used to separate copper from gold[ ]. the salt which we call _sal-artificiosus_,[ ] is made from a _libra_ each of vitriol, alum, saltpetre, and sulphur not exposed to the fire, and half a _libra_ of sal-ammoniac; these ingredients when crushed are heated with one part of lye made from the ashes used by wool dyers, one part of unslaked lime, and four parts of beech ashes. the ingredients are boiled in the lye until the whole has been dissolved. then it is immediately dried and kept in a hot place, lest it turn into oil; and afterward when crushed, a _libra_ of lead-ash is mixed with it. with each _libra_ of this powdered compound one and a half _unciae_ of the copper is gradually sprinkled into a hot crucible, and it is stirred rapidly and frequently with an iron rod. when the crucible has cooled and been broken up, the button of gold is found. the second method for parting is the following. two _librae_ of sulphur not exposed to the fire, and four _librae_ of refined salt are crushed and mixed; a sixth of a _libra_ and half an _uncia_ of this powder is added to a _bes_ of granules made of lead, and twice as much copper containing gold; they are heated together in an earthen crucible until they melt. when cooled, the button is taken out and purged of slag. from this button they again make granules, to a third of a _libra_ of which is added half a _libra_ of that powder of which i have spoken, and they are placed in alternate layers in the crucible; it is well to cover the crucible and to seal it up, and afterward it is heated over a gentle fire until the granules melt. soon afterward, the crucible is taken off the fire, and when it is cool the button is extracted. from this, when purified and again melted down, the third granules are made, to which, if they weigh a sixth of a _libra_, is added one half an _uncia_ and a _sicilicus_ of the powder, and they are heated in the same manner, and the button of gold settles at the bottom of the crucible. the third method is as follows. from time to time small pieces of sulphur, enveloped in or mixed with wax, are dropped into six _librae_ of the molten copper, and consumed; the sulphur weighs half an _uncia_ and a _sicilicus_. then one and a half _sicilici_ of powdered saltpetre are dropped into the same copper and likewise consumed; then again half an _uncia_ and a _sicilicus_ of sulphur enveloped in wax; afterward one and a half _sicilici_ of lead-ash enveloped in wax, or of minium made from red-lead. then immediately the copper is taken out, and to the gold button, which is now mixed with only a little copper, they add _stibium_ to double the amount of the button; these are heated together until the _stibium_ is driven off; then the button, together with lead of half the weight of the button, are heated in a cupel. finally, the gold is taken out of this and quenched, and if there is a blackish colour settled in it, it is melted with a little of the _chrysocolla_ which the moors call borax; if too pale, it is melted with _stibium_, and acquires its own golden-yellow colour. there are some who take out the molten copper with an iron ladle and pour it into another crucible, whose aperture is sealed up with lute, and they place it over glowing charcoal, and when they have thrown in the powders of which i have spoken, they stir the whole mass rapidly with an iron rod, and thus separate the gold from the copper; the former settles at the bottom of the crucible, the latter floats on the top. then the aperture of the crucible is opened with the red-hot tongs, and the copper runs out. the gold which remains is re-heated with _stibium_, and when this is exhaled the gold is heated for the third time in a cupel with a fourth part of lead, and then quenched. the fourth method is to melt one and a third _librae_ of the copper with a sixth of a _libra_ of lead, and to pour it into another crucible smeared on the inside with tallow or gypsum; and to this is added a powder consisting of half an _uncia_ each of prepared sulphur, verdigris, and saltpetre, and an _uncia_ and a half of _sal coctus_. the fifth method consists of placing in a crucible one _libra_ of the copper and two _librae_ of granulated lead, with one and a half _unciae_ of _sal-artificiosus_; they are at first heated over a gentle fire and then over a fiercer one. the sixth method consists in heating together a _bes_ of the copper and one-sixth of a _libra_ each of sulphur, salt, and _stibium_. the seventh method consists of heating together a _bes_ of the copper and one-sixth each of iron scales and filings, salt, _stibium_, and glass-galls. the eighth method consists of heating together one _libra_ of the copper, one and a half _librae_ of sulphur, half a _libra_ of verdigris, and a _libra_ of refined salt. the ninth method consists of placing in one _libra_ of the molten copper as much pounded sulphur, not exposed to the fire, and of stirring it rapidly with an iron rod; the lump is ground to powder, into which quicksilver is poured, and this attracts to itself the gold. gilded copper articles are moistened with water and placed on the fire, and when they are glowing they are quenched with cold water, and the gold is scraped off with a brass rod. by these practical methods gold is separated from copper. either copper or lead is separated from silver by the methods which i will now explain.[ ] this is carried on in a building near by the works, or in the works in which the gold or silver ores or alloys are smelted. the middle wall of such a building is twenty-one feet long and fifteen feet high, and from this a front wall is distant fifteen feet toward the river; the rear wall is nineteen feet distant, and both these walls are thirty-six feet long and fourteen feet high; a transverse wall extends from the end of the front wall to the end of the rear wall; then fifteen feet back a second transverse wall is built out from the front wall to the end of the middle wall. in that space which is between those two transverse walls are set up the stamps, by means of which the ores and the necessary ingredients for smelting are broken up. from the further end of the front wall, a third transverse wall leads to the other end of the middle wall, and from the same to the end of the rear wall. the space between the second and third transverse walls, and between the rear and middle long walls, contains the cupellation furnace, in which lead is separated from gold or silver. the vertical wall of its chimney is erected upon the middle wall, and the sloping chimney-wall rests on the beams which extend from the second transverse wall to the third; these are so located that they are at a distance of thirteen feet from the middle long wall and four from the rear wall, and they are two feet wide and thick. from the ground up to the roof-beams is twelve feet, and lest the sloping chimney-wall should fall down, it is partly supported by means of many iron rods, and partly by means of a few tie-beams covered with lute, which extend from the small beams of the sloping chimney-wall to the beams of the vertical chimney-wall. the rear roof is arranged in the same way as the roof of the works in which ore is smelted. in the space between the middle and the front long walls and between the second[ ] and the third transverse walls are the bellows, the machinery for depressing and the instrument for raising them. a drum on the axle of a water-wheel has rundles which turn the toothed drum of an axle, whose long cams depress the levers of the bellows, and also another toothed drum on an axle, whose cams raise the tappets of the stamps, but in the opposite direction. so that if the cams which depress the levers of the bellows turn from north to south, the cams of the stamps turn from south to north. [illustration (cupellation furnace): a--rectangular stones. b--sole-stone. c--air-holes. d--internal walls. e--dome. f--crucible. g--bands. h--bars. i--apertures in the dome. k--lid of the dome. l--rings. m--pipes. n--valves. o--chains.] lead is separated from gold or silver in a cupellation furnace, of which the structure consists of rectangular stones, of two interior walls of which the one intersects the other transversely, of a round sole, and of a dome. its crucible is made from powder of earth and ash; but i will first speak of the structure and also of the rectangular stones. a circular wall is built four feet and three palms high, and one foot thick; from the height of two feet and three palms from the bottom, the upper part of the interior is cut away to the width of one palm, so that the stone sole may rest upon it. there are usually as many as fourteen stones; on the outside they are a foot and a palm wide, and on the inside narrower, because the inner circle is much smaller than the outer; if the stones are wider, fewer are required, if narrower more; they are sunk into the earth to a depth of a foot and a palm. at the top each one is joined to the next by an iron staple, the points of which are embedded in holes, and into each hole is poured molten lead. this stone structure has six air-holes near the ground, at a height of a foot above the ground; they are two feet and a palm from the bottom of the stones; each of these air-holes is in two stones, and is two palms high, and a palm and three digits wide. one of them is on the right side, between the wall which protects the main wall from the fire, and the channel through which the litharge flows out of the furnace crucible; the other five air-holes are distributed all round at equal distances apart; through these escapes the moisture which the earth exhales when heated, and if it were not for these openings the crucible would absorb the moisture and be damaged. in such a case a lump would be raised, like that which a mole throws up from the earth, and the ash would float on the top, and the crucible would absorb the silver-lead alloy; there are some who, because of this, make the rear part of the structure entirely open. the two inner walls, of which one intersects the other, are built of bricks, and are a brick in thickness. there are four air-holes in these, one in each part, which are about one digit's breadth higher and wider than the others. into the four compartments is thrown a wheelbarrowful of slag, and over this is placed a large wicker basket full of charcoal dust. these walls extend a cubit above the ground, and on these, and on the ledge cut in the rectangular stones, is placed the stone sole; this sole is a palm and three digits thick, and on all sides touches the rectangular stones; if there are any cracks in it they are filled up with fragments of stone or brick. the front part of the sole is sloped so that a channel can be made, through which the litharge flows out. copper plates are placed on this part of the sole-stone so that the silver-lead or other alloy may be more rapidly heated. a dome which has the shape of half a sphere covers the crucible. it consists of iron bands and of bars and of a lid. there are three bands, each about a palm wide and a digit thick; the lowest is at a distance of one foot from the middle one, and the middle one a distance of two feet from the upper one. under them are eighteen iron bars fixed by iron rivets; these bars are of the same width and thickness as the bands, and they are of such a length, that curving, they reach from the lower band to the upper, that is two feet and three palms long, while the dome is only one foot and three palms high. all the bars and bands of the dome have iron plates fastened on the underside with iron wire. in addition, the dome has four apertures; the rear one, which is situated opposite the channel through which the litharge flows out, is two feet wide at the bottom; toward the top, since it slopes gently, it is narrower, being a foot, three palms, and a digit wide; there is no bar at this place, for the aperture extends from the upper band to the middle one, but not to the lower one. the second aperture is situated above the channel, is two and a half feet wide at the bottom, and two feet and a palm at the top; and there is likewise no bar at this point; indeed, not only does the bar not extend to the lower band, but the lower band itself does not extend over this part, in order that the master can draw the litharge out of the crucible. there are besides, in the wall which protects the principal wall against the heat, near where the nozzles of the bellows are situated, two apertures, three palms wide and about a foot high, in the middle of which two rods descend, fastened on the inside with plates. near these apertures are placed the nozzles of the bellows, and through the apertures extend the pipes in which the nozzles of the bellows are set. these pipes are made of iron plates rolled up; they are two palms three digits long, and their inside diameter is three and a half digits; into these two pipes the nozzles of the bellows penetrate a distance of three digits from their valves. the lid of the dome consists of an iron band at the bottom, two digits wide, and of three curved iron bars, which extend from one point on the band to the point opposite; they cross each other at the top, where they are fixed by means of iron rivets. on the under side of the bars there are likewise plates fastened by rivets; each of the plates has small holes the size of a finger, so that the lute will adhere when the interior is lined. the dome has three iron rings engaged in wide holes in the heads of iron claves, which fasten the bars to the middle band at these points. into these rings are fastened the hooks of the chains with which the dome is raised, when the master is preparing the crucible. on the sole and the copper plates and the rock of the furnace, lute mixed with straw is placed to a depth of three digits, and it is pounded with a wooden rammer until it is compressed to a depth of one digit only. the rammer-head is round and three palms high, two palms wide at the bottom, and tapering upward; its handle is three feet long, and where it is set into the rammer-head it is bound around with an iron band. the top of the stonework in which the dome rests is also covered with lute, likewise mixed with straw, to the thickness of a palm. all this, as soon as it becomes loosened, must be repaired. [illustration (cupellation furnace): a--an artificer tamping the crucible with a rammer. b--large rammer. c--broom. d--two smaller rammers. e--curved iron plates. f--part of a wooden strip. g--sieve. h--ashes. i--iron shovel. k--iron plate. l--block of wood. m--rock. n--basket made of woven twigs. o--hooked bar. p--second hooked bar. q--old linen rag. r--bucket. s--doeskin. t--bundles of straw. v--wood. x--cakes of lead alloy. y--fork. z--another workman covers the outside of the furnace with lute where the dome fits on it. aa--basket full of ashes. bb--lid of the dome. cc--the assistant standing on the steps pours charcoal into the crucible through the hole at the top of the dome. dd--iron implement with which the lute is beaten. ee--lute. ff--ladle with which the workman or master takes a sample. gg--rabble with which the scum of impure lead is drawn off. hh--iron wedge with which the silver mass is raised.] the artificer who undertakes the work of parting the metals, distributes the operation into two shifts of two days. on the one morning he sprinkles a little ash into the lute, and when he has poured some water over it he brushes it over with a broom. then he throws in sifted ashes and dampens them with water, so that they could be moulded into balls like snow. the ashes are those from which lye has been made by letting water percolate through them, for other ashes which are fatty would have to be burnt again in order to make them less fat. when he has made the ashes smooth by pressing them with his hands, he makes the crucible slope down toward the middle; then he tamps it, as i have described, with a rammer. he afterward, with two small wooden rammers, one held in each hand, forms the channel through which the litharge flows out. the heads of these small rammers are each a palm wide, two digits thick, and one foot high; the handle of each is somewhat rounded, is a digit and a half less in diameter than the rammer-head, and is three feet in length; the rammer-head as well as the handle is made of one piece of wood. then with shoes on, he descends into the crucible and stamps it in every direction with his feet, in which manner it is packed and made sloping. then he again tamps it with a large rammer, and removing his shoe from his right foot he draws a circle around the crucible with it, and cuts out the circle thus drawn with an iron plate. this plate is curved at both ends, is three palms long, as many digits wide, and has wooden handles a palm and two digits long, and two digits thick; the iron plate is curved back at the top and ends, which penetrate into handles. there are some who use in the place of the plate a strip of wood, like the rim of a sieve; this is three digits wide, and is cut out at both ends that it may be held in the hands. afterward he tamps the channel through which the litharge discharges. lest the ashes should fall out, he blocks up the aperture with a stone shaped to fit it, against which he places a board, and lest this fall, he props it with a stick. then he pours in a basketful of ashes and tamps them with the large rammer; then again and again he pours in ashes and tamps them with the rammer. when the channel has been made, he throws dry ashes all over the crucible with a sieve, and smooths and rubs it with his hands. then he throws three basketsful of damp ashes on the margin all round the edge of the crucible, and lets down the dome. soon after, climbing upon the crucible, he builds up ashes all around it, lest the molten alloy should flow out. then, having raised the lid of the dome, he throws a basketful of charcoal into the crucible, together with an iron shovelful of glowing coals, and he also throws some of the latter through the apertures in the sides of the dome, and he spreads them with the same shovel. this work and labour is finished in the space of two hours. an iron plate is set in the ground under the channel, and upon this is placed a wooden block, three feet and a palm long, a foot and two palms and as many digits wide at the back, and two palms and as many digits wide in front; on the block of wood is placed a stone, and over it an iron plate similar to the bottom one, and upon this he puts a basketful of charcoal, and also an iron shovelful of burning charcoals. the crucible is heated in an hour, and then, with the hooked bar with which the litharge is drawn off, he stirs the remainder of the charcoal about. this hook is a palm long and three digits wide, has the form of a double triangle, and has an iron handle four feet long, into which is set a wooden one six feet long. there are some who use instead a simple hooked bar. after about an hour's time, he stirs the charcoal again with the bar, and with the shovel throws into the crucible the burning charcoals lying in the channel; then again, after the space of an hour, he stirs the burning charcoals with the same bar. if he did not thus stir them about, some blackness would remain in the crucible and that part would be damaged, because it would not be sufficiently dried. therefore the assistant stirs and turns the burning charcoal that it may be entirely burnt up, and so that the crucible may be well heated, which takes three hours; then the crucible is left quiet for the remaining two hours. when the hour of eleven has struck, he sweeps up the charcoal ashes with a broom and throws them out of the crucible. then he climbs on to the dome, and passing his hand in through its opening, and dipping an old linen rag in a bucket of water mixed with ashes, he moistens the whole of the crucible and sweeps it. in this way he uses two bucketsful of the mixture, each holding five roman _sextarii_,[ ] and he does this lest the crucible, when the metals are being parted, should break open; after this he rubs the crucible with a doe skin, and fills in the cracks. then he places at the left side of the channel, two fragments of hearth-lead, laid one on the top of the other, so that when partly melted they remain fixed and form an obstacle, that the litharge will not be blown about by the wind from the bellows, but remain in its place. it is expedient, however, to use a brick in the place of the hearth-lead, for as this gets much hotter, therefore it causes the litharge to form more rapidly. the crucible in its middle part is made two palms and as many digits deeper.[ ] there are some who having thus prepared the crucible, smear it over with incense[ ], ground to powder and dissolved in white of egg, soaking it up in a sponge and then squeezing it out again; there are others who smear over it a liquid consisting of white of egg and double the amount of bullock's blood or marrow. some throw lime into the crucible through a sieve. afterward the master of the works weighs the lead with which the gold or silver or both are mixed, and he sometimes puts a hundred _centumpondia_[ ] into the crucible, but frequently only sixty, or fifty, or much less. after it has been weighed, he strews about in the crucible three small bundles of straw, lest the lead by its weight should break the surface. then he places in the channel several cakes of lead alloy, and through the aperture at the rear of the dome he places some along the sides; then, ascending to the opening at the top of the dome, he arranges in the crucible round about the dome the cakes which his assistant hands to him, and after ascending again and passing his hands through the same aperture, he likewise places other cakes inside the crucible. on the second day those which remain he, with an iron fork, places on the wood through the rear aperture of the dome. when the cakes have been thus arranged through the hole at the top of the dome, he throws in charcoal with a basket woven of wooden twigs. then he places the lid over the dome, and the assistant covers over the joints with lute. the master himself throws half a basketful of charcoal into the crucible through the aperture next to the nozzle pipe, and prepares the bellows, in order to be able to begin the second operation on the morning of the following day. it takes the space of one hour to carry out such a piece of work, and at twelve all is prepared. these hours all reckoned up make a sum of eight hours. now it is time that we should come to the second operation. in the morning the workman takes up two shovelsful of live charcoals and throws them into the crucible through the aperture next to the pipes of the nozzles; then through the same hole he lays upon them small pieces of fir-wood or of pitch pine, such as are generally used to cook fish. after this the water-gates are opened, in order that the machine may be turned which depresses the levers of the bellows. in the space of one hour the lead alloy is melted; and when this has been done, he places four sticks of wood, twelve feet long, through the hole in the back of the dome, and as many through the channel; these sticks, lest they should damage the crucible, are both weighted on the ends and supported by trestles; these trestles are made of a beam, three feet long, two palms and as many digits wide, two palms thick, and have two spreading legs at each end. against the trestle, in front of the channel, there is placed an iron plate, lest the litharge, when it is extracted from the furnace, should splash the smelter's shoes and injure his feet and legs. with an iron shovel or a fork he places the remainder of the cakes through the aperture at the back of the dome on to the sticks of wood already mentioned. the native silver, or silver glance, or grey silver, or ruby silver, or any other sort, when it has been flattened out[ ], and cut up, and heated in an iron crucible, is poured into the molten lead mixed with silver, in order that impurities may be separated. as i have often said, this molten lead mixed with silver is called _stannum_[ ]. [illustration (cupellation furnace): a--furnace. b--sticks of wood. c--litharge. d--plate. e--the foreman when hungry eats butter, that the poison which the crucible exhales may not harm him, for this is a special remedy against that poison.] when the long sticks of wood are burned up at the fore end, the master, with a hammer, drives into them pointed iron bars, four feet long and two digits wide at the front end, and beyond that one and a half digits wide and thick; with these he pushes the sticks of wood forward and the bars then rest on the trestles. there are others who, when they separate metals, put two such sticks of wood into the crucible through the aperture which is between the bellows, as many through the holes at the back, and one through the channel; but in this case a larger number of long sticks of wood is necessary, that is, sixty; in the former case, forty long sticks of wood suffice to carry out the operation. when the lead has been heated for two hours, it is stirred with a hooked bar, that the heat may be increased. if it be difficult to separate the lead from the silver, he throws copper and charcoal dust into the molten silver-lead alloy. if the alloy of argentiferous gold and lead, or the silver-lead alloy, contains impurities from the ore, then he throws in either equal portions of argol and venetian glass or of sal-ammoniac, or of venetian glass and of venetian soap; or else unequal portions, that is, two of argol and one of iron rust; there are some who mix a little saltpetre with each compound. to one _centumpondium_ of the alloy is added a _bes_ or a _libra_ and a third of the powder, according to whether it is more or less impure. the powder certainly separates the impurities from the alloy. then, with a kind of rabble he draws out through the channel, mixed with charcoal, the scum, as one might say, of the lead; the lead makes this scum when it becomes hot, but that less of it may be made it must be stirred frequently with the bar. within the space of a quarter of an hour the crucible absorbs the lead; at the time when it penetrates into the crucible it leaps and bubbles. then the master takes out a little lead with an iron ladle, which he assays, in order to find what proportion of silver there is in the whole of the alloy; the ladle is five digits wide, the iron part of its handle is three feet long and the wooden part the same. afterward, when they are heated, he extracts with a bar the litharge which comes from the lead and the copper, if there be any of it in the alloy. wherefore, it might more rightly be called _spuma_ of lead than of silver[ ]. there is no injury to the silver, when the lead and copper are separated from it. in truth the lead becomes much purer in the crucible of the other furnace, in which silver is refined. in ancient times, as the author pliny[ ] relates, there was under the channel of the crucible another crucible, and the litharge flowed down from the upper one into the lower one, out of which it was lifted up and rolled round with a stick in order that it might be of moderate weight. for which reason, they formerly made it into small tubes or pipes, but now, since it is not rolled round a stick, they make it into bars. if there be any danger that the alloy might flow out with the litharge, the foreman keeps on hand a piece of lute, shaped like a cylinder and pointed at both ends; fastening this to a hooked bar he opposes it to the alloy so that it will not flow out. [illustration (cleansing of silver cakes): a--cake. b--stone. c--hammer. d--brass wire. e--bucket containing water. f--furnace from which the cake has been taken, which is still smoking. g--labourer carrying a cake out of the works.] now when the colour begins to show in the silver, bright spots appear, some of them being almost white, and a moment afterward it becomes absolutely white. then the assistant lets down the water-gates, so that, the race being closed, the water-wheel ceases to turn and the bellows are still. then the master pours several buckets of water on to the silver to cool it; others pour beer over it to make it whiter, but this is of no importance since the silver has yet to be refined. afterward, the cake of silver is raised with the pointed iron bar, which is three feet long and two digits wide, and has a wooden handle four feet long fixed in its socket. when the cake of silver has been taken from the crucible, it is laid upon a stone, and from part of it the hearth-lead, and from the other part the litharge, is chipped away with a hammer; then it is cleansed with a bundle of brass wire dipped in water. when the lead is separated from the silver, more silver is frequently found than when it was assayed; for instance, if before there were three _unciae_ and as many _drachmae_ in a _centumpondium_, they now sometimes find three _unciae_ and a half[ ]. often the hearth-lead remaining in the crucible is a palm deep; it is taken out with the rest of the ashes and is sifted, and that which remains in the sieve, since it is hearth-lead, is added to the hearth-lead[ ]. the ashes which pass through the sieve are of the same use as they were at first, for, indeed, from these and pulverised bones they make the cupels. finally, when much of it has accumulated, the yellow _pompholyx_ adhering to the walls of the furnace, and likewise to those rings of the dome near the apertures, is cleared away. [illustration (crane for cupellation furnace): a--crane-post. b--socket. c--oak cross-sills. d--band. e--roof-beam. f--frame. g--lower small cross-beam. h--upright timber. i--bars which come from the sides of the crane-post. k--bars which come from the sides of the upright timber. l--rundle drums. m--toothed wheels. n--chain. o--pulley. p--beams of the crane-arm. q--oblique beams supporting the beams of the crane-arm. r--rectangular iron plates. s--trolley. t--dome of the furnace. v--ring. x--three chains. y--crank. z--the crane-post of the other contrivance. aa--crane-arm. bb--oblique beam. cc--ring of the crane-arm. dd--the second ring. ee--lever-bar. ff--third ring. gg--hook. hh--chain of the dome. ii--chain of the lever-bar.] i must also describe the crane with which the dome is raised. when it is made, there is first set up a rectangular upright post twelve feet long, each side of which measures a foot in width. its lower pinion turns in a bronze socket set in an oak sill; there are two sills placed crosswise so that the one fits in a mortise in the middle of the other, and the other likewise fits in the mortise of the first, thus making a kind of a cross; these sills are three feet long and one foot wide and thick. the crane-post is round at its upper end and is cut down to a depth of three palms, and turns in a band fastened at each end to a roof-beam, from which springs the inclined chimney wall. to the crane-post is affixed a frame, which is made in this way: first, at a height of a cubit from the bottom, is mortised into the crane-post a small cross-beam, a cubit and three digits long, except its tenons, and two palms in width and thickness. then again, at a height of five feet above it, is another small cross-beam of equal length, width, and thickness, mortised into the crane-post. the other ends of these two small cross-beams are mortised into an upright timber, six feet three palms long, and three-quarters wide and thick; the mortise is transfixed by wooden pegs. above, at a height of three palms from the lower small cross-beam, are two bars, one foot one palm long, not including the tenons, a palm three digits wide, and a palm thick, which are mortised in the other sides of the crane-post. in the same manner, under the upper small cross-beam are two bars of the same size. also in the upright timber there are mortised the same number of bars, of the same length as the preceding, but three digits thick, a palm two digits wide, the two lower ones being above the lower small cross-beam. from the upright timber near the upper small cross-beam, which at its other end is mortised into the crane-post, are two mortised bars. on the outside of this frame, boards are fixed to the small cross-beams, but the front and back parts of the frame have doors, whose hinges are fastened to the boards which are fixed to the bars that are mortised to the sides of the crane-post. then boards are laid upon the lower small cross-beam, and at a height of two palms above these there is a small square iron axle, the sides of which are two digits wide; both ends of it are round and turn in bronze or iron bearings, one of these bearings being fastened in the crane-post, the other in the upright timber. about each end of the small axle is a wooden disc, of three palms and a digit radius and one palm thick, covered on the rim with an iron band; these two discs are distant two palms and as many digits from each other, and are joined with five rundles; these rundles are two and a half digits thick and are placed three digits apart. thus a drum is made, which is a palm and a digit distant from the upright timber, but further from the crane-post, namely, a palm and three digits. at a height of a foot and a palm above this little axle is a second small square iron axle, the thickness of which is three digits; this one, like the first one, turns in bronze or iron bearings. around it is a toothed wheel, composed of two discs a foot three palms in diameter, a palm and two digits thick; on the rim of this there are twenty-three teeth, a palm wide and two digits thick; they protrude a palm from the wheel and are three digits apart. and around this same axle, at a distance of two palms and as many digits toward the upright timber, is another disc of the same diameter as the wheel and a palm thick; this turns in a hollowed-out place in the upright timber. between this disc and the disc of the toothed wheel another drum is made, having likewise five rundles. there is, in addition to this second axle, at a height of a cubit above it, a small wooden axle, the journals of which are of iron; the ends are bound round with iron rings so that the journals may remain firmly fixed, and the journals, like the little iron axles, turn in bronze or iron bearings. this third axle is at a distance of about a cubit from the upper small cross-beam; it has, near the upright timber, a toothed wheel two and a half feet in diameter, on the rim of which are twenty-seven teeth; the other part of this axle, near the crane-post, is covered with iron plates, lest it should be worn away by the chain which winds around it. the end link of the chain is fixed in an iron pin driven into the little axle; this chain passes out of the frame and turns over a little pulley set between the beams of the crane-arm. above the frame, at a height of a foot and a palm, is the crane-arm. this consists of two beams fifteen feet long, three palms wide, and two thick, mortised into the crane-post, and they protrude a cubit from the back of the crane-post and are fastened together. moreover, they are fastened by means of a wooden pin which penetrates through them and the crane-post; this pin has at the one end a broad head, and at the other a hole, through which is driven an iron bolt, so that the beams may be tightly bound into the crane-post. the beams of the crane-arm are supported and stayed by means of two oblique beams, six feet and two palms long, and likewise two palms wide and thick; these are mortised into the crane-post at their lower ends, and their upper ends are mortised into the beams of the crane-arm at a point about four feet from the crane-post, and they are fastened with iron nails. at the back of the upper end of these oblique beams, toward the crane-post, is an iron staple, fastened into the lower sides of the beams of the crane-arm, in order that it may hold them fast and bind them. the outer end of each beam of the crane-arm is set in a rectangular iron plate, and between these are three rectangular iron plates, fixed in such a manner that the beams of the crane-arm can neither move away from, nor toward, each other. the upper sides of these crane-arm beams are covered with iron plates for a length of six feet, so that a trolley can move on it. the body of the trolley is made of wood from the ostrya or any other hard tree, and is a cubit long, a foot wide, and three palms thick; on both edges of it the lower side is cut out to a height and width of a palm, so that the remainder may move backward and forward between the two beams of the crane-arm; at the front, in the middle part, it is cut out to a width of two palms and as many digits, that a bronze pulley, around a small iron axle, may turn in it. near the corners of the trolley are four holes, in which as many small wheels travel on the beams of the crane-arm. since this trolley, when it travels backward and forward, gives out a sound somewhat similar to the barking of a dog, we have given it this name[ ]. it is propelled forward by means of a crank, and is drawn back by means of a chain. there is an iron hook whose ring turns round an iron pin fastened to the right side of the trolley, which hook is held by a sort of clavis, which is fixed in the right beam of the crane-arm. at the end of the crane-post is a bronze pulley, the iron axle of which is fastened in the beams of the crane-arm, and over which the chain passes as it comes from the frame, and then, penetrating through the hollow in the top of the trolley, it reaches to the little bronze pulley of the trolley, and passing over this it hangs down. a hook on its end engages a ring, in which are fixed the top links of three chains, each six feet long, which pass through the three iron rings fastened in the holes of the claves which are fixed into the middle iron band of the dome, of which i have spoken. therefore when the master wishes to lift the dome by means of the crane, the assistant fits over the lower small iron axle an iron crank, which projects from the upright beam a palm and two digits; the end of the little axle is rectangular, and one and a half digits wide and one digit thick; it is set into a similar rectangular hole in the crank, which is two digits long and a little more than a digit wide. the crank is semi-circular, and one foot three palms and two digits long, as many digits wide, and one digit thick. its handle is straight and round, and three palms long, and one and a half digits thick. there is a hole in the end of the little axle, through which an iron pin is driven so that the crank may not come off. the crane having four drums, two of which are rundle-drums and two toothed-wheels, is more easily moved than another having two drums, one of which has rundles and the other teeth. many, however, use only a simple contrivance, the pivots of whose crane-post turn in the same manner, the one in an iron socket, the other in a ring. there is a crane-arm on the crane-post, which is supported by an oblique beam; to the head of the crane-arm a strong iron ring is fixed, which engages a second iron ring. in this iron ring a strong wooden lever-bar is fastened firmly, the head of which is bound by a third iron ring, from which hangs an iron hook, which engages the rings at the ends of the chains from the dome. at the other end of the lever-bar is another chain, which, when it is pulled down, raises the opposite end of the bar and thus the dome; and when it is relaxed the dome is lowered. [illustration (cupellation furnace at freiberg): a--chamber of the furnace. b--its bed. c--passages. d--rammer. e--mallet. f--artificer making tubes from litharge according to the roman method. g--channel. h--litharge. i--lower crucible or hearth. k--stick. l--tubes.] in certain places, as at freiberg in meissen, the upper part of the cupellation furnace is vaulted almost like an oven. this chamber is four feet high and has either two or three apertures, of which the first, in front, is one and a half feet high and a foot wide, and out of this flows the litharge; the second aperture and likewise the third, if there be three, are at the sides, and are a foot and a half high and two and a half feet wide, in order that he who prepares the crucible may be able to creep into the furnace. its circular bed is made of cement, it has two passages two feet high and one foot wide, for letting out the vapour, and these lead directly through from one side to the other, so that the one passage crosses the other at right angles, and thus four openings are to be seen; these are covered at the top by rocks, wide, but only a palm thick. on these and on the other parts of the interior of the bed made of cement, is placed lute mixed with straw, to a depth of three digits, as it was placed over the sole and the plates of copper and the rocks of that other furnace. this, together with the ashes which are thrown in, the master or the assistant, who, upon his knees, prepares the crucible, tamps down with short wooden rammers and with mallets likewise made of wood. [illustration (cupellation furnace in poland): a--furnace similar to an oven. b--passage. c--iron bars. d--hole through which the litharge is drawn out. e--crucible which lacks a dome. f--thick sticks. g--bellows.] the cupellation furnace in poland and hungary is likewise vaulted at the top, and is almost similar to an oven, but in the lower part the bed is solid, and there is no opening for the vapours, while on one side of the crucible is a wall, between which and the bed of the crucible is a passage in place of the opening for vapours; this passage is covered by iron bars or rods extending from the wall to the crucible, and placed a distance of two digits from each other. in the crucible, when it is prepared, they first scatter straw, and then they lay in it cakes of silver-lead alloy, and on the iron bars they lay wood, which when kindled heats the crucible. they melt cakes to the weight of sometimes eighty _centumpondia_ and sometimes a hundred _centumpondia_[ ]. they stimulate a mild fire by means of a blast from the bellows, and throw on to the bars as much wood as is required to make a flame which will reach into the crucible, and separate the lead from the silver. the litharge is drawn out on the other side through an aperture that is just wide enough for the master to creep through into the crucible. the moravians and carni, who very rarely make more than a _bes_ or five-sixths of a _libra_ of silver, separate the lead from it, neither in a furnace resembling an oven, nor in the crucible covered by a dome, but on a crucible which is without a cover and exposed to the wind; on this crucible they lay cakes of silver-lead alloy, and over them they place dry wood, and over these again thick green wood. the wood having been kindled, they stimulate the fire by means of a bellows. [illustration (refining silver): a--pestle with teeth. b--pestle without teeth. c--dish or tray full of ashes. d--prepared tests placed on boards or shelves. e--empty tests. f--wood. g--saw.] [illustration (refining silver): a--straight knife having wooden handles. b--curved knife likewise having wooden handles. c--curved knife without wooden handles. d--sieve. e--balls. f--iron door which the master lets down when he refines silver, lest the heat of the fire should injure his eyes. g--iron implement on which the wood is placed when the liquid silver is to be refined. h--its other part passing through the ring of another iron implement enclosed in the wall of the furnace. i--tests in which burning charcoal has been thrown.] i have explained the method of separating lead from gold or silver. now i will speak of the method of refining silver, for i have already explained the process for refining gold. silver is refined in a refining furnace, over whose hearth is an arched chamber built of bricks; this chamber in the front part is three feet high. the hearth itself is five feet long and four wide. the walls are unbroken along the sides and back, but in front one chamber is placed over the other, and above these and the wall is the upright chimney. the hearth has a round pit, a cubit wide and two palms deep, into which are thrown sifted ashes, and in this is placed a prepared earthenware "test," in such a manner that it is surrounded on all sides by ashes to a height equal to its own. the earthenware test is filled with a powder consisting of equal portions of bones ground to powder, and of ashes taken from the crucible in which lead is separated from gold or silver; others mix crushed brick with the ashes, for by this method the powder attracts no silver to itself. when the powder has been made up and moistened with water, a little is thrown into the earthenware test and tamped with a wooden pestle. this pestle is round, a foot long, and a palm and a digit wide, out of which extend six teeth, each a digit thick, and a digit and a third long and wide, and almost a digit apart; these six teeth form a circle, and in the centre of them is the seventh tooth, which is round and of the same length as the others, but a digit and a half thick; this pestle tapers a little from the bottom up, that the upper part of the handle may be round and three digits thick. some use a round pestle without teeth. then a little powder is again moistened, and thrown into the test, and tamped; this work is repeated until the test is entirely full of the powder, which the master then cuts out with a knife, sharp on both sides, and turned upward at both ends so that the central part is a palm and a digit long; therefore it is partly straight and partly curved. the blade is one and a half digits wide, and at each end it turns upward two palms, which ends to the depth of a palm are either not sharpened or they are enclosed in wooden handles. the master holds the knife with one hand and cuts out the powder from the test, so that it is left three digits thick all round; then he sifts the powder of dried bones over it through a sieve, the bottom of which is made of closely-woven bristles. afterward a ball made of very hard wood, six digits in diameter, is placed in the test and rolled about with both hands, in order to make the inside even and smooth; for that matter he may move the ball about with only one hand. the tests[ ] are of various capacities, for some of them when prepared hold much less than fifteen _librae_ of silver, others twenty, some thirty, others forty, and others fifty. all these tests thus prepared are dried in the sun, or set in a warm and covered place; the more dry and old they are the better. all of them, when used for refining silver, are heated by means of burning charcoal placed in them. others use instead of these tests an iron ring; but the test is more useful, for if the powder deteriorates the silver remains in it, while there being no bottom to the ring, it falls out; besides, it is easier to place in the hearth the test than the iron ring, and furthermore it requires much less powder. in order that the test should not break and damage the silver, some bind it round with an iron band. [illustration (refining silver): a--grate. b--brass block. c--block of wood. d--cakes of silver. e--hammer. f--block of wood channelled in the middle. g--bowl full of holes. h--block of wood fastened to an iron implement. i--fir-wood. k--iron bar. l--implement with a hollow end. the implement which has a circular end is shown in the next picture. m--implement, the extremity of which is bent upwards. n--implement in the shape of tongs.] in order that they may be more easily broken, the silver cakes are placed upon an iron grate by the refiner, and are heated by burning charcoal placed under them. he has a brass block two palms and two digits long and wide, with a channel in the middle, which he places upon a block of hard wood. then with a double-headed hammer, he beats the hot cakes of silver placed on the brass block, and breaks them in pieces. the head of this hammer is a foot and two digits long, and a palm wide. others use for this purpose merely a block of wood channelled in the top. while the fragments of the cake are still hot, he seizes them with the tongs and throws them into a bowl with holes in the bottom, and pours water over them. when the fragments are cooled, he puts them nicely into the test by placing them so that they stand upright and project from the test to a height of two palms, and lest one should fall against the other, he places little pieces of charcoal between them; then he places live charcoal in the test, and soon two twig basketsful of charcoal. then he blows in air with the bellows. this bellows is double, and four feet two palms long, and two feet and as many palms wide at the back; the other parts are similar to those described in book vii. the nozzle of the bellows is placed in a bronze pipe a foot long, the aperture in this pipe being a digit in diameter in front and quite round, and at the back two palms wide. the master, because he needs for the operation of refining silver a fierce fire, and requires on that account a vigorous blast, places the bellows very much inclined, in order that, when the silver has melted, it may blow into the centre of the test. when the silver bubbles, he presses the nozzle down by means of a small block of wood moistened with water and fastened to an iron rod, the outer end of which bends upward. the silver melts when it has been heated in the test for about an hour; when it is melted, he removes the live coals from the test and places over it two billets of fir-wood, a foot and three palms long, a palm two digits wide, one palm thick at the upper part, and three digits at the lower. he joins them together at the lower edges, and into the billets he again throws the coals, for a fierce fire is always necessary in refining silver. it is refined in two or three hours, according to whether it was pure or impure, and if it is impure it is made purer by dropping granulated copper or lead into the test at the same time. in order that the refiner may sustain the great heat from the fire while the silver is being refined, he lets down an iron door, which is three feet long and a foot and three palms high; this door is held on both ends in iron plates, and when the operation is concluded, he raises it again with an iron shovel, so that its edge holds against the iron hook in the arch, and thus the door is held open. when the silver is nearly refined, which may be judged by the space of time, he dips into it an iron bar, three and a half feet long and a digit thick, having a round steel point. the small drops of silver that adhere to the bar he places on the brass block and flattens with a hammer, and from their colour he decides whether the silver is sufficiently refined or not. if it is thoroughly purified it is very white, and in a _bes_ there is only a _drachma_ of impurities. some ladle up the silver with a hollow iron implement. of each _bes_ of silver one _sicilicus_ is consumed, or occasionally when very impure, three _drachmae_ or half an _uncia_[ ]. [illustration (cleansing of silver cakes): a--implement with a ring. b--ladle. c--its hole. d--pointed bar. e--forks. f--cake of silver laid upon the implement shaped like tongs. g--tub of water. h--block of wood, with a cake laid upon it. i--hammer. k--silver again placed upon the implement resembling tongs. l--another tub full of water. m--brass wires. n--tripod. o--another block. p--chisel. q--crucible of the furnace. r--test still smoking.] the refiner governs the fire and stirs the molten silver with an iron implement, nine feet long, a digit thick, and at the end first curved toward the right, then curved back in order to form a circle, the interior of which is a palm in diameter; others use an iron implement, the end of which is bent directly upward. another iron implement has the shape of tongs, with which, by compressing it with his hands, he seizes the coals and puts them on or takes them off; this is two feet long, one and a half digits wide, and the third of a digit thick. when the silver is seen to be thoroughly refined, the artificer removes the coals from the test with a shovel. soon afterward he draws water in a copper ladle, which has a wooden handle four feet long; it has a small hole at a point half-way between the middle of the bowl and the edge, through which a hemp seed just passes. he fills this ladle three times with water, and three times it all flows out through the hole on to the silver, and slowly quenches it; if he suddenly poured much water on it, it would burst asunder and injure those standing near. the artificer has a pointed iron bar, three feet long, which has a wooden handle as many feet long, and he puts the end of this bar into the test in order to stir it. he also stirs it with a hooked iron bar, of which the hook is two digits wide and a palm deep, and the iron part of its handle is three feet long and the wooden part the same. then he removes the test from the hearth with a shovel or a fork, and turns it over, and by this means the silver falls to the ground in the shape of half a sphere; then lifting the cake with a shovel he throws it into a tub of water, where it gives out a great sound. or else, having lifted the cake of silver with a fork, he lays it upon the iron implement similar to tongs, which are placed across a tub full of water; afterward, when cooled, he takes it from the tub again and lays it on the block made of hard wood and beats it with a hammer, in order to break off any of the powder from the test which adheres to it. the cake is then placed on the implement similar to tongs, laid over the tub full of water, and cleaned with a bundle of brass wire dipped into the water; this operation of beating and cleansing is repeated until it is all clean. afterward he places it on an iron grate or tripod; the tripod is a palm and two digits high, one and a half digits wide, and its span is two palms wide; then he puts burning charcoal under the tripod or grate, in order again to dry the silver that was moistened by the water. finally, the royal inspector[ ] in the employment of the king or prince, or the owner, lays the silver on a block of wood, and with an engraver's chisel he cuts out two small pieces, one from the under and the other from the upper side. these are tested by fire, in order to ascertain whether the silver is thoroughly refined or not, and at what price it should be sold to the merchants. finally he impresses upon it the seal of the king or the prince or the owner, and, near the same, the amount of the weight. [illustration (refining silver): a--muffle. b--its little windows. c--its little bridge. d--bricks. e--iron door. f--its little window. g--bellows. h--hammer-chisel. i--iron ring which some use instead of the test. k--pestle with which the ashes placed in the ring are pounded.] there are some who refine silver in tests placed under iron or earthenware muffles. they use a furnace, on the hearth of which they place the test containing the fragments of silver, and they place the muffle over it; the muffle has small windows at the sides, and in front a little bridge. in order to melt the silver, at the sides of the muffle are laid bricks, upon which the charcoal is placed, and burning firebrands are put on the bridge. the furnace has an iron door, which is covered on the side next to the fire with lute in order that it may not be injured. when the door is closed it retains the heat of the fire, but it has a small window, so that the artificers may look into the test and may at times stimulate the fire with the bellows. although by this method silver is refined more slowly than by the other, nevertheless it is more useful, because less loss is caused, for a gentle fire consumes fewer particles than a fierce fire continually excited by the blast of the bellows. if, on account of its great size, the cake of silver can be carried only with difficulty when it is taken out of the muffle, they cut it up into two or three pieces while it is still hot, with a wedge or a hammer-chisel; for if they cut it up after it has cooled, little pieces of it frequently fly off and are lost. end of book x. footnotes: [ ] _vile a precioso_. [ ] the reagents mentioned in this book are much the same as those of book vii, where (p. ) a table is given showing the latin and old german terms. footnotes in explanation of our views as to these substances may be most easily consulted through the index. [ ] _aqua valens_, literally strong, potent, or powerful water. it will appear later, from the method of manufacture, that hydrochloric, nitric, and sulphuric acids and _aqua regia_ were more or less all produced and all included in this term. we have, therefore, used either the term _aqua valens_ or simply _aqua_ as it occurs in the text. the terms _aqua fortis_ and _aqua regia_ had come into use prior to agricola, but he does not use them; the alchemists used various terms, often _aqua dissolvia_. it is apparent from the uses to which this reagent was put in separating gold and silver, from the method of clarifying it with silver and from the red fumes, that agricola could have had practical contact only with nitric acid. it is probable that he has copied part of the recipes for the compounds to be distilled from the alchemists and from such works as the _probierbüchlein_. in any event he could not have had experience with them all, for in some cases the necessary ingredients for making nitric acid are not all present, and therefore could be of no use for gold and silver separation. the essential ingredients for the production of this acid by distillation, were saltpetre, water, and either vitriol or alum. the other substances mentioned were unnecessary, and any speculation as to the combinations which would result, forms a useful exercise in chemistry, but of little purpose here. the first recipe would no doubt produce hydrochloric acid. [ ] agricola, in the _interpretatio_, gives the german equivalent for the latin _aerugo_ as _spanschgrün_--"because it was first brought to germany from spain; foreigners call it _viride aeris_ (copper green)." the english "verdigris" is a corruption of _vert de grice_. both verdigris and white lead were very ancient products, and they naturally find mention together among the ancient authors. the earliest description of the method of making is from the rd century b.c., by theophrastus, who says ( - ): "but these are works of art, as is also ceruse (_psimythion_) to make which, lead is placed in earthen vessels over sharp vinegar, and after it has acquired some thickness of a kind of rust, which it commonly does in about ten days, they open the vessels and scrape off, as it were, a kind of foulness; they then place the lead over the vinegar again, repeating over and over again the same method of scraping it till it is wholly dissolved; what has been scraped off they then beat to powder and boil for a long time; and what at last subsides to the bottom of the vessel is the white lead.... also in a manner somewhat resembling this, verdigris (_ios_) is made, for copper is placed over lees of wine (grape refuse?), and the rust which it acquires by this means is taken off for use. and it is by this means that the rust which appears is produced." (based on hill's translation.) vitruvius (vii, ), dioscorides (v, ), and pliny (xxxiv, and ), all describe the method of making somewhat more elaborately. [ ] _amiantus_ (_interpretatio_ gives _federwis_, _pliant_, _salamanderhar_). from agricola's elaborate description in _de natura fossilium_ (p. ) there can be no doubt that he means asbestos. this mineral was well-known to the ancients, and is probably earliest referred to ( rd century b.c.) by theophrastus in the following passage ( ): "there is also found in the mines of scaptesylae a stone, in its external appearance somewhat resembling wood, on which, if oil be poured, it burns; but when the oil is burnt away, the burning of the stone ceases, as if it were in itself not liable to such accidents." there can be no doubt that strabo (x, ) describes the mineral: "at carystus there is found in the earth a stone, which is combed like wool, and woven, so that napkins are made of this substance, which, when soiled, are thrown into the fire and cleaned, as in the washing of linen." it is also described by dioscorides (v, ) and pliny (xix, ). asbestos cloth has been found in pre-augustinian roman tombs. [ ] this list of four recipes is even more obscure than the previous list. if they were distilled, the first and second mixtures would not produce nitric acid, although possibly some sulphuric would result. the third might yield nitric, and the fourth _aqua regia_. in view of the water, they were certainly not used as cements, and the first and second are deficient in the vital ingredients. [ ] _distillation_, at least in crude form, is very old. aristotle (_meteorologica_, iv.) states that sweet water can be made by evaporating salt-water and condensing the steam. dioscorides and pliny both describe the production of mercury by distillation (note , p. ). the alchemists of the alexandrian school, from the st to the th centuries, mention forms of imperfect apparatus--an ample discussion of which may be found in kopp, _beiträge zur geschichte der chemie_, braunschweig, , p. . [ ] it is desirable to note the contents of the residues in the retort, for it is our belief that these are the materials to which the author refers as "lees of the water which separates gold from silver," in many places in book vii. they would be strange mixtures of sodium, potassium, aluminium sulphates, with silica, brickdust, asbestos, and various proportions of undigested vitriol, salt, saltpetre, alum, iron oxides, etc. their effect must have been uncertain. many old german metallurgies also refer to the _todenkopf der scheidwasser_, among them the _probierbüchlein_ before agricola, and after him lazarus ercker (_beschreibung allerfürnemsten_, etc., prague, ). see also note , p. . [ ] this use of silver could apply to one purpose only, that is, the elimination of minor amounts of hydrochloric from the nitric acid, the former originating no doubt from the use of salt among the ingredients. the silver was thus converted into a chloride and precipitated. this use of a small amount of silver to purify the nitric acid was made by metallurgists down to fairly recent times. biringuccio (iv, ) and lazarus ercker (p. ) both recommend that the silver be dissolved first in a small amount of acid, and the solution poured into the newly-manufactured supply. they both recommend preserving this precipitate and its cupellation after melting with lead--which agricola apparently overlooked. [ ] in this description of parting by nitric acid, the author digresses from his main theme on pages and , to explain a method apparently for small quantities where the silver was precipitated by copper, and to describe another cryptic method of precipitation. these subjects are referred to in notes and below. the method of parting set out here falls into six stages: _a_--cupellation, _b_--granulation, _c_--solution in acid, _d_--treatment of the gold residues, _e_--evaporation of the solution, _f_--reduction of the silver nitrate. for nitric acid parting, bullion must be free from impurities, which cupellation would ensure; if copper were left in, it would have the effect he mentions if we understand "the silver separated from the gold soon unites with it again," to mean that the silver unites with the copper, for the copper would go into solution and come down with the silver on evaporation. agricola does not specifically mention the necessity of an excess of silver in this description, although he does so elsewhere, and states that the ratio must be at least three parts silver to one part gold. the first description of the solution of the silver is clear enough, but that on p. is somewhat difficult to follow, for the author states that the bullion is placed in a retort with the acid, and that distillation is carried on between each additional charge of acid. so far as the arrangement of a receiver might relate to the saving of any acid that came over accidentally in the boiling, it can be understood, but to distill off much acid would soon result in the crystallization of the silver nitrate, which would greatly impede the action of subsequent acid additions, and finally the gold could not be separated from such nitrate in the way described. the explanation may be (apart from incidental evaporation when heating) that the acids used were very weak, and that by the evaporation of a certain amount of water, not only was the acid concentrated, but room was provided for the further charges. the acid in the gold wash-water, mentioned in the following paragraph, was apparently thus concentrated. the "glass" mentioned as being melted with litharge, argols, nitre, etc., was no doubt the silver nitrate. the precipitation of the silver from the solution as a chloride, by the use of salt, so generally used during the th and th centuries, was known in agricola's time, although he does not mention it. it is mentioned in geber and the _probierbüchlein_. the clarity of the latter on the subject is of some interest (p. a): "how to pulverise silver and again make it into silver. take the silver and dissolve it in water with the _starckenwasser_, _aqua fort_, and when that is done, take the silver water and pour it into warm salty water, and immediately the silver settles to the bottom and becomes powder. let it stand awhile until it has well settled, then pour away the water from it and dry the settlings, which will become a powder like ashes. afterward one can again make it into silver. take the powder and put it on a _test_, and add thereto the powder from the settlings from which the _aqua forte_ has been made, and add lead. then if there is a great deal, blow on it until the lead has incorporated itself ... blow it until it _plickt_ (_blickens_). then you will have as much silver as before." [ ] the silver is apparently precipitated by the copper of the bowl. it would seem that this method was in considerable use for small amounts of silver nitrate in the th century. lazarus ercker gives elaborate directions for this method (_beschreibung allerfürnemsten_, etc., prague, , p. ). [ ] we confess to a lack of understanding of this operation with leaves of lead and copper. [ ] we do not understand this "appearance of black." if the nitrate came into contact with organic matter it would, of course, turn black by reduction of the silver, and sunlight would have the same effect. [ ] this would be equal to from to parts of copper in , . [ ] as _siliquae_ are _uncia_, then / _siliqua_ in _unciae_ would equal one part silver in , parts gold, or about . fine. [ ] the object of this treatment with sulphur and copper is to separate a considerable portion of silver from low-grade bullion (_i.e._, silver containing some gold), in preparation for final treatment of the richer gold-silver alloy with nitric acid. silver sulphide is created by adding sulphur, and is drawn off in a silver-copper regulus. after the first sentence, the author uses silver alone where he obviously means silver "containing some gold," and further he speaks of the "gold lump" (_massula_) where he likewise means a button containing a great deal of silver. for clarity we introduced the term "regulus" for the latin _mistura_. the operation falls into six stages: _a_, granulation; _b_, sulphurization of the granulated bullion; _c_, melting to form a combination of the silver sulphide with copper into a regulus, an alloy of gold and silver settling out; _d_, repetition of the treatment to abstract further silver from the "lump;" _e_, refining the "lump" with nitric acid; _f_, recovery of the silver from the regulus by addition of lead, liquation and cupellation. the use of a "circle of fire" secures a low temperature that would neither volatilize the sulphur nor melt the bullion. the amount of sulphur given is equal to a ratio of parts bullion and parts sulphur. we are not certain about the translation of the paragraph in relation to the proportion of copper added to the granulated bullion; because in giving definite quantities of copper to be added in the contingencies of various original copper contents in the bullion, it would be expected that they were intended to produce some positive ratio of copper and silver. however, the ratio as we understand the text in various cases works out to irregular amounts, _i.e._, parts of silver to , . , , . , . , . , or parts of copper. in order to obtain complete separation there should be sufficient sulphur to have formed a sulphide of the copper as well as of the silver, or else some of the copper and silver would come down metallic with the "lump". the above ratio of copper added to the sulphurized silver, in the first instance would give about parts of copper and parts of sulphur to parts of silver. the copper would require . parts of sulphur to convert it into sulphide, and the silver about parts, or a total of . parts required against parts furnished. it is plain, therefore, that insufficient sulphur is given. further, the litharge would probably take up some sulphur and throw down metallic lead into the "lump". however, it is necessary that there should be some free metallics to collect the gold, and, therefore, the separation could not be complete in one operation. in any event, on the above ratios the "gold lump" from the first operation was pretty coppery, and contained some lead and probably a good deal of silver, because the copper would tend to desulphurize the latter. the "powder" of glass-galls, salt, and litharge would render the mass more liquid and assist the "gold lump" to separate out. the roman silver _sesterce_, worth about - / pence or . american cents, was no doubt used by agricola merely to indicate an infinitesimal quantity. the test to be applied to the regulus by way of cupellation and parting of a sample with nitric acid, requires no explanation. the truth of the description as to determining whether the gold had settled out, by using a chalked iron rod, can only be tested by actual experiment. it is probable, however, that the sulphur in the regulus would attack the iron and make it black. the re-melting of the regulus, if some gold remains in it, with copper and "powder" without more sulphur, would provide again free metallics to gather the remaining gold, and by desulphurizing some silver this button would probably not be very pure. from the necessity for some free metallics besides the gold in the first treatment, it will be seen that a repetition of the sulphur addition and re-melting is essential gradually to enrich the "lump". why more copper is added is not clear. in the second melting, the ratio is parts of the "gold lump", parts of sulphur and parts copper. in this case the added copper would require about parts sulphur, and if we consider the deficiency of sulphur in the first operations pertained entirely to the copper, then about . parts would be required to make good the shortage, or in other words the second addition of sulphur is sufficient. in the final parting of the "lump" it will be noticed that the author states that the silver ratio must be arranged as three of silver to one of gold. as to the recovery of the silver from the regulus, he states that _librae_ of silver give _librae_ of _regulus_. to this, _librae_ of lead are added, and it is melted in the "second" furnace, and the litharge and hearth-lead made are re-melted in the "first" furnace, the cakes made being again treated in the "third" furnace to separate the copper and lead. the "first" is usually the blast furnace, the "second" furnace is the cupellation furnace, and the "third" the liquation furnace. it is difficult to understand this procedure. the charge sent to the cupellation furnace would contain between % and % copper, and between % and % sulphur. however, possibly the sulphur and copper could be largely abstracted in the skimmings from the cupellation furnace, these being subsequently liquated in the "third" furnace. it may be noted that two whole lines from this paragraph are omitted in the editions of _de re metallica_ after . for historical note on sulphur separation see page . [ ] there can be no doubt that in most instances agricola's _stibium_ is antimony sulphide, but it does not follow that it was the mineral _stibnite_, nor have we considered it desirable to introduce the precision of either of these modern terms, and have therefore retained the latin term where the sulphide is apparently intended. the use of antimony sulphide to part silver from gold is based upon the greater affinity of silver than antimony for sulphur. thus the silver, as in the last process, is converted into a sulphide, and is absorbed in the regulus, while the metallic antimony alloys with the gold and settles to the bottom of the pot. this process has several advantages over the sulphurization with crude sulphur; antimony is a more convenient vehicle of sulphur, for it saves the preliminary sulphurization with its attendant difficulties of volatilization of the sulphur; it also saves the granulation necessary in the former method; and the treatment of the subsequent products is simpler. however, it is possible that the sulphur-copper process was better adapted to bullion where the proportion of gold was low, because the fineness of the bullion mentioned in connection with the antimonial process was apparently much higher than the previous process. for instance, a _bes_ of gold, containing , , or double _sextulae_ of silver would be . , . or . fine. the antimonial method would have an advantage over nitric acid separation, in that high-grade bullion could be treated direct without artificial decrease of fineness required by inquartation to about . fine, with the consequent incidental losses of silver involved. the process in this description falls into six operations: _a_, sulphurization of the silver by melting with antimony sulphide; _b_, separation of the gold "lump" (_massula_) by jogging; _c_, re-melting the regulus (_mistura_) three or four times for recovery of further "lumps"; _d_, re-melting of the "lump" four times, with further additions of antimony sulphide; _e_, cupellation of the regulus to recover the silver; _f_, cupellation of the antimony from the "lump" to recover the gold. percy seems to think it difficult to understand the insistence upon the addition of copper. biringuccio (iv, ) states, among other things, that copper makes the ingredients more liquid. the later metallurgists, however, such as ercker, lohneys, and schlüter, do not mention this addition; they do mention the "swelling and frothing," and recommend that the crucible should be only partly filled. as to the copper, we suggest that it would desulphurize part of the antimony and thus free some of that metal to collect the gold. if we assume bullion of the medium fineness mentioned and containing no copper, then the proportions in the first charge would be about parts gold, parts silver, parts sulphur, parts antimony, and parts copper. the silver and copper would take up . parts of sulphur, and thus free about . parts of antimony as metallics. it would thus appear that the amount of metallics provided to assist the collection of the gold was little enough, and that the copper in freeing . parts of the antimony was useful. it appears to have been necessary to have a large excess of antimony sulphide; for even with the great surplus in the first charge, the reaction was only partial, as is indicated by the necessity for repeated melting with further antimony. the later metallurgists all describe the separation of the metallic antimony from the gold as being carried out by oxidation of the antimony, induced by a jet of air into the crucible, this being continued until the mass appears limpid and no cloud forms in the surface in cooling. agricola describes the separation of the silver from the regulus by preliminary melting with argols, glass-gall, and some lead, and subsequent cupellation of the lead-silver alloy. the statement that unless this preliminary melting is done, the cupel will absorb silver, might be consonant with an attempt at cupellation of sulphides, and it is difficult to see that much desulphurizing could take place with the above fluxes. in fact, in the later descriptions of the process, iron is used in this melting, and we are under the impression that agricola had omitted this item for a desulphurizing reagent. at the dresden mint, in the methods described by percy (metallurgy silver and gold, p. ) the gold lumps were tested for fineness, and from this the amount of gold retained in the regulus was computed. it is not clear from agricola's account whether the test with nitric acid was applied to the regulus or to the "lumps". for historical notes see p. . [ ] as will be shown in the historical note, this process of separating gold and silver is of great antiquity--in all probability the only process known prior to the middle ages, and in any event, the first one used. in general the process was performed by "cementing" the disintegrated bullion with a paste and subjecting the mass to long-continued heat at a temperature under the melting point of the bullion. the cement (_compositio_) is of two different species; in the first species saltpetre and vitriol and some aluminous or silicious medium are the essential ingredients, and through them the silver is converted into nitrate and absorbed by the mass; in the second species, common salt and the same sort of medium are the essentials, and in this case the silver is converted into a chloride. agricola does not distinguish between these two species, for, as shown by the text, his ingredients are badly mixed. the process as here described falls into five operations: _a_, granulation of the bullion or preparation of leaves; _b_, heating alternate layers of cement and bullion in pots; _c_, washing the gold to free it of cement; _d_, melting the gold with borax or soda; _e_, treatment of the cement by way of melting with lead and cupellation to recover the silver. investigation by boussingault (_ann. de chimie_, , p. - ), d'elhuyar (_bergbaukunde_, leipzig, , vol. ii, p. ), and percy (metallurgy of silver and gold, p. ), of the action of common salt upon silver under cementation conditions, fairly well demonstrated the reactions involved in the use of this species of cement. certain factors are essential besides salt: _a_, the admission of air, which is possible through the porous pots used; _b_, the presence of some moisture to furnish hydrogen; _c_, the addition of alumina or silica. the first would be provided by agricola in the use of new pots, the second possibly by use of wood fuel in a closed furnace, the third by the inclusion of brickdust. the alumina or silica at high temperatures decomposes the salt, setting free hydrochloric acid and probably also free chlorine. the result of the addition of vitriol in agricola's ingredients is not discussed by those investigators, but inasmuch as vitriol decomposes into sulphuric acid under high temperatures, this acid would react upon the salt to free hydrochloric acid, and thus assist to overcome deficiencies in the other factors. it is possible also that sulphuric acid under such conditions would react directly upon the silver to form silver sulphates, which would be absorbed into the cement. as nitric acid is formed by vitriol and saltpetre at high temperatures, the use of these two substances as a cementing compound would produce nitric acid, which would at once attack the silver to form silver nitrate, which would be absorbed into the melted cement. in this case the brickdust probably acted merely as a vehicle for the absorption, and to lower the melting point of the mass and prevent fusion of the metal. while nitric acid will only part gold and silver when the latter is in great excess, yet when applied as fumes under cementation conditions it appears to react upon a minor ratio of silver. while the reactions of the two above species of compounds can be accounted for in a general way, the problem furnished by agricola's statements is by no means simple, for only two of his compounds are simply salt cements, the others being salt and nitre mixtures. an inspection of these compounds produces at once a sense of confusion. salt is present in every compound, saltpetre in all but two, vitriol in all but three. lewis (_traité singulier de métallique_, paris, , ii, pp. - ), in discussing these processes, states that salt and saltpetre must never be used together, as he asserts that in this case _aqua regia_ would be formed and the gold dissolved. agricola, however, apparently found no such difficulty. as to the other ingredients, apart from nitre, salt, vitriol, and brickdust, they can have been of no use. agricola himself points out that ingredients of "metallic origin" corrupt the gold and that brickdust and common salt are sufficient. in a description of this process in the _probierbüchlein_ (p. ), no nitre is mentioned. this booklet does mention the recovery of the silver from the cement by amalgamation with mercury--the earliest mention of silver amalgamation. [ ] while a substance which we now know to be natural zinc sulphate was known to agricola (see note , p. ), it is hardly possible that it is referred to here. if green vitriol be dehydrated and powdered, it is white. [ ] the processes involved by these "other" compounds are difficult to understand, because of the lack of information given as to the method of operation. it might be thought that these were five additional recipes for cementing pastes, but an inspection of their internal composition soon dissipates any such assumption, because, apart from the lack of brickdust or some other similar necessary ingredient, they all contain more or less sulphur. after describing a preliminary treatment of the bullion by cupellation, the author says: "then the silver is sprinkled with two _unciae_ of that powdered compound and is stirred. afterward it is poured into another crucible ... and violently shaken. the rest is performed according to the process i have already explained." as he has already explained four or five parting processes, it is not very clear to which one this refers. in fact, the whole of this discussion reads as if he were reporting hearsay, for it lacks in every respect the infinite detail of his usual descriptions. in any event, if the powder was introduced into the molten bullion, the effect would be to form some silver sulphides in a regulus of different composition depending upon the varied ingredients of different compounds. the enriched bullion was settled out in a "lump" and treated "as i have explained," which is not clear. [ ] historical note on parting gold and silver. although the earlier classics contain innumerable references to refining gold and silver, there is little that is tangible in them, upon which to hinge the metallurgy of parting the precious metals. it appears to us, however, that some ability to part the metals is implied in the use of the touchstone, for we fail to see what use a knowledge of the ratio of gold and silver in bullion could have been without the power to separate them. the touchstone was known to the greeks at least as early as the th century b.c. (see note , p. ), and a part of theophrastus' statement (lxxviii.) on this subject bears repetition in this connection: "the nature of the stone which tries gold is also very wonderful, as it seems to have the same power as fire; which is also a test of that metal.... the trial by fire is by the colour and the quantity lost by it, but that of the stone is made only by rubbing," etc. this trial by fire certainly implies a parting of the metals. it has been argued from the common use of _electrum_--a gold-silver alloy--by the ancients, that they did not know how to part the two metals or they would not have wasted gold in such a manner, but it seems to us that the very fact that _electrum_ was a positive alloy ( % gold, % silver), and that it was deliberately made (pliny xxxiii, ) and held of value for its supposed superior brilliancy to silver and the belief that goblets made of it detected poison, is sufficient answer to this. to arrive by a process of elimination, we may say that in the middle ages, between and a.d., there were known four methods of parting these metals: _a_, parting by solution in nitric acid; _b_, sulphurization of the silver in finely-divided bullion by heating it with sulphur, and the subsequent removal of the silver sulphide in a regulus by melting with copper, iron, or lead; _c_, melting with an excess of antimony sulphide, and the direct conversion of the silver to sulphide and its removal in a regulus; _d_, cementation of the finely-divided bullion with salt, and certain necessary collateral re-agents, and the separation of the silver by absorption into the cement as silver chloride. inasmuch as it can be clearly established that mineral acids were unknown to the ancients, we can eliminate that method. further, we may say at once that there is not, so far as has yet been found, even a remote statement that could be applied to the sulphide processes. as to cementation with salt, however, we have some data at about the beginning of the christian era. before entering into a more detailed discussion of the history of various processes, it may be useful, in a word, to fix in the mind of the reader our view of the first authority on various processes, and his period. ( ) separation by cementation with salt, strabo (?) b.c.- a.d.; pliny - a.d. ( ) separation by sulphur, theophilus, - a.d. ( ) separation by nitric acid, geber, prior to th century. ( ) separation by antimony sulphide, basil valentine, end th century, or _probierbüchlein_, beginning th century. ( ) separation by antimony sulphide and copper, or sulphur and copper, _probierbüchlein_, beginning th century. ( ) separation by cementation with saltpetre, agricola, . ( ) separation by sulphur and iron, schlüter, . ( ) separation by sulphuric acid, d'arcet, . ( ) separation by chloride gas, thompson, . ( ) separation electrolytically, latter part th century. parting by cementation. the following passage from strabo is of prime interest as the first definite statement on parting of any kind (iii, , ): "that when they have melted the gold and purified it by means of a kind of aluminous earth, the residue left is _electrum_. this, which contains a mixture of silver and gold, being again subjected to the fire, the silver is separated and the gold left (pure); for this metal is easily dissipated and fat, and on this account gold is most easily molten by straw, the flame of which is soft, and bearing a similarity (to the gold) causes it easily to dissolve, whereas coal, besides wasting a great deal, melts it too much, by reason of its vehemence, and carries it off (in vapour)." this statement has provoked the liveliest discussion, not only on account of the metallurgical interest and obscurity, but also because of differences of view as to its translation; we have given that of mr. h. c. hamilton (london, ). a review of this discussion will be found in percy's metallurgy of gold and silver, p. . that it refers to cementation at all hangs by a slender thread, but it seems more nearly this than anything else. pliny (xxxiii, ) is a little more ample: "(the gold) is heated with double its weight of salt and thrice its weight of _misy_, and again with two portions of salt and one of a stone which they call _schistos_. the _virus_ is drawn out when these things are burnt together in an earthen crucible, itself remaining pure and incorrupt, the remaining ash being preserved in an earthen pot and mixed with water as a lotion for _lichen_ (ring-worm) on the face." percy (metallurgy silver and gold, p. ) rightly considers that this undoubtedly refers to the parting of silver and gold by cementation with common salt. especially as pliny further on states that with regard to _misy_, "in purifying gold they mix it with this substance." there can be no doubt from the explanations of pliny and dioscorides that _misy_ was an oxidized pyrite, mostly iron sulphate. assuming the latter case, then all of the necessary elements of cementation, _i.e._, vitriol, salt, and an aluminous or silicious element, are present. the first entirely satisfactory evidence on parting is to be found in theophilus ( th century), and we quote the following from hendrie's translation (p. ): "of heating the gold. take gold, of whatsoever sort it may be, and beat it until thin leaves are made in breadth three fingers, and as long as you can. then cut out pieces that are equally long and wide and join them together equally, and perforate through all with a fine cutting iron. afterwards take two earthen pots proved in the fire, of such size that the gold can lie flat in them, and break a tile very small, or clay of the furnace burned and red, weigh it, powdered, into two equal parts, and add to it a third part salt for the same weight; which things being slightly sprinkled with urine, are mixed together so that they may not adhere together, but are scarcely wetted, and put a little of it upon a pot about the breadth of the gold, then a piece of the gold itself, and again the composition, and again the gold, which in the digestion is thus always covered, that gold may not be in contact with gold; and thus fill the pot to the top and cover it above with another pot, which you carefully lute round with clay, mixed and beaten, and you place it over the fire, that it may be dried. in the meantime compose a furnace from stones and clay, two feet in height, and a foot and a half in breadth, wide at the bottom, but narrow at the top, where there is an opening in the middle, in which project three long and hard stones, which may be able to sustain the flame for a long time, upon which you place the pots with the gold, and cover them with other tiles in abundance. then supply fire and wood, and take care that a copious fire is not wanting for the space of a day and night. in the morning taking out the gold, again melt, beat and place it in the furnace as before. again also, after a day and night, take it away and mixing a little copper with it, melt it as before, and replace it upon the furnace. and when you have taken it away a third time, wash and dry it carefully, and so weighing it, see how much is wanting, then fold it up and keep it." the next mention is by geber, of whose date and authenticity there is great doubt, but, in any event, the work bearing his name is generally considered to be prior to the th, although he has been placed as early as the th century. we quote from russell's translation, pp. and , which we have checked with the latin edition of : "sol, or gold, is beaten into thin plates and with them and common salt very well prepared lay upon lay in a vessel of calcination which set into the furnace and calcine well for three days until the whole is subtily calcined. then take it out, grind well and wash it with vinegar, and dry it in the sun. afterwards grind it well with half its weight of cleansed _sal-armoniac_; then set it to be dissolved until the whole be dissolved into most clear water." further on: "now we will declare the way of cementing. seeing it is known to us that cement is very necessary in the examen of perfection, we say it is compounded of inflammable things. of this kind are, all blackening, flying, penetrating, and burned things; as is vitriol, _sal-armoniac_, _flos aeris_ (copper oxide scales) and the ancient _fictile_ stone (earthen pots), and a very small quantity, or nothing, of sulphur, and urine with like acute and penetrating things. all these are impasted with urine and spread upon thin plates of that body which you intend shall be examined by this way of probation. then the said plates must be laid upon a grate of iron included in an earthen vessel, yet so as one touch not the other that the virtue of the fire may have free and equal access to them. thus the whole must be kept in fire in a strong earthen vessel for the space of three days. but here great caution is required that the plates may be kept but not melt." albertus magnus ( - ) _de mineralibus et rebus metallicis_, lib. iv, describes the process as follows:--"but when gold is to be purified an earthen vessel is made like a cucurbit or dish, and upon it is placed a similar vessel; and they are luted together with the tenacious lute called by alchemists the lute of wisdom. in the upper vessel there are numerous holes by which vapour and smoke may escape; afterwards the gold in the form of short thin leaves is arranged in the vessel, the leaves being covered consecutively with a mixture obtained by mixing together soot, salt, and brick dust; and the whole is strongly heated until the gold becomes perfectly pure and the base substances with which it was mixed are consumed." it will be noted that salt is the basis of all these cement compounds. we may also add that those of biringuccio and all other writers prior to agricola were of the same kind, our author being the first to mention those with nitre. parting with nitric acid. the first mention of nitric acid is in connection with this purpose, and, therefore, the early history of this reagent becomes the history of the process. mineral acids of any kind were unknown to the greeks or romans. the works of the alchemists and others from the th to the th centuries, have been well searched by chemical historians for indications of knowledge of the mineral acids, and many of such suspected indications are of very doubtful order. in any event, study of the alchemists for the roots of chemistry is fraught with the greatest difficulty, for not only is there the large ratio of fraud which characterised their operations, but there is even the much larger field of fraud which characterised the authorship and dates of writing attributed to various members of the cult. the mention of saltpetre by roger bacon ( - ), and albertus magnus ( - ), have caused some strain to read a knowledge of mineral acids into their works, but with doubtful result. further, the monk theophilus ( - ) is supposed to have mentioned products which would be mineral acids, but by the most careful scrutiny of that work we have found nothing to justify such an assertion, and it is of importance to note that as theophilus was a most accomplished gold and silver worker, his failure to mention it is at least evidence that the process was not generally known. the transcribed manuscripts and later editions of such authors are often altered to bring them "up-to-date." the first mention is in the work attributed to geber, as stated above, of date prior to the th century. the following passage from his _de inventione veritatis_ (nuremberg edition, , p. ) is of interest:--"first take one _libra_ of vitriol of cyprus and one-half _libra_ of saltpetre and one-quarter of alum of jameni, extract the _aqua_ with the redness of the alembic--for it is very solvative--and use as in the foregoing chapters. this can be made acute if in it you dissolve a quarter of sal-ammoniac, which dissolves gold, sulphur, and silver." distilling vitriol, saltpetre and alum would produce nitric acid. the addition of sal-ammoniac would make _aqua regia_; geber used this solvent water--probably without being made "more acute"--to dissolve silver, and he crystallized out silver nitrate. it would not be surprising to find all the alchemists subsequent to geber mentioning acids. it will thus be seen that even the approximate time at which the mineral-acids were first made cannot be determined, but it was sometime previous to the th century, probably not earlier than the th century. beckmann (hist. of inventions ii, p. ) states that it appears to have been an old tradition that acid for separating the precious metals was first used at venice by some germans; that they chiefly separated the gold from spanish silver and by this means acquired great riches. beckmann considers that the first specific description of the process seems to be in the work of william budaeus (_de asse_, , iii, p. ), who speaks of it as new at this time. he describes the operation of one, le conte, at paris, who also acquired a fortune through the method. beckmann and others have, however, entirely overlooked the early _probierbüchlein_. if our conclusions are correct that the first of these began to appear at about , then they give the first description of inquartation. this book (see appendix) is made up of recipes, like a cook-book, and four or five different recipes are given for this purpose; of these we give one, which sufficiently indicates a knowledge of the art (p. ): "if you would part them do it this way: beat the silver which you suppose to contain gold, as thin as possible; cut it in small pieces and place it in 'strong' water (_starkwasser_). put it on a mild fire till it becomes warm and throws up blisters or bubbles. then take it and pour off the water into a copper-bowl; let it stand and cool. then the silver settles itself round the copper bowl; let the silver dry in the copper bowl, then pour the water off and melt the silver in a crucible. then take the gold also out of the glass _kolken_ and melt it together." biringuccio ( , book vi.) describes the method, but with much less detail than agricola. he made his acid from alum and saltpetre and calls it _lacque forti_. parting with sulphur. this process first appears in theophilus ( - ), and in form is somewhat different from that mentioned by agricola. we quote from hendrie's translation, p. , "how gold is separated from silver. when you have scraped the gold from silver, place this scraping in a small cup in which gold or silver is accustomed to be melted, and press a small linen cloth upon it, that nothing may by chance be abstracted from it by the wind of the bellows, and placing it before the furnace, melt it; and directly lay fragments of sulphur in it, according to the quantity of the scraping, and carefully stir it with a thin piece of charcoal until its fumes cease; and immediately pour it into an iron mould. then gently beat it upon the anvil lest by chance some of that black may fly from it which the sulphur has burnt, because it is itself silver. for the sulphur consumes nothing of the gold, but the silver only, which it thus separates from the gold, and which you will carefully keep. again melt this gold in the same small cup as before, and add sulphur. this being stirred and poured out, break what has become black and keep it, and do thus until the gold appear pure. then gather together all that black, which you have carefully kept, upon the cup made from the bone and ash, and add lead, and so burn it that you may recover the silver. but if you wish to keep it for the service of niello, before you burn it add to it copper and lead, according to the measure mentioned above, and mix with sulphur." this process appears in the _probierbüchlein_ in many forms, different recipes containing other ingredients besides sulphur, such as salt, saltpetre, sal-ammoniac, and other things more or less effective. in fact, a series of hybrid methods between absolute melting with sulphur and cementation with salt, were in use, much like those mentioned by agricola on p. . parting with antimony sulphide. the first mention of this process lies either in basil valentine's "triumphant chariot of antimony" or in the first _probierbüchlein_. the date to be assigned to the former is a matter of great doubt. it was probably written about the end of the th century, but apparently published considerably later. the date of the _probierbüchlein_ we have referred to above. the statement in the "triumphal chariot" is as follows (waite's translation, p. - ): "the elixir prepared in this way has the same power of penetrating and pervading the body with its purifying properties that antimony has of penetrating and purifying gold.... this much, however, i have proved beyond a possibility of doubt, that antimony not only purifies gold and frees it from foreign matter, but it also ameliorates all other metals, but it does the same for animal bodies." there are most specific descriptions of this process in the other works attributed to valentine, but their authenticity is so very doubtful that we do not quote. the _probierbüchlein_ gives several recipes for this process, all to the same metallurgical effect, of which we quote two: "how to separate silver from gold. take part of golden silver, part of _spiesglass_, part copper, part lead; melt them together in a crucible. when melted pour into the crucible pounded sulphur and directly you have poured it in cover it up with soft lime so that the fumes cannot escape, and let it get cold and you will find your gold in a button. put that same in a pot and blow on it." "how to part gold and silver by melting or fire. take as much gold-silver as you please and granulate it; take _mark_ of these grains, _mark_ of powder; put them together in a crucible. cover it with a small cover, put it in the fire, and let it slowly heat; blow on it gently until it melts; stir it all well together with a stick, pour it out into a mould, strike the mould gently with a knife so that the button may settle better, let it cool, then turn the mould over, strike off the button and twice as much _spiesglas_ as the button weighs, put them in a crucible, blow on it till it melts, then pour it again into a mould and break away the button as at first. if you want the gold to be good always add to the button twice as much _spiesglass_. it is usually good gold in three meltings. afterward take the button, place it on a cupel, blow on it till it melts. and if it should happen that the gold is covered with a membrane, then add a very little lead, then it shines (_plickt_) and becomes clearer." biringuccio ( ) also gives a fairly clear exposition of this method. all the old refiners varied the process by using mixtures of salt, antimony sulphide, and sulphur, in different proportions, with and without lead or copper; the net effect was the same. later than agricola these methods of parting bullion by converting the silver into a sulphide and carrying it off in a regulus took other forms. for instance, schlüter (_hütte-werken_, braunschweig, ) describes a method by which, after the granulated bullion had been sulphurized by cementation with sulphur in pots, it was melted with metallic iron. lampadius (_grundriss einer allgemeinen hüttenkunde_, göttingen, ) describes a treatment of the bullion, sulphurized as above, with litharge, thus creating a lead-silver regulus and a lead-silver-gold bullion which had to be repeatedly put through the same cycle. the principal object of these processes was to reduce silver bullion running low in gold to a ratio acceptable for nitric acid treatment. before closing the note on the separation of gold and silver, we may add that with regard to the three processes largely used to-day, the separation by solution of the silver from the bullion by concentrated sulphuric acid where silver sulphate is formed, was first described by d'arcet, paris, in ; the separation by introducing chlorine gas into the molten bullion and thus forming silver chlorides was first described by lewis thompson in a communication to the society of arts, , and was first applied on a large scale by f. b. miller at the sydney mint in - ; we do not propose to enter into the discussion as to who is the inventor of electrolytic separation. [ ] there were three methods of gilding practised in the middle ages--the first by hammering on gold leaf; the second by laying a thin plate of gold on a thicker plate of silver, expanding both together, and fabricating the articles out of the sheets thus prepared; and the third by coating over the article with gold amalgam, and subsequently driving off the mercury by heat. copper and iron objects were silver-plated by immersing them in molten silver after coating with sal-ammoniac or borax. tinning was done in the same way. [ ] see note , p. , for complete discussion of amalgamation. [ ] these nine methods of separating gold from copper are based fundamentally upon the sulphur introduced in each case, whereby the copper is converted into sulphides and separated off as a matte. the various methods are much befogged by the introduction of extraneous ingredients, some of which serve as fluxes, while others would provide metallics in the shape of lead or antimony for collection of the gold, but others would be of no effect, except to increase the matte or slag. inspection will show that the amount of sulphur introduced in many instances is in so large ratio that unless a good deal of volatilization took place there would be insufficient metallics to collect the gold, if it happened to be in small quantities. in a general way the auriferous button is gradually impoverished in copper until it is fit for cupellation with lead, except in one case where the final stage is accomplished by amalgamation. the lore of the old refiners was much after the order of that of modern cooks--they treasured and handed down various efficacious recipes, and of those given here most can be found in identical terms in the _probierbüchlein_, some editions of which, as mentioned before, were possibly fifty years before _de re metallica_. this knowledge, no doubt, accumulated over long experience; but, so far as we are aware, there is no description of sulphurizing copper for this purpose prior to the publication mentioned. [ ] _sal artificiosus_. the compound given under this name is of quite different ingredients from the stock fluxes given in book vii under the same term. the method of preparation, no doubt, dehydrated this one; it would, however, be quite effective for its purpose of sulphurizing the copper. there is a compound given in the _probierbüchlein_ identical with this, and it was probably agricola's source of information. [ ] throughout the book the cupellation furnace is styled the _secunda fornax_ (glossary, _treibeherd_). except in one or two cases, where there is some doubt as to whether the author may not refer to the second variety of blast furnace, we have used "cupellation furnace." agricola's description of the actual operation of the old german cupellation is less detailed than that of such authors as schlüter (_hütte-werken_, braunschweig, ) or winkler (_beschreibung der freyberger schmelz huttenprozesse_, freyberg, ). the operation falls into four periods. in the first period, or a short time after melting, the first scum--the _abzug_--arises. this material contains most of the copper, iron, zinc, or sulphur impurities in the lead. in the second period, at a higher temperature, and with the blast turned on, a second scum arises--the _abstrich_. this material contains most of the antimony and arsenical impurities. in the third stage the litharge comes over. at the end of this stage the silver brightens--"_blicken_"--due to insufficient litharge to cover the entire surface. winkler gives the following average proportion of the various products from a charge of _centners_:-- _abzug_ _centners_, containing % lead _abstrich_ - / " " % " _herdtplei_ - / " " % " impure litharge " " % " litharge " " % " --- total _centners_ he estimates the lead loss at from % to %, and gives the average silver contents of _blicksilber_ as about %. many analyses of the various products may be found in percy (metallurgy of lead, pp. - ), schnabel and lewis (metallurgy, vol. i, p. ); but as they must vary with every charge, a repetition of them here is of little purpose. historical note on cupellation. the cupellation process is of great antiquity, and the separation of silver from lead in this manner very probably antedates the separation of gold and silver. we can be certain that the process has been used continuously for at least , years, and was only supplanted in part by pattinson's crystallization process in , and further invaded by parks' zinc method in , and during the last fifteen years further supplanted in some works by electrolytic methods. however, it yet survives as an important process. it seems to us that there is no explanation possible of the recovery of the large amounts of silver possessed from the earliest times, without assuming reduction of that metal with lead, and this necessitates cupellation. if this be the case, then cupellation was practised in b.c. the subject has been further discussed on p. . the first direct evidence of the process, however, is from the remains at mt. laurion (note , p. ), where the period of greatest activity was at b.c., and it was probably in use long before that time. of literary evidences, there are the many metaphorical references to "fining silver" and "separating dross" in the bible, such as job (xxviii, ), psalms (xii, , lxvi, ), proverbs (xvii, ). the most certain, however, is jeremiah (vi, - ): "they are all brass [_sic_] and iron; they are corrupters. the bellows are burned, the lead is consumed in the fire, the founder melteth in vain; for the wicked are not plucked away. reprobate silver shall men call them." jeremiah lived about b.c. his contemporary ezekiel (xxii, ) also makes remark: "all they are brass and tin and iron and lead in the midst of the furnace; they are even the dross of the silver." among greek authors theognis ( th century b.c.) and hippocrates ( th century b.c.) are often cited as mentioning the refining of gold with lead, but we do not believe their statements will stand this construction without strain. aristotle (problems xxiv, ) makes the following remark, which has been construed not only as cupellation, but also as the refining of silver in "tests." "what is the reason that boiling water does not leap out of the vessel ... silver also does this when it is purified. hence those whose office it is in the silversmiths' shops to purify silver, derive gain by appropriation to themselves of the sweepings of silver which leap out of the melting-pot." the quotation of diodorus siculus from agatharchides ( nd century b.c.) on gold refining with lead and salt in egypt we give in note , p. . the methods quoted by strabo ( b.c.- a.d.) from polybius ( - b.c.) for treating silver, which appear to involve cupellation, are given in note , p. . it is not, however, until the beginning of the christian era that we get definite literary information, especially with regard to litharge, in dioscorides and pliny. the former describes many substances under the terms _scoria_, _molybdaena_, _scoria argyros_ and _lithargyros_, which are all varieties of litharge. under the latter term he says (v, ): "one kind is produced from a lead sand (concentrates?), which has been heated in the furnaces until completely fused; another (is made) out of silver; another from lead. the best is from attica, the second (best) from spain; after that the kinds made in puteoli, in campania, and at baia in sicily, for in these places it is mostly produced by burning lead plates. the best of all is that which is a bright golden colour, called _chrysitis_, that from sicily (is called) _argyritis_, that made from silver is called _lauritis_." pliny refers in several passages to litharge (_spuma argenti_) and to what is evidently cupellation, (xxxiii, ): "and this the same agency of fire separates part into lead, which floats on the silver like oil on water" (xxxiv, ). "the metal which flows liquid at the first melting is called _stannum_, the second melting is silver; that which remains in the furnace is _galena_, which is added to a third part of the ore. this being again melted, produced lead with a deduction of two-ninths." assuming _stannum_ to be silver-lead alloy, and _galena_ to be _molybdaena_, and therefore litharge, this becomes a fairly clear statement of cupellation (see note , p. ). he further states (xxxiii, ): "there is made in the same mines what is called _spuma argenti_ (litharge). there are three varieties of it; the best, known as _chrysitis_; the second best, which is called _argyritis_; and a third kind, which is called _molybditis_. and generally all these colours are to be found in the same tubes (see p. ). the most approved kind is that of attica; the next, that which comes from spain. _chrysitis_ is the product from the ore itself; _argyritis_ is made from the silver, and _molybditis_ is the result of smelting of lead, which is done at puteoli, and from this has its name. all three are made as the material when smelted flows from an upper crucible into a lower one. from this last it is raised with an iron bar, and is then twirled round in the flames in order to make it less heavy (made in tubes). thus, as may be easily perceived from the name, it is in reality the _spuma_ of a boiling substance--of the future metal, in fact. it differs from slag in the same way that the scum of a liquid differs from the lees, the one being purged from the material while purifying itself, the other an excretion of the metal when purified." the works of either theophilus ( - a.d.) or geber (prior to the th century) are the first where adequate description of the cupel itself can be found. the uncertainty of dates renders it difficult to say which is earliest. theophilus (hendrie's trans., p. ) says: "how gold is separated from copper: but if at any time you have broken copper or silver-gilt vessels, or any other work, you can in this manner separate the gold. take the bones of whatever animal you please, which (bones) you may have found in the street, and burn them, being cold, grind them finely, and mix with them a third part of beechwood ashes, and make cups as we have mentioned above in the purification of silver; you will dry these at the fire or in the sun. then you carefully scrape the gold from the copper, and you will fold this scraping in lead beaten thin, and one of these cups being placed in the embers before the furnace, and now become warm, you place in this fold of lead with the scraping, and coals being heaped upon it you will blow it. and when it has become melted, in the same manner as silver is accustomed to be purified, sometimes by removing the embers and by adding lead, sometimes by re-cooking and warily blowing, you burn it until, the copper being entirely absorbed, the gold may appear pure." we quote geber from the nuremberg edition of , p. : "now we describe the method of this. take sifted ashes or _calx_, or the powder of the burned bones of animals, or all of them mixed, or some of them; moisten with water, and press it with your hand to make the mixture firm and solid, and in the middle of this bed make a round solid crucible and sprinkle a quantity of crushed glass. then permit it to dry. when it is dry, place into the crucible that which we have mentioned which you intend to test. on it kindle a strong fire, and blow upon the surface of the body that is being tested until it melts, which, when melted, piece after piece of lead is thrown upon it, and blow over it a strong flame. when you see it agitated and moved with strong shaking motion it is not pure. then wait until all of the lead is exhaled. if it vanishes and does not cease its motion it is not purified. then again throw lead and blow again until the lead separates. if it does not become quiet again, throw in lead and blow on it until it is quiet and you see it bright and clear on the surface." cupellation is mentioned by most of the alchemists, but as a metallurgical operation on a large scale the first description is by biringuccio in . [ ] in agricola's text this is "first,"--obviously an error. [ ] the roman _sextarius_ was about a pint. [ ] this sentence continues, _ipsa vero media pars praeterea digito_, to which we are unable to attribute any meaning. [ ] _thus_, or _tus_--"incense." [ ] one _centumpondium_, roman, equals about . lbs. avoirdupois; one _centner_, old german, equals about . lbs. avoirdupois. therefore, if german weights are meant, the maximum charge would be about . short tons; if roman weights, about . short tons. [ ] see description, p. . [ ] _stannum_, as a term for lead-silver alloys, is a term which agricola (_de natura fossilium_, pp. - ) adopted from his views of pliny. in the _interpretatio_ and the glossary he gives the german equivalent as _werk_, which would sufficiently identify his meaning were it not obvious from the context. there can be little doubt that pliny uses the term for lead alloys, but it had come into general use for tin before agricola's time. the roman term was _plumbum candidum_, and as a result of agricola's insistence on using it and _stannum_ in what he conceived was their original sense, he managed to give considerable confusion to mineralogic literature for a century or two. the passages from pliny, upon which he bases his use, are (xxxiv, ): "the metal which flows liquid at the first melting in the furnace is called _stannum_, the second melting is silver," etc. (xxxiv, ): "when copper vessels are coated with _stannum_ they produce a less disagreeable flavour, and it prevents verdigris. it is also remarkable that the weight is not increased.... at the present day a counterfeit _stannum_ is made by adding one-third of white copper to tin. it is also made in another way, by mixing together equal parts of tin and lead; this last is called by some _argentarium_.... there is also a composition called _tertiarium_, a mixture of two parts of lead and one of tin. its price is twenty _denarii_ per pound, and it is used for soldering pipes. persons still more dishonest mix together equal parts of _tertiarium_ and tin, and calling the compound _argentarium_, when it is melted coat articles with it." although this last passage probably indicates that _stannum_ was a tin compound, yet it is not inconsistent with the view that the genuine _stannum_ was silver-lead, and that the counterfeits were made as stated by pliny. at what period the term _stannum_ was adopted for tin is uncertain. as shown by beckmann (hist. of inventions ii, p. ), it is used as early as the th century in occasions where tin was undoubtedly meant. we may point out that this term appears continuously in the official documents relating to cornish tin mining, beginning with the report of william de wrotham in . [ ] the latin term for litharge is _spuma argenti_, spume of silver. [ ] pliny, xxxiii, . this quotation is given in full in the footnote p. . agricola illustrates these "tubes" of litharge on p. . [ ] assuming roman weights, three _unciae_ and three _drachmae_ per _centumpondium_ would be about ozs., and the second case would equal about ozs. per short ton. [ ] agricola uses throughout _de re metallica_ the term _molybdaena_ for this substance. it is obvious from the context that he means saturated furnace bottoms--the _herdpley_ of the old german metallurgists--and, in fact, he himself gives this equivalent in the _interpretatio_, and describes it in great detail in _de natura fossilium_ (p. ). the derivatives coined one time and another from the greek _molybdos_ for lead, and their applications, have resulted in a stream of wasted ink, to which we also must contribute. agricola chose the word _molybdaena_ in the sense here used from his interpretation of pliny. the statements in pliny are a hopeless confusion of _molybdaena_ and _galena_. he says (xxxiii, ): "there are three varieties of it (litharge)--the best-known is _chrysitis_; the second best is called _argyritis_; and a third kind is called _molybditis_.... _molybditis_ is the result of the smelting of lead.... some people make two kinds of litharge, which they call _scirerytis_ and _peumene_; and a third variety being _molybdaena_, will be mentioned with lead." (xxxiv, ): "_molybdaena_, which in another place i have called _galena_, is an ore of mixed silver and lead. it is considered better in quality the nearer it approaches to a golden colour and the less lead there is in it; it is also friable and moderately heavy. when it is boiled with oil it becomes liver-coloured, adheres to the gold and silver furnaces, and in this state it is called _metallica_." from these two passages it would seem that _molybdaena_, a variety of litharge, might quite well be hearth-lead. further (in xxxiv, ), he says: "the metal which flows liquid at the first melting in the furnace is called _stannum_, at the second melting is silver, that which remains in the furnace is _galena_." if we still maintain that _molybdaena_ is hearth-lead, and _galena_ is its equivalent, then this passage becomes clear enough, the second melting being cupellation. the difficulty with pliny, however, arises from the passage (xxxiii, ), where, speaking of silver ore, he says: "it is impossible to melt it except with lead ore, called _galena_, which is generally found next to silver veins." agricola (_bermannus_, p. , &c.), devotes a great deal of inconclusive discussion to an attempt to reconcile this conflict of pliny, and also that of dioscorides. the probable explanation of this conflict arises in the resemblance of cupellation furnace bottoms to lead carbonates, and the native _molybdaena_ of dioscorides; and some of those referred to by pliny may be this sort of lead ores. in fact, in one or two places in book ix, agricola appears to use the term in this sense himself. after agricola's time the term _molybdaenum_ was applied to substances resembling lead, such as graphite, and what we now know as _molybdenite_ (_mos_{ }_). some time in the latter part of the th century, an element being separated from the latter, it was dubbed _molybdenum_, and confusion was five times confounded. [ ] agricola here refers to the german word used in this connection, _i.e._, _hundt_, a dog. [ ] if agricola means the german _centner_, this charge would be from about . to . short tons. if he is using roman weights, it would be from about to . short tons. [ ] the refining of silver in "tests" (latin _testa_) is merely a second cupellation, with greater care and under stronger blast. stirring the mass with an iron rod serves to raise the impurities which either volatilize as litharge or, floating to the edges, are absorbed into the "test." the capacity of the tests, from _librae_ to _librae_, would be from about to ozs. troy. [ ] a _drachma_ of impurities in a _bes_, would be one part in , or . fine. a loss of a _sicilicus_ of silver to the _bes_, would be one part in , or about . %; three _drachmae_ would equal . %, and half an _uncia_ . %, or would indicate that the original bullion had a fineness in the various cases of about , , and . [ ] _praefectus regis_. book xi. different methods of parting gold from silver, and, on the other hand, silver from gold, were discussed in the last book; also the separation of copper from the latter, and further, of lead from gold as well as from silver; and, lastly, the methods for refining the two precious metals. now i will speak of the methods by which silver must be separated from copper, and likewise from iron.[ ] [illustration (building plan for refinery): six long walls: a--the first. b--the first part of the second. c--the further part of the second. d--the third. e--the fourth. f--the fifth. g--the sixth. fourteen transverse walls: h--the first. i--the second. k--the third. l--the fourth. m--the fifth. n--the sixth. o--the seventh. p--the eighth. q--the ninth. r--the tenth. s--the eleventh. t--the twelfth. v--the thirteenth. x--the fourteenth.] the _officina_, or the building necessary for the purposes and use of those who separate silver from copper, is constructed in this manner. first, four long walls are built, of which the first, which is parallel with the bank of a stream, and the second, are both two hundred and sixty-four feet long. the second, however, stops at one hundred and fifty-one feet, and after, as it were, a break for a length of twenty-four feet, it continues again until it is of a length equal to the first wall. the third wall is one hundred and twenty feet long, starting at a point opposite the sixty-seventh foot of the other walls, and reaching to their one hundred and eighty-sixth foot. the fourth wall is one hundred and fifty-one feet long. the height of each of these walls, and likewise of the other two and of the transverse walls, of which i will speak later on, is ten feet, and the thickness two feet and as many palms. the second long wall only is built fifteen feet high, because of the furnaces which must be built against it. the first long wall is distant fifteen feet from the second, and the third is distant the same number of feet from the fourth, but the second is distant thirty-nine feet from the third. then transverse walls are built, the first of which leads from the beginning of the first long wall to the beginning of the second long wall; and the second transverse wall from the beginning of the second long wall to the beginning of the fourth long wall, for the third long wall does not reach so far. then from the beginning of the third long wall are built two walls--the one to the sixty-seventh foot of the second long wall, the other to the same point in the fourth long wall. the fifth transverse wall is built at a distance of ten feet from the fourth transverse wall toward the second transverse wall; it is twenty feet long, and starts from the fourth long wall. the sixth transverse wall is built also from the fourth long wall, at a point distant thirty feet from the fourth transverse wall, and it extends as far as the back of the third long wall. the seventh transverse wall is constructed from the second long wall, where this first leaves off, to the third long wall; and from the back of the third long wall the eighth transverse wall is built, extending to the end of the fourth long wall. then the fifth long wall is built from the seventh transverse wall, starting at a point nineteen feet from the second long wall; it is one hundred and nine feet in length; and at a point twenty-four feet along it, the ninth transverse wall is carried to the third end of the second long wall, where that begins again. the tenth transverse wall is built from the end of the fifth long wall, and leads to the further end of the second long wall; and from there the eleventh transverse wall leads to the further end of the first long wall. behind the fifth long wall, and five feet toward the third long wall, the sixth long wall is built, leading from the seventh transverse wall; its length is thirty-five feet, and from its further end the twelfth transverse wall is built to the third long wall, and from it the thirteenth transverse wall is built to the fifth long wall. the fourteenth transverse wall divides into equal parts the space which lies between the seventh transverse wall and the twelfth. the length, height, breadth, and position of the walls are as above. their archways, doors, and openings are made at the same time that the walls are built. the size of these and the way they are made will be much better understood hereafter. i will now speak of the furnace hoods and of the roofs. the first side[ ] of the hood stands on the second long wall, and is similar in every respect to those whose structure i explained in book ix, when i described the works in whose furnaces are smelted the ores of gold, silver, and copper. from this side of the hood a roof, which consists of burnt tiles, extends to the first long wall; and this part of the building contains the bellows, the machinery for compressing them, and the instruments for inflating them. in the middle space, which is situated between the second and third transverse walls, an upright post eight feet high and two feet thick and wide, is erected on a rock foundation, and is distant thirteen feet from the second long wall. on that upright post, and in the second transverse wall, which has at that point a square hole two feet high and wide, is placed a beam thirty-four feet and a palm long. another beam, of the same length, width, and thickness, is fixed on the same upright post and in the third transverse wall. the heads of those two beams, where they meet, are joined together with iron staples. in a similar manner another post is erected, at a distance of ten feet from the first upright post in the direction of the fourth wall, and two beams are laid upon it and into the same walls in a similar way to those i have just now described. on these two beams and on the fourth long wall are fixed seventeen cross-beams, forty-three feet and three palms long, a foot wide, and three palms thick; the first of these is laid upon the second transverse wall, the last lies along the third and fourth transverse walls; the rest are set in the space between them. these cross-beams are three feet apart one from the other. in the ends of these cross-beams, facing the second long wall, are mortised the ends of the same number of rafters reaching to those timbers which stand upright on the second long wall, and in this manner is made the inclined side of the hood in a similar way to the one described in book ix. to prevent this from falling toward the vertical wall of the hood, there are iron rods securing it, but only a few, because the four brick chimneys which have to be built in that space partly support it. twelve feet back are likewise mortised into the cross-beams, which lie upon the two longitudinal beams and the fourth long wall, the lower ends of as many rafters, whose upper ends are mortised into the upper ends of an equal number of similar rafters, whose lower ends are mortised to the ends of the beams at the fourth long wall. from the first set of rafters[ ] to the second set of rafters is a distance of twelve feet, in order that a gutter may be well placed in the middle space. between these two are again erected two sets of rafters, the lower ends of which are likewise mortised into the beams, which lie on the two longitudinal beams and the fourth long wall, and are interdistant a cubit. the upper ends of the ones fifteen feet long rest on the backs of the rafters of the first set; the ends of the others, which are eighteen feet long, rest on the backs of the rafters of the second set, which are longer; in this manner, in the middle of the rafters, is a sub-structure. upon each alternate cross-beam which is placed upon the two longitudinal beams and the fourth long wall is erected an upright post, and that it may be sufficiently firm it is strengthened by means of a slanting timber. upon these posts is laid a long beam, upon which rests one set of middle rafters. in a similar manner the other set of middle rafters rests on a long beam which is placed upon other posts. besides this, two feet above every cross-beam, which is placed on the two longitudinal beams and the fourth long wall, is placed a tie-beam which reaches from the first set of middle rafters to the second set of middle rafters; upon the tie-beams is placed a gutter hollowed out from a tree. then from the back of each of the first set of middle rafters a beam six feet long reaches almost to the gutter; to the lower end of this beam is attached a piece of wood two feet long; this is repeated with each rafter of the first set of middle rafters. similarly from the back of each rafter of the second set of middle rafters a little beam, seven feet long, reaches almost to the gutter; to the lower end of it is likewise attached a short piece of wood; this is repeated on each rafter of the second set of middle rafters. then in the upper part, to the first and second sets of principal rafters are fastened long boards, upon which are fixed the burnt tiles; and in the same manner, in the middle part, they are fastened to the first and second sets of middle rafters, and at the lower part to the little beams which reach from each rafter of the first and second set of middle rafters almost to the gutter; and, finally, to the little boards fastened to the short pieces of wood are fixed shingles of pine-wood extending into the gutter, so that the violent rain or melted snow may not penetrate into the building. the substructures in the interior which support the second set of rafters, and those on the opposite side which support the third, being not unusual, i need not explain. in that part of the building against the second long wall are the furnaces, in which exhausted liquation cakes which have already been "dried" are smelted, that they may recover once again the appearance and colour of copper, inasmuch as they really are copper. the remainder of the room is occupied by the passage which leads from the door to the furnaces, together with two other furnaces, in one of which the whole cakes of copper are heated, and in the other the exhausted liquation cakes are "dried" by the heat of the fire. likewise, in the room between the third and seventh[ ] transverse walls, two posts are erected on rock foundation; both of them are eight feet high and two feet wide and thick. the one is at a distance of thirteen feet from the second long wall; the other at the same distance from the third long wall; there is a distance of thirteen feet between them. upon these two posts and upon the third transverse wall are laid two longitudinal beams, forty-one feet and one palm long, and two feet wide and thick. two other beams of the same length, width, and thickness are laid upon the upright posts and upon the seventh transverse wall, and the heads of the two long beams, where they meet, are joined with iron staples. on these longitudinal beams are again placed twenty-one transverse beams, thirteen feet long, a foot wide, and three palms thick, of which the first is set on the third transverse wall, and the last on the seventh transverse wall; the rest are laid in the space between these two, and they are distant from one another three feet. into the ends of the transverse beams which face the second long wall, are mortised the ends of the same number of rafters erected toward the upright posts which are placed upon the second long wall, and in this manner is made the second inclined side wall of the hood. into the ends of the transverse beams facing the third long wall, are mortised the ends of the same number of rafters rising toward the rafters of the first inclined side of the second hood, and in this manner is made the other inclined side of the second hood. but to prevent this from falling in upon the opposite inclined side of the hood, and that again upon the opposite vertical one, there are many iron rods reaching from some of the rafters to those opposite them; and this is also prevented in part by means of a few tie-beams, extending from the back of the rafters to the back of those which are behind them. these tie-beams are two palms thick and wide, and have holes made through them at each end; each of the rafters is bound round with iron bands three digits wide and half a digit thick, which hold together the ends of the tie-beams of which i have spoken; and so that the joints may be firm, an iron nail, passing through the plate on both sides, is driven through the holes in the ends of the beams. since one weight counter-balances another, the rafters on the opposite hoods cannot fall. the tie-beams and middle posts which have to support the gutters and the roof, are made in every particular as i stated above, except only that the second set of middle rafters are not longer than the first set of middle rafters, and that the little beams which reach from the back of each rafter of the second set of middle rafters nearly to the gutter are not longer than the little beams which reach from the back of each rafter of the first set of middle rafters almost to the gutter. in this part of the building, against the second long wall, are the furnaces in which copper is alloyed with lead, and in which "slags" are re-smelted. against the third long wall are the furnaces in which silver and lead are liquated from copper. the interior is also occupied by two cranes, of which one deposits on the ground the cakes of copper lifted out of the moulding pans; the other lifts them from the ground into the second furnace. on the third and the fourth long walls are set twenty-one beams eighteen feet and three palms long. in mortises in them, two feet behind the third long wall, are set the ends of the same number of rafters erected opposite to the rafters of the other inclined wall of the second furnace hood, and in this manner is made the third inclined wall, exactly similar to the others. the ends of as many rafters are mortised into these beams where they are fixed in the fourth long wall; these rafters are erected obliquely, and rest against the backs of the preceding ones and support the roof, which consists entirely of burnt tiles and has the usual substructures. in this part of the building there are two rooms, in the first of which the cakes of copper, and in the other the cakes of lead, are stored. in the space enclosed between the ninth and tenth transverse walls and the second and fifth long walls, a post twelve feet high and two feet wide and thick is erected on a rock foundation; it is distant thirteen feet from the second long wall, and six from the fifth long wall. upon this post and upon the ninth transverse wall is laid a beam thirty-three feet and three palms long, and two palms wide and thick. another beam, also of the same length, width and thickness, is laid upon the same post and upon the tenth transverse wall, and the ends of these two beams where they meet are joined by means of iron staples. on these beams and on the fifth long wall are placed ten cross-beams, eight feet and three palms long, the first of which is placed on the ninth transverse wall, the last on the tenth, the remainder in the space between them; they are distant from one another three feet. into the ends of the cross-beams facing the second long wall, are mortised the ends of the same number of rafters inclined toward the posts which stand vertically upon the second long wall. this, again, is the manner in which the inclined side of the furnace hood is made, just as with the others; at the top where the fumes are emitted it is two feet distant from the vertical side. the ends of the same number of rafters are mortised into the cross-beams, where they are set in the fifth long wall; each of them is set up obliquely and rests against the back of one of the preceding set; they support the roof, made of burnt tiles. in this part of the building, against the second long wall, are four furnaces in which lead is separated from silver, together with the cranes by means of which the domes are lifted from the crucibles. in that part of the building which lies between the first long wall and the break in the second long wall, is the stamp with which the copper cakes are crushed, and the four stamps with which the accretions that are chipped off the walls of the furnace are broken up and crushed to powder, and likewise the bricks on which the exhausted liquation cakes of copper are stood to be "dried." this room has the usual roof, as also has the space between the seventh transverse wall and the twelfth and thirteenth transverse walls. [illustration (hearths for melting lead cakes): a--hearth. b--rocks sunk into the ground. c--walls which protect the fourth long wall from damage by fire. d--dipping-pot. e--masses of lead. f--trolley. g--its wheels. h--crane. i--tongs. k--wood. l--moulds. m--ladle. n--pick. o--cakes.] at the sides of these rooms are the fifth, the sixth, and the third long walls. this part of the building is divided into two parts, in the first of which stand the little furnaces in which the artificer assays metals; and the bone ash, together with the other powders, are kept here. in the other room is prepared the powder from which the hearths and the crucibles of the furnaces are made. outside the building, at the back of the fourth long wall, near the door to the left as you enter, is a hearth in which smaller masses of lead are melted from large ones, that they may be the more easily weighed; because the masses of lead, just as much as the cakes of copper, ought to be first prepared so that they can be weighed, and a definite weight can be melted and alloyed in the furnaces. to begin with, the hearth in which the masses of lead are liquefied is six feet long and five wide; it is protected on both sides by rocks partly sunk into the earth, but a palm higher than the hearth, and it is lined in the inside with lute. it slopes toward the middle and toward the front, in order that the molten lead may run down and flow out into the dipping-pot. there is a wall at the back of the hearth which protects the fourth long wall from damage by the heat; this wall, which is made of bricks and lute, is four feet high, three palms thick, and five feet long at the bottom, and at the top three feet and two palms long; therefore it narrows gradually, and in the upper part are laid seven bricks, the middle ones of which are set upright, and the end ones inclined; they are all thickly coated with lute. in front of the hearth is a dipping-pot, whose pit is a foot deep, and a foot and three palms wide at the top, and gradually narrows. when the masses of lead are to be melted, the workman first places the wood in the hearth so that one end of each billet faces the wall, and the other end the dipping-pot. then, assisted by other workmen, he pushes the mass of lead forward with crowbars on to a low trolley, and draws it to the crane. the trolley consists of planks fastened together, is two and one-half feet wide and five feet long, and has two small iron axles, around which at each end revolve small iron wheels, two palms in diameter and as many digits wide. the trolley has a tongue, and attached to this is a rope, by which it is drawn to the crane. the crane is exactly similar to those in the second part of the works, except that the crane-arm is not so long. the tongs in whose jaws[ ] the masses of lead are seized, are two feet a palm and two digits long; both of the jaws, when struck with a hammer, impinge upon the mass and are driven into it. the upper part of both handles of the tongs are curved back, the one to the right, the other to the left, and each handle is engaged in one of the lowest links of two short chains, which are three links long. the upper links are engaged in a large round ring, in which is fixed the hook of a chain let down from the pulley of the crane-arm. when the crank of the crane is turned, the mass is lifted and is carried by the crane-arm to the hearth and placed on the wood. the workmen wheel up one mass after another and place them in a similar manner on the wood of the hearth; masses which weigh a total of about a hundred and sixty _centumpondia_[ ] are usually placed upon the wood and melted at one time. then a workman throws charcoal on the masses, and all are made ready in the evening. if he fears that it may rain, he covers it up with a cover, which may be moved here and there; at the back this cover has two legs, so that the rain which it collects may flow down the slope on to the open ground. early in the morning of the following day, he throws live coals on the charcoal with a shovel, and by this method the masses of lead melt, and from time to time charcoal is added. the lead, as soon as it begins to run into the dipping-pot, is ladled out with an iron ladle into copper moulds such as the refiners generally use. if it does not cool immediately he pours water over it, and then sticks the pointed pick into it and pulls it out. the pointed end of the pick is three palms long and the round end is two digits long. it is necessary to smear the moulds with a wash of lute, in order that, when they have been turned upside down and struck with the broad round end of the pick, the cakes of lead may fall out easily. if the moulds are not washed over with the lute, there is a risk that they may be melted by the lead and let it through. others take hold of a billet of wood with their left hand, and with the heavy lower end of it they pound the mould, and with the right hand they stick the point of the pick into the cake of lead, and thus pull it out. then immediately the workman pours other lead into the empty moulds, and this he does until the work of melting the lead is finished. when the lead is melted, something similar to litharge is produced; but it is no wonder that it should be possible to make it in this case, when it used formerly to be produced at puteoli from lead alone when melted by a fierce fire in the cupellation furnace.[ ] afterward these cakes of lead are carried into the lead store-room. [illustration (stamp-mill for breaking copper cakes): a--block of wood. b--upright posts. c--transverse beams. d--head of the stamp. e--its tooth. f--the hole in the stamp-stem. g--iron bar. h--masses of lead. i--the bronze saddle. k--axle. l--its arms. m--little iron axle. n--bronze pipe.] the cakes of copper, put into wheelbarrows, are carried into the third part of the building, where each is laid upon a saddle, and is broken up by the impact of successive blows from the iron-shod stamp. this machine is made by placing upon the ground a block of oak, five feet long and three feet wide and thick; it is cut out in the middle for a length of two feet and two palms, a width of two feet, and a depth of three palms and two digits, and is open in front; the higher part of it is at the back, and the wide part lies flat in the block. in the middle of it is placed a bronze saddle. its base is a palm and two digits wide, and is planted between two masses of lead, and extends under them to a depth of a palm on both sides. the whole saddle is three palms and two digits wide, a foot long, and two palms thick. upon each end of the block stands a post, a cubit wide and thick, the upper end of which is somewhat cut away and is mortised into the beams of the building. at a height of four feet and two digits above the block there are joined to the posts two transverse beams, each of which is three palms wide and thick; their ends are mortised into the upright posts, and holes are bored through them; in the holes are driven iron claves, horned in front and so driven into the post that one of the horns of each points upward and the other downward; the other end of each clavis is perforated, and a wide iron wedge is inserted and driven into the holes, and thus holds the transverse beams in place. these transverse beams have in the middle a square opening three palms and half a digit wide in each direction, through which the iron-shod stamp passes. at a height of three feet and two palms above these transverse beams there are again two beams of the same kind, having also a square opening and holding the same stamp. this stamp is square, eleven feet long, three palms wide and thick; its iron shoe is a foot and a palm long; its head is two palms long and wide, a palm two digits thick at the top, and at the bottom the same number of digits, for it gradually narrows. but the tail is three palms long; where the head begins is two palms wide and thick, and the further it departs from the same the narrower it becomes. the upper part is enclosed in the stamp-stem, and it is perforated so that an iron bolt may be driven into it; it is bound by three rectangular iron bands, the lowest of which, a palm wide, is between the iron shoe and the head of the stamp; the middle band, three digits wide, follows next and binds round the head of the stamp, and two digits above is the upper one, which is the same number of digits wide. at a distance of two feet and as many digits above the lowest part of the iron shoe, is a rectangular tooth, projecting from the stamp for a distance of a foot and a palm; it is two palms thick, and when it has extended to a distance of six digits from the stamp it is made two digits narrower. at a height of three palms upward from the tooth there is a round hole in the middle of the stamp-stem, into which can be thrust a round iron bar two feet long and a digit and a half in diameter; in its hollow end is fixed a wooden handle two palms and the same number of digits long. the bar rests on the lower transverse beam, and holds up the stamp when it is not in use. the axle which raises the stamp has on each side two arms, which are two palms and three digits distant from each other, and which project from the axle a foot, a palm and two digits; penetrating through them are bolts, driven in firmly; the arms are each a palm and two digits wide and thick, and their round heads, for a foot downward on either side, are covered with iron plates of the same width as the arms and fastened by iron nails. the head of each arm has a round hole, into which is inserted an iron pin, passing through a bronze pipe; this little axle has at the one end a wide head, and at the other end a perforation through which is driven an iron nail, lest this little axle should fall out of the arms. the bronze pipe is two palms long and one in diameter; the little iron axle penetrates through its round interior, which is two digits in diameter. the bronze pipe not only revolves round the little iron axle, but it also rotates with it; therefore, when the axle revolves, the little axle and the bronze tube in their turn raise the tooth and the stamp. when the little iron axle and the bronze pipe have been taken out of the arms, the tooth of the stamps is not raised, and other stamps may be raised without this one. further on, a drum with spindles fixed around the axle of a water-wheel moves the axle of a toothed drum, which depresses the sweeps of the bellows in the adjacent fourth part of the building; but it turns in the contrary direction; for the axis of the drum which raises the stamps turns toward the north, while that one which depresses the sweeps of the bellows turns toward the south. [illustration (hearths for heating copper cakes): a--back wall. b--walls at the sides. c--upright posts. d--chimney. e--the cakes arranged. f--iron plates. g--rocks. h--rabble with two prongs. i--hammers.] those cakes which are too thick to be rapidly broken by blows from the iron-shod stamp, such as are generally those which have settled in the bottom of the crucible,[ ] are carried into the first part of the building. they are there heated in a furnace, which is twenty-eight feet distant from the second long wall and twelve feet from the second transverse wall. the three sides of this furnace are built of rectangular rocks, upon which bricks are laid; the back furnace wall is three feet and a palm high, and the rear of the side walls is the same; the side walls are sloping, and where the furnace is open in front they are only two feet and three palms high; all the walls are a foot and a palm thick. upon these walls stand upright posts not less thick, in order that they may bear the heavy weight placed upon them, and they are covered with lute; these posts support the sloping chimney and penetrate through the roof. moreover, not only the ribs of the chimney, but also the rafters, are covered thickly with lute. the hearth of the furnace is six feet long on each side, is sloping, and is paved with bricks. the cakes of copper are placed in the furnace and heated in the following way. they are first of all placed in the furnace in rows, with as many small stones the size of an egg between, so that the heat of the fire can penetrate through the spaces between them; indeed, those cakes which are placed at the bottom of the crucible are each raised upon half a brick for the same reason. but lest the last row, which lies against the mouth of the furnace, should fall out, against the mouth are placed iron plates, or the copper cakes which are the first taken from the crucible when copper is made, and against them are laid exhausted liquation cakes or rocks. then charcoal is thrown on the cakes, and then live coals; at first the cakes are heated by a gentle fire, and afterward more charcoal is added to them until it is at times three-quarters of a foot deep. a fiercer fire is certainly required to heat the hard cakes of copper than the fragile ones. when the cakes have been sufficiently heated, which usually occurs within the space of about two hours, the exhausted liquation cakes or the rocks and the iron plate are removed from the mouth of the furnace. then the hot cakes are taken out row after row with a two-pronged rabble, such as the one which is used by those who "dry" the exhausted liquation cakes. then the first cake is laid upon the exhausted liquation cakes, and beaten by two workmen with hammers until it breaks; the hotter the cakes are, the sooner they are broken up; the less hot, the longer it takes, for now and then they bend into the shape of copper basins. when the first cake has been broken, the second is put on to the other fragments and beaten until it breaks into pieces, and the rest of the cakes are broken up in the same manner in due order. the head of the hammer is three palms long and one wide, and sharpened at both ends, and its handle is of wood three feet long. when they have been broken by the stamp, if cold, or with hammers if hot, the fragments of copper or the cakes are carried into the store-room for copper. the foreman of the works, according to the different proportions of silver in each _centumpondium_ of copper, alloys it with lead, without which he could not separate the silver from the copper.[ ] if there be a moderate amount of silver in the copper, he alloys it fourfold; for instance, if in three-quarters of a _centumpondium_ of copper there is less than the following proportions, _i.e._: half a _libra_ of silver, or half a _libra_ and a _sicilicus_, or half a _libra_ and a _semi-uncia_, or half a _libra_ and _semi-uncia_ and a _sicilicus_, then rich lead--that is, that from which the silver has not yet been separated--is added, to the amount of half a _centumpondium_ or a whole _centumpondium_, or a whole and a half, in such a way that there may be in the copper-lead alloy some one of the proportions of silver which i have just mentioned, which is the first alloy. to this "first" alloy is added such a weight of de-silverized lead or litharge as is required to make out of all of these a single liquation cake that will contain approximately two _centumpondia_ of lead; but as usually from one hundred and thirty _librae_ of litharge only one hundred _librae_ of lead are made, a greater proportion of litharge than of de-silverized lead is added as a supplement. since four cakes of this kind are placed at the same time into the furnace in which the silver and lead is liquated from copper, there will be in all the cakes three _centumpondia_ of copper and eight _centumpondia_ of lead. when the lead has been liquated from the copper, it weighs six _centumpondia_, in each _centumpondium_ of which there is a quarter of a _libra_ and almost a _sicilicus_ of silver. only seven _unciae_ of the silver remain in the exhausted liquation cakes and in that copper-lead alloy which we call "liquation thorns"; they are not called by this name so much because they have sharp points as because they are base. if in three-quarters of a _centumpondium_ of copper there are less than seven _uncia_ and a _semi-uncia_ or a _bes_ of silver, then so much rich lead must be added as to make in the copper and lead alloy one of the proportions of silver which i have already mentioned. this is the "second" alloy. to this is again to be added as great a weight of de-silverized lead, or of litharge, as will make it possible to obtain from that alloy a liquation cake containing two and a quarter _centumpondia_ of lead, in which manner in four of these cakes there will be three _centumpondia_ of copper and nine _centumpondia_ of lead. the lead which liquates from these cakes weighs seven _centumpondia_, in each _centumpondium_ of which there is a quarter of a _libra_ of silver and a little more than a _sicilicus_. about seven _unciae_ of silver remain in the exhausted liquation cakes and in the liquation thorns, if we may be allowed to make common the old name (_spinae_ = thorns) and bestow it upon a new substance. if in three-quarters of a _centumpondium_ of copper there is less than three-quarters of a _libra_ of silver, or three-quarters and a _semi-uncia_, then as much rich lead must be added as will produce one of the proportions of silver in the copper-lead alloy above mentioned; this is the "third" alloy. to this is added such an amount of de-silverized lead or of litharge, that a liquation cake made from it contains in all two and three-quarters _centumpondia_ of lead. in this manner four such cakes will contain three _centumpondia_ of copper and eleven _centumpondia_ of lead. the lead which these cakes liquate, when they are melted in the furnace, weighs about nine _centumpondia_, in each _centumpondium_ of which there is a quarter of a _libra_ and more than a _sicilicus_ of silver; and seven _unciae_ of silver remain in the exhausted liquation cakes and in the liquation thorns. if, however, in three-quarters of a _centumpondium_ of copper there is less than ten-twelfths of a _libra_ or ten-twelfths of a _libra_ and a _semi-uncia_ of silver, then such a proportion of rich lead is added as will produce in the copper-lead alloy one of the proportions of silver which i mentioned above; this is the "fourth" alloy. to this is added such a weight of de-silverized lead or of litharge, that a liquation cake made from it contains three _centumpondia_ of lead, and in four cakes of this kind there are three _centumpondia_ of copper and twelve _centumpondia_ of lead. the lead which is liquated therefrom weighs about ten _centumpondia_, in each _centumpondium_ of which there is a quarter of a _libra_ and more than a _semi-uncia_ of silver, or seven _unciae_; a _bes_, or seven _unciae_ and a _semi-uncia_, of silver remain in the exhausted liquation cakes and in the liquation thorns. [illustration (blast furnaces): a--furnace in which "slags" are re-smelted. b--furnace in which copper is alloyed with lead. c--door. d--forehearths on the ground. e--copper moulds. f--rabble. g--hook. h--cleft stick. i--arm of the crane. k--the hook of its chain.] against the second long wall in the second part of the building, whose area is eighty feet long by thirty-nine feet wide, are four furnaces in which the copper is alloyed with lead, and six furnaces in which "slags" are re-smelted. the interior of the first kind of furnace is a foot and three palms wide, two feet three digits long; and of the second is a foot and a palm wide and a foot three palms and a digit long. the side walls of these furnaces are the same height as the furnaces in which gold or silver ores are smelted. as the whole room is divided into two parts by upright posts, the front part must have, first, two furnaces in which "slags" are re-melted; second, two furnaces in which copper is alloyed with lead; and third, one furnace in which "slags" are re-melted. the back part of the room has first, one furnace in which "slags" are re-melted; next, two furnaces in which copper is alloyed with lead; and third, two furnaces in which "slags" are re-melted. each of these is six feet distant from the next; on the right side of the first is a space of three feet and two palms, and on the left side of the last one of seven feet. each pair of furnaces has a common door, six feet high and a cubit wide, but the first and the tenth furnace each has one of its own. each of the furnaces is set in an arch of its own in the back wall, and in front has a forehearth pit; this is filled with a powder compound rammed down and compressed in order to make a crucible. under each furnace is a hidden receptacle for the moisture,[ ] from which a vent is made through the back wall toward the right, which allows the vapour to escape. finally, to the right, in front, is the copper mould into which the copper-lead alloy is poured from the forehearth, in order that liquation cakes of equal weight may be made. this copper mould is a digit thick, its interior is two feet in diameter and six digits deep. behind the second long wall are ten pairs of bellows, two machines for compressing them, and twenty instruments for inflating them. the way in which these should be made may be understood from book ix. the smelter, when he alloys copper with lead, with his hand throws into the heated furnace, first the large fragments of copper, then a basketful of charcoal, then the smaller fragments of copper. when the copper is melted and begins to run out of the tap-hole into the forehearth, he throws litharge into the furnace, and, lest part of it should fly away, he first throws charcoal over it, and lastly lead. as soon as he has thrown into the furnace the copper and the lead, from which alloy the first liquation cake is made, he again throws in a basket of charcoal, and then fragments of copper are thrown over them, from which the second cake may be made. afterward with a rabble he skims the "slag" from the copper and lead as they flow into the forehearth. such a rabble is a board into which an iron bar is fixed; the board is made of elder-wood or willow, and is ten digits long, six wide, and one and a half digits thick; the iron bar is three feet long, and the wooden handle inserted into it is two and a half feet long. while he purges the alloy and pours it out with a ladle into the copper mould, the fragments of copper from which he is to make the second cake are melting. as soon as this begins to run down he again throws in litharge, and when he has put on more charcoal he adds the lead. this operation he repeats until thirty liquation cakes have been made, on which work he expends nine hours, or at most ten; if more than thirty cakes must be made, then he is paid for another shift when he has made an extra thirty. at the same time that he pours the copper-lead alloy into the copper mould, he also pours water slowly into the top of the mould. then, with a cleft stick, he takes a hook and puts its straight stem into the molten cake. the hook itself is a digit and a half thick; its straight stem is two palms long and two digits wide and thick. afterward he pours more water over the cakes. when they are cold he places an iron ring in the hook of the chain let down from the pulley of the crane arm; the inside diameter of this ring is six digits, and it is about a digit and a half thick; the ring is then engaged in the hook whose straight stem is in the cake, and thus the cake is raised from the mould and put into its place. the copper and lead, when thus melted, yield a small amount of "slag"[ ] and much litharge. the litharge does not cohere, but falls to pieces like the residues from malt from which beer is made. _pompholyx_ adheres to the walls in white ashes, and to the sides of the furnace adheres _spodos_. in this practical manner lead is alloyed with copper in which there is but a moderate portion of silver. if, however, there is much silver in it, as, for instance, two _librae_, or two _librae_ and a _bes_, to the _centumpondium_,--which weighs one hundred and thirty-three and a third _librae_, or one hundred and forty-six _librae_ and a _bes_,[ ]--then the foreman of the works adds to a _centumpondium_ of such copper three _centumpondia_ of lead, in each _centumpondium_ of which there is a third of a _libra_ of silver, or a third of a _libra_ and a _semi-uncia_. in this manner three liquation cakes are made, which contain altogether three _centumpondia_ of copper and nine _centumpondia_ of lead.[ ] the lead, when it has been liquated from the copper, weighs seven _centumpondia_; and in each _centumpondium_--if the _centumpondium_ of copper contain two _librae_ of silver, and the lead contain a third of a _libra_--there will be a _libra_ and a sixth and more than a _semi-uncia_ of silver; while in the exhausted liquation cakes, and in the liquation thorns, there remains a third of a _libra_. if a _centumpondium_ of copper contains two _librae_ and a _bes_ of silver, and the lead a third of a _libra_ and a _semi-uncia_, there will be in each liquation cake one and a half _librae_ and a _semi-uncia_, and a little more than a _sicilicus_ of silver. in the exhausted liquation cakes there remain a third of a _libra_ and a _semi-uncia_ of silver. [illustration (furnaces enriching copper bottoms): a--furnace. b--forehearth. c--dipping-pot. d--cakes.] if there be in the copper only a minute proportion of silver, it cannot be separated easily until it has been re-melted in other furnaces, so that in the "bottoms" there remains more silver and in the "tops" less.[ ] this furnace, vaulted with unbaked bricks, is similar to an oven, and also to the cupellation furnace, in which the lead is separated from silver, which i described in the last book. the crucible is made of ashes, in the same manner as in the latter, and in the front of the furnace, three feet above the floor of the building, is the mouth out of which the re-melted copper flows into a forehearth and a dipping-pot. on the left side of the mouth is an aperture, through which beech-wood may be put into the furnace to feed the fire. if in a _centumpondium_ of copper there were a sixth of a _libra_ and a _semi-uncia_ of silver, or a quarter of a _libra_, or a quarter of a _libra_ and a _semi-uncia_--there is re-melted at the same time thirty-eight _centumpondia_ of it in this furnace, until there remain in each _centumpondium_ of the copper "bottoms" a third of a _libra_ and a _semi-uncia_ of silver. for example, if in each _centumpondium_ of copper not yet re-melted, there is a quarter of a _libra_ and a _semi-uncia_ of silver, then the thirty-eight _centumpondia_ that are smelted together must contain a total of eleven _librae_ and an _uncia_ of silver. since from fifteen _centumpondia_ of re-melted copper there was a total of four and a third _librae_ and a _semi-uncia_ of silver, there remain only two and a third _librae_. thus there is left in the "bottoms," weighing twenty-three _centumpondia_, a total of eight and three-quarter _librae_ of silver. therefore, each _centumpondium_ of this contains a third of a _libra_ and a _semi-uncia_, a _drachma_, and the twenty-third part of a _drachma_ of silver; from such copper it is profitable to separate the silver. in order that the master may be more certain of the number of _centumpondia_ of copper in the "bottoms," he weighs the "tops" that have been drawn off from it; the "tops" were first drawn off into the dipping-pot, and cakes were made from them. fourteen hours are expended on the work of thus dividing the copper. the "bottoms," when a certain weight of lead has been added to them, of which alloy i shall soon speak, are melted in the blast furnace; liquation cakes are then made, and the silver is afterward separated from the copper. the "tops" are subsequently melted in the blast furnace, and re-melted in the refining furnace, in order that red copper shall be made[ ]; and the "tops" from this are again smelted in the blast furnace, and then again in the refining furnace, that therefrom shall be made _caldarium_ copper. but when the copper, yellow or red or _caldarium_ is re-smelted in the refining furnace, forty _centumpondia_ are placed in it, and from it they make at least twenty, and at most thirty-five, _centumpondia_. about twenty-two _centumpondia_ of exhausted liquation cakes and ten of yellow copper and eight of red, are simultaneously placed in this latter furnace and smelted, in order that they may be made into refined copper. the copper "bottoms" are alloyed in three different ways with lead.[ ] first, five-eighths of a _centumpondium_ of copper and two and three-quarters _centumpondia_ of lead are taken; and since one liquation cake is made from this, therefore two and a half _centumpondia_ of copper and eleven _centumpondia_ of lead make four liquation cakes. inasmuch as in each _centumpondium_ of copper there is a third of a _libra_ of silver, there would be in the whole of the copper ten-twelfths of a _libra_ of silver; to these are added four _centumpondia_ of lead re-melted from "slags," each _centumpondium_ of which contains a _sicilicus_ and a _drachma_ of silver, which weights make up a total of an _uncia_ and a half of silver. there is also added seven _centumpondia_ of de-silverized lead, in each _centumpondium_ of which there is a _drachma_ of silver; therefore in the four cakes of copper-lead alloy there is a total of a _libra_, a _sicilicus_ and a _drachma_ of silver. in each single _centumpondium_ of lead, after it has been liquated from the copper, there is an _uncia_ and a _drachma_ of silver, which alloy we call "poor" argentiferous lead, because it contains but little silver. but as five cakes of that kind are placed together in the furnace, they liquate from them usually as much as nine and three-quarters _centumpondia_ of poor argentiferous lead, in each _centumpondium_ of which there is an _uncia_ and a _drachma_ of silver, or a total of ten _unciae_ less four _drachmae_. of the liquation thorns there remain three _centumpondia_, in each _centumpondium_ of which there are three _sicilici_ of silver; and there remain four _centumpondia_ of exhausted liquation cakes, each _centumpondium_ of which contains a _semi-uncia_ or four and a half _drachmae_. inasmuch as in a _centumpondium_ of copper "bottoms" there is a third of a _libra_ and a _semi-uncia_ of silver, in five of those cakes there must be more than one and a half _unciae_ and half a _drachma_ of silver. then, again, from another two and a half _centumpondia_ of copper "bottoms," together with eleven _centumpondia_ of lead, four liquation cakes are made. if in each _centumpondium_ of copper there was a third of a _libra_ of silver, there would be in the whole of the _centumpondia_ of base metal five-sixths of a _libra_ of the precious metal. to this copper is added eight _centumpondia_ of poor argentiferous lead, each _centumpondium_ of which contains an _uncia_ and a _drachma_ of silver, or a total of three-quarters of a _libra_ of silver. there is also added three _centumpondia_ of de-silverized lead, in each _centumpondium_ of which there is a _drachma_ of silver. therefore, four liquation cakes contain a total of a _libra_, seven _unciae_, a _sicilicus_ and a _drachma_ of silver; thus each _centumpondium_ of lead, when it has been liquated from the copper, contains an _uncia_ and a half and a _sicilicus_ of silver, which alloy we call "medium" silver-lead. then, again, from another two and a half _centumpondia_ of copper "bottoms," together with eleven _centumpondia_ of lead, they make four liquation cakes. if in each _centumpondium_ of copper there were likewise a third of a _libra_ of silver, there will be in all the weight of the base metal five-sixths of a _libra_ of the precious metal. to this is added nine _centumpondia_ of medium silver-lead, each _centumpondium_ of which contains an _uncia_ and a half and a _sicilicus_ of silver; or a total of a _libra_ and a quarter and a _semi-uncia_ and a _sicilicus_ of silver. and likewise they add two _centumpondia_ of poor silver-lead, in each of which there is an _uncia_ and a _drachma_ of silver. therefore the four liquation cakes contain two and a third _librae_ of silver. each _centumpondium_ of lead, when it has been liquated from the copper, contains a sixth of a _libra_ and a _semi-uncia_ and a _drachma_ of silver. this alloy we call "rich" silver-lead; it is carried to the cupellation furnace, in which lead is separated from silver. i have now mentioned in how many ways copper containing various proportions of silver is alloyed with lead, and how they are melted together in the furnace and run into the casting pan. [illustration (crane for liquation cakes): a--crane. b--drum consisting of rundles. c--toothed drum. d--trolley and its wheels. e--triangular board. f--cakes. g--chain of the crane. h--its hook. i--ring. k--the tongs.] now i will speak of the method by which lead is liquated from copper simultaneously with the silver. the liquation cakes are raised from the ground with the crane, and placed on the copper plates of the furnaces. the hook of the chain let down from the arm of the crane, is inserted in a ring of the tongs, one jaw of which has a tooth; a ring is engaged in each of the handles of the tongs, and these two rings are engaged in a third, in which the hook of the chain is inserted. the tooth on the one jaw of the tongs is struck by a hammer, and driven into the hole in the cake, at the point where the straight end of the hook was driven into it when it was lifted out of the copper mould; the other jaw of the tongs, which has no tooth, squeezes the cake, lest the tooth should fall out of it; the tongs are one and a half feet long, each ring is a digit and a half thick, and the inside is a palm and two digits in diameter. those cranes by which the cakes are lifted out of the copper pans and placed on the ground, and lifted up again from there and placed in the furnaces, are two in number--one in the middle space between the third transverse wall and the two upright posts, and the other in the middle space between the same posts and the seventh transverse wall. the rectangular crane-post of both of these is two feet wide and thick, and is eighteen feet from the third long wall, and nineteen from the second long wall. there are two drums in the framework of each--one drum consisting of rundles, the other being toothed. the crane-arm of each extends seventeen feet, three palms and as many digits from the post. the trolley of each crane is two feet and as many palms long, a foot and two digits wide, and a palm and two digits thick; but where it runs between the beams of the crane-arm it is three digits wide and a palm thick; it has five notches, in which turn five brass wheels, four of which are small, and the fifth much larger than the rest. the notches in which the small wheels turn are two palms long and as much as a palm wide; those wheels are a palm wide and a palm and two digits in diameter; four of the notches are near the four corners of the trolley; the fifth notch is between the two front ones, and it is two palms back from the front. its pulley is larger than the rest, and turns in its own notch; it is three palms in diameter and one palm wide, and grooved on the circumference, so that the iron chain may run in the groove. the trolley has two small axles, to the one in front are fastened three, and to the one at the back, the two wheels; two wheels run on the one beam of the crane-arm, and two on the other; the fifth wheel, which is larger than the others, runs between those two beams. those people who have no cranes place the cakes on a triangular board, to which iron cleats are affixed, so that it will last longer; the board has three iron chains, which are fixed in an iron ring at the top; two workmen pass a pole through the ring and carry it on their shoulders, and thus take the cake to the furnace in which silver is separated from copper. from the vicinity of the furnaces in which copper is mixed with lead and the "slags" are re-melted, to the third long wall, are likewise ten furnaces, in which silver mixed with lead is separated from copper. if this space is eighty feet and two palms long, and the third long wall has in the centre a door three feet and two palms wide, then the spaces remaining at either side of the door will be thirty-eight feet and two palms; and if each of the furnaces occupies four feet and a palm, then the interval between each furnace and the next one must be a foot and three palms; thus the width of the five furnaces and four interspaces will be twenty-eight feet and a palm. therefore, there remain ten feet and a palm, which measurement is so divided that there are five feet and two digits between the first furnace and the transverse wall, and as many feet and digits between the fifth furnace and the door; similarly in the other part of the space from the door to the sixth furnace, there must be five feet and two digits, and from the tenth furnace to the seventh transverse wall, likewise, five feet and two digits. the door is six feet and two palms high; through it the foreman of the _officina_ and the workmen enter the store-room in which the silver-lead alloy is kept. [illustration (liquation furnace): a--sole-stones. b--rectangular stones. c--copper plates. d--front panel. e--side panels. f--bar. g--front end of the long iron rods. h--short chain. i--hooked rod. k--wall which protects the third long wall from injury by fire. l--third long wall. m--feet of the panels. n--iron blocks. o--cakes. p--hearth. q--receiving-pit.] each furnace has a bed, a hearth, a rear wall, two sides and a front, and a receiving-pit. the bed consists of two sole-stones, four rectangular stones, and two copper plates; the sole-stones are five feet and a palm long, a cubit wide, a foot and a palm thick, and they are sunk into the ground, so that they emerge a palm and two digits; they are distant from each other about three palms, yet the distance is narrower at the back than the front. each of the rectangular stones is two feet and as many palms long, a cubit wide, and a cubit thick at the outer edge, and a foot and a palm thick on the inner edge which faces the hearth, thus they form an incline, so that there is a slope to the copper plates which are laid upon them. two of these rectangular stones are placed on one sole-stone; a hole is cut in the upper edge of each, and into the holes are placed iron clamps, and lead is poured in; they are so placed on the sole-stones that they project a palm at the sides, and at the front the sole-stones project to the same extent; if rectangular stones are not available, bricks are laid in their place. the copper plates are four feet two palms and as many digits long, a cubit wide, and a palm thick; each edge has a protuberance, one at the front end, the other at the back; these are a palm and three digits long, and a palm wide and thick. the plates are so laid upon the rectangular stones that their rear ends are three digits from the third long wall; the stones project beyond the plate the same number of digits in front, and a palm and three digits at the sides. when the plates have been joined, the groove which is between the protuberances is a palm and three digits wide, and four feet long, and through it flows the silver-lead which liquates from the cakes. when the plates are corroded either by the fire or by the silver-lead, which often adheres to them in the form of stalactites, and is chipped off, they are exchanged, the right one being placed to the left, and the left one, on the contrary, to the right; but the left side of the plates, which, when the fusion of the copper took place, came into contact with the copper, must lie flat; so that when the exchange of the plates has been carried out, the protuberances, which are thus on the underside, raise the plate from the stones, and they have to be partially chipped off, lest they should prove an impediment to the work; and in each of their places is laid a piece of iron, three palms long, a digit thick at both ends, and a palm thick in the centre for the length of a palm and three digits. the passage under the plates between the rectangular stones is a foot wide at the back, and a foot and a palm wide at the front, for it gradually widens out. the hearth, which is between the sole-stones, is covered with a bed of hearth-lead, taken from the crucible in which lead is separated from silver. the rear end is the highest, and should be so high that it reaches to within six digits of the plates, from which point it slopes down evenly to the front end, so that the argentiferous lead alloy which liquates from the cakes can flow into the receiving-pit. the wall built against the third long wall in order to protect it from injury by fire, is constructed of bricks joined together with lute, and stands on the copper plates; this wall is two feet, a palm and two digits high, two palms thick, and three feet, a palm and three digits wide at the bottom, for it reaches across both of them; at the top it is three feet wide, for it rises up obliquely on each side. at each side of this wall, at a height of a palm and two digits above the top of it, there is inserted in a hole in the third long wall a hooked iron rod, fastened in with molten lead; the rod projects two palms from the wall, and is two digits wide and one digit thick; it has two hooks, the one at the side, the other at the end. both of these hooks open toward the wall, and both are a digit thick, and both are inserted in the last, or the adjacent, links of a short iron chain. this chain consists of four links, each of which is a palm and a digit long and half a digit thick; the first link is engaged in the first hole in a long iron rod, and one or other of the remaining three links engages the hook of the hooked rod. the two long rods are three feet and as many palms and digits long, two digits wide, and one digit thick; both ends of both of these rods have holes, the back one of which is round and a digit in diameter, and in this is engaged the first link of the chain as i have stated; the hole at the front end is two digits and a half long and a digit and a half wide. this end of each rod is made three digits wide, while for the rest of its length it is only two digits, and at the back it is two and a half digits. into the front hole of each rod is driven an iron bar, which is three feet and two palms long, two digits wide and one thick; in the end of this bar are five small square holes, two-thirds of a digit square; each hole is distant from the other half a digit, the first being at a distance of about a digit from the end. into one of these holes the refiner drives an iron pin; if he should desire to make the furnace narrower, then he drives it into the last hole; if he should desire to widen it, then into the first hole; if he should desire to contract it moderately, then into one of the middle holes. for the same reason, therefore, the hook is sometimes inserted into the last link of the chain, and sometimes into the third or the second. the furnace is widened when many cakes are put into it, and contracted when there are but few, but to put in more than five is neither usual nor possible; indeed, it is because of thin cakes that the walls are contracted. the bar has a hump, which projects a digit on each side at the back, of the same width and thickness as itself. these humps project, lest the bar should slip through the hole of the right-hand rod, in which it remains fixed when it, together with the rods, is not pressing upon the furnace walls. [illustration (liquation furnaces): a--furnace in which the operation of liquation is being performed. b--furnace in which it is not being performed. c--receiving-pit. d--moulds. e--cakes. f--liquation thorns.] there are three panels to the furnace--two at the sides, one in front and another at the back. those which are at the sides are three feet and as many palms and two digits long, and two feet high; the front one is two feet and a palm and three digits long, and, like the side ones, two feet high. each consists of iron bars, of feet, and of iron plates. those which are at the side have seven bars, the lower and upper of which are of the same length as the panels; the former holds up the upright bars; the latter is placed upon them; the uprights are five in number, and have the same height as the panels; the middle ones are inserted into holes in the upper and lower bars; the outer ones are made of one and the same bar as the lower and upper ones. they are two digits wide and one thick. the front panel has five bars; the lower one holds similar uprights, but there are three of them only; the upper bar is placed on them. each of these panels has two feet fixed at each end of the lower bar, and these are two palms long, one wide, and a digit thick. the iron plates are fastened to the inner side of the bars with iron wire, and they are covered with lute, so that they may last longer and may be uninjured by the fire. there are, besides, iron blocks three palms long, one wide, and a digit and a half thick; the upper surface of these is somewhat hollowed out, so that the cakes may stand in them; these iron blocks are dipped into a vessel in which there is clay mixed with water, and they are used only for placing under the cakes of copper and lead alloy made in the furnaces. there is more silver in these than in those which are made of liquation thorns, or furnace accretions, or re-melted "slags." two iron blocks are placed under each cake, in order that, by raising it up, the fire may bring more force to bear upon it; the one is put on the right bed-plate, the other on the left. finally, outside the hearth is the receiving-pit, which is a foot wide and three palms deep; when this is worn away it is restored with lute alone, which easily retains the lead alloy. if four liquation cakes are placed on the plates of each furnace, then the iron blocks are laid under them; but if the cakes are made from copper "bottoms," or from liquation thorns, or from the accretions or "slags," of which i have partly written above and will further describe a little later, there are five of them, and because they are not so large and heavy, no blocks are placed under them. pieces of charcoal six digits long are laid between the cakes, lest they should fall one against the other, or lest the last one should fall against the wall which protects the third long wall from injury by fire. in the middle empty spaces, long and large pieces of charcoal are likewise laid. then when the panels have been set up, and the bar has been closed, the furnace is filled with small charcoal, and a wicker basket full of charcoal is thrown into the receiving-pit, and over that are thrown live coals; soon afterward the burning coal, lifted up in a shovel, is spread over all parts of the furnace, so that the charcoal in it may be kindled; any charcoal which remains in the receiving-pit is thrown into the passage, so that it may likewise be heated. if this has not been done, the silver-lead alloy liquated from the cakes is frozen by the coldness of the passage, and does not run down into the receiving-pit. after a quarter of an hour the cakes begin to drip silver-lead alloy,[ ] which runs down through the openings between the copper plates into the passage. when the long pieces of charcoal have burned up, if the cakes lean toward the wall, they are placed upright again with a hooked bar, but if they lean toward the front bar they are propped up by charcoal; moreover, if some cakes shrink more than the rest, charcoal is added to the former and not to the others. the silver drips together with the lead, for both melt more rapidly than copper. the liquation thorns do not flow away, but remain in the passage, and should be turned over frequently with a hooked bar, in order that the silver-lead may liquate away from them and flow down into the receiving pit; that which remains is again melted in the blast furnace, while that which flows into the receiving pit is at once carried with the remaining products to the cupellation furnace, where the lead is separated from the silver. the hooked bar has an iron handle two feet long, in which is set a wooden one four feet long. the silver-lead which runs out into the receiving-pit is poured out by the refiner with a bronze ladle into eight copper moulds, which are two palms and three digits in diameter; these are first smeared with a lute wash so that the cakes of silver-lead may more easily fall out when they are turned over. if the supply of moulds fails because the silver-lead flows down too rapidly into the receiving-pit, then water is poured on them, in order that the cakes may cool and be taken out of them more rapidly; thus the same moulds may be used again immediately; if no such necessity urges the refiner, he washes over the empty moulds with a lute wash. the ladle is exactly similar to that which is used in pouring out the metals that are melted in the blast furnace. when all the silver-lead has run down from the passage into the receiving-pit, and has been poured out into copper moulds, the thorns are drawn out of the passage into the receiving-pit with a rabble; afterward they are raked on to the ground from the receiving-pit, thrown with a shovel into a wheelbarrow, and, having been conveyed away to a heap, are melted once again. the blade of the rabble is two palms and as many digits long, two palms and a digit wide, and joined to its back is an iron handle three feet long; into the iron handle is inserted a wooden one as many feet in length. the residue cakes, after the silver-lead has been liquated from the copper, are called "exhausted liquation cakes" (_fathiscentes_), because when thus smelted they appear to be dried up. by placing a crowbar under the cakes they are raised up, seized with tongs, and placed in the wheelbarrow; they are then conveyed away to the furnace in which they are "dried." the crowbar is somewhat similar to those generally used to chip off the accretions that adhere to the walls of the blast furnace. the tongs are two and a half feet long. with the same crowbar the stalactites are chipped off from the copper plates from which they hang, and with the same instrument the iron blocks are struck off the exhausted liquation cakes to which they adhere. the refiner has performed his day's task when he has liquated the silver-lead from sixteen of the large cakes and twenty of the smaller ones; if he liquates more than this, he is paid separately for it at the price for extraordinary work. silver, or lead mixed with silver, which we call _stannum_, is separated by the above method from copper. this silver-lead is carried to the cupellation furnace, in which lead is separated from silver; of these methods i will mention only one, because in the previous book i have explained them in detail. amongst us some years ago only forty-four _centumpondia_ of silver-lead and one of copper were melted together in the cupellation furnaces, but now they melt forty-six _centumpondia_ of silver-lead and one and a half _centumpondia_ of copper; in other places, usually a hundred and twenty _centumpondia_ of silver-lead alloy and six of copper are melted, in which manner they make about one hundred and ten _centumpondia_ more or less of litharge and thirty of hearth-lead. but in all these methods the silver which is in the copper is mixed with the remainder of silver; the copper itself, equally with the lead, will be changed partly into litharge and partly into hearth-lead.[ ] the silver-lead alloy which does not melt is taken from the margin of the crucible with a hooked bar. [illustration (exhausted liquation cakes): a--cakes. b--hammer.] the work of "drying" is distributed into four operations, which are performed in four days. on the first--as likewise on the other three days--the master begins at the fourth hour of the morning, and with his assistant chips off the stalactites from the exhausted liquation cakes. they then carry the cakes to the furnace, and put the stalactites upon the heap of liquation thorns. the head of the chipping hammer is three palms and as many digits long; its sharp edge is a palm wide; the round end is three digits thick; the wooden handle is four feet long. the master throws pulverised earth into a small vessel, sprinkles water over it, and mixes it; this he pours over the whole hearth, and sprinkles charcoal dust over it to the thickness of a digit. if he should neglect this, the copper, settling in the passages, would adhere to the copper bed-plates, from which it can be chipped off only with difficulty; or else it would adhere to the bricks, if the hearth was covered with them, and when the copper is chipped off these they are easily broken. on the second day, at the same time, the master arranges bricks in ten rows; in this manner twelve passages are made. the first two rows of bricks are between the first and the second openings on the right of the furnace; the next three rows are between the second and third openings, the following three rows are between the third and the fourth openings, and the last two rows between the fourth and fifth openings. these bricks are a foot and a palm long, two palms and a digit wide, and a palm and two digits thick; there are seven of these thick bricks in a row, so there are seventy all together. then on the first three rows of bricks they lay exhausted liquation cakes and a layer five digits thick of large charcoal; then in a similar way more exhausted liquation cakes are laid upon the other bricks, and charcoal is thrown upon them; in this manner seventy _centumpondia_ of cakes are put on the hearth of the furnace. but if half of this weight, or a little more, is to be "dried," then four rows of bricks will suffice. those who dry exhausted liquation cakes[ ] made from copper "bottoms" place ninety or a hundred _centumpondia_[ ] into the furnace at the same time. a place is left in the front part of the furnace for the topmost cakes removed from the forehearth in which copper is made, these being more suitable for supporting the exhausted liquation cakes than are iron plates; indeed, if the former cakes drip copper from the heat, this can be taken back with the liquation thorns to the first furnace, but melted iron is of no use to us in these matters. when the cakes of this kind have been placed in front of the exhausted liquation cakes, the workman inserts the iron bar into the holes on the inside of the wall, which are at a height of three palms and two digits above the hearth; the hole to the left penetrates through into the wall, so that the bar may be pushed back and forth. this bar is round, eight feet long and two digits in diameter; on the right side it has a haft made of iron, which is about a foot from the right end; the aperture in this haft is a palm wide, two digits high, and a digit thick. the bar holds the exhausted liquation cakes opposite, lest they should fall down. when the operation of "drying" is completed, a workman draws out this bar with a crook which he inserts into the haft, as i will explain hereafter. [illustration (drying furnace for liquation): a--side walls. b--front arch. c--rear arch. d--wall in the rear arch. e--inner wall. f--vent holes. g--chimney. h--hearth. i--tank. k--pipe. l--plug. m--iron door. n--transverse bars. o--upright bars. p--plates. q--rings of the bars. r--chains. s--rows of bricks. t--bar. v--its haft. x--copper bed-plates.] in order that one should understand those things of which i have spoken, and concerning which i am about to speak, it is necessary for me to give some information beforehand about the furnace and how it is to be made. it stands nine feet from the fourth long wall, and as far from the wall which is between the second and fourth transverse walls. it consists of walls, an arch, a chimney, an interior wall, and a hearth; the two walls are at the sides; and they are eleven feet three palms and two digits long, and where they support the chimney they are eight feet and a palm high. at the front of the arch they are only seven feet high; they are two feet three palms and two digits thick, and are made either of rock or of bricks; the distance between them is eight feet, a palm and two digits. there are two of the arches, for the space at the rear between the walls is also arched from the ground, in order that it may be able to support the chimney; the foundations of these arches are the walls of the furnace; the span of the arch has the same length as the space between the walls; the top of the arch is five feet, a palm and two digits high. in the rear arch there is a wall made of bricks joined with lime; this wall at a height of a foot and three palms from the ground has five vent-holes, which are two palms and a digit high, a palm and a digit wide, of which the first is near the right interior wall, and the last near the left interior wall, the remaining three in the intervening space; these vent-holes penetrate through the interior of the wall which is in the arch. half-bricks can be placed over the vent-holes, lest too much air should be drawn into the furnace, and they can be taken out at times, in order that he who is "drying" the exhausted liquation cakes may inspect the passages, as they are called, to see whether the cakes are being properly "dried." the front arch is three feet two palms distant from the rear one; this arch is the same thickness as that of the rear arch, but the span is six feet wide; the interior of the arch itself is of the same height as the walls. a chimney is built upon the arches and the walls, and is made of bricks joined together with lime; it is thirty-six feet high and penetrates through the roof. the interior wall is built against the rear arch and both the side walls, from which it juts out a foot; it is three feet and the same number of palms high, three palms thick, and is made of bricks joined together with lute and smeared thickly with lute, sloping up to the height of a foot above it. this wall is a kind of shield, for it protects the exterior walls from the heat of the fire, which is apt to injure them; the latter cannot be easily re-made, while the former can be repaired with little work. the hearth is made of lute, and is covered either with copper plates, such as those of the furnaces in which silver is liquated from copper, although they have no protuberances, or it may be covered with bricks, if the owners are unwilling to incur the expense of copper plates. the wider part of the hearth is made sloping in such a manner that the rear end reaches as high as the five vent-holes, and the front end of the hearth is so low that the back of the front arch is four feet, three palms and as many digits above it, and the front five feet, three palms and as many digits. the hearth beyond the furnaces is paved with bricks for a distance of six feet. near the furnace, against the fourth long wall, is a tank thirteen feet and a palm long, four feet wide, and a foot and three palms deep. it is lined on all sides with planks, lest the earth should fall into it; on one side the water flows in through pipes, and on the other, if the plug be pulled out, it soaks into the earth; into this tank of water are thrown the cakes of copper from which the silver and lead have been separated. the fore part of the front furnace arch should be partly closed with an iron door; the bottom of this door is six feet and two digits wide; the upper part is somewhat rounded, and at the highest point, which is in the middle, it is three feet and two palms high. it is made of iron bars, with plates fastened to them with iron wire, there being seven bars--three transverse and four upright--each of which is two digits wide and half a digit thick. the lowest transverse bar is six feet and two palms long; the middle one has the same length; the upper one is curved and higher at the centre, and thus longer than the other two. the upright bars are two feet distant from one another; both the outer ones are two feet and as many palms high; but the centre ones are three feet and two palms. they project from the upper curved transverse bar and have holes, in which are inserted the hooks of small chains two feet long; the topmost links of these chains are engaged in the ring of a third chain, which, when extended, reaches to one end of a beam which is somewhat cut out. the chain then turns around the beam, and again hanging down, the hook in the other end is fastened in one of the links. this beam is eleven feet long, a palm and two digits wide, a palm thick, and turns on an iron axle fixed in a nearby timber; the rear end of the beam has an iron pin, which is three palms and a digit long, and which penetrates through it where it lies under a timber, and projects from it a palm and two digits on one side, and three digits on the other side. at this point the pin is perforated, in order that a ring may be fixed in it and hold it, lest it should fall out of the beam; that end is hardly a digit thick, while the other round end is thicker than a digit. when the door is to be shut, this pin lies under the timber and holds the door so that it cannot fall; the pin likewise prevents the rectangular iron band which encircles the end of the beam, and into which is inserted the ring of a long hook, from falling from the end. the lowest link of an iron chain, which is six feet long, is inserted in the ring of a staple driven into the right wall of the furnace, and fixed firmly by filling in with molten lead. the hook suspended at the top from the ring should be inserted in one of these lower links, when the door is to be raised; when the door is to be let down, the hook is taken out of that link and put into one of the upper links. [illustration (drying furnace for liquation): a--the door let down. b--bar. c--exhausted liquation cakes. d--bricks. e--tongs.] on the third day the master sets about the principal operation. first he throws a basketful of charcoals on to the ground in front of the hearth, and kindles them by adding live coals, and having thrown live coals on to the cakes placed within, he spreads them equally all over with an iron shovel. the blade of the shovel is three palms and a digit long, and three palms wide; its iron handle is two palms long, and the wooden one ten feet long, so that it can reach to the rear wall of the furnace. the exhausted liquation cakes become incandescent in an hour and a half, if the copper was good and hard, or after two hours, if it was soft and fragile. the workman adds charcoal to them where he sees it is needed, throwing it into the furnace through the openings on both sides between the side walls and the closed door. this opening is a foot and a palm wide. he lets down the door, and when the "slags" begin to flow he opens the passages with a bar; this should take place after five hours; the door is let down over the upper open part of the arch for two feet and as many digits, so that the master can bear the violence of the heat. when the cakes shrink, charcoal should not be added to them lest they should melt. if the cakes made from poor and fragile copper are "dried" with cakes made from good hard copper, very often the copper so settles into the passages that a bar thrust into them cannot penetrate them. this bar is of iron, six feet and two palms long, into which a wooden handle five feet long is inserted. the refiner draws off the "slags" with a rabble from the right side of the hearth. the blade of the rabble is made of an iron plate a foot and a palm wide, gradually narrowing toward the handle; the blade is two palms high, its iron handle is two feet long, and the wooden handle set into it is ten feet long. [illustration (drying furnace for liquation): a--the door raised. b--hooked bar. c--two-pronged rake. d--tongs. e--tank.] when the exhausted liquation cakes have been "dried," the master raises the door in the manner i have described, and with a long iron hook inserted into the haft of the bar he draws it through the hole in the left wall from the hole in the right wall; afterward he pushes it back and replaces it. the master then takes out the exhausted liquation cakes nearest to him with the iron hook; then he pulls out the cakes from the bricks. this hook is two palms high, as many digits wide, and one thick; its iron handle is two feet long, and the wooden handle eleven feet long. there is also a two-pronged rake with which the "dried" cakes are drawn over to the left side so that they may be seized with tongs; the prongs of the rake are pointed, and are two palms long, as many digits wide, and one digit thick; the iron part of the handle is a foot long, the wooden part nine feet long. the "dried" cakes, taken out of the hearth by the master and his assistants, are seized with other tongs and thrown into the rectangular tank, which is almost filled with water. these tongs are two feet and three palms long, both the handles are round and more than a digit thick, and the ends are bent for a palm and two digits; both the jaws are a digit and a half wide in front and sharpened; at the back they are a digit thick, and then gradually taper, and when closed, the interior is two palms and as many digits wide. the "dried" cakes which are dripping copper are not immediately dipped into the tank, because, if so, they burst in fragments and give out a sound like thunder. the cakes are afterward taken out of the tank with the tongs, and laid upon the two transverse planks on which the workmen stand; the sooner they are taken out the easier it is to chip off the copper that has become ash-coloured. finally, the master, with a spade, raises up the bricks a little from the hearth, while they are still warm. the blade of the spade is a palm and two digits long, the lower edge is sharp, and is a palm and a digit wide, the upper end a palm wide; its handle is round, the iron part being two feet long, and the wooden part seven and a half feet long. on the fourth day the master draws out the liquation thorns which have settled in the passages; they are much richer in silver than those that are made when the silver-lead is liquated from copper in the liquation furnace. the "dried" cakes drip but little copper, but nearly all their remaining silver-lead and the thorns consist of it, for, indeed, in one _centumpondium_ of "dried" copper there should remain only half an _uncia_ of silver, and there sometimes remain only three _drachmae_.[ ] some smelters chip off the metal adhering to the bricks with a hammer, in order that it may be melted again; others, however, crush the bricks under the stamps and wash them, and the copper and lead thus collected is melted again. the master, when he has taken these things away and put them in their places, has finished his day's work. [illustration (dried liquation cakes): a--tank. b--board. c--tongs. d--"dried" cakes taken out of the tanks. e--block. f--rounded hammer. g--pointed hammer.] the assistants take the "dried" cakes out of the tank on the next day, place them on an oak block, and first pound them with rounded hammers in order that the ash-coloured copper may fall away from them, and then they dig out with pointed picks the holes in the cakes, which contain the same kind of copper. the head of the round hammer is three palms and a digit long; one end of the head is round and two digits long and thick; the other end is chisel-shaped, and is two digits and a half long. the sharp pointed hammer is the same length as the round hammer, but one end is pointed, the other end is square, and gradually tapers to a point. the nature of copper is such that when it is "dried" it becomes ash coloured, and since this copper contains silver, it is smelted again in the blast furnaces.[ ] [illustration (copper refining furnace): a--hearth of the furnace. b--chimney. c--common pillar. d--other pillars. the partition wall is behind the common pillar and not to be seen. e--arches. f--little walls which protect the partition wall from injury by the fire. g--crucibles. h--second long wall. i--door. k--spatula. l--the other spatula. m--the broom in which is inserted a stick. n--pestles. o--wooden mallet. p--plate. q--stones. r--iron rod.] i have described sufficiently the method by which exhausted liquation cakes are "dried"; now i will speak of the method by which they are made into copper after they have been "dried." these cakes, in order that they may recover the appearance of copper which they have to some extent lost, are melted in four furnaces, which are placed against the second long wall in the part of the building between the second and third transverse walls. this space is sixty-three feet and two palms long, and since each of these furnaces occupies thirteen feet, the space which is on the right side of the first furnace, and on the left of the fourth, are each three feet and three palms wide, and the distance between the second and third furnace is six feet. in the middle of each of these three spaces is a door, a foot and a half wide and six feet high, and the middle one is common to the master of each of the furnaces. each furnace has its own chimney, which rises between the two long walls mentioned above, and is supported by two arches and a partition wall. the partition wall is between the two furnaces, and is five feet long, ten feet high, and two feet thick; in front of it is a pillar belonging in common to the front arches of the furnace on either side, which is two feet and as many palms thick, three feet and a half wide. the front arch reaches from this common pillar to another pillar that is common to the side arch of the same furnace; this arch on the right spans from the second long wall to the same pillar, which is two feet and as many palms wide and thick at the bottom. the interior of the front arch is nine feet and a palm wide, and eight feet high at its highest point; the interior of the arch which is on the right side, is five feet and a palm wide, and of equal height to the other, and both the arches are built of the same height as the partition wall. imposed upon these arches and the partition wall are the walls of the chimney; these slope upward, and thus contract, so that at the upper part, where the fumes are emitted, the opening is eight feet in length, one foot and three palms in width. the fourth wall of the chimney is built vertically upon the second long wall. as the partition wall is common to the two furnaces, so its superstructure is common to the two chimneys. in this sensible manner the chimney is built. at the front each furnace is six feet two palms long, and three feet two palms wide, and a cubit high; the back of each furnace is against the second long wall, the front being open. the first furnace is open and sloping at the right side, so that the slags may be drawn out; the left side is against the partition wall, and has a little wall built of bricks cemented together with lute; this little wall protects the partition wall from injury by the fire. on the contrary, the second furnace has the left side open and the right side is against the partition wall, where also it has its own little wall which protects the partition wall from the fire. the front of each furnace is built of rectangular rocks; the interior of it is filled up with earth. then in each of the furnaces at the rear, against the second long wall, is an aperture through an arch at the back, and in these are fixed the copper pipes. each furnace has a round pit, two feet and as many palms wide, built three feet away from the partition wall. finally, under the pit of the furnace, at a depth of a cubit, is the hidden receptacle for moisture, similar to the others, whose vent penetrates through the second long wall and slopes upward to the right from the first furnace, and to the left from the second. if copper is to be made the next day, then the master cuts out the crucible with a spatula, the blade of which is three digits wide and as many palms long, the iron handle being two feet long and one and a half digits in diameter; the wooden handle inserted into it is round, five feet long and two digits in diameter. then, with another cutting spatula, he makes the crucible smooth; the blade of this spatula is a palm wide and two palms long; its handle, partly of iron, partly of wood, is similar in every respect to the first one. afterward he throws pulverised clay and charcoal into the crucible, pours water over it, and sweeps it over with a broom into which a stick is fixed. then immediately he throws into the crucible a powder, made of two wheelbarrowsful of sifted charcoal dust, as many wheelbarrowsful of pulverised clay likewise sifted, and six basketsful of river sand which has passed through a very fine sieve. this powder, like that used by smelters, is sprinkled with water and moistened before it is put into the crucible, so that it may be fashioned by the hands into shapes similar to snowballs. when it has been put in, the master first kneads it and makes it smooth with his hands, and then pounds it with two wooden pestles, each of which is a cubit long; each pestle has a round head at each end, but one of these is a palm in diameter, the other three digits; both are thinner in the middle, so that they may be held in the hand. then he again throws moistened powder into the crucible, and again makes it smooth with his hands, and kneads it with his fists and with the pestles; then, pushing upward and pressing with his fingers, he makes the edge of the crucible smooth. after the crucible has been made smooth, he sprinkles in dry charcoal dust, and again pounds it with the same pestles, at first with the narrow heads, and afterward with the wider ones. then he pounds the crucible with a wooden mallet two feet long, both heads of which are round and three digits in diameter; its wooden handle is two palms long, and one and a half digits in diameter. finally, he throws into the crucible as much pure sifted ashes as both hands can hold, and pours water into it, and, taking an old linen rag, he smears the crucible over with the wet ashes. the crucible is round and sloping. if copper is to be made from the best quality of "dried" cakes, it is made two feet wide and one deep, but if from other cakes, it is made a cubit wide and two palms deep. the master also has an iron band curved at both ends, two palms long and as many digits wide, and with this he cuts off the edges of the crucible if they are higher than is necessary. the copper pipe is inclined, and projects three digits from the wall, and has its upper end and both sides smeared thick with lute, that it may not be burned; but the underside of the pipe is smeared thinly with lute, for this side reaches almost to the edge of the crucible, and when the crucible is full the molten copper touches it. the wall above the pipe is smeared over with lute, lest that should be damaged. he does the same to the other side of an iron plate, which is a foot and three palms long and a foot high; this stands on stones near the crucible at the side where the hearth slopes, in order that the slag may run out under it. others do not place the plates upon stones, but cut out of the plate underneath a small piece, three digits long and three digits wide; lest the plate should fall, it is supported by an iron rod fixed in the wall at a height of two palms and the same number of digits, and it projects from the wall three palms. then with an iron shovel, whose wooden handle is six feet long, he throws live charcoal into the crucible; or else charcoal, kindled by means of a few live coals, is added to them. over the live charcoal he lays "dried" cakes, which, if they were of copper of the first quality, weigh all together three _centumpondia_, or three and a half _centumpondia_; but if they were of copper of the second quality, then two and a half _centumpondia_; if they were of the third quality, then two _centumpondia_ only; but if they were of copper of very superior quality, then they place upon it six _centumpondia_, and in this case they make the crucible wider and deeper.[ ] the lowest "dried" cake is placed at a distance of two palms from the pipe, the rest at a greater distance, and when the lower ones are melted the upper ones fall down and get nearer to the pipe; if they do not fall down they must be pushed with a shovel. the blade of the shovel is a foot long, three palms and two digits wide, the iron part of the handle is two palms long, the wooden part nine feet. round about the "dried" cakes are placed large long pieces of charcoal, and in the pipe are placed medium-sized pieces. when all these things have been arranged in this manner, the fire must be more violently excited by the blast from the bellows. when the copper is melting and the coals blaze, the master pushes an iron bar into the middle of them in order that they may receive the air, and that the flame can force its way out. this pointed bar is two and a half feet long, and its wooden handle four feet long. when the cakes are partly melted, the master, passing out through the door, inspects the crucible through the bronze pipe, and if he should find that too much of the "slag" is adhering to the mouth of the pipe, and thus impeding the blast of the bellows, he inserts the hooked iron bar into the pipe through the nozzle of the bellows, and, turning this about the mouth of the pipe, he removes the "slags" from it. the hook on this bar is two digits high; the iron part of the handle is three feet long; the wooden part is the same number of palms long. now it is time to insert the bar under the iron plate, in order that the "slags" may flow out. when the cakes, being all melted, have run into the crucible, he takes out a sample of copper with the third round bar, which is made wholly of iron, and is three feet long, a digit thick, and has a steel point lest its pores should absorb the copper. when he has compressed the bellows, he introduces this bar as quickly as possible into the crucible through the pipe between the two nozzles, and takes out samples two, three, or four times, until he finds that the copper is perfectly refined. if the copper is good it adheres easily to the bar, and two samples suffice; if it is not good, then many are required. it is necessary to smelt it in the crucible until the copper adhering to the bar is seen to be of a brassy colour, and if the upper as well as the lower part of the thin layer of copper may be easily broken, it signifies that the copper is perfectly melted; he places the point of the bar on a small iron anvil, and chips off the thin layer of copper from it with a hammer.[ ] [illustration (copper refining): a--pointed bar. b--thin copper layer. c--anvil. d--hammer.] [illustration (copper refining): a--crucible. b--board. c--wedge-shaped bar. d--cakes of copper made by separating them with the wedge-shaped bar. e--tongs. f--tub.] if the copper is not good, the master draws off the "slags" twice, or three times if necessary--the first time when some of the cakes have been melted, the second when all have melted, the third time when the copper has been heated for some time. if the copper was of good quality, the "slags" are not drawn off before the operation is finished, but at the time they are to be drawn off, he depresses the bar over both bellows, and places over both a stick, a cubit long and a palm wide, half cut away at the upper part, so that it may pass under the iron pin fixed at the back in the perforated wood. this he does likewise when the copper has been completely melted. then the assistant removes the iron plate with the tongs; these tongs are four feet three palms long, their jaws are about a foot in length, and their straight part measures two palms and three digits, and the curved a palm and a digit. the same assistant, with the iron shovel, throws and heaps up the larger pieces of charcoal into that part of the hearth which is against the little wall which protects the other wall from injury by fire, and partly extinguishes them by pouring water over them. the master, with a hazel stick inserted into the crucible, stirs it twice. afterward he draws off the slags with a rabble, which consists of an iron blade, wide and sharp, and of alder-wood; the blade is a digit and a half in width and three feet long; the wooden handle inserted in its hollow part is the same number of feet long, and the alder-wood in which the blade is fixed must have the figure of a rhombus; it must be three palms and a digit long, a palm and two digits wide, and a palm thick. subsequently he takes a broom and sweeps the charcoal dust and small coal over the whole of the crucible, lest the copper should cool before it flows together; then, with a third rabble, he cuts off the slags which may adhere to the edge of the crucible. the blade of this rabble is two palms long and a palm and one digit wide, the iron part of the handle is a foot and three palms long, the wooden part six feet. afterward he again draws off the slags from the crucible, which the assistant does not quench by pouring water upon them, as the other slags are usually quenched, but he sprinkles over them a little water and allows them to cool. if the copper should bubble, he presses down the bubbles with the rabble. then he pours water on the wall and the pipes, that it may flow down warm into the crucible, for, the copper, if cold water were to be poured over it while still hot, would spatter about. if a stone, or a piece of lute or wood, or a damp coal should then fall into it, the crucible would vomit out all the copper with a loud noise like thunder, and whatever it touches it injures and sets on fire. subsequently he lays a curved board with a notch in it over the front part of the crucible; it is two feet long, a palm and two digits wide, and a digit thick. then the copper in the crucible should be divided into cakes with an iron wedge-shaped bar; this is three feet long, two digits wide, and steeled on the end for the distance of two digits, and its wooden handle is three feet long. he places this bar on the notched board, and, driving it into the copper, moves it forward and back, and by this means the water flows into the vacant space in the copper, and he separates the cake from the rest of the mass. if the copper is not perfectly smelted the cakes will be too thick, and cannot be taken out of the crucible easily. each cake is afterward seized by the assistant with the tongs and plunged into the water in the tub; the first one is placed aside so that the master may re-melt it again immediately, for, since some "slags" adhere to it, it is not as perfect as the subsequent ones; indeed, if the copper is not of good quality, he places the first two cakes aside. then, again pouring water over the wall and the pipes, he separates out the second cake, which the assistant likewise immerses in water and places on the ground together with the others separated out in the same way, which he piles upon them. these, if the copper was of good quality, should be thirteen or more in number; if it was not of good quality, then fewer. if the copper was of good quality, this part of the operation, which indeed is distributed into four parts, is accomplished by the master in two hours; if of mediocre quality, in two and a half hours; if of bad quality, in three. the "dried" cakes are re-melted, first in the first crucible and then in the second. the assistant must, as quickly as possible, quench all the cakes with water, after they have been cut out of the second crucible. afterward with the tongs he replaces in its proper place the iron plate which was in front of the furnace, and throws the charcoal back into the crucible with a shovel. meanwhile the master, continuing his work, removes the wooden stick from the bars of the bellows, so that in re-melting the other cakes he may accomplish the third part of his process; this must be carefully done, for if a particle from any iron implement should by chance fall into the crucible, or should be thrown in by any malevolent person, the copper could not be made until the iron had been consumed, and therefore double labour would have to be expended upon it. finally, the assistant extinguishes all the glowing coals, and chips off the dry lute from the mouth of the copper pipe with a hammer; one end of this hammer is pointed, the other round, and it has a wooden handle five feet long. because there is danger that the copper would be scattered if the _pompholyx_ and _spodos_, which adhere to the walls and the hood erected upon them, should fall into the crucible, he cleans them off in the meantime. every week he takes the copper flowers out of the tub, after having poured off the water, for these fall into it from the cakes when they are quenched.[ ] the bellows which this master uses differ in size from the others, for the boards are seven and a half feet long; the back part is three feet wide; the front, where the head is joined on is a foot, two palms and as many digits. the head is a cubit and a digit long; the back part of it is a cubit and a palm wide, and then becomes gradually narrower. the nozzles of the bellows are bound together by means of an iron chain, controlled by a thick bar, one end of which penetrates into the ground against the back of the long wall, and the other end passes under the beam which is laid upon the foremost perforated beams. these nozzles are so placed in a copper pipe that they are at a distance of a palm from the mouth; the mouth should be made three digits in diameter, that the air may be violently expelled through this narrow aperture. there now remain the liquation thorns, the ash-coloured copper, the "slags," and the _cadmia_.[ ] liquation cakes are made from thorns in the following manner.[ ] there are taken three-quarters of a _centumpondium_ of thorns, which have their origin from the cakes of copper-lead alloy when lead-silver is liquated, and as many parts of a _centumpondium_ of the thorns derived from cakes made from once re-melted thorns by the same method, and to them are added a _centumpondium_ of de-silverized lead and half a _centumpondium_ of hearth-lead. if there is in the works plenty of litharge, it is substituted for the de-silverized lead. one and a half _centumpondia_ of litharge and hearth-lead is added to the same weight of primary thorns, and half a _centumpondium_ of thorns which have their origin from liquation cakes composed of thorns twice re-melted by the same method (tertiary thorns), and a fourth part of a _centumpondium_ of thorns which are produced when the exhausted liquation cakes are "dried." by both methods one single liquation cake is made from three _centumpondia_. in this manner the smelter makes every day fifteen liquation cakes, more or less; he takes great care that the metallic substances, from which the first liquation cake is made, flow down properly and in due order into the forehearth, before the material of which the subsequent cake is to be made. five of these liquation cakes are put simultaneously into the furnace in which silver-lead is liquated from copper, they weigh almost fourteen _centumpondia_, and the "slags" made therefrom usually weigh quite a _centumpondium_. in all the liquation cakes together there is usually one _libra_ and nearly two _unciae_ of silver, and in the silver-lead which drips from those cakes, and weighs seven and a half _centumpondia_, there is in each an _uncia_ and a half of silver. in each of the three _centumpondia_ of liquation thorns there is almost an _uncia_ of silver, and in the two _centumpondia_ and a quarter of exhausted liquation cakes there is altogether one and a half _unciae_; yet this varies greatly for each variety of thorns, for in the thorns produced from primary liquation cakes made of copper and lead when silver-lead is liquated from the copper, and those produced in "drying" the exhausted liquation cakes, there are almost two _unciae_ of silver; in the others not quite an _uncia_. there are other thorns besides, of which i will speak a little further on. those in the carpathian mountains who make liquation cakes from the copper "bottoms" which remain after the upper part of the copper is divided from the lower, in the furnace similar to an oven, produce thorns when the poor or mediocre silver-lead is liquated from the copper. these, together with those made of cakes of re-melted thorns, or made with re-melted litharge, are placed in a heap by themselves; but those that are made from cakes melted from hearth-lead are placed in a heap separate from the first, and likewise those produced from "drying" the exhausted liquation cakes are placed separately; from these thorns liquation cakes are made. from the first heap they take the fourth part of a _centumpondium_, from the second the same amount, from the third a _centumpondium_,--to which thorns are added one and a half _centumpondia_ of litharge and half a _centumpondium_ of hearth-lead, and from these, melted in the blast furnace, a liquation cake is made; each workman makes twenty such cakes every day. but of theirs enough has been said for the present; i will return to ours. the ash-coloured copper[ ] which is chipped off, as i have stated, from the "dried" cakes, used some years ago to be mixed with the thorns produced from liquation of the copper-lead alloy, and contained in themselves, equally with the first, two _unciae_ of silver; but now it is mixed with the concentrates washed from the accretions and the other material. the inhabitants of the carpathian mountains melt this kind of copper in furnaces in which are re-melted the "slags" which flow out when the copper is refined; but as this soon melts and flows down out of the furnace, two workmen are required for the work of smelting, one of whom smelts, while the other takes out the thick cakes from the forehearth. these cakes are only "dried," and from the "dried" cakes copper is again made. the "slags"[ ] are melted continually day and night, whether they have been drawn off from the alloyed metals with a rabble, or whether they adhered to the forehearth to the thickness of a digit and made it smaller and were taken off with spatulas. in this manner two or three liquation cakes are made, and afterward much or little of the "slag," skimmed from the molten alloy of copper and lead, is re-melted. such liquation cakes should weigh up to three _centumpondia_, in each of which there is half an _uncia_ of silver. five cakes are placed at the same time in the furnace in which argentiferous lead is liquated from copper, and from these are made lead which contains half an _uncia_ of silver to the _centumpondium_. the exhausted liquation cakes are laid upon the other baser exhausted liquation cakes, from both of which yellow copper is made. the base thorns thus obtained are re-melted with a few baser "slags," after having been sprinkled with concentrates from furnace accretions and other material, and in this manner six or seven liquation cakes are made, each of which weighs some two _centumpondia_. five of these are placed at the same time in the furnace in which silver-lead is liquated from copper; these drip three _centumpondia_ of lead, each of which contains half an _uncia_ of silver. the basest thorns thus produced should be re-melted with only a little "slag." the copper alloyed with lead, which flows down from the furnace into the forehearth, is poured out with a ladle into oblong copper moulds; these cakes are "dried" with base exhausted liquation cakes. the thorns they produce are added to the base thorns, and they are made into cakes according to the method i have described. from the "dried" cakes they make copper, of which some add a small portion to the best "dried" cakes when copper is made from them, in order that by mixing the base copper with the good it may be sold without loss. the "slags," if they are utilisable, are re-melted a second and a third time, the cakes made from them are "dried," and from the "dried" cakes is made copper, which is mixed with the good copper. the "slags," drawn off by the master who makes copper out of "dried" cakes, are sifted, and those which fall through the sieve into a vessel placed underneath are washed; those which remain in it are emptied into a wheelbarrow and wheeled away to the blast furnaces, and they are re-melted together with other "slags," over which are sprinkled the concentrates from washing the slags or furnace accretions made at this time. the copper which flows out of the furnace into the forehearth, is likewise dipped out with a ladle into oblong copper moulds; in this way nine or ten cakes are made, which are "dried," together with bad exhausted liquation cakes, and from these "dried" cakes yellow[ ] copper is made. [illustration (copper refining): a--furnace. b--forehearth. c--oblong moulds.] the _cadmia_,[ ] as it is called by us, is made from the "slags" which the master, who makes copper from "dried" cakes, draws off together with other re-melted base "slags"; for, indeed, if the copper cakes made from such "slags" are broken, the fragments are called _cadmia_; from this and yellow copper is made _caldarium_ copper in two ways. for either two parts of _cadmia_ are mixed with one of yellow copper in the blast furnaces, and melted; or, on the contrary, two parts of yellow copper with one of _cadmia_, so that the _cadmia_ and yellow copper may be well mixed; and the copper which flows down from the furnace into the forehearth is poured out with a ladle into oblong copper moulds heated beforehand. these moulds are sprinkled over with charcoal dust before the _caldarium_ copper is to be poured into them, and the same dust is sprinkled over the copper when it is poured in, lest the _cadmia_ and yellow copper should freeze before they have become well mixed. with a piece of wood the assistant cleanses each cake from the dust, when it is turned out of the mould. then he throws it into the tub containing hot water, for the _caldarium_ copper is finer if quenched in hot water. but as i have so often made mention of the oblong copper moulds, i must now speak of them a little; they are a foot and a palm long, the inside is three palms and a digit wide at the top, and they are rounded at the bottom. the concentrates are of two kinds--precious and base.[ ] the first are obtained from the accretions of the blast furnace, when liquation cakes are made from copper and lead, or from precious liquation thorns, or from the better quality "slags," or from the best grade of concentrates, or from the sweepings and bricks of the furnaces in which exhausted liquation cakes are "dried"; all of these things are crushed and washed, as i explained in book viii. the base concentrates are made from accretions formed when cakes are cast from base thorns or from the worst quality of slags. the smelter who makes liquation cakes from the precious concentrates, adds to them three wheelbarrowsful of litharge and four barrowsful of hearth-lead and one of ash-coloured copper, from all of which nine or ten liquation cakes are melted out, of which five at a time are placed in the furnace in which silver-lead is liquated from copper; a _centumpondium_ of the lead which drips from these cakes contains one _uncia_ of silver. the liquation thorns are placed apart by themselves, of which one basketful is mixed with the precious thorns to be re-melted. the exhausted liquation cakes are "dried" at the same time as other good exhausted liquation cakes. the thorns which are drawn off from the lead, when it is separated from silver in the cupellation furnace[ ], and the hearth-lead which remains in the crucible in the middle part of the furnaces, together with the hearth material which has become defective and has absorbed silver-lead, are all melted together with a little slag in the blast furnaces. the lead, or rather the silver-lead, which flows from the furnace into the forehearth, is poured out into copper moulds such as are used by the refiners; a _centumpondium_ of such lead contains four _unciae_ of silver, or, if the hearth was defective, it contains more. a small portion of this material is added to the copper and lead when liquation cakes are made from them, if more were to be added the alloy would be much richer than it should be, for which reason the wise foreman of the works mixes these thorns with other precious thorns. the hearth-lead which remains in the middle of the crucible, and the hearth material which absorbs silver-lead, is mixed with other hearth-lead which remains in the cupellation furnace crucible; and yet some cakes, made rich in this manner, may be placed again in the cupellation furnaces, together with the rest of the silver-lead cakes which the refiner has made. the inhabitants of the carpathian mountains, if they have an abundance of finely crushed copper[ ] or lead either made from "slags," or collected from the furnace in which the exhausted liquation cakes are dried, or litharge, alloy them in various ways. the "first" alloy consists of two _centumpondia_ of lead melted out of thorns, litharge, and thorns made from hearth-lead, and of half a _centumpondium_ each of lead collected in the furnace in which exhausted liquation cakes are "dried," and of copper _minutum_, and from these are made liquation cakes; the task of the smelter is finished when he has made forty liquation cakes of this kind. the "second" alloy consists of two _centumpondia_ of litharge, of one and a quarter _centumpondia_ of de-silverized lead or lead from "slags," and of half a _centumpondium_ of lead made from thorns, and of as much copper _minutum_. the "third" alloy consists of three _centumpondia_ of litharge and of half a _centumpondium_ each of de-silverized lead, of lead made from thorns, and of copper _minutum contusum_. liquation cakes are made from all these alloys; the task of the smelters is finished when they have made thirty cakes. the process by which cakes are made among the tyrolese, from which they separate the silver-lead, i have explained in book ix. silver is separated from iron in the following manner. equal portions of iron scales and filings and of _stibium_ are thrown into an earthenware crucible which, when covered with a lid and sealed, is placed in a furnace, into which air is blown. when this has melted and again cooled, the crucible is broken; the button that settles in the bottom of it, when taken out, is pounded to powder, and the same weight of lead being added, is mixed and melted in a second crucible; at last this button is placed in a cupel and the lead is separated from the silver.[ ] there are a great variety of methods by which one metal is separated from other metals, and the manner in which the same are alloyed i have explained partly in the eighth book of _de natura fossilium_, and partly i will explain elsewhere. now i will proceed to the remainder of my subject. end of book xi. footnotes: [ ] the whole of this book is devoted to the subject of the separation of silver from copper by liquation, except pages - on copper refining, and page on the separation of silver from iron. we believe a brief outline of the liquation process here will refresh the mind of the reader, and enable him to peruse the book with more satisfaction. the fundamental principle of the process is that if a copper-lead alloy, containing a large excess of lead, be heated in a reducing atmosphere, above the melting point of lead but below that of copper, the lead will liquate out and carry with it a large proportion of the silver. as the results are imperfect, the process cannot be carried through in one operation, and a large amount of bye-products is created which must be worked up subsequently. the process, as here described, falls into six stages. st, melting the copper and lead in a blast furnace to form "liquation cakes"--that is, the "leading." if the copper contain too little silver to warrant liquation directly, then the copper is previously enriched by melting and drawing off from a settling pot the less argentiferous "tops" from the metal, liquation cakes being made from the enriched "bottoms." nd, liquation of the argentiferous lead from the copper. this work was carried out in a special furnace, to which the admission of air was prevented as much as possible in order to prevent oxidation. rd, "drying" the residual copper, which retained some lead, in a furnace with a free admission of air. the temperature was raised to a higher degree than in the liquation furnace, and the expelled lead was oxidized. th, cupellation of the argentiferous lead. th, refining of the residual copper from the "drying" furnace by oxidation of impurities and poling in a "refining furnace." th, re-alloy and re-liquation of the bye-products. these consist of: _a_, "slags" from "leading"; _b_, "slags" from "drying"; _c_, "slags" from refining of the copper. all of these "slags" were mainly lead oxides, containing some cuprous oxides and silica from the furnace linings; _d_, "thorns" from liquation; _e_, "thorns" from "drying"; _f_, "thorns" from skimmings during cupellation; these were again largely lead oxides, but contained rather more copper and less silica than the "slags"; _g_, "ash-coloured copper," being scales from the "dried" copper, were cuprous oxides, containing considerable lead oxides; _h_, concentrates from furnace accretions, crushed bricks, &c. the discussion of detailed features of the process has been reserved to notes attached to the actual text, to which the reader is referred. as to the general result of liquation, karsten (see below) estimates the losses in the liquation of the equivalent of lbs. of argentiferous copper to amount to - lbs. of lead and to lbs. of copper. percy (see below) quotes results at lautenthal in the upper harz for the years - , showing losses of % of the silver, . % of the copper, and . lbs. of lead to the lbs. of copper, or say, % of the lead; and a cost of £ s. per ton of copper. the theoretical considerations involved in liquation have not been satisfactorily determined. those who may wish to pursue the subject will find repeated descriptions and much discussion in the following works, which have been freely consulted in the notes which follow upon particular features of the process. it may be mentioned that agricola's treatment of the subject is more able than any down to the th century. ercker (_beschreibung allerfürnemsten mineralischen_, etc., prague, ). lohneys (_bericht vom bergwercken_, etc., zellerfeldt, ). schlüter (_gründlicher unterricht von hütte-werken_, braunschweig, ). _karsten_ (_system der metallurgie v._ and _archiv für bergbau und hüttenwesen_, st series, ). berthier (_annales des mines_, , ii.). percy (metallurgy of silver and gold, london, ). nomenclature.--this process held a very prominent position in german metallurgy for over four centuries, and came to have a well-defined nomenclature of its own, which has never found complete equivalents in english, our metallurgical writers to the present day adopting more or less of the german terms. agricola apparently found no little difficulty in adapting latin words to his purpose, but stubbornly adhered to his practice of using no german at the expense of long explanatory clauses. the following table, prepared for convenience in translation, is reproduced. the german terms are spelled after the manner used in most english metallurgies, some of them appear in agricola's glossary to _de re metallica_. english. latin. german. blast furnace _prima fornax_ _schmeltzofen_ liquation furnace _fornax in qua argentum et _saigernofen_ plumbum ab aere secernuntur_ drying furnace _fornax in qua aerei panes _darrofen_ fathiscentes torrentur_ refining hearth _fornax in qua panes aerei _gaarherd_ torrefacti coquuntur_ cupellation _secunda fornax_, or _treibherd_ furnace _fornax in qua plumbum ab argento separatur_ leading _mistura_ _frischen_ liquating _stillare_, or _distillare_ _saigern_ "drying" _torrere_ _darren_ refining _aes ex panibus torrefactis _gaarmachen_ conficere_ liquation cakes _panes ex aere ac plumbo misti_ _saigerstock_ exhausted _panes fathiscentes_ _kiehnstock_, liquation cakes or _kinstocke_ "dried" cakes _panes torrefacti_ _darrlinge_ slags from leading _recrementa_ _frischschlacke_ (with explanatory phrases) slags from drying _recrementa_ _darrost_ (with explanatory phrases) slags from refining _recrementa_ _gaarschlacke_ (with explanatory phrases) liquation thorns _spinae_ _saigerdörner_, (with explanatory phrases) or _röstdörner_ thorns from "drying" _spinae_ _darrsöhle_ (with explanatory phrases) thorns from _spinae_ _abstrich_ cupellation (with explanatory phrases) silver-lead or _stannum_ _saigerwerk_ or liquated _saigerblei_ silver-lead ash-coloured copper _aes cinereum_ _pickschiefer_ or _schifer_ furnace accretions _cadmiae_ _offenbrüche_ or "accretions" historical note.--so far as we are aware, this is the first complete discussion of this process, although it is briefly mentioned by one writer before agricola--that is, by biringuccio (iii, , ), who wrote ten years before this work was sent to the printer. his account is very incomplete, for he describes only the bare liquation, and states that the copper is re-melted with lead and re-liquated until the silver is sufficiently abstracted. he neither mentions "drying" nor any of the bye-products. in his directions the silver-lead alloy was cupelled and the copper ultimately refined, obviously by oxidation and poling, although he omits the pole. in a.d. theophilus (p. , hendrie's trans.) describes melting lead out of copper ore, which would be a form of liquation so far as separation of these two metals is concerned, but obviously not a process for separating silver from copper. this passage is quoted in the note on copper smelting (note on p. ). a process of such well-developed and complicated a character must have come from a period long before agricola; but further than such a surmise, there appears little to be recorded. liquation has been during the last fifty years displaced by other methods, because it was not only tedious and expensive, but the losses of metal were considerable. [ ] _paries_,--"partition" or "wall." the author uses this term throughout in distinction to _murus_, usually applying the latter to the walls of the building and the former to furnace walls, chimney walls, etc. in order to gain clarity, we have introduced the term "hood" in distinction to "chimney," and so far as possible refer to the _paries_ of these constructions and furnaces as "side of the furnace," "side of the hood," etc. [ ] from this point on, the construction of the roofs, in the absence of illustration, is hopeless of intelligent translation. the constant repetition of "_tignum_," "_tigillum_," "_trabs_," for at least fifteen different construction members becomes most hopelessly involved, especially as the author attempts to distinguish between them in a sort of "house-that-jack-built" arrangement of explanatory clauses. [ ] in the original text this is given as the "fifth," a manifest impossibility. [ ] _chelae_,--"claws." [ ] if roman weights, this would be . short tons, and . tons if german _centner_ is meant. [ ] this is, no doubt, a reference to pliny's statement (xxxiii, ) regarding litharge at puteoli. this passage from pliny is given in the footnote on p. . puteoli was situated on the bay of naples. [ ] by this expression is apparently meant the "bottoms" produced in enriching copper, as described on p. . [ ] the details of the preparation of liquation cakes--"leading"--were matters of great concern to the old metallurgists. the size of the cakes, the proportion of silver in the original copper and in the liquated lead, the proportion of lead and silver left in the residual cakes, all had to be reached by a series of compromises among militant forces. the cakes were generally two and one-half to three and one-half inches thick and about two feet in diameter, and weighed to lbs. this size was wonderfully persistent from agricola down to modern times; and was, no doubt, based on sound experience. if the cakes were too small, they required proportionately more fuel and labour; whilst if too large, the copper began to melt before the maximum lead was liquated. the ratio of the copper and lead was regulated by the necessity of enough copper to leave a substantial sponge mass the shape of the original cake, and not so large a proportion as to imprison the lead. that is, if the copper be in too small proportion the cakes break down; and if in too large, then insufficient lead liquates out, and the extraction of silver decreases. ercker (p. - ) insists on the equivalent of about copper to . lead; lohneys (p. ), copper to or lead. schlüter (p. , etc.) insists on a ration of copper to about lead. kerl (_handbuch der metallurgischen hüttenkunde_, ; vol. iii., p. ) gives copper to to parts lead. agricola gives variable amounts of parts copper to from to parts lead. as to the ratio of silver in the copper, or to the cakes, there does not, except the limit of payability, seem to have been any difficulty on the minimum side. on the other hand, ercker, lohneys, schlüter, and karsten all contend that if the silver ran above a certain proportion, the copper would retain considerable silver. these authors give the outside ratio of silver permissible for good results in one liquation at what would be equivalent to to ozs. per ton of cakes, or about to ozs. per ton on the original copper. it will be seen, however, that agricola's cakes greatly exceed these values. a difficulty did arise when the copper ran low in silver, in that the liquated lead was too poor to cupel, and in such case the lead was used over again, until it became rich enough for this purpose. according to karsten, copper containing less than an equivalent of to ozs. per ton could not be liquated profitably, although the upper harz copper, according to kerl, containing the equivalent of about ozs. per ton, was liquated at a profit. in such a case the cakes would run only to ozs. per ton. it will be noticed that in the eight cases given by agricola the copper ran from to over ozs. per ton, and in the description of enrichment of copper "bottoms" the original copper runs ozs., and "it cannot be separated easily"; as a result, it is raised to ozs. per ton before treatment. in addition to the following tabulation of the proportions here given by agricola, the reader should refer to footnotes and , where four more combinations are tabulated. it will be observed from this table that with the increasing richness of copper an increased proportion of lead was added, so that the products were of similar value. it has been assumed (see footnote p. ), that roman weights are intended. it is not to be expected that metallurgical results of this period will "tie up" with the exactness of the modern operator's, and it has not been considered necessary to calculate beyond the nearest pennyweight. where two or more values are given by the author the average has been taken. st charge. nd charge. rd charge. th charge. amount of . lbs. . lbs. . lbs. . lbs. argentiferous copper amount of lead . " . " . " . " weight of each cake . " . " . " . " average value of ozs. ozs. ozs. ozs. charge dwts. dwts. dwts. dwts. per cent. of copper . % % . % % average value of ozs. ozs. ozs. ozs. original copper dwts. dwts. dwts. dwts. per ton weight of . lbs. . lbs. . lbs. lbs. argentiferous lead liquated out average value of ozs. ozs. ozs. ozs. liquated lead per ton weight of residues lbs. lbs. lbs. lbs. (residual copper and thorns) average value of ozs. ozs. ozs. ozs. to residues per ton ozs. extraction of . % . % % . % silver into the argentiferous lead [ ] see p. . [ ] an analysis of this "slag" by karsten (_archiv_. st series ix, p. ) showed . % lead oxide, . % cuprous oxide, . % silica (from the fuel and furnace linings), together with some iron alumina, etc. the _pompholyx_ and _spodos_ were largely zinc oxide (see note, p. ). [ ] this description of a _centumpondium_ which weighed either - / _librae_, or - / _librae_, adds confusion to an already much mixed subject (see appendix c.). assuming the german _pfundt_ to weigh , troy grains, and the roman _libra_ , grains, then a _centner_ would weigh . _librae_, which checks up fairly well with the second case; but under what circumstances a _centner_ can weigh - / _librae_ we are unable to record. at first sight it might appear from this statement that where agricola uses the word _centumpondium_ he means the german _centner_. on the other hand, in the previous five or six pages the expressions one-third, five-sixths, ten-twelfths of a _libra_ are used, which are even divisions of the roman _unciae_ to one _libra_, and are used where they manifestly mean divisions of units. if agricola had in mind the german scale, and were using the _libra_ for a _pfundt_ of _untzen_, these divisions would amount to fractions, and would not total the _sicilicus_ and _drachma_ quantities given, nor would they total any of the possibly synonymous divisions of the german _untzen_ (see also page ). [ ] if we assume roman weights, the charge in the first case can be tabulated as follows, and for convenience will be called the fifth charge:-- th charge ( cakes). amount of copper . lbs. amount of lead . lbs. weight of each cake . lbs. average value of charge ozs. dwts. per cent. of copper % average value of original copper per ton ozs. dwts. grs. weight of argentiferous lead liquated out . lbs. average value of liquated lead per ton ozs. dwts. weight of residues lbs. average value of residues per ton ozs. (about). extraction of silver into the argentiferous lead % the results given in the second case where the copper contains _librae_ and a _bes_ per _centumpondium_ do not tie together at all, for each liquation cake should contain _librae_ - / _unciae_, instead of - / _librae_ and / _uncia_ of silver. [ ] in this enrichment of copper by the "settling" of the silver in the molten mass the original copper ran, in the two cases given, ozs. dwts. and ozs. dwt. per ton. the whole charge weighed , lbs., and contained in the second case ozs. troy, omitting fractions. on melting, , lbs. were drawn off as "tops," containing ozs. of silver, or running ozs. per ton, and there remained , lbs. of "bottoms," containing ozs. of silver, or averaging ozs. per ton. it will be noticed later on in the description of making liquation cakes from these copper bottoms, that the author alters the value from one-third _librae_, a _semi-uncia_ and a _drachma_ per _centumpondium_ to one-third of a _libra_, _i.e._, from ozs. to ozs. dwts. per ton. in the glossary this furnace is described as a _spleisofen_, _i.e._, a refining hearth. [ ] the latter part of this paragraph presents great difficulties. the term "refining furnace" is given in the latin as the "second furnace," an expression usually applied to the cupellation furnace. the whole question of refining is exhaustively discussed on pages to . exactly what material is meant by the term red (_rubrum_), yellow (_fulvum_) and _caldarium_ copper is somewhat uncertain. they are given in the german text simply as _rot_, _geel_, and _lebeter kupfer_, and apparently all were "coarse" copper of different characters destined for the refinery. the author states in _de natura fossilium_ (p. ): "copper has a red colour peculiar to itself; this colour in smelted copper is considered the most excellent. it, however, varies. in some it is red, as in the copper smelted at neusohl.... other copper is prepared in the smelters where silver is separated from copper, which is called yellow copper (_luteum_), and is _regulare_. in the same place a dark yellow copper is made which is called _caldarium_, taking its name among the germans from a caldron.... _regulare_ differs from _caldarium_ in that the former is not only fusible, but also malleable; while the latter is, indeed, fusible, but is not ductile, for it breaks when struck with the hammer." later on in _de re metallica_ (p. ) he describes yellow copper as made from "baser" liquation thorns and from exhausted liquation cakes made from thorns. these products were necessarily impure, as they contained, among other things, the concentrates from furnace accretions. therefore, there was ample source for zinc, arsenic or other metallics which would lighten the colour. _caldarium_ copper is described by pliny (see note, p. ), and was, no doubt, "coarse" copper, and apparently agricola adopted this term from that source, as we have found it used nowhere else. on page the author describes making _caldarium_ copper from a mixture of yellow copper and a peculiar _cadmia_, which he describes as the "slags" from refining copper. these "slags," which are the result of oxidation and poling, would contain almost any of the metallic impurities of the original ore, antimony, lead, arsenic, zinc, cobalt, etc. coming from these two sources the _caldarium_ must have been, indeed, impure. [ ] the liquation of these low-grade copper "bottoms" required that the liquated lead should be re-used again to make up fresh liquation cakes, in order that it might eventually become rich enough to warrant cupellation. in the following table the "poor" silver-lead is designated (a) the "medium" (b) and the "rich" (c). the three charges here given are designated sixth, seventh, and eighth for purposes of reference. it will be seen that the data is insufficient to complete the ninth and tenth. moreover, while the author gives directions for making four cakes, he says the charge consists of five, and it has, therefore, been necessary to reduce the volume of products given to this basis. th charge. th charge. th charge. amount of copper . lbs. . lbs. . lbs. bottoms amount of lead . lbs. . lbs. . lbs. (slags) of (a) of (b) amount of . lbs. . lbs. . lbs. (a) de-silverized lead weight of each cake . lbs. . lbs. . lbs. average value of ozs. ozs. ozs. charge per ton dwts. dwts. dwts. per cent. of copper . % . % . % average value per ozs. ozs. ozs. ton original copper dwts. dwts. dwts. average value per ozs. ozs. ozs. ton of dwts. (slags) dwts. (a) dwts. (a) average value per ozs. ozs. ozs. ton of dwt. (lead) dwt. (lead) dwts. (b) weight of liquated . lbs. lead average value of ozs. ozs. ozs. the liquated lead dwts. (a) dwts. (b) dwts. (c) per ton weight of exhausted . lbs. liquation cakes average value of ozs. the exhausted dwts. liquation cakes per ton weight of liquation . lbs. thorns average value of ozs. the liquation dwts. thorns per ton extraction of % silver into the liquated lead [ ] for the liquation it was necessary to maintain a reducing atmosphere, otherwise the lead would oxidize; this was secured by keeping the cakes well covered with charcoal and by preventing the entrance of air as much as possible. moreover, it was necessary to preserve a fairly even temperature. the proportions of copper and lead in the three liquation products vary considerably, depending upon the method of conducting the process and the original proportions. from the authors consulted (see note p. ) an average would be about as follows:--the residual copper--exhausted liquation cakes--ran from to % lead; the liquated lead from to % copper; and the liquation thorns, which were largely oxidized, contained about % copper oxides, % lead oxides, together with impurities, such as antimony, arsenic, etc. the proportions of the various products would obviously depend upon the care in conducting the operation; too high temperature and the admission of air would increase the copper melted and oxidize more lead, and thus increase the liquation thorns. there are insufficient data in agricola to adduce conclusions as to the actual ratios produced. the results given for the th charge (note , p. ) would indicate about % lead in the residual copper, and would indicate that the original charge was divided into about % of residual copper, % of liquation thorns, and % of liquated lead. this, however, was an unusually large proportion of liquation thorns, some of the authors giving instances of as low as %. [ ] the first instance given, of _centumpondia_ ( , lbs.) lead and one _centumpondium_ ( . lbs.) copper, would indicate that the liquated lead contained . % copper. the second, of _centumpondia_ ( , lbs.) lead and - / _centumpondia_ copper ( lbs.), would indicate % copper; and in the third, _centumpondia_ ( , lbs.) lead and six copper ( lbs.) would show . % copper. this charge of _centumpondia_ in the cupellation furnace would normally make more than _centumpondia_ of litharge and of hearth-lead, _i.e._, saturated furnace bottoms. the copper would be largely found in the silver-lead "which does not melt," at the margin of the crucible. these skimmings are afterward referred to as "thorns." it is difficult to understand what is meant by the expression that the silver which is in the copper is mixed with the remaining (_reliquo_) silver. the coppery skimmings from the cupellation furnace are referred to again in note , p. . [ ] a further amount of lead could be obtained in the first liquation, but a higher temperature is necessary, which was more economical to secure in the "drying" furnace. therefore, the "drying" was really an extension of liquation; but as air was admitted the lead and copper melted out were oxidized. the products were the final residual copper, called by agricola the "dried" copper, together with lead and copper oxides, called by him the "slags," and the scale of copper and lead oxides termed by him the "ash-coloured copper." the german metallurgists distinguished two kinds of slag: the first and principal one, the _darrost_, and the second the _darrsöhle_, this latter differing only in that it contained more impurities from the floor of the furnace, and remained behind until the furnace cooled. agricola possibly refers to these as "more liquation thorns," because in describing the treatment of the bye-products he refers to thorns from the process, whereas in the description of "drying" he usually refers to "slags." a number of analyses of these products, given by karsten, show the "dried" copper to contain from . to . % copper, and from . to . % lead; the "slag" to contain . to . % lead oxide, and from . to . % cuprous oxide, with to % silica from the furnace bottoms, together with some other impurities; the "ash-coloured copper" to contain about % cuprous oxide and % lead oxide, with some metallic copper and minor impurities. an average of proportions given by various authors shows, roughly, that out of _centners_ of "exhausted" liquation cakes, containing about % copper and % lead, there were about _centners_ of "dried" copper, _centners_ of "slag," and - / _centners_ of "ash-coloured copper." according to karsten, the process fell into stages; first, at low temperature some metallic lead appeared; second, during an increasing temperature for over to hours the slags ran out; third, there was a period of four hours of lower temperature to allow time for the lead to diffuse from the interior of the cakes; and fourth, during a period of eight hours the temperature was again increased. in fact, the latter portion of the process ended with the economic limit between leaving some lead in the copper and driving too much copper into the "slags." agricola gives the silver contents of the "dried" copper as _drachmae_ to _centumpondium_, or equal to about ozs. per ton; and assuming that the copper finally recovered from the bye-products ran no higher, then the first four charges (see note on p. ) would show a reduction in the silver values of from to %; the th and th charges (note on p. ) of about %. [ ] if roman weights, this would equal from , lbs. to , lbs. [ ] one half _uncia_, or three _drachmae_ of silver would equal either ozs. or ozs. per ton. if we assume the values given for residual copper in the first four charges (note p. ) of ozs., this would mean an extraction of, roughly, % of the silver from the exhausted liquation cakes. [ ] see note , p. . [ ] assuming roman weights: _centumpondia_ = . lbs. - / " = . " " = . " - / " = . " " = . " [ ] this description of refining copper in an open hearth by oxidation with a blast and "poling"--the _gaarmachen_ of the germans--is so accurate, and the process is so little changed in some parts of saxony, that it might have been written in the th century instead of the th. the best account of the old practice in saxony after agricola is to be found in schlüter's _hütte werken_ (braunschweig, , chap. cxviii.). the process has largely been displaced by electrolytic methods, but is still in use in most refineries as a step in electrolytic work. it may be unnecessary to repeat that the process is one of subjecting the molten mass of impure metal to a strong and continuous blast, and as a result, not only are the impurities to a considerable extent directly oxidized and taken off as a slag, but also a considerable amount of copper is turned into cuprous oxide. this cuprous oxide mostly melts and diffuses through the metallic copper, and readily parting with its oxygen to the impurities further facilitates their complete oxidation. the blast is continued until the impurities are practically eliminated, and at this stage the molten metal contains a great deal of dissolved cuprous oxide, which must be reduced. this is done by introducing a billet of green wood ("poling"), the dry distillation of which generates large quantities of gases, which reduce the oxide. the state of the metal is even to-day in some localities tested by dipping into it the point of an iron rod; if it be at the proper state the adhering copper has a net-like appearance, should be easily loosened from the rod by dipping in water, is of a reddish-copper colour and should be quite pliable; if the metal is not yet refined, the sample is thick, smooth, and detachable with difficulty; if over-refined, it is thick and brittle. by allowing water to run on to the surface of the molten metal, thin cakes are successively formed and taken off. these cakes were the article known to commerce over several centuries as "rosetta copper." the first few cakes are discarded as containing impurities or slag, and if the metal be of good quality the cakes are thin and of a red colour. their colour and thinness, therefore, become a criterion of purity. the cover of charcoal or charcoal dust maintained upon the surface of the metal tended to retard oxidation, but prevented volatilization and helped to secure the impurities as a slag instead. karsten (_archiv._, st series, p. ) gives several analyses of the slag from refining "dried" copper, showing it to contain from . to . % lead oxide, . to . % cuprous oxide, and . to . silica (from the furnace bottoms), with minor quantities of iron, antimony, etc. the "bubbles" referred to by agricola were apparently the shower of copper globules which takes place upon the evolution of sulphur dioxide, due to the reaction of the cuprous oxide upon any remaining sulphide of copper when the mass begins to cool. historical note.--it is impossible to say how the ancients refined copper, beyond the fact that they often re-smelted it. such notes as we can find are set out in the note on copper smelting (note , p. ). the first authentic reference to poling is in theophilus ( to a.d., hendrie's translation, p. ), which shows a very good understanding of this method of refining copper:--"of the purification of copper. take an iron dish of the size you wish, and line it inside and out with clay strongly beaten and mixed, and it is carefully dried. then place it before a forge upon the coals, so that when the bellows act upon it the wind may issue partly within and partly above it, and not below it. and very small coals being placed round it, place the copper in it equally, and add over it a heap of coals. when by blowing a long time this has become melted, uncover it and cast immediately fine ashes of coals over it, and stir it with a thin and dry piece of wood as if mixing it, and you will directly see the burnt lead adhere to these ashes like a glue, which being cast out again superpose coals, and blowing for a long time, as at first, again uncover it, and then do as you did before. you do this until at length by cooking it you can withdraw the lead entirely. then pour it over the mould which you have prepared for this, and you will thus prove if it be pure. hold it with the pincers, glowing as it is, before it has become cold, and strike it with a large hammer strongly over the anvil, and if it be broken or split you must liquefy it anew as before. if, however, it should remain sound, you will cool it in water, and you cook other (copper) in the same manner." biringuccio (iii, ) in describes the process briefly, but omits the poling, an essential in the production of malleable copper. [ ] _pompholyx_ and _spodos_ were impure zinc oxides (see note , p. ). the copper flowers were no doubt cupric oxide. they were used by the ancients for medicinal purposes. dioscorides (v, ) says: "of flowers of copper, which some call the scrapings of old nails, the best is friable; it is gold-coloured when rubbed, is like millet in shape and size, is moderately bright, and somewhat astringent. it should not be mixed with copper filings, with which it is often adulterated. but this deception is easily detected, for when bitten in the teeth the filings are malleable. it (the flowers) is made when the copper fused in a furnace has run into the receptacle through the spout pertaining to it, for then the workmen engaged in this trade cleanse it from dirt and pour clear water over it in order to cool it; from this sudden condensation the copper spits and throws out the aforesaid flowers." pliny (xxxiv, ) says: "the flower, too, of copper (_æris flos_) is used in medicine. this is made by fusing copper, and then removing it to another furnace, where the repeated blast makes the metal separate into small scales like millet, known as flowers. these scales also fall off when the cakes of metal are cooled in water; they become red, too, like the scales of copper known as '_lepis_,' by use of which the flowers of copper are adulterated, it being also sold for it. these are made when hammering the nails that are made from the cakes of copper. all these methods are carried on in the works of cyprus; the difference between these substances is that the _squamae_ (copper scales) are detached from hammering the cakes, while the flower falls off spontaneously." agricola (_de nat. fos._, p. ) notes that "flowers of copper (_flos æris_) have the same properties as 'roasted copper.'" [ ] it seems scarcely necessary to discuss in detail the complicated "flow scheme" of the various minor bye-products. they are all re-introduced into the liquation circuit, and thereby are created other bye-products of the same kind _ad infinitum_. further notes are given on:-- liquation thorns note . slags " . ash-coloured copper " . concentrates " . _cadmia_ " . there are no data given, either by agricola or the later authors, which allow satisfactory calculation of the relative quantities of these products. a rough estimate from the data given in previous notes would indicate that in one liquation only about % of the original copper came out as refined copper, and that about % of the original lead would go to the cupellation furnace, _i.e._, about % of the original metal sent to the blast furnace would go into the "thorns," "slags," and "ash-coloured copper." the ultimate losses were very great, as given before (p. ), they probably amounted to % of the silver, % copper, and % of the lead. [ ] there were the following classes of thorns:-- st. from liquation. nd. from drying. rd. from cupellation. in a general way, according to the later authors, they were largely lead oxide, and contained from % to % cuprous oxide. if a calculation be made backward from the products given as the result of the charge described, it would appear that in this case they must have contained at least one-fifth copper. the silver in these liquation cakes would run about ozs. per ton, in the liquated lead about ozs. per ton, and in the liquation thorns ozs. per ton. the extraction into the liquated lead would be about % of the silver. [ ] the "ash-coloured copper" is a cuprous oxide, containing some % lead oxide; and if agricola means they contained two _unciae_ of silver to the _centumpondium_, then they ran about ozs. per ton, and would contain much more silver than the mass. [ ] there are three principal "slags" mentioned-- st. slag from "leading." nd. slag from "drying." rd. slag from refining the copper. from the analyses quoted by various authors these ran from % to % lead oxide, % to % cuprous oxide, and considerable silica from the furnace bottoms. they were reduced in the main into liquation cakes, although agricola mentions instances of the metal reduced from "slags" being taken directly to the "drying" furnace. such liquation cakes would run very low in silver, and at the values given only averaged ozs. per ton; therefore the liquated lead running the same value as the cakes, or less than half that of the "poor" lead mentioned in note , p. , could not have been cupelled directly. [ ] see note , p. , for discussion of yellow and _caldarium_ copper. [ ] this _cadmia_ is given in the glossary and the german translation as _kobelt_. a discussion of this substance is given in the note on p. ; and it is sufficient to state here that in agricola's time the metal cobalt was unknown, and the substances designated _cadmia_ and _cobaltum_ were arsenical-cobalt-zinc minerals. a metal made from "slag" from refining, together with "base" thorns, would be very impure; for the latter, according to the paragraph on concentrates a little later on, would contain the furnace accretions, and would thus be undoubtedly zincky. it is just possible that the term _kobelt_ was used by the german smelters at this time in the sense of an epithet--"black devil" (see note , p. ). [ ] it is somewhat difficult to see exactly the meaning of base (_vile_) and precious (_preciosum_) in this connection. while "base" could mean impure, "precious" could hardly mean pure, and while "precious" could mean high value in silver, the reverse does not seem entirely _apropos_. it is possible that "bad" and "good" would be more appropriate terms. [ ] the skimmings from the molten lead in the early stages of cupellation have been discussed in note , p. . they are probably called thorns here because of the large amount of copper in them. the lead from liquation would contain % to % of copper, and this would be largely recovered in these skimmings, although there would be some copper in the furnace bottoms--hearth-lead--and the litharge. these "thorns" are apparently fairly rich, four _unciae_ to the _centumpondium_ being equivalent to about ozs. per ton, and they are only added to low-grade liquation material. [ ] _particulis aeris tusi_. unless this be the fine concentrates from crushing the material mentioned, we are unable to explain the expression. [ ] this operation would bring down a button of antimony under an iron matte, by de-sulphurizing the antimony. it would seem scarcely necessary to add lead before cupellation. this process is given in an assay method, in the _probierbüchlein_ (folio ) years before _de re metallica_: "how to separate silver from iron: take that silver which is in iron _plechen_ (_plachmal_), pulverize it finely, take the same iron or _plec_ one part, _spiesglasz_ (antimony sulphide) one part, leave them to melt in a crucible placed in a closed _windtofen_. when it is melted, let it cool, break the crucible, chip off the button that is in the bottom, and melt it in a crucible with as much lead. then break the crucible, and seek from the button in the cupel, and you will find what silver it contains." book xii. previously i have dealt with the methods of separating silver from copper. there now remains the portion which treats of solidified juices; and whereas they might be considered as alien to things metallic, nevertheless, the reasons why they should not be separated from it i have explained in the second book. solidified juices are either prepared from waters in which nature or art has infused them, or they are produced from the liquid juices themselves, or from stony minerals. sagacious people, at first observing the waters of some lakes to be naturally full of juices which thickened on being dried up by the heat of the sun and thus became solidified juices, drew such waters into other places, or diverted them into low-lying places adjoining hills, so that the heat of the sun should likewise cause them to condense. subsequently, because they observed that in this wise the solidified juices could be made only in summer, and then not in all countries, but only in hot and temperate regions in which it seldom rains in summer, they boiled them in vessels over a fire until they began to thicken. in this manner, at all times of the year, in all regions, even the coldest, solidified juices could be obtained from solutions of such juices, whether made by nature or by art. afterward, when they saw juices drip from some roasted stones, they cooked these in pots in order to obtain solidified juices in this wise also. it is worth the trouble to learn the proportions and the methods by which these are made. i will therefore begin with salt, which is made from water either salty by nature, or by the labour of man, or else from a solution of salt, or from lye, likewise salty. water which is salty by nature, is condensed and converted into salt in salt-pits by the heat of the sun, or else by the heat of a fire in pans or pots or trenches. that which is made salty by art, is also condensed by fire and changed into salt. there should be as many salt-pits dug as the circumstance of the place permits, but there should not be more made than can be used, although we ought to make as much salt as we can sell. the depth of salt-pits should be moderate, and the bottom should be level, so that all the water is evaporated from the salt by the heat of the sun. the salt-pits should first be encrusted with salt, so that they may not suck up the water. the method of pouring or leading sea-water into salt-pits is very old, and is still in use in many places. the method is not less old, but less common, to pour well-water into salt-pits, as was done in babylon, for which pliny is the authority, and in cappadocia, where they used not only well-water, but also spring-water. in all hot countries salt-water and lake-water are conducted, poured or carried into salt-pits, and, being dried by the heat of the sun, are converted into salt.[ ] while the salt-water contained in the salt-pits is being heated by the sun, if they be flooded with great and frequent showers of rain the evaporation is hindered. if this happens rarely, the salt acquires a disagreeable[ ] flavour, and in this case the salt-pits have to be filled with other sweet water. [illustration (salt pans): a--sea. b--pool. c--gate. d--trenches. e--salt basins. f--rake. g--shovel.] salt from sea-water is made in the following manner. near that part of the seashore where there is a quiet pool, and there are wide, level plains which the inundations of the sea do not overflow, three, four, five, or six trenches are dug six feet wide, twelve feet deep, and six hundred feet long, or longer if the level place extends for a longer distance; they are two hundred feet distant from one another; between these are three transverse trenches. then are dug the principal pits, so that when the water has been raised from the pool it can flow into the trenches, and from thence into the salt-pits, of which there are numbers on the level ground between the trenches. the salt-pits are basins dug to a moderate depth; these are banked round with the earth which was dug in sinking them or in cleansing them, so that between the basins, earth walls are made a foot high, which retain the water let into them. the trenches have openings, through which the first basins receive the water; these basins also have openings, through which the water flows again from one into the other. there should be a slight fall, so that the water may flow from one basin into the other, and can thus be replenished. all these things having been done rightly and in order, the gate is raised that opens the mouth of the pool which contains sea-water mixed with rain-water or river-water; and thus all of the trenches are filled. then the gates of the first basins are opened, and thus the remaining basins are filled with the water from the first; when this salt-water condenses, all these basins are incrusted, and thus made clean from earthy matter. then again the first basins are filled up from the nearest trench with the same kind of water, and left until much of the thin liquid is converted into vapour by the heat of the sun and dissipated, and the remainder is considerably thickened. then their gates being opened, the water passes into the second basins; and when it has remained there for a certain space of time the gates are opened, so that it flows into the third basins, where it is all condensed into salt. after the salt has been taken out, the basins are filled again and again with sea-water. the salt is raked up with wooden rakes and thrown out with shovels. [illustration (salt wells): a--shed. b--painted signs. c--first room. d--middle room. e--third room. f--two little windows in the end wall. g--third little window in the roof. h--well. i--well of another kind. k--cask. l--pole. m--forked sticks in which the porters rest the pole when they are tired.] salt-water is also boiled in pans, placed in sheds near the wells from which it is drawn. each shed is usually named from some animal or other thing which is pictured on a tablet nailed to it. the walls of these sheds are made either from baked earth or from wicker work covered with thick mud, although some may be made of stones or bricks. when of brick they are often sixteen feet high, and if the roof rises twenty-four feet high, then the walls which are at the ends must be made forty feet high, as likewise the interior partition walls. the roof consists of large shingles four feet long, one foot wide, and two digits thick; these are fixed on long narrow planks placed on the rafters, which are joined at the upper end and slope in opposite directions. the whole of the under side is plastered one digit thick with straw mixed with lute; likewise the roof on the outside is plastered one and a half feet thick with straw mixed with lute, in order that the shed should not run any risk of fire, and that it should be proof against rain, and be able to retain the heat necessary for drying the lumps of salt. each shed is divided into three parts, in the first of which the firewood and straw are placed; in the middle room, separated from the first room by a partition, is the fireplace on which is placed the caldron. to the right of the caldron is a tub, into which is emptied the brine brought into the shed by the porters; to the left is a bench, on which there is room to lay thirty pieces of salt. in the third room, which is in the back part of the house, there is made a pile of clay or ashes eight feet higher than the floor, being the same height as the bench. the master and his assistants, when they carry away the lumps of salt from the caldrons, go from the former to the latter. they ascend from the right side of the caldron, not by steps, but by a slope of earth. at the top of the end wall are two small windows, and a third is in the roof, through which the smoke escapes. this smoke, emitted from both the back and the front of the furnace, finds outlet through a hood through which it makes its way up to the windows; this hood consists of boards projecting one beyond the other, which are supported by two small beams of the roof. opposite the fireplace the middle partition has an open door eight feet high and four feet wide, through which there is a gentle draught which drives the smoke into the last room; the front wall also has a door of the same height and width. both of these doors are large enough to permit the firewood or straw or the brine to be carried in, and the lumps of salt to be carried out; these doors must be closed when the wind blows, so that the boiling will not be hindered. indeed, glass panes which exclude the wind but transmit the light, should be inserted in the windows in the walls. they construct the greater part of the fireplace of rock-salt and of clay mixed with salt and moistened with brine, for such walls are greatly hardened by the fire. these fireplaces are made eight and a half feet long, seven and three quarters feet wide, and, if wood is burned in them, nearly four feet high; but if straw is burned in them, they are six feet high. an iron rod, about four feet long, is engaged in a hole in an iron foot, which stands on the base of the middle of the furnace mouth. this mouth is three feet in width, and has a door which opens inward; through it they throw in the straw. [illustration (salt caldron): a--fireplace. b--mouth of fireplace. c--caldron. d--posts sunk into the ground. e--cross-beams. f--shorter bars. g--iron hooks. h--staples. i--longer bars. k--iron rod bent to support the caldron.] the caldrons are rectangular, eight feet long, seven feet wide, and half a foot high, and are made of sheets of iron or lead, three feet long and of the same width, all but two digits. these plates are not very thick, so that the water is heated more quickly by the fire, and is boiled away rapidly. the more salty the water is, the sooner it is condensed into salt. to prevent the brine from leaking out at the points where the metal plates are fastened with rivets, the caldrons are smeared over with a cement made of ox-liver and ox-blood mixed with ashes. on each side of the middle of the furnace two rectangular posts, three feet long, and half a foot thick and wide are set into the ground, so that they are distant from each other only one and a half feet. each of them rises one and a half feet above the caldron. after the caldron has been placed on the walls of the furnace, two beams of the same width and thickness as the posts, but four feet long, are laid on these posts, and are mortised in so that they shall not fall. there rest transversely upon these beams three bars, three feet long, three digits wide, and two digits thick, distant from one another one foot. on each of these hang three iron hooks, two beyond the beams and one in the middle; these are a foot long, and are hooked at both ends, one hook turning to the right, the other to the left. the bottom hook catches in the eye of a staple, whose ends are fixed in the bottom of the caldron, and the eye projects from it. there are besides, two longer bars six feet long, one palm wide, and three digits thick, which pass under the front beam and rest upon the rear beam. at the rear end of each of the bars there is an iron hook two feet and three digits long, the lower end of which is bent so as to support the caldron. the rear end of the caldron does not rest on the two rear corners of the fireplace, but is distant from the fireplace two thirds of a foot, so that the flame and smoke can escape; this rear end of the fireplace is half a foot thick and half a foot higher than the caldron. this is also the thickness and height of the wall between the caldron and the third room of the shed, to which it is adjacent. this back wall is made of clay and ashes, unlike the others which are made of rock-salt. the caldron rests on the two front corners and sides of the fireplace, and is cemented with ashes, so that the flames shall not escape. if a dipperful of brine poured into the caldron should flow into all the corners, the caldron is rightly set upon the fireplace. the wooden dipper holds ten roman _sextarii_, and the cask holds eight dippers full[ ]. the brine drawn up from the well is poured into such casks and carried by porters, as i have said before, into the shed and poured into a tub, and in those places where the brine is very strong it is at once transferred with the dippers into the caldron. that brine which is less strong is thrown into a small tub with a deep ladle, the spoon and handle of which are hewn out of one piece of wood. in this tub rock-salt is placed in order that the water should be made more salty, and it is then run off through a launder which leads into the caldron. from thirty-seven dippersful of brine the master or his deputy, at halle in saxony,[ ] makes two cone-shaped pieces of salt. each master has a helper, or in the place of a helper his wife assists him in his work, and, in addition, a youth who throws wood or straw under the caldron. he, on account of the great heat of the workshop, wears a straw cap on his head and a breech cloth, being otherwise quite naked. as soon as the master has poured the first dipperful of brine into the caldron the youth sets fire to the wood and straw laid under it. if the firewood is bundles of faggots or brushwood, the salt will be white, but if straw is burned, then it is not infrequently blackish, for the sparks, which are drawn up with the smoke into the hood, fall down again into the water and colour it black. [illustration (salt caldron): a--wooden dipper. b--cask. c--tub. d--master. e--youth. f--wife. g--wooden spade. h--boards. i--baskets. k--hoe. l--rake. m--straw. n--bowl. o--bucket containing the blood. p--tankard which contains beer.] in order to accelerate the condensation of the brine, when the master has poured in two casks and as many dippersful of brine, he adds about a roman _cyathus_ and a half of bullock's blood, or of calf's blood, or buck's blood, or else he mixes it into the nineteenth dipperful of brine, in order that it may be dissolved and distributed into all the corners of the caldron; in other places the blood is dissolved in beer. when the boiling water seems to be mixed with scum, he skims it with a ladle; this scum, if he be working with rock-salt, he throws into the opening in the furnace through which the smoke escapes, and it is dried into rock-salt; if it be not from rock-salt, he pours it on to the floor of the workshop. from the beginning to the boiling and skimming is the work of half-an-hour; after this it boils down for another quarter-of-an-hour, after which time it begins to condense into salt. when it begins to thicken with the heat, he and his helper stir it assiduously with a wooden spatula, and then he allows it to boil for an hour. after this he pours in a _cyathus_ and a half of beer. in order that the wind should not blow into the caldron, the helper covers the front with a board seven and a half feet long and one foot high, and covers each of the sides with boards three and three quarters feet long. in order that the front board may hold more firmly, it is fitted into the caldron itself, and the side-boards are fixed on the front board and upon the transverse beam. afterward, when the boards have been lifted off, the helper places two baskets, two feet high and as many wide at the top, and a palm wide at the bottom, on the transverse beams, and into them the master throws the salt with a shovel, taking half-an-hour to fill them. then, replacing the boards on the caldron, he allows the brine to boil for three quarters of an hour. afterward the salt has again to be removed with a shovel, and when the baskets are full, they pile up the salt in heaps. in different localities the salt is moulded into different shapes. in the baskets the salt assumes the form of a cone; it is not moulded in baskets alone, but also in moulds into which they throw the salt, which are made in the likeness of many objects, as for instance tablets. these tablets and cones are kept in the higher part of the third room of the house, or else on the flat bench of the same height, in order that they may dry better in the warm air. in the manner i have described, a master and his helper continue one after the other, alternately boiling the brine and moulding the salt, day and night, with the exception only of the annual feast days. no caldron is able to stand the fire for more than half a year. the master pours in water and washes it out every week; when it is washed out he puts straw under it and pounds it; new caldrons he washes three times in the first two weeks, and afterward twice. in this manner the incrustations fall from the bottom; if they are not cleared off, the salt would have to be made more slowly over a fiercer fire, which requires more brine and burns the plates of the caldron. if any cracks make their appearance in the caldron they are filled up with cement. the salt made during the first two weeks is not so good, being usually stained by the rust at the bottom where incrustations have not yet adhered. although salt made in this manner is prepared only from the brine of springs and wells, yet it is also possible to use this method in the case of river-, lake-, and sea-water, and also of those waters which are artificially salted. for in places where rock-salt is dug, the impure and the broken pieces are thrown into fresh water, which, when boiled, condenses into salt. some, indeed, boil sea-salt in fresh water again, and mould the salt into the little cones and other shapes. [illustration (salt boiling): a--pool. b--pots. c--ladle. d--pans. e--tongs.] some people make salt by another method, from salt water which flows from hot springs that issue boiling from the earth. they set earthenware pots in a pool of the spring-water, and into them they pour water scooped up with ladles from the hot spring until they are half full. the perpetual heat of the waters of the pool evaporates the salt water just as the heat of the fire does in the caldrons. as soon as it begins to thicken, which happens when it has been reduced by boiling to a third or more, they seize the pots with tongs and pour the contents into small rectangular iron pans, which have also been placed in the pool. the interior of these pans is usually three feet long, two feet wide, and three digits deep, and they stand on four heavy legs, so that the water flows freely all round, but not into them. since the water flows continuously from the pool through the little canals, and the spring always provides a new and copious supply, always boiling hot, it condenses the thickened water poured into the pans into salt; this is at once taken out with shovels, and then the work begins all over again. if the salty water contains other juices, as is usually the case with hot springs, no salt should be made from them. [illustration (salt boiling): a--pots. b--tripod. c--deep ladle.] others boil salt water, and especially sea-water, in large iron pots; this salt is blackish, for in most cases they burn straw under them. some people boil in these pots the brine in which fish is pickled. the salt which they make tastes and smells of fish. [illustration (salt evaporated on faggots): a--trench. b--vat into which the salt water flows. c--ladle. d--small bucket with pole fastened into it.] those who make salt by pouring brine over firewood, lay the wood in trenches which are twelve feet long, seven feet wide, and two and one half feet deep, so that the water poured in should not flow out. these trenches are constructed of rock-salt wherever it is to be had, in order that they should not soak up the water, and so that the earth should not fall in on the front, back and sides. as the charcoal is turned into salt at the same time as the salt liquor, the spaniards think, as pliny writes[ ], that the wood itself turns into salt. oak is the best wood, as its pure ash yields salt; elsewhere hazel-wood is lauded. but with whatever wood it be made, this salt is not greatly appreciated, being black and not quite pure; on that account this method of salt-making is disdained by the germans and spaniards. [illustration (lye making): a--large vat. b--plug. c--small tub. d--deep ladle. e--small vat. f--caldron.] the solutions from which salt is made are prepared from salty earth or from earth rich in salt and saltpetre. lye is made from the ashes of reeds and rushes. the solution obtained from salty earth by boiling, makes salt only; from the other, of which i will speak more a little later, salt and saltpetre are made; and from ashes is derived lye, from which its own salt is obtained. the ashes, as well as the earth, should first be put into a large vat; then fresh water should be poured over the ashes or earth, and it should be stirred for about twelve hours with a stick, so that it may dissolve the salt. then the plug is pulled out of the large vat; the solution of salt or the lye is drained into a small tub and emptied with ladles into small vats; finally, such a solution is transferred into iron or lead caldrons and boiled, until the water having evaporated, the juices are condensed into salt. the above are the various methods for making salt. (illustration p. .) [illustration (nitrum-pits): a--nile. b--nitrum-pits, such as i conjecture them to be.[ ]] _nitrum_[ ] is usually made from _nitrous_ waters, or from solutions or from lye. in the same manner as sea-water or salt-water is poured into salt-pits and evaporated by the heat of the sun and changed into salt, so the _nitrous_ nile is led into _nitrum_ pits and evaporated by the heat of the sun and converted into _nitrum_. just as the sea, in flowing of its own will over the soil of this same egypt, is changed into salt, so also the nile, when it overflows in the dog days, is converted into _nitrum_ when it flows into the _nitrum_ pits. the solution from which _nitrum_ is produced is obtained from fresh water percolating through _nitrous_ earth, in the same manner as lye is made from fresh water percolating through ashes of oak or hard oak. both solutions are taken out of vats and poured into rectangular copper caldrons, and are boiled until at last they condense into _nitrum_. [illustration (soda making): a--vat in which the soda is mixed. b--caldron. c--tub in which _chrysocolla_ is condensed. d--copper wires. e--mortar.] native as well as manufactured _nitrum_ is mixed in vats with urine and boiled in the same caldrons; the decoction is poured into vats in which are copper wires, and, adhering to them, it hardens and becomes _chrysocolla_, which the moors call _borax_. formerly _nitrum_ was compounded with cyprian verdigris, and ground with cyprian copper in cyprian mortars, as pliny writes. some _chrysocolla_ is made of rock-alum and sal-ammoniac.[ ] [illustration (saltpetre making): a--caldron. b--large vat into which sand is thrown. c--plug. d--tub. e--vat containing the rods.] saltpetre[ ] is made from a dry, slightly fatty earth, which, if it be retained for a while in the mouth, has an acrid and salty taste. this earth, together with a powder, are alternately put into a vat in layers a palm deep. the powder consists of two parts of unslaked lime and three parts of ashes of oak, or holmoak, or italian oak, or turkey oak, or of some similar kind. each vat is filled with alternate layers of these to within three-quarters of a foot of the top, and then water is poured in until it is full. as the water percolates through the material it dissolves the saltpetre; then, the plug being pulled out from the vat, the solution is drained into a tub and ladled out into small vats. if when tested it tastes very salty, and at the same time acrid, it is good; but, if not, then it is condemned, and it must be made to percolate again through the same material or through a fresh lot. even two or three waters may be made to percolate through the same earth and become full of saltpetre, but the solutions thus obtained must not be mixed together unless all have the same taste, which rarely or never happens. the first of these solutions is poured into the first vat, the next into the second, the third into the third vat; the second and third solutions are used instead of plain water to percolate through fresh material; the first solution is made in this manner from both the second and third. as soon as there is an abundance of this solution it is poured into the rectangular copper caldron and evaporated to one half by boiling; then it is transferred into a vat covered with a lid, in which the earthy matter settles to the bottom. when the solution is clear it is poured back into the same pan, or into another, and re-boiled. when it bubbles and forms a scum, in order that it should not run over and that it may be greatly purified, there is poured into it three or four pounds of lye, made from three parts of oak or similar ash and one of unslaked lime. but in the water, prior to its being poured in, is dissolved rock-alum, in the proportion of one hundred and twenty _librae_ of the former to five _librae_ of the latter. shortly afterward the solution will be found to be clear and blue. it is boiled until the waters, which are easily volatile (_subtiles_), are evaporated, and then the greater part of the salt, after it has settled at the bottom of the pan, is taken out with iron ladles. then the concentrated solution is transferred to the vat in which rods are placed horizontally and vertically, to which it adheres when cold, and if there be much, it is condensed in three or four days into saltpetre. then the solution which has not congealed, is poured out and put on one side or re-boiled. the saltpetre being cut out and washed with its own solution, is thrown on to boards that it may drain and dry. the yield of saltpetre will be much or little in proportion to whether the solution has absorbed much or little; when the saltpetre has been obtained from lye, which purifies itself, it is somewhat clear and pure. the purest and most transparent, because free from salt, is made if it is drawn off at the thickening stage, according to the following method. there are poured into the caldron the same number of _amphorae_ of the solution as of _congii_ of the lye of which i have already spoken, and into the same caldron is thrown as much of the already made saltpetre as the solution and lye will dissolve. as soon as the mixture effervesces and forms scum, it is transferred to a vat, into which on a cloth has been thrown washed sand obtained from a river. soon afterward the plug is drawn out of the hole at the bottom, and the mixture, having percolated through the sand, escapes into a tub. it is then reduced by boiling in one or another of the caldrons, until the greater part of the solution has evaporated; but as soon as it is well boiled and forms scum, a little lye is poured into it. then it is transferred to another vat in which there are small rods, to which it adheres and congeals in two days if there is but little of it, or if there is much in three days, or at the most in four days; if it does not condense, it is poured back into the caldron and re-boiled down to half; then it is transferred to the vat to cool. the process must be repeated as often as is necessary. others refine saltpetre by another method, for with it they fill a pot made of copper, and, covering it with a copper lid, set it over live coals, where it is heated until it melts. they do not cement down the lid, but it has a handle, and can be lifted for them to see whether or not the melting has taken place. when it has melted, powdered sulphur is sprinkled in, and if the pot set on the fire does not light it, the sulphur kindles, whereby the thick, greasy matter floating on the saltpetre burns up, and when it is consumed the saltpetre is pure. soon afterward the pot is removed from the fire, and later, when cold, the purest saltpetre is taken out, which has the appearance of white marble, the earthy residue then remains at the bottom. the earths from which the solution was made, together with branches of oak or similar trees, are exposed under the open sky and sprinkled with water containing saltpetre. after remaining thus for five or six years, they are again ready to be made into a solution. pure saltpetre which has rested many years in the earth, and that which exudes from the stone walls of wine cellars and dark places, is mixed with the first solution and evaporated by boiling. thus far i have described the methods of making _nitrum_, which are not less varied or multifarious than those for making salt. now i propose to describe the methods of making alum,[ ] which are likewise neither all alike, nor simple, because it is made from boiling aluminous water until it condenses to alum, or else from boiling a solution of alum which is obtained from a kind of earth, or from rocks, or from pyrites, or other minerals. [illustration (vitriol making): a--tanks. b--stirring poles. c--plug. d--trough. e--reservoir. f--launder. g--lead caldron. h--wooden tubs sunk into the earth. i--vats in which twigs are fixed.] this kind of earth having first been dug up in such quantity as would make three hundred wheelbarrow loads, is thrown into two tanks; then the water is turned into them, and if it (the earth) contains vitriol it must be diluted with urine. the workmen must many times a day stir the ore with long, thick sticks in order that the water and urine may be mixed with it; then the plugs having been taken out of both tanks, the solution is drawn off into a trough, which is carved out of one or two trees. if the locality is supplied with an abundance of such ore, it should not immediately be thrown into the tanks, but first conveyed into open spaces and heaped up, for the longer it is exposed to the air and the rain, the better it is; after some months, during which the ore has been heaped up in open spaces into mounds, there are generated veinlets of far better quality than the ore. then it is conveyed into six or more tanks, nine feet in length and breadth and five in depth, and afterward water is drawn into them of similar solution. after this, when the water has absorbed the alum, the plugs are pulled out, and the solution escapes into a round reservoir forty feet wide and three feet deep. then the ore is thrown out of the tanks into other tanks, and water again being run into the latter and the urine added and stirred by means of poles, the plugs are withdrawn and the solution is run off into the same reservoir. a few days afterward, the reservoirs containing the solution are emptied through a small launder, and run into rectangular lead caldrons; it is boiled in them until the greater part of the water has evaporated. the earthy sediment deposited at the bottom of the caldron is composed of fatty and aluminous matter, which usually consists of small incrustations, in which there is not infrequently found a very white and very light powder of asbestos or gypsum. the solution now seems to be full of meal. some people instead pour the partly evaporated solution into a vat, so that it may become pure and clear; then pouring it back into the caldron, they boil it again until it becomes mealy. by whichever process it has been condensed, it is then poured into a wooden tub sunk into the earth in order to cool it. when it becomes cold it is poured into vats, in which are arranged horizontal and vertical twigs, to which the alum clings when it condenses; and thus are made the small white transparent cubes, which are laid to dry in hot rooms. if vitriol forms part of the aluminous ore, the material is dissolved in water without being mixed with urine, but it is necessary to pour that into the clear and pure solution when it is to be re-boiled. this separates the vitriol from the alum, for by this method the latter sinks to the bottom of the caldron, while the former floats on the top; both must be poured separately into smaller vessels, and from these into vats to condense. if, however, when the solution was re-boiled they did not separate, then they must be poured from the smaller vessels into larger vessels and covered over; then the vitriol separating from the alum, it condenses. both are cut out and put to dry in the hot room, and are ready to be sold; the solution which did not congeal in the vessels and vats is again poured back into the caldron to be re-boiled. the earth which settled at the bottom of the caldron is carried back to the tanks, and, together with the ore, is again dissolved with water and urine. the earth which remains in the tanks after the solution has been drawn off is emptied in a heap, and daily becomes more and more aluminous in the same way as the earth from which saltpetre was made, but fuller of its juices, wherefore it is again thrown into the tanks and percolated by water. [illustration (alum making): a--furnace. b--enclosed space. c--aluminous rock. d--deep ladle. e--caldron. f--launder. g--troughs.] aluminous rock is first roasted in a furnace similar to a lime kiln. at the bottom of the kiln a vaulted fireplace is made of the same kind of rock; the remainder of the empty part of the kiln is then entirely filled with the same aluminous rocks. then they are heated with fire until they are red hot and have exhaled their sulphurous fumes, which occurs, according to their divers nature, within the space of ten, eleven, twelve, or more hours. one thing the master must guard against most of all is not to roast the rock either too much or too little, for on the one hand they would not soften when sprinkled with water, and on the other they either would be too hard or would crumble into ashes; from neither would much alum be obtained, for the strength which they have would be decreased. when the rocks are cooled they are drawn out and conveyed into an open space, where they are piled one upon the other in heaps fifty feet long, eight feet wide, and four feet high, which are sprinkled for forty days with water carried in deep ladles. in spring the sprinkling is done both morning and evening, and in summer at noon besides. after being moistened for this length of time the rocks begin to fall to pieces like slaked lime, and there originates a certain new material of the future alum, which is soft and similar to the _liquidae medullae_ found in the rocks. it is white if the stone was white before it was roasted, and rose-coloured if red was mixed with the white; from the former, white alum is obtained, and from the latter, rose-coloured. a round furnace is made, the lower part of which, in order to be able to endure the force of the heat, is made of rock that neither melts nor crumbles to powder by the fire. it is constructed in the form of a basket, the walls of which are two feet high, made of the same rock. on these walls rests a large round caldron made of copper plates, which is concave at the bottom, where it is eight feet in diameter. in the empty space under the bottom they place the wood to be kindled with fire. around the edge of the bottom of the caldron, rock is built in cone-shaped, and the diameter of the bottom of the rock structure is seven feet, and of the top ten feet; it is eight feet deep. the inside, after being rubbed over with oil, is covered with cement, so that it may be able to hold boiling water; the cement is composed of fresh lime, of which the lumps are slaked with wine, of iron-scales, and of sea-snails, ground and mixed with the white of eggs and oil. the edges of the caldron are surmounted with a circle of wood a foot thick and half a foot high, on which the workmen rest the wooden shovels with which they cleanse the water of earth and of the undissolved lumps of rock that remain at the bottom of the caldron. the caldron, being thus prepared, is entirely filled through a launder with water, and this is boiled with a fierce fire until it bubbles. then little by little eight wheelbarrow loads of the material, composed of roasted rock moistened with water, are gradually emptied into the caldron by four workmen, who, with their shovels which reach to the bottom, keep the material stirred and mixed with water, and by the same means they lift the lumps of undissolved rock out of the caldron. in this manner the material is thrown in, in three or four lots, at intervals of two or three hours more or less; during these intervals, the water, which has been cooled by the rock and material, again begins to boil. the water, when sufficiently purified and ready to congeal, is ladled out and run off with launders into thirty troughs. these troughs are made of oak, holm oak, or turkey oak; their interior is six feet long, five feet deep, and four feet wide. in these the water congeals and condenses into alum, in the spring in the space of four days, and in summer in six days. afterward the holes at the bottom of the oak troughs being opened, the water which has not congealed is drawn off into buckets and poured back into the caldron; or it may be preserved in empty troughs, so that the master of the workmen, having seen it, may order his helpers to pour it into the caldron, for the water which is not altogether wanting in alum, is considered better than that which has none at all. then the alum is hewn out with a knife or a chisel. it is thick and excellent according to the strength of the rock, either white or pink according to the colour of the rock. the earthy powder, which remains three to four digits thick as the residue of the alum at the bottom of the trough is again thrown into the caldron and boiled with fresh aluminous material. lastly, the alum cut out is washed, and dried, and sold. alum is also made from crude pyrites and other aluminous mixtures. it is first roasted in an enclosed area; then, after being exposed for some months to the air in order to soften it, it is thrown into vats and dissolved. after this the solution is poured into the leaden rectangular pans and boiled until it condenses into alum. the pyrites and other stones which are not mixed with alum alone, but which also contain vitriol, as is most usually the case, are both treated in the manner which i have already described. finally, if metal is contained in the pyrites and other rock, this material must be dried, and from it either gold, silver, or copper is made in a furnace. vitriol[ ] can be made by four different methods; by two of these methods from water containing vitriol; by one method from a solution of _melanteria_, _sory_ and _chalcitis_; and by another method from earth or stones mixed with vitriol. [illustration (vitriol making): a--tunnel. b--bucket. c--pit.] the vitriol water is collected into pools, and if it cannot be drained into them, it must be drawn up and carried to them in buckets by a workman. in hot regions or in summer, it is poured into out-of-door pits which have been dug to a certain depth, or else it is extracted from shafts by pumps and poured into launders, through which it flows into the pits, where it is condensed by the heat of the sun. in cold regions and in winter these vitriol waters are boiled down with equal parts of fresh water in rectangular leaden caldrons; then, when cold, the mixture is poured into vats or into tanks, which pliny calls wooden fish-tanks. in these tanks light cross-beams are fixed to the upper part, so that they may be stationary, and from them hang ropes stretched with little stones; to these the contents of the thickened solutions congeal and adhere in transparent cubes or seeds of vitriol, like bunches of grapes. [illustration (vitriol making): a--caldron. b--tank. c--cross-bars. d--ropes. e--little stones.] by the third method vitriol is made out of _melanteria_ and _sory_. if the mines give an abundant supply of _melanteria_ and _sory_, it is better to reject the _chalcitis_, and especially the _misy_, for from these the vitriol is impure, particularly from the _misy_. these materials having been dug and thrown into the tanks, they are first dissolved with water; then, in order to recover the pyrites from which copper is not rarely smelted and which forms a sediment at the bottom of the tanks, the solution is transferred to other vats, which are nine feet wide and three feet deep. twigs and wood which float on the surface are lifted out with a broom made of twigs, and afterward all the sediment settles at the bottom of this vat. the solution is poured into a rectangular leaden caldron eight feet long, three feet wide, and the same in depth. in this caldron it is boiled until it becomes thick and viscous, when it is poured into a launder, through which it runs into another leaden caldron of the same size as the one described before. when cold, the solution is drawn off through twelve little launders, out of which it flows into as many wooden tubs four and a half feet deep and three feet wide. upon these tubs are placed perforated crossbars distant from each other from four to six digits, and from the holes hang thin laths, which reach to the bottom, with pegs or wedges driven into them. the vitriol adheres to these laths, and within the space of a few days congeals into cubes, which are taken away and put into a chamber having a sloping board floor, so that the moisture which drips from the vitriol may flow into a tub beneath. this solution is re-boiled, as is also that solution which was left in the twelve tubs, for, by reason of its having become too thin and liquid, it did not congeal, and was thus not converted into vitriol. [illustration (vitriol making): a--wooden tub. b--cross-bars. c--laths. d--sloping floor of the chamber. e--tub placed under it.] [illustration (vitriol making): a--caldron. b--moulds. c--cakes.] the fourth method of making vitriol is from vitriolous earth or stones. such ore is at first carried and heaped up, and is then left for five or six months exposed to the rain of spring and autumn, to the heat of summer, and to the rime and frost of winter. it must be turned over several times with shovels, so that the part at the bottom may be brought to the top, and it is thus ventilated and cooled; by this means the earth crumbles up and loosens, and the stone changes from hard to soft. then the ore is covered with a roof, or else it is taken away and placed under a roof, and remains in that place six, seven, or eight months. afterward as large a portion as is required is thrown into a vat, which is half-filled with water; this vat is one hundred feet long, twenty-four feet wide, eight feet deep. it has an opening at the bottom, so that when it is opened the dregs of the ore from which the vitriol comes may be drawn off, and it has, at the height of one foot from the bottom, three or four little holes, so that, when closed, the water may be retained, and when opened the solution flows out. thus the ore is mixed with water, stirred with poles and left in the tank until the earthy portions sink to the bottom and the water absorbs the juices. then the little holes are opened, the solution flows out of the vat, and is caught in a vat below it; this vat is of the same length as the other, but twelve feet wide and four feet deep. if the solution is not sufficiently vitriolous it is mixed with fresh ore; but if it contains enough vitriol, and yet has not exhausted all of the ore rich in vitriol, it is well to dissolve the ore again with fresh water. as soon as the solution becomes clear, it is poured into the rectangular leaden caldron through launders, and is boiled until the water is evaporated. afterward as many thin strips of iron as the nature of the solution requires, are thrown in, and then it is boiled again until it is thick enough, when cold, to congeal into vitriol. then it is poured into tanks or vats, or any other receptacle, in which all of it that is apt to congeal does so within two or three days. the solution which does not congeal is either poured back into the caldron to be boiled again, or it is put aside for dissolving the new ore, for it is far preferable to fresh water. the solidified vitriol is hewn out, and having once more been thrown into the caldron, is re-heated until it liquefies; when liquid, it is poured into moulds that it may be made into cakes. if the solution first poured out is not satisfactorily thickened, it is condensed two or three times, and each time liquefied in the caldron and re-poured into the moulds, in which manner pure cakes, beautiful to look at, are made from it. the vitriolous pyrites, which are to be numbered among the mixtures (_mistura_), are roasted as in the case of alum, and dissolved with water, and the solution is boiled in leaden caldrons until it condenses into vitriol. both alum and vitriol are often made out of these, and it is no wonder, for these juices are cognate, and only differ in the one point,--that the former is less, the latter more, earthy. that pyrites which contains metal must be smelted in the furnace. in the same manner, from other mixtures of vitriolic and metalliferous material are made vitriol and metal. indeed, if ores of vitriolous pyrites abound, the miners split small logs down the centre and cut them off in lengths as long as the drifts and tunnels are wide, in which they lay them down transversely; but, that they may be stable, they are laid on the ground with the wide side down and the round side up, and they touch each other at the bottom, but not at the top. the intermediate space is filled with pyrites, and the same crushed are scattered over the wood, so that, coming in or going out, the road is flat and even. since the drifts or tunnels drip with water, these pyrites are soaked, and from them are freed the vitriol and cognate things. if the water ceases to drip, these dry and harden, and then they are raised from the shafts, together with the pyrites not yet dissolved in the water, or they are carried out from the tunnels; then they are thrown into vats or tanks, and boiling water having been poured over them, the vitriol is freed and the pyrites are dissolved. this green solution is transferred to other vats or tanks, that it may be made clear and pure; it is then boiled in the lead caldrons until it thickens; afterward it is poured into wooden tubs, where it condenses on rods, or reeds, or twigs, into green vitriol. sulphur is made from sulphurous waters, from sulphurous ores, and from sulphurous mixtures. these waters are poured into the leaden caldrons and boiled until they condense into sulphur. from this latter, heated together with iron-scales, and transferred into pots, which are afterward covered with lute and refined sulphur, another sulphur is made, which we call _caballinum_.[ ] [illustration (sulphur making): a--pots having spouts. b--pots without spouts. c--lids.] the ores[ ] which consist mostly of sulphur and of earth, and rarely of other minerals, are melted in big-bellied earthenware pots. the furnaces, which hold two of these pots, are divided into three parts; the lowest part is a foot high, and has an opening at the front for the draught; the top of this is covered with iron plates, which are perforated near the edges, and these support iron rods, upon which the firewood is placed. the middle part of the furnace is one and a half feet high, and has a mouth in front, so that the wood may be inserted; the top of this has rods, upon which the bottom of the pots stand. the upper part is about two feet high, and the pots are also two feet high and one digit thick; these have below their mouths a long, slender spout. in order that the mouth of the pot may be covered, an earthenware lid is made which fits into it. for every two of these pots there must be one pot of the same size and shape, and without a spout, but having three holes, two of which are below the mouth and receive the spouts of the two first pots; the third hole is on the opposite side at the bottom, and through it the sulphur flows out. in each furnace are placed two pots with spouts, and the furnace must be covered by plates of iron smeared over with lute two digits thick; it is thus entirely closed in, but for two or three vent-holes through which the mouths of the pots project. outside of the furnace, against one side, is placed the pot without a spout, into the two holes of which the two spouts of the other pots penetrate, and this pot should be built in at both sides to keep it steady. when the sulphur ore has been placed in the pots, and these placed in the furnace, they are closely covered, and it is desirable to smear the joint over with lute, so that the sulphur will not exhale, and for the same reason the pot below is covered with a lid, which is also smeared with lute. the wood having been kindled, the ores are heated until the sulphur is exhaled, and the vapour, arising through the spout, penetrates into the lower pot and thickens into sulphur, which falls to the bottom like melted wax. it then flows out through the hole, which, as i said, is at the bottom of this pot; and the workman makes it into cakes, or thin sticks or thin pieces of wood are dipped in it. then he takes the burning wood and glowing charcoal from the furnace, and when it has cooled, he opens the two pots, empties the residues, which, if the ores were composed of sulphur and earth, resemble naturally extinguished ashes; but if the ores consisted of sulphur and earth and stone, or sulphur and stone only, they resemble earth completely dried or stones well roasted. afterward the pots are re-filled with ore, and the whole work is repeated. [illustration (sulphur making): a--long wall. b--high walls. c--low walls. d--plates. e--upper pots. f--lower pots.] the sulphurous mixture, whether it consists of stone and sulphur only, or of stone and sulphur and metal, may be heated in similar pots, but with perforated bottoms. before the furnace is constructed, against the "second" wall of the works two lateral partitions are built seven feet high, three feet long, one and a half feet thick, and these are distant from each other twenty-seven feet. between them are seven low brick walls, that measure but two feet and the same number of digits in height, and, like the other walls, are three feet long and one foot thick; these little walls are at equal distances from one another, consequently they will be two and one half feet apart. at the top, iron bars are fixed into them, which sustain iron plates three feet long and wide and one digit thick, so that they can bear not only the weight of the pots, but also the fierceness of the fire. these plates have in the middle a round hole one and a half digits wide; there must not be more than eight of these, and upon them as many pots are placed. these pots are perforated at the bottom, and the same number of whole pots are placed underneath them; the former contain the mixture, and are covered with lids; the latter contain water, and their mouths are under the holes in the plates. after wood has been arranged round the upper pots and ignited, the mixture being heated, red, yellow, or green sulphur drips from it and flows down through the hole, and is caught by the pots placed underneath the plates, and is at once cooled by the water. if the mixture contains metal, it is reserved for smelting, and, if not, it is thrown away. the sulphur from such a mixture can best be extracted if the upper pots are placed in a vaulted furnace, like those which i described among other metallurgical subjects in book viii., which has no floor, but a grate inside; under this the lower pots are placed in the same manner, but the plates must have larger holes. [illustration (bitumen making): a--lower pot. b--upper pot. c--lid.] others bury a pot in the ground, and place over it another pot with a hole at the bottom, in which pyrites or _cadmia_, or other sulphurous stones are so enclosed that the sulphur cannot exhale. a fierce fire heats the sulphur, and it drips away and flows down into the lower pot, which contains water. (illustration p. ). [illustration (bitumen making): a--bituminous spring. b--bucket. c--pot. d--lid.] bitumen[ ] is made from bituminous waters, from liquid bitumen, and from mixtures of bituminous substances. the water, bituminous as well as salty, at babylon, as pliny writes, was taken from the wells to the salt works and heated by the great heat of the sun, and condensed partly into liquid bitumen and partly into salt. the bitumen being lighter, floats on the top, while the salt being heavier, sinks to the bottom. liquid bitumen, if there is much floating on springs, streams and rivers, is drawn up in buckets or other vessels; but, if there is little, it is collected with goose wings, pieces of linen, _ralla_, shreds of reeds, and other things to which it easily adheres, and it is boiled in large brass or iron pots by fire and condensed. as this bitumen is put to divers uses, some mix pitch with the liquid, others old cart-grease, in order to temper its viscosity; these, however long they are boiled in the pots, cannot be made hard. the mixtures containing bitumen are also treated in the same manner as those containing sulphur, in pots having a hole in the bottom, and it is rare that such bitumen is not highly esteemed. [illustration (chrysocolla making): a--mouth of the tunnel. b--trough. c--tanks. d--little trough.] since all solidified juices and earths, if abundantly and copiously mixed with the water, are deposited in the beds of springs, streams or rivers, and the stones therein are coated by them, they do not require the heat of the sun or fire to harden them. this having been pondered over by wise men, they discovered methods by which the remainder of these solidified juices and unusual earths can be collected. such waters, whether flowing from springs or tunnels, are collected in many wooden tubs or tanks arranged in consecutive order, and deposit in them such juices or earths; these being scraped off every year, are collected, as _chrysocolla_[ ] in the carpathians and as ochre in the harz. there remains glass, the preparation of which belongs here, for the reason that it is obtained by the power of fire and subtle art from certain solidified juices and from coarse or fine sand. it is transparent, as are certain solidified juices, gems, and stones; and can be melted like fusible stones and metals. first i must speak of the materials from which glass is made; then of the furnaces in which it is melted; then of the methods by which it is produced. it is made from fusible stones and from solidified juices, or from other juicy substances which are connected by a natural relationship. stones which are fusible, if they are white and translucent, are more excellent than the others, for which reason crystals take the first place. from these, when pounded, the most excellent transparent glass was made in india, with which no other could be compared, as pliny relates. the second place is accorded to stones which, although not so hard as crystal, are yet just as white and transparent. the third is given to white stones, which are not transparent. it is necessary, however, first of all to heat all these, and afterward they are subjected to the pestle in order to break and crush them into coarse sand, and then they are passed through a sieve. if this kind of coarse or fine sand is found by the glass-makers near the mouth of a river, it saves them much labour in burning and crushing. as regards the solidified juices, the first place is given to soda; the second to white and translucent rock-salt; the third to salts which are made from lye, from the ashes of the musk ivy, or from other salty herbs. yet there are some who give to this latter, and not to the former, the second place. one part of coarse or fine sand made from fusible stones should be mixed with two parts of soda or of rock-salt or of herb salts, to which are added minute particles of _magnes_.[ ] it is true that in our day, as much as in ancient times, there exists the belief in the singular power of the latter to attract to itself the vitreous liquid just as it does iron, and by attracting it to purify and transform green or yellow into white; and afterward fire consumes the _magnes_. when the said juices are not to be had, two parts of the ashes of oak or holmoak, or of hard oak or turkey oak, or if these be not available, of beech or pine, are mixed with one part of coarse or fine sand, and a small quantity of salt is added, made from salt water or sea-water, and a small particle of _magnes_; but these make a less white and translucent glass. the ashes should be made from old trees, of which the trunk at a height of six feet is hollowed out and fire is put in, and thus the whole tree is consumed and converted into ashes. this is done in winter when the snow lies long, or in summer when it does not rain, for the showers at other times of the year, by mixing the ashes with earth, render them impure; for this reason, at such times, these same trees are cut up into many pieces and burned under cover, and are thus converted into ashes. [illustration (glass-making furnace): a--lower chamber of the first furnace. b--upper chamber. c--vitreous mass.] some glass-makers use three furnaces, others two, others only one. those who use three, melt the material in the first, re-melt it in the second, and in the third they cool the glowing glass vessels and other articles. of these the first furnace must be vaulted and similar to an oven. in the upper chamber, which is six feet long, four feet wide, and two feet high, the mixed materials are heated by a fierce fire of dry wood until they melt and are converted into a vitreous mass. and if they are not satisfactorily purified from dross, they are taken out and cooled and broken into pieces; and the vitreous pieces are heated in pots in the same furnace. [illustration (glass-making furnace): a--arches of the second furnace. b--mouth of the lower chamber. c--windows of the upper chamber. d--big-bellied pots. e--mouth of the third furnace. f--recesses for the receptacles. g--openings in the upper chamber. h--oblong receptacles.] the second furnace is round, ten feet in diameter and eight feet high, and on the outside, so that it may be stronger, it is encompassed by five arches, one and one half feet thick; it consists in like manner of two chambers, of which the lower one is vaulted and is one and one half feet thick. in front this chamber has a narrow mouth, through which the wood can be put into the hearth, which is on the ground. at the top and in the middle of its vault, there is a large round hole which opens to the upper chamber, so that the flames can penetrate into it. between the arches in the walls of the upper chamber are eight windows, so large that the big-bellied pots may be placed through them on to the floor of the chamber, around the large hole. the thickness of these pots is about two digits, their height the same number of feet, and the diameter of the belly one and a half feet, and of the mouth and bottom one foot. in the back part of the furnace is a rectangular hole, measuring in height and width a palm, through which the heat penetrates into a third furnace which adjoins it. this third furnace is rectangular, eight feet long and six feet wide; it also consists of two chambers, of which the lower has a mouth in front, so that firewood may be placed on the hearth which is on the ground. on each side of this opening in the wall of the lower chamber is a recess for oblong earthenware receptacles, which are about four feet long, two feet high, and one and a half feet wide. the upper chamber has two holes, one on the right side, the other on the left, of such height and width that earthenware receptacles may be conveniently placed in them. these latter receptacles are three feet long, one and a half feet high, the lower part one foot wide, and the upper part rounded. in these receptacles the glass articles, which have been blown, are placed so that they may cool in a milder temperature; if they were not cooled slowly they would burst asunder. when the vessels are taken from the upper chamber, they are immediately placed in the receptacles to cool. [illustration (glass-making furnaces): a--lower chamber of the other second furnace. b--middle one. c--upper one. d--its opening. e--round opening. f--rectangular opening.] some who use two furnaces partly melt the mixture in the first, and not only re-melt it in the second, but also replace the glass articles there. others partly melt and re-melt the material in different chambers of the second furnace. thus the former lack the third furnace, and the latter, the first. but this kind of second furnace differs from the other second furnace, for it is, indeed, round, but the interior is eight feet in diameter and twelve feet high, and it consists of three chambers, of which the lowest is not unlike the lowest of the other second furnace. in the middle chamber wall there are six arched openings, in which are placed the pots to be heated, and the remainder of the small windows are blocked up with lute. in the middle top of the middle chamber is a square opening a palm in length and width. through this the heat penetrates into the upper chamber, of which the rear part has an opening to receive the oblong earthenware receptacles, in which are placed the glass articles to be slowly cooled. on this side, the ground of the workshop is higher, or else a bench is placed there, so that the glass-makers may stand upon it to stow away their products more conveniently. those who lack the first furnace in the evening, when they have accomplished their day's work, place the material in the pots, so that the heat during the night may melt it and turn it into glass. two boys alternately, during night and day, keep up the fire by throwing dry wood on to the hearth. those who have but one furnace use the second sort, made with three chambers. then in the evening they pour the material into the pots, and in the morning, having extracted the fused material, they make the glass objects, which they place in the upper chamber, as do the others. the second furnace consists either of two or three chambers, the first of which is made of unburnt bricks dried in the sun. these bricks are made of a kind of clay that cannot be easily melted by fire nor resolved into powder; this clay is cleaned of small stones and beaten with rods. the bricks are laid with the same kind of clay instead of lime. from the same clay the potters also make their vessels and pots, which they dry in the shade. these two parts having been completed, there remains the third. [illustration (glass making): a--blow-pipe. b--little window. c--marble. d--forceps. e--moulds by means of which the shapes are produced.] the vitreous mass having been made in the first furnace in the manner i described, is broken up, and the assistant heats the second furnace, in order that the fragments may be re-melted. in the meantime, while they are doing this, the pots are first warmed by a slow fire in the first furnace, so that the vapours may evaporate, and then by a fiercer fire, so that they become red in drying. afterward the glass-makers open the mouth of the furnace, and, seizing the pots with tongs, if they have not cracked and fallen to pieces, quickly place them in the second furnace, and they fill them up with the fragments of the heated vitreous mass or with glass. afterward they close up all the windows with lute and bricks, with the exception that in each there are two little windows left free; through one of these they inspect the glass contained in the pot, and take it up by means of a blow-pipe; in the other they rest another blow-pipe, so that it may get warm. whether it is made of brass, bronze, or iron, the blow-pipe must be three feet long. in front of the window is inserted a lip of marble, on which rests the heaped-up clay and the iron shield. the clay holds the blow-pipe when it is put into the furnace, whereas the shield preserves the eyes of the glass-maker from the fire. all this having been carried out in order, the glass-makers bring the work to completion. the broken pieces they re-melt with dry wood, which emits no smoke, but only a flame. the longer they re-melt it, the purer and more transparent it becomes, the fewer spots and blisters there are, and therefore the glass-makers can carry out their work more easily. for this reason those who only melt the material from which glass is made for one night, and then immediately make it up into glass articles, make them less pure and transparent than those who first produce a vitreous mass and then re-melt the broken pieces again for a day and a night. and, again, these make a less pure and transparent glass than do those who melt it again for two days and two nights, for the excellence of the glass does not consist solely in the material from which it is made, but also in the melting. the glass-makers often test the glass by drawing it up with the blowpipes; as soon as they observe that the fragments have been re-melted and purified satisfactorily, each of them with another blow-pipe which is in the pot, slowly stirs and takes up the glass which sticks to it in the shape of a ball like a glutinous, coagulated gum. he takes up just as much as he needs to complete the article he wishes to make; then he presses it against the lip of marble and kneads it round and round until it consolidates. when he blows through the pipe he blows as he would if inflating a bubble; he blows into the blow-pipe as often as it is necessary, removing it from his mouth to re-fill his cheeks, so that his breath does not draw the flames into his mouth. then, twisting the lifted blow-pipe round his head in a circle, he makes a long glass, or moulds the same in a hollow copper mould, turning it round and round, then warming it again, blowing it and pressing it, he widens it into the shape of a cup or vessel, or of any other object he has in mind. then he again presses this against the marble to flatten the bottom, which he moulds in the interior with his other blow-pipe. afterward he cuts out the lip with shears, and, if necessary, adds feet and handles. if it so please him, he gilds it and paints it with various colours. finally, he lays it in the oblong earthenware receptacle, which is placed in the third furnace, or in the upper chamber of the second furnace, that it may cool. when this receptacle is full of other slowly-cooled articles, he passes a wide iron bar under it, and, carrying it on the left arm, places it in another recess. the glass-makers make divers things, such as goblets, cups, ewers, flasks, dishes, plates, panes of glass, animals, trees, and ships, all of which excellent and wonderful works i have seen when i spent two whole years in venice some time ago. especially at the time of the feast of the ascension they were on sale at morano, where are located the most celebrated glass-works. these i saw on other occasions, and when, for a certain reason, i visited andrea naugerio in his house which he had there, and conversed with him and francisco asulano. end of book xii. footnotes: [ ] the history of salt-making in salt-pans, from sea-water or salt springs, goes further back than human records. from an historical point of view the real interest attached to salt lies in the bearing which localities rich in either natural salt or salt springs, have had upon the movements of the human race. many ancient trade routes have been due to them, and innumerable battles have been fought for their possession. salt has at times served for currency, and during many centuries in nearly every country has served as a basis of taxation. these subjects do not, however, come within the scope of this text. for the quotation from pliny referred to, see note below, on bitumen. [ ] the first edition gives _graviorem_, the latter editions _gratiorem_, which latter would have quite the reverse meaning from the above. [ ] the following are approximately the english equivalents:-- pints. quarts. gallons. _cyathus_ . _cyathi_ = _quartarius_ . _quartarii_ = _sextarius_ . _sextarii_ = _congius_ . . _sextarii_ = _modius_ . . . _congii_ = _amphora_ . . . the dipper mentioned would thus hold about one and one quarter gallons, and the cask ten gallons. [ ] the salt industry, founded upon salt springs, is still of importance to this city. it was a salt centre of importance to the germanic tribes before charles, the son of charlemagne, erected a fortress here in . mention of the salt works is made in the charter by otto i., conveying the place to the diocese of magdeburg, in . [ ] pliny xxxi., - . "in the gallic provinces in germany they pour salt water upon burning wood. the spaniards in a certain place draw the brine from wells, which they call _muria_. they indeed think that the wood turns to salt, and that the oak is the best, being the kind which is itself salty. elsewhere the hazel is praised. thus the charcoal even is turned into salt when it is steeped in brine. whenever salt is made with wood it is black." [ ] we have elsewhere in this book used the word "soda" for the latin term _nitrum_, because we believe as used by agricola it was always soda, and because some confusion of this term with its modern adaptation for saltpetre (nitre) might arise in the mind of the reader. fortunately, agricola usually carefully mentions other alkalis, such as the product from lixiviation of ashes, separately from his _nitrum_. in these paragraphs, however, he has soda and potash hopelessly mixed, wherefore we have here introduced the latin term. the actual difference between potash and soda--the _nitrum_ of the ancients, and the _alkali_ of geber (and the glossary of agricola), was not understood for two hundred years after agricola, when duhamel made his well-known determinations; and the isolation of sodium and potassium was, of course, still later by fifty years. if the reeds and rushes described in this paragraph grew near the sea, the salt from lixiviation would be soda, and likewise the egyptian product was soda, but the lixiviation of wood-ash produces only potash; as seen above, all are termed _nitrum_ except the first. historical notes.--the word _nitrum_, _nitron_, _nitri_, _neter_, _nether_, or similar forms, occurs in innumerable ancient writings. among such references are jeremiah (ii., ) proverbs (xxv., ), herodotus (ii., , ), aristotle (_prob._ i., , _de mirab._ ), theophrastus (_de igne_ ed. heinsii, hist. plants iii., ), dioscorides (v., ), pliny (xiv., , and xxxi., ). a review of disputations on what salts this term comprised among the ancients would itself fill a volume, but from the properties named it was no doubt mostly soda, more rarely potash, and sometimes both mixed with common salt. there is every reason to believe from the properties and uses mentioned, that it did not generally comprise nitre (saltpetre)--into which superficial error the nomenclature has led many translators. the preparation by way of burning, and the use of _nitrum_ for purposes for which we now use soap, for making glass, for medicines, cosmetics, salves, painting, in baking powder, for preserving food, embalming, etc., and the descriptions of its taste in "nitrous" waters,--all answer for soda and potash, but not for saltpetre. it is possible that the common occurrence of saltpetre as an efflorescence on walls might naturally lead to its use, but in any event its distinguishing characteristics are nowhere mentioned. as sal-ammoniac occurred in the volcanoes in italy, it also may have been included in the _nitrum_ mentioned. _nitrum_ was in the main exported from egypt, but theophrastus mentions its production from wood-ash, and pliny very rightly states that burned lees of wine (argol) had the nature of _nitrum_. many of the ancient writers understood that it was rendered more caustic by burning, and still more so by treatment with lime. according to beckmann (hist. of inventions ii., p. ), the form of the word _natron_ was first introduced into europe by two travellers in egypt, peter ballon and prosper alpinus, about . the word was introduced into mineralogy by linnaeus in . in the first instance _natron_ was applied to soda and potash in distinction to _nitre_ for saltpetre, and later _natron_ was applied solely to soda. it is desirable to mention here two other forms of soda and potash which are frequently mentioned by agricola. "ashes which wool dyers use" (_cineres quo infectores lanarum utuntur_).--there is no indication in any of agricola's works as to whether this was some special wood-ash or whether it was the calcined residues from wool washing. the "yolk" or "suint" of wool, originating from the perspiration of the animal, has long been a source of crude potash. the water, after washing the wool, is evaporated, and the residue calcined. it contains about % k_{ }co_{ }, the remainder being sodium and potassium sulphates. another reason for assuming that it was not a wood-ash product, is that these products are separately mentioned. in either event, whether obtained from wool residues or from lixiviation of wood-ash, it would be an impure potash. in some methods of wool dyeing, a wash of soda was first given, so that it is barely possible that this substance was sodium carbonate. "salt made from the ashes of musk ivy" (_sal ex anthyllidis cinere factus_,--glossary, _salalkali_). this would be largely potash. [ ] this wondrous illustration of soda-making from nile water is no doubt founded upon pliny (xxxi., ). "it is made in almost the same manner as salt, except that sea-water is put into salt pans, whereas in the nitrous pans it is water of the nile; these, with the subsidence of the nile during the forty days, are impregnated with _nitrum_." [ ] this paragraph displays hopeless ignorance. borax was known to agricola and greatly used in his time; it certainly was not made from these compounds, but was imported from central asia. sal-ammoniac was also known in his time, and was used like borax as a soldering agent. the reaction given by agricola would yield free ammonia. the following historical notes on borax and sal-ammoniac may be of service. borax.--the uncertainties of the ancient distinctions in salts involve borax deeply. the word _baurach_ occurs in geber and the other early alchemistic writings, but there is nothing to prove that it was modern borax. there cannot be the slightest doubt, however, that the material referred to by agricola as _borax_ was our borax, because of the characteristic qualities incidentally mentioned in book vii. that he believed it was an artificial product from _nitrum_ is evident enough from his usual expression "_chrysocolla_ made from _nitrum_, which the moors call _borax_." agricola, in _de natura fossilium_ (p. - ), makes the following statements, which could leave no doubt on the subject:--"native _nitrum_ is found in the earth or on the surface.... it is from this variety that the venetians make _chrysocolla_, which i call _borax_.... the second variety of artificial _nitrum_ is made at the present day from the native _nitrum_, called by the arabs _tincar_, but i call it usually by the greek name _chrysocolla_; it is really the arabic _borax_.... this _nitrum_ does not decrepitate nor fly out of the fire; however, the native variety swells up from within." the application of the word _chrysocolla_ (_chrysos_, gold; _colla_, solder) to soldering materials, and at the same time to the copper mineral, is of greek origin. if any further proof were needed as to the substance meant by agricola, it lies in the word _tincar_. for a long time the borax of europe was imported from central asia, through constantinople and venice, under the name of _tincal_ or _tincar_. when this trade began, we do not know; evidently before agricola's time. the statement here of making borax from alum and sal-ammoniac is identical with the assertion of biringuccio (ii., ). sal-ammoniac.--the early history of this--ammonium chloride--is also under a cloud. pliny (xxxi., ) speaks of a _sal-hammoniacum_, and dioscorides (v., ) uses much the same word. pliny describes it as from near the temple of ammon in egypt. none of the distinctive characteristics of sal-ammoniac are mentioned, and there is every reason to believe it was either common salt or soda. herodotus, strabo, and others mention common salt sent from about the same locality. the first authentic mention is in geber, who calls it _sal-ammoniacum_, and describes a method of making, and several characteristic reactions. it was known in the middle ages under various names, among them _sal-aremonicum_. agricola (_de nat. fos._, iii., p. ) notes its characteristic quality of volatilization. "sal-ammoniac ... in the fire neither crackles nor flies out, but is totally consumed." he also says (p. ): "borax is used by goldsmiths to solder gold, likewise silver. the artificers who make iron needles (tacks?) similarly use sal-ammoniac when they cover the heads with tin." the statement from pliny mentioned in this paragraph is from xxxiii., , where he describes the _chrysocolla_ used as gold solder as made from verdigris, _nitrum_, and urine in the way quoted. it is quite possible that this solder was sal-ammoniac, though not made in quite this manner. pliny refers in several places (xxxiii., , , , and , xxxv., , etc.) to _chrysocolla_, about which he is greatly confused as between gold-solder, the copper mineral, and a green pigment, the latter being of either mineral origin. [ ] saltpetre was secured in the middle ages in two ways, but mostly from the treatment of calcium nitrate efflorescence on cellar and similar walls, and from so-called saltpetre plantations. in this description of the latter, one of the most essential factors is omitted until the last sentence, _i.e._, that the nitrous earth was the result of the decay of organic or animal matter over a long period. such decomposition, in the presence of potassium and calcium carbonates--the lye and lime--form potassium and calcium nitrates, together with some magnesium and sodium nitrates. after lixiviation, the addition of lye converts the calcium and magnesium nitrates into saltpetre, _i.e._, ca(no_{ })_{ } + k_{ }co_{ } = caco_{ } + kno_{ }. the carbonates precipitate out, leaving the saltpetre in solution, from which it was evaporated and crystallized out. the addition of alum as mentioned would scarcely improve the situation. the purification by repeated re-solution and addition of lye, and filtration, would eliminate the remaining other salts. the purification with sulphur, however, is more difficult to understand. in this case the saltpetre is melted and the sulphur added and set alight. such an addition to saltpetre would no doubt burn brilliantly. the potassium sulphate formed would possibly settle to the bottom, and if the "greasy matter" were simply organic impurities, they might be burned off. this method of refining appears to have been copied from biringuccio (x., ), who states it in almost identical terms. historical note.--as mentioned in note above, it is quite possible that the ancients did include efflorescence of walls under _nitrum_; but, so far as we are aware, no specific mention of such an occurrence of _nitrum_ is given, and, as stated before, there is every reason to believe that all the substances under that term were soda and potash. especially the frequent mention of the preparation of _nitrum_ by way of burning, argues strongly against saltpetre being included, as they would hardly have failed to notice the decrepitation. argument has been put forward that greek fire contained saltpetre, but it amounts to nothing more than argument, for in those receipts preserved, no salt of any kind is mentioned. it is most likely that the leprosy of house-walls of the mosaic code (leviticus xiv., to ) was saltpetre efflorescence. the drastic treatment by way of destruction of such "unclean" walls and houses, however, is sufficient evidence that this salt was not used. the first certain mention of saltpetre (_sal petrae_) is in geber. as stated before, the date of this work is uncertain; in any event it was probably as early as the th century. he describes the making of "solvative water" with alum and saltpetre, so there can be no doubt as to the substance (see note on p. , on nitric acid). there is also a work by a nebulous marcus graecus, where the word _sal petrosum_ is used. and it appears that roger bacon (died ) and albertus magnus (died ) both had access to that work. bacon uses the term _sal petrae_ frequently enough, and was the first to describe gunpowder (_de mirabili potestate artis et naturae_ ). he gives no mention of the method of making his _sal petrae_. agricola uses throughout the latin text the term _halinitrum_, a word he appears to have coined himself. however, he gives its german equivalent in the _interpretatio_ as _salpeter_. the only previous description of the method of making saltpetre, of which we are aware, is that of biringuccio ( ), who mentions the boiling of the excrescences from walls, and also says a good deal about boiling solutions from "nitrous" earth, which may or may not be of "plantation" origin. he also gives this same method of refining with sulphur. in any event, this statement by agricola is the first clear and complete description of the saltpetre "plantations." saltpetre was in great demand in the middle ages for the manufacture of gunpowder, and the first record of that substance and of explosive weapons necessarily involves the knowledge of saltpetre. however, authentic mention of such weapons only begins early in the th century. among the earliest is an authority to the council of twelve at florence to appoint persons to make cannon, etc., ( ), references to cannon in the stores of the tower of london, , &c. [ ] there are three methods of manufacturing alum described by agricola, the first and third apparently from shales, and the second from alum rock or "alunite." the reasons for assuming that the first process was from shales, are the reference to the "aluminous earth" as ore (_venae_) coming from "veins," and also the mixture of vitriol. in this process the free sulphuric acid formed by the oxidation of pyrites reacts upon the argillaceous material to form aluminium sulphate. the decomposed ore is then placed in tanks and lixiviated. the solution would contain aluminium sulphate, vitriol, and other impurities. by the addition of urine, the aluminium sulphate would be converted into ammonia alum. agricola is, of course, mistaken as to the effect of the addition, being under the belief that it separated the vitriol from the alum; in fact, this belief was general until the latter part of the th century, when lavoisier determined that alum must have an alkali base. nor is it clear from this description exactly how they were separated. in a condensed solution allowed to cool, the alum would precipitate out as "alum meal," and the vitriol would "float on top"--in solution. the reference to "meal" may represent this phenomenon, and the re-boiling referred to would be the normal method of purification by crystallization. the "asbestos" and gypsum deposited in the caldrons were no doubt feathery and mealy calcium sulphate. the alum produced would, in any event, be mostly ammonia alum. the second process is certainly the manufacture from "alum rock" or "alunite" (the hydrous sulphate of aluminium and potassium), such as that mined at la tolfa in the papal states, where the process has been for centuries identical with that here described. the alum there produced is the double basic potassium alum, and crystallizes into cubes instead of octahedra, _i.e._, the roman alum of commerce. the presence of much ferric oxide gives the rose colour referred to by agricola. this account is almost identical with that of biringuccio (ii., ), and it appears from similarity of details that agricola, as stated in his preface, must have "refreshed his mind" from this description; it would also appear from the preface that he had himself visited the locality. the third process is essentially the same as the first, except that the decomposition of the pyrites was hastened by roasting. the following obscure statement of some interest occurs in agricola's _de natura fossilium_, p. :--"... alum is made from vitriol, for when oil is made from the latter, alum is distilled out (_expirat_). this absorbs the clay which is used in cementing glass, and when the operation is complete the clay is macerated with pure water, and the alum is soon afterward deposited in the shape of small cubes." assuming the oil of vitriol to be sulphuric acid and the clay "used in cementing glass" to be kaolin, we have here the first suggestion of a method for producing alum which came into use long after. "burnt alum" (_alumen coctum_).--agricola frequently uses this expression, and on p. , describes the operation, and the substance is apparently the same as modern dehydrated alum, often referred to as "burnt alum." historical notes.--whether the ancients knew of alum in the modern sense is a most vexed question. the greeks refer to a certain substance as _stypteria_, and the romans refer to this same substance as _alumen_. there can be no question as to their knowledge and common use of vitriol, nor that substances which they believed were entirely different from vitriol were comprised under the above names. beckmann (hist. of inventions, vol. i., p. ) seems to have been the founder of the doctrine that the ancient _alumen_ was vitriol, and scores of authorities seem to have adopted his arguments without inquiry, until that belief is now general. one of the strongest reasons put forward was that alum does not occur native in appreciable quantities. apart from the fact that the weight of this argument has been lost by the discovery that alum does occur in nature to some extent as an aftermath of volcanic action, and as an efflorescence from argillaceous rocks, we see no reason why the ancients may not have prepared it artificially. one of the earliest mentions of such a substance is by herodotus (ii., ) of a thousand talents of _stypteria_, sent by amasis from egypt as a contribution to the rebuilding of the temple of delphi. diodorus (v., ) mentions the abundance which was secured from the lipari islands (stromboli, etc.), and a small quantity from the isle of melos. dioscorides (v., ) mentions egypt, lipari islands, melos, sardinia, armenia, etc., "and generally in any other places where one finds red ochre (_rubrica_)." pliny (xxxv., ) gives these same localities, and is more explicit as to how it originates--"from an earthy water which exudes from the earth." of these localities, the lipari islands (stromboli, etc.), and melos are volcanic enough, and both lipari and melos are now known to produce natural alum (dana. syst. min., p. ; and tournefort, "_relation d'un voyage du levant_." london, , _lettre_ iv., vol. .). further, the hair-like alum of dioscorides, repeated by pliny below, was quite conceivably fibrous _kalinite_, native potash alum, which occurs commonly as an efflorescence. be the question of native alum as it may--and vitriol is not much more common--our own view that the ancient _alumen_ was alum, is equally based upon the artificial product. before entering upon the subject, we consider it desirable to set out the properties of the ancient substance, a complete review of which is given by pliny (xxxv., ), he obviously quoting also from dioscorides, which, therefore, we do not need to reproduce. pliny says:-- "not less important, or indeed dissimilar, are the uses made of _alumen_; by which name is understood a sort of salty earth. of this, there are several kinds. in cyprus there is a white _alumen_, and a darker kind. there is not a great difference in their colour, though the uses made of them are very dissimilar,--the white _alumen_ being employed in a liquid state for dyeing wool bright colours, and the dark-coloured _alumen_, on the other hand, for giving wool a sombre tint. gold is purified with black _alumen_. every kind of _alumen_ is from a _limus_ water which exudes from the earth. the collection of it commences in winter, and it is dried by the summer sun. that portion of it which first matures is the whitest. it is obtained in spain, egypt, armenia, macedonia, pontus, africa, and the islands of sardinia, melos, lipari, and strongyle; the most esteemed, however, is that of egypt, the next best from melos. of this last there are two kinds, the liquid _alumen_, and the solid. liquid _alumen_, to be good, should be of a limpid and milky appearance; when rubbed, it should be without roughness, and should give a little heat. this is called _phorimon_. the mode of detecting whether it has been adulterated is by pomegranate juice, for, if genuine, the mixture turns black. the other, or solid, is pale and rough and turns dark with nut-galls; for which reason it is called _paraphoron_. liquid _alumen_ is naturally astringent, indurative, and corrosive; used in combination with honey, it heals ulcerations.... there is one kind of solid _alumen_, called by the greeks _schistos_, which splits into filaments of a whitish colour; for which reason some prefer calling it _trichitis_ (hair like). _alumen_ is produced from the stone _chalcitis_, from which copper is also made, being a sort of coagulated scum from that stone. this kind of _alumen_ is less astringent than the others, and is less useful as a check upon bad humours of the body.... the mode of preparing it is to cook it in a pan until it has ceased being a liquid. there is another variety of _alumen_ also, of a less active nature, called _strongyle_. it is of two kinds. the fungous, which easily dissolves, is utterly condemned. the better kind is the pumice-like kind, full of small holes like a sponge, and is in round pieces, more nearly white in colour, somewhat greasy, free from grit, friable, and does not stain black. this last kind is cooked by itself upon charcoal until it is reduced to pure ashes. the best kind of all is that called _melinum_, from the isle of melos, as i have said, none being more effectual as an astringent, for staining black, and for indurating, and none becomes more dry.... above all other properties of _alumen_ is its remarkable astringency, whence its greek name.... it is injected for dysentry and employed as a gargle." the lines omitted refer entirely to medical matters which have no bearing here. the following paragraph (often overlooked) from pliny (xxxv., ) also has an important bearing upon the subject:--"in egypt they employ a wonderful method of dyeing. the white cloth, after it is pressed, is stained in various places, not with dye stuffs, but with substances which absorb colours. these applications are not apparent on the cloth, but when it is immersed in a caldron of hot dye it is removed the next moment brightly coloured. the remarkable circumstance is that although there be only one dye in the caldron yet different colours appear in the cloth." it is obvious from pliny's description above, and also from the making of vitriol (see note , p. ), that this substance was obtained from liquor resulting from natural or artificial lixiviation of rocks--in the case of vitriols undoubtedly the result of decomposition of pyritiferous rocks (such as _chalcitis_). such liquors are bound to contain aluminum sulphate if there is any earth or clay about, and whether they contained alum would be a question of an alkali being present. if no alkali were present in this liquor, vitriol would crystallize out first, and subsequent condensation would yield aluminum sulphate. if alkali were present, the alum would crystallize out either before or with the vitriol. pliny's remark, "that portion of it which first matures is whitest", agrees well enough with this hypothesis. no one will doubt that some of the properties mentioned above belong peculiarly to vitriol, but equally convincing are properties and uses that belong to alum alone. the strongly astringent taste, white colour, and injection for dysentry, are more peculiar to alum than to vitriol. but above all other properties is that displayed in dyeing, for certainly if we read this last quotation from pliny in conjunction with the statement that white _alumen_ produces bright colours and the dark kind, sombre colours, we have the exact reactions of alum and vitriol when used as mordants. therefore, our view is that the ancient salt of this character was a more or less impure mixture ranging from alum to vitriol--"the whiter the better." further, considering the ancient knowledge of soda (_nitrum_), and the habit of mixing it into almost everything, it does not require much flight of imagination to conceive its admixture to the "water," and the absolute production of alum. whatever may have been the confusion between alum and vitriol among the ancients, it appears that by the time of the works attributed to geber ( th or th century), the difference was well known. his work (_investigationes perfectiones_, iv.) refers to _alumen glaciale_ and _alumen jameni_ as distinguished from vitriol, and gives characteristic reactions which can leave no doubt as to the distinction. we may remark here that the repeated statement apparently arising from meyer (history of chemistry, p. ) that geber used the term _alum de rocca_ is untrue, this term not appearing in the early latin translations. during the th century alum did come to be known in europe as _alum de rocca_. various attempts have been made to explain the origin of this term, ranging from the italian root, a "rock," to the town of rocca in syria, where alum was supposed to have been produced. in any event, the supply for a long period prior to the middle of the th century came from turkey, and the origin of the methods of manufacture described by agricola, and used down to the present day, must have come from the orient. in the early part of the th century, a large trade in alum was done between italy and asia minor, and eventually various italians established themselves near constantinople and smyrna for its manufacture (dudae, _historia byzantina venetia_, , p. ). the alum was secured by burning the rock, and lixiviation. with the capture of constantinople by the turks ( ), great feeling grew up in italy over the necessity of buying this requisite for their dyeing establishments from the infidel, and considerable exertion was made to find other sources of supply. some minor works were attempted, but nothing much eventuated until the appearance of one john de castro. from the commentaries of pope pius ii. ( , p. ), it appears that this italian had been engaged in dyeing cloth in constantinople, and thus became aware of the methods of making alum. driven out of that city through its capture by the turks, he returned to italy and obtained an office under the apostolic chamber. while in this occupation he discovered a rock at tolfa which appeared to him identical with that used at constantinople in alum manufacture. after experimental work, he sought the aid of the pope, which he obtained after much vicissitude. experts were sent, who after examination "shed tears of joy, they kneeling down three times, worshipped god and praised his kindness in conferring such a gift on their age." castro was rewarded, and the great papal monopoly was gradually built upon this discovery. the industry firmly established at tolfa exists to the present day, and is the source of the roman alum of commerce. the pope maintained this monopoly strenuously, by fair means and by excommunication, gradually advancing the price until the consumers had greater complaint than against the turks. the history of the disputes arising over the papal alum monopoly would alone fill a volume. by the middle of the th century alum was being made in spain, holland, and germany, and later in england. in her efforts to encourage home industries and escape the tribute to the pope, elizabeth (see note on p. ) invited over "certain foreign chymistes and mineral masters" and gave them special grants to induce them to "settle in these realmes." among them was cornelius devoz, to whom was granted the privilege of "mining and digging in our realm of england for allom and copperas." what devoz accomplished is not recorded, but the first alum manufacture on a considerable scale seems to have been in yorkshire, by one thomas chaloner (about ), who was supposed to have seduced workmen from the pope's alum works at tolfa, for which he was duly cursed with all the weight of the pope and church. (pennant, tour of scotland, ). [ ] the term for vitriol used by the roman authors, followed by agricola, is _atramentum sutorium_, literally shoemaker's blacking, the term no doubt arising from its ancient (and modern) use for blackening leather. the greek term was _chalcanthon_. the term "vitriol" seems first to appear in albertus magnus (_de mineralibus_, _liber_ v.), who died in , where he uses the expression "_atramentum viride a quibusdam vitreolum vocatur_." agricola (_de nat. foss._, p. ) states, "in recent years the name _vitriolum_ has been given to it." the first adequate description of vitriol is by dioscorides (v., ), as follows:--"vitriol (_chalcanthon_) is of one genus, and is a solidified liquid, but it has three different species. one is formed from the liquids which trickle down drop by drop and congeal in certain mines; therefore those who work in the cyprian mines call it _stalactis_. petesius calls this kind _pinarion_. the second kind is that which collects in certain caverns; afterward it is poured into trenches, where it congeals, whence it derives its name _pectos_. the third kind is called _hephthon_ and is mostly made in spain; it has a beautiful colour but is weak. the manner of preparing it is as follows: dissolving it in water, they boil it, and then they transfer it to cisterns and leave it to settle. after a certain number of days it congeals and separates into many small pieces, having the form of dice, which stick together like grapes. the most valued is blue, heavy, dense, and translucent." pliny (xxxiv., ) says:--"by the name which they have given to it, the greeks indicate the similar nature of copper and _atramentum sutorium_, for they call it _chalcanthon_. there is no substance of an equally miraculous nature. it is made in spain from wells of this kind of water. this water is boiled with an equal quantity of pure water, and is then poured into wooden tanks (fish ponds). across these tanks there are fixed beams, to which hang cords stretched by little stones. upon these cords adheres the _limus_ (agricola's 'juice') in drops of a vitreous appearance, somewhat resembling a bunch of grapes. after removal, it is dried for thirty days. it is of a blue colour, and of a brilliant lustre, and is very like glass. its solution is the blacking used for colouring leather. _chalcanthon_ is made in many other ways: its kind of earth is sometimes dug from ditches, from the sides of which exude drops, which solidify by the winter frosts into icicles, called _stalagmia_, and there is none more pure. when its colour is nearly white, with a slight tinge of violet, it is called _leukoïon_. it is also made in rock basins, the rain water collecting the _limus_ into them, where it becomes hardened. it is also made in the same way as salt by the intense heat of the sun. hence it is that some distinguish two kinds, the mineral and the artificial; the latter being paler than the former and as much inferior to it in quality as it is in colour." while pliny gives prominence to blue vitriol, his solution for colouring leather must have been the iron sulphate. there can be no doubt from the above, however, that both iron and copper sulphates were known to the ancients. from the methods for making vitriol given here in _de re metallica_, it is evident that only the iron sulphate would be produced, for the introduction of iron strips into the vats would effectually precipitate any copper. it is our belief that generally throughout this work, the iron sulphate is meant by the term _atramentum sutorium_. in _de natura fossilium_ (p. - ) agricola gives three varieties of _atramentum sutorium_,--_viride_, _caeruleum_, and _candidum_, _i.e._, green, blue, and white. thus the first mention of white vitriol (zinc sulphate) appears to be due to him, and he states further (p. ): "a white sort is found, especially at goslar, in the shape of icicles, transparent like crystals." and on p. : "since i have explained the nature of vitriol and its relatives, which are obtained from cupriferous pyrites, i will next speak of an acrid solidified juice which commonly comes from _cadmia_. it is found at annaberg in the tunnel driven to the saint otto mine; it is hard and white, and so acrid that it kills mice, crickets, and every kind of animal. however, that feathery substance which oozes out from the mountain rocks and the thick substance found hanging in tunnels and caves from which saltpetre is made, while frequently acrid, does not come from _cadmia_." dana (syst. of min., p. ) identifies this as _goslarite_--native zinc sulphate. it does not appear, however, that artificial zinc vitriol was made in agricola's time. schlüter (_huette-werken_, braunschweig , p. ) states it to have been made for the first time at rammelsberg about . it is desirable here to enquire into the nature of the substances given by all of the old mineralogists under the latinized greek terms _chalcitis_, _misy_, _sory_, and _melanteria_. the first mention of these minerals is in dioscorides, who (v., - ) says: "the best _chalcitis_ is like copper. it is friable, not stony, and is intersected by long brilliant veins.... _misy_ is obtained from cyprus; it should have the appearance of gold, be hard, and when pulverised it should have the colour of gold and sparkle like stars. it has the same properties as _chalcitis_.... the best is from egypt.... one kind of _melanteria_ congeals like salt in the entries to copper mines. the other kind is earthy and appears on the surface of the aforesaid mines. it is found in the mines of cilicia and other regions. the best has the colour of sulphur, is smooth, pure, homogenous, and upon contact with water immediately becomes black.... those who consider _sory_ to be the same as _melanteria_, err greatly. _sory_ is a species of its own, though it is not dissimilar. the smell of _sory_ is oppressive and provokes nausea. it is found in egypt and in other regions, as libya, spain, and cyprus. the best is from egypt, and when broken is black, porous, greasy, and astringent." pliny (xxxiv., - ) says:--"that is called _chalcitis_ from which, as well as itself copper (?) is extracted by heat. it differs from _cadmia_ in that this is obtained from rocks near the surface, while that is taken from rocks below the surface. also _chalcitis_ is immediately friable, being naturally so soft as to appear like compressed wool. there is also this other distinction; _chalcitis_ contains three other substances, copper, _misy_, and _sory_. of each of these we shall speak in their appropriate places. it contains elongated copper veins. the most approved kind is of the colour of honey; it is streaked with fine sinuous veins and is friable and not stony. it is considered most valuable when fresh.... the _sory_ of egypt is the most esteemed, being much superior to that of cyprus, spain, and africa; although some prefer the _sory_ from cyprus for affections of the eyes. but from whatever nation it comes, the best is that which has the strongest odour, and which, when ground up, becomes greasy, black, and spongy. it is a substance so unpleasant to the stomach that some persons are nauseated by its smell. some say that _misy_ is made by the burning of stones in trenches, its fine yellow powder being mixed with the ashes of pine-wood. the truth is, as i said above, that though obtained from the stone, it is already made and in solid masses, which require force to detach them. the best comes from the works of cyprus, its characteristics being that when broken it sparkles like gold, and when ground it presents a sandy appearance, but on the contrary, if heated, it is similar to _chalcitis_. _misy_ is used in refining gold...." agricola's views on the subject appear in _de natura fossilium_. he says (p. ):--"the cupriferous pyrites (_pyrites aerosus_) called _chalcitis_ is the mother and cause of _sory_--which is likewise known as mine _vitriol_ (_atramentum metallicum_)--and _melanteria_. these in turn yield vitriol and such related things. this may be seen especially at goslar, where the nodular lumps of dark grey colour are called vitriol stone (_lapis atramenti_). in the centre of them is found greyish pyrites, almost dissolved, the size of a walnut. it is enclosed on all sides, sometimes by _sory_, sometimes by _melanteria_. from them start little veinlets of greenish vitriol which spread all over it, presenting somewhat the appearance of hairs extending in all directions and cohering together.... there are five species of this solidified juice, _melanteria_, _sory_, _chalcitis_, _misy_, and vitriol. sometimes many are found in one place, sometimes all of them, for one originates from the other. from pyrites, which is, as one might say, the root of all these juices, originates the above-mentioned _sory_ and _melanteria_. from _sory_, _chalcitis_, and _melanteria_ originate the various kinds of vitriol.... _sory_, _melanteria_, _chalcitis_, and _misy_ are always native; vitriol alone is either native or artificial. from them vitriol effloresces white, and sometimes green or blue. _misy_ effloresces not only from _sory_, _melanteria_, and _chalcitis_, but also from all the vitriols, artificial as well as natural.... _sory_ and _melanteria_ differ somewhat from the others, but they are of the same colours, grey and black; but _chalcitis_ is red and copper-coloured; _misy_ is yellow or gold-coloured. all these native varieties have the odour of lightning (brimstone), but _sory_ is the most powerful. the feathery vitriol is soft and fine and hair-like, and _melanteria_ has the appearance of wool and it has a similarity to salt; all these are rare and light; _sory_, _chalcitis_, and _misy_ have the following relations. _sory_ because of its density has the hardness of stone, although its texture is very coarse. _misy_ has a very fine texture. _chalcitis_ is between the two; because of its roughness and strong odour it differs from _melanteria_, although they do not differ in colour. the vitriols, whether natural or artificial, are hard and dense ... as regarding shape, _sory_, _chalcitis_, _misy_, and _melanteria_ are nodular, but _sory_ is occasionally porous, which is peculiar to it. _misy_ when it effloresces in no great quantity from the others is like a kind of pollen, otherwise it is nodular. _melanteria_ sometimes resembles wool, sometimes salt." the sum and substance, therefore, appears to be that _misy_ is a yellowish material, possibly ochre, and _sory_ a blackish stone, both impregnated with vitriol. _chalcitis_ is a partially decomposed pyrites; and _melanteria_ is no doubt native vitriol. from this last term comes the modern _melanterite_, native hydrous ferrous sulphate. dana (system of mineralogy, p. ) considers _misy_ to be in part _copiapite_--basic ferric sulphate--but any such part would not come under agricola's objection to it as a source of vitriol. the disabilities of this and _chalcitis_ may, however, be due to their copper content. [ ] agricola (_de nat. fos._, ) says:--"there is a species of artificial sulphur made from sulphur and iron hammer-scales, melted together and poured into moulds. this, because it heals scabs of horses, is generally called _caballinum_." it is difficult to believe such a combination was other than iron sulphide, but it is equally difficult to understand how it was serviceable for this purpose. [ ] inasmuch as pyrites is discussed in the next paragraph, the material of the first distillation appears to be native sulphur. until the receiving pots became heated above the melting point of the sulphur, the product would be "flowers of sulphur," and not the wax-like product. the equipment described for pyrites in the next paragraph would be obviously useful only for coarse material. but little can be said on the history of sulphur; it is mentioned often enough in the bible and also by homer (od. xxii., ). the greeks apparently knew how to refine it, although neither dioscorides nor pliny specifically describes such an operation. agricola says (_de nat. fos._, ): "sulphur is of two kinds; the mineral, which the latins call _vivum_, and the greeks _apyron_, which means 'not exposed to the fire' (_ignem non expertum_) as rightly interpreted by celsius; and the artificial, called by the greeks _pepyromenon_, that is, 'exposed to the fire.'" in book x., the expression _sulfur ignem non expertum_ frequently appears, no doubt in agricola's mind for native sulphur, although it is quite possible that the greek distinction was between "flowers" of sulphur and the "wax-like" variety. [ ] the substances referred to under the names _bitumen_, _asphalt_, _maltha_, _naphtha_, _petroleum_, _rock-oil_, etc., have been known and used from most ancient times, and much of our modern nomenclature is of actual greek and roman ancestry. these peoples distinguished three related substances,--the greek _asphaltos_ and roman _bitumen_ for the hard material,--greek _pissasphaltos_ and roman _maltha_ for the viscous, pitchy variety--and occasionally the greek _naphtha_ and roman _naphtha_ for petroleum proper, although it is often enough referred to as liquid _bitumen_ or liquid _asphaltos_. the term _petroleum_ apparently first appears in agricola's _de natura fossilium_ (p. ), where he says the "oil of bitumen ... now called _petroleum_." bitumen was used by the egyptians for embalming from pre-historic times, _i.e._, prior to b.c., the term "mummy" arising from the persian word for bitumen, _mumiai_. it is mentioned in the tribute from babylonia to thotmes iii., who lived about b.c. (wilkinson, ancient egyptians i., p. ). the egyptians, however, did not need to go further afield than the sinai peninsula for abundant supplies. bitumen is often cited as the real meaning of the "slime" mentioned in genesis (xi., ; xiv., ), and used in building the tower of babel. there is no particular reason for this assumption, except the general association of babel, babylon, and bitumen. however, the hebrew word _sift_ for pitch or bitumen does occur as the cement used for moses's bulrush cradle (exodus ii., ), and moses is generally accounted about b.c. other attempts to connect biblical reference to petroleum and bitumen revolve around job xxix., , deut. xxxii., , maccabees ii., i, , matthew v., , but all require an unnecessary strain on the imagination. the plentiful occurrence of bitumen throughout asia minor, and particularly in the valley of the euphrates and in persia, is the subject of innumerable references by writers from herodotus ( - b.c.) down to the author of the company prospectus of recent months. herodotus (i., ) and diodorus siculus (i) state that the walls of babylon were mortared with bitumen--a fact partially corroborated by modern investigation. the following statement by herodotus (vi., ) is probably the source from which pliny drew the information which agricola quotes above. in referring to a well at ardericca, a place about miles from ancient susa, in persia, herodotus says:--"for from the well they get bitumen, salt, and oil, procuring it in the way that i will now describe: they draw with a swipe, and instead of a bucket they make use of the half of a wine-skin; with this the man dips and, after drawing, pours the liquid into a reservoir, wherefrom it passes into another, and there takes three different shapes. the salt and bitumen forthwith collect and harden, while the oil is drawn off into casks. it is called by the persians _rhadinace_, is black, and has an unpleasant smell." (rawlinson's trans. iii., p. ). the statement from pliny (xxxi., ) here referred to by agricola, reads:--"it (salt) is made from water of wells poured into salt-pans. at babylon the first condensed is a bituminous liquid like oil which is burned in lamps. when this is taken off, salt is found beneath. in cappadocia also the water from both wells and springs is poured into salt-pans." when petroleum began to be used as an illuminant it is impossible to say. a passage in aristotle's _de mirabilibus_ ( ) is often quoted, but in reality it refers only to a burning spring, a phenomenon noted by many writers, but from which to its practical use is not a great step. the first really definite statement as to the use of petroleum as an illuminant is strabo's quotation (xvi., , ) from posidonius: "asphaltus is found in great abundance in babylonia. eratosthenes describes it as follows:--the liquid _asphaltus_, which is called _naphtha_, is found in susa; the dry kind, which can be made solid, in babylonia. there is a spring of it near the euphrates.... others say that the liquid kind is also found in babylonia.... the liquid kind, called _naphtha_, is of a singular nature. when it is brought near the fire, the fire catches it.... posidonius says that there are springs of _naphtha_ in babylonia, some of which produce white, others black _naphtha_; the first of these, i mean white _naphtha_, which attracts flame, is liquid sulphur; the second or black _naphtha_ is liquid _asphaltus_, and is burnt in lamps instead of oil." (hamilton's translation, vol. iii., p. ). eratosthenes lived about b.c., and posidonius about years later. dioscorides (i., ), after discussing the usual sources of bitumen says: "it is found in a liquid state in agrigentum in sicily, flowing on streams; they use it for lights in lanterns in place of oil. those who call the sicilian kind oil are under a delusion, for it is agreed that it is a kind of liquid bitumen." pliny adds nothing much new to the above quotations, except in regard to these same springs (xxxv., ) that "the inhabitants collect it on the panicles of reeds, to which it quickly adheres and they use it for burning in lamps instead of oil." agricola (_de natura fossilium_, book iv.) classifies petroleum, coal, jet, and obsidian, camphor, and amber as varieties of bitumen, and devotes much space to the refutation of the claims that the last two are of vegetable origin. [ ] agricola (_de natura fossilium_, p. ) in discussing substances which originate from copper, gives among them green _chrysocolla_ (as distinguished from borax, etc., see note above), and says: "native _chrysocolla_ originates in veins and veinlets, and is found mostly by itself like sand, or adhering to metallic substances, and when scraped off from this appears similar to its own sand. occasionally it is so thin that very little can be scraped off. or else it occurs in waters which, as i have said, wash these minerals, and afterward it settles as a powder. at neusohl in the carpathians, green water flowing from an ancient tunnel wears away this _chrysocolla_ with it. the water is collected in thirty large reservoirs, where it deposits the _chrysocolla_ as a sediment, which they collect every year and sell,"--as a pigment. this description of its occurrence would apply equally well to modern _chrysocolla_ or to malachite. the solution from copper ores would deposit some sort of green incrustation, of carbonates mostly. [ ] the statement in pliny (xxxvi., ) to which agricola refers is as follows: "then as ingenuity was not content with the mixing of _nitrum_, they began the addition of _lapis magnes_, because of the belief that it attracts liquefied glass as well as iron. in a similar manner many kinds of brilliant stones began to be added to the melting, and then shells and fossil sand. authors tell us that the glass of india is made of broken crystal, and in consequence nothing can compare with it. light and dry wood is used for fusing, _cyprium_ (copper?) and _nitrum_ being added, particularly _nitrum_ from ophir etc." a great deal of discussion has arisen over this passage, in connection with what this _lapis magnes_ really was. pliny (xxxvi., ) describes the lodestone under this term, but also says: "there (in ethiopia) also is _haematites magnes_, a stone of blood colour, which shows a red colour if crushed, or of saffron. the _haematites_ has not the same property of attracting iron as _magnes_." relying upon this sentence for an exception to the ordinary sort of _magnes_, and upon the impossible chemical reaction involved, most commentators have endeavoured to show that lodestone was not the substance meant by pliny, but manganese, and thus they find here the first knowledge of this mineral. there can be little doubt that pliny assumed it to be the lodestone, and agricola also. whether the latter had any independent knowledge on this point in glass-making or was merely quoting pliny--which seems probable--we do not know. in any event, biringuccio, whose work preceded _de re metallica_ by fifteen years, does definitely mention manganese in this connection. he dismisses this statement of pliny with the remark (p. - ): "the ancients wrote about lodestones, as pliny states, and they mixed it together with _nitrum_ in their first efforts to make glass." the following passage from this author (p. - ), however, is not only of interest in this connection, but also as possibly being the first specific mention of manganese under its own name. moreover, it has been generally overlooked in the many discussions of the subject. "of a similar nature (to _zaffir_) is also another mineral called _manganese_, which is found, besides in germany, at the mountain of viterbo in tuscany ... it is the colour of _ferrigno scuro_ (iron slag?). in melting it one cannot obtain any metal ... but it gives a very fine colour to glass, so that the glass workers use it in their pigments to secure an azure colour.... it also has such a property that when put into melted glass it cleanses it and makes it white, even if it were green or yellow. in a hot fire it goes off in a vapour like lead, and turns into ashes." to enter competently into the discussion of the early history of glass-making would employ more space than can be given, and would lead but to a sterile end. it is certain that the art was pre-grecian, and that the egyptians were possessed of some knowledge of making and blowing it in the xi dynasty (according to petrie , b.c.), the wall painting at beni hassen, which represents glass-blowing, being attributed to that period. the remains of a glass factory at tel el amarna are believed to be of the xviii dynasty. (petrie, , b.c.). the art reached a very high state of development among the greeks and romans. no discussion of this subject omits pliny's well-known story (xxxvi, ), which we also add: "the tradition is that a merchant ship laden with _nitrum_ being moored at this place, the merchants were preparing their meal on the beach, and not having stones to prop up their pots, they used lumps of _nitrum_ from the ship, which fused and mixed with the sands of the shore, and there flowed streams of a new translucent liquid, and thus was the origin of glass." appendix a. agricola's works. georgius agricola was not only the author of works on mining and allied subjects, usually associated with his name, but he also interested himself to some extent in political and religious subjects. for convenience in discussion we may, therefore, divide his writings on the broad lines of ( ) works on mining, geology, mineralogy, and allied subjects; ( ) works on other subjects, medical, religious, critical, political, and historical. in respect especially to the first division, and partially with regard to the others, we find three principal cases: (_a_) works which can be authenticated in european libraries to-day; (_b_) references to editions of these in bibliographies, catalogues, etc., which we have been unable to authenticate; and (_c_) references to works either unpublished or lost. the following are the short titles of all of the published works which we have been able to find on the subjects allied to mining, arranged according to their present importance:--_de re metallica_, first edition, ; _de natura fossilium_, first edition, ; _de ortu et causis subterraneorum_, first edition, ; _bermannus_, first edition, ; _rerum metallicarum interpretatio_, first edition, ; _de mensuris et ponderibus_, first edition, ; _de precio metallorum et monetis_, first edition, ; _de veteribus et novis metallis_, first edition, ; _de natura eorum quae effluunt ex terra_, first edition, ; _de animantibus subterraneis_, first edition, . of the "lost" or unpublished works, on which there is some evidence, the following are the most important:--_de metallicis et machinis_, _de ortu metallorum defensio ad jacobum scheckium_, _de jure et legibus metallicis_, _de varia temperie sive constitutione aeris_, _de terrae motu_, and _commentariorum, libri vi_. the known published works upon other subjects are as follows:--latin grammar, first edition, ; two religious tracts, first edition, ; _galen_ (joint revision of greek text), first edition, ; _de bello adversus turcam_, first edition, ; _de peste_, first edition, . the lost or partially completed works on subjects unrelated to mining, of which some trace has been found, are:--_de medicatis fontibus_, _de putredine solidas partes_, etc., _castigationes in hippocratem_, _typographia mysnae et toringiae_, _de traditionibus apostolicis_, _oratio de rebus gestis ernesti et alberti_, _ducum saxoniae_. review of principal works. before proceeding with the bibliographical detail, we consider it desirable to review briefly the most important of the author's works on subjects related to mining. _de natura fossilium._ this is the most important work of agricola, excepting _de re metallica_. it has always been printed in combination with other works, and first appeared at basel, . this edition was considerably revised by the author, the amended edition being that of , which we have used in giving references. the work comprises ten "books" of a total of folio pages. it is the first attempt at systematic mineralogy, the minerals[ ] being classified into ( ) "earths" (clay, ochre, etc.), ( ) "stones properly so-called" (gems, semi-precious and unusual stones, as distinguished from rocks), ( ) "solidified juices" (salt, vitriol, alum, etc.), ( ) metals, and ( ) "compounds" (homogeneous "mixtures" of simple substances, thus forming such minerals as galena, pyrite, etc.). in this classification agricola endeavoured to find some fundamental basis, and therefore adopted solubility, fusibility, odour, taste, etc., but any true classification without the atomic theory was, of course, impossible. however, he makes a very creditable performance out of their properties and obvious characteristics. all of the external characteristics which we use to-day in discrimination, such as colour, hardness, lustre, etc., are enumerated, the origin of these being attributed to the proportions of the peripatetic elements and their binary properties. dana, in his great work[ ], among some fourscore minerals which he identifies as having been described by agricola and his predecessors, accredits a score to agricola himself. it is our belief, however, that although in a few cases agricola has been wrongly credited, there are still more of which priority in description might be assigned to him. while a greater number than fourscore of so-called species are given by agricola and his predecessors, many of these are, in our modern system, but varieties; for instance, some eight or ten of the ancient species consist of one form or another of silica. book i. is devoted to mineral characteristics--colour, brilliance, taste, shape, hardness, etc., and to the classification of minerals; book ii., "earths"--clay, lemnian earth, chalk, ochre, etc.; book iii., "solidified juices"--salt, _nitrum_ (soda and potash), saltpetre, alum, vitriol, chrysocolla, _caeruleum_ (part azurite), orpiment, realgar, and sulphur; book iv., camphor, bitumen, coal, bituminous shales, amber; book v., lodestone, bloodstone, gypsum, talc, asbestos, mica, calamine, various fossils, geodes, emery, touchstones, pumice, fluorspar, and quartz; book vi., gems and precious stones; book vii., "rocks"--marble, serpentine, onyx, alabaster, limestone, etc.; book viii., metals--gold, silver, quicksilver, copper, lead, tin, antimony, bismuth, iron, and alloys, such as electrum, brass, etc.; book ix., various furnace operations, such as making brass, gilding, tinning, and products such as slags, furnace accretions, _pompholyx_ (zinc oxide), copper flowers, litharge, hearth-lead, verdigris, white-lead, red-lead, etc.; book x., "compounds," embracing the description of a number of recognisable silver, copper, lead, quicksilver, iron, tin, antimony, and zinc minerals, many of which we set out more fully in note , page . _de ortu et causis subterraneorum._ this work also has always been published in company with others. the first edition was printed at basel, ; the second at basel, , which, being the edition revised and added to by the author, has been used by us for reference. there are five "books," and in the main they contain agricola's philosophical views on geologic phenomena. the largest portion of the actual text is occupied with refutations of the ancient philosophers, the alchemists, and the astrologers; and these portions, while they exhibit his ability in observation and in dialectics, make but dull reading. those sections of the book which contain his own views, however, are of the utmost importance in the history of science, and we reproduce extensively the material relating to ore deposits in the footnotes on pages to . briefly, book i. is devoted to discussion of the origin and distribution of ground waters and juices. the latter part of this book and a portion of book ii. are devoted to the origin of subterranean heat, which he assumes is in the main due to burning bitumen--a genus which with him embraced coal--and also, in a minor degree, to friction of internal winds and to burning sulphur. the remainder of book ii. is mainly devoted to the discussion of subterranean "air", "vapour", and "exhalations", and he conceives that volcanic eruptions and earthquakes are due to their agency, and in these hypotheses he comes fairly close to the modern theory of eruptions from explosions of steam. "vapour arises when the internal heat of the earth or some hidden fire burns earth which is moistened with vapour. when heat or subterranean fire meets with a great force of vapour which cold has contracted and encompassed in every direction, then the vapour, finding no outlet, tries to break through whatever is nearest to it, in order to give place to the insistent and urgent cold. heat and cold cannot abide together in one place, but expel and drive each other out of it by turns". as he was, we believe, the first to recognise the fundamental agencies of mountain sculpture, we consider it is of sufficient interest to warrant a reproduction of his views on this subject: "hills and mountains are produced by two forces, one of which is the power of water, and the other the strength of the wind. there are three forces which loosen and demolish the mountains, for in this case, to the power of the water and the strength of the wind we must add the fire in the interior of the earth. now we can plainly see that a great abundance of water produces mountains, for the torrents first of all wash out the soft earth, next carry away the harder earth, and then roll down the rocks, and thus in a few years they excavate the plains or slopes to a considerable depth; this may be noticed in mountainous regions even by unskilled observers. by such excavation to a great depth through many ages, there rises an immense eminence on each side. when an eminence has thus arisen, the earth rolls down, loosened by constant rain and split away by frost, and the rocks, unless they are exceedingly firm, since their seams are similarly softened by the damp, roll down into the excavations below. this continues until the steep eminence is changed into a slope. each side of the excavation is said to be a mountain, just as the bottom is called a valley. moreover, streams, and to a far greater extent rivers, effect the same results by their rushing and washing; for this reason they are frequently seen flowing either between very high mountains which they have created, or close by the shore which borders them.... nor did the hollow places which now contain the seas all formerly exist, nor yet the mountains which check and break their advance, but in many parts there was a level plain, until the force of winds let loose upon it a tumultuous sea and a scathing tide. by a similar process the impact of water entirely overthrows and flattens out hills and mountains. but these changes of local conditions, numerous and important as they are, are not noticed by the common people to be taking place at the very moment when they are happening, because, through their antiquity, the time, place, and manner in which they began is far prior to human memory. the wind produces hills and mountains in two ways: either when set loose and free from bonds, it violently moves and agitates the sand; or else when, after having been driven into the hidden recesses of the earth by cold, as into a prison, it struggles with a great effort to burst out. for hills and mountains are created in hot countries, whether they are situated by the sea coasts or in districts remote from the sea, by the force of winds; these no longer held in check by the valleys, but set free, heap up the sand and dust, which they gather from all sides, to one spot, and a mass arises and grows together. if time and space allow, it grows together and hardens, but if it be not allowed (and in truth this is more often the case), the same force again scatters the sand far and wide.... then, on the other hand, an earthquake either rends and tears away part of a mountain, or engulfs and devours the whole mountain in some fearful chasm. in this way it is recorded the cybotus was destroyed, and it is believed that within the memory of man an island under the rule of denmark disappeared. historians tell us that taygetus suffered a loss in this way, and that therasia was swallowed up with the island of thera. thus it is clear that water and the powerful winds produce mountains, and also scatter and destroy them. fire only consumes them, and does not produce at all, for part of the mountains--usually the inner part--takes fire." the major portion of book iii. is devoted to the origin of ore channels, which we reproduce at some length on page . in the latter part of book iii., and in books iv. and v., he discusses the principal divisions of the mineral kingdom given in _de natura fossilium_, and the origin of their characteristics. it involves a large amount of what now appears fruitless tilting at the peripatetics and the alchemists; but nevertheless, embracing, as agricola did, the fundamental aristotelian elements, he must needs find in these same elements and their subordinate binary combinations cause for every variation in external character. _bermannus._ this, agricola's first work in relation to mining, was apparently first published at basel, . the work is in the form of a dialogue between "bermannus," who is described as a miner, mineralogist, and "a student of mathematics and poetry," and "nicolaus ancon" and "johannes naevius," both scholars and physicians. ancon is supposed to be of philosophical turn of mind and a student of moorish literature, naevius to be particularly learned in the writings of dioscorides, pliny, galen, etc. "bermannus" was probably an adaptation by agricola of the name of his friend lorenz berman, a prominent miner. the book is in the main devoted to a correlation of the minerals mentioned by the ancients with those found in the saxon mines. this phase is interesting as indicating the natural trend of agricola's scholastic mind when he first comes into contact with the sciences to which he devoted himself. the book opens with a letter of commendation from erasmus, of rotterdam, and with the usual dedication and preface by the author. the three conversationalists are supposed to take walks among the mines and to discuss, incidentally, matters which come to their attention; therefore the book has no systematic or logical arrangement. there are occasional statements bearing on the history, management, titles, and methods used in the mines, and on mining lore generally. the mineralogical part, while of importance from the point of view of giving the first description of several minerals, is immensely improved upon in _de natura fossilium_, published years later. it is of interest to find here the first appearance of the names of many minerals which we have since adopted from the german into our own nomenclature. of importance is the first description of bismuth, although, as pointed out on page , the metal had been mentioned before. in the revised collection of collateral works published in , the author makes many important changes and adds some new material, but some of the later editions were made from the unrevised older texts. _rerum metallicarum interpretatio._ this list of german equivalents for latin mineralogical terms was prepared by agricola himself, and first appears in the collection of _de ortu et causis_, _de natura fossilium_, etc., being repeated in all subsequent publications of these works. it consists of some latin mineralogical and metallurgical terms, many of which are of agricola's own coinage. it is of great help in translation and of great value in the study of mineralogic nomenclature. _de mensuris et ponderibus._ this work is devoted to a discussion of the greek and roman weights and measures, with some correlation to those used in saxony. it is a careful work still much referred to by students of these subjects. the first edition was published at paris in , and in the edition at basel appears, for the first time, _de precio metallorum et monetis_. _de veteribus et novis metallis._ this short work comprises folio pages, and first appears in the collection of collateral works. it consists mainly of historical and geographical references to the occurrence of metals and mines, culled from the greek and latin classics, together with some information as to the history of the mines in central europe. the latter is the only original material, and unfortunately is not very extensive. we have incorporated some of this information in the footnotes. _de animantibus subterraneis._ this short work was first printed in basel, , and consists of one chapter of folio pages. practically the whole is devoted to the discussion of various animals who at least a portion of their time live underground, such as hibernating, cave-dwelling, and burrowing animals, together with cave-dwelling birds, lizards, crocodiles, serpents, etc. there are only a few lines of remote geological interest as to migration of animals imposed by geologic phenomena, such as earthquakes, floods, etc. this book also discloses an occasional vein of credulity not to be expected from the author's other works, in that he apparently believes aristotle's story of the flies which were born and lived only in the smelting furnace; and further, the last paragraph in the book is devoted to underground gnomes. this we reproduce in the footnote on page . _de natura eorum quae effluunt ex terra._ this work of four books, comprising folio pages, first appears in the collection. as the title indicates, the discussion is upon the substances which flow from the earth, such as water, bitumen, gases, etc. altogether it is of microscopic value and wholly uninteresting. the major part refers to colour, taste, temperature, medicinal uses of water, descriptions of rivers, lakes, swamps, and aqueducts. bibliographical notes. for the following we have mainly to thank miss kathleen schlesinger, who has been employed many months in following up every clue, and although the results display very considerable literary activity on the part of the author, they do not by any means indicate miss schlesinger's labours. agricola's works were many of them published at various times in combination, and therefore to set out the title and the publication of each work separately would involve much repetition of titles, and we consequently give the titles of the various volumes arranged according to dates. for instance, _de natura fossilium_, _de ortu et causis_, _de veteribus et novis metallis_, _de natura eorum quae effluunt ex terra_, and _interpretatio_ have always been published together, and the latin and italian editions of these works always include _bermannus_ as well. moreover, the latin _de re metallica_ of includes all of these works. we mark with an asterisk the titles to editions which we have been able to authenticate by various means from actual books. those unmarked are editions which we are satisfied do exist, but the titles of which are possibly incomplete, as they are taken from library catalogues, etc. other editions to which we find reference and of which we are not certain are noted separately in the discussion later on.[ ] * ( vo): _georgii agricolae medici, bermannus sive de re metallica._ (froben's mark). _basileae in aedibus frobenianis anno. mdxxx._ bound with this edition is (p. - ), at least occasionally, _rerum metallicarum appellationes juxta vernaculam germanorum linguam, autori plateano_. _basileae in officina frobeniana_, anno. mdxxx. * ( vo): _georgii agricolae medici libri quinque de mensuris et ponderibus: in quibus plaeraque à budaeo et portio parum animadversa diligenter excutiuntur. opus nunc primum in lucem aeditum._ (wechelus's mark). _parisiis. excudebat christianus wechelus, in vico iacobaeo, sub scuto basileiensi, anno mdxxxiii._ pages and index of pages. * ( to): _georgii agricolae medici libri quinque. de mensuris et ponderibus: in quibus pleraque à budaeo et portio parum animadversa diligenter excutiuntur._ (froben's mark). _basileae ex officina frobeniana anno mdxxxiii. cum gratia et privilegio caesareo ad sex annos._ ( to): _georgii agricolae. epistola ad plateanum, cui sunt adiecta aliquot loca castigata in libris de mensuris et ponderibus nuper editis._ froben, basel, . * ( vo): _georgii agricolae medici libri v. de mensuris et ponderibus: in quibus pleraque à budaeo et portio parum animadversa diligenter excutiuntur._ (printer's mark). at the end of index: _venitüs per juan anto. de nicolinis de sabio, sumptu vero et requisitione dñi melchionis sessae. anno. dñi mdxxxv. mense julii._ folios. on back of title page is given: _liber primus de mensuris romanis, secundus de mensuris graecis, tertius de rerum quas metimur pondere, quartus de ponderibus romanis, quintus de ponderibus graecis._ * ( vo): _georgii agricolae medici bermannus sive de re metallica._ _parisiis. apud hieronymum gormontiú. in vico jacobeo sub signotrium coronarum._ . * ( vo): _georgii agricolae medici bermannus, sive de metallica ab accurata autoris recognitione et emendatione nunc primum editus cum nomenclatura rerum metallicarum. eorum lipsiae in officina valentini papae anno. mdxlvi._ * (folio): _georgii agricolae de ortu et causis subterraneorum lib. v. de natura eorum quae effluunt ex terra lib. iiii. de natura fossilium lib. x. de veteribus et novis metallis, lib. ii. bermannus sive de re metallica dialogus. interpretatio germanica vocum rei metallicae addito indice faecundissimo._ _apud hieron frobenium et nicolaum episcopium basileae, mdxlvi. cum privilegio imp. maiestatis ad quinquennium._ * ( vo): _georgii agricolae de animantibus subterraneis liber._ froben, basel, mdxlix. * ( vo): _di georgio agricola de la generatione de le cose, che sotto la terra sono, e de le cause de' loro effetti e natura, lib. v. de la natura di quelle cose, che de la terra scorrono lib. iiii. de la natura de le cose fossili, e che sotto la terra si cavano lib. x. de le minere antiche e moderne lib. ii. il bermanno, ò de le cose metallice dialogo, recato tutto hora dal latino in buona lingua volgare._ (vignette of sybilla surrounded by the words)--_qv al piv fermo e il mio foglio È il mio presaggio._ _col privilegio del sommo pontefice papa giulio iii. et del illustriss. senato veneto per anni. xx._ (colophon). _in vinegia per michele tramezzino, mdl._ * (folio): _georgii agricolae. de mensuris et ponderibus rom. atque graec. lib. v. de externis mensuris et ponderibus lib. ii. ad ea quae andreas alciatus denuo disputavit de mensuris et ponderibus brevis defensio lib. i. de mensuris quibus intervalla metimur lib. i. de restituendis ponderibus atque mensuris. lib. i. de precio metallorum et monetis. lib. iii._ _basileae._ froben. mdl. _cum privilegio imp. maiestatis ad quinquennium._[ ] * (folio): _georgii agricolae de re metallica libri xii. quibus officia, instrumenta, machinae, ac omnia denique ad metallicam spectantia, non modo luculentissime describuntur, sed et per effigies, suis locis insertas, adjunctis latinis, germanicisque appellationibus ita ob oculos ponuntur, ut clarius tradi non possint eiusdem de animantibus subterraneis liber, ab autore recognitus: cum indicibus diversis, quicquid in opere tractatum est, pulchre demonstrantibus._ (froben's mark). _basileae mdlvi. cum privilegio imperatoris in annos v. et galliarum regis ad sexennium._ folio pages and preface, glossary and index amounting to pages. this is the first edition of _de re metallica_. we reproduce this title-page on page xix. * (folio): _vom bergkwerck xii bücher darinn alle empter, instrument, gezeuge, unnd alles zu disem handel gehörig, mitt schönen figuren vorbildet, und klärlich beschriben seindt erstlich in lateinischer sprach durch den hochgelerten und weittberümpten herrn georgium agricolam, doctorn und. bürgermeistern der churfürstlichen statt kempnitz, jezundt aber verteüscht durch den achtparen. unnd hochgelerten herrn philippum bechium, philosophen, artzer und in der loblichen universitet zu basel professorn._ _gedruckt zu basel durch jeronymus froben und niclausen bischoff im jar mitt keiserlicher freyheit._ * (folio): _georgii agricolae de ortu et causis subterraneorum lib. v. de natura eorum quae effluunt ex terra lib. iv. de natura fossilium lib. x. de veteribus et novis metallis lib. ii. bermannus, sive de re metallica dialogus liber. interpretatio germanica vocum rei metallicae, addito duplici indice, altero rerum, altero locorum omnia ab ipso authore, cum haud poenitenda accessione, recens recognita._ _froben, et episcop. basileae mdlviii. cum imp. maiestatis renovato privilegio ad quinquennium._ pages and index. as the title states, this is a revised edition by the author, and as the changes are very considerable it should be the one used. the italian translation and the wittenberg edition, mentioned below, are taken from the edition, and are, therefore, very imperfect. * (folio): second edition of _de re metallica_ including _de animantibus subterraneis_, with same title as the first edition except the addition, after the body of the title, of the words _atque omnibus nunc iterum ad archetypum diligenter restitutis et castigatis_ and the year mdlxi. pages and pages of glossary and index. * (folio): _opera di giorgio agricola de l'arte de metalli partita in xii. libri, ne quali si descrivano tutte le sorti, e qualità de gli uffizii, de gli strumenti, delle macchine, e di tutte l'altre cose attenenti a cotal arte, non pure con parole chiare ma eziandio si mettano a luoghi loro le figure di dette cose, ritratte al naturale, con l'aggiunta de nomi di quelle, cotanto chiari, e spediti, che meglio non si puo desiderare, o havere._ _aggiugnesi il libro del medesimo autore, che tratta de gl' animali di sottoterra da lui stesso corretto et riveduto. tradotti in lingua toscana da m. michelangelo florio fiorentino._ _con l'indice di tutte le cose piu notabili alla fine_ (froben's mark) _in basilea per hieronimo frobenio et nicolao episcopio, mdlxiii._ pages with pages of index. * (folio): _bergwerck buch: darinn nicht allain alle empte instrument gezeug und alles so zu diesem handel gehörig mit figuren vorgebildet und klärlich beschriben, etc. durch den hochgelehrten ... herrn georgium agricolam der artzney doctorn und burgermeister der churfürstlichen statt kemnitz erstlich mit grossem fleyss mühe und arbeit in latein beschriben und in zwölff bücher abgetheilt: nachmals aber durch den achtbarn und auch hochgelehrten philippum bechium philosophen artzt und in der löblichen universitet zu basel professorn mit sonderm fleyss teutscher nation zu gut verteutscht und an tag geben. allen berckherrn gewercken berckmeistern geschwornen schichtmeistern steigern berckheuwern wäschern und schmeltzern nicht allein nützlich und dienstlich sondern auch zu wissem hochnotwendig._ _mit römischer keys. may freyheit nicht nachzutrucken._ _getruckt in der keyserlichen reichsstatt, franckfort am mayn, etc. im jahr mdlxxx._ * ( mo): _georgii agricolae de ortu et causis subterraneorum lib. v. de natura eorum quae effluunt ex terra, lib. iv. de natura fossilium lib. x. de veteribus et novis metallis lib. ii. bermannus, sive de re metallica dialogus. interpretatio germanica vocum rei metallicae._ _addito indice faecundissimo, plurimos jam annos à germanis, et externarum quoque nationum doctissimis viris, valde desiderati et expetiti._ _nunc vero in rei metallicae studiosorum gratiam recensiti, in certa capita distributi, capitum argumentis, et nonnullis scholiis marginalibus illustrati à johanne sigfrido philos: et medicinae doctore et in illustri julia professore ordinario._ _accesserunt de metallicis rebus et nominibus observationes variae et eruditae, ex schedis georgii fabricii, quibus ea potissimum explicantur, quae georgius agricola praeteriit_. _wittebergae sumptibus zachariae schüreri bibliopolae typis andreae rüdingeri, ._ there are pages in the work of agricola proper, the notes of fabricius comprising a further pages, and the index pages. * ( vo): _georgii agricolae de animantibus subterraneis liber hactenus à multis desideratus, nunc vero in gratiam studiosorum seorsim editus, in certa capita divisus, capitum argumentis et nonnullis marginalibus exornatus à johanne sigfrido, phil. & med. doctore_, etc. _wittebergae. typis meisnerianis: impensis zachariae. schureri bibliop. anno. mdcxiv._ * (folio): _georgii agricolae kempnicensis medici ac philosophi clariss. de re metallica libri xii quibus officia, instrumenta, machinae, ac omnia denique ad metallicam spectantia, non modo luculentissimè describuntur; sed et per effigies, suis locis insertas adjunctis latinis, germanicisque; appellationibus, ita ob oculos ponuntur, ut clarius tradi non possint._ _ejusdem de animantibus subterraneis liber, ab autore recognitus cum indicibus diversis quicquid in opere tractatum est, pulchrè demonstrantibus._ (vignette of man at assay furnace). _basileae helvet. sumptibus itemque typis chalcographicis ludovici regis anno mdcxxi._ pages and pages glossary and indices. * (folio): _bergwerck buch darinnen nicht allein alle empter instrument gezeug und alles so zu disem handel gehörig mit figuren vorgebildet und klärlich beschrieben:.... durch den hochgelehrten und weitberühmten herrn georgium agricolam, der artzney doctorn und burgermeister der churfürstlichen statt kemnitz erstlich mit grossem fleiss mühe und arbeit in latein beschrieben und in zwölff bücher abgetheilt: nachmals aber durch den achtbarn und auch hochgelehrten philippum bechium. philosophen, artzt, und in der loblichen universitet zu basel professorn mit sonderm fleiss teutscher nation zu gut verteutscht und an tag geben und nun zum andern mal getruckt._ _allen bergherrn gewercken bergmeistern geschwornen schichtmeistern steigern berghäwern wäschern unnd schmeltzern nicht allein nutzlich und dienstlich sondern auch zu wissen hochnohtwendig._ (vignette of man at assay furnace). _getruckt zu basel inverlegung ludwig königs im jahr, mdcxxi._ pages pages glossary--no index. * (folio): _georgii agricolae kempnicensis medici ac philosophi clariss. de re metallica libri xii. quibus officia, instrumenta, machinae, ac omnia denique ad metallicam spectantia, non modo luculentissimè describuntur: sed et per effigies, suis locis insertas, adjunctis latinis, germanicisque appellationibus, ita ob oculos ponuntur, ut clarius tradi non possint. quibus accesserunt hac ultima editione, tractatus ejusdem argumenti, ab eodem conscripti, sequentes._ _de animantibus subterraneis lib. i., de ortu et causis subterraneorum lib. v., de natura eorum quae effluunt ex terra lib. iv., de natura fossilium lib. x., de veteribus et novis metallis lib. ii., bermannus sive de re metallica, dialogus lib. i._ _cum indicibus diversis, quicquid in opere tractatum est, pulchrè demonstrantibus._ (vignette of assayer and furnace). _basileae sumptibus et typis emanuelis könig. anno mdclvii._ folio, pages and pages of glossary and indices. this is a very serviceable edition of all of agricola's important works, and so far as we have noticed there are but few typographical errors. * ( vo): _gespräch vom bergwesen, wegen seiner fürtrefflich keit aus dem lateinischen in das deutsche übersetzet, mit nützl. anmerkungen erläutert. u. mit einem ganz neuen zusatze von zlüglicher anstellung des bergbaues u. von der zugutemachung der erze auf den hüttenwerken versehen von johann gottlieb stör._ _rotenburg a. d. fulda, hermstädt ._ pages. * ( vo): _georg agricola's bermannus eine einleitung in die metallurgischen schriften desselben, übersetzt und mit exkursionen herausgegeben von friedrich august schmid. haushalts- und befahrungs-protokollist im churf. vereinigten bergamte zu st. annaberg._ _freyberg . bey craz und gerlach._ * - ( vo). _georg agrikola's mineralogische schriften übersetzt und mit erläuternden anmerkungen. begleitet von ernst lehmann bergamts-assessor, berg- gegen- und receszschreiber in dem königl. sächs. bergamte voigtsberg der jenaischen societät für die gesammte mineralogie ehrenmitgliede._ _freyberg, - . bey craz und gerlach._ this german translation consists of four parts: the first being _de ortu et causis_, the second _de natura eorum quae effluunt ex terra_, and the third in two volumes _de natura fossilium_, the fourth _de veteribus et novis metallis_; with glossary and index to the four parts. we give the following notes on other possible prints, as a great many references to the above works occur in various quarters, of date other than the above. unless otherwise convinced it is our belief that most of these refer to the prints given above, and are due to error in giving titles or dates. it is always possible that such prints do exist and have escaped our search. _de re metallica._ leupold, richter, schmid, van der linden, mercklinus and eloy give an vo edition of _de re metallica_ without illustrations, schweinfurt, . we have found no trace of this print. leupold, van der linden, richter, schmid and eloy mention an vo edition, wittenberg, . it is our belief that this refers to the wittenberg edition of the selected works, which contains a somewhat similar title referring in reality to _bermannus_, which was and is still continually confused with _de re metallica_. ferguson mentions a german edition, schweinfurt, vo, . we can find no trace of this; it may refer to the schweinfurt edition mentioned above. _de natura fossilium._ leupold and gatter refer to a folio edition of . this was probably an error for either the or the editions. watt refers to an edition of combined with _de medicatis fontibus_. we find no trace of such edition, nor even that the latter work was ever actually printed. he also refers to an edition of and one of , this probably being an error for the edition of the subsidiary works and the _de re metallica_ of . leupold also refers to an edition of , this probably being an error for . _de ortu et causis._ albinus, hofmann, jacobi, schmid, richter, and reuss mention an edition of . this we believe to be an error in giving the date of the dedication instead of that of the publication ( ). albinus and ferguson give an edition of , which date is, we believe, an error for . ferguson gives an edition of the italian translation as ; we believe this should be . draud gives an edition of ; probably this should be . _bermannus._ albinus, schmid, reuss, richter, and weinart give the first edition as . we have been unable to learn of any actual copy of that date, and it is our belief that the date is taken from the dedication instead of from the publication, and should be . leupold, schmid, and reuss give an edition by froben in ; we have been unable to confirm this. leupold also gives an edition of (folio), and jöcher gives an edition of geneva (folio); we have also been unable to find this, and believe the latter to be a confusion with the _de re metallica_ of , as it is unlikely that _bermannus_ would be published by itself in folio. the catalogue of the library at siena (vol. iii., p. ) gives _il bermanno, vinegia_, , vo. we have found no trace of this edition elsewhere. _de mensuris et ponderibus._ albinus and schmid mention an edition of , and one of . the biographie universelle, paris, gives one of , and leupold one of , all of which we have been unable to find. an epitome of this work was published at various times, sometimes in connection with editions of vitruvius; so far as we are aware on the following dates, , , , . there also appear extracts in relation to liquid measures in works entitled _vocabula rei numariae ponderum et mensurarum_, etc. paul eber and caspar peucer, _lipsiae_, , and in same wittenberg, . _de veteribus et novis metallis._ watt gives an edition, basel, , and paris, ; we believe this is incorrect and refers to _bermannus_. reuss mentions a folio print of basel, . we consider this very unlikely. _de natura eorum quae effluunt ex terra._ albinus, hofmann, schmid, jacobi, richter, reuss, and weinart give an edition of . we believe this is again the dedication instead of the publication date ( ). _de animantibus subterraneis._ van der linden gives an edition at schweinfurt, vo, . although we have been unable to find a copy, this slightly confirms the possibility of an octavo edition of _de re metallica_ of this date, as they were usually published together. leupold gives assurance that he handled an octavo edition of wittenberg, , _cum notis johann sigfridi_. we think he confused this with _bermannus sive de re metallica_ of that date and place. schmid, richter, and draud all refer to an edition similarly annotated, leipzig, , vo. we have no trace of it otherwise. unpublished works on subjects related to mining. agricola apparently projected a complete series of works covering the whole range of subjects relating to minerals: geology, mineralogy, mining, metallurgy, history of metals, their uses, laws, etc. in a letter[ ] from fabricius to meurer (march, ), the former states that agricola intended writing about books (chapters) in addition to those already published, and to the twelve books _de re metallica_ which he was about to publish. apparently a number of these works were either unfinished or unpublished at agricola's death, for his friend george fabricius seems to have made some effort to secure their publication, but did not succeed, through lack of sympathy on the part of agricola's family. hofmann[ ] states on this matter: "his intentions were frustrated mainly through the lack of support with which he was met by the heirs of the mineralogist. these, as he complains to a councillor of the electorate, christopher von carlovitz, in , and to paul eber in another letter, adopted a grudging and ungracious tone with regard to his proposal to collect all agricola's works left behind, and they only consented to communicate to him as much as they were obliged by express command of the prince. at the prince's command they showed him a little, but he supposed that there was much more that they had suppressed or not preserved. the attempt to purchase some of the works--the elector had given fabricius money for the purpose ( nummos unciales)--proved unavailing, owing to the disagreeableness of agricola's heirs. it is no doubt due to these regrettable circumstances that all the works of the industrious scholar did not come down to us." the "disagreeableness" was probably due to the refusal of the protestant townsfolk to allow the burial of agricola in the cathedral at chemnitz. so far as we know the following are the unpublished or lost works. _de jure et legibus metallicis._ this work on mining law is mentioned at the end of book iv. of _de re metallica_, and it is referred to by others apparently from that source. we have been unable to find any evidence that it was ever published. _de varia temperie sive constitutione aeris._ in a letter[ ] to johann naevius, agricola refers to having a work in hand of this title. _de metallis et machinis._ hofmann[ ] states that a work of this title by agricola, dated basel , was sold to someone in america by a frankfort-on-main bookseller in . this is apparently the only reference to it that we know of, and it is possibly a confusion of titles or a "separate" of some chapters from _de re metallica_. _de ortu metallorum defensio ad jacobum scheckium._ referred to by fabricius in a letter[ ] to meurer. if published was probably only a tract. _de terrae motu._ in a letter[ ] from agricola to meurer (jan. , ) is some reference which might indicate that he was formulating a work on earthquakes under this title, or perhaps may be only incidental to the portions of _de ortu et causis_ dealing with this subject. _commentariorum in quibus utriusque linguae scriptorum locos difficiles de rebus subterraneis explicat, libri vi._ agricola apparently partially completed a work under some such title as this, which was to embrace chapters entitled _de methodis_ and _de demonstratione_. the main object seems to have been a commentary on the terms and passages in the classics relating to mining, mineralogy, etc. it is mentioned in the preface of _de veteribus et novis metallis_, and in a letter[ ] from one of froben's firm to agricola in , where it is suggested that agricola should defer sending his new commentaries until the following spring. the work is mentioned by albinus[ ], and in a letter from georg fabricius to meurer on the nd jan. ,[ ] in another from g. fabricius, to his brother andreas on oct. , ,[ ] and in a third from fabricius to melanchthon on december th, [ ], in which regret is expressed that the work was not completed by agricola. writings not related to mining, including lost or unpublished works. _latin grammar._ this was probably the first of agricola's publications, the full title to which is _georgii agricolae glaucii libellus de prima ac simplici institutione grammatica. excusum lipsiae in officina melchioris lottheri. anno mdxx._ ( to), folios.[ ] there is some reason to believe that agricola also published a greek grammar, for there is a letter[ ] from agricola dated march th, , in which henicus camitianus is requested to send a copy to stephan roth. _theological tracts._ there are preserved in the zwickau rathsschul library[ ] copies by stephan roth of two tracts, the one entitled, _deum non esse auctorem peccati_, the other, _religioso patri petri fontano, sacre theologie doctori eximio georgius agricola salutem dicit in christo_. the former was written from leipzig in , and the latter, although not dated, is assigned to the same period. both are printed in _zwei theologische abhandlungen des georg agricola_, an article by otto clemen, _neuen archiv fur sächsische geschichte_, etc., dresden, . there is some reason (from a letter of fabricius to melanchthon, dec. th, ) to believe that agricola had completed a work on the unwritten traditions concerning the church. there is no further trace of it. _galen._ agricola appears to have been joint author with andreas asulanus and j. b. opizo of a revision of this well-known greek work. it was published at venice in , under the title of _galeni librorum_, etc., etc. agricola's name is mentioned in a prefatory letter to opizo by asulanus. _de bello adversus turcam._ this political tract, directed against the turks, was written in latin and first printed by froben, basel, . it was translated into german apparently by agricola's friend laurenz berman, and published under the title _oration anrede und vormanunge ... widder den türcken_ by frederich peypus, nuremberg, in ( vo), and either in or by wolfgang stöckel, dresden, to. it was again printed in latin by froben, basel, , to; by h. grosius, leipzig, , vo; it was included among other works published on the same subject by nicholas reusnerus, leipzig, ; by michael lantzenberger, frankfurt-am-main, , to. further, there is reference by watt to an edition at eisleben, , of which we have no confirmation. there is another work on the subject, or a revision by the author mentioned by albinus[ ] as having been, after agricola's death, sent to froben by george fabricius to be printed; nothing further appears in this matter however. _de peste._ this work on the plague appears to have been first printed by froben, basel, , vo. the work was republished at schweinfurt, , and at augsburg in , under various editors. it would appear from albinus[ ] that the work was revised by agricola and in froben's hands for publication after the author's death. _de medicatis fontibus._ this work is referred to by agricola himself in _de natura eorum_,[ ] in the prefatory letter in _de veteribus et novis metallis_; and albinus[ ] quotes a letter of agricola to sebastian munster on the subject. albinus states (_bergchronik_, p. ) that to his knowledge it had not yet been published. conrad gesner, in his work _excerptorum et observationum de thermis_, which is reprinted in _de balneis_, venice, , after agricola's _de natura eorum_, states[ ] concerning agricola _in libris quos de medicatis fontibus instituerit copiosus se dicturum pollicetur_. watt mentions it as having been published in , , , and . he, however, apparently confuses it with _de natura eorum_. we are unable to state whether it was ever printed or not. a note of inquiry to the principal libraries in germany gave a negative result. _de putredine solidas partes humani corporis corrumpente._ this work, according to albinus was received by fabricius a year after agricola's death, but whether it was published or not is uncertain.[ ] _castigationes in hippocratem et galenum._ this work is referred to by agricola in the preface of _bermannus_, and albinus[ ] mentions several letters referring to the preparation of the work. there is no evidence of publication. _typographia mysnae et toringiae._ it seems from agricola's letter[ ] to munster that agricola prepared some sort of a work on the history of saxony and of the royal family thereof at the command of the elector and sent it to him when finished, but it was never published as written by agricola. albinus, hofmann, and struve give some details of letters in reference to it. fabricius in a letter[ ] dated nov. , asks meurer to send agricola some material for it; in a letter from fabricius to meurer dated oct. , , it appears that the elector had granted agricola thalers to assist in the work. after agricola's death the material seems to have been handed over to fabricius, who made use of it (as he states in the preface) in preparing the work he was commissioned by the elector to write, the title of which was, _originum illustrissimae stirpis saxonicae libri_, and was published in leipzig, . it includes on page a fragment of a work entitled _oratio de rebus gestis ernesti et alberti ducum saxoniae_, by agricola. works wrongly attributed to georgius agricola. the following works have been at one time or another wrongly attributed to georgius agricola:-- _galerazeya sive revelator secretorum de lapide philosophorum_, cologne, and , by one daniel agricola, which is merely a controversial book with a catch-title, used by catholics for converting heretics. _rechter gebrauch der alchimey_, a book of miscellaneous receipts which treats very slightly of transmutation.[ ] _chronik der stadt freiberg_ by a georg agricola (died ), a preacher at freiberg. _dominatores saxonici_, by the same author. _breviarum de asse_ by guillaume bude. _de inventione dialectica_ by rudolph agricola. footnotes: [ ] see footnote , page . [ ] system of mineralogy. [ ] the following are the titles of the works referred to in this discussion:-- petrus albinus: _meissnische land und berg chronica in welcher ein wollnstendige description des landes_, etc., dresden, (contains part i, _commentatorium de mysnia_). _newe chronica und beschreibung des landes zu meissen_, pp. to , besides preface and index, and part ii. _meissnische bergk chronica_, dresden, , pp. to , besides preface and index. adam daniel richter: _umständliche ... chronica der ... stadt chemnitz nebst beygefügten urkunden_, pts. to, zittau & leipzig, . ben. g. weinart: _versuch einer litteratur d. sächsischen geschichte und staats kunde_, leipzig, . friedrich august schmid: _georg agrikola's bermannus: einleitung in die metallurgischen schriften desselben_, freyberg, craz & gerlach. , pp. viii., - . franz ambros reuss: _mineralogische geographie van böhmen_. vols. to, dresden, - . (agricola vol. i, p. ). jacob leupold: _prodromus bibliothecae metallicae_, corrected, continued, and augmented by f. e. brückmann. wolfenbüttel, , s.v. agricola. christian gottlieb göcher: _allgemeines gelehrten-lexicon_, with continuation and supplements by adelung, leipzig, , s.v. agricola. john anton van der linden: _de scriptis medicis, libri duo_, amsterdam, , s.v. georgius agricola. nicolas françois joseph eloy: _dictionnaire historique de la médecine_, liége & francfort (chez j. f. bassompierre), , vo (agricola p. , vol. i). georg abraham mercklinus: _lindenius renovatus de scriptis medicis continuati ... amplificati_, etc., amsterdam, , s.v. georgius agricola. john ferguson: _bibliotheca chemica_: a catalogue of the alchemical, chemical, and pharmaceutical books in the collection of the late james young of kelly & durris, esq., l.l.d., f.r.s., f.r.s.e. glasgow, , to, vols., s.v. agricola. christoph wilhelm gatterer: _allgemeines repertorium der mineralogischen, bergwerks und salz werkswissenschaftlichen literatur_, göttingen, , vol. i. dr. reinhold hofmann: _dr. georg agricola, ein gelehrtenleben aus dem zeitalter der reformation_, vo, gotha, . georg heinrich jacobi: _der mineralog georgius agricola und sein verhältnis zur wissenschaft seiner zeit_, etc., vo. zwickau ( ), (_dissertation_--leipzig). georg draud: _bibliotheca classica_, frankfurt-am-main, . b. g. struve: _bibliotheca saxonica_, vo, halle, . [ ] albinus states (p. ): _omnes simul editi anno. , iterum , basileae_, as though two separate editions. [ ] _g. fabricii epistolae ad w. meurerum et alios aequales_, by baumgarten-crusius, leipzig, , p. . [ ] _dr. georg agricola_, gotha, , pp. - . [ ] albinus, _landchronik_, pp. - . [ ] _dr. georg agricola_, p. . [ ] _baumgarten-crusius_, p. . [ ] _virorum clarorum saec. xvi. et xvii._ _epistolae selectae_ by ernst weber, leipzig, , p. . [ ] nicholas episcopius to georg agricola, sept. , , published in schmid's _bermannus_ p. . see also hofmann, op. cit. pp. and . [ ] _meissnische landchronik_, dresden, , p. . [ ] printed in baumgarten-crusius, pp. - , letter xlviii. [ ] printed in hermann peter's _meissner jahresbericht der fürstenschule_, , p. . [ ] baumgarten-crusius. _georgii fabricii chemnicensis epistolae_, leipzig, , p. . [ ] there is a copy of this work in the rathsschul library at zwickau. [ ] in the rathsschul library at zwickau. [ ] contained in vols. xxxvii. and xl. of stephan roth's _kollectanenbände_ volumes of transcripts. [ ] _landchronik_, p. . [ ] op. cit., p. . [ ] book iv. [ ] op. cit., p. . [ ] page . [ ] see baumgarten-crusius, p. , letter from georg fabricius. [ ] op. cit., p. . [ ] albinus, op. cit., p. . [ ] baumgarten-crusius, p. . [ ] see ferguson, _bibliotheca chemica_, s.v. daniel agricola. appendix b. ancient authors. we give the following brief notes on early works containing some reference to mineralogy, mining, or metallurgy, to indicate the literature available to agricola and for historical notes bearing upon the subject. references to these works in the footnotes may be most easily consulted through the personal index. greek authors.--only a very limited greek literature upon subjects allied to mining or natural science survives. the whole of the material of technical interest could be reproduced on less than twenty of these pages. those of most importance are: aristotle ( - b.c.), theophrastus ( - b.c.), diodorus siculus ( st century b.c.), strabo ( b.c.- a.d.), and dioscorides ( st century a.d.). aristotle, apart from occasional mineralogical or metallurgical references in _de mirabilibus_, is mostly of interest as the author of the peripatetic theory of the elements and the relation of these to the origin of stones and metals. agricola was, to a considerable measure, a follower of this school, and their views colour much of his writings. we, however, discuss elsewhere[ ] at what point he departed from them. especially in _de ortu et causis_ does he quote largely from aristotle's _meteorologica_, _physica_, and _de coelo_ on these subjects. there is a spurious work on stones attributed to aristotle of some interest to mineralogists. it was probably the work of some arab early in the middle ages. theophrastus, the principal disciple of aristotle, appears to have written at least two works relating to our subject--one "on stones", and the other on metals, mining or metallurgy, but the latter is not extant. the work "on stones" was first printed in venice in , and the greek text, together with a fair english translation by sir john hill, was published in london in under the title "theophrastus on stones"; the translation is, however, somewhat coloured with hill's views on mineralogy. the work comprises short paragraphs, and would, if reproduced, cover but about four of these pages. in the first paragraphs are the peripatetic view of the origin of stones and minerals, and upon the foundation of aristotle he makes some modifications. the principal interest in theophrastus' work is the description of minerals; the information given is, however, such as might be possessed by any ordinary workman, and betrays no particular abilities for natural philosophy. he enumerates various exterior characteristics, such as colour, tenacity, hardness, smoothness, density, fusibility, lustre, and transparence, and their quality of reproduction, and then proceeds to describe various substances, but usually omits his enumerated characteristics. apart from the then known metals and certain "earths" (ochre, marls, clay, etc.), it is possible to identify from his descriptions the following rocks and minerals:--marble, pumice, onyx, gypsum, pyrites, coal, bitumen, amber, azurite, chrysocolla, realgar, orpiment, cinnabar, quartz in various forms, lapis lazuli, emerald, sapphire, diamond, and ruby. altogether there are some sixteen distinct mineral species. he also describes the touchstone and its uses, the making of white-lead and verdigris, and of quicksilver from cinnabar. diodorus siculus was a greek native of sicily. his "historical library" consisted of some books, of which parts of are extant. the first print was in latin, , and in greek in ; the first translation into english was by thomas stocker, london, , and later by g. booth, . we have relied upon booth's translation, but with some amendments by friends, to gain more literal statement. diodorus, so far as relates to our subject, gives merely the occasional note of a traveller. the most interesting paragraphs are his quotation from agatharchides on egyptian mining and upon british tin. strabo was also a geographer. his work consists of books, and practically all survive. we have relied upon the most excellent translation of hamilton and falconer, london, , the only one in english. mines and minerals did not escape such an acute geographer, and the matters of greatest interest are those with relation to spanish mines. dioscorides was a greek physician who wrote entirely from the standpoint of materia medica, most of his work being devoted to herbs; but book v. is devoted to minerals and rocks, and their preparation for medicinal purposes. the work has never been translated into english, and we have relied upon the latin translation of matthioli, venice, , and notes upon the greek text prepared for us by mr. c. katopodes. in addition to most of the substances known before, he, so far as can be identified, adds schist, _cadmia_ (blende or calamine), _chalcitis_ (copper sulphide), _misy_, _melanteria_, _sory_ (copper or iron sulphide oxidation minerals). he describes the making of certain artificial products, such as copper oxides, vitriol, litharge, _pompholyx_, and _spodos_ (zinc and/or arsenical oxides). his principal interest for us, however, lies in the processes set out for making his medicines. occasional scraps of information relating to the metals or mines in some connection are to be found in many other greek writers, and in quotations by them from others which are not now extant, such as polybius, posidonius, etc. the poets occasionally throw a gleam of light on ancient metallurgy, as for instance in homer's description of vulcan's foundry; while the historians, philosophers, statesmen, and physicians, among them herodotus, xenophon, demosthenes, galen, and many others, have left some incidental references to the metals and mining, helpful to gleaners from a field, which has been almost exhausted by time. even archimedes made pumps, and hero surveying instruments for mines. roman authors.--pre-eminent among all ancient writers on these subjects is, of course, pliny, and in fact, except some few lines by vitruvius, there is practically little else in extant roman literature of technical interest, for the metallurgical metaphors of the poets and orators were threadbare by this time, and do not excite so much interest as upon their first appearance among the greeks and hebrews. pliny (caius plinius secundus) was born a.d., and was killed by eruption of vesuvius a.d. his natural history should be more properly called an encyclopædia, the whole comprising books; but only portions of the last four books relate to our subject, and over one-half of the material there is upon precious stones. to give some rough idea of the small quantity of even this, the most voluminous of ancient works upon our subject, we have made an estimate that the portions of metallurgical character would cover, say, three pages of this text, on mining two pages, on building and precious stones about ten pages. pliny and dioscorides were contemporaries, and while pliny nowhere refers to the greek, internal evidence is most convincing, either that they drew from the same source, or that pliny drew from dioscorides. we have, therefore, throughout the text given precedence in time to the greek author in matters of historical interest. the works of pliny were first printed at venice in . they have passed dozens of editions in various languages, and have been twice translated into english. the first translation by philemon holland, london, , is quite impossible. the second translation, by bostock and riley, london, , was a great advance, and the notes are most valuable, but in general the work has suffered from a freedom justifiable in the translation of poetry, but not in science. we have relied upon the latin edition of janus, leipzig, . the frequent quotations in our footnotes are sufficient indication of the character of pliny's work. in general it should be remembered that he was himself but a compiler of information from others, and, so far as our subjects are concerned, of no other experience than most travellers. when one considers the reliability of such authors to-day on technical subjects, respect for pliny is much enhanced. further, the text is no doubt much corrupted through the generations of transcription before it was set in type. so far as can be identified with any assurance, pliny adds but few distinct minerals to those enumerated by theophrastus and dioscorides. for his metallurgical and mining information we refer to the footnotes, and in general it may be said that while those skilled in metallurgy can dimly see in his statements many metallurgical operations, there is little that does not require much deduction to arrive at a conclusion. on geology he offers no new philosophical deductions of consequence; the remote connection of building stones is practically all that can be enumerated, lest one build some assumption of a knowledge of ore-deposits on the use of the word "vein". one point of great interest to this work is that in his search for latin terms for technical purposes agricola relied almost wholly upon pliny, and by some devotion to the latter we have been able to disentangle some very puzzling matters of nomenclature in _de re metallica_, of which the term _molybdaena_ may be cited as a case in point. vitruvius was a roman architect of note of the st century b.c. his work of ten books contains some very minor references to pumps and machinery, building stones, and the preparation of pigments, the latter involving operations from which metallurgical deductions can occasionally be safely made. his works were apparently first printed in rome in . there are many editions in various languages, the first english translation being from the french in . we have relied upon the translation of joseph gwilt, london, , with such alterations as we have considered necessary. mediÆval authors.--for convenience we group under this heading the writers of interest from roman times to the awakening of learning in the early th century. apart from theophilus, they are mostly alchemists; but, nevertheless, some are of great importance in the history of metallurgy and chemistry. omitting a horde of lesser lights upon whom we have given some data under the author's preface, the works principally concerned are those ascribed to avicenna, theophilus, geber, albertus magnus, roger bacon, and basil valentine. judging from the preface to _de re metallica_, and from quotations in his subsidiary works, agricola must have been not only familiar with a wide range of alchemistic material, but also with a good deal of the arabic literature, which had been translated into latin. the arabs were, of course, the only race which kept the light of science burning during the dark ages, and their works were in considerable vogue at agricola's time. avicenna ( - ) was an arabian physician of great note, a translator of the greek classics into arabic, and a follower of aristotle to the extent of attempting to reconcile the peripatetic elements with those of the alchemists. he is chiefly known to the world through the works which he compiled on medicine, mostly from the greek and latin authors. these works for centuries dominated the medical world, and were used in certain european universities until the th century. a great many works are attributed to him, and he is copiously quoted by agricola, principally in his _de ortu et causis_, apparently for the purpose of exposure. theophilus was a monk and the author of a most illuminating work, largely upon working metal and its decoration for ecclesiastical purposes. an excellent translation, with the latin text, was published by robert hendrie, london, , under the title "an essay upon various arts, in three books, by theophilus, called also rugerus, priest and monk." hendrie, for many sufficient reasons, places the period of theophilus as the latter half of the th century. the work is mainly devoted to preparing pigments, making glass, and working metals, and their conversion into ecclesiastical paraphernalia, such as mural decoration, pictures, windows, chalices, censers, bells, organs, etc. however, he incidentally describes the making of metallurgical furnaces, cupellation, parting gold and silver by cementation with salt, and by melting with sulphur, the smelting of copper, liquating lead from it, and the refining of copper under a blast with poling. geber was until recent years considered to be an arab alchemist of a period somewhere between the th and th centuries. a mere bibliography of the very considerable literature which exists in discussion of who, where, and at what time the author was, would fill pages. those who are interested may obtain a start upon such references from hermann kopp's _beiträge zur geschichte der chemie_, braunschweig, , and in john ferguson's _bibliotheca chemica_, glasgow, . berthelot, in his _chimie au moyen age_, paris, , considers the works under the name of geber were not in the main of arabic origin, but composed by some latin scholar in the th century. in any event, certain works were, under this name, printed in latin as early as - , and have passed innumerable editions since. they were first translated into english by richard russell, london, , and we have relied upon this and the nuremberg edition in latin of . this work, even assuming berthelot's view, is one of the most important in the history of chemistry and metallurgy, and is characterised by a directness of statement unique among alchemists. the making of the mineral acids--certainly nitric and _aqua regia_, and perhaps hydrochloric and sulphuric--are here first described. the author was familiar with saltpetre, sal-ammoniac, and alkali, and with the acids he prepared many salts for the first time. he was familiar with amalgamation, cupellation, the separation of gold and silver by cementation with salt and by nitric acid. his views on the primary composition of bodies dominated the alchemistic world for centuries. he contended that all metals were composed of "spiritual" sulphur (or arsenic, which he seems to consider a special form of sulphur) and quicksilver, varying proportions and qualities yielding different metals. the more the quicksilver, the more "perfect" the metal. albertus magnus (albert von bollstadt) was a dominican monk, afterwards bishop, born about , and died about . he was rated the most learned man of his time, and evidence of his literary activities lies in the complete edition of his works issued by pierre jammy, lyons, , which comprises folio volumes. however, there is little doubt that a great number of works attributed to him, especially upon alchemy, are spurious. he covered a wide range of theology, logic, alchemy, and natural science, and of the latter the following works which concern our subject are considered genuine:--_de rebus metallicis et mineralibus_, _de generatione et corruptione_, and _de meteoris_. they are little more than compilations and expositions of the classics muddled with the writings of the arabs, and in general an attempt to conciliate the peripatetic and alchemistic schools. his position in the history of science has been greatly over-estimated. however, his mineralogy is, except for books on gems, the only writing of any consequence at all on the subject between pliny and agricola, and while there are but two or three minerals mentioned which are not to be found in the ancient authors, this work, nevertheless, deserves some place in the history of science, especially as some attempt at classification is made. agricola devotes some thousands of words to the refutation of his "errors." roger bacon ( - ) was a franciscan friar, a lecturer at oxford, and a man of considerable scientific attainments for his time. he was the author of a large number of mathematical, philosophical, and alchemistic treatises. the latter are of some importance in the history of chemistry, but have only minute bearing upon metallurgy, and this chiefly as being one of the earliest to mention saltpetre. basil valentine is the reputed author of a number of alchemistic works, of which none appeared in print until early in the th century. internal evidence seems to indicate that the "triumphant chariot of antimony" is the only one which may possibly be authentic, and could not have been written prior to the end of the th or early th century, although it has been variously placed as early as . to this work has been accredited the first mention of sulphuric and hydrochloric acid, the separation of gold and silver by the use of antimony (sulphide), the reduction of the antimony sulphide to the metal, the extraction of copper by the precipitation of the sulphate with iron, and the discovery of various antimonial salts. at the time of the publication of works ascribed to valentine practically all these things were well known, and had been previously described. we are, therefore, in much doubt as to whether this author really deserves any notice in the history of metallurgy. early th century works.--during the th century, and prior to _de re metallica_, there are only three works of importance from the point of view of mining technology--the _nützlich bergbüchlin_, the _probierbüchlein_, and biringuccio's _de la pirotechnia_. there are also some minor works by the alchemists of some interest for isolated statements, particularly those of paracelsus. the three works mentioned, however, represent such a stride of advance over anything previous, that they merit careful consideration. _eyn nützlich bergbüchlin._ under this title we frequently refer to a little booklet on veins and ores, published at the beginning of the th century. the title page of our copy is as below:-- [illustration (title page)] this book is small vo, comprises folios without pagination, and has no typographical indications upon the title page, but the last line in the book reads: _gedruckt zu erffurd durch johan loersfelt, _. another edition in our possession, that of "frankfurt am meyn", , by christian egenolph, is entitled _bergwerk und probierbüchlin_, etc., and contains, besides the above, an extract and plates from the _probierbüchlein_ (referred to later on), and a few recipes for assay tests. all of these booklets, of which we find mention, comprise instructions from daniel, a skilled miner, to knappius, "his mining boy". although the little books of this title are all anonymous, we are convinced, largely from the statement in the preface of _de re metallica_, that one calbus of freiberg was the original author of this work. agricola says: "two books have been written in our tongue: the one on the assaying of mineral substances and metals, somewhat confused, whose author is unknown; the other 'on veins', of which pandulfus anglus is also said to have written, _although the german book was written by calbus of freiberg, a well-known doctor; but neither of them accomplished the task he had begun_." he again refers to calbus at the end of book iii.[ ] of _de re metallica_, and gives an almost verbatim quotation from the _nützlich bergbüchlin_. jacobi[ ] says: "calbus fribergius, so called by agricola himself, is certainly no other than the freiberg doctor, rühlein von c(k)albe." there are also certain internal evidences that support agricola's statement, for the work was evidently written in meissen, and the statement of agricola that the book was unfinished is borne out by a short dialogue at the end of the earlier editions, designed to introduce further discussion. calbus (or dr. ulrich rühlein von kalbe) was a very active citizen of freiberg, having been a town councillor in , burgomaster in , a mathematician, mining surveyor, founder of a school of liberal arts, and in general a physician. he died in .[ ] the book possesses great literary interest, as it is, so far as we are aware, undoubtedly the first work on mining geology, and in consequence we have spent some effort in endeavour to find the date of its first appearance. through the courtesy of m. polain, who has carefully examined for us the _nützlich bergbüchlein_ described in marie pellechet's _catalogue général des incunables des bibliothèques publiques de france_,[ ] we have ascertained that it is similar as regards text and woodcuts to the erfurt edition, . this copy in the bibliothèque nationale is without typographical indications, and m. polain considers it very possible that it is the original edition printed at the end of the fifteenth or beginning of the sixteenth centuries. mr. bennett brough,[ ] quoting hans von dechen,[ ] states that the first edition was printed at augsburg in , no copy of which seems to be extant. the librarian at the school of mines at freiberg has kindly furnished us with the following notes as to the titles of the copies in that institution:--( ) _eyn wolgeordent und nützlich bergbüchlein_, etc., worms, [ ] and [ ] (the place and date are written in), ( ) the same as ours ( ); ( ) the same, heinrich steyner, augsburg, ; ( ) the same, . on comparing these various editions (to which may be added one probably published in nürnberg by friedrich peypus in [ ]) we find that they fall into two very distinct groups, characterised by their contents and by two entirely different sets of woodcuts. group i. (_a_) _eyn nützlich bergbüchlein_ (in _bibl. nat._, paris) before (?). (_b_) ditto, erfurt, . group ii. (_c_) _wolgeordent nützlich bergbüchlein_, worms, peter schöfern, . (_d_) _wolgeordent nützlich bergbüchlein_, worms, peter schöfern, . (_e_) _bergbüchlin von erkantnus der berckwerck_, nürnberg, undated, (?). (_f_) _bergwerckbuch & probirbuch_, christian egenolph, frankfurt-am-meyn, . (_g_) _wolgeordent nützlich bergbüchlein_, augsburg, heinrich steyner, . (_h_) _wolgeordent nützlich bergbüchlein_, augsburg, heinrich steyner, . there are also others of later date toward the end of the sixteenth century. the _büchlein_ of group i. terminate after the short dialogue between daniel and knappius with the words: _mitt welchen das kleinspeissig ertz geschmeltzt soil werden_; whereas in those of group ii. these words are followed by a short explanation of the signs used in the woodcuts, and by directions for colouring the woodcuts, and in some cases by several pages containing definitions of some mining terms. in the editions of group i. the woodcut on the title page represents a miner hewing ore in a vein and two others working a windlass. in those of group ii. the woodcut on the title page represents one miner hewing on the surface, another to the right carting away ore in a handcart, and two others carrying between them a heavy timber. in our opinion group i. represents the older and original work of calbus; but as we have not seen the copy in the _bibliothèque nationale_, and the augsburg edition of has only so far been traced to veith's catalogue,[ ] the question of the first edition cannot be considered settled at present. in any event, it appears that the material grafted on in the second group was later, and by various authors. the earliest books comprise ten chapters, in which daniel delivers about , words of instruction. the first four chapters are devoted to the description of veins and the origin of the metals, of the remaining six chapters one each to silver, gold, tin, copper, iron, lead, and quicksilver. among the mining terms are explained the meaning of country rock (_zechstein_), hanging and footwalls (_hangends_ and _liegends_), the strike (_streichen_), dip (_fallen_), and outcrop (_ausgehen_). of the latter two varieties are given, one of the "whole vein," the other of the _gesteins_, which may be the ore-shoot. various veins are illustrated, and also for the first time a mining compass. the account of the origin of the metals is a muddle of the peripatetics, the alchemists, and the astrologers, for which acknowledgment to albertus magnus is given. they are represented to originate from quicksilver and sulphur through heat, cold, dampness, and dryness, and are drawn out as exhalations through the veins, each metal owing its origin to the special influence of some planet; the moon for silver, saturn for lead, etc. two types of veins are mentioned, "standing" (_stehendergang_) and flat (_flachgang_). stringers are given the same characteristics as veins, but divided into hanging, footwall, and other varieties. prominence is also given to the _geschick_ (selvage seams or joints?). the importance of the bearing of the junctions of veins and stringers on enrichment is elaborated upon, and veins of east-west strike lying upon a south slope are considered the best. from the following notes it will be seen that two or three other types of deposits besides veins are referred to. in describing silver veins, of peculiar interest is the mention of the association of bismuth (_wismuth_), this being, we believe, the first mention of that metal, galena (_glantz_), quartz (_quertz_), spar (_spar_), hornstone (_hornstein_), ironstone and pyrites (_kies_), are mentioned as gangue materials, "according to the mingling of the various vapours." the term _glasertz_ is used, but it is difficult to say if silver glance is meant; if so, it is the first mention of this mineral. so far as we know, this is the first use of any of the terms in print. gold alluvial is described, part of the gold being assumed as generated in the gravel. the best alluvial is in streams running east and west. the association of gold with pyrites is mentioned, and the pyrites is found "in some places as a complete stratum carried through horizontally, and is called a _schwebender gang_." this sort of occurrence is not considered very good "because the work of the heavens can be but little completed on account of the unsuitability of the position." gold pyrites that comes in veins is better. tin is mentioned as found in alluvial, and also in veins, the latter being better or worse, according to the amount of pyrites, although the latter can be burned off. tin-stone is found in masses, copper ore in schist and in veins sometimes with pyrites. the ore from veins is better than schist. iron ore is found in masses, and sometimes in veins; the latter is the best. "the iron veins with good hanging- and foot-walls are not to be despised, especially if their strike be from east to west, their dip to the south, the foot-wall and outcrop to the north, then if the ironstone is followed down, the vein usually reveals gold or other valuable ore". lead ore is found in _schwebenden gang_ and _stehenden gang_. quicksilver, like other ore, is sometimes found in brown earth, and sometimes, again, in caves where it has run out like water. the classification of veins is the same as in _de re metallica_.[ ] the book generally, however, seems to have raised agricola's opposition, for the quotations are given in order to be demolished. _probierbüchlein._ agricola refers in the preface of _de re metallica_ to a work in german on assaying and refining metals, and it is our belief that it was to some one of the little assay books published early in the th century. there are several of them, seemingly revised editions of each other; in the early ones no author's name appears, although among the later editions various names appear on the title page. an examination of these little books discloses the fact that their main contents are identical, for they are really collections of recipes after the order of cookery books, and intended rather to refresh the memory of those already skilled than to instruct the novice. the books appear to have grown by accretions from many sources, for a large number of methods are given over and over again in the same book with slight variations. we reproduce the title page of our earliest copy. [illustration (title page)] the following is a list of these booklets so far as we have been able to discover actual copies:-- _date._ _place._ _publisher._ _title (short)._ _author._ unknown unknown unknown _probierbüchlein_ anon. (undated; but catalogue of british museum suggests augsburg, .) magdeburg _probirbüchleyn anon. tzu gotteslob_ augsburg unknown _probierbuch aller anon. sachsischer ertze_ frankfurt a. _bergwerck und anon. meyn probierbüchlein_ augsburg heinrich _probirbüchlein_ anon. steyner, vo. augsburg ditto, ditto _probirbüchlein_ anon. augsburg ditto, ditto _probirbüchlein_ anon. augsburg math. francke, _probirbüchlein_ zach. lochner to augsburg vo. _probirbuch_ sam. zimmermann franckfurt _probierbüchlein_ anon. a. meyn ditto _probierbüchlein fremde cyriacus und subtile kunst_ schreittmann ditto _probierbüchlein_ anon. ditto _probierbüchlein darinn modestin fachs gründlicher bericht_ dresden to _metallische probier c. c. schindler kunst_ _bericht vom ursprung und erkenntniss der metallischen erze_ amsterdam _probierbüchlein darinn modestin fachs gründlicher bericht_ leipzig _probierbüchlein darinn modestin fachs gründlicher bericht_ leipzig _probierbüchlein darinn modestin fachs gründlicher bericht_ nürnberg mo. _deutliche vorstellung anon. der probier kunst_ lübeck vo. _neu-eröffnete probier anon. buch_ frankfurt vo. _scheid-künstler ... anon. and leipzig alle ertz und metalle ... probiren_ rotenburg an vo. _probierbuch aus k. a. scheidt der fulde erfahrung aufgesetzt_ as mentioned under the _nützlich bergbüchlein_, our copy of that work, printed in , contains only a portion of the _probierbüchlein_. ferguson[ ] mentions an edition of , and the freiberg school of mines catalogue gives also frankfort, , and nürnberg, . the british museum copy of earliest date, like the title page reproduced, contains no date. the title page woodcut, however, in the museum copy is referred from that above, possibly indicating an earlier date of the museum copy. the booklets enumerated above vary a great deal in contents, the successive prints representing a sort of growth by accretion. the first portion of our earliest edition is devoted to weights, in which the system of "lesser weights" (the principle of the "assay ton") is explained. following this are exhaustive lists of touch-needles of various composition. directions are given with regard to assay furnaces, cupels, muffles, scorifiers, and crucibles, granulated and leaf metals, for washing, roasting, and the preparation of assay charges. various reagents, including glass-gall, litharge, salt, iron filings, lead, "alkali", talc, argol, saltpetre, sal-ammoniac, alum, vitriol, lime, sulphur, antimony, _aqua fortis_, or _scheidwasser_, etc., are made use of. various assays are described and directions given for crucible, scorification, and cupellation tests. the latter part of the book is devoted to the refining and parting of precious metals. instructions are given for the separation of silver from iron, from lead, and from antimony; of gold from silver with antimony (sulphide) and sulphur, or with sulphur alone, with "_scheidwasser_," and by cementation with salt; of gold from copper with sulphur and with lead. the amalgamation of gold and silver is mentioned. the book is diffuse and confused, and without arrangement or system, yet a little consideration enables one of experience to understand most statements. there are over recipes, with, as said before, much repetition; for instance, the parting of gold and silver by use of sulphur is given eight times in different places. the final line of the book is: "take this in good part, dear reader, after it, please god, there will be a better." in truth, however, there are books on assaying four centuries younger that are worse. this is, without doubt, the first written word on assaying, and it displays that art already full grown, so far as concerns gold and silver, and to some extent copper and lead; for if we eliminate the words dependent on the atomic theory from modern works on dry assaying, there has been but very minor progress. the art could not, however, have reached this advanced stage but by slow accretion, and no doubt this collection of recipes had been handed from father to son long before the th century. it is of wider interest that these booklets represent the first milestone on the road to quantitative analysis, and in this light they have been largely ignored by the historians of chemistry. internal evidence in book vii. of _de re metallica_, together with the reference in the preface, leave little doubt that agricola was familiar with these booklets. his work, however, is arranged more systematically, each operation stated more clearly, with more detail and fresh items; and further, he gives methods of determining copper and lead which are but minutely touched upon in the _probierbüchlein_, while the directions as to tin, bismuth, quicksilver, and iron are entirely new. biringuccio (vanuccio). we practically know nothing about this author. from the preface to the first edition of his work it appears he was styled a mathematician, but in the text[ ] he certainly states that he was most of his time engaged in metallurgical operations, and that in pursuit of such knowledge he had visited germany. the work was in italian, published at venice in , the title page of the first edition as below:-- [illustration (title page)] it comprises ten chapters in folios demi-octavo. other italian editions of which we find some record are the second at venice, ; third, venice, ; fourth, venice, ; fifth, bologna, . a french translation, by jacques vincent, was published in paris, , and this translation was again published at rouen in . of the ten chapters the last six are almost wholly devoted to metal working and founding, and it is more largely for this description of the methods of making artillery, munitions of war and bells that the book is celebrated. in any event, with the exception of a quotation which we give on page on silver amalgamation, there is little of interest on our subject in the latter chapters. the first four chapters are undoubtedly of importance in the history of metallurgical literature, and represent the first work on smelting. the descriptions are, however, very diffuse, difficult to follow, and lack arrangement and detail. but like the _probierbüchlein_, the fact that it was written prior to _de re metallica_ demands attention for it which it would not otherwise receive. the ores of gold, silver, copper, lead, tin, and iron are described, but much interrupted with denunciations of the alchemists. there is little of geological or mineralogical interest, he too holding to a muddle of the classic elements astrology and alchemy. he has nothing of consequence to say on mining, and dismisses concentration with a few words. upon assaying his work is not so useful as the _probierbüchlein_. on ore smelting he describes the reduction of iron and lead ores and cupriferous silver or gold ores with lead. he gives the barest description of a blast furnace, but adds an interesting account of a _reverbero_ furnace. he describes liquation as consisting of one operation; the subsequent treatment of the copper by refining with an oxidizing blast, but does not mention poling; the cupellation of argentiferous lead and the reduction of the litharge; the manufacture of nitric acid and that method of parting gold and silver. he also gives the method of parting with antimony and sulphur, and by cementation with common salt. among the side issues, he describes the method of making brass with calamine; of making steel; of distilling quicksilver; of melting out sulphur; of making vitriol and alum. he states that _arsenico_ and _orpimento_ and _etrisagallio_ (realgar) are the same substance, and are used to colour copper white. in general, biringuccio should be accredited with the first description (as far as we are aware) of silver amalgamation, of a reverberatory furnace, and of liquation, although the description is not complete. also he is, so far as we are aware, the first to mention cobalt blue (_zaffre_) and manganese, although he classed them as "half" metals. his descriptions are far inferior to agricola's; they do not compass anything like the same range of metallurgy, and betray the lack of a logical mind. _other works._ there are several works devoted to mineralogy, dating from the fifteenth and early sixteenth centuries, which were, no doubt, available to agricola in the compilation of his _de natura fossilium_. they are, however, practically all compiled from the jeweller's point of view rather than from that of the miner. among them we may mention the poem on precious stones by marbodaeus, an author who lived from to , but which was first printed at vienna in ; _speculum lapidum_, a work on precious stones, by camilli leonardi, first printed in venice in . a work of wider interest to mineralogists is that by christoph entzelt (or enzelius, encelio, encelius, as it is variously given), entitled _de re metallica_, and first printed in . the work is five years later than _de natura fossilium_, but contains much new material and was available to agricola prior to his revised editions. footnotes: [ ] see pages and . [ ] page . [ ] _der mineralog georgius agricola_, zwickau, , p. . [ ] andreas möller, _theatrum freibergense chronicum_, etc., freiberg, . [ ] paris, , vol. i. p. . [ ] cantor lectures, london, april . [ ] hans von dechen, _das älteste deutsche bergwerksbuch_, reprint from _zts. für bergrecht bd. xxvi._, bonn, . [ ] panzer's _annalen_, nürnberg, , p. , gives an edition worms _bei_ peter schöfern, . [ ] the royal library at dresden and the state library at munich have each a copy, dated , worms. [ ] hans von decken _op. cit._, p. - . [ ] _annales typographiae augustanae ab ejus origine, mccclxvi. usque ad. an. m.d.xxx. accedit dom franc. ant. veith. diatribe de origine ... artis typographicae in urbe augusta vindelica edidit...._ georgius g. zapf., augsburg, , x. p. . [ ] see p. . [ ] _bibliotheca chemica_. [ ] book i., chap. . appendix c. weights and measures. as stated in the preface, the nomenclature to be adopted for weights and measures has presented great difficulty. agricola uses, throughout, the roman and the romanized greek scales, but in many cases he uses these terms merely as lingual equivalents for the german quantities of his day. moreover the classic language sometimes failed him, whereupon he coined new latin terms adapted from the roman scale, and thus added further confusion. we can, perhaps, make the matter clearer by an illustration of a case in weights. the roman _centumpondium_, composed of _librae_, the old german _centner_ of _pfundt_, and the english hundredweight of pounds can be called lingual equivalents. the first weighs about , troy grains, the second , , and the third , . while the divisions of the _centumpondium_ and the _centner_ are the same, the _libra_ is divided into _unciae_ and the _pfundt_ into _untzen_, and in most places a summation of the units given proves that the author had in mind the roman ratios. however, on p. he makes the direct statement that the _centumpondium_ weighs _librae_, which would be about the correct weight if the _centumpondium_ referred to was a _centner_. if we take an example such as "each _centumpondium_ of lead contains one _uncia_ of silver", and reduce it according to purely lingual equivalents, we should find that it runs . troy ounces per short ton, on the basis of roman values, and . ounces per short ton, on the basis of old german. if we were to translate these into english lingual equivalents of one ounce per hundredweight, then the value would be . ounces per short ton. several possibilities were open in translation: first, to calculate the values accurately in the english units; second, to adopt the nearest english lingual equivalent; third, to introduce the german scale of the period; or, fourth, to leave the original latin in the text. the first would lead to an indefinite number of decimals and to constant doubt as to whether the values, upon which calculations were to be based, were roman or german. the second, that is the substitution of lingual equivalents, is objectionable, not only because it would indicate values not meant by the author, but also because we should have, like agricola, to coin new terms to accommodate the lapses in the scales, or again to use decimals. in the third case, that is in the use of the old german scale, while it would be easier to adapt than the english, it would be more unfamiliar to most readers than the latin, and not so expressive in print, and further, in some cases would present the same difficulties of calculation as in using the english scale. nor does the contemporary german translation of _de re metallica_ prove of help, for its translator adopted only lingual equivalents, and in consequence the summation of his weights often gives incorrect results. from all these possibilities we have chosen the fourth, that is simply to reproduce the latin terms for both weights and measures. we have introduced into the footnotes such reductions to the english scale as we considered would interest readers. we have, however, digressed from the rule in two cases, in the adoption of "foot" for the latin _pes_, and "fathom" for _passus_. apart from the fact that these were not cases where accuracy is involved, agricola himself explains (p. ) that he means the german values for these particular terms, which, fortunately, fairly closely approximate to the english. further, we have adopted the anglicized words "digit", "palm", and "cubit", instead of their latin forms. for purposes of reference, we reproduce the principal roman and old german scales, in so far as they are used by agricola in this work, with their values in english. all students of weights and measures will realize that these values are but approximate, and that this is not an occasion to enter upon a discussion of the variations in different periods or by different authorities. agricola himself is the author of one of the standard works on ancient weights and measures (see appendix a), and further gives fairly complete information on contemporary scales of weight and fineness for precious metals in book vii. p. etc., to which we refer readers. roman scales of weights. troy grains. _siliqua_ = . _siliquae_ = _scripulum_ . _scripula_ = _sextula_ . _sextulae_ = _uncia_ . _unciae_ = _libra_ . _librae_ = _centumpondium_ . also _scripulum_ = . _scripula_ = _drachma_ . _drachmae_ = _sicilicus_ . _sicilici_ = _uncia_ . _unciae_ = _bes_ . scale of fineness (agricola's adaptation). _siliquae_ = unit of _siliquae_ _units of siliquae_ = _semi-sextula_ _semi-sextulae_ = _duella_ _duellae_ = _bes_ old german scale of weights. troy grains. _pfennig_ = . _pfennige_ = _quintlein_ . _quintlein_ = _loth_ . _loth_ = _untzen_ . _untzen_ = _mark_ . _mark_ = _pfundt_ . _pfundt_ = _centner_ . scale of fineness. _grenlin_ = _gran_ _gran_ = _krat_ _krat_ = _mark_ roman long measure. inches. _digitus_ = . _digiti_ = _palmus_ . _palmi_ = _pes_ . - / _pedes_ = _cubitus_ . _pedes_ = _passus_ . also roman _uncia_ = . _unciae_ = pes . greek long measure. inches. _dactylos_ = . _dactyloi_ = _palaiste_ . _palaistai_ = _pous_ . - / _pous_ = _pechus_ . _pous_ = _orguia_ . old german long measure. inches. _querfinger_ = . _querfinger_ = _werckschuh_ . _werckschuh_ = _elle_ . _elle_ = _lachter_ . also _zoll_ = . _zoll_ = _werkschuh_ roman liquid measure. cubic inches. pints. _quartarius_ = . . _quartarii_ = _sextarius_ . . _sextarii_ = _congius_ . . _sextarii_ = _modius_ . . _congii_ = _amphora_ . . (agricola nowhere uses the saxon liquid measures, nor do they fall into units comparable with the roman). general index. note.--the numbers in heavy type refer to the text; those in plain type to the footnotes, appendices, etc. abandonment of mines, = = abertham. mines at, = =; = =; abolite, _abstrich_, ; abydos. gold mines of, = =; lead figure from, _abzug_, ; ; _achates_ (_see_ agate). accidents to miners, = - = accounts (mining), = - = adit, _aeris flos_ (_see_ copper flowers). _aeris squama_ (_see_ copper scales). _aes caldarium_, _aes luteum_, _aes nigrum_, _aes purum fossile_ (_see_ native copper). _aes rude plumbei coloris_ (_see_ copper glance). _aes ustum_ (_see_ roasted copper). _aetites_, africa. iron, tin, agate, agriculture. mining compared with, = = ailments of miners (_see_ maladies of miners). air currents in mines, = =; = = alabaster, alchemists, xxvii-xxx; ; agricola's opinion of, xii; =xxvii.= amalgamation, assaying, = =; discovery of acids, ; distillation, aljustrel tablet, - alkali, alloys, assaying of, = - = alluvial mining, = - =; - alston moor, altenberg, =xxxi=; vi. collapse of mine, = = miners poisoned, = = tin working appliances, = =; = =; = = alum, = - =; - a solidified juice, elizabethan charter, in roasted pyrites, = = in _sal artificiosus_, = = latin and german terms, ; papal monopoly, use in making nitric acid, = =; amalgam. parting the gold from, = =; amalgamation, of gilt objects, = = mills, = - = amber, = =; amethyst, _amiantus_ (_see_ asbestos). ampulla, = - =; annaberg, vi; =xxxi=; = =; = =; profits, = = ant, venomous, = = antimony, ; ; minerals, smelting of, = =; = = use as type-metal, ; antimony sulphide, ; ; parting gold and silver with, = =; ; parting gold from copper, = = parting silver and iron, = = antwerp, scale of weights, = = apex law, ; - _aqua regia_, ; ; _aqua valens_ (_see also_ nitric acid), = - =; ; clarification with silver, = =; cleansing gold-dust with, = = parting precious metals with, = - = _arbores dissectae_ (lagging), archimedes, screw of, architecture. knowledge necessary for miners, = = _area fodinarum_ (_see_ meer). argentiferous copper ores, smelting of, = - = argentite, _argentum purum in venis_ (_see_ native silver). _argentum rude plumbei coloris_ (_see_ silver glance). _argentum rude rubrum translucidum_ (_see_ ruby silver). argol, ; as a flux, = =; = =; = = use in melting silver nitrate, = = use in smelting gold dust, = - = argonauts, arithmetical science. knowledge necessary for miners, = = armenia, stone of, arsenic (_see also_ orpiment _and_ realgar), ; _arsenicum_, arsenopyrite, asbestos, = =; ; ash-coloured copper, = - =; ; - ; from liquation, = - = ashes which wool dyers use (_see also_ potash), ; ; use in assaying, = - = ash of lead, = - =; ; ash of musk ivy (_see also_ potash and _nitrum_), = - =; asphalt, _asphaltites_ (_see_ dead sea). assay balances (_see_ balances). assay fluxes (_see_ fluxes). assay furnaces, = - =; crucible, = - = muffle, = - =; = = assaying (_see also_ _probierbüchlein_), = =; ; ; amalgamation, = = bismuth, = = copper, = = cupellation, = = gold and silver alloys, = = gold ore, = - = iron ore, = = lead, = - = silver, = - = silver and copper alloys, = - = tin, = = tin and silver alloys, = = assay muffles (_see_ muffles). assay ton, = =; assyrian copper, asthma, = = astronomy. knowledge necessary for miners, = = atarnea. mines near, = =; athens. mining law, sea power and mines, silver mines (_see_ mt. laurion, mines of). _atramentum sutorium_ (_see also_ vitriol), ; _atramentum sutorium candidum_, _atramentum sutorium rubrum_, = =; _aurichalcum_, ; _auripigmentum_ (_see_ orpiment). azure, ; ; an indication of copper, = = an indication of gold, = = colour of flame, = = azurite ; ; babel, tower of, babylonia. bitumen in, use of lead, babytace. gold buried by inhabitants, = =; = = baebelo, = =; balances, = =; = - = barite, barmaster, of high peak, bars, for furnace work, = = baskets, for hoisting, = = batea, = = beer, = =; bell, to call workmen, = = bellows, = - =; = = ancient use of, ; ; assay furnace, = =; = = mine ventilation with, = - = beni hassen, inscriptions at, _berg-geel_, bergmeister, = =; = =; = =; = =; ; deals with forfeited shares, = - = jurors, = = bergmeister's clerk, = =; _bergzinober_ (_see_ quicksilver). bermius (bermium), mt. (_see_ mt. bermius). bismuth, = =; ; assaying ores of, = = indication of silver, = = minerals, ; smelting of, = - =; = = the "roof of silver," = =; _zaffre_, bitumen. ancient knowledge of, ; - ; colour of fumes, = = dead sea, = = distillation, = = from springs, = = harmful to metals, = = roasting from ore, = =; = =; = = solidified juice, = = _bituminosa cadmia_ (_see_ _cadmia bituminosa_). blast, regulation of, = =; = = blasting, blende, bleyberg, bloodstone, ; bloom, _blütstein_ (_see_ ironstone). bohemia. antimony sulphide, pestilential vapours, = = sifting ore in, = = smelting, = = bone-ash, = =; borax, ; ; method of manufacture, = = use in gold smelting, = =; = =; = = use in assaying, = =; = = bornite, boundary stones, = =; boundaries, = =; = = bowls for alluvial washing, = =; = =; = =; = = brass, ; ; ancient methods of making, - ; breaking ore, = - = brick dust. used in cementation, = =; used in making nitric acid, = = brine (_see also_ salt). evaporation of, = - = britain. lead-silver smelting, miners mentioned by pliny, tin trade, - british museum. egyptian gold-mining, egyptian lead, egyptian steel, bromyrite, bronze. historical notes, ; ; bronze age, ; = =; bryle (outcrop), buckets, for hoisting ore, = - =; = = buddle, ; ; divided, = - = simple, = - =; = - = bullion, pouring into bars, = = burning ore, = =; = =; burnt alum, = =; ; _cadmia_ (_see also_ zinc, _pompholyx_, _and_ cobalt), = =; ; - ancient ore of brass, from dust chambers, = = from liquation, = =; from roasting matte, = = poisonous to miners, = =; roasting, = = smelting for gold and silver, = = _cadmia bituminosa_, = =; ; _cadmia fornacis_ (_see_ furnace accretions). _cadmia fossilis_ (_see_ calamine _and_ blende). _cadmia metallica_ (_see also_ cobalt), = =; _caeruleum_ (_see_ azure). cakes of melted pyrites, ; a flux, = = roasting of, = - = use in smelting, = = calaëm (_see also_ zinc), = = calamine, ; ; ; calcite, calcspar, = =; _caldarium_ copper, = =; = =; ; caldrons, for evaporating salts, = = _calmei_ (_see_ calamine). cameros. zinc found at, camphor, = =; ; cam-shaft, = - =; _canales_ (ore channels), ; ; ore shoots in, = = cannon, = = cardinal points, = =; = = carnelian, _carneol_ (_see_ carnelian). _carni_, cupellation, = = smelting of lead ores, = = carpathian mountains. liquation practice in, = =; = = sieves, = = stamp-milling, = = carthage. mines in spain, = = castulo (cazlona), cementation (_see also_ parting gold from silver), = - =; ; _centumpondium_, ; ; scale of weights, = - = cerargurite, _cerussa_ (_see_ white-lead). cerussite, chain pumps, = - = chalcanthite, _chalcanthum_ (_see also_ vitriol), ; chalcedony, _chalcitis_, ; indication of copper, = = chalcocite, ; chalcopyrite, chaldean antimony, chemistry. origin, xxvii; chemnitz. agricola appointed city physician, vii. agricola elected burgomaster, viii; ix. quarrel over agricola's burial, xi. china, grand canal of, chinese. early copper smelting, early iron, early silver metallurgy, early zinc smelting, _chrysocolla_ (_see also_ borax), ; ; ; collection in vats, = = colour of fumes, = = indication of copper, = = indication of gold, = = mineral, smelting of, = = church, share in mines, = = cimolite, cinnabar (_see_ quicksilver _and_ _minium_). claim, in american title, cloth. lining sluices, = = ventilation by shaking, = = coal, cobalt, ; ; - cobalt-blue, ; from lead smelting, king hiram's experience with, poisonous to miners, relation to _cadmia_, relation to bismuth, smelting ores of, cobalt-arsenic minerals (_see_ arsenic). cobaltite, _cobaltum cineraceum_ (_see_ smallite). _cobaltum ferri colore_ (_see_ cobaltite). _cobaltum nigrum_ (_see_ abolite). coiners, = =; coins, = - =; = = colchis. alluvial gold washing, = = cologne. scale of weights, = = companies, mining, = - =; fraudulent dealing, = = investment in, = = compass, = - =; ; divisions of the, = =; = = swiss, = =; concentrates. from washing liquation products, = = sintering of, = = smelting of, = =; = - =; = = concentration, = - =; ; _congius_, ; , constantinople, alum trade, consumption. miners liable to, = = _conterfei_ (_see_ zinc). contracts, method of setting, = = copiapite, copper (_see also_ liquation), ; ; assay of, = =; = = granulation of, = = indications of, = = parting from gold, = - = parting gold from silver, = - =; ratio in liquation cakes, ; residues from liquation, = = rosette, = = copper-filings, = =; ; copper flowers, = =; ; ; pliny's description, copper glance, = =; copper matte. roasting, = = smelting, = - = copper ore (_see also_ copper smelting, _etc._), assaying, = - = copper pyrites, = =; copper refining, = - =; ; ; - breaking cakes, = - = enrichment of silver by settling, roman method, rosette copper, copper scales, ; ; ; use in assaying, = = copper schists (_see also_ mannsfeld copper slates), method of smelting, = = copper smelting, = - =; = =; = =; invention of appliances, - cornwall. ancient tin mining, early german miners, early mining law, early ore dressing, influence on german mining, "knockers," mining terms, ; ; ; royal geol. soc. transactions, _coticula_ (_see_ touchstone). _counterfeht_ (_see_ zinc). crane. for cupellation furnaces, = - = for lead cakes, = = for liquation cakes, = = cremnitz. age of mines, = = width of veins, = = crinoid stems, croppings, = =; crosscuts, = = crowbars, = = crucible. assay, = =; = =; = =; = =; of blast furnaces, = =; = = _crudaria_, crushing mills (_see_ stamp-mill _and_ mills). crushing ore, = =; = - =; crystal (_crystallum_), cumberland. early report on ores of, roman lead furnaces, cup-bearer. right to a meer, = = cupellation, = - =; - buildings and furnaces, = - =; brightening of the silver, = =, = = in assaying, = = in "tests," = = latin and german terms, ; litharge, = = cupels, = - =; ; drying of, = = moulds, = = cupric oxide, cuprite, ; _cyanus_ (_see also_ azurite), cyprus. ancient copper smelting, _dach_, _dactylos_, ; dangers to miners, = - = _darrlinge_, _darrofen_, _darrsöhle_, dawling, of a vein, dead sea. bitumen in, = = decemviral college, = = _decumanus_ (_see_ tithe gatherer). _demensum_ (_see_ measure). demons (_see also_ gnomes), = =; derbyshire (_see also_ high peak). early ore washing, introduction jigging sieve, mining law, ; - descent into mines, = = devon. mining law, dilleugher, dioptra, _diphrygum_, dip of veins, = - = dippas, dippers, = = of pumps, = = _discretores_ (_see_ sorters). distillation, for making nitric acid, = = of amalgam, = = of quicksilver, = - = _distributor_, divining rod, = - =; ; divisions of the compass, = =; = = drainage of mines, = =; = - = with buckets, = = with chain pumps, = = with rag and chain pumps, = = with suction pumps, = = with water bags, = = drawing. knowledge necessary for miners, = = drifts, = =; = =; timbering of, = = drusy veins, = =; "drying" liquation residues (_see also_ liquation), = - =; ; furnaces for, = =; = =; silver extracted by, = = slags from, dumps, working of, = = dust chambers, = =; = =; dutins, (timbers), dynamite, "earths." agricola's view of, ; ; extraordinary, = = peripatetic view of, ; egyptians. alluvial mining, antimony, bronze, ; copper smelting, crushing and concentration, furnaces, glass making, gold mining, iron, maps, mining law, silver and lead metallurgy, tin, ; egyptian screw (_see_ archimedes, screw of). eifel. spalling ore, = = _eisenertz_ (_see_ ironstone). _eisenglantz_ (_see_ ironstone). eisleben. heap roasting, = =; _electrum_, ; ; elements, peripatetic theory of, emery, erbisdorff. tin strakes, = = _excoctores_ (_see_ smelters). exhalations. from veins, = =; = = exhausted liquation cakes (_see_ liquation cakes, exhausted). fans, ventilation, = - = fathom, ; = =; _federwis_, (_see also_ asbestos), ; feldspar, _ferrugo_ (_see_ iron-rust). _ferrum purum_ (_see_ native iron). _fibrae_ (_see_ stringers). fineness, scales of, ; fire-setting, = - =; - firstum mines (_see_ fürst). fissure vein (_see_ _vena profunda_). flame. determination of metal by, = = determination of required flux by, = = flint, as a flux, float, from veins, = = flookan, flue-dust, = - = _fluores_ (_see_ fluorspar). fluorspar, ; ; indication of ore, = = _flüsse_ (_see_ fluorspar). fluxes (_see also_ argol, saltpetre, limestone, stones which easily melt, _etc._), = - =; ; ; ; basic, de-sulphurizing, = =; for smelting, = =; = =; = =; = = reducing, = =; stock fluxes for assaying, = = sulphurizing, = =; footwall, = =; = = forehearth, = =; = - =; = =; for tin furnaces, = =; = = foreman (_see_ mining foreman). forest-fires, = =; forest of dean, forest of mendip, _formae_, _fossa latens_ (_see also_ drifts), _fossa latens transversa_ (_see also_ crosscuts), _fossores_ (_see_ miners). founders' hoards, ; fractional meers, = = france. mediæval mining law, free mining cities, freiberg, =xxxi.= age of the mines, = = bergmeister, = = division of shares, = =; = =; = = first discovery of veins, = =; flooding of mines, = = method of cupellation, = = fullers' earth, fumes. from heated ore, = = poisonous, = - = _fundamentum_ (_see also_ footwall), _fundgrube_ (_see also_ meer), furnaces, = - =; = =; = =; ; assaying (_see_ assay furnaces). bismuth smelting, = - = burning tin concentrates, = = cementation, = = copper smelting, = - = cupellation, = - =; = - = "drying" liquated copper, = - = enriching copper bottoms, = = gold and silver ores, = - = heating copper cakes, = = iron smelting, = - =; latin and german terms, lead ores, = - = liquation of silver, = = melting lead cakes, = = nitric acid making, = = parting precious metals with antimony, = - = quicksilver distillation, = - = refining copper, = - = refining silver, = =; = = refining tin, = = roasting, = - = smelting liquation slags, = = tin smelting, = - =; = = furnace accretions, ; ; removal of, = = furnace hoods, = = fürst. mines of, = =; _gaarherd_ (_see_ refining-hearth). _gaarmachen_ (_see_ copper refining). gad, galena, ; ; ; bismuth distinguished from, smelting of, = - = gangue minerals, garlic. magnet weakened by, = = garnets, = = gases (_see also_ fumes) from fire-setting, = = _gedigen eisen, silber_, etc. (_see_ native iron, silver, etc.). _gel atrament_ (_see_ _misy_). gems, = =; geology. agricola's views, germans. english mining influenced by, mining men imported into england, ore-dressing methods, - _geschwornen_ (in saxon mines), geyer, =xxxi=; = =; vi. shafts, tin-strakes, = = gilding, removal from objects, = =; = = gips (_see_ gypsum). gittelde. smelting of lead ore, = = _glantz_ (_see_ galena). _glasertz_ (_see_ silver glance). _glasköpfe_ (_see_ ironstone). glass, = - = blowing, = = furnaces, = - = from sand, glass-galls, ; as a flux, = =; = =; = =; = = use in parting gold from copper, = = use in smelting gold concentrates, = =; = = _glette_ (_see_ litharge). _glimmer_ (_see_ mica). gnomes. in mines, = =; ; ; goblins (_see_ gnomes). god's gift mine (_see_ gottsgaab mine). gold (_see also_ gold ores, parting, smelting, stamp-mill, _etc._). alluvial mining, = - =; alluvial streams, = = amalgamation, gold-dust, = = historical notes, ; indications of, = =; = = lust for, not the fault of the metal, = = minerals, minerals associated with, = - = smelting of ores, = - =; = =; = =; = =; = = wickedness caused by, = - = gold concentrates, = - =; golden fleece, = =; gold ores, = - = amalgamation, = - =; assay by amalgamation, = - = assay by fire, = - = flux used in assaying, = = flux used in smelting, = = smelting in blast furnace, = - = smelting cupriferous ores, = - = smelting in lead bath, = = smelting pyritiferous ore, = - = stamp-milling, = = _goldstein_ (_see_ touchstone). goslar, = =; = =; lead smelting, = = native zinc vitriol, roasting ores, = =; spalling hard ore, = = goslarite, ; gottsgaab mine, vi; vii; = =; gounce, grand canal of china, granulation methods for bullion, = = granulation of copper, = = greeks. antimony, brass making, copper smelting, iron and steel making, metallurgy from egypt, mining law, ore dressing, quicksilver, silver-lead smelting, smelting appliances, grey antimony (_see also_ _stibium_), ; ; griffins, groom of the chamber. right to a meer, = = groove (_see also_ shafts), ground sluices, = - = ground waters, - _grünspan_ (_see_ verdigris). _gulden_, ; gunpowder. first use for blasting in mines, invention of, gypsum, hade, _haematites_ (_see_ ironstone). _halinitrum_ (_see_ saltpetre). halle, salt industry, = = hammers, = = with water power, = = hangingwall, = =; = = harz miners. agricola consulted, vii. antimony sulphide, first mining charter, first stamp-mill, pumps, = = hauling appliances (_see also_ whims _and_ windlasses), = - =; heap roasting, = - = hearth-lead (_see also_ _molybdaena_), = =; ; ; as a flux, = = use in smelting, = =; = =; = = hearths. for bismuth smelting, = - = for melting lead, = =; = = heavenly host mine (_see_ _himmelisch höz_ mine). heavy spar, hebrews. knowledge of antimony, silver-lead smelting, term for tin, hematite, hemicycle (_hemicyclium_), = - = _heraclion_ (_see_ lodestone). _herdplei_ (_see_ hearth-lead). hiero, king, = =; high peak (derbyshire). mining law, nomenclature in mines, saxon customs, connection with, ; _himmelisch höz_ mine, = =; = =; hoe, = = holidays of miners, = = horn silver, horns of deer, = = hornstone, = =; hungary. cupellation, = = _hüttenrauch_ (_see_ _pompholyx_). iglau, charter of, incense in cupellation furnaces, = = indications of ore, = =; = =; = = _ingestores_ (_see_ shovellers). india. steel, zinc, _intervenium_, = =; = = investment in mines, = - = iron, ; ; cast, censure of, = = indications of, = = malleable, smelting, = - = sulphur harmful to, = = iron age, iron filings (_see also_ iron-scales), use in assaying, = =; = =; = = iron ore. assaying of, = = smelting of, = - = iron-rust, = =; = =; ; iron-scales, flux, = = use in smelting gold, = = use in smelting silver, = = use in making nitric acid, = = use in parting gold from copper, = = iron-slag, as a flux, = =; = = ironstone, = =; italians. alluvial mining in germany, = = italy. mining formerly forbidden, = = jade, japan. steel, jasper, ; _jaspis_, jet, jigging sieve, = =; ; joachimsthal, vi. first stamp-mill, mining shares and profits, = =; = = _jüdenstein_ (_see_ _lapis judaicus_). juices, ; agricola's theory, ; from springs and streams, = = stone juice, ; tastes of, = = juices, solidified. agricola's view of, ; extraction of metals from, = = preparation of, = = julian alps. stamp-milling in, = = junctions (_see_ veins, intersections of). _jurati_ (_see_ jurors). jurors, = =; = =; = =; in english mining custom, relations to bergmeister, = =; justinian code. mines, _kalchstein_ (_see_ limestone). _kammschale_, kaolinite (_see_ porcelain clay). _katzensilber_ (_see_ mica). king. deputy, = = right to a meer, = = _kinstock_ (_see_ liquation cakes, exhausted). _kis_ (_see_ pyrites). knockers (_see_ gnomes). _kobelt_ (_see_ cobalt). kölergang vein, = = königsberg. fire-setting, _kupferglas ertz_ (_see_ copper glance). _kupferschiefer_ (_see_ copper schists). kuttenberg. depths of shafts, labour condition in mining title, = =; - lacedaemonians (_see_ spartans). _lachter_ (_see_ fathom). ladderways in shafts, = =; = = ladle for bullion, = = _lapis aerarius_ (_see_ copper ore). _lapis alabandicus_, _lapis judaicus_, = =; _lapis specularis_ (_see_ gypsum). laths (lagging), la tolfa. alum manufacture, discovery of, laurion (laurium), mt. (_see_ mt. laurion, mines of). lautental, liquation at, law (_see_ mining law). law-suits over shares in mines, = = lead, ; ; censure of, = = cupellation, = - = melting prior to liquation, = = in liquation cakes, = - =; ; refining silver, = - = smelting of ores, = - =; = = use in assaying, = =; = =; = =; = =; = =; = = washing in sluices, = = lead-ash, = =; ; as a flux, = = use in parting gold from copper, = = lead bath, = = lead-glass, lead granules, = =; = =; leading (in liquation), = =; = =; = =; ; ; components of the charge, = - = lead ochre, ; ; lead ore. assay methods, = - = roasting, = = smelting in blast furnace, = =; = = lease, in australian title, leaves, preparation of bullion into, = = leberthal, lees of _aqua_ which separates gold from silver, ; ; as a flux, = =; = = lees of vinegar (_see also_ argol), as a flux, = =; = =; = =; lees of wine (_see_ argol). lemnos, island of, = = lemnian earth, leprosy of house walls (_see_ saltpetre). level (_see also_ drift), level, plummet (_see_ plummet level). limestone, ; as a flux, = =; = = limonite, limp, linares. hannibal's mines near, lipari islands. alum from, liquated silver-lead (_see_ _stannum_ _and_ silver-lead). liquation, = - =; ; ash-coloured copper from, = = buildings for, furnace, = - =; historical note on, losses, ; nomenclature, liquation cakes, = - =; ; ; enrichment of the lead, = =; extraction of silver from, from bye-products of liquation, = - = from copper bottoms, = =; proportion of lead in rich silver copper, = = liquation cakes, exhausted, = - =; = =; ; liquation slags, ; ; furnaces for, = = treatment of, = = liquation thorns, = =; = =; ; ; from cupellation, = =; from "drying" copper residues, = = litharge (_see also_ cupellation), = =; = - =; ; ; ; use in reducing silver nitrate, = = use in smelting, = =; = =; = = _lithargyrum_ (_see_ litharge). lodestone, = =; ; ; compass, _los pozos de anibal_, _lotores_ (_see_ washers). lusitania. gold alluvial, = = sluices for gold washing, = = tin smelting, = = lute, preparation of for furnace linings, = - = lydia. mining law, the king's mines, lye, = =; ; use in making fluxes, = = use in parting, = = _magister metallicorum_ (_see_ bergmeister). _magister monetariorum_ (_see_ master of the mint). _magnes_ (_see also_ lodestone _and_ manganese), = =; ; ; magnet, = = garlic, = = _magnetis_ (_see_ mica). magnetite, malachite, ; maladies of miners, = - = maltha, manager (_see_ mine manager). manganese, ; mannsfeld copper slates, = - =; = =; ; map-making, marble, = =; ; marcasite, ; ; _marga_ (_see_ marl). marienberg, =xxxi=; vi. marl, marmelstein (_see_ marble). _marmor_ (_see_ marble). _marmor alabastrites_ (_see_ alabaster). _marmor glarea_, massicot (_see also_ lead ochre), ; ; master of the horse, = = master of the mint, = =; matte (_see_ cakes of melted pyrites). matte smelting, = - = measure (unit of mining area), = =; measures, - ; ; medicine. knowledge necessary for miners, = = _medulla saxorum_ (_see_ porcelain clay). meer, = - = boundary stones, = = on _vena cumulata_, = = on _vena dilatata_, = = meissen. dumps from mines, = = _melanteria_, = =; ; indication of copper, = = melanterite, melos, island of, _menning_ (_see_ red-lead). _mergel_ (_see_ marl). metals, ; ; advantages and uses, = =; = = necessity to man, =xxv=; = - = not responsible for evil passions, = = _metreta_, mexico. patio process, mica, middle ages, mining law of, mills for grinding ore, = - =; mimes (_see also_ gnomes), mine captain, = =; mine manager, = =; = =; ; mineral kingdom, agricola's divisions of, minerals, ; ; ; compound, ; mixed, ; miners, = - =; = =; duties and punishments, = =; = = law (_see_ mining law). litigation among, = = slaves as, = = mines. abandonment of, = = conditions desirable, = - = investments in, = - = management of, = =; = = names of, = = mines royal, company of, mining (_see also_ sett, lease, claim, meer, _etc._). criticisms of, = - = harmless and honourable, = =; = =; = = methods of breaking ore, = - = stoping, = = mining clerk, = =; = =; = =; mining companies (_see_ companies, mining). mining foreman, = - =; frauds by, = - = mining law, - boundary stones, = = drainage requirements, = - = england, - europe, forfeiture of title, = - = france, greek and roman, middle ages, - right of overlord, landowner, state and miner, tunnels, = - = mining prefect, = =; = =; mining rights (_see_ mining law _and_ meer). mining terms, old english, ; mining tools, = - = buckets for ore, = - = buckets for water, = = trucks, = = wheelbarrows, = = _minium_, quicksilver from, red-lead, _minium secundarium_ (_see_ red-lead). mispickel (_mistpuckel_), _misy_ (the mineral), ; ; an indication of copper, = = use in parting gold and silver, _mitlere und obere offenbrüche_ (_see_ furnace accretions). _modius_, ; moglitz. tin working, = = moil, _molybdaena_, ; ; ; ; term for lead carbonates, ; molybdenite, _monetarius_ (_see_ coiners). money, assaying of, = - = morano glass factories, = = moravia. cupellation, = = stamp-milling, = = washing gold ore, = = mordants, mortar-box, = - =; = =; = =; mountains. formation of, = = mt. bermius. gold mines of, = =; mt. laurion, mines of, = =; - ; crushing and concentration of ores, cupellation, mining law, smelting appliances, xenophon on, = = mt. sinai. ancient copper smelting, ; muffle furnaces, = - =; = = muffles, = =; = =; refining silver, = - = mühlberg, battle of, x. _murrhina_ (_see_ chalcedony). muskets, = = mycenae. copper, silver-lead smelting, names of mines, = = naphtha, native copper, native iron, native minerals, = = native silver, = =; natron (_see_ _nitrum_). neolithic furnaces, neusohl, method of screening ore, = = newbottle abbey, nitocris, bridge of, nitric acid (_see also_ _aqua valens_), = - =; ; ; assay parting gold and silver, = = testing silver regulus with, = = use in cleaning gold dust, = = _nitrum_ (_see also_ soda), ; nomenclature, i; mining law, ; mining officials, ; _norici_, conveyance of ore, = = normans. mining law in england, notary, = =; nubia. early gold-mining, nuremberg, scale of weights, = = _obolus_, _ochra nativa_, ochre yellow, _offenbrüche_ (_see_ furnace accretions). olynthus. betrayal to philip of macedon, = = operculum, = =; orbis, = =; ore (_see various metals_, assaying, mining, _etc._). ore channels (_see_ canales). ore deposits, theory of, xiii; - ore dressing, = - = burning, = = hand spalling, = - = sorting, = - = _orguia_, = =; ; _orichalcum_ (_see_ _aurichalcum_). orpiment, ; ; colour of fumes, = = harmful to metals, = = indication of gold, etc., = = roasted from ore, = = use in assaying, = = outcrops, ; ox-blood in salt making, = = pactolus, gold sands of, park's process, parting gold from copper, = - = parting gold from silver, = - =; - antimony sulphide, = - =; - ; cementation, = - =; = - =; = = chlorine gas, ; electrolysis, ; nitric acid, = - =; ; ; nitric acid (in assaying), = - = sulphur and copper, = - =; ; sulphuric acid, ; partitions, passau, peace of, ix. _passus_, ; patio process, - pattinson's process, peak, the (_see_ high peak). _pentremites_, pergamum. brazen ox of, = = mines near, = =; peripatetics, xii. theory of ore deposits, = =; view of wealth, = = persians. ancient mining law, _pes_, ; pestles, = =; = = petroleum, - phalaris, brazen bull of, = = philosophy. knowledge necessary for miners, = = phoenicians. copper and bronze, in thasos, tin, - picks, = - = _pickschiefer_ (_see_ ash-coloured copper). placer mining, = - = _pleigeel_ (_see_ lead ochre). _pleiweis_ (_see_ white-lead). pleygang vein, = = _plumbago_, _plumbum candidum_, ; ; _plumbum cinereum_, ; _plumbum nigrum lutei coloris_, ; plummet level. standing, = =; suspended, = =; = =; pockets in alluvial sluices, = - = poisonous fumes (_see_ fumes). poland. cupellation, = = lead ore washing, = = lead smelting, = = _poletae_, tablets of the, poling copper, = - =; - pompeiopolis. arsenic mine at, _pompholyx_, ; - ; from copper refinings, = = from cupellation, = = from dust-chambers, = = from roasting ore, = = poisonous, = =; used for brass making, porcelain clay, potash, = - =; ; ; in _sal artificiosus_, = = pottery, egyptian, potosi, pozos de anibal, los, _pous_, ; _praefectus cuniculi_, _praefectus fodinae_ (_see_ mine manager). _praefectus metallorum_ (_see_ mining prefect). _praeses cuniculi_, _praeses fodinae_ (_see_ mining foreman). precious and base metals, primgap, _procurator metallorum_, prospecting, = = proustite, pumps, = - =; chain, = - = rag and chain, = - = suction, = - = _purgator argenti_ (_see_ silver refiner). purser, puteoli, = = pyrargyrite, _pyriten argentum_, pyrites (_see also_ cakes of melted pyrites), ; ; ; as a flux, = = assay for gold, = = in tin concentrates, = = latin and german terms, roasting, = - = roasting cakes of, = - = smelting for gold and silver, = =; = = used in making vitriol, _pyrites aerosus_ (_see_ copper pyrites). _pyrites aurei coloris_ (_see_ copper pyrites). quartz (_see also_ stones which easily melt), as a flux, an indication of ore, = = material of glass, silver ore, = = smelting of, = = _quarzum_ (_see_ quartz). quertze, quicksilver, ; ; ; amalgamation of gilt objects, = = amalgamation of gold dust, = = amalgamation of gold ores, = =; assaying methods, = = ore, - use in assaying gold ore, = = rag and chain pumps, = - = rake veins, rammelsberg. collapse of mines, = = discovery, early vitriol making, _rauchstein_, realgar, ; ; colour of fumes, = = harmful to metals, = = indication of ore, = = roasted from ore, = = _rederstein_ (_see_ _trochitis_). red-lead, ; ; use in parting gold from copper, = = use in parting gold from silver, = = refined salt, = =; = =; refinery for silver and copper, = - = refining gold from copper, = - = refining gold from silver, = - = refining-hearth, refining silver, = - =; ; refining silver from lead, = = reformation, the, v; viii. re-opening of old mines, = = revival of learning. agricola's position in, xiii. reward lease, in australian law, rhaetia, rhaetian alps. stamp milling in, = = ring-fire, = = rio tinto mines. roman methods of smelting, roman water-wheels, risks of mining, = - = rither (a horse), roasted copper, = =; ; roasting, = - =; heap roasting, = - = in furnaces, = = mattes, = - = prior to assaying, = = rocks, = =; rock-salt, = =; use in cementation, = = roman alum, romans. amalgamation, antimony, brass making, companies, copper smelting, - mining law, minium company, quicksilver, roasting, silver-lead smelting, washing of ore, rosette copper, = =; _rosgeel_ (_see_ realgar). ruby copper, ; ruby silver, ; assaying of, = = cupellation, = = _rudis_ ores, rust (_see_ iron-rust). sabines, = = _saigerdörner_ (_see_ liquation thorns). _saigerwerk_ (_see_ _stannum_). _salamander har_ (_see_ asbestos). salamis, battle of, sal-ammoniac, = =; ; in cements for parting gold and silver, = - = in making _aqua valens_, = = uses in cupellation, = = uses in making _aqua regia_, uses in parting gold from copper, = = _sal artificiosus_, = =; = =; in assaying, = = as a flux, = = salt, = =; = =; ; ; as a flux, = - = pans, = =; = = solidified juice, use in cementation, = =; use in parting gold from copper, = =; = = use in smelting ores, = =; = = wells, = - = salt made from ashes of musk ivy, ; _sal torrefactus_, = =; ; _sal tostus_, = =; ; saltpetre, = - =; ; ; as a flux, = =; = - =; = =; = = in smelting gold concentrates, = = uses in cementation, = =; uses in making nitric acid, = =; = =; = =; = = uses in melting silver nitrate, = = sampling copper bullion, = = sand, = = _sandaraca_ (_see_ realgar). sandiver (_see_ glass-galls). _sarda_ (_see_ carnelian). saxony. high peak customs from, ; political state in agricola's time, viii; ix. reformation, ix. _saxum calcis_ (_see_ limestone). scales of fineness, ; scapte-hyle, mines of, schemnitz. age of mines, = = gunpowder for blasting, pumps, = = schist, _schistos_ (_see_ ironstone). schlackenwald. ore washing, = = schmalkalden league, ix. schmalkalden war, ix; x. schneeberg, =xxxi=; vi. cobalt, = = depth of shafts, ore stamping, shares, = = st. george mine, = =; ; _schwartz-atrament_ (_see_ _melanteria_ _and_ _sory_). scorification assay, = = scorifier, = =; = =; assays in, = =; = = screening ore (_see_ sifting ore). screens (_see also_ screening), in stamp-mill, = = _scriba fodinarum_ (_see_ mining clerk). _scriba magistri metallicorum_ (_see_ bergmeister's clerk). _scriba partium_ (_see_ share clerk). scum of lead from cupellation, = = scythians. wealth condemned, = =; = = seams in the rocks, = =; ; indications of ore, = =; = = sea-water, salt from, = - = _sesterce_, sett, settling pits, = =; shaft-houses, = = shafts, = - =; = - = surveys of, = - = _venae cumulatae_, = = shakes, share clerk, = =; = =; share in mines (_see_ companies, mining). shears for cutting native silver, = = shift, = =; shoes (stamp), = - =; shovellers, = =; = =; _sideritis_ (_see_ lodestone). _siegelstein_ (_see_ lodestone). sieves. for charcoal, = = for crushed ore, = - =; = = sifting ore, = - = _signator publicus_ (_see_ notary). _silberweis_ (_see_ mica). _silex_, ; silver (_see also_ assaying, liquation, parting, refining, _etc._), ; ; amalgamation, ; assaying, = - = cupellation, = - =; = = "drying" copper residues from liquation, enrichment in copper bottoms, = =; exhausted liquation cakes, indicated by bismuth, etc., = = liquation, = - =; ; ; parting from gold (_see_ parting gold and silver). parting from iron, = =; precipitation from solution in copper bowl, = = refining, = - =; ; smelting of ores, = - =; = =; = =; = =; = =; = = use in clarification of nitric acid, = =; silver, ruby (_see_ ruby silver). silver glance, assaying, = = cupellation, = = dressing, = = silver-lead alloy (_see_ _stannum_, _etc._). silver ores, = =; assaying, = - = assaying cupriferous ores, = = fluxes required in assaying, = = smelting cupriferous ores, = - = silver-plating, silver refiner, = =; silver refining (_see_ refining). silver veins, = = singing by miners, = = sintering concentrates, = = slags (_see also_ liquation slags), from blast furnace, = =; = = from liquation, ; ; slaves as miners, = =; in greek mines, = =; ; slough (tunnel), sluices, = =; = - = smallite, smalt, _smega_, smelters, smelting (_see also various metals_), = - =; - assaying compared, = = building for, = - = objects of, = = _smirgel_ (_see_ emery). _smiris_ (_see_ emery). smyrna. mines near, snake-bites, soda (_see also_ _nitrum_), = =; = =; ; as a flux, = =; = = historical notes, ; solidified juice, sole, solidified juices (_see_ juices, solidified). _solifuga_, = =; sorters, sorting ore, = - = _sory_, ; ; sows, = =; = =; spain (_see also_ lusitania). ancient silver-lead mines, ; ancient silver mines of carthage, = = ancient tin mines, - spalling ore, = - = _spangen_ (_see_ _trochitis_). _spanschgrün_ (_see_ verdigris). spartans. gold and silver forbidden, = =; = = interference with athenian mines, spat (_see_ heavy spar). spelter, sphalerite, _spiauter_, _spiesglas_ (_see_ _stibium_). spines of fishes for cupels, = = _spodos_, = =; ; ; _spuma argenti_ (_see_ litharge). staffordshire. first pumping engine, stalagmites, stall roasting, = - = stamp, for breaking copper cakes, = - = for crushing crucible lining, = - = stamping refined silver, = = stamp-mill, = - =; - ; wet ore, = - =; = - = standing plummet level (_see_ plummet level). stannaries, _stannum_, ; ; ; steel, = - =; - ; _steiger_, _steinmarck_ (_see_ porcelain clay). stemple (stull), stephanite, sternen mine, = =; steward (of high peak mines), st. george mine (schneeberg), = =; ; _stibium_ (_see also_ antimony _and_ antimony sulphide), ; ; ; flux to be added to, = = in assaying, = - = in cementation, = - = indication of silver, = = in making nitric acid, = = in parting gold and silver, = - =; = = in parting gold from copper, = = in treatment of gold concentrates, = =; = = stibnite, ; st. lorentz mine, = =; = = stockwerke (_see_ _vena cumulata_). stoics. views on wealth, = = _stomoma_, = = stone juice, ; stones. agricola's view of, ; ; various orders of fusibility, = = "stones which easily melt" (_see also_ quartz), ; as a flux, = =; = =; in making nitric acid, = = in smelting, = =; = =; = = smelting of, = = stool (of a drift), stope, = = stoping, = = _venae cumulatae_, = = _venae dilatatae_, = =; = = strake, = - =; ; canvas, = - =; = =; = =; egyptians, greeks, short, = - =; washing tin concentrates, = - = strata, = = streaming, = - = stringers, = =; ; ; indication of ore, = = mining method, = = styria, = = subterranean heat, ; suction pumps, = - = sulphides, ; sulphur, = - =; ; colour of fumes, = = harmful to metals, = = in assaying, = - = in parting gold from copper, = =; in parting gold from silver, = - =; ; in smelting gold dust, = = roasted from ores, = =; = = solidified juice, sulphur "not exposed to the fire," = =; = =; surveyor's field, = =; = =; surveying, = - =; necessary for miners, = = rod, = - = suspended plummet level (_see_ plummet level). swiss compass, = =; swiss surveyors, = = _symposium_, = = tap-hole, = =; = = tappets, = =; = =; tapping-bar, = = tarshish, tin trade, tartar (cream of), ; _tectum_ (hangingwall), _terra sigillata_ (_see_ lemnian earth). "tests", refining silver in, = - =; ; _thaler_, thasos, mines of, = =; = =; _theamedes_, theodosian code. mines, thorns (_see_ liquation thorns). thuringia. roasting pyrites, = = sluices of gold washing, = = tigna (wall plate), timbering. of ladderways and shafts, = =; = =; = = of stopes, = = of tunnels and drifts, = - = tin, - ; ; alluvial mining, = - = assaying ore, = = assaying for silver, = = colour of fumes, = = concentrates, = - =; = - = cornish treatment, refining, = - = smelting, = - = stamp-milling, = - = streaming, = - = washing, = =; = =; = = _tincar_ or _tincal_ (_see_ borax). tithe gatherer, = =; = =; = =; tithe on metals, = =; _toden kopff_, _tofstein_ (_see_ _tophus_). tolfa, la (_see_ la tolfa). tools, = - = _topfstein_ (_see_ _tophus_). _tophus_, ; ; as a flux, = =; = =; = = tortures. with metals, = = without metals, = = touch-needles, = - =; touchstone, = - =; ; ; ; mineral, uses, = =; = =; = = trade-routes. salt-deposits influence on, transport of ore, = - = trent, bishop of. charter ( ), triangles in surveying, = - = tripoli, _trochitis_, = =; trolley, = =; = =; = = troy. lead found in, troy weights, ; ; trucks, = = tunnels, = =; law, = - = surveys of, = - = timbering, = = turin papyrus, ; turn (winze), _tuteneque_, _tuttanego_, tutty, twitches of the vein, twyer, tye, type. _stibium_ used for, ; tyrants. inimical to miners, = = tyrolese. smelting, = =; = = ulcers, = =; _uncia_ (length), = =; ; _uncia_ (weight), ; undercurrents (_see_ sluices). united states. apex law, _vectiarii_ (_see_ windlass men). veins, = =; = - =; = - =; barren, = =; = = direction of, = - = drusy, = =; = =; = = hardness variable, = = indications, = - = intersections of, = =; = =; = =; = =; = = _vena_. use of term, ; _vena cumulata_, = =; = =; = =; ; mining method, = = mining rights, = = _vena dilatata_, = =; = =; = =; = - =; ; junctions with _vena profunda_, = =; = = mining method, = - = mining rights, = - = washing lead ore from, = = _vena profunda_, = =; = =; = =; = =; = =; = =; = =; ; cross veins, = = functions, = =; = =; = =; = = mining rights, = - = venetian glass, factories, = = in assaying, = =; = =; = = in cupellation, = = venice. glass-factories, = = parting with nitric acid, scale of weights, = = ventilation, = - =; = = with bellows, = - = with fans, = - = with linen cloths, = = with windsails, = - = verdigris, ; ; ; in cementation, = =; = = indication of ore, = = in making nitric acid, = = in parting gold from copper, = = vermilion. adulteration with red-lead, poisonous, = = villacense lead, = =; vinegar. use in breaking rocks, = =; use in cleansing quicksilver, = = use in roasting matte, = = use in softening ore, = = _virgula divina_ (_see_ divining rod). vitriol, = =; ; ; ; in assaying, = - = in cementation, = =; indication of copper, = = in making nitric acid, = - = in roasted ores, = = in _sal artificiosus_, = = native, native blue, native white, red, white, volcanic eruptions, washers, washing ore (_see also_ concentration, screening ore, _etc._), = - = water-bags, = - =; = = water-buckets, = - = water-wheels, = =; = =; = =; = = water-tank, under blast furnaces, = - = wealth, = - = wedges, = = weights, = - =; - ; ; _weisser kis_, _werckschuh_, ; westphalia. smelting lead ore, = = spalling ore, = = wheelbarrows, = = whims, = - = white-lead, ; ; ; white schist, = =; = =; ; winding appliances (_see_ hauling appliances). windlasses, = =; = =; windlass men, = =; winds. greek and roman names, = = sailors' names, = =; = = winds (winze), windsails, = - = winzes, wittenberg, capitulation of, ix. wizards. divining rods, = = workmen, = =; = = woughs, _zaffre_, zeitz, xi. zinc (_see also_ _cadmia_ _and_ cobalt). historical notes, - ; minerals, - zinck (_see_ zinc). zinc oxides, ; zinc sulphate (_see_ vitriol). _zincum_ (_see_ zinc). _zoll_, ; zwickau, vi. _zwitter_, index to persons and authorities. note.--the numbers in heavy type refer to the text; those in plain type to the footnotes, appendices, etc. acosta, joseph de, aeschylus. amber, aesculapius. love of gold, = = africanus (alchemist), =xxvii=; xxviii agatharchides. cupellation, egyptian gold mining, ; ; fire-setting, agathocles. money, = = agathodaemon (alchemist), =xxvii=; xxviii agricola, daniel, agricola, georg (a preacher at freiberg), agricola, georgius. assaying, biography, v-xvi founder of science, xiv geologist, xii; ; interest in _gottsgaab_ mine, vii; mineralogist, xii; ; paracelsus compared with, xiv real name, v works, appendix a see also: _bermannus._ _de animantibus._ _de natura eorum_, etc. _de natura fossilium._ _de ortu et causis._ _de peste._ _de precio metallorum._ _de re metallica._ _de veteribus metallis._ etc. agricola, rudolph, albert the brave, duke of meissen, viii albertus magnus (albert von bollstadt), xxx; alluvial gold, = = cementation, metallic arsenic, metals, saltpetre, zinc, albinus, petrus, v; cuntz von glück, alpinus, prosper, alyattes, king of lydia. mines owned by, = =; american institute of mining engineers, ; anacharsis. invention of bellows, anacreon of teos. money despised by, = =; = = anaxagoras. money despised by, = = anna, daughter of agricola, vii anna, wife of agricola, vii antiphanes. on wealth, = = apollodorus, apulejus (alchemist), =xxvii=; xxix archimedes. king hiero's crown, = = machines, ardaillon, edouard. mt. laurion, ; ; aristippus. gold, = =; = = aristodemus. money, = = aristotle, xii; amber, athenian mines, ; burning springs, coal, cupellation, distillation, lodestone, nitrum, ores of brass, quicksilver, silver from forest fires, theory of ore deposits, wealth of, = = arnold de villa nova. (_see_ villa nova, arnold de). athenaeus. silver from forest fires, augurellus, johannes aurelius (alchemist), =xxvii=; xxx augustinus pantheus (alchemist), =xxvii= augustus, elector of saxony, =ix= dedication of _de re metallica_, =xxv= letter to agricola, =xv= avicenna, xxx; bacon, roger, xxx; saltpetre, ; badoarius, franciscus, =xxvii= balboa, v. n. de, v ballon, peter, barba, alonso, ; barbarus, hermolaus, =xxvii= barrett, w. f., becher, j. j., bechius, philip, xv beckmann, johann. _alumen_, amalgamation, _nitrum_, parting with nitric acid, stamp-mills, _stannum_, tin, _bergbüchlein_ (_see_ _nützlich bergbüchlin_). _bergwerks lexicon_, ; ; berman, lorenz, vi; _bermannus_, ; ; vi arsenical minerals, bismuth, ; _cadmia_, cobalt, fluorspar, _molybdaena_, schist, shafts, zinc, berthelot, m. p. e., ; berthier, bias of priene. wealth, = =; = = biringuccio, vannuccio, agricola indebted to, =xxvii= amalgamation of silver ores, assaying, assay ton, brass making, clarifying nitric acid, copper refining, copper smelting, cupellation, liquation, manganese, parting precious metals, ; ; roasting, steel making, _zaffre_, boeckh, august, boerhaave, hermann, xxix borlase, w. c. bronze celts, borlase, william. cornish miners in germany, born, ignaz edler von, boussingault, j. b., boyle, robert. divining rod, brough, bennett, bruce, j. c., brunswick, duke henry of (_see_ henry, duke of brunswick). budaeus, william (guillaume bude), ; cadmus, calbus (_see also_ _nützlich bergbüchlin_), ; =xxvi=; xxvii alluvial gold, = = caligula. gold from _auripigmentum_, callides (alchemist), =xxvii=; xxviii callimachus. on wealth, = = camerarius, =viii= canides (alchemist), =xxvii=; xxviii carew, richard. cornish mining law, cornish ore-dressing, carlyle, w. a. ancient rio tinto smelting, carne, joseph. cornish cardinal points, casibrotius, leonardus, vi _castigationes in hippocratem et galenum_, castro, john de, chabas, f. j., chaloner, thomas, chanes (alchemist), =xxvii=; xxviii charles v. of spain, =ix= agricola sent on mission to, =x= chevreul, m. e., _chronik der stadt freiberg_, cicero. divining rod, wealth of, = = cincinnatus l. quintius, = = circe. magic rod, = = cleopatra. as an alchemist, =xxvii=; xxix collins, a. l. columbus, christopher, v columella, moderatus, =xxv=; =xxvi= comerius, =xxvii=; xxix _commentariorum ... libri vi._, conrad (graf cuntz von glück), = =; corduba, don juan de, cortes, hernando, =v= cramer, john, crassus, marcus. love of gold, = = crates, the theban. money despised by, = = croesus, king of lydia. mines owned by, = =; ctesias. divining rod, ctesibius. machines, curio, claudius. love of gold, = = curius, marcus. gold of samnites, = =; = = dana, j. d., alum, copiapite, emery, lemnian earth, minerals of agricola, zinc vitriol, danae. jove and, = = d'arcet, j. parting with sulphuric acid, day, st. john v. ancient steel making, _de animantibus subterraneis_, ; =vii= editions, gnomes, = =; _de bello adversus turcam_, _de inventione dialectica_, _de jure et legibus metallicis_, = =; _de medicatis fontibus_, _de mensuris et ponderibus_, editions, weights and measures, = =; _de metallis et machinis_, democritus (alchemist), =xxvii=; xxviii demosthenes. mt. laurion mines, ; _de natura eorum quae effluunt ex terra_, ; = = dedication, vii editions, _de natura fossilium_, ; ; iii; xii alum, amber, antimony, argol, arsenical minerals, asbestos, bismuth, bitumen, borax, brass making, _cadmia_, _caldarium_ copper, camphor, _chrysocolla_, coal, cobalt, copper flowers, ; copper scales, crinoid stems, emery, fluorspar, goslar ores, goslar smelting, iron ores, iron smelting, jet, _lapis judaicus_, lead minerals, mannsfeld ores, _melanteria_, mineral kingdom, _misy_, _molybdaena_, native metals, petroleum, _pompholyx_, ; pyrites, quicksilver, _rudis_ minerals, sal-ammoniac, silver glance, _sory_, _spodos_, _stannum_, stones which easily melt, sulphur, _tophus_, touchstone, white schist, zinc, _de ortu et causis subterraneorum_, ; ; iii; vii; xii; xiii earths, gangue minerals, gold in alluvial, = = ground waters, juices, metals, solidified juices, stones, touchstone, veins, _de ortu metallorum defensio ad j. scheckium_, _de peste_, ; viii _de precio metallorum et monetis_, ; mention by agricola, = =; = = _de putredine solidas partes_, etc., _de re metallica_, i; xiii; xiv-xvi editions, ; xiv title page, =xix= de soto, fernandes, v _de terrae motu_, _de varia temperie sive constitutione aeris_, _de veteribus et novis metallis_, ; ; vii; =xxvi=; agricola's training, vi conrad, discovery of mines, = =; ; _gottsgaab_ mine, devoz (de voz), cornelius, ; diodorus siculus, alum, bitumen, cupellation, drainage of spanish mines, egyptian gold mining, fire-setting, lead, silver from forest fires, = = tin, diogenes laertius, ; ; dioscorides, ; alum, antimony, argol, arsenic minerals, asbestos, bitumen, brass making, burned lead, _cadmia_, _chalcitis_, copper flowers, ; copper smelting, cupellation, distillation apparatus, dust-chambers, ; emery, lead, lead minerals, lemnian earth, litharge, lodestone, _melanteria_, _misy_, naphtha, _pompholyx_, ; quicksilver, ; red-lead, sal-ammoniac, _sory_, _spodos_, verdigris, vitriol, white-lead, diphilos, ; diphilus (poet). gold, = = _dominatores saxonici_, draud, g., dudae. alum trade, elizabeth, queen of england. charters to alum makers, ; dedication of italian _de re metallica_ to, xv importation of german miners, ; eloy, n. f. j., entzelt (enzelius, encelio), erasmus, vi; viii; xiv ercker, lazarus. amalgamation, liquation, ; nitric acid preparation, parting gold and silver, ; eriphyle. love of gold, = = ernest, elector of saxony, viii euripides. amber mentioned by, plutus, = =; = = ezekiel, prophet. antimony, cupellation, tin, fabricius, george. agricola's death, x friendship with agricola, viii laudatory poem on agricola, =xxi= letters, ix; x; xiv; xv posthumous editor of agricola, ; fairclough, h. r., iii farinator, mathias, xxvi ferdinand, king of austria. agricola sent on mission to, x badoarius sent on mission to, =xxvii= ferguson, john. editions of _de re metallica_, xvi; feyrabendt, sigmundi, xv figuier, l., flach, jacques. aljustrel tablet, florio, michelangelo, xv förster, johannes, vi francis, col. grant, ; francis i., king of france, ix frederick, elector of saxony, viii; ix froben, publisher of _de re metallica_, xiv; xv frontinus, sextus julius, galen. agricola's revision of, ; vi lemnian earth, mention by agricola, _galerazeya sive revelator secretorum_, etc., gama, vasco da, v ganse (gaunse), joachim, ; gatterer, c. w., geber, =xxvii=; xxx; alum, = = assaying, cementation, cupels, nitric acid, origin of metals, precipitation of silver nitrate, _genesis, book of_, xii; george, duke of saxony, ix; = =; gesner, conrad, gibbon, edward, glauber, j. r., glück, cuntz von (_see_ conrad). gmelin, j. f., göcher, c. g., godolphin, sir francis, gowland, william. ancient bronze, ; ; early smelting, graecus, marcus. saltpetre, grommestetter, paul, grymaldo, leodigaris, xvi gyges, king of lydia. mines owned by, = =; hannibal. alps broken by vinegar, spanish mines, = =; hardy, william, heath, thomas. on hero, heliodorus (alchemist), =xxvii=; xxix henckel, j. f., ; ; hendrie, r., hennebert, e., henry, duke of brunswick, vii henry, duke of meissen, ix hermes (alchemist), =xxvi=; xxviii hermes (mercury). magic rod, hero. underground surveying, herodotus. alum, bitumen, lead, mines of thrace, _nitrum_, hertel, valentine, xiv hiero, king of syracuse. crown, hill, john, _auripigmentum_, himilce, wife of hannibal, hippocrates. cupellation, ; lodestone, hiram, king of tyre. mines, hofmann, dr. r. biography of agricola, v; xi; ; homer. amber, divining rod, = =; lead, smelting, steel, sulphur, tin, hommel, w. early zinc smelting, horace. metals, = = wealth, = =; = = hordeborch, johannes, vii houghstetter, daniel, houghton, thomas, humphrey, william. jigging sieve, hunt, robert. roman lead smelting, inama-sternegg, k. t. von, _interpretatio rerum metallicarum_ (_see_ _rerum metall. interpretatio_). irene, daughter of agricola, vii jacobi, g. h. biography of agricola, v; calbus, xxvii; jagnaux, raoul. ancient zinc, jason. golden fleece, jeremiah. bellows, cupellation, lead smelting, _nitrum_, jezebel. use of antimony, job. refining silver, johannes (alchemist), =xxvii=; xxviii john, elector of saxony, ix john, king of england. mining claims, john frederick, elector of saxony, ix josephus. dead sea bitumen, jove. danae legend, = = justin, = = juvenal. money, = = karsten, k. j. b. liquation, ; ; ; ; ; kerl, bruno. liquation, könig, emanuel, xv könig, ludwig, xv kopp, dr. hermann, ; lampadius, g. a., lasthenes. love of gold, = = _latin grammar_ (agricola), leonardi, camilli, leupold, jacob, xv; _leviticus_. leprosy of walls, lewis, g. r, lewis, libavis, andrew, lieblein, j. d. c., linnaeus, charles, livy. hannibal's march over the alps, lohneys, g. e. liquation, ; parting with antimony, zinc, ; lucretia, daughter of agricola, vii lucretius. forest fires melting veins, = = lully, raymond, =xxvii=; xxx luscinus, fabricius. gold, = =; = = luther, martin, v; vi; viii; ix lycurgus (athenian orator). prosecution of diphilos, ; lycurgus (spartan legislator). wealth prohibited by, = =; = = magellan, f. de, v maltitz, sigismund, manlove, edward, ; marbodaeus, marcellinus, ammianus. on thucydides, marcellus, nonius, xxxi maria the jewess, =xxvii=; xxviii mathesius, johann. cobalt, conrad mentioned by, _de re metallica_, xiv king hiram's mines, matthew paris. cornish miners in germany, maurice, elector of saxony, =xxv=; viii; ix; x mawe, j., maximilian, emperor, = =; meissen, dukes of (_see under personal names_: albert, henry, _etc._). melanchthon. relations with agricola, viii; x menander. riches, = = mercklinus, g. a., mercury (_see_ hermes). merlin (magician), =xxvii=; xxx meurer, wolfgang. letters, ix; x meyer, ernst von, ; meyner, matthias, vii midas, king of lydia. mines owned by, = =; miller, f. b., minerva. magic rod, = = morris, w. o'c., mosellanus, petrus, vi moses. bitumen, lead, refining gold, rod of horeb, ; = = müller, max. ancient iron, naevius. money, = = nash, w. g. rio tinto mine, naumachius. gold and silver, = = neckam, alexander. compass, newcomen, thomas, nicander. on coal, nicias. sosias and slaves of, = =; _nützlich bergbüchlin_, ; =xxvi=; xxvii alluvial gold, bismuth, ; compass, ; ore-deposits, ore-shoots, veins, ; ; olympiodorus (alchemist), =xxvii=; xxx oppel, van (_see_ van oppel). orus chrysorichites (alchemist), =xxvii=; xxviii osthanes (alchemist), =xxvii=; xxix otho the great, otho, prince, ovid. mining censured by, = = pandulfus anglus, =xxvi= pantaenetus. demosthenes' oration against, ; pantheus, augustinus (alchemist), =xxvii= paracelsus, xiv; xxx divining rod, zinc, ; paris, matthew (_see_ matthew paris). pebichius (alchemist), =xxvii=; xxviii pelagius (alchemist), =xxvii= pennent, thomas, percy, john. cementation, ; cupellation, liquation, parting with antimony, ; peregrinus, petrus. compass, petasius (alchemist), =xxvii=; xxviii petrie, w. m. f. egyptian iron, mt. sinai copper, pettus, sir john, xvi; phaenippus. demosthenes' oration against, ; phaeton's sisters, pherecrates, =xxvi= philemon. riches, philip of macedonia, philip, peter, phillips, j. a., philo. lost work on mining, =xxvi= phocion. bribe of alexander, = =; = = phocylides. gold, = = photius, fire-setting, pindar. wealth, = =; pius ii, pope. alum maker, pizarro, f., =v= plateanus, petrus, xiv plautus. gold, = = pliny (caius plinius secundus), =xxvi=; alluvial mining, ; alum, amalgamation, amber, antimony, argol, _arrhenicum_, asbestos, bitumen, = =; brass, british miners, cadmia, cementation, chrysocolla, copper flowers and scales, ; copper smelting, cupellation, drainage of spanish mines, _electrum_, fire-setting, galena, glass, ; hannibal's silver mine, = =; hoisting ore, = =; iron, jew-stone, lead, lemnian earth, litharge, = =; ; lodestone, manganese (?), metallurgical appliances, _misy_, _molybdaena_, ; naphtha, _nitrum_, ore-dressing, outcrops, _pompholyx_, protection from poison, quicksilver, red-lead, roasting, sal-ammoniac, salt from wood, silver-lead smelting, _sory_, _spodos_, _stannum_, tin, spanish, _tophus_, touchstone, = =; turfs in sluices, = =; _vena_, ventilation with wet cloths, = =; verdigris, vitriol, white-lead, plutarch, pluto, = = polybius. ore washing, silver-lead smelting, ; polymnestor, king of thrace. love of gold, = =; = = pörtner, hans, posepny, franz, posidonius. asphalt and naphtha, drainage of spanish mines, silver from forest fires, priam, king of troy. gold mines of, = =; _probierbüchlein_, ; =xxvi= amalgamation, antimony, assaying, assay ton, bismuth, cementation, nitric acid, parting, ; ; precipitation of silver nitrate, residues from distillation of nitric acid, ; roasting, stock fluxes, ; touchstone, propertius. gold, = = pryce, william. adam's fall, divining rod, juices, ore-deposits, stamp-mill, stringers, psalms. silver refining, pulsifer, wm. h., pygmalion. love of gold, = =; = = rachaidibus (alchemist), =xxvii= rameses i. map of mines, rameses iii. leaden objects dating from, raspe, r. e., rawlinson, george, ray, p. chandra. indian zinc, raymond, rossiter w., _rechter gebrauch der alchimey_, _rerum metallicarum interpretatio_, ; vii; reuss, f. a., richter, a. d., v; rodianus (alchemist), =xxvii=; xxviii rössler, b., royal geological society of cornwall, rühlein von kalbe (_see_ calbus). salmoneus. lightning, = = sandwich, earl of, trans. barba's book, sappho. wealth, = = savery, thomas, saxony, dukes and electors of. (_see under personal names_: albert, ernest, _etc._). schliemann, h., schlüter, c. a. artificial zinc vitriol, copper refining, cupellation, liquation, ; parting with sulphur, schmid, f. a., v; xv; schnabel and lewis, scott, sir walter. "antiquary," seneca. wealth of, = = seneferu. copper mines, seti i. map of mine, shaw, peter, xxviii shoo king. copper and lead, ; iron, shutz, christopher, sigfrido, joanne. ed. agricola's works, xv socrates. riches, = =; = =; = =; = = solinus, c. julius. _solifuga_, = =; solomon, king. cobalt in mines, solon. scarcity of silver under, sosias, the thracian. slaves employed by, = = stahl, g. e., staunton, sir george, stephanus (alchemist), =xxvii=; xxx stephenson, george, strabo, arsenical minerals, asbestos, asphalt, ; bellows, cementation, cupellation, drainage of spanish mines, forest fires melting veins, high stacks, lydian mines, ; mt. laurion, silver-lead smelting, spanish ore-washing, zinc (?), strato. lost work on mines, =xxvi=; =xxvii=; xii struve, b. g., synesius (alchemist), =xxvii=; xxix tantalus, taphnutia (alchemist), =xxvii=; xxviii tapping, thomas, thales of miletus. amber, themistocles. athenian mine royalties, theodor, son of agricola, vii theognis. cupellation, on greed, = = plutus, = = refining gold, _theological tracts_ (agricola), theophilus (alchemist), =xxvii=; xxviii theophilus the monk, brass making, calamine, cementation, copper refining, copper smelting, cupels, divining rod, liquation, metallurgical appliances, parting with sulphur, roasting, theophrastus, xii; amber, arsenical minerals, asbestos, assaying, coal, copper minerals, copper ore, emery, lodestone, lost works, =xxvi=; origin of minerals, parting precious metals, quicksilver, ; touchstone, verdigris, vermilion, white-lead, ; thompson, lewis, thoth. hermes trismegistos, xxix thotmes iii. lead, ; thucydides. mining prefect, = =; ; tibullus. wealth condemned by, = = timocles. riches, = = timocreon of rhodes. plutus, = = tournefort, joseph p. de, tubal cain. instructor in metallurgy, tursius, = = twain, mark. merlin, xxx _typographia mysnae et toringiae_, ulloa, don antonio de, ulysses. magic rod, = = valentine, basil, xxx; antimony, divining rod, parting with antimony, zinc, valerius, son of agricola, vii van der linden, j. a., van oppel, xiii; varro, marcus, =xxvi= vasco da gama (_see_ gama, vasco da). veiga, estacia de, velasco, dom pedro de, veradianus (alchemist), =xxvii=; xxviii villa nova, arnold de (alchemist), =xxvii=; xxx virgil. avarice condemned by, = = vitruvius, amalgamation, hiero's crown, pumps, ; red-lead, surveying, verdigris, white-lead, vladislaus iii., king of poland, = = von oppel (_see_ van oppel). voz, cornelius de (_see_ devoz, cornelius). wallerius, j. g., ; watt, james, watt, robert, xxvii wefring, basilius, xiv weindle, caspar, weinart, b. g., weller, j. g., v werner, a. g., xiii; wilkinson, j. gardner. bitumen, egyptian bellows, egyptian gold-washing, williams, john, winkler, k. a., wrotham, william de, ; ; xenophon. athenian mines, = =; = =; ; fruitfulness of mines, = = mining companies, mine slaves, ; quoted by agricola, = =; = = zimmerman, c. f., zosimus (alchemist), =xxvii=; xxix index to illustrations. alum making, = = amalgamation mill, = = ampulla, = =; = = argonauts, = = assay balances (_see_ balances). assay crucible, = = assay furnaces. crucible, = = muffle, = =; = = balances, = = baling water, = = bars, for furnace work, = =; = = batea, = = bellows. for blast furnaces, = =; = =; = =; = =; = = for mine ventilation, = =; = =; = = for tin furnace, = = bismuth smelting, = =; = =; = =; = = bitumen making, = = bitumen spring, = = bowls for alluvial washing (_see also_ batea), = = buckets. for hoisting ore, = = for hoisting water, = = buddle, = =; = =; = =; = = building plan for refinery, = = building plan for smelter, = = chain pumps, = =; = =; = = _chrysocolla_ making, = = circular fire (_see_ ring-fire). clay washing, = =; = = compass, = =; = =; = =; = = copper mould for assaying, = = copper refining, = =; = = copper refining furnace, = = crane. for cupellation furnace, = = for liquation cakes, = = crowbars, = = cupel, = = mould, = = cupellation furnace, = =; = =; = = at freiberg, = = in poland, = = cutting metal, = = descent into mines, = = dipping-pots, = =; = =; = =; = =; = =; = = distillation (_see_ nitric acid _and_ quicksilver). divining rod, = = dogs packing ore, = = drifts, = = drying furnace for liquation, = =; = =; = = dust chambers, = =; = = fans, ventilation, = =; = =; = =; = = fire-buckets, = = fire pump, = = fire-setting, = = forehearth, = =; = =; = =; = =; = =; = =; = = frames (or sluices) for washing ore or alluvial, = - =; = - =; = - = furnaces. assaying (_see_ assay furnaces). blast, = =; = =; = =; = =; = =; = =; = =; = =; = =; = =; = =; = = copper refining, = = cupellation, = =; = =; = =; = =; = = distilling sulphur, = = enriching copper bottoms, = = glass-making, = =; = =; = =; = = iron smelting, = =; = = lead smelting (_see also_ furnaces, blast), = = liquation, = =; = =; = =; = =; = = nitric acid making, = = nitric acid parting, = = parting precious metals with antimony, = = ditto cementation, = = quicksilver distillation, = - = refining silver, = =; = =; = = roasting, = = steel making, = = tin burning, = = tin smelting, = = gad, = = glass making, = = furnaces, = =; = =; = = ground sluicing, = =; = =; = =; = =; = = hammers, = = with water-power, = =; = = heap roasting, = =; = = hearths. for bismuth smelting, = =; = = for heating copper cakes, = = for melting lead, = = for melting lead cakes, = = for refining tin, = = for roasting, = = hemicycle, = = hoe, = = _intervenium_, = = iron fork for metal, = = iron hook for assaying, = = iron smelting, = =; = = iron tools, = = jigging sieve, = = ladders, = = ladle for metal, = = lead mould for assaying, = = liquation cakes. dried, = = liquation cakes, exhausted, = = liquation furnaces, = =; = =; = =; = =; = = lye making, = = matte roasting, = =; = = meers, shape of, = =; = =; = =; = =; = = mills for grinding ore, = =; = = muffle furnaces, = =; = = muffles, = = nitric acid making, = = _nitrum_ pits, = = _operculum_, = = _orbis_, = a= parting precious metals. with antimony, = = by cementation, = = with nitric acid, = = with sulphur, = = picks, = = plummet level. standing, = = suspended, = = pumps. chain, = =; = =; = = duplex suction, = =; = =; = = rag and chain, = =; = =; = =; = = suction, = =; = =; = =; = =; = =; = = quicksilver distillation, = =; = =; = =; = =; = = rag and chain pumps, = =; = =; = =; = =; = = rammers for fire-clay, = =; = = ring-fire, for parting with sulphur, = = roasting (_see also_ heap _and_ stall roasting), = =; = =; = =; = =; = =; = = rosette copper making, = = salt. boiling, = =; = =; = = caldron, = =; = = evaporated on faggots, = = pans, = = wells, = = saltpetre making, = = saxon lead furnace, = = scorifier, = = seams in the rocks, = =; = =; = =; = =; = = shafts. inclined, = = timbering, = = vertical, = =; = = shears for cutting metal, = = shield for muffle furnace, = = sifting ore, = =; = =; = =; = =; = =; = =; = =; = = silver. cakes, cleansing of, = =; = = refining, = =; = =; = =; = = sleigh for ore, = = sluicing tin, = =; = =; = =; = = smelter, plan of building, = = soda making, = = sorting ore, = =; = = spalling ore, = =; = =; = = stall roasting. matte, = =; = = ore, = =; = = stamp-mill, = =; = =; = =; = =; = =; = =; = =; = = for breaking copper cakes, = = stamps, = = steel furnace, = = strake, = =; = =; = =; = =; = =; = =; = =; = = canvas, = =; = =; = =; = =; = = streaming for tin, = = stringers. associated, = = _fibra dilatata_, = = _fibra incumbens_, = = oblique, = = transverse, = = surveying. rods, = a= shafts and tunnels, = = triangles, = =; = =; = =; = =; = =; = =; = = suction pumps (_see_ pumps). sulphur making, = =; = = tap-holes in furnaces, = = tapping-bar, = =; = = "tests" for refining silver, = =; = = timbering. shafts, = = tunnels, = = tin. bars, = = burning, = = refining, = = smelting, = =; = = touch-needles, = = trays for washing alluvial, = = tread whim, = = trough, = = for washing alluvial, = =; = = trucks, = = tunnels, = =; = =; = =; = = timbering, = = veins. barren, = = beginning of, = = cavernous, = = curved, = = end of, = = head of, = = horizontal, = = intersections of, = =; = =; = =; = =; = = solid, = = strike of, = =; = = _vena cumulata_, = =; = = _vena dilatata_, = =; = =; = =; = =; = =; = =; = = _vena profunda_, = =; = =; = =; = =; = =; = =; = =; = = ventilating with damp cloth (_see also_ bellows, fans, and windsails), = = vitriol making, = =; = =; = =; = =; = = wagons, for hauling ore, = = washing ore (_see_ sifting ore). water tanks, under furnaces, = = wedges, = = weights, for assay balances, = = westphalian lead smelting, = = wheelbarrows, = = whims. horse, = =; = = tread, = = windlasses, = =; = =; = = winds, direction of, = = windsails for ventilation, = =; = =; = = transcriber's notes. this document includes quotes from very early authors. as such, it's no surprise that there are many spelling and punctuation irregularities. also the authors were american, but writing for a british journal. in addition, whether "ae" and "oe" appear as ligatures or separate characters seems to be fairly random. unless there was a clearly preferred spelling choice, variants were kept as is. all changes are explicitly documented below. noted spelling variants that were preserved include: "aluminum" and "aluminium;" "ampullas" and "ampullae;" "beechwood" and "beech-wood;" "blütstein" and "blüt stein;" "brick dust" and "brickdust;" "calcspar," "calc spar" and "calc-spar;" derivatives of "crossbar" and "cross-bar," and similarly for "crosscut," "crosspiece," etc.; (hans von) "dechen" and "decken;" "desulphurizing" and "de-sulphurizing;" "dissension" and "dissention" (and their plurals); "distill" and "distil" (and derivatives); "encrusted" and "incrusted;" "enquire" and "inquire" (and derivatives); "ensure" and "insure;" (lazarus) "ercker" and "erckern;" "flavor" and "flavour;" "fluor-spar" and "fluorspar;" "flusse" and "flüsse;" (rotenburg an der) "fulda" and "fulde;" "gatter" and "gatterer" may be the same person; "gold workers," "goldworkers" and "gold-workers;" "gray" and "grey" (and derivatives); "grove" and "groove" (english mining term for a shaft); "halitum" and "halitus;" "henckel" and "henkel;" "holm oak" and "holmoak;" "homogenous" and "homogeneous;" daniel "houghsetter," "houghstetter" and "hochstetter;" "joannes" and "johannes" (the alchemist); "johanes" and "johannes" (aurelius augurellus), a.k.a. "john aurelio augurello;" "jüdenstein" and "jüden stein;" "kinstock" and "kinstocke;" "lautental" and "lautenthal;" "lawsuit" and "law-suit;" "leipsic" and "leipzig;" "krat" and "kratt;" "mosaic" and "mosaick;" "mineralogic" and "mineralogical;" "nützlich bergbüchlin," "nützliche bergbüchlin," "nützlich bergbüchlein," and "nützliche bergbüchlein;" "organisation" and "organization;" (thomas) "pennant" and "pennent;" "probier büchlein," "probierbüchlin," "probierbüchlein," "probirbüchlein," and "probirbüchleyn" (which may be different books in some cases); derivatives of "pulverise" and "pulverize;" "reagent" and "re-agent" (and their plurals); derivatives of "recognise" and "recognize;" "republished" and "re-published;" "salamander har" and "salamanderhar;" "seashore" and "sea-shore;" "semicircle" and "semi-circle" (and derivatives); "shovelful" and "shovel-ful;" "spiesglas," "spiesglass," and "spiesglasz;" "turkey oak" and "turkey-oak;" "vannucci," "vannuccio" and "vanuccio" (biringuccio); "vectarii" and "vectiarii;" derivatives of "volatilise" and "volatilize." there appears to be no rule whether punctuation following a quote should be inside or outside the quotation marks. the text was simply left as is. there appears to be no rule whether roman numerals have periods after them or not; even references to the same document may differ. the text was simply left as is. for the text version of the document, replaced the oe-ligature with the separate characters "oe." also removed the macron from the "e" in "pectos." some footnote numbers are skipped. to avoid confusion with references to the footnotes, none of the footnotes were re-numbered. in particular, book i does not have footnote ; book vi does not have footnote ; book viii does not have footnote , or ; book ix does not have footnote ; book xi does not have footnote . inserted missing anchor for footnote on page v. changed "albertham" to "abertham" on page vii: "the god's gift mine at abertham." changed "honored" to "honoured" on page xi: "most honoured citizens." treated the explanatory text on page xxiv as a footnote (number ) and created its anchor on page xxi. changed "license" to "licence" in the note on page xxiv: "only poets have licence." changed "bibliotheque" to "bibliothèque" in the footnote on page xxix: "the bibliothèque nationale." changed "theosebeia" to "theosebia" and inserted closing double quotation mark after "written to theosebia, etc....'" on page xxx. left "loadstone" on page although it's spelled "lodestone" everywhere else, because it's in a quote. changed "silver-mines" to "silver mines" on page : "the silver mines at freiberg." removed the extra comma after "ll." in footnote on page : "odes, i., , ll. - ;" and in footnote on page : "satires, ii., , ll. - ." changed "realised" to "realized" on page : "his hopes are not realized." removed extra double quotation mark from before "probable that the work" on page . changed "hipprocrene" to "hippocrene" in footnote on page : "named hippocrene after that horse." changed "joachimstal" to "joachimsthal" on page . adjusted the formats of the captions to the illustrations on page , , and to be consistent with other captions. removed extra double quotation mark after "not a metal" in the footnote from page . changed "foot walls and hanging walls" to "footwalls and hangingwalls" on page . changed "hanging-wall" to "hangingwall" in footnote on page : "into the hangingwall." changed "phaenippis" to "phaenippus" in the footnote on page : "the other against phaenippus." inserted double quotation mark after "droit francais et etranger" in the footnote on page . changed "inama-strenegg" to "inama-sternegg" in the footnote on page . changed "himmelich" to "himmelisch" on page : "himmelisch höz." "himmelsch hoz" was retained as a variant elsewhere. changed "shovelers" to "shovellers" on page : "miners, shovellers, windlass men." the table in the note on page refers to note on p. . it would make more sense to refer to note , but was left as is. changed "chrusos" to "chrysos" in the footnote on page : "(chrysos, gold and kolla, solder)." the footnote on page contains the reference "(see note xx., p. x)." rather than roman numerals, this appears to be a placeholder to a reference that was not filled in. perhaps it should be "(see note , p. )," but it was left as is. changed "tinstone" to "tin-stone" in the footnote on page . changed "de la pirotechnica" to "de la pirotechnia" in the footnote on page . changed "mansfeld" to "mannsfeld" in the footnote on page : "mannsfeld copper schists." changed "coasa" to "coass" in the footnote on page : "cobaltite (coass)." changed "phoenecians" to "phoenicians" on page : "phoenicians must have possessed." changed "hanging wall" to "hangingwall" on page : "the hangingwall and the footwall." changed "venæ dilatatæ" (ae-ligature) to "venae dilatatae" on page : "mine venae dilatatae lying down." changed "venæ cumulatæ" (ae-ligature) to "venae cumulatae" on page : "as to venae cumulatae." changed "watts's" to "watt's" in footnote on page : "watt's improvements." changed "locks" to "blocks" on page : "blocks, and plates." something is wrong with the sentence on page that ends with the reference to footnote . one metreta is larger than one-sixth of a congius. perhaps "metreta" and "congius" should be swapped in this sentence, but it was left as is. changed "bail" to "bale" on page : "iron semi-circular bale." changed "fosilium" to "fossilium" twice in the footnote on page : "de natura fossilium." changed "decends" to "descends" on page : "descends into an underground chamber," and again on page : "the plank descends." changed "pig-skin" to "pigskin" in the caption to the illustration on page : "pigskin sacks." left "vapor" as is in footnote on page although it's spelled "vapour" everywhere else, because it's in a quote. changed "de hydrated" to "dehydrated" in the footnote on page : "probably dehydrated alum." changed "na_{ }co_{ }" to "na_{ }co_{ }" in the footnote on page . changed "fore-part" to "forepart" on page : "the forepart lies." changed "four-fold" to "fourfold" on page : "with fourfold curves." changed "or" to "of" on page : "an ore of copper." changed "factictius" to "facticius" in the footnote on page : "sal facticius." changed "interpretaltio" to "interpretatio" in footnote on page : "interpretatio, die heffe." changed "loehneys" to "lohneys" in footnote on page . "cramner" in footnote on page may be a typo for "cramer," but it was left as is. changed "neutralized" to "neutralised" in footnote on page : "neutralised by the nitre." changed "notes" to "note" in footnote on page : "note ." changed "liquified" to "liquefied" on page : "has become sufficiently liquefied." changed "touchneedles" to "touch-needles" in footnote on page : "detailed account of touch-needles." the reference to page in footnote on page does not seem to make sense, but was not changed. perhaps the reference should be to footnote on page . in the table on page , the entries for the th and st needles do not add up, because the entry for the number of sextulae of copper belongs in the st needle, not the th. this was corrected. however, there are other errors in this table, which are not so obvious and were not corrected. in particular, the entries for the nd, th and st needles do not add correctly. in the table on page , the number for the siliquae of copper was sometimes in the sextulae column. these were corrected. the affected lines were the ones for needles , and . there is some other error (uncorrected) for the th needle; probably it should have another sextula of silver. filled in the missing " " in the line for the th needle in the table on page . changed " " to " " in the line for the rd weight in the table for the "greater" weights on page . changed "stele" to "stelae" on page : "certain stelae." changed "hanging-wall" to "hangingwall" on page : "the hangingwall rock;" and on page : "from the hangingwall." changed "lead" to "led" in the footnote on page : "led through a series." changed "humpfrey" to "humphrey" in the footnote on page : "william humphrey." changed "erbisdroff" to "erbisdorff" on page : "tin-stuff of schlackenwald and erbisdorff." changed "colleced" to "collected" on page : "concentrates are collected." changed "civilisation" to "civilization" in footnote on page : "glimmer of civilization." changed "chapter ix" to "book ix" in footnote from page . changed "thothmes" to "thotmes" in footnote on page : "the time of thotmes iii." changed "unseasonable" to "unreasonable" on page : "yet it is not unreasonable." inserted "l--" in the caption for the illustration on page . footnote , p. , refers to a note on p. , but there is no such note. changed "carni" to "carni" in the caption to the illustration on page . removed extra right parenthesis at end of footnote , from page , and footnote , from page . changed "agatharcides" to "agatharchides" in the footnote on page , and again in the footnote on page . changed "bare" to "bars" on page : "the lattice-like bars sells." changed "nütliche" to "nützliche" in footnote on page : "the nützliche bergbüchlein in association." changed "threequarters" to "three-quarters" on page : "three-quarters of a foot." changed "the spout from the opercula extends" to "the spouts from the opercula extend" in the caption to the illustration on page . changed "earthern" to "earthen" on page : "melted with copper in a red hot earthen crucible." changed "boussingalt" to "boussingault" in footnote on page : "investigation by boussingault." footnote , on page , refers to a discussion on page ; there is no such discussion. perhaps the note on page was intended, but no change was made. the reference to p. in the footnote on page doesn't seem to make sense. perhaps the reference should be to the note on p. or the illustration on p. , but it was not changed. changed "agricolas'" to "agricola's" in footnote on page . changed "roman" to "roman" in the caption to the figure on page . changed "pinewood" to "pine-wood" on page : "shingles of pine-wood." changed "fore-hearths" to "forehearths" in the caption to the illustration on page . changed "or" to "of" in the table in footnote on page : " . lbs. of (a)." changed "near-by" to "nearby" on page : "in a nearby timber." changed "fore-hearth" to "forehearth" on page : "into the forehearth," and on page : "into the forehearth." changed "sideboards" to "side-boards" on page : "the side-boards are fixed." changed superscripts to subscripts in footnote on page : "ca(no_{ })_{ } + k_{ }co_{ } = caco_{ } + kno_{ }." changed "crystallised" to "crystallized" in footnote on page . changed "hydros" to "hydrous" in the footnote on page : "the hydrous sulphate." changed "octrahedra" to "octahedra" in the footnote on page . changed "subtance" to "substance" in footnote on page : "that feathery substance." changed "ventholes" to "vent-holes" on page : "two or three vent-holes." changed "prehistoric" to "pre-historic" on page : "from pre-historic times." changed "rawlinsons, trans." to "rawlinson's trans." in the footnote on page . changed "neavius" to "naevius" on page : "johannes naevius." changed "unständliche" to "umständliche" in footnote on page : "umständliche ... chronica." changed "watts" to "watt" on page : "watt mentions it." changed "begininng" to "beginning" on page : "beginning of the sixteenth centuries." changed "oxidising" to "oxidizing" on page : "an oxidizing blast." changed "oryguia" to "orguia" on page . changed the reference for annaberg on page from "xxi" to "xxxi." changed "ceragurite" to "cerargurite" in its index entry on page . changed "fibræ" to "fibrae" (ae-ligature) in its index entry on page . changed the reference for glass on page from " - " to " - ." changed two references for magnes on page from " " to " ." changed the reference for nuremberg, scale of weights on page from " " to " ." changed "pickscheifer" to "pickschiefer" in its index entry on page . changed the reference for proustite on page , and the references for pyrargyrite, for ruby silver, for silver, for silver glance and for silver ores on page , from " " to " ." changed the reference for quicksilver on page from " " to " ." changed "stuices" to "sluices" on page , in the index entry for "pockets in alluvial sluices." changed the references for schneeberg, st. george mine and for st. george mine on page from " " to " ." changed "steinmack" to "steinmarck" in its index entry on page . in the index to persons and authorities (starting page ), there are a number of references to page that appear to make more sense as references to , but which were not changed. changed the reference for venice, scale of weights on page from " " to " ." changed the reference for de mensuris et ponderibus, weights and measures on page from " " to " ." changed the reference for de natura eorum quae effluunt ex terra, dedication on page from "viii" to "vii." changed the reference for de precio metallorum et monetis on page from " " to " ." changed "diphilus" to "diphilos" in its index entry on page . changed the references for forehearth and for furnaces, blast on page from " " to " ." changed the references for pumps, suction on page from " ; " to " ; ." changed the reference for "tests" for refining silver on page from " " to " ." transcriber's note: minor typographical errors have been corrected without note. irregularities and inconsistencies in the text have been retained as printed. subscripted text is indicated with curly braces: { }. words printed in italics are marked with underlines: _italics_. the a b c of mining _a handbook for prospectors_ treating fully of exploratory and preparatory work of the physical properties of ores, field geology, the occurrence and associations of minerals, methods of chemical analysis and assay, blow-pipe tests, promising indications, and simple methods of working valuable deposits, together with chapters on quartz and hydraulic mining and especial detailed information on placer mining, with an addenda on camp life and medical hints. by charles a. bramble, d.l.s., late of the editorial staff of "the engineering and mining journal," and formerly a crown lands and mineral surveyor for the dominion of canada. _illustrated._ chicago and new york: rand, mcnally & company, publishers. copyright, , by rand, mcnally & co. preface. owing to recent rich discoveries in more than one mining field, hundreds of shrewd, intelligent men without experience in prospecting are turning their attention to that arduous pursuit--to such this book is offered as a safe guide. a complex subject has been treated as simply as its nature permitted, and when a scientific term could not be avoided, the explanation in the glossary has been offered. charles a. bramble, d.l.s. preface to second edition. a steady demand for this work has shown that it fills a want, and serves the purpose for which it was written. in issuing this second edition, a few compositors' errors that had crept in, owing to the author being in a very remote region while the book was going through the press, have been corrected, but no material changes in the text were found desirable. contents. the a b c of mining. page chapter i--prospecting, ii--how to test for minerals, iii--blow-pipe tests, iv--economic ores and minerals, v--mining, vi--camp life, vii--surveying, viii--floating a company, ix--medical hints, x--dynamite, xi--atomic weights, xii--odds and ends, glossary, a b c of mining. chapter i. prospecting. many men seem to think that should their destinies lead them into parts of the world where there is mineral wealth they will have little chance of discovering the deposits without the technical education of a mining engineer. this is wrong. the fact is that the sphere of the prospector does not cover that of the engineer. the work of the one ends where that of the other begins, and many of the most successful discoverers of metallic wealth have been entirely ignorant of the methods by which a great mine should be opened, developed, and worked. a few simple tools and a not very deep knowledge of assaying, with an observant eye and a brain quick to deduce inferences from what that eye has seen, are the most valuable assets of a prospector. in time he will gain experience, and experience will teach him much that he could not learn in any college nor from any book. each mining district differs from every other, and it has been found that certain rules which hold good in one region, and guide the seeker after wealth to the hidden treasure that has been stored up for eons of time, do not apply in another region. to show what may be done with imperfect, improvised apparatus, an australian assayer, who has since become famous, started up country in his youth with the following meager outfit: a cheap pair of scales, a piece of cheese cloth, a tin ring - / inches by / inch, a small brass door-knob, some powdered borax, some carbonate of soda and argol, a few pounds of lead lining taken from a tea chest, an empty jam pot, a short steel drill, a red flower pot. with this modest collection of implements he made forty assays of gold ores that turned out to be correct when repeated in a laboratory. about the best advice that can be given to a man who has determined to go to some out of the way region where there is a possibility of his discovering minerals is to recommend him to visit the nearest museum and gain an acquaintance with the common rocks. should he be unable to do this he had better provide himself with small, inexpensive specimens from the shop of some dealer. it is almost impossible to teach a beginner to distinguish the various rocks by any amount of printed instruction; the only way to learn to recognize them is to handle them and note carefully their color, weight, and the minerals that go to make them up. the explorer should be able to recognize at a glance, or at any rate after a very short inspection, the sedimentary rocks, such as sandstone and limestone; the metamorphic rocks, that is, rocks that have been altered by the agency of great subterranean heat in ages long past, and which were probably stratified rocks at one period, such as granite and gneiss, and the truly igneous rocks--trap, diabase, diorite, etc. he must know also that mysterious rock which the western miner calls porphyry, and to which is ascribed most wonderful virtues in the way of ore attraction; while dolerite and dolomite must be to him familiar terms and substances. this sounds easy enough but the student will find that a good deal of hard work is necessary before he can readily recognize each of these rocks. it is even more necessary that he should learn the metals thoroughly. each one differs from all the rest in some particular. often this difference will be an obscure one, but to the careful investigator the recognition of the substance will be in the end certain. they may differ in weight, in color, in hardness, in a dozen different ways, so that to the man who has made a study of this subject a determination is always possible. on account of the wonderful discoveries in the canadian northwest and in alaska, the eyes of thousands are turned towards those fields. wonderfully rich placer ground has already been found and there can be no reason to doubt that very much larger areas remain unproved. where this gold comes from is an open question; geologists, mineralogists and chemists, not to mention mining engineers and practical prospectors, have disputed over the source of the gold already found, but it must be confessed that there are almost as many theories as there are disputants. could it be known with certainty how and under what conditions the gold got where it is found, the problem of seeking for it might be made easier. unfortunately this is not the case, and all prospecting for the home of the precious metal is more or less a groping in the dark. we do know that the heaviest particles of gold do not travel far from where they were first deposited, because gold is so enormously heavy--its specific gravity being about nineteen times that of water--it seeks the bottom of the stream and stays there. it is not an invariable rule that the gold increases in coarseness as the stream is ascended, but it is a very general one. on some rivers rich and poor stretches of gold-bearing gravel succeed one another as the explorer makes his way up or down stream. this is difficult to account for, but in many cases is believed to be caused by the modern river robbing the bed of some one or more ancient water-courses whose beds crossed the valley of the present stream. this may or may not be the case. we only know that the miners who found coarse gold on the lower regions of such rivers as the frazer were miserably disappointed when they reached stretches near the source and found nothing but flour gold. this same feature has been noticed in some of the alaskan rivers. it is quite within the bounds of probability that no very rich quartz veins exist in alaska. it does not follow from the richness of the placers that the gold is derived from very rich quartz lodes, because this amount of gold may really represent the product of a vast amount of rock that has been ground to powder and washed away in the course of ages. the gold would not travel far, and the deposits being unearthed to-day have been accumulating in these northern streams since the world was young; water-courses are nature's ground sluices. it is possible that one stream has cut through the drainage of another. sometimes this has impoverished the first and enriched the second, while in other cases the reverse has obtained. upheavals have formed faults[ ] and fractured the strata, and the gold may have been deposited by solution in these fractures. often the soil will have been washed away from near the top of the mountain, so that layers of stratified rock are seen to be duplicated on each side while they are covered at the summit. the prospector keeps his eye open as he goes along and notes carefully the character of the fragments of rock he finds in the streams. quartz, diorite, diabase, and porphyry pebbles are grounds for expecting a profitable result, but of course there is no certainty of such a happy issue. as soon as the district begins to be fairly well known certain discoveries are made that invariably render prospecting easier. local peculiarities are noted; certain characters are found to be common to the ore-bearing bodies or deposits; the lines of deposits become known, and a good deal of light is then shed upon a very difficult problem. as a rule, when the fragments of quartz, pyrite, chalcopyrite, or galena are rough, they have not traveled far, and the lode from which they have been derived should be close at hand. water and attrition soon round these minerals on their sharp edges, and thus show that they have come from some little distance. [ ] dislocation of the strata. in some countries, especially where vegetation is scanty, the outcrop of a body of mineral may be traced by a difference in the vegetation. in south africa a chain of pools usually follows the course of a line fault, which in its turn marks where an intrusive lode carrying mineral separates two different formations. as a rule, any heavy mineral is worth investigating. even in remote regions silver, mercury, tin, nickel, platinum, copper, and several other metals are worth paying attention to. if they are too far away from the railroad or the steamboat to-day they may not be so next year, for civilization advances with giant stride in these days and never faster than when transportation companies are reaching forth to some newly discovered mineral field. one of the greatest drawbacks to prospecting in the north is the dense growths of moss and forest that cover the ground. in most of the western states, in south africa, and in australia this drawback does not exist and prospecting was by that much the easier. however, as a compensation, there is abundant water in alaska and the northwest, while it was and is almost entirely absent in several other regions that possess immense bodies of ore which are not available for this very reason. quartz has been called the mother of gold, and certainly quartz and gold are inseparably connected to-day. as to where gold may be found the best reply that can be given is in the words of the old miner, who, when asked that question, said: "where it be's; there it be's," and then added, "and there ben't i." although most prospectors travel alone from sheer necessity, there can be no doubt that three or four men forming a party and working together have the advantage. they can do their work cheaper, more thoroughly, and more surely. by co-operating they may carry a more complete outfit. should any accident happen help is at hand, whereas the solitary wanderer often dies as the result of some accident that would have been trivial had he had a companion. three or four claims may be worked in conjunction with one another at far less proportionate expense than a single one could. nature's preparation for the reception of great ore deposits is somewhat as follows: the crust of the earth is prepared for the reception of the metals by great outbursts of igneous or melted rocks; the metals themselves being carried in suspension in the heated water that everywhere traverses the strata. these metals are deposited in the veins as soon as the waters begin to cool, and the pressure to which they were subjected from deep down in the earth's crust is removed. a great mineral country is usually marked by the outcrops of the veins being persistent in their courses and traceable for many miles, though very probably many breaks may occur in these outcrops. the rocks associated with great ore bodies are lime, porphyry, granite, shales, slates, quartzites, and diabase. fragments of mineral and gangue, known to the miners as float, may be littered over the hills and encumber the courses of the stream. a central line of eruption may often be traced by masses of altered rock, and beds of lava or other volcanic products. we find the granite has been melted and the limestone has acquired magnesia, and thus become dolomatized. whenever a heavy deposit of pyrites, or mundic, is found mineral probably exists below. the cubes of pyrite are not always valueless, they may contain gold in addition to the iron and sulphur. when the pyrites decay under the influence of the weather, and leave the quartz honeycombed, these cavities often contain concentrated gold; for which reason you often get a higher assay from the surface than from any point lower down in the vein. in sinking the shaft soon gets below this altered quartz and the ores are then combined with sulphur. they have become sulphides, and are harder to treat. the prospector should therefore act very cautiously when trying to develop a mine with a small capital behind him; because, although the first ore may be adapted for stamping, he may find, before he has gone down fifty feet, that it can only be treated in a smelter, and that all the money he has put into crushing apparatus is wasted. without the prospector there would be no mining and the world would yet be in the stone age. he is not appreciated at anything like his real worth. he requires ability and experience, push and perseverance. prospecting is a search for valuable minerals. he may not be very deeply learned in either geology or mineralogy, but he must have a keen eye and good natural powers of observation. there are some sixty or seventy elements in the world, and the most common is oxygen. nearly all the coloring matter of rocks comes from iron. wind, frost, rain, snow, and heat, cause a crumbling of the different rocks, and running water wears them away, and carries off and distributes the particles. by this agency, and by floating ice, they are often removed to long distances. the action of internal heat renews the deposits of mineral by eruption, or by hot springs, but this means of renewal was much more powerful in the past than it is now. organic matter found in the crust of the earth was derived from animals or vegetables. coal is a legacy from forests that flourished ages ago, while petroleum is all that remains of vast schools of fishes that swarmed in devonian seas. stratified rocks are either sand, clay, or calcareous, which means lime-bearing. in their natural position they were horizontal, but owing to subsequent volcanic action they are, in some localities, tilted at all conceivable angles. the eruptive rocks have burst through them in places, changed their character, divided them by intrusive masses, and generally enriched them with mineral deposits. everything now known points to the theory that the contents of veins were deposited in the lodes by infiltration. in a few instances famous mines have no veins, but are literally hills of mineral; they are then of low grade, but much more remunerative than average high grade mines, owing the vast quantity of ore, and the ease with which it can be mined. the famous treadwell mine, on douglas island, alaska, has ore that is worth less than four dollars a ton, but it is quarried, and stamps work day and night. there is about a dollar a ton profit, and hundreds of thousands of tons are treated annually. the tin mine known as mount bischoff, in tasmania, and the burra copper mine in australia are other instances. each of these deposits was found as an outcropping on the bare top of a low hill, and none of them has walls. a fault may throw the vein up or down, and a good deal of exploration may have to be done before it is recovered. a lenticular vein consists of a series of double pointed ore bodies like lenses which may be strung out, overlapping, or not. the outcrop of a vein is never the same as its strike, except on a level surface. a stringer of ore branching off from the main vein is known as a chute, shoot, or chimney. in developing a ledge or lode, first find out what the ore is. gold is shown in the mortar, especially after roasting. silver may be recognized at sight, or by assay tests, or blow pipe; copper, by its vivid colors,--green or blue for carbonate and red for oxide or metallic copper. the ore often differs in various parts of the vein. explore your lode along the surface, across, and down its dip. when you find it continuous it will be time enough to think of a vertical shaft. the top of a shaft must be timbered with logs, so as to give sufficient fall to get rid of the mineral when it is hoisted. the first thing the prospector has to consider is his outfit. the more complete this is the better, but ninety-nine times out of a hundred the difficulties of transportation in a wild region are so enormous that he will have to do without a great many things that he would like to have. he must endeavor to make up for the lack of tools by ingenuity; then he may get along fairly well. a pan, he must have. in this he will wash carefully all his samples. then, a flask of quicksilver is more precious to him even than gold; for, having it, he can resort to pan-amalgamation, which will save the precious metal even when it is in minute particles. this process may be described as follows: a pound or two of the ore in powder is placed in the pan and water is added until the mass becomes a thin pulp. one ounce of quicksilver and a small piece of that deadly poison, known to the chemist as cyanide of potash, and as prussic acid to the ordinary man, should be added, and the mass should be stirred thoroughly, for two hours if you can stand it. then turn in water and wash off the dirt and the amalgam will be found in the bottom of the pan. this you must collect very carefully. you should have a square piece of chamois skin or a piece of strong white cotton cloth. in either case the amalgam is put in the center of this square and the cloth twisted until all the superfluous quicksilver is pressed out and your amalgam remains nearly free from mercury. this amalgam placed on a shovel and held over a brisk fire will soon show the yellow color of gold. if you have no mould you may make one of clay, put your gold therein with a little borax, and very soon, the fire being hot enough, you will have a tiny ingot of the precious metal. but most prospectors are satisfied when they have obtained their sponge gold, and do not carry their operations further in these rough and ready tests. the prospector of to-day is often a very different man from his predecessor of a generation ago. the old gold hunter used to sally forth armed with a pick, shovel and pan, and usually a very little grub. in his stead men are now taking the field who have had the benefits of a thorough education, both practical and theoretical, and provided with all the equipment necessary for their work. some of these men carry an outfit somewhat as follows: an iron mortar holding half a gallon, together with a pestle a rough scale for pulp, a more delicate one showing troy grains and pennyweights, a -mesh sieve, a burro furnace and muffle, one cupel mould, a couple of dozen scorifiers, tongs to handle the cupel and scorifiers, two annealing cups, a spirit lamp, a dozen test tubes, a pouring mould, five or six pounds of borax and about as much carbonate of soda, five pounds of bone ash, ditto of granulated lead, a pint of nitric acid, ditto of hydrochloric acid, ditto sulphuric acid, ditto of ammonia, twice as much alcohol and two pounds or so of granulated zinc. as a blow pipe outfit he will take a blow pipe, spirit lamp, nitrate of cobalt in solution, cyanide of potash, yellow prussiate of potash, red prussiate of potash, a sheet or two of filtering paper and a couple of three-inch glass filters. with this outfit he can determine any mineral he may come across. by patience and observation the man who starts out to take up prospecting as a road to fortune may easily master the rudiments of his business. it will not take him long to become familiar with the commoner rocks, and the more valuable ores. his own rough tests in the field must be confirmed by competent assayers upon his return to civilization, and in this matter he should be very guarded. the most reliable assays are made either at the different government assay offices or by some of the large metallurgical works whose reputation is world wide. prospecting is hard work, but the life is healthy and full of excitement, only the explorer should have courage, hope, and good temper, for each and every one will be as necessary in his chosen vocation as his pan and pick. when alluvial or placer gold has been found it is reasonable to suppose that the vein from which it was derived may also reward diligent search, for it is undoubtedly true that most placer gold has come from quartz veins. this, however, is believed not to be invariably the case, a recent school of mineralogists contending that pure masses of alluvial gold have been formed from the accretion or growth of the gold deposited from certain gold salts. this is in any case probably exceptional, and the prospector who finds gold in gravel should seek in the adjacent country for the quartz lodes from which it came. important deposits may be expected at or about the line of unconformability where slates, shales, quartzites, sandstones, limestones, schists and other sedimentary deposits are pierced by intrusive masses of igneous rocks. veins filling the cracks that once existed between two differing rocks are known as contact veins. such veins are often very rich. curiously enough large masses of true igneous rock rarely contain valuable deposits of mineral, but where such intrusive masses cut dikes or walls of porphyry, or diorite, the region is worthy of careful investigation. [illustration: pocket lens.] in an open country the prospector should keep to the hill tops if on the lookout for veins, as the outcrops show more distinctly on the bare ridges, but alluvial deposits are only found in valleys and along the borders of streams. in any case, much of the northern part of this continent can only be prospected by following the streams, on account of the dense growth of forest with which the soil is covered. the true line of strike of a vein can be determined only on a level stretch. the line of strike and the line of dip are always at right angles to one another; the outcrop may follow the strike or it may not. a pick, shovel, and pan, are absolutely necessary to a prospector's proper equipment. a good pocket lens, cheesecloth screen, and small iron pestle and mortar are often useful. the pan is the most essential part of the outfit, and is always bright from use. the regular gold miner's pan is - / inches in diameter across the top, inches across the bottom and - / inches deep. the best are made of sheet iron and have a joint around the bottom rim which is of some assistance in retaining the spangles of gold. a more primitive instrument than the pan is the batea. this requires more skill than the pan, and is much in favor with south american miners. it is made of hard wood, inches in diameter, - / inches deep in the center, inside measurement, and sloping gradually to nothing at the sides. the horn spoon has been handed on from antiquity. it is made from a black ox horn, at least a black one is the best as it shows the gold better; it is eight to ten inches long by three inches wide, cut off obliquely. when gold is suspected in quartz, but there is visible to the naked eye more or less iron, copper, and other base metals, it is well to crush the quartz into coarse fragments. roast on a shovel or other convenient tool over a hot fire, and finally pulverize in the mortar. if panned it will now reveal much of its gold, while, had these measures not been taken, the sample might have given negative results and been declared valueless. after pulverizing, the ore should be passed through the cheese cloth screen before panning. if the approximate value of the ore is sought, the sample must be dried and weighed before crushing; and the resulting gold weighed. thus: sample is to , lbs. as gold found is to ans. about cubic feet of quartz weigh a ton before being disturbed; when broken to medium sized lumps cubic feet may be taken as representing a ton. although experience teaches the miner to estimate very closely the value of his sample, it is better for the tyro to have a small pair of scales with grain weights. a grain of gold, if tolerably pure, is equal to four cents. above all things avoid the too common error of panning the pick of the rock, as a false estimate is bound to follow and only too probably eventual loss. a yard of gravel before being dug makes one and a half yards afterwards. a pan of dirt is usually about pounds, although it is not well to fill quite full in actual work. many a valuable mine has been found by following up "float" ore. float is detached fragments of the vein or gangue, and it becomes more and more abundant as the lode is approached until it finally ceases abruptly. this indicates that the vein has been reached or passed, and a trench dug throughout the alluvial soil at right angles to the assumed line of the vein will probably reveal it. the float and mineral of course drift down hill; if the side of the mountain be saddle-shaped the float will spread out like a fan as it washes down, but if concave the force of gravity will concentrate it within a narrow space in the ravine. float found at the foot of a hill has come, as a rule, from that hill. the nearer the vein the less worn will be the edges of the float and mineral. the gangue or vein-rock in which the metal is found may be calcite or calc spar, fluor spar, heavy spar or baryta, or quartz. gold is almost always found in this last matrix. the upper parts of most quartz lodes are usually oxidized, that is to say, the atmosphere has acted upon the iron pyrites, freeing the sulphur and staining the quartz yellow, red, or brown, by oxide of iron. this is known as "gossan" or the "iron hat." such quartz is frequently honeycombed and rotten. below the water level these veins run to sulphides in which decomposition has not set in, and the gold contained in the quartz is no longer "free milling," i.e. will not give up its gold to mercury without a preliminary treatment. whenever the explorer comes across a mass of gossan he should sink a trial shaft to the vein, as it is almost certain that below the oxidized sulphides a body of mineral exists likely to encourage mining operations. native gold is malleable, will flatten out under the hammer, and a steel knife will cut it with ease. it almost invariably contains silver, sometimes to the extent of one-fifth. a little practice will enable the prospector to recognize it, for there is but one king metal. much gold is derived from copper and iron pyrites, and silver and lead ores are a very large source of supply. gold is found in gravel of every variety, from finest pipe-clay to boulders weighing tons. sometimes volcanic eruptions have covered these deposits since the ancient rivers laid them down, and in many cases their courses do not in the least agree with the valleys of the shrunken streams that have replaced them. gold may be distributed through the whole thickness of a bed, but ninety-nine times out of a hundred the richest layer of gravel is just above the bed rock upon which all the gravel rests. gold may even be found among the grass roots, especially in dry localities where there has been little water to carry it downward. when the bed rock consists of upturned slates the gold frequently penetrates it for some little distance. sand is nearly always poorer than gravel. the experience of miners in the victoria gold fields is that gold is always found on the bars or points, and not in the deep pools and bends. the great difficulty with which any but the very finest particles of gold can be moved by water accounts for the value of the deposits depending largely upon the local rocks. it is very fortunate that gold's specific gravity is so great, for were it less its recovery would be much more difficult. the sluices and other apparatus of the miner are really nothing but the operations of nature imitated on a much smaller scale. there is one thing, however, time, that nature can afford to expend in prodigious periods, while man must not waste a single minute. it not being possible to point out where the ancient river beds lie, smothered as they are by hundreds of feet of overlying drift, lava, and other later deposits, the only feasible plan is a series of boring with the diamond drill. when gold has been discovered the finder must act with the greatest prudence, for even gold may be bought too dear. the surest test is a mill run, that is passing to tons through all the operations of crushing, milling, roasting, amalgamating, etc., and so ascertaining what returns are likely to be obtainable when the deposit is worked on a commercial scale. true sampling is necessary. all parts of the vein should be included, and the lode cross-cut by galleries in more than one spot. it is the very great necessity of these expensive preparatory explorations that has given rise to the saying, "quartz mining is for rich men." many gold mines have been abandoned as unprofitable that could have been mined at a profit had their owners been wealthy and enterprising enough to do a great deal of expensive prospecting by diamond drill, cross cuts, drifts and rises. in one instance that came to the writer's knowledge a clever mining engineer cleared nearly $ , profit by leasing for a term of years a gold mine that was supposed to be exhausted. a drill hole sunk less than feet below the old workings revealed a pocket of ore in the vein, and paying quartz was found for many hundred feet below. with the improvements in electricity made recently a cheap power has been provided that will permit many mines to be reopened. the saving in working expenses effected by introducing electricity is often very large; after the plant is once installed the cost is almost nil where turbines can be employed to furnish the power to the generators. machinery capable of delivering power at a distance of several miles from the plant, may be operated at very reasonable cost as compared to that of other prime movers. discoveries of many deposits that have in time been successfully mined were the result of chance. no skill guided the finder; he merely stumbled upon his luck just as the wayfarer once in a while hits his toe against a well-filled pocketbook. for instance, a south australian squatter picked up a piece of copper ore that a wombat had thrown out of his burrow, and the result was the discovery of the great wallaroo lode. the first diamond from south africa was picked up by an ignorant bush boy and kept with a lot of worthless pebbles in the private collection of the boy's master; no suspicion existed of its value until a passing trader had carried it away and obtained $ , for it in capetown. gold was first discovered in california in by the superintendent of a sawmill who saw it glistening in the flume. similarly gold was discovered in both australia and brazil by the purest chance. had not a tree been uprooted by the wind the vast deposits of soft hematite iron ore in the biwabic iron mines of the mesabi range, minnesota, might have remained unknown for many a long year to come. in the desolate region to the northward of lake huron great stores of nickel ore exist. these mines, which may some day regulate the price of the metal all the world over, were exposed in a railway cutting; no one dreamed of their existence. the redington quicksilver mine in california was discovered by some roadmakers. tradition relates that the enormously rich silver mines of potosi, in bolivia, were discovered by the accidental uprooting of a bush having spangles of silver ore attached to its roots. this was in , and two hundred years later a similar streak of luck revealed the wealth of the catorce district of mexico, from which in thirty years, ore to the value of $ , , was taken. moreover, the search for one mineral often leads to the discovery of another. the comstock lode was first worked for gold, and the miners threw away the black sulphide of silver worth $ , to the ton. the broken hill mine in australia was claimed as a tin deposit by its finder; it is now the greatest silver producer in australasia. such instances could be multiplied almost indefinitely, chance entering into a majority of mineral discoveries. on the other hand, it has happened, not infrequently, that purely scientific deductions and calculations have brought to light stores of mineral wealth. certain minerals are likely to be found associated. cassiterite goes with boron and tourmaline, topaz, fluor spar and lithia-mica; all containing fluorine. it is also found with wolfram, chlorite and arsenical pyrites. magnetite is often accompanied by rocks containing garnet, epidote and hornblende. zinc blend and galena may occupy the same vein, which is likely to be of baryta or heavy spar. much galena carries silver. gold is associated with many metallic sulphides such as iron, magnetic, and copper pyrites, mispickel, galena, blend, stibnite and tetrahedrite. gypsum accompanies salt. surface indications may be described as: form of ground, color, outcrop, decomposed and detached mineral, mineral deposits from springs, altered or peculiar vegetation and other similar guides. a hard quartz outcrop often stands up like a wall and is traceable for miles. the rainbow silver bearing lode of butte, montana, stood feet above the surface. soft minerals, such as clay, are cut into and sunk below the surrounding level. deposits of kaolin or china clay are usually so found. any special bright coloration of the rocks of a district merits investigation. copper gives green, blue, and red stains; iron, red or brown; manganese, black; lead, green, yellow or white; cobalt, pink; cinnabar or quicksilver, vermilion. the nickel deposits of new caledonia were made known to the world by the explorer garnier in , his curiosity having been aroused by the delicate green coating given the rocks by an ore containing water, quartz, nickel and magnesium. hard beds of shale decompose on the surface into soft clay, and a still more noticeable change is the conversion of ores containing sulphur into oxides. this chemical change causes the gossan or "iron hat," for which token of underlying wealth the prospector should be eternally watchful. this alteration may extend downward four or five hundred feet from the surface, but in such cases the true weathering has ceased long before the limit of discoloration is reached, and the change of substance is due to the filtering of surface waters through the vein. gossan varies greatly in its nature. galena becomes anglesite, cerussite, pyromorphite and mimetite. copper pyrite changes into native copper, melaconite, cuprite, malachite, chessylite, or perhaps into a phosphate, arsenate, or silicate of the metal. carbonate of manganese gives the black oxides and silver sulphide ores are, after weathering, known as native silver, kerargyrite and embolite. the ore in the gossan is very generally more valuable than it will be below, and this is especially true of gold and silver ores. the gold having been set free from the close embrace in which the iron pyrite held it previous to the latter's oxidation, it is now readily caught by quicksilver. silver under similar conditions becomes chloride, and likewise amalgamates without difficulty. seams containing native sulphur often show no trace of that element on the surface, having weathered into a soft, white, gray or yellowish-white granular, or pulverulent, variety of gypsum. veins of asbestos often decompose into a white powder found in the crevices of the rocks; fibrous asbestos existing in the interior. petroleum shows in an iridescent film upon still pools, and the odor is a sure guide to its nature. a "dipping-needle" is valuable to the prospector on the lookout for iron ore; by its use he may discover masses of magnetic ore and trace their extent. as he carries the compass over the ground the needle dips toward any iron mass he approaches; directly over the ore it becomes vertical. [illustration: miner's dipping needle.] in a wilderness country strength of body and endurance are important qualifications. the prospector must, moreover, have such general knowledge of geology and mineralogy as to be able to recognize all valuable minerals and confirm his conjecture by simple tests. pick, shovel and pan must be handled skillfully, while the rifle, shotgun and paddle must also be understood. for in the unsettled parts of the country the traveler must even yet rely to some extent upon the fish and game he may be able to secure, and every old prospector becomes a trained hunter and camper. knowing how to bake bread is sometimes more valuable than much mathematics; ability to build a rough boat is often the one hope of salvation. in sinking a short shaft in a sunny country a large mirror, inclined at a suitable angle over the shaft, will give sufficient light. lodes or veins following the general trend of the auriferous quartz are much more likely to be rich than are those that cross it. gold is never distributed evenly in veins, though it may be in great beds of low grade material; but more often rich areas alternate with barren portions. where quartz veins are small and the rich pockets separated by wide intervals of poor gangue the gravel of the district will usually be similar in character. as this condition obtains in the upper yukon district as far as the gravels are concerned, it will probably be found to hold good for the quartz leads, when they shall have been discovered. the more nearly the gold formation approaches to the crystalline schists, the poorer will the quality of the gold be through the larger percentage of silver found in it. in slates the proportion may be gold to silver; in schists it has been known to be a ratio of to . with the discovery of valuable gold-bearing gravel on the bare hillsides of the northwest, a vast region has been added to the area the prospector may explore to advantage. no experience acquired in ordinary american placer grounds is likely to be of much use in detecting these higher gold-bearing gravels of the yukon, but they appear to be somewhat similar in character to the new zealand terraces. terrace-prospecting requires perseverance and the use of some brains, as it is infinitely harder than creek-prospecting. these terraces or benches are the remains of old river beds. the whole bench must be carefully scanned over because the gold is quite as likely to be in one part as in the other. sometimes it is in half a dozen different layers one above the other. sometimes the old river terraces are entirely covered by landslides, and the majority of such deposits are not likely ever to be found, as it is almost impossible to guess at locations. in new zealand gold has been found on table-lands nearly , feet above sea level, and according to recent information valuable claims have been discovered in alaska on the very summits of the rounded hills on each side of el dorado creek. to understand how such deposits as those of the northwest may have been made, suppose that such a vein as that of the idaho, which has been worked for a depth , feet by a width of , feet, and from which $ , , have been taken, to have been worn down by glacial or other forces. is it not conceivable that the gold would gradually have accumulated in the nearest canyon? [illustration: dolly.] to obtain suitable samples of the vein a dolly is an efficient apparatus. this is practically a very simple, crude, stamp mill. on the end of a solid log, firmly fixed in the ground and standing four feet or so above the surface, a square -inch hole is cut in which are fitted wrought iron bars inches deep by / inch wide, and separated by equal intervals. these bars taper below so as to permit free passage of the pounded mineral. a wooden box surrounding the grating keeps the ore in place. a block of wood, shod with iron, forms the stamper. the miner hauls on the handles at every blow. the gold is saved on the lower table. no one of experience in mining would look for brown hematite in a granite range, nor for black band, though such might be a likely region for red hematite or magnatite. the explorer should be familiar in theory at least with the locality where he may expect to find valuable minerals. for instance, should he be searching for some heavy, detached substance that is usually found in placer deposits he will keep to the low ground and examine carefully the beds of the streams. on the other hand, should his quest be for some ore that is more properly a component of a lode or vein he will examine the side hills and summits where denudation will certainly have exposed such deposits. then he must know the appearance of each ore, and with the methods of making rough and ready tests he must be perfectly familiar. gold is always more or less intimately associated with quartz. oxide of tin is said never to have been found more than two miles from some granite rock, one of the components of which was muscovite or white mica. the junction of slates and schists with igneous or metamorphic rocks often proves a valuable find of mineral. rocks for the purposes of the explorer may be grouped under three heads: igneous; metamorphic; stratified. the first includes lavas; trachytes, grayish with rough fracture and mainly glassy; dark basalts: and traps, such as greenstone. obsidian is a volcanic glass. metamorphic rocks are thought to have once been stratified, but to have been altered by heat. they comprise granite, of quartz feldspar and mica; syenite, containing hornblende instead of mica; gneiss, like granite, but showing lines of stratification; mica schist, made up of mica and quartz and separating easily into layers; slates. stratified rocks are those deposits from water, such as sandstone, limestone, clay, etc. a prospecting shaft need not be of large dimensions. one feet square is amply large for any depth down to feet, but it must be kept plumb. sometimes shafts are sunk through the pay streak in alluvial gravel, without it being detected. frequent panning will guard against this mistake. in the klondike region it is said early prospectors missed very rich deposits, that have since been discovered, by stopping short of true bed rock, being misled by a bed of harder gravel that they thought was bottom. silver almost invariably carries some gold. the dark ironstone hat already referred to is a good indication of silver ore beneath; it is generally composed of conglomerates cemented by oxides of iron and manganese. galena, which is sometimes so rich in silver as to be worth working for that metal, may often be followed by surface indications; namely, a white limy track with detached fragments of float ore in the surface soil. the blowpipe or fire assay quickly determines silver ore. tin in lode, stream, or alluvial deposits occurs only as an oxide, but its appearance is varied. it may be almost any color and shape. it is always near granite, containing white mica known as muscovite. the minerals for which it is most easily mistaken are: sp. gravity. streak. wolfram to - / red, brown or black. rutile . light brown. tourmaline . whitish. black jack . yellow, white. the magnetic or dipping needle is used in new jersey, as follows, according to the state geologist, w. h. scranton, m.e.: "an attraction which is confined to a very small spot and is lost in passing a few feet from it, is most likely to be caused by a boulder of ore or particles of magnetite with rock. an attraction which continues on steadily in the direction of the strike of the rock for a distance of many feet or rods, indicates a vein of ore; and if it is positive and strongest towards the southwest, it is reasonable to conclude that the vein begins with the attraction there. if the attraction diminishes in going northwest, and finally dies out without becoming negative, it indicates that the vein has continued on without break or ending until too far off to move the compass needle. if, in passing towards the northwest, along the line of attraction, the south pole is drawn down, it indicates the end of the vein or an offset. if, on continuing further, still in the same direction, positive attraction is found, it shows that the vein is not ended, but if no attraction is shown, there is no indication as to the continuance of the ore. "in crossing veins of ore from southwest to northwest, when the dip of the rock and ore is as usual to the southeast, positive attraction is first observed to come on gradually, and the northwest edge of the vein is indicated by the needle suddenly showing negative attraction just at the point of passing off it. this change of attraction will be less marked as the depth of the vein is greater, or as the strike is nearer north and south. the steadiness and continuance of the attraction is a much better indication of ore than the strength or amount of the attraction. the ore may vary in its susceptibility to the magnetic influence from impurities in its substance; it does vary according to the position in which it lies, that is according to its dip and strike; and it also varies very much according to its distance beneath the surface." further instructions are given in the paper from which the foregoing extract was taken, some of which follow: "it is sufficient to say that the first examinations are made by passing over the ground with the compass in a northwest and southwest direction, at intervals of a few rods, until indications of ore are found. then the ground should be examined more carefully by crossing the line of attraction at intervals of a few feet, and marking the points upon which observations have been made, and recording the amount of attraction. observations with the ordinary compass should be made, and the variation of the horizontal needle be noted. in this way materials may soon be accumulated for staking out the line of attraction, or for constructing a map for study or reference. "after sufficient exploration with the magnetic needle, it still remains to prove the value of the vein by uncovering the ore, examining its quality, measuring the size of the vein, and estimating the cost of mining and marketing it. uncovering should first be done in trenches dug across the line of attraction, and carried quite down to the rock. when the ore is in this way proved to be of value regular mining may begin. in places where there are offsets in the ore, or where it has been subject to bends, folds, or other irregularities, so that the miner is at fault in what direction to proceed, explorations may be made with the diamond drill." chapter ii. how to test for minerals. when the mineralogist wishes to know the names of the specimen he holds in his hand, he, in the case of a mineral difficult to determine, considers all the following properties: crystalline form and structure, cleavage, fracture, tenacity, hardness, specific gravity as compared with that of water, luster, color and streak, transparency or otherwise, taste, odor, chemical composition tested by analysis, pyrognostic characters as determined by the use of the blowpipe, mode of occurrence and associated minerals. crystalline form and structure. unfortunately the science of crystallography is extremely complicated and long study is necessary to master it; once acquired, however, it is of paramount usefulness to the student. according to dana there are six systems, to one of which every crystal may be referred. they are: ( ) isometric; ( ) tetragonal; ( ) hexagonal or rhombohedral; ( ) orthorhombic; ( ) monoclinic; ( ) triclinic. in the isometric system there are three equal axes at right angles to each other. in the tetragonal system there are three axes at right angles to each other. two of these are equal, while the third, or vertical angle, is longer or shorter. there are two divisions of the hexagonal system; the hexagonal system properly so-called, and its rhombohedral division. all forms are referred to four axes, three equal axes inclined to each other at angles degrees in a common horizontal plane, and a fourth vertical axis at right angles, and longer or shorter. the rhombohedral division comprises crystals having but three planes of symmetry, intersecting at angles of degrees in the vertical axis. they are regarded as half forms of the corresponding hexagonal crystals. in the orthorhombic system there are three unequal axes at right angles to each other. in the monoclinic system there are three unequal axes, of which one, the lateral axis, is inclined to the vertical, while the angles between the others are right angles. in the triclinic system there are three unequal axes and these intersections are all oblique. the student who wishes to pursue this subject further should consult dana's system of mineralogy. physical mineralogy. cleavage is the line of easiest separation in a mineral. it may be perfect, imperfect, interrupted, etc. fracture, referring to any surface except that of a cleavage fall, may be uneven, conchoidal (shell-like), hackly (rough), etc. tenacity refers to such qualities as brittle, sectile, malleable, flexible, or elastic. hardness is represented by the difficulty with which a smooth surface is scratched. the scale in general ore was devised by mohs. it is: . talc. scratched by the finger nail. . gypsum. ditto, but with more difficulty. will not scratch a copper coin. . calcite. scratched by a copper coin. . fluorite. is not scratched by a copper coin and does not scratch glass. . apatite. scratches glass, but with difficulty. is readily scratched by a knife. . feldspar. scratches glass with ease. is difficult to scratch by knife. . quartz. cannot be scratched by a knife and readily scratches glass. . topaz. harder. . corundum. harder. . diamond. scratches any other substance. hardness may be intermediate. for instance, any mineral that scratched quartz and is soft enough to be scratched by topaz, in turn would be rated at . . specific gravity. this is the density of mineral and other substances compared with that of water. it is particularly valuable in determining heavy metals. to find the specific gravity of any solid body divide its weight in air by the loss of weight in water, at a temperature as near degrees f. as possible, and the quotient will equal the specific gravity. in the case of gases, such as nitrogen, oxygen, etc., hydrogen is taken as the unit. luster. there are seven kinds of luster, viz: metallic, the luster of metals; adamantine, that of the diamond; vitreous, of broken glass; resinous, of the yellow resins; greasy; pearly; silky. there are five degrees of intensity of luster recognized, viz: splendent; shining; glistening; glimmering; dull. color and streak. the streak is the color of the powder of the mineral when rubbed on unglazed porcelain, or scratched with a knife. transparency. minerals may be transparent, sub-transparent, translucent, sub-translucent, opaque. taste. minerals may be salt, bitter, sweet, etc. odor. this test is not of much use with most minerals until heat is applied. all the petroleum oils, however, are often detected by their odor. chemical composition. this may always be determined by suitable tests with reagents. pyrognostic characters. as a means of readily determining the nature of a specimen the blowpipe is unrivalled--if in the hands of one who understands it. mode of occurrence and associated minerals. a knowledge of these matters often assists in a determination. a regular fire assay is not within reach of many prospectors, for the necessary apparatus cannot, as a rule, be carried in the wilderness. whenever possible, however, a fire assay gives the truest results, especially in the case of gold and silver. [illustration: scale for weighing ore.] the operation includes testing the ore, sampling and pulverizing, weighing the ore and reagents, calcination and roasting, reduction and fusion, distillation and sublimation, scorification and cupellation, inquartation and parting the gold and silver, weighing and tabulating. "notes on assaying" by dr. ricketts is a very useful manual to have at hand. a tolerably complete outfit includes: a pair of scales for weighing ore and buttons of base metal. it should take ounces in each pan, and show / of a grain. a bullion scale to be kept strictly for the precious metals. loaded with one gramme, it should show / of a milligramme. [illustration: assay balance for bullion.] weights. avoirdupois; troy, metric and "assay." assay weights save much calculation. the unit of the system is a weight of . grammes. its derivation is as follows: lbs. : a.t. :: oz. troy : milligramme. to use this system, weigh out one a.t. of the ore and whatever number of milligrammes of gold and silver the assay gives indicates an equal number of troy ounces to the ton of lbs. avoirdupois. a muffle and a melting furnace, portable and of medium size, are handy, though furnaces may be built of ordinary brick, lined with fire brick, that would be better for permanent use. the fuels may be coke, anthracite or bituminous coal, charcoal, oil or gas. [illustration: assay furnace.] [illustration: portable assay furnace.] crucibles of black lead, french clay, hessian sand, and quicklime are necessary to hold the assay. [illustration: french clay. hessian. crucibles.] [illustration: scorifier] [illustration: steel cupel mould.] roasting dishes, scorifiers and cupels are required. the cupel is made of the ashes of burnt bone, and it is better to make them on the spot, as the bone ash may be carried anywhere without damage, whereas the cupels are very fragile. the bone ash is moistened with water, stamped in a cupel mould, and allowed to dry slowly. a good one will absorb its own weight of lead, but it is better to calculate on its absorbing but three-quarters of that amount. [illustration: scorification furnace.] [illustration: scorification mould.] the crucible, scorification and cupel tongs, a couple of hammers, iron pestle and mortar, sieves from to mesh, and scorification mould complete the requisite tools. [illustration: hammer.] [illustration: horn spoon.] [illustration: steel mortar.] [illustration: alcohol lamp.] in addition, however, the assayer will require quite a bulky lot of apparatus, reagents and chemicals. all dealers keep lists of assayers' supplies on hand, and a full and complete assortment will cost about $ in new york or chicago. quart bottles, with glass stoppers; ordinary corked bottles, ring stands, alcohol lamps, wash bottles, test tubes, horn spoons, iron pans, parting flasks, annealing cups, glazed black paper--these will suffice, provided the assayer has, as well, the outfit recommended for blow-pipe work. [illustration: test tube.] dry reagents, such as litharge, borax (crystallized), silica, cyanide of potassium, yellow prussiate of potash, argol, charcoal, starch, metallic iron, pure lead, nitre, powdered lime, sulphur, carbonate of ammonia and common salt are necessary. as solvents and precipitants, distilled water, sulphuric, nitric and hydrochloric acids, chloride of sodium, nitrate of silver and sulphuretted hydrogen are also indispensable. this will seem rather a formidable list, and so, under certain conditions, it may be; indeed, where means of transport is limited, all regular assay work must be postponed until the return to civilization. assaying is not, however, difficult, being mostly a matter of rule of thumb, and correct results may be arrived at without a deep knowledge of chemistry, although such knowledge will never come amiss. a preliminary examination will show what the ore probably is. the blow-pipe is especially useful, though to the skilled assayer often unnecessary. the ore is first powdered, and any metallic flakes picked out and tested separately. a fair sample must be selected, otherwise all the work will be thrown away and the result be valueless. the next step is weighing the ore and the reagents. moisture is drawn off by heating in a crucible, a low heat being sufficient. roasting will eliminate sulphur, antimony, arsenic, etc., and must take place in a flat dish, so that the air may have free access. the powder should be stirred frequently. reduction is the operation of removing oxygen, and it takes place usually in a crucible or scorifier. scorification consists in placing the ore in an open dish with proper reagents, and collecting all the volatile ingredients in the slag. cupellation, on the other hand, collects them in the bone ash, of which the cupel is composed. when silver must be separated from gold, it is sometimes convenient to increase its proportion by the addition of some known weight of the inferior metal. after fusing, the globule is placed in nitric acid, and the silver parted from the gold, which may then be weighed. this result subtracted from the weight of the original globule gives the amount of silver. to test an ore for gold, take a pound of it, crush in mortar and pass through a fine sieve. take one-fourth ounce troy of the powder. place in scorifier with an equal amount of litharge. cover with borax that has been melted and powdered, and put the scorifier in the muffle of the furnace. a blacksmith's forge might do at a pinch. heat until the mass has become a fluid, possibly twenty or thirty minutes. next pour into the scorification mould, and, after the slag has set, remove it with a hammer. hammer the button into a cube and place it in the cupel, which must first have been thoroughly heated. heat until all the base metal has been absorbed by the cupel and the button has "brightened," or flashed; when this occurs, remove the cupel to the front of the muffle, cool, and remove the button with pincers. weigh it, and you have the amount of gold and silver in / -ounce troy. a simple sum in proportion gives the amount in a ton. all ores containing sulphur, arsenic, antimony, or zinc, should be roasted. there are three stages in the scorification process; roasting, fusion, and scorification. during the first, the heat should be moderate until fumes cease to be given off; during the second, the heat is raised and a play of colors is seen on the surface of the lead; in the closing stage, the heat is lowered for a time until the slag covers the lead, when it is again raised for a short time and the scorifier removed. brittle buttons may be due to arsenic, antimony, zinc or litharge, and must be re-scorified before cupellation, with more lead. take the cupel slowly from the fire to avoid "spitting," by which portions of the buttons are lost. watch closely for the brightening. silver is volatile at a high heat, but when the muffle is almost white, the metal well fused and clean, the fumes rising slowly, and the cupel a cherry red, all is going smoothly. if the fumes rise rapidly, the muffle is too hot. on the other hand, dense, falling fumes show the temperature is too low. lead that is poor in silver stands the highest heat without vitiating the assay. when the material in the cupel "freezes," i.e., the absorption by the cupel stops, reject the assay and try again, giving more heat or more lead. gold. practically, the metal most prospectors seek is gold. it is so enormously valuable and constitutes so very small a percentage of any ore, that care must be taken or it may escape detection and be lost. panning is the miner's method. he crushes his ore thoroughly, and places it in the pan with water; then, with a motion easy to learn but difficult to describe, he swirls the water around, allowing a little of it to escape at each revolution, carrying with it the rubbish, until finally he has a little black sand and perhaps a few grains of yellow substance, which is gold. mica, or fool's gold, puzzles nobody but the ignoramus. true, it looks like gold in certain positions and lights, but gold will beat out thin under the hammer, just as lead would, while mica will break up into a floury powder. mica is very light, while gold is very heavy; so there is no excuse for confounding the two. if an ore contains sulphurets and gold, the latter may be coated with some sulphur or arsenic, which would prevent the gold from amalgamating. the only remedy for this is roasting. no single acid will dissolve gold, but a solution known as aqua regia, made up of three parts of hydrochloric acid and one part of nitric acid, dissolves it. if to the solution so obtained you add some sulphate of iron, you will get a precipitate which is metallic gold, although it does not look like it, as it is brown in color; but if you place this precipitate in a crucible and heat, you will get a yellow bead of pure gold. another test for gold is to take the solution as above obtained and add thereto a solution of chloride of tin, when you obtain a purple coloration that has been called the purple of cassius. gold may be distinguished from all other metals by the three following tests: it is yellow; it may be flattened by the hammer; it is not acted upon by nitric acid. pure gold is soft, and the point of a knife will scratch it deeply. pounded in a mortar, the pulverized mineral should be passed through a cheese-cloth screen stretched over a loop of wood. if the course contains much pyrite, it must be roasted before washing in the pan and amalgamating. sample well, weigh out two pounds, put it in a black iron pan, with four ounces of mercury, four ounces of salt, four ounces of soda and a half gallon of boiling water. stir with a green stick, and agitate until the mercury has been able to reach all the gold. pan off into another dish so as to lose no mercury, squeeze the amalgam through chamois leather or new calico previously wetted. the pill of hard amalgam may be placed on a shovel over the fire or in a clay tobacco pipe and retorted. gold is readily acted upon by the mixture of nitric and hydrochloric acids known as aqua regia, or by any solution producing chlorine. some of the mixtures which attack it are bisulphate of soda, nitrate of soda and common salt, hydrochloric acid and potassium chlorate, and bleaching powder. the action is more rapid in hot than in cold solutions, and impure gold is more easily dissolved than pure. mercury dissolves gold rapidly at ordinary temperatures, the amalgam being solid, pasty or liquid. gold rubbed with mercury is immediately penetrated by it. an amalgam containing per cent. of mercury is liquid; . per cent., pasty; per cent., crystalline. these amalgams heated gradually to a bright red heat lose all their mercury, and hardly any gold. about one-tenth of per cent. of mercury remains in the gold until it is refined by melting. the veins from which the gold of the world is won do not, on an average, hold the precious metal in greater proportion than one part of gold in , parts of veinstone. under favorable conditions a proportion not one-fifth as rich as this, may yield a rich return. in hydraulic mining on a large scale, one part of gold in , , parts of gravel has paid a dividend. a test known as darton's is believed to be a valuable means of detecting minute quantities of gold in rocks, ore tailings, etc. "small parts are chipped from all the sides of a mass of rock, amounting in all to about / ounce. this is powdered in a steel mortar and well mixed. about half is placed in a capacious test tube, and then the tube is partly filled with a solution made by dissolving gr. of iodine and gr. of iodide of potassium, in about - / ounces water. the mixture thus formed is shaken and warmed. after all particles have subsided, dip a piece of fine white filter paper in it; allow it to remain for a moment; then let it drain, and dry it over the spirit lamp. it is next placed upon a piece of platinum foil held in a pincers, and heated to redness over the flame. the paper is speedily consumed; and after again heating to burn off all carbon, it is allowed to cool and is then examined. if at all purple, gold is present in the ore, and the relative amount may be approximately deduced. this method takes little time, and is trustworthy." black sand, which is iron, often with some platinum and iridium, sometimes interferes with the result of a gold assay. attwood recommends the following method as applicable to such a case: "take to grains and attack with aqua regia in a flask; cool for about thirty minutes or more; dilute with water and filter. if gold is present, it will now be held in solution in the filtrate. remove the filter and evaporate the filtrates to dryness; then add a little hydrochloric acid, evaporate and re-dissolve the dry salt in warm water; add to the solution so formed proto-sulphate of iron; which will throw down the gold in the form of a fine, dark precipitate. the precipitate is seldom fine, being mixed with oxides of iron, and must now be dried in the filter paper, and both burned over the lamp in a porcelain dish. then mix the dried precipitate with three times its weight of lead; fuse, scorify and cupel. in case platinum, iridium, etc., are found associated with the gold, an extra amount of fine silver should be added before cupellation, and the gold button will be found pure." in one of his reports the state mineralogist of california gives a most lucid description of a mechanical assay of gold-bearing sands, stamped ore, etc., etc. he states: "it must be understood that this is only a working test. it does not give all the gold in the rock, as shown by a careful fire assay, but what is of equal importance to the mine-owner, mill-man, and practical miner, it gives what he can reasonably expect to save in a good quartz mill. it is really milling on a small scale. it is generally very correct and reliable, if a quantity of material be sampled. the only operation which requires much skill is the washing, generally well understood by those who are most likely to avail themselves of the instructions. these rules apply equally to placer gravels. take a quantity of the ore--the larger the better--and break it into egg-sized pieces. spread on a good floor, and with a shovel mix very thoroughly; then shovel into three piles, placing one shovelful upon each in succession until all is disposed of. two of the piles may then be put into bags. the remaining pile is spread on the floor, mixed as before, and shovelled in the same manner into three piles. this is repeated according to the quantity sampled, until the last pile does not contain more than pounds of ore. as the quantity on the floor becomes smaller, the lumps must be broken finer until at last they should not exceed one inch in diameter. the remainder is reduced by a hammer and iron ring to the size of peas. the whole pounds is then spread out, and after careful mixing portions are lifted with a flat knife, taking up the fine dust with the larger fragments, until about pounds have been gathered. this quantity is then ground down fine with the muller, and passed through a -mesh sieve. if the rock is rich, the last portion will be found to contain some free gold in flattened discs, which will not pass this sieve. these must be placed with the pulverized ore, and the whole thoroughly mixed, if the quantity is small, but if large must be treated separately, and the amount of gold allotted to the whole pounds and noted when the final calculation is made. "from the thoroughly-mixed sample, two kilogrammes ( grammes) must be carefully laid out. this is placed in a pan or, better, in a batea, and carefully washed down until the gold begins to appear. clean water is then used, and, when the pan and the small residue are cleaned, most of the water is poured off and a globule of pure mercury (which must be free from gold) is dropped in, a piece of cyanide of potassium being added with it. as the cyanide dissolves, a rotary motion is given the dish, best done by holding the arms stiff and moving the body. as the mercury rolls over and ploughs through the sand, under the influence of the cyanide it will collect together all the particles of free gold. when it is certain that all is collected, the mercury may be carefully transferred to a small porcelain cup or test tube, and boiled with strong nitric acid, which must be pure. when the mercury is all dissolved the acid is poured off, more nitric acid applied cold, and rejected, and the gold is then washed with distilled water and dried. "the object of washing with acid the second time is to remove any nitrate of mercury which might remain with the gold, and which is immediately precipitated if water is first used. "the resulting gold is not pure, but has the composition of the natural alloy. before accurate calculations of value are possible, the gold must be obtained pure and weighed carefully. to purify the gold it should be melted with silver, rolled out or hammered thin, boiled twice with nitric acid, washed, dried, and heated to redness. "the method of calculating this assay is simple. it will be observed that grammes represent a ton of pounds; then each gramme will be the equivalent of one pound avoirdupois, or one th part of the whole, and the decimals of a gramme to the decimals of a pound. suppose the ore yielded by the assay just described, fine gold weighing . gramme, it must be quite evident that a ton of the ore would yield the same decimal of one pound. now one pound of gold is worth $ . , and it is only necessary to multiply this value by the weight of gold obtained in grammes and decimals to find the value of the gold in a ton of ore--$ . Ã� . --$ . . the cyanide solution should be kept rather weak, as gold is slightly soluble in strong solutions of cyanide of potassium. cyanide is a deadly poison." touchstones are useful in deciding the probable value of gold alloys. several pieces of the metal under examination are cut with a cold chisel, and the fresh edges drawn over the touchstone. these streaks are touched with nitric acid on a glass rod. should no reaction follow, the gold is at least fine. wipe the stone with soft linen and try with test acid, made by mixing parts of chemically pure nitric acid with two parts of hydrochloric acid, adding parts distilled water by measure. if this has no effect, take a touch needle marked , and make a similar streak on the stone samples. compare, and, if necessary, continue with the other needles, using a higher number each time. an approximate estimate of the sample will soon be obtained. should the gold seem poorer than fine, try with the copper or silver needle. practice and a good eye soon make this method very certain in its results. retorted amalgam is likely to contain mercury. to test for it, put a small fragment into a closed glass tube, taking care that it falls quite to the bottom. heat the gold over a spirit lamp, and a deposit of mercury will soon be seen upon the colder sides of the tube above the bottom. the tube may be broken and the mercury collected into a globule under water. in mining regions gold dust passes current as coin, according to what is supposed to be its value. occasionally counterfeit dust is offered. the readiest means by which it may be detected are as follows: the dust from any one district is always much alike, and any unusual appearance should create suspicion. try any doubtful pieces on a small anvil, remembering that gold is extremely malleable. test some of the gold with nitric acid; effervescence or evolution of red fumes, or coloration of the acid prove impurities to be present. place two watch-glasses (most useful in chemical tests) on paper; the one on a white sheet, the other on a black, and with a glass rod convey a few drops of nitric acid from the dish to each. to the glass on white paper add a drop or two of ammonia; a blue color would indicate copper. to the other add hydrochloric acid; should a white precipitate form, it proves silver. if no action is noticed, even after heating the dish, the dust is genuine. as "dust" is sometimes merely copper coated with gold, the better plan is to cut all the larger grains in two, so that the acid may attack the copper should it be present. copper. copper is a very easy mineral to test for. first crush the ore and dissolve it in nitric acid by heating. then dilute with some water, and add ammonia. the solution should turn dark blue. the carbonate ores of copper do not extend deep in the mine. their places are taken by copper pyrites. sulphide ores are usually difficult to treat, and when they are to be tested it is better to roast them before trying the tests for color. test for copper may also be made as follows: the sample must be pulverized. take an ounce of the powder, and place in a porcelain cup. add forty drops of nitric acid, twenty drops of sulphuric acid and twelve drops of hydrochloric acid. boil over the spirit lamp until white fumes arise. when cool, mix with a little water. filter and add a nail or two to the liquid. the copper will be precipitated, and may be gathered up and weighed. the amount of copper in the sample multiplied by , will be the copper in a ton of the ore. should copper be suspected, roast the powdered ore and mix with an equal quantity of salt and candle grease or other fat; then cast into the fire, and the characteristic flame of copper--first blue and then green--will appear. this test is better made at night. coal. coal is often more valuable than gold, and the prospector should be prepared to estimate the value of any seams he may come across during his travels. the following is a very rough but wonderfully effective test for coal. take a clay pipe, pulverize your sample, weigh off twenty pennyweights, and place it in the bowl of the pipe. make a cover with some damp clay. dry thoroughly, and put the bowl upside down over a flame. the gas in the coal will come out through the stem, and may be lit with a match. let the pipe cool after the gas has all escaped, break off the covering of clay, and if the coal was adapted for coke the result will be a lump of that substance in the bowl. weigh this. the difference in weight between the coke and the twenty pennyweights of coal that were placed in the bowl will represent the combustible matter forced out by the heat. now take this coke and burn it on a porcelain dish over the lamp. you will have more or less ash left, and the difference in weight of the ash and the coke will be the amount of fixed carbon in the coal. your test is complete, and it need not have cost you even the pipe. sulphur is a detriment to coal, and if you notice much of it in the escaping fumes, you may be sure your sample is not worth much. mercury. cinnabar, the common ore of mercury, is a sulphide. scratch it with a knife, and the streak will be bright crimson. dissolve the ore in nitric acid, add a solution of caustic potash, and you have a yellow precipitate. a very pretty test is to place the ore pulverized in a glass tube with some chloride of lime; close the top of the tube, and place a smaller one therein, so bent that it will pass into a basin of water; heat the bottom of the tube containing the ore and lime, keeping the upper part and the small tube cold with wet rags, and you will have a deposit of quicksilver in the basin. silver. silver ore may be detected by dissolving a small quantity in a test tube with a few drops of nitric acid. boil until all the red fumes disappear. let the solution cool, and add a little water. filter the whole, and add a few drops of muriatic acid, which will precipitate the white chloride of silver. dissolve this precipitate with ammonia; then add nitric acid once more. exposed to the light, the precipitate soon shows a violet tint. pure silver is the brightest of metals, of a brilliant white hue, with rich luster. to detect chloride of silver in a pulp, rub harshly with a clean, bright and wet copper cartridge or coin, and if there be silver in the pulp the copper will be coated with it. graphite will also whiten copper, but the film is easily rubbed off. nickel. nickel may be determined as follows: a little of the powdered ore taken up on the point of a penknife, and dissolved in a mixture of ten drops of nitric and five drops of muriatic acid, should be boiled over a lamp for a few minutes, and ten or twelve drops of water added. a small quantity of ferrocyanide of potash will throw down a whitish-green precipitate, indicating nickel. platinum. platinum is a most refractory metal to treat, as it must be boiled for at least two hours in the mixture of muriatic and nitric acid, known as aqua regia. a small amount of alcohol is to be added to the solution, and the latter filtered. the platinum is precipitated with ammonia chloride. manganese. manganese may be proved as follows: a few grains of powdered ore are placed in a test-tube, with three or four drops of sulphuric acid. two or three grains of granulated lead or litharge being dropped in, the color will become pink should manganese be in the ore. a preliminary examination of a mineral may be made with a pocket lens and a penknife. with the first, any conspicuous constituents may be recognized, while a scratch with the point of the latter will give an idea as to the softness or hardness of the mineral. should much quartz (silica) be present, a sharp blow with the steel will cause sparks. the next test should be with some ore powdered and held over a spirit flame. a drop or two of water and a drop of sulpho-cyanide of potash will reveal iron, should such be present, by a deep red coloration. to another portion add one drop of hydrochloric acid, and a dense, curdy precipitate will indicate silver, if there be any. added to the same original nitric acid solution, several drops of ammonia water would detect copper by a blue color. antimony, tin, aluminum, zinc, cobalt and nickel, uranium and titanium are best shown by the blowpipe. carbonates, that is those minerals that contain carbon and oxygen in addition to the metal, effervesce when brought into contact with hydrochloric acid. some sandstones have a small amount of lime carbonate, and must be tried under the lens, as the bubbles are microscopic. these tests are extremely useful, but by no means infallible, owing to so few ores being pure. when the explorer wishes to know all the constituents of the ore he has found, he must analyze it. an analysis gives every substance in the ore. such examinations may be either by the "dry" or "wet" methods, though usually the term "analysis" is restricted to the latter, and "fire assay" is used to describe the former. the wet assay for silver, lead or mercury is effected as follows: drop a little powdered ore in a test tube; add nitric acid; dilute with / water; warm gently over the spirit lamp. it may dissolve or it may not. in the latter case, add four times as much hydrochloric acid. should all these attempts fail, a fresh sample must be taken, and equal parts of sodium carbonate and potassium carbonate added, and the whole strongly heated in a platinum crucible. the contents, after cooling, is dissolved in dilute nitric acid. in any case the assay will now be dissolved, and will be in the solution. filter. pour ten drops into a test tube; add three or four drops of hydrochloric acid. a precipitate appears. it may be silver, lead or mercury. if silver, it grows dark violet after exposure to sunlight, or or drops of ammonia dissolves it in a few moments. should it not dissolve, it is lead or mercury. test for lead by filtering, and heating some of the precipitate on charcoal before the blow-pipe. a bead and yellow incrustation indicate lead. should none of these things happen, then the metal is mercury. filter; place in glass tubes; heat gently, and a mirror of quicksilver will appear on the sides of the glass. this is as far as the prospector, without the various reagents and chemicals that the analyst has always at hand, will be able to go. more complex treatment must be reserved until a return to civilization. chapter iii. blow-pipe tests. [illustration: blow-pipe.] as a means of readily detecting the presence of minerals in their ores the blow-pipe, in the hands of a skillful operator, is unrivaled. nor is this skill at all hard to come by; two or three weeks' patient study under a good master should teach a great deal, and subsequently proficiency would come by practice in the field. unfortunately, some very clever men have become so enthusiastic as to blow-pipe work that they have devised methods by which the amount of metal in an ore as well as its nature may be determined, but in so doing have so enlarged the amount of apparatus, and complicated the tests so seriously that the simplicity of the blow-pipe outfit is in danger of being lost, and its chief advantage of being forgotten; for there are many better ways of determining the value of an ore. a good assay or, better still, a mill run, is worth incomparably more than any quantitative blow-pipe test, even when conducted by a plattner. the chemical blow-pipe is made of brass or german silver, with platinum tip. the best fuel, taking everything into consideration, is a paraffin candle in cold climates, and a stearine candle in hot ones. tallow may do in an emergency, but it requires too much snuffing. [illustration: reducing flame.] the blow-pipe can produce two flames. the one known as the reducing flame, and generally printed as r.f.; and the oxidizing flame, represented by the initials o.f. in the first the substance under examination is heated out of contact with the air and parts with its oxygen. in the second, it is heated in the air and absorbs oxygen. [illustration: oxidizing flame.] well-burnt pine or willow charcoal in slabs inches by - / inches is the material upon which the mineral to be tested is placed. a small shallow depression is scraped out of one side of it and the assay placed therein. platinum wire, some inches long, conveniently fused into a piece of glass tube as a handle, is used to test the coloration of minerals in the flame. this should be cleaned occasionally in dilute sulphuric acid and then washed in water. a small pair of forceps with platinum points serve a great variety of purposes, but the beginner must be careful not to heat metallic substances in them to a red heat, as he may thereby cause an alloy of the metal with the platinum and spoil them for future use. [illustration: agate mortar.] glass tubing one-twelfth to one-quarter inch in diameter and from four to six inches in length is used for a variety of purposes. from this material what are known as closed tubes may be made by heating a piece of the tubing at or about its center over a spirit lamp, and, when the glass has fused, pulling it apart. these closed tubes are used in heating substances out of contact with the air. a small agate mortar is indispensable. it must be used for grinding substances softer than itself to a powder, but it will break if rapped sharply. a small jeweler's hammer is used to flatten metallic globules upon any hard surface a regular blow-pipe outfit would include a small anvil for this purpose, but it is hardly necessary, as any iron or steel surface will do. [illustration: magnet.] [illustration: lens.] [illustration: nest of test tubes.] a magnet will detect the presence of any magnetic mineral, especially if it is reduced to powder and the test made under water. two small files, one three-cornered and the other rat-tailed, must be included in the list of requisites. by means of the former, glass tubing may be notched and pulled or pushed apart, and the latter is necessary in fitting glass tubing to the cork of wash-bottles and other apparatus. a good lens is indispensable. that known as the coddington is as good as any. a dozen test tubes of hard glass, with stand, in small and medium sizes, should not be forgotten. a glass funnel - / inches in diameter is requisite in filtering. the circular filter papers are folded in four and placed in the funnel, point down, three thicknesses of the paper being on one side of the funnel and one thickness on the other. a wash-bottle is made from a flask into which a sound cork has been placed with holes in it for two pieces of glass tubing. the one serves as a mouth-piece into which the operator blows, while the other, reaching almost to the bottom of the bottle and ending in a spout outside the cork, permits a stream of water to be forced out of the bottle when it is blown into. a few glass rods in short lengths do for stirrers. a little ingenuity is better than much apparatus. of reagents, all those to be found in a well-appointed laboratory may occasionally be of service, but the rough and ready prospector can get along fairly well with the following: carbonate of soda, borax, microcosmic salt, cobalt solution, cyanide of potassium, lead granulated, bone ash, test papers of blue litmus and turmeric, the former for proving the presence of acid in a solution and the latter that of an alkali. the foregoing are all dry reagents. among the wet reagents are: water--clean rainwater--or, better still, distilled water; hydrochloric acid, sulphuric acid, nitric acid, ammonia, nitrate of cobalt. heating a mineral with carbonate of soda on charcoal is accomplished as follows: the pulverized mineral, intimately mixed with three times its bulk of carbonate of soda, is placed in the cavity on the coal. tin ore, which is very difficult to reduce, should have a fragment of cyanide of potassium placed upon it after it has been heated for a few seconds, and the flame is then reapplied. a globule of metal should result, and perhaps an incrustation on the coal. the reaction is as follows: metal. globule. incrustation. gold. yellow, malleable. none. silver. white, malleable. none. copper. red, malleable. none. lead. white, malleable. red when hot, yellow when cold. bismuth. white, brittle. red when hot, yellow when cold. zinc. none. yellow when hot, white when cold. antimony. white, brittle, fumes. white. a small loop is made at the end of the platinum wire, and it is heated and dipped in borax; heated again, then touched while hot to the powdered mineral and heated once more. the following colors are obtained: color of bead. o.f. r.f. metal. red or yellow, hot. bottle-green. iron. yellow or colorless, cold. blue, hot or cold. blue. cobalt. green, hot; blue, cold. red. copper. amethyst. colorless. manganese. green. green. chromium. violet, hot; red-brown, cold. gray. nickel. the substance to be tested is generally powdered and moistened, placed in the cavity and covered or not as circumstances may demand, with a pinch of carbonate of soda or other suitable reagent. the following results may be obtained: antimony. place the mineral in the cavity with a little of carbonate of soda, and blow upon it with the inner or oxidizing flame. this is formed by inserting the blow-pipe an eighth of an inch into the flame and blowing steadily. a white incrustation on the coal, and a brittle button of antimony should be the result. lead. treat the suspected lead ore the same way, and you will get a yellow incrustation on the coal and a button of malleable lead. zinc. proceed as above, and after blowing for a few seconds moisten the incrustation with a drop of nitrate of cobalt. heat once more, but this time use the outer or reducing flame, which is produced by keeping the point of the blow-pipe a little outside the flame and blowing more gently than before, so that the whole flame playing upon the coal may be yellow in color. a green incrustation will be an evidence of zinc. copper. as usual, mix the ore and the soda into a paste and fuse it with the oxidizing flame. dig the mass out of the charcoal with the point of a knife and rub it in the mortar with water. now decant into a test tube, and, allowing the sediment to settle, pour off the water. if there was copper in the ore, red scales will be found in the test tube. arsenic. heat in the inner flame for a second or two, and if the ore contains arsenic you will notice an odor of garlic. tin. this is a very difficult ore to reduce, but the addition of a little cyanide of potash to the powdered ore will make it easier. fuse, after moistening on the charcoal, in the oxidizing flame, and you will probably obtain small globules of tin. silver. make a paste of the ore with carbonate of soda; add a small piece of lead and fuse into a button. make a second paste of bone ash and water, and after you have dried it with a gentle flame place the button of silver and lead on the bone ash, and turn on the oxidizing flame. the lead will disappear, leaving a silver globule. should it not be pure white, but more or less tinged with yellow, it probably contains gold; and if the button be dissolved in nitric acid, whatever remains behind is gold. sometimes it is desirable to determine whether tellurium is present in an ore. this is very easy to find out. all that is required is a blow-pipe, alcohol lamp and a porcelain dish. break off a small piece of the ore, place it in the dish previously warmed, blow upon the ore with the blow-pipe until it is oxidized, then drop a little sulphuric acid on the ore and dish. if tellurium be present, carmine and purple colors on the assay will proclaim the fact. bismuth ores are very heavy; usually they have more or less antimony associated with them, which is a drawback, as the separation is an expensive matter and the returns are less than they would be from a low grade pure ore. in testing for this metal, dissolve a crushed sample in nitric acid and then add potash in excess. if the ore is one containing bismuth, you should have a white precipitate; if it contains cobalt, you will get a bluish-green coloration. bismuth is worth about fifty cents a pound if pure and free from antimony. galena is often mistaken for other ores, specular iron ore for instance. if the ore be crushed and heated in nitric acid until dissolved, some water added, and an addition made to the solution of a few drops of ferrocyanide of potassium, a dark blood-red precipitate is thrown down. if the ore were galena, there would be no coloration. the so-called steel galena which carries a little zinc is generally richer in silver than the ordinary cube galena, though the reverse is sometimes the case. if lead ore be dissolved in nitric acid, the solution diluted, and some hydrochloric acid added, a white precipitate is thrown down. add ammonia and the precipitate remains unaltered. the blow-pipe operator has to learn to breathe and blow at the same time; the breathing he does through the nostrils, the blowing is produced by the natural tendency of the cheeks to collapse when distended with air. a skillful operator can blow for many minutes at a time without the slightest fatigue. to identify cinnabar, the ore from which quicksilver is obtained, make a paste of the substance in powder and carbonate of soda. heat in the open tube, and a globule of mercury will result. sulphur turns silver black. make a paste with carbonate of soda, heat on the charcoal, and removing the mass with the point of a knife lay it on a silver coin and moisten. a black sulphide of silver should show quickly on the coin if sulphur is present. magnesia gives a faint pink color when heated and treated with nitrate of cobalt on coal. alumina under the same circumstances give a blue color. roasting is an oxidizing process, the substance being heated in air, so that it may absorb oxygen. the test by reduction with soda on coal in the r.f. is particularly valuable in the case of copper ore, as little as per cent. being detected. chapter iv. economic ores and minerals. aluminum is derived from two ores, cryolite and bauxite. this metal has made rapid strides into favor during the past half-dozen years. although known since , it remained a rare substance in the metallic form, though it is the most abundant of any of the metals in its ore. in ordinary clay there is an inexhaustible source of aluminum. but the ores that yield the metal cheaply are few. until recently, cryolite, found abundantly in greenland, was the chief source of the metal, but now bauxite is used in its place. bauxite is a limonite iron ore in which a part of the iron has been replaced by aluminum. it is found in alabama, georgia and arkansas, as well as in europe. aluminum is white, and very light in weight. it does not tarnish easily. the chemical composition of these ores is: aluminum. cryolite, al{ }f{ }. naf . per cent. bauxite, al{ }o{ }. h{ }o . per cent. in the production of this metal in the united states was , pounds. in it rose to , , pounds. the only firm producing aluminum is the pittsburg manufacturing company of buffalo, n.y., who reduce the metal from bauxite, which they obtain in the southern states. one of the latest uses for this metal is for gold miners' pans. the french seem to keep ahead of the rest of the world in finding new uses for aluminum. most of the supply of cryolite comes from greenland, where it occurs in veins running through gneiss rocks. glass-makers use it and pay good prices for it. lately makers of aluminum also buy it, as it contains per cent. of that metal. a new aluminum-bearing mineral, discovered in new mexico and in ohio, is called native alum. it gives . per cent. alumina, and may be treated by solution in warm water, filtration, evaporation and roasting. no estimate has yet been made of the amount available. as bauxite promises to be in greater demand in the future than in the present, owing to the ever-increasing demand for aluminum, the prospector will do well to make himself thoroughly familiar with its appearance. it is creamy white when free from iron, and the grains are like little peas, or pisolitic. it contains water, aluminum, silica, and generally iron. the french beds near the town of baux are miles long and feet thick. in the united states, beds have been found in alabama, georgia and arkansas. the georgia beds are turning out three-fifths of the bauxite produced in america. the ore is in beds and pockets, and enough has been prospected to assure a supply for some years to come, unless the demand should grow very decidedly, in which case a scarcity might soon be felt. the american ore is easier to work than the french, and manufacturers prefer it to any they can import, even though the cost is higher and the percentage of aluminum smaller. the arkansas deposits are as thick as the french, and only feet above the level of the tide. imported bauxite cost $ to $ a ton in new york city. american ore costs $ to $ a long ton. best selected georgia brings $ . should the deposits of bauxite give out, the manufacturers of aluminum would probably fall back on cryolite. at tvigtuk, on the west coast of greenland, it exists, as a very heavy vein, in gneiss. it is semitransparent, and snow-white. impurities may stain it yellow or red or even black. its specific gravity is . , and its hardness . to . it is fusible in the flame of a candle, and yields hydrofluoric acid if treated with sulphuric acid. it is still used for making soda and aluminum salts, and an imitation porcelain. it is also in general use as a flux. amber. this is a fossil resin, or gum, and may often be found in lignite beds. recent discoveries have been made on the coast of british columbia that are expected to supply the world. all pipe-smokers know it. antimony. the commercial ore of this metal is the sulphide known as stibnite, or gray antimony. its composition when pure is per cent. antimony and per cent. sulphur. hardness is ; gravity, . ; luster, metallic; opaque; gray; cleavage, perfect. fracture, conchoidal. texture, granular to massive. the ore tarnishes quickly, is easily melted, or dissolved in hydrochloric acid. the associated minerals are generally the ores of lead, zinc, and carbonate of iron. baryta may be the gangue or veinstone. antimony is worth from to cents a pound. although antimony occurs in many minerals, the only commercial source is the sulphide, stibnite. antimony is used as an alloy in type metal, pewter, and babbitt metals. it is injurious to copper, even one-tenth of one per cent. reducing the value of that metal very considerably. the price varies greatly, being now about cents a pound. the composition of stibnite is: antimony. stibnite, sb{ }s{ } . per cent. the production of antimony in this country is not very large. the output of was but , tons, valued at $ , . the ore is worth from $ to $ a ton delivered at staten island, n.y. apatite suffered in demand when the cheap phosphates of south carolina were discovered, and these in turn are being ousted from the markets of the world by thomas slag, an artificial phosphate, and by the easily-mined natural phosphates of algeria. the price varies with the quality of the rock, from $ . to $ per ton, averaging in , $ . . apatite is a phosphate of lime, containing per cent. of phosphoric acid. it occurs in the old crystalline and primary rocks of canada, but although still of some value it has yielded the position it once occupied to the carolina phosphate deposits, which, although not so rich in acid, are softer, and less expensive to utilize. apatite is doubtless derived from the remains of animals or fishes that lived in the distant past. the colors are often beautiful--green, pink, gray, etc.--but the sheen is always white. hardness of . . specific gravity, . . asbestos. this fibrous silicate of magnesia and lime is to be looked for among primary rocks near serpentine dike. the fibers of this material may be woven into cloth that will be fire-proof. it is of considerable, though fluctuating, value. the demand for this material is likely to increase, though at present the supply is fully equal to demand. it is being used in germany to make fire-proof paper, and in quebec to make asbestos plaster for covering wood-work. it is generally quarried in open pits, the rock being crushed in a rock-breaker, and the fiber freed from adhering particles of rock and dust. it is then sorted, the longest fibers going into the first quality heap. the production in in the united states was tons, value $ , ; in canada, , tons, value $ , . borax. this mineral is borate of soda. its composition is: per cent. boric acid, per cent. soda, and per cent. water. its gravity is . . hardness, . . it is white, and has a sweetish taste. borax is valuable, but occurring as it does as an incrustation upon the ground over large areas, a detailed description would be superfluous, as the explorer will surely recognize it should he find it. clay. a good bed of clay may be of value in an accessible region. brick-clay contains silica, alumina, iron, etc. potters' clay is made by suspending ordinary brick-clay in water, and running off the water and fine particles suspended therein. these are allowed to settle, and, when dry, are fine potters' clay. the better the clay, the larger the percentage of potters' clay. fire-clay should contain per cent. of silica, and per cent. of alumina. mixed with sand and burnt into bricks, it will resist great heat. light-colored clays are preferable for this purpose, as iron is prejudicial to a good fire-brick. kaolin is the finest porcelain clay, and the best comes from china, japan or france. it is a product of decay in feldspar rocks. the potash is washed out, and the silica and alumina left as parts of a white clay of fine grain. coal. anthracite is bituminous coal that has been subjected to great heat and pressure; in plain language, baked. it contains over per cent. of carbon. specific gravity . to . . hardness, . to . . the ash left after burning is white or red. there is little or no sulphur in anthracite. it does not coke. there are three main divisions of coal, arranged according to their carbon, water and ash. they are: carbon. water. ash. anthracite - p.c. - p.c. - p.c. bituminous - p.c. - p.c. - p.c. lignite - p.c. - p.c. - p.c. good bituminous coal contains about per cent. of carbon, but the composition varies greatly. cannel coal is a variety of bituminous that gives off much gas. it burns with a bright flame in an open grate, igniting as easily as a candle. lignite is intermediate between coal and peat. all the rocky mountain coals are lignites. it is a very inferior coal at its worst, while at its best it is nearly the equal of a poor bituminous coal. some coals will coke and others will not; nothing but a trial can settle this matter in each individual case. good coking coal is very valuable. cobalt. cobalt ores are always found in veins with other metals. pure cobalt is extremely rare. cobalt colors are used for porcelain painting, glass-staining, etc. chromium. all chrome is obtained from chromite, which contains per cent. of chrome sesqui-oxide, the remainder being iron protoxide. hardness, . ; gravity, . ; luster, sub-metallic; opaque. steel-gray to almost black. harsh. brittle. cleavage, imperfect. fracture, uneven. texture, massive to granular. chromite in gravel looks like shot. serpentine often contains it, when it is apt to resemble a fine-grained magnetite. it is used chiefly in iron and steel alloys, and in making armor plate. it is also used in dyeing fabrics and in paint manufacture. but little chrome ore is produced in the united states. the importation in was , tons, value $ . per ton. chromite, feocr{ }o{ } - this ore is merchantable at $ to $ per ton. domestic ore ranges from $ to $ a ton, while the pure imported ores are worth $ a ton. the yearly consumption in the united states is about , tons, and the american production tons. this ore is useful as a lining for furnaces, and the demand promises to become important. newfoundland is said to contain large deposits. copper. native copper occurs in the lake superior region, but the demands of commerce are supplied from chalcopyrite or copper pyrites, and tetrahedrite or gray copper ore. many different ores of copper may exist in the same vein. on the surface an iron cap of gossan reveals the deposit; immediately below may be black oxide of copper with some malachite, lower down red oxide, and below the water-line copper sulphides. the following are the principal copper ores: sp. gravity. hardness. p. c. cu. native copper . . chalcopyrite . . enargite . . tetrahedite . . to . chalcocite . . bornite . . melaconite . . to . cuprite . . chrysocolla . . the common ore is native copper, often associated with native silver, the two remaining, chemically, quite distinct. some masses of copper occur that are too large to handle and must be cut by cold chisels, a method that costs more for labor than the value of the metal. the lake superior mines produce , , pounds of copper a year, while those of montana made the gigantic output of , , pounds in . the great anaconda mine, of butte, is the heaviest producer, yielding more than half the state's total. during the new york copper market rate varied between . cents and . cents per pound. copper is probably abundant in the shape of pyrites in many parts of canada, especially in the northwest, and prospectors in that region should search diligently for it. the lake superior mines are unique in being deposits of native copper. owing to the great demand for copper following upon the extraordinary spread of electricity, copper properties have become so enormously valuable that, possibly, the explorer will be quite as fortunate in finding copper as in finding gold. moreover, with the exception of spain and chili, the united states has no serious rivals in copper production,--montana and michigan, producing the greater part of the output. the famous calumet and hecla mine, in michigan, is now down , feet and still yields ore. the most copper ores are not difficult to distinguish. every one is familiar with the ruddy hue of pure copper, the color of the native metal. it may be flattened under the hammer or cut with the knife. a little of the ore mixed with grease colors a flame green. copper ores are heavy, and generally of a bright color, either red, blue, green, yellow or brown. corundum. nine hundred and seventy tons of this abrasive were produced in the united states in ; value, $ , . corundum is found in feldspar veins, and associated with chlorites in serpentine rock. north carolina furnishes half the corundum marketed. the presence of this substance is always indicated in the south by serpentine, chrysolite, or olivine rocks; experience being the only guide the miners have in finding new deposits. the contacts of the olivine rocks with gneiss usually produce rich deposits. corundum is the hardest substance known, next to the diamond. it is used as a polishing powder. emery is an impure corundum containing iron. corundum is composed of per cent. aluminum and per cent. oxygen. specific gravity is . hardness, . feldspar. the maine, pennsylvania, new york, and connecticut ores are worth $ to $ per long ton ( , pounds) at point of production. fluorspar. the american market is supplied by ore from rosiclare, ill., marion, ky., hardin co., ill., and liumpton co., ky., and imported spar. it is worth $ a ton of , pounds. this spar is softer than quartz and of most brilliant colors, varying through the yellows, greens, blues and reds, to pure white. the streak is always white. specific gravity, . hardness, . it is worth mining when abundant and accessible. gems. gems are to be looked for in a country of crystalline rock, such as granite, gneiss, dolomite, etc. topaz and ruby are generally discovered in crystalline limestones, while turquoise is usually found in clay slate. it is not likely that the american prospector will come upon the true oriental ruby; he will more probably find the garnet. the ruby is next to the diamond in hardness and in value, and consists practically of pure alumina. the garnet is but as hard as quartz, and is a silicate of alumina with lime and a little iron. they crystallize in different systems, the more valuable gem belonging to the rhombohedral, and the less valuable to the isometric system. the turquoise which has lately been found in arizona is not a crystal. the blue color which distinguishes it is derived from copper. it is a phosphate of alumina with water in composition. in form it is kidney shaped or stalactitic. lazulite, a far less valuable substance, is also blue, but as it crystallizes in the monoclinic system it should not be mistaken for turquoise. moreover, lazulite is softer and contains magnesia and lime, which the turquoise does not. lapis lazuli, which is also occasionally mistaken for turquoise, belongs to the regular or isometric system; it is commonly massive or compact, and is a silicate of alumina with some lime and iron. it is found in syenite, crystalline, limestone, and often associated with pyrites and mica. topaz belongs to the orthorhombic system. it is a silicate of alumina with fluorine. powdered, mixed, and heated with microcosmic salt in the open tube, fluorine is disengaged with its characteristic odor, and etching action upon glass. with the blow pipe on charcoal, heated with the cobalt solution, it gives the fine blue color of alumina. the explorer who comes upon any hard, brightly colored stone, that may possibly turn out a gem, should preserve it carefully until he returns to some city, when it should be submitted to an expert. the value of a gem depends upon so many qualities that it were hopeless for the tyro to endeavor to arrive at any just estimate of it. he might ruin a superb specimen, without becoming one bit the wiser. a few of the more prominent characters of valuable gems follow: name. sp. gravity. hardness. color. aquamarine . . blue. emerald . . green. diamond . . colorless. garnet . . claret. opal . . opaline. ruby . . dark red. tourmaline . . various. turquoise . . blue, green. ultramarine . . blue to green. graphite. this mineral is commonly known as black lead, or plumbago. it is the same in composition as the diamond, viz.: per cent. carbon. specific gravity, to . . hardness, . to . . color, black. greasy. of value when free from impurities. used in making pencils, stove polish, crucibles, etc. found in the earlier rocks. gypsum. a sulphate of lime occurring in great beds. burnt, it becomes plaster of paris. iron. this, the most important of all metals, is found in various forms. the ores of iron are: sp. gravity. hardness. p. c. fe. native ore . . magnetite . . hematite . . limonite . . siderite . . pyrite . . native iron is only found in meteorites that have come from space. magnetite is loadstone ore; the powder is reddish black, and the ore, dark brown to black. it is found in the older rocks and is an important ore. hematite varies from metallic to dull in luster. there are many varieties of it, known as ironstone, ocher, needle ore, etc. hematite may be slightly magnetic. immense beds exist in the triassic sandstones, and in the secondary rocks below the coal measures. the powder and streak of limonite are always yellow; it is an important ore. siderite assumes many forms. it is called spathic ore, clay-ironstone, carbonate of iron, black band, etc. most of these carbonate iron ores only range between and per cent. of metallic iron, but are in demand as fluxes for other iron ores. the pyritic ores of iron, including marcasite, pyrrhotite and mispickel, are often taken for gold by the inexperienced. in an accessible region pyrites may be valuable, as they are bought by makers of sulphuric acid. iron is so low in price that vast deposits exist which cannot be made use of because they would be too expensive to mine. a deep bed, or a narrow one, or the slightest difficulty in transportation, would preclude any profitable development. it is known that enormous areas in northern labrador, for instance, are full of iron deposits, yet there seems no chance of their having the slightest economic value for a long time, if ever. conditions of commerce very different to those now obtaining will have to exist before they can be utilized. iron ore is most favorably situated for profitable extraction when it is near coking coal and beds of limestone; the former for fuel, the latter for flux. occasionally such regions as that of lake superior may be able to compete successfully with others, although they do not possess the necessary smelting facilities, because these deficiencies are counterbalanced by inexhaustive stores of easily mined ores, and transportation facilities unrivaled in cheapness. lead. the two important sources of supply are galena and cerussite. the former contains per cent. of lead, and frequently some silver and gold. it is so distinctive as to be easily recognized. luster, metallic; opaque; lead-gray; harsh. brittle to sectile (may be cut). cleavage, perfect. fracture, even to sub-conchoidal. structure, granular or foliated, tabular, or fibrous. specific gravity is . , and hardness, . . the carbonate cerussite contains about per cent. lead. luster, vitreous to resinous. translucent. color, gray. smooth. brittle. cleavage, perfect to imperfect. fracture, conchoidal. massive to granular. rich carbonate ores look like clay, and are undoubtedly often passed by. the economic ores of lead are: lead. galena pbs . p.c. cerussite pbco{ } . p.c. anglesite pbso{ } . p.c. pyromorphite pb{ }p{ }o{ } plus / pbcl{ } . p.c. lead ores are frequently rich in silver. they occur in limestone, sandstone, granite and clay. the commercial ores are galena, which is easily recognized by its steel-like cubes, and the carbonates. these latter are like lightly colored clays when in powder and are very apt to be overlooked. fluor spar is as favorable a gangue for lead as quartz is for gold. the rocky mountains are the principal american sources of this metal, but a very large amount comes from the mississippi valley. in the mountains the ore is a by-product, in silver smelting, being obtained from argentiferous galena, while in missouri, kansas, wisconsin and illinois lead and zinc are found free from any mixture with the precious metal. the age of these deposits varies from lower silurian or cambrian to the carboniferous. the ore is found in limestone rocks,--sometimes in flat openings parallel to the almost horizontal beds, or else in gash veins almost at right angles to these. as lead is often found in dolomite limestone, that is, limestone carrying almost as much magnesia as lime, and this rock was undoubtedly deposited in a shallow sea, geologists incline to the belief that therefore the lead is due to a growth of seaweeds in whose ash this metal and zinc are known to occur. at any rate, these deposits now have great economic value, and the lead and zinc ore is easily got at. galena and zinc blende frequently resemble one another, but they may be distinguished by this infallible sign: the powder of galena is black, and that of blende brown, or yellow. lithographic stone. this is a very fine grained compact limestone from bavaria. so far nothing equal to the imported stone has been found in america. the distinguishing qualities are: gray, drab or yellow; porous, yet not too soft; of fine texture, and free from veins and inequalities. manganese. manganese ores in amounted in the united states to , tons, value $ , . this mineral is used for bleaching and making oxygen, and in steel manufacture. pyrolusite contains per cent. manganese. hardness, . . specific gravity, . . luster, metallic. opaque. gray to bluish black. harsh. brittle. cleavage, imperfect. fracture, uneven. granular, massive. manganite is harder, . ; its specific gravity is . . luster, sub-metallic. cleavage, perfect. texture, fibrous. wad is an impure ore of manganese found in bogs, of little or no value. pyrolusite mno{ } . braunite mn{ }o{ } . psilomelane (variable) ? franklinite, a zinc-manganese ore, is also a common source of supply. an ore to be commercially valuable should contain from to per cent. metallic manganese, and not over . to . per cent. phosphorus. to determine the value of manganese ores a somewhat intricate calculation is necessary. delivered at bessemer, pa., the carnegie steel company pays according to the following sliding scale: per cent. mn. per unit over p.c. fe. mn. p.c. c c p.c. c c p.c. c c p.c. c c p.c. c c p.c. c c c c moreover, for each one per cent. of silica in excess of eight per cent. a deduction of fifteen cents a ton is made, and a deduction of one cent per unit of manganese is made for each / of one per cent. of phosphorous present in excess of / per cent. from which it is evident that there can be little profit in impure deposits of manganese. mercury. quicksilver usually occurs in the form of cinnabar, though occasional deposits of pure metal are found in drops and small pockets, in limestone and the softer secondary rocks, including shales and slates. as the appearance of quicksilver must be familiar to all, cinnabar alone needs description. its specific gravity is . ; its hardness, . . it is a red brown earthy ore, the powder of which is a dull red. it is generally found in sandstone, though it occasionally occurs in slates, shales and serpentine. heated gently with lime cinnabar yields quicksilver. if copper be held over the fumes of mercury it will be coated with a light film of the metal. an alloy with silver has been found. mercury is heavy, extremely brilliant, and mobile. the composition of cinnabar is: per cent. hg. cinnabar hgs . although but three american states have supplied this metal, this country has held rank as second producer. of these california is by far the most important. oregon and utah having never had any but a small and spasmodic output. judging by californian experience, the prospector is most likely to find cinnabar, the ore from which the quicksilver of commerce is derived, in metamorphic rocks. mercury is always sold in flasks of - / pounds. the production of mercury by the united states (california) was , flasks in , which were valued at $ , , . the following table shows the rock in which the most famous californian quicksilver mines are: mine. county. rock. sulphur creek colusa serpentine. abbott lake shale-serpentine. great western lake serpentine. (?) Ã�tna napa sandstone. corona napa sandstone-serpentine. aat hill napa sandstone. new almaden santa clara shale-serpentine. barton siskiyou shale-sandstone. cinnabar king sonoma sandstone-serpentine. altoona trinity porphyry-serpentine. a study of the foregoing shows that serpentine is almost as intimately connected with quicksilver as is quartz with gold, or granite with tin. these are the things that prospectors should make a note of. with the great increase of gold mining and the limited store of cinnabar that is available that ore seems certain to rise in value before long. mica. the value of indian mica varies from ¢ a pound for sheets in. Ã� in. to $ a pound for sheets in. Ã� in. the white mica in large sheets is valuable. the amber-colored, and spotted, are used for insulating purposes in electric plants, while the coarser sorts are ground and used as lubricants, or in fire-proof paint manufacture. nickel. this ore is never found in metallic form, but always in combination. pyrrhotite, or magnetic pyrites, is the source of about all the nickel of commerce. this ore has been already noticed under iron. rare but valuable ores of nickel are millerite, nickelite, glance, and nickel bloom. per cent. nickel. millerite nis . niccolite nias . some of the nickel of commerce is derived from nickelliferous pyrrhotite. petroleum. crude petroleum is never found in metamorphic or igneous rocks. the stratified rocks of the devonian, carboniferous and cretaceous ages are most likely to hold it. the crude oil is almost black, and consists of about per cent. of carbon, and per cent. of hydrogen. a long iron-shod stick is all the prospector requires to take with him in his search for surface indications of oil. the warmer the day the easier the search, as the oil rises to the surface of the streams, and is found in greater quantities than on cold days. oil existing in the lower rocks ascends through them until it accumulates under some layer that will not let it pass through. in this condition deep boring finds it, the rod usually tapping gas first. petroleum may be noticed oozing out of gravel banks, or floating as a scum on the surface, whenever abundant. it has been found in rocks of widely different age, from extremely ancient formations to some that did not precede man by so very long, geologically speaking. platinum. this metal is only found native. its gravity is very high, from to . hardness, to . . luster, metallic. opaque. whitish-gray. smooth. ductile. cleavage, none. fracture, hackly. texture, granular, fine. platinum is unaffected by acids, but if alloyed with per cent. of silver it dissolves in nitric acid. almost infusible. platinum occurs with placer gold in the beds of streams. usually it is in small grains, but one or two large nuggets are on record from brazil and siberia. serpentine rocks are believed to have originally held the platinum found in the beds of rivers, but none has been found in veins. the entire product of the united states was ounces in ; valued at $ , . in there was none produced. silver. silver is generally found in serpentine, trap, sandstone, limestone, shale, or porphyry rocks, the gangue being quartz, calc, fluor, or heavy spar. all silver ores are heavy, and many of them are sectile, i.e., may be cut with the knife. western men test for silver by heating the ore and dipping it into water. some metal comes to the surface in a greasy scum, should silver be present. native silver is found occasionally. owing to the fall in value of this metal its future is not assured. it has fallen, during the past year, once to forty-nine cents an ounce, and this has had a most disastrous effect upon many silver mines, forcing them to suspend operations. should the fall continue, as seems likely, and the price of silver go down to forty cents an ounce, little will be produced except as a by-product in the treatment of argentiferous lead ores. as silver enters into chemical combination with sulphur easily, as is seen by the black film that forms on silver articles in a room where gas is burnt, most silver ores are sulphides. the very abundance of silver has caused its great fall in value, and it does not appear that it is ever likely to remain for long at a price exceeding fifty cents an ounce, owing to the ease with which it may be produced, and the large quantities that must find their way to market through it being a by-product in lead smelting. from to the comstock lode in nevada produced $ , , . this lode is a belt of quartz, , feet long and several hundred wide, and is a contact vein between diorite and diabase. in america galena is the principal source of silver; the chlorides and oxides rank next; while, lastly, some silver is parted from gold when it reaches the mint, as gold always contains more or less of that metal. no precise statement as to the manner of its occurrence may be made since it is found in many different positions, and is associated with all sorts of minerals. it is never found in placer deposits, as it breaks up under the influence of water, air, etc. its original source is doubtless the igneous rocks, where it occurs in association with augite, hornblende and mica. silver may be expected in mountainous regions of recent origin. between and the world's product rose from $ , , to $ , , . three quarters of this came from the western hemisphere. the commercial ores of silver are: silver. argentite ag{ }s . per cent. proustite ag{ }sas{ }s{ } . per cent. prysagyrite ag{ }ssb{ }s{ } . per cent. stephanite ag{ }ssb{ }s{ } . per cent. cesargerite agcl . per cent. the anaconda mine in butte is the largest producer of silver in the country. in its output was , , ounces. the anaconda is also the heaviest copper producer in the united states, its yield of copper being , , pounds. sulphur. brimstone is found native in the neighborhood of volcanoes, extinct or active. it is also derived from iron pyrites. color, yellow. hardness, . specific gravity, . luster, resinous. smooth. sectile. texture, crystalline. talc. the scientific name of this mineral is steatite. it contains silica and magnesia. its green color, pearly luster, and greasy feel, are very characteristic. it is not attacked by boiling sulphuric acid. useful in the arts, but of no great value. tin. the composition of cassiterite, the commercial ore of tin, is sno{ }; equal to . per cent. of metallic tin. cassiterite or tin stone is a heavy ore which occurs in alluvial deposits or in the beds of streams. it will be one of the latest ores the young prospector will find himself able to name with certainty. granite, with white mica as one of its constituents, has so far always been associated with tin. the american continent yields little tin, and it is not likely the prospector in either the western states or in canada will stumble upon it, though a good deposit of stream tin would enrich him in a short time, for the metal is in great demand. the streak, when the metal is scratched with a knife point, is whitey-gray and very distinctive. tin may some day be found in the northern rockies, as there is plenty of granite, which is favorable to this metal. it is worth about thirteen cents a pound, and a vein must yield more than five per cent. of metal to pay the cost of mining and dressing. cassiterite, the principal tin ore, would have to be roasted. most of the european tin mines were first worked for the copper they contained. the copper was found in the capping, but as they gained in depth they became more and more valuable for their tin. some of the cornish mines are three-quarters of a mile in depth. very lately tin has been discovered and mined in vast quantities in the straits settlements, india. as it is found in the streams the expense of mining is very light, and it is killing the european mines. the cornish miners put their tin ore on a shovel when they wish to test it. the sample is first crushed fine and a few skillful shakes get rid of all the gangue, leaving behind the tin and wolfram. this wolfram is always associated, in cornwall, with the tin and it is got rid of by roasting. australasia and cornwall produce most of the tin used in commerce. tin is not found native. specific gravity of cassiterite is . to . hardness, . to . luster, vitreous to adamantine. translucent to opaque. brown, black, gray, red or yellow. harsh. brittle. massive. the appearance of this metal is so variable that nothing but a test with reagents determines it with certainty. granite is frequently the country rock in which tin is found. zinc. this is another ore that never occurs native. calamine or silicate of zinc is the great producing ore. composition: zinc oxide, per cent; silicate, per cent; water, per cent. specific gravity, to . . hardness, . to . luster, vitreous. translucent. white. harsh. brittle. cleavage, perfect. fracture, uneven. texture, granular crystalline. calamine is a difficult mineral to detect without experience, as when impure it does not look in the least like a metallic ore. it would be taken for clay or shale. this ore results from the decomposition of zinc blende. blende contains per cent. zinc and per cent. sulphur. it is often dark brown or black from iron, otherwise it may be red, green or bluish. it is a troublesome impurity in silver ores. smithsonite is a carbonate much resembling, and often found with, calamine. other zinc ores are merely curiosities and do not affect the commercial value of the metal. in the new jersey mines the zinc ores are the oxides zincite and willemite, and the zinc-iron oxide franklinite. in the missouri region, on the other hand, sphalerite and blende are the typical ores. blende generally associates with the lead sulphide, galena. the joplin district in southwestern missouri and the adjoining region in kansas are now mainly supplying the markets of the country, though the new jersey deposits are very valuable. joplin ore assaying to per cent. has varied greatly in price during the past four years. the lowest quotation was $ a ton, the highest $ . . zinc is derived mainly from the following half dozen ores: zinc. sphalerite zns . per cent. zincite zno . per cent. smithsonite znoco{ } . per cent. franklinite (variable) (?) . per cent. willemite zno.so{ } . per cent. calamine zno.sio{ }.ho{ } . per cent. chapter v. mining. although the scope of this work does not include the very complex problem involved in the working of a great mine, prospecting and the simpler mining operations are so intimately connected that it would not be desirable to make mention of the one and ignore the other, because the prospector must perforce become a miner as soon as he discovers mineral, even though his operations should not go beyond a shallow trial shaft. the simplest method of hoisting dirt or rock out of a shaft, after it has become too deep for the sinker to throw the stuff out with a spade, is by a bucket and windlass, which may be either single or double, according to the power required. in northwestern canada, where the present gold excitement has attracted so many thousand pioneers, the miners have hitherto been content with a windlass. for their purpose it answers well, as they sink through gravel and not more than thirty feet at the most before reaching the bed rock. the alluvial flats in which the coarse gold of the upper yukon has been discovered, are composed of gravel that is invariably frozen, summer as well as winter, and which requires to be thawed out before it can be worked with a pick. strangely enough, dynamite cannot be used, as the ground is so elastic under the frost that the tamping simply blows out and the required effect is not produced. this peculiar condition has led the men, who are mining in that part of the continent, to adopt methods very similar to those used in siberia, where, also, the ground is permanently frozen to a great depth. after scratching the surface of the soil, and removing the deep moss that invariably covers it, they light large fires over night and in the morning remove the few inches of thawed soil underneath the ashes. by this painfully slow method they eventually sink to the richer gravel, fifteen or twenty, or even thirty, feet below the surface, though there are few shafts of this depth on the klondike and the other gold-bearing creeks about which we have heard so much. when the bed rock is reached and the few inches of decayed surface removed, the miner builds his fire against the side of the shaft, placing some inclined logs over it as a roof, and goes to bed. when he awakes next day several feet of the soil have fallen down over the logs, and this he has to hoist. it is at this stage that the windlass worked by his companion, or partner, demonstrates its value. in a very short time all the gravel that the fire has thawed out is hoisted to the surface, and added to the dump, where it must remain until the warmth of summer shall have thawed the streams and permitted sluicing. [illustration: miner's gold pan.] a sluice is really nothing more nor less than a trough, open at the top, in which the gold is sorted from the lighter gravel and dirt by running water. the grade varies according to the coarseness of the gold. very fine gold would be carried away by too swift a current, while coarse gold will resist almost a torrent. the sluice is built in joints, usually a dozen feet in length; the sides may be six inches or a foot deep, and the width varies from one to two feet. there is no rule in this matter, but owing to the extravagant price of lumber--as much as a hundred and fifty dollars a thousand feet, board measure--the tendency is to make the sluices very small and very short, thereby saving nothing but the very coarsest gold. a properly constructed sluice should be several hundred feet in length, and the inclination should not be more than one foot in twelve, while it may, in a case of fine gold, be advisable to diminish this inclination by at least a fourth. riffles, or cross-pieces, are placed across the sluice at intervals of a few feet, and slats are placed lengthwise, filling up the intervals between the riffles. into the crevices and interstices of these obstructions the heavy gold sinks by its own weight, and every few days, or weeks, as the case may warrant, the miner shuts off the water by closing the gate at the head of the sluice, removes the slats and riffles, beginning at the joint nearest the head and working towards the tail of the sluiceway, and collects all the gold that has accumulated. this is a very simple form of mining, but it is not the simplest. much gold has been recovered from the gravel in which nature has placed it by the aid of the pan, a sheet iron dish modeled on the housewife's bread pan. next to the pan the cradle is as little complicated as anything used in the winning of gold. after this comes the long tom, a considerable improvement upon the cradle, but it necessitates more water and more men. [illustration: horse whim.] the horse whim is used in developing many a western prospect. the windlass does not work well below forty feet, and where fuel and water are to be had any sensible man will use steam power for deep mining, but there is a gap between the windlass and the steam hoist which the horse whim fills acceptably. to a depth of feet a horse whim can usually handle the rock and water. it is inexpensive, in the first outlay, and costs but little to run. you can bring your bucket from a shaft a hundred and fifty feet deep in two and a half minutes, and with a seven hundred pound capacity in the bucket, in forty-five trips you could raise fifteen tons a day. a shaft three hundred feet deep would require four hours' steady work to bring to surface the same amount. a fair speed with a one-horse whim from a three hundred foot shaft is one hundred buckets per shift of ten hours, but the prospector rarely has to figure on shafts of that depth. if the mine turns out well it is likely to be in the hands of a powerful company (of which he should be the principal shareholder) before the three hundred foot level is reached. the weight of the horse whim is about eight hundred pounds. it can be taken to pieces and packed anywhere that a mule can travel; the heaviest piece will not weigh more than a hundred pounds. [illustration: prospecting mill with horse power.] a small stamp mill, run by horse power, is a very favorite machine with western men, where the ore is free milling. the mortar in which the stamps work has copper plates amalgamated with mercury inside, and copper tables with amalgamated plates over which the pulp passes after oozing through a fine screen in front of the mortar. these little mills are so constructed that they can be taken apart or put together in an hour or two. they require but one horse power and will do good clean work up to their capacity. the following are the specifications of a good one: total weight , pounds. weight of heaviest piece pounds. weight of stamp pounds. drops per minute to . capacity per hour to pounds. diameter of pulley inches. price, with horse power, about $ . a diamond drill is a most useful adjunct to exploration of a mine or deposit. it is, essentially, a hollow drill which may be lengthened at will, rotating rapidly and carrying a crown of "bort" or black diamonds at its extremity, that eats into the strata very quickly. holes , feet deep have been driven by the diamond drill, but such extensive investigations of the earth's crust are tremendously costly, and may only be undertaken by governments or rich companies. for a depth of feet, however, the expense need not exceed $ , . the cost of the plant for drilling would be $ , more. water is pumped down the hollow center of the drill, to keep it cool. the great advantage of the diamond over the percussion drill is that it permits the saving of a core, so that the character of the rocks and minerals passed through may be known. the diamond drill does better work in hard strata than it does in soft. the rate, in limestone, may be about two feet an hour, down to a depth of feet. a complete outfit for boring with the diamond drill includes a steam engine and boiler, diamond crown, lining tubes, rods, and various minor accessories. hydraulic mining is the cheapest known method of recovering gold. in four years the north bloomfield mining company of california worked , , cubic yards, which yielded only . cents of gold per cubic yard, and realized some profit. very poor gravel will pay when the conditions are good. cheap water, grades of four inches in a hundred, ample dumping room, big banks of light gravel, large areas of deposits, labor at a dollar a day, and a clever superintendent, make a combination that will yield a profit out of three-cent gravel. miners speak of "surface" and "deep" placers; of "hill claims;" of "bench claims" on the old river terraces; of "gulch diggings;" of "bar claims" on the sand bars of existing rivers; of "beach sands" or those that in a few favored localities border the ocean. a "sluice" is a long boxway to catch the gold; a "drift" is a tunnel into the gold-bearing gravel; and hydraulic diggings are those in which water under pressure is used to disintegrate the gravel. a ground-sluice is a trench cut through the bed rock. the roughness of the natural floor serves for riffles. booming is a process requiring a large accumulation of water in a reservoir, which may be discharged at once, and carry all the material that has collected below the pass, with one full tide, into the sluices. this practice is extremely ancient; pliny mentions it in his natural history. deep mining may be divided into drifting and hydraulic mining. in the former the metal is won by means of tunnels and drifts or horizontal passageways along the length of the deposit. it is usually resorted to in districts where a flow of lava has covered the gold-bearing gravel, and made hydraulic mining impossible. it is followed in alaska for another reason, viz., because the constantly frozen ground will not permit of the more remunerative method. the gravel is carried to the mouth of the tunnel and there dumped to be washed in the sluices. when "cemented" it must be broken up by stamps. rich deep placers may be worked by drifting, but whenever practicable hydraulicing is to be preferred as giving better results. it yields from four to six times the amount of gold that drifting does. thorough exploration should precede the expenditure of large sums in a hydraulic plant. even should the explorations result in finding barren gravels the money will have been well spent in saving the cost of an unproductive plant. black sand (magnetic iron) almost always accompanies gold, but this alone is no sign that gold is present, as black sand may usually be obtained by grinding and washing crystalline rocks. ditches and flumes of wood or metal are used to bring the water for hydraulic mining from the region where it was impounded in a catch basin, often a distance of many miles. it is said $ , , have been invested in ditches and flumes, mining and agricultural, in the western states, and new flumes are being planned every month. some of them consist of wrought iron pipe carried over ravines by trestles feet high. in planning a ditch the miner must see to it that his water supply is at a sufficient elevation to command the ground. the more pressure the water works under the better. the supply should be continuous, or at least be available during the whole working season. ditches in regions of deep snow should have a southern exposure. all streams crossed by the ditch should be diverted into it, to counteract leakage and other loss. waste gates must be provided every half mile. ditches are better than flumes. narrow, deep, and steep ditches are to be preferred in mountainous regions, and the reverse in valleys with soft soil. some californian ditches with a capacity of cubic feet per second and grades of to feet per mile have been built. [illustration: section of ditch.] [illustration: section of flume.] sometimes the face of the country requires flumes; they may even be hung along the face of a cliff. in shattered ground and where water is scarce flumes are better than ditches. the grade for a flume is usually to feet per mile and its capacity is smaller than that of a ditch. pine planking - / inches by to inches, and feet long, is the dimension stuff generally preferred. a flume feet inches square requires posts, caps, and sills of Ã� inch; stringers Ã� inch. great care is needed at curves to avoid slack water and splashing. the boxes must be shortened and the outer side wedged up until the water flows as evenly as in the straight stretches. should anchor ice form the water must be shut off at once. the life of a flume seldom exceeds a dozen years, whereas at the end of a similar period a ditch would be carrying per cent more water than at first, owing to the sides and bottom having become consolidated. wrought iron pipes are employed largely in california to replace ditches and flumes. when the pipe crosses a ravine it is known as an inverted siphon. piping is also used to convey water from the "pressure box" to the "gates" and "nozzle." wrought iron pipes have to stand pressure varying from pounds to pounds to the square inch. air valves or blow-offs must be provided at intervals to allow the escape of air from the pipe while filling, and to prevent a collapse of the pipe after a break. a covering of coal-tar should be given the pipe both inside and out. cost varies from one dollar to two dollars a running foot. the pressure box ends the ditch and from it the water passes into the supply pipe. the head of water is measured from this point. a box to catch sand and gravel, with a side opening and sunk below the level of the ditch, is called the "sand box." one and a half inch plank is generally the material out of which the pressure box is made. the depth of water in it is such that the mouth of the pipe is always under water. a grating in front of the pipe catches all rubbish. as no air must be allowed to get into the pipe the water must be kept quiet and deep at the pipe-head; this is insured by dividing the box into compartments, the first receiving the water and discharging it through suitable openings into the second. the water supply and the discharge should be equal. the water passes down the feed pipe, iron gates distributing it to the discharge pipes. water must be turned on gradually, and the air valves must be open. the piping terminates in a nozzle with knuckle-joint and lateral movement. nothing but the most secure bolting to heavy timber and the heavy weighting of the last length of pipe should be relied upon to keep the hydraulic giant in its place. should it once begin bucking every man within reach of the powerful column of water is in imminent danger. the nozzle is directed by means of a larger deflecting nozzle, which receives the impact of the water and causes the main nozzle to swing right or left, up or down, as the case may demand. a derrick capable of moving heavy boulders, and driven by water power, is a necessity in all hydraulic mining. masts feet high and booms feet long are sometimes used, the motive power coming from a "hurdy gurdy" direct impact wheel. experiments have shown that the bucket has much to do with the power of the wheel. for instance, when the water impinged against a flat bucket the efficiency of the wheel was less than per cent. of what it should have been in theory, whereas, with the pelton bucket, it rose to . per cent. there is a great amount of so-called cement, or in other words consolidated gravel, in all the northern placers, and in many california deposits, as well. in the old cariboo diggings on the upper frazer, strong companies are now pulverizing the ancient cements that resisted all the efforts of the miners with powder and stamp mill, and are deriving large profits therefrom. black powder gives even better results than dynamite in gravel. the usual allowance of powder is pounds in weight for every , cubic feet of ground to be moved. make drifts t-shaped, and tamp the main drift almost to the junction with the arms, which should be parallel to the face it is required to dislodge. [illustration: pelton water wheel.] sluices have their maximum discharge when set straight. increased grade may be given below any unavoidable curves with advantage, and the outer side of the sluice must always be raised. steps or "drops" in the sluices help in the recovery of the gold. in general, a grade of - - / inches to the -foot box is found best; this is equal to a - - / per cent. grade. exceptional instances are on record, however, where grades ran from - / per cent. to per cent. in a to per cent. grade the water in the sluice should be inches deep at least. the following table gives useful details: sluice. grade. water. ft. Ã� in. to p.c. , to , m. in. ft. Ã� in. p.c. , to , m. in. ft. Ã� in. - / p.c. to , m. in. "the longer the better," is the sluice-builder's motto. the best "riffles" are made of blocks of pine to inches deep, wedged into the bottom of the sluices. they are laid in rows separated by a space of an inch or an inch and a half. riffle strips keep them in position, these latter being laid crosswise on the bottom. when worn down to five inches, the blocks should be replaced. this amount of wear will probably require six months. stone and longitudinal riffles running lengthwise of the box are often preferred. an undercurrent is a broad sluice set at a heavy grade below the level of the main sluice. the fine stuff drops through a grating, while the coarse gravel continues on down the sluice. refuse material from quartz, hydraulic or other mines is known as tailings. tailings are deposited on a dump, which in the case of a hydraulic claim must be sufficiently spacious to receive the thousands of yards of debris deposited on it each day. when available a narrow, deep canyon, or a tunnel, may take the places of dumps. quicksilver is used in the sluices, to flasks being used every fortnight in a long sluice. it is not placed in the last or feet. in working, keep the face of the bank "square." washing should be carried on continuously. watches must be set over the sluices, or gold is likely to be missed. as an extra precaution, the sluices should be run full of gravel before shutting off the water. there is no fixed custom regulating "clean ups." some managers do so every days, others run two or three months, others again clean up but once in a season. in large operations, the first , feet of sluice are cleaned up every fortnight; the remaining boxes once a year. sluices are cleaned from the head downward, the blocks being taken up for that purpose. the amalgam of gold and quicksilver is collected in sheet iron buckets. the final step is reached when the amalgam is retorted and melted in a graphite crucible. the principle of which the hydraulic miner takes advantage is the great specific gravity of gold as compared with water and rock. to illustrate this quality it may be noted that on a smooth surface inclined at an angle of in , subjected to a heavy stream of water, per cent. of the fine gold in gravel does not travel three feet. the loss of quicksilver fed into sluices will vary, even under good management, from per cent. to per cent. of the amount fed to the boxes. hydraulic mines under favorable conditions are very paying investments. gravel yielding cents a cubic yard has been worked for cents a cubic yard, at the rate of a million cubic yards a year. on another large claim , cubic yards were worked for cents a cubic yard, yielding cents a cubic yard. river dredging is another form of gold winning that has been brought to a great state of perfection in new zealand. although the dredge has not yet acquired the importance in america that was expected, it is successful on one or two western rivers, and as the subject becomes better understood it is conceivable that american mining engineers will be as successful in devising improved dredges as they have been in all other branches of their profession. in new zealand the bucket dredge has proved more satisfactory than the suction dredge, although a hasty conclusion would probably give the latter the palm. at bannack, mont., the bucyrus company has several dredges in successful operation. one is feet long, feet wide, and draws inches of water. it is very substantially made, and weighs nearly , pounds. before such a dredge is launched, a dam is built across the gulch to impound sufficient water. as the gravel is dredged and washed, it is dumped astern of the dredge, which, in the case of a shallow creek, moves up to the excavation made by the buckets. the boilers of this dredge are double, and together have h.p. there are buckets, and each one has a horizontal drag of eight feet, a capacity of five cubic feet, and travels at the rate of fourteen feet a minute. after treatment by trommels, or revolving screens, coppers, and sluices, and finally by a centrifugal pump, the now almost valueless gravel goes overboard again, leaving behind per cent. of the gold it once held. the traction dredge is really a land-mining machine, as it is adapted for work on land nearly flat, where but little water is obtainable. the machine travels on bogie tracks. a -h.p. boiler supplies the water. a boom, feet long, carries a shovel of . cubic yards' capacity, and moves cubic yards each hour. mr. john w. gray, one of the best authorities, has recently written to the mining and scientific press of san francisco a most interesting description of the progress made in saving the gold from the streams in new zealand. he says, in part: "after great effort, numerous trials, many failures and some large losses, this system of gaining gold has been evolved from crude beginnings into a systematic and satisfactory method of mining. dredging for gold is now attracting attention and bids fair to become an established form of mining for that metal. in new zealand, where more work of this nature has been done than elsewhere, the evolution of the industry has been the work of years. the rivers upon which dredging operations are carried on are swift-flowing streams, subject to frequent floods, having a considerable depth of gravel, with boulders and runs of pay dirt interstratified. the conditions are, therefore, not the best for economical and successful work, and it is not surprising that many failures have occurred. the runs of gold are, however, often extensive and rich, and operations carried on upon such reaches have in a number of cases given satisfactory results. "the improved form of dredge is a double pontoon, with ladder and chain-bucket arrangement between. screens separate the coarse from the fine material. wide sluicing tables catch the gold, centrifugal pumps supply the water, and waste material is handled by elevators. the power is usually steam, although electricity is used in a few instances, where conditions are favorable. the dredges vary in size and capacity, but are now built of large size and great strength. twenty thousand dollars is the cost of a large dredge with all the latest contrivances. under favorable conditions, material has been handled without loss that only yielded a grain of gold to the cubic yard. the real cost in actual continued working is believed to be very much in excess of that figure where average conditions exist. "one dredge on the clyde side of the shotover, working to a depth of twenty feet below water level, lifted tons per hour when operating. the profit on eleven dredges for the four weeks ending july , , was an average of $ , for each dredge. "so far in this country (united states), with a few exceptions, dredging operations for gold have not been financially successful. from crude beginnings, however, the machines have been rapidly improved and perfected, until now, in some localities, dredges believed to be the most complete yet constructed are being put in operation, and results are promised, not yet attained, in the way of economical working and high percentage of saving. during the last few years, a number of dredges have been operated in california, british columbia, idaho, montana and colorado, but with poor success. very few prove themselves capable of paying their way. some of the machines were faulty within themselves, others were entirely unable to cope with the swift currents and large boulders of the streams upon which they were operated. this latter is said to have notably proved the case with the dredges tried upon the frazer and ouesenelle rivers. "dredging operations on grasshopper creek, near bannack, mont., are now carried on successfully upon a large scale. the upper sacramento river, in this state, has a dredge doing profitable work, and, in a small way, dredging is successful upon the kzamath. a dredge upon that river, composed of two flat boats with a large steel scoop between, is able to cut and hoist the gravel and soft bed rock, and to handle boulders of from four to six tons' weight. the dredge is run day and night, has a -h.p. engine, and requires three men for each shift. in gravel to feet deep, cubic yards can be handled every twenty-four hours. cost of dredge, $ , . "a large dredge of the chain-bucket variety is operating in northern mexico, in a dry country, where there is little water. the actual capacities of these machines are , and yards per hour. "perhaps the most interesting dredge yet brought to the notice of the public is one lately built by the risdon iron works, san francisco, and now operating upon the yuba river, near smartsville, cal. it is of the elevator, or chain-bucket, type, feet long, composed of two pontoons, separated by a space five feet in width, in which is operated the ladder carrying the buckets. one man controls the dredge by means of a power winch with six drums. four drums carry lines from the corners of the dredge to anchorages on shore--one a head-line and one the ladder line. the machine is to dredge to a depth of feet, and is said to have a gross capacity of cubic yards per hour. the material discharges from the buckets into a revolving and perforated screen. this segregates the large material, which is then conveyed away by the tailings elevator. water ( , gallons per minute) is supplied to the revolving screen for washing and sluicing purposes by a centrifugal pump, and the fine stuff falls through the holes in the screen into a distributing box, from which it passes to a set of gold-saving tables and thence to a flume. the tables are covered with cocoa matting and expanded metal. the top tumbler of bucket-chain is operated by a vertical compound condensing engine indicating h.p., which also operates the pump. it is claimed for this dredge that in any ground not deeper than feet below water level or more than feet above, and which contains boulders of not more than one ton weight, the material can be handled at from to cents per cubic yard. if the capacity of the machine is given without deduction for water raised, imperfect filling and general delays, and the increase in volume of the gravel when broken up in filling the buckets, the actual working capacity would be less, and from these causes and the losses from wear and tear, breakages and repairs, the cost of operating would be increased. the cost of the dredge complete upon the river is said to have been $ , . "in the evolution of the dredge into the elevator or chain-bucket machine, now the popular form, the various kinds of dredges were given trials. the dipper dredge is not adapted to dredging for gold, and some of the gold is lost. with agitation of the gravel the gold soon settles and is not recovered. it is also very difficult, if not impossible, to construct a dipper dredge that is water-tight. another objection is that the material is supplied intermittently, thus making necessary certain undesirable arrangements for supplying the material in a continuous flow to the gold-saving tables. the same objections apply with greater force to the clam-shell form of dredge. it is by no means water-tight, and loses most of the gold in the act of dredging and bringing up the gravel. the objections would seem not to have the same force if applied to hard cemented gravel or to gravel with sufficient clay or other binding material to make it consistent. it is well to remember that these forms of dredges are, in many positions, economical of operation. "the hydraulic dredge has had fair trials and proved a failure. large storms greatly lessen the efficiency of this form of dredge, and numerous boulders hamper the pumping work. the suction force, being intense near the pipe and decreasing rapidly a short distance away, causes the sand and gravel to be carried off, leaving the gold behind. a centrifugal pump is therefore of little use to catch coarse gold, or to clear a hard, uneven bottom. cutters do not remove the trouble, since the gravel is dispersed by the cutting, and the gold is separated therefrom. "these objections would not obtain under certain conditions, and it would seem quite possible that conditions might be found existing where the suction dredges might be arranged to do good work. a dredging company is now constructing, at seattle, two dredges of the suction type to operate upon the yukon river. this would indicate that there are those who believe that deposits occur in and along that river which can be successfully worked in this way. "the chain-bucket machine, the popular form for operating under average conditions, is a combination of the following elements: an excavating apparatus which clears the bottom and handles the material with little agitation and slowly and continuously delivers a regular quantity of gravel to the gold-saving appliances; revolving screen to receive and wash the material and separate the coarse from the fine; an elevator or contrivance for carrying off the coarse gravel and stones; gold-saving arrangements, or tables, over which the fine material passes and upon which the gold is caught; a pumping apparatus to supply water for washing and sluicing. "the proper capacity of a machine seems to be regulated by the capacity of the gold-saving appliances. the tables should be as wide as possible, with frequent drops, and the fine material should be distributed over the tables in a thin film. the tables are covered with plush or cocoa matting, and sufficient water supplied to keep the material clear. the material should be supplied evenly, continuously, and regularly to the tables. care and attention are required to catch the fine gold. a disregard of the foregoing directions results in great loss, more particularly in the fine gold. mechanical skill is required to properly design and construct a dredge, and the care of a competent mechanic is necessary to see that the machine is kept in order and economically operated. the saving of the gold, however, is what makes dredging operations a commercial success. a man skilled in these matters should be in charge of running operations. dredges should be built of determined capacities, and should be designed to suit the conditions under which they are to operate. careful examination and investigation of the ground to be worked should be made beforehand, and the surrounding conditions studied, and it goes without saying that these matters require engineering skill and experience. "the field for dredging for gold seems large. where the proper conditions exist, it is a system which commends itself, and which gives promise, in competent hands, of being an economical method of mining. there is probably a very large extent of country where dredging for gold will be carried on profitably. the ground need not be in a river, if there is seepage water sufficient to float the dredge and supply clear water for the saving of the gold. dredging requires little water as compared with that required for sluicing and elevating, and this water can, in many dry localities, be supplied at small expense, where a supply for hydraulic work or elevating would cost a very large sum, or be impossible at any cost. any power suitable for driving the prime motors can be utilized to run the dredge. indeed, it would seem as if a system of mining was about to be perfected which may make possible the profitable working of many deposits not easy to be worked by other methods, and which may, in many instances, solve problems regarding the successful working of deposits which hitherto have seemed most perplexing and even impossible of solution. some doubt exists as to possible economical dredging operations under the water of torrential streams. the strong currents, the frequent floods, and many large boulders found in the channels of such streams make the working of the machines difficult and costly. this would not be so much the case in the long stretches of less current, nor would it be so at all in the valley-like reaches in the lower portions of rich streams, nor in the wide, flat portions of country where the streams enter the plains." very few gold-bearing lodes contain nothing but free gold; on the contrary, they carry the bulk of their values in the form of sulphurets, having more or less gold incorporated, and even when the gold is native and free-milling at the surface, it is generally changed into sulphurets as depth is gained. so the miner has to consider methods of recovery more complicated and expensive than simple amalgamation with mercury, for upon gold included in pyrites mercury has no effect. titanic iron, hematite, and tungstate of iron often hold gold, or soft clay ores carry it in their midst, and such combinations tax all the skill of the mining engineer merely to save a respectable percentage of the assay value. sometimes chlorination and sometimes cyanization are the measures tried, but supposing the preliminary treatment to have been by stamps in the battery, concentrating is one of the main reliances of the mill man. the blanket table is undoubtedly the oldest type of concentrating machine, but it is very inferior to modern inventions. percussion tables often do good work. in this system a sharp and frequently repeated blow is given the table, in such fashion as to make the heavy material separate from the light. "shaking" and "rocking" tables are favored in some mills, and they give better results on fine gold than any of the previously mentioned devices. but the best machine so far invented is the frue vanner--an endless rubber band drawn over an inclined table, having both revolving and side motions. the lighter particles are carried off by water, and the heavier collected in a trough. [illustration: frue vanner.] veins, lodes, or ledges, may be found in stratified or unstratified rocks, and in the former they generally cut the beds at an angle. veins are bounded by walls. the rock in which a vein is found is a country rock. smooth walls are called "slickensides." the upper wall of an inclined vein is the hanging wall; the other the foot wall. a layer of clay between the veins and wall is a selvage. a mass of rock enclosed in the vein is a horse. the vein stone, or gangue, is all that part of a vein that is not mineral. [illustration: a fault.] the throw of a fault in a vein is measured by the amount of vertical displacement. when the miner comes to a fault, he should follow the greater angle in his attempt to recover the lode. for instance, on mining along a b to the line of fault x y, the exploration will be continued downward, because the angle a b y is greater than the angle a b x. mercury that has been "sickened," that is to say, has lost its brightness and power of amalgamating, may often be cured by washing with an extremely weak solution of sulphuric acid and adding a little zinc. as regards the comparative merits of chlorination and cyanization, it may be said the one is the equal of the other. under certain conditions, chlorine gives a higher percentage of gold; under others the same may be said of cyanide. a description of either process would be out of place, however, in a simple elementary work. handed down through the centuries, the primitive arrastra is still useful in certain contingencies. it is like a cider mill in its principle, and was probably suggested by recollections of that machine, or else of the spanish wine-press. a circular, shallow pit, a dozen feet or more in diameter, is first paved with hard, uncut stones of granite, basalt, or other hard rock. this pavement is a foot thick, and beneath it is a bed of puddled clay inches deep. a vertical shaft with an arm, or arms, revolves in the center of the arrastra. grinding blocks weighing , or perhaps even , pounds, are fastened to the arms by chains or rawhide strips. the forward part of each stone is raised a couple of inches off the floor. mule, horse, water or steam power may be used, the speed ranging from to turns a minute. nothing can be simpler, less expensive, or save a greater proportion of the value in the ore than the arrastra. its limited capacity is its worst fault. an arrastra feet in diameter will treat or pounds of ore at a charge, and handle one ton a day of hours. ores that were so poor they yielded nothing to the stamp mill have paid well with the arrastra. this humble device may be used to advantage, probably in some of the poorer gold-bearing cemented gravels of the northwest. the ore should be crushed to pigeon-egg size. small quantities of mercury, about a tablespoonful to every five tons of gravel, has been found a satisfactory proportion in california. in a permanent arrastra a layer of neatly-dressed and pointed stones is laid in hydraulic cement. a fair-sized arrastra will require pounds of quartz to charge it, and the material must be broken into pigeon-egg size. after the machine has been started, and a little water added from time to time, little else need to be done for four or five hours, and this is perhaps one of the reasons for which it has always been so favored in indolent mexico. at this stage, the quartz and ore will be very finely pulverized, and water should be added until the pulp is as thin as cream. quicksilver must now be added in the proportion of - / ounce for every supposed ounce of gold in the ore being treated. two hours' further grinding is given, and water then admitted until the paste is quite thin, the speed of the arrastra being reduced at the same time so as to allow the amalgam and quicksilver to sink to the bottom. a half an hour of this treatment suffices and the thin mud is run off, leaving the gold and amalgam on the floor of the arrastra. a second charge of broken quartz is put in and the operation repeated, the clean-up not taking place oftener than every ten days, and sometimes only at intervals of a month or so. the rougher the bottom the longer the interval between clean-ups, as all the stone work must be taken up each time and all the sand and mud between them must be washed carefully. the arrastra is extremely valuable to the poor man who, having discovered a gold-bearing vein, wishes to transfer some of the metal into his own pocket, at the least possible outlay. its cheapness places it within reach of all, while a stamp will cost a good deal. then again the amalgamation being more perfect in the arrastra than in any other mill, it is particularly suited for the poor, lean ores. it is, however, only adapted to those that are free-milling, others not being suited to this form of apparatus, nor, indeed, to any save very costly plants. some arrastras have been built to treat old tailings, and have paid well when water power could be used. free-milling gold and high-grade silver and gold ores are those usually treated. the flagging should be of tough, coarse rock; granite, basalt or compact quartz are all good. this flagging should be at the very least a foot thick. when the arms of a -foot arrastra are revolving times a minute, the outer stone is traveling feet a minute. round holes closed by wooden plugs, or a side gate, lets the liquid mud out. some mill men use chemicals in the arrastra; potassium cyanide, and wood ashes or lye are probably the most useful, as the latter cuts grease and the former gives life to the quicksilver. rich silver ores are treated with blue stone and salt. when the pulp has been ground sufficiently, quicksilver is added, sometimes pounds being put in a single charge. a -foot arrastra will never treat more than two tons a day, and often no more than one-half that. one man a shift can look after a couple of arrastras, and the owner, in case of one arrastra that is working on tailings, often does everything himself. overshot wheels, or turbines, or hurdy-gurdies, furnish the power in many cases. a simple mule-power arrastra may be built for $ . a side hill should be chosen for the site of a battery. ample water power is necessary, though provision may be made for saving it in catch basins should such a course be desired. moreover, there must be plenty of room below the mill for the tailings, as it may be desirable at some future time to put them through a second course of treatment. [illustration: stamp battery.] automatic ore-feeders are always put in by good mill men. in cold climates the water that goes through the mill should be heated, and this may be done by the exhaust steam, but care is necessary that no grease get into it, as it would prevent the gold from amalgamating. the stamps for a light mill may be or in number, and weigh from to pounds. tables must be water-tight, with half an inch to one inch drop to the foot, according to the fineness of the gold. below them tables, having the same inclination and covered with blanketing, are used to retain specks of gold that have passed over the plates without amalgamating. [illustration: three stamp battery.] after the concentrated materials, always spoken of as the concentrates, have passed over the tables, they are often roasted to get rid of the sulphur, arsenic, etc., and afterwards treated with quicksilver in the pan, or tin, with chlorine or cyanide. these processes belong, however, to the domain of the professional chemist and metallurgist, and require the knowledge and experience of an expert to stand a chance of success. the coarseness of the mortar screens is subject to infinite variety, according to individual preference. the number of holes to the square inch ranges between and in australia, and between and , in the united states. the holes, when round, agree in numbers with those of sewing-machine needles, from to . when slots are preferred to holes, they are generally / -inch in length and no. diameter. russia sheet iron, or sheet steel / -inch thick is the material of which they are made. it should weigh one pound to the square foot, be very soft and tough, have a clean, smooth surface, and show no rust or flaws. in australia / sheet copper is preferred. the holes in any case must be punched in the sheet so that the rough edges are turned, and thus any pulp that finds its way into one of the holes is certain to get out again and not clog. a battery may require sets of screens a year; each screen having a surface of about - / square feet. russia iron screens endure to days. as the work a stamp can do depends entirely upon how much pulp can escape through the screen in any given time, the latter is evidently a very important detail of a battery. prospecting stamp batteries differ from ordinary batteries, chiefly in being of light build and weight. amalgam coming from battery stamps is often mixed with all sorts of rubbish. after being gathered, it is dried with a sponge, foreign matter picked off the surface and clean quicksilver added. soft unglazed paper thrust into the mercury removes the last vestiges of water, and then a card is drawn vertically or a piece of blanket horizontally across the mercury to clean it of iron. after squeezing, the amalgam is retorted. [illustration: gold retort.] all the amalgam is placed in one large kettle and, if possible, the latter is put on a strong table having an inclined surface with a groove and hole at the lower end to catch any stray globules of quicksilver. sodium amalgam, one ounce to each pounds of mercury, is put in the amalgam kettle and the whole stirred. this sodium amalgam is not absolutely necessary, but is desirable. after some minutes, water is poured on the mercury and the whole stirred. all dirt rises to the surface and is removed with a sponge. the cleaning is continued until the mercury seems absolutely free from any impurity, when it is dried with a sponge. it is next turned into pointed bags of stout canvas and force applied until most of the quicksilver has squeezed through. the amalgam remains behind. the quicksilver still contains some gold, but it had better remain if the mercury is to be used again, as gold attracts gold; it can always be recovered by retorting. sodium amalgam is best made by the miner himself, enough for one clean-up at a time. metallic sodium and quicksilver are the necessary ingredients; the former being kept in a wide-mouthed bottle covered with coal oil. a frying-pan makes a useful mixer. it must be dry and clean. five pounds of clean mercury is poured into the pan, and dried with a sponge, and heated beyond the boiling-point of water, but not much above, or there will be a sensible loss of mercury. a piece of sodium is wiped dry, cut into / -inch squares and placed with a long pair of tongs in the center of the warm quicksilver, which, by the way, is now off the fire and in the open air, the operator meanwhile keeping religiously to windward of it, unless he courts salivation and all its attendant ills. as soon as the sodium touches the mercury a flash and mild explosion will follow, but after a few cubes have been introduced into the frying-pan, always in the center, this will cease. as soon as a solid mass of amalgam forms in the middle of the pan, the contents must be stirred slowly, and a little more sodium added. the whole mass now crystallizes out, and if put into closely-stopped bottles it will keep without further protection for a little time. once opened, each bottle must be used. observe all these directions faithfully, then there will be no danger of inhaling mercurial fumes nor of being blown to atoms. after the amalgam is once made, it is safe as sugar. in retorting amalgam never fill the flask too full, and apply the heat gradually, and always from the top of the flask downward. the rocker is a box inches long, inches wide on the bottom, sloped like a cradle, and with rockers at each end. [illustration: cross section of rocker.] a hopper inches square and inches deep, having an iron bottom perforated with / -inch holes, occupies the top. a light canvas-covered frame is stretched under this, forming a riffle. riffles, and occasionally amalgamated copper plates, are placed in the bottom. the gravel is fed into the hopper, the cradle being then rocked by one hand while water is fed by a dipper with the other. the cradle must be placed on an inclination while being worked, and under the influence of the continued side-to-side rocking the dirt is quickly disintegrated, passes through the riddle and falls on the apron. from the apron it is conveyed to the inner end of the cradle floor, from which it flows over the riffles, or bars, and out at the mouth. the difference in level of the floor is generally about - / inches, but this may be varied according to the nature of the dirt treated. large stones in the riddle or hopper must be thrown out, but smaller ones assist in breaking up the lumps of dirt. every little while the pebbles are turned out and looked over for nuggets. clean-ups are necessary two or three times a day. the hopper is taken off first, then the apron is slid out, and washed in a bucket or tub containing clean water, and finally the gold and amalgam are collected in an iron spoon from behind the riffle bars, and panned out. gravel requires at least three times its own weight of water to wash it. the most convenient way is to lead the water from a stream through a pipe discharging directly over the hopper, but this is, of course, impracticable in some places. more often the water is led to a little pit on the right hand side of the operator, from which he ladles it up as required. one man can wash from one to three cubic yards daily according to the character of the dirt, but every time he stops the machine to feed it with gravel or to empty the riddle, the sand will pack, and must be removed before washing can go on. two men can wash nearly three times as much dirt in a day as one man. but in any case, the rocker is only a primitive machine, having a capacity but one-fifth as great as that of the long tom, and but one-tenth that of a very poor sluice, but as it is cheap, requires but little water, and saves a high percentage of coarse gold, the rocker will continue to be used in many districts. the long tom was invented many years ago by georgia miners. [illustration: long tom.] it is a trough feet by to inches at the upper end, and inches at the lower, and inches deep. the grade is usually in . a sheet iron plate forms the lower end of the trough. these figures refer to the upper trough. the lower or riffle-box is feet long by feet wide, with a fall equal to that of the trough and a sufficient depth to keep the material and water from spilling over the sides. it should have four riffles. for this means of saving the gold, to work satisfactorily, the metal must be coarse and the water plentiful. [illustration: sluice boxes.] every sluice is an inclined channel through which flows a stream of water, carrying away all the lighter matter thrown into it, and separating it from the heavy. when the operations would not be permanent enough, or sometimes for other reasons, a ground sluice is preferred to the ordinary box sluice made of boards. ground sluicing requires, however, six times as much water as does a box sluice to do the same amount of work. it is simply a gutter in the bed rock, and if the bottom is hard and uneven its inequalities will arrest the gold; if not, a number of boulders too heavy to be moved by the stream are put into the sluice to act as riffles. no mercury is used. the water is turned off and the collected coarse gold washed in the pan. sluice boxes may be any length, from to , feet. they vary in width from to feet, though generally or inches. the grade is proportioned to the fineness of the gold, varying from inches to feet to the -foot box or length. the bottom should be of - / inch plank, and the sides of -inch boards. the boxes are made inches wider at the upper end than at the lower, so as to telescope. the best method found yet for arresting fine gold is the copper plate amalgamated with mercury on its face. these plates are never used at the head of a sluice or other situation where there is much coarse gold, as they would be superfluous in such a situation, but are placed some distance down the sluice and are most efficacious in arresting the "flour," or excessively fine gold. plates are always of copper above / inch thick, and may be feet or more long, and of a width suited to the capacity of the sluice. when treated with quicksilver, they become as brittle as glass, and must be handled with care. the copper plate is first washed with a weak solution of nitric acid, and then mercury that has been treated with a weak nitric acid solution is rubbed on the plate. as this surface of quicksilver wears off, it may be replaced by a little fresh mercury. any green slime on a plate is an evidence of copper salts in the water. it must be scraped off and the spot rubbed with fresh quicksilver. gold attracts gold, therefore the plates should not be cleaned up too often. copper plates may be freed from gold by heating them over a fire and causing the quicksilver to evaporate slowly. the plates, after being cooled, are rubbed with dilute muriatic acid and covered with damp cloths for one night. they are then rubbed with a solution containing salt peter and sal ammoniac, and once more heated over some hot coals, but not allowed to get red hot. soon the gold scale rises in blisters; the plates are then removed from the fire and scraped. those parts of the plates that have not yielded up their gold must be re-treated and fired until they do so. all these scales of gold are then collected in a porcelain dish, the base metals are dissolved out with nitric acid, and the gold is then smelted. corrosive sublimate should be placed in the crucible as long as any blue flame is seen to come from it. some mill men prefer to amalgamate their copper plates with silver amalgam, claiming that silver-coated plates save a higher percentage of gold. to amalgamate in this way take some silver bullion, or silver coin, and dissolve in weak nitric acid, only just strong enough to act upon the silver. (if you use too much nitric acid you will waste mercury and make the amalgam harder than it should be for the best results.) after crystals have formed, quicksilver must be added, heating gently meanwhile, until a thick, pasty amalgam has formed. let this new compound stand for some hours, and squeeze through chamois as usual. the proportion of silver may be about ounce to the square foot of copper to be plated. in facing new copper plates with this amalgam, they should be washed first with dilute nitric acid; then in clear water; the ball of amalgam being rubbed over their surfaces, some little force being applied. plates should not be used for hours after coating. porous copper plates of the best quality, and not too heavily rolled, should be used. follow the amalgam with a swab, and rub the alloy well into the plate. zinc amalgam (preferable when mine water containing sulphuric acid is used in the battery) is applied to the plate after it has been cleaned with a moderately dilute mixture of sulphuric acid and water. the zinc-quicksilver ball is rubbed in and applied while the plate is still wet. zinc amalgam is prepared as follows: cut zinc-sheet into small pieces; wash in weak sulphuric acid; and dissolve in mercury. when the quicksilver will take no more zinc, squeeze through chamois and rub in. zinc-coated plates should stand a week before being used. very weak sulphuric acid will always clean these plates of any scum that may form before they have received a gold coat. sometimes the miner will be troubled with impure gold after retorting. if the metal is very dark this shade may come from the presence of large amounts of iron. a heavy proportion of mineral salts, such as chloride of calcium (cacl), sodium (nacl), and magnesium (ngcl{ }), in the battery water sometimes accounts for this. in such cases amalgamate, retort, pulverize and roast. then smelt with borax, the iron passing into the slag. if necessary smelt a second time, when the gold should be pure enough to dispose of. in extreme cases, the gold may weigh but one-fifth of the amalgam treated. in districts where sufficient water for sluicing is not procurable, dry washing is resorted to. nothing but rich, coarse gold can be worked by this method, and the dry washer rarely delves far below the surface for his gold. in the mexican deserts the dirt is laid on raw hide, all the large pebbles picked out and the sand rubbed as fine as possible between the hands. the sand is placed in a batea and winnowed by tossing in the air, the lighter material being blown to leaward and the heavy gold falling into the batea. a form of winnowing machine has been patented, which may be driven by horse or hand-power, which is said to give satisfaction. it works by forcing a strong blast of air from a fan through a canvas screen. the inventor claims that it will do the work of three men, and work dirt for - / cents a cubic yard. when there is a tendency in the material to cake, dry washing is impossible. chapter vi. camp life. the indian truthfully observes: "white man make heap big fire; keep far off. indian make little fire; get close. all same." the small fire does best in the circular tepee tent, made of canvas or leather, in use on the plains. the tepee is quite an institution, but it is generally as full of smoke as a kitchen chimney, and for that reason cannot truthfully be recommended. in theory, the smoke should all pass out of the opening in the top. by using no second skin and carefully excluding all air from around the lower rim of the tepee, it will become an admirable place to cure hams, fish, etc., by the original smoke-dried process. the scripture declares that he that tarrieth over the wine cup has red eyes next morning, and so has he that sleeps in a smoky tepee. properly made, however, the tepee is the thing where wood is scarce. some original spirits are said to have started for dawson city, n.w.t., a few years ago with bicycles and push carts. if these means of transport had sufficed, the world would have learnt something, as heretofore a canoe and a sturdy pair of legs were supposed to help the wayfarer in that region better than anything else. that is in summer; in winter, the dog-train is the quickest mode of travel. in the western states and in british columbia pack horses or mules do the most of the prospector's freighting, and in the far north he either carries his outfit on his back or else transports it by canoe in summer, or by dog-train after the rivers have frozen. [illustration: hudson's bay dog sled.] no amount of written instructions will teach a man to throw a diamond hitch, or handle a canoe in swift water. a lesson or two from an expert will, however, set his thoughts in the right direction, and in time he may become proficient. canoeing, freighting and chopping are three things that are best begun in boyhood; no one ever yet became marvelously proficient in any one of them that began after reaching adult age. [illustration: yukon sled and harness.] dog teams are made up of from three to six dogs; a full-sized team dragging a load of pounds forty miles a day for a week at a time. in the hudson bay region the dogs are harnessed one behind the other, but on the yukon each pulls by a separate trace, and the team spreads out like a fan when at work. after christmas the snow-shoe is generally a necessity in the north. without "paddles" on the feet the explorer could hardly make his way through the woods, while with them on he sails along gayly, making a bee-line over frozen lake and water courses, and taking windfalls and down timber in his stride. the shoe in vogue in the forest is short and almost round, and flat, while that of the plains is very long, upturned at the toe, and narrow. there is a reason for these modifications, as the tyro will soon find out should he substitute the one for the other in the native habitat of either. but the loop by which the shoe is fastened on the foot is always the same. the string is made of moose hide; stretched, and greased before use. caribou, or reindeer hide, makes the best filling, but horse or bull hide will do at a pinch. the frame is usually of ground ash, or some other tough, hard wood. a camp kit of cooking utensils often begins and ends with a frying-pan and tin kettle. certainly when traveling light, these things should be the last to go, as with them all things are possible, even to amalgamating and retorting the precious metals. the frying-pan must have a socket instead of a long handle, as the latter may be cut from a bush at any time. a low, broad kettle boils in less time than a deep, narrow one of the same cubic capacity. all provisions should be kept in canvas bags. matches in a leather case or safe, or in a corked bottle. blankets are never kicked off if sewn up at foot and side into a sleeping bag. the existence of the prospector being passed in regions where the so-called benefits of civilization have not penetrated, he is generally a healthy, happy, hopeful man. especially, hopeful. i do not remember ever meeting one that was not brimful of expectation and trust in the future. possibly prospectors that have become pessimistic drop out of the ranks. now the man who elects to dwell with nature has only himself to thank if he does not like his lodgings. he can be comfortable or wretched, according to his knowledge of woodcraft and wilderness residence. whereas the tyro starts out with the avowed intention of "roughing it," the veteran is particularly careful to take matters as smoothly as he may, being well assured that in any case there will be enough inevitable discomfort in his lot to satisfy any reasonable craving. it is just the same in other walks of life; the sailor, the trapper and the soldier each learns to look after his own comfort and to seize every opportunity of making life as pleasant as possible. the three prime wants are food, clothing and shelter, and their importance is in the order named. now, food is something that is painfully scarce in many parts of the world, and one of the great problems of wilderness travel is to provide transport for the supplies that must be carried from civilization. a rigorous northern climate necessitates a large consumption of strong, heat-producing food, while in the tropics the explorer gets along very comfortably with rice or an occasional skinny fowl, with plantains for dessert, and plenty of boiled and filtered water. compare such a diet with that of nansen, the arctic explorer! he and his companion lived and waxed fat on a diet of lean bear's meat three times a day, washed down by draughts of melted snow water. moreover, although government expeditions, provided with every canned and potted luxury the stores contain, have suffered the ravages of scurvy, these two adventurous norwegians, living on the food their rifles had provided, did not know what sickness meant. other travelers have found that they fared better by copying to some extent the manner and customs of the natives. fat seal blubber gives wonderful resisting power against cold, it is said; while a mild, unstimulating diet of rice suits the liver better under the equator than the bass ale and roast beef galore. on this continent the working man found out long ago that pork and beans suits him nicely. the lumberman says: "it sticks to the ribs," by which robust, if not classical, phrase he means that he can chop longer without feeling hungry on pork and beans than on almost any other food. the laborer having found by experience that the side of a pig and a sack of beans was a good combination to have in the larder, the man of science after a couple of hundred years or so of deliberation confirms the discovery by announcing that the flesh of a swine mixed with the fruit of the bean contains all the carbo-hydrates, etc., necessary to sustain life. the moral of all this is that pork and beans must not be forgotten when outfitting. a few other things being desirable, the following list may be consulted to advantage by the prospective prospector. this list should suffice for feeding one man for months: sugar pounds. apples (evaporated) pounds. salt pounds. salt pork pounds. pepper pound. condensed milk case. flour barrels. candles box. matches boxes. soap doz. bars. tea / case. beans pounds. the dictates of fashion being unheard on the mountain side, and beneath the pines, dress resolves itself into a mere question of warmth and comfort. cut is of importance truly, but only insomuch as it allows free play to the limbs; to the arms in digging, and to the legs in climbing the stiff side of a canyon. home-spun, heavy tanned duck, corduroy or moleskin, and flannel underclothing should be the mainstays of a miner's wardrobe. rubber boots and slickers are also necessary to his comfort, while for winter use a heavy mackinaw overcoat, or even fur, for the extreme north, is advisable. when actually at work the miner is more often in his shirt sleeves than not, and cold indeed must the day be if an old woodsman is caught traveling through the forest with his burly form encased in furs. for arctic conditions akin to those found on the upper yukon an outfit such as the following should be chosen: heavy knitted undershirts. flannel shirts. pairs worsted socks. pairs overstockings. pair miner's boots. pair gum boots. pairs moccasins. suit homespun. horsehide jacket. pair moleskin trousers. broad-brimmed felt hat. fur cap. mackinaw overcoat. pairs flannel mitts. pair fur mitts. muffler. suit oil slickers. pairs blankets. in cold weather the feet, fingers and face require the most care. the first should be stowed into two pairs of wool socks, and a long pair of knee-high oversocks be drawn over these. boots must be replaced by moccasins. a pair of thick worsted mitts, and a pair of leather mitts outside, keep the hands warm enough even at degrees below zero. at degrees below put on an extra pair--or go home until the weather moderates. the favorite style of architecture in the wilderness is neither doric nor the gothic nor yet the renaissance. it is called the dugout. the beauty of the dugout is its extreme simplicity. a hole in the side of a dry bank, a few sods or logs for roof, and there you have it. a veteran miner goes to earth as easily as a rabbit, and, like bunny, is never at a loss for an habitation. next to the dugout the log cabin deserves mention, while the wattle and daub or 'dobe certainly secures third honors. the only drawback to the pre-eminence of the log cabin is that to make it you must have logs--just as the cook always insists on pigeons before she makes pigeon pie--and logs are in some districts only known as museum specimens. now, the dugout or the 'dobe only require a gravel bank, or one of those deposits of argilite that the vulgar persist in calling clay; were it not for this fatal ease of getting, every miner and prospector would doubtless prefer living in a snug log hut, there to await in peace, comfort, and dignity the arrival of the representative of the "english syndicate" to whom he is destined to sell his claim. napoleon found, after fighting his way across europe and back again, that his troops were more healthy bivouacking in the open than sheltered in tents. in truth, the tent is a very uncomfortable and unhealthy make-shift; cold, hot, and damp, by turns, and often badly ventilated. a simple lean-to shelter, and a roaring fire are infinitely preferable where wood is abundant. but it takes a lot of wood to keep a bivouac warm on a winter's night; as much perhaps as would feed a fair-sized family furnace for a month. the trappers' fire is a most regal blaze. two back logs; a pair of "hand junks" and a "forestick" are the foundation upon which the structure is reared, but the edifice itself often consumes a tall, full-limbed rock maple, or a stately birch between the setting of the sun and the rising of the same. there are three ways of making a fire; the first is suited for a "wooden" country; the second is used by "lo," and other prairie travelers, where fuel is scarce. if overtaken by storm in any wild northern region, do as the animals and indians do under like circumstances: seek the nearest shelter and lie close until the weather has moderated. the secret is to conserve your energy, not to fritter it away fighting a power against which you may make no real headway. a shallow, brush-lined gully; the lea of a bank, or small clump of trees; these and other seemingly slight protections sometimes mean life instead of death. the experienced woodsman never leaves camp without matches in his pocket; and in winter he carries a few pieces of dry birch bark in the bosom of his hunting shirt, as he knows how vitally necessary it is on occasions to be able to kindle a blaze at very short notice. a tent should never be pitched loosely, as no matter how fine the evening the weather ere morning may be tempestuous in the extreme, and the unpleasantness of having a tent come down about one's ears in the dark must be experienced to be realized. also, never pitch a tent with the doorway toward the northwest in winter, because that is the quarter from which comes the cold. in summer, from june until mid-august, the mosquito, the black fly and the midge or sand fly, make life a burden in the north. the best remedy for the mosquito and black fly is a mixture of tar and olive oil, of the consistency of cream, rubbed on all exposed parts of the person. a dark green veil will also keep the insect pests out of the eyes, mouth and ears, and in winter is better than snow goggles to avert blindness. but, unfortunately, it interferes with the enjoyment of the pipe, and hence is not in much favor with woodsmen. to make good bread it is not necessary to take either yeast cakes or mixing pan into the wilderness. an old hand thinks himself rich with a few pounds of flour in his sack, and soon has a batch of bread baking that would turn many a housewife green with envy. he proceeds in this fashion: a visit to the nearest hardwood ridge shows him a green parasitic lichen growing on the bark of the maples (lungwort). some of this he gathers, and steeps it over night in warm water near the embers. in the morning he mixes his flour into a paste with this decoction, using the bag as a pan. the dough is next covered with a cloth and set in a warm corner to rise; a few hours later it is re-kneaded and baked. the result should be delicious bread. some of the leaven, or raised dough, may be kept, and will suffice for the next batch of bread, and so on ad infinitum. making bed takes longer in camp than in the city, but the result is just as satisfactory. nothing more comforting than a couch of fir boughs has been devised by man. choosing a level spot the woodsman cuts several armfuls of the feathery tips of the fir balsam. these he places in layers like shingles on a roof, beginning at the foot and laying the butt of each bough toward the head. if sufficiently deep, say a couple of feet or so, such a bed will be soft and elastic for a night or two, when it will require re-laying. fragrant it always is, with the delicious aroma of the fir balsam. the white man stretches himself instinctively feet to the fire; the indian just as instinctively reclines with his side to it--and his way is the most philosophical. strange as it may seem, the greatest danger the wanderer runs is on his return to civilization. land surveyors, engineers, and others whose work calls them into camp for months at a stretch, dread their first night in a feather bed. they find by experience that they are lucky if they escape with nothing more serious than a heavy cold. hot, stuffy air, and poor ventilation cause the trouble. leaving the window wide open will almost always prevent these evil consequences, and allow the constitution to become once more tolerant of a lack of oxygen. in the wilderness, notwithstanding, wet, cold, and exposure, such ills as consumption, pneumonia, bronchitis, etc., are unheard of. boat building and net making are two arts that the prospector will do well to master. a few weeks passed in a building yard, and a half dozen lessons from an old fisherman will teach him all that he requires of these simple but extremely useful accomplishments. the best food for sustaining life in the north is pemmican. it was once made out of buffalo meat, but now the flesh of the moose, or caribou, or of the deer, is substituted. the meat is cut in thin flakes and air-dried; then a mixture is made of one-third dried meat, one-third pure haunch fat, and one-third service berries (a. canadensis). these are rammed by main force into a bag of green hide, and pounded until as solid as a rock. such a solid mass of food will keep for years in a cool climate. perhaps the reader may be inclined to exclaim: "why so much about the north; why not more about the east, south or west?" my reply to such would be: because the great finds of the future will surely be made in the north. dr. g. w. dawson, the best authority on the subject, has said there are , , square miles of virgin territory in canada to-day, and no doubt a very large proportion of it contains mineral deposits. this , , square miles he divides into sixteen separate areas, some half as large as ireland, others half that of europe, and in none of them has the footfall of a white man yet been echoed. chapter vii. surveying. a man, to make a success of prospecting, must have what is known as "a good eye for a country." given that faculty he will readily pick up the little knowledge of surveying that is sometimes almost indispensable. a tape measure, and a prismatic or surveying compass, are all that he is likely to require in laying off to his own satisfaction the extent of his claim, or any similar simple operation. the surveying compass has two fixed sights, and a jacob staff mounting, into which a wooden support is inserted. the north end of the compass is always pointed ahead, while the needle, which of course indicates the magnetic north, gives the bearing of the line run toward that north. now, magnetic north is not by any means the same thing as true north, in fact in very few localities on the earth's surface are they the same, and then never for long. in the extreme east of the united states the needle points some twenty degrees to the west of true north, and in alaska it points thirty-five degrees to the eastward of it. there is therefore one meridian somewhere in the central valley where the true north corresponds with the magnetic north, but as the magnetic pole is always shifting this never remains true of the same meridian for long. [illustration: surveying compass.] when there is no local magnetism from iron ores, or rocks containing magnetite, the needle is fairly reliable, though never perfectly accurate, but when such attraction exists the compass is unsatisfactory. such areas of attraction, however, are usually limited, and by squinting back, taking what is known as a "back sight," a local attraction may be detected, and in that case ranging by rods must be resorted to until the compass needle once more seeks its true position. to range by rods the course of the line having been determined by retracing the route followed to the last reliable mark, a stake is driven in at that point, and the surveyor standing some little distance behind it on the correct line directs an assistant to place another rod in such a position that the first hides it from view. it will then be on a prolongation of the line, and this operation being continued the surveyor will, in due time, find himself beyond the reach of the local attraction that deflected his needle and can resume compass work. a chain is feet long. oftentimes in mountainous or brush-covered countries a half chain of feet, made of light wire links, is preferred. two men do the chaining, which could of course be done by means of an ordinary tape measure in an emergency, the leader carrying ten pins of iron or wood, and the rear man taking one up as each chain is measured off. when all are used, ten chains ( / mile) have been covered. the men exchange pins and the tally man, usually the hind chainman, calls out "tally one," and cuts a notch in a stick. careful chaining is the essence of good surveying. the chain must always be kept horizontal, or else an allowance made for the inclination at which it was held when the measurement was taken, otherwise the results will be misleading, for all surveyors' measurements of areas are theoretically on a flat surface. to ascertain the height of a tree, tower, etc., fold a square of paper across, and glancing along the hypothenuse (longest side) of the right angle so found, ascertain at what point your line of sight just catches the top of the object. then its height is the same distance as the distance from where you stand to its foot, or the length of a plumb line falling from its summit, together with the height of your eye above the ground, added. [illustration] another method is to measure the shadow of the object on a level surface, next measure your own. then as your shadow is to your height so is the shadow of the object to its height. the area of a square is equal to the square of one of its sides. the area of a triangle is equal to the base multiplied by half the height. the areas of figures containing more than three sides may always be found by resolving such figures into a series of right angled triangles. very frequently the surveyor is called upon to measure an inaccessible line. there are many ways of solving such a problem, but one of the simplest is as follows: [illustration] supposing the required distance is that from bank to bank of a river (y-x). then lay off the base line y-m, driving stakes at each end; make m-p at right angles to y-m. sight from p to x, and drive in a stake at z. then: z m : m p :: z y : y x. while these simple surveying problems are easily solved, the prospector should never forget that mine surveying requires skill, experience and accuracy. he will do well always to call in the service of a mining engineer should his "prospect" ever become a full-fledged mine, as little errors of direction are particularly costly mistakes when they occur underground. should you wish to lay off a certain acreage as a square, proceed as follows: as there are ten square chains to one acre, multiply the content in acres by to reduce to square chains. then find the square root of this number of square chains, and that will be the length of a side of the square required. for instance: to lay off acres as a square: times equals square chains. whose square root is . . ans. the plot must be chains links square. seventy average paces is almost exactly equal to the side of a square acre. if you know the content and length of one of the sides of a rectangular figure it is easy to lay it off. thus: given a claim chains long, how wide must it be to cover acres? times equals square chains. divided by equals . ans. chains wide. chapter viii. floating a company. should the prospector discover mineral that increases in amount as the mine is opened, and shows that it is likely to prove a profitable deposit, he will have little difficulty in selling out to some wealthy syndicate. but if his mine is likely to become a big producer he should try rather to organize a company, of which he should be a shareholder--the controlling one if possible--as then the output of the mine will probably make him a rich man. it is rare that a prospector selling outright obtains anything but a fraction of the value of a good mine. nor is it reasonable to suppose he should. when he sells, the profits of the buyers are all in the future, and may never materialize. they take all risk, and consequently insist upon a bargain. the more money a prospector can invest in the development of a good mine the better price he is likely to get when he sells. business men dearly like to see great masses of ore in the shafts and cuts, and are always more willing to pay a handsome price when they know something distinctly promising about the purchase. let the prospector, therefore, lay open his prospect as thoroughly as he can with the means at his disposal, and if he has faith--as he should have--in the mine he is selling, let him take a good big block of stock in part payment. he must see to it, too, that sufficient working capital is provided, as there are very few mines that pay expenses from the start. sometimes, when the shareholders are very timid, and but little money has been paid into the treasury in the first instance, they become restive after a call or two and refuse to honor further demands. this has been the ruin of many a promising venture. supposing, however, that this mistake has been avoided, and that sufficient funds are in the treasury to meet all likely, legitimate drains upon it, the question of officers remains a weighty one. the board of directors should be level-headed, shrewd men, with common-sense, business ideas; the secretary should understand his work; and the mining engineer placed in charge of the mine should be one whose professional knowledge is equal to the demands of the position. the secretary must have such a knowledge of the proper price of labor, and material, as to detect any extravagance on the part of the manager. at least one member of the board of directors should understand mining. good salaries paid to the mining engineer or manager, and to the secretary, will be money well spent, provided they are competent. cheap men have no business in such responsible positions, where the handling and wise expenditure of large sums of money necessitate brains and special training. as to the mine manager, he should be a miner, surveyor, metallurgist, assayer, bookkeeper and half-dozen other things rolled into one, and that one an honest man. very low grade ore would probably pay in the hands of such a paragon of perfection--but he must be sought for long and diligently, and even then he may not be found. new processes are to be shunned until they have proved their worth and ceased to be new. no sooner is a mine floated than all sorts of knaves and fools appear on the scene, with new and wonderful appliances for saving . per cent. of all the value in the ore. be rude to them. drive them away with sticks and stones if necessary, but as you value your salvation do not hearken to them. let some one else do the experimenting; when you know a process is good, the time will have come to spend money on it. there are at the present moment thousands of tons of costly machinery rusting in lonely rocky mountain canyons that were in their day "novelties," warranted to save all the values in the ore, while the unfortunate shareholders, whose misspent money freighted these things to their final resting place, are now, perchance, "touching" the belated chicago or new york pedestrians for a nickel. the only real guide to the economic value of an ore is the treatment of a large bulk of it in the mill. plenty of ore should be kept blocked out ahead of the workings. the more ore in sight the better for the future of the mine. lastly, remember that thieving sometimes takes place on rather a large scale, and be on the watch to detect it. but there is a bright side to mining as well as a dark, and those fortunate men who paid , or cents for the stock of a mine that now sells for $ can see it quite plainly; and there are many such. mining is not a gamble as some would have the world believe, but a legitimate occupation, demanding great nerve and skill, and sometimes great patience, but not infrequently rewarding the possessors of these admirable attributes by wealth almost inexhaustible. chapter ix. medical hints. miners as a rule are a healthy, hardy lot of men, but nevertheless they are occasionally taken ill, and there is very seldom a doctor near at hand. moreover, by the very nature of their work they are particularly liable to accidents. the so-called miner's consumption is caused by want of fresh air. the miner passes most of his life in places where there is a great deficiency of oxygen. deep down in the mine the air is usually very bad, being full of smoke and damp, and the hut in which he sleeps is too often overcrowded, while the places in which he seeks his amusement, should he live in a mining camp, are usually little better. the remedy for this state of affairs is to get all the fresh air possible, then consumption is not to be feared. should poison have been swallowed, an emetic ought to be given as quickly as possible. mustard, or salt and warm water, are tolerably efficacious, but a dose of grains of ipecac is more effectual. while the emetic is acting, the patient should drink freely of warm water or warm milk. in case of apparent drowning the body should be stripped down to the waist, rapidly dried, placed on a flat surface with the head and shoulders raised a little, and hot bricks applied to the feet. breathing should be imitated by raising the arms above the head and turning the body on its side; turn the body back on the face and press the arms down to the side. do this about sixteen times a minute, and keep it up half an hour if necessary. in case of a wound which bleeds freely, a distinction must be made between blood issuing from a vein and blood issuing from an artery. in the first instance, it will be nearly black, or at least very dark; in the second, it will be bright red and spurt forth. when from a vein, bleeding must be controlled by pressure below the wound, that is, farther away from the heart, while in the case of an artery, which is always more dangerous, immediate pressure must be made above the wound on the line of the artery between the wound and the heart. a pebble rolled up in a handkerchief and tied around the limb, with the stone directly above the artery, and tightened by twisting a stick in it, is a good rough-and-ready means to stop bleeding. sometimes a pad should be placed between the handkerchief and the artery. anything that excludes the air, such as wheat flour, or olive oil, or boiled linseed, or grated raw potato, is good to spread over a burn. if any considerable surface is burned the patient is in great danger, but small burns are rarely fatal, although they may be very painful. the best application of all is linseed oil and lime water. scurvy is a disease that is very much to be dreaded whenever fresh meat and vegetables are scarce. it is now thought to be a condition of acid-poisoning, and the remedy is alkaline salts, such as carbonate of soda or carbonate of potash. lime juice is also an anti-scorbutic. in cold weather a diet of almost exclusively fresh fat meat will keep off scurvy. pneumonia is usually most fatal in crowded camps, where the men do not get a sufficient amount of pure, fresh air. chapter x. dynamite. dynamite should be stored in a magazine which must be dry, cool, and well ventilated. bricks are best, but when built of wood, the frame should be covered inside and out with boards allowing the air to have free circulation between the walls, so that the inner wall may not be heated by the sun. do not store your caps with your dynamite. if powder was well made, it is as good a dozen years afterwards as it was on the day it came from the mill. most accidents occur in thawing dynamite. dynamite freezes between and degrees far., that is, degrees above the freezing point of water, and although it does not explode, if heated slowly, until degrees far. is reached, yet the quick application of dry heat may explode it at degrees far. this makes it so dangerous, for a stick of powder hot enough to explode under certain conditions may be held in the hand with little inconvenience. powder should be thawed by placing it in a water-tight vessel and the vessel set in hot water. it should never be placed on or under a stove, or in an oven, or on a boiler wall to thaw out, as is so often done by the unthinking. frozen dynamite is especially liable to explode from heat quickly applied. nevertheless, reckless men will continue to blow themselves to pieces by foolhardy carelessness. frozen powder is unfit for use. it will burn or smoulder, and some of it may be left in the drill hole to explode when it is not wanted to. chapter xi. atomic weights. the atomic weight of a mineral is the proportion in which its elements are united, i.e., they represent the weights of the different atoms in the minerals. hydrogen, being lightest, is made the unit. supposing it becomes desirable to find the proportional weights of the elements of any substance with a known chemical formula. multiply the atomic weight of each element by the number of atoms of such element, and add these products together; this will give the weight of all. the proportion of each is arrived at by a simple calculation. for instance: how much metallic silver is there in pounds of argentite, or silver glance, whose composition is ag{ }s? then ag equals times ,-- . s equals times ,-- . so that in every pounds of the glance there are pounds of metallic silver, and by proportion we find its percentage is . . the following tables give the symbols, atomic weights and specific gravities of certain abundant elements. rare elements are omitted: symbol. at. wt. sp. gr. aluminum al . . antimony sb . . arsenic as . barium ba . bismuth bi . calcium ca . carbon c . chromium cr . . cobalt co . . copper cu . . gold (aurum) au . . hydrogen h . . iodine i . . iron (ferrum) fe . . lead (plumbum) pb . . manganese mn . . mercury (hydrargyrum) hg . nickel ni . . nitrogen n . . oxygen o . . phosphorus p . . platinum pt . . potassium (kalium) k . . selenium se . . silicon si . . silver (argentum) ag . . sodium (natrium) na . . sulphur s . . tellurium te . . tin (stannum) sn . . zinc zn . . chapter xii. odds and ends. miner's inch. a miner's inch of water varies in different states, and is, therefore, not a fixed quantity. in some states it means the quantity of water that will flow through an orifice one inch square on the bottom or side of a box under a pressure of four inches. under these conditions a miner's inch will discharge cubic feet, or , gallons every twenty-four hours, which is at the rate of gallons a minute. fifty of these miner's inches are equal to a cubic foot of water discharged every second. one cubic foot of water a second would be sufficient to supply the wants of seven thousand city dwellers. in calculating the amount of water required by a stamp mill it is usual to allow gallons for every stamp, gallons for every pan, gallons for every settler, gallons for every fruevanner, gallons for a concentrator, gallons for a jig, and - / gallons for every horse-power of a boiler each hour. if the water after passing through the mill is impounded and used over again, the loss will be about per cent. lumber in a log. to find: multiply the diameter in inches at the small end by one-half the number of inches, and again multiply this product by the length of the log in feet; this product divided by will give the number of feet of one-inch boards the log will make. horse-power of boilers. for horizontal, tubular and flue boilers, divide the number of feet of heating surface by ; this will give the horse-power. a cord of pine wood weighing , pounds is about equal to , pounds of soft coal for steam purposes. each foot of grate should burn pounds of soft coal, or of wood, per hour, with a natural draught. horse-power of an engine. multiply the area of the cylinder in square inches by the average effective pressure in pounds to the square inch, deducting three pounds per square inch for friction. multiply this remainder by the speed of the piston in feet per minute, and divide by , . the quotient will be the true horse-power. horse-power of pelton wheel. the pelton wheel is in high favor with california miners. when the head of water is known in feet, multiply by . and the product is the horse-power that one miner's inch of water will give. assaying. the muffle furnaces of the morgan crucible company of battersea are favorably known. the most useful size is that taking a "d" muffle, - / inches by inches by - / inches. a cheap "testing" outfit. sometimes the pioneer is forced to attempt a good many investigations with very simple apparatus. should he possess the following, he can achieve much: a spirit lamp, candle, blow-pipe, magnet, a bottle of hydrochloric acid, quart glass jar, three test tubes with corks, two feet of glass tubing (hard glass), copper wire, two square inches of tin plate, forceps and test paper. such an outfit could certainly be bought for $ . weight of earth, sand, gravel, etc. a ton of shingle averages cubic feet. a ton of pit sand averages cubic feet. a ton of earth averages cubic feet. a ton of river sand averages cubic feet. a ton of coarse gravel averages cubic feet. a ton of clay averages cubic feet. a ton of marl averages cubic feet. a ton of chalk averages cubic feet. weights of ores and rocks. quartz, pounds a cubic foot; silver glance, pounds; ruby silver, ; brittle silver, ; horn silver, ; antimony glance, ; cinnabar, ; copper pyrites, ; gray copper, ; galena, ; zinc blende, ; iron pyrites, ; limestone, ; clay, . california pump. a very useful pump, in regions where transportation is a problem, is the california pump. it is a rough chain-pump. a box inches by inches, inside measurement, and feet to feet in length, according to requirements, forms a tube reaching from the water to be removed to the level at which it is to be discharged. in this an endless band of stout canvas or leather works, passing under a roller at the lower end, which is immersed in the water. at the higher end the belt passes around a drum worked by water, horse, or manual power. on the belt are wooden or metal projections that fit the box, forcing the water upward as the drum revolves. hydraulic data. the prospector, and more especially the miner, will do well to commit the following figures to memory: an imperial gallon of water weighs pounds. gallons multiplied by . equals cubic feet. cubic feet multiplied by . equals gallons. gallons multiplied by . equals cubic inches. cubic inches multiplied by . equals gallons. cubic feet multiplied by . equals pounds. pounds multiplied by . equals cubic feet. gallons multiplied by . equals tons. tons multiplied by equals gallons. tons multiplied by . equals cubic feet. a head of feet gives a pressure of about - / pounds to the square inch. let h represent the head of water in feet, and p the pressure to the square inch. then: h equals p times . . p equals h times . . a fire lute. to make a fire-proof joint between the lid and body of a retort, or crucible, use the following as a lute: quartz sand. parts. clay (pure as possible) parts. horse dung part. mix and temper like mortar. contents of a vein. to find the number of cubic feet per fathom of matter in a vein, multiply its thickness in inches by . great care is requisite in estimating the ore in a vein or the amount of mineral in sight. very clever men often make grave mistakes in such calculations. a make-shift flux. rough smelting may be done with powdered white glass, though either borax or carbonate of soda is better. as soon as the gold is melted and the flux fluid and still, remove the bulk of the flux with an iron spoon, and pour the metal into a clay mould. crush the flux for gold. saving blast samples. place a quantity of spruce boughs over a hole before firing the shot, and very few stones will fly. a simple retort. squeeze the quicksilver amalgam containing gold through a chamois skin or piece of cotton until it is as dry as you can get it. then take a large potato, cut off one end and hollow out a piece of it large enough to receive the amalgam. heat a shovel or a piece of sheet iron red hot, hold the potato up and press the shovel to it, covering the amalgam. as soon as the potato sticks fast to the shovel, turn it over so that the potato is on the top and place it over the fire and keep it red hot until the retorting is finished. as soon as it cools, loosen the potato with a knife, and the gold will be underneath and the quicksilver in the potato. the quicksilver may be recovered by bruising the potato to pulp in a cup with water. cleaning amalgamated plates. [illustration] a very simple plan for getting the gold off an amalgamated copper plate is as follows: take out the surface dirt for the depth of nine inches over an area a little larger than the plate to be scaled; place six bricks around the excavation as supports for the plate. make a brick fire, and let it burn down to red hot embers. lay the plate on three iron bars resting on the bricks, and cover the face with strips of old blanket soaked in a strong solution of borax. keep the blankets wet with the solution, and when the amalgam is white, remove the plate and scrape. calculating weight of ore. measure the cubic contents of the mass; multiply this by the weight of one cubic foot of the mineral. for small masses, where no scales are at hand, fill a bucket with water, and stand it in an empty barrel. fill the bucket brimful; introduce the rock, or ore, and measure the water it displaces. find the number of cubic inches in the overflow by reference to the following table: gallon equals cubic inches. quart equals . cubic inches. pint equals . cubic inches. gill equals . cubic inches. multiply the total so found by the specific gravity of the ore, and the result will be the answer sought. supposing the bottom of the bin to be wedge-shaped, measure half the height from the bottom to the top and multiply the number of feet by the width and length, both in feet. this will give number of cubic feet in the bin. multiply the number of cubic feet by the weight of one cubic foot of the ore, and the result will show the number of pounds of ore the bin will hold. divide by , to reduce to tons. mining regulations. the mining regulations of every country differ, and the prospector must learn by heart the provisions of the one he works under. a claim notice written with a hard pencil or surveyor's marking lead on a soft pine board will last for years. weights and measures. troy weight. grains pennyweight. pwts. ounce. ounces pound. long measure. inches foot. feet yard. yards fathom. - / feet rod. rods chain. chains furlong. furlongs mile. square measure. sq. feet sq. yard. - / sq. yds. sq. rod. sq. rods sq. rood. sq. roods sq. acre. sq. acres sq. mile. an acre is feet square. land measure. . inches link. links rod. rods chain. chains mile. avoirdupois weight. drams ounce. ounces pound. pounds quarter. quarters cwt. cwt. ( , pounds) ton. apothecary's weight. grains scruple. scruples dram. drams ounce. ounces pound. glossary. adamantine--having diamond luster. adit--a horizontal tunnel from the surface draining a mine. alluvium--deposit by streams. amalgamation--combining mercury with another metal. analysis--a chemical search whereby the nature (qualitative) and amount (quantitative) of the components of a substance are found out. aqua regia--a mixture of parts hydrochloric acid with part strong nitric acid. arenaceous--sandy. argentiferous--silver-bearing. argillaceous--clay-bearing. arrastra--a rotary and primitive mill. assay--a test. assay-ton-- . - grammes. auriferous--gold-bearing. bar--obstruction in the bed of a river. bar-diggings--claims in the shallows of streams. base metals--those not classed as precious. batea--mexican gold-washing dish. battery--a set of stamps for crushing. bed--a seam or deposit. bed-rock--solid stratum below porous material. bench--old river bed; also called a terrace. booming--the sudden discharge of accumulated water. bort--black diamond. calcite--carbonate of lime. canon--pronounced canyon; a gorge. carat--about grains troy. cement--compacted gravel. color--a speck of gold. country rock--the rock enclosing a vein. cradle--a mining apparatus; also called a rocker. cupriferous--copper-bearing. decrepitate--crackling when hot. development--work done in opening a mine. dip--the inclination of a vein at right angles to its length. dolly--a primitive stamp-mill. drift--a horizontal gallery in a mine; or the rubbish left by the last ice age. drifting--driving a tunnel. dump--a heap of vein stuff, etc. exploitation--the actual mining following exploration. fathom--six feet. fault--a break in a vein or bed. float-gold--fine grains that do not sink in the water. float--veinstone or ore by which a vein is traced. flume--wooden troughs carrying water. flux--material added to help fusion. foliated--in thin layers. gangue--veinstone. gouge--a selvage of clay between vein and country rock. grade--the inclination of a ditch, etc. grating--perforated iron sheet, or bars with spaces. gravel--broken down, rounded rock fragments. ground sluice--a gutter in which gold is washed. iridescent--showing the hues of the rainbow. litharge--proto oxide of lead. long tom--a machine for saving alluvial gold. marl--clay containing lime. miner's inch--an arbitrary measure of water regulated by local custom. mundic--iron pyrites. open cut--a surface working. outcrop--that part of a vein showing on the surface. oxidation--a chemical union with oxygen. oxide--combination of a metal with oxygen. panning--washing gravel, or crushed rock, in a gold-miner's pan to detect gold, etc. peroxide--the oxide of any substance that is richest in oxygen. placer--a deposit of valuable metal in gravel. plat--a map from an original survey. plumbago--graphite or black lead. precipitate--matter separated from a solution. pulp--pulverized ore mixed with water. quarry--an open working. quartz--silica. quartzose--containing a large proportion of quartz. reduce--to turn ore into metal by taking away oxygen. riffle--a groove or strip to catch gold and mercury in a sluice. roasting--heating in contact with air. shaft--a pit giving access to a vein or working. stratum--bed or layer. striated--marked with parallel workings. strip--to remove overlying material from a vein. sulphate--a salt containing sulphuric acid. sulphide--a combination of sulphur and a metal. sulphurets--when the miner employs this term he usually means pyrites. tailings--the refuse matter after ore has been crushed. throw--the movements of vein caused by a fault; it may be up or down. translucent--if light passes through a mineral, it is translucent; if you can see the details of an object through it, it is transparent. underlie--the same thing as dip. unstratified--without stratification or bedding. wash dirt--auriferous gravel or clay. whim--a machine for hoisting by a revolving drum. winze--an interior shaft connecting the levels. zinc--white oxide of zinc. getting gold: a practical treatise for prospectors, miners, and students. by j. c. f. johnson, f. g. s., member of the aust. inst. of mining engineers; author of "practical mining," "the genesiology of gold," etc. preparer's note this text was prepared from a edition, published by charles griffin & company, limited; exeter street, strand, london. it is the second edition, revised. numerous drawings and diagrams have been omitted. preface some six years ago the author published a small book entitled "practical mining," designed specially for the use of those engaged in the always fascinating, though not as invariably profitable, pursuit of "getting gold." of this ten thousand copies were sold, nearly all in australasia, and the work is now out of print. the london _mining journal_ of september th, , said of it: "we have seldom seen a book in which so much interesting matter combined with useful information is given in so small a space." the gold-mining industry has grown considerably since , and it appeared to the writer that the present would be a propitious time to bring out a similar work, but with a considerably enlarged scope. what has been aimed at is to make "getting gold" a compendium, in specially concrete form, of useful information respecting the processes of winning from the soil and the after-treatment of gold and gold ores, including some original practical discoveries by the author. practical information, original and selected, is given to mining company directors, mine managers, quartz mill operators, and prospectors. in "rules of thumb," chapters xi. and xii., will be found a large number of useful hints on subjects directly and indirectly connected with gold-mining. the author's mining experience extends back thirty years and he therefore ventures to believe with some degree of confidence that the information, original or compiled, which the book contains, will be found both useful and profitable to those who are in any capacity interested in the gold-mining industry. j. c. f. j. london, november, . getting gold chapter i introductory gold is a name to charm by. it is desired by all nations, and is the one metal the supply of which never exceeds the demand. some one has aptly said, "gold is the most potent substance on the surface of our planet." tom hood sings: gold, gold, gold, gold! bright and yellow, hard and cold; molten, graven, hammered, rolled, heavy to get, and light to hold; stolen, borrowed, squandered, doled. that this much appreciated metal is heavy to get is proved by the high value which has been placed on it from times remote to date, and that it is light to hold most of us know to our cost. we read no farther than the second chapter in the bible when we find mention of gold. there moses speaks of "the land of havilah, where there is gold"; and in genesis, chapter xxiv., we read that abraham's servant gave rebekah an earring of half a shekel weight, say dwt. grs., and "two bracelets of ten shekels weight," or about / ozs. then throughout the scriptures, and, indeed, in all historic writings, we find frequent mention of the king of metals, and always it is spoken of as a commodity highly prized. i have sometimes thought, however, that either we are mistaken in the weights used by the hebrew nation in early days, or that the arithmetic of those times was not quite "according to cocker." we read, i. kings x. and xli., that solomon in one year received no less than six hundred and three score and six talents of gold. if a talent of gold was, as has been assumed, shekels of grains each, the value of the golden treasure accumulated in this one year by the hebrew king would have been , , pounds sterling. considering that the only means of "getting gold" in those days was a most primitive mode of washing it from river sands, or a still more difficult and laborious process of breaking the quartz from the lode without proper tools or explosives, and then slowly grinding it by hand labour between two stones, the amount mentioned is truly enormous. of this treasure the queen of sheba, who came to visit the hebrew monarch, contributed a hundred and twenty talents, or, say, , pounds worth. where the land of ophir, whence this golden lady came, was really situated has evoked much controversy, but there is now a general opinion that ophir was on the east coast of africa, somewhere near delagoa bay, in the neighbourhood of the limpopo and sabia rivers. it should be mentioned that the name of the "black but comely" queen was sabia, which may or may not be a coincidence, but it is certainly true that the rivers of this district have produced gold from prehistoric times till now. the discovery of remarkable ruins in the newly acquired province of mashonaland, which evince a high state of civilisation in the builders, may throw some light on this interesting subject. the principal value of gold is as a medium of exchange, and its high appreciation is due, first, to the fact that it is in almost universal request; and, secondly, to its comparative scarcity; yet, oddly enough, with the exception of that humble but serviceable metal iron, gold is the most widely distributed metal known. few, if any, countries do not possess it, and in most parts of the world, civilised and uncivilised, it is mined for and brought to market. the torrid, temperate, and frigid zones are almost equally auriferous. siberia, mid-asia, most parts of europe, down to equatorial and southern africa in the old world, and north, central, and southern america, with australasia, in what may be termed the new world, are all producers of gold in payable quantities. in the earlier ages, the principal source of the precious metal was probably africa, which has always been prolific in gold. to this day there are to be seen in the southern provinces of egypt excavations and the remains of old mine buildings and appliances left by the ancient gold-miners, who were mostly state prisoners. some of these mines were worked by the pharaohs of, and before, the time of moses; and in these dreadful places thousands of israelites were driven to death by the taskmaster's whip. amongst the old appliances is one which approximated very closely to the amalgamating, or blanket table, of a modern quartz mill. the grinding was done between two stones, and possibly by means of such primitive mechanism as is used to-day by the natives of korea. the korean mill is simply a large hard stone to which a rocking motion is given by manual power by means of the bamboo handles while the ore is crushed between the upper and basement stone. solomon says "there is no new thing under the sun"; certainly there is much that is not absolutely new in appliances for gold extraction. i lately learned that the principle of one of our newest concentrating machines, the frue vanner, was known in india and the east centuries ago; and we have it on good authority--that of pliny--that gold saving by amalgamation with mercury was practised before the christian era. it will not be surprising then if, ere long, some one claims to have invented the korean mill, with improvements. few subjects in mineralogical science have evoked more controversy than the origin of gold. in the middle ages, and, indeed, down to the time of that great philosopher, sir isaac newton, who was himself bitten with the craze, it was widely believed that, by what was known as transmutation, the baser metals might be changed to gold; and much time and trouble were expended in attempts to make gold--needless to say without the desired result. doubtless, however, many valuable additions to chemical science, and also some useful metallic alloys, were thus discovered. the latest startling statement on this subject comes from, of course, the wonderland of the world, america. in a recently published journal it is said that a scientific metallurgist there has succeeded in producing absolutely pure gold, which stands all tests, from silver. needless to say, if this were true, at all events the much vexed hi-metallic question would be solved at once and for all time. it is now admitted by all specialists that the royal metal, though differing in material respects in its mode of occurrence from its useful but more plebeian brethren of the mineral kingdom, has yet been deposited under similar conditions from mineral salts held in solution. the first mode of obtaining this much desired metal was doubtless by washing the sand of rivers which flowed through auriferous strata. some of these, such as the lydian stream, pactolus, were supposed to renew their golden stores miraculously each year. what really happened was that the winter floods detached portions of auriferous drift from the banks, which, being disintegrated by the rush and flow of the water, would naturally deposit in the still reaches and eddies any gold that might be contained therein. the mode of washing was exactly that carried on by the natives in some districts of africa to-day. a wooden bowl was partly filled with auriferous sand and mud, and, standing knee-deep in the stream, the operator added a little water, and caused the contents of the bowl to take a circular motion, somewhat as the modern digger does with his tin dish, with this difference, that his ancient prototype allowed the water and lighter particles to escape over the rim as he swirled the stuff round and round. i presume, in finishing the operation, he collected the golden grains by gently lapping the water over the reduced material, much as we do now. i have already spoken of the mode in which auriferous lode-stuff was treated in early times--i.e., by grinding between stones. this is also practised in africa to-day, and we have seen that the koreans, with mongolian acuteness, have gone a step farther, and pulverise the quartz by rocking one stone on another. in south america the arrastra is still used, which is simply the application of horse or mule power to the stone-grinding process, with use of mercury. the principal sources of the gold supply of the modern world have been, first, south america, transylvania in europe, siberia in asia, california in north america, and australia. africa has always produced gold from time immemorial. the later development in the johannesburg district, transvaal, which has absorbed during the last few years so many millions of english capital, is now, after much difficulty and disappointment--thanks to british pluck and skill--producing splendidly. the yield for was , , ounces--a yield never before equalled by lode-mining from one field. in the year gold was discovered in california, at sutor's sawmill, sacramento valley, where, on the water being cut off, yellow specks and small nuggets were found in the tail race. the enormous "rush" which followed is a matter of history and the subject of many romances, though the truth has, in this instance, been stranger than fiction. the yield of the precious metal in california since that date up to amounts to , , pounds. following close on the american discovery came that of australia, the credit of which has usually been accorded to hargraves, a returned californian digger, who washed out payable gold at lewis ponds creek, near bathurst, in . but there is now no reason to doubt that gold had previously been discovered in several parts of that great island continent. it may be news to many that the first gold mine worked in australia was opened about twelve miles from adelaide city, s.a., in the year . this mine was called the victoria; several of the company's scrip are preserved in the public library; but some two years previous to this a man named edward proven had found gold in the same neighbourhood. most governments nowadays encourage in every possible way the discovery of gold-fields, and rewards ranging from hundreds to thousands of pounds are given to successful prospectors of new auriferous districts. the reward the new south wales authorities meted out to a wretched convict, who early in this century had dared to find gold, was a hundred lashes vigorously laid on to his already excoriated back. the man then very naturally admitted that the alleged discovery was a fraud, and that the nugget produced was a melted down brass candlestick. one would have imagined that even in those unenlightened days it would not have been difficult to have found a scientist sufficiently well informed to put a little nitric acid on the supposed nugget, and so determine whether it was the genuine article, without skinning a live man first to ascertain. my belief is that the unfortunate fellow really found gold, but, as mr. deas thompson, the then colonial secretary, afterwards told hargraves in discouraging his reported discovery, "you must remember that as soon as australia becomes known as a gold-producing country it is utterly spoiled as a receptacle for convicts." this, then, was the secret of the unwillingness of the authorities to encourage the search for gold, and it is after all due to the fact that the search was ultimately successful beyond all precedent, that australia has been for so many years relieved of the curse of convictism, and has ceased once and for all to be a depot for the scoundrelism of britain--"hurrah for the bright red gold!" since the year to date the value of the gold raised in the australasian colonies has realised the enormous amount of nearly , , pounds. one cannot help wondering where it all goes. mulhall gives the existing money of the world at million pounds, of which millions are paper, millions silver, and millions gold. from to the world consumed by melting down plate, etc., tons of silver more than it mined. from to the value of gold was about / times that of silver. from to it was times the value of silver and now exceeds it over twenty times. in the world had million pounds of money; in , million pounds; and in , million pounds sterling. the gold first worked for in australia, as in other places, was of course alluvial, by which is usually understood loose gold in nuggets, specks, and dust, lying in drifts which were once the beds of long extinct streams and rivers, or possibly the moraines of glaciers, as in new zealand. further on the differences will be mentioned between "alluvial" and "reef" or lode gold, for that there is a difference in origin in many occurrences, is, i think, provable. i hold, and hold strongly, that true alluvial gold is not always derived from the disintegration of lodes or reefs. for instance, the "welcome nugget" certainly never came from a reef. no such mass of gold, or anything approaching it, has ever yet been taken from a quartz matrix. it was found at bakery hill, ballarat, in , weight ozs., and sold for , pounds. this was above its actual value. the "welcome stranger," a still larger mass of gold, was found amongst the roots of a tree at dunolly, victoria, in , by two starved out "fossickers" named deeson and oates. the weight of this, the largest authenticated nugget ever found was / ozs., and it was sold for , pounds, but it was rendered useless as a specimen by the finders, who spent a night burning it to remove the adhering quartz. but the ordinary digger neither hopes nor expects to unearth such treasures as these. he is content to gather together by means of puddling machine, cradle, long tom, or even puddling tub and tin dish, the scales, specks, dust, and occasional small nuggets ordinarily met with in alluvial "washes." having sunk to the "wash," or "drift," the digger, by means of one or more of the appliances mentioned above, proceeds to separate the gold from the clay and gravel in which it is found. of course in large alluvial claims, where capital is employed, such appliances are superseded by steam puddles, buddles, and other machinery, and sometimes mercury is used to amalgamate the gold when very fine. hydraulicing is the cheapest form of alluvial mining, but can only be profitably carried out where extensive drifts, which can be worked as quarry faces, and unlimited water exist in the same neighbourhood. when such conditions obtain a few grains of gold to the yard or ton will pay handsomely. lode or reef mining, is a more expensive and complicated process, requiring much skill and capital. first, let me explain what a lode really is. the american term is "ledge," and it is not inappropriate or inexpressive. imagine then a ledge, or kerbstone, continuing to unknown depths in the earth at any angle varying from perpendicular to nearly horizontal. this kerbstone is totally distinct from the rocks which enclose it; those on one side may be slate, on the other, sandstone; but the lode, separated usually by a small band of soft material known to miners as "casing," or "fluccan," preserves always an independent existence, and in many instances is practically bottomless so far as human exploration is concerned. there are, however, reefs or lodes which are not persistent in depth. sometimes the lode formation is found only in the upper and newer strata, and cuts out when, say, the basic rocks (such as granite, etc.) are reached. again, there is a form of lode known among miners as a "gash" vein. it is sometimes met with in the older crystalline slates, particularly when the lode runs conformably with the cleavage of the rock. much ignorance is displayed on the subject of lode formation and the deposition of metals therein, even by mining men of long experience. many still insist that lodes, particularly those containing gold, are of igneous origin, and point to the black and brown ferro-manganic outcrops in confirmation. it must be admitted that often the upper portions of a lode present a strong appearance of fire agency, but exactly the same appearance can be caused by oxidation of iron and manganese in water. it may now be accepted as a proven fact that no true lode has been formed, or its metals deposited except by aqueous action. that is to say, the bulk of the lode and all its metalliferous contents were once held in solution in subterranean waters, which were ejected by geysers or simply filtered into fissures formed either by the shrinkage of the earth's crust in process of cooling or by volcanic force. it is not contended that the effect of the internal fires had no influence on the formation of metalliferous veins, indeed, it is certain that they had, but the action was what is termed hydrothermal (hot water); and such action we may see in progress to-day in new zealand, where hot springs stream or spout above the surface, when the silica and lime impregnated water, reduced in heat and released from pressure, begins forthwith to deposit the minerals previously held in solution. hence the formation of the wondrous pink and white terrace, destroyed by volcanic action some eight years since, which grew almost while you watched; so rapidly was the silica deposited that a dead beetle or ti-tree twig left in the translucent blue water for a few days became completely coated and petrified. gold differs in its mode of occurrence from other metals in many respects; but there is no doubt that it was once held in aqueous solution and deposited in its metallic form by electro-chemical action. it is true we do not find oxides, carbonates, or bromides of gold in nature, nor can we feel quite sure that gold now exists naturally as a sulphide, chloride, or silicate, though the presumption is strongly that it does. if so, the deposition of the gold may be ceaselessly progressing. generally reef gold is finer as to size of the particles, and, as a rule, inferior in quality to alluvial. thus, in addition to the extra labor entailed in breaking into one of the hardest of rocks, quartz, the _madre de oro_ ("mother of gold") of the spaniards, there is the additional labour required to pulverise the rock so as to set free the tiniest particles of the noble metal it so jealously guards. there is also the additional difficult operation of saving and gathering together these small specks, and so producing the massive cakes and bars of gold in their marketable state. having found payable gold in quartz on the surface, the would-be miner has next to ascertain two things. first, the strike or course of the lode; and secondly, its underlie, or dip. the strike, or course, is the direction which the lode takes lengthwise. in australia the term "underlie" is used to designate the angle from the perpendicular at which the lode lies in its enclosing rocks, and by "dip" the angle at which it dips or inclines lengthwise on its course. thus, at one point the cap of a lode may appear on the surface, and some distance further the cap may be hundreds of feet below. usually a shaft is sunk in the reef to prove the underlie, and a level, or levels, driven on the course to ascertain its direction underground, also if the gold extends, and if so, how far. this being proved, next a vertical shaft is sunk on the hanging or upper wall side, and the reef is either tapped thereby, or a cross-cut driven to intersect it. we will now assume that our miners have found their lode payable, and have some hundreds of tons of good gold-bearing stone in sight or at the surface. they must next provide a reducing plant. of means for crushing or triturating quartz there is no lack, and every year gives us fresh inventions for the purpose, each one better than that which preceded it, according to its inventor. most practical men, however, prefer to continue the use of the stamper battery, which is virtually a pestle and mortar on a large scale. why we adhere to this form of pulverising machine is that, though somewhat wasteful of power, it is easily understood, its wearing parts are cheaply and expeditiously replaced, and it is so strong that even the most perversely stupid workman cannot easily break it or put it out of order. the stone, being pounded into sand of such degree of fineness as the gold requires, passes through a perforated iron plate called a "grating," or "screen," on to an inclined surface of copper plates faced with mercury, having small troughs, or "riffles," containing mercury, placed at certain distances apart. the crushed quartz is carried over these copper "tables," as they are termed, thence over the blanket tables--that is, inclined planes covered with coarse serge, blankets, or other flocculent material--so that the heavy particles may be caught in the hairs, or is passed over vanners or concentrating machines. the resulting "concentrates" are washed off from time to time and reserved for secondary treatment. to begin with, they are roasted to get rid of the sulphur, arsenic, etc., which would interfere with the amalgamation or lixiviation, and then either ground to impalpable fineness in one of the many triturating pans with mercury, or treated by chlorine or potassium cyanide. if, however, we are merely amalgamating, then at stated periods the battery and pans are cleaned out, the amalgam rubbed or scraped from the copper plates and raised from the troughs and riffles. it is then squeezed through chamois leather, or good calico will do as well, and retorted in a large iron retort, the nozzle of which is kept in water so as to convert the mercury vapour again to the metallic form. the result is a spongy cake of gold, which is either sold as "retorted" gold or smelted into bars. the other and more scientific methods of extracting the precious metal from its matrices, such as lixiviation or leaching, by means of solvents (chlorine, cyanogen, hyposulphite of soda, etc.), will be more fully described later on. chapter ii gold prospecting--alluvial and general it is purposed in this chapter to deal specially with the operation of searching for valuable mineral by individuals or small working parties. it is well known that much disappointment and loss accrue through lack of knowledge by prospectors, who with all their enterprise and energy are often very ignorant, not only of the probable locality, mode of occurrence, and widely differing appearance of the various valuable minerals, but also of the best means of locating and testing the ores when found. it is for the information of such as these that this chapter is mainly intended, not for scientists or miners of large experience. all of us who have had much to do with mining know that the majority of the best mineral finds have been made by the purest accident; often by men who had no mining knowledge whatever; and that many valuable discoveries have been delayed, or, when made, abandoned as not payable, from the same cause--ignorance of the rudiments of mineralogy and mining. i have frequently been asked by prospectors, when inspecting new mineral fields, what rudimentary knowledge will be most useful to them and how it can be best obtained. if a man can spare the time a course of lessons at some accredited school of mines will be, undoubtedly, the best possible training; but if he asks what books he should read in order to obtain some primary technical instruction, i reply: first, an introductory text-book of geology, which will tell him in the simplest and plainest language all he absolutely requires to know on this important subject. every prospector should understand elementary geology so far as general knowledge of the history of the structure of the earth's crust and of the several actions that have taken place in the past, or are now in operation, modifying its conditions. he may with advantage go a few steps further and learn to classify the various formations into systems, groups, and series: but he can acquire all that he need absolutely know from this useful little s. d. book. next, it is advisable to learn something about the occurrence and appearance of the valuable minerals and the formations in which they are found. for all practical purposes i can recommend cox and ratte's "mines and minerals," one of the technical education series of new south wales, which deals largely with the subject from an australian standpoint, and is therefore particularly valuable to the australian miner, but which will be found applicable to most other gold-bearing countries. i must not, however, omit to mention an admirably compiled _multum in parvo_ volume prepared by mr. g. goyder, jun., government assayer and assay instructor at the school of mines, adelaide. it is called the "prospectors' pocketbook," costs only one shilling, is well bound, and of handy size to carry. in brief, plain language it describes how a man, having learned a little of assaying, may cheaply provide himself with a portable assay plant, and fluxes, and also gives considerable general information on the subject of minerals, their occurrence and treatment.[*] [*] another excellent and really practical book is prof. cole's "practical aids in geology" (second edition), s. d. it may here be stated that some twelve years ago i did a large amount of practical silver assaying on the barrier (broken hill), which was not then so accessible a place as it is now, and got closely correct results from a number of different mines, with an extemporised plant almost amusing in its simplicity. all i took from adelaide were a small set of scales capable of determining the weight of a button down to ozs. to the ton, a piece of cheese cloth to make a screen or sieve, a tin ring / in. diameter, by / in. high, a small brass door knob to use as a cupel mould, and some powdered borax, carbonate of soda, and argol for fluxes; while for reducing lead i had recourse to the lining of a tea-chest, which lead contains no silver--john chinaman takes good care of that. my mortar was a jam tin, without top or bottom, placed on an anvil; the pestle a short steel drill. the blacksmith at mundi mundi station made me a small wrought iron crucible, also a pair of bent tongs from a piece of fencing-wire. the manager gave me a small common red flower pot for a muffle, and with the smith's forge (the fire built round with a few blocks of talcose schist) for a furnace, my plant was complete. i burned and crushed bones to make my bone-dust for cupelling, and thus provided made nearly forty assays, some of which were afterwards checked in adelaide, in each instance coming as close as check assays generally do. nowadays one can purchase cheaply a very effective portable plant, or after a few lessons a man may by practice make himself so proficient with the blowpipe as to obtain assay results sufficiently accurate for most practical purposes. coming then to the actual work of prospecting. what the prospector requires to know is, first, the usual locality of occurrence of the more valuable minerals; secondly, their appearance; thirdly, a simple mode of testing. with respect to occurrence, the older sandy and clay slates, chlorite slates, micaceous, and hornblendic schists, particularly at or near their junction with the intrusive granite and diorite, generally form the most likely geological country for the finding of mineral lodes, particularly gold, silver and tin. but those who have been engaged in practical mining for long, finding by experience that no two mineral fields are exactly alike in all their characteristics, have come to the conclusion that it is unwise to form theories as to why metals should or should not be found in certain enclosing rocks or matrices. some of the best reef gold got in victoria has been obtained in dead white, milky-looking quartz almost destitute of base metal. in south australia reef gold is almost invariably associated with iron, either as oxide, as "gossan;" or ferruginous calcite, "limonite;" or granular silica, conglomerated by iron, the "ironstone" which forms the capping or outcrop of many of our reefs, and which is often rich in gold. but to show that it is unsafe to decide off-hand in what class of matrix metals will or will not be found, i may say that in my own experience i have seen payable gold in the following materials:-- quartz, dense and milky, also in quartz of nearly every colour and appearance, saccharoidal, crystalline, nay, even in clear glass-like six-sided prismatic crystals, and associated with silver, copper, lead, arsenic, iron as sulphide, oxide, carbonate, and tungstate, antimony, bismuth, nickel, zinc, lead, and other metals in one form or another; in slate, quartzite, mica schist, granite, diorite, porphyry, felsite, calcite, dolomite, common carbonate of iron, siliceous sinter from a hot spring, as at mount morgan; as alluvial gold in drifts formed of almost all these materials; and once, perhaps the most curious matrix of all, a small piece of apparently alluvial gold, naturally imbedded in a shaly piece of coal. this specimen, i think, is in the sydney museum. one thing, however, the prospector may make sure of: he will always find gold more or less intimately associated with silica (quartz) in one or other of its many forms, just as he will always find cassiterite (oxide of tin) in the neighbourhood of granite containing muscovite (white mica), which so many people will persist in terming talc. it is stated to be a fact that tin has never been found more than about two miles from such granite. from what has been said of its widely divergent occurrences it will be admitted that the cornish miners' saying with regard to metals generally applies with great force to gold: "where it is, there it is": and "cousin jack" adds, with pathetic emphasis, "and where it is generally, there i ain't." i have already spoken of the geological "country rock" in which red gold is most likely to be discovered--i.e., the junction of the slates and schists with the igneous or metamorphic (altered) rocks, or in this vicinity. old river beds formed of gravelly drifts in the same neighbourhood may probably contain alluvial gold, or shallow deposits of "wash" on hillsides and in valleys will often carry good surface gold. this is sometimes due to the denudation, or wearing away, of the hills containing quartz-veins--that is, where the alluvial gold really was derived from such veins, which, popular opinion to the contrary, is not always the case. much disappointment and loss of time and money may sometimes be prevented if prospectors will realise that _all_ alluvial gold does not come from the quartz veins or reefs; and that following up an alluvial lead, no matter how rich, will not inevitably develop a payable gold lode. sometimes gold, evidently of reef origin, is found in the alluvial; but in that case it is generally fine as regards the size of the particles, more or less sharp-edged, or crystalline in form if recently shed; while such gold is often of poorer quality than the true alluvial which occurs in mammillary (breast-like) nuggets, and is of a higher degree of purity as gold. the ordinary non-scientific digger will do well to give credence to this view of the case, and will often thereby save himself much useless trouble. sometimes also the alluvial gold, coarser in size than true reef-born alluvial, is derived almost _in situ_ from small quartz "leaders," or veins, which the grinding down of the face of the slates has exposed; these leaders in time being also broken and worn, set free the gold they have contained, which does not, as a rule, travel far, but sometimes becomes water-worn by the rubbing over it of the disintegrated fragments of rock. but the heavy, true alluvial gold, in great pure masses, mammillary, or botryoidal (like a bunch of grapes) in shape, have assuredly been formed by accretion on some metallic base, from gold salts in solution, probably chloride, but possibly sulphide. nuggets, properly so-called, are never found in quartz lodes; but, as will be shown later, a true nugget having all the characteristics of so-called water-worn alluvial may be artificially formed on a small piece of galena, or pyrites, by simply suspending the base metal by a thread in a vessel containing a weak solution of chloride of gold in which a few hard-wood chips are thrown. prospecting for alluvial gold at shallow depths is a comparatively easy process, requiring no great amount of technical knowledge. usually the first gold is got at or near the surface and then traced to deep leads, if such exist. at mount brown goldfield, n.s.w., in , i saw claimholders turning out to work equipped only with a small broom made of twigs and a tin dish. with the broom they carefully swept out the crevices of the decomposed slate as it was exposed on the surface, and putting the resulting dust and fragments into the tin dish proceeded to dry blow it. the _modus operandi_ is as follows: the operator takes the dish about half full of dirt, and standing with his back or side to the wind, if there be any, begins throwing the stuff up and catching it, or sometimes slowly pouring it from one dish to another, the wind in either case carrying away the finer particles. he then proceeds to reduce the quantity by carefully extracting the larger fragments of rock, till eventually he has only a handful or so of moderately fine "dirt" which contains any gold there may be. if in good sized nuggets it is picked out, if in smaller pieces or fine grains the digger slowly blows the sand and dust aside with his breath, leaving the gold exposed. this process is both tedious and unhealthy, and of course can only be carried out with very dry surface dirt. the stuff in which the gold occurred at mount brown was composed of broken slate with a few angular fragments of quartz. yet, strange to say, the gold was invariably waterworn in appearance. dry blowing is now much in vogue on the west australian fields owing to the scarcity of water; but the great objection is first, the large amount of dust the unfortunate dry blower has to carry about his person, and secondly, that the peck of dirt which is supposed to last most men a life time has to be made a continuous meal of every day. for wet alluvial prospecting the appliances, besides pick and shovel, are puddling tub, tin dish, and cradle; the latter, a man handy with tools can easily make for himself. in sinking, the digger should be careful to avoid making his shaft inconveniently small, and not to waste his energy by sinking a large "new chum" hole, which usually starts by being about three times too large for the requirements at the surface, but narrows in like a funnel at feet or less. a shaft, say feet by feet inches and sunk plumb, the ends being half rounded, is large enough for all requirements to a considerable depth, though i have seen smart men, when they were in a hurry to reach the drift, get down in a shaft even less in size. the novice who is trying to follow or to find a deep lead must fully understand that the present bed of the surface river may not, in fact seldom does, indicate the ancient watercourses long since buried either by volcanic or diluvial action, which contain the rich auriferous deposits for which he is seeking; and much judgment and considerable underground exploration are often required to decide on the true course of leads. only by a careful consideration of all the geological surroundings can an approximate idea be obtained from surface inspection alone; and the whole probable conditions which led to the present contour of the country must be carefully taken into account. how am i to know the true bottom when i see it? asks the inexperienced digger. well, nothing but long experience and intelligent observation will prevent mistakes at times, particularly in deep ground; but as a general rule, though it may sound paradoxical, you may know the bottom by the top. that is, we will assume you are sinking in, say, to feet ground in a gully on the bank of which the country rock is exposed, and is, say, for instance, a clay slate or sandy slate set at a certain angle; then, in all probability, unless there be a distinct fault or change in the country rock between the slate outcrop and your shaft, the bottom will be a similar slate, standing at the same angle; and this will very probably be overlaid by a deposit of pipeclay, formed by the decomposition of the slates. from the crevices of these slates, sometimes penetrating to a considerable distance, you may get gold, but it is useless attempting to sink through them. if the outcropping strata be a soft calcareous (limy) sandstone or soft felspathic rock, and that be also the true bottom, great care should be exercised or one is apt to sink through the bottom, which may be very loose and decomposed. i have known mistakes made in this way when many feet have been sunk, and driven through what was actually bed rock, though so soft as to deceive even men of experience. the formation, however, must be the guide, and except in some specially difficult cases, a man can soon tell when he is really on bed rock or "bottom." on an alluvial lead the object of every one is to "get on the gutter," that is, to reach the lowest part of the old underground watercourse, through which for centuries the gold may have been accretionising from the percolation of the mineral-impregnated water; or, when derived from reefs or broken down leaders, the flow of water has acted as a natural sluice wherein the gold is therefore most thickly collected. sometimes the lead runs for miles and is of considerable width, at others it is irregular, and the gold-bearing "gutter" small and hard to find. in many instances, for reasons not readily apparent, the best gold is not found exactly at the lowest portion of these narrow gutters, but a little way up the sides. this fact should be taken into consideration in prospecting new ground, for many times a claim has been deserted after cleaning up the "bottom," and another man has got far better gold considerably higher up on the sides of the gutter. for shallow alluvial deposits, where a man quickly works out his by feet claim, it may be cheaper at times to "paddock" the whole ground--that is, take all away from surface to bottom, but if he is in wet ground and he has to drive, great care should be taken to properly secure the roof by means of timber. how this may best be done the local circumstances only can decide. chapter iii lode or reef prospecting the preceding chapter dealt more especially with prospecting as carried on in alluvial fields. i shall now treat of preliminary mining on lodes or "reefs." as has already been stated, the likeliest localities for the occurrence of metalliferous deposits are at or near the junction of the older sedimentary formations with the igneous or intrusive rocks, such as granites, diorites, etc. in searching for payable lodes, whether of gold, silver, copper, or even tin in some forms of occurrence, the indications are often very similar. the first prospecting is usually done on the hilltops or ridges, because, owing to denudation by ice or water which have bared the bedrock, the outcrops are there more exposed, and thence the lodes are followed down through the alluvial covered plains, partly by their "strike" or "trend," and sometimes by other indicating evidences, which the practical miner has learned to know. for instance, a lesson in tracing the lode in a grass covered country was taught me many years ago by an old prospector who had struck good gold in the reef at a point some distance to the east of what had been considered the true course. i asked him why he had opened the ground in that particular place. said he, "some folks don't use their eyes. you stand here and look towards that claim on the rise where the reef was last struck. now, don't you see there is almost a track betwixt here and there where the grass and herbage is more withered than on either side? why? well, because the hard quartz lode is close to the surface all the way, and there is no great depth of soil to hold the moisture and make the grass grow." i have found this simple lesson in practical prospecting of use since. but the strike or course of a quartz reef is more often indicated by outcrops, either of the silica itself or ironstone "blows," as the miners call them, but the term is a misnomer, as it argues the easily disproved igneous theory of veins of ejection, meaning thereby that the quartz with its metalliferous contents was thrown out in a molten state from the interior of the earth. this has in no case occurred, and the theory is an impossible one. true lodes are veins of injection formed by the infiltration of silicated waters carrying the metals also in solution. this water filled the fissures caused either by the cooling of the earth's crust, or formed by sudden upheavals of the igneous rocks. sometimes in alluvial ground the trend of the reef will be revealed by a track of quartz fragments, more or less thickly distributed on the surface and through the superincumbent soil. follow these along, and at some point, if the lode be continuous, a portion of its solid mass will generally be found to protrude and can then again be prospected. there is no rule as to the trend or strike of lodes, except that a greater number are found taking a northerly and southerly course than one which is easterly and westerly. at all events, such is the case in australia, but it cannot be said that either has the advantage in being more productive. some of the richest mines in australasia have been in lodes running easterly and westerly, while gold, tin, and copper, in great quantity and of high percentage to the ton, have been got in such mines as mount morgan, mount bischoff, and the burra, where there are no lodes properly so-called at all. mount morgan is the richest and most productive gold mine in australasia and amongst the best in the world. its yield for was , oz. of gold, valued at , pounds. dividends paid in , , pounds. this mine was opened in . up to may , , the total yield was , , ozs. of gold, sold at , , pounds, from which , , pounds have been paid in dividends. (see _mining journal_, for oct. , .) mount morgan shareholders have, in other words, divided over / tons of standard gold. the burra burra mine, about miles from adelaide, in a direction a little to the east of north, was found in by a shepherd named pickett. it is singularly situated on bald hills standing feet above the surrounding country. the ores obtained from this copper mine had been chiefly red oxides, very rich blue and green carbonates, including malachite, and also native copper. the discovery of this mine, supporting, as it did at one time, a large population, marked a new era in the history of the colony. the capital invested in it was , pounds in pound shares, and no subsequent call was ever made upon the shareholders. the total amount paid in dividends was , pounds. after being worked by the original owners for some years the mine was sold to a new company, but during the last few years it has not been worked, owing in some degree to the low price of copper and also to the fact that the deposit then being worked apparently became exhausted. for many years the average yield was from , to , tons of ore, averaging to per cent of copper. it is stated that, during the twenty-nine and a half years in which the mine was worked, the company expended , , in general expenses. the output of ore during the same period amounted to , tons, equal to , tons of copper. this, at the average price of copper, amounted to a money value of , , pounds. the mine stopped working in . mount bischoff, tasmania, has produced, since the formation of the company to december , , tons of tin ore. it is still in full work and likely to be for years to come. each of these immense metalliferous deposits was found outcropping on the summit of a hill of comparatively low altitude. there are no true walls nor can the ore be traced away from the hill in lode form. these occurrences are generally held to be due to hydrothermal or geyser action. then again lodes are often very erratic in their course. slides and faults throw them far from their true line, and sometimes the lode is represented by a number of lenticular (double-pointed in section) masses of quartz of greater or less length, either continuing point to point or overlapping, "splicing," as the miners call it. such formations are very common in west australia. all this has to be considered and taken into account when tracing the run of stone. this tyro also must carefully remember that in rough country where the lode strikes across hills and valleys, the line of the cap or outcrop will apparently be very sinuous owing to the rises and depressions of the surface. many people even now do not understand that true lodes or reefs are portions of rock or material differing from the surrounding and enclosing strata, and continuing down to unknown depths at varying angles. therefore, if you have a north and south lode outcropping on a hill and crossing an east and west valley, the said lode, underlying east, when you have traced its outcrop to the lowest point in the valley, between the two hills, will be found to be a greater or less distance, according to the angle of its dip or underlie, to the east of the outcrop on the hill where it was first seen. if it be followed up the next hill it will come again to the west, the amount of apparent deviation being regulated by the height of the hills and depth of the valley. a simple demonstration will make this plain. take a piece of half-inch pine board, ft. long and in. wide, and imagine this to be a lode; now cut a half circle out of it from the upper edge with a fret saw and lean the board say at an angle of degrees to the left, look along the top edge, which you are to consider as the outcrop on the high ground, the bottom of the cut being the outcrop in the valley, and it will be seen that the lowest portion of the cut is some inches to the right; so it is with the lode, and in rough country very nice judgment is required to trace the true course. for indications, never pass an ironstone "blow" without examination. remember the pregnant cornish saying with regard to mining and the current aphorism, "the iron hat covers the golden head." "cousin jack," put it "iron rides a good horse." the ironstone outcrop may cover a gold, silver, copper or tin lode. if you are searching for gold, the presence of the royal metal should be apparent on trial with the pestle and mortar; if silver, either by sight in one of its various forms or by assay, blowpipe or otherwise; copper will reveal itself by its peculiar colour, green or blue carbonates, red oxides, or metallic copper. it is an easy metal to prospect for, and its percentage is not difficult to determine approximately. tin is more difficult to identify, as it varies so greatly in appearance. having found your lode and ascertained its course, you want next to ascertain its value. as a rule (and one which it will be well to remember) if you cannot find payable metal, particularly in gold "reef" prospecting, at or near the surface, it is not worth while to sink, unless, of course, you design to strike a shoot of metal which some one has prospected before you. the idea is exploded that auriferous lodes necessarily improve in value with depth. the fact is that the metal in any lode is not, as a rule, equally continuous in any direction, but occurs in shoots dipping at various angles in the length of the lode, in bunches or sometimes in horizontal layers. nothing but actual exploiting with pick, powder, and brains, particularly brains, will determine this point. where there are several parallel lodes and a rich shoot has been found in one and the length of the payable ore ascertained, the neighbouring lodes should be carefully prospected opposite to the rich spot, as often similar valuable deposits will thus be found. having ascertained that you have, say, a gold reef payable at surface and for a reasonable distance along its course, you next want to ascertain its underlie or dip, and how far the payable gold goes down. as a general rule in many parts of australia--though by no means an inflexible rule--a reef running east of north and west of south will underlie east; if west of north and east of south it will go down to the westward and so round the points of the compass till you come to east and west; when if the strike of the lodes in the neighbourhood has come round from north-east to east and west the underlie will be to the south; if the contrary was the case, to the north. it is surprising how often this mode of occurrence will be found to obtain. but i cannot too strongly caution the prospector not to trust to theory but to prove his lode and his metal by following it down on the underlie. "stick to your gold" is an excellent motto. as a general thing it is only when the lode has been proved by an underlie shaft to water level and explored by driving on its course for a reasonable distance that one need begin to think of vertical shafts and the scientific laying out of the mine. a first prospecting shaft need not usually be more than ft. by ft. or even ft. by ft. in., particularly in dry country. one may often see in hard country stupid fellows wasting time, labour, and explosives in sinking huge excavations as much as ft. by ft. in solid rock, sometimes following down inches of quartz. when your shaft is sunk a few feet, you should begin to log up the top for at least ft. or ft., so as to get a tip for your "mullock" and lode stuff. this is done by getting a number of logs, say inches diameter, lay one ft. log on each side of your shaft, cut two notches in it ft. apart opposite the ends of the shaft, lay across it a ft. log similarly notched, so making a frame like a large oxford picture frame. continue this by piling one set above another till the desired height is attained, and on the top construct a rough platform and erect your windlass. if you have an iron handle and axle i need not tell you how to set up a windlass, but where timber is scarce you may put together the winding appliance described in the chapter headed "rules of thumb." if you have "struck it rich" you will have the pleasure of seeing your primitive windlass grow to a "whip," a "whim," and eventually to a big powerful engine, with its huge drum and eiffel tower-like "poppet heads," or "derrick," with their great spindle pulley wheels revolving at dizzy speed high in air. "how shall i know if i have payable gold so as to save time and trouble in sinking?" says the novice. truly it is a most important part of the prospector's art, whether he be searching for alluvial or reef gold, stream or lode tin, copper, or other valuable metal. i presume you know gold when you see it? if you don't, and the doubtful particle is coarse enough, take a needle and stick the point into the questionable specimen. if gold the steel point will readily prick it; if pyrites or yellow mica the point will glance off or only scratch it. the great importance of the first prospect from the reef is well shown by the breathless intensity with which the two bearded, bronzed pioneer prospectors in some trackless australian wild bend over the pan in which the senior "mate" is slowly reducing the sample of powdered lode stuff. how eagerly they examine the last pinch of "black sand" in the corner of the dish. prosperity and easy times, or poverty and more "hard graft" shall shortly be revealed in the last dexterous turn of the pan. let us hope it is a "pay prospect." the learner, if he be far afield and without appliances of any kind, can only guess his prospect. an old prospector will judge from six ounces of stuff within a few pennyweights what will be the yield of a ton. i have seen many a good prospect broken with the head of a pick and panned in a shovel, but for reef prospecting you should have a pestle and mortar. the handiest for travelling is a mortar made from a mercury bottle cut in half, and a not too heavy wrought iron pestle with a hardened face. to be particular you require a fine screen in order to get your stuff to regulated fineness. the best for the prospector, who is often on the move, is made from a piece of cheesecloth stretched over a small hoop. if you would be more particular take a small spring balance or an improvised scale, such as is described in mr. goyder's excellent little book, p. , which will enable you to weigh down to one-thousandth of a grain. it is often desirable to burn your stone before crushing, as it is thus more easily triturated and will reveal all its gold; but remember, that if it originally contained much pyrites, unless a similar course is adopted when treated in the battery, some of the gold will be lost in the pyrites. having crushed your gangue to a fine powder you proceed to pan it off in a similar manner to that of washing out alluvial earth, except that in prospecting quartz one has to be much more particular, as the gold is usually finer. the pan is taken in both hands, and enough water to cover the prospect by a few inches is admitted. the whole is then swirled round, and the dirty water poured off from time to time till the residue is clean quartz sand and heavy metal. then the pan is gently tipped, and a side to side motion is given to it, thus causing the heavier contents to settle down in the corner. next the water is carefully lapped in over the side, the pan being now tilted at a greater angle until the lighter particles are all washed away. the pan is then once more righted, and very little water is passed over the pinch of heavy mineral a few times, when the gold will be revealed in a streak along the bottom. in this operation, as in all others, only practice will make perfect, and a few practical lessons are worth whole pages of written instruction. to make an amalgamating assay that will prove the amount of gold which can be got from a ton of your lode, take a number of samples from different parts, both length and breadth. the drillings from the blasting bore-holes collected make the best test. when finely triturated weigh off one or two pounds, place in a black iron pan (it must not be tinned), with ozs. of mercury, ozs. salt, ozs. soda, and about half a gallon of boiling water; then, with a stick, stir the pulp constantly, occasionally swirling the dish as in panning off, till you feel certain that every particle of the gangue has come in contact with the mercury; then carefully pan off into another dish so as to lose no mercury. having got your amalgam clean squeeze it through a piece of chamois leather, though a good quality of new calico previously wetted will do as well. the resulting pill of hard amalgam can then be wrapped in a piece of brown paper, placed on an old shovel, and the mercury driven off over a hot fire; or a clay tobacco pipe, the mouth being stopped with clay, makes a good retort (see "rules of thumb," pipe and potato retorting). the residue will be retorted gold, which, on being weighed and the result multiplied by for a lb. assay, or by for lb., will give the amount of gold per ton which an ordinary battery might be expected to save. thus grain to the pound, lbs. to the ton, would show that the stuff contained oz. dwt. gr. per ton. if there should be much base metal in your sample such as say stibnite (sulphide of antimony), a most troublesome combination to the amalgamator--instead of the formula mentioned above add to your mercury about one dwt. of zinc shavings or clippings, and to your water sufficient sulphuric acid to bring it to about the strength of vinegar (weaker, if anything, not stronger), place your material preferably in an earthenware or enamelled basin if procurable, but iron will do, and intimately mix by stirring and shaking till all particles have had an opportunity to combine with the mercury. retort as before described. this device is my own invention. the only genuine test after all is the battery, and that, owing to various causes, is often by no means satisfactory. first, there is a strong, almost unconquerable temptation to select the stone, thus making the testing of a few tons give an unduly high average; but more often the trouble is the other way. the stuff is sent to be treated at some inefficient battery with worn-out boxes, shaky foundations, and uneven tables, sometimes with the plates not half amalgamated, or coated with impurities, the whole concern superintended by a man who knows as little about the treatment of auriferous quartz by the amalgamating or any other processes as a dingo does of the differential calculus. result: dwt. to the ton in the retort, dwt. in the tailings, and a payable claim declared a "duffer." when the lode is really rich, particularly if it be carrying coarse gold, and owing to rough country, or distance, a good battery is not available, excellent results in a small way may be obtained by the somewhat laborious, but simple, process of "dollying." a dolly is a one man power single stamp battery, or rather an extra sized pestle and mortar (see "rules of thumb"). silver lodes and lodes which frequently carry more or less gold, are often found beneath the dark ironstone "blows," composed of conglomerates held together by ferric and manganic oxides; or, where the ore is galena, the surface indications will frequently be a whitish limey track sometimes extending for miles, and nodules or "slugs" of that ore will generally be found on the surface from place to place. most silver ores are easily recognisable, and readily tested by means of the blowpipe or simple fire assay. sometimes the silver on being tested is found to contain a considerable percentage of gold as in the great comstock lode in nevada. ore from the big broken hill silver load, new south wales, also contains an appreciable quantity of the more precious metal. a natural alloy of gold containing per cent silver, termed electrum, is the lowest grade of the noble metal. tin, lode, and stream, or alluvial, occurs only as an oxide, termed cassiterite, and yet you can well appreciate the compliment one cornish miner pays to another whose cleverness he wishes to commend, when he says of him, "aw, he do know tin," when you look at a representative collection of tin ores. in various shapes, from sharp-edged crystals to mammillary-shaped nuggets of wood-tin; from masses of lbs. weight to a fine sand, like gunpowder, in colour black, brown, grey, yellow, red, ruby, white, and sometimes a mingling of several colours, it does require much judgment to know tin. stream tin is generally associated with alluvial gold. when such is the case there is no difficulty in saving the gold if you save the tin, for the yellow metal is of much greater specific gravity. as the natural tin is an oxide, and therefore not susceptible to amalgamation, the gold can be readily separated by means of mercury. lode tin sometimes occurs in similar quartz veins to those in which gold is got, and is occasionally associated with gold. tin is also found, as at eurieowie, in dykes, composed of quartz crystals and large scales of white mica, traversing the older slates. a similar occurrence takes place at mount shoobridge and at bynoe harbour, in the northern territory of south australia; indeed, one could not readily separate the stone from these three places if it were mixed. as before stated tin will never be found far from granite, and that granite must have white mica as one of its constituents. it is seldom found in the darker coloured rocks, or in limestone country, but it sometimes occurs in gneiss, mica schist, and chlorite schist. numerous other minerals are at times mistaken for tin, the most common of which are tourmaline or schorl, garnet, wolfram (which is a tungstate of iron with manganese), rutile or titanic acid, blackjack or zinc blende, together with magnetic, titanic, and specular iron in fine grains. this rough and ready mode of determining whether the ore is tin is by weight and by scratching or crushing, when, what is called the "streak" is obtained. the colour of the tin streak is whitey-grey, which, when once known, is not easily mistaken. the specific gravity is about . . wolfram, which is most like it, is a little heavier, from . to . , but its streak is red, brown, or blackish-brown. rutile is much lighter, . , and the streak light-brown; tourmaline is only . . blackjack is . , and its streak yellowish-white. i have seen several pounds weight to the dish got in some of the new south wales shallow sinking tin-fields, and, as a rule, payable gold was also present. fourteen years ago i told western australian people, when on a visit to that colony, that the neighbourhood of the darling range would produce rich tin. lately this had been proved to be the case, and i look forward to a great development of the tin mining industry in the south-western portion of westralia. the tin "wash" in question may also contain gold, as the country rock of the neighbourhood is such as gold is usually found in.[*] [*] since this book was in the printers' hands, the discovery of payable gold has been reported from this district. a detailed discussion of methods of prospecting will be found in chapter ii. of le neve foster's "ore and stone mining," and mr. s. herbert cox's "handbook for prospectors." chapter iv the genesiology of gold--auriferous lodes up to a comparatively recent time it was considered heretical for any one to advance the theory that gold had been deposited where found by any other agency than that of fire. as late as mr. henry rosales convinced himself, and apparently the victorian government also, that quartz veins with their enclosed metal had been ejected from the interior of the earth in a molten state. his essay, which is very ingenious and cleverly written, obtained a prize which the government had offered, but probably mr. rosales himself would not adduce the same arguments in support of the volcanic or igneous theory to-day. his phraseology is very technical; so much so that the ordinary inquirer will find it somewhat difficult to follow his reasoning or understand his arguments, which have apparently been founded only on the occurrence of gold in some of the earlier discovered quartz lodes, and the conclusions at which he arrived are not borne out by later experience. he says:--"while, however, there are not apparent signs of mechanical disturbances, during the long period that elapsed from the cooling of the earth's surface to the deposition of the silurian and cambrian systems, it is to be presumed that the internal igneous activity of the earth's crust was in full force, so that on the inner side of it, in obedience to the laws of specific gravity, chemical attraction, and centrifugal force, a great segregation of silica in a molten state took place. this molten silica continually accumulating, spreading, and pressing against the horizontal cambro-silurian beds during a long period at length forced its way through the superincumbent strata in all directions; and it is abundantly evident, under the conditions of this force and the resistance offered to its action, that the line it would and must choose would be along any continuous and slightly inclined diagonal, at times crossing the strata of the schists, though generally preferring to develop itself and egress between the cleavage planes and dividing seams of the different schistose beds." he goes on to say, "another argument to the same end (i.e., the igneous origin) may be shown from the fact that the auriferous quartz lodes have exercised a manifest metamorphic action on the adjacent walls or casing; they have done so partly in a mineralogical sense, but generally there has been a metamorphic alteration of the rock." mr. rosales then tells his readers, what we all know must be the case, that the gold would be volatilised by the heat, as would be also the other metals, which he says, were in the form of arseniurets and sulphurets; but he fails to explain how the sublimated metals afterwards reassumed their metallic form. seeing that, in most cases, they would be hermetically enclosed in molten and quickly solidifying silica they could not be acted on to any great extent by aqueous agency. neither does mr. rosales's theory account at all for auriferous lodes; which below water level are composed of a solid mass of sulphide of iron with traces of other sulphides, gold, calcspar, and a comparatively small percentage of silica. nor will it satisfactorily explain the auriferous antimonial silica veins of the new england district, new south wales, in which quantities of angular and unaltered fragments of slate from the enclosing rocks are found imbedded in the quartz. with respect to the metamorphism of the enclosing rocks to a greater degree of hardness, which mr. rosales considered was due to heat, it should be remembered that these rocks in their original state were much softer and more readily fusible than the quartz, consequently all would have been molten and mingled together instead of showing as a rule clearly defined walls. it is much more rational to suppose that the increased hardness imparted to the slates and schists at or near their contact with the lode is due to an infiltration of silica from the silicated solution which at one time filled the fissure. few scientists can now be found to advance the purely igneous theory of lode formation, though it must be admitted that volcanic action has probably had much influence not only in the formation of mineral veins, but also on the occurrence of the minerals therein. but the action was hydrothermal, just such as was seen in course of operation in new zealand a few years ago when, in the rotomahana district, one could actually see the growing of the marvellous white and pink terraces formed by the release of silica from the boiling water exuding from the hot springs, which water, so soon as the heat and pressure were removed, began to deposit its silica very rapidly; while at the thames gold-field, in the same country hot, silicated water continuously boiled out of the walls of some of the lodes after the quartz had been removed and re-deposited a siliceous sinter thereon. on this subject i note the recently published opinions of professor lobley, a gentleman whose scientific reputation entitles his utterances to respect, but who, when he contends that gold is not found in the products of volcanic action is, i venture to think, arguing from insufficient premises. certainly his theories do not hold good either in australasia or america where gold is often, nay, more usually, found at, or near, either present or past regions of volcanic action. it is always gratifying to have one's theories confirmed by men whose opinions carry weight in the scientific world. about seventeen years ago i first published certain theories on gold deposition, which, even then, were held by many practical men, and some scientists, to be open to question. of late years, however, the theory of gold occurrence by deposition from mineral salts has been accepted by all but the "mining experts" who infest and afflict the gold mining camps of the world. these opine that gold ought to occur in "pockets" only (meaning thereby their own). recently professor joseph le conte, at a meeting of the american institute of mining engineers, criticised a notable essay on the "genesis of ore deposits," by bergrath f. posepny. the professor's general conclusions are: . "ore deposits, using the term in its widest sense, may take place from any kinds of waters, but especially from alkaline solutions, for these are the natural solvents of metallic sulphides, and metallic sulphides are usually the original form of such deposits." . "they may take place from waters at any temperature and any pressure, but mainly from those at high temperature and under heavy pressure, because, on account of their great solvent power, such waters are heavily freighted with metals." . "the depositing waters may be moving in any direction, up-coming, horizontally moving, or even sometimes down-going, but mainly up-coming; because by losing heat and pressure at every step such waters are sure to deposit abundantly." . "deposits may take place in any kind of waterways--in open fissures, in incipient fissures, joints, cracks, and even in porous sandstone, but especially in great open fissures, because these are the main highways of ascending waters from the greatest depths." . "deposits may be found in many regions and in many kinds of rocks, but mainly in mountain regions, and in metamorphic and igneous rocks, because the thermosphere is nearer the surface, and ready access thereto through great fissures is found mostly in these regions and in these rocks." these views are in accordance with nearly all modern research into this interesting and fruitful subject. among the theories which they discredit is that ore bodies may usually be assumed to become richer in depth. as applied to gold lodes the teaching of experience does not bear out this view. if it be taken into account that the time in which most of our auriferous siliceous lodes were formed was probably that indicated in genesis as before the first day or period when "the earth was without form and void, and darkness was upon the face of the deep," it will be realised that the action we behold now taking place in a small way in volcanic regions, was probably then almost universal. the crust of the earth had cooled sufficiently to permit water to lie on its surface, probably in hot shallow seas, like the late lake rotomahana. plutonic action would be very general, and volcanic mud, ash, and sand would be ejected and spread far and wide, which, sinking to the bottom of the water, may possibly be the origin of what we now designate the azoic or metamorphic slates and schists, as also the early cambrian and silurian strata. these, from the superincumbent weight and internal heat, became compacted, and, in some cases, crystallised, while at the same time, from the ingress of the surface waters to the heated regions below, probably millions of geysers were spouting their mineral impregnated waters in all directions; and in places where the crust was thin, explosions of super-heated steam caused huge upheavals, rifts, and chasms, into which these waters returned, to be again ejected, or to be the cause of further explosions. later, as the cooling-process continued, there would be shrinkages of the earth's crust causing other fissures; intrusive granites further dislocated and upheaved the slates. about this age, probably, when really dry land began to appear, came the first formation of mineral lodes, and the waters, heavily charged with silicates, carbonates of lime, sulphides, etc., in solution, commenced to deposit their contents in solid form when the heat and pressure were removed. i am aware that part of the theory here propounded as to the probable mode of formation of the immense sedimentary beds of the archaic or azoic period is not altogether orthodox--i.e., that the origin of these beds is largely due to the ejection of mud, sand, and ashes from subterraneous sources, which, settling in shallow seas, were afterwards altered to their present form. it is difficult, however, to believe that at this very early period of geologic history so vast a time had elapsed as would be required to account for these enormous depositions of sediment, if they were the result only of the degradation of previously elevated portions of the earth's surface by water agency. glacial action at that time would be out of the question. but what about the metals? whence came the metallic gold of our reefs and drifts? what was it originally--a metal or a metallic salt, and if the latter, what was its nature?--chloride, sulphide, or silicate, one, or all three? i incline to the latter hypothesis. all three are known, and the chemical conditions of the period were favorable for their natural production. assuming that they did exist, the task of accounting for the mode of occurrence of our auriferous quartz lodes is comparatively simple. chloride of gold is at present day contained in sea water and in some mineral waters, and would have been likely to be more abundant during the azoic and early paleozoic period. sulphide of gold would have been produced by the action of sulphuretted hydrogen; hence probably our auriferous pyrites lodes, while silicate of gold might have resulted from a combination of gold chlorides with silicic acid, and thus the frequent presence of gold in quartz is accounted for. a highly interesting and instructive experiment, showing how gold might be, and probably was, deposited in quartz veins, was carried out by professor bischof some years ago. he, having prepared a solution of chloride of gold, added thereto a solution of silicate of potash, whereupon, as he states, the yellow colour of the chloride disappeared, and in half an hour the fluid turned blue, and a gelatinous dark-blue precipitate appeared and adhered to the sides of the vessel. in a few days moss-like forms were seen on the surface of the precipitate, presumably approximating to what we know as dendroidal gold--that is, having the appearance of moss, fern, or twigs. after allowing the precipitate to remain undisturbed under water for a month or two a decomposition took place, and in the silicate of gold specks of metallic gold appeared. from this, the professor argues, and with good show of reason, that as we know now that the origin of our quartz lodes was the silicates contained in certain rocks, it is probable that a natural silicate of gold may be combined with these silicates. if this can be demonstrated, the reason for the almost universal occurrence of gold in quartz is made clear. about , mr. skey, analyst to the new zealand geological survey department, made a number of experiments of importance in respect to the occurrence of gold. these experiments were summarised by sir james hector in an address to the wellington philosophical society in . mr. skey's experiments disproved the view generally held that gold is unaffected by sulphur or sulphuretted hydrogen gas, and showed that these elements combined with avidity, and that the gold thus treated resisted amalgamation with mercury. mr. skey proved the act of absorption of sulphur by gold to be a chemical act, and that electricity was generated in sufficient quantity and intensity during the process to decompose metallic solutions. sulphur in certain forms had long been known to exercise a prejudicial effect upon the amalgamation of gold, but this had always been attributed to the combination of the sulphur with the quicksilver used. now, however, it is certain that the sulphurising of the gold must be taken into account. we must remember that the particles of gold in the stone may be enveloped with a film of auriferous sulphide, by which they are protected from the solvent actions of the mercury. the sulphurisation of the gold gives no ocular manifestation by change of colour or perceptible increase of weight, as in the case of the formation of sulphides of silver, lead and other metals, on account of the extremely superficial action of the sulphur, and hence probably the existence of the gold sulphide escaped detection by chemists. closely allied to this subject is the investigation of the mode in which certain metals are reduced from their solutions by metallic sulphides, or, in common language, the influence which the presence of such substances as mundic and galena may exercise in effecting the deposit of pure metals, such as gold, in mineral lodes. the close relation which the richness of gold veins bears to the prevalence of pyrites has been long familiar both to scientific observers and to practical miners. the gold is an after deposit to the pyrites, and, as mr. skey was the first to explain, due to its direct reducing influences. by a series of experiments mr. skey proved that the reduction of the metal was due to the direct action of the sulphide, and showed that each grain of iron pyrites, when thoroughly oxidised, will reduce / grains of gold from its solution as chloride. he also included salts of platina and silver in this general law, and demonstrated that solutions of any of these metals traversing a vein rock containing certain sulphides would be decomposed, and the pure metal deposited. we are thus enabled to comprehend the constant association of gold, or native alloys of gold and silver, in veins which traverse rocks containing an abundance of pyrites, whether they have been formed as the result of either sub-aqueous volcanic outburst or by the metamorphism of the deeper-seated strata which compose the superficial crust of the earth. mr. skey also showed by very carefully conducted experiments that the metallic sulphides are not only better conductors of electricity than has hitherto been supposed, but that when paired they were capable of exhibiting strong electro-motive power. thus, if galena and zinc blende in acid solutions be connected in the usual manner by a voltaic pair, sulphuretted hydrogen is evolved from the surface of the former, and a current generated which is sufficient to reduce gold, silver or copper from their solutions in coherent electro-plate films. the attributing of this property of generating voltaic currents, hitherto supposed to be almost peculiar to metals, to such sulphides as are commonly found in metalliferous veins, further led mr. skey to speculate how far the currents discovered to exist in such veins by mr. e. f. fox might be produced by the gradual oxidation of mixed sulphides, and that veins containing bands of different metallic sulphides, bounded by continuing walls, and saturated with mineral waters, may constitute under some circumstances a large voltaic battery competent to produce electro-deposition of metals, and that the order of the deposit of these mineral lodes will be found to bear a definite relation to the order in which the sulphides rank in the table of their electro-motive power. these researches may lead to some clearer comprehension of the law which regulates the distribution of auriferous veins, and may explain why in some cases the metal should be nearly pure, while in others it is so largely alloyed with silver. the following extract was lately clipped from a mining paper. if true, the experiment is interesting:-- "an american scientist has just concluded a very interesting and suggestive experiment. he took a crushed sample of rich ore from cripple creek, which carried ozs. of gold per ton, and digested it in a very weak solution of sodium chloride and sulphate of iron, making the solution correspond as near as practicable to the waters found in nature. the ore was kept in a place having a temperature little less than boiling water for six weeks, when all the gold, except one ounce per ton, was found to have gone into solution. a few small crystals of pyrite were then placed in the bottle of solution, and the gold began immediately to precipitate on them. it was noticeable, however, that the pyrite crystals which were free from zinc, galena, or other extraneous matter received no gold precipitate. those which had such foreign associations were beautifully covered with fine gold crystals." experimenting in a somewhat similar direction abut twelve months since, i found that the west australian mine water, with the addition of an acid, was a solvent of gold. the idea of boiling it did not occur to me, as the action was rapid in cold water. assuming, then, that gold originally existed as a mineral salt, when and how did it take metallic form? doubtless, just in the same manner as we now (by means of well-known reagents which are common in nature) precipitate it in the laboratory. with regard to that found in quartz lodes finely disseminated through the gangue, the change was brought about by the same agency which caused the silicic acid to solidify and take the form in which we now see it in the quartz veins. silica is soluble in solutions of alkaline carbonates, as shown in new zealand geysers; the solvent action being increased by heat and pressure, so also would be the silicate or sulphide of gold. when, however, the waters with their contents were released from internal pressure and began to lose their heat the gold would be precipitated together with the salts of some other metals, and would, where the waters could percolate, begin to accretionise, thus forming the heavy or specimen gold of some reefs. on this class of deposition i shall have more to say when treating of the origin of alluvial gold in the form of nuggets. mr. g. f. becker, of the united states geological survey, writing of the geology of the comstock lode, says:--"baron von richthofen was of opinion that fluorine and chlorine had played a large part of the ore deposition in the comstock, and this the writer is not disposed to deny; but, on the other hand, it is plain that most of the phenomena are sufficiently accounted for on the supposition that the agents have been merely solutions of carbonic and hydro-sulphuric acids. these reagents will attack the bisilicates and felspars. the result would be carbonates and sulphides of metals, earth, alkalies, and free quartz, but quartz and sulphides of the metals are soluble in solutions of carbonates and sulphides of the earths and alkalies, and the essential constituents of the ore might, therefore, readily be conveyed to openings in the vein where they would have been deposited on relief of pressure and diminution of temperature. an advance boring on the ft. level of the yellow jacket struck a powerful stream of water at ft. (in the west country), which was heavily charged with hydrogen sulphide, and had a temperature of degrees f., and there is equal evidence of the presence of carbonic acid in the water of the lower levels. a spring on the ft. level of the yellow jacket which showed a temperature of about degrees f., was found to be depositing a sinter largely composed of carbonates." it may be worth while here to speak of the probable reason why gold, and indeed almost all the metals generally occur in shutes in the lodes; and why, as is often the case, these shutes are found to be more or less in a line with each other in parallel lodes, and why also the junction of two lodes is frequently specially productive. the theory with respect to these phenomena which appears most feasible is, that at these points certain chemical action has taken place, by which the deposition of the metals has been specially induced. generally a careful examination of the enclosing rocks where the shute is found will reveal some points of difference from the enclosing rocks at other parts of the course of the lode, and when ore shutes are found parallel in reefs running on the same course, bands or belts of similar country rock will be found at the productive points. from this we may fairly reason that at these points the slow stream filling the lode cavity met with a reagent percolating from this particular band of rock, which caused the deposition of its metals; and, indeed, i am strongly disposed to believe that the deposition of metals, particularly in some loose lodes, may even now be proceeding. but as in nature's laboratory the processes, if certain, are slow, this theory may be difficult to prove. why the junction of lodes is often found to be more richly metalliferous than neighbouring parts is probably because there the depositing reagents met. this theory is well put by mr. s. herbert cox, late of sydney, in his useful book, "mines and minerals." he says:--"it is a well-known fact in all mining districts that the junctions of lodes are generally the richest points, always supposing that this junction takes place in 'kindly country,' and the explanation of this we think is simple on the aqueous theory of filling of lodes. the water which is traversing two different channels of necessity passes through different belts of country, and will thus have different minerals in solution. as a case in point, let us suppose that the water in one lode contained in solution carbonates of lime, and the alkalies and silica derived form a decomposition of felspars; and that the other, charged with hydro-sulphuric acid, brought with it sulphide of gold dissolved in sulphide of lime. the result of these two waters meeting would be that carbonate of lime would be formed, hydro-sulphuric acid would be set free, and sulphide of gold would be deposited, as well as silica, which was formerly held in solution by the carbonic acid." most practical men who have given the subject attention will, i think, be disposed to coincide with this view, though there are some who hold that the occurrence of these parallel ore shutes and rich deposits at the junctions of lodes is due to extraneous electrical agency. of this, however i have failed to find any satisfactory evidence. there is, however, proof that lodes are actually re-forming and the action observed is very interesting as showing how the stratification in some lodes has come about. instances are not wanting of the growth of silica on the sides of the drives in mines. this was so in some of the mines on the thames, new zealand, previously mentioned, where in some cases the deposition was so rapid as to be noticeable from day to day, whilst the big pump was actually choked by siliceous deposits. in old auriferous workings which have been under water for years, in many parts of the world, formations of iron and silica have been found on the walls and roof, while in mining tunnels which have been long unused stalactites composed of silica and calcite have formed. then, again, experiments made by the late professor cosmo newbery, in victoria, showed that a distinctly appreciable amount of gold, iron, and silica (the latter in granular form) could be extracted from solid mine timber; which had been submerged for a considerable time. this reaction then must be in progress at the present time, and doubtless under certain conditions pyrites would eventually take the place of the timber, as is the case with some of the long buried driftwood found in victorian deep leads. again, we know that the water from some copper mines is so charged with copper sulphate that if scrap iron be thrown into it, the iron will be taken up by the sulphuric acid, and metallic copper deposited in its place. all this tends to prove that the deposition of metals from their salts, though probably not now as rapid as formerly, is still ceaselessly going on in some place or another where the necessary conditions are favourable. with regard to auriferous pyritic lodes, it does not appear even now to be clear, as some scientists assert, that their gold is never found in chemical combination with the sulphides of the base metals. on the contrary, i think much of the evidence points in the other direction. i have long been of opinion that it is really so held in many of the ferro-sulphides and arsenio-ferro sulphides. on this subject mr. t. atherton contributed a short article in to the _australian mining standard_ which is worthy of notice. he says, referring to an occurrence of a natural sulphide of gold: "the existence of gold, in the form of a natural sulphide in conjunction with pyrites, has often been advanced theoretically, as a possible occurrence; but up to the present time has, i believe, never been established as an actual fact. during my investigation on the ore of the deep creek mines, nambucca, new south wales, i have found in them what i believe to be gold existing as a natural sulphide. the lode is a large irregular one of pure arsenical pyrites carrying, in addition to gold and silver, nickel and cobalt. it exists in a felsite dyke immediately on the coast. surrounding it on all sides are micaceous schists, and in the neighbourhood about half a mile distant is a large granite hill about feet high. in the lode and its walls are large quantities of pyro-phyllite, and in some parts of the mine there are deposits of pure white translucent mica, but in the ore itself it is a yellow or pale olive green, and is never absent from the pyrites. "from the first i was much struck with the exceedingly fine state of division in which the gold existed in the ore. after roasting and very carefully grinding down in an agate mortar, i have never been able to get any pieces of gold exceeding one-thousandth of an inch in diameter, and the greater quantity is very much finer than this. careful dissolving of the pyrites and gangue so as to leave the gold intact failed to find it in any larger diameter. as this was a very unusual experience in investigations on many other kinds of pyrites, i was led further into the matter. "ultimately, after a number of experiments, there was nothing left but to test for gold existing as a natural sulphide. taking gr. of ore from a sample assaying oz. fine gold per ton, grinding it finely and heating for some hours with yellow sodium sulphide--on decomposing the filtrate and treating for gold i got a result at the rate of oz. per ton. this was repeated several times with the same result. "this sample came from the lode at the ft. level, whilst samples from the higher levels where the ore is more oxidised, although carrying the gold in exactly the same degree of fineness, do not give as high a percentage of auric sulphide. "it would appear that all the gold in the pyrites (and i have never found any gold existing apart from the pyrites) has originally taken its place there as a sulphide." professor newbery, who made many valuable suggestions on the subject, says, speaking of gold in pyritous lodes: "as it (the gold salt) may have been in the same solution that deposited the pyrites, which probably contained its iron in the form of proto-carbonate with sulphates, it was not easy at first to imagine any ordinary salt of gold; but this i find can be accomplished with very dilute solutions in the presence of an alkaline carbonate and a large excess of carbonic acid, both of which are common constituents of mineral waters, especially in victoria. this is true of chloride of gold, and if the sulphide is required in solution, it is only necessary to charge the solution with an excess of sulphuretted hydrogen. in this matter both sulphides may be retained in the same solution, depositing gradually with the escape of the carbonic acid." pyritic lodes usually contain a considerable proportion of calcareous matter, mostly carbonates, and consequently it appears not improbable that the gold may remain in some instances as a sulphide, particularly in samples of pyrites, in which it cannot be detected even by the microscope until by calcination the iron sulphide is changed to an oxide, wherein the gold may be seen in minute metallic specks. the whole subject is full of interest, and careful scientific investigation may lead to astonishing results. chapter v the genesiology of gold--auriferous drifts having considered the origin of auriferous lodes, and the mode by which in all probability the gold was conveyed to them and deposited as a metal, it is necessary also to inquire into the derivation of the gold of our auriferous drifts, and the reasons for its occurrence therein. when quite a lad on the victorian alluvial fields, i frequently heard old diggers assert that gold grew in the drifts where found. at the time we understood this to mean that it grew like potatoes; and, although not prepared with a scientific argument to prove that such was not so, the idea was generally laughed at. i have lived to learn that these old hard-heads were nearer the truth than possibly they clearly realised, and that gold does actually grow or agglomerate; and, indeed, is probably even now thus growing, though it is likely that the chemical and electric action in the mineral waters flowing through the drifts is not in this age nearly so active as formerly. most boys have tried the experiment of dipping a clean-bladed knife into sulphate of copper, and so depositing on the steel a film of copper, which adheres closely until worn away. this is a simple demonstration of a hydro-metallurgical process, though probably young hopeful is not aware of the fact; and it is really by an enlargement of this process that our beautiful and artistic gold-and silver-plated ware is produced. in the great laboratory of nature similar chemical depositions have taken place in the past, and may still be in progress; indeed, there is sound scientific reason to suppose that in certain localities this is even now the case, and that in this way much of our so-called alluvial gold has been formed, that is, by the deposition on metallic bases of the gold held in solution. we will, however, take, to begin with, the generally accepted theory as to the occurrence of alluvial gold. first, let it be said, that certain alluvial gold is unquestionably derived from the denudation of quartz lodes. such is the gold dust found in many asiatic and african rivers, in the great placer mines of california, as also the gold dust gained from the beach sand on the west coast of new zealand, or in the enormous alluvial drifts of the shoalhaven valley, new south wales. of the first, many fabulous tales are told to account for its being found in particular spots each summer after the winter floods, and miraculous agency was asserted, while the early beachcombers of the hokitika district found an equally ridiculous derivation for their gold, which was always more plentiful after heavy weather. they imagined that the breakers were disintegrating some abnormally rich auriferous reefs out at sea, and that the resultant gold was washed up on the beach. the facts are simply, with regard to the rivers, that the winter floods break down the drifts in the banks and agitate the auriferous detritus, thus acting as natural sluices, and cause the metal to accumulate in favourable spots; whilst on the new zealand coast the heavy seas breaking on the shingly beach, carry off the lighter particles, leaving behind the gold, which is so much heavier. these beaches are composed, as also are the "terraces" behind, of enormous glacial and fluvial deposits, all containing more or less gold, and extend inland to the foot of the mountains. it is almost certain that the usually fine gold got by hydraulicing in californian canyons, in the gullies of the new zealand alps, and the great new south wales drifts, is largely the result of the attrition of the boulders and gravel of moraines, which has thus freed, to a certain extent, the auriferous particles. but when we find large nuggety masses of high carat gold in the beds of dead rivers, another origin has to be sought. as previously stated, there is fair reason to assume that at least three salts of gold have existed, and, possibly, may still be found in nature--silicate, sulphide, and chloride. all of these are soluble and in the presence of certain reagents, also existing naturally, can be deposited in metallic form. therefore, if, as is contended, reef gold was formed with the reefs from solutions in mineral waters, by inferential reasoning it can be shown that much of our alluvial gold was similarly derived. the commonly accepted theory, however, is that the alluvial matter of our drifts has been ground out of the solid siliceous lodes by glacial and fluvial action, and that the auriferous leads have been formed by the natural sluicing operations of former streams. to this, however, there are several insuperable objections. first, how comes it that alluvial gold is usually superior in purity to the "reef" gold immediately adjacent? second, why is it that masses of gold, such as the huge nuggets found in victoria and new south wales, have never been discovered in lodes? third, how is it that these heavy masses which, from their specific gravity, should be found only at the very bottom of the drifts, if placed by water action, are sometimes found in all positions from the surface to the bottom of the "wash"? and, lastly, why is it that when an alluvial lead is traced up to, or down from, an auriferous reef, that the light, angular gold lies close to the roof, while the heavy masses are often placed much farther away? any one who has worked a ground sluice knows how extremely difficult it is with a strong head of water to shift from its position an ounce of solid gold. what, then, would be the force required to remove the welcome nugget? under certain circumstances, niagara would not be equal to the task. the generally smooth appearance of alleged alluvial gold is adduced as an argument in favour of its having been carried by water from its original place of deposit, and thus in transit become waterworn; while some go so far as to say that it was shot out of the reefs in a molten state. the latter idea has been already disposed of, but if not, it may be dismissed with the statement that the heat which would melt silica in the masses met with in lodes would sublimate any gold contained, and dissipate it, not in nuggets but in fumes. with regard to the assumed waterworn appearance of alluvial gold, i have examined with the microscope the smooth surface of more than one apparently waterworn nugget, and found that it was not scratched and abraded, as would have been the case had it been really waterworn, but that it presented the same appearance, though infinitely finer in grain, as the surface of a piece of metal fresh from the electrical plating-bath. mr. daintree, of the victorian geological survey, many years ago discovered accidentally that gold chloride would deposit its metal on a metallic base in the presence of any organic substance. mr. daintree found that a piece of undissolved gold in a bottle containing chloride of gold in solution had, owing to a portion of the cork having fallen into the liquid, grown or accretionised so much that it could not be extracted through the neck. this lead mr. charles wilkinson, who has contributed much to our scientific knowledge of metallurgy, to experiment further in the same direction. he says: "using the most convenient salt of gold, the terchloride, and employing wood as the decomposing agent, in order to imitate as closely as possible the organic matter supposed to decompose the solution circulating through the drifts, i first immersed a piece of cubic iron pyrites taken from the coal formation of cape otway, far distant from any of our gold rocks, and therefore less likely to contain gold than other pyrites. the specimen (no. ) was kept in dilute solution for about three weeks, and is completely covered with a bright film of gold. i afterwards filed off the gold from one side of a cube crystal to show the pyrites itself and the thickness of the surrounding coating, which is thicker than ordinary notepaper. if the conditions had continued favourable for a very lengthened period, this specimen would doubtless have formed the nucleus of a large nugget. iron, copper, and arsenical pyrites, antimony, galena, molybdenite, zinc blende, and wolfram were treated in the above manner with similar results. in the above experiments a small chip of wood was employed as the decomposing agent. in one instance i used a piece of leather. all through the wood and leather gold was disseminated in fine particles, and when cut through the characteristic metallic lustre was brightly reflected. the first six of these sulphides were also operated upon simply in the solution without organic matter; but they remained unaltered." wilkinson found that when the solution of gold chloride was as strong as, say, four grains to the ounce of water, that the pyrites or other base began to decompose, and the iron sulphide changed to yellow oxide, the "gossan" of our lodes, and that though the gold was deposited, this occurred in an irregular way, and it was coated with a dark brown powdery film something like the "black gold," often found in drifts containing much ferruginous matter. such were the curious victorian nuggets spondulix and lothair. professor newbery also made a number of similar experiments, and arrived at like results. he states as follows: "i placed a cube of galena in a solution of chloride of gold, with free access of air, and put in organic matter; gold was deposited as usual, in a bright metallic film, apparently completely coating the cube. after a few months the film burst along the edges of the cube, and remained in that state with the cracks open without any further alteration in size or form being apparent. upon removing it a few days ago and breaking it open, i found that a large portion of the galena had been decomposed, forming chloride and sulphate of lead and free sulphur, which were mixed together, encasing a small nucleus of undecomposed sulphate of lead. the formation of these salts had exerted sufficient force to burst open the gold coating, which upon the outside had the mammillary form noticed by wilkinson, while the inside was rough and irregular with crystals forcing their way into the lead salts. had this action continued undisturbed, the result would have been a nugget with a nucleus of lead salts, or if there had been a current to remove the results of decomposition, a nugget without a nucleus of foreign matter." but newbery also made another discovery which still further establishes the probability of the accretionary growth of gold in drifts. in the first experiments both investigators used organic substances as the reagent to cause the deposit of gold on its base, and in each case these substances whether woodchips, leather, or even dead flies, were found to be so absolutely impregnated with gold as to leave a golden skeleton when afterwards burned. timber found in the ballarat deep leads has been proved to be similarly impregnated. newbery found that gold could also be deposited on sulphurets without any other reagent. he says: "in our mineral sulphurets, however, we have agents which are not only capable of reducing gold and silver from solution, but besides are capable of locating them when so reduced in coherent and bulky masses. thus the aggregation of the nuggety forms of gold from solution becomes a still more simple matter, only one reagent being necessary, so that there is a greater probability of such depositions obtaining than were a double process necessary. knowing the action of sulphides, the manner or the mode of formation of a portion at least of these nuggets seems apparent. conceive a stream or river fed by springs rising in a country intersected by auriferous reefs, and consequently in this case carrying gold in solution; the drift of such a country must be to a greater or lesser extent pyritous, so that the _debris_ forming the beds of these streams or rivers will certainly contain nodules of such matters disseminated or even stopping them in actual contact with the flow of water. it follows, then, from what has been previously affirmed, that there will be a reduction of gold by these nodules, and that the metal thus reduced will be firmly attached to them, at first in minute spangles isolated from each other, but afterwards accumulating and connecting in a gradual manner at that point of the pyritous mass most subject to the current until a continuous film of some size appears. this being formed the pyrites and gold are to a certain extent polarised, the film or irregular but connected mass of gold forming the negative, and the pyrites the positive end of a voltaic pair; and so according as the polarisation is advanced to completion the further deposition of gold is changed in its manner from an indiscriminate to an orderly and selective deposition concentrated upon the negative or gold plate. the deposition of gold being thus controlled, its loss by dispersion or from the crumbling away of the sustaining pyrites is nearly or quite prevented, a conservative effect which we could scarcely expect to obtain if organic matter were the reducing agent. meanwhile there is a gradual wasting away of the pyrites or positive pole, its sulphur being oxidised to sulphuric acid and its iron to sesquioxide of iron, or hematite, a substance very generally associated with gold nuggets. according to the original size of the pyritous mass, the protection it receives from the action of oxidising substances other than gold, the strength of the gold solution, length of exposure to it, the rate of supply and velocity of stream, will be the size of the gold nugget. as to the size of a pyritous mass necessary to produce in this manner a large nugget, it is by no means considerable. a mass of common pyrites (bisulphide of iron) weighing only lbs. is competent for the construction of the famous 'welcome nugget,' an australian find having weight equal to lbs. avoirdupois. such masses of pyrites are by no means uncommon in our drifts or the beds of our mountain streams. thus we find that no straining of the imagination is required to conceive of this mode of formation for the huge masses of gold found in australia in particular, such as the welcome nugget, lbs. oz.; the welcome stranger, a surface nugget, lbs. after smelting; the braidwood specimen nugget, lbs., two-thirds gold; besides many other large masses of almost virgin gold which have been obtained from time to time in the alluvial diggings." the author has made a number of experiments in the same direction, but more with the idea of demonstrating how possibly gold may in certain cases have been deposited in siliceous formations after such formations had solidified. some of the results were remarkable and indeed unexpected. i found that i could produce artificial specimens of auriferous quartz from stone which had previously contained no gold whatever, also that it was not absolutely necessary that the stone so treated should contain any metallic sulphides. the following was contributed by the author and is from the "transactions" of the australasian institute of mining engineers for :-- "the deposition of gold. "the question as to how gold was originally deposited in our auriferous lodes is one to which a large amount of attention has been given, both by mineralogists and practical miners, and which has been hotly argued by those who held the igneous theory and those who pronounced for the aqueous theory. it was held by the former that as gold was not probably existent in nature in any but its metallic form, therefore it had been deposited in its siliceous matrix while in a molten state, and many ingenious arguments were adduced in support of this contention. of late, however, most scientific men, and indeed many purely empirical inquirers (using the word empirical in its strict sense) have come to the conclusion that though the mode in which they were composed was not always identical, all lodes, including auriferous formations, were primarily derived from mineral-impregnated waters which deposited their contents in fissures caused either by the cooling of the earth's crust or by volcanic agency. "the subject is one which has long had a special attraction for the writer, who has published several articles thereon, wherein it was contended that not only was gold deposited in the lodes from aqueous solution, but that some gold found in form of nuggets had not been derived from lodes but was nascent in its alluvial bed; and for this proof was afforded by the fact that certain nuggets have been unearthed having the shape of an adjacent pebble or angular fragment of stone indented in them. moreover, no true nugget of any great size has ever been found in a lode such as the welcome, oz., or the welcome stranger, oz.; while it was accidentally discovered some years ago that gold could be induced to deposit itself from its mineral salt to the metallic state on any suitable base, such as iron sulphide. "following out this fact, i have experimented with various salts of gold, and have obtained some very remarkable results. i have found it practicable to produce most natural looking specimens of auriferous quartz from stone which previously, as proved by assay, contained no gold whatever. moreover, the gold, which penetrates the stone in a thorough manner, assumes some of the more natural forms. it is always more or less mammillary, but at times, owing to causes which i have not yet quite satisfied myself upon, is decidedly dendroidal, as may be seen in one of the specimens which i have submitted to members. moreover, i find it possible to moderate the colour and to produce a specimen in which the gold shall be as ruddy yellow as in the ferro-oxide gangue of mount morgan, or to tone it to the pale primrose hue of the product of the croydon mines. "i note that the action of the bath in which the stone is treated has a particularly disintegrating effect on many of the specimens. some, which before immersion were of a particularly flinty texture, became in a few weeks so friable that they could be broken up by the fingers. so far as my experiments have extended they have proved this, that it was not essential that the silica and gold should have been deposited at the one time in auriferous lodes. a non-auriferous siliceous solution may have filled a fissure, and, after solidifying, some volcanic disturbance may have forced water impregnated with a gold salt through the interstices of the lode formation, when, if the conditions were favourable, the gold would be deposited in metallic forms. i prefer, for reasons which will probably be understood, not to say exactly by what process my results are obtained, but submit specimens for examination. "( ) piece of previously non-gold bearing stone. locality near adelaide, now showing gold freely in mammillary and dendroidal form. "( ) stone from new south wales, showing gold artificially introduced in interstices and on face. "( ) stone from west australia, very glassy looking, now thoroughly impregnated with gold; the mammillary formation being particularly noticeable. "( ) somewhat laminated quartz from victoria, containing a little antimony sulphide. in this specimen the gold not only shows on the surface but penetrates each of the laminations, as is proved by breaking. "( ) consists of fragments of crystallised carbonate of lime from tarrawingee, in which the gold is deposited in spots, in appearance like ferrous oxide, until submitted to the magnifying glass. "the whole subject is worthy of much more time than i can possibly give it. the importance lies in this: that having found how the much desired metal may have been deposited in its matrix, the knowledge should help to suggest how it may be economically extracted therefrom." a very remarkable nugget weighing / oz. was sluiced from near the surface in one of my own mining properties at woodside, south australia, some years ago, which illustrated the nuclear theory very beautifully. this nugget is very irregular in shape, fretted and chased as though with a jeweller's graving tool, showing plainly the shape of the pyritous crystals on which it was formed while the interstices were filled with red hematite iron just as found in artificially formed nuggets on a sulphide of iron base. the author has a nugget from the same locality weighing about / oz. which exhibits in a marked degree the same characteristics, as indeed does most of the alluvial gold found in the mount lofty ranges; also a nugget from near the centre of australia weighing four ounces, in which the original crystals of pyrites are reproduced in gold just as an iron horse-shoe, placed in a launder through which cupriferously impregnated water flows, will in time be changed to nearly pure copper and yet retain its shape. now with regard to the four points i have put as to the apparent anomalies of occurrence of alluvial gold. the reason why alluvial gold is of finer quality as a rule than reef is probably because while gold and silver, which have a considerable affinity for each other, were presumably dissolved from their salts and held in solution in the same mineral water, they would in many cases not be deposited together, for the reason that silver is most readily deposited in the presence of alkalies, which would be found in excess in mineral waters coming direct from the basic rocks, while gold is induced to precipitate more quickly in acid solutions, which would be the character of the waters after they had been exposed to atmospheric action and to contact with organic matters. this, then, may explain not only the comparatively greater purity of the alluvial gold, but also why big nuggets are found so far from auriferous reefs, and also why heavy masses of gold have been frequently unearthed from among the roots even of living trees, but more particularly in drifts containing organic matter, such as ancient timber. all, then, that has been adduced goes to establish the belief that the birthplace of our gold is in certain of the earlier rocks comprising the earth's crust, and that its appearance as the metal we value so highly is the result of electro-chemical action, such as we can demonstrate in the laboratory. chapter vi gold extraction we now come to a highly important part of our subject, the practical treatment of ores and matrixes for the extraction of the metals contained. the methods employed are multitudinous, but may be divided into four classes, namely, washing, amalgamating with mercury, chlorinating, cyaniding and other leaching processes, and smelting. the first is used in alluvial gold and tin workings and in preparing some silver, copper, and other ores for smelting, and consists merely in separating the heavier metals and minerals from their gangues by their greater specific gravity in water. the second includes the trituration of the gangue and the extraction of its gold or silver by means of mercury. chlorinating and leaching generally is a process whereby metals are first changed by chemical action into their mineral salts, as chloride of gold, nitrate of silver, sulphate of copper, and being dissolved in water are afterwards redeposited in the metallic form by means of well-known re-agents. in really successful mining it is in the last degree important that the mode of extraction of metals in the most scientific manner should be thoroughly understood, but as a general rule the science of metallurgy is but very superficially grasped even by those whose special business it is to treat ore bodies in order to extract their metalliferous contents, and whether in quartz crushing mill, lixiviating, or smelting works there is much left to be desired in the method of treating our ores. my attention was recently attracted to an article written by mr. f. a. h. rauft, m.e., from which i make the following extract: he says, speaking of the german treatment of ores and the mode of procedure in australia, "it is high time that government stepped in and endeavoured by prompt and decisive action to bring the mining industry upon a sound and legitimate basis. though our ranges abound in all kinds of minerals that might give employment to hundreds of thousands of people, mining is carried on in a desultory, haphazard fashion. there is no system, and the treatment of ores is of necessity handed over to the tender mercies of men who have not even an idea of what an intricate science metallurgy has become in older countries. during many years of practical experience i have never known a single instance where a lode, on being worked, gave a return according to assay, and i have never known any mine where some of the precious metals could not be found in the tailings or slag. the germans employ hundreds of men in working for zinc which produces some two or three per cent to the ton; here the same percentage of tin could hardly be made payable, and this, mark you, is owing not to cheaper labour alone, but chiefly to the labour-saving appliances and the results of the researches of such gigantic intellects as professor kerl and many others, of whom we in this country never even hear. go into any of the great mining works of central germany, and you may see acres covered by machinery ingeniously constructed to clean, break, and sort, and ultimately deliver the ores into trucks or direct into the furnace, and the whole under the supervision of a youngster or two. when a parcel of ore arrives at any of the works, say freiberg or clausthal, it is carefully assayed by three or four different persons and then handed over to practical experts, who are expected to produce the full amount of previous metal according to assay; and if by any chance they do not, a fixed percentage of the loss is deducted from their salary; or, if the result is in excess of this assay which is more frequently the case, a small bonus is added to their pay. compare this system with our own wasteful, reckless method of dealing with our precious metals, and we may hide our heads in very shame." all really practical men will, i think, endorse mr. rauft's opinion. well organised and conducted schools of mines will gradually ameliorate this unsatisfactory state of things, and i hope before long that we shall have none but qualified certificated men in our mines. in the meantime a few practical hints, particularly on that very difficult branch of the subject, the saving of gold, will, it is hoped, be found of service. the extraction of gold from the soil is an industry so old that its first introduction is lost in the mist of ages. as before stated, gold is one of the most widely disseminated of the metals, and man, so soon as he had risen from the lowest forms of savagery, began to be attracted by the kingly metal, which he found to be easily fashioned into articles of ornament and use, and to be practically non-corrodable. what we now term the dish or pan, then, doubtless generally a wooden bowl, was the appliance first used; but they had also an arrangement, somewhat like our modern blanket tables, over which the auriferous sand was passed by means of a stream of water. the sands of some of the rivers from which portions of the gold supply of the old world was derived are still washed over year after year in exactly the same manner as was employed, probably, thousands of years ago, the labour, very arduous, being often carried on by women, who, standing knee deep in water, pan off the sand in wooden bowls much as the digger in modern alluvial fields does with his tin dish. the resulting gold often consists of but a grain or two of fine dust-gold, which is carefully collected in quills, and so exported or traded for goods. the digger of to-day having discovered payable alluvial dirt at such a depth as to permit of its being profitably worked by small parties of men with limited or no capital, procures first a half hogshead for a puddling tub, a "cradle," or "long tom," and tin dish. the "wash dirt," as the auriferous drift is usually termed, contains a considerable admixture of clay of a more or less tenacious character, and the bulk of this has to be puddled and so disintegrated before the actual separation of the gold is attempted in the cradle or dish. this is done in the tub by constantly stirring with a shovel, and changing the water as it becomes charged with the floating argillaceous, or clayey, particles. the gravel is then placed in the hopper of the cradle which separates the larger stones and pebbles, the remainder passing down over inclined ledges as the cradle is slowly rocked and supplied with water. at the bottom of each ledge is a riffle to arrest the particles of gold. sometimes, when the gold is very fine, amalgamated copper plates are introduced and the lower ledges are covered with green baize to act as blanket tables and catch gold which might otherwise be lost. a long tom is a trough some feet in length by inches in width at the upper end, widening to inches at the lower end; it is about inches deep and has a fall of inch to a foot. an iron screen is placed at the lower end where large stones are caught, and below this screen is the riffle box, feet long, feet wide, and having the same inclination as the upper trough. it is fitted with several riffles in which mercury is sometimes placed. much more work can be done with this appliance than with the cradle, which it superseded. of course, the gold must be coarse and water plentiful. when, however, the claim is paying, and the diggings show signs of some permanency, a puddling machine is constructed. this is described in the chapter called "rules of thumb." hydraulicing and ground sluicing is a very cheap and effective method of treating large quantities of auriferous drift, and, given favourable circumstances, such as a plentiful supply of water with good fall and extensive loose auriferous deposits, a very few grains to the ton or load can be made to give payable returns. the water is conveyed in flumes, or pipes to a point near where it is required, thence in wrought iron pipes gradually reduced in size and ending in a great nozzle somewhat like that of a fireman's hose. the "monitor," as it is sometimes called, is generally fixed on a movable stand, so arranged that the strong jet of water can be directed to any point by a simple adjustment. a "face" is formed in the drift, and the water played against the lower portion of the ledge, which is quickly undermined, and falls only to be washed away in the stream of water, which is conducted through sluices with riffles, and sometimes over considerable lengths of amalgamated copper plates. this class of mining has been most extensively carried out in california and new zealand, and some districts of victoria, but the truly enormous drifts of the shoalhaven district in new south wales must in the near future add largely to the world's gold supply. these drifts which are auriferous from grass roots to bed rock extend for nearly fifty miles, and are in places over feet deep. want of capital and want of knowledge has hitherto prevented their being profitably worked on a large scale. the extraction of reef gold from its matrix is a much more complicated process, and the problem how most effectively to obtain that great desideratum--a complete separating and saving operation--is one which taxes the skill and evokes the ingenuity of scientific men all over the world. the difficulty is that as scarcely any two gangues, or matrixes, are exactly alike, the treatment which is found most effective on one mine will often not answer in another. much also depends on the proportion of gold to the ton of rock under treatment, as the most scientific and perfect processes of lixiviation hitherto adopted will not pay, even when all other conditions are favourable, if the amount of gold is much under half an ounce to the ton and even then will leave but a very small profit. if, however, the gold is "free," and the lode large, a very few pennyweights (or "dollars," as the americans say) to the ton will pay handsomely. the mode of extraction longest in vogue, and after all the cheapest and most effective, for free milling ores where the gold is not too fine, is amalgamation with mercury, which metal has a strong affinity for gold, silver, and copper. as to crushing appliances, i shall not say much. "their name is legion for they are many," and the same may be said of concentrators. it may be old-fashioned, but i admit my predilection is still in favour of the stamper-battery, for the reason that though it may be slower in proportion to the power employed, it is simple and not liable to get out of order, a great advantage when one has so often to depend on men who bring to their work a supply principally of main strength and stupidity. for the same reason i prefer the old draw and lift, and plunger pumps to newer but more complicated water-lifters. on both these points, however, i am constrained to admit that my opinion has recently been somewhat shaken. i have lately seen two appliances which appear to mark a new era in the scientific progress of mining. one is the "griffin mill," the other the "lemichel siphon elevateur." the first is in some respects on the principle of the huntingdon mill. the latter, if the inventor may be believed and the results seem to show he can be, will be a wonderful factor in developing not only mining properties where a preponderance of water is the trouble, but also in providing an automatic, and therefore extremely cheap, mode of water-raising and supply, which in simplicity is thus far unexampled. atmospheric pressure alone is relied on. the well-known process of the syphon is the basis, but with this essential difference, that a large proportion of the water drawn up to the apex of the syphon is super-elevated to heights regulated by the fall obtained in the outlet leg. this elevation can be repeated almost indefinitely by returning the waste water to the reservoirs. the lemichel syphon is a wonderful, yet most simple application of natural force. the inlet leg of the syphon is larger in diameter than the outlet leg, and is provided at the bottom with a valve or "clack." the outlet leg has a tap at its base. at the apex are two chambers, with an intermediary valve, regulated by a counterpoise weighted lever. the first chamber has also a vertical valve and pipe. when the tap of the outlet leg is turned, the water flows as in an ordinary syphon, but owing to the rapid automatic opening and shutting of the valve in the first chamber about per cent of the water is diverted, and may be raised to a height of many feet above the top of the syphon. it need not be impressed on practical men that if this invention will perform anything like what is claimed for it, its value can hardly be calculated. after a careful inspection of the appliance in operation, i believe it will do all that is stated. another invention is combined with this which, by a very small expenditure of fuel, will enable the first point of atmospheric pressure to be attained. in this way the unwatering of mines may be very inexpensively effected, or water for irrigation purposes may be raised from an almost level stream. the griffin mill is a centrifugal motion crusher with one roller only, which, by an ingenious application of motive force, revolves in an opposite direction to its initial momentum, and which evolves a force of lb. against the tire, which is only inches in diameter. for hard quartz the size should be increased by at least inches. it is claimed for this mill that it will pulverise to a gauge of holes to the square inch from / to / tons per hour, or, say roughly, tons per week. the huntingdon mill is a good crusher and amalgamator where the material to be operated on is comparatively soft, but does not do such good work when the stone is of a hard flinty nature. a no. dodge stone-breaker working about hours will keep a five-foot huntingdon mill going hours, and an automatic feeder is essential. for that matter both are almost essential for an ordinary stamper battery, and will certainly increase the crushing capacity and do better work from the greater regularity of the feed. a h.-p. (nominal) engine of good type is sufficient for huntingdon mill, rock breaker, self-feeder and steam pump. a five-foot mill under favourable circumstances will crush about as much as eight head of medium weight stamps. the grusonwek ball mills, made by krupp of germany, also that made by the austral otis company, melbourne, are fast and excellent crushing triturating appliances for either wet or dry working, but are specially suited only for ores when the gold is fine and evenly distributed in the stone. the trituration is effected by revolving the stone in a large cylinder together with a number of steel balls of various sizes, the attrition of which with the rock quickly grinds it to powder of any required degree of fineness. more mines have been ruined by bad mill management probably than by bad mining, though every experienced man must have seen in his time many most flagrant instances of bungling in the latter respect. shafts are often sunk on the wrong side of the lode or too near or too far away therefrom, while instances have not been wanting where the (mis) manager has, after sinking his shaft, driven in the opposite direction to that where the lode should be found. a common error is that of erecting machinery before there is sufficient ore in sight to make it certain that enough can be provided to keep the plant going. in mines at a distance from the centre of direction it is almost impossible to check mistakes of this description, caused by the ignorance or over sanguineness of the mine superintendent, and they are often as disastrous as they are indefensible. another fertile source of failure is the craze for experimenting with untried inventions, alleged to be improvements on well-known methods. a rule in the most scientific of card games, whist, is "when in doubt lead trumps." it might be paraphrased for mining thus: "when in doubt about machinery use that which has been proved." let some one else do the experimenting. the success of a quartz mine depends as much on favourable working conditions as on its richness in gold. thus it may be that a mine carrying or oz. of gold to the ton but badly circumstanced as to distance, mountainous roads, lack of wood and water, in some cases a plethora of the latter, or irregularly faulted country, may be less profitable than another showing only or dwt., but favourably situated. it is usually desirable to choose for the battery site, when possible, the slope of a hill which consists of rock that will give a good foundation for your battery. the economical working depends greatly on the situation, which is generally fixed more or less, in the proximity of the water. the advantages of having ample water for battery purposes, or of using water as a motive power, are so great that it is very often desirable to construct a tramway of considerable length, when, by so doing, that power can be utilised; hence most quartz mills are placed near streams, or in valleys where catchment dams can be effectively constructed, except, of course, in districts where much water has to be pumped from the mine. if water-power can be used, the water-motor will necessarily be placed as low as possible, in order to obtain the fullest available power. one point is essential. special care must be taken to keep the appliances above the flood-level. if the water in the stream is not sufficient to carry off the tailings, the battery should be placed at such a height as to leave sufficient slope for tailings' dumps. this is more important when treating ore of such value that the tailings are worth saving for secondary treatment. in this case provision should be made for tailings, dams, or slime pits. whether the battery is worked by water, steam, or gas power, an ample supply of water is absolutely necessary, at least until some thoroughly effective mode of dry treatment is established. if it can be possibly arranged the water should be brought in by gravitation, and first cost is often least cost; but where this is impossible, pumps of sufficient capacity, not only to provide the absolute quantity used, but to meet any emergency, should be erected. the purer the water the better it will be for amalgamating purposes, and in cold climates it is desirable to make provision for heating the water supplied to the battery. this can be done by means of steam from the boiler led through the feed tanks; but where the boiler power is not more than required, waste steam from the engine may be employed, but care must be taken that no greasy matter comes in contact with the plates. the exhaust steam from the engine may be utilised by carrying it through tubes fitted in an ordinary gallon tank. reducing appliances have often to be placed in districts where the water supply is insufficient for the battery. when this is so every available means must be adopted for saving the precious liquid, such as condensing the exhaust steam from the engine. this may be done by conducting it through a considerable length of ordinary zinc piping, such as is used for carrying the water from house roofs. also tailings pits should be made, in which the tailings and slimes are allowed to settle, and the cleared water is pumped back to be again used. these pits should, where practicable, be cemented. it is usual, also, to have one or two tailings dams at different levels; the tailings are run into the upper dam, and are allowed to settle; the slimes overflow from it into the lower dam, and are there deposited, while the cleared water is pumped back to the battery. arrangements are made by which all these reservoirs can be sluiced out when they are filled with accumulated tailings. it is well not to leave the sluicing for too long a period, as when the slimes and tailings are set hard they are difficult to remove. where a permanent reducing plant is to be erected, whatever form of mill may be adopted, it is better for many reasons to use automatic ore feeders. of these the best two i have met are the "tulloch" and "challenge" either of which can be adapted to any mill and both do good work. by their use the reducing capacity of the mill is increased, and the feeding being regular the wear and tear is decreased, while by the regulated feeding of the "pulp" in the battery box or mortar can be maintained at any degree of consistency which may be found desirable, and thus the process of amalgamation will be greatly facilitated. the only objection which can be urged against the automatic feeder is that the steel points of picks, gads, drills, and other tools may be allowed to pass into the mortar or mill, and thus cause considerable wear and tear. this, i think, can be avoided by the adoption of the magnet device, described in "rules of thumb." there are many mines where to dwt. of gold cover all the cost, the excess being clear profit. in fact there are mines which with a yield of / to dwt. a ton, and crushing with water power, have actually yielded large profits. on the other hand, mines which have given extraordinary trial crushings have not paid working expenses. everything depends on favourable local conditions and proper management. having decided what class of crushing machinery you will adopt, the first point is to fix on the best possible site for its erection. this requires much judgment, as success or failure may largely depend on the position of your machinery. one good rule is to get your crusher as reasonably high as possible, as it is cheaper to pump your feed water a few feet higher so as to get a good clear run for your tailings, and also to give you room to erect secondary treatment appliances, such as concentrators and amalgamators below your copper plates and blanket strakes. next, and this is most important, see that your foundations are solid and strong. a very large number of the failures of quartz milling plants is due to neglect of this rule. i once knew a genius who erected a -lead mill in a new district, and who adopted the novel idea of placing a "bed log" laterally beneath his stampers. the log was laid in a little cement bed which, when the battery started, was not quite dry. the effect was comical to every one but the unfortunate owners. it was certainly the liveliest, but at the same time one of the most ineffective batteries i have seen. in a stamp mill the foundations are usually made of hard wood logs about to feet long, set on end, the bottom end resting on rock and set round with cement concrete. these are bolted together, and the "box" or mortar is bolted to them. the horizontal logs to carry the "horses" or supports for the battery frame should also be of good size, and solidly and securely bolted. the same applies to your engine-bed, but whether it be of timber, or mason work, above all things provide that the whole of your work is set out square and true to save after-wear and friction. considerable difference of opinion exists as to the most effective weight for stamps. my experience has been that this largely depends on the nature of your rock, as does also the height for the drop. i have usually found that with medium stamps, say to / cwt. with fair drop and lively action, about falls per minute, the best results were obtained, but the tendency of modern mill men is towards the heavier stamps, cwt. and even heavier. to find the horse-power required to drive a battery, multiply the weight of one stamp by the number of stamps in the battery; the height of lift in feet by the number of lifts per minute; add one-third of the product for friction, and the result will be the number of feet-lbs. per minute; divide this by , which is the number of feet-lbs. per minute equal to h.-p. and the result will be the h.-p. required. thus if a stamp weighs lb. and you have five in the box, and each stamp has a lift of in. = . ft. and strikes blows per minute, then x x . x = , ; one-third of , = , which added to , = , ; and , divided by , = . h.-p. or . h.-p. each stamp. the total weight of a battery, including stamper box, stampers, etc., may be roughly estimated at about ton per stamp. medium weight stampers, including shank cam, disc, head, and shoe, weigh from to lb., and need about / h.-p. to work them. the quantity of water required for the effective treatment of gold-bearing rock in a stamper battery varies according to the composition of the material to be operated upon, but generally it is more than the inexperienced believe. for instance, "mullocky" lode stuff, containing much clayey matter or material carrying a large percentage of heavy metal, such as titanic iron or metallic sulphides, will need a larger quantity of water per stamp than clean quartz. a fair average quantity would be to gallons per hour for each box of five stamps. in general practice i have seldom found gallons per hour more than sufficient. as to the most effective mesh for the screen or grating no definite rule can be given, as that depends so largely on the size of the gold particles contained in the gangue. the finer the particles the closer must be the mesh, and nothing but careful experiment will enable the battery manager to decide this most important point. the american slotted screens are best; they wear better than the punched gratings and can be used of finer gauge. woven steel wire gauze is employed with good effect in some mills where especially fine trituration is required. this class of screen requires special care as it is somewhat fragile, but with intelligent treatment does good work. the fall or inclination of the tables, both copper and blanket strakes, is also regulated by the class of ore. if it should be heavy then the fall must be steeper. a fair average drop is / inch to the foot. be careful that your copper tables are thoroughly water-tight, for remember you are dealing with a very volatile metal, quicksilver; and where water will percolate mercury will penetrate. the blanket tables are simply a continuation of the mercury tables, but covered with strips of coarse blanket, green baize, or other flocculent material, intended to arrest the heavier metallic particles which, owing to their refractory nature, have not been amalgamated. the blanket table is, however, a very unsatisfactory concentrator at best, and is giving place to mechanical concentrators of various descriptions. an ancient egyptian gold washing table was used by the egyptians in treating the gold ores of lower egypt. the ore was first ground, it is likely by means of some description of stone arrasts and then passed over the sloping table with water, the gold being retained in the riffles. in these the material would probably be mechanically agitated. although for its era ingenious it will be plain to practical men that if the gold were fine the process would be very ineffective. possibly, but of this i have no evidence, mercury was used to retain the gold on the riffles, as previously stated. this method of saving the precious metal was known to the ancients. at a mine of which i was managing director the lode was almost entirely composed of sulphide of iron, carbonate of lime or calcspar, with a little silica. in this case it has been found best to crush without mercury, then run the pulp into pans, where it is concentrated. the concentrates are calcined in a common reverberatory furnace, and afterwards amalgamated with mercury in a special pan, the results as to the proportion of gold extracted being very satisfactory; but it does not therefore follow that this process would be the most suitable in another mine where the lode stuff, though in some respects similar, yet had points of difference. i was lately consulted with respect to the treatment of a pyritic ore in a very promising mine, but could not recommend the above treatment, because though the pyrites in the gangue was similar, the bulk of the lode consisted of silica, consequently there would be a great waste of power in triturating the whole of the stuff to what, with regard to much of it, would be an unnecessary degree of fineness. i am of opinion that in cases such as this, where it is not intended to adopt the chlorination or cyanogen process, it will be found most economical to crush to a coarse gauge, concentrate, calcine the concentrates, and finally amalgamate in some suitable amalgamator. probably for this mode of treatment krom rolls would be found more effective reducing agents than stampers, as with them the bulk of the ore can be broken to any required gauge and there would consequently be less loss in "slimes." the great art in effective battery work is to crush your stuff to the required fineness only, and then to provide that each particle is brought into contact with the mercury either in box, trough, plate, or pan. to do this the flow of water must be carefully regulated; neither so much must be used as to carry the stuff off too quickly nor so little as to cause the troughs and plates to choke. in cold weather the water may be warmed by passing the feed-pipe through a tank into which the steam from the engine exhausts, and this will be found to keep the mercury bright and lively. but be careful no engine oil or grease mingles with the water, as grease on the copper tables will absolutely prevent amalgamation. the first point, then, is to crush the gangue effectively, the degree of fineness being regulated by the fineness of the gold itself. this being done, then comes the question of saving the gold. if the quartz be clean, and the gold unmixed with base metal, the difficulty is small. all that is required is to ensure that each particle of the royal metal shall be brought into contact with the mercury. the main object is to arrest the gold at the earliest possible stage; therefore, if you are treating clean stone containing free gold, either coarse or fine, i advise the use of mercury in the boxes, for the reason that a considerable proportion of the gold will be caught thereby, and settling to the bottom, or adhering to amalgamated plates in the boxes, where such are used, will not be afterwards affected by the crushing action, which might otherwise break up, or "flour," the mercury. on the whole, i rather favour the use of mercury in the box at any time, unless the ore is very refractory--that is, contains too great a proportion of base metals, particularly sulphides of iron, arsenic, etc., when the result will not be satisfactory, but may entail great loss by the escape of floured mercury carrying with it particles of gold. here only educated intelligence, with experience, will assist the battery manager to adopt the right system. the crushed stuff--generally termed the "pulp"--passes from the boxes through the "screens" or "gratings," and so on to the "tables"--i.e., sheets of copper amalgamated on the upper surface with mercury, and sometimes electroplated with silver and afterwards treated with mercury. unless the quartz is very clean, and, consequently light, i am opposed to the form of stamper box with mercury troughs cast in the "lip," nor do i think that a trough under the lip is a good arrangement, as it usually gets so choked and covered with the heavy clinging base metals as to make it almost impossible for the gold to come in contact with the mercury. it will be found better where the gold is fine, or the gangue contains much base metal, to run the pulp from the lip of the battery into a "distributor." the distributor is a wooden box the full width of the "mortar," having a perforated iron bottom set some three to four inches above the first copper plate, which should come up under the lip. the effect of this arrangement is that the pulp is dashed on the plate by the falling water, and the gold at once coming in contact with the mercury begins to accumulate and attract that which follows, till the amalgam becomes piled in little crater-shaped mounds, and thus per cent of the gold is saved on the top plate. i have tried a further adaptation of this process when treating ores containing a large percentage of iron oxide, where the bulk of the gold is impalpably fine, and contained in the "gossan." at the end of the blanket table, or at any point where the crushed stuff last passes before going to the "tailings heap," or "sludge pit," a "saver" is placed. the saver is a strong box about in. square by ft. high, one side of which is removable, but must fit tight. nine slots are cut inside at in. apart, and into these are fitted nine square perforated copper plates, having about eighty to a hundred / in. holes in each; the perforations should not come opposite each other. these plates are to be amalgamated on both sides with mercury, in which a very little sodium has been placed (if acid ores are being treated, zinc should be employed in place of sodium, and to prevent the plates becoming bare, if the stuff is very poor, thick zinc amalgam may be used with good effect; but in that case discontinue the sodium, and occasionally, if required, say once or twice in the day, mix an ounce of sulphuric acid in a quart of water and slowly pour it into the launder above the saver). underneath the "saver" you require a few riffles, or troughs, to catch any waste mercury, but if not overfed there should be no waste. this simple appliance, which is automatic and requires little attention, will sometimes arrest a considerable quantity of gold. we now come to the subsidiary processes of battery work, the "cleaning" of plates, and "scaling" same when it is desired to get all the gold off them, the cleaning and retorting of amalgam, and of the mercury, smelting gold, etc. plates should be tenderly treated, kept as smooth as possible, and when cleaning up after crushing, in your own battery, the amalgam--except, say, at half-yearly intervals--should be removed with a rubber only; the rubber is simply a square of black indiarubber or soft pine wood. when crushing rich ore, and you want to get nearly all the gold off your plates, the scraper may be resorted to. this is usually made by the mine blacksmith from an old flat file which is cut in half, the top turned over, beaten out to a sharp blade, and kept sharp by touching it up on the grinding-stone. this, if carefully used, will remove the bulk of the amalgam without injury to the plate. various methods of "scaling" plates will be found among "rules of thumb." where base metals are present in the lode stuff frequent retortings of the mercury, say not less than once a month, will be found to have a good effect in keeping it pure and active. for this purpose, and in order to prevent stoppage of the machinery, a double quantity is necessary, so that half may be used alternately. less care is required in retorting the mercury than in treating the amalgam, as the object in the one case is more to cleanse the metal of impurities than to save gold, which will for the most part have been extracted by squeezing through the chamois leather or calico. a good strong heat may therefore at once be applied to the retort and continued, the effect being to oxidise the arsenic, antimony, lead, etc., which, in the form of oxides, will not again amalgamate with the mercury, but will either lie on its surface under the water, into which the nozzle of the retort is inserted, or will float away on the surface of the water. i have also found that covering the top of the mercury with a few inches of broken charcoal when retorting has an excellent purifying effect. in retorting amalgam, much care and attention is required. first, never fill the retort too full, give plenty of room for expansion; for, when the heat is applied, the amalgam will rise like dough in an oven, and may be forced into the discharge pipe, the consequence being a loss of amalgam or the possible bursting of the retort. next, be careful in applying the heat, which should be done gradually, commencing at the top. this is essential to prevent waste and to turn out a good-looking cake of gold, which all battery managers like to do, even if they purpose smelting into bars. sometimes special difficulties crop up in the process of separating the gold from the amalgam. at the first "cleaning up" on the frasers mine at southern cross, west australia, great consternation was excited by the appearance of the retorted gold, which, as an old miner graphically put it, was "as black as the hind leg of a crow," and utterly unfit for smelting, owing to the presence of base metals. some time after this i was largely interested in the blackborne mine in the same district when a similar trouble arose. this i succeeded in surmounting, but a still more serious one was too much for me--i.e., the absence of payable gold in the stone. i give here an extract from the _australian mining standard_, of december th, , with reference to the mode of cleaning the amalgam which i adopted. new method of separating gold from impure amalgam. i had submitted to me lately a sample of amalgam from a mine in west australia which amalgam had proved a complete puzzle to the manager and amalgamator. the mint returns showed a very large proportion of impurity, even in the smelted gold. when retorted only, the mint authorities refused to take it after they had treated two cakes, one of oz., which yielded only oz. dwt. standard gold, and one of oz., which gave oz. dwt. the gold smelted on the mine was nearly as bad proportionately. thus, oz. smelted down at the mint to oz. dwt. and oz. to oz. dwt. the impurity was principally iron, a most unusual thing in my experience, and was due to two causes revealed by assay of the ore and analysis of the mine water, viz., an excess of arsenate of iron in the stone, and the presence in large proportions of mineral salts, principally chloride of calcium cacl., sodium nacl, and magnesium mgcl , in the mine water used in the battery. the exact analysis of the water was as follows:-- carbonate of iron feco . grains per gallon carbonate of calcium caco . grains per gallon sulphate of calcium caso . grains per gallon chloride of calcium cacl . grains per gallon chloride of magnesium mgcl . grains per gallon chloride of sodium or common salt nacl . grains per gallon total solid matter . = . oz. to the gallon. it will be seen, then, that this water is nearly four times more salt that that of the sea. the effect of using a water of this character, as i have previously found, is to cause the amalgamation of considerable quantities of iron with the gold as in this case. i received oz. of amalgam, and having found what constituted its impurities proceeded to experiment as to its treatment. when retorted on the mine it was turned out in a black cake so impure as almost to make it impossible to smelt properly. i found the same result on first retorting, and after a number of experiments which need not be recapitulated though some were fairly effective, i hit on the following method, which was found to be most successful and will probably be so found in other localities where similarly unfavourable conditions prevail. i took a small ball of amalgam, placed it in a double fold of new fine grained calico, and after soaking in hot water put it under a powerful press. the weight of the ball before pressing was gr. from this gr. of mercury was expressed and five-eighths of a grain of gold was retorted from this expressed mercury. the residue, in the form of a dark, grey, and very friable cake, was powdered up between the fingers and retorted, when it became a brown powder; it was afterwards calcined on a flat sheet in the open air; result, gr. of russet-coloured powder. smelted with borax, the iron oxide readily separated with the slag; result, gr. gold - fine; a second smelting brought this up to - fine. proportion of smelted gold to amalgam, one-fifth. the principal point about this mode of treatment is the squeezing out of the mercury, whereby the amalgam goes into the retort in the form of powder, thus preventing the slagging of the iron and enclosure of the gold. the second point of importance is thorough calcining before smelting. of course it would be practicable, if desired, to treat the powder with hydrochloric acid, and thus remove all the iron, but in a large way this would be too expensive, and my laboratory treatment, though necessarily on a small scale, was intended to be on a practical basis. the amalgam at this mine was in this way afterwards treated with great success. for the information of readers who do not understand the chemical symbols it may be said that feco is carbonate of iron; caco is carbonate of calcium; caso is sulphate of calcium; cacl is chloride of calcium; mgcl is chloride of magnesium; nacl is chloride of sodium, or common salt. chapter vii gold extraction--secondary processes and lixiviation before any plan is adopted for treating the ore in a new mine the management should very seriously and carefully consider the whole circumstances of the case, taking into account the quantity and quality of the lode stuff to be operated on, and ascertain by analysis what are its component parts, for, as before stated, the treatment which will yield most satisfactory results with a certain class of gangue on one mine will sometimes, even when the material is apparently similar, prove a disastrous failure in another. some time since i was glad to note that the manager of a prominent mine strongly discountenanced the purchase of any extracting plant until he was fully satisfied as to the character of the bulk of the ore he would have to treat. it would be well for the pockets of shareholders and the reputation of managers, if more of our mine superintendents followed this prudent and sensible course. having treated on gold extraction with mercury by amalgamated plates and their accessories, something must be said about secondary modes of saving in connection with the amalgamation process. the operations described hitherto have been the disintegration of the gold-bearing material and the extraction therefrom of the coarser free gold. but it must be understood that most auriferous lode stuff contains a proportion of sulphides of various metals, wherein a part of the gold, usually in a very finely divided state, is enclosed, and on this gold the mercury has no influence. also many lodes contain hard heavy ferric ores, such as titanic iron, tungstate of iron, and hematite, in which gold is held. in others, again, are found considerable quantities of soft powdery iron oxide or "gossan," and compounds such as limonite, aluminous clay, etc., which, under the action of the crushing mill become finely divided and float off in water as "slimes," carrying with them atoms of gold, often microscopically small. to save the gold in such matrixes as these is an operation which even the best of our mechanical appliances have not yet fully accomplished. where there is not too great a proportion of base metals on which the solvent will act, and when the material is rich enough in gold to pay for the extra cost of treatment, chlorination or cyanisation are the best modes of extraction yet practically adopted. presuming, however, that we are working by the amalgamation process, and have crushed our stone and obtained the free gold, the next requirement is an effective concentrator. of these there are many before the public, and some do excellent work, but do not act equally well in all circumstances. the first and most primitive is the blanket table, previously mentioned; but it can hardly be said to be very effective, and requires constant attention and frequent changing and washing of the strips of blanket. instead of blanket tables percussion tables are sometimes used, to which a jerking motion is given against the flow of the water and pulp, and by this means the heavier minerals are gathered towards the upper part of the table, and are from thence removed from time to time as they become concentrated. i have seen this appliance doing fairly good work, but it is by no means a perfect concentrator. another form of "shaking table" is one in which the motion is given sideways, and this, whether amalgamated, or provided with small riffles, or covered with blanket, keeps the pulp lively and encourages the retention of the heavier particles, whether of gold or base metals containing gold. there has also been devised a rocking table the action of which is analogous to that of the ordinary miner's cradle. this appliance, working somewhat slowly, swings on rockers from side to side, and is usually employed in mills where, owing to the complexity of the ore, difficulties have been met with in amalgamating the gold. riffles are provided and even very fine gold is sometimes effectively recovered by their aid. the frue vanner will, as a rule, act well when the pulp is sufficiently fine. it is really a adaptation of an old and simple apparatus used in china and india for washing gold dust from the sands of rivers. the original consisted of an endless band of strong cloth or closely woven matting, run on two horizontal rollers placed about seven feet apart, one being some inches lower than the other. the upper is caused to revolve by means of a handle. the cloth is thus dragged upwards against a small stream of water and sand fed to it by a second man, the first man not only turning the handle but giving a lateral motion to the band by means of a rope tied to one side. chinamen were working these forerunners of the frue vanner forty years ago in australia, and getting fair returns. the frue vanner is an endless indiarubber band drawn over an inclined table, to which a revolving and side motion is given by ingenious automatic mechanism, the pulp being automatically fed from the upper end, and the concentrates collected in a trough containing water in which the band is immersed in its passage under the table; the lighter particles wash over the lower end. the only faults with the vanner are--first, it is rather slow; and secondly, though so ingenious it is just a little complicated in construction for the average non-scientific operative. of pan concentrators there is an enormous selection, the principle in most being similar--i.e., a revolving muller, which triturates the sand, so freeing the tiny golden particles and admitting of their contact with the mercury. the mistake with respect to most of these machines is the attempt to grind and amalgamate in one operation. even when the stone under treatment contains no deleterious compounds the simple action of grinding the hard siliceous particles has a bad effect on the quicksilver, causing it to separate into small globules, which either oxidising or becoming coated with the impurities contained in the ore will not reunite, but wash away in the slimes and take with them a percentage of the gold. as a grinder and concentrator, and in some cases as an amalgamator, when used exclusively for either purpose, the watson and denny pan is effective; but although successfully used at one mine i know, the mode there adopted would, for reasons previously given, be very wasteful in many other mines. there is considerable misconception, even among men with some practical knowledge, as to the proper function of these secondary saving appliances; and sometimes good machines are condemned because they will not perform work for which they were never intended. it cannot be too clearly realized that the correct order of procedure for extracting the gold held in combination with base metals is--first, reduction of the particles to a uniform gauge and careful concentration only; next, the dissipation, usually by simple calcination, of substances in the concentrates inimical to the thorough absorption of the gold by the mercury; and lastly, the amalgamation of the gold and mercury. for general purposes, where the gangue has not been crushed too fine, i think the duncan pan will usually be found effective in saving the concentrates. in theory it is an enlargement of the alluvial miner's tin dish, and the motion imparted to it is similar to the eccentric motion of that simple separator. the calcining may be effectively carried out in an ordinary reverberatory furnace, the only skill required being to prevent over roasting and so slagging the concentrates; or not sufficiently calcining so as to remove all deleterious constituents; the subject, however, is fully treated in chapter viii. for amalgamating i prefer some form of settler to any further grinding appliance, but i note also improvements in the rotary amalgamating barrel, which, though slow, is, under favourable conditions, an effective amalgamator. the introduction of steam under pressure into an iron cylinder containing a charge of concentrates with mercury is said to have produced good results, and i am quite prepared to believe such would be the case, as we have long known that the application of steam to ores in course of amalgamation facilitates the process considerably. some seventeen years since i was engaged on the construction of a dry amalgamator in which sublimated mercury was passed from a retort through the descending gangue in a vertical cylinder, the material thence falling through an aperture into a revolving settler, the object being to save water on mines in dry country. the model, about quarter size, was completed when my attention was called to an american invention, in which the same result was stated to be attained more effectively by blowing the mercury spray through the triturated material by means of a steam jet. i had already encountered a difficulty, since found so obstructive by experimentalists in the same direction, that is, the getting of the mercury back into its liquid metallic form. this difficulty i am now convinced can be largely obviated by my own device of using a very weak solution of sulphuric acid (it can hardly be too weak) and adding a small quantity of zinc to the mercury. it is perfectly marvellous how some samples of mercury "sickened" or "floured" by bad treatment, may be brought back to the bright limpid metal by a judicious use of these inexpensive materials. thus it will probably be found practicable to crush dry and amalgamate semi-dry by passing the material in the form of a thin pasty mass to a settler, as in the old south american arrastra, and, by slowly stirring, recover the mercury, and with it the bulk of the gold. the following is from the _australian mining standard_, and was headed "amalgamation without overflow": "recent experiments at the ballarat school of mines have proved that a deliverance from difficulties is at hand from an unexpected quarter. the despised chilian mill and wheeler pan, discarded at many mines, will solve the problem, but the keynote of success is amalgamation without overflow. dispense with the overflow and the gold is saved. "two typical mines--the great mercury proprietary gold mine, of kuaotunu, n.z., the other, the pambula, n.s.w.--have lately been conducting a series of experiments with the object of saving their fine gold in an economical manner. the last and best trials made by these companies were at the ballarat school of mines, where amalgamation without overflow was put to a crucial test, in each case with the gratifying result that ninety-six per cent of the precious metal was secured. what this means to the great mercury mine, for instance, can easily be imagined when it is understood that notwithstanding all the latest gold-saving adjuncts during the last six months tons of ore, worth l. s. _ d. a ton, have been put through for a saving of l. s. _ d. only; or in other words over two-thirds of the gold has gone to waste (for the time being) in the tailings, and in the tailings at the present moment lie the dividends that should have cheered shareholders' hearts. "and now for the _modus operandi_, which, it must be remembered, is not hedged in by big royalties to any one, rights, patent or otherwise. the ore to be treated is first calcined, then put through a rock-breaker or stamper battery in a perfectly dry state. if the battery is used, ordinary precautions, of course, must be taken to prevent waste, or the dust becoming obnoxious to the workmen. the ore is then transferred to the chilian mill and made to the consistency of porridge, the quicksilver being added. when the principal work of amalgamation is done (experience soon teaching the amount of grinding necessary), from the chilian mill the paste (so to say) is passed to a wheeler or any other good pan of a similar type, when the gold-saving operation is completed." this being an experiment in the same direction as my own, i tried it on a small scale. i calcined some very troublesome ore till it was fairly "sweet," triturated it, and having reduced it with water to about the consistency of invalid's gruel, put it into a little berdan pan made from a "camp oven," which i had used for treating small quantities of concentrates, and from time to time drove a spray of mercury, wherein a small amount of zinc had been dissolved, into the pasty mass by means of a steam jet, added about half an ounce of sulphuric acid and kept the pan revolving for several hours. the result was an unusually successful amalgamation and consequent extraction--over ninety per cent. steam--or to use the scientific term, hydro-thermal action--has played such an important part in the deposition of metals that i cannot but think that under educated intelligence it will prove a powerful agent in their extraction. about fourteen years ago i obtained some rather remarkable results from simply boiling auriferous ferro-sulphides in water. there is in this alone an interesting, useful, and profitable field for investigation and experiment. the most scientific and perfect mode of gold extraction (when the conditions are favourable) is lixiviation by means of chlorine, potassium cyanide, or other aurous solvent, for by this means as much as per cent of the gold contained in suitable ores can be converted into its mineral salt, and being dissolved in water, re-deposited in metallic form for smelting; but lode stuff containing much lime would not be suitable for chlorination, or the presence of a considerable proportion of such a metal as copper, particularly in metallic form, would be fatal to success, while cyanide of potassium will also attack metals other than gold, and hence discount the effect of this solvent. the earlier practical applications of chlorine to gold extraction were known as mears' and plattner's processes, and consisted in placing the material to be operated on in vats with water, and introducing chlorine gas at the bottom, the mixture being allowed to stand for a number of hours, the minimum about twelve, the maximum forty-eight. the chlorinated water was then drawn off containing the gold in solution which was deposited as a brown powder by the addition of sulphate of iron. great improvements on this slow and imperfect method have been made of late years, among the earlier of which was that of messrs. newbery and vautin. they placed the pulp with water in a gaslight revolving cylinder, into which the chlorine was introduced, and atmospheric air to a pressure of lb. to the square inch was pumped in. the cylinder with its contents was revolved for two hours, then the charge was withdrawn and drained nearly dry by suction, the resultant liquid being slowly filtered through broken charcoal on which the chloride crystals were deposited, in appearance much like the bromo-chlorides of silver ore seen on some of the black manganic oxides of the barrier silver mines. the charcoal, with its adhering chlorides, was conveyed to the smelting-house and the gold smelted into bars of extremely pure metal. messrs. newbery and vautin claimed for their process decreased time for the operation with increased efficiency. at mount morgan, when i visited that celebrated mine, they were using what might be termed a composite adaptation process. their chlorination works, the largest in the world, were putting through tons per week. the ore as it came from the mine was fed automatically into krom roller mills, and after being crushed and sifted to regulation gauge was delivered into trucks and conveyed to the roasting furnaces, and thence to cooling floors, from which it was conveyed to the chlorinating shed. here were long rows of revolving barrels, on the newbery-vautin principle, but with this marked difference, that the pressure in the barrel was obtained from an excess of the gas itself, generated from a charge of chloride of lime and sulphuric acid. on leaving the barrels the pulp ran into settling vats, somewhat on the plattner plan, and the clear liquid having been drained off was passed through a charcoal filter, as adopted by newbery and vautin. the manager, mr. wesley hall, stated that he estimated cost per ton was not more than s., and he expected shortly to reduce that when he began making his own sulphuric acid. as he was obtaining over oz. to the ton the process was paying very well, but it will be seen that the price would be prohibitive for poor ores unless they could be concentrated before calcination. the pollok process is a newer, and stated to be a cheaper mode of lixiviation by chlorine. it is the invention of mr. j. h. pollok, of glasgow university, and a strong company was formed to work it. with him the gas is produced by the admixture of bisulphate of sodium (instead of sulphuric acid, which is a very costly chemical to transport) and chloride of lime. water is then pumped into a strong receptacle containing the material for treatment and powerful hydraulic pressure is applied. the effect is stated to be the rapid change of the metal into its salt, which is dissolved in the water and afterwards treated with sulphate of iron, and so made to resume its metallic form. it appears, however, to me that there is no essential difference in the pressure brought to bear for the quickening of the process. in each case it is an air cushion, induced in the one process by the pumping in of air to a cylinder partly filled with water, and in the other by pumping in water to a cylinder partly filled with air. the process of extracting gold from lode stuff and tailings by means of cyanide of potassium is now largely used and may be thus briefly described:--it is chiefly applied to tailings, that is, crushed ore that has already passed over the amalgamating and blanket tables. the tailings are placed in vats, and subjected to the action of solutions of cyanide of potassium of varying strengths down to . per cent. these dissolve the gold, which is leached from the tailings, passed through boxes in which it is precipitated either by means of zinc shavings, electricity, or to the precipitant. the solution is made up to its former strength and passed again through fresh tailings. when the tailings contain a quantity of decomposed pyrites, partly oxidised, the acidity caused by the freed sulphuric acid requires to be neutralised by an alkali, caustic soda being usually employed. when "cleaning up," the cyanide solution in the zinc precipitating boxes is replaced by clean water. after careful washing in the box, to cause all pure gold and zinc to fall to the bottom, the zinc shavings are taken out. the precipitates are then collected, and after calcination in a special furnace for the purpose of oxidising the zinc, are smelted in the usual manner. the following description of an electrolytic method of gold deposition from a cyanide solution was given by mr. a. l. eltonhead before the engineers' club of philadelphia. a description of the process is as follows:--"the ore is crushed to a certain fineness, depending on the character of the gangue. it is then placed in leaching vats, with false bottoms for filtration, similar to other leaching plants. a solution of cyanide of potassium and other chemicals of known percentage is run over the pulp and left to stand a certain number of hours, depending on the amount of metal to be extracted. it is then drained off and another charge of the same solution is used, but of less strength, which is also drained. the pulp is now washed with clean water, which leaches all the gold and silver out, and leaves the tailings ready for discharge, either in cars or sluiced away by water, if it is plentiful. "the chemical reaction of cyanide of potassium with gold is as follows, according to elsner:-- au + kcy + o + h o = kaucy + kho. "that is, a double cyanide of gold and potassium is formed. "all filtered solutions and washings from the leaching vats are saved and passed through a precipitating 'box' of novel construction, which may consist either of glass, iron or wood, and be made in any shape, either oval, round, or rectangular--if the latter, it will be about ft. long, ft. wide and ft. high--and is partitioned off lengthwise into five compartments. under each partition, on the inside or bottom of the 'box,' grooves may be cut a quarter-to a half-inch deep, extending parallel with the partitions to serve as a reservoir for the amalgam, and give a rolling motion to the solution as it passes along and through the four compartments. the centre compartment is used to hold the lead or other suitable anode and electrolyte. "the anode is supported on a movable frame or bracket, so it may be moved either up or down as desired, it being worked by thumb-screws at each end. "the electrolyte may consist of saturated solutions of soluble alkaline metals and earth. the sides or partitions of each compartment dip into the mercury, which must cover the 'box' evenly on the bottom to the depth of about a half-inch. "amalgamated copper strips or discs are placed in contact with the mercury and extended above it, to allow the gold and silver solution of cyanide to come in contact. "the electrodes are connected with the dynamo; the anode of lead being positive and the cathode of mercury being negative. the dynamo is started, and a current of high amperage and low voltage is generated, generally to amperes, and with sufficient pressure to decompose the electrolyte between the anode and the cathode. "as the gas is generated at the anode, a commotion is created in the liquid, which brings a fresh and saturated solution of electrolyte between the electrodes for electrolysis, and makes it continuous in its action. "the solution of double cyanide of gold, silver, and potassium, which has been drained from the leaching vats, is passed over the mercury in the precipitating 'box' when the decomposition of the electrolyte by the electric current is being accomplished, the gold and silver are set free and unite with the mercury, and are also deposited on the plates or discs of copper, forming amalgam, which is collected and made marketable by the well known and tried methods. the above solution is regenerated with cyanide of potassium by the setting free of the metals in the passage over the 'box.' "in using this solution again for a fresh charge of pulp, it is reinforced to the desired percentage, or strengthened with cyanide of potassium and other chemicals, and is always in good condition for continuing the operation of dissolving. "the potassium acting on the water of the solution creates nascent hydrogen and potassium hydrate; the nascent hydrogen sets free the metals (gold and silver), which are precipitated into the mercury and form amalgam, leaving hydrocyanic acid; this latter combines with the potassium hydrate of the former reaction, thus forming cyanide of potassium. there are other reactions for which i have not at present the chemical formulas. "as the solution passes over the mercury, the centre compartment of the 'box' is moved slowly longitudinally, which spreads the mercury, the solution is agitated and comes in perfect contact with the mercury, as well as the amalgamated plates or discs of copper, ensuring a perfect precipitation. "it is not always necessary to precipitate all the gold and silver from the solution, for it is used over and over again indefinitely; but when it is required, it can be done perfectly and cheaply in a very short time. "no solution leached from the pulp, containing cyanide of potassium, gold and silver, need be run to waste, which is in itself an enormous saving over the use of zinc shavings when handling large quantities of pulp and solution. "some of the advantages the electro-chemical process has over other cyanide processes are: its cleanliness, quickness of action, cheapness, and large saving of cyanide of potassium by regeneration; not wasting the solutions, larger recovery of the gold and silver from the solutions; the cost of recovery less; the loss of gold, silver, and cyanide of potassium reduced to a minimum; the use of caustic alkali in such quantity as may be desired to keep the cyanide solution from being destroyed by the solidity of the pulp, and also sometimes to give warmth, as a warm cyanide solution will dissolve gold and silver quicker than a cold one. these caustic alkalies do not interfere with or prevent the perfect precipitation of the metals. the bullion recovered in this process is very fine, while the zinc-precipitated bullion is only about fine. "the gold and silver is dissolved, and then precipitated in one operation, which we know cannot be done in the 'chlorination process'; besides, the cost of plant and treatment is much less in the above-described process. "the electro-chemical process, which i have hastily sketched will, i think, be the future cheap method of recovering fine or flour gold from our mines and waste tailings or ore dumps. "without going into details of cost of treatment, i will state that with a plant of a capacity of handling , tons of pulp per month, the cost should not exceed s. per ton, but that may be cheapened by labour-saving devices. there being no expensive machinery, a plant could be very cheaply erected wherever necessary." chapter viii calcination or roasting of ores the object of calcining or roasting certain ores before treatment is to dissipate the sulphur or sulphides of arsenic, antimony, lead, etc., which are inimical to treatment, whether by ordinary mercuric amalgamation or lixiviation. the effect of the roasting is first to sublimate and drive off as fumes the sulphur and a proportion of the objectionable metals. what is left is either iron oxide, "gossan," or the oxides of the other metals. even lead can thus be oxidised, but requires more care as it melts nearly as readily as antimony and is much less volatile. the oxides in the thoroughly roasted ore will not amalgamate with mercury, and are not acted on by chlorine or cyanogen. to effect the oxidation of sulphur, it is necessary not only to bring every particle of sulphur into contact with the oxygen of the air, but also to provide adequate heat to the particles sufficient to raise them to the temperature that will induce oxidation. no appreciable effect follows the mere contact of air with sulphur particles at atmospheric temperature; but if the particles be raised to a temperature of degrees fahr., the sulphur is oxidised to the gaseous sulphur dioxide. the same action effects the elimination of the arsenic and antimony associated with gold and silver ores, as when heated to a certain constant temperature these metals readily oxidise. the science of calcination consists of the method by which the sulphide ores, having been crushed to a proper degree of fineness, are raised to a sufficient temperature and brought into intimate contact with atmospheric air. it will be obvious then that the most effective method of roasting will be one that enables the particles to be thoroughly oxidised at the lowest cost in fuel and in the most rapid manner. the roasting processes in practical use may be divided into three categories: _first or a process._--roasting on a horizontal and stationary hearth, the flame passing over a mass of ore resting on such hearth. in order to expose the upper surface of the ore to contact with air the material is turned over by manual labour. this furnace of the reverberatory type is provided with side openings by which the turning over of the ore can be manually effected, and the new ore can be charged and afterwards withdrawn. _second or b process._--roasting in a revolving hearth placed at a slight incline angle from the horizontal. the furnace is of cylindrical form and is internally lined with refractory material. it has projections that cause the powdered ore to be lifted above the flame, and, at a certain height, to fall through the flame and so be rapidly raised to the temperature required to effect the oxidation of the oxidisable minerals which it is desired to extract. the rate, or speed, of revolution of this revolving furnace obviously depends upon the character of the ore under treatment; it may vary from two revolutions per minute down to one revolution in thirty minutes. any kind of fuel is available, but that of a gaseous character is stated to be by far the most efficient. any ordinary cylinder of a length of ft., and a diameter of ft. in., inclined ft. in. in its length, will calcine from to tons per diem. another form of rotating furnace is one in which the axis is horizontal. it is much shorter than the inclined type, and the feeding and removal of the ore is effected by the opening of a retort lid door provided at the side of the furnace. openings provided at each end of the furnace permit the passage of the flame through it, and the revolution of the furnace turns over the powdered ore and brings it into more or less sustained contact with the oxidising flame. the exposure of the ore to this action is continued sufficiently long to ensure the more or less complete oxidation of the ore particles. _third or c process._--in this process the powdered ore is allowed to fall in a shower from a considerable height, through the centre of a vertical shaft up which a flame ascends; the powdered ore in falling through the flame is heated to an oxidising temperature, and the sulphides are thus depleted of their sulphur and become oxides. another modification of this direct fall or shaft furnace is that in which the fall of the ore is checked by cross-bars or inclined plates placed across the shaft; this causes a longer oxidising exposure of the ore particles. when the sulphur contents of pyritous ores are sufficiently high, and after the ore has been initially fired with auxiliary carbonaceous fuel, it is unnecessary, in a properly designed roasting furnace, to add fuel to the ore to enable the heat for oxidation to be obtained. the oxidation or burning of the sulphur will provide all the heat necessary to maintain the continuity of the process. the temperature necessary for effecting the elimination of both sulphur and arsenic is not higher than that equivalent to dull red heat; and provided that there is a sufficient mass of ore maintained in the furnace, the potential heat resulting from the oxidation of the sulphur will alone be adequate to provide all that is necessary to effect the calcination. types of furnaces of the different classes that are in actual use. "a" or reverberatory class. the construction of this furnace has already been sufficiently described. if the roasting is performed in a muffle chamber, the arrangement employed by messrs. leach and neal, limited, of derby, and designed by mr. b. h. thwaite, c.e., can be advantageously employed in this furnace, which is fired with gaseous fuel. the sensible heat of the waste gases is utilised to heat the air employed for combustion; and by a controllable arrangement of combustion, a flame of over feet in length is obtained, with the result that the furnace from end to end is maintained at a uniform temperature. by this system, and with gaseous fuel firing, a very considerable economy in fuel and in repairs to furnace, and a superior roasting effect, have been obtained. where the ordinary reverberatory hearth is fired with solid coal from an end grate, the temperature is at its maximum near the firing end, and tails off at the extreme gas outlet end. the ores in this furnace should therefore be fed in at the colder end of the hearth and be gradually worked or "rabbled" forward to the firing end. one disadvantage of the reverberatory furnace is the fact that it is impossible to avoid the incursion of air during the manual rabbling action, and this tends to cool the furnace. the cost of roasting, to obtain the more or less complete oxidation, or what is known in mining parlance as a "sweet roast" (because a perfectly roasted ore is nearly odourless) varies considerably, the variation depending of course upon the character of the ore and the cost of labour and fuel. there are several modifications of the reverberatory furnace in use, designed mechanically to effect the rabbling. one of the most successful is that known as the horse-shoe furnace. in plan the hearth of the furnace resembles a horse-shoe. the stirring of the ore over the hearth is effected by means of carriages fixed in the centre of the furnace and having laterally projecting arms, carrying stirrers, that move along the hearth and turn over the pulverised ore. in operation, half the carriages are traversing the furnace, and half are resting in the cooling space, so that a control over the temperature of the stirrers is established. this furnace is stated to be more economical in labour than other mechanically stirred reverberatory furnaces, and there is also said to be an economy in fuel. usually the mechanical stirring furnaces give trouble and should be avoided, but the horse-shoe type possesses qualifications worthy of consideration. "b."--the revolving cylinder furnace. of these the best known to me are: the howell-white, the bruckner, the thwaite-denny, and the molesworth. the bruckner is a cylinder, turning on the horizontal axis and carried by four rollers. the batch of ore usually charged into the two charging hoppers weighs about four tons. when the two charging doors are brought under the hopper mouth, the contents of the hopper fall directly into the cylinder. the ends or throats of the furnace are reduced just sufficiently to allow the flame evolved from a grated furnace to pass completely through the cylinder. a characteristic size for this bruckner furnace is one having a length of feet and a diameter of feet. a furnace of this capacity will have an inclusive weight (iron and brickwork) of tons. the time of operation, with the bruckner, will vary with the character of the ore under treatment and the nature of the fuel employed. four hours is the minimum and twelve hours should be the maximum time of operation. by the addition of common salt with the batch of ore, such of its constituents as are amenable to the action of chlorine are chlorinated as well as freed from sulphur. where the ore contains any considerable quantity of silver which should be saved, the addition of the salt is necessary as the silver is very liable to become so oxidised in the process of roasting as to render its after treatment almost impossible. i know a case in point where an average of nearly five ounces of silver to the ton, at that time worth s., was lost owing to ignorance on this subject. had the ore been calcined with salt, nacl, the bulk of this silver would have been amalgamated and thus saved. it was the extraordinary fineness of the gold saved by amalgamation as against my tests of the ore by fire assay that put me on the track of a most indefensible loss. _the howell-white furnace._--this furnace consists of a cast iron revolving cylinder, averaging feet in length and ft. in. in diameter, which revolves on four friction rollers, resting on truck wheels, rotated by ordinary gearing. the power required for effecting the revolution should not exceed four indicated horse-power. the cylinder is internally lined with firebrick, projecting pieces causing the powdered ore to be raised over the flame through which it showers, and is thereby subjected to the influence of heat and to direct contact oxidation. the inclination of the cylinder, which is variable, promotes the gradual descension of the ore from the higher to the lower end. it is fed into the upper end, by a special form of feed hopper, and is discharged into a pit at the lower end, from which the ore can be withdrawn at any time. the gross weight of the furnace, which is, however, made in segments to be afterwards bolted together, is some ninety to one hundred tons. the furnace is fired with coal on a grated hearth, built at the lower end; it is more economical both in fuel and in labour than an ordinary reverberatory furnace. _the thwaite-denny revolving furnace._--this new type of furnace, which is fired with gaseous fuel, is stated to combine the advantages of the stetefeldt, the howell-white, and the bruckner. it is constructed as follows:--three short cylinders, conical in shape and of graduated dimensions, are superimposed one over the other, their ends terminating in two vertical shafts of brickwork, by which the three cylinders are connected. the powdered ore is fed into the uppermost cylinder and gravitates through the series. the highest cylinder is the largest in diameter, the lowest the smallest. the gas flame, burnt in a bunsen arrangement, enters the smallest end of the lowest cylinder and passes through it; then returns through the series and the ore is reduced by the expulsion of its sulphur, arsenic, etc., as it descends from the top to the bottom. the top cylinder is made larger than the one below it and the middle cylinder is made larger than the lowest one in proportion to the increased bulk of gases and ore. the powdered ore in descending through the cylinders is lifted up and showers through the flame, falling in its descent a distance of over feet. by the time it reaches the bottom the ore is thoroughly roasted. provision is made for the introduction of separate supplies of air and gas into each cylinder; this enables the oxidising treatment to be controlled exactly as desired so as to effect the best results with all kinds of ore. each cylinder is driven from its own independent gearing, and the speed of each cylinder can be varied at will. the output of this type of furnace, the operations of which appear to be more controllable than those of similar appliances, depends, of course, upon the nature of the ore, but may be considered to range within the limits of twelve to fifty tons in twenty-four hours, and the cost of roasting will vary from s. d. to s. per ton, depending upon the quality of ore and of fuel. the gaseous fuel generating system permits not only the absolute control over the temperature in the furnace, but the use of the commonest kinds of coal, and even charcoal is available. the power required to drive the thwaite-denny furnace is four indicated horse-power. _the molesworth furnace_ also is a revolving cylindrical appliance, which, to say the least of it, is in many respects novel and ingenious. it consists of a slightly cone-shaped, cast-iron cylinder about fourteen feet long, the outlet end being the larger to allow for the expansion of the gases. internal studs are so arranged as to keep the ore agitated; and spiral flanges convey it to the outlet end continually, shooting it across the cylinder. the cylinder is encased in a brick furnace. the firing is provided from _outside_, the inventor maintaining that the products of combustion are inimical to rapid oxidisation, to specially promote which he introduces an excess of oxygen produced in a small retort set in the roof of the furnace and fed from time to time with small quantities of nitrate of soda and sulphuric acid. ores containing much sulphur virtually calcine themselves. i have seen this appliance doing good work. the difficulties appeared to be principally mechanical. there are other furnaces which work with outside heat, but i have not seen them in action. "c."--shaft type of furnace in one form of this furnace, instead of allowing the ore to descend in a direct clear fall the descent is impeded by inclined planes placed at different levels in the height of the shaft, the ore descending from one plane to the other. _the stetefeldt shaft furnace._--although very expensive in first cost, has many advantages. no motive power is required and the structure of the furnace is of a durable character. its disadvantages are:--want of control, and the occasionally imperfect character of the roasting originating therefrom. three sizes of stetefeldt's furnaces are constructed: the largest will roast from to tons per diem. the intermediate will roast from to tons per diem. the smallest will roast from to tons per diem. a good furnace should bring down the sulphur contents even of concentrates so as to be innocuous to mercuric amalgamation. the sulphur left in the ore should never be allowed to exceed two per cent. a forty per cent pyritous or other sulphide ore should be roasted in a revolving furnace in thirty to forty minutes, and without any auxiliary fuel. for ordinary purposes a -foot chimney is adequate for furnace work; such a chimney four feet square inside at the base, tapering to ' " at the summit, will require , red bricks, and fire-bricks for an internal lining to a height of feet from the base of the chimney shaft. when second-hand lancashire or cornish boiler flues are available, they make admirable and inexpensive chimneys. the advantage of wrought-iron or steel chimneys lies in the convenience of removal and erection. they should be made in sections of feet long, three steel wire guy-ropes attached to a ring, riveted to a ring two-thirds of the height of the chimney, and attached to holdfasts driven into the ground; tightening couplings should be provided for each wire. flue dust depositing chambers should be built in the line of the flues between the furnace and the chimney; they consist simply of carefully built brick chambers, with openings to enable workmen to enter and rapidly clear away the deposited matters. the chambers, three or four times the cross sectional area of the chimney flue, and ten to twenty feet long, can be built of brickwork, set in cement; the walls are provided with a cavity, filled with sand or portland cement, so that there will be no danger of the incursion of air. in all furnace work the greatest possible precautions should be taken to prevent the least cracking of either joints or bricks. it is surprising how much the inadequate draft of a good chimney is due to cracks or orifices in the flues; and therefore a competent furnace-man should see to it that his flues are thoroughly sound, and free from openings through which the air can enter.[*] [*] for full details of the most recent improvements in the cyanide process and in other methods of extraction, the reader is referred to dr. t. k. rose's "metallurgy of gold," third edition. chapter ix motor power and its transmission it is unnecessary to describe methods by which power for mining purposes has been obtained--that is, up to within the last five years--beyond a general statement, that when water power has been available in the immediate locality of the mine, this cheap natural source of power has been called upon to do duty. steam has been the alternative agent of power production applied in many different ways, but labouring under as many disadvantages, chief of which are lack of water, scarcity of fuel and cost of transit of machinery. sometimes condensing steam-engines have been employed. for the generation of steam the semi-portable and semi-tubular have been the type of boiler that has most usually been brought into service. needless to say, when highly mineralised mine water only is available the adoption of this class of boiler is attended with anything but satisfactory results. recently, however, there is strong evidence that where steam is the power agent to be employed the water-tube type of boiler is likely to be employed, and to the exclusion of all other forms of apparatus for the generation of steam. the advantages of this type, particularly the tubulous form (or a small water tube), made as it is in sections, offers unrivalled facilities for transport service. the heaviest parts need not exceed cwt. in weight, and require neither heavy nor yet expensive brickwork foundations. waterless power. the difficulties in finding water to drive a steam plant are often of such a serious character as to involve the abandonment of many payable mines; therefore, a motive power that does not require the aqueous agent will be a welcome boon. it will be a source of gratification to many a gold-claim holder to know that practical science has enabled motive power to be produced without the necessity of water, except a certain very small quantity, which once supplied will not require to be renewed, unless to compensate for the loss due to atmospheric evaporation. any carbonaceous fuel, such as, say, lignite, coal, or charcoal, can be employed. the latter can be easily produced by the method described in the chapter on "rules of thumb," or by building a kiln by piling together a number of trunks of trees, or fairly large-sized branches, cut so that they can be built up in a compact form. the pile, after being covered with earth, is then lighted from the base, and if there are no inlets for the air except the limited proportion required for the smouldering fire at the base, the whole of the timber will be gradually carbonised to charcoal of good quality, which is available for the waterless power plant. the waterless power plant consists of two divisions: first, a gas generating plant; secondly, an internal combustion or gas engine in which the gas is burnt, producing by thermo-dynamic action the motive power required. the system known as the thwaite power gas system is not only practically independent of the use of water, but its efficiency in converting fuel heat into work is so high that no existing steam plant will be able to compete with it. the weight of raw timber, afterwards to be converted into charcoal, that will be required to produce an effective horse-power for one hour equals lb. if coal is the fuel / lb. per e.h.p. for one hour's run. if lignite is the fuel / lb. per e.h.p. for one hour's run. the plant is simple to work, and as no steam boiler is required the danger of explosions is removed. no expensive chimney is necessary for the waterless power plant. where petroleum oil can be cheaply obtained, say for twopence per gallon, one of the otto cycle oil engines, for powers up to indicated horse-power, can be advantageously employed. these engines have the advantage of being a self-contained power, requiring neither chimney nor steam boiler, and may be said to be a waterless power. the objection is the necessity to rely upon oil as fuel, and the dangers attending the storage of oil. a good oil engine should not require to use more than a pint of refined petroleum per indicated horse-power working for one hour. fortunately for the mining industry electricity, that magic and mysterious agency, has come to its assistance, in permitting motive power to be transmitted over distances of even as much as miles with comparatively little loss of the original power energy. given, that on a coal or lignite field, or at a waterfall, horse-power is developed by the combustion of fuel or by the fall of water driving a turbine, this power can be electrically transmitted to a mine or group of mines, say miles away, with only a loss of some horse-power. for twenty miles the loss on transmission should not exceed horse-power so that and horse-power respectively are available at the mines. no other system offers such remarkable efficiencies of power transmission. the new multiphase alternating electric generating and power transmission system is indeed so perfect as to leave practically no margin for improvement. the multiphase electric motor can be directly applied to the stamp battery and ore-breaker driving-shaft and to the shaft of the amalgamating pans. approximate power required to drive the machinery of a mine. rock breaker effective horse-power amalgamating pan effective horse-power grinding pan effective horse-power single stamp of lb. dropping times per minute . effective horse-power settlers effective horse-power ordinary hoisting lift effective horse-power allow per cent in addition for overcoming friction. besides this electrical distribution power, which should not cost more than three farthings per effective horse-power per hour, the electrical energy can be employed for lighting the drives and the shafts of the mine. the modern electrical mine lamps leave little to be desired. also it is anticipated that once the few existing difficulties have been surmounted electric drilling will supplant all other methods. electric power can be employed for pumping, for shot firing, for hauling, and for innumerable purposes in a mine. electricity lends itself most advantageously to so many and varied processes, even in accelerating the influence of cyanide solutions on gold, and in effecting the magnetic influence on metallic particles in separating processes; while applied to haulage purposes, either on aerial lines or on tram or railroads, it is an immediate and striking success. it is anticipated that in the near future the mines on the randt, south africa, will be electrically driven from a coalfield generating station located on the coalfields some thirty miles from johannesburg. such a plant made up of small multiples of highly efficient machines will enable mine-owners to obtain a reliable power to any extent at immediate command and at a reasonable charge in proportion to the power used. this wholesale supply of power will be a godsend to a new field, enabling the opening up to be greatly expedited; and no climatic difficulties, such as dry seasons, or floods, need interfere with the regular running of the machinery. the same system of power-generation at a central station is to be applied to supply power to the mines of western australia. chapter x company formation and operations all the world over, the operation of winning from the soil and rendering marketable the many valuable ores and mine products which abound is daily becoming more and more a scientific business which cannot be too carefully entered into or too skilfully conducted. the days of the dolly and windlass, of the puddler, cradle, and tin dish, are rapidly receding; and mining, either in lode or alluvial working, is being more generally recognised as one of the exact sciences. in the past, mining has been carried on in a very haphazard fashion, to which much of its non-success may be attributed. but the dawn of better days has arrived, and with the advent of schools of mines and technical colleges there will in future be less excuse for ignorance in this most important industry. this chapter will be devoted to company formation and working, in which mistakes leading to very serious consequences daily occur. it is not necessary to go deeply into the question why, in the mining industry more than any other, it should be deemed desirable as a general rule to carry on operations by means of public companies, but, as a matter of fact, few names can be mentioned of men who mine extensively single handed. yet, risky as it is, mining can hardly be said to be more subject to unpreventable vicissitudes than, say, pastoral pursuits, in which private individuals risk, and often lose or make, enormous sums of money. however, it is with mining companies we are now dealing, and with the errors made in the formation and after conduct of these associations. the initial mistake most often made is that sufficient working capital is not called up or provided in the floating of the company. promoters trust to get sufficient from the ground forthwith to ensure further development; the consequence being that, as nearly per cent of mining properties require a very considerable expenditure of capital before permanent profits can be relied on, the inexperienced shareholders who started with inflated hopes of enormous returns and immediate dividends become disheartened and forfeit their shares by refusing to pay calls, and thus many good properties are sacrificed. in england, the companies are often floated fully paid-up, but the same initial error of providing too little money for the equipment and effective working of the mine is usually fallen into. again, far too many companies are floated on the report of some self-styled mining expert, often a man, who, like the schoolmaster of the last century, has qualified for the position by failing in every other business he has attempted. these men acquire a few geological and mining phrases, and by more or less skilfully interlarding these with statements of large lodes and big returns they supply reports seductive enough to float the most worthless properties and cause the waste of thousands of pounds. but the trouble does not end here. when the company is to be formed, some lawyer, competent or otherwise, is instructed to prepare articles of association, rules, etc.; which, three times out of four, is accomplished by a liberal employment of scissors and paste. such rules may, or may not, be suited to the requirements of the organisation. generally no one troubles much about the matter, though on these rules depends the future efficient working of the company, and sometimes its very existence. then directors have to be appointed, and these are seldom selected because of any special knowledge of mining they may possess, but as a rule simply because they are large shareholders or prominent men whose names look well in a prospectus. these gentlemen forthwith engage a secretary, usually on the grounds that he is the person who has tendered lowest, to provide office accommodation and keep the accounts; and not from any particular knowledge he has of the true requirements of the position. the way in which some directors contrive to spend their shareholders' money is humorously commented on by a westralian paper which describes a great machinery consignment lately landed in the neighbourhood of the boulder kalgoorlie. "it would seem as if the purchaser had been let loose blindfold in a prehistoric material-founder's old iron yard, and having bought up the whole stock, had shipped it off. the feature of the entire antediluvian show is the liberal allowance of material devoted to destruction. massive kibbles, such as were used in coal mines half a century ago, are arranged alongside a winding engine, built in the middle of the century, and evidently designed for hauling the kibbles from a depth of feet. nothing less than horse-power will stir the trucks for underground use, and their design is distinctly of the antique type. the engine is built to correspond--of a kind that might have served to raise into position the pillars of baalbec, and the mass of metal in it fairly raises a blush to the iron cheek of frailer modern constructions. the one grand use to which this monster could be put would be to employ it as a kedge for the australian continent in the event of it dragging its present anchors and drifting down south, but as modern mining machinery the whole consignment is worth no more than its value as scrap-iron, which in its present position is a fraction or two less than nothing." next, a man to manage the mine has to be obtained, and some one is placed in charge, of whose capabilities the directors have no direct knowledge. being profoundly ignorant of practical mining they are incompetent to examine him as to his qualifications, or to check his mode of working, so as to ascertain whether he is acting rightly or not. all they have to rely on are some certificates often too carelessly given and too easily obtained. finally, quite a large proportion of the allottees of shares have merely applied for them with the intention of selling out on the first opportunity at a premium, hence they have no special interest in the actual working of the mine. now let us look at the prospects of the association thus formed. the legal manager or secretary, often a young and inexperienced man, knows little more than how to keep an ordinary set of books, and not always that. he is quite ignorant of the actual requirements of the mine, or what is a fair price to pay for labour, appliances, or material. he cannot check the expenditure of the mining manager, who may be a rogue or a fool or both, for we have had samples of all sorts to our sorrow. the directors are in like case. even where the information is honestly supplied, they cannot judge whether the work is being properly carried out or is costing a fair price, and the mining manager is left to his own devices, with no one to check him nor any with whom he can consult in specially difficult cases. thus matters drift to the almost certain conclusion of voluntary or compulsory winding up; and so many a good property is ruined, and promising mines, which have never had a reasonable trial, are condemned as worthless. but let us ask, would any other business, even such as are less subject to unforeseen vicissitudes than mining, succeed under similar circumstances? it is now very generally agreed that to the profitable development of mining new countries, at all events, must look mainly for prosperity, while other industries are growing. therefore, we cannot too seriously consider how we may soonest make our mines successful. what is the remedy for the unsatisfactory state of affairs we have experienced? the answer is a more practical system of working from the inception. although it may evoke some difference of opinion i consider it both justifiable and desirable that the state should take some oversight of mining matters, at all events in the case of public companies. it would be a salutary rule that the promoters of any mining undertaking should, before they are allowed to place it on the market, obtain and pay for the services of a competent government mining inspector, who need not necessarily be a government officer, but might, like licensed surveyors, be granted a certificate of competency either by a school of mines or by some qualified board of examiners. the certificate of such inspector that the property was as represented, should be given before the prospectus was issued. it is arguable whether even further oversight might not be properly be taken by the state and the report of a qualified officer be compulsory that the property was reasonably worth the value placed upon it in the prospectus. probably it will be contended that such restrictions would be an undue interference with private rights, and the old aphorism about a fool and his folly will be quoted. there are doubtless fools so infatuated that if they were brayed in a ten hundred-weight stamp-battery the "foolishness that had not departed from them" would give a highly payable percentage to the ton. yet the state in other matters tries by numerous laws to protect such from their folly. a man may not sell a load of wood without the certificate from a licensed weighbridge or a loaf of bread without, if required, having to prove its weight; and we send those to gaol who practise on the credulity and cupidity of fools by means of the "confidence trick." why not, therefore, where interests which may be said to be national are involved, endeavour to ensure fair dealing? then with regard to the men who are to manage the mines, seeing that a man may not become captain or mate of a river steamboat without some certificate on competency, nor drive her engines before he has passed an examination to prove his fitness, surely it is not too much to say that the mine manager or engineer, to whose care are often confided the lives of hundreds of men, and the expenditure of thousands of pounds, should be required to obtain a recognised diploma to prove his qualifications. the examinations might be made comparatively easy at first, but afterwards, when by the establishment of schools and mines the facilities have been afforded for men to thoroughly qualify, the standard should be raised; and after a date to be fixed no man should be permitted to assume the charge of a mine or become one of its officers without a proper certificate of competency from some recognised school of mines or technical college. the effect of such a regulation would in a few years produce most beneficial results. in new zealand, whose "progressive" legislature i do not generally commend, they have, in the matter of mine management, at all events, taken a step in the right direction. there a mine manager, before he obtains his certificate, must have served at least two years underground, and has to pass through a severe examination, lasting for days, in all subjects relating to mining and machinery connected with mining. in addition, he must prove his capacity by making an underground survey, and then plotting his work. the examination is a stiff one, as may be judged from the fact that between and , only candidates passed. then the conditions were made easier, and from that date to , passed. of the students who gained first-class honours, have left for south africa or australia, in both of which countries new zealand certificated men are held in high estimation. but returning to the formation of the company, care should be taken in appointing directors that at least one member of the board is selected on account of his special technical knowledge of mining, and others for their special business capacity. the ornamental men with high sounding names should not be required in legitimate ventures. also, it is most important that the business manager or secretary should be a specially qualified man, who by experience has learned what are the requirements of a mine doing a certain amount of work, so that a proper check may be kept on the expenses. the more companies such a secretary has the better, as one qualified man can supervise a large staff of clerks, who would themselves be qualifying for similar work, and gaining a useful and varied experience of mining business. an office of this description having charge of a large number of mines is, in its way, a technical school, and lads trained therein would be in demand as mine pursers, a very responsible and necessary officer in a big mine. with respect to the men to whom the actual mining and treatment of ores and machinery is committed the greatest mistakes of the past have been that too much has been required from one man, a combination not to be found probably in one man in a thousand. such admirable crichtons are rare in any profession or business, and that of mining is no exception. men who profess too much are to be distrusted. your best men are they who concentrate their energies and intellects in special directions. the mining manager should, if possible, be chosen from men holding certificates of competency from some technical mining school and, of course, should, in addition, have some practical experience, not necessarily as head manager. he should understand practical mine surveying and calculation of quantities, be able to dial and plot out his workings, and prepare an intelligible plan thereof for the use of the directors, and should understand sufficient of physics, particularly pneumatics and hydraulics, to ensure thoroughly efficient pumping operations without loss of power from unnecessarily heavy appliances. any other scientific knowledge applicable to his business which he may have acquired will tell in his favour, but he must, above all things, be a thoroughly practical man. such men will in time be more readily procurable, as boys who have passed through the various schools of mines will be sent to learn their business practically at the mines just as we now, having given a lad a course of naval instruction, send him to sea to learn the practical part of his life's work. but, of course, more is wanted on a mine than a man who can direct the sinking of shafts, driving of levels, and stoping of the lode. much loss and disappointment have resulted in the past from unsuitable, ineffective, or badly designed and erected machinery, whether for working the mine or treating the ores. to obviate this defect a first-class mining engineer is required. then, also, day by day we are more surely learning that mining in all its branches is a science, and that the treatment of ores and extraction of the metals is daily becoming more and more the work of the laboratory rather than of the rule-of-thumb procedure of the past. every mine, whether it be of gold, silver, tin, copper, or other metal, requires the supervision of a thoroughly qualified metallurgist and chemist, and one who is conversant with the newest processes for the extraction of the metals from their ores and matrices. it has then been stated that to ensure effective working each mine requires, in addition to competent directors, a business manager, mining-manager, and assistants, engineer, chemist, and metallurgist, with assistant assayers, etc., all highly qualified men. but it will be asked, how are many struggling mines in sparsely populated countries to obtain the services of all these eminent scientists? the reply is by co-operation. one of the most ruinous mistakes of the past has been that each little mining venture has started on an independent course, with different management, separate machinery, etc. can it then be wondered at that our gold-mining is not always successful? under a co-operative system all that each individual mine would require would be a qualified, practical miner capable of opening and securing the ground in a miner-like manner, and a good working engineer; and in gold-mining, where the gold is free in its matrix, a professional amalgamator, or lixiviator. for the rest, half a dozen or more mines may collectively retain the services of a mine manager of high attainments as general inspector and superintendent, and the same system could be adopted with respect to an advising metallurgist and an engineer. for gold, as indeed for other metals, a central extracting works, where the ores could be scientifically treated in quantity, might be erected at joint cost, or might easily be arranged for as a separate business. a very fruitful cause of failure is the fatuous tendency of directors and mine managers to adopt new processes and inventions simply because they are new. as an inventor in a small way myself, and one who is always on the watch for improved methods, i do not wish to discourage intelligent progress; but the greatest care should be exercised by those having the control of the money of shareholders in mining properties before adopting any new machinery or process. we have seen, and unfortunately shall see, many a promising mining company brought to grief by this popular error. the directors of mining companies might, to use an american saying, "paste this in their hats" as a useful and safe aphorism. "let others do the experimenting; we are willing to pay only for proved improvements." i can cordially endorse every word of the following extracts from messrs. mcdermott and duffield's admirable little work, "losses in gold amalgamation." "some directors of mining companies are naturally inclined to listen to the specious promises of inventors of novel processes and new machinery, forgetting their own personal disadvantage in any argument on such matters, and assuming a confidence in the logic of their own conclusions, while they ignore the fruitful experience of thousands of practical men who are engaged in the mining business. the repeated failures of directors in sending out new machinery to their mines ought by this time to be a sufficient warning against increasing risks that are at once natural and unavoidable, and to deter them from plunging their shareholders into experiments which, in ninety-nine cases out of a hundred, result in nothing but excessive and needless expenses. "it is certain that new machines and new processes are, and will be, given attention by mining men in proportion to their probable merits; but the proper place for experiments is in a mill already as successful as under known processes it can be made. in a new enterprise, even when the expense of an experiment is undertaken by the inventor, the loss to the mine-owner in case of failure must be very great, both in time and general running expenses. directors should not believe that a willingness to risk cash in proving an invention is necessarily any proof of value of the same; it is only a measure of the faith of the inventor, which is hardly a safe standard to risk shareholders' money by. "the variety of modifications in approved processes ought at least to suggest the desirability of exhausting the known, before drawing on the unknown and purely speculative. it should also be borne in mind that what might appear at first sight to be new processes, and even new machinery, are, in fact, often nothing but old contrivances and plausible theories long ago exploded among practical men. "many mining companies have been ruined, without any reference to their mines, through men deciding on the reasonableness of new process and machinery who have no knowledge of the business in hand. it is assumed often, that if an inventor or manufacturer of new machinery will agree to guarantee success, or take no pay if not successful, the company takes no risk. in actual fact a whole year is wasted in most cases, failure spoils the reputation of the company, running expenses have continued, and further working capital cannot be raised, because all concerned have lost confidence by the failure to obtain returns promised. all this in addition to the regular, unavoidable risks of mining itself, which may, at any moment during the year lost, call for increased expenses and increased faith in ultimate success. to the mining man who makes money by the business, the natural risks of mining is all he will take; it is sufficient; and when he invests more money in machinery he takes good care that he takes no chances of either failure or delay. "the following are rules which no mining company or individual mine-owner can afford to neglect. "( ) the risk should be confined to mining. no body of directors is justified in taking a shareholder's money and investing it in new processes or machinery when the subscription was simply for a mining venture. directors are invariably incapable of deciding whether a so-called improvement in machinery or process is really so or not, and the reasonable course is to follow established precedents. "( ) the risk of selecting an incompetent manager should be reduced to minimum by taking a man with a successful record in the particular work to be done. the manager selected should be prohibited, as much as the directors, from experimenting with new methods or machinery. a really experienced man will require no check in this direction, as he will not risk ruining his reputation. "( ) the only time for a company to experiment is when the mine is paying well by the usual methods, and the treasury is in a condition to speculate a little in possible improvements without jeopardising regular returns." probably this is the best place to insert another word of warning to directors who are not mining specialists, and also to investors in gold mining shares. assays of auriferous lode material are almost invariably worthless as a guide in the real value of the stone in quantity. the one way to decide this is by battery treatment in bulk, and then only after many tons have been put through. the reason is obvious. first, the prospector or company promoter, if he knows it, is not in the least likely to pick the worst piece of stone in the heap for assay; and, secondly, even should the sample be selected with the sole object of getting a fair result, no living man can judge the value of a gold lode by the result of treatment of an ounce of stone. so when you see it stated that messrs. oro and gildenstein, the celebrated assayers, have found that a sample of rock from the golden mint mine, golconda, assays at the rate of , oz. dwt. and gr. to the ton, and that there are thousands of tons of similar stone in sight, the statement should be received with due caution. the assay is doubtless correct, but the deductions therefrom are most misleading. a few words of advice also to directors of mine-purchasing companies and syndicates, of which there are now so many in existence, may probably be found of value. it is not good policy as a general rule to buy entirely undeveloped properties, unless such have been inspected by your own man, who is both competent and trustworthy, and who should have indeed an interest in the profits. large areas, although so popular in england, do not compensate for large bodies of payable ore; the most remunerative mine is generally one of comparatively small area, but containing a large lode formation of payable but often low grade, ore. it is worse still, of course, to buy a practically worked out mine, though this too is sometimes done. it must be remembered that mining, though often so profitable, is nevertheless a destructive industry, thus differing from agriculture, which is productive, and manufactures, which are constructive. every ton of stone broken and treated from even the best gold mine in the world makes that mine the poorer by one ton of valuable material; thus, to buy a mining property on its past reputation for productiveness is, as a rule, questionable policy, unless you know there is sufficient good ore in sight to cover the purchase cost and leave a profit. one of the greatest causes of non-success of gold-mining ventures, particularly when worked by public companies, is the lack of actual personal supervision, and hence, among other troubles, is that ultra-objectionable one--gold stealing from the mills, or, in alluvial mining, from the tail races. as to the former, the following appeared in in the london _mining journal_, and is, i think, worthy of the close consideration of mine directors in all parts of the world:-- "no one that has not experienced the evil of gold thieving from reduction mills can have any idea of the pernicious element it is, and the difficulty, once that it has got 'well hold,' of rooting it out. it permeates every class of society in the district connected with the industry, and managers, amalgamators, assayers, accountants, aye, even bank officials, are 'all on the job' to 'get a bit' while there is an opportunity. to exterminate the hateful monster requires on the part of the mine proprietors combined, stern and drastic measures undertaken under the personal supervision of one or more of their directors, and in many instances necessitating the removal of the whole of the official staff." the writer narrates how about twenty years ago he was led to suspect that in an australian mine running forty head of stamps, in which he held a controlling interest, the owners were being defrauded of about a fourth of the gold really contained in the ore, and the successful steps taken to check the robbery. "we first of all dispensed with the services of the general manager, and then issued the following instructions to the mine and mill managers, i remaining at the mine to see them carried out until i substituted a practical local man as agent, who afterwards carried on the work most efficiently:-- "(a) both of these officials to keep separate books and accounts; in other words, to be distinct departments. "(b) the ore formerly was all thrown together and put through the mill. i subdivided it into four classes, a, b, c, and d, representing deep levels north and upper levels north, deep levels south and upper levels south, and allotted to each class ten heads of stamps at the mill. "(c) the mine manager to try three prospects, forenoon and afternoon of each day, from the dumps of each of the four classes and record in a book to be kept for that purpose the estimated mill yield of each one. "(d) the mill manager was required to do the same at the mill and keep his record. "(e) there were four underground bosses in each shift, twelve in all. i had a book fixed at the top of the shaft in which i required each of these men, at the expiry of every shift, to record any change in the faces of the quartz and particularly in regard to quality. "(f) having divided the ore into four classes i instructed the amalgamators, of which there were two in each shift, six in all, that i required the amalgam from each to be kept separate, with the object of ascertaining what each part of the mine produced. "(g) i procured padlocks for the covering boards of the mercury tables and gave the keys to the amalgamators with instructions that they were not to hand them over to any one except the exchange shift without my written authority, and instructed them that they should clean down the plates every three hours, and after cleaning down the amalgam, buckets to be placed in the cleaning room, which i instructed to be kept locked and the key in charge of the watchman night and day. "(h) the whole of the amalgam taken from the plates during each twenty-four hours to be cleaned and squeezed by the two amalgamators on duty every forenoon at nine o'clock in the presence of the mill manager, who should weigh each lot and enter it in a book to be kept for the purpose, and the entry to be signed by the mill manager and both amalgamators as witnesses. "(i) every alternate friday the mortars (boxes) to be cleaned out; the work to be commenced punctually at eight a.m. by the six amalgamators in the presence of the mill manager, assisted by the three amalgam cleaning room watchmen and the four battery feeders on duty, prohibiting any of them from leaving until the cleaning up was finished, and the amalgam cleaned, squeezed and weighed, and the amount entered by the mill manager in the record look and attested by the amalgamators. "i think the intelligent readers (particularly those with a knowledge of the business) will see the drift of the above regulations, viz., for there to be any peculation the whole of the battery staff--fourteen in all--would have to participate in it, and the number was too many to keep a secret. formerly the amalgam cleaning room was sacred to the mill manager, and on announcing to that official the new instructions he at once tendered his resignation in a tone of offended dignity, immediately followed by that of the mine manager. it is a significant fact that shortly afterwards these two officials purchased a large mill and other property at a cost of ten thousand pounds, and that the mine yielded for the following three years during which i was connected with it an average of over dwt. to the ton, as against formerly to dwt. "the reader must draw his own conclusions. i used to make it a practice to visit the mine daily and prospect the ore, and having the mine and mill managers' daily prospecting as a guide as well as my own, every man at the mill knew it was impossible for them to thieve without my detecting it; moreover, i made it a rule to discharge any of the mill employees that i discovered were interested in any small private claims. "the crux of the whole thing is having a practical miner at the head of affairs, and it is impossible for him to thieve if the work is carried out in the manner i have described." to bring the whole matter to a conclusion. it may be taken as a safe axiom that to make gold mining in the mine as distinct from mining on the stock exchange really profitable the same system of economy, of practical supervision, and scientific knowledge which is now adopted in all other businesses must be applied to the raising and extraction of the metal. then, and not till then, will genuine mining take the place to which it is entitled amongst our industries. chapter xi rules of thumb this chapter has been headed as above because a number of the rules and recipes given are simply practical expedients, not too closely scientific. my endeavour has been to supply practical and useful information in language as free from technicalities as possible, so as to adapt it to the ordinary miner, mill operator and prospector, many of whom have had no scientific training. some of the expedients are original devices educed by what we are told is the mother of inventions; others are hints given by practical old prospectors who had met with difficulties which would be the despair of a man brought up within reach of forge, foundry, machine shop, or tradesmen generally. there are many highly ingenious and useful contrivances besides these i have given. living places the health of the prospector, especially in a new country, depends largely on his housing--in which particular many men are foolishly careless, for although they are aware that they will be camped out for long periods, yet all the shelter they rely on is a miserable calico tent, often without a "fly," while in some cases they sometimes even sleep on the wet, or dusty, ground. such persons fully deserve the ill health which sooner or later overtakes them. a little forethought and very moderate ingenuity would render their camp comparatively healthy and comfortable. in summer the tent is the hottest, and in winter the coldest of domiciles. the "pizie" or "adobie" hut, or, where practicable, the "dugout," are much to be preferred, especially the latter. "pizie" or "adobie" is simply surface soil kneaded with water and either moulded between boards like concrete, to construct the walls, or made into large sun-dried bricks. salt water should not be used, as it causes the wall to be affected by every change of weather. a properly constructed house of this material, where the walls are protected by overhanging eaves, are practically everlasting, and the former have been standing for centuries. there are buildings of pizie or adobie in mexico, california and australia which are as good as new, although the latter were built nearly a century ago. adobie dwellings are warm in winter and cool in summer, and can be kept clean and healthy by occasional coatings of lime whitewash. the dugout is even more simple in construction. a cutting, say ten feet wide, is put into the base of a hill for say twelve feet until the back wall is, say, ten feet high, the sides starting from nothing to that height. the front and such portion as is required of the side walls are next constructed of pizie or rough stone, with mud mortar, and the roof either gabled or skillion of bough, grass, or reed thatch, and covered with pizie, over which is sometimes put another thin layer of thatch to prevent the pizie being washed away by heavy rain. nothing can be more snug and comfortable than such a house, unless the cows, as mark twain narrates, make things "monotonous" by persistently tumbling down the chimney. when the burra copper mines were in full work in australia, the banks of the burra creek were honeycombed like a rabbit warren with the "dugout homes" of the cornish miners. the ruins of these old dugouts now extend for miles, and look something like an uncovered pompeii. when water is scarce and the tent has to be retained, much can be done to make the camp snug. i occupied a very comfortable camp once, of which my then partner, a dane, was the architect. we called it "the bungalow," and it was constructed as follows: first we set up our tent, ft. by ft., formed of calico, but lined with green baize, and covered with a well set fly. next we put in four substantial forked posts about ft. high and ft. apart, with securely fixed cross pieces, and on the top was laid a rough flat roof of brush thatch; the sides were then treated in the same way, but not so thickly, being merely intended as a breakwind. the tent with its two comfortable bunks was placed a little to one side, the remaining space being used as a dining and sitting room all through the summer. except in occasional seasons of heavy rain, when we were saved the trouble of washing our dishes, the tent was only used for sleeping purposes, and as a storehouse for clothes and perishable provisions. i have "dwelt in marble halls" since then, but never was food sweeter or sleep sounder than in the old bush bungalow. a bush bed to make a comfortable bush bedplace, take four forked posts about ft. in. long and to in. in diameter at the top; mark out your bedplace accurately and put a post at each corner, about ft. in the ground. take two poles about ft. long, and having procured two strong five-bushel corn sacks, cut holes in the bottom corners, put the poles through, bringing the mouths of the sacks together, and secure them there with a strong stitch or two. put your poles on the upright forked sticks, and you have a couch that even sancho panza would have envied. it is as well to fix stretchers or cross stays between the posts at head and foot. in malarial countries, sleeping on the ground is distinctly dangerous, and as such districts are usually thickly timbered, the northern territory hammock is an admirable device, more particularly where mosquitoes abound. northern territory hammock this hammock, which is almost a standing bedplace when rigged, is constructed as follows:--to a piece of strong canvas feet long and / feet wide, put a broad hem, say / inches wide at each end. into this hem run a rough stick, about feet inches by inches diameter. round the centre of the stick pass a piece of strong three-quarter inch rope, to feet long and knot it, so as to leave a short end in which a metal eye is inserted. to each end of the two sticks a piece of quarter-inch lashing, about feet long, is securely attached. to make the mosquito covering take feet of ordinary strong cheese cloth, and two pieces of strong calico of the same size as the canvas bed; put hems in the ends of the upper one large enough to take half-inch sticks, to all four extremities of which feet of whipcord is to be attached. the calico forms the top and bottom of what we used to call the "meat safe," the sides being of cheese cloth. a small, flapped opening is left on the lower side. when once inside you are quite safe from mosquito bites. to rig the above, two trees are chosen to feet apart, or two stayed poles can be erected if no trees are available. the bed is rigged about feet from the ground by taking the rope round the trees or poles, and pulling the canvas taut by means of the metal eyelet. then the lashings at the extremities of the sticks are fixed about feet further up the trees and you have a bed something between a hammock and a standing bed. the mosquito net is fixed above the hammock in a similar manner, except that it does not require the centre stay. an old friend of mine once had a rather startling experience which caused him to swear by the northern territory hammock. he was camped near the banks of a muddy creek on the daly river, and had fortunately hung his "meat safe" about four feet high. the night was very dark, and some hours after retiring he heard a crash among his tin camp utensils, and the noise of some animal moving below him. thinking his visitor was a stray "dingo," or wild dog, he gave a yell to frighten the brute away, and hearing it go, he calmly went to sleep again. had he known who his caller really was, he would not have felt so comfortable. in the morning on the damp ground below, he found the tracks of a fourteen foot alligator, which was also out prospecting, but which, fortunately, had not thought of investigating the "meat safe." purifying water there is not a more fertile disease distributor, particularly in a new country, than water. the uninitiated generally take it for granted that so long as water looks clear it is necessarily pure and wholesome; as a matter of fact the contrary is more usually the case, except in very well watered countries, and such, as a rule, are not those in which gold is most plentifully got by the average prospector. i have seen foolish fellows, who were parched with a long tramp, drink water in quantity in which living organisms could be seen with the naked eye, without taking even the ordinary precaution of straining it through a piece of linen. if they contracted hydatids, typhoid fever, or other ailments, which thin our mining camps of the strong, lusty, careless youths, who could wonder? the best of all means of purifying water from organic substances is to boil it. if it be very bad, add carbon in the form of the charcoal from your camp fire. if it be thick, you may, with advantage, add a little of the ash also. i once rode forty-five miles with nearly beaten horses to a native well, or rock hole, to find water, the next stage being over fifty miles further. the well was found, but the water in it was very bad; for in it was the body of a dead kangaroo which had apparently been there for weeks. the wretched horses, half frantic with thirst, did manage to drink a few mouthfuls, but we could not. i filled our largest billycan, holding about a gallon, slung it over the fire and added, as the wood burnt down, charcoal, till the top was covered to a depth of two inches. with the charcoal there was, of course, a little ash containing bi-carbonate of potassium. the effect was marvellous. so soon as the horrible soup came to the boil, the impurities coagulated, and after keeping it at boiling temperature for about half an hour, it was removed from the fire, the cinders skimmed out, and the water allowed to settle, which it did very quickly. it was then decanted off into an ordinary prospector's pan, and some used to make tea (the flavour of which can be better imagined than described); the remainder was allowed to stand all night, a few pieces of charcoal being added. in the morning it was bright, clear, and absolutely sweet. this experience is worth knowing as many a bad attack of typhoid and other fevers would be averted if practical precautions of this kind were only used. to obtain water from roots the greatest necessity of animal life is water. there are, however, vast areas of the earth's surface where this most precious element is lamentably lacking, and such, unfortunately, is the case in many rich auriferous districts. to the practical man there are many indications of water. these, of course, vary in different countries. sometimes it is the herbage, but probably, the best of all is the presence of carnivorous animals and birds. these are never found far from water. in australia the not over-loved wily old crow is a pretty sure indicator of water within reasonable distance--water may be extracted from the roots of the mallee (_eucalyptus dumosa_ and _gracilis_)--the box (_eucalyptus hemiphloia_) and the water bush (_hakea leucoptera_). to extract it the roots are dug up, cut into lengths of about a foot, and placed upright in a can; the lower ends being a few inches above the bottom. it is simply astonishing how much wholesome, if at times somewhat astringent, water may thus be obtained in a few hours, particularly at night. _hakea leucoptera_. "pins and needles."--maiden, in his work "useful native plants of australia," says: "in an experiment on a water-yielding _hakea_, the first root, about half an inch in diameter and six or eight feet long, yielded quickly, and in large drops about a wine-glass full of really excellent water." this valuable, though not particularly ornamental shrub (for it never attains to the dimensions of a tree), is found, to the best of my belief, in all parts of australia, although it is said to be absent from west australia. as to this i don't feel quite sure. i have seen it "from the centre of the sea" as far west as streaky bay, and believe i have seen it further west still. considering the great similarity of much of the flora of south africa to that of australia, it is probable that some species of the water-bearing _hakea_ might be found there. it can readily be recognised by its acicular, needle-like leaves, and more particularly by its peculiarly shaped seed vessel, which resembles the pattern on an old-fashioned indian shawl. if the water found is too impure for drinking purposes and the trouble arises from visible animalculae only, straining through a pocket-handkerchief is better than nothing; the carbon filter is better still; but nothing is so effective as boiling. a carbon filter is a tube with a wad of compressed carbon inserted, through which the water is sucked, but as a rule clay-coloured water is comparatively innocuous, but beware of the bright, limpid water of long stagnant rock water-holes. to make an effective filter take a nail-can, keg, cask, or any other vessel, or even an ordinary wooden case (well tarred inside, if possible, to make it water-tight). make a hole or several holes in the bottom, and set it over a tank or bucket. into the bottom of the filter put ( ) a few inches of washed broken stone; ( ) about four inches of charcoal; ( ) say three inches of clean coarse sand (if not to hand you can manufacture it by crushing quartz with your pestle and mortar), and ( ) alternate layers of charcoal and sand until the vessel is half filled. fill the top half with water, and renew from time to time, and you have a filter which is as effective as the best london made article. _but it is better to boil your water whether you filter afterwards or not._ clear the inside of the water-cask frequently, and occasionally add to the water a little condy's fluid, as it destroys organic matter. a useful cement for stopping leaky places in casks is made as follows: tallow parts, lard parts, sifted wood ash parts. mix together by heating, and apply with a knife blade which has just been heated. canvas water bags are easily made, and are very handy for carrying small supplies of drinking-water when prospecting in a dry country; they have the advantage of keeping the water cool in the hottest weather, by reason on the evaporation. the mouthpiece is made of the neck of a bottle securely sewn in. medicine case medicine is also a matter well worthy of thought. the author's worst enemy would not call him a mollycoddle, yet he has never travelled in far wilds without carrying something in the way of medicine. first, then, on this subject, it cannot be too often reiterated that if common epsom salts were a guinea an ounce instead of a penny the medicine would be valued accordingly, but it is somewhat bulky. what i especially recommend, however, is a small pocket-case of the more commonly known homeopathic remedies, "mother tinctures," which are small, light, and portable, with a small simple book of instructions. though generally an allopath in practice, i once saved my own life, and have certainly helped others by a little knowledge in diagnosing complaints and having simple homeopathic remedies at hand to be used in the first stages of what might otherwise have been serious illnesses. producing fire every one has heard, and most believe, that fire may be easily produced by rubbing together two pieces of wood. i have seen it done by natives, but they seldom make use of the operation, which is generally laborious, preferring to carry lighted fire sticks for miles. i have never succeeded in the experiment. sometimes, however, it is almost a matter of life or death to be able to produce fire. the back of a pocket knife, or an old file with a fragment of flint, quartz, or pyrites struck smartly together over the remains of a burnt piece of calico, will in deft hands produce a spark which can be fanned to a glow, and so ignite other material, till a fire is produced. also it may not be generally known that he who carries a watch carries a "burning glass" with which he can, in clear weather, produce fire at will. all that is required is to remove the glass of your watch and carefully three parts fill it with water (salt or fresh). this forms a lens which, held steadily, will easily ignite any light, dry, inflammable substance. when firearms are carried, cut a cartridge so that only about a quarter of the charge of powder remains. damp some powder and rub it on a small piece of dry cotton cloth or well-rubbed brown paper. push a loose pellet of this into the barrel, insert your half cartridge, fire at the ground, when the wad will readily ignite, and can be blown into flame. to copy correspondence the prospector is not usually a business man; hence in dealing with business men who, like hamlet, are "indifferent honest," he frequently comes to grief through not having a copy of his correspondence. it is most desirable, therefore, either to carry a carbon paper duplicating book and a stylus, or by adding a little sugar to good ordinary black ink you may make a copying ink; then with the aid of a "yellow back" octavo novel, two pieces of board, and some ordinary tissue paper, you may take a copy of any letter you send. to provide a simple telegraphic code buy a couple of cheap small dictionaries of the same edition, send one to your correspondent with an intimation that he is to read up or down so many words from the one indicated when receiving a message. thus, if i want to say "claim is looking well," i take a shilling dictionary, send a copy to my correspondent with the intimation that the real word is seven down, and telegraph--"civilian looking weird;" this, if looked up in worcester's little pocket dictionary, for instance, will read "claim looking well." any dictionary will do, so long as both parties have a copy and understand which is the right word. by arrangement this plan can be varied from time to time if you have any idea that your code can be read by others. a serviceable soap wood ashes from the camp fire are boiled from day to day in a small quantity of water, and allowed to settle, the clear liquid being decanted off. when the required quantity of weak lye has been accumulated, evaporate by boiling, till a sufficient degree of strength has been obtained. now melt down some mutton fat, and, while hot, add to the boiling lye. continue boiling and stirring till the mixture is about the consistency of thick porridge, pour into any convenient flat vessel, and let it stand till cool. if you have any resin in store, a little powdered and added gradually to the melting tallow, before mixing with the lye, will stiffen your soap. to cross a flooded stream take a half-gallon, or larger, tin "billy can," enclose it in a strong cotton handkerchief or cotton cloth, knotting same over the lid, invert, and, taking the knot in the hand, you have a floating appliance which will sustain you in any water, whether you are a swimmer or not. the high silk hat of civilisation would act as well as the can, but these are not usually found far afield. to make a hide bucket at times when prospecting in an "incline" or "underlay" shaft, particularly where the walls of the lode are irregular, a hide bucket will be found preferable to an iron one. the mode of manufacture is as follows: procure an ox hide, "green," if possible; if dry, it should be soaked until quite soft. cut some thin strips of hide for sewing or lacing. now shape a bag or pocket of size sufficient to hold about a hundredweight of stone, and by puncturing the edges with a knife, marline-spike, or other pointed tool, sew together; make a handle of twisted or pleated hide, and having filled your bucket with dry sand or earth let it stand till the whole is quite dry, when it will be properly distended and will maintain its shape until worn out. to make a "slush lamp" where candles are scarce and kerosine is not, a "slush lamp" is a useful substitute. take an old but sound quart tin pannikin, half fill it with sand or earth, and prepare a thin stick of pine, round which wrap a strip of soft cotton cloth. the stick should be about half an inch longer than the depth of the pannikin. melt some waste fat, fill the pannikin therewith, push the stick down into the earth at the bottom, and you have a light, which, if not equal to the electric or incandescent gas burner, is quite serviceable. in australia the soft velvety core of the "bottle brush," _banksia marginata_, is often used instead of the cotton wick. chapter xii rules of thumb mining appliances and methods a temporary forge what prospector has not at times been troubled for the want of a forge? to steel or harden a pick or sharpen a drill is comparatively easy, but there is often a difficulty in getting a forge. big single action bellows are sometimes bought at great expense, and some ingenious fellows have made an imitation of the blacksmith's bellows by means of sheepskins and rough boards. with inadequate material and appliances to hand, the following will be found easier to construct and more lasting when constructed. only a single piece of iron is required, and, at a pinch, one could even dispense with that by using a slab of talcose material, roughly shaping a hearth therein and making a hole for the blast. first, construct a framing about the height of an ordinary smith's forge. this can made with saplings and bark, or better still, if available, out of an empty packing case about three feet square. fill the frame or case with slightly damped earth and ram it tight, leaving the usual hollow hearth. then form a chamber below the perforated hearth opening to the rear. now construct a centrifugal fan, such as is used for the ventilation of shallow shafts and workings. set this up behind the hearth and revolve by means of a wooden multiplying wheel. a piece of ordinary washing line rope, or sash line rope, well resined if resin can be got--but pitch, tar, or wax will do by adding a little fine dust to prevent sticking--is used as a belt. with very rough materials a handy man can thus make a forge that will answer ordinary requirements.--n.b. do not use clay for your hearth bed unless you can get a highly aluminous clay, and can give it full time to dry before the forge fire is lit. ordinary surface soil, not too sandy, acts well, if damped and rammed thoroughly. of course, if you can get an iron nozzle for your blower the whole operation is simplified. simple way of making charcoal dig a pit feet square by feet deep and fill with fuel. after lighting, see that the pit is kept full. the hot embers will gradually sink to the bottom. the fuel should be kept burning fiercely until the pit seems almost full, when more fuel should be added, raising the heap about a foot above the level of the ground. the earth dug out of the pit should then be shovelled back over the burning mass. after leaving it to cool for hours the pit will be found nearly full of charcoal. about one-quarter the weight of the dry fuel used should be recovered in charcoal. rough smelting on the mine rough smelting on the mine is effected with a flux of borax, carbonate of soda, or, as i have often done, with some powdered white glass. when the gold is smelted and the flux has settled down quietly in a liquid state, the bulk of the latter may be removed, to facilitate pouring into the mould, by dipping an iron rod alternately into the flux and then into a little water, and knocking off the ball of congealed flux which adheres after each dip. this flux should, however, be crushed with a pestle and mortar and panned off, as, in certain cases, it may contain tiny globules of gold. misfires in blasting one of the most common sources of accident in mining operations is due either to carelessness or to the use of defective material in blasting. a shot misses, generally for one of two reasons; either the explosive, the cap, or the fuse (most often the latter), is inferior or defective; or the charging is incompletely performed. sometimes the fuse is not placed properly in the detonator, or the detonator is not properly enclosed in the cartridge, or the fuse is injured by improper tamping. if several shots have been fired together, particularly at the change of a "shift," the men who have to remove the broken material may in so doing explode the missed charge. or, more inexcusable still, men will often be so foolish as to try to clear out the drill hole and remove the missed cartridge. when a charge is known to have missed all that is necessary to do in order to discharge it safely is to remove a few inches of "tamping" from the top of the drill hole, place in the bore a plug of dynamite with cap and fuse attached, put an inch or two of tamping over it and fire, when the missed charge will also be exploded. of course, judgment must be used and the depth of the drill taken into consideration. as a rule, miners use far more tamping than is at all requisite. the action of the charge will generally be found quite as effective with a few inches of covering matter as with a foot or more, while the exploding of misfire cartridges is rendered simple, as no removal of tamping is required before placing the top "plug" in case of misfire. to prevent loss of rich specimens in blasting when blasting the cap of a lode, particularly on rich shutes of gold, the rock is apt to fly, and rich specimens may be thrown far afield and so be lost. a simple way of avoiding this is to procure a quantity of boughs, which tie into loose bundles, placing the leafy parts alternately end for end. before firing, pile these bundles over the blast and, if care is used, very few stones will fly. the same device may be used in wide shallow shafts. a simple mode of retorting small quantities of amalgam clean your amalgam and squeeze it as hard as possible through strong calico or chamois leather. take a large sound potato, cut off about a quarter from one end and scoop out a hole in the centre about twice as big as the ball of amalgam. procure a piece of flat iron--an old spade will do as well as anything--insert the amalgam, and, having placed the potato, cut side downwards, thereon, put the plate of iron on the forge, heat up first gently, then stronger, till separation has taken place, when the gold will be found in a bright clean button on the plate and the mercury in fine globules in the potato, from which it can be re-collected by breaking up the partly or wholly cooked tuber under water in an enamelled or ordinary crockery basin. to retort small quantities of mercury for amalgamating assay tests get two new tobacco pipes similar in shape, with the biggest bowls and longest stems procurable. break off the stem of one close to the bowl and fill the hole with well worked clay (some battery slimes make the best luting clay). set the stemless pipe on end in a clay bed, and fill with amalgam, pass a bit of thin iron or copper wire beneath it, and bend the ends of the wire upwards. now fit the whole pipe, bowl inverted, on to the under one, luting the edges of both well with clay. twist the wire over the top with a pair of nippers till the two bowls are fitted closely together, and you have a retort that will stand any heat necessary to thoroughly distil mercury. a simple mode of ascertaining the nominal horse-power of an engine multiply the internal diameter of the cylinder by itself and strike off the last figure of the quotient. the diameter is " x " ____ . the h.p. is . the following rules will be found more professionally accurate from an engineering standpoint, though the term "horse-power" is not now generally employed. _to find the nominal horse-power_.--for _non-condensing_ engines: multiply the square of the diameter of the cylinder in inches by and divide the product by . for _condensing_ engines: multiply the square of the diameter of the cylinder in inches by and divide the product by . _to find the actual horse-power_ of an engine, multiply the area of the cylinder in square inches by the average effective pressure in pounds per square inch, less lb. per square inch as the frictional allowance, and also by the speed of the piston in feet per minute, dividing the product by , , and the quotient will be the actual horse-power. "scaling" copper plates to "scale" copper plates they may be put over a charcoal or coke fire to slowly sublimate the quicksilver. where possible, the fireplace of a spare boiler can be utilised, using a thin red fire. after the entire evaporation of the quicksilver the plates should be slowly cooled, rubbed with hydrochloric acid, and put in a damp place overnight, then rubbed with a solution of sal ammoniac and nitre in equal parts, and again heated slowly over a red fire. they must not be allowed to get red hot; the proper degree of heat is indicated by the gold scale rising in blisters, when the plates should be taken from the fire and the gold scraped off. any part of the plate on which the gold has not blistered should be again rubbed with the solution and fired. the gold scale should be collected in a glass or earthen dish and covered with nitric acid, till all the copper is dissolved, when the gold can be smelted in the usual way; but after it is melted corrosive sublimate should be put in the crucible till a blue flame ceases to be given off. _a second method_ the simplest plan i know is to have a hole dug nine inches deep by about the size of the plate to be scaled; place a brick at each corner, and on each side, halfway between, get up a good fire; let it burn down to strong embers, or use charcoal, then place the plate on three bars of iron extending between the three pairs of bricks, have a strong solution of borax ready in which soak strips of old "table blanket," laying these over the plate and sprinkling them with the borax solution when the plate gets too hot. after a time the deposit of mercury and gold on the plate will assume a white, efflorescent appearance, and may then be readily parted from the copper. _another method_ heat the plate over an open fire, to drive off the mercury; after which, let it cool, and saturate with dilute sulphuric acid for three hours, or longer; then sprinkle over the surface a mixture of equal parts of common salt and sal ammoniac, and heat to redness; then cool, and the gold scale comes off freely; the scale is then boiled in nitric or sulphuric acid, to remove the copper, previous to melting. plates may be scaled about once in six months, and will under ordinary circumstances produce about one ounce of clean gold for each superficial foot of copper surface employed. i always paint the back of the plate with a mixture of boiled oil and turpentine, or beeswax dissolved in turpentine, to prevent the acid attacking the copper. how to supply mercury to mortar boxes i am indebted for the following to mr. j. m. drake, who, speaking of his experience on the wentworth mine, n.s.w., says: "fully per cent of the gold is saved on the outside plates, only a small quantity remaining in the mortar. the plates have a slope of in. to ft. no wells are used, the amalgam traps saving any quicksilver which may leach off the plates. the quicksilver is added every hour in the mortar. the quantity is regulated by the mill manager in the following manner: three pieces of wood, in. wide by in. long by in. thick, have holes in. deep bored in each of them. these holes will just take a small oz. phial. the mill manager puts the required quantity of quicksilver in each bottle and the batteryman empties one bottle in each mortar every hour; and puts it back in the hole upside down. each block of wood lasts eight hours, the duration of one man's shift." this of course is for a -head mill with four mortars or "boxes." i commend this as an excellent mode of supplying the mercury to the boxes or mortars. the quantity to be added depends on circumstances. a careless battery attendant will often put in too much or too little when working without the automatic feeder. i have known an attendant on suddenly awaking to the fact half through his shift, that he had forgotten to put in any mercury, to then empty into the stamper box two or three pounds weight; with what effect may be easily surmised. how water should enter stamper boxes the following extract which relates to californian gold mill practices is from bulletin no. of the california state mining bureau. i quite agree with the practice. "the battery water should enter both sides of the mortar in an even quantity, and should be sufficient to keep a fairly thick pulp which will discharge freely through the grating or screen. about cubic feet of water per ton of crushed ore may be considered an average, or to cubic feet per stamp per hour. "screens of different materials and with different orifices are used; the materials comprise wire cloth of brass or steel, tough russian sheet iron, english tinned plate, and, quite recently, aluminium bronze. the 'aluminium bronze' plates are much longer lived than either of the other kinds, and have the further advantage that, when worn out, they can be sold for the value of the metal for remelting; these plates are bought and sold by the pound, and are said to contain per cent of copper and per cent of aluminium. steel screens are not so much used, on account of their liability to rust." i have had no experience with the aluminium bronze screen. i presume, however, that it is used only for mills where mercury is not put in the mortars, otherwise, it would surely become amalgamated. the same remark applies to brass wire cloth and tinned plate. unless the metal of which they are composed will not readily amalgamate with mercury, i should be chary of using new screen devices. mercury is a most insidious metal and is often found most unexpectedly in places in the battery where it should not be. probably aluminium steel would be better than any substance mentioned. it would be hard, light, strong, and not readily corrodible. i am not aware if it has been tried. under the heading of "power for mills" the following is taken from the same source. power for mills "as the pelton wheel seems to find the most frequent application in california, it may be convenient for millmen to have the following rule, applicable to these wheels: "when the head of water is known in feet, multiply it by . , and the product is the horse-power obtainable from one miner's inch of water. "the power necessary for different mill parts is: for each lb. stamp, dropping in. times per minute, . h.-p. for each lb. stamp, dropping in. times per minute, . h.-p. for each lb. stamp, dropping in. times per minute, . h.-p. for an -inch by -inch blake pattern rock-breaker . h.-p. for a frue or triumph vanner, with revolutions per min. . h.-p. for a -feet clean-up pan, making revolutions per min. . h.-p. for an amalgamating barrel, making revolutions per min. . h.-p. for a mechanical batea, making revolutions per min. . h.-p." the writer has had small practical experience of the working of that excellent hydraulic motor, the pelton wheel, but if by horse-power in the table given is meant nominal horse-power, it appears to be high. working with cwt. stamps, blows a minute, one horse-power nominal will be found sufficient with any good modern engine, which has no further burden than raising the stamps and pumping the feed water. it is always well, however, particularly when providing engine power, to err on the right side, and make provision for more than is absolutely needed for actual battery requirements. this rule applies with equal potency to pumping engines. to avoid loss in cleaning up the following is a hint to quartz mill managers with respect to that common source of loss of gold involved in the almost inevitable loss of mercury in cleaning up operations. i have known hundreds of pounds' worth of gold to be recovered from an old quartz mill site by the simple process of washing up the ground under the floor. if you cannot afford to floor the whole of the battery with smooth concrete, at all events smoothly concrete the floor of the cleaning-up room, and let the floor slope towards the centre: where a sink is provided. any lost mercury must thus find its way to the centre, where it will collect and can be panned off from time to time. of course an underground drain and mercury trap must be provided. iron extractor when using self-feeders, fragments of steel tools are especially liable to get into the battery boxes or other crushing appliance where they sometimes cause great mischief. i believe the following plan would be a practicable remedy for this evil. by a belt from the cam or counter shaft, cause a powerful electric magnet to extract all magnetic particles; then, by a simple ratchet movement, at intervals withdraw the magnet and drop the adhering fragments into a receptacle by automatically switching off the electric current. a powerful ordinary horseshoe magnet might probably do just as well, but would require to be re-magnetised from time to time. to silver copper plates to silver copper plates, that is, to amalgamate them on the face with mercury, is really a most simple operation, though many batterymen make a great mystery of it. indeed, when i first went into a quartz mill the process deemed necessary was not only a very tedious one, but very dirty also. to amalgamate with silver, in fact, to silver-plate your copper without resort to the electro-plating bath, take any old silver (failing that, silver coin will do, but is more expensive), and dissolve it in somewhat dilute nitric acid, using only just sufficient acid as will assist the process. after some hours place the ball of amalgam in a piece of strong new calico and squeeze out any surplus mercury. about an ounce of silver to the foot of copper is sufficient. to apply it on new plates use nitric acid applied with a swab to free the surface of the copper from oxides or impurities, then rub the ball of amalgam over the surface using some little force. it is always well when coating copper plates with silver or zinc by means of mercury to let them stand dry for a day or two before using, as the mercury oxidises and the coating metal more closely adheres. only the very best copper plate procurable should be used for battery tables; bad copper will always give trouble, both in the first "curing," and after treatment. it should not be heavily rolled copper, as the more porous the metal the more easily will the mercury penetrate and amalgamate. i cannot agree that any good is attained by scouring the plates with sand and alkalies, as recommended in some books on the subject; on the contrary, i prefer the opposite mode of treatment, and either face the plates with nitrate of silver and nitrate of mercury, or else with sulphate of zinc and mercury, in the form of what is called zinc amalgam. if mine water, which often contains a little free sulphuric acid, is being used, the latter plan is preferable. the copper should be placed smoothly on the wooden table and secured firmly thereto by copper tacks. if the plate should be bent or buckled, it may be flattened by beating it with a heavy hammer, taking care to interpose a piece of inch-thick soft wood between hammer and plate. to coat with mercury only, procure some nitrate of mercury. this is easily made by placing mercury in an earthenware bowl, pouring somewhat dilute nitric acid on it, and letting it stand till the metallic mercury is changed to a white crystal. dense reddish-brown fumes will arise, which are injurious if breathed, so the operation should be conducted either in the open air, or where there is a draught. having your silvering solution ready, which is to be somewhat diluted with water, next take two swabs, with handles about inches long, dip the first into a basin containing dilute nitric acid, and rub it rapidly over about a foot of the surface of the plate; the oxide of copper will be absolutely removed, and the surface of the copper rendered pure and bright; then take the other swab, wet with the dilute nitric of mercury, and pass it over the clean surface, rubbing it well in. continue this till the whole plate has a coating of mercury. it may be well to go over it more than once. now turn on the water and wash the plate clean, sprinkle with metallic mercury, rubbing it upwards until the plate will hold no more. a basin with nitrate of mercury may be kept handy, and the plates touched up from time to time for a few days until they get amalgamated with gold, after which, unless you have much base metal to contend with, they will give no further trouble. it must be remembered, however, that an excessive use of nitric acid will result in waste of mercury, which will be carried off in a milky stream with the water; and also that it will cause the amalgam to become very hard, and less active in attracting other particles of gold. if you are treating the plate with nitrate of silver prepared as already mentioned, clean the plate with dilute nitric acid, rub the surface with the ball of amalgam, following with the swab and fairly rubbing in. it will be well to prepare the plate some days before requiring to use it, as a better adhesion of the silver and copper takes place than if mercury is applied at once. to amalgamate with zinc amalgam, clean the copper plate by means of a swab, with fairly strong sulphuric acid diluted with water; then while wet apply the zinc-mercury mixture and well rub in. to prepare the zinc-amalgam, clip some zinc (the lining of packing cases will do) into small pieces and immerse them in mercury after washing them with a little weak sulphuric acid and water to remove any coating of oxide. when the mercury will absorb no more zinc, squeeze through chamois leather or calico (as for silver amalgam), and well rub in. the plate thus prepared should stand for a few days, dry, before using. if, before amalgamation with gold takes place, oxide of copper or other scum should rise on this plate a little very dilute sulphuric acid will instantly remove it. sodium and cyanide of potassium are frequently used in dressing-plates, but the former should be very sparingly employed, as it will often do more harm than good by taking up all sorts of base metals with the amalgam, and so presenting a surface which the gold will pass over without adhering to. where water is scarce, and is consequently used over and over again, lime may be added to the pulp, or, if lime is not procurable, wood ashes may be used. the effect is two-fold; the lime not only tends to "sweeten" sulphide ores and keep the tables clean, but also causes the water to cleanse itself more quickly of the slimes, which will be more rapidly precipitated. when zinc amalgam is used, alkalies would, of course, be detrimental. when no other water than that from the mine is available, difficulties often arise owing to the impurities it contains. these are various, but among the most common are the soluble sulphates, and sometimes free sulphuric acid evolved by the oxidisation of metallic sulphides. in the presence of this difficulty, do one of two things; either _utilise_ or _neutralise_. in certain cases, i recommend the former. sometime since i was treating, for gold extraction, material from a mine which was very complex in character, and for which i coined the term "polysynthetic." this contained about half a dozen different sulphides. the upper parts of the lode being partially oxidised, free sulphuric acid (h so ) was evolved. i therefore, following out a former discovery, added a little metallic zinc to the mercury in the boxes and on the plates with excellent results. when the free acid in the ore began to give out in the lower levels i added minute quantities of sulphuric acid to the water from time to time. i have since found, however, that with some water, particularly west australian, the reaction is so feeble (probably owing to the lime and magnesia present) as to make this mode of treatment unsuitable. how to make a dolly i have seen some rather elaborate dollies, intended to be worked with amalgamating tables, but the usual prototype of the quartz mill is set up, more or less, as follows: a tree stump, from in. to a foot diameter, is levelled off smoothly at about ft. from the ground; on this is firmly fixed a circular plate of / in. iron, say in. in diameter; a band of / in. iron, about or in. in height, fits more or less closely round the plate. this is the battery box. a beam of heavy wood, about in. diameter and ft. long, shod with iron, is vertically suspended, about in. above the stump, from a flexible sapling with just sufficient spring in it to raise the pestle to the required height. about ft. from the bottom the hanging beam is pierced with an augur hole and a rounded piece of wood, / in. by in., is driven through to serve as a handle for the man who is to do the pounding. his mate breaks the stone to about in. gauge and feeds the box, lifting the ring from time to time to sweep off the triturated gangue, which he screens through a sieve into a pan and washes off, either by means of a cradle or simply by panning. in dollying it generally pays to burn the stone, as so much labour in crushing is thus saved. a couple of small kilns to hold about a ton each dug out of a clay bank will be found to save fuel where firewood is scarce, and will more thoroughly burn the stone and dissipate the base metals, but it must be remembered that gold from burnt stone is liable to become so encrusted with the base metal oxides as to be difficult to amalgamate. rough windlass make two st. andrew's crosses with four saplings, the upper angle being shorter than the lower; fix these upright, one at each end of the shaft; stay them together by cross pieces till you have constructed something like a "horse," such as is used for sawing wood, the crutch being a little over feet high. select a leg for a windlass barrel, about in. diameter and a foot longer than the distance between the supports, as straight as is procurable; cut in it two circular slots about an inch deep by in. wide to fit into the forks; at one end cut a straight slot in. deep across the face. now get a crooked bough, as nearly the shape of a handle as nature has produced it, and trim it into right angular shape, fit one end into the barrel, and you have a windlass that will pull up many a ton of stuff. puddler this is made by excavating a circular hole about ft. in. deep and, say ft. in diameter. an outer and inner wall are then constructed of slabs ft. in. in height to ground level, the outer wall being thus ft. and the inner ft. in circumference. the circular space between is floored with smooth hardwood slabs or boards, and the whole made secure and water-tight. in the middle of the inner enclosure a stout post is planted, to stand a few inches above the wall, and the surrounding space is filled up with clay rammed tight. a strong iron pin is inserted in the centre of the post, on which is fitted a revolving beam, which hangs across the whole circumference of the machine and protrudes a couple of feet or so on each side. to this beam are attached, with short chains, a couple of drags made like v-shaped harrows by driving a piece of red iron through a heavy frame, shaped as a rectangular triangle. to one end of the beam an old horse is attached, who, as he slowly walks round the circular track, causes the harrows and drags to so puddle the washdirt and water in the great wooden enclosure that the clay is gradually disintegrated, and flows off with the water which is from time to time admitted. the clean gravel is then run through a "cradle," "long tom," or "sluice," and the gold saved. this, of course, is the simplest form of gold mining. in the great alluvial mines other and more intricate appliances are used but the principle of extraction is the same. a makeshift pump to make a temporary small "draw-lift" pump, which will work down to a hundred feet or more if required, take a large size common suction douglas pump, and, after removing the top and handle, fix the pump as close to the highest level of the water in the shaft as can be arranged. now make a square water-tight wooden column of slightly greater capacity than the suction pipe, fix this to the top of the pump, and by means of wooden rods, work the whole from the surface, using either a longer levered handle or, with a little ingenuity, horse-power. if you can get it the iron downpipe used to carry the water from the guttering of houses is more easily adapted for the pipe column; then, also, iron pump rods can be used but i have raised water between and feet with a large size douglas pump provided only with a wooden column and rods. squeezing amalgam for squeezing amalgam, strong calico, not too coarse, previously soaked in clean water, is quite as good as ordinary chamois leather. some gold is fine enough to escape through either. mercury extractor the mercury extractor or amalgam separator is a machine which is very simple in construction, and is stated to be most efficient in extracting quicksilver from amalgam, as it requires but from two to three minutes to extract the bulk of the mercury from one hundred pounds of amalgam, leaving the amalgam drier than when strained in the ordinary way by squeezing through chamois leather or calico. the principle is that of the de laval cream separator--i.e., rapid centrifugal motion. the appliance is easily put together, and as easily taken apart. the cylinder is made of steel, and is run at a very high rate of speed. the general construction of the appliance is as follows: the casing or receiver is a steel cylinder, which has a pivot at the bottom to receive the step for an upright hollow shaft, to which a second cylinder of smaller diameter is attached. the second cylinder is perforated, and a fine wire cloth is inserted. the mercury, after passing through the cloth, is discharged through the perforations. when the machine is revolved at great speed, the mercury is forced into the outside cylinder, leaving the amalgam, which has been first placed in a calico or canvas bag, in a much drier state than it could be strained by hand. while not prepared to endorse absolutely all that is claimed for this appliance, i consider that it has mechanical probability on its side, and that where large quantities of amalgam have to be treated it will be found useful and effective. sluice plates i am indebted to mr. f. w. drake for the following account of sluice plates, which i have never tried, but think the device worth attention: "an addition has been made to the gold-saving appliances by the placing of what are called in america, 'sluice plates' below the ordinary table. the pulp now flows over an amalgamating surface, ft. long by ft. wide, sloping / in. to the foot, and is then contracted into a copper-plated sluice ft. long by in. wide, having a fall of in. to the foot. our mill manager (mr. g. c. knapp) advocated these sluice plates for a long time before i would consent to a trial. i contended that as we got little or no amalgam from the lower end of our table plates there was no gold going away capable of being recovered by copper plates; and even if it were, narrow sluice plates were a step in the wrong direction. if anything the amalgamating surface should be widened to give the particles of gold a better chance to settle. his argument was that the conditions should be changed; by narrowing the stream and giving it less fall, gold, which was incapable of amalgamation on the wide plates, would be saved. we finally put one in, and it proved so successful that we now have one at the end of each table. the per-centage recovered on the sluice plates, of the total yield, varies, and has been as follows:--october, . per cent; november, . per cent; december, . per cent; january, . per cent; february, . per cent." measuring inaccessible distances to ascertain the width of a difficult gorge, a deep river, or treacherous swamp without crossing and measuring, sight a conspicuous object at the edge of the bank on the farther side; then as nearly opposite and square as possible plant a stake about five feet high, walk along the nearer margin to what you guess to be half the distance across (exactitude in this respect is not material to the result), there plant another stake, and continuing in a straight line put in a third. the stakes must be equal distances apart and as nearly as possible at a right angle to the first line. now, carrying in hand a fourth stake, strike a line inland at right angles to the base and as soon as sighting over the fourth stake, you can get the fourth and second stakes and the object on the opposite shore in line your problem is complete. the distance between no. and no. stakes is the same as that between no. and the opposite bank. to set out a right angle with a tape measure ft. on the line to which you wish to run at right angles, and put pegs at a and b; then, with the end of the tape held carefully at a, take ft., and have the ft. mark held at b. take the ft. mark and pull from a and b until the tape lies straight and even, you will then have the point c perpendicular to ab. continue straight lines by sighting over two sticks in the well-known way. _another method_.--stick a pin in each corner of a square board, and look diagonally across them, first in the direction of the line to which you wish to run at right angles, and then for the new line sight across the other two pins. a simple levelling instrument fasten a common carpenter's square in a slit to the top of a stake by means of a screw, and then tie a plumb-line at the angle so that it may hang along the short arm, when the plumb-line hangs vertically and sights may be taken over it. a carpenter's spirit-level set on an adjustable stand will do as well. the other arm will then be a level. another very simple, but effective, device for finding a level line is by means of a triangle of wood made of half-inch boards from to ft. long. to make the legs level, set the triangle up on fairly level ground, suspend a plummet from the top and mark on the cross-piece where the line touches it. then reverse the triangle, end for end, exactly, and mark the new line the plumb-line makes. now make a new mark exactly half way between the two, and when the plumb-line coincides with this, the two legs are standing on level ground. for short water races this is a very handy method of laying out a level line. to measure the height of a standing tree take a stake about your own height, and walking from the butt of the tree to what you judge to be the height of the timber portion you want, drive your stake into the ground till the top is level with your eyes; now lie straight out on your back, placing your feet against the stake, and sight a point on the tree. ab equals bc. if bc is, say ft., that will be the height of your "stick of timber." thus, much labour may be saved in felling trees the timber portion of which may afterwards be found to be too short for your purpose. levelling by aneroid barometer this should be used more for ascertaining relatively large differences in altitudes than for purposes where any great nicety is required. for hills under ft., the following rule will give a very close approximation, and is easily remembered, because degrees, the assumed temperature, agrees with degrees, the significant figures in the , factor, while the fractional correction contains _two fours_. observe the altitudes and also the temperatures on the fahrenheit thermometer at top and bottom respectively, of the hill, and take the mean between them. let b represent the mean altitude and b the mean temperature. then x b - b/b + b = height of the hill in feet for the temperature of degrees. add / of this result for every degree the mean temperature exceeds degrees; or subtract as much for every degree below degrees. to determine heights of objects _by shadows_ set up vertically a stick of known length, and measure the length of its shadow upon a horizontal or other plane; measure also the length of the shadow thrown by the object whose height is required. then it will be:--as the length of the stick's shadow is to the length of the stick itself, so is the length of the shadow of the object to the object's height. _by reflection_ place a vessel of water upon the ground and recede from it until you see the top of the object reflected from the surface of the water. then it will be:--as your horizontal distance from the point of reflection is to the height of your eye above the reflecting surface, so is the horizontal distance of the foot of the object from the vessel to its altitude above the said surface. _instrumentally_ read the vertical angle, and multiply its natural tangent by the distance between instrument and foot of object; the result is the height. when much accuracy is not required vertical angles can be measured by means of a quadrant of simple construction. the arc ab is a quadrant, graduated in degrees from b to a; c, the point from which the plummet p is suspended, being the centre of the quadrant. _when_ the sights ac are directed towards any object, s, the degrees in the arc, bp, are the measure of the angle of elevation, sad, of the object. to find the depth of a shaft _rule_:--square the number of seconds a stone takes to reach the bottom and multiply by . thus, if a stone takes seconds to fall to the bottom of a shaft-- squared = ; and x = feet, the required depth of shaft. description of plan for re-using water where water is scarce it may be necessary to use it repeatedly. in a case of this kind in egypt, the arab miners have adopted an ingenious method which may be adapted to almost any set of conditions. at a is a sump or water-pit; b is an inclined plane on which the mineral is washed and whence the water escapes into a tank c; d is a conduit for taking the water back to a; e is a conduit or lever pump for raising the water. a certain amount of filtration could easily be managed during the passage from c to a. cooling compound for heated bearings mercurial ointment mixed with black cylinder oil and applied every quarter of an hour, or as often as expedient. the following is also recommended as a good cooling compound for heavy bearings:--tallow lb., plumbage oz., sugar of lead oz. melt the tallow with gentle heat and add the other ingredients, stirring until cold. cleaning greasy plummer blocks when, through carelessness or unpreventable cause, plummer blocks and other detachable portions of machinery become clogged with sticky deposits of grease and impurities, a simple mode of cleansing the same is to take about parts by weight of boiling water, to which add about or parts of ordinary washing soda. keep the water on the boil and place therein the portions of the machine that are to be cleaned; this treatment has the effect of quickly loosening all grease, oil, and dirt, after which the metal is thoroughly washed and dried. the action of the lye is to form with the grease a soap soluble in water. to prevent lubricating oil hardening upon the parts of the machinery when in use, add a third part of kerosene. an excellent anti-friction compound for use on cams and stamper shanks, which will be harmless should it drop into the mortar or stamper boxes, is graphite (black-lead) and soft soap. when the guides are wooden, the soft soap need not be added; black-lead made into a paste with water will act admirably. to clean brass oxalic acid oz., rotten stone oz., powdered gum arabic / oz., sweet oil oz. rub on with a piece of rag. a solvent for rust it is often very difficult, and sometimes impossible, to remove rust from articles made of iron. those which are very thickly coated are most easily cleaned by being immersed in a nearly saturated solution of chloride of tin. the length of time they remain in this bath is determined by the thickness of the coating of rust. generally from twelve to twenty-four hours is long enough. to protect iron and steel from rust the following method is but little known, although it deserves preference over many others. add oz. of quicklime to / pints of cold water. let the mixture stand until the supernatant fluid is entirely clear. then pour this off, and mix with it enough olive oil to form a thick cream, or rather to the consistency of melted and re-congealed butter. grease the articles of iron or steel with this compound, and then wrap them up in paper, or if this cannot be done, apply the mixture somewhat more thickly. to keep machinery from rusting take oz. of camphor, dissolve it in lb. of melted lard; mix with it (after removing the scum) as much fine black-lead as will give it an iron colour; clean the machinery, and smear it with this mixture. after twenty-four hours rub off and clean with soft, linen cloth. this mixture will keep machinery clean for months under ordinary circumstances. fire-lute an excellent fire-lute is made of eight parts sharp sand, two parts good clay, and one part horse-dung; mix and temper like mortar. rope-splicing a short splice is made by unlaying the ends of two pieces of rope to a sufficient length, then interlaying them, draw them close and push the strands of one under the strands of the other several times. this splice makes a thick lump on the rope and is only used for slings, block-straps, cables, etc. principles of mining +--------------------------------------------------------------+ | published by the | | mcgraw-hill book company | | new york | | | | successors to the book departments of the | | mcgraw publishing company hill publishing company | | | | publishers of books for | | electrical world the engineering and mining journal | | engineering record power and the engineer | | electric railway journal american machinist | | metallurgical and chemical engineering | +--------------------------------------------------------------+ principles of mining valuation, organization and administration copper, gold, lead, silver, tin and zinc by herbert c. hoover _member american institute of mining engineers, mining and metallurgical society of america, société des ingénieurs civils de france, fellow royal geographical society, etc._ first edition _fourth thousand_ mcgraw-hill book company west th street, new york bouverie street, london, e.c. preface. this volume is a condensation of a series of lectures delivered in part at stanford and in part at columbia universities. it is intended neither for those wholly ignorant of mining, nor for those long experienced in the profession. the bulk of the material presented is the common heritage of the profession, and if any one may think there is insufficient reference to previous writers, let him endeavor to find to whom the origin of our methods should be credited. the science has grown by small contributions of experience since, or before, those unnamed egyptian engineers, whose works prove their knowledge of many fundamentals of mine engineering six thousand eight hundred years ago. if i have contributed one sentence to the accumulated knowledge of a thousand generations of engineers, or have thrown one new ray of light on the work, i shall have done my share. i therefore must acknowledge my obligations to all those who have gone before, to all that has been written that i have read, to those engineers with whom i have been associated for many years, and in particular to many friends for kindly reply to inquiry upon points herein discussed. contents. chapter . valuation of copper, gold, lead, silver, tin, and zinc lode mines determination of average metal content; sampling, assay plans, calculations of averages, percentage of errors in estimate from sampling. chapter ii. mine valuation (_continued_) calculation of quantities of ore, and classification of ore in sight. chapter iii. mine valuation (_continued_) prospective value. extension in depth; origin and structural character of the deposit; secondary enrichment; development in neighboring mines; depth of exhaustion. chapter iv. mine valuation (_continued_) recoverable percentage of the gross assay value; price of metals; cost of production. chapter v. mine valuation (_continued_) redemption or amortization of capital and interest. chapter vi. mine valuation (_concluded_) valuation of mines with little or no ore in sight; valuations on second-hand data; general conduct of examinations; reports. chapter vii. development of mines entry to the mine; tunnels; vertical, inclined, and combined shafts; location and number of shafts. chapter viii. development of mines (_continued_) shape and size of shafts; speed of sinking; tunnels. chapter ix. development of mines (_concluded_) subsidiary development: stations; crosscuts; levels; interval between levels; protection of levels; winzes and rises. development in the prospecting stage; drilling. chapter x. stoping methods of ore-breaking; underhand stopes; overhand stopes; combined stope. valuing ore in course of breaking. chapter xi. methods of supporting excavation timbering; filling with waste; filling with broken ore; pillars of ore; artificial pillars; caving system. chapter xii. mechanical equipment conditions bearing on mine equipment; winding appliances; haulage equipment in shafts; lateral underground transport; transport in stopes. chapter xiii. mechanical equipment (_continued_) drainage: controlling factors; volume and head of water; flexibility; reliability; power conditions; mechanical efficiency; capital outlay. systems of drainage,--steam pumps, compressed-air pumps, electrical pumps, rod-driven pumps, bailing; comparative value of various systems. chapter xiv. mechanical equipment (_concluded_) machine drilling: power transmission; compressed air _vs._ electricity; air drills; machine _vs._ hand drilling. workshops. improvement in equipment. chapter xv. ratio of output to the mine determination of possible maximum; limiting factors; cost of equipment; life of the mine; mechanical inefficiency of patchwork plant; overproduction of base metal; security of investment. chapter xvi. administration labor efficiency; skill; intelligence; application coördination; contract work; labor unions; real basis of wages. chapter xvii. administration (_continued_) accounts and technical data and reports; working costs; division of expenditure; inherent limitations in accuracy of working costs; working cost sheets. general technical data; labor, supplies, power, surveys, sampling, and assaying. chapter xviii. administration (_concluded_) administrative reports. chapter xix. the amount of risk in mining investments risk in valuation of mines; in mines as compared with other commercial enterprises. chapter xx. the character, training, and obligations of the mining engineering profession index principles of mining. chapter i. valuation of copper, gold, lead, silver, tin, and zinc lode mines. determination of average metal content; sampling, assay plans, calculations of averages, percentage of errors in estimate from sampling. the following discussion is limited to _in situ_ deposits of copper, gold, lead, silver, tin, and zinc. the valuation of alluvial deposits, iron, coal, and other mines is each a special science to itself and cannot be adequately discussed in common with the type of deposits mentioned above. the value of a metal mine of the order under discussion depends upon:-- _a_. the profit that may be won from ore exposed; _b_. the prospective profit to be derived from extension of the ore beyond exposures; _c_. the effect of a higher or lower price of metal (except in gold mines); _d_. the efficiency of the management during realization. the first may be termed the positive value, and can be approximately determined by sampling or test-treatment runs. the second and the third may be termed the speculative values, and are largely a matter of judgment based on geological evidence and the industrial outlook. the fourth is a question of development, equipment, and engineering method adapted to the prospects of the enterprise, together with capable executive control of these works. it should be stated at the outset that it is utterly impossible to accurately value any mine, owing to the many speculative factors involved. the best that can be done is to state that the value lies between certain limits, and that various stages above the minimum given represent various degrees of risk. further, it would be but stating truisms to those engaged in valuing mines to repeat that, because of the limited life of every mine, valuation of such investments cannot be based upon the principle of simple interest; nor that any investment is justified without a consideration of the management to ensue. yet the ignorance of these essentials is so prevalent among the public that they warrant repetition on every available occasion. to such an extent is the realization of profits indicated from the other factors dependent upon the subsequent management of the enterprise that the author considers a review of underground engineering and administration from an economic point of view an essential to any essay upon the subject. while the metallurgical treatment of ores is an essential factor in mine economics, it is considered that a detailed discussion of the myriad of processes under hypothetic conditions would lead too far afield. therefore the discussion is largely limited to underground and administrative matters. the valuation of mines arises not only from their change of ownership, but from the necessity in sound administration for a knowledge of some of the fundamentals of valuation, such as ore reserves and average values, that managerial and financial policy may be guided aright. also with the growth of corporate ownership there is a demand from owners and stockholders for periodic information as to the intrinsic condition of their properties. the growth of a body of speculators and investors in mining stocks and securities who desire professional guidance which cannot be based upon first-hand data is creating further demand on the engineer. opinions in these cases must be formed on casual visits or second-hand information, and a knowledge of men and things generally. despite the feeling of some engineers that the latter employment is not properly based professionally, it is an expanding phase of engineers' work, and must be taken seriously. although it lacks satisfactory foundation for accurate judgment, yet the engineer can, and should, give his experience to it when the call comes, out of interest to the industry as a whole. not only can he in a measure protect the lamb, by insistence on no investment without the provision of properly organized data and sound administration for his client, but he can do much to direct the industry from gambling into industrial lines. an examination of the factors which arise on the valuation of mines involves a wide range of subjects. for purposes of this discussion they may be divided into the following heads:-- . _determination of average metal contents of the ore._ . _determination of quantities of ore._ . _prospective value._ . _recoverable percentage of gross value._ . _price of metals._ . _cost of production._ . _redemption or amortization of capital and interest._ . _valuation of mines without ore in sight._ . _general conduct of examination and reports._ determination of average metal contents of the ore. three means of determination of the average metal content of standing ore are in use--previous yield, test-treatment runs, and sampling. previous yield.--there are certain types of ore where the previous yield from known space becomes the essential basis of determination of quantity and metal contents of ore standing and of the future probabilities. where metals occur like plums in a pudding, sampling becomes difficult and unreliable, and where experience has proved a sort of regularity of recurrence of these plums, dependence must necessarily be placed on past records, for if their reliability is to be questioned, resort must be had to extensive test-treatment runs. the lake superior copper mines and the missouri lead and zinc mines are of this type of deposit. on the other sorts of deposits the previous yield is often put forward as of important bearing on the value of the ore standing, but such yield, unless it can be _authentically_ connected with blocks of ore remaining, is not necessarily a criterion of their contents. except in the cases mentioned, and as a check on other methods of determination, it has little place in final conclusions. test parcels.--treatment on a considerable scale of sufficiently regulated parcels, although theoretically the ideal method, is, however, not often within the realm of things practical. in examination on behalf of intending purchasers, the time, expense, or opportunity to fraud are usually prohibitive, even where the plant and facilities for such work exist. even in cases where the engineer in management of producing mines is desirous of determining the value of standing ore, with the exception of deposits of the type mentioned above, it is ordinarily done by actual sampling, because separate mining and treatment of test lots is generally inconvenient and expensive. as a result, the determination of the value of standing ore is, in the great majority of cases, done by sampling and assaying. sampling.--the whole theory of sampling is based on the distribution of metals through the ore-body with more or less regularity, so that if small portions, that is samples, be taken from a sufficient number of points, their average will represent fairly closely the unit value of the ore. if the ore is of the extreme type of irregular metal distribution mentioned under "previous yield," then sampling has no place. how frequently samples must be taken, the manner of taking them, and the quantity that constitutes a fair sample, are matters that vary with each mine. so much depends upon the proper performance of this task that it is in fact the most critical feature of mine examination. ten samples properly taken are more valuable than five hundred slovenly ones, like grab samples, for such a number of bad ones would of a surety lead to wholly wrong conclusions. given a good sampling and a proper assay plan, the valuation of a mine is two-thirds accomplished. it should be an inflexible principle in examinations for purchase that every sample must be taken under the personal supervision of the examining engineer or his trusted assistants. aside from throwing open the doors to fraud, the average workman will not carry out the work in a proper manner, unless under constant supervision, because of his lack of appreciation of the issues involved. sampling is hard, uncongenial, manual labor. it requires a deal of conscientiousness to take enough samples and to take them thoroughly. the engineer does not exist who, upon completion of this task, considers that he has got too many, and most wish that they had taken more. the accuracy of sampling as a method of determining the value of standing ore is a factor of the number of samples taken. the average, for example, of separate samples from each square inch would be more accurate than those from each alternate square inch. however, the accumulated knowledge and experience as to the distribution of metals through ore has determined approximately the manner of taking such samples, and the least number which will still by the law of averages secure a degree of accuracy commensurate with the other factors of estimation. as metals are distributed through ore-bodies of fissure origin with most regularity on lines parallel to the strike and dip, an equal portion of ore from every point along cross-sections at right angles to the strike will represent fairly well the average values for a certain distance along the strike either side of these cross-sections. in massive deposits, sample sections are taken in all directions. the intervals at which sample sections must be cut is obviously dependent upon the general character of the deposit. if the values are well distributed, a longer interval may be employed than in one subject to marked fluctuations. as a general rule, five feet is the distance most accepted. this, in cases of regular distribution of values, may be stretched to ten feet, or in reverse may be diminished to two or three feet. the width of ore which may be included for one sample is dependent not only upon the width of the deposit, but also upon its character. where the ore is wider than the necessary stoping width, the sample should be regulated so as to show the possible locus of values. the metal contents may be, and often are, particularly in deposits of the impregnation or replacement type, greater along some streak in the ore-body, and this difference may be such as to make it desirable to stope only a portion of the total thickness. for deposits narrower than the necessary stoping width the full breadth of ore should be included in one sample, because usually the whole of the deposit will require to be broken. in order that a payable section may not possibly be diluted with material unnecessary to mine, if the deposit is over four feet and under eight feet, the distance across the vein or lode is usually divided into two samples. if still wider, each is confined to a span of about four feet, not only for the reason given above, but because the more numerous the samples, the greater the accuracy. thus, in a deposit twenty feet wide it may be taken as a good guide that a test section across the ore-body should be divided into five parts. as to the physical details of sample taking, every engineer has his own methods and safeguards against fraud and error. in a large organization of which the writer had for some years the direction, and where sampling of mines was constantly in progress on an extensive scale, not only in contemplation of purchase, but where it was also systematically conducted in operating mines for working data, he adopted the above general lines and required the following details. a fresh face of ore is first broken and then a trench cut about five inches wide and two inches deep. this trench is cut with a hammer and moil, or, where compressed air is available and the rock hard, a small air-drill of the hammer type is used. the spoil from the trench forms the sample, and it is broken down upon a large canvas cloth. afterwards it is crushed so that all pieces will pass a half-inch screen, mixed and quartered, thus reducing the weight to half. whether it is again crushed and quartered depends upon what the conditions are as to assaying. if convenient to assay office, as on a going mine, the whole of the crushing and quartering work can be done at that office, where there are usually suitable mechanical appliances. if the samples must be taken a long distance, the bulk for transport can be reduced by finer breaking and repeated quartering, until there remain only a few ounces. precautions against fraud.--much has been written about the precautions to be taken against fraud in cases of valuations for purchase. the best safeguards are an alert eye and a strong right arm. however, certain small details help. a large leather bag, arranged to lock after the order of a mail sack, into which samples can be put underground and which is never unfastened except by responsible men, not only aids security but relieves the mind. a few samples of country rock form a good check, and notes as to the probable value of the ore, from inspection when sampling, are useful. a great help in examination is to have the assays or analyses done coincidentally with the sampling. a doubt can then always be settled by resampling at once, and much knowledge can be gained which may relieve so exhaustive a program as might be necessary were results not known until after leaving the mine. assay of samples.--two assays, or as the case may be, analyses, are usually made of every sample and their average taken. in the case of erratic differences a third determination is necessary. assay plans.--an assay plan is a plan of the workings, with the location, assay value, and width of the sample entered upon it. in a mine with a narrow vein or ore-body, a longitudinal section is sufficient base for such entries, but with a greater width than one sample span it is desirable to make preliminary plans of separate levels, winzes, etc., and to average the value of the whole payable widths on such plans before entry upon a longitudinal section. such a longitudinal section will, through the indicated distribution of values, show the shape of the ore-body--a step necessary in estimating quantities and of the most fundamental importance in estimating the probabilities of ore extension beyond the range of the openings. the final assay plan should show the average value of the several blocks of ore, and it is from these averages that estimates of quantities must be made up. calculations of averages.--the first step in arriving at average values is to reduce erratic high assays to the general tenor of other adjacent samples. this point has been disputed at some length, more often by promoters than by engineers, but the custom is very generally and rightly adopted. erratically high samples may indicate presence of undue metal in the assay attributable to unconscious salting, for if the value be confined to a few large particles they may find their way through all the quartering into the assay. or the sample may actually indicate rich spots of ore; but in any event experience teaches that no dependence can be put upon regular recurrence of such abnormally rich spots. as will be discussed under percentage of error in sampling, samples usually indicate higher than the true value, even where erratic assays have been eliminated. there are cases of profitable mines where the values were all in spots, and an assay plan would show % of the assays _nil_, yet these pockets were so rich as to give value to the whole. pocket mines, as stated before, are beyond valuation by sampling, and aside from the previous yield recourse must be had to actual treatment runs on every block of ore separately. after reduction of erratic assays, a preliminary study of the runs of value or shapes of the ore-bodies is necessary before any calculation of averages. a preliminary delineation of the boundaries of the payable areas on the assay plan will indicate the sections of the mine which are unpayable, and from which therefore samples can be rightly excluded in arriving at an average of the payable ore (fig. ). in a general way, only the ore which must be mined need be included in averaging. the calculation of the average assay value of standing ore from samples is one which seems to require some statement of elementals. although it may seem primitive, it can do no harm to recall that if a dump of two tons of ore assaying twenty ounces per ton be added to a dump of five tons averaging one ounce per ton, the result has not an average assay of twenty-one ounces divided by the number of dumps. likewise one sample over a width of two feet, assaying twenty ounces per ton, if averaged with another sample over a width of five feet, assaying one ounce, is no more twenty-one ounces divided by two samples than in the case of the two dumps. if common sense were not sufficient demonstration of this, it can be shown algebraically. were samples equidistant from each other, and were they of equal width, the average value would be the simple arithmetical mean of the assays. but this is seldom the case. the number of instances, not only in practice but also in technical literature, where the fundamental distinction between an arithmetical and a geometrical mean is lost sight of is amazing. to arrive at the average value of samples, it is necessary, in effect, to reduce them to the actual quantity of the metal and volume of ore represented by each. the method of calculation therefore is one which gives every sample an importance depending upon the metal content of the volume of ore it represents. the volume of ore appertaining to any given sample can be considered as a prismoid, the dimensions of which may be stated as follows:-- _w_ = width in feet of ore sampled. _l_ = length in feet of ore represented by the sample. _d_ = depth into the block to which values are assumed to penetrate. we may also let:-- _c_ = the number of cubic feet per ton of ore. _v_ = assay value of the sample. then _wld_/c_ = tonnage of the prismoid.* _v wld_/c_ = total metal contents. [footnote *: strictly, the prismoidal formula should be used, but it complicates the study unduly, and for practical purposes the above may be taken as the volume.] the average value of a number of samples is the total metal contents of their respective prismoids, divided by the total tonnage of these prismoids. if we let _w_, _w_ , _v_, _v_ etc., represent different samples, we have:-- _v(_wld_/_c_) + _v_ (_w_ _l_ _d_ /_c_) + _v_ (_w_ _l_ _d_ /_c_) --------------------------------------------------------------------- _wld_/_c_ + _w_ _l_ _d_ /_c_ + _w_ _l_ _d_ /_c_ = average value. this may be reduced to:-- (_vwld_) + (_v_ _w_ _l_ _d_ ) + (_v_ _w_ _l_ _d_ ,), etc. --------------------------------------------------------------- (_wld_) + (_w_ _l_ _d_ ) + (_w_ _l_ _d_ ), etc. as a matter of fact, samples actually represent the value of the outer shell of the block of ore only, and the continuity of the same values through the block is a geological assumption. from the outer shell, all the values can be taken to penetrate equal distances into the block, and therefore _d_, _d_ , _d_ may be considered as equal and the equation becomes:-- (_vwl_) + (_v_ _w_ _l_ ) + (_v_ _w_ _l_ ), etc. --------------------------------------------------- (_wl_) + (_w_ _l_ ) + (_w_ _l_ ), etc. the length of the prismoid base _l_ for any given sample will be a distance equal to one-half the sum of the distances to the two adjacent samples. as a matter of practice, samples are usually taken at regular intervals, and the lengths _l_, _l_ , _l_ becoming thus equal can in such case be eliminated, and the equation becomes:-- (_vw_) + (_v_ _w_ ) + (_v_ _w_ ), etc. ---------------------------------------- _w_ + _w_ + _w_ , etc. the name "assay foot" or "foot value" has been given to the relation _vw_, that is, the assay value multiplied by the width sampled.[*] it is by this method that all samples must be averaged. the same relation obviously can be evolved by using an inch instead of a foot, and in narrow veins the assay inch is generally used. [footnote *: an error will be found in this method unless the two end samples be halved, but in a long run of samples this may be disregarded.] where the payable cross-section is divided into more than one sample, the different samples in the section must be averaged by the above formula, before being combined with the adjacent section. where the width sampled is narrower than the necessary stoping width, and where the waste cannot be broken separately, the sample value must be diluted to a stoping width. to dilute narrow samples to a stoping width, a blank value over the extra width which it is necessary to include must be averaged with the sample from the ore on the above formula. cases arise where, although a certain width of waste must be broken with the ore, it subsequently can be partially sorted out. practically nothing but experience on the deposit itself will determine how far this will restore the value of the ore to the average of the payable seam. in any event, no sorting can eliminate all such waste; and it is necessary to calculate the value on the breaking width, and then deduct from the gross tonnage to be broken a percentage from sorting. there is always an allowance to be made in sorting for a loss of good ore with the discards. percentage of error in estimates from sampling.--it must be remembered that the whole theory of estimation by sampling is founded upon certain assumptions as to evenness of continuity and transition in value and volume. it is but a basis for an estimate, and an estimate is not a statement of fact. it cannot therefore be too forcibly repeated that an estimate is inherently but an approximation, take what care one may in its founding. while it is possible to refine mathematical calculation of averages to almost any nicety, beyond certain essentials it adds nothing to accuracy and is often misleading. it is desirable to consider where errors are most likely to creep in, assuming that all fundamental data are both accurately taken and considered. sampling of ore _in situ_ in general has a tendency to give higher average value than the actual reduction of the ore will show. on three west australian gold mines, in records covering a period of over two years, where sampling was most exhaustive as a daily régime of the mines, the values indicated by sampling were % higher than the mill yield plus the contents of the residues. on the witwatersrand gold mines, the actual extractable value is generally considered to be about to % of the average shown by sampling, while the mill extractions are on average about to % of the head value coming to the mill. in other words, there is a constant discrepancy of about to % between the estimated value as indicated by mine samples, and the actual value as shown by yield plus the residues. at broken hill, on three lead mines, the yield is about % less than sampling would indicate. this constancy of error in one direction has not been so generally acknowledged as would be desirable, and it must be allowed for in calculating final results. the causes of the exaggeration seem to be:-- _first_, inability to stope a mine to such fine limitations of width, or exclusion of unpayable patches, as would appear practicable when sampling, that is by the inclusion when mining of a certain amount of barren rock. even in deposits of about normal stoping width, it is impossible to prevent the breaking of a certain amount of waste, even if the ore occurrence is regularly confined by walls. if the mine be of the impregnation type, such as those at goldfield, or kalgoorlie, with values like plums in a pudding, and the stopes themselves directed more by assays than by any physical differences in the ore, the discrepancy becomes very much increased. in mines where the range of values is narrower than the normal stoping width, some wall rock must be broken. although it is customary to allow for this in calculating the average value from samples, the allowance seldom seems enough. in mines where the ore is broken on to the top of stopes filled with waste, there is some loss underground through mixture with the filling. _second_, the metal content of ores, especially when in the form of sulphides, is usually more friable than the matrix, and in actual breaking of samples an undue proportion of friable material usually creeps in. this is true more in lead, copper, and zinc, than in gold ores. on several gold mines, however, tests on accumulated samples for their sulphide percentage showed a distinctly greater ratio than the tenor of the ore itself in the mill. as the gold is usually associated with the sulphides, the samples showed higher values than the mill. in general, some considerable factor of safety must be allowed after arriving at calculated average of samples,--how much it is difficult to say, but, in any event, not less than %. chapter ii. mine valuation (_continued_). calculation of quantities of ore, and classification of ore in sight. as mines are opened by levels, rises, etc., through the ore, an extension of these workings has the effect of dividing it into "blocks." the obvious procedure in determining tonnages is to calculate the volume and value of each block separately. under the law of averages, the multiplicity of these blocks tends in proportion to their number to compensate the percentage of error which might arise in the sampling or estimating of any particular one. the shapes of these blocks, on longitudinal section, are often not regular geometrical figures. as a matter of practice, however, they can be subdivided into such figures that the total will approximate the whole with sufficient closeness for calculations of their areas. the average width of the ore in any particular block is the arithmetical mean of the width of the sample sections in it,[*] if the samples be an equal distance apart. if they are not equidistant, the average width is the sum of the areas between samples, divided by the total length sampled. the cubic foot contents of a particular block is obviously the width multiplied by the area of its longitudinal section. [footnote *: this is not strictly true unless the sum of the widths of the two end-sections be divided by two and the result incorporated in calculating the means. in a long series that error is of little importance.] the ratio of cubic feet to tons depends on the specific gravity of the ore, its porosity, and moisture. the variability of ores throughout the mine in all these particulars renders any method of calculation simply an approximation in the end. the factors which must remain unknown necessarily lead the engineer to the provision of a margin of safety, which makes mathematical refinement and algebraic formulæ ridiculous. there are in general three methods of determination of the specific volume of ores:-- _first_, by finding the true specific gravity of a sufficient number of representative specimens; this, however, would not account for the larger voids in the ore-body and in any event, to be anything like accurate, would be as expensive as sampling and is therefore of little more than academic interest. _second_, by determining the weight of quantities broken from measured spaces. this also would require several tests from different portions of the mine, and, in examinations, is usually inconvenient and difficult. yet it is necessary in cases of unusual materials, such as leached gossans, and it is desirable to have it done sooner or later in going mines, as a check. _third_, by an approximation based upon a calculation from the specific gravities of the predominant minerals in the ore. ores are a mixture of many minerals; the proportions vary through the same ore-body. despite this, a few partial analyses, which are usually available from assays of samples and metallurgical tests, and a general inspection as to the compactness of the ore, give a fairly reliable basis for approximation, especially if a reasonable discount be allowed for safety. in such discount must be reflected regard for the porosity of the ore, and the margin of safety necessary may vary from to %. if the ore is of unusual character, as in leached deposits, as said before, resort must be had to the second method. the following table of the weights per cubic foot and the number of cubic feet per ton of some of the principal ore-forming minerals and gangue rocks will be useful for approximating the weight of a cubic foot of ore by the third method. weights are in pounds avoirdupois, and two thousand pounds are reckoned to the ton. ============================================ | | number of | weight per | cubic feet | cubic foot | per ton of | | lb. ------------------|------------|------------ antimony | . | . sulphide | . | . arsenical pyrites | . | . barium sulphate | . | . calcium: | | fluorite | . | . gypsum | . | . calcite | . | . copper | . | . calcopyrite | . | . bornite | . | . malachite | . | . azurite | . | . chrysocolla | . | . iron (cast) | . | . magnetite | . | . hematite | . | . limonite | . | . pyrite | . | . carbonate | . | . lead | . | . galena | . | . carbonate | . | . manganese oxide | . | . rhodonite | . | . magnesite | . | . dolomite | . | . quartz | . | . quicksilver | . | . cinnabar | . | . sulphur | . | . tin | . | . oxide | . | . zinc | . | . blende | . | . carbonate | . | . silicate | . | . andesite | . | . granite | . | . diabase | . | . diorite | . | . slates | . | . sandstones | . | . rhyolite | . | . ============================================ the specific gravity of any particular mineral has a considerable range, and a medium has been taken. the possible error is inconsequential for the purpose of these calculations. for example, a representative gold ore may contain in the main % quartz, and % iron pyrite, and the weight of the ore may be deduced as follows:-- quartz, % x . = . iron pyrite, % x . = . ----- . cubic feet per ton. most engineers, to compensate porosity, would allow twelve to thirteen cubic feet per ton. classification of ore in sight. the risk in estimates of the average value of standing ore is dependent largely upon how far values disclosed by sampling are assumed to penetrate beyond the tested face, and this depends upon the geological character of the deposit. from theoretical grounds and experience, it is known that such values will have some extension, and the assumption of any given distance is a calculation of risk. the multiplication of development openings results in an increase of sampling points available and lessens the hazards. the frequency of such openings varies in different portions of every mine, and thus there are inequalities of risk. it is therefore customary in giving estimates of standing ore to classify the ore according to the degree of risk assumed, either by stating the number of sides exposed or by other phrases. much discussion and ink have been devoted to trying to define what risk may be taken in such matters, that is in reality how far values may be assumed to penetrate into the unbroken ore. still more has been consumed in attempts to coin terms and make classifications which will indicate what ratio of hazard has been taken in stating quantities and values. the old terms "ore in sight" and "profit in sight" have been of late years subject to much malediction on the part of engineers because these expressions have been so badly abused by the charlatans of mining in attempts to cover the flights of their imaginations. a large part of volume x of the "institution of mining and metallurgy" has been devoted to heaping infamy on these terms, yet not only have they preserved their places in professional nomenclature, but nothing has been found to supersede them. some general term is required in daily practice to cover the whole field of visible ore, and if the phrase "ore in sight" be defined, it will be easier to teach the laymen its proper use than to abolish it. in fact, the substitutes are becoming abused as much as the originals ever were. all convincing expressions will be misused by somebody. the legitimate direction of reform has been to divide the general term of "ore in sight" into classes, and give them names which will indicate the variable amount of risk of continuity in different parts of the mine. as the frequency of sample points, and consequently the risk of continuity, will depend upon the detail with which the mine is cut into blocks by the development openings, and upon the number of sides of such blocks which are accessible, most classifications of the degree of risk of continuity have been defined in terms of the number of sides exposed in the blocks. many phrases have been coined to express such classifications; those most currently used are the following:-- positive ore \ ore exposed on four sides in blocks of a size ore developed / variously prescribed. ore blocked out ore exposed on three sides within reasonable distance of each other. probable ore \ ore developing / ore exposed on two sides. possible ore \ the whole or a part of the ore below the ore expectant / lowest level or beyond the range of vision. no two of these parallel expressions mean quite the same thing; each more or less overlies into another class, and in fact none of them is based upon a logical footing for such a classification. for example, values can be assumed to penetrate some distance from every sampled face, even if it be only ten feet, so that ore exposed on one side will show some "positive" or "developed" ore which, on the lines laid down above, might be "probable" or even "possible" ore. likewise, ore may be "fully developed" or "blocked out" so far as it is necessary for stoping purposes with modern wide intervals between levels, and still be in blocks too large to warrant an assumption of continuity of values to their centers (fig. ). as to the third class of "possible" ore, it conveys an impression of tangibility to a nebulous hazard, and should never be used in connection with positive tonnages. this part of the mine's value comes under extension of the deposit a long distance beyond openings, which is a speculation and cannot be defined in absolute tons without exhaustive explanation of the risks attached, in which case any phrase intended to shorten description is likely to be misleading. [illustration: fig. .--longitudinal section of a mine, showing classification of the exposed ore. scale, feet = inch.] therefore empirical expressions in terms of development openings cannot be made to cover a geologic factor such as the distribution of metals through a rock mass. the only logical basis of ore classification for estimation purposes is one which is founded on the chances of the values penetrating from the surface of the exposures for each particular mine. ore that may be calculated upon to a certainty is that which, taking into consideration the character of the deposit, can be said to be so sufficiently surrounded by sampled faces that the distance into the mass to which values are assumed to extend is reduced to a minimum risk. ore so far removed from the sampled face as to leave some doubt, yet affording great reason for expectation of continuity, is "probable" ore. the third class of ore mentioned, which is that depending upon extension of the deposit and in which, as said above, there is great risk, should be treated separately as the speculative value of the mine. some expressions are desirable for these classifications, and the writer's own preference is for the following, with a definition based upon the controlling factor itself. they are:-- proved ore ore where there is practically no risk of failure of continuity. probable ore ore where there is some risk, yet warrantable justification for assumption of continuity. prospective ore ore which cannot be included in the above classes, nor definitely known or stated in any terms of tonnage. what extent of openings, and therefore of sample faces, is required for the ore to be called "proved" varies naturally with the type of deposit,--in fact with each mine. in a general way, a fair rule in gold quartz veins below influence of secondary alteration is that no point in the block shall be over fifty feet from the points sampled. in limestone or andesite replacements, as by gold or lead or copper, the radius must be less. in defined lead and copper lodes, or in large lenticular bodies such as the tennessee copper mines, the radius may often be considerably greater,--say one hundred feet. in gold deposits of such extraordinary regularity of values as the witwatersrand bankets, it can well be two hundred or two hundred and fifty feet. "probable ore" should be ore which entails continuity of values through a greater distance than the above, and such distance must depend upon the collateral evidence from the character of the deposit, the position of openings, etc. ore beyond the range of the "probable" zone is dependent upon the extension of the deposit beyond the realm of development and will be discussed separately. although the expression "ore in sight" may be deprecated, owing to its abuse, some general term to cover both "positive" and "probable" ore is desirable; and where a general term is required, it is the intention herein to hold to the phrase "ore in sight" under the limitations specified. chapter iii. mine valuation (_continued_). prospective value.[*] extension in depth; origin and structural character of the deposit; secondary enrichment; development in neighboring mines; depth of exhaustion. [footnote *: the term "extension in depth" is preferred by many to the phrase "prospective value." the former is not entirely satisfactory, as it has a more specific than general application. it is, however, a current miner's phrase, and is more expressive. in this discussion "extension in depth" is used synonymously, and it may be taken to include not alone the downward prolongation of the ore below workings, but also the occasional cases of lateral extension beyond the range of development work. the commonest instance is continuance below the bottom level. in any event, to the majority of cases of different extension the same reasoning applies.] it is a knotty problem to value the extension of a deposit beyond a short distance from the last opening. a short distance beyond it is "proved ore," and for a further short distance is "probable ore." mines are very seldom priced at a sum so moderate as that represented by the profit to be won from the ore in sight, and what value should be assigned to this unknown portion of the deposit admits of no certainty. no engineer can approach the prospective value of a mine with optimism, yet the mining industry would be non-existent to-day were it approached with pessimism. any value assessed must be a matter of judgment, and this judgment based on geological evidence. geology is not a mathematical science, and to attach a money equivalence to forecasts based on such evidence is the most difficult task set for the mining engineer. it is here that his view of geology must differ from that of his financially more irresponsible brother in the science. the geologist, contributing to human knowledge in general, finds his most valuable field in the examination of mines largely exhausted. the engineer's most valuable work arises from his ability to anticipate in the youth of the mine the symptoms of its old age. the work of our geologic friends is, however, the very foundation on which we lay our forecasts. geologists have, as the result of long observation, propounded for us certain hypotheses which, while still hypotheses, have proved to account so widely for our underground experience that no engineer can afford to lose sight of them. although there is a lack of safety in fixed theories as to ore deposition, and although such conclusions cannot be translated into feet and metal value, they are nevertheless useful weights on the scale where probabilities are to be weighed. a method in vogue with many engineers is, where the bottom level is good, to assume the value of the extension in depth as a sum proportioned to the profit in sight, and thus evade the use of geological evidence. the addition of various percentages to the profit in sight has been used by engineers, and proposed in technical publications, as varying from to %. that is, they roughly assess the extension in depth to be worth one-fifth to one-third of the whole value of an equipped mine. while experience may have sometimes demonstrated this to be a practical method, it certainly has little foundation in either science or logic, and the writer's experience is that such estimates are untrue in practice. the quantity of ore which may be in sight is largely the result of managerial policy. a small mill on a large mine, under rapid development, will result in extensive ore-reserves, while a large mill eating away rapidly on the same mine under the same scale of development would leave small reserves. on the above scheme of valuation the extension in depth would be worth very different sums, even when the deepest level might be at the same horizon in both cases. moreover, no mine starts at the surface with a large amount of ore in sight. yet as a general rule this is the period when its extension is most valuable, for when the deposit is exhausted to feet, it is not likely to have such extension in depth as when opened one hundred feet, no matter what the ore-reserves may be. further, such bases of valuation fail to take into account the widely varying geologic character of different mines, and they disregard any collateral evidence either of continuity from neighboring development, or from experience in the district. logically, the prospective value can be simply a factor of how _far_ the ore in the individual mine may be expected to extend, and not a factor of the remnant of ore that may still be unworked above the lowest level. an estimation of the chances of this extension should be based solely on the local factors which bear on such extension, and these are almost wholly dependent upon the character of the deposit. these various geological factors from a mining engineer's point of view are:-- . the origin and structural character of the ore-deposit. . the position of openings in relation to secondary alteration. . the size of the deposit. . the depth to which the mine has already been exhausted. . the general experience of the district for continuity and the development of adjoining mines. the origin and structural character of the deposit.--in a general way, the ore-deposits of the order under discussion originate primarily through the deposition of metals from gases or solutions circulating along avenues in the earth's crust.[*] the original source of metals is a matter of great disagreement, and does not much concern the miner. to him, however, the origin and character of the avenue of circulation, the enclosing rock, the influence of the rocks on the solution, and of the solutions on the rocks, have a great bearing on the probable continuity of the volume and value of the ore. [footnote *: the class of magmatic segregations is omitted, as not being of sufficiently frequent occurrence in payable mines to warrant troubling with it here.] all ore-deposits vary in value and, in the miner's view, only those portions above the pay limit are ore-bodies, or ore-shoots. the localization of values into such pay areas in an ore-deposit are apparently influenced by: . the distribution of the open spaces created by structural movement, fissuring, or folding as at bendigo. . the intersection of other fractures which, by mingling of solutions from different sources, provided precipitating conditions, as shown by enrichments at cross-veins. . the influence of the enclosing rocks by:-- (a) their solubility, and therefore susceptibility to replacement. (b) their influence as a precipitating agent on solutions. (c) their influence as a source of metal itself. (d) their texture, in its influence on the character of the fracture. in homogeneous rocks the tendency is to open clean-cut fissures; in friable rocks, zones of brecciation; in slates or schistose rocks, linked lenticular open spaces;--these influences exhibiting themselves in miner's terms respectively in "well-defined fissure veins," "lodes," and "lenses." (e) the physical character of the rock mass and the dynamic forces brought to bear upon it. this is a difficult study into the physics of stress in cases of fracturing, but its local application has not been without results of an important order. . secondary alteration near the surface, more fully discussed later. it is evident enough that the whole structure of the deposit is a necessary study, and even a digest of the subject is not to be compressed into a few paragraphs. from the point of view of continuity of values, ore-deposits may be roughly divided into three classes. they are:-- . deposits of the infiltration type in porous beds, such as lake superior copper conglomerates and african gold bankets. . deposits of the fissure vein type, such as california quartz veins. . replacement or impregnation deposits on the lines of fissuring or otherwise. in a general way, the uniformity of conditions of deposition in the first class has resulted in the most satisfactory continuity of ore and of its metal contents. in the second, depending much upon the profundity of the earth movements involved, there is laterally and vertically a reasonable basis for expectation of continuity but through much less distance than in the first class. the third class of deposits exhibits widely different phenomena as to continuity and no generalization is of any value. in gold deposits of this type in west australia, colorado, and nevada, continuity far beyond a sampled face must be received with the greatest skepticism. much the same may be said of most copper replacements in limestone. on the other hand the most phenomenal regularity of values have been shown in certain utah and arizona copper mines, the result of secondary infiltration in porphyritic gangues. the mississippi valley lead and zinc deposits, while irregular in detail, show remarkable continuity by way of reoccurrence over wide areas. the estimation of the prospective value of mines where continuity of production is dependent on reoccurrence of ore-bodies somewhat proportional to the area, such as these mississippi deposits or to some extent as in cobalt silver veins, is an interesting study, but one that offers little field for generalization. the position of the openings in relation to secondary alteration.--the profound alteration of the upper section of ore-deposits by oxidation due to the action of descending surface waters, and their associated chemical agencies, has been generally recognized for a great many years. only recently, however, has it been appreciated that this secondary alteration extends into the sulphide zone as well. the bearing of the secondary alteration, both in the oxidized and upper sulphide zones, is of the most sweeping economic character. in considering extension of values in depth, it demands the most rigorous investigation. not only does the metallurgical character of the ores change with oxidation, but the complex reactions due to descending surface waters cause leaching and a migration of metals from one horizon to another lower down, and also in many cases a redistribution of their sequence in the upper zones of the deposit. the effect of these agencies has been so great in many cases as to entirely alter the character of the mine and extension in depth has necessitated a complete reëquipment. for instance, the mt. morgan gold mine, queensland, has now become a copper mine; the copper mines at butte were formerly silver mines; leadville has become largely a zinc producer instead of lead. from this alteration aspect ore-deposits may be considered to have four horizons:-- . the zone near the outcrop, where the dominating feature is oxidation and leaching of the soluble minerals. . a lower horizon, still in the zone of oxidation, where the predominant feature is the deposition of metals as native, oxides, and carbonates. . the upper horizon of the sulphide zone, where the special feature is the enrichment due to secondary deposition as sulphides. . the region below these zones of secondary alteration, where the deposit is in its primary state. these zones are seldom sharply defined, nor are they always all in evidence. how far they are in evidence will depend, among other things, upon the amount and rapidity of erosion, the structure and mineralogical character of the deposit, and upon the enclosing rock. if erosion is extremely rapid, as in cold, wet climates, and rough topography, or as in the case of glaciation of the lake copper deposits, denudation follows close on the heels of alteration, and the surface is so rapidly removed that we may have the primary ore practically at the surface. flat, arid regions present the other extreme, for denudation is much slower, and conditions are most perfect for deep penetration of oxidizing agencies, and the consequent alteration and concentration of the metals. the migration of metals from the top of the oxidized zone leaves but a barren cap for erosion. the consequent effect of denudation that lags behind alteration is to raise slowly the concentrated metals toward the surface, and thus subject them to renewed attack and repeated migration. in this manner we can account for the enormous concentration of values in the lower oxidized and upper sulphide zones overlying very lean sulphides in depth. some minerals are more freely soluble and more readily precipitated than others. from this cause there is in complex metal deposits a rearrangement of horizontal sequence, in addition to enrichment at certain horizons and impoverishment at others. the whole subject is one of too great complexity for adequate consideration in this discussion. no engineer is properly equipped to give judgment on extension in depth without a thorough grasp of the great principles laid down by van hise, emmons, lindgren, weed, and others. we may, however, briefly examine some of the theoretical effects of such alteration. zinc, iron, and lead sulphides are a common primary combination. these metals are rendered soluble from their usual primary forms by oxidizing agencies, in the order given. they reprecipitate as sulphides in the reverse sequence. the result is the leaching of zinc and iron readily in the oxidized zone, thus differentially enriching the lead which lags behind, and a further extension of the lead horizon is provided by the early precipitation of such lead as does migrate. therefore, the lead often predominates in the second and the upper portion of the third zone, with the zinc and iron below. although the action of all surface waters is toward oxidation and carbonation of these metals, the carbonate development of oxidized zones is more marked when the enclosing rocks are calcareous. in copper-iron deposits, the comparatively easy decomposition and solubility and precipitation of the copper and some iron salts generally result in more extensive impoverishment of these metals near the surface, and more predominant enrichment at a lower horizon than is the case with any other metals. the barren "iron hat" at the first zone, the carbonates and oxides at the second, the enrichment with secondary copper sulphides at the top of the third, and the occurrence of secondary copper-iron sulphides below, are often most clearly defined. in the easy recognition of the secondary copper sulphides, chalcocite, bornite, etc., the engineer finds a finger-post on the road to extension in depth; and the directions upon this post are not to be disregarded. the number of copper deposits enriched from unpayability in the first zone to a profitable character in the next two, and unpayability again in the fourth, is legion. silver occurs most abundantly in combination with either lead, copper, iron, or gold. as it resists oxidation and solution more strenuously than copper and iron, its tendency when in combination with them is to lag behind in migration. there is thus a differential enrichment of silver in the upper two zones, due to the reduction in specific gravity of the ore by the removal of associated metals. silver does migrate somewhat, however, and as it precipitates more readily than copper, lead, zinc, or iron, its tendency when in combination with them is towards enrichment above the horizons of enrichment of these metals. when it is in combination with lead and zinc, its very ready precipitation from solution by the galena leaves it in combination more predominantly with the lead. the secondary enrichment of silver deposits at the top of the sulphide zone is sometimes a most pronounced feature, and it seems to be the explanation of the origin of many "bonanzas." in gold deposits, the greater resistance to solubility of this metal than most of the others, renders the phenomena of migration to depth less marked. further than this, migration is often interfered with by the more impervious quartz matrix of many gold deposits. where gold is associated with large quantities of base metals, however, the leaching of the latter in the oxidized zone leaves the ore differentially richer, and as gold is also slightly soluble, in such cases the migration of the base metals does carry some of the gold. in the instance especially of impregnation or replacement deposits, where the matrix is easily permeable, the upper sulphide zone is distinctly richer than lower down, and this enrichment is accompanied by a considerable increase in sulphides and tellurides. the predominant characteristic of alteration in gold deposits is, however, enrichment in the oxidized zone with the maximum values near the surface. the reasons for this appear to be that gold in its resistance to oxidation and wholesale migration gives opportunities to a sort of combined mechanical and chemical enrichment. in dry climates, especially, the gentleness of erosion allows of more thorough decomposition of the outcroppings, and a mechanical separation of the gold from the detritus. it remains on or near the deposit, ready to be carried below, mechanically or otherwise. in wet climates this is less pronounced, for erosion bears away the croppings before such an extensive decomposition and freeing of the gold particles. the west australian gold fields present an especially prominent example of this type of superficial enrichment. during the last fifteen years nearly eight hundred companies have been formed for working mines in this region. although from four hundred of these high-grade ore has been produced, some thirty-three only have ever paid dividends. the great majority have been unpayable below oxidation,--a distance of one or two hundred feet. the writer's unvarying experience with gold is that it is richer in the oxidized zone than at any point below. while cases do occur of gold deposits richer in the upper sulphide zone than below, even the upper sulphides are usually poorer than the oxidized region. in quartz veins preëminently, evidence of enrichment in the third zone is likely to be practically absent. tin ores present an anomaly among the base metals under discussion, in that the primary form of this metal in most workable deposits is an oxide. tin in this form is most difficult of solution from ground agencies, as witness the great alluvial deposits, often of considerable geologic age. in consequence the phenomena of migration and enrichment are almost wholly absent, except such as are due to mechanical penetration of tin from surface decomposition of the matrix akin to that described in gold deposits. in general, three or four essential facts from secondary alteration must be kept in view when prognosticating extensions. oxidation usually alters treatment problems, and oxidized ore of the same grade as sulphides can often be treated more cheaply. this is not universal. low-grade ores of lead, copper, and zinc may be treatable by concentration when in the form of sulphides, and may be valueless when oxidized, even though of the same grade. copper ores generally show violent enrichment at the base of the oxidized, and at the top of the sulphide zone. lead-zinc ores show lead enrichment and zinc impoverishment in the oxidized zone but have usually less pronounced enrichment below water level than copper. the rearrangement of the metals by the deeper migration of the zinc, also renders them metallurgically of less value with depth. silver deposits are often differentially enriched in the oxidized zone, and at times tend to concentrate in the upper sulphide zone. gold deposits usually decrease in value from the surface through the whole of the three alteration zones. size of deposits.--the proverb of a relation between extension in depth and size of ore-bodies expresses one of the oldest of miners' beliefs. it has some basis in experience, especially in fissure veins, but has little foundation in theory and is applicable over but limited areas and under limited conditions. from a structural view, the depth of fissuring is likely to be more or less in proportion to its length and breadth and therefore the volume of vein filling with depth is likely to be proportional to length and width of the fissure. as to the distribution of values, if we eliminate the influence of changing wall rocks, or other precipitating agencies which often cause the values to arrange themselves in "floors," and of secondary alteration, there may be some reason to assume distribution of values of an extent equal vertically to that displayed horizontally. there is, as said, more reason in experience for this assumption than in theory. a study of the shape of a great many ore-shoots in mines of fissure type indicates that when the ore-shoots or ore-bodies are approaching vertical exhaustion they do not end abruptly, but gradually shorten and decrease in value, their bottom boundaries being more often wedge-shaped than even lenticular. if this could be taken as the usual occurrence, it would be possible (eliminating the evident exceptions mentioned above) to state roughly that the minimum extension of an ore-body or ore-shoot in depth below any given horizon would be a distance represented by a radius equal to one-half its length. by length is not meant necessarily the length of a horizontal section, but of one at right angles to the downward axis. on these grounds, which have been reënforced by much experience among miners, the probabilities of extension are somewhat in proportion to the length and width of each ore-body. for instance, in the a mine, with an ore-shoot feet long and feet wide, on its bottom level, the minimum extension under this hypothesis would be a wedge-shaped ore-body with its deepest point feet below the lowest level, or a minimum of say , tons. similarly, the b mine with five ore-bodies, each hundred feet long and feet wide, exposed on its lowest level, would have a minimum of five wedges feet deep at their deepest points, or say , tons. this is not proposed as a formula giving the total amount of extension in depth, but as a sort of yardstick which has experience behind it. this experience applies in a much less degree to deposits originating from impregnation along lines of fissuring and not at all to replacements. development in neighboring mines.--mines of a district are usually found under the same geological conditions, and show somewhat the same habits as to extension in depth or laterally, and especially similar conduct of ore-bodies and ore-shoots. as a practical criterion, one of the most intimate guides is the actual development in adjoining mines. for instance, in kalgoorlie, the great boulder mine is (march, ) working the extension of ivanhoe lodes at points feet below the lowest level in the ivanhoe; likewise, the block lead mine at broken hill is working the central ore-body on the central boundary some feet below the central workings. such facts as these must have a bearing on assessing the downward extension. depth of exhaustion.--all mines become completely exhausted at some point in depth. therefore the actual distance to which ore can be expected to extend below the lowest level grows less with every deeper working horizon. the really superficial character of ore-deposits, even outside of the region of secondary enrichment is becoming every year better recognized. the prospector's idea that "she gets richer deeper down," may have some basis near the surface in some metals, but it is not an idea which prevails in the minds of engineers who have to work in depth. the writer, with some others, prepared a list of several hundred dividend-paying metal mines of all sorts, extending over north and south america, australasia, england, and africa. notes were made as far as possible of the depths at which values gave out, and also at which dividends ceased. although by no means a complete census, the list indicated that not % of mines (outside banket) that have yielded profits, ever made them from ore won below feet. of mines that paid dividends, % did not show profitable value below feet, and a sad majority died above . failures at short depths may be blamed upon secondary enrichment, but the majority that reached below this influence also gave out. the geological reason for such general unseemly conduct is not so evident. conclusion.--as a practical problem, the assessment of prospective value is usually a case of "cut and try." the portion of the capital to be invested, which depends upon extension, will require so many tons of ore of the same value as that indicated by the standing ore, in order to justify the price. to produce this tonnage at the continued average size of the ore-bodies will require their extension in depth so many feet--or the discovery of new ore-bodies of a certain size. the five geological weights mentioned above may then be put into the scale and a basis of judgment reached. chapter iv. mine valuation (_continued_). recoverable percentage of the gross assay value; price of metals; cost of production. the method of treatment for the ore must be known before a mine can be valued, because a knowledge of the recoverable percentage is as important as that of the gross value of the ore itself. the recoverable percentage is usually a factor of working costs. practically every ore can be treated and all the metal contents recovered, but the real problem is to know the method and percentage of recovery which will yield the most remunerative result, if any. this limit to profitable recovery regulates the amount of metal which should be lost, and the amount of metal which consequently must be deducted from the gross value before the real net value of the ore can be calculated. here, as everywhere else in mining, a compromise has to be made with nature, and we take what we can get--profitably. for instance, a copper ore may be smelted and a % recovery obtained. under certain conditions this might be done at a loss, while the same ore might be concentrated before smelting and yield a profit with a % recovery. an additional % might be obtained by roasting and leaching the residues from concentration, but this would probably result in an expenditure far greater than the value of the % recovered. if the ore is not already under treatment on the mine, or exactly similar ore is not under treatment elsewhere, with known results, the method must be determined experimentally, either by the examining engineer or by a special metallurgist. where partially treated products, such as concentrates, are to be sold, not only will there be further losses, but deductions will be made by the smelter for deleterious metals and other charges. all of these factors must be found out,--and a few sample smelting returns from a similar ore are useful. to cover the whole field of metallurgy and discuss what might apply, and how it might apply, under a hundred supposititious conditions would be too great a digression from the subject in hand. it is enough to call attention here to the fact that the residues from every treatment carry some metal, and that this loss has to be deducted from the gross value of the ore in any calculations of net values. price of metals. unfortunately for the mining engineer, not only has he to weigh the amount of risk inherent in calculations involved in the mine itself, but also that due to fluctuations in the value of metals. if the ore is shipped to custom works, he has to contemplate also variations in freights and smelting charges. gold from the mine valuer's point of view has no fluctuations. it alone among the earth's products gives no concern as to the market price. the price to be taken for all other metals has to be decided before the mine can be valued. this introduces a further speculation and, as in all calculations of probabilities, amounts to an estimate of the amount of risk. in a free market the law of supply and demand governs the value of metals as it does that of all other commodities. so far, except for tariff walls and smelting rings, there is a free market in the metals under discussion. the demand for metals varies with the unequal fluctuations of the industrial tides. the sea of commercial activity is subject to heavy storms, and the mine valuer is compelled to serve as weather prophet on this ocean of trouble. high prices, which are the result of industrial booms, bring about overproduction, and the collapse of these begets a shrinkage of demand, wherein consequently the tide of price turns back. in mining for metals each pound is produced actually at a different cost. in case of an oversupply of base metals the price will fall until it has reached a point where a portion of the production is no longer profitable, and the equilibrium is established through decline in output. however, in the backward swing, due to lingering overproduction, prices usually fall lower than the cost of producing even a much-diminished supply. there is at this point what we may call the "basic" price, that at which production is insufficient and the price rises again. the basic price which is due to this undue backward swing is no more the real price of the metal to be contemplated over so long a term of years than is the highest price. at how much above the basic price of depressed times the product can be safely expected to find a market is the real question. few mines can be bought or valued at this basic price. an indication of what this is can be gained from a study of fluctuations over a long term of years. it is common to hear the average price over an extended period considered the "normal" price, but this basis for value is one which must be used with discretion, for it is not the whole question when mining. the "normal" price is the average price over a long term. the lives of mines, and especially ore in sight, may not necessarily enjoy the period of this "normal" price. the engineer must balance his judgments by the immediate outlook of the industrial weather. when lead was falling steadily in december, , no engineer would accept the price of that date, although it was then below "normal"; his product might go to market even lower yet. it is desirable to ascertain what the basic and normal prices are, for between them lies safety. since there have been three cycles of commercial expansion and contraction. if the average prices are taken for these three cycles separately ( - ), - , - ) it will be seen that there has been a steady advance in prices. for the succeeding cycles lead on the london exchange,[*] the freest of the world's markets was £ _s._ _d._, £ _s._ _d._, and £ _s._ _d._ respectively; zinc, £ _s._ _d._, £ _s._ _d._, and £ _s._ _d._; and standard copper, £ _s._ _d._, £ _s._ _d._, and £ _s._ _d._ it seems, therefore, that a higher standard of prices can be assumed as the basic and normal than would be indicated if the general average of, say, twenty years were taken. during this period, the world's gold output has nearly quadrupled, and, whether the quantitative theory of gold be accepted or not, it cannot be denied that there has been a steady increase in the price of commodities. in all base-metal mining it is well to remember that the production of these metals is liable to great stimulus at times from the discovery of new deposits or new processes of recovery from hitherto unprofitable ores. it is therefore for this reason hazardous in the extreme to prophesy what prices will be far in the future, even when the industrial weather is clear. but some basis must be arrived at, and from the available outlook it would seem that the following metal prices are justifiable for some time to come, provided the present tariff schedules are maintained in the united states: [footnote *: all london prices are based on the long ton of , lbs. much confusion exists in the copper trade as to the classification of the metal. new york prices are quoted in electrolytic and "lake"; london's in "standard." "standard" has now become practically an arbitrary term peculiar to london, for the great bulk of copper dealt in is "electrolytic" valued considerably over "standard."] ========================================================================== | lead | spelter | copper | tin | silver |------------|----------|----------|----------|--------------- |london| n.y.|lon.| n.y.|lon.| n.y.|lon.| n.y.| lon. | n.y. | ton |pound|ton |pound|ton |pound|ton |pound|per oz.|per oz. ------------|------|-----|----|-----|----|-----|----|-----|-------|------- basic price | £ . |$. |£ |$. |£ |$. |£ |$. | _d._|$. normal price| . | . | | . | | . | | . | | . ========================================================================== in these figures the writer has not followed strict averages, but has taken the general outlook combined with the previous records. the likelihood of higher prices for lead is more encouraging than for any other metal, as no new deposits of importance have come forward for years, and the old mines are reaching considerable depths. nor does the frenzied prospecting of the world's surface during the past ten years appear to forecast any very disturbing developments. the zinc future is not so bright, for metallurgy has done wonders in providing methods of saving the zinc formerly discarded from lead ores, and enormous supplies will come forward when required. the tin outlook is encouraging, for the supply from a mining point of view seems unlikely to more than keep pace with the world's needs. in copper the demand is growing prodigiously, but the supplies of copper ores and the number of copper mines that are ready to produce whenever normal prices recur was never so great as to-day. one very hopeful fact can be deduced for the comfort of the base metal mining industry as a whole. if the growth of demand continues through the next thirty years in the ratio of the past three decades, the annual demand for copper will be over , , tons, of lead over , , tons, of spelter , , tons, of tin , tons. where such stupendous amounts of these metals are to come from at the present range of prices, and even with reduced costs of production, is far beyond any apparent source of supply. the outlook for silver prices is in the long run not bright. as the major portion of the silver produced is a bye product from base metals, any increase in the latter will increase the silver production despite very much lower prices for the precious metal. in the meantime the gradual conversion of all nations to the gold standard seems a matter of certainty. further, silver may yet be abandoned as a subsidiary coinage inasmuch as it has now but a token value in gold standard countries if denuded of sentiment. cost of production. it is hardly necessary to argue the relative importance of the determination of the cost of production and the determination of the recoverable contents of the ore. obviously, the aim of mine valuation is to know the profits to be won, and the profit is the value of the metal won, less the cost of production. the cost of production embraces development, mining, treatment, management. further than this, it is often contended that, as the capital expended in purchase and equipment must be redeemed within the life of the mine, this item should also be included in production costs. it is true that mills, smelters, shafts, and all the paraphernalia of a mine are of virtually negligible value when it is exhausted; and that all mines are exhausted sometime and every ton taken out contributes to that exhaustion; and that every ton of ore must bear its contribution to the return of the investment, as well as profit upon it. therefore it may well be said that the redemption of the capital and its interest should be considered in costs per ton. the difficulty in dealing with the subject from the point of view of production cost arises from the fact that, except possibly in the case of banket gold and some conglomerate copper mines, the life of a metal mine is unknown beyond the time required to exhaust the ore reserves. the visible life at the time of purchase or equipment may be only three or four years, yet the average equipment has a longer life than this, and the anticipation for every mine is also for longer duration than the bare ore in sight. for clarity of conclusions in mine valuation the most advisable course is to determine the profit in sight irrespective of capital redemption in the first instance. the questions of capital redemption, purchase price, or equipment cost can then be weighed against the margin of profit. one phase of redemption will be further discussed under "amortization of capital" and "ratio of output to the mine." the cost of production depends upon many things, such as the cost of labor, supplies, the size of the ore-body, the treatment necessary, the volume of output, etc.; and to discuss them all would lead into a wilderness of supposititious cases. if the mine is a going concern, from which reliable data can be obtained, the problem is much simplified. if it is virgin, the experience of other mines in the same region is the next resource; where no such data can be had, the engineer must fall back upon the experience with mines still farther afield. use is sometimes made of the "comparison ton" in calculating costs upon mines where data of actual experience are not available. as costs will depend in the main upon items mentioned above, if the known costs of a going mine elsewhere be taken as a basis, and subtractions and additions made for more unfavorable or favorable effect of the differences in the above items, a fairly close result can be approximated. mine examinations are very often inspired by the belief that extended operations or new metallurgical applications to the mine will expand the profits. in such cases the paramount questions are the reduction of costs by better plant, larger outputs, new processes, or alteration of metallurgical basis and better methods. if every item of previous expenditure be gone over and considered, together with the equipment, and method by which it was obtained, the possible savings can be fairly well deduced, and justification for any particular line of action determined. one view of this subject will be further discussed under "ratio of output to the mine." the conditions which govern the working costs are on every mine so special to itself, that no amount of advice is very useful. volumes of advice have been published on the subject, but in the main their burden is not to underestimate. in considering the working costs of base-metal mines, much depends upon the opportunity for treatment in customs works, smelters, etc. such treatment means a saving of a large portion of equipment cost, and therefore of the capital to be invested and subsequently recovered. the economics of home treatment must be weighed against the sum which would need to be set aside for redemption of the plant, and unless there is a very distinct advantage to be had by the former, no risks should be taken. more engineers go wrong by the erection of treatment works where other treatment facilities are available, than do so by continued shipping. there are many mines where the cost of equipment could never be returned, and which would be valueless unless the ore could be shipped. another phase of foreign treatment arises from the necessity or advantage of a mixture of ores,--the opportunity of such mixtures often gives the public smelter an advantage in treatment with which treatment on the mine could never compete. fluctuation in the price of base metals is a factor so much to be taken into consideration, that it is desirable in estimating mine values to reduce the working costs to a basis of a "per unit" of finished metal. this method has the great advantage of indicating so simply the involved risks of changing prices that whoso runs may read. where one metal predominates over the other to such an extent as to form the "backbone" of the value of the mine, the value of the subsidiary metals is often deducted from the cost of the principal metal, in order to indicate more plainly the varying value of the mine with the fluctuating prices of the predominant metal. for example, it is usual to state that the cost of copper production from a given ore will be so many cents per pound, or so many pounds sterling per ton. knowing the total metal extractable from the ore in sight, the profits at given prices of metal can be readily deduced. the point at which such calculation departs from the "per-ton-of-ore" unto the per-unit-cost-of-metal basis, usually lies at the point in ore dressing where it is ready for the smelter. to take a simple case of a lead ore averaging %: this is to be first concentrated and the lead reduced to a concentrate averaging % and showing a recovery of % of the total metal content. the cost per ton of development, mining, concentration, management, is to this point say $ per ton of original crude ore. the smelter buys the concentrate for % of the value of the metal, less the smelting charge of $ per ton, or there is a working cost of a similar sum by home equipment. in this case . tons of ore are required to produce one ton of concentrates, and therefore each ton of concentrates costs $ . . this amount, added to the smelting charge, gives a total of $ . for the creation of % of one ton of finished lead, or equal to . cents per pound which can be compared with the market price less %. if the ore were to contain ounces of silver per ton, of which ounces were recovered into the leady concentrates, and the smelter price for the silver were cents per ounce, then the $ . thus recovered would be subtracted from $ . , making the apparent cost of the lead . cents per pound. chapter v. mine valuation (_continued_). redemption or amortization of capital and interest. it is desirable to state in some detail the theory of amortization before consideration of its application in mine valuation. as every mine has a limited life, the capital invested in it must be redeemed during the life of the mine. it is not sufficient that there be a bare profit over working costs. in this particular, mines differ wholly from many other types of investment, such as railways. in the latter, if proper appropriation is made for maintenance, the total income to the investor can be considered as interest or profit; but in mines, a portion of the annual income must be considered as a return of capital. therefore, before the yield on a mine investment can be determined, a portion of the annual earnings must be set aside in such a manner that when the mine is exhausted the original investment will have been restored. if we consider the date due for the return of the capital as the time when the mine is exhausted, we may consider the annual instalments as payments before the due date, and they can be put out at compound interest until the time for restoration arrives. if they be invested in safe securities at the usual rate of about %, the addition of this amount of compound interest will assist in the repayment of the capital at the due date, so that the annual contributions to a sinking fund need not themselves aggregate the total capital to be restored, but may be smaller by the deficiency which will be made up by their interest earnings. such a system of redemption of capital is called "amortization." obviously it is not sufficient for the mine investor that his capital shall have been restored, but there is required an excess earning over and above the necessities of this annual funding of capital. what rate of excess return the mine must yield is a matter of the risks in the venture and the demands of the investor. mining business is one where % above provision for capital return is an absolute minimum demanded by the risks inherent in mines, even where the profit in sight gives warranty to the return of capital. where the profit in sight (which is the only real guarantee in mine investment) is below the price of the investment, the annual return should increase in proportion. there are thus two distinct directions in which interest must be computed,--first, the internal influence of interest in the amortization of the capital, and second, the percentage return upon the whole investment after providing for capital return. there are many limitations to the introduction of such refinements as interest calculations in mine valuation. it is a subject not easy to discuss with finality, for not only is the term of years unknown, but, of more importance, there are many factors of a highly speculative order to be considered in valuing. it may be said that a certain life is known in any case from the profit in sight, and that in calculating this profit a deduction should be made from the gross profit for loss of interest on it pending recovery. this is true, but as mines are seldom dealt with on the basis of profit in sight alone, and as the purchase price includes usually some proportion for extension in depth, an unknown factor is introduced which outweighs the known quantities. therefore the application of the culminative effect of interest accumulations is much dependent upon the sort of mine under consideration. in most cases of uncertain continuity in depth it introduces a mathematical refinement not warranted by the speculative elements. for instance, in a mine where the whole value is dependent upon extension of the deposit beyond openings, and where an expected return of at least % per annum is required to warrant the risk, such refinement would be absurd. on the other hand, in a witwatersrand gold mine, in gold and tin gravels, or in massive copper mines such as bingham and lake superior, where at least some sort of life can be approximated, it becomes a most vital element in valuation. in general it may be said that the lower the total annual return expected upon the capital invested, the greater does the amount demanded for amortization become in proportion to this total income, and therefore the greater need of its introduction in calculations. especially is this so where the cost of equipment is large proportionately to the annual return. further, it may be said that such calculations are of decreasing use with increasing proportion of speculative elements in the price of the mine. the risk of extension in depth, of the price of metal, etc., may so outweigh the comparatively minor factors here introduced as to render them useless of attention. in the practical conduct of mines or mining companies, sinking funds for amortization of capital are never established. in the vast majority of mines of the class under discussion, the ultimate duration of life is unknown, and therefore there is no basis upon which to formulate such a definite financial policy even were it desired. were it possible to arrive at the annual sum to be set aside, the stockholders of the mining type would prefer to do their own reinvestment. the purpose of these calculations does not lie in the application of amortization to administrative finance. it is nevertheless one of the touchstones in the valuation of certain mines or mining investments. that is, by a sort of inversion such calculations can be made to serve as a means to expose the amount of risk,--to furnish a yardstick for measuring the amount of risk in the very speculations of extension in depth and price of metals which attach to a mine. given the annual income being received, or expected, the problem can be formulated into the determination of how many years it must be continued in order to amortize the investment and pay a given rate of profit. a certain length of life is evident from the ore in sight, which may be called the life in sight. if the term of years required to redeem the capital and pay an interest upon it is greater than the life in sight, then this extended life must come from extension in depth, or ore from other direction, or increased price of metals. if we then take the volume and profit on the ore as disclosed we can calculate the number of feet the deposit must extend in depth, or additional tonnage that must be obtained of the same grade, or the different prices of metal that must be secured, in order to satisfy the demanded term of years. these demands in actual measure of ore or feet or higher price can then be weighed against the geological and industrial probabilities. the following tables and examples may be of assistance in these calculations. table . to apply this table, the amount of annual income or dividend and the term of years it will last must be known or estimated factors. it is then possible to determine the _present_ value of this annual income after providing for amortization and interest on the investment at various rates given, by multiplying the annual income by the factor set out. a simple illustration would be that of a mine earning a profit of $ , annually, and having a total of , , tons in sight, yielding a profit of $ a ton, or a total profit in sight of $ , , , thus recoverable in ten years. on a basis of a % return on the investment and amortization of capital (table i), the factor is . x $ , = $ , , as the present value of the gross profits exposed. that is, this sum of $ , , , if paid for the mine, would be repaid out of the profit in sight, together with % interest if the annual payments into sinking fund earn %. table i. present value of an annual dividend over -- years at --% and replacing capital by reinvestment of an annual sum at %. ======================================================= years | % | % | % | % | % | % -------|-------|-------|-------|-------|-------|------- | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | | | | | | | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | | | | | | | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | | | | | | | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . ======================================================= condensed from inwood's tables. table ii is practically a compound discount table. that is, by it can be determined the present value of a fixed sum payable at the end of a given term of years, interest being discounted at various given rates. its use may be illustrated by continuing the example preceding. table ii. present value of $ , or £ , payable in -- years, interest taken at --%. =================================== years | % | % | % | % ------|------|------|------|------- | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | | | | | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | | | | | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | | | | | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . =================================== condensed from inwood's tables. if such a mine is not equipped, and it is assumed that $ , are required to equip the mine, and that two years are required for this equipment, the value of the ore in sight is still less, because of the further loss of interest in delay and the cost of equipment. in this case the present value of $ , , in two years, interest at %, the factor is . x , , = $ , , . from this comes off the cost of equipment, or $ , , leaving $ , as the present value of the profit in sight. a further refinement could be added by calculating the interest chargeable against the $ , equipment cost up to the time of production. table iii. =========================================================================== annual | number of years of life required to yield--% interest, and in rate of | addition to furnish annual instalments which, if reinvested at dividend.| % will return the original investment at the end of the period. ---------|----------------------------------------------------------------- % | % | % | % | % | % | % | | | | | | | . | | | | | | . | . | | | | | . | . | . | | | | . | . | . | . | | | . | . | . | . | . | | | | | | | | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | | | | | | | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | | | | | | | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | | | | | | | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . =========================================================================== table iii. this table is calculated by inversion of the factors in table i, and is the most useful of all such tables, as it is a direct calculation of the number of years that a given rate of income on the investment must continue in order to amortize the capital (the annual sinking fund being placed at compound interest at %) and to repay various rates of interest on the investment. the application of this method in testing the value of dividend-paying shares is very helpful, especially in weighing the risks involved in the portion of the purchase or investment unsecured by the profit in sight. given the annual percentage income on the investment from the dividends of the mine (or on a non-producing mine assuming a given rate of production and profit from the factors exposed), by reference to the table the number of years can be seen in which this percentage must continue in order to amortize the investment and pay various rates of interest on it. as said before, the ore in sight at a given rate of exhaustion can be reduced to terms of life in sight. this certain period deducted from the total term of years required gives the life which must be provided by further discovery of ore, and this can be reduced to tons or feet of extension of given ore-bodies and a tangible position arrived at. the test can be applied in this manner to the various prices which must be realized from the base metal in sight to warrant the price. taking the last example and assuming that the mine is equipped, and that the price is $ , , , the yearly return on the price is %. if it is desired besides amortizing or redeeming the capital to secure a return of % on the investment, it will be seen by reference to the table that there will be required a life of . years. as the life visible in the ore in sight is ten years, then the extensions in depth must produce ore for . years longer-- , , tons. if the ore-body is , feet long and feet wide, it will furnish of gold ore , tons per foot of depth; hence the ore-body must extend , feet deeper to justify the price. mines are seldom so simple a proposition as this example. there are usually probabilities of other ore; and in the case of base metal, then variability of price and other elements must be counted. however, once the extension in depth which is necessary is determined for various assumptions of metal value, there is something tangible to consider and to weigh with the five geological weights set out in chapter iii. the example given can be expanded to indicate not only the importance of interest and redemption in the long extension in depth required, but a matter discussed from another point of view under "ratio of output." if the plant on this mine were doubled and the earnings increased to % ($ , per annum) (disregarding the reduction in working expenses that must follow expansion of equipment), it will be found that the life required to repay the purchase money,--$ , , ,--and % interest upon it, is about . years. as at this increased rate of production there is in the ore in sight a life of five years, the extension in depth must be depended upon for . years, or only , tons,--that is, feet of extension. similarly, the present value of the ore in sight is $ , greater if the mine be given double the equipment, for thus the idle money locked in the ore is brought into the interest market at an earlier date. against this increased profit must be weighed the increased cost of equipment. the value of low grade mines, especially, is very much a factor of the volume of output contemplated. chapter vi. mine valuation (_concluded_). valuation of mines with little or no ore in sight; valuations on second-hand data; general conduct of examinations; reports. a large number of examinations arise upon prospecting ventures or partially developed mines where the value is almost wholly prospective. the risks in such enterprises amount to the possible loss of the whole investment, and the possible returns must consequently be commensurate. such business is therefore necessarily highly speculative, but not unjustifiable, as the whole history of the industry attests; but this makes the matter no easier for the mine valuer. many devices of financial procedure assist in the limitation of the sum risked, and offer a middle course to the investor between purchase of a wholly prospective value and the loss of a possible opportunity to profit by it. the usual form is an option to buy the property after a period which permits a certain amount of development work by the purchaser before final decision as to purchase. aside from young mines such enterprises often arise from the possibility of lateral extension of the ore-deposit outside the boundaries of the property of original discovery (fig. ), in which cases there is often no visible ore within the property under consideration upon which to found opinion. in regions where vertical side lines obtain, there is always the possibility of a "deep level" in inclined deposits. therefore the ground surrounding known deposits has a certain speculative value, upon which engineers are often called to pass judgment. except in such unusual occurrences as south african bankets, or lake superior coppers, prospecting for deep level of extension is also a highly speculative phase of mining. the whole basis of opinion in both classes of ventures must be the few geological weights,--the geology of the property and the district, the development of surrounding mines, etc. in any event, there is a very great percentage of risk, and the profit to be gained by success must be, proportionally to the expenditure involved, very large. it is no case for calculating amortization and other refinements. it is one where several hundreds or thousands of per cent hoped for on the investment is the only justification. opinions and valuations upon second-hand data. some one may come forward and deprecate the bare suggestion of an engineer's offering an opinion when he cannot have proper first-hand data. but in these days we have to deal with conditions as well as theories of professional ethics. the growing ownership of mines by companies, that is by corporations composed of many individuals, and with their stocks often dealt in on the public exchanges, has resulted in holders whose interest is not large enough to warrant their undertaking the cost of exhaustive examinations. the system has produced an increasing class of mining speculators and investors who are finding and supplying the enormous sums required to work our mines,--sums beyond the reach of the old-class single-handed mining men. every year the mining investors of the new order are coming more and more to the engineer for advice, and they should be encouraged, because such counsel can be given within limits, and these limits tend to place the industry upon a sounder footing of ownership. as was said before, the lamb can be in a measure protected. the engineer's interest is to protect him, so that the industry which concerns his own life-work may be in honorable repute, and that capital may be readily forthcoming for its expansion. moreover, by constant advice to the investor as to what constitutes a properly presented and managed project, the arrangement of such proper presentation and management will tend to become an _a priori_ function of the promoter. sometimes the engineer can make a short visit to the mine for data purposes,--more often he cannot. in the former case, he can resolve for himself an approximation upon all the factors bearing on value, except the quality of the ore. for this, aside from inspection of the ore itself, a look at the plans is usually enlightening. a longitudinal section of the mine showing a continuous shortening of the stopes with each succeeding level carries its own interpretation. in the main, the current record of past production and estimates of the management as to ore-reserves, etc., can be accepted in ratio to the confidence that can be placed in the men who present them. it then becomes a case of judgment of men and things, and here no rule applies. advice must often be given upon data alone, without inspection of the mine. most mining data present internal evidence as to credibility. the untrustworthy and inexperienced betray themselves in their every written production. assuming the reliability of data, the methods already discussed for weighing the ultimate value of the property can be applied. it would be possible to cite hundreds of examples of valuation based upon second-hand data. three will, however, sufficiently illustrate. first, the r mine at johannesburg. with the regularity of this deposit, the development done, and a study of the workings on the neighboring mines and in deeper ground, it is a not unfair assumption that the reefs will maintain size and value throughout the area. the management is sound, and all the data are given in the best manner. the life of the mine is estimated at six years, with some probabilities of further ore from low-grade sections. the annual earnings available for dividends are at the rate of about £ , per annum. the capital is £ , in £ shares. by reference to the table on page it will be seen that the present value of £ , spread over six years to return capital at the end of that period, and give % dividends in the meantime, is . x £ , = £ , , ÷ , = £ _s_. _d_. per share. so that this mine, on the assumption of continuity of values, will pay about % and return the price. seven per cent is, however, not deemed an adequate return for the risks of labor troubles, faults, dykes, or poor patches. on a % basis, the mine is worth about £ _s_. per share. second, the g mine in nevada. it has a capital of $ , , in $ shares, standing in the market at cents each. the reserves are , tons, yielding a profit for yearly division of $ per ton. it has an annual capacity of about , tons, or $ , net profit, equal to % on the market value. in order to repay the capital value of $ , , and % per annum, it will need a life of (table iii) years, of which - / are visible. the size of the ore-bodies indicates a yield of about , tons per foot of depth. at an exhaustion rate of , tons per annum, the mine would need to extend to a depth of over a thousand feet below the present bottom. there is always a possibility of finding parallel bodies or larger volumes in depth, but it would be a sanguine engineer indeed who would recommend the stock, even though it pays an apparent %. third, the b mine, with a capital of $ , , in , , shares of $ each. the promoters state that the mine is in the slopes of the andes in peru; that there are , , tons of "ore blocked out"; that two assays by the assayers of the bank of england average % copper; that the copper can be produced at five cents per pound; that there is thus a profit of $ , , in sight. the evidences are wholly incompetent. it is a gamble on statements of persons who have not the remotest idea of sound mining. general conduct of examination. complete and exhaustive examination, entailing extensive sampling, assaying, and metallurgical tests, is very expensive and requires time. an unfavorable report usually means to the employer absolute loss of the engineer's fee and expenses. it becomes then the initial duty of the latter to determine at once, by the general conditions surrounding the property, how far the expenditure for exhaustive examination is warranted. there is usually named a money valuation for the property, and thus a peg is afforded upon which to hang conclusions. very often collateral factors with a preliminary sampling, or indeed no sampling at all, will determine the whole business. in fact, it is becoming very common to send younger engineers to report as to whether exhaustive examination by more expensive men is justified. in the course of such preliminary inspection, the ore-bodies may prove to be too small to insure adequate yield on the price, even assuming continuity in depth and represented value. they may be so difficult to mine as to make costs prohibitive, or they may show strong signs of "petering out." the ore may present visible metallurgical difficulties which make it unprofitable in any event. a gold ore may contain copper or arsenic, so as to debar cyanidation, where this process is the only hope of sufficiently moderate costs. a lead ore may be an amorphous compound with zinc, and successful concentration or smelting without great penalties may be precluded. a copper ore may carry a great excess of silica and be at the same time unconcentratable, and there may be no base mineral supply available for smelting mixture. the mine may be so small or so isolated that the cost of equipment will never be justified. some of these conditions may be determined as unsurmountable, assuming a given value for the ore, and may warrant the rejection of the mine at the price set. it is a disagreeable thing to have a disappointed promoter heap vituperation on an engineer's head because he did not make an exhaustive examination. although it is generally desirable to do some sampling to give assurance to both purchaser and vendor of conscientiousness, a little courage of conviction, when this is rightly and adequately grounded, usually brings its own reward. supposing, however, that conditions are right and that the mine is worth the price, subject to confirmation of values, the determination of these cannot be undertaken unless time and money are available for the work. as was said, a sampling campaign is expensive, and takes time, and no engineer has the moral right to undertake an examination unless both facilities are afforded. curtailment is unjust, both to himself and to his employer. how much time and outlay are required to properly sample a mine is obviously a question of its size, and the character of its ore. an engineer and one principal assistant can conduct two sampling parties. in hard rock it may be impossible to take more than five samples a day for each party. but, in average ore, ten samples for each is reasonable work. as the number of samples is dependent upon the footage of openings on the deposit, a rough approximation can be made in advance, and a general idea obtained as to the time required. this period must be insisted upon. reports. reports are to be read by the layman, and their first qualities should be simplicity of terms and definiteness of conclusions. reports are usually too long, rather than too short. the essential facts governing the value of a mine can be expressed on one sheet of paper. it is always desirable, however, that the groundwork data and the manner of their determination should be set out with such detail that any other engineer could come to the same conclusion if he accepted the facts as accurately determined. in regard to the detailed form of reports, the writer's own preference is for a single page summarizing the main factors, and an assay plan, reduced to a longitudinal section where possible. then there should be added, for purposes of record and for submission to other engineers, a set of appendices going into some details as to the history of the mine, its geology, development, equipment, metallurgy, and management. a list of samples should be given with their location, and the tonnages and values of each separate block. a presentation should be made of the probabilities of extension in depth, together with recommendations for working the mine. general summary. the bed-rock value which attaches to a mine is the profit to be won from proved ore and in which the price of metal is calculated at some figure between "basic" and "normal." this we may call the "_a_" value. beyond this there is the speculative value of the mine. if the value of the "probable" ore be represented by _x_, the value of extension of the ore by _y_, and a higher price for metal than the price above assumed represented by _z_, then if the mine be efficiently managed the value of the mine is _a_ + _x_ + _y_ + _z_. what actual amounts should be attached to _x, y, z_ is a matter of judgment. there is no prescription for good judgment. good judgment rests upon a proper balancing of evidence. the amount of risk in _x, y, z_ is purely a question of how much these factors are required to represent in money,--in effect, how much more ore must be found, or how many feet the ore must extend in depth; or in convertible terms, what life in years the mine must have, or how high the price of metal must be. in forming an opinion whether these requirements will be realized, _x, y, z_ must be balanced in a scale whose measuring standards are the five geological weights and the general industrial outlook. the wise engineer will put before his clients the scale, the weights, and the conclusion arrived at. the shrewd investor will require to know these of his adviser. chapter vii. development of mines. entry to the mine; tunnels; vertical, inclined, and combined shafts; location and number of shafts. development is conducted for two purposes: first, to search for ore; and second, to open avenues for its extraction. although both objects are always more or less in view, the first predominates in the early life of mines, the prospecting stage, and the second in its later life, the producing stage. it is proposed to discuss development designed to embrace extended production purposes first, because development during the prospecting stage is governed by the same principles, but is tempered by the greater degree of uncertainty as to the future of the mine, and is, therefore, of a more temporary character. entry to the mine. there are four methods of entry: by tunnel, vertical shaft, inclined shaft, or by a combination of the last two, that is, by a shaft initially vertical then turned to an incline. combined shafts are largely a development of the past few years to meet "deep level" conditions, and have been rendered possible only by skip-winding. the angle in such shafts (fig. ) is now generally made on a parabolic curve, and the speed of winding is then less diminished by the bend. the engineering problems which present themselves under "entry" may be divided into those of:-- . method. . location. . shape and size. the resolution of these questions depends upon the:-- a. degree of dip of the deposit. b. output of ore to be provided for. c. depth at which the deposit is to be attacked. d. boundaries of the property. e. surface topography. f. cost. g. operating efficiency. h. prospects of the mine. [illustration: fig. .--showing arrangement of the bend in combined shafts.] from the point of view of entrance, the coöperation of a majority of these factors permits the division of mines into certain broad classes. the type of works demanded for moderate depths (say vertically , to , feet) is very different from that required for great depths. to reach great depths, the size of shafts must greatly expand, to provide for extended ventilation, pumping, and winding necessities. moreover inclined shafts of a degree of flatness possible for moderate depths become too long to be used economically from the surface. the vast majority of metal-mining shafts fall into the first class, those of moderate depths. yet, as time goes on and ore-deposits are exhausted to lower planes, problems of depth will become more common. one thing, however, cannot be too much emphasized, especially on mines to be worked from the outcrop, and that is, that no engineer is warranted, owing to the speculation incidental to extension in depth, in initiating early in the mine's career shafts of such size or equipment as would be available for great depths. moreover, the proper location of a shaft so as to work economically extension of the ore-bodies is a matter of no certainty, and therefore shafts of speculative mines are tentative in any event. another line of division from an engineering view is brought about by a combination of three of the factors mentioned. this is the classification into "outcrop" and "deep-level" mines. the former are those founded upon ore-deposits to be worked from or close to the surface. the latter are mines based upon the extension in depth of ore-bodies from outcrop mines. such projects are not so common in america, where the law in most districts gives the outcrop owner the right to follow ore beyond his side-lines, as in countries where the boundaries are vertical on all sides. they do, however, arise not alone in the few american sections where the side-lines are vertical boundaries, but in other parts owing to the pitch of ore-bodies through the end lines (fig. ). more especially do such problems arise in america in effect, where the ingress questions have to be revised for mines worked out in the upper levels (fig. ). [illustration: fig. .--longitudinal section showing "deep level" project arising from dip of ore-body through end-line.] if from a standpoint of entrance questions, mines are first classified into those whose works are contemplated for moderate depths, and those in which work is contemplated for great depth, further clarity in discussion can be gained by subdivision into the possible cases arising out of the factors of location, dip, topography, and boundaries. mines of moderate depths. case i. deposits where topographic conditions permit the alternatives of shaft or tunnel. case ii. vertical or horizontal deposits, the only practical means of attaining which is by a vertical shaft. case iii. inclined deposits to be worked from near the surface. there are in such instances the alternatives of either a vertical or an inclined shaft. case iv. inclined deposits which must be attacked in depth, that is, deep-level projects. there are the alternatives of a compound shaft or of a vertical shaft, and in some cases of an incline from the surface. mines to great depths. case v. vertical or horizontal deposits, the only way of reaching which is by a vertical shaft. case vi. inclined deposits. in such cases the alternatives are a vertical or a compound shaft. case i.--although for logical arrangement tunnel entry has been given first place, to save repetition it is proposed to consider it later. with few exceptions, tunnels are a temporary expedient in the mine, which must sooner or later be opened by a shaft. case ii. vertical or horizontal deposits.--these require no discussion as to manner of entry. there is no justifiable alternative to a vertical shaft (fig. ). [illustration: fig. .--cross-sections showing entry to vertical or horizontal deposits. case ii.] [illustration: fig. .--cross-section showing alternative shafts to inclined deposit to be worked from surface. case iii.] case iii. inclined deposits which are intended to be worked from the outcrop, or from near it (fig. ).--the choice of inclined or vertical shaft is dependent upon relative cost of construction, subsequent operation, and the useful life of the shaft, and these matters are largely governed by the degree of dip. assuming a shaft of the same size in either alternative, the comparative cost per foot of sinking is dependent largely on the breaking facilities of the rock under the different directions of attack. in this, the angles of the bedding or joint planes to the direction of the shaft outweigh other factors. the shaft which takes the greatest advantage of such lines of breaking weakness will be the cheapest per foot to sink. in south african experience, where inclined shafts are sunk parallel to the bedding planes of hard quartzites, the cost per foot appears to be in favor of the incline. on the other hand, sinking shafts across tight schists seems to be more advantageous than parallel to the bedding planes, and inclines following the dip cost more per foot than vertical shafts. an inclined shaft requires more footage to reach a given point of depth, and therefore it would entail a greater total expense than a vertical shaft, assuming they cost the same per foot. the excess amount will be represented by the extra length, and this will depend upon the flatness of the dip. with vertical shafts, however, crosscuts to the deposit are necessary. in a comparative view, therefore, the cost of the crosscuts must be included with that of the vertical shaft, as they would be almost wholly saved in an incline following near the ore. the factor of useful life for the shaft enters in deciding as to the advisability of vertical shafts on inclined deposits, from the fact that at some depth one of two alternatives has to be chosen. the vertical shaft, when it reaches a point below the deposit where the crosscuts are too long (_c_, fig. ), either becomes useless, or must be turned on an incline at the intersection with the ore (_b_). the first alternative means ultimately a complete loss of the shaft for working purposes. the latter has the disadvantage that the bend interferes slightly with haulage. the following table will indicate an hypothetical extreme case,--not infrequently met. in it a vertical shaft , feet in depth is taken as cutting the deposit at the depth of feet, the most favored position so far as aggregate length of crosscuts is concerned. the cost of crosscutting is taken at $ per foot and that of sinking the vertical shaft at $ per foot. the incline is assumed for two cases at $ and $ per foot respectively. the stoping height upon the ore between levels is counted at feet. dip of | depth of | length of |no. of crosscuts| total length deposit from | vertical | incline | required from | of crosscuts, horizontal | shaft | required | v shaft | feet -------------|-------------|-------------|----------------|--------------- ° | , | , | | ° | , | , | | , ° | , | , | | , ° | , | , | | , ° | , | , | | , ° | , | , | | , ========================================================================== cost of |cost vertical| total cost | cost of incline|cost of incline crosscuts $ | shaft $ | of vertical | $ per foot | $ per foot per foot | per foot |and crosscuts| | -------------|-------------|-------------|----------------|--------------- $ , | $ , | $ , | $ , | $ , , | , | , | , | , , | , | , | , | , , | , | , | , | , , | , | , | , | , , | , | , | , | , from the above examples it will be seen that the cost of crosscuts put at ordinary level intervals rapidly outruns the extra expense of increased length of inclines. if, however, the conditions are such that crosscuts from a vertical shaft are not necessary at so frequent intervals, then in proportion to the decrease the advantages sway to the vertical shaft. most situations wherein the crosscuts can be avoided arise in mines worked out in the upper levels and fall under case iv, that of deep-level projects. there can be no doubt that vertical shafts are cheaper to operate than inclines: the length of haul from a given depth is less; much higher rope speed is possible, and thus the haulage hours are less for the same output; the wear and tear on ropes, tracks, or guides is not so great, and pumping is more economical where the cornish order of pump is used. on the other hand, with a vertical shaft must be included the cost of operating crosscuts. on mines where the volume of ore does not warrant mechanical haulage, the cost of tramming through the extra distance involved is an expense which outweighs any extra operating outlay in the inclined shaft itself. even with mechanical haulage in crosscuts, it is doubtful if there is anything in favor of the vertical shaft on this score. [illustration: fig. .--cross-section showing auxiliary vertical outlet.] in deposits of very flat dips, under °, the case arises where the length of incline is so great that the saving on haulage through direct lift warrants a vertical shaft as an auxiliary outlet in addition to the incline (fig. ). in such a combination the crosscut question is eliminated. the mine is worked above and below the intersection by incline, and the vertical shaft becomes simply a more economical exit and an alternative to secure increased output. the north star mine at grass valley is an illustration in point. such a positive instance borders again on case iv, deep-level projects. in conclusion, it is the writer's belief that where mines are to be worked from near the surface, coincidentally with sinking, and where, therefore, crosscuts from a vertical shaft would need to be installed frequently, inclines are warranted in all dips under ° and over °. beyond ° the best alternative is often undeterminable. in the range under ° and over °, although inclines are primarily necessary for actual delivery of ore from levels, they can often be justifiably supplemented by a vertical shaft as a relief to a long haul. in dips of less than °, as in those over °, the advantages again trend strongly in favor of the vertical shaft. there arise, however, in mountainous countries, topographic conditions such as the dip of deposits into the mountain, which preclude any alternative on an incline at any angled dip. case iv. inclined deposits which must be attacked in depth (fig. ).--there are two principal conditions in which such properties exist: first, mines being operated, or having been previously worked, whose method of entry must be revised; second, those whose ore-bodies to be attacked do not outcrop within the property. the first situation may occur in mines of inadequate shaft capacity or wrong location; in mines abandoned and resurrected; in mines where a vertical shaft has reached its limit of useful extensions, having passed the place of economical crosscutting; or in mines in flat deposits with inclines whose haul has become too long to be economical. three alternatives present themselves in such cases: a new incline from the surface (_a b f_, fig. ), or a vertical shaft combined with incline extension (_c d f_), or a simple vertical shaft (_h g_). a comparison can be first made between the simple incline and the combined shaft. the construction of an incline from the surface to the ore-body will be more costly than a combined shaft, for until the horizon of the ore is reached (at _d_) no crosscuts are required in the vertical section, while the incline must be of greater length to reach the same horizon. the case arises, however, where inclines can be sunk through old stopes, and thus more cheaply constructed than vertical shafts through solid rock; and also the case of mountainous topographic conditions mentioned above. [illustration: fig. .--cross-section of inclined deposit which must be attacked in depth.] from an operating point of view, the bend in combined shafts (at _d_) gives rise to a good deal of wear and tear on ropes and gear. the possible speed of winding through a combined shaft is, however, greater than a simple incline, for although haulage speed through the incline section (_d f_) and around the bend of the combined shaft is about the same as throughout a simple incline (_a f_), the speed can be accelerated in the vertical portion (_d c_) above that feasible did the incline extend to the surface. there is therefore an advantage in this regard in the combined shaft. the net advantages of the combined over the inclined shaft depend on the comparative length of the two alternative routes from the intersection (_d_) to the surface. certainly it is not advisable to sink a combined shaft to cut a deposit at feet in depth if a simple incline can be had to the surface. on the other hand, a combined shaft cutting the deposit at , feet will be more advisable than a simple incline , feet long to reach the same point. the matter is one for direct calculation in each special case. in general, there are few instances of really deep-level projects where a complete incline from the surface is warranted. in most situations of this sort, and in all of the second type (where the outcrop is outside the property), actual choice usually lies between combined shafts (_c d f_) and entire vertical shafts (_h g_). the difference between a combined shaft and a direct vertical shaft can be reduced to a comparison of the combined shaft below the point of intersection (_d_) with that portion of a vertical shaft which would cover the same horizon. the question then becomes identical with that of inclined _versus_ verticals, as stated in case iii, with the offsetting disadvantage of the bend in the combined shaft. if it is desired to reach production at the earliest date, the lower section of a simple vertical shaft must have crosscuts to reach the ore lying above the horizon of its intersection (_e_). if production does not press, the ore above the intersection (_eb_) can be worked by rises from the horizon of intersection (_e_). in the use of rises, however, there follow the difficulties of ventilation and lowering the ore down to the shaft, which brings expenses to much the same thing as operating through crosscuts. the advantages of combined over simple vertical shafts are earlier production, saving of either rises or crosscuts, and the ultimate utility of the shaft to any depth. the disadvantages are the cost of the extra length of the inclined section, slower winding, and greater wear and tear within the inclined section and especially around the bend. all these factors are of variable import, depending upon the dip. on very steep dips,--over °,--the net result is in favor of the simple vertical shaft. on other dips it is in favor of the combined shaft. cases v and vi. mines to be worked to great depths,--over , feet.--in case v, with vertical or horizontal deposits, there is obviously no desirable alternative to vertical shafts. in case vi, with inclined deposits, there are the alternatives of a combined or of a simple vertical shaft. a vertical shaft in locations (_h_, fig. ) such as would not necessitate extension in depth by an incline, would, as in case iv, compel either crosscuts to the ore or inclines up from the horizon of intersection (_e_). apart from delay in coming to production and the consequent loss of interest on capital, the ventilation problems with this arrangement would be appalling. moreover, the combined shaft, entering the deposit near its shallowest point, offers the possibility of a separate haulage system on the inclined and on the vertical sections, and such separate haulage is usually advisable at great depths. in such instances, the output to be handled is large, for no mine of small output is likely to be contemplated at such depth. several moderate-sized inclines from the horizon of intersection have been suggested (_ef_, _dg_, _ch_, fig. ) to feed a large primary shaft (_ab_), which thus becomes the trunk road. this program would cheapen lateral haulage underground, as mechanical traction can be used in the main level, (_ec_), and horizontal haulage costs can be reduced on the lower levels. moreover, separate winding engines on the two sections increase the capacity, for the effect is that of two trains instead of one running on a single track. shaft location.--although the prime purpose in locating a shaft is obviously to gain access to the largest volume of ore within the shortest haulage distance, other conditions also enter, such as the character of the surface and the rock to be intersected, the time involved before reaching production, and capital cost. as shafts must bear two relations to a deposit,--one as to the dip and the other as to the strike,--they may be considered from these aspects. vertical shafts must be on the hanging-wall side of the outcrop if the deposit dips at all. in any event, the shaft should be far enough away to be out of the reach of creeps. an inclined shaft may be sunk either on the vein, in which case a pillar of ore must be left to support the shaft; or, instead, it may be sunk a short distance in the footwall, and where necessary the excavation above can be supported by filling. following the ore has the advantage of prospecting in sinking, and in many cases the softness of the ground in the region of the vein warrants this procedure. it has, however, the disadvantage that a pillar of ore is locked up until the shaft is ready for abandonment. moreover, as veins or lodes are seldom of even dip, an inclined shaft, to have value as a prospecting opening, or to take advantage of breaking possibilities in the lode, will usually be crooked, and an incline irregular in detail adds greatly to the cost of winding and maintenance. these twin disadvantages usually warrant a straight incline in the footwall. inclines are not necessarily of the same dip throughout, but for reasonably economical haulage change of angle must take place gradually. [illustration: fig. .--longitudinal section showing shaft arrangement proposed for very deep inclined deposits.] in the case of deep-level projects on inclined deposits, demanding combined or vertical shafts, the first desideratum is to locate the vertical section as far from the outcrop as possible, and thus secure the most ore above the horizon of intersection. this, however, as stated before, would involve the cost of crosscuts or rises and would cause delay in production, together with the accumulation of capital charges. how important the increment of interest on capital may become during the period of opening the mine may be demonstrated by a concrete case. for instance, the capital of a company or the cost of the property is, say, $ , , , and where opening the mine for production requires four years, the aggregate sum of accumulated compound interest at % (and most operators want more from a mining investment) would be $ , . under such circumstances, if a year or two can be saved in getting to production by entering the property at a higher horizon, the difference in accumulated interest will more than repay the infinitesimal extra cost of winding through a combined shaft of somewhat increased length in the inclined section. the unknown character of the ore in depth is always a sound reason for reaching it as quickly and as cheaply as possible. in result, such shafts are usually best located when the vertical section enters the upper portion of the deposit. the objective in location with regard to the strike of the ore-bodies is obviously to have an equal length of lateral ore-haul in every direction from the shaft. it is easier to specify than to achieve this, for in all speculative deposits ore-shoots are found to pursue curious vagaries as they go down. ore-bodies do not reoccur with the same locus as in the upper levels, and generally the chances to go wrong are more numerous than those to go right. number of shafts.--the problem of whether the mine is to be opened by one or by two shafts of course influences location. in metal mines under cases ii and iii (outcrop properties) the ore output requirements are seldom beyond the capacity of one shaft. ventilation and escape-ways are usually easily managed through the old stopes. under such circumstances, the conditions warranting a second shaft are the length of underground haul and isolation of ore-bodies or veins. lateral haulage underground is necessarily disintegrated by the various levels, and usually has to be done by hand. by shortening this distance of tramming and by consolidation of the material from all levels at the surface, where mechanical haulage can be installed, a second shaft is often justified. there is therefore an economic limitation to the radius of a single shaft, regardless of the ability of the shaft to handle the total output. other questions also often arise which are of equal importance to haulage costs. separate ore-shoots or ore-bodies or parallel deposits necessitate, if worked from one shaft, constant levels through unpayable ground and extra haul as well, or ore-bodies may dip away from the original shaft along the strike of the deposit and a long haulage through dead levels must follow. for instance, levels and crosscuts cost roughly one-quarter as much per foot as shafts. therefore four levels in barren ground, to reach a parallel vein or isolated ore-body , feet away, would pay for a shaft , feet deep. at a depth of , feet, at least six levels might be necessary. the tramming of ore by hand through such a distance would cost about double the amount to hoist it through a shaft and transport it mechanically to the dressing plant at surface. the aggregate cost and operation of barren levels therefore soon pays for a second shaft. if two or more shafts are in question, they must obviously be set so as to best divide the work. under cases iv, v, and vi,--that is, deep-level projects,--ventilation and escape become most important considerations. even where the volume of ore is within the capacity of a single shaft, another usually becomes a necessity for these reasons. their location is affected not only by the locus of the ore, but, as said, by the time required to reach it. where two shafts are to be sunk to inclined deposits, it is usual to set one so as to intersect the deposit at a lower point than the other. production can be started from the shallower, before the second is entirely ready. the ore above the horizon of intersection of the deeper shaft is thus accessible from the shallower shaft, and the difficulty of long rises or crosscuts from that deepest shaft does not arise. chapter viii. development of mines (_continued_). shape and size of shafts; speed of sinking; tunnels. shape of shafts.--shafts may be round or rectangular.[*] round vertical shafts are largely applied to coal-mines, and some engineers have advocated their usefulness to the mining of the metals under discussion. their great advantages lie in their structural strength, in the large amount of free space for ventilation, and in the fact that if walled with stone, brick, concrete, or steel, they can be made water-tight so as to prevent inflow from water-bearing strata, even when under great pressure. the round walled shafts have a longer life than timbered shafts. all these advantages pertain much more to mining coal or iron than metals, for unsound, wet ground is often the accompaniment of coal-measures, and seldom troubles metal-mines. ventilation requirements are also much greater in coal-mines. from a metal-miner's standpoint, round shafts are comparatively much more expensive than the rectangular timbered type.[**] for a larger area must be excavated for the same useful space, and if support is needed, satisfactory walling, which of necessity must be brick, stone, concrete, or steel, cannot be cheaply accomplished under the conditions prevailing in most metal regions. although such shafts would have a longer life, the duration of timbered shafts is sufficient for most metal mines. it follows that, as timber is the cheapest and all things considered the most advantageous means of shaft support for the comparatively temporary character of metal mines, to get the strains applied to the timbers in the best manner, and to use the minimum amount of it consistent with security, and to lose the least working space, the shaft must be constructed on rectangular lines. [footnote *: octagonal shafts were sunk in mexico in former times. at each face of the octagon was a whim run by mules, and hauling leather buckets.] [footnote **: the economic situation is rapidly arising in a number of localities that steel beams can be usefully used instead of timber. the same arguments apply to this type of support that apply to timber.] the variations in timbered shaft design arise from the possible arrangement of compartments. many combinations can be imagined, of which figures , , , , , and are examples. [illustration: fig. . fig. . fig. . fig. . fig. . fig. .] the arrangement of compartments shown in figures , , , and gives the greatest strength. it permits timbering to the best advantage, and avoids the danger underground involved in crossing one compartment to reach another. it is therefore generally adopted. any other arrangement would obviously be impossible in inclined or combined shafts. size of shafts.--in considering the size of shafts to be installed, many factors are involved. they are in the main:-- _a_. amount of ore to be handled. _b_. winding plant. _c_. vehicle of transport. _d_. depth. _e_. number of men to be worked underground. _f_. amount of water. _g_. ventilation. _h_. character of the ground. _i_. capital outlay. _j_. operating expense. it is not to be assumed that these factors have been stated in the order of relative importance. more or less emphasis will be attached to particular factors by different engineers, and under different circumstances. it is not possible to suggest any arbitrary standard for calculating their relative weight, and they are so interdependent as to preclude separate discussion. the usual result is a compromise between the demands of all. certain factors, however, dictate a minimum position, which may be considered as a datum from which to start consideration. _first_, a winding engine, in order to work with any economy, must be balanced, that is, a descending empty skip or cage must assist in pulling up a loaded one. therefore, except in mines of very small output, at least two compartments must be made for hoisting purposes. water has to be pumped from most mines, escape-ways are necessary, together with room for wires and air-pipes, so that at least one more compartment must be provided for these objects. we have thus three compartments as a sound minimum for any shaft where more than trivial output is required. _second_, there is a certain minimum size of shaft excavation below which there is very little economy in actual rock-breaking.[*] in too confined a space, holes cannot be placed to advantage for the blast, men cannot get round expeditiously, and spoil cannot be handled readily. the writer's own experience leads him to believe that, in so far as rock-breaking is concerned, to sink a shaft fourteen to sixteen feet long by six to seven feet wide outside the timbers, is as cheap as to drive any smaller size within the realm of consideration, and is more rapid. this size of excavation permits of three compartments, each about four to five feet inside the timbers. [footnote *: notes on the cost of shafts in various regions which have been personally collected show a remarkable decrease in the cost per cubic foot of material excavated with increased size of shaft. variations in skill, in economic conditions, and in method of accounting make data regarding different shafts of doubtful value, but the following are of interest:-- in australia, eight shafts between and feet long by to feet wide cost an average of $ . per cubic foot of material excavated. six shafts to feet long by to feet wide cost an average of $ . per cubic foot; seven shafts to feet long and to feet wide cost an average of $ . per cubic foot. in south africa, eleven shafts to feet long by to feet wide cost an average of $ . per cubic foot; five shafts to feet long by feet wide, cost $ . ; and seven shafts feet by feet cost $ . per cubic foot.] the cost of timber, it is true, is a factor of the size of shaft, but the labor of timbering does not increase in the same ratio. in any event, the cost of timber is only about % of the actual shaft cost, even in localities of extremely high prices. _third_, three reasons are rapidly making the self-dumping skip the almost universal shaft-vehicle, instead of the old cage for cars. first, there is a great economy in labor for loading into and discharging from a shaft; second, there is more rapid despatch and discharge and therefore a larger number of possible trips; third, shaft-haulage is then independent of delays in arrival of cars at stations, while tramming can be done at any time and shaft-haulage can be concentrated into certain hours. cages to carry mine cars and handle the same load as a skip must either be big enough to take two cars, which compels a much larger shaft than is necessary with skips, or they must be double-decked, which renders loading arrangements underground costly to install and expensive to work. for all these reasons, cages can be justified only on metal mines of such small tonnage that time is no consideration and where the saving of men is not to be effected. in compartments of the minimum size mentioned above (four to five feet either way) a skip with a capacity of from two to five tons can be installed, although from two to three tons is the present rule. lighter loads than this involve more trips, and thus less hourly capacity, and, on the other hand, heavier loads require more costly engines. this matter is further discussed under "haulage appliances." we have therefore as the economic minimum a shaft of three compartments (fig. ), each four to five feet square. when the maximum tonnage is wanted from such a shaft at the least operating cost, it should be equipped with loading bins and skips. the output capacity of shafts of this size and equipment will depend in a major degree upon the engine employed, and in a less degree upon the hauling depth. the reason why depth is a subsidiary factor is that the rapidity with which a load can be drawn is not wholly a factor of depth. the time consumed in hoisting is partially expended in loading, in acceleration and retardation of the engine, and in discharge of the load. these factors are constant for any depth, and extra distance is therefore accomplished at full speed of the engine. vertical shafts will, other things being equal, have greater capacity than inclines, as winding will be much faster and length of haul less for same depth. since engines have, however, a great tractive ability on inclines, by an increase in the size of skip it is usually possible partially to equalize matters. therefore the size of inclines for the same output need not differ materially from vertical shafts. the maximum capacity of a shaft whose equipment is of the character and size given above, will, as stated, decrease somewhat with extension in depth of the haulage horizon. at feet, such a shaft if vertical could produce to tons per hour comfortably with an engine whose winding speed was feet per minute. as men and material other than ore have to be handled in and out of the mine, and shaft-sinking has to be attended to, the winding engine cannot be employed all the time on ore. twelve hours of actual daily ore-winding are all that can be expected without auxiliary help. this represents a capacity from such a depth of to , tons per day. a similar shaft, under ordinary working conditions, with an engine speed of , feet per minute, should from, say, , feet have a capacity of about to tons daily. it is desirable to inquire at what stages the size of shaft should logically be enlarged in order to attain greater capacity. a considerable measure of increase can be obtained by relieving the main hoisting engine of all or part of its collateral duties. where the pumping machinery is not elaborate, it is often possible to get a small single winding compartment into the gangway without materially increasing the size of the shaft if the haulage compartments be made somewhat narrower (fig. ). such a compartment would be operated by an auxiliary engine for sinking, handling tools and material, and assisting in handling men. if this arrangement can be effected, the productive time of the main engine can be expanded to about twenty hours with an addition of about two-thirds to the output. where the exigencies of pump and gangway require more than two and one-half feet of shaft length, the next stage of expansion becomes four full-sized compartments (fig. ). by thus enlarging the auxiliary winding space, some assistance may be given to ore-haulage in case of necessity. the mine whose output demands such haulage provisions can usually stand another foot of width to the shaft, so that the dimensions come to about feet to feet by feet to feet outside the timbers. such a shaft, with three- to four-ton skips and an appropriate engine, will handle up to tons per hour from a depth of , feet. the next logical step in advance is the shaft of five compartments with four full-sized haulage ways (fig. ), each of greater size than in the above instance. in this case, the auxiliary engine becomes a balanced one, and can be employed part of the time upon ore-haulage. such a shaft will be about feet to feet long by feet wide outside the timbers, when provision is made for one gangway. the capacity of such shafts can be up to , tons a day, depending on the depth and engine. when very large quantities of water are to be dealt with and rod-driven pumps to be used, two pumping compartments are sometimes necessary, but other forms of pumps do not require more than one compartment,--an additional reason for their use. for depths greater than , feet, other factors come into play. ventilation questions become of more import. the mechanical problems on engines and ropes become involved, and their sum-effect is to demand much increased size and a greater number of compartments. the shafts at johannesburg intended as outlets for workings , feet deep are as much as feet by feet outside timbers. it is not purposed to go into details as to sinking methods or timbering. while important matters, they would unduly prolong this discussion. besides, a multitude of treatises exist on these subjects and cover all the minutiæ of such work. speed of sinking.--mines may be divided into two cases,--those being developed only, and those being operated as well as developed. in the former, the entrance into production is usually dependent upon the speed at which the shaft is sunk. until the mine is earning profits, there is a loss of interest on the capital involved, which, in ninety-nine instances out of a hundred, warrants any reasonable extra expenditure to induce more rapid progress. in the case of mines in operation, the volume of ore available to treatment or valuation is generally dependent to a great degree upon the rapidity of the extension of workings in depth. it will be demonstrated later that, both from a financial and a technical standpoint, the maximum development is the right one and that unremitting extension in depth is not only justifiable but necessary. speed under special conditions or over short periods has a more romantic than practical interest, outside of its value as a stimulant to emulation. the thing that counts is the speed which can be maintained over the year. rapidity of sinking depends mainly on:-- _a_. whether the shaft is or is not in use for operating the mine. _b_. the breaking character of the rock. _c_. the amount of water. the delays incident to general carrying of ore and men are such that the use of the main haulage engine for shaft-sinking is practically impossible, except on mines with small tonnage output. even with a separate winch or auxiliary winding-engine, delays are unavoidable in a working shaft, especially as it usually has more water to contend with than one not in use for operating the mine. the writer's own impression is that an average of feet per month is the maximum possibility for year in and out sinking under such conditions. in fact, few going mines manage more than feet a year. in cases of clean shaft-sinking, where every energy is bent to speed, feet per month have been averaged for many months. special cases have occurred where as much as feet have been achieved in a single month. with ordinary conditions, , feet in a year is very good work. rock awkward to break, and water especially, lowers the rate of progress very materially. further reference to speed will be found in the chapter on "drilling methods." tunnel entry.--the alternative of entry to a mine by tunnel is usually not a question of topography altogether, but, like everything else in mining science, has to be tempered to meet the capital available and the expenditure warranted by the value showing. in the initial prospecting of a mine, tunnels are occasionally overdone by prospectors. often more would be proved by a few inclines. as the pioneer has to rely upon his right arm for hoisting and drainage, the tunnel offers great temptations, even when it is long and gains but little depth. at a more advanced stage of development, the saving of capital outlay on hoisting and pumping equipment, at a time when capital is costly to secure, is often sufficient justification for a tunnel entry. but at the stage where the future working of ore below a tunnel-level must be contemplated, other factors enter. for ore below tunnel-level a shaft becomes necessary, and in cases where a tunnel enters a few hundred feet below the outcrop the shaft should very often extend to the surface, because internal shafts, winding from tunnel-level, require large excavations to make room for the transfer of ore and for winding gear. the latter must be operated by transmitted power, either that of steam, water, electricity, or air. where power has to be generated on the mine, the saving by the use of direct steam, generated at the winding gear, is very considerable. moreover, the cost of haulage through a shaft for the extra distance from tunnel-level to the surface is often less than the cost of transferring the ore and removing it through the tunnel. the load once on the winding-engine, the consumption of power is small for the extra distance, and the saving of labor is of consequence. on the other hand, where drainage problems arise, they usually outweigh all other considerations, for whatever the horizon entered by tunnel, the distance from that level to the surface means a saving of water-pumpage against so much head. the accumulation of such constant expense justifies a proportioned capital outlay. in other words, the saving of this extra pumping will annually redeem the cost of a certain amount of tunnel, even though it be used for drainage only. in order to emphasize the rapidity with which such a saving of constant expense will justify capital outlay, one may tabulate the result of calculations showing the length of tunnel warranted with various hypothetical factors of quantity of water and height of lift eliminated from pumping. in these computations, power is taken at the low rate of $ per horsepower-year, the cost of tunneling at an average figure of $ per foot, and the time on the basis of a ten-year life for the mine. feet of tunnel paid for in years with under-mentioned conditions. ============================================================= feet of | , | , | , | , | , , water lift | gallons | gallons | gallons | gallons | gallons avoided |per diem |per diem |per diem |per diem |per diem -----------|---------|---------|---------|---------|--------- | | , | , | , | , | , | , | , | , | , | , | , | , | , | , | , | , | , | , | , , | , | , | , | , | , ============================================================= the size of tunnels where ore-extraction is involved depends upon the daily tonnage output required, and the length of haul. the smallest size that can be economically driven and managed is about - / feet by feet inside the timbers. such a tunnel, with single track for a length of , feet, with one turn-out, permits handling up to tons a day with men and animals. if the distance be longer or the tonnage greater, a double track is required, which necessitates a tunnel at least feet wide by - / feet to feet high, inside the timbers. there are tunnel projects of a much more impressive order than those designed to operate upper levels of mines; that is, long crosscut tunnels designed to drain and operate mines at very considerable depths, such as the sutro tunnel at virginia city. the advantage of these tunnels is very great, especially for drainage, and they must be constructed of large size and equipped with appliances for mechanical haulage. chapter ix. development of mines (_concluded_). subsidiary development;--stations; crosscuts; levels; interval between levels; protection of levels; winzes and rises. development in the prospecting stage; drilling. subsidiary development. stations, crosscuts, levels, winzes, and rises follow after the initial entry. they are all expensive, and the least number that will answer is the main desideratum. stations.--as stations are the outlets of the levels to the shaft, their size and construction is a factor of the volume and character of the work at the levels which they are to serve. if no timber is to be handled, and little ore, and this on cages, the stations need be no larger than a good sized crosscut. where timber is to be let down, they must be ten to fifteen feet higher than the floor of the crosscut. where loading into skips is to be provided for, bins must be cut underneath and sufficient room be provided to shift the mine cars comfortably. such bins are built of from to tons' capacity in order to contain some reserve for hoisting purposes, and in many cases separate bins must be provided on opposite sides of the shaft for ore and waste. it is a strong argument in favor of skips, that with this means of haulage storage capacity at the stations is possible, and the hoisting may then go on independently of trucking and, as said before, there are no idle men at the stations. [illustration: fig. .--cross-section of station arrangement for skip-haulage in vertical shaft.] [illustration: fig. .--cross-section of station arrangement for skip-haulage in vertical shaft.] it is always desirable to concentrate the haulage to the least number of levels, for many reasons. among them is that, where haulage is confined to few levels, storage-bins are not required at every station. figures , , , and illustrate various arrangements of loading bins. crosscuts.--crosscuts are for two purposes, for roadway connection of levels to the shaft or to other levels, and for prospecting purposes. the number of crosscuts for roadways can sometimes be decreased by making the connections with the shaft at every second or even every third level, thus not only saving in the construction cost of crosscuts and stations, but also in the expenses of scattered tramming. the matter becomes especially worth considering where the quantity of ore that can thus be accumulated warrants mule or mechanical haulage. this subject will be referred to later on. [illustration: fig. .--arrangement of loading chutes in vertical shaft.] on the second purpose of crosscuts,--that of prospecting,--one observation merits emphasis. this is, that the tendency of ore-fissures to be formed in parallels warrants more systematic crosscutting into the country rock than is done in many mines. [illustration: fig. .--cross-section of station arrangement for skip-haulage in inclined shaft.] levels. the word "level" is another example of miners' adaptations in nomenclature. its use in the sense of tunnels driven in the direction of the strike of the deposit has better, but less used, synonyms in the words "drifts" or "drives." the term "level" is used by miners in two senses, in that it is sometimes applied to all openings on one horizon, crosscuts included. levels are for three purposes,--for a stoping base; for prospecting the deposit; and for roadways. as a prospecting and a stoping base it is desirable that the level should be driven on the deposit; as a roadway, that it should constitute the shortest distance between two points and be in the soundest ground. on narrow, erratic deposits the levels usually must serve all three purposes at once; but in wider and more regular deposits levels are often driven separately for roadways from the level which forms the stoping base and prospecting datum. there was a time when mines were worked by driving the level on ore and enlarging it top and bottom as far as the ground would stand, then driving the next level to feet below, and repeating the operation. this interval gradually expanded, but for some reason feet was for years assumed to be the proper distance between levels. scattered over every mining camp on earth are thousands of mines opened on this empirical figure, without consideration of the reasons for it or for any other distance. the governing factors in determining the vertical interval between levels are the following:-- _a_. the regularity of the deposit. _b_. the effect of the method of excavation of winzes and rises. _c_. the dip and the method of stoping. regularity of the deposit.--from a prospecting point of view the more levels the better, and the interval therefore must be determined somewhat by the character of the deposit. in erratic deposits there is less risk of missing ore with frequent levels, but it does not follow that every level need be a through roadway to the shaft or even a stoping base. in such deposits, intermediate levels for prospecting alone are better than complete levels, each a roadway. nor is it essential, even where frequent levels are required for a stoping base, that each should be a main haulage outlet to the shaft. in some mines every third level is used as a main roadway, the ore being poured from the intermediate ones down to the haulage line. thus tramming and shaft work, as stated before, can be concentrated. effect of method of excavating winzes and rises.--with hand drilling and hoisting, winzes beyond a limited depth become very costly to pull spoil out of, and rises too high become difficult to ventilate, so that there is in such cases a limit to the interval desirable between levels, but these difficulties largely disappear where air-winches and air-drills are used. the dip and method of stoping.--the method of stoping is largely dependent upon the dip, and indirectly thus affects level intervals. in dips under that at which material will "flow" in the stopes--about ° to °--the interval is greatly dependent on the method of stope-transport. where ore is to be shoveled from stopes to the roadway, the levels must be comparatively close together. where deposits are very flat, under °, and walls fairly sound, it is often possible to use a sort of long wall system of stoping and to lay tracks in the stopes with self-acting inclines to the levels. in such instances, the interval can be expanded to or even feet. in dips between ° and °, tracks are not often possible, and either shoveling or "bumping troughs"[*] are the only help to transport. with shoveling, intervals of feet[**] are most common, and with troughs the distance can be expanded up to or feet. [footnote *: page .] [footnote **: intervals given are measured on the dip.] in dips of over ° to °, depending on the smoothness of the foot wall, the distance can again be increased, as stope-transport is greatly simplified, since the stope materials fall out by gravity. in timbered stopes, in dips over about °, intervals of to feet are possible. in filled stopes intervals of over feet present difficulties in the maintenance of ore-passes, for the wear and tear of longer use often breaks the timbers. in shrinkage-stopes, where no passes are to be maintained and few winzes put through, the interval is sometimes raised to feet. the subject is further discussed under "stoping." another factor bearing on level intervals is the needed insurance of sufficient points of stoping attack to keep up a certain output. this must particularly influence the manager whose mine has but little ore in reserve. [illustration: fig. .] protection of levels.--until recent years, timbering and occasional walling was the only method for the support of the roof, and for forming a platform for a stoping base. where the rock requires no support sublevels can be used as a stoping base, and timbering for such purpose avoided altogether (figs. , , ). in such cases the main roadway can then be driven on straight lines, either in the walls or in the ore, and used entirely for haulage. the subheading for a stoping base is driven far enough above or below the roadway (depending on whether overhand or underhand stoping is to be used) to leave a supporting pillar which is penetrated by short passes for ore. in overhand stopes, the ore is broken directly on the floor of an upper sublevel; and in underhand stopes, broken directly from the bottom of the sublevel. the method entails leaving a pillar of ore which can be recovered only with difficulty in mines where stope-support is necessary. the question of its adoption is then largely one of the comparative cost of timbering, the extra cost of the sublevel, and the net value of the ore left. in bad swelling veins, or badly crushing walls, where constant repair to timbers would be necessary, the use of a sublevel is a most useful alternative. it is especially useful with stopes to be left open or worked by shrinkage-stoping methods. if the haulage level, however, is to be the stoping base, some protection to the roadway must be provided. there are three systems in use,--by wood stulls or sets (figs. , , ), by dry-walling with timber caps (fig. ), and in some localities by steel sets. stulls are put up in various ways, and, as their use entails the least difficulty in taking the ore out from beneath the level, they are much favored, but are applicable only in comparatively narrow deposits. winzes and rises. these two kinds of openings for connecting two horizons in a mine differ only in their manner of construction. a winze is sunk underhand, while a rise is put up overhand. when the connection between levels is completed, a miner standing at the bottom usually refers to the opening as a rise, and when he goes to the top he calls it a winze. this confusion in terms makes it advisable to refer to all such completed openings as winzes, regardless of how they are constructed. in actual work, even disregarding water, it costs on the average about % less to raise than to sink such openings, for obviously the spoil runs out or is assisted by gravity in one case, and in the other has to be shoveled and hauled up. moreover, it is easier to follow the ore in a rise than in a winze. it usually happens, however, that in order to gain time both things are done, and for prospecting purposes sinking is necessary. the number of winzes required depends upon the method of stoping adopted, and is mentioned under "stoping." after stoping, the number necessary to be maintained open depends upon the necessities of ventilation, of escape, and of passageways for material to be used below. where stopes are to be filled with waste, more winzes must be kept open than when other methods are used, and these winzes must be in sufficient alignment to permit the continuous flow of material down past the various levels. in order that the winzes should deliver timber and filling to the most advantageous points, they should, in dipping ore-bodies, be as far as possible on the hanging wall side. development in the early prospecting stage. the prime objects in the prospecting stage are to expose the ore and to learn regarding the ore-bodies something of their size, their value, metallurgical character, location, dip, strike, etc.,--so much at least as may be necessary to determine the works most suitable for their extraction or values warranting purchase. in outcrop mines there is one rule, and that is "follow the ore." small temporary inclines following the deposit, even though they are eventually useless; are nine times out of ten justified. in prospecting deep-level projects, it is usually necessary to layout work which can be subsequently used in operating the mine, because the depth involves works of such considerable scale, even for prospecting, that the initial outlay does not warrant any anticipation of revision. such works have to be located and designed after a study of the general geology as disclosed in adjoining mines. practically the only method of supplementing such information is by the use of churn- and diamond-drills. drilling.--churn-drills are applicable only to comparatively shallow deposits of large volume. they have an advantage over the diamond drill in exposing a larger section and in their application to loose material; but inability to determine the exact horizon of the spoil does not lend them to narrow deposits, and in any event results are likely to be misleading from the finely ground state of the spoil. they are, however, of very great value for preliminary prospecting to shallow horizons. two facts in diamond-drilling have to be borne in mind: the indication of values is liable to be misleading, and the deflection of the drill is likely to carry it far away from its anticipated destination. a diamond-drill secures a small section which is sufficiently large to reveal the geology, but the values disclosed in metal mines must be accepted with reservations. the core amounts to but a little sample out of possibly large amounts of ore, which is always of variable character, and the core is most unlikely to represent the average of the deposit. two diamond-drill holes on the oroya brownhill mine both passed through the ore-body. one apparently disclosed unpayable values, the other seemingly showed ore forty feet in width assaying $ per ton. neither was right. on the other hand, the predetermination of the location of the ore-body justified expenditure. a recent experiment at johannesburg of placing a copper wedge in the hole at a point above the ore-body and deflecting the drill on reintroducing it, was successful in giving a second section of the ore at small expense. the deflection of diamond-drill holes from the starting angle is almost universal. it often amounts to a considerable wandering from the intended course. the amount of such deflection varies with no seeming rule, but it is probable that it is especially affected by the angle at which stratification or lamination planes are inclined to the direction of the hole. a hole has been known to wander in a depth of , feet more than feet from the point intended. various instruments have been devised for surveying deep holes, and they should be brought into use before works are laid out on the basis of diamond-drill results, although none of the inventions are entirely satisfactory. chapter x. stoping. methods of ore-breaking; underhand stopes; overhand stopes; combined stope. valuing ore in course of breaking. there is a great deal of confusion in the application of the word "stoping." it is used not only specifically to mean the actual ore-breaking, but also in a general sense to indicate all the operations of ore-breaking, support of excavations, and transportation between levels. it is used further as a noun to designate the hole left when the ore is taken out. worse still, it is impossible to adhere to miners' terms without employing it in every sense, trusting to luck and the context to make the meaning clear. the conditions which govern the method of stoping are in the main:-- _a_. the dip. _b_. the width of the deposit. _c_. the character of the walls. _d_. the cost of materials. _e_. the character of the ore. every mine, and sometimes every stope in a mine, is a problem special to itself. any general consideration must therefore be simply an inquiry into the broad principles which govern the adaptability of special methods. a logical arrangement of discussion is difficult, if not wholly impossible, because the factors are partially interdependent and of varying importance. for discussion the subject may be divided into: . methods of ore-breaking. . methods of supporting excavation. . methods of transport in stopes. methods of ore-breaking. the manner of actual ore-breaking is to drill and blast off slices from the block of ground under attack. as rock obviously breaks easiest when two sides are free, that is, when corners can be broken off, the detail of management for blasts is therefore to set the holes so as to preserve a corner for the next cut; and as a consequence the face of the stope shapes into a series of benches (fig. ),--inverted benches in the case of overhand stopes (figs. , ). the size of these benches will in a large measure depend on the depth of the holes. in wide stopes with machine-drills they vary from to feet; in narrow stopes with hand-holes, from two to three feet. [illustration: fig. .] the position of the men in relation to the working face gives rise to the usual primary classification of the methods of stoping. they are:-- . underhand stopes, . overhand stopes, . combined stopes. these terms originated from the direction of the drill-holes, but this is no longer a logical basis of distinction, for underhand holes in overhand stopes,--as in rill-stoping,--are used entirely in some mines (fig. ). [illustration: fig. .] underhand stopes.--underhand stopes are those in which the ore is broken downward from the levels. inasmuch as this method has the advantage of allowing the miner to strike his blows downward and to stand upon the ore when at work, it was almost universal before the invention of powder; and was applied more generally before the invention of machine-drills than since. it is never rightly introduced unless the stope is worked back from winzes through which the ore broken can be let down to the level below, as shown in figures and . [illustration: fig. .] this system can be advantageously applied only in the rare cases in which the walls require little or no support, and where very little or no waste requiring separation is broken with the ore in the stopes. to support the walls in bad ground in underhand stopes would be far more costly than with overhand stopes, for square-set timbering would be most difficult to introduce, and to support the walls with waste and stulls would be even more troublesome. any waste broken must needs be thrown up to the level above or be stored upon specially built stages--again a costly proceeding. a further drawback lies in the fact that the broken ore follows down the face of the stope, and must be shoveled off each bench. it thus all arrives at a single point,--the winze,--and must be drawn from a single ore-pass into the level. this usually results not only in more shoveling but in a congestion at the passes not present in overhand stoping, for with that method several chutes are available for discharging ore into the levels. where the walls require no support and no selection is desired in the stopes, the advantage of the men standing on the solid ore to work, and of having all down holes and therefore drilled wet, gives this method a distinct place. in using this system, in order to protect the men, a pillar is often left under the level by driving a sublevel, the pillar being easily recoverable later. the method of sublevels is of advantage largely in avoiding the timbering of levels. [illustration: fig. .--longitudinal section of an underhand stope.] overhand stopes.--by far the greatest bulk of ore is broken overhand, that is broken upward from one level to the next above. there are two general forms which such stopes are given,--"horizontal" and "rill." [illustration: fig. .--horizontal-cut overhand stope--longitudinal section.] the horizontal "flat-back" or "long-wall" stope, as it is variously called, shown in figure , is operated by breaking the ore in slices parallel with the levels. in rill-stoping the ore is cut back from the winzes in such a way that a pyramid-shaped room is created, with its apex in the winze and its base at the level (figs. and ). horizontal or flat-backed stopes can be applied to almost any dip, while "rill-stoping" finds its most advantageous application where the dip is such that the ore will "run," or where it can be made to "run" with a little help. the particular application of the two systems is dependent not only on the dip but on the method of supporting the excavation and the ore. with rill-stoping, it is possible to cut the breaking benches back horizontally from the winzes (fig. ), or to stagger the cuts in such a manner as to take the slices in a descending angle (figs. and ). [illustration: fig. .--rill-cut overhand stope--longitudinal section.] in the "rill" method of incline cuts, all the drill-holes are "down" holes (fig. ), and can be drilled wet, while in horizontal cuts or flat-backed stopes, at least part of the holes must be "uppers" (fig. ). aside from the easier and cheaper drilling and setting up of machines with this kind of "cut," there is no drill dust,--a great desideratum in these days of miners' phthisis. a further advantage in the "rill" cut arises in cases where horizontal jointing planes run through the ore of a sort from which unduly large masses break away in "flat-back" stopes. by the descending cut of the "rill" method these calamities can be in a measure avoided. in cases of dips over º the greatest advantage in "rill" stoping arises from the possibility of pouring filling or timber into the stope from above with less handling, because the ore and material will run down the sides of the pyramid (figs. and ). thus not only is there less shoveling required, but fewer ore-passes and a less number of preliminary winzes are necessary, and a wider level interval is possible. this matter will be gone into more fully later. [illustration: fig. .--rill-cut overhand stope-longitudinal section.] combined stopes.--a combined stope is made by the coincident working of the underhand and "rill" method (fig. ). this order of stope has the same limitations in general as the underhand kind. for flat veins with strong walls, it has a great superiority in that the stope is carried back more or less parallel with the winzes, and thus broken ore after blasting lies in a line on the gradient of the stope. it is, therefore, conveniently placed for mechanical stope haulage. a further advantage is gained in that winzes may be placed long distances apart, and that men are not required, either when at work or passing to and from it, to be ever far from the face, and they are thus in the safest ground, so that timber and filling protection which may be otherwise necessary is not required. this method is largely used in south africa. [illustration: fig. .--longitudinal section of a combined stope.] minimum width of stopes.--the minimum stoping width which can be consistently broken with hand-holes is about inches, and this only where there is considerable dip to the ore. this space is so narrow that it is of doubtful advantage in any case, and inches is more common in narrow mines, especially where worked with white men. where machine-drills are used about feet is the minimum width feasible. resuing.--in very narrow veins where a certain amount of wall-rock must be broken to give working space, it pays under some circumstances to advance the stope into the wall-rock ahead of the ore, thus stripping the ore and enabling it to be broken separately. this permits of cleaner selection of the ore; but it is a problem to be worked out in each case, as to whether rough sorting of some waste in the stopes, or further sorting at surface with inevitable treatment of some waste rock, is more economical than separate stoping cuts and inevitably wider stopes. valuing ore in course of breaking.--there are many ores whose payability can be determined by inspection, but there are many of which it cannot. continuous assaying is in the latter cases absolutely necessary to avoid the treatment of valueless material. in such instances, sampling after each stoping-cut is essential, the unprofitable ore being broken down and used as waste. where values fade into the walls, as in impregnation deposits, the width of stopes depends upon the limit of payability. in these cases, drill-holes are put into the walls and the drillings assayed. if the ore is found profitable, the holes are blasted out. the gauge of what is profitable in such situations is not dependent simply upon the average total working costs of the mine, for ore in that position can be said to cost nothing for development work and administration; moreover, it is usually more cheaply broken than the average breaking cost, men and machines being already on the spot. chapter xi. methods of supporting excavation. timbering; filling with waste; filling with broken ore; pillars of ore; artificial pillars; caving system. most stopes require support to be given to the walls and often to the ore itself. where they do require support there are five principal methods of accomplishing it. the application of any particular method depends upon the dip, width of ore-body, character of the ore and walls, and cost of materials. the various systems are by:-- . timbering. . filling with waste. . filling with broken ore subsequently withdrawn. . pillars of ore. . artificial pillars built of timbers and waste. . caving. timbering.--at one time timbering was the almost universal means of support in such excavations, but gradually various methods for the economical application of waste and ore itself have come forward, until timbering is fast becoming a secondary device. aside from economy in working without it, the dangers of creeps, or crushing, and of fires are sufficient incentives to do away with wood as far as possible. there are three principal systems of timber support to excavations,--by stulls, square-sets, and cribs. stulls are serviceable only where the deposit is so narrow that the opening can be bridged by single timbers between wall and wall (figs. and ). this system can be applied to any dip and is most useful in narrow deposits where the walls are not too heavy. stulls in inclined deposits are usually set at a slightly higher angle than that perpendicular to the walls, in order that the vertical pressure of the hanging wall will serve to tighten them in position. the "stull" system can, in inclined deposits, be further strengthened by building waste pillars against them, in which case the arrangement merges into the system of artificial pillars. [illustration: fig. .--longitudinal section of stull-supported stope.] [illustration: fig. .--longitudinal section showing square-set timbering.] [illustration: fig. .--square-set timbering on inclined ore-body. showing ultimate strain on timbers.] square-sets (figs. and ), that is, trusses built in the opening as the ore is removed, are applicable to almost any dip or width of ore, but generally are applied only in deposits too wide, or to rock too heavy, for stulls. such trusses are usually constructed on vertical and horizontal lines, and while during actual ore-breaking the strains are partially vertical, ultimately, however, when the weight of the walls begins to be felt, these strains, except in vertical deposits, come at an angle to lines of strength in the trusses, and therefore timber constructions of this type present little ultimate resistance (fig. ). square-set timbers are sometimes set to present the maximum resistance to the direction of strain, but the difficulties of placing them in position and variations in the direction of strain on various parts of the stope do not often commend the method. as a general rule square-sets on horizontal lines answer well enough for the period of actual ore-breaking. the crushing or creeps is usually some time later; and if the crushing may damage the whole mine, their use is fraught with danger. reënforcement by building in waste is often resorted to. when done fully, it is difficult to see the utility of the enclosed timber, for entire waste-filling would in most cases be cheaper and equally efficient. [illustration: fig. .--"cribs."] there is always, with wood constructions, as said before, the very pertinent danger of subsequent crushing and of subsidence in after years, and the great risk of fires. both these disasters have cost comstock and broken hill mines, directly or indirectly, millions of dollars, and the outlay on timber and repairs one way or another would have paid for the filling system ten times over. there are cases where, by virtue of the cheapness of timber, "square-setting" is the most economical method. again, there are instances where the ore lies in such a manner--particularly in limestone replacements--as to preclude other means of support. these cases are being yearly more and more evaded by the ingenuity of engineers in charge. the author believes it soon will be recognized that the situation is rare indeed where complete square-setting is necessarily without an economical alternative. an objection is sometimes raised to filling in favor of timber, in that if it become desirable to restope the walls for low-grade ore left behind, such stopes could only be entered by drawing the filling, with consequent danger of total collapse. such a contingency can be provided for in large ore-bodies by installing an outer shell of sets of timber around the periphery of the stope and filling the inside with waste. if the crushing possibilities are too great for this method then, the subsequent recovery of ore is hopeless in any event. in narrow ore-bodies with crushing walls recovery of ore once left behind is not often possible. the third sort of timber constructions are cribs, a "log-house" sort of structure usually filled with waste, and more fully discussed under artificial pillars (fig. ). the further comparative merits of timbering with other methods will be analyzed as the different systems are described. filling with waste.--the system of filling stope-excavations completely with waste in alternating progress with ore-breaking is of wide and increasingly general application (figs. , , , ). although a certain amount of waste is ordinarily available in the stopes themselves, or from development work in the mine, such a supply must usually be supplemented from other directions. treatment residues afford the easiest and cheapest handled material. quarried rock ranks next, and in default of any other easy supply, materials from crosscuts driven into the stope-walls are sometimes resorted to. in working the system to the best advantage, the winzes through the block of ore under attack are kept in alignment with similar openings above, in order that filling may be poured through the mine from the surface or any intermediate point. winzes to be used for filling should be put on the hanging-wall side of the area to be filled, for the filling poured down will then reach the foot-wall side of the stopes with a minimum of handling. in some instances, one special winze is arranged for passing all filling from the surface to a level above the principal stoping operations; and it is then distributed along the levels into the winzes, and thus to the operating stopes, by belt-conveyors. [illustration: fig. .--longitudinal section. rill stope filled with waste.] [illustration: fig. .--longitudinal section. horizontal stope filled with waste.] [illustration: fig. .--longitudinal section. waste-filled stope with dry-walling of levels and passes.] in this system of stope support the ore is broken at intervals alternating with filling. if there is danger of much loss from mixing broken ore and filling, "sollars" of boards or poles are laid on the waste. if the ore is very rich, old canvas or cowhides are sometimes put under the boards. before the filling interval, the ore passes are built close to the face above previous filling and their tops covered temporarily to prevent their being filled with running waste. if the walls are bad, the filling is kept close to the face. if the unbroken ore requires support, short stulls set on the waste (as in fig. ) are usually sufficient until the next cut is taken off, when the timber can be recovered. if stulls are insufficient, cribs or bulkheads (fig. ) are also used and often buried in the filling. [illustration: fig. .--cross-section of fig. on line _a-b_.] both flat-backed and rill-stope methods of breaking are employed in conjunction with filled stopes. the advantages of the rill-stopes are so patent as to make it difficult to understand why they are not universally adopted when the dip permits their use at all. in rill-stopes (figs. and ) the waste flows to its destination with a minimum of handling. winzes and ore-passes are not required with the same frequency as in horizontal breaking, and the broken ore always lies on the slope towards the passes and is therefore also easier to shovel. in flat-backed stopes (fig. ) winzes must be put in every feet or so, while in rill-stopes they can be double this distance apart. the system is applicable by modification to almost any width of ore. it finds its most economical field where the dip of the stope floor is over °, when waste and ore, with the help of the "rill," will flow to their destination. for dips from under about ° to about ° or °, where the waste and ore will not "flow" easily, shoveling can be helped by the use of the "rill" system and often evaded altogether, if flow be assisted by a sheet-iron trough described in the discussion of stope transport. further saving in shoveling can be gained in this method, by giving a steeper pitch to the filling winzes and to the ore-passes, by starting them from crosscuts in the wall, and by carrying them at greater angles than the pitch of the ore (fig. ). these artifices combined have worked out most economically on several mines within the writer's experience, with the dip as flat as °. for very flat dips, where filling is to be employed, rill-stoping has no advantage over flat-backed cuts, and in such cases it is often advisable to assist stope transport by temporary tracks and cars which obviously could not be worked on the tortuous contour of a rill-stope, so that for dips under ° advantage lies with "flat-backed" ore-breaking. [illustration: fig. .--cross-section showing method of steepening winzes and ore passes.] on very wide ore-bodies where the support of the standing ore itself becomes a great problem, the filling system can be applied by combining it with square-setting. in this case the stopes are carried in panels laid out transversally to the strike as wide as the standing strength of the ore permits. on both sides of each panel a fence of lagged square-sets is carried up and the area between is filled with waste. the panels are stoped out alternately. the application of this method at broken hill will be described later. (see pages and figs. and .) the same type of wide ore-body can be managed also on the filling system by the use of frequent "bulkheads" to support the ore (fig. ). compared with timbering methods, filling has the great advantage of more effective support to the mine, less danger of creeps, and absolute freedom from the peril of fire. the relative expense of the two systems is determined by the cost of materials and labor. two extreme cases illustrate the result of these economic factors with sufficient clearness. it is stated that the cost of timbering stopes on the le roi mine by square-sets is about cents per ton of ore excavated. in the ivanhoe mine of west australia the cost of filling stopes with tailings is about cents per ton of ore excavated. at the former mine the average cost of timber is under $ per m board-measure, while at the latter its price would be $ per m board-measure; although labor is about of the same efficiency and wage, the cost in the ivanhoe by square-setting would be about cents per ton of ore broken. in the le roi, on the other hand, no residues are available for filling. to quarry rock or drive crosscuts into the walls might make this system cost cents per ton of ore broken if applied to that mine. the comparative value of the filling method with other systems will be discussed later. filling with broken ore subsequently withdrawn.--this order of support is called by various names, the favorite being "shrinkage-stoping." the method is to break the ore on to the roof of the level, and by thus filling the stope with broken ore, provide temporary support to the walls and furnish standing floor upon which to work in making the next cut (figs. , , and .) as broken material occupies to % more space than rock _in situ_, in order to provide working space at the face, the broken ore must be drawn from along the level after each cut. when the area attacked is completely broken through from level to level, the stope will be full of loose broken ore, which is then entirely drawn off. a block to be attacked by this method requires preliminary winzes only at the extremities of the stope,--for entry and for ventilation. where it is desired to maintain the winzes after stoping, they must either be strongly timbered and lagged on the stope side, be driven in the walls, or be protected by a pillar of ore (fig. ). the settling ore and the crushing after the stope is empty make it difficult to maintain timbered winzes. [illustration: fig. .--longitudinal section of stope filled with broken ore.] where it can be done without danger to the mine, the empty stopes are allowed to cave. if such crushing would be dangerous, either the walls must be held up by pillars of unbroken ore, as in the alaska treadwell, where large "rib" pillars are left, or the open spaces must be filled with waste. filling the empty stope is usually done by opening frequent passes along the base of the filled stope above, and allowing the material of the upper stope to flood the lower one. this program continued upwards through the mine allows the whole filling of the mine to descend gradually and thus requires replenishment only into the top. the old stopes in the less critical and usually exhausted territory nearer the surface are sometimes left without replenishing their filling. the weight of broken ore standing at such a high angle as to settle rapidly is very considerable upon the level; moreover, at the moment when the stope is entirely drawn off, the pressure of the walls as well is likely to be very great. the roadways in this system therefore require more than usual protection. three methods are used: (_a_) timbering; (_b_) driving a sublevel in the ore above the main roadway as a stoping-base, thus leaving a pillar of ore over the roadway (fig. ); (_c_) by dry-walling the levels, as in the baltic mine, michigan (figs. and ). by the use of sublevels the main roadways are sometimes driven in the walls (fig. ) and in many cases all timbering is saved. to recover pillars left below sublevels is a rather difficult task, especially if the old stope above is caved or filled. the use of pillars in substitution for timber, if the pillars are to be lost, is simply a matter of economics as to whether the lost ore would repay the cost of other devices. [illustration: fig. .--cross-section of "shrinkage" stope.] frequent ore-chutes through the level timbers, or from the sublevels, are necessary to prevent lodgment of broken ore between such passes, because it is usually too dangerous for men to enter the emptying stope to shovel out the lodged remnants. where the ore-body is wide, and in order that there may be no lodgment of ore, the timbers over the level are set so as to form a trough along the level; or where pillars are left, they are made "a"-shaped between the chutes, as indicated in figure . [illustration: fig. .--cross-section of "shrinkage" stope.] the method of breaking the ore in conjunction with this means of support in comparatively narrow deposits can be on the rill, in order to have the advantage of down holes. usually, however, flat-back or horizontal cuts are desirable, as in such an arrangement it is less troublesome to regulate the drawing of the ore so as to provide proper head room. where stopes are wide, ore is sometimes cut arch-shaped from wall to wall to assure its standing. where this method of support is not of avail, short, sharply tapering stulls are put in from the broken ore to the face (fig. ). when the cut above these stulls is taken out, they are pulled up and are used again. this method of stoping is only applicable when:-- . the deposit dips over °, and thus broken material will freely settle downward to be drawn off from the bottom. . the ore is consistently payable in character. no selection can be done in breaking, as all material broken must be drawn off together. . the hanging wall is strong, and will not crush or spall off waste into the ore. . the ore-body is regular in size, else loose ore will lodge on the foot wall. stopes opened in this manner when partially empty are too dangerous for men to enter for shoveling out remnants. the advantages of this system over others, where it is applicable, are:-- (_a_) a greater distance between levels can be operated and few winzes and rises are necessary, thus a great saving of development work can be effected. a stope to feet long can be operated with a winze at either end and with levels or feet apart. (_b_) there is no shoveling in the stopes at all. (_c_) no timber is required. as compared with timbering by stulling, it will apply to stopes too wide and walls too heavy for this method. moreover, little staging is required for working the face, since ore can be drawn from below in such a manner as to allow just the right head room. (_d_) compared to the system of filling with waste, coincidentally with breaking (second method), it saves altogether in some cases the cost of filling. in any event, it saves the cost of ore-passes, of shoveling into them, and of the detailed distribution of the filling. compared with other methods, the system has the following disadvantages, that: _a_. the ore requires to be broken in the stopes to a degree of fineness which will prevent blocking of the chutes at the level. when pieces too large reach the chutes, nothing will open them but blasting,--to the damage of timbers and chutes. some large rocks are always liable to be buried in the course of ore-breaking. _b_. practically no such perfection of walls exists, but some spalling of waste into the ore will take place. a crushing of the walls would soon mean the loss of large amounts of ore. _c_. there is no possibility of regulating the mixture of grade of ore by varying the working points. it is months after the ore is broken before it can reach the levels. _d_. the breaking of % more ore than immediate treatment demands results in the investment of a considerable sum of money. an equilibrium is ultimately established in a mine worked on this system when a certain number of stopes full of completely broken ore are available for entire withdrawal, and there is no further accumulation. but, in any event, a considerable amount of broken ore must be held in reserve. in one mine worked on this plan, with which the writer has had experience, the annual production is about , tons and the broken ore represents an investment which, at %, means an annual loss of interest amounting to cents per ton of ore treated. _e_. a mine once started on the system is most difficult to alter, owing to the lack of frequent winzes or passes. especially is this so if the only alternative is filling, for an alteration to the system of filling coincident with breaking finds the mine short of filling winzes. as the conditions of walls and ore often alter with depth, change of system may be necessary and the situation may become very embarrassing. _f_. the restoping of the walls for lower-grade ore at a later period is impossible, for the walls of the stope will be crushed, or, if filled with waste, will usually crush when it is drawn off to send to a lower stope. the system has much to recommend it where conditions are favorable. like all other alternative methods of mining, it requires the most careful study in the light of the special conditions involved. in many mines it can be used for some stopes where not adaptable generally. it often solves the problem of blind ore-bodies, for they can by this means be frequently worked with an opening underneath only. thus the cost of driving a roadway overhead is avoided, which would be required if timber or coincident filling were the alternatives. in such cases ventilation can be managed without an opening above, by so directing the current of air that it will rise through a winze from the level below, flow along the stope and into the level again at the further end of the stope through another winze. [illustration: fig. .--longitudinal section. ore-pillar support in narrow stopes.] support by pillars of ore.--as a method of mining metals of the sort under discussion, the use of ore-pillars except in conjunction with some other means of support has no general application. to use them without assistance implies walls sufficiently strong to hold between pillars; to leave them permanently anywhere implies that the ore abandoned would not repay the labor and the material of a substitute. there are cases of large, very low-grade mines where to abandon one-half the ore as pillars is more profitable than total extraction, but the margin of payability in such ore must be very, very narrow. unpayable spots are always left as pillars, for obvious reasons. permanent ore-pillars as an adjunct to other methods of support are in use. such are the rib-pillars in the alaska treadwell, the form of which is indicated by the upward extension of the pillars adjacent to the winzes, shown in figure . always a careful balance must be cast as to the value of the ore left, and as to the cost of a substitute, because every ore-pillar can be removed at some outlay. temporary pillars are not unusual, particularly to protect roadways and shafts. they are, when left for these purposes, removed ultimately, usually by beginning at the farther end and working back to the final exit. [illustration: fig. .--horizontal plan at levels of broken hill. method of alternate stopes and ore-pillars.] [illustration: fig. .--longitudinal section of figure .] a form of temporary ore-pillars in very wide deposits is made use of in conjunction with both filling and timbering (figs. , , ). in the use of temporary pillars for ore-bodies to feet wide at broken hill, stopes are carried up at right angles to the strike, each fifty feet wide and clear across the ore-body (figs. and ). a solid pillar of the same width is left in the first instance between adjacent stopes, and the initial series of stopes are walled with one square-set on the sides as the stope is broken upward. the room between these two lines of sets is filled with waste alternating with ore-breaking in the usual filling method. when the ore from the first group of alternate stopes (_abc_, fig. ) is completely removed, the pillars are stoped out and replaced with waste. the square-sets of the first set of stopes thus become the boundaries of the second set. entry and ventilation are obtained through these lines of square-sets, and the ore is passed out of the stopes through them. [illustration: fig. .--cross-section of stull support with waste reënforcement.] artificial pillars.--this system also implies a roof so strong as not to demand continuous support. artificial pillars are built in many different ways. the method most current in fairly narrow deposits is to reënforce stulls by packing waste above them (figs. and ). not only is it thus possible to economize in stulls by using the waste which accumulates underground, but the principle applies also to cases where the stulls alone are not sufficient support, and yet where complete filling or square-setting is unnecessary. when the conditions are propitious for this method, it has the comparative advantage over timber systems of saving timber, and over filling systems of saving imported filling. moreover, these constructions being pillar-shaped (fig. ), the intervals between them provide outlets for broken ore, and specially built passes are unnecessary. the method has two disadvantages as against the square-set or filling process, in that more staging must be provided from which to work, and in stopes over six feet the erection of machine-drill columns is tedious and costly in time and wages. [illustration: fig. .--longitudinal section of stull and waste pillars.] in wide deposits of markedly flat, irregular ore-bodies, where a definite system is difficult and where timber is expensive, cribs of cord-wood or logs filled with waste after the order shown in figure , often make fairly sound pillars. they will not last indefinitely and are best adapted to the temporary support of the ore-roof pending filling. the increased difficulty in setting up machine drills in such stopes adds to the breaking costs,--often enough to warrant another method of support. [illustration: fig. .--sublevel caving system.] caving systems.--this method, with variations, has been applied to large iron deposits, to the kimberley diamond mines, to some copper mines, but in general it has little application to the metal mines under consideration, as few ore-bodies are of sufficiently large horizontal area. the system is dependent upon a large area of loose or "heavy" ground pressing directly on the ore with weight, such that if the ore be cut into pillars, these will crush. the details of the system vary, but in general the _modus operandi_ is to prepare roadways through the ore, and from the roadways to put rises, from which sublevels are driven close under the floating mass of waste and ore,--sometimes called the "matte" (fig. ). the pillars between these sublevels are then cut away until the weight above crushes them down. when all the crushed ore which can be safely reached is extracted, retreat is made and another series of subopenings is then driven close under the "matte." the pillar is reduced until it crushes and the operation is repeated. eventually the bottom strata of the "matte" become largely ore, and a sort of equilibrium is reached when there is not much loss in this direction. "top slicing" is a variation of the above method by carrying a horizontal stope from the rises immediately under the matte, supporting the floating material with timber. at kimberley the system is varied in that galleries are run out to the edge of the diamond-iferous area and enlarged until the pillar between crushes. in the caving methods, between and % of the ore is removed by the preliminary openings, and as they are all headings of some sort, the average cost per ton of this particular ore is higher than by ordinary stoping methods. on the other hand, the remaining to % of the ore costs nothing to break, and the average cost is often remarkably low. as said, the system implies bodies of large horizontal area. they must start near enough to the surface that the whole superincumbent mass may cave and give crushing weight, or the immediately overhanging roof must easily cave. all of these are conditions not often met with in mines of the character under review. chapter xii. mechanical equipment. conditions bearing on mine equipment; winding appliances; haulage equipment in shafts; lateral underground transport; transport in stopes. there is no type of mechanical engineering which presents such complexities in determination of the best equipment as does that of mining. not only does the economic side dominate over pure mechanics, but machines must be installed and operated under difficulties which arise from the most exceptional and conflicting conditions, none of which can be entirely satisfied. compromise between capital outlay, operating efficiency, and conflicting demands is the key-note of the work. these compromises are brought about by influences which lie outside the questions of mechanics of individual machines, and are mainly as follows:-- . continuous change in horizon of operations. . uncertain life of the enterprise. . care and preservation of human life. . unequal adaptability of power transmission mediums. . origin of power. _first._--the depth to be served and the volume of ore and water to be handled, are not only unknown at the initial equipment, but they are bound to change continuously in quantity, location, and horizon with the extension of the workings. _second._--from the mine manager's point of view, which must embrace that of the mechanical engineer, further difficulty presents itself because the life of the enterprise is usually unknown, and therefore a manifest necessity arises for an economic balance of capital outlay and of operating efficiency commensurate with the prospects of the mine. moreover, the initial capital is often limited, and makeshifts for this reason alone must be provided. in net result, no mineral deposit of speculative ultimate volume of ore warrants an initial equipment of the sort that will meet every eventuality, or of the kind that will give even the maximum efficiency which a free choice of mining machinery could obtain. _third._--in the design and selection of mining machines, the safety of human life, the preservation of the health of workmen under conditions of limited space and ventilation, together with reliability and convenience in installing and working large mechanical tools, all dominate mechanical efficiency. for example, compressed-air transmission of power best meets the requirements of drilling, yet the mechanical losses in the generation, the transmission, and the application of compressed air probably total, from first to last, to %. _fourth._--all machines, except those for shaft haulage, must be operated by power transmitted from the surface, as obviously power generation underground is impossible. the conversion of power into a transmission medium and its transmission are, at the outset, bound to be the occasions of loss. not only are the various forms of transmission by steam, electricity, compressed air, or rods, of different efficiency, but no one system lends itself to universal or economical application to all kinds of mining machines. therefore it is not uncommon to find three or four different media of power transmission employed on the same mine. to illustrate: from the point of view of safety, reliability, control, and in most cases economy as well, we may say that direct steam is the best motive force for winding-engines; that for mechanical efficiency and reliability, rods constitute the best media of power transmission to pumps; that, considering ventilation and convenience, compressed air affords the best medium for drills. yet there are other conditions as to character of the work, volume of water or ore, and the origin of power which must in special instances modify each and every one of these generalizations. for example, although pumping water with compressed air is mechanically the most inefficient of devices, it often becomes the most advantageous, because compressed air may be of necessity laid on for other purposes, and the extra power required to operate a small pump may be thus most cheaply provided. _fifth._--further limitations and modifications arise out of the origin of power, for the sources of power have an intimate bearing on the type of machine and media of transmission. this very circumstance often compels giving away efficiency and convenience in some machines to gain more in others. this is evident enough if the principal origins of power generation be examined. they are in the main as follows:-- _a_. water-power available at the mine. _b_. water-power available at a less distance than three or four miles. _c_. water-power available some miles away, thus necessitating electrical transmission (or purchased electrical power). _d_. steam-power to be generated at the mine. _e_. gas-power to be generated at the mine. _a_. with water-power at the mine, winding engines can be operated by direct hydraulic application with a gain in economy over direct steam, although with the sacrifice of control and reliability. rods for pumps can be driven directly with water, but this superiority in working economy means, as discussed later, a loss of flexibility and increased total outlay over other forms of transmission to pumps. as compressed air must be transmitted for drills, the compressor would be operated direct from water-wheels, but with less control in regularity of pressure delivery. _b_. with water-power a short distance from the mine, it would normally be transmitted either by compressed air or by electricity. compressed-air transmission would better satisfy winding and drilling requirements, but would show a great comparative loss in efficiency over electricity when applied to pumping. despite the latter drawback, air transmission is a method growing in favor, especially in view of the advance made in effecting compression by falling water. _c_. in the situation of transmission too far for using compressed air, there is no alternative but electricity. in these cases, direct electric winding is done, but under such disadvantages that it requires a comparatively very cheap power to take precedence over a subsidiary steam plant for this purpose. electric air-compressors work under the material disadvantage of constant speed on a variable load, but this installation is also a question of economics. the pumping service is well performed by direct electrical pumps. _d_. in this instance, winding and air-compression are well accomplished by direct steam applications; but pumping is beset with wholly undesirable alternatives, among which it is difficult to choose. _e_. with internal combustion engines, gasoline (petrol) motors have more of a position in experimental than in systematic mining, for their application to winding and pumping and drilling is fraught with many losses. the engine must be under constant motion, and that, too, with variable loads. where power from producer gas is used, there is a greater possibility of installing large equipments, and it is generally applied to the winding and lesser units by conversion into compressed air or electricity as an intermediate stage. one thing becomes certain from these examples cited, that the right installation for any particular portion of the mine's equipment cannot be determined without reference to all the others. the whole system of power generation for surface work, as well as the transmission underground, must be formulated with regard to furnishing the best total result from all the complicated primary and secondary motors, even at the sacrifice of some members. each mine is a unique problem, and while it would be easy to sketch an ideal plant, there is no mine within the writer's knowledge upon which the ideal would, under the many variable conditions, be the most economical of installation or the most efficient of operation. the dominant feature of the task is an endeavor to find a compromise between efficiency and capital outlay. the result is a series of choices between unsatisfying alternatives, a number of which are usually found to have been wrong upon further extension of the mine in depth. in a general way, it may be stated that where power is generated on the mine, economy in labor of handling fuel, driving engines, generation and condensing steam where steam is used, demand a consolidated power plant for the whole mine equipment. the principal motors should be driven direct by steam or gas, with power distribution by electricity to all outlying surface motors and sometimes to underground motors, and also to some underground motors by compressed air. much progress has been made in the past few years in the perfection of larger mining tools. inherently many of our devices are of a wasteful character, not only on account of the need of special forms of transmission, but because they are required to operate under greatly varying loads. as an outcome of transmission losses and of providing capacity to cope with heavy peak loads, their efficiency on the basis of actual foot-pounds of work accomplished is very low. the adoption of electric transmission in mine work, while in certain phases beneficial, has not decreased the perplexity which arises from many added alternatives, none of which are as yet a complete or desirable answer to any mine problem. when a satisfactory electric drill is invented, and a method is evolved of applying electricity to winding-engines that will not involve such abnormal losses due to high peak load then we will have a solution to our most difficult mechanical problems, and electricity will deserve the universal blessing which it has received in other branches of mechanical engineering. it is not intended to discuss mine equipment problems from the machinery standpoint,--there are thousands of different devices,--but from the point of view of the mine administrator who finds in the manufactory the various machines which are applicable, and whose work then becomes that of choosing, arranging, and operating these tools. the principal mechanical questions of a mine may be examined under the following heads:-- . shaft haulage. . lateral underground transport. . drainage. . rock drilling. . workshops. . improvements in equipment. shaft haulage. winding appliances.--no device has yet been found to displace the single load pulled up the shaft by winding a rope on a drum. of driving mechanisms for drum motors the alternatives are the steam-engine, the electrical motor, and infrequently water-power or gas engines. all these have to cope with one condition which, on the basis of work accomplished, gives them a very low mechanical efficiency. this difficulty is that the load is intermittent, and it must be started and accelerated at the point of maximum weight, and from that moment the power required diminishes to less than nothing at the end of the haul. a large number of devices are in use to equalize partially the inequalities of the load at different stages of the lift. the main lines of progress in this direction have been:-- _a_. the handling of two cages or skips with one engine or motor, the descending skip partially balancing the ascending one. _b_. the use of tail-ropes or balance weights to compensate the increasing weight of the descending rope. _c_. the use of skips instead of cages, thus permitting of a greater percentage of paying load. _d_. the direct coupling of the motor to the drum shaft. _e_. the cone-shaped construction of drums,--this latter being now largely displaced by the use of the tail-rope. the first and third of these are absolutely essential for anything like economy and speed; the others are refinements depending on the work to be accomplished and the capital available. steam winding-engines require large cylinders to start the load, but when once started the requisite power is much reduced and the load is too small for steam economy. the throttling of the engine for controlling speed and reversing the engine at periodic stoppages militates against the maximum expansion and condensation of the steam and further increases the steam consumption. in result, the best of direct compound condensing engines consume from to pounds of steam per horse-power hour, against a possible efficiency of such an engine working under constant load of less than pounds of steam per horse-power hour. it is only within very recent years that electrical motors have been applied to winding. even yet, all things considered, this application is of doubtful value except in localities of extremely cheap electrical power. the constant speed of alternating current motors at once places them at a disadvantage for this work of high peak and intermittent loads. while continuous-current motors can be made to partially overcome this drawback, such a current, where power is purchased or transmitted a long distance, is available only by conversion, which further increases the losses. however, schemes of electrical winding are in course of development which bid fair, by a sort of storage of power in heavy fly-wheels or storage batteries after the peak load, to reduce the total power consumption; but the very high first cost so far prevents their very general adoption for metal mining. winding-engines driven by direct water- or gas-power are of too rare application to warrant much discussion. gasoline driven hoists have a distinct place in prospecting and early-stage mining, especially in desert countries where transport and fuel conditions are onerous, for both the machines and their fuel are easy of transport. as direct gas-engines entail constant motion of the engine at the power demand of the peak load, they are hopeless in mechanical efficiency. like all other motors in mining, the size and arrangement of the motor and drum are dependent upon the duty which they will be called upon to perform. this is primarily dependent upon the depth to be hoisted from, the volume of the ore, and the size of the load. for shallow depths and tonnages up to, say, tons daily, geared engines have a place on account of their low capital cost. where great rope speed is not essential they are fully as economical as direct-coupled engines. with great depths and greater capacities, speed becomes a momentous factor, and direct-coupled engines are necessary. where the depth exceeds , feet, another element enters which has given rise to much debate and experiment; that is, the great increase of starting load due to the increased length and size of ropes and the drum space required to hold it. so far the most advantageous device seems to be the whiting hoist, a combination of double drums and tail rope. on mines worked from near the surface, where depth is gained by the gradual exhaustion of the ore, the only prudent course is to put in a new hoist periodically, when the demand for increased winding speed and power warrants. the lack of economy in winding machines is greatly augmented if they are much over-sized for the duty. an engine installed to handle a given tonnage to a depth of , feet will have operated with more loss during the years the mine is progressing from the surface to that depth than several intermediate-sized engines would have cost. on most mines the uncertainty of extension in depth would hardly warrant such a preliminary equipment. more mines are equipped with over-sized than with under-sized engines. for shafts on going metal mines where the future is speculative, an engine will suffice whose size provides for an extension in depth of , feet beyond that reached at the time of its installation. the cost of the engine will depend more largely upon the winding speed desired than upon any other one factor. the proper speed to be arranged is obviously dependent upon the depth of the haulage, for it is useless to have an engine able to wind , feet a minute on a shaft feet deep, since it could never even get under way; and besides, the relative operating loss, as said, would be enormous. haulage equipment in the shaft.--originally, material was hoisted through shafts in buckets. then came the cage for transporting mine cars, and in more recent years the "skip" has been developed. the aggrandized bucket or "kibble" of the cornishman has practically disappeared, but the cage still remains in many mines. the advantages of the skip over the cage are many. some of them are:-- _a_. it permits to % greater load of material in proportion to the dead weight of the vehicle. _b_. the load can be confined within a smaller horizontal space, thus the area of the shaft need not be so great for large tonnages. _c_. loading and discharging are more rapid, and the latter is automatic, thus permitting more trips per hour and requiring less labor. _d_. skips must be loaded from bins underground, and by providing in the bins storage capacity, shaft haulage is rendered independent of the lateral transport in the mine, and there are no delays to the engine awaiting loads. the result is that ore-winding can be concentrated into fewer hours, and indirect economies in labor and power are thus effected. _e_. skips save the time of the men engaged in the lateral haulage, as they have no delay waiting for the winding engine. loads equivalent to those from skips are obtained in some mines by double-decked cages; but, aside from waste weight of the cage, this arrangement necessitates either stopping the engine to load the lower deck, or a double-deck loading station. double-deck loading stations are as costly to install and more expensive to work than skip-loading station ore-bins. cages are also constructed large enough to take as many as four trucks on one deck. this entails a shaft compartment double the size required for skips of the same capacity, and thus enormously increases shaft cost without gaining anything. altogether the advantages of the skip are so certain and so important that it is difficult to see the justification for the cage under but a few conditions. these conditions are those which surround mines of small output where rapidity of haulage is no object, where the cost of station-bins can thus be evaded, and the convenience of the cage for the men can still be preserved. the easy change of the skip to the cage for hauling men removes the last objection on larger mines. there occurs also the situation in which ore is broken under contract at so much per truck, and where it is desirable to inspect the contents of the truck when discharging it, but even this objection to the skip can be obviated by contracting on a cubic-foot basis. skips are constructed to carry loads of from two to seven tons, the general tendency being toward larger loads every year. one of the most feasible lines of improvement in winding is in the direction of larger loads and less speed, for in this way the sum total of dead weight of the vehicle and rope to the tonnage of ore hauled will be decreased, and the efficiency of the engine will be increased by a less high peak demand, because of this less proportion of dead weight and the less need of high acceleration. lateral underground transport. inasmuch as the majority of metal mines dip at considerable angles, the useful life of a roadway in a metal mine is very short because particular horizons of ore are soon exhausted. therefore any method of transport has to be calculated upon a very quick redemption of the capital laid out. furthermore, a roadway is limited in its daily traffic to the product of the stopes which it serves. men and animals.--some means of transport must be provided, and the basic equipment is light tracks with push-cars, in capacity from half a ton to a ton. the latter load is, however, too heavy to be pushed by one man. as but one car can be pushed at a time, hand-trucking is both slow and expensive. at average american or australian wages, the cost works out between and cents a ton per mile. an improvement of growing import where hand-trucking is necessary is the overhead mono-rail instead of the track. if the supply to any particular roadway is such as to fully employ horses or mules, the number of cars per trip can be increased up to seven or eight. in this case the expense, including wages of the men and wear, tear, and care of mules, will work out roughly at from to cents per ton mile. manifestly, if the ore-supply to a particular roadway is insufficient to keep a mule busy, the economy soon runs off. mechanical haulage.--mechanical haulage is seldom applicable to metal mines, for most metal deposits dip at considerable angles, and therefore, unlike most coal-mines, the horizon of haulage must frequently change, and there are no main arteries along which haulage continues through the life of the mine. any mechanical system entails a good deal of expense for installation, and the useful life of any particular roadway, as above said, is very short. moreover, the crooked roadways of most metal mines present difficulties of negotiation not to be overlooked. in order to use such systems it is necessary to condense the haulage to as few roadways as possible. where the tonnage on one level is not sufficient to warrant other than men or animals, it sometimes pays (if the dip is steep enough) to dump everything through winzes from one to two levels to a main road below where mechanical equipment can be advantageously provided. the cost of shaft-winding the extra depth is inconsiderable compared to other factors, for the extra vertical distance of haulage can be done at a cost of one or two cents per ton mile. moreover, from such an arrangement follows the concentration of shaft-bins, and of shaft labor, and winding is accomplished without so much shifting as to horizon, all of which economies equalize the extra distance of the lift. there are three principal methods of mechanical transport in use:-- . cable-ways. . compressed-air locomotives. . electrical haulage. cable-ways or endless ropes are expensive to install, and to work to the best advantage require double tracks and fairly straight roads. while they are economical in operation and work with little danger to operatives, the limitations mentioned preclude them from adoption in metal mines, except in very special circumstances such as main crosscuts or adit tunnels, where the haulage is straight and concentrated from many sources of supply. compressed-air locomotives are somewhat heavy and cumbersome, and therefore require well-built tracks with heavy rails, but they have very great advantages for metal mine work. they need but a single track and are of low initial cost where compressed air is already a requirement of the mine. no subsidiary line equipment is needed, and thus they are free to traverse any road in the mine and can be readily shifted from one level to another. their mechanical efficiency is not so low in the long run as might appear from the low efficiency of pneumatic machines generally, for by storage of compressed air at the charging station a more even rate of energy consumption is possible than in the constant cable and electrical power supply which must be equal to the maximum demand, while the air-plant consumes but the average demand. electrical haulage has the advantage of a much more compact locomotive and the drawback of more expensive track equipment, due to the necessity of transmission wire, etc. it has the further disadvantages of uselessness outside the equipped haulage way and of the dangers of the live wire in low and often wet tunnels. in general, compressed-air locomotives possess many attractions for metal mine work, where air is in use in any event and where any mechanical system is at all justified. any of the mechanical systems where tonnage is sufficient in quantity to justify their employment will handle material for from . to cents per ton mile. tracks.--tracks for hand, mule, or rope haulage are usually built with from - to -pound rails, but when compressed-air or electrical locomotives are to be used, less than -pound rails are impossible. as to tracks in general, it may be said that careful laying out with even grades and gentle curves repays itself many times over in their subsequent operation. further care in repair and lubrication of cars will often make a difference of % in the track resistance. transport in stopes.--owing to the even shorter life of individual stopes than levels, the actual transport of ore or waste in them is often a function of the aboriginal shovel plus gravity. as shoveling is the most costly system of transport known, any means of stoping that decreases the need for it has merit. shrinkage-stoping eliminates it altogether. in the other methods, gravity helps in proportion to the steepness of the dip. when the underlie becomes too flat for the ore to "run," transport can sometimes be helped by pitching the ore-passes at a steeper angle than the dip (fig. ). in some cases of flat deposits, crosscuts into the walls, or even levels under the ore-body, are justifiable. the more numerous the ore-passes, the less the lateral shoveling, but as passes cost money for construction and for repair, there is a nice economic balance in their frequency. mechanical haulage in stopes has been tried and finds a field under some conditions. in dips under ° and possessing fairly sound hanging-wall, where long-wall or flat-back cuts are employed, temporary tracks can often be laid in the stopes and the ore run in cars to the main passes. in such cases, the tracks are pushed up close to the face after each cut. further self-acting inclines to lower cars to the levels can sometimes be installed to advantage. this arrangement also permits greater intervals between levels and less number of ore-passes. for dips between ° and ° where the mine is worked without stope support or with occasional pillars, a very useful contrivance is the sheet-iron trough--about eighteen inches wide and six inches deep--made in sections ten or twelve feet long and readily bolted together. in dips ° to ° this trough, laid on the foot-wall, gives a sufficiently smooth surface for the ore to run upon. when the dip is flat, the trough, if hung from plugs in the hanging-wall, may be swung backward and forward. the use of this "bumping-trough" saves much shoveling. for handling filling or ore in flat runs it deserves wider adoption. it is, of course, inapplicable in passes as a "bumping-trough," but can be fixed to give smooth surface. in flat mines it permits a wider interval between levels and therefore saves development work. the life of this contrivance is short when used in open stopes, owing to the dangers of bombardment from blasting. in dips steeper than ° much of the shoveling into passes can be saved by rill-stoping, as described on page . where flat-backed stopes are used in wide ore-bodies with filling, temporary tracks laid on the filling to the ore-passes are useful, for they permit wider intervals between passes. in that underground engineer's paradise, the witwatersrand, where the stopes require neither timber nor filling, the long, moderately pitched openings lend themselves particularly to the swinging iron troughs, and even endless wire ropes have been found advantageous in certain cases. where the roof is heavy and close support is required, and where the deposits are very irregular in shape and dip, there is little hope of mechanical assistance in stope transport. chapter xiii. mechanical equipment. (_continued_). drainage: controlling factors; volume and head of water; flexibility; reliability; power conditions; mechanical efficiency; capital outlay. systems of drainage,--steam pumps, compressed-air pumps, electrical pumps, rod-driven pumps, bailing; comparative value of various systems. with the exception of drainage tunnels--more fully described in chapter viii--all drainage must be mechanical. as the bulk of mine water usually lies near the surface, saving in pumping can sometimes be effected by leaving a complete pillar of ore under some of the upper levels. in many deposits, however, the ore has too many channels to render this of much avail. there are six factors which enter into a determination of mechanical drainage systems for metal mines:-- . volume and head of water. . flexibility to fluctuation in volume and head. . reliability. . capital cost. . the general power conditions. . mechanical efficiency. in the drainage appliances, more than in any other feature of the equipment, must mechanical efficiency be subordinated to the other issues. flexibility.--flexibility in plant is necessary because volume and head of water are fluctuating factors. in wet regions the volume of water usually increases for a certain distance with the extension of openings in depth. in dry climates it generally decreases with the downward extension of the workings after a certain depth. moreover, as depth progresses, the water follows the openings more or less and must be pumped against an ever greater head. in most cases the volume varies with the seasons. what increase will occur, from what horizon it must be lifted, and what the fluctuations in volume are likely to be, are all unknown at the time of installation. if a pumping system were to be laid out for a new mine, which would peradventure meet every possible contingency, the capital outlay would be enormous, and the operating efficiency would be very low during the long period in which it would be working below its capacity. the question of flexibility does not arise so prominently in coal-mines, for the more or less flat deposits give a fixed factor of depth. the flow is also more steady, and the volume can be in a measure approximated from general experience. reliability.--the factor of reliability was at one time of more importance than in these days of high-class manufacture of many different pumping systems. practically speaking, the only insurance from flooding in any event lies in the provision of a relief system of some sort,--duplicate pumps, or the simplest and most usual thing, bailing tanks. only cornish and compressed-air pumps will work with any security when drowned, and electrical pumps are easily ruined. general power conditions.--the question of pumping installation is much dependent upon the power installation and other power requirements of the mine. for instance, where electrical power is purchased or generated by water-power, then electrical pumps have every advantage. or where a large number of subsidiary motors can be economically driven from one central steam- or gas-driven electrical generation plant, they again have a strong call,--especially if the amount of water to be handled is moderate. where the water is of limited volume and compressed-air plant a necessity for the mine, then air-driven pumps may be the most advantageous, etc. mechanical efficiency.--the mechanical efficiency of drainage machinery is very largely a question of method of power application. the actual pump can be built to almost the same efficiency for any power application, and with the exception of the limited field of bailing with tanks, mechanical drainage is a matter of pumps. all pumps must be set below their load, barring a few possible feet of suction lift, and they are therefore perforce underground, and in consequence all power must be transmitted from the surface. transmission itself means loss of power varying from to %, depending upon the medium used. it is therefore the choice of transmission medium that largely governs the mechanical efficiency. systems of drainage.--the ideal pumping system for metal mines would be one which could be built in units and could be expanded or contracted unit by unit with the fluctuation in volume; which could also be easily moved to meet the differences of lifts; and in which each independent unit could be of the highest mechanical efficiency and would require but little space for erection. such an ideal is unobtainable among any of the appliances with which the writer is familiar. the wide variations in the origin of power, in the form of transmission, and in the method of final application, and the many combinations of these factors, meet the demands for flexibility, efficiency, capital cost, and reliability in various degrees depending upon the environment of the mine. power nowadays is generated primarily with steam, water, and gas. these origins admit the transmission of power to the pumps by direct steam, compressed air, electricity, rods, or hydraulic columns. direct steam-pumps.--direct steam has the disadvantage of radiated heat in the workings, of loss by the radiation, and, worse still, of the impracticability of placing and operating a highly efficient steam-engine underground. it is all but impossible to derive benefit from the vacuum, as any form of surface condenser here is impossible, and there can be no return of the hot soft water to the boilers. steam-pumps fall into two classes, rotary and direct-acting; the former have the great advantage of permitting the use of steam expansively and affording some field for effective use of condensation, but they are more costly, require much room, and are not fool-proof. the direct-acting pumps have all the advantage of compactness and the disadvantage of being the most inefficient of pumping machines used in mining. taking the steam consumption of a good surface steam plant at pounds per horse-power hour, the efficiency of rotary pumps with well-insulated pipes is probably not over %, and of direct-acting pumps from % down to %. the advantage of all steam-pumps lies in the low capital outlay,--hence their convenient application to experimental mining and temporary pumping requirements. for final equipment they afford a great deal of flexibility, for if properly constructed they can be, with slight alteration, moved from one horizon to another without loss of relative efficiency. thus the system can be rearranged for an increased volume of water, by decreasing the lift and increasing the number of pumps from different horizons. compressed-air pumps.--compressed-air transmission has an application similar to direct steam, but it is of still lower mechanical efficiency, because of the great loss in compression. it has the superiority of not heating the workings, and there is no difficulty as to the disposal of the exhaust, as with steam. moreover, such pumps will work when drowned. compressed air has a distinct place for minor pumping units, especially those removed from the shaft, for they can be run as an adjunct to the air-drill system of the mine, and by this arrangement much capital outlay may be saved. the cost of the extra power consumed by such an arrangement is less than the average cost of compressed-air power, because many of the compressor charges have to be paid anyway. when compressed air is water-generated, they have a field for permanent installations. the efficiency of even rotary air-driven pumps, based on power delivered into a good compressor, is probably not over %. electrical pumps.--electrical pumps have somewhat less flexibility than steam- or air-driven apparatus, in that the speed of the pumps can be varied only within small limits. they have the same great advantage in the easy reorganization of the system to altered conditions of water-flow. electricity, when steam-generated, has the handicap of the losses of two conversions, the actual pump efficiency being about % in well-constructed plants; the efficiency is therefore greater than direct steam or compressed air. where the mine is operated with water-power, purchased electric current, or where there is an installation of electrical generating plant by steam or gas for other purposes, electrically driven pumps take precedence over all others on account of their combined moderate capital outlay, great flexibility, and reasonable efficiency. in late years, direct-coupled, electric-driven centrifugal pumps have entered the mining field, but their efficiency, despite makers' claims, is low. while they show comparatively good results on low lifts the slip increases with the lift. in heads over feet their efficiency is probably not % of the power delivered to the electrical generator. their chief attractions are small capital cost and the compact size which admits of easy installation. rod-driven pumps.--pumps of the cornish type in vertical shafts, if operated to full load and if driven by modern engines, have an efficiency much higher than any other sort of installation, and records of to % are not unusual. the highest efficiency in these pumps yet obtained has been by driving the pump with rope transmission from a high-speed triple expansion engine, and in this plant an actual consumption of only pounds of steam per horse-power hour for actual water lifted has been accomplished. to provide, however, for increase of flow and change of horizon, rod-driven pumps must be so overpowered at the earlier stage of the mine that they operate with great loss. of all pumping systems they are the most expensive to provide. they have no place in crooked openings and only work in inclines with many disadvantages. in general their lack of flexibility is fast putting them out of the metal miner's purview. where the pumping depth and volume of water are approximately known, as is often the case in coal mines, this, the father of all pumps, still holds its own. hydraulic pumps.--hydraulic pumps, in which a column of water is used as the transmission fluid from a surface pump to a corresponding pump underground has had some adoption in coal mines, but little in metal mines. they have a certain amount of flexibility but low efficiency, and are not likely to have much field against electrical pumps. bailing.--bailing deserves to be mentioned among drainage methods, for under certain conditions it is a most useful system, and at all times a mine should be equipped with tanks against accident to the pumps. where the amount of water is limited,--up to, say, , gallons daily,--and where the ore output of the mine permits the use of the winding-engine for part of the time on water haulage, there is in the method an almost total saving of capital outlay. inasmuch as the winding-engine, even when the ore haulage is finished for the day, must be under steam for handling men in emergencies, and as the labor of stokers, engine-drivers, shaft-men, etc., is therefore necessary, the cost of power consumed by bailing is not great, despite the low efficiency of winding-engines. comparison of various systems.--if it is assumed that flexibility, reliability, mechanical efficiency, and capital cost can each be divided into four figures of relative importance,--_a_, _b_, _c_, and _d_, with _a_ representing the most desirable result,--it is possible to indicate roughly the comparative values of various pumping systems. it is not pretended that the four degrees are of equal import. in all cases the factor of general power conditions on the mine may alter the relative positions. ==================================================================== |direct|compressed| |steam-| | |steam | air |electricity|driven|hydraulic|bailing |pumps | | | rods | columns | tanks -------------|------|----------|-----------|------|---------|------- flexibility. | _a_ | _a_ | _b_ | _d_ | _b_ | _a_ reliability. | _b_ | _b_ | _b_ | _a_ | _d_ | _a_ mechanical | | | | | | efficiency.| _c_ | _d_ | _b_ | _a_ | _c_ | _d_ capital cost | _a_ | _b_ | _b_ | _d_ | _d_ | -- ==================================================================== as each mine has its special environment, it is impossible to formulate any final conclusion on a subject so involved. the attempt would lead to a discussion of a thousand supposititious cases and hypothetical remedies. further, the description alone of pumping machines would fill volumes, and the subject will never be exhausted. the engineer confronted with pumping problems must marshal all the alternatives, count his money, and apply the tests of flexibility, reliability, efficiency, and cost, choose the system of least disadvantages, and finally deprecate the whole affair, for it is but a parasite growth on the mine. chapter xiv. mechanical equipment (_concluded_). machine drilling: power transmission; compressed air _vs_. electricity; air drills; machine _vs_. hand drilling. work-shops. improvement in equipment. for over two hundred years from the introduction of drill-holes for blasting by caspar weindel in hungary, to the invention of the first practicable steam percussion drill by j. j. crouch of philadelphia, in , all drilling was done by hand. since crouch's time a host of mechanical drills to be actuated by all sorts of power have come forward, and even yet the machine-drill has not reached a stage of development where it can displace hand-work under all conditions. steam-power was never adapted to underground work, and a serviceable drill for this purpose was not found until compressed air for transmission was demonstrated by dommeiller on the mt. cenis tunnel in . the ideal requirements for a drill combine:-- a. power transmission adapted to underground conditions. b. lightness. c. simplicity of construction. d. strength. e. rapidity and strength of blow. f. ease of erection. g. reliability. h. mechanical efficiency. i. low capital cost. no drill invented yet fills all these requirements, and all are a compromise on some point. power transmission; compressed air _vs_. electricity.--the only transmissions adapted to underground drill-work are compressed air and electricity, and as yet an electric-driven drill has not been produced which meets as many of the requirements of the metal miner as do compressed-air drills. the latter, up to date, have superiority in simplicity, lightness, ease of erection, reliability, and strength over electric machines. air has another advantage in that it affords some assistance to ventilation, but it has the disadvantage of remarkably low mechanical efficiency. the actual work performed by the standard - / -inch air-drill probably does not amount to over two or three horse-power against from fifteen to eighteen horse-power delivered into the compressor, or mechanical efficiency of less than %. as electrical power can be delivered to the drill with much less loss than compressed air, the field for a more economical drill on this line is wide enough to create eventually the proper tool to apply it. the most satisfactory electric drill produced has been the temple drill, which is really an air-drill driven by a small electrically-driven compressor placed near the drill itself. but even this has considerable deficiencies in mining work; the difficulties of setting up, especially for stoping work, and the more cumbersome apparatus to remove before blasting are serious drawbacks. it has deficiencies in reliability and greater complication of machinery than direct air. air-compression.--the method of air-compression so long accomplished only by power-driven pistons has now an alternative in some situations by the use of falling water. this latter system is a development of the last twelve years, and, due to the low initial outlay and extremely low operating costs, bids fair in those regions where water head is available not only to displace the machine compressor, but also to extend the application of compressed air to mine motors generally, and to stay in some environments the encroachment of electricity into the compressed-air field. installations of this sort in the west kootenay, b.c., and at the victoria copper mine, michigan, are giving results worthy of careful attention. mechanical air-compressors are steam-, water-, electrical-, and gas-driven, the alternative obviously depending on the source and cost of power. electrical- and gas- and water-driven compressors work under the disadvantage of constant speed motors and respond little to the variation in load, a partial remedy for which lies in enlarged air-storage capacity. inasmuch as compressed air, so far as our knowledge goes at present, must be provided for drills, it forms a convenient transmission of power to various motors underground, such as small pumps, winches, or locomotives. as stated in discussing those machines, it is not primarily a transmission of even moderate mechanical efficiency for such purposes; but as against the installation and operation of independent transmission, such as steam or electricity, the economic advantage often compensates the technical losses. where such motors are fixed, as in pumps and winches, a considerable gain in efficiency can be obtained by reheating. it is not proposed to enter a discussion of mechanical details of air-compression, more than to call attention to the most common delinquency in the installation of such plants. this deficiency lies in insufficient compression capacity for the needs of the mine and consequent effective operation of drills, for with under pounds pressure the drills decrease remarkably in rapidity of stroke and force of the blow. the consequent decrease in actual accomplishment is far beyond the ratio that might be expected on the basis of mere difference of pressure. another form of the same chronic ill lies in insufficient air-storage capacity to provide for maintenance of pressure against moments when all drills or motors in the mine synchronize in heavy demand for air, and thus lower the pressure at certain periods. air-drills.--air-drills are from a mechanical point of view broadly of two types,--the first, in which the drill is the piston extension; and the second, a more recent development for mining work, in which the piston acts as a hammer striking the head of the drill. from an economic point of view drills may be divided into three classes. first, heavy drills, weighing from to pounds, which require two men for their operation; second, "baby" drills of the piston type, weighing from to pounds, requiring one man with occasional assistance in setting up; and third, very light drills almost wholly of the hammer type. this type is built in two forms: a heavier type for mounting on columns, weighing about pounds; and a type after the order of the pneumatic riveter, weighing as low as pounds and worked without mounting. the weight and consequent mobility of a drill, aside from labor questions, have a marked effect on costs, for the lighter the drill the less difficulty and delay in erection, and consequent less loss of time and less tendency to drill holes from one radius, regardless of pointing to take best advantage of breaking planes. moreover, smaller diameter and shorter holes consume less explosives per foot advanced or per ton broken. the best results in tonnage broken and explosive consumed, if measured by the foot of drill-hole necessary, can be accomplished from hand-drilling and the lighter the machine drill, assuming equal reliability, the nearer it approximates these advantages. the blow, and therefore size and depth of hole and rapidity of drilling, are somewhat dependent upon the size of cylinders and length of stroke, and therefore the heavier types are better adapted to hard ground and to the deep holes of some development points. their advantages over the other classes lie chiefly in this ability to bore exceedingly hard material and in the greater speed of advance possible in development work; but except for these two special purposes they are not as economical per foot advanced or per ton of ore broken as the lighter drills. the second class, where men can be induced to work them one man per drill, saves in labor and gains in mobility. many tests show great economy of the "baby" type of piston drills in average ground over the heavier machines for stoping and for most lateral development. all piston types are somewhat cumbersome and the heavier types require at least four feet of head room. the "baby" type can be operated in less space than this, but for narrow stopes they do not lend themselves with the same facility as the third class. the third class of drills is still in process of development, but it bids fair to displace much of the occupation of the piston types of drill. aside from being a one-man drill, by its mobility it will apparently largely reproduce the advantage of hand-drilling in ability to place short holes from the most advantageous angles and for use in narrow places. as compared with other drills it bids fair to require less time for setting up and removal and for change of bits; to destroy less steel by breakages; to dull the bits less rapidly per foot of hole; to be more economical of power; to require much less skill in operation, for judgment is less called upon in delivering speed; and to evade difficulties of fissured ground, etc. and finally the cost is only one-half, initially and for spares. its disadvantage so far is a lack of reliability due to lightness of construction, but this is very rapidly being overcome. this type, however, is limited in depth of hole possible, for, from lack of positive reverse movement, there is a tendency for the spoil to pack around the bit, and as a result about four feet seems the limit. the performance of a machine-drill under show conditions may be anything up to ten or twelve feet of hole per hour on rock such as compact granite; but in underground work a large proportion of the time is lost in picking down loose ore, setting up machines, removal for blasting, clearing away spoil, making adjustments, etc. the amount of lost time is often dependent upon the width of stope or shaft and the method of stoping. situations which require long drill columns or special scaffolds greatly accentuate the loss of time. further, the difficulties in setting up reflect indirectly on efficiency to a greater extent in that a larger proportion of holes are drilled from one radius and thus less adapted to the best breaking results than where the drill can easily be reset from various angles. the usual duty of a heavy drill per eight-hour shift using two men is from to feet of hole, depending upon the rock, facilities for setting up, etc., etc.[*] the lighter drills have a less average duty, averaging from to feet per shift. [footnote *: over the year in twenty-eight mines compiled from alaska to australia, an average of . feet was drilled per eight-hour shift by machines larger than three-inch cylinder.] machine _vs_. hand-drilling.--the advantages of hand-drilling over machine-drilling lie, first, in the total saving of power, the absence of capital cost, repairs, depreciation, etc., on power, compresser and drill plant; second, the time required for setting up machine-drills does not warrant frequent blasts, so that a number of holes on one radius are a necessity, and therefore machine-holes generally cannot be pointed to such advantage as hand-holes. hand-holes can be set to any angle, and by thus frequent blasting yield greater tonnage per foot of hole. third, a large number of comparative statistics from american, south african, and australian mines show a saving of about % in explosives for the same tonnage or foot of advance by hand-holes over medium and heavy drill-holes. the duty of a skilled white man, single-handed, in rock such as is usually met below the zone of oxidation, is from to feet per shift, depending on the rock and the man. two men hand-drilling will therefore do from / to / of the same footage of holes that can be done by two men with a heavy machine-drill, and two men hand-drilling will do from / to / the footage of two men with two light drills. the saving in labor of from to % by machine-drilling may or may not be made up by the other costs involved in machine-work. the comparative value of machine- and hand-drilling is not subject to sweeping generalization. a large amount of data from various parts of the world, with skilled white men, shows machine-work to cost from half as much per ton or foot advanced as hand-work to % more than handwork, depending on the situation, type of drill, etc. in a general way hand-work can more nearly compete with heavy machines than light ones. the situations where hand-work can compete with even light machines are in very narrow stopes where drills cannot be pointed to advantage, and where the increased working space necessary for machine drills results in breaking more waste. further, hand-drilling can often compete with machine-work in wide stopes where long columns or platforms must be used and therefore there is much delay in taking down, reërection, etc. many other factors enter into a comparison, however, for machine-drilling produces a greater number of deeper holes and permits larger blasts and therefore more rapid progress. in driving levels under average conditions monthly footage is from two to three times as great with heavy machines as by hand-drilling, and by lighter machines a somewhat less proportion of greater speed. the greater speed obtained in development work, the greater tonnage obtained per man in stoping, with consequent reduction in the number of men employed, and in reduction of superintendence and general charges are indirect advantages for machine-drilling not to be overlooked. the results obtained in south africa by hand-drilling in shafts, and its very general adoption there, seem to indicate that better speed and more economical work can be obtained in that way in very large shafts than by machine-drilling. how far special reasons there apply to smaller shafts or labor conditions elsewhere have yet to be demonstrated. in large-dimension shafts demanding a large number of machines, the handling of long machine bars and machines generally results in a great loss of time. the large charges in deep holes break the walls very irregularly; misfires cause more delay; timbering is more difficult in the face of heavy blasting charges; and the larger amount of spoil broken at one time delays renewed drilling, and altogether the advantages seem to lie with hand-drilling in shafts of large horizontal section. the rapid development of special drills for particular conditions has eliminated the advantage of hand-work in many situations during the past ten years, and the invention of the hammer type of drill bids fair to render hand-drilling a thing of the past. one generalization is possible, and that is, if drills are run on - pounds' pressure they are no economy over hand-drilling. workshops. in addition to the ordinary blacksmithy, which is a necessity, the modern tendency has been to elaborate the shops on mines to cover machine-work, pattern-making and foundry-work, in order that delays may be minimized by quick repairs. to provide, however, for such contingencies a staff of men must be kept larger than the demand of average requirements. the result is an effort to provide jobs or to do work extravagantly or unnecessarily well. in general, it is an easy spot for fungi to start growing on the administration, and if custom repair shops are available at all, mine shops can be easily overdone. a number of machines are now in use for sharpening drills. machine-sharpening is much cheaper than hand-work, although the drills thus sharpened are rather less efficient owing to the difficulty of tempering them to the same nicety; however, the net results are in favor of the machines. improvement in equipment. not only is every mine a progressive industry until the bottom gives out, but the technology of the industry is always progressing, so that the manager is almost daily confronted with improvements which could be made in his equipment that would result in decreasing expenses or increasing metal recovery. there is one test to the advisability of such alterations: how long will it take to recover the capital outlay from the savings effected? and over and above this recovery of capital there must be some very considerable gain. the life of mines is at least secured over the period exposed in the ore-reserves, and if the proposed alteration will show its recovery and profit in that period, then it is certainly justified. if it takes longer than this on the average speculative ore-deposit, it is a gamble on finding further ore. as a matter of practical policy it will be found that an improvement in equipment which requires more than three or four years to redeem itself out of saving, is usually a mechanical or metallurgical refinement the indulgence in which is very doubtful. chapter xv. ratio of output to the mine. determination of the possible maximum; limiting factors; cost of equipment; life of the mine; mechanical inefficiency of patchwork plant; overproduction of base metal; security of investment. the output obtainable from a given mine is obviously dependent not only on the size of the deposit, but also on the equipment provided,--in which equipment means the whole working appliances, surface and underground. a rough and ready idea of output possibilities of inclined deposits can be secured by calculating the tonnage available per foot of depth from the horizontal cross-section of the ore-bodies exposed and assuming an annual depth of exhaustion, or in horizontal deposits from an assumption of a given area of exhaustion. few mines, at the time of initial equipment, are developed to an extent from which their possibilities in production are evident, for wise finance usually leads to the erection of some equipment and production before development has been advanced to a point that warrants a large or final installation. moreover, even were the full possibilities of the mine known, the limitations of finance usually necessitate a less plant to start with than is finally contemplated. therefore output and equipment are usually growing possibilities during the early life of a mine. there is no better instance in mine engineering where pure theory must give way to practical necessities of finance than in the determination of the size of equipment and therefore output. moreover, where finance even is no obstruction, there are other limitations of a very practical order which must dominate the question of the size of plant giving the greatest technical economy. it is, however, useful to state the theoretical considerations in determining the ultimate volume of output and therefore the size of equipments, for the theory will serve to illuminate the practical limitations. the discussion will also again demonstrate that all engineering is a series of compromises with natural and economic forces. output giving least production cost.--as one of the most important objectives is to work the ore at the least cost per ton, it is not difficult to demonstrate that the minimum working costs can be obtained only by the most intensive production. to prove this, it need only be remembered that the working expenses of a mine are of two sorts: one is a factor of the tonnage handled, such as stoping and ore-dressing; the other is wholly or partially dependent upon time. a large number of items are of this last order. pumping and head-office expenses are almost entirely charges independent of the tonnage handled. superintendence and staff salaries and the like are in a large proportion dependent upon time. many other elements of expense, such as the number of engine-drivers, etc., do not increase proportionately to increase in tonnage. these charges, or the part of them dependent upon time apart from tonnage, may be termed the "fixed charges." there is another fixed charge more obscure yet no less certain. ore standing in a mine is like money in a bank drawing no interest, and this item of interest may be considered a "fixed charge," for if the ore were realized earlier, this loss could be partially saved. this subject is further referred to under "amortization." if, therefore, the time required to exhaust the mine be prolonged by the failure to maintain the maximum output, the total cost of working it will be greater by the fixed charges over such an increased period. conversely, by equipping on a larger scale, the mine will be exhausted more quickly, a saving in total cost can be made, and the ultimate profit can be increased by an amount corresponding to the time saved from the ravages of fixed charges. in fine, the working costs may be reduced by larger operations, and therefore the value of the mine increased. the problem in practice usually takes the form of the relative superiority of more or of fewer units of plant, and it can be considered in more detail if the production be supposed to consist of units averaging say tons per day each. the advantage of more units over less will be that the extra ones can be produced free of fixed charges, for these are an expense already involved in the lesser units. this extra production will also enjoy the interest which can be earned over the period of its earlier production. moreover, operations on a larger scale result in various minor economies throughout the whole production, not entirely included in the type of expenditure mentioned as "fixed charges." we may call these various advantages the "saving of fixed charges" due to larger-scale operations. the saving of fixed charges amounts to very considerable sums. in general the items of working cost alone, mentioned above, which do not increase proportionately to the tonnage, aggregate from to % of the total costs. where much pumping is involved, the percentage will become even greater. the question of the value of the mine as affected by the volume of output becomes very prominent in low-grade mines, where, if equipped for output on too small a scale, no profits at all could be earned, and a sufficient production is absolutely imperative for any gain. there are many mines in every country which with one-third of their present rate of production would lose money. that is, the fixed charges, if spread over small output, would be so great per ton that the profit would be extinguished by them. in the theoretical view, therefore, it would appear clear that the greatest ultimate profit from a mine can be secured only by ore extraction under the highest pressure. as a corollary to this it follows that development must proceed with the maximum speed. further, it follows that the present value of a mine is at least partially a factor of the volume of output contemplated. factors limiting the output. although the above argument can be academically defended, there are, as said at the start, practical limitations to the maximum intensity of production, arising out of many other considerations to which weight must be given. in the main, there are five principal limitations:-- . cost of equipment. . life of the mine. . mechanical inefficiency of patchwork plant. . overproduction of base metal. . security of investment. cost of equipment.--the "saving of fixed charges" can only be obtained by larger equipment, which represents an investment. mining works, shafts, machinery, treatment plants, and all the paraphernalia cost large sums of money. they become either worn out or practically valueless through the exhaustion of the mines. even surface machinery when in good condition will seldom realize more than one-tenth of its expense if useless at its original site. all mines are ephemeral; therefore virtually the entire capital outlay of such works must be redeemed during the life of the mine, and the interest on it must also be recovered. the certain life, with the exception of banket and a few other types of deposit, is that shown by the ore in sight, plus something for extension of the deposit beyond exposures. so, against the "savings" to be made, must be set the cost of obtaining them, for obviously it is of no use investing a dollar to save a total of ninety cents. the economies by increased production are, however, of such an important character that the cost of almost any number of added units (within the ability of the mine to supply them) can be redeemed from these savings in a few years. for instance, in a californian gold mine where the working expenses are $ and the fixed charges are at the low rate of cents per ton, one unit of increased production would show a saving of over $ , per annum from the saving of fixed charges. in about three years this sum would repay the cost of the additional treatment equipment. if further shaft capacity were required, the period would be much extended. on a western copper mine, where the costs are $ and the fixed charges are cents per ton, one unit of increased production would effect a saving of the fixed charges equal to the cost of the extra unit in about three years. that is, the total sum would amount to $ , , or enough to provide almost any type of mechanical equipment for such additional tonnage. the first result of vigorous development is to increase the ore in sight,--the visible life of the mine. when such visible life has been so lengthened that the period in which the "saving of fixed charges" will equal the amount involved in expansion of equipment, then from the standpoint of this limitation only is the added installation justified. the equipment if expanded on this practice will grow upon the heels of rapid development until the maximum production from the mine is reached, and a kind of equilibrium establishes itself. conversely, this argument leads to the conclusion that, regardless of other considerations, an equipment, and therefore output, should not be expanded beyond the redemption by way of "saving from fixed charges" of the visible or certain life of the mine. in those mines, such as at the witwatersrand, where there is a fairly sound assurance of definite life, it is possible to calculate at once the size of plant which by saving of "fixed charges" will be eventually the most economical, but even here the other limitations step in to vitiate such policy of management,--chiefly the limitation through security of investment. life of the mine.--if carried to its logical extreme, the above program means a most rapid exhaustion of the mine. the maximum output will depend eventually upon the rapidity with which development work may be extended. as levels and other subsidiary development openings can be prepared in inclined deposits much more quickly than the shaft can be sunk, the critical point is the shaft-sinking. as a shaft may by exertion be deepened at least feet a year on a going mine, the provision of an equipment to eat up the ore-body at this rate of sinking means very early exhaustion indeed. in fact, had such a theory of production been put into practice by our forefathers, the mining profession might find difficulty in obtaining employment to-day. such rapid exhaustion would mean a depletion of the mineral resources of the state at a pace which would be alarming. mechanical inefficiency of patchwork plant.--mine equipments on speculative mines (the vast majority) are often enough patchwork, for they usually grow from small beginnings; but any scheme of expansion based upon the above doctrine would need to be modified to the extent that additions could be in units large in ratio to previous installations, or their patchwork character would be still further accentuated. it would be impossible to maintain mechanical efficiency under detail expansion. overproduction of base metal.--were this intensity of production of general application to base metal mines it would flood the markets, and, by an overproduction of metal depress prices to a point where the advantages of such large-scale operations would quickly vanish. the theoretical solution in this situation would be, if metals fell below normal prices, let the output be reduced, or let the products be stored until the price recovers. from a practical point of view either alternative is a policy difficult to face. in the first case, reduction of output means an increase of working expenses by the spread of fixed charges over less tonnage, and this in the face of reduced metal prices. it may be contended, however, that a falling metal market is usually the accompaniment of a drop in all commodities, wherefore working costs can be reduced somewhat in such times of depression, thereby partially compensating the other elements making for increased costs. falls in commodities are also the accompaniment of hard times. consideration of one's workpeople and the wholesale slaughter of dividends to the then needy stockholders, resulting from a policy of reduced production, are usually sufficient deterrents to diminished output. the second alternative, that of storing metal, means equally a loss of dividends by the investment of a large sum in unrealized products, and the interest on this sum. the detriment to the market of large amounts of unsold metal renders such a course not without further disadvantages. security of investment.--another point of view antagonistic to such wholesale intensity of production, and one worthy of careful consideration, is that of the investor in mines. the root-value of mining stocks is, or should be, the profit in sight. if the policy of greatest economy in production costs be followed as outlined above, the economic limit of ore-reserves gives an apparently very short life, for the ore in sight will never represent a life beyond the time required to justify more plant. thus the "economic limit of ore in reserve" will be a store equivalencing a period during which additional equipment can be redeemed from the "saving of fixed charges," or three or four years, usually. the investor has the right to say that he wants the guarantee of longer life to his investment,--he will in effect pay insurance for it by a loss of some ultimate profit. that this view, contradictory to the economics of the case, is not simply academic, can be observed by any one who studies what mines are in best repute on any stock exchange. all engineers must wish to have the industry under them in high repute. the writer knows of several mines paying % on their stocks which yet stand lower in price on account of short ore-reserves than mines paying less annual returns. the speculator, who is an element not to be wholly disregarded, wishes a rise in his mining stock, and if development proceeds at a pace in advance of production, he will gain a legitimate rise through the increase in ore-reserves. the investor's and speculator's idea of the desirability of a proved long life readily supports the technical policy of high-pressure development work, but not of expansion of production, for they desire an increasing ore-reserve. even the metal operator who is afraid of overproduction does not object to increased ore-reserves. on the point of maximum intensity of development work in a mine all views coincide. the mining engineer, if he takes a machiavellian view, must agree with the investor and the metal dealer, for the engineer is a "fixed charge" the continuance of which is important to his daily needs. the net result of all these limitations is therefore an invariable compromise upon some output below the possible maximum. the initial output to be contemplated is obviously one upon which the working costs will be low enough to show a margin of profit. the medium between these two extremes is determinable by a consideration of the limitations set out,--and the cash available. when the volume of output is once determined, it must be considered as a factor in valuation, as discussed under "amortization." chapter xvi. administration. labor efficiency; skill; intelligence; application coordination; contract work; labor unions; real basis of wages. the realization from a mine of the profits estimated from the other factors in the case is in the end dependent upon the management. good mine management is based upon three elementals: first, sound engineering; second, proper coördination and efficiency of every human unit; third, economy in the purchase and consumption of supplies. the previous chapters have been devoted to a more or less extended exposition of economic engineering. while the second and third requirements are equally important, they range in many ways out of the engineering and into the human field. for this latter reason no complete manual will ever be published upon "how to become a good mine manager." it is purposed, however, to analyze some features of these second and third fundamentals, especially in their interdependent phases, and next to consider the subject of mine statistics, for the latter are truly the microscopes through which the competence of the administration must be examined. the human units in mine organization can be divided into officers and men. the choice of mine officers is the assembling of specialized brains. their control, stimulation, and inspiration is the main work of the administrative head. success in the selection and control of staff is the index of executive ability. there are no mathematical, mechanical, or chemical formulas for dealing with the human mind or human energies. labor.--the whole question of handling labor can be reduced to the one term "efficiency." not only does the actual labor outlay represent from to % of the total underground expenses, but the capacity or incapacity of its units is responsible for wider fluctuations in production costs than the bare predominance in expenditure might indicate. the remaining expense is for supplies, such as dynamite, timber, steel, power, etc., and the economical application of these materials by the workman has the widest bearing upon their consumption. efficiency of the mass is the resultant of that of each individual under a direction which coördinates effectively all units. the lack of effectiveness in one individual diminishes the returns not simply from that man alone; it lowers the results from numbers of men associated with the weak member through the delaying and clogging of their work, and of the machines operated by them. coördination of work is a necessary factor of final efficiency. this is a matter of organization and administration. the most zealous stoping-gang in the world if associated with half the proper number of truckers must fail to get the desired result. efficiency in the single man is the product of three factors,--skill, intelligence, and application. a great proportion of underground work in a mine is of a type which can be performed after a fashion by absolutely unskilled and even unintelligent men, as witness the breaking-in of savages of low average mentality, like the south african kaffirs. although most duties can be performed by this crudest order of labor, skill and intelligence can be applied to it with such economic results as to compensate for the difference in wage. the reason for this is that the last fifty years have seen a substitution of labor-saving machines for muscle. such machines displace hundreds of raw laborers. not only do they initially cost large sums, but they require large expenditure for power and up-keep. these fixed charges against the machine demand that it shall be worked at its maximum. for interest, power, and up-keep go on in any event, and the saving on crude labor displaced is not so great but that it quickly disappears if the machine is run under its capacity. to get its greatest efficiency, a high degree of skill and intelligence is required. nor are skill and intelligence alone applicable to labor-saving devices themselves, because drilling and blasting rock and executing other works underground are matters in which experience and judgment in the individual workman count to the highest degree. how far skill affects production costs has had a thorough demonstration in west australia. for a time after the opening of those mines only a small proportion of experienced men were obtainable. during this period the rock broken per man employed underground did not exceed the rate of tons a year. in the large mines it has now, after some eight years, attained to tons. how far intelligence is a factor indispensable to skill can be well illustrated by a comparison of the results obtained from working labor of a low mental order, such as asiatics and negroes, with those achieved by american or australian miners. in a general way, it may be stated with confidence that the white miners above mentioned can, under the same physical conditions, and with from five to ten times the wage, produce the same economic result,--that is, an equal or lower cost per unit of production. much observation and experience in working asiatics and negroes as well as americans and australians in mines, leads the writer to the conclusion that, averaging actual results, one white man equals from two to three of the colored races, even in the simplest forms of mine work such as shoveling or tramming. in the most highly skilled branches, such as mechanics, the average ratio is as one to seven, or in extreme cases even eleven. the question is not entirely a comparison of bare efficiency individually; it is one of the sum total of results. in mining work the lower races require a greatly increased amount of direction, and this excess of supervisors consists of men not in themselves directly productive. there is always, too, a waste of supplies, more accidents, and more ground to be kept open for accommodating increased staff, and the maintenance of these openings must be paid for. there is an added expense for handling larger numbers in and out of the mine, and the lower intelligence reacts in many ways in lack of coördination and inability to take initiative. taking all divisions of labor together, the ratio of efficiency as measured in amount of output works out from four to five colored men as the equivalent of one white man of the class stated. the ratio of costs, for reasons already mentioned, and in other than quantity relation, figures still more in favor of the higher intelligence. the following comparisons, which like all mine statistics must necessarily be accepted with reservation because of some dissimilarity of economic surroundings, are yet on sufficiently common ground to demonstrate the main issue,--that is, the bearing of inherent intelligence in the workmen and their consequent skill. four groups of gold mines have been taken, from india, west australia, south africa, and western america. all of those chosen are of the same stoping width, to feet. all are working in depth and with every labor-saving device available. all dip at about the same angle and are therefore in much the same position as to handling rock. the other conditions are against the white-manned mines and in favor of the colored. that is, the indian mines have water-generated electric power and south africa has cheaper fuel than either the american or australian examples. in both the white-manned groups, the stopes are supported, while in the others no support is required. ======================================================================= | tons of | average |tons | | material | number of men | per |cost per group of mines | excavated | employed | man | ton of |over period|---------------| per |material |compiled[ ]|colored| white |annum| broken ----------------------------|-----------|-------|-------|-----|-------- four kolar mines[ ] | , | , | | . | $ . six australian mines[ ] | , , | -- | , | . | . three witwatersrand mines[ ]| , , | , | , | . | . five american mines[ ] | , , | -- | , | . | . ======================================================================= [footnote : indian wages average about cents per day.] [footnote : white men's wages average about $ per day.] [footnote : about two-fifths of the colored workers were negroes, and three-fifths chinamen. negroes average about cents, and chinamen about cents per day, including keep.] [footnote : wages about $ . . tunnel entry in two mines.] [footnote : includes rock broken in development work. in the case of the specified african mines, the white labor is employed almost wholly in positions of actual or semi-superintendence, such as one white man in charge of two or three drills. in the indian case, in addition to the white men who are wholly in superintendence, there were of the natives enumerated some in positions of semi-superintendence, as contractors or headmen, working-gangers, etc.] one issue arises out of these facts, and that is that no engineer or investor in valuing mines is justified in anticipating lower costs in regions where cheap labor exists. in supplement to sheer skill and intelligence, efficiency can be gained only by the application of the man himself. a few months ago a mine in california changed managers. the new head reduced the number employed one-third without impairing the amount of work accomplished. this was not the result of higher skill or intelligence in the men, but in the manager. better application and coördination were secured from the working force. inspiration to increase of exertion is created less by "driving" than by recognition of individual effort, in larger pay, and by extending justifiable hope of promotion. a great factor in the proficiency of the mine manager is his ability to create an _esprit-de-corps_ through the whole staff, down to the last tool boy. friendly interest in the welfare of the men and stimulation by competitions between various works and groups all contribute to this end. contract work.--the advantage both to employer and employed of piece work over wage needs no argument. in a general way, contract work honorably carried out puts a premium upon individual effort, and thus makes for efficiency. there are some portions of mine work which cannot be contracted, but the development, stoping, and trucking can be largely managed in this way, and these items cover to % of the total labor expenditure underground. in development there are two ways of basing contracts,--the first on the footage of holes drilled, and the second on the footage of heading advanced. in contract-stoping there are four methods depending on the feet of hole drilled, on tonnage, on cubic space, and on square area broken. all these systems have their rightful application, conditioned upon the class of labor and character of the deposit. in the "hole" system, the holes are "pointed" by some mine official and are blasted by a special crew. the miner therefore has little interest in the result of the breaking. if he is a skilled white man, the hours which he has wherein to contemplate the face usually enable him to place holes to better advantage than the occasional visiting foreman. with colored labor, the lack of intelligence in placing holes and blasting usually justifies contracts per "foot drilled." then the holes are pointed and blasted by superintending men. on development work with the foot-hole system, unless two working faces can be provided for each contracting party, they are likely to lose time through having finished their round of holes before the end of the shift. as blasting must be done outside the contractor's shifts, it means that one shift per day must be set aside for the purpose. therefore not nearly such progress can be made as where working the face with three shifts. for these reasons, the "hole" system is not so advantageous in development as the "foot of advance" basis. in stoping, the "hole" system has not only a wider, but a sounder application. in large ore-bodies where there are waste inclusions, it has one superiority over any system of excavation measurement, namely, that the miner has no interest in breaking waste into the ore. the plan of contracting stopes by the ton has the disadvantage that either the ore produced by each contractor must be weighed separately, or truckers must be trusted to count correctly, and to see that the cars are full. moreover, trucks must be inspected for waste,--a thing hard to do underground. so great are these detailed difficulties that many mines are sending cars to the surface in cages when they should be equipped for bin-loading and self-dumping skips. the method of contracting by the cubic foot of excavation saves all necessity for determining the weight of the output of each contractor. moreover, he has no object in mixing waste with the ore, barring the breaking of the walls. this system therefore requires the least superintendence, permits the modern type of hoisting, and therefore leaves little justification for the survival of the tonnage basis. where veins are narrow, stoping under contract by the square foot or fathom measured parallel to the walls has an advantage. the miner has no object then in breaking wall-rock, and the thoroughness of the ore-extraction is easily determined by inspection. bonus systems.--by giving cash bonuses for special accomplishment, much the same results can be obtained in some departments as by contracting. a bonus per foot of heading gained above a minimum, or an excess of trucks trammed beyond a minimum, or prizes for the largest amount done during the week or month in special works or in different shifts,--all these have a useful application in creating efficiency. a high level of results once established is easily maintained. labor unions.--there is another phase of the labor question which must be considered and that is the general relations of employer and employed. in these days of largely corporate proprietorship, the owners of mines are guided in their relations with labor by engineers occupying executive positions. on them falls the responsibility in such matters, and the engineer becomes thus a buffer between labor and capital. as corporations have grown, so likewise have the labor unions. in general, they are normal and proper antidotes for unlimited capitalistic organization. labor unions usually pass through two phases. first, the inertia of the unorganized labor is too often stirred only by demagogic means. after organization through these and other agencies, the lack of balance in the leaders often makes for injustice in demands, and for violence to obtain them and disregard of agreements entered upon. as time goes on, men become educated in regard to the rights of their employers, and to the reflection of these rights in ultimate benefit to labor itself. then the men, as well as the intelligent employer, endeavor to safeguard both interests. when this stage arrives, violence disappears in favor of negotiation on economic principles, and the unions achieve their greatest real gains. given a union with leaders who can control the members, and who are disposed to approach differences in a business spirit, there are few sounder positions for the employer, for agreements honorably carried out dismiss the constant harassments of possible strikes. such unions exist in dozens of trades in this country, and they are entitled to greater recognition. the time when the employer could ride roughshod over his labor is disappearing with the doctrine of "_laissez faire_," on which it was founded. the sooner the fact is recognized, the better for the employer. the sooner some miners' unions develop from the first into the second stage, the more speedily will their organizations secure general respect and influence.[*] [footnote *: some years of experience with compulsory arbitration in australia and new zealand are convincing that although the law there has many defects, still it is a step in the right direction, and the result has been of almost unmixed good to both sides. one of its minor, yet really great, benefits has been a considerable extinction of the parasite who lives by creating violence.] the crying need of labor unions, and of some employers as well, is education on a fundamental of economics too long disregarded by all classes and especially by the academic economist. when the latter abandon the theory that wages are the result of supply and demand, and recognize that in these days of international flow of labor, commodities and capital, the real controlling factor in wages is efficiency, then such an educational campaign may become possible. then will the employer and employee find a common ground on which each can benefit. there lives no engineer who has not seen insensate dispute as to wages where the real difficulty was inefficiency. no administrator begrudges a division with his men of the increased profit arising from increased efficiency. but every administrator begrudges the wage level demanded by labor unions whose policy is decreased efficiency in the false belief that they are providing for more labor. chapter xvii. administration (_continued_). accounts and technical data and reports; working costs; division of expenditure; inherent limitations in accuracy of working costs; working cost sheets. general technical data; labor, supplies, power, surveys, sampling, and assaying. first and foremost, mine accounts are for guidance in the distribution of expenditure and in the collection of revenue; secondly, they are to determine the financial progress of the enterprise, its profit or loss; and thirdly, they are to furnish statistical data to assist the management in its interminable battle to reduce expenses and increase revenue, and to enable the owner to determine the efficiency of his administrators. bookkeeping _per se_ is no part of this discussion. the fundamental purpose of that art is to cover the first two objects, and, as such, does not differ from its application to other commercial concerns. in addition to these accounting matters there is a further type of administrative report of equal importance--that is the periodic statements as to the physical condition of the property, the results of exploration in the mine, and the condition of the equipment. accounts. the special features of mine accounting reports which are a development to meet the needs of this particular business are the determination of working costs, and the final presentation of these data in a form available for comparative purposes. the subject may be discussed under:-- . classes of mine expenditure. . working costs. . the dissection of expenditures departmentally. . inherent limitations in the accuracy of working costs. . working cost sheets. in a wide view, mine expenditures fall into three classes, which maybe termed the "fixed charges," "proportional charges," and "suspense charges" or "capital expenditure." "fixed charges" are those which, like pumping and superintendence, depend upon time rather than tonnage and material handled. they are expenditures that would not decrease relatively to output. "proportional charges" are those which, like ore-breaking, stoping, supporting stopes, and tramming, are a direct coefficient of the ore extracted. "suspense charges" are those which are an indirect factor of the cost of the ore produced, such as equipment and development. these expenditures are preliminary to output, and they thus represent a storage of expense to be charged off when the ore is won. this outlay is often called "capital expenditure." such a term, though in common use, is not strictly correct, for the capital value vanishes when the ore is extracted, but in conformity with current usage the term "capital expenditure" will be adopted. except for the purpose of special inquiry, such as outlined under the chapter on "ratio of output," "fixed charges" are not customarily a special division in accounts. in a general way, such expenditures, combined with the "proportional charges," are called "revenue expenditure," as distinguished from the capital, or "suspense," expenditures. in other words, "revenue" expenditures are those involved in the daily turnover of the business and resulting in immediate returns. the inherent difference in character of revenue and capital expenditures is responsible for most of the difficulties in the determination of working costs, and most of the discussion on the subject. working costs.--"working costs" are a division of expenditure for some unit,--the foot of opening, ton of ore, a pound of metal, cubic yard or fathom of material excavated, or some other measure. the costs per unit are usually deduced for each month and each year. they are generally determined for each of the different departments of the mine or special works separately. further, the various sorts of expenditure in these departments are likewise segregated. in metal mining the ton is the universal unit of distribution for administrative purpose, although the pound of metal is often used to indicate final financial results. the object of determination of "working costs" is fundamentally for comparative purposes. together with other technical data, they are the nerves of the administration, for by comparison of detailed and aggregate results with other mines and internally in the same mine, over various periods and between different works, a most valuable check on efficiency is possible. further, there is one collateral value in all statistical data not to be overlooked, which is that the knowledge of its existence induces in the subordinate staff both solicitude and emulation. the fact must not be lost sight of, however, that the wide variations in physical and economic environment are so likely to vitiate conclusions from comparisons of statistics from two mines or from two detailed works on the same mine, or even from two different months on the same work, that the greatest care and discrimination are demanded in their application. moreover, the inherent difficulties in segregating and dividing the accounts which underlie such data, render it most desirable to offer some warning regarding the limits to which segregation and division may be carried to advantage. as working costs are primarily for comparisons, in order that they may have value for this purpose they must include only such items of expenditure as will regularly recur. if this limitation were more generally recognized, a good deal of dispute and polemics on the subject might be saved. for this reason it is quite impossible that all the expenditure on the mine should be charged into working costs, particularly some items that arise through "capital expenditure." the dissection of expenditures departmentally.--the final division in the dissection of the mine expenditure is in the main:-- /( ) general expenses. / ore-breaking. \ | | supporting stopes. | various _revenue._< ( ) ore extraction. < trucking ore. | expenditures | \ hoisting. | for labor, \( ) pumping. | supplies, power, / shaft-sinking. | repairs, etc., | station-cutting. > worked out per | crosscutting. | ton or foot /( ) development. < driving. | advanced _capital | | rising. | over each or < | winzes. | department. suspense._ | \ diamond drilling. / | | ( ) construction and \ various works. \ equipment. / the detailed dissection of expenditures in these various departments with view to determine amount of various sorts of expenditure over the department, or over some special work in that department, is full of unsolvable complications. the allocation of the direct expenditure of labor and supplies applied to the above divisions or special departments in them, is easily accomplished, but beyond this point two sorts of difficulties immediately arise and offer infinite field for opinion and method. the first of these difficulties arises from supplementary departments on the mine, such as "power," "repairs and maintenance," "sampling and assaying." these departments must be "spread" over the divisions outlined above, for such charges are in part or whole a portion of the expense of these divisions. further, all of these "spread" departments are applied to surface as well as to underground works, and must be divided not only over the above departments but also over the surface departments,--not under discussion here. the common method is to distribute "power" on a basis of an approximation of the amount used in each department; to distribute "repairs and maintenance," either on a basis of shop returns, or a distribution over all departments on the basis of the labor employed in those departments, on the theory that such repairs arise in this proportion; to distribute sampling and assaying over the actual points to which they relate at the average cost per sample or assay. "general expenses," that is, superintendence, etc., are often not included in the final departments as above, but are sometimes "spread" in an attempt to charge a proportion of superintendence to each particular work. as, however, such "spreading" must take place on the basis of the relative expenditure in each department, the result is of little value, for such a basis does not truly represent the proportion of general superintendence, etc., devoted to each department. if they are distributed over all departments, capital as well as revenue, on the basis of total expenditure, they inflate the "capital expenditure" departments against a day of reckoning when these charges come to be distributed over working costs. although it may be contended that the capital departments also require supervision, such a practice is a favorite device for showing apparently low working costs in the revenue departments. the most courageous way is not to distribute general expenses at all, but to charge them separately and directly to revenue accounts and thus wholly into working costs. the second problem is to reduce the "suspense" or capital charges to a final cost per ton, and this is no simple matter. development expenditures bear a relation to the tonnage developed and not to that extracted in any particular period. if it is desired to preserve any value for comparative purposes in the mining costs, such outlay must be charged out on the basis of the tonnage developed, and such portion of the ore as is extracted must be written off at this rate; otherwise one month may see double the amount of development in progress which another records, and the underground costs would be swelled or diminished thereby in a way to ruin their comparative value from month to month. the ore developed cannot be satisfactorily determined at short intervals, but it can be known at least annually, and a price may be deduced as to its cost per ton. in many mines a figure is arrived at by estimating ore-reserves at the end of the year, and this figure is used during the succeeding year as a "redemption of development" and as such charged to working costs, and thus into revenue account in proportion to the tonnage extracted. this matter is further elaborated in some mines, in that winzes and rises are written off at one rate, levels and crosscuts at another, and shafts at one still lower, on the theory that they lost their usefulness in this progression as the ore is extracted. this course, however, is a refinement hardly warranted. plant and equipment constitute another "suspense" account even harder to charge up logically to tonnage costs, for it is in many items dependent upon the life of the mine, which is an unknown factor. most managers debit repairs and maintenance directly to the revenue account and leave the reduction of the construction outlay to an annual depreciation on the final balance sheet, on the theory that the plant is maintained out of costs to its original value. this subject will be discussed further on. inherent limitations in accuracy of working costs.--there are three types of such limitations which arise in the determination of costs and render too detailed dissection of such costs hopeless of accuracy and of little value for comparative purposes. they are, first, the difficulty of determining all of even direct expenditure on any particular crosscut, stope, haulage, etc.; second, the leveling effect of distributing the "spread" expenditures, such as power, repairs, etc.; and third, the difficulties arising out of the borderland of various departments. of the first of these limitations the instance may be cited that foremen and timekeepers can indicate very closely the destination of labor expense, and also that of some of the large items of supply, such as timber and explosives, but the distribution of minor supplies, such as candles, drills, picks, and shovels, is impossible of accurate knowledge without an expense wholly unwarranted by the information gained. to determine at a particular crosscut the exact amount of steel, and of tools consumed, and the cost of sharpening them, would entail their separate and special delivery to the same place of attack and a final weighing-up to learn the consumption. of the second sort of limitations, the effect of "spread" expenditure, the instance may be given that the repairs and maintenance are done by many men at work on timbers, tracks, machinery, etc. it is hopeless to try and tell how much of their work should be charged specifically to detailed points. in the distribution of power may be taken the instance of air-drills. although the work upon which the drill is employed can be known, the power required for compression usually comes from a common power-plant, so that the portion of power debited to the air compressor is an approximation. the assumption of an equal consumption of air by all drills is a further approximation. in practice, therefore, many expenses are distributed on the theory that they arise in proportion to the labor employed, or the machines used in the various departments. the net result is to level down expensive points and level up inexpensive ones. the third sort of limitation of accounting difficulty referred to, arises in determining into which department are actually to be allocated the charges which lie in the borderland between various primary classes of expenditure. for instance, in ore won from development,--in some months three times as much development may be in ore as in other months. if the total expense of development work which yields ore be charged to stoping account, and if cost be worked out on the total tonnage of ore hoisted, then the stoping cost deduced will be erratic, and the true figures will be obscured. on the other hand, if all development is charged to 'capital account' and the stoping cost worked out on all ore hoisted, it will include a fluctuating amount of ore not actually paid for by the revenue departments or charged into costs. this fluctuation either way vitiates the whole comparative value of the stoping costs. in the following system a compromise is reached by crediting "development" with an amount representing the ore won from development at the average cost of stoping, and by charging this amount into "stoping." a number of such questions arise where the proper division is simply a matter of opinion. the result of all these limitations is that a point in detail is quickly reached where no further dissection of expenditure is justified, since it becomes merely an approximation. the writer's own impression is that without an unwarrantable number of accountants, no manager can tell with any accuracy the cost of any particular stope, or of any particular development heading. therefore, aside from some large items, such detailed statistics, if given, are to be taken with great reserve. working cost sheets.--there are an infinite number of forms of working cost sheets, practically every manager having a system of his own. to be of greatest value, such sheets should show on their face the method by which the "spread" departments are handled, and how revenue and suspense departments are segregated. when too much detail is presented, it is but a waste of accounting and consequent expense. where to draw the line in this regard is, however, a matter of great difficulty. no cost sheet is entirely satisfactory. the appended sheet is in use at a number of mines. it is no more perfect than many others. it will be noticed that the effect of this system is to throw the general expenses into the revenue expenditures, and as little as possible into the "suspense" account. general technical data. for the purposes of efficient management, the information gathered under this head is of equal, if not superior, importance to that under "working costs." such data fall generally under the following heads:-- labor.--returns of the shifts worked in the various departments for each day and for the month; worked out on a monthly basis of footage progress, tonnage produced or tons handled per man; also where possible the footage of holes drilled, worked out per man and per machine. supplies.--daily returns of supplies used; the principal items worked out monthly in quantity per foot of progress, or per ton of ore produced. power.--fuel, lubricant, etc., consumed in steam production, worked out into units of steam produced, and this production allocated to the various engines. where electrical power is used, the consumption of the various motors is set out. surveys.--the need of accurate plans requires no discussion. aside from these, the survey-office furnishes the returns of development footage, measurements under contracts, and the like. sampling and assaying.--mine sampling and assaying fall under two heads,--the determination of the value of standing ore, and of products from the mine. the sampling and assaying on a going mine call for the same care and method as in cases of valuation of the mine for purchase,--the details of which have been presented under "mine valuation,"--for through it, guidance must not only be had to the value of the mine and for reports to owners, but the detailed development and ore extraction depend on an absolute knowledge of where the values lie. chapter xviii. administration (_concluded_). administrative reports. in addition to financial returns showing the monthly receipts, expenditures, and working costs, there must be in proper administration periodic reports from the officers of the mine to the owners or directors as to the physical progress of the enterprise. such reports must embrace details of ore extraction, metal contents, treatment recoveries, construction of equipment, and the results of underground development. the value of mines is so much affected by the monthly or even daily result of exploration that reports of such work are needed very frequently,--weekly or even daily if critical work is in progress. these reports must show the width, length, and value of the ore disclosed. the tangible result of development work is the tonnage and grade of ore opened up. how often this stock-taking should take place is much dependent upon the character of the ore. the result of exploration in irregular ore-bodies often does not, over short periods, show anything tangible in definite measurable tonnage, but at least annually the ore reserve can be estimated. in mines owned by companies, the question arises almost daily as to how much of and how often the above information should be placed before stockholders (and therefore the public) by the directors. in a general way, any company whose shares are offered on the stock exchange is indirectly inviting the public to become partners in the business, and these partners are entitled to all the information which affects the value of their property and are entitled to it promptly. moreover, mining is a business where competition is so obscure and so much a matter of indifference, that suppression of important facts in documents for public circulation has no justification. on the other hand, both the technical progress of the industry and its position in public esteem demand the fullest disclosure and greatest care in preparation of reports. most stockholders' ignorance of mining technology and of details of their particular mine demands a great deal of care and discretion in the preparation of these public reports that they may not be misled. development results may mean little or much, depending upon the location of the work done in relation to the ore-bodies, etc., and this should be clearly set forth. the best opportunity of clear, well-balanced statements lies in the preparation of the annual report and accounts. such reports are of three parts:-- . the "profit and loss" account, or the "revenue account." . the balance sheet; that is, the assets and liabilities statement. . the reports of the directors, manager, and consulting engineer. the first two items are largely matters of bookkeeping. they or the report should show the working costs per ton for the year. what must be here included in costs is easier of determination than in the detailed monthly cost sheets of the administration; for at the annual review, it is not difficult to assess the amount chargeable to development. equipment expenditure, however, presents an annual difficulty, for, as said, the distribution of this item is a factor of the life of the mine, and that is unknown. if such a plant has been paid for out of the earnings, there is no object in carrying it on the company's books as an asset, and most well-conducted companies write it off at once. on the other hand, where the plant is paid for out of capital provided for the purpose, even to write off depreciation means that a corresponding sum of cash must be held in the company's treasury in order to balance the accounts,--in other words, depreciation in such an instance becomes a return of capital. the question then is one of policy in the company's finance, and in neither case is it a matter which can be brought into working costs and leave them any value for comparative purposes. indeed, the true cost of working the ore from any mine can only be told when the mine is exhausted; then the dividends can be subtracted from the capital sunk and metal sold, and the difference divided over the total tonnage produced. the third section of the report affords wide scope for the best efforts of the administration. this portion of the report falls into three divisions: (_a_) the construction and equipment work of the year, (_b_) the ore extraction and treatment, and (_c_) the results of development work. the first requires a statement of the plant constructed, its object and accomplishment; the second a disclosure of tonnage produced, values, metallurgical and mechanical efficiency. the third is of the utmost importance to the stockholder, and is the one most often disregarded and obscured. upon this hinges the value of the property. there is no reason why, with plans and simplicity of terms, such reports cannot be presented in a manner from which the novice can judge of the intrinsic position of the property. a statement of the tonnage of ore-reserves and their value, or of the number of years' supply of the current output, together with details of ore disclosed in development work, and the working costs, give the ground data upon which any stockholder who takes interest in his investment may judge for himself. failure to provide such data will some day be understood by the investing public as a _prima facie_ index of either incapacity or villainy. by the insistence of the many engineers in administration of mines upon the publication of such data, and by the insistence of other engineers upon such data for their clients before investment, and by the exposure of the delinquents in the press, a more practicable "protection of investors" can be reached than by years of academic discussion. chapter xix. the amount of risk in mining investments. risk in valuation of mines; in mines as compared with other commercial enterprises. from the constant reiteration of the risks and difficulties involved in every step of mining enterprise from the valuation of the mine to its administration as a going concern, the impression may be gained that the whole business is one great gamble; in other words, that the point whereat certainties stop and conjecture steps in is so vital as to render the whole highly speculative. far from denying that mining is, in comparison with better-class government bonds, a speculative type of investment, it is desirable to avow and emphasize the fact. but it is none the less well to inquire what degree of hazard enters in and how it compares with that in other forms of industrial enterprise. mining business, from an investment view, is of two sorts,--prospecting ventures and developed mines; that is, mines where little or no ore is exposed, and mines where a definite quantity of ore is measurable or can be reasonably anticipated. the great hazards and likewise the aladdin caves of mining are mainly confined to the first class. although all mines must pass through the prospecting stage, the great industry of metal production is based on developed mines, and it is these which should come into the purview of the non-professional investor. the first class should be reserved invariably for speculators, and a speculator may be defined as one who hazards all to gain much. it is with mining as an investment, however, that this discussion is concerned. risk in valuation of mines.--assuming a competent collection of data and efficient management of the property, the risks in valuing are from step to step:-- . the risk of continuity in metal contents beyond sample faces. . the risk of continuity in volume through the blocks estimated. . the risk of successful metallurgical treatment. . the risk of metal prices, in all but gold. . the risk of properly estimating costs. . the risk of extension of the ore beyond exposures. . the risk of management. as to the continuity of values and volumes through the estimated area, the experience of hundreds of engineers in hundreds of mines has shown that when the estimates are based on properly secured data for "proved ore," here at least there is absolutely no hazard. metallurgical treatment, if determined by past experience on the ore itself, carries no chance; and where determined by experiment, the risk is eliminated if the work be sufficiently exhaustive. the risk of metal price is simply a question of how conservative a figure is used in estimating. it can be eliminated if a price low enough be taken. risk of extension in depth or beyond exposures cannot be avoided. it can be reduced in proportion to the distance assumed. obviously, if no extension is counted, there is nothing chanced. the risk of proper appreciation of costs is negligible where experience in the district exists. otherwise, it can be eliminated if a sufficiently large allowance is taken. the risk of failure to secure good management can be eliminated if proved men are chosen. there is, therefore, a basic value to every mine. the "proved" ore taken on known metallurgical grounds, under known conditions of costs on minimum prices of metals, has a value as certain as that of money in one's own vault. this is the value previously referred to as the "_a_" value. if the price (and interest on it pending recovery) falls within this amount, there is no question that the mine is worth the price. what the risk is in mining is simply what amount the price of the investment demands shall be won from extension of the deposit beyond known exposures, or what higher price of metal must be realized than that calculated in the "_a_" value. the demands on this _x, y_ portion of the mine can be converted into tons of ore, life of production, or higher prices, and these can be weighed with the geological weights and the industrial outlook. mines compared to other commercial enterprises.--the profits from a mining venture over and above the bed-rock value _a_, that is, the return to be derived from more extensive ore-recovery and a higher price of metal, may be compared to the value included in other forms of commercial enterprise for "good-will." such forms of enterprise are valued on a basis of the amount which will replace the net assets plus (or minus) an amount for "good-will," that is, the earning capacity. this good-will is a speculation of varying risk depending on the character of the enterprise. for natural monopolies, like some railways and waterworks, the risk is less and for shoe factories more. even natural monopolies are subject to the risks of antagonistic legislation and industrial storms. but, eliminating this class of enterprise, the speculative value of a good-will involves a greater risk than prospective value in mines, if properly measured; because the dangers of competition and industrial storms do not enter to such a degree, nor is the future so dependent upon the human genius of the founder or manager. mining has reached such a stage of development as a science that management proceeds upon comparatively well-known lines. it is subject to known checks through the opportunity of comparisons by which efficiency can be determined in a manner more open for the investor to learn than in any other form of industry. while in mining an estimate of a certain minimum of extension in depth, as indicated by collateral factors, may occasionally fall short, it will, in nine cases out of ten, be exceeded. if investment in mines be spread over ten cases, similarly valued as to minimum of extension, the risk has been virtually eliminated. the industry, if reduced to the above basis for financial guidance, is a more profitable business and is one of less hazards than competitive forms of commercial enterprises. in view of what has been said before, it may be unnecessary to refer again to the subject, but the constant reiteration by wiseacres that the weak point in mining investments lies in their short life and possible loss of capital, warrants a repetition that the _a, b, c_ of proper investment in mines is to be assured, by the "_a_" value, of a return of the whole or major portion of the capital. the risk of interest and profit may be deferred to the _x, y_ value, and in such case it is on a plane with "good-will." it should be said at once to that class who want large returns on investment without investigation as to merits, or assurance as to the management of the business, that there is no field in this world for the employment of their money at over %. unfortunately for the reputation of the mining industry, and metal mines especially, the business is often not conducted or valued on lines which have been outlined in these chapters. there is often the desire to sell stocks beyond their value. there is always the possibility that extension in depth will reveal a glorious eldorado. it occasionally does, and the report echoes round the world for years, together with tributes to the great judgment of the exploiters. the volume of sound allures undue numbers of the venturesome, untrained, and ill-advised public to the business, together with a mob of camp-followers whose objective is to exploit the ignorant by preying on their gambling instincts. thus a considerable section of metal mining industry is in the hands of these classes, and a cloud of disrepute hangs ever in the horizon. there has been a great educational campaign in progress during the past few years through the technical training of men for conduct of the industry, by the example of reputable companies in regularly publishing the essential facts upon which the value of their mines is based, and through understandable nontechnical discussion in and by some sections of the financial and general press. the real investor is being educated to distinguish between reputable concerns and the counters of gamesters. moreover, yearly, men of technical knowledge are taking a stronger and more influential part in mining finance and in the direction of mining and exploration companies. the net result of these forces will be to put mining on a better plane. chapter xx. the character, training, and obligations of the mining engineering profession. in a discussion of some problems of metal mining from the point of view of the direction of mining operations it may not be amiss to discuss the character of the mining engineering profession in its bearings on training and practice, and its relations to the public. the most dominant characteristic of the mining engineering profession is the vast preponderance of the commercial over the technical in the daily work of the engineer. for years a gradual evolution has been in progress altering the larger demands on this branch of the engineering profession from advisory to executive work. the mining engineer is no longer the technician who concocts reports and blue prints. it is demanded of him that he devise the finance, construct and manage the works which he advises. the demands of such executive work are largely commercial; although the commercial experience and executive ability thus become one pier in the foundation of training, the bridge no less requires two piers, and the second is based on technical knowledge. far from being deprecated, these commercial phases cannot be too strongly emphasized. on the other hand, i am far from contending that our vocation is a business rather than a profession. for many years after the dawn of modern engineering, the members of our profession were men who rose through the ranks of workmen, and as a result, we are to this day in the public mind a sort of superior artisan, for to many the engine-driver is equally an engineer with the designer of the engine, yet their real relation is but as the hand to the brain. at a later period the recruits entered by apprenticeship to those men who had established their intellectual superiority to their fellow-workers. these men were nearly always employed in an advisory way--subjective to the executive head. during the last few decades, the advance of science and the complication of industry have demanded a wholly broader basis of scientific and general training for its leaders. executive heads are demanded who have technical training. this has resulted in the establishment of special technical colleges, and compelled a place for engineering in the great universities. the high intelligence demanded by the vocation itself, and the revolution in training caused by the strengthening of its foundations in general education, has finally, beyond all question, raised the work of application of science to industry to the dignity of a profession on a par with the law, medicine, and science. it demands of its members equally high mental attainments,--and a more rigorous training and experience. despite all this, industry is conducted for commercial purposes, and leaves no room for the haughty intellectual superiority assumed by some professions over business callings. there is now demanded of the mining specialist a wide knowledge of certain branches of civil, mechanical, electrical, and chemical engineering, geology, economics, the humanities, and what not; and in addition to all this, engineering sense, executive ability, business experience, and financial insight. engineering sense is that fine blend of honesty, ingenuity, and intuition which is a mental endowment apart from knowledge and experience. its possession is the test of the real engineer. it distinguishes engineering as a profession from engineering as a trade. it is this sense that elevates the possessor to the profession which is, of all others, the most difficult and the most comprehensive. financial insight can only come by experience in the commercial world. likewise must come the experience in technical work which gives balance to theoretical training. executive ability is that capacity to coördinate and command the best results from other men,--it is a natural endowment. which can be cultivated only in actual use. the practice of mine engineering being so large a mixture of business, it follows that the whole of the training of this profession cannot be had in schools and universities. the commercial and executive side of the work cannot be taught; it must be absorbed by actual participation in the industry. nor is it impossible to rise to great eminence in the profession without university training, as witness some of our greatest engineers. the university can do much; it can give a broad basis of knowledge and mental training, and can inculcate moral feeling, which entitles men to lead their fellows. it can teach the technical fundamentals of the multifold sciences which the engineer should know and must apply. but after the university must come a schooling in men and things equally thorough and more arduous. in this predominating demand for commercial qualifications over the technical ones, the mining profession has differentiated to a great degree from its brother engineering branches. that this is true will be most apparent if we examine the course through which engineering projects march, and the demands of each stage on their road to completion. the life of all engineering projects in a general way may be divided into five phases:[*]-- [footnote *: these phases do not necessarily proceed step by step. for an expanding works especially, all of them may be in process at the same time, but if each item be considered to itself, this is the usual progress, or should be when properly engineered.] . determination of the value of the project. . determination of the method of attack. . the detailed delineation of method, means, and tools. . the execution of the works. . the operation of the completed works. these various stages of the resolution of an engineering project require in each more or less of every quality of intellect, training, and character. at the different stages, certain of these qualities are in predominant demand: in the first stage, financial insight; in the second, "engineering sense"; in the third, training and experience; in the fourth and fifth, executive ability. a certain amount of compass over the project during the whole five stages is required by all branches of the engineering profession,--harbor, canal, railway, waterworks, bridge, mechanical, electrical, etc.; but in none of them so completely and in such constant combination is this demanded as in mining. the determination of the commercial value of projects is a greater section of the mining engineer's occupation than of the other engineering branches. mines are operated only to earn immediate profits. no question of public utility enters, so that all mining projects have by this necessity to be from the first weighed from a profit point of view alone. the determination of this question is one which demands such an amount of technical knowledge and experience that those who are not experts cannot enter the field,--therefore the service of the engineer is always demanded in their satisfactory solution. moreover, unlike most other engineering projects, mines have a faculty of changing owners several times during their career, so that every one has to survive a periodic revaluation. from the other branches of engineering, the electrical engineer is the most often called upon to weigh the probabilities of financial success of the enterprise, but usually his presence in this capacity is called upon only at the initial stage, for electrical enterprises seldom change hands. the mechanical and chemical branches are usually called upon for purely technical service on the demand of the operator, who decides the financial problems for himself, or upon works forming but units in undertakings where the opinion on the financial advisability is compassed by some other branch of the engineering profession. the other engineering branches, even less often, are called in for financial advice, and in those branches involving works of public utility the profit-and-loss phase scarcely enters at all. given that the project has been determined upon, and that the enterprise has entered upon the second stage, that of determination of method of attack, the immediate commercial result limits the mining engineer's every plan and design to a greater degree than it does the other engineering specialists. the question of capital and profit dogs his every footstep, for all mines are ephemeral; the life of any given mine is short. metal mines have indeed the shortest lives of any. while some exceptional ones may produce through one generation, under the stress of modern methods a much larger proportion extend only over a decade or two. but of more pertinent force is the fact that as the certain life of a metal mine can be positively known in most cases but a short period beyond the actual time required to exhaust the ore in sight, not even a decade of life to the enterprise is available for the estimates of the mining engineer. mining works are of no value when the mine is exhausted; the capital invested must be recovered in very short periods, and therefore all mining works must be of the most temporary character that will answer. the mining engineer cannot erect a works that will last as long as possible; it is to last as long as the mine only, and, in laying it out, forefront in his mind must be the question, can its cost be redeemed in the period of use of which i am certain it will find employment? if not, will some cheaper device, which gives less efficiency, do? the harbor engineer, the railway engineer, the mechanical engineer, build as solidly as they can, for the demand for the work will exist till after their materials are worn out, however soundly they construct. our engineer cousins can, in a greater degree by study and investigation, marshal in advance the factors with which they have to deal. the mining engineer's works, on the other hand, depend at all times on many elements which, from the nature of things, must remain unknown. no mine is laid bare to study and resolve in advance. we have to deal with conditions buried in the earth. especially in metal mines we cannot know, when our works are initiated, what the size, mineralization, or surroundings of the ore-bodies will be. we must plunge into them and learn,--and repent. not only is the useful life of our mining works indeterminate, but the very character of them is uncertain in advance. all our works must be in a way doubly tentative, for they are subject to constant alterations as they proceed. not only does this apply to our initial plans, but to our daily amendment of them as we proceed into the unknown. mining engineering is, therefore, never ended with the initial determination of a method. it is called upon daily to replan and reconceive, coincidentally with the daily progress of the constructions and operation. weary with disappointment in his wisest conception, many a mining engineer looks jealously upon his happier engineering cousin, who, when he designs a bridge, can know its size, its strains, and its cost, and can wash his hands of it finally when the contractor steps in to its construction. and, above all, it is no concern of his whether it will pay. did he start to build a bridge over a water, the width or depth or bottom of which he could not know in advance, and require to get its cost back in ten years, with a profit, his would be a task of similar harassments. as said before, it is becoming more general every year to employ the mining engineer as the executive head in the operation of mining engineering projects, that is, in the fourth and fifth stages of the enterprise. he is becoming the foreman, manager, and president of the company, or as it may be contended by some, the executive head is coming to have technical qualifications. either way, in no branch of enterprise founded on engineering is the operative head of necessity so much a technical director. not only is this caused by the necessity of executive knowledge before valuations can be properly done, but the incorporation of the executive work with the technical has been brought about by several other forces. we have a type of works which, by reason of the new conditions and constant revisions which arise from pushing into the unknown coincidentally with operating, demands an intimate continuous daily employment of engineering sense and design through the whole history of the enterprise. these works are of themselves of a character which requires a constant vigilant eye on financial outcome. the advances in metallurgy, and the decreased cost of production by larger capacities, require yearly larger, more complicated, and more costly plants. thus, larger and larger capitals are required, and enterprise is passing from the hands of the individual to the financially stronger corporation. this altered position as to the works and finance has made keener demands, both technically and in an administrative way, for the highly trained man. in the early stages of american mining, with the moderate demand on capital and the simpler forms of engineering involved, mining was largely a matter of individual enterprise and ownership. these owners were men to whom experience had brought some of the needful technical qualifications. they usually held the reins of business management in their own hands and employed the engineer subjectively, when they employed him at all. they were also, as a rule, distinguished by their contempt for university-trained engineers. the gradually increasing employment of the engineer as combined executive and technical head, was largely of american development. many english and european mines still maintain the two separate bureaus, the technical and the financial. such organization is open to much objection from the point of view of the owner's interests, and still more from that of the engineer. in such an organization the latter is always subordinate to the financial control,--hence the least paid and least respected. when two bureaus exist, the technical lacks that balance of commercial purpose which it should have. the ambition of the theoretical engineer, divorced from commercial result, is complete technical nicety of works and low production costs without the regard for capital outlay which the commercial experience and temporary character of mining constructions demand. on the other hand, the purely financial bureau usually begrudges the capital outlay which sound engineering may warrant. the result is an administration that is not comparable to the single head with both qualifications and an even balance in both spheres. in america, we still have a relic of this form of administration in the consulting mining engineer, but barring his functions as a valuer of mines, he is disappearing in connection with the industry, in favor of the manager, or the president of the company, who has administrative control. the mining engineer's field of employment is therefore not only wider by this general inclusion of administrative work, but one of more responsibility. while he must conduct all five phases of engineering projects coincidentally, the other branches of the profession are more or less confined to one phase or another. they can draw sharper limitations of their engagements or specialization and confine themselves to more purely technical work. the civil engineer may construct railway or harbor works; the mechanical engineer may design and build engines; the naval architect may build ships; but given that he designed to do the work in the most effectual manner, it is no concern of his whether they subsequently earn dividends. he does not have to operate them, to find the income, to feed the mill, or sell the product. the profit and loss does not hound his footsteps after his construction is complete. although it is desirable to emphasize the commercial side of the practice of the mining engineer's profession, there are other sides of no less moment. there is the right of every red-blooded man to be assured that his work will be a daily satisfaction to himself; that it is a work which is contributing to the welfare and advance of his country; and that it will build for him a position of dignity and consequence among his fellows. there are the moral and public obligations upon the profession. there are to-day the demands upon the engineers which are the demands upon their positions as leaders of a great industry. in an industry that lends itself so much to speculation and chicanery, there is the duty of every engineer to diminish the opportunity of the vulture so far as is possible. where he can enter these lists has been suggested in the previous pages. further than to the "investor" in mines, he has a duty to his brothers in the profession. in no profession does competition enter so obscurely, nor in no other are men of a profession thrown into such terms of intimacy in professional work. from these causes there has arisen a freedom of disclosure of technical results and a comradery of members greater than that in any other profession. no profession is so subject to the capriciousness of fortune, and he whose position is assured to-day is not assured to-morrow unless it be coupled with a consideration of those members not so fortunate. especially is there an obligation to the younger members that they may have opportunity of training and a right start in the work. the very essence of the profession is that it calls upon its members to direct men. they are the officers in the great industrial army. from the nature of things, metal mines do not, like our cities and settlements, lie in those regions covered deep in rich soils. our mines must be found in the mountains and deserts where rocks are exposed to search. thus they lie away from the centers of comfort and culture,--they are the outposts of civilization. the engineer is an officer on outpost duty, and in these places he is the camp leader. by his position as a leader in the community he has a chieftainship that carries a responsibility besides mere mine management. his is the responsibility of example in fair dealing and good government in the community. in but few of its greatest works does the personality of its real creator reach the ears of the world; the real engineer does not advertise himself. but the engineering profession generally rises yearly in dignity and importance as the rest of the world learns more of where the real brains of industrial progress are. the time will come when people will ask, not who paid for a thing, but who built it. to the engineer falls the work of creating from the dry bones of scientific fact the living body of industry. it is he whose intellect and direction bring to the world the comforts and necessities of daily need. unlike the doctor, his is not the constant struggle to save the weak. unlike the soldier, destruction is not his prime function. unlike the lawyer, quarrels are not his daily bread. engineering is the profession of creation and of construction, of stimulation of human effort and accomplishment. index. accounts. administration. administrative reports. air-compression. -drills. alteration, secondary. alternative shafts to inclined deposit. amortization of capital and interest. animals for underground transport. annual demand for base metals. report. artificial pillars. assay foot. inch. of samples. plans. assaying. a value of mine. averages, calculation. bailing. balance sheet. basic price. value of mine. benches. bend in combined shafts. bins. blocked-out ore. blocks. bonanzas, origin. bonus systems, of work. breaking ore. broken hill, levels. ore-pillars. bumping-trough. cable-ways. cages. calculation of averages. of quantities of ore. capital expenditure. caving systems. churn-drills. chutes, loading, in vertical shaft. classification of ore in sight. combined shaft. stopes. commercial value of projects, determination. compartments for shaft. compressed-air locomotives. -air pumps. _vs_. electricity for drills. content, average metal, determining. metal, differences. contract work. copper, annual demand. deposits. ores, enrichment. cost of entry into mine. of equipment. production. per foot of sinking. working. cribs. crosscuts. cross-section of inclined deposit which must be attacked in depth. showing auxiliary vertical outlet. crouch, j. j. cubic feet per ton of ore. foot contents of block. deep-level mines. demand for metals. departmental dissection of expenditures. deposits, _in situ_. ore, classes. regularity. size. structure. depth of exhaustion. determination of average metal contents of ore. development in early prospecting stage. in 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years of life required to yield --% interest. zinc deposits. leaching. contributions from the museum of history and technology: paper the beginnings of cheap steel _philip w. bishop_ steel before the 's bessemer and his competitors robert mushet ebbw vale and the bessemer process mushet and bessemer william kelly's air-boiling process conclusions the beginnings of cheap steel by philip w. bishop _other inventors claimed a part in the invention of the bessemer process of making steel. here, the contemporary discussion in the technical press is re-examined to throw light on the relations of these various claimants to the iron and steel industry of their time, as having a possible connection with the antagonism shown by the ironmasters toward bessemer's ideas._ the author: _philip w. bishop is curator of arts and manufactures, museum of history and technology, in the smithsonian institution's united states national museum._ the development of the world's productive resources during the th century, accelerated in general by major innovations in the field of power, transportation, and textiles, was retarded by the occurrence of certain bottlenecks. one of these affected the flow of suitable and economical raw materials to the machine tool and transportation industries: in spite of a rapid growth of iron production, the methods of making steel remained as they were in the previous century; and outputs remained negligible. in the decade - , this situation was completely changed in great britain and in europe generally; and when the united states emerged from the civil war, that country found itself in a position to take advantage of the european innovations and to start a period of growth which, in the next years, was to establish her as the world's largest producer of steel. this study reviews the controversy as to the origin of the process which, for more than years[ ] provided the greater part of the steel production of the united states. it concerns four men for whom priority of invention in one or more aspects of the process has been claimed. [ ] from through , "bessemer" production accounted for not less than percent of united states steel production. from through , percent of all steel came from this source: historical statistics of the united states - (washington, u.s. department of commerce, bureau of the census, ), tables j. - at p. . the process consists in forcing through molten cast iron, held in a vessel called a converter, a stream of cold air under pressure. the combination of the oxygen in the air with the silicon and carbon in the metal raises the temperature of the latter in a spectacular way and after "blowing" for a certain period, eliminates the carbon from the metal. since steel of various qualities demands the inclusion of from . to . percent of carbon, the blow has to be terminated before the elimination of the whole carbon content; or if the carbon content has been eliminated the appropriate percentage of carbon has to be put back. this latter operation is carried out by adding a precise quantity of manganiferous pig-iron (spiegeleisen) or ferromanganese, the manganese serving to remove the oxygen, which has combined with the iron during the blow. the controversy which surrounded its development concerned two aspects of the process: the use of the cold air blast to raise the temperature of the molten metal, and the application of manganese to overcome the problem of control of the carbon and oxygen content. bessemer, who began his experiments in the making of iron and steel in , secured his first patent in great britain in january , and was persuaded to present information about his discovery to a meeting of the british association for the advancement of science held at cheltenham, gloucestershire, in august . his title "the manufacture of iron without fuel" was given wide publicity in great britain and in the united states. among those who wrote to the papers to contest bessemer's theories were several claimants to priority of invention. two men claimed that they had anticipated bessemer in the invention of a method of treating molten metal with air-blasts for the purpose of "purifying" or decarbonizing iron. both were americans. joseph gilbert martien, of newark, new jersey, who at the time of bessemer's address was working at the plant of the ebbw vale iron works, in south wales, secured a provisional patent a few days before bessemer obtained one of his series of patents for making cast steel, a circumstance which provided ammunition for those who wished to dispute bessemer's somewhat spectacular claims. william kelly, an ironmaster of eddyville, kentucky, brought into action by an american report of bessemer's british association paper, opposed the granting of a united states patent to bessemer and substantiated, to the satisfaction of the commissioner of patents, his claim to priority in the "air boiling" process. a third man, this one a scot resident in england, intervened to claim that he had devised the means whereby martien's and bessemer's ideas could be made practical. he was robert mushet of coleford, gloucestershire, a metallurgist and self-appointed "sage" of the british iron and steel industry who also was associated with the ebbw vale iron works as a consultant. he, like his american contemporaries, has become established in the public mind as one upon whom henry bessemer was dependent for the origin and success of his process. since bessemer was the only one of the group to make money from the expansion of the steel industry consequent upon the introduction of the new technique, the suspicion has remained that he exploited the inventions of the others, if indeed he did not steal them. in this study, based largely upon the contemporary discussion in the technical press, the relation of the four men to each other is re-examined and an attempt is made to place the controversy of - in focus. the necessity for a reappraisal arises from the fact that today's references to the origin of bessemer steel[ ] often contain chronological and other inaccuracies arising in many cases from a dependence on secondary and sometimes unreliable sources. as a result, kelly's contribution has, perhaps, been overemphasized, with the effect of derogating from the work of another american, alexander lyman holley, who more than any man is entitled to credit for establishing bessemer steel in america.[ ] [ ] see especially material distributed by the american iron and steel institute in connection with its celebration of the centennial of steel: "steel centennial ( ), press information," prepared by hill and knowlton, inc., and released by the institute as of may , . [ ] holley's work is outside the scope of this paper. belatedly, his biography is now being written. it can hardly fail to substantiate the contention that during his short life ( - ) holley, who negotiated the purchase of the american rights to bessemer's process, also adapted his methods to the american scene and laid a substantial part of the foundation for the modern american steel industry. steel before the 's in spite of a rapid increase in the use of machines and the overwhelming demand for iron products for the expanding railroads, the use of steel had expanded little prior to . the methods of production were still largely those of a century earlier. slow preparation of the steel by cementation or in crucibles meant a disproportionate consumption of fuel and a resulting high cost. production in small quantities prevented the adoption of steel in uses which required large initial masses of metal. steel was, in fact, a luxury product. the work of réaumur and, especially, of huntsman, whose development of cast steel after secured an international reputation for sheffield, had established the cementation and crucible processes as the primary source of cast steel, for nearly years. josiah marshall heath's patents of , were the first developments in the direction of cheaper steel, his process leading to a reduction of from to percent in the price of good steel in the sheffield market.[ ] heath's secret was the addition to the charge of from to percent of carburet of manganese[ ] as a deoxidizer. heath's failure to word his patent so as to cover also his method of producing carburet of manganese led to the effective breakdown of that patent and to the general adoption of his process without payment of license or royalty. in spite of this reduction in the cost of its production, steel remained, until after the midpoint of the century, an insignificant item in the output of the iron and steel industry, being used principally in the manufacture of cutlery and edge tools. [ ] andrew ure, _dictionary of arts, manufactures and mines_, new york, , p. . [ ] see abridgement of british patent of quoted by james s. jeans, _steel_, london, , p. ff. it is not clear that heath was aware of the precise chemical effect of the use of manganese in this way. the stimulus towards new methods of making steel and, indeed, of making new steels came curiously enough from outside the established industry, from a man who was not an ironmaster--henry bessemer. the way in which bessemer challenged the trade was itself unusual. there are few cases in which a stranger to an industry has taken the risk of giving a description of a new process in a public forum like a meeting of the british association for the advancement of science. he challenged the trade, not only to attack his theories but to produce evidence from their own plants that they could provide an alternative means of satisfying an emergent demand. whether or not bessemer is entitled to claim priority of invention, one can but agree with the ironmaster who said:[ ] "mr. bessemer has raised such a spirit of enquiry throughout ... the land as must lead to an improved system of manufacture." [ ] _mining journal_, , vol. , p. . bessemer and his competitors henry bessemer ( - ), an englishman of french extraction, was the son of a mechanical engineer with a special interest in metallurgy. his environment and his unusual ability to synthesize his observation and experience enabled bessemer to begin a career of invention by registering his first patent at the age of . his active experimenting continued until his death, although the public record of his results ended with a patent issued on the day before his seventieth birthday. a total of british patents[ ] bear his name, not all of them, by any means, successful in the sense of producing a substantial income. curiously, bessemer's financial stability was assured by the success of an invention he did not patent. this was a process of making bronze powder and gold paint, until the 's a secret held in germany. bessemer's substitute for an expensive imported product, in the then state of the patent laws, would have failed to give him an adequate reward if he had been unable to keep his process secret. to assure this reward, he had to design, assemble, and organize a plant capable of operation with a minimum of hired labor and with close security control. the fact that he kept the method secret for years, suggests that his machinery[ ] (bessemer describes it as virtually automatic in operation) represented an appreciation of coordinated design greatly in advance of his time. his experience must have directly contributed to his conception of his steel process not as a metallurgical trick but as an industrial process; for when the time came, bessemer patented his discovery as a process rather than as a formula. [ ] _sir henry bessemer, f.r.s., an autobiography_, london, , p. . [ ] _ibid._, p. ff. in the light of subsequent developments, it is necessary to consider bessemer's attitude toward the patent privilege. he describes his secret gold paint as an example of "what the public has had to pay for not being able to give ... security to the inventor" in a situation where the production of the material "could not be identified as having been made by any particular form of mechanism."[ ] the inability to obtain a patent over the method of production meant that the disclosure of his formula, necessary for patent specification, would openly invite competitors, including the germans, to evolve their own techniques. bessemer concludes:[ ] had the invention been patented, it would have become public property in fourteen years from the date of the patent, after which period the public would have been able to buy bronze powder at its present [_i.e._, _ca._ ] market price, viz. from two shillings and three pence to two shillings and nine pence per pound. but this important secret was kept for about thirty-five years and the public had to pay excessively high prices for twenty-one years longer than they would have done had the invention become public property in fourteen years, as it would have been if patented. even this does not represent all the disadvantages resulting from secret manufacture. while every detail of production was a profound secret, there were no improvements made by the outside public in any one of the machines employed during the whole thirty-five years; whereas during the fourteen years, if the invention had been patented, there would, in all probability have been many improved machines invented and many novel features applied to totally different manufactures. [ ] _ibid._, p. . [ ] _ibid._, p. . while these words, to some extent, were the rationalizations of an old man, bessemer's career showed that his philosophy had a practical foundation; and, if this was indeed his belief, the episode explains in large measure bessemer's later insistence on the legal niceties of the patent procedure. the effect of this will be seen. bessemer's intervention in the field of iron and steel was preceded by a period of experiments in the manufacture of glass. here bessemer claims to have made glass for the first time in the open hearth of a reverberatory furnace.[ ] his work in glass manufacture at least gave him considerable experience in the problems of fusion under high temperatures and provided some support for his later claim that in applying the reverberatory furnace to the manufacture of malleable iron as described in his first patent of january , he had in some manner anticipated the work of c. w. siemens and emil martin.[ ] [ ] _ibid._, p. ff. [ ] _ibid._, p. . bessemer's assertion that he had approached "within measurable distance" of anticipating the siemens-martin process, made in a paper presented at a meeting of the american society of mechanical engineers (_transactions of the american society of mechanical engineers_, , vol. , p. ), evoked strong criticism of bessemer's lack of generosity (_ibid._, p. ). one commentator, friendly to bessemer, put it that "bessemer's relation to the open-hearth process was very much like kelly's to the bessemer process.... although he was measurably near to the open-hearth process, he did not follow it up and make it a commercial success...." (_ibid._, p. ). the general interest in problems of ordnance and armor, stimulated by the crimean war ( - ), was shared by bessemer, whose ingenuity soon produced a design for a projectile which could provide its own rotation when fired from a smooth-bore gun.[ ] bessemer's failure to interest the british war office in the idea led him to submit his design to the emperor napoleon iii. trials made with the encouragement of the emperor showed the inadequacy of the cast-iron guns of the period to deal with the heavier shot; and bessemer was presented with a new problem which, with "the open mind which derived from a limited knowledge of the metallurgy of war," he attacked with impetuosity. within three weeks of his experiments in france, he had applied for a patent for "improvements in the manufacture of iron and steel."[ ] this covered the fusion of steel with pig or cast iron and, though this must be regarded as only the first practical step toward the bessemer process,[ ] it was his experiments with the furnace which provided bessemer with the idea for his later developments. [ ] british patent , november , . [ ] bessemer, _op. cit._ (footnote ), p. he received british patent , dated january , . [ ] see james w. dredge, "henry bessemer - ," _transactions of the american society of mechanical engineers_, , vol. , p. . these were described in his patent dated october , (british patent ). this patent is significant to the present study because his application for an american patent, based on similar specifications, led to the interference of william kelly and to the subsequent denial of the american patent.[ ] in british patent bessemer proposed to convert his steel in crucibles, arranged in a suitable furnace and each having a vertical tuyère, through which air under pressure was forced through the molten metal. as dredge[ ] points out, bessemer's association of the air blast with the increase in the temperature of the metal "showed his appreciation of the end in view, and the general way of attaining it, though his mechanical details were still crude and imperfect." [ ] see u.s. patent office, decision of commissioner of patents, dated april , , in kelly vs. bessemer interference. this is further discussed below (p. ). [ ] dredge, _op. cit._ (footnote ), p. . [illustration: figure .--bessemer's design for a converter, as shown in u.s. patent . this patent, dated november , , corresponds with british patent , dated february , . the more familiar design of converter appeared first in british patent , march , . the contrast with kelly's schematic drawing in fig. (p. ) is noticeable.] experiments were continued and several more british patents were applied for before bessemer made his appearance before the british association on august , .[ ] bessemer described his first converter and its operation in some detail. although he was soon to realize that he "too readily allowed myself to bring my inventions under public notice,"[ ] bessemer had now thrown out a challenge which eventually had to be taken up, regardless of the strength of the vested interests involved. the provocation came from his claims that the product of the first stage of the conversion was the equivalent of charcoal iron, the processes following the smelting being conducted without contact with, or the use of, any mineral fuel; and that further blowing could be used to produce any quality of metal, that is, a steel with any desired percentage of carbon. yet, the principal irritant to the complacency of the ironmaster must have been bessemer's attack on an industry which had gone on increasing the size of its smelting furnaces, thus improving the uniformity of its pig-iron, without modifying the puddling process, which at best could handle no more than to pounds of iron at a time, divided into the "homeopathic doses" of or pounds capable of being handled by human labor.[ ] bessemer's claim to "do" pounds of metal in minutes against the puddling furnace's output of pounds in two hours was calculated to arouse the opposition of those who feared the loss of capital invested in puddling furnaces and of those who suspected that their jobs might be in jeopardy. the ensuing criticism of bessemer has to be interpreted, therefore, with this in mind; not by any means was it entirely based on objective consideration of the method or the product.[ ] [ ] bessemer's paper was reported in _the times_, london, august , . by the time the transactions of the british association were prepared for publication, the controversy aroused by bessemer's claim to manufacture "malleable iron and steel without fuel" had broken out and it was decided not to report the paper. dredge (_op. cit._, footnote , p. ) describes this decision as "sagacious." [ ] bessemer, _op. cit._ (footnote ), p. . [ ] _the times_, london, august , . [ ] david mushet recognized that bessemer's great feature was this effort to "raise the after processes ... to a level commensurate with the preceding case" (_mining journal_, , p. ). within a month of his address, bessemer had sold licenses to several ironmasters (outside sheffield) and so provided himself with capital with which to continue his development work; but he refused to sell his patents outright to the ebbw vale iron works and by this action, as will be seen, he created an enemy for himself. the three years between and , when bessemer opened his own steel works in sheffield, were occupied in tracing the causes of his initial difficulties. there was continued controversy in the technical press. bessemer (unless he used a _nom-de-plume_) took no part in it and remained silent until he made another public appearance before the institution of civil engineers in london (may ). by this time bessemer's process was accepted as a practical one, and the claims of robert mushet to share in his achievement was becoming clamorous. robert mushet robert (forester) mushet ( - ), born in the forest of dean, gloucestershire, of a scots father (david, - ) himself a noted contributor to the metallurgy of iron and steel, is, like the american william kelly, considered by many to have been a victim of bessemer's astuteness--or villainy. because of robert mushet's preference for the quiet of coleford, many important facts about his career are lacking; but even if his physical life was that of a recluse, his frequent and verbose contributions to the correspondence columns of the technical press made him well-known to the iron trade. it is from these letters that he must be judged. in view of his propensity to intervene pontifically in every discussion concerning the manufacture of iron and steel, it is somewhat surprising that he refrained from comment on bessemer's british association address of august for more than fourteen months. the debate was opened over the signature of his brother david who shared the family facility with the pen.[ ] recognizing bessemer's invention as a "congruous appendage to [the] now highly developed powers of the blast furnace" which he describes as "too convenient, too powerful and too capable of further development to be superseded by any retrograde process," david mushet greeted bessemer's discovery as "one of the greatest operations ever devised in metallurgy."[ ] a month later, however, david mushet had so modified his opinion of bessemer as to come to the conclusion that the latter "must indeed be classed with the most unfortunate inventors." he gave as his reason for this turnabout his discovery that joseph martien had demonstrated his process of "purifying" metal successfully and had indeed been granted a provisional patent a month before bessemer. the sharp practice of martien's patent lawyer, mushet claimed, had deprived him of an opportunity of proving priority of invention against bessemer. mushet was convinced that martien's was the first in the field.[ ] [ ] see _mining journal_, , vol. , pp. and . david mushet withdrew from the discussion after and his relapse into obscurity is only broken by an appeal for funds for the family of henry cort. a biographer of the mushets is of the opinion that robert mushet wrote these letters and obtained david's signature to them (fred m. osborn, _the story of the mushets_, london, , p. , footnote). the similarity in the style of the two brothers is extraordinary enough to support this idea. if this is so, robert mushet who disagreed with himself as "sideros" was also in controversy with himself writing as "david." [ ] _mining journal_, , vol. , p. . [ ] _ibid._, pp. and . the case of martien will be discussed below (p. ). david mushet had overlooked bessemer's patent of january , . robert mushet's campaign on behalf of his own claims to have made the bessemer process effective was introduced in october , two years after the beginning of bessemer's experiment and after one year of silence on bessemer's part. writing as "sideros"[ ] he gave credit to martien for "the great discovery that pig-iron can, whilst in the fluid state, be purified ... by forcing currents of air under it ...," though martien had failed to observe the use of temperature by the "deflation of the iron itself"; and for discovering that-- when the carbon has been all, or nearly all, dissipated, the temperature increases to an almost inconceivable extent, so that the mass, when containing only as much carbon as is requisite to constitute with it cast steel ... still retains a perfect degree of fluidity. [ ] _mining journal_, , vol. , p. . robert mushet was a constant correspondent of the _mining journal_ from . the adoption of a pseudonym, peculiar apparently to - (see _dictionary of national biography_, vol. , p. ), enabled him to carry on two debates at a time and also to sing his own praises. this, says "sideros," was no new observation; "it had been before the metallurgical world, both practical and scientific, for centuries," but bessemer was the first to show that this generation of heat could be attained by blowing cold air through the melted iron. mushet goes on to show, however, that the steel thus produced by bessemer was not commercially valuable because the sulphur and phosphorous remained, and the dispersion of oxide of iron through the mass "imported to it the inveterate hot-short quality which no subsequent operation could expel." "sideros" concludes that bessemer's discovery was "at least for a time" now shelved and arrested in its progress; and it had been left "to an individual of the name of mushet" to show that if "fluid metallic manganese" were combined with the fluid bessemer iron, the portion of manganese thus alloyed would unite with the oxygen of the oxide and pass off as slag, removing the hot-short quality of the iron. robert mushet had demonstrated his product to "sideros" and had patented his discovery, though "not one print, literary or scientific, had condescended to notice it." "sideros" viewed mushet's discovery as a "spark amongst dry faggots that will one day light up a blaze which will astonish the world when the unfortunate inventor can no longer reap the fruits of his life-long toil and unflinching perseverance." in an ensuing letter he[ ] summed up the situation as he saw it: nothing that mr. mushet can hereafter invent can entitle him to the merit of mr. bessemer's great discovery ... and ... nothing that mr. bessemer may hereafter patent can deprive mr. robert mushet of having been the first to remove the obstacles to the success of mr. bessemer's process. [ ] _ibid._, p. . mushet's distinction between an inventor and a patentee is indicative of the disdain of a son of david mushet for an amateur (see also p. ). bessemer still did not intervene in the newspaper discussion; nor had he had any serious supporters, at least in the early stage.[ ] [ ] one william green had commented extensively on david mushet's early praise of the bessemer process and on his sudden reversal in favor of martien soon after bessemer's british association address (_mechanics' magazine_, , vol. , p. ff.). green wrote from caledonian road, and the proximity to baxter house, bessemer's london headquarters, suggests the possibility that green was writing for bessemer. publication in the _mining journal_ of a list of mushet's patents,[ ] evidently in response to sideros' complaint, now presented bessemer with notice of robert mushet's activity, even if he had not already observed his claims as they were presented to the patent office. mushet, said the _mining journal_-- appears to intend to carry on his researches from the point where mr. j. g. martien left off and is proceeding on the bessemer plan of patenting each idea as it occurs to his imaginative brain. he proposes to make both iron and steel but does not appear to have quite decided as to the course of action ... to accomplish his object, and therefore claims various processes, some of which are never likely to realize the inventor's expectations, although decidedly novel, whilst others are but slight modification of inventions which have already been tried and failed. [ ] _mining journal_, , vol. , p. . the contemporary attitude is reflected in another comment by the _mining journal_:[ ] although the application of chemical knowledge to the manufacture of malleable iron cannot fail to produce beneficial results, the quality of the metal depends more upon the mechanical than the chemical processes.... without wishing in any way to discourage the iron chemists, we have no hesitation in giving this as our opinion which we shall maintain until the contrary be actually proved. with regard to steel, there may be a large field for chemical research ... however, we believe that unless the iron be of a nature adapted for the manufacture of steel by ordinary processes, the purely chemical inventions will only give a metal of a very uniform quality. [ ] _ibid._, p. . another correspondent, william green, was of the opinion that mushet's "new compounds and alloys," promised well as an auxiliary to the bessemer process but that "the evil which it was intended to remove was more visionary than real." bessemer's chief difficulty was the phosphorus, not the oxide of iron "as mr. mushet assumes." this, bessemer no doubt would deal with in due course, but meanwhile he did well "to concentrate his energies upon the steel operations," after which he would have time to tackle "the difficulties which have so far retarded the iron operations."[ ] [ ] _ibid._, p. . mushet[ ] claims to have taken out his patent of september , , covering the famous "triple compound," after he-- had fully ascertained, upon the ordinary scale of manufacture that air-purified cast-iron, when treated as set forth in my specifications, would afford tough malleable iron ... i found, however, that the remelting of the coke pig-iron, in contact with coke fuel, hardened the iron too much, and it became evident that an air-furnace was more proper for my purpose ... [the difficulties] arose, not from any defect in my process, but were owing to the small quantity of the metal operated upon and the imperfect arrangement of the purifying vessel, which ought to be so constituted that it may be turned upon an axis, the blast taken off, the alloy added and the steel poured out through a spout ... _such a purifying vessel mr. bessemer has delineated in one of his patents._ [ ] _ibid._, p. (italics supplied). mushet also claimed to have designed his own "purifying and mixing" furnace, of -ton capacity, which he had submitted to the ebbw vale iron works "many months ago," without comment from them. there is an intriguing reference to the painful subject of two patents not proceeded with, and not discussed "in the avaricious hope that the parties connected with the patents will make me honorable amends ... these patents were suppressed without my knowledge or consent." lest his qualifications should be questioned, mushet concludes: i do not profess to be an iron chemist, but i have undoubtedly made more experiments upon the subject of iron and steel than any man now living and i am thereby enabled to say that all i know is but little in comparison with what has yet to be discovered. so began mushet's claim to have solved bessemer's problem, a claim which was to fill the correspondence columns of the engineering journals for the next ten years. interpretation of this correspondence is made difficult by our ignorance of the facts concerning the control of mushet's patents. these have to be pieced together from his scattered references to the subject. his experiments were conducted, at least nearly up to the close of the year , with the cooperation of thomas brown of the ebbw vale iron works.[ ] the price of this assistance was apparently half interest in mushet's patents, though for reasons which mushet does not explain the deed prepared to effect the transfer was never executed.[ ] mushet continued, however, to regard the patents as "wholly my own, though at the same time, i am bound in honor to take no unfair advantage of the non-execution of that deed." a possible explanation of this situation may be found in ebbw vale's activities in connection with martien and bessemer, as well as with an austrian inventor, uchatius. [ ] _ibid._, p. . [ ] _ibid._, p. . ebbw vale and the bessemer process after his british association address in august , bessemer had received applications from several ironmasters for licenses, which were issued in return for a down payment and a nominal royalty of pence per ton. among those who started negotiations was mr. thomas brown of ebbw vale iron works, one of the largest of the south wales plants. he proposed, however, instead of a license, an outright purchase of bessemer's patents for £ , . bessemer refused to sell, and according to his[ ] account-- intense disappointment and anger quite got the better of [brown] and for the moment he could not realize the fact of my refusal.... [he then] left me very abruptly, saying in an irritated tone ... "i'll make you see the matter differently yet" and slammed the door after him. [ ] bessemer, _op. cit._ (footnote ), p. . david mushet's advocacy of martien's claim to priority over bessemer has already been noticed (p. ). from him we learn[ ] that martien's experiments leading to his patent of september , , had been carried out at the ebbw vale works in south wales, where he engaged in "perfecting the renton process."[ ] martien's own process consisted in passing air through metal as it was run in a trough from the furnace and before it passed into the puddling furnace. [ ] _mining journal_, , vol. , p. . [ ] james renton's process (u.s. patent , december , ) had been developed at newark, new jersey, in . it was a modification of the puddling furnace, in which the ore and carbon were heated in tubs, utilizing the waste heat of the reverberatory furnace (see the _mechanics' magazine_, vol. , p. , ). renton died at newark in september (_mechanics' magazine_, , vol. , p. ). it is known that martien's patent was in the hands of the ebbw vale iron works by march .[ ] this fact must be added to our knowledge that mushet's patent of september , was drawn up with a specific reference to the application of his "triple compound" to "iron ... purified by the action of air, in the manner invented by joseph gilbert martien,"[ ] and that this and his other manganese patents were under the effective control of ebbw vale. it seems a reasonable deduction from these circumstances that brown's offer to buy out bessemer and his subsequent threat were the consequences of a determination by ebbw vale to attack bessemer by means of patent infringement suits. [ ] _mining journal_, , vol. , p. . [ ] british patent , september , . some aspects of the ebbw vale situation are not yet explained. martien came to south wales from newark, new jersey, where he had been manager of renton's patent semi-bituminous coal furnace, owned by james quimby, and where he had something to do with the installation of renton's first furnace in . the first furnace was unsuccessful.[ ] martien next appears in britain, at the ebbw vale iron works. no information is available as to whether martien's own furnace was actually installed at ebbw vale, although as noted above, david mushet claims to have been invited to see it there. [ ] joseph p. lesley, _the iron manufacturer's guide_, new york, , p. . martien's name is spelled marteen. a description of the furnace is given in _scientific american_ of february , , (vol. , p. ). in the patent interference proceedings referred to below, it was stated that the furnace was in successful operation in . martien secured an american patent for his process in and to file his application appears to have gone to the united states, where he remained at least until october .[ ] he seems to have taken the opportunity to apply for another patent for a furnace similar to that of james renton. this led to interferences proceedings in which martien showed that he had worked on this furnace at bridgend, glamorganshire (one of the ebbw vale plants), improving renton's design by increasing the number of "deoxydizing tubes." this variation in renton's design was held not patentable, and in any case renton's firm was able to show that they had successfully installed the furnace at newark in - , while martien could not satisfy the commissioner that his installation had been made before september . priority was therefore awarded to quimby, brown, renton, and creswell.[ ] [ ] u.s. patent , february , . a correspondent of the _mining journal_ ( , vol. , p. ) states that martien had not returned to england by october . [ ] u.s. patent office, decision of commissioner of patents, dated may , in the matter of interference between the application of james m. quimby and others ... and of joseph martien. since renton had not patented his furnace in great britain, martien's use of his earlier knowledge of renton's work and of his experience at bridgend in an attempt to upset renton's priority is a curious and at present unexplainable episode. perhaps the early records of the ebbw vale iron works, if they exist, will show whether this episode was in some way linked to the firm's optimistic combination of the british patents of martien and mushet. that ebbw vale exerted every effort to find an alternative to bessemer's process is suggested, also, by their purchase in of the british rights to the uchatius process, invented by an austrian army officer. the provisional patent specifications, dated october , , showed that uchatius proposed to make cast steel directly from pig-iron by melting granulated pig-iron in a crucible with pulverized "sparry iron" (siderite) and fine clay or with gray oxide of manganese, which would determine the amount of carbon combining with the iron. this process, which was to prove commercially successful in great britain and in sweden but was not used in america,[ ] appeared to ebbw vale to be something from which, "we can have steel produced at the price proposed by mr. bessemer, notwithstanding the failure of his process to fulfil the promise."[ ] [ ] j. s. jeans, _op. cit._ (footnote ), p. . the process is not mentioned by james m. swank, _history of the manufacture of iron in all ages_, philadelphia, american iron and steel association, . [ ] _mining journal_, , vol. , p. . so far as is known only one direct attempt was made, presumably instigated by ebbw vale, to enforce their patents against bessemer, who records[ ] a visit by mushet's agent some two or three months before a renewal fee on mushet's basic manganese patents became payable in . bessemer "entirely repudiated" mushet's patents and offered to perform his operations in the presence of mushet's lawyers and witnesses at the sheffield works so that a prosecution for infringement "would be a very simple matter." that, he says, was the last heard from the agent or from mushet on the subject.[ ] the renewal fee was not paid and the patents were therefore abandoned by ebbw vale and their associates, a fact which did not come to mushet's knowledge until , when he himself declared that the patent "was never in my hands at all [so] that i could not enforce it."[ ] [ ] bessemer, _op. cit._ (footnote ), p. . [ ] the american iron and steel institute's "steel centennial ( ) press information" (see footnote ), includes a pamphlet, "kelly lighted the fireworks ..." by vaughn shelton (new york, ), which asserts (p. ) that bessemer paid the renewal fee and became the owner of mushet's "vital" patent. [ ] robert mushet, _the bessemer-mushet process_, cheltenham, , p. ; _the engineer_, , vol. , pp. and . further support for the thesis that ebbw vale's policy was in part dictated by a desire to make bessemer "see the matter differently" is to be found in the climatic episode. work on martien's patents had not been abandoned and in certain patents were taken out by george parry, ebbw vale's furnace manager. these, represented as improvements of martien's designs, were regarded by bessemer as clear infringements of his own patents.[ ] when it came to bessemer's knowledge that ebbw vale was proposing to "go to the public" for additional capital with which to finance, in part, a large scale working of parry's process, he threatened the financial promoter with injunctions and succeeded in opening negotiations for a settlement. all the patents "which had been for years suspended" over bessemer were turned over to him for £ , . ebbw vale, thereupon, issued their prospectus[ ] with the significant statement that the directors "have agreed for a license for the manufacture of steel by the bessemer process which, from the peculiar resources they possess, they will be enabled to produce in very large quantities...." so bessemer became the owner of the martien and parry patents. mushet's basic patents no longer existed. [ ] _the engineer_, , vol. , p. . bessemer, _op. cit._ (footnote ), p. . [ ] _mining journal_, , vol. , p. . mushet and bessemer that mushet was "used" by ebbw vale against bessemer is, perhaps, only an assumption; but that he was badly treated by ebbw vale is subject to no doubt. mushet's business capacity was small but it is difficult to believe that he could have been so foolish as to assign an interest in his patents to ebbw vale without in some way insuring his right of consultation about their disposition. he claims that even in the drafting of his specifications he was obliged to follow die demands of ebbw vale, which firm, believing, "on the advice of mr. hindmarsh, the most eminent patent counsel of the day,"[ ] that martien's patent outranked bessemer's, insisted that mushet link his process to martien's. this, as late as , mushet believed to be in effective operation.[ ] his later repudiation of the process as an absurd and impracticable patent process "possessing neither value nor utility"[ ] may more truly represent his opinion, especially as, when he wrote his comment, he still did not know of the disappearance of his patents. [ ] _the engineer_, , vol. , p. . [ ] _ibid._, p. . [ ] mushet, _op. cit._ (footnote ), p. . mushet's boast[ ] that he had never been into an ironworks other than his own in coleford is a clue to the interpretation of his behavior in general and also of his frequent presumptuous claims. when, for instance, the development of the uchatius process was publicized, he gave his opinion[ ] that the process was a useless one and had been patented before uchatius "understood its nature"; yet later[ ] he could claim that the process was "in fact, my own invention and i had made and sold the steel thus produced for some years previously to the date of captain uchatius' patent". moreover, he claims to have instructed uchatius' agents in its operation! he may, at this later date, have recalled his challenge (the first of many such) in which he offered uchatius' agent in england to pay a monetary penalty if he could not show a superior method of producing "sound serviceable cast steel from british coke pig-iron, _on the stomic plan_ and without any mixture of clay, oxide of manganese or any of these pot destroying ingredients."[ ] [ ] _ibid._, p. . [ ] _mining journal_, , vol. , p. . [ ] mushet, _op. cit._ (footnote ), p. . the uchatius process became the "you-cheat-us" process to mushet (_mining journal_, , vol. , p. ). [ ] _mining journal_, , vol. , p. (italics supplied). it was david mushet (or robert, using his brother's name)[ ] who accused bessemer, or rather his patent agent, carpmael, of sharp practice in connection with martien's specification, an allegation later supported by martien's first patent agent, avery.[ ] the story was that for the drafting of his final specification, martien, presumably with the advice of the ebbw vale iron works, consulted the same carpmael, as "the leading man" in the field. the latter advised that the provisional specification restricted martien to the application of his method to iron flowing in a channel or gutter from the blast furnace, and so prevented him from applying his aeration principle in any kind of receptacle. in effect, carpmael was acting unprofessionally by giving bessemer the prior claim to the use of a receptacle. according to mushet, martien had in fact "actually and publicly proved" his process in a receptacle and not in a gutter, so that his claim to priority could be maintained on the basis of the provisional specification. [ ] see footnote . [ ] _mining journal_, , vol. , pp. , . this, like other mushet allegations, was ignored by bessemer, and probably with good reason. at any rate, martien's american patent is in terms similar to those of the british specification; he or his advisers seem to have attached no significance to the distinction between a gutter and a receptacle. mushet's claim to have afforded bessemer the means of making his own process useful is still subject to debate. unfortunately, documentation of the case is almost wholly one sided, since his biggest publicizer was mushet himself. an occasional editorial in the technical press and a few replies to mushet's "lucubrations" are all the material which exists, apart from bessemer's own story. mushet and at least five other men patented the use of manganese in steel making in ; his own provisional specification was filed within a month of the publication of bessemer's british association address in august . so it is strange that robert mushet did not until more than a year later join in the controversy which followed that address.[ ] in one of his early letters he claims to have made of "his" steel a bridge rail of pounds weight; although his brother insists that he saw the same rail in the ebbw vale offices in london in the spring of , when it was presented as a specimen of uchatius steel![ ] robert mushet's indignant "advertisement" of january , ,[ ] reiterating his parentage of this sample, also claimed a double-headed steel rail "made by me under another of my patent processes," and sent to derby to be laid down there to be "subjected to intense vertricular triturations." mushet's description of the preparation of this ingot[ ] shows that it was derived from "bessemer scrap" made by ebbw vale in the first unsuccessful attempts of that firm to simulate the bessemer process. this scrap mushet had remelted in pots with spiegel in the proportions of pounds of scrap to of melted spiegel. it was his claim that the rail was rolled direct from the ingot, something bessemer himself could not do at that time. [ ] october , , writing as "sideros" (_mining journal_, , vol. , p. ). [ ] _mining journal_, , vol. , p. , and , vol. , p. . [ ] _ibid._ ( ), p. . [ ] mushet, _op. cit._ (footnote ), p. . the phrase quoted is typical of mushet's style. this was the beginning of a series of claims by mushet as to his essential contributions to bessemer's invention. the silence of the latter during this period is impressive, for according to bessemer's own account[ ] his british association address was premature, and although the sale of licenses actually provided him with working funds, the impatience of those experimenting with the process and the flood of competing "inventions" all embarrassed him at the most critical stage of this development of the process: "it was, however, no use for me to argue the matter in the press. all that i could say would be mere talk and i felt that action was necessary, and not words."[ ] [ ] bessemer, _op. cit._ (footnote ), pp. ff. and ff. [ ] _ibid._, p. . action took the form of continued experiments and, by the end of , a decision to build his own plant at sheffield.[ ] an important collateral development resulted from the visit to london in may of g. f. goransson of gefle, sweden. using bessemer equipment, goransson began trials of the process in november and by october was able to report: "our firm has now entirely given up the manufacture of bar iron, and our blast furnaces and tilt mills are now wholly employed in making steel by the bessemer process, which may, therefore, be now considered an accomplished commercial fact."[ ] [ ] this enterprise, started in conjunction with galloway's of manchester, one of the firms licensed by bessemer to make his equipment, was under way by april (see _mining journal_, , vol. , p. ). [ ] _mining journal_, , vol. , p. . mushet commented (p. ) that he had done the same thing "eighteen months ago." goransson was later to claim considerable improvements on the method of introducing the blast, and, in consequence, the first effective demonstration of the bessemer method[ ]--this at a time when bessemer was still remelting the product of his converter in crucibles, after granulating the steel in water. if mushet is to be believed, this success of goransson's was wholly due to his ore being "totally free from phosphorous and sulphur."[ ] however, bessemer's own progress was substantial, for his sheffield works were reported as being in active operation in april , and a price for his engineers' tool and spindle steel was included in the _mining journal_ "mining market" weekly quotations for the first time[ ] on june , . [ ] swank, _op. cit._ (footnote ), p. . [ ] _the engineer_, , vol. , p. . [ ] _mining journal_, , vol. , pp. and . the price quotation was continued until april . in may bessemer gave a paper, his first public pronouncement since august , before the institution of civil engineers.[ ] the early process, he admitted, had led to failure because the process had not reduced the quantity of sulphur and phosphorous, but his account is vague as to the manner in which he dealt with this problem: steam and pure hydrogen gas were tried, with more or less success in the removal of sulphur, and various flues, composed chiefly of silicates of the oxide of iron and manganese were brought in contact with the fluid metal, during the process and the quantity of phosphorous was thereby reduced. [ ] _the engineer_, , vol. , p. . but the clear implication is that the commercial operation at sheffield was based on the use of the best swedish pig iron and the hematite pig from workington. the use of manganese as standard practice at this time is not referred to,[ ] but the rotary converter and the use of ganister linings are mentioned for the first time. [ ] jeans, _op. cit._ (footnote ), p. refers to the hematite ores of lancashire and cumberland as "the ores hitherto almost exclusively used in the bessemer process." a definitive account of the swedish development of the bessemer process, leading to a well-documented claim that the first practical realization of the process was achieved in sweden in july , was recently published (per carlberg, "early production of bessemer steel at edsken," _journal of the iron and steel institute, great britain_, july , vol. , p. ). mushet had, with some intuition, found opportunity to reassert his contributions to bessemer a few days before this address, describing his process as perhaps lacking "the extraordinary merit of mr. bessemer," being "merely a vigorous offshoot proceeding from that great discovery; but, combined with mr. bessemer's process, it places within the reach of every iron manufacturer to produce cast steel at the same cost for which he can now make his best iron."[ ] [ ] _the engineer_, , vol. , p. . bessemer's intention to present his paper had been announced in april. one of mushet's replies to the paper itself took the form of the announcement of his provisional patent for the use of his triple compound which, in the opinion of _the mining journal_ appeared to be "but a very slight modification of several of mr. bessemer's inventions." another half dozen patents appeared within two months, "so that it is apparent that mr. mushet's failure to make the public appreciate his theories has not injured his inventive faculties."[ ] these patents include, besides variations on his "triple compound" theme, his important patent on the use of tungsten for cutting tools, later to be known as mushet steel.[ ] [ ] _mining journal_, , vol. , p. and . another mushet patent is described as so much like uchatius' process that it would seem to be almost unpatentable. [ ] see jeans, _op. cit._ (footnote ), p. . mushet's formal pronouncement on bessemer's paper, dated june , , is perhaps his most intelligible communication on the subject. he alone "from the first consistently advocated the merits and pointed out the defects of the bessemer process," and within a few days of the british association address he had shown ebbw vale "where the defect would be found and what would remedy" it. it was not, in fact, the presence of one-tenth of a percent of sulphur or phosphorous which affected the result if the bessemer process were combined with his process by adding a triple compound of iron, carbon, and manganese to the pig. "there never was a bar of first-rate cast steel made by the bessemer process alone"; (and that included goransson's product) "and there never can be, but a cheap kind of steel applicable to several purposes may be thus produced." after emphasizing the uniqueness of his attempt to make bessemer's process successful, he asserts:[ ] in short, i merely availed myself of a great metallurgical fact, _which has been for years_ before the eyes of the metallurgical world, namely that the presence of metallic manganese in iron and steel conferred upon both an amount of toughness either when cold or when heated, which the presence at the same time of a notable amount of sulphur and phosphorous could not overcome. [ ] _the engineer_, , vol. , p. (italics supplied). it is noted that mushet's american patent ( , of may , ) prefers the use of iron "as free as possible from sulphur and phosphorous." the succeeding years were enlivened, one by one, by some controversy in which mushet invoked the shadow of his late father as support for some pronouncement, or "edict," as some said, on the subject of making iron and steel. in , on the question of suitable metal for artillery, later to be the subject of high controversy among the leading experts of the day, mushet found a ready solution in his own gun metal. this he had developed fifteen years before. it was of a tensile strength better even than that of krupp of essen who was then specializing in the making of large blocks of cast steel for heavy forgings, and particularly for guns. indeed, he was able publicly to challenge krupp to produce a cast gun metal or cast steel to stand test against his.[ ] a year later his attack on the distinguished french metallurgist fremy, whom he describes as an "ass" for his interest in the so-called cyanogen process of steel making, did little to enhance his reputation, whatever the scientific justification for his attack. his attitude toward the use of new zealand (taranaki) metalliferous sand, which he had previously favored and then condemned in such a way as to "injure a project he can no longer control,"[ ] was another example of a public behavior evidently resented. [ ] _the engineer_, , vol. , pp. , , and _passim_. [ ] _the engineer_, , vol. , pp. , , , . by mid- , on the other hand, bessemer was beginning to meet with increasing respect from the trade. the society of engineers received a dispassionate account of the achievement at the sheffield works from e. riley, whose firm (dowlais) was among the earlier and disappointed licensees of the process.[ ] in august , five years after the ill-fated address before the british association, the institution of mechanical engineers, meeting in sheffield, the center of the british steel trade, heard papers from bessemer and from john brown, a famous ironmaster. the latter described the making of bessemer rails, the product which above all was to absorb the bessemer plants in america after . after the meeting, the engineers visited bessemer's works; and later it was reported,[ ] "at messrs. john brown and company's works, the bessemer process was repeated on a still larger scale and a heavy armor plate rolled in the presence of some visitors...." [ ] _the engineer_, , vol. , p. . [ ] _ibid._, p. . these proceedings invited robert mushet's intervention. still under the impression that his patent was still alive and, with martien's, in the "able hands" of the ebbw vale iron company, he condemned bessemer for his "lack of grace" to do him justice, and took the occasion to indict the patent system which denied him and martien the fruits of their labors.[ ] [ ] _ibid._, pp. and . _the engineer_ found mushet's position untenable on the very grounds he was pleading--that patents should not be issued to different men at different times for the same thing; and showed that bessemer in his patents of january , , and later, had clearly anticipated mushet. in a subsequent article, _the engineer_ disposed of martien's and mushet's claims with a certain finality. the ebbw vale iron works had spent £ , trying to carry out the martien process and it was unlikely that they would have allowed bessemer to infringe upon that patent if they had any grounds for a case. bessemer was not imitating mushet. the latter's "triple compound" required manganese pig-iron (with a content of to percent of manganese) at £ per ton while bessemer used an oxide of manganese (at a percent concentration): at £ per ton. the alloy of manganese and other materials now used in the atmospheric process contains percent of manganese a proportion which could never be obtained from the blast furnace, owing to the highly oxidisable nature of that metal. and it is absolutely necessary, in order to apply any useful alloy of iron, carbon and manganese, in the manufacture of malleable iron and very soft steel that the manganese should be largely in excess of the carbon present.[ ] [ ] _ibid._, p. . there is an intriguing reference in this editorial to an interference on behalf of martien against a bessemer application for a u.s. patent. no dates are given and the case has not been located in the record of u.s. patent commissioner's decision. sufficient answer to mushet was at any rate available in the fact that many hundreds of tons of excellent "bessemer metal" made without any mixture of manganese or spiegeleisen in any form were in successful use. and, moreover, spiegeleisen was not a discovery of robert mushet or an exclusive product of germany since it had been made for twenty years at least from tow law (durham) ores. if bessemer had refused mushet a license (and this was an admitted fact), bessemer's refusal must have been made in self-defense: mr. mushet having set up a number of claims for "improvements" upon which claims, we have a right to suppose, he was preparing to take toll from mr. bessemer, but which claims, the latter gentleman discovered, in time, were worthless and accordingly declined any negotiations with the individual making them.[ ] [ ] _ibid._, p. . mushet's claims were by this time rarely supported in the periodicals. one interesting article in his favor came in from a source of special interest to the american situation. mushet's american patent[ ] had been bought by an american group interested in the kelly process at about this time,[ ] and bessemer's american rights had also been sold to an american group that included alexander lyman holley,[ ] who had long been associated with zerah colburn, another american engineer. colburn, who subsequently ( ) established the london periodical _engineering_ and is regarded as one of the founders of engineering journalism, was from onward a frequent contributor to other trade papers in london. colburn's article of [ ] seems to have been of some importance to mushet, who, in the prospectus of the titanic steel and iron company, ltd., issued soon after, brazenly asserted[ ] that, "by the process of mr. mushet _especially when in combination with the bessemer process_, steel as good as swedish steel" would be produced at £ per ton. mushet may have intended to invite a patent action, but evidently bessemer could now more than ever afford to ignore the "sage of coleford." [ ] u.s. patent , dated may , . the patent was not renewed when application was made in , on the grounds that the original patent had been made co-terminal with the british patent. the latter had been abandoned "by mushet's own fault" so that no right existed to an american renewal (u.s. patent office, decision of commissioner of patents, dated september , ). [ ] see below, p. . the exact date of the purchase of mushet's patent is not known. [ ] _engineering_, , vol. , p. . the deal was completed in . [ ] _the engineer_, , vol. , pp. , . [ ] _mining journal_, , vol. , pp. and (italics supplied). it has not yet been possible to ascertain if this company was successful. mushet writes from this time on from cheltenham, where the company had its offices. research continues in this interesting aspect of his career. the year saw mushet less provocative and more appealing; as for instance: "it was no fault of mr. bessemer's that my patent was lost, but he ought to acknowledge his obligations to me in a manly, straightforward manner and this would stamp him as a great man as well as a great inventor."[ ] [ ] _mining engineer_, , vol. , p. . but bessemer evidently remained convinced of the security of his own patent position. in an address before the british association at birmingham in september he made his first public reply to mushet.[ ] in his long series of patents mushet had attempted to secure-- almost every conceivable mode of introducing manganese into the metal.... manganese and its compounds were so claimed under all imaginable conditions that if this series of patents could have been sustained in law, it would have been utterly impossible for [me] to have employed manganese with steel made by his process, although it was considered by the trade to be impossible to make steel from coke-made iron without it. [ ] _the engineer_, , vol. , p. . the failure of those who controlled mushet's batch of patents to renew them at the end of three years, bessemer ascribed to the low public estimation to which mushet's process had sunk in , and he had therefore, "used without scruple any of these numerous patents for manganese without feeling an overwhelming sense of obligation to the patentee." he was now using ferromanganese made in glasgow. another alloy, consisting of to percent of metallic manganese was also available to him from germany. this renewed publicity brought forth no immediate reply from mushet, but a year later he was invited to read a paper before the british association. a report on the meeting stated that in his paper he repeated his oft-told story, and that "he still thought that the accident (of the non-payment of the patent stamp duties) ought not to debar him from receiving the reward to which he was justly entitled." bessemer, who was present, reiterated his constant willingness to submit the matter to the courts of law, but pointed out that mushet had not accepted the challenge.[ ] [ ] _mechanics' magazine_, , vol. , p. . three months later, in december , mushet's daughter called on bessemer and asked his help to prevent the loss of their home: "they tell me you use my father's inventions and are indebted to him for your success." bessemer replied characteristically: i use what your father has no right to claim; and if he had the legal position you seem to suppose, he could stop my business by an injunction tomorrow and get many thousands of pounds compensation for my infringement of his rights. the only result which followed from your father taking out his patents was that they pointed out to me some rights which i already possessed, but of which i was not availing myself. thus he did me some service and even for this unintentional service, i cannot live in a state of indebtedness.... with that he gave miss mushet money to cover a debt for which distraint was threatened.[ ] soon after this action, bessemer made mushet a "small allowance" of £ a year. bessemer's reasons for making this payment, he describes as follows: "there was a strong desire on my part to make him (mushet) my debtor rather than the reverse, and the payment had other advantages: the press at that time was violently attacking my patent and there was the chance that if any of my licensees were thus induced to resist my claims, all the rest might follow the example."[ ] [ ] bessemer, _op. cit._ (footnote ), p. . [ ] _ibid._ mushet's titanic steel and iron company was liquidated in and its principal asset, "r. mushet's special steel," that is, his tungsten alloy tool metal, was taken over by the sheffield firm of samuel osborn and company. the royalties from this, with bessemer's pension seem to have left mushet in a reasonably comfortable condition until his death in ;[ ] but even the award of the bessemer medal by the iron and steel institute in failed to remove the conviction that he had been badly treated. one would like to know more about the politics which preceded the award of the trade's highest honor. bessemer at any rate was persuaded to approve of the presentation and attended the meeting. mushet himself did not accept the invitation, "as i may probably not be then alive."[ ] the president of the institute emphasized the present good relations between mushet and bessemer and the latter recorded that the hatchet had "long since" been buried. yet mushet continued to brood over the injustice done to him and eventually recorded his story of the rise and progress of the "bessemer-mushet" process in a pamphlet[ ] written apparently without reference to his earlier statements and so committing himself to many inconsistencies. [ ] see fred m. osborn, _the story of the mushets_, london, . [ ] _journal of the iron and steel institute_, , p. . [ ] robert mushet, _the bessemer-mushet process_, cheltenham, . william kelly's "air-boiling" process an account of bessemer's address to the british association was published in the _scientific american_ on september , .[ ] on september , , martien filed application for a u.s. patent on his furnace and mushet for one on the application of his triple compound to cast iron "purified or decarbonized by the action of air blown or forced into ... its particles while it is in a molten ... state."[ ] mushet, by this time, had apparently decided to generalize the application of his compound instead of citing its use in conjunction with martien's process, or, as he put it, he had been obliged to do for his english specification by the ebbw vale iron works. [ ] _scientific american_, , vol. , p. . [ ] u.s. patent , dated may , . martien's u.s. patent was granted as , dated february , . [illustration: figure .--only known design for kelly's air-boiling furnace, from u.s. patent . _a_ is "the flue to carry off the carbonic gas formed in decarbonizing the iron," _b_ is the port through which the charge of fluid iron is received, _c_ and _c'_ are the tuyères, and _d_ is the tap hole for letting out the refined metal.] the discussion in the _scientific american_, which was mostly concerned with martien's claim to priority, soon evoked a letter from william kelly. writing under date of september , , from the suwanee iron works, eddyville, kentucky, he claimed to have started "a series of experiments" in november which had been witnessed by hundreds of persons and "discussed amongst the ironmasters, etc., of this section, all of whom are perfectly familiar with the whole principle ... as discovered by me nearly five years ago." a number of english puddlers had visited him to see his new process. "several of them have since returned to england and may have spoken of my invention there." kelly expected "shortly to have the invention perfected and bring it before the public."[ ] [ ] _scientific american_, , vol. , p. , kelly's suggestion of piracy of his ideas was later enlarged upon by his biographer john newton boucher, _william kelly: a true history of the so-called bessemer process_, greensburg, pennsylvania, . bessemer's application for an american patent was granted during the week ending november , , and kelly began his interference proceedings sometime before january .[ ] [ ] _ibid._, p. . kelly's notice of his intention to take testimony was addressed to bessemer on january , . see papers on "interference, william kelly vs. henry bessemer decision april , ." u.s. patent office records. quotations below are from this file, which is now permanently preserved in the library of the u.s. patent office. kelly's witnesses were almost wholly from the ranks of employees or former employees. the only exception was dr. alfred h. champion, a physician of eddyville. dr. champion describes a meeting in the fall of with "two or three practical ironmasters and others" at which kelly described his process and invited all present to see it in operation. he stated: the company present all differed in opinion from mr. kelly and appealed to me as a chemist in confirmation of their doubts. i at once decided that mr. kelly was correct in his theory and then went on to explain the received opinion of chemists a century ago on this subject, and the present received opinion which was in direct confirmation of the novel theory of mr. kelly. i also mentioned the analogy of said kelly's process in decarbonising iron to the process of decarbonising blood in the human lungs. the doctor does not say, specifically, if he or any of the "company" went to see the process in operation. kelly obtained affidavits from another seventeen witnesses. ten of these recorded their recollections of experiments conducted in . five described the work. two knew of or had seen both. one of the last group was john b. evans who became forge manager of kelly's union forge, a few miles from suwanee. this evidence is of interest since a man in his position should have been in a position to tell something about the results of kelly's operations in terms of usable metal. unfortunately, he limits himself to a comment on the metal which had chilled around a tuyère which had been sent back to the forge ("it was partly malleable and partly refined pig-iron") and to an account of a conversation with others who had worked some of kelly's "good wrought iron" made by the new process. only one of the witnesses (william soden) makes a reference to the phenomenon which is an accompaniment of the blowing of a converter: the prolonged and violent emission of sparks and flames which startled bessemer in his first use of the process[ ] and which still provides an exciting, if not awe-inspiring, interlude in a visit to a steel mill. soden refers, without much excitement, to a boiling commotion, but the results of kelly's "air-boiling" were, evidently, not such as to impress the rest of those who claimed to have seen his furnace in operation. only five of the total of eighteen of the witnesses say that they witnessed the operations. soden, incidentally, knew of seven different "air-boiling" furnaces, some with four and some with eight tuyères, but he also neglected to report on the use of the metal. [ ] bessemer, _op. cit._ (footnote ), p. . as is well known, kelly satisfied the acting commissioner that he had "made this invention and showed it by drawings and experiment as early as ," and he was awarded priority by the acting commissioner's decision of april , , and u.s. patent was granted him as of june , . the _scientific american_ sympathized with bessemer's realization that his american patent was "of no more value to him than so much waste paper" but took the opportunity of chastising kelly for his negligence in not securing a patent at a much earlier date and complained of a patent system which did not require an inventor to make known his discovery promptly. the journal advocated a "certain fixed time" after which such an inventor "should not be allowed to subvert a patent granted to another who has taken proper measures to put the public in possession of the invention."[ ] [ ] _scientific american_, , vol. , p. . little authentic is known about kelly's activities following the grant of his patent. his biographer[ ] does not document his statements, many of which appear to be based on the recollections of members of kelly's family, and it is difficult to reconcile some of them with what few facts are available. kelly's own account of his invention,[ ] itself undated, asserts that he could "refine fifteen hundredweight of metal in from five to ten minutes," his furnace "supplying a cheap method of making run-out metal" so that "after trying it a few days we entirely dispensed with the old and troublesome run-out fires."[ ] this statement suggests that kelly's method was intended to do just this; and it is not without interest to note that several of his witnesses in the interference proceedings, refer to bringing the metal "to nature," a term often used in connection with the finery furnace. if this is so, his assumption that he had anticipated bessemer was based on a misapprehension of what the latter was intending to do, that is, to make steel. [ ] boucher, _op. cit._ (footnote ). [ ] u.s. bureau of the census, _report on the manufacturers of the united states at the tenth census (june , ) ..., manufacture of iron and steel_, report prepared by james m. swank, special agent, washington, , p. . mr. swank was secretary of the american iron and steel association. this material was included in his _history of the manufacture of iron in all ages_, philadelphia, , p. . [ ] _ibid._, p. . the run-out fire (or "finery" fire) was a charcoal fire "into which pig-iron, having been melted and partially refined in one fire, was run and further refined to convert it to wrought iron by the lancashire hearth process," according to a. k. osborn, _an encyclopaedia of the iron and steel industry_, new york, . this statement leaves the reader under the impression that the process was in successful use. it is to be contrasted with the statement quoted above (page ), dated september , when the process had, clearly, not been perfected. in this connection, it should be noted that in the report on the suwanee iron works, included in _the iron manufacturer's guide_,[ ] it is stated that "it is at this furnace that mr. kelly's process for refining iron in the hearth has been most fully experimented upon." [ ] j. p. lesley, _op. cit._ (footnote ), p. . the preface is dated april , . the data was largely collected by joseph lesley of philadelphia, brother of the author, during a tour of several months. since suwanee production is given for weeks only of (_i.e._, through november or , ) it is concluded that lesley's visit was in the last few weeks of . a major financial crisis affected united states business in the fall of . it began in the first week of october and by october the _economist_ (london) reported that the banks of the united states had "almost universally suspended specie payment."[ ] kelly was involved in this crisis and his plant was closed down. according to swank,[ ] some experiments were made to adapt kelly's process to need of rolling mills at the cambria iron works in and , kelly himself being at johnstown, at least in june . that the experiments were not particularly successful is suggested by the lack of any american contributions to the correspondence in the english technical journals. kelly was not mentioned as having done more than interfere with bessemer's first patent application. the success of the latter in obtaining patents[ ] in the united states in november , covering "the conversion of molten crude iron ... into steel or malleable iron, without the use of fuel ..." also escaped the attention of both english and american writers. [ ] _economist_ (london), , vol. , pp. , . [ ] swank, _op. cit._ (footnote ), p. . john fritz, in his _autobiography_ (new york, , p. ), refers to experiments during his time at johnstown, _i.e._, between june and july . _the iron manufacturer's guide_ (see footnote ) also refers to kelly's process as having "just been tried with great success" at cambria. [ ] u.s. patents , dated november , , and , dated november , . bessemer's unsuccessful application corresponded with his british patent , of (see footnote ). it was not until that the question arose as to what happened to kelly's process. the occasion was the publication of an account of bessemer's paper at the sheffield meeting of the (british) society of mechanical engineers on august , . accepting the evidence of "the complete industrial success" of bessemer's process, the _scientific american_[ ] asked: "would not some of our enterprising manufacturers make a good operation by getting hold of the [kelly] patent and starting the manufacture of steel in this country?" [ ] _scientific american_, , new ser., vol. , pp. - . there was no response to this rhetorical question, but a further inquiry as to whether the kelly patent "could be bought"[ ] elicited a response from kelly. writing from hammondsville, ohio, kelly[ ] said, in part: i would say that the new england states and new york would be sold at a fair rate.... i removed from kentucky about three years ago, and now reside at new salisbury about three miles from hammondsville and sixty miles from pittsburg. accept my thanks for your kind efforts in endeavoring to draw the attention of the community to the advantages of my process. [ ] _ibid._, p. . [ ] _ibid._, p. . this letter suggests that the kelly process had been dormant since . whether or not as a result of the publication of this letter, interest was resumed in kelly's experiments. captain eber brock ward of detroit and z. s. durfee of new bedford, massachusetts, obtained control of kelly's patent. durfee himself went to england in the fall of in an attempt to secure a license from bessemer. he returned to the united states in the early fall of , assuming that he was the only "citizen of the united states" who had even seen the bessemer apparatus.[ ] [ ] his claim is somewhat doubtful. alexander lyman holley, who was later to be responsible for the design of most of the first bessemer plants in the united states had been in england in , , and . in view of his interest in ordnance and armor, it is unlikely that bessemer could have escaped his alert observation. his first visit specifically in connection with the bessemer process appears to have been in , but he is said to have begun to interest financiers and ironmasters in the bessemer process after his visit in (_engineering_, , vol. , p. ). in june, , w. f. durfee, a cousin of z. s. durfee, was asked by ward to report on kelly's process. the report[ ] was unfavorable. "the description of [the apparatus] used by mr. kelly at his abandoned works in kentucky satisfied me that it was not suited for an experiment on so large a scale as was contemplated at wyandotte [detroit]." since it was "confidently expected that z. s. durfee would be successful in his efforts to purchase [bessemer's patents], it was thought only to be anticipating the acquisition of property rights ... to use such of his inventions as best suited the purpose in view." [ ] w. f. durfee: "an account of the experimental steel works at wyandotte, michigan," _transactions of the american society of mechanical engineers_, , vol. , p. ff. thus the first "bessemer" plant in the united states came into being without benefit of a license and supported only by a patent "not suited" for a large experiment. kelly seems to have had no part in these developments. they took some time to come to formation. although the converter was ready by september , the blowing engine was not completed until the spring of and the first "blow" successfully made in . it may be no more than a coincidence that the start of production seems to have been impossible before the arrival in this country of a young man, l. m. hart, who had been trained in bessemer operations at the plant of the jackson brothers at st. seurin (near bordeaux) france. the jacksons had become bessemer's partners in respect of the french rights; and the recruitment of hart suggests the possibility that it was from this french source that z. s. durfee obtained his initial technical data on the operation of the bessemer process.[ ] [ ] research in the french sources continues. the arrival of l. m. hart at boston is recorded as of april , , his ship being the ss _africa_ out of liverpool, england (archives of the united states, card index of passenger arrivals - list no. ). during the organization of the plant at wyandotte, kelly was called back to cambria, probably by daniel j. morrell, who, later, became a partner with ward and z. s. durfee in the formation of the kelly pneumatic process company.[ ] we learn from john e. fry,[ ] the iron moulder who was assigned to help kelly, that-- in mr. kelly returned to johnstown for a crucial, and as it turned out, a final series of experiments by him with a rotative [bessemer converter] _made abroad and imported for his purpose_. this converter embodied in its materials and construction several of mr. bessemer's patented factors, of which, up to the close of mr. kelly's experiments above noted, he seemed to have no knowledge or conception. and it was as late as on the occasion of his return in , to operate the experimental bessemer converter, that he first recognized, by its adoption, the necessity for or the importance of any after treatment of, or additions required by the blown metal to convert it into steel. [ ] swank, _op. cit._ (footnote ), p. . [ ] _johnstown daily democrat_, souvenir edition, autumn (italics supplied). mr. fry was at the cambria iron works from until after . fry later asserted[ ] that kelly's experiments in were simply attempts to copy bessemer's methods. (the possibility is under investigation that the so-called "pioneer converter" now on loan to the u.s. national museum from the bethlehem steel company, is the converter referred to by fry.) [ ] _engineering_, , vol. , p. . william kelly, in effect, disappeared from the record until when he applied for an extension of his patent of june , . the application was opposed (by whom, the record does not state) on the grounds that the invention was not novel when it was originally issued, and that it would be against the public interest to extend its term. the commissioner ruled that,[ ] on the first question, it was settled practice of the patent office not to reconsider former decisions on questions of fact; the novelty of kelly's invention had been re-examined when the patent was reissued in november . testimony showed that the patent was very valuable; and that kelly "had been untiring in his efforts to introduce it into use but the opposition of iron manufacturers and the amount of capital required prevented him from receiving anything from his patent until within very few years past." kelly's expenditures were shown to have amounted to $ , , whereas he had received only $ , . since no evidence was filed in support of the public interest aspect of the case, the commissioner found no substantial reason for denying the extension; indeed "very few patentees are able to present so strong grounds for extension as the applicant in the case." [ ] see u.s. patent office, decision of commissioner of patents, dated june , . in a similar application in the previous year, bessemer had failed to win an extension of his u.s. patent , of november , , for the sole reason that his british patent with which it had been made co-terminal had duly expired at the end of its fourteen years of life, and it would have been inequitable to give bessemer protection in the united states while british iron-masters were not under similar restraint. but if it had not been for this consideration, bessemer "would be justly entitled to what he asks on this occasion." the commissioner[ ] observed: "it may be questioned whether [bessemer] was first to discover the principle upon which his process was founded. but we owe its reduction to practice to his untiring industry and perseverance, his superior skill and science and his great outlay." [ ] u.s. patent office, decision of commissioner of patents dated february , . conclusions martien was probably never a serious contender for the honor of discovering the atmospheric process of making steel. in the present state of the record, it is not an unreasonable assumption that his patent was never seriously exploited and that the ebbw vale iron works hoped to use it, in conjunction with the mushet patents, to upset bessemer's patents. the position of mushet is not so clear, and it is hoped that further research can eventually throw a clearer light on his relationship with the ebbw vale iron works. it may well be that the "opinion of metallurgists in later years"[ ] is sound, and that both mushet and bessemer had successfully worked at the same problem. the study of mushet's letters to the technical press and of the attitude of the editors of those papers to mushet suggests the possibility that he, too, was used by ebbw vale for the purposes of their attacks on bessemer. mushet admits that he was not a free agent in respect of these patents, and the failure of ebbw vale to ensure their full life under english patent law indicates clearly enough that by the firm had realized that their position was not strong enough to warrant a legal suit for infringement against bessemer. their purchase of the uchatius process and their final attempt to develop martien's ideas through the parry patents, which exposed them to a very real risk of a suit by bessemer, are also indications of the politics in the case. mushet seems to have been a willing enough victim of ebbw vale's scheming. his letters show an almost presumptuous assumption of the mantle of his father; while his sometimes absurd claims to priority of invention (and demonstration) of practically every new idea in the manufacturing of iron and steel progressively reduced the respect for his name. bessemer claims an impressive array of precedents for the use of manganese in steel making and, given his attitude to patents and his reliance on professional advice in this respect, he should perhaps, be given the benefit of the doubt. a dispassionate judgment would be that bessemer owed more to the development work of his swedish licensees than to mushet. [ ] william t. jeans, _the creators of the age of steel_, london, . kelly's right to be adjudged the joint inventor of what is now often called the kelly-bessemer process is questionable.[ ] admittedly, he experimented in the treatment of molten metal with air blasts, but it is by no means clear, on the evidence, that he got beyond the experimental stage. it is certain that he never had the objective of making steel, which was bessemer's primary aim. nor is there evidence that his process was taken beyond the experimental stage by the cambria works. the rejection of his "apparatus" by w. f. durfee must have been based, to some extent at least, upon the johnstown trials. there are strong grounds then, for agreeing with one historian[ ] who concludes: the fact that kelly was an american is evidently the principal reason why certain popular writers have made much of an invention that, had not bessemer developed his process, would never have attracted notice. kelly's patent proved very useful to industrial interests in this country as a bargaining weapon in negotiations with the bessemer group for the exchange of patent rights. [ ] bessemer dealt with kelly's claim to priority in a letter to _engineering_, , vol. , p. . [ ] louis c. hunter, "the heavy industries since ," in h. f. williamson (editor), _the growth of the american economy_, new york, , p. . kelly's suggestion[ ] that some british puddlers may have communicated his secret to bessemer can, probably, never be verified. all that can be said is that bessemer was not an ironman; his contacts with the iron trade were, so far as can be ascertained, nonexistent until he himself invaded sheffield. so it is unlikely that such a secret would have been taken to him, even if he were a well-known inventor. [ ] later developed into a dramatic story by boucher, _op. cit._ (footnote ). contributions from the museum of history and technology: paper mine pumping in agricola's time and later _robert p. multhauf_ _by robert p. multhauf_ mine pumping in agricola's time and later _coins are a source of information much used by historians. elaborately detailed mining landscapes on th-century german coins in the national museum, discovered by the curator of numismatics and brought to the author's attention, led to this study of early mine-pumping devices._ the author: _robert p. multhauf is curator of science and technology, museum of history and technology, in the smithsonian institution's united states national museum._ the habit of heavy reliance on a single source for the substance of the history of medieval and renaissance mining techniques in europe has led to a rather drastic over-simplification of that history, a condition which persists tenaciously in the recent accounts of parsons, wolf, and bromehead.[ ] our preoccupation with agricola, who has been well known to the english-language public since the hoovers' translation of , seems to have inhibited the investigation of the development of the machines he describes so elegantly. more seriously, the opinion that mining techniques remained essentially the same for a century or two beyond his time appears to have hardened into a conviction.[ ] the history of the technology of mining, as distinguished from metallurgy, is largely a history of mechanization, and that mechanization has until the last century consisted principally in the development of what agricola calls _tractoriae_--hauling machines. that hauling machines of some complexity, archimedian screws and a kind of noria, were used by the romans for dewatering mines has been known for some time. evidence of the survival of this technology beyond the fall of rome remains to be found, and it is generally agreed that mining activity declined through the first millenium. the revival and extension of mining in the central european areas of german settlement is thought to have occurred from the th century, with an intensive development of the region known to agricola (erzgebirge) in the th century.[ ] this revival appears to have paralleled in general the political and cultural revival, but, as in any mining region, the exhaustion of easily workable surface deposits marked a critical point, when the necessity of deeper mining led to the construction of supported tunnels and the introduction of machinery for removing ores and water from deep mines. on the basis of revisions of capital structure and mining law which he regards as inspired by the financial necessities of deep mining, bechtel dates this development from the mid- th century.[ ] the mid- th century situation is confused by the occurrence of the black death, which reduced mining activity drastically, and the events of which bechtel speaks have been put as much as a century later.[ ] in any case, the development of deep-mining methods had clearly made considerable progress in nonferrous mines when the _de re metallica_ was written, in . [illustration: figure .--brunswick silver - / taler, johann friedrich, . (_u. s. national museum, paul a. straub coll.; smithsonian photo -c._)] mine-pumping machinery illustrated by brunswick multiple talers these large silver coins weighing up to ounces were first issued in in brunswick by duke julius ( - ) of the wolfenbuttel line. their historical background is rather unusual and interesting. in the duke decided to increase the output of his silver mines in the harz and arranged for the opening of three new mines. in order to insure the retention of a portion of this increased silver output under his control, the duke decided to issue an entirely new kind of silver coin which he called "loeser," meaning redeemer. these were larger than taler-size pieces, and were struck in denominations from - / to talers. the duke ordered that each of his subjects was to purchase one of these large coins, the size of the coin to be acquired depending on the individual's wealth. the owners were not allowed to use these pieces in everyday trade, but could pawn them in case of dire need. they were expected to produce them at any time upon demand. thus a means of hoarding, a "treasure piece," was created, and the risk of draining the country's wealth through replacement of good, full-weight silver coins with imported base currency was to some extent limited. at the same time, the duke had a considerable sum of money at his disposal in case of emergency. similar loesers were issued up to by different rulers of brunswick. some of the later issues are commemorative in character and might have served for presentation purposes. the workmanship of the majority is exquisite. they portray personages real and ideal and ornate coats of arms, in addition to the elaborate mining landscapes shown here. the u. s. national museum is fortunate in having a number of examples through the generosity of mr. paul a. straub. for calling my attention to these coins, and for other invaluable assistance, i am indebted to the former curator of the numismatic collections of the u. s. national museum, the late stuart mosher, and to the present curator, dr. v. clain-stefanelli. figure shows an overshot waterwheel driving through stangenkunsten pumps in three separate shafts, each covered by the typical conical shaft house. it is possible that these shaft houses also cover horse whims used to operate bucket hoists such as that shown in the lower center. a house with three chimneys in the background may be the smelter. the horse over whose head the deity holds a wreath is a symbol of luneberg. for a detailed description of the mechanical equipment of this era we are largely indebted to agricola. he classifies hauling machines into four types; the ordinary bucket windlass, the piston (suction) pump, the chain of dippers, and the rag and chain pump. although the first three had been known in antiquity, and the last perhaps a century before his time,[ ] their use in mining would appear to date from the mid- th century or later. his is not an historical account, and one who attempts to compare it with others of contemporary or later times encounters a difficulty in his use of descriptive latin names rather than the common german names used by most others. english and german editors have interpreted them as follows:[ ] _latin_ _english_ _german_ bulga water bucket wasserkubel, kehrrad orbiculis suction pump pumpe situlis chain of dippers kannen (werke), bulgenkunst[ ] machina, quae pilis rag and chain heinzenkunst, taschenkunst[ ] aquas hauriut pump [illustration: figure .--brunswick silver - / taler, ernst august, . (_u. s. national museum, paul a. straub coll.; smithsonian photo -a._)] figure shows two shaft-houses covering pumps driven by stangenkunsten. the source of power, hidden by the curious "log cabin" at the right, was probably a waterwheel. i have not found evidence that the stangenkunst was used to operate bucket hoists, as appears to be the case here. it will be noticed that the above and below ground portions of these illustrations do not correlate precisely. this coin, like the others, shows miners doing various things familiar from agricola--divining, digging, carrying, and operating windlasses. figure exhibits the principal advantage of the stangenkunst, in its utilization to connect a waterwheel located in a valley stream to driven machinery on the mountain some distance above. the lute-playing girl (lautenspielerin) refers to the lautental mine. a stangenkunst (fig. ) existed here as recently as . the mines shown in figures - are in the harz region. figures and show the st. anna mine in the erzgebirge, near freiberg, as illustrated on a medal in the brunswick museum. prominent in figure is an aqueduct, one function of which is to supply a waterwheel in the house below, which in turn delivers power through the stangenkunst to two open shafts. the reverse (fig. ), an unusually fine view of the inner workings of a mine, shows, above ground, a typical horse whim driving a bucket windlass. below ground is shown a crank-driven piston pump typical of those driven by stangenkunst. in this case, however, it is driven by an underground vertical treadmill. [illustration: figure .--brunswick silver taler, ernst august, . (_u. s. national museum, paul a. straub coll.; smithsonian photo -a._)] [illustration: figure .--medal, , showing st. anna mine, near freiberg. (_photo courtesy of stadtisches museum, braunschweig._)] [illustration: figure .--reverse of medal shown in figure . (_photo courtesy of stadtisches museum, braunschweig._)] the resemblance of the german term for bag (bulge) to the latin term for bucket (bulga) instead of the latin term for bag (canalis), and the presence of buckets (kübeln), bags (bulgen), pockets (taschen), or cans (kannen) as components of three of agricola's four categories of hauling machines are reasons enough for the apparent superfluity of german names, if not for his decision to avoid the use of german names. but it should also be noted that the names sometimes refer to a pump and its prime mover considered as a single machine. such is the case with the kehrrad, a bucket windlass driven by a reversible waterwheel which agricola describes as his largest hauling machine.[ ] agricola describes hauling devices of these four types, the diversity resulting generally from the application of three types of prime movers, men, horses, and waterwheels, and in the endowment of each in turn with a mechanical advantage in the form of gearing.[ ] although he does not specify clearly the relative importance of the various pumps, the majority ( ) use man as the prime mover. he speaks of the advantages of some, noting that the horse whim has a power two and a half times that of the man windlass, and emphasizing the even greater power available in flowing water "when a running stream can be diverted to a mine." the most powerful machine then in use for deep mines appears to have been the horse-powered rag and chain pump. such, then, were the important mining machines of this early period of deep mining, according to the leading authority. but did they continue, as has been claimed, to be the only important machines of the subsequent century? g. e. lohneyss,[ ] writing a little over a half century after the publication of _de re metallica_, declared: the old miners [alten bergleute] had heintzen, kerratt, bulgenkunst, taschen-kunst, pumpen, with which one lifted water with cans on pulleys or with a treadmill; and they devised and constructed these in which the poor people moved like cattle and wore themselves out. at that time they had powerful machines (kunst) using swift water, although it cost much to erect and maintain them, and was very dangerous since an iron chain of a bulgenkunst alone often weighed centner [over tons] and more. but today's artisan [jetzigen künstler] far surpasses the old ... since we have in the present time invented many other mining machines; such as the _stangenkunst mit dem krummen zapffen_, which raises water at small cost over lachter [ feet]. [illustration: figure .--stangenkunst, showing driving wheel, feldkunst, and kunstkreuz. from h. calvör (see footnote ).] the stangenkunst, which can be roughly translated as "rod work with crank," was a piston pump driven through a crank and rods by a prime mover located at a distant point. agricola describes a crank-driven piston pump, calling it a new machine invented ten years earlier.[ ] but it is not driven bya distant prime mover. like his other water-powered hauling machines it can only be used "when a running stream can be diverted to a mine." so far as we can determine from internal evidence, agricola did not know the stangenkunst. although the full development of the stangenkunst came later, it was apparently introduced in agricola's time. its introduction to the erzgebirge has been put as early as .[ ] according to another authority it was introduced to the harz in by one heinrich eschenbach of meissen.[ ] its significance is only made clear to us by later authorities. as shown in figure it was adapted to the utilization of a distant stream, through the feldstangen, an extended horizontal series of reciprocating rods, and the kunstkreuz (fig. ), a lever in the shape of a cross for changing at right angles the direction of power transmission. these improvements may have been almost contemporaneous with agricola, as calvör mentions the use of the feldkunst, which term signified the extended rods, as having been known in . the disadvantage of moving the weight of a long extension of rods was obviated, during the th century, through the use of a double set of balanced rods, resembling a pantograph. at some later date the horse whim was fitted with a crank and adapted to the stangenkunst,[ ] thus permitting the establishment of a veritable power network, as suggested in figure . the freiberg mine director martin planer reported in the installation since of thirty-eight "kunsten und zeugen" in mines under his charge. that these were water-powered machines is clear from his remark that their cost was only to percent that of "pferden und knechten."[ ] it is likely that many if not most were stangenkunsten, for mining treatises of the th and th centuries testify to the continuous extension of this mechanism.[ ] perhaps the most striking evidence of its importance is its representation on the illustrated coinage of the th century. these multiple talers (figs. , , ), happy products of the ingenious fiscal policies of the dukes of brunswick, picture mining activity in the th century no less elegantly than do the woodcuts of _de re metallica_ a century earlier. the stangenkunst received its most spectacular application in france, in its application to the driving of the second- and third-stage pumps in the famous waterworks at marly ( - ), but its real importance is better illustrated in central europe, by the many descriptions and drawings showing its use in the mines, driving machinery as distant as a mile[ ] from the source of power. [illustration: figure .--feldgestange (stangenkunst) near lautental. from c. matschoss, _technische kulturdenkmal_, munich, .] it seems, therefore, that lohneyss' "old miners" were those described by agricola, and that the mine-hauling machinery used in central european mines changed in the century after him far more than has been recognized.[ ] this thesis may further cast some light on other technological questions. the connection between the urgency of the problem of mine drainage in england, and the invention of the steam engine, has often been suggested.[ ] perhaps the "backwardness" of germany in steam-engine experimentation, and later in the introduction of the newcomen engine, was to some extent due to the adequacy of existing machinery to meet the problem of mine flooding, for it is not clear that this problem existed on the continent.[ ] [illustration: figure .--the waterworks at marly-le-roi, on the seine river, built in to supply the fountains at the royal palace at versailles. from a print by de fer, . (_smithsonian photo ._)] a comparison of the techniques described by agricola with those of a century later suggests that this was a century of significant progress in that earlier industrial revolution described by mumford as his "eotechnic phase," characterized by "the diminished use of human beings as prime movers, and the separation of the production of energy from its application and immediate control."[ ] footnotes: [ ] w. b. parsons, _engineers and engineering in the renaissance_, baltimore, . abraham wolf, _a history of science, technology, and philosophy in the th and th centuries_, new york, ; and _a history of science, technology and philosophy in the eighteenth century_, london, . c. m. bromehead, "mining and quarrying to the seventeenth century," in charles singer and others, _a history of technology_, vol. , oxford, . [ ] according to parsons (_op. cit._, footnote , p. ) the introduction of machinery worked by animals and falling water, "radical improvements" of the th century, fixed the development of the art "until the eighteenth, and, in some respects, even well into the nineteenth century." wolf in his _history of science ... in the eighteenth century_ (p. , see footnote ) agrees, saying that "apart from [the steam engine] mining methods remained [during the th century] essentially similar to those described in agricola's _de re metallica_." bromehead (_op. cit._, footnote , p. ), in referring to the date also sees "no appreciable change in methods of mining since agricola." [ ] parsons, _op. cit._ (footnote ), p. . t. a. rickard, _man and metals_, new york, , vol. , pp. - . [ ] heinrich bechtel, _wirtschaftstil des deutschen spätmittelalters_, munich, , pp. - . bechtel calls this one of the most revolutionary industrial developments of the middle ages. [ ] rickard (_op. cit._, footnote , pp. - , ) also speaks of a decline through the exhaustion of surface deposits, but dates the revival - . he supports this conclusion by statistics on the leading mine at rammelsberg, which was unproductive from the black death ( ) to , and only slightly active before . [ ] according to f. m. feldhaus (_die technik_, leipzig and berlin, , p. .), a manuscript illustration of this type of pump, which he calls schöpfkolbenkette, appears in the mariano codex latinus , b. , dated , in the munich hofbibliothek. [ ] based on a comparison of the following editions of agricola, _de re metallica_: froben, basel, (in latin; the first edition); _the mining magazine_, london, (english translation by h. c. and l. h. hoover); vdi, berlin, (german translation by carl schiffner). [ ] the emergence of the term kunst in german mining terminology is connected with the application of water power, especially to pumping (see heinrich veith, _deutsches berg-wörterbuch_, breslau, , article "kunst"). [ ] according to veith (_op. cit._, footnote , p. ), b. rössler, in his _speculum metallurgiae politissimum_ (dresden, , p. ) says that the taschenkunst (pocket-work) was used with a pipe, like the rag and chain pump, and the translator of the german ( ) edition of _de re metallica_ also uses heinzen and taschen interchangeably. calvör and others, however, seem to use taschenkunst for the ordinary chain of dippers, which seems better suited to its literal meaning. [ ] agricola, _op. cit._ (footnote ), ed. hoover, p. . his contemporary and fellow-townsman mathesius equates the kehrrad to the bulgenkunst (_sarepta_, p. , nurnberg, ). according to veith (_op. cit._, footnote , p. ), sebastian münster in his _cosmographei ..._ (p. , basel, ), had previously mentioned its use in the mines of meissen; and its introduction has been put as early as by otto vogel ("christopher pohlem und seine beziehungen zum harzer bergbäu," _beiträge zur geschichte der technik und industrie_, , vol. , p. .) [ ] agricola, _op. cit._ (footnote ), ed. hoover, pp. - . [ ] g. e. lohneyss, _bericht von bergwerken_, ?, n. p., p. . [ ] agricola, _op. cit._ (footnote ), ed. hoover, pp. - . the crank was centuries old at this time, and had been applied to pumping earlier than the time mentioned by agricola, although perhaps not in mining. a drawing dated shows an archimedian screw turned by a crank (feldhaus, _op. cit._, footnote , p. ). the _mittelalterliche hausbuch_ (ed. h. t. bossert and w. f. storck, leipzig, , tafel ), a german description of technology that appeared in , shows an arrangement very like that described by agricola, although not in mining service. [ ] o. fritsche and a. wagenbreth, "die wasserhaltungs-maschinen bei agricola und sein einfluss auf ihre weitere entwicklung," in _deutsche akademie der wissenschaft zu berlin_, _georgius agricola_, (east) berlin: akademie verlag, , p. . [ ] hennig calvör, _acta historico-chronologico-mechanica circa metallurgiam ..._, braunschweig, , pp. - . [ ] i have been unable to find an early reference to this innovation, which appears in a sketch of - illustrating conrad matschoss', "die maschinen des deutschen berg- und hüttenwesens vor jahren," _beiträge zur geschichte der technik und industrie_ ( ), band i, p. . its introduction may be connected with the appearance of the term rosskunst for the horse windlass, known earlier as the göpel. [ ] "bericht des bergverwalters martin planer über den stand des freiberger bergbaues im jahre ," ed. r. wengler, _mittheilungen freiberger altertumsverein_, , vol. , pp. - . [ ] the description of the stangenkunst in its various modifications is one of the chief topics of the previously cited work of calvör (footnote ), and from his and other references it is clear that the subject was also treated extensively by such earlier writers as lohneyss ( ) and rössler ( ). [ ] fritsche and wagenbreth, _op. cit._ (footnote ), p. . [ ] the hauling of ores, as opposed to water, seems to have remained as shown by agricola until the end of the th century. in , however, the famous swedish engineer christopher polhem built at falun a water-powered conveyer system which brought the ore from the point of origin in the mine to the smelter in a single operation, terminating with the automatic unloading of the buckets (vogel, _op. cit._, footnote , p. ). [ ] dickinson, h. w., _a short history of the steam engine_, new york, n. d., p. . [ ] in edward browne visited hungary and the erzgebirge. his report on the trip, _a brief account of some travels in diverse parts of europe_ ( nd ed., london, , p. ), says little about machinery, but does not mention flooding as a serious problem. of an -fathom mine called auff der halsbrucker, near freiberg, he says "they are not so much troubled with water, and have very good engines to draw water out." yet the chain of dippers and rag and chain pump were evidently fallen into disuse, as they do not appear among the mining machines reported by fritsche and wagenbreth as having been described by lohneyss ( ) or rössler ( ); and fritsche and wagenbreth declare that german hydraulic machinery was able to compete with the steam engine in mine dewatering for some time into the th century (_op. cit._, footnote , pp. , ). [ ] lewis mumford, _technics and civilization_, new york, , p. . transcriber's notes: passages in italics are indicated by _underscore_. printer's inconsistencies in hyphenation usage have been retained. transcriber's note: this book was originally printed using variously both italic and bold fonts for emphasis. the underline character (_) has been used here to delimit text originally in _italic_ font and the equals symbol (=) to delimit text originally in =bold= font. * * * * * mining laws of ohio compiled by the department of industrial relations columbus, ohio the f.j. heer printing co. bound at the state bindery =foreword.= =the department of industrial relations.= the act of the eighty-fourth general assembly, known as house bill two hundred forty-nine, found in ohio laws at page , became effective on july , . this law provides for the reorganization of the executive department of the state government and is an administrative code centralizing related executive functions and activities for better administrative care and control. all duties, rights, liabilities, authority and privileges relating to mines and mining, formerly had and exercised under the law by the industrial commission of ohio, was, by the above mentioned law, conferred upon and imposed in the department of industrial relations to be administered by the director of industrial relations. this pamphlet contains all the provisions of the general code of ohio directly relating to mines and mining, their operation, control and management, put into convenient form for the information and guidance of employers, employes and the general public, for whose benefit and observance they have been enacted. in any section of the law herein given where the phrase "industrial commission" or "the industrial commission of ohio," or "chief inspector of mines" is found, the phrase "the department of industrial relations" is to be read, because such department has, by the law first above mentioned, been given the powers and duties before had by such commission. all the statutes printed in this pamphlet are in full force and effect. the department of industrial relations, william robinett, _chief, division of mines_. =notice.= where there is more than one section relating to the same subject matter, the additional section references have been placed at the end of these sections in parenthesis. persons are also requested to consult the table of contents as well as the classified index which is given in minute detail. also read carefully the _penalties_ which are provided in section for violation of all laws commencing with duty of county coroner in section , and ending with section , with the exception of sections , and , for which no penalties are provided. table of contents. sections. relating to chief and district inspectors - relating to county recorder and county coroner relating to owner, lessee or agent - relating to superintendent, mine-foreman and over-seer - relating to stableman and fire-boss relating to employes generally - relating to persons not employes general provisions - relating to oil and gas well through coal measures relating to illuminating oil for mines - relating to penalties relating to fines collected, prosecutions, when act takes effect, and repeals - regulating and prohibiting solid shooting - - regulation of weighing of coal - - relating to employment of minors - relating to department of industrial relations - - - relating to chief inspector of mines and district inspectors of mines. mining laws of ohio sec. . repealed. (appointment of chief.) sec. . [=qualifications of chief inspector of mines.=] no person shall be appointed chief inspector of mines unless he has a competent knowledge, insofar as such sciences relate to mining, of chemistry, the mineralogy and geology of this state, a practical knowledge of the different systems of working and ventilating mines, the nature and properties of the noxious and poisonous gases in mines, particularly fire-damp, the best means of preventing the accumulation of such gases, and the best means of removing the same. he shall also have had at least five years actual practical experience in mining in this state, shall have a knowledge of mine engineering, and shall have a practical knowledge of the uses and dangers of electricity as applied at, in, and around mines. sec. . the industrial commission of ohio shall appoint, with the approval of the governor, and upon recommendation of the chief deputy of the division of mines and mining, five district inspectors of mines in addition to those now in such service, making in all the number of district inspectors of mines seventeen. sec. . [=qualifications of district inspectors of mines.=] no person shall be appointed district inspector of mines unless he has been a resident of the district for which he is appointed, for at least two years, has had at least five years' actual practical experience in mining in this state, has a practical knowledge of the best methods of working and ventilating mines, of the nature and properties of noxious and poisonous gases, particularly fire-damp, of the best means of detecting the presence of and preventing accumulation of such gases and the best means of removing the same, and has a practical knowledge of the uses and dangers of electricity as applied at, in and around mines. sec. . repealed. (devoting entire time to duties.) sec. . repealed. (bond.) sec. . [=offices of inspectors.=] the chief inspector of mines shall have an office at the seat of government, in which he shall keep the maps and plans of all mines in the state, and all records, correspondence, papers, apparatus, and other property belonging to the state, pertaining to his office, in accessible and convenient form for reference by persons entitled to examine them, all of which he shall deliver to his successor in office. the persons entitled to examine maps, plans, records and papers of a mine, shall be the owner, lessee or agent of such mine; the persons financially interested in such mine; the owner, or owners, of land adjoining such mine; the owner, or owners, of land adjacent to such mine; the owner, lessee or agent of a mine adjacent to such mine; and the authorized representatives of the employes of such mine. the chief inspector of mines shall not permit such maps, plans, records and papers to be removed from his office, and shall not furnish copies thereof to any persons, except by request of the owner, lessee or agent of the mine to which such maps, plans, records and papers pertain. each district inspector shall keep his office in such place in his district as is central and convenient. sec. . repealed. h.b. --sec. , o.l.; . (salaries and expenses of inspectors.) sec. . [=duties of chief inspector.=] the chief inspector of mines shall designate the counties, or portions thereof, which shall compose the different districts, and may change such districts whenever in his judgment the best interests of the service so require. he shall issue such instructions, and make such rules and regulations for the government of the district inspectors of mines consistent with the powers and duties vested in them by law, as will secure uniformity of action and proceedings throughout all the districts. the chief inspector of mines may order one district inspector of mines to the assistance of any other, or may make temporary transfers of district inspectors of mines, when, in his judgment, the efficiency of the service demands or permits, and with the consent of the governor, may remove any district inspector of mines for reasonable cause. the chief inspector of mines shall give such personal assistance to the district inspectors of mines as they may need, and make such personal inspection of the mines as he deems necessary and his other duties permit. he shall keep in his office and carefully preserve all maps, surveys, reports and other papers, required by law to be filed with him, and arrange and preserve them as a permanent record of ready, convenient and connected reference. he shall, upon receipt of a report of the district inspector of mines, or of a committee of miners, covering the conditions of a mine, promptly mail a copy thereof to the general office of the owner, lessee or agent of such mine. (sec. .) sec. . [=duty in case of fatal accident.=] upon receiving notice from the owner, lessee or agent that a fatal accident has occurred at a mine, the chief inspector of mines shall go, or order one of the district inspectors of mines to go, at once to the mine at which such accident occurred, inquire into its cause, and make a written report setting forth fully the condition of that part of the mine wherein the accident occurred, and the cause thereof. such report shall be filed by the chief inspector of mines in his office, and a copy mailed to the general office of the owner, lessee or agent of such mine. (sec. , , , .) sec. . repealed. (annual report.) sec. . [=duties of district inspectors of mines.=] each district inspector of mines shall examine each mine in his district, in which men are employed, as often as practicable, and mines employing more than ten persons, at intervals not exceeding three months between examinations, noting particularly the condition of the boilers and machinery, the location and condition of the buildings, the condition of the workings of the mine, the condition of the traveling and haulways, the circulation and condition of the air and drainage, and shall see that the provisions of this act are complied with. upon the completion of the examination of a mine, he shall within a reasonable time thereafter, report in writing to the chief inspector of mines, the conditions of the mine, showing the extent to which the provisions of this act are complied with or violated. (sec. .) sec. . [=district inspectors as sealers of weights and measures.=] the district inspectors of mines are hereby vested with all the powers and authority of county auditors as sealers of weights and measures in the different counties of this state, but shall exercise such authority in connection with weights and measures at mines, only. each district inspector of mines may upon his regular examination of a mine, and shall, upon the written request of the duly authorized representatives of the miners, the owner, lessee, or agent, or the interested land owner, test the accuracy of the scales at any time, and post in the weight house a certificate provided by the chief inspector of mines, certifying the condition of the scales, provided that such tests be made at a reasonable time without unnecessary inference with the use of such scales. (sec. .) [=duty of district inspectors in case of controversy.=] in case of a controversy or disagreement between the district inspector of mines, and the owner, lessee or agent of a mine, or persons working therein, or in case of emergency requiring counsel, the district inspector of mines may call upon the chief inspector of mines for such assistance and counsel as is necessary. sec. . [=inspectors shall exercise discretion.=] each inspector shall exercise discretion in the enforcement of the provisions of this act. if he finds that any matter, thing or practice, connected with any mine, and not prohibited by law, is dangerous or defective, (or that from a rigid enforcement of any of the express provisions of this act, such matter, thing or practice would become dangerous or defective), so as in his opinion to tend to the bodily injury of any person, such inspector shall give notice in writing to the owner, lessee, or agent of the mine, of the particulars in which such mine or any matter, thing, or practice connected therewith is dangerous or defective, and require it to be remedied by making such changes as the conditions may require. provided, however, that in the exercise of the foregoing provisions relating to the application of electricity or electric wires, the judgment of the chief inspector of mines and the district inspector of mines, jointly shall be required. (sec. - .) sec. . [=inspectors shall have access to mines.=] for the purpose of making the examinations provided for in this act, the chief inspector of mines, and each district inspector of mines, may enter any mine at reasonable times, by day or night, but in such manner as will not unnecessarily impede the working of the mine, and the owner, lessee or agent thereof shall furnish the means necessary for such entry and examination. [=examination of record of minors employed.=] the district inspector of mines shall examine the record kept by the mine foreman, of boys under sixteen years of age employed in each mine, and report to the chief inspector of mines, the number of such person employed in and about each mine, and enforce the provisions of this act relative to their employment. (sec. - .) "the provisions of section , and g.c. do not permit the employment of children under years of age in, about or in connection with any mine. such employment is governed by the provisions of section g.c." opinion no. office of the attorney general, state of ohio, december , . sec. . [=report of district inspector to chief inspector.=] on or before each monday, each district inspector of mines shall make and file in the office of the chief inspector of mines, a record showing the number of mines in the district examined by him during the preceding week, the number of persons employed in and about such mines, the date of each examination, condition of each mine examined, whether the laws relating to mines and mining are being observed or violated, and, if violated, the nature and extent of such violations, progress made in safeguarding the lives and protecting the health of the employes in and about the mines, together with such other facts of public interest concerning the condition of mines and the development and progress in mining, as he deems proper. (sec. .) sec. . [=duties of chief inspector and oil and gas well inspector.=] the chief deputy inspector of mines and the oil and gas well inspector shall designate the townships in the various coal producing counties of ohio, which shall be considered coal bearing or coal producing townships, to be included under the regulations as prescribed in section relating to the mapping, drilling and abandonment of oil, gas or test wells. the chief deputy inspector of mines shall allow all matter pertaining to the mapping and drilling of oil and gas wells to be under the direct supervision of the oil and gas well inspector, except when wells are to be drilled, or have been drilled directly adjacent to some mining operation, or in case any arrangement for the drilling of an oil or gas well must necessarily be made in mutual understanding and consideration with some mining operation, or whenever the proper protection of the coal deposits is in question. the oil and gas well inspector shall supervise the granting of permits to drill or abandon a well, the filing and reprinting of maps of oil, gas or test wells, and see that all the provisions relating to the mapping, drilling, and abandonment of such wells are strictly complied with. in any case where the plugging method as outlined in section cannot be applied, or if applied, would be found ineffective in carrying out the intended protection, which the law is meant to give, the oil and gas well inspector may designate the method of plugging to be used, in all such cases causing the abandonment report to show the manner in which the work was done. the oil and gas well inspector shall designate the counties or townships thereof which shall compose the different districts of the respective deputy oil and gas well inspectors, or change such districts whenever in his judgment the best interests of the service so demands. he shall issue instructions and regulations for the government of the deputy inspectors as will be consistent with the powers and duties vested in them by law, and secure the proper protection which the law intended. the oil and gas well inspector shall give such personal assistance to the deputy inspectors as they may need and make such personal inspection as he deems necessary throughout all the districts, at any time. each deputy oil and gas well inspector shall carry out the instructions of the oil and gas well inspector with reference to the enforcement of the regulations provided in section , or other regulations that are deemed necessary to insure the protection which this section intends. any person, firm or corporation dissatisfied with the ruling of the chief deputy inspector of mines, or the oil and gas well inspector under the provisions of this section shall have the right of appeal to the industrial commission of ohio within ten days from the date of such ruling. =chief inspector of mines shall provide and maintain rescue apparatus.= sec. . the chief inspector of mines shall provide and maintain, at the expense of the state, one rescue car fully equipped with not less than twelve approved oxygen breathing devices complete, one recharging equipment for recharging oxygen cylinders, twelve extra oxygen cylinders, two resuscitating outfits complete, forty approved safety lamps, one naphtha tank, twenty portable electric lamps complete, with storage batteries, and all necessary instruments and chemical tests, together with all necessary supplies and appliances therefor. the rescue car with its equipment, shall be stationed at such point as may be designated by the chief inspector of mines, and may be transferred, by his direction, at any time to any point within the state for the purpose of facilitating the efficient inspection of mines and conducting rescue work, and to demonstrate the various appliances and instruct persons in their use in first aid and rescue work. the rescue car with its equipment shall be continuously in charge of one person who shall be appointed by the chief inspector of mines, with the approval of the governor, and who shall receive a salary of twelve hundred dollars per annum, together with all necessary expenses incurred in the discharge of his duties. the person in charge of said rescue car shall, before entering upon the discharge of the duties connected therewith, give a bond to the state in the sum of two thousand dollars with two or more sureties approved by the governor conditioned for the faithful discharge of the duties of his office. such bond with the approval of the governor and the oath of office endorsed thereon shall be deposited with the secretary of state and kept in his office. ( o.l. .) =five rescue stations to be provided and maintained; equipment of same.= sec. - . the industrial commission of ohio shall provide and maintain at the expense of the state, five rescue stations, each station to be equipped with not less than five approved breathing devices complete, one recharging or refilling pump for recharging oxygen cylinders, five extra oxygen cylinders, one resuscitating outfit, five approved mine safety lamps, five approved electric mine safety lamps complete, one lamp testing cabinet, not less than one thousand feet of three inch hose with standard connection and nozzles complete, one anemometer, one first aid cabinet and supplies, six stretchers with woolen blankets for each, and one automobile truck of sufficient capacity to transport equipment from station to any mine located within the district in which the rescue station is located. =location of stations; superintendent; salary.= such rescue stations shall be centrally located within the coal producing counties, so as to cover the largest number of mines within the shortest period of time, and each rescue station shall be continually in charge of a superintendent who shall be appointed by the industrial commission of ohio with the approval of the governor, who shall receive a salary in a sum equal to that provided for district inspectors of mines, together with all necessary expenses incurred in the discharge of his duties. =qualifications of superintendent.= the qualifications of superintendents of rescue stations shall be the same as that of district inspector of mines, namely, that no person shall be appointed superintendent of rescue stations unless he has been a resident of the district for which he is appointed for at least two years, has had at least five years' actual practical experience in mining in this state, has a practical knowledge of the best methods of working and ventilating mines of the nature and properties of noxious and poisonous gases, particularly fire damp, of the best means of detecting the presence of and preventing accumulation of such gases and the best means of removing the same, and has a practical knowledge of the uses and dangers of electricity as applied at, in and around mines. =duties of superintendent.= each superintendent of rescue station shall devote his entire time to the duties of his office, and shall at all times keep the equipment of such station in constant state of repair and be ready to meet any emergency that may arise at any mine at any time, either day or night. he shall teach and train first aid and rescue crews in the use of first aid and rescue equipment and shall be required to keep his station at all times in a clean and sanitary condition, and subject to such rules and regulations as the industrial commission of ohio may from time to time establish. ( o.l. .) sec. . [=action for non-compliance with provisions of this act.=] if the appliances of a mine for the safety of the persons working therein do not conform to the provisions of this act, or if the owner, lessee or agent disregards the requirements thereof, on application by the chief inspector of mines in the name of the state, any court of competent jurisdiction may enjoin or restrain the owner, lessee or agent from operating such mine, until it is made to conform to the provisions of this act. such remedy shall be cumulative, and shall not affect any other proceedings authorized by law against such owner, lessee or agent for the matter complained of in the action. (sec. - .) sec. . [=failure to make map and forfeiture.=] upon the refusal or neglect of the owner, lessee or agent of a mine to make and file a map, or any addition thereto, within sixty days after being directed to do so by the chief inspector of mines, as provided for in this act, the chief inspector of mines may cause such map or addition thereto to be made in duplicate at the expense of such owner, lessee or agent, the cost of which shall be recoverable against such owner, lessee or agent, in the name of the chief inspector of mines in any court of competent jurisdiction in the county in which such mine is located, or in franklin county. (sec. , , , .) sec. . [=complaint against district inspector; how made.=] when written charges of neglect of duty, incompetency, or malfeasance in office against any district inspector of mines, are made and filed with the chief inspector of mines, signed by not less than fifteen employes, or an owner, lessee or agent of a mine, the chief inspector of mines shall promptly investigate such charges, and advise in writing, addressed to the complainant whose name appears first in the charges, the result of such investigation. [=complaint against chief inspector, how made; appeal.=] when written charges of neglect of duty, incompetency or malfeasance in office against the chief inspector of mines, are made and filed with the governor, signed by not less than fifteen employes, or the owner, lessee or agent of a mine, or if not less than fifteen employes, or the owner, lessee or agent of a mine, having filed charges against a district inspector of mines with the chief inspector of mines, are dissatisfied with the result of the investigation made by him, and appealed to the governor by filing the same charges against such district inspector of mines with the governor, he shall make, or cause to be made, an investigation of such charges, and advise in writing, addressed to the complainant whose name appears first in the charges, the result of such investigation. sec. . [=appeal and hoard of examiners.=] after such appeal from the decision of the chief inspector of mines, or after charges have been filed against the chief inspector of mines with the governor, and the result of the investigation made by him, or at his instance, is unsatisfactory to the complainant, and notice thereof is given to the governor in writing by said complainant, accompanied with a bond in the sum of five hundred dollars, payable to the state, conditioned for the payment of all costs and expenses of the investigation of such charges, in the event such charges are not sustained, and signed by two or more responsible freeholders, the governor shall convene a board of examiners, consisting of two practical miners, one chemist, one mining engineer, and one mine operator at such time and place as he directs, giving ten days' notice thereof to the inspector against whom the charges are made, and also to the person whose name appears first in the charges. [=duties of board.=] when so convened, and being duly sworn truly to try and decide upon the charges made, the board of examiners shall summon any witnesses desired by either party, and examine them, on oath, administered by a member of the board. depositions may be read on such examination as in other cases. the board shall examine fully into the truth of such charges and report the result of its investigation to the governor; and, according to its finding, award the costs and expenses of such investigation against the inspector or the persons signing the bond. the costs and expenses of such investigation shall include a compensation of five dollars per day for each member of the board, for the time occupied in the trial, and in traveling to and from his home, together with all legitimate expenses which shall be paid from the state treasury on the certificate of the president of such board. the attorney general shall proceed to collect such costs and expenses, and pay them into the state treasury. sec. . [=this act shall not create new office or displace any officer.=] no change herein made in the name of an office existing when this act takes effect shall create a new office. the incumbents of offices when this act takes effect, the duties of which are herein defined, or the filling of which is herein provided for, shall hold their respective offices for the full term for which they were severally elected or appointed, the same as if this act had not been passed. =relating to county recorder and county coroner.= sec. . [=duty of recorder.=] the recorder of the county, when presented with a map of an abandoned mine, by the owner, lessee or agent thereof, as provided for in this act, shall properly label, file and preserve the same as a part of the records of the land upon which said mine is located. (sec. .) [=duty of coroner.=] upon receiving notice of a death occurring at a mine, as provided for in this act, the coroner shall hold an inquest forthwith upon the body of such person, inquire carefully into the cause of his death, and within ten days after such inquest, return a copy of his findings, with a description of the body, and all the testimony before him, to the chief inspector of mines. upon request of the owner, lessee or agent of the mine where such person was employed, shall furnish a copy thereof to such owner, lessee or agent, for which such coroner shall be entitled to a fee of ten cents per legal cap page, but in no case more than five dollars for any one inquest, for copy furnished owner or lessee. (sec. ; penalty, sec. .) =relating to owner, lessee or agent.= sec. . [=ventilation of mines.=] the owner, lessee or agent of a mine, shall provide and maintain the necessary artificial means of capacity and power capable of supplying the required ventilation, and shall maintain a sufficient volume of air, not less per minute than one hundred and fifty cubic feet for each person, and five hundred cubic feet for each animal working therein, measured at the intake, and distributed so as to expel or dilute and render harmless, explosive, poisonous and noxious gases. [=additional requirements where fire-damp is present.=] the owner, lessee or agent of a mine generating fire-damp, so as to be detected by a safety lamp, shall, in addition to the foregoing, provide and maintain not less than fifty cubic feet of air per minute for each person working therein. (sec. , , ; penalty, sec. .) sec. . [=ventilating appliances.=] in each mine, the doors used in assisting or directing the ventilation thereof, shall be hung so that they will close themselves, and shall be kept closed except while persons or cars are passing through same. each door, not operated automatically, through which cars are required to pass, shall have an attendant, whose first duty shall be to open it for transportation, and prevent it from standing open longer than necessary for cars to pass through, and, persons in charge of cars passing through automatic doors shall be required to keep a close watch over such doors, and if any such door fails to close, they shall promptly close same and report such fact to the mine foreman. this shall not prevent the attendant from performing other duties, provided the door is not kept open longer than is necessary for cars to pass through. where necessary, a refuge place shall be provided at each door for the safety of the attendant. (sec. , ; penalty, sec. .) sec. . [=ventilation of mines while persons working therein.=] at each mine where the ventilation is not continuous, it shall be started a sufficient length of time prior to the appointed time for any person, or persons, working therein to enter, to clear the mine of explosive, poisonous and noxious gases, and shall be kept in operation a sufficient length of time after the appointed time for such employes to leave their working places, for all persons to be out of the mine. (sec. , , ; penalty, sec. .) [=pressure gauges.=] at each mine generating fire-damp so as to be detected by a safety lamp, and wherein twenty or more persons are employed, a recording pressure gauge for the purpose of recording the pressure or vacuum of the main air current, shall be provided and maintained, which shall be kept in constant use, and records preserved for ninety days, subject to the inspection of the chief inspector of mines and the district inspector of mines. (penalty, sec. .) sec. . [=competent person or persons shall be designated as fire-boss.=] the owner, lessee or agent of a mine generating fire-damp so as to be detected by a safety lamp, shall designate a competent person or persons as fire boss or fire bosses, who shall make a thorough examination of each working place in the mine every morning with a standard safety lamp, not more than three hours prior to the appointed time for the employes to enter the mine. as evidence of such examination, the fire boss shall mark with chalk upon the face of the coal, or in some other conspicuous place, his initials and date of the month upon which the examination is made. if there is any standing gas discovered, he must leave a danger signal across every entrance to such place. [=examination of other than working places.=] each mine generating fire-damp so as to be detected by a safety lamp, shall be kept free from standing gas. all traveling ways, entrances to old workings, and places not in the actual course of working, shall be carefully examined with a safety lamp by the fire boss not more than three hours before the appointed time for persons employed therein to enter. parts of the mine not in the actual course of working and available, shall be examined not less than once each three days, and shall be so fenced as to prevent persons from inadvertently entering therein. (sec. , ; penalty, sec. .) sec. . [=breakthroughs and brattices.=] from a point where the seam is reached in the opening of a mine, to a point not exceeding a distance of four hundred feet therefrom, breakthroughs shall be made between main entries, where there are no rooms worked, not more than one hundred feet apart, provided such entries are not advanced beyond the point where the breakthrough will be made until the breakthrough is complete. breakthroughs between entries, except as hereinbefore provided, shall be made not exceeding sixty feet apart. where there is a solid block on one side of a room, breakthroughs shall be made between such room and the adjacent room not to exceed sixty feet apart; where there is a breast or group of rooms, a breakthrough shall be made on one side or the other of each room, except the room adjoining said block, not to exceed forty feet from the outside corner of the breakthrough to the nearest corner of the entrance to the room, and on the opposite side of the same room a breakthrough shall be made, not to exceed eighty feet from the outside corner of the breakthrough to the nearest corner of the entrance to the room, and thereafter breakthroughs shall be made not to exceed eighty feet apart on each side of the room. no working place, except those provided for within a distance of four hundred feet of the principal openings of a mine, shall be driven more than eighty feet in advance of a breakthrough or air-way. the required air current shall be conducted to the breakthrough nearest the face of such entry or room. all breakthroughs between entries, and when necessary between rooms, except the one nearest the working face, shall be closed and made air-tight by brattice, trap doors or other means, so that the current of air in circulation may sweep to the interior of the mine. brattices between permanent inlet and outlet airways shall be constructed in a substantial manner of brick, masonry, concrete, or non-perishable material. in mines generating fire-damp, so as to be detected by a safety lamp, the air current shall be conducted by brattice, or other means, near enough to the working face to expel the fire-damp, and prevent the accumulation of the same. (penalty, sec. .) sec. . [=safe appliances for hoisting persons.=] the owner, lessee or agent of a mine shall provide and maintain safe appliances, approved by the district inspector of mines, for the ingress and egress of persons in each shaft, designated by such owner, lessee or agent as a means of ingress and egress for persons employed therein. when there is but one shaft available for ingress and egress from any unavoidable cause, the appliances therein shall be kept available to persons therein employed at all times. when such appliances in any shaft are rendered unavailable from any cause, the same shall be restored without delay. [=emergency appliances.=] when the only means of egress is by vertical shaft, in which cages or elevators are used as a means of hoisting persons therein employed, and the power for operating same is derived from but one source, the owner, lessee or agent shall provide and keep on hand for use in the event of an accident to the hoisting apparatus or the power by which same is operated, a suitable windlass, capable of hoisting the persons from the mine. [=competent engineers.=] the owner, lessee or agent of a mine worked by a shaft or slope, shall put in charge of an engine used for lowering into or hoisting out of such mine persons employed therein, only experienced, competent and sober engineers. (sec. , ; penalty, sec. .) sec. . [=metal speaking tube and safety appliances.=] the owner, lessee or agent of a mine operated by shaft, shall provide and maintain a metal tube suitable for conversation between persons, connecting the engine room with the top and bottom of such shaft; an approved safety catch, a sufficient cover, and rings or other adequate handholds for ten persons, on all cages used for lowering and hoisting persons: such cages to be protected on each side by a boiler plate not less than one-fourth inch in thickness, and not less than three feet high, and shall provide an approved safety gate at the top of each shaft, an adequate brake to control the drum used for lowering or hoisting persons in shafts or slopes, and an indicator on all machines used for such purpose, to show the location of cages in shaft or slope. no cage having an unstable or self-dumping platform shall be used for the carriage of persons unless such platform is securely locked. (sec. , ; penalty, sec. .) sec. . [=hoisting and lowering of persons.=] the owner, lessee or agent of a mine, at which the only means of ingress and egress for the persons employed therein is by a vertical shaft or shafts, of fifty feet or more in depth, shall designate one or more persons whose duty shall be to attend to the lowering and hoisting of persons into and out of such mine, and give and receive the proper signals, governing the movement of the cage while engaged in handling men. not more than ten persons shall be lowered or hoisted at any one time. the lowering of persons shall begin in time for persons to reach their working places by hour appointed for mine to commence work and continue until starting time. hoisting of persons shall commence at time for mine to cease work, and continue until all have had time to be hoisted. persons may be hoisted at such other times as will not interfere with the hoisting of coal, or other products. no person shall be lowered into or hoisted out of a mine, with powder, explosives, tools or material on any cage, in the same shaft, and no person shall be lowered or hoisted in a vertical shaft in a mine car. when the vertical shaft is less than fifty feet in depth, and a stairway approved by the district inspector of mines is not provided, the owner, lessee or agent shall be required to lower or hoist persons, as above prescribed, but when such stairway is provided, the hoisting of persons shall not be required. sec. . [=owner, lessee or agent shall provide second opening.=] the owner, lessee or agent of a mine shall not employ or permit any person to work therein except as hereinafter provided, unless to every seam worked in such mine there are at least two openings, separated by natural strata of not less than one hundred feet in breadth at any point, by which distinct means of ingress and egress are always available to the persons therein employed. such openings need not belong to the same mine so long as the persons employed therein have safe, ready and available means of ingress and egress, by not less than two openings, provided, however, that no air shaft with a ventilating furnace at the bottom be designated or used as a means of ingress or egress. the provisions of this section shall not apply to opening a new mine while being worked for the purpose of making the second opening and the communication therewith, and the making of the landing or bottom and extending of the main entries one hundred feet while such communication is being made; to a mine in which the second opening has become unavailable from any cause while said second opening is being restored or another is being made; nor to a mine in which the second opening has become unavailable by reason of the final robbing of the pillars previous to abandonment, so long as not more than twenty persons in either case are employed therein at one time. [=fire protection to shafts.=] at each mine at which the only means of egress is by vertical shaft, the owner, lessee or agent shall provide adequate fire protection to secure the safety of such shaft, or shafts, and, when but one shaft is the only available means of egress, shall keep in attendance a competent person at all times while persons are inside of such mine. (penalty, sec. .) sec. . [=separate traveling ways.=] the owner, lessee or agent of a mine shall provide and maintain, in safe condition for the purpose provided, two separate and distinct traveling ways from the interior workings of the mine, each of which shall be available to not less than one opening to the surface. one of such traveling ways may be designated by such owner, lessee or agent as the principal traveling way. one of such traveling ways may be designated as the escapement way. the provisions of this section shall not prohibit such owner, lessee or agent from designating more than one principal traveling way, or more than one escapement way, so long as the provisions hereof are complied with. [=traveling ways and refuge holes.=] the owner, lessee or agent of a mine worked by shaft, shall provide and keep free from obstruction, a traveling or passage way from one side of the shaft bottom to the other. slopes and mechanical haulage ways used as traveling ways by persons employed in a mine shall be made of a sufficient width to give not less than three feet of space between the rib and adjacent rail of track to permit persons to pass moving cars with safety. if found impracticable to make such slopes or mechanical haulage ways of sufficient width as provided, refuge holes not less than six feet in width and clearing the adjacent rail of the track not less than four feet, and not more than sixty feet apart, shall be made on one side of the slope or mechanical haulage way and whitewashed. the refuge holes shall be kept free from obstruction, and the roof and sides made secure. (sec. , ; penalty, sec. .) sec. . [=detached locomotive from moving train. traveling way where locomotive is detached.=] at a mine, or in any part thereof, where a locomotive is detached from a moving train of cars for the purpose of dropping such cars past the locomotive, and the haulage way at such point is designated as the principal traveling way, a traveling way, not less than three feet wide and separated from the track by a pillar of coal or substantial fence, shall be provided at one side of that portion of the track from where the locomotive will be detached to the switch of the siding. such traveling way shall be made on the same side of the track as the refuge holes. in no case shall a locomotive be detached from a train of moving cars, for the purpose of making a drop thereof, more than one hundred feet from the switch of the siding. (sec. , ; penalty, sec. .) [=additional means of egress when inundation is probable.=] at any mine where there is a stream or body of water on the surface, or in the workings of a mine, at a higher level, which is likely to break through into such mine and inundate either the traveling or escapement way of such mine, so as to prevent the egress of persons employed therein, the owner, lessee or agent, shall, upon the written order of the chief inspector of mines, provide and maintain an additional opening by means of which such persons may escape without using the traveling or escapement way likely to be inundated. (sec. ; penalty, sec. .) sec. . [=duties of owner, lessee or agent relating to supplying timber.=] the owner, lessee or agent of a mine shall keep an adequate supply of suitable timber constantly on hand, and deliver to the working place of each miner, the props of approximate length, caps and other timbers necessary to securely prop the roof thereof: such props, caps, and other timbers, shall be delivered in mine cars at point where the miner receives his empty cars, or unloaded at the entrance to the room. (sec. , ; penalty, sec. .) sec. . [=provisions for persons injured at mines.=] the owner, lessee or agent of a mine at, in or around which, more than ten persons are employed, shall furnish for each thirty-five men so employed a properly constructed stretcher, a woolen blanket, a waterproof blanket, a sufficient quantity of bandages and linen and such other necessary requisites for use in case of accident as may from time to time be prescribed by the industrial commission of ohio. at mines generating fire-damp so as to be detected by a safety lamp, a sufficient quantity of olive or linseed oil shall be kept for use in emergencies. it shall be the duty of each mine foreman to keep in a safe and dry place in the territory over which he has charge such stretchers, woolen and waterproof blankets and other supplies. he shall care for the same and keep them in a dry and sanitary condition always ready for use. (sec. , , , ; penalty, sec. .) sec. - . [=owner, lessee or agent shall provide and maintain wash room.=] every owner, operator, lessee or agent of a coal mine, where ten or more persons are employed, shall provide and keep in repair a wash room, convenient to the principal mine entrance, adequate for the accommodation of the employes, for the purpose of washing and changing their clothes when entering and returning from the mine. such wash room shall be properly lighted and heated, supplied with warm and cold water and adequate and proper facilities for washing purposes. sec. - a. [=penalty.=] whoever, being the owner, operator, lessee or agent of a coal mine where ten or more persons are employed, fails or neglects, after ninety days from the taking effect of this act, to comply with the provisions of section - of the general code, or violates any of the provisions thereof, shall be fined not less than two hundred nor more than five hundred dollars. (this act became effective june , .) ( o.l. .) sec. - . [=owner, lessee or agent shall install telephone system.=] every owner, operator, lessee or agent of a coal mine, where twenty or more persons are employed, shall install, and maintain in efficient working condition, a telephone connecting each main switch of such mine with an outside telephone so connected and maintained as to permit communication with persons outside of the mine with persons on the main switch or switches or other points inside of the mine that may be designated by the district mine inspector. sec. - . [=penalty.=] whoever, being the owner, operator, lessee or agent of a coal mine, where twenty or more persons are employed, fails or neglects, after six months from the taking effect of this act, to comply with the provisions of section - of the general code, or violates any of the provisions thereof, shall be fined not less than two hundred nor more than one thousand dollars. (this act became effective june , .) ( o.l. - .) sec. . [=owner or lessee shall make map of mine.=] the owner, lessee or agent of a mine having an excavation of fifteen thousand cubic yards, or more, shall cause to be made, on a scale of not less than two hundred feet per inch, an accurate map thereof, which shall show the following: the boundary lines and names of the owners of the surface of each tract under which excavation is made, and for not less than five hundred feet contiguous thereto, and under which excavations are likely to be made during the ensuing year, together with all streams and bodies of standing water; the township and county lines coming within the limits of such map, with the name of each plainly marked close to and parallel with such lines; the title, the name or number of the mine, or both, the township and county in which located; the section lines, with the number of each, marked plainly within the sections; the location of the mine openings, railroad tracks, public highways, oil and gas wells, magazines and buildings, and plainly marked with name of each; the location and extent of the excavations and connection with the surface survey; the direction of the air current, or air currents by arrows; the location and extent, so far as known or obtainable, of the excavation of any other mine or mines within the limits of the map; the boundary lines of the tracts of coal owned or leased within the limits of the map; the elevation of the floor of the excavation, above mean tide at sandy hook, at or near the boundary line or lines of the coal owned or leased where the coal is adjacent to coal owned by a person, firm or corporation, other than the owner or lessee of such mine, and where the excavations of such mine cease or may be approached by another mine, at points not exceeding three hundred feet apart, and referenced to some permanent monument near the main opening of such mine, and shown on the map and plainly marked bench mark, with the elevation of same. (sec. , , , ; penalty, sec. .) sec. . [=addition to map, and certificate of engineer and mine-foreman.=] the owner, lessee or agent of a mine shall cause to be made, a map or an addition to the next previous map thereof, annually, and semi-annually if so directed in writing by the chief inspector of mines, showing the excavations and the information required by the preceding section, to date of survey. the map, or maps, required by this and the preceding section, and any addition thereto, shall have the certificate of the engineer making same, and of the mine-foreman in charge of the mine at the time of the survey, acknowledged before, a notary public or justice of the peace, thereon in the following form: i, the undersigned, hereby certify that this map is correct, and shows all the information required by section nine hundred and thirty-five of the general code, and covers the period ending .............................................. ............................. engineer. acknowledged before me a ...................... this .............. day of ...................................... ............................. i, the undersigned, hereby certify that i am a mine-foreman at the mine represented by this map, and to the best of my knowledge and belief the same correctly represents the excavations of the mine for the period ending ............................................................ ............................. mine-foreman. acknowledged before me a ....................... this ................ day of .................................... ............................. (sec. , , ; penalty, sec. .) sec. . [=owner, lessee or agent shall file map of abandoned mine with county recorder and chief inspector of mines.=] the owner, lessee or agent of a mine, before the pillars are drawn previous to the abandonment of a mine, or any part thereof, shall cause to be made a correct map of such mine, or part thereof, showing its area and workings to the day of the abandonment; the pillars drawn previous to abandonment; and file such map within ninety days after the abandonment of such mine, in the office of the recorder of the county where such mine is located, and with the chief inspector of mines at his office. such map shall have attached thereto the usual certificate of the mining engineer making it, and the mine-foreman in charge of the underground workings of the mine, and such owner, lessee or agent shall pay to the recorder for filing such map, a fee of fifty cents. (sec. .) [=copy of map to be filed with chief inspector.=] the owner, lessee or agent of a mine shall keep at the office thereof, open to the inspection of the chief inspector of mines, and the district inspector of mines, a copy of the latest map of such mine, with any addition thereto, and shall furnish a copy thereto to the chief inspector of mines at his office. (sec. , , , ; penalty, sec. .) =precaution when approaching abandoned mine.= sec. . whenever any working place of a mine approaches within one hundred feet of the abandoned workings of another mine, as indicated by an accurate survey, or while driving any working place within a distance of one hundred feet thereof, and such abandoned, mine cannot be explored, or when same contains fire-damp, or water which may inundate such working place, the mine-foreman shall not permit such working place to be advanced until a drill hole has been extended not less than twelve feet in the center of such working place, and a flank hole not less than twelve feet extended on each rib, starting at the working place after taking out each cut or crossing. whenever the limits of the workings of an abandoned mine are not known by actual survey, the above rule shall apply whenever any working place approaches within one hundred and fifty feet of the supposed limits of such abandoned mine. in addition to the precautions provided for in this act when approaching or working parallel with such an abandoned mine, the owner, lessee or agent shall, upon the demand of the chief inspector or district inspector of mines, provide competent shot firers to do the shot firing in all the working places advancing or running parallel with such abandoned mine; the shot firing to be done when all other workmen are out of the mine. the chief inspector or district inspector of mines shall order shot firers at any mine when in their judgment the safety of property or employes require same. ( o.l. .) sec. . [=notice must be sent to chief inspector in certain cases.=] the owner, lessee or agent of a mine shall give notice to the chief inspector of mines in the following cases: when a change occurs in the name of the mine, in the name of the owner, lessee or agent thereof, or in the officers of an incorporated company owning or operating such mine; when a working is commenced for the opening of a new shaft, slope or mine; when a mine is abandoned, or the working thereof discontinued; when the working of a mine is commenced, after an abandonment or discontinuance thereof for a period of more than three months; when the pillars of a mine are about to be removed or robbed; when a squeeze, crush, or fire occurs, or a dangerous body of gas is found, or any cause or change that may seem to affect the safety of persons employed therein. (sec. ; penalty, sec. .) sec. . [=notice of accidents.=] the owner, lessee or agent of a mine at which loss of life occurs by accident, shall give notice thereof, by telegram, forthwith, to the office of the chief inspector of mines, and to the coroner of the county in which such accident occurs; and, within twenty-four hours next after loss of life or personal injury has occurred, the owner, lessee or agent of the mine shall send to the chief inspector of mines a report in writing, of the accident, specifying the character and cause thereof, the names of the persons killed or injured, and the nature of the injuries. if a personal injury thereafter results in the death of the person injured, as soon as such death comes to his knowledge, the owner, lessee or agent shall give notice thereof forthwith, in writing, to the chief inspector of mines, and to the coroner of the county in which such accident occurred. (sec. , , , ; penalty, sec. .) [=return of owner, lessee or agent.=] the owner, lessee or agent of a mine, shall, on or before the thirty-first day of january of each year, send to the office of the chief inspector of mines, upon blanks furnished by him, a correct return, specifying with respect to the year ending on the preceding thirty-first of december, the quantity of coal mined, and the number of persons ordinarily employed at, in, and around such mine, distinguishing the persons below and above ground, and give such other information as required by such blanks. (penalty, sec. .) sec. . [=test weights to be provided.=] the owner, lessee or agent of a coal mine, at which the earnings of ten or more persons depend upon the weights of coal mined, shall provide and keep accessible for the purpose of testing the weigh scales as provided elsewhere in this act, the following standard test weights, properly sealed: where the coal mined is weighed upon hopper or pan scales, two standard test weights of fifty pounds each; where the coal mined is weighed upon railroad track scales, ten standard test weights of fifty pounds each. (sec. .) [=owner, lessee or agent shall provide safety lamps.=] the owner, lessee or agent of a mine generating fire-damp, so as to be detected by a safety lamp, shall keep on hand in proper condition for use, not less than four approved safety lamps, and upon request of the district inspector of mines, shall provide such additional safety lamps as in his judgment may be required to meet any probable emergency. [=owner, lessee or agent shall provide shields on mining machines.=] the owner, lessee or agent of a mine, shall provide and maintain a sufficient shield on each mining machine used in such mine, as may be authorized by the chief inspector of mines, or the district inspector of mines, for the protection of those employed in operating same. (sec. ; penalty, sec. .) =signal code.= sec. . [=signals at mines, how conducted; devices to be used.=] at each mine operated by shaft, the means of signaling to and from the bottom man, the top man, and the engineer shall consist of a tube, or tubes, or wire encased in wood or iron pipes, through which signals shall be communicated by electricity, compressed air, or other devices. the following signals are provided for use at mines where signals are required: =signal code.= =from the bottom to the top.= [=one ring or whistle.=] one ring or whistle from the bottom to the top shall signify to hoist coal or the empty cage, and also to stop either when in motion. [=two rings or whistles.=] two rings or whistles shall signify to lower cage. [=three rings or whistles.=] three rings or whistles shall signify that men are coming up; when return signal is received from the engineer, men will get on the cage, and cager shall ring or whistle one to start. [=four rings or whistles.=] four rings or whistles shall signify to hoist slowly, implying danger. [=five rings or whistles.=] five rings or whistles shall signify accident in the mine and a call for a stretcher. =from the top to the bottom.= [=one ring or whistle.=] one ring or whistle from the top to the bottom shall signify: all ready, get on cage. [=two rings or whistles.=] two rings or whistles shall signify: send away empty cage. [=addition to code, when allowed; code must be posted at top and bottom.=] provided, that the management of any mine, may, with the consent of the district inspector of mines, add to this code of signals in his discretion, for the purpose of increasing its efficiency, or of promoting the safety of the men in said mine, but whatever code may be established and in use at any mine must be furnished by the mining department, conspicuously posted at the top and at the bottom and in the engine room, for the information and instruction of all persons concerned. [=emergency signal in shafts.=] at each mine where persons are hoisted in a vertical shaft, an emergency signal shall be provided in such manner that persons can give signals from the cage, in the event that cage is stopped between the top and bottom landings. (sec. ; penalty, sec. .) sec. . [=lights in mines.=] the owner, lessee or agent of each mine shall provide an enclosed lard or signal oil lamp or lantern or incandescent electric light at such point or points in the mine as may be necessary for the proper safety of persons, especially at the top of extreme grades. no open light shall be used for fixed or stationary purposes; no open torches or lamps larger than the lamps provided for in this act for use as open lights, and no coal oil or kerosene lamp or lanterns, shall be used in a mine. this, however, shall not prevent the use of a torch or blow-torch for mechanical purposes other than illumination. (sec. .) [=light or signal on locomotives and trains.=] the owner, lessee or agent of a mine at which locomotives are used for hauling the coal, shall keep a light on the front end of the locomotive when it is in use, and when the locomotive is run ahead of the trip, and the trip-rider is not required to ride the rear car of the trip, a signal, light or marker, approved by the district inspector of mines, shall be carried on the rear end of the trip to indicate when the trip has passed. cars shall not be pushed ahead of the locomotive where it can be avoided, and when cars are run ahead of the locomotive a light shall be carried on the front end of the trip and the cars shall not be moved at a speed greater than four miles per hour. when rope haulage is used, an enclosed light shall be carried on the front end of each train so hauled. when a mechanical haulage trip passes through an automatic door having no attendant other than persons in charge of such trip, the trip-rider shall be required to ride the rear car of the trip while passing though such door, and see that it closes after the trip passes through. (sec. , ; penalty, sec. .) sec. . [=employment of minors.=] the owner, lessee or agent of a mine shall not employ, or permit to work therein, any boy under fourteen years of age; nor employ, or permit to work therein, any boy under fifteen years of age during a term of the public schools, in the district in which he resides. (sec. , .) (see child labor law, sec. , page ----). "the provisions of section , and g.c. do not permit the employment of children under years of age in, about or in connection with any mine. such employment is governed by the provisions of section g.c." opinion no. office of the attorney general, state of ohio, december , . [=removal of combustible matter.=] whenever an entry or air-way becomes so dry that the air becomes charged with dust, the owner, lessee or agent shall cause such entry or air-way to be sprinkled, and all accumulated matter, explosive in its nature, shall be removed from the mine. (sec. .) [=quantity of oil in mine restricted.=] no oil shall be taken into or stored in a mine except as may be required to be opened for use within two days thereafter; and in no case shall more than two barrels of oil be kept at any one place, and not more than ten barrels of oil shall be had in a mine at any one time. all waste oil and empty barrels shall be promptly removed from the mine. (sec. , .) [=location of boilers at mine.=] the permanent boilers used for generating steam, and the buildings containing the boilers, shall not be nearer than sixty feet to any mine opening or to a building or inflammable structure connected with or surrounding such opening. (penalty, sec. .) sec. . [=relating to underground stables.=] the owner, lessee or agent of a coal mine at which the live stock is kept underground, shall observe the following: the stable or stall shall be separated from the main inlet and main outlet air-courses by not less than twenty feet of solid strata or a solid wall of brick or masonry not less than twelve inches in thickness, except at two doors not more than five feet wide, which shall be made of steel plate not less than one-quarter inch in thickness and hinged to the solid strata or masonry without the use of wood; the ventilation for the stable shall be taken from main inlet air-course by a by-pass or separate split and returned to the main outlet air-course so that the air passing the stables will not enter the inward working places of the mine, and arranged so that the by-pass or split can readily be closed at both inlet and outlet sides of the stable by steel doors hinged to the solid strata or masonry without the use of wood; the construction of the stable inside shall be free from pine or light lumber; shall be of brick or masonry as much as practicable, and any timber used shall be of hardwood of a cross section not less than three by six inches; no hay or straw shall be taken into the mine or stable unless same be compressed into compact bales, and then only from time to time in such quantities as will be required for two days' use; no greater quantity of hay or straw shall be stored in the mine or stable, and when such is taken into the mine it shall be taken inside the stable at once; the lights used in the stable shall be incandescent electric lamps, placed so that same will not be injured by the stock or by persons required to enter the stable, or lanterns of railroad type suitable for using lard or signal oil, and only such oil shall be used therein; all refuse and waste shall be promptly removed from the stable and the mine, and shall not be allowed to accumulate. stables constructed underground after the passage and approval of this act, shall be located not nearer than one hundred and fifty feet of any opening to the mine used as a means of ingress or egress. (sec. , ; penalty, sec. .) sec. . [=relating to use of gasoline in mines.=] no gasoline, naphtha or kerosene engine shall be used in a mine, except for operating pumping machinery where electric, compressed air or steam power is not available or cannot be transmitted to the pump, and then the owner, lessee or agent shall observe the following: notice shall be made to the chief inspector of mines before installing, and the installation and operation shall be subject to his approval: no wood or inflammable material shall be permitted nearer than twenty-five feet of the engine: the supply tank from which the gasoline, naphtha or kerosene is fed to the engine, shall be of metal, with a suitable screw cap opening, fitted with a gasket, so as to make the tank air-tight and prevent the escape of gas into the atmosphere, and the tank kept free from leaks: the gasoline, naphtha or kerosene shall be fed from a tank to the carburetor or mixer by metal tubes securely connected so as to reduce the possibility of leaks to a minimum: the exhaust from the engine shall be conducted by means of metal pipes into the return air current, so that the fumes of combustion will not enter the workings of the mine where the men are required to work, or be conducted in an upcast shaft or slope not used as a means of ingress or egress, or through metal pipes to the surface: at no time shall there be more than five gallons of gasoline, naphtha or kerosene in the supply tank; at no time shall more than five gallons of same be taken into the mine at any one time, and at no time shall there be more than ten gallons in the mine, including that in the supply tank: no gasoline, naphtha or kerosene shall be taken into the mine except in metallic cans, with a screw cap opening at the top, fitted with a suitable gasket: no package or can, or the supply tank of an engine, containing gasoline, naphtha or kerosene, shall be opened until ready to make the transfer from the package or can to the supply tank, and in transferring, a funnel shall be used so as to avoid spilling the gasoline, naphtha or kerosene, and the cap on the supply tank shall be immediately closed: in no case shall the package, can, or the supply tank, be opened, with any open light or other thing containing fire within twenty-five feet of same. (penalty, sec. .) sec. . [=relating to use of electricity in mines.=] the owner, lessee or agent of a mine in which electricity is used as a means of power, shall observe the following in the application thereof: [=trolley wires.=] all trolley wires shall be carried at least six inches outside of and parallel with the track rail on the side the trolley wire is located. when regular height is less than six feet six inches from top of rail, the lower side of trolley wire must not exceed six inches from the roof or cross-timber with hangers now in use, with hangers not to exceed twenty-five feet between centers, and the tension sufficient to keep all wires from sagging and to prevent trolley wheel from coming in contact with roof or cross-timbers. all new hangers hereafter installed shall not exceed five inches in depth from lower side of the trolley wire to the roof or cross-timbers. [=wires crossing traveling ways.=] all trolley and positive feed wires crossing places where persons or animals are required to travel, shall be safely guarded or protected from such persons or animals coming in contact therewith. [=wires opposite rooms and refuge holes.=] all trolley and positive feed wires shall be placed on opposite side of track from refuge holes or necks of rooms. [=bare wires; when not to extend into working places.=] no trolley wire shall be extended into or maintained in any room while being used as a working place; no trolley or feed wire shall be extended into any entry beyond the outside corner of the last breakthrough. [=switches and circuit-breakers.=] switches or circuit-breakers shall be provided to control the current at the mine, and at all important points in the mine. [=machine feed wires and insulators.=] all machine feed wires shall be placed as near the rib and roof or cross-timbers as practicable; the positive wire to be carried not to exceed three inches from the rib and roof or cross-timbers, measured at the insulators, which shall be so placed as to keep the wire at least six inches outside of the track rail on the side the wire is located. insulators shall be placed not exceeding fifty feet apart, and all wires shall be carried so that same will be not less than six inches outside of the track rail at any point on the side the wire is located. all positive wires shall be carried on glass or porcelain insulators, or insulators equally efficient. all negative wires shall be carried on suitable fixtures, and when carried in same entry as the positive wire, shall be carried on the same side of the entry as the positive wire, and as close to it as practicable. when machine or feed wires are carried in same entry as trolley wire, they shall be placed on the same side as the trolley wire, between trolley wire and rib. nothing in the foregoing shall require negative wires being carried in same entry with positive wire. [=wires in shafts or slopes.=] when necessary to carry wires down shafts or slopes used as travelways, the wires must be thoroughly cased or protected, so that persons cannot be shocked therefrom. [=wires; how placed in rooms.=] positive machine feed wires, when extended into rooms, shall be placed not nearer than four feet of the track, where the room is of sufficient width, and the same shall only be connected to the positive wire or wires on the entry while in actual use. the material used for making such connection shall be of sufficient length to reach across the entry, and when same is disconnected, it shall be kept with the machine operating at such point or working place. no electric wires shall be extended into any room unless a one hundred and fifty foot cable will not reach the face of the room, and then not beyond the outside corner of the last breakthrough. [=protection of terminal ends.=] all terminal ends of positive wires shall be guarded so as to prevent persons inadvertently coming in contact therewith. [=connection of negative wires, pipe lines and track. bonding of track.=] the bonded track, the negative wires and metallic pipe lines, when coming near each other, may be connected together at intervals not exceeding five hundred feet, and any track used as the return or earth system shall be properly bonded. in no case shall a pipe line, or any part thereof, be used exclusively as the return, and when connected to the earth system, the negative wire or bonded track shall be of ample capacity, exclusive of the pipe line, to carry the current. [=trolley wires; how erected.=] the trolley wire shall be carried upon hangers or other fixtures which will properly insulate it from contact with the roof or other substances, and so the trolley wheel can trail without the necessity of being constantly attended for that purpose, and no trolley shall be run on any wire not so carried. [=locomotive must not be operated improperly.=] no locomotive shall be operated by means of a person holding and sliding upon or frequently making contact with the positive wire with any device attached to the cable as a substitute for a trolley, but these provisions shall not prohibit the operation of a locomotive by means of a cable without the use of the trolley, provided the cable be connected to and disconnected from the positive wire when the locomotive is not in motion. [=protection to machine cable crossing entry track.=] means shall be provided by which machine runners may readily carry the machine cable from the machine to the feed wires on one side of the entry, either under or over the track rails, in the entry where such wires are located, and so the cable will not come in contact with such track rails, thereby reducing the danger of shock to persons or animals required to travel such entry, to the minimum. (sec. , ; penalty, sec. .) sec. . [=voltage at mines hereafter electrically equipped.=] the owner, lessee or agent of a mine at which electricity with a pressure or potential of more than three hundred and twenty-five volts, or alternating current, is used, shall in addition to the provisions of the preceding section, observe the following: [=limit to voltage in or about working places.=] at each mine equipped with electric power after the passage and approval of this act, the current used to operate gathering locomotives, mining machines, shearing machines, drills and other machinery, used in or about the working places of the mine, shall not exceed in pressure or potential, three hundred and twenty-five volts, direct current, as shown at the nearest switchboard, and the wires conducting the power from the nearest switchboard shall not carry a higher pressure or potential. [=relating to alternating current.=] at each mine equipped with electric power alternating current may be used to convert alternating current to direct current, and to operate motors permanently installed above ground and in underground substations, or buildings especially prepared for them, in a manner subject to the approval of the chief and district mine inspectors, but no wires carrying alternating current shall be used underground except same be carried in an entry or passageway where persons and animals are not permitted to travel. [=relating to higher voltage mines hereafter equipped.=] at each mine equipped with electric power after the passage and approval of this act, when the current used to operate haulage locomotives, pumps and other machinery not located in or about the working places of the mine, is of a pressure or potential in excess of three hundred and twenty-five volts, direct current, the entry or passage way where such wires are carried shall not be designated or permitted to be used as the principal traveling way, and when designated or used as the escapement way, the wires shall be protected so that persons required to travel near same in emergencies will not inadvertently come in contact therewith. no pressure in excess of six hundred and fifty volts at the switchboard shall be used underground. [=relating to higher voltage, mines heretofore equipped.=] at each mine equipped with electric power prior to the passage and approval of this act, where the pressure or potential is in excess of three hundred and twenty-five volts, direct current, or where alternating current is used, and the conditions surrounding the use of same are such, in the opinion of the chief inspector of mines, that the provisions of the preceding section do not provide the required protection from shock to persons employed therein, such additional safeguards shall be employed as may be required by the chief inspector of mines, and the district inspector of mines, jointly. (see. , ; penalty, sec. .) sec. . [=relating to construction of new mines.=] any person, firm or corporation beginning the opening of a mine, whether such person, firm or corporation be the owner, lessee or agent of the property upon which such mine is located, or not, shall observe the following in the construction of such mine: if the opening be a slope or vertical shaft, no explosive used therein shall be fired by means of a squib or fuse after the same is extended more than twenty-five feet from the surface, and thereafter and until the slope or shaft reaches the seam, and the entry or landing be extended beyond a breakthrough or other place driven at right angles thereto, no explosive shall be fired except by means of an electric battery operated from the surface after all persons are on the surface. a substantial structure to sustain sheave wheels or pulleys, ropes and loads, shall be provided, and if the opening be a shaft, the same shall be placed at a height of not less than twenty feet above the tipping place. a landing platform shall be arranged in such manner that no material can fall into the shaft while the bucket is being emptied, and in no case shall the shaft be sunk to a depth of more than thirty feet without such structures. if the bucket used for hoisting material is to land on a truck, the track on which said truck is operated, and the platform, shall be so constructed that material cannot fall into the shaft. rock and coal shall not be hoisted from a shaft or slope except in a bucket or cage attached to the rope by a safety hook, clevis, or other safe attachment, and the bucket or cage securely locked so that same cannot tip or empty while being hoisted. the rope shall be fastened to the side of the drum, and not less than three coils of rope shall always remain on the drum. after the shaft reaches a depth of one hundred feet, the same shall be provided with guides and guide attachments, applied in such a manner as to prevent the bucket from swinging while being lowered or hoisted, and said guides and guide attachments shall be maintained at a distance of not more than seventy-five feet from the bottom of the shaft. the sides of all shafts shall be properly secured for safety, and no loose rock or material shall be allowed to remain on any timber in the shaft after each blast. all loose timber, tools, and materials, shall be kept away from the top of the shaft, so as to reduce the danger of same falling down the shaft. where explosive gas is encountered, the person in charge shall see that the shaft or slope is examined before each shift of men enter to work, and before the men descend after each blast. provision shall be made for the proper ventilation of the slope, or shaft, so that persons working therein will have the necessary air. an efficient brake shall be attached to each drum of an engine used in hoisting material and persons, and all machinery, ropes and chains connected therewith shall be carefully examined once each twelve hours. not more than four persons shall be lowered or hoisted in or on a bucket at one time, and no person shall be permitted to ride on a loaded bucket. the bucket used in lowering or hoisting persons shall be equipped with proper safety devices, so that same cannot become detached from the rope or cable, and cannot tip or turn upside down while being so used. the chief inspector of mines, and the district inspector of mines, shall have jurisdiction over such mine when the shaft or slope reaches a depth of twenty-five feet, and such person, firm or corporation shall comply with any order issued by either or both of them with respect to the safety of persons employed. other than the provisions herein, the provisions of this act shall not apply to the opening of a mine until such opening reaches the seam, and the entry or landing be extended beyond a breakthrough, or other place driven at right angles thereto. (penalty, sec. .) sec. . [=additional openings; when and how provided for.=] when in the opinion of the district inspector of mines together with the chief inspector of mines, the ways and means of egress in any mine under their jurisdiction, from the interior working places to the surface, as provided for in this act, are inadequate as a safe and ready means of escape in case of probable emergency, and there are extra hazards of a permanent nature that cannot be removed either from long distance from the interior working places to the exterior openings for egress, from danger of fire at any point, or any other cause that probably will result in the entombment of persons working therein, they shall jointly give notice in writing to the owner, lessee or agent of such mine, and require an additional opening by shaft, slope or drift, from the surface; the location of the interior end of such shaft, slope, or drift, to be sufficiently near the interior working places in that part of the mine where such persons are endangered, to afford such persons safe and ready means of escape, free from such hazards. (sec. ; penalty sec. .) =relating to superintendent, mine-foreman and over-seer.= sec. . [=duties of superintendent.=] the superintendent in charge of a mine shall see that the provisions of this act are carried out, and shall, in case of an accident resulting in the death of or injury to persons, carefully investigate such accident, and report to the chief inspector of mines, as provided for in this act, and to the owner, lessee or agent of the mine. he shall give such other notice to the chief inspector of mines as required by the provisions of this act, and shall co-operate with the mine-foreman and direct him as may be necessary in securing a compliance with the provisions of this act, and the safety of the persons employed in the mine. nothing herein shall prohibit the superintendent from fulfilling the duties of mine-foreman. (sec. , , , ; penalty, sec. .) sec. . [=duties of mine foreman.=] the mine-foreman shall attend personally to his duties in the mine, carry out all the provisions set forth in this act, see that the regulations prescribed for each class of workmen under his charge are carried out in the strictest manner possible, and see that any deviations from any of them are promptly adjusted. (sec. , .) [=when ventilation stops.=] in case of accident to a ventilating fan, or its machinery, whereby the ventilation of the mine would be seriously interrupted, he shall promptly order the men to immediately withdraw from the mine and not return to their work until the ventilation has been restored, and his permission to enter is given; if at a mine which generates fire-damp, he shall not order them to return until the mine has been thoroughly examined by him, or his assistant, and reported to be safe. (sec. , , .) [=dangerous places fenced.=] he shall see that all dangerous places are properly fenced off, and proper danger signal boards are hung on such fencing that they may be plainly seen; he shall also travel all air-ways, and examine all the accessible openings to old workings as often as is necessary to insure their safety. (sec. .) [=examination of working places.=] he shall examine each working place, or have it examined by his assistant, at least once each alternate day that persons are or should be at work therein and oftener, when, in his judgment, the circumstances require. he shall instruct pick miners and machine runners regarding the width of working places. (sec. .) sec. . [=when working place is unsafe.=] when a working place becomes unsafe from any cause, he shall order the person or persons working therein, to cease mining or loading, and not to remain in such working place, except as may be necessary to make it safe, until it is made safe. (sec. .) [=supplying of props and timber.=] he shall see that the working place of each miner is kept supplied with props of approximate length, caps, and other timbers necessary to securely prop the roof thereof. when he examines a working place, he shall observe the condition of the roof and timbering, and instruct the workmen therein as to the proper method of timbering for the security of the roof. he shall give such instructions to drivers, motormen, trip-riders, and other persons, as may be necessary to keep a supply of timber in each working place. (sec. , .) [=miner without props or timber.=] when he finds a miner in a working place without the necessary props, caps or timbers to securely prop the roof thereof, he shall order such miner to leave such working place until the required timber is supplied, which he shall attend to promptly, and shall order that no cars be delivered to such miner, until timber is supplied. (sec. , .) [=measure and report of ventilation.=] he shall keep a careful watch over the ventilating apparatus and air-ways, and measure the ventilation at least once each week, at the inlet and outlet, and at or near the face of all entries; which measurement shall be noted on blanks furnished by the chief inspector of mines. on the first day of each month, he shall sign such blanks, properly filled with the actual measurements, and forward them to the chief inspector of mines. (sec. , , , .) [=record of boys employed.=] he shall keep a record of the boys under sixteen years of age employed by him, or by any other person, giving the name, age, place of birth, name and residence of parents, and character of employment. he shall require written evidence from the parent or guardian of each said minors, that the requirements of the school laws of this state have been complied with. (sec. , .) (see child labor law, sec. .) "the provisions of section , and g.c. do not permit the employment of children under years of age in, about or in connection with any mine. such employment is governed by the provisions of section g.c." opinion no. office of the attorney general, state of ohio, december , . [=assistant mine-foreman.=] the duties of mine-foreman shall apply to assistant mine-foreman, when acting for the mine-foreman, or in discharging the duties thereof. (sec. , ; penalty, sec. .) sec. . [=relating to over-seer.=] the over-seer shall visit the working place of each inexperienced person engaged at mining or loading, at such intervals as provided for in this act, and instruct them as to their work and safety and assist them in caring for their safety. he shall instruct such persons not to handle or use any explosives except in his presence, until they have been employed in a mine not less than three months, and not then until he is satisfied that such persons are fully competent to handle and use same with safety. when, in his judgment, such persons require more frequent supervision than provided for in this act, he shall visit their working places as frequently as in his judgment the circumstances require. the foregoing shall not prohibit the mine-foreman from fulfilling the duties of overseer, so long as all the provisions of this act are complied with. (sec. ; penalty, sec. .) =relating to the stableman and fire-boss.= sec. . [=duties of stableman.=] the stable man shall see that the provisions of this act relating to stables are carried out, and shall forbid persons not required by duty, to enter the stable or loiter in or about same, whether the stable be inside of the mine or on the surface. (sec. , .) [=duties of fire-boss.=] the fire-boss shall examine with a safety lamp each working place, whether same is in the actual course of working or not, the traveling ways and entrances to old workings in the mine every morning, not more than three hours prior to the appointed time for the employes to enter the mine. as evidence of such examination, he shall mark with chalk upon the face of the coal, or in some other conspicuous place, his initials and date of the month. if there is any standing gas discovered, he shall leave a danger signal across every entrance to such place. [=report on blackboard.=] he shall make a report on a blackboard provided on the outside of the mine for that purpose, and arrange so the men can conveniently inspect it, showing the condition of the mine as to the presence of fire-damp, and indicating the place, or places, where present, if any is present, before he permits any person to enter the mine. he shall examine parts of the mine not in the actual course of working and available, not less than once each three days. [=written report.=] the fire-boss shall make a written report, which shall be kept in the office, or some place at the mine where it can be seen by the mine inspector when called for. he shall see that every part of the mine is kept free from standing gas, and that all old workings are properly fenced off, as provided for in this act. he shall return to the mine with the miners and remain there at least one hour, attending to the removal of any standing gas. he shall examine the mine on idle days and sundays if any men are required to work in any part of it, and if more than three hours elapse between the day turn leaving and night turn starting, the places to be worked by night turn must be examined by him with a safety lamp, and reported safe before persons go to them. (sec. , ; penalty, sec. .) =relating to employes generally.= sec. . [=duties of miner. examination of working place.=] each miner shall examine his working place upon entering same, and shall not commence to mine or load until it is made safe. he shall be very careful to keep his working place in a safe condition at all times. (sec. .) [=shall cease work when place is dangerous.=] should he at any time find his place becoming dangerous from any cause or condition, he shall at once cease work, and notify the mine-foreman, or assistant mine-foreman, of such danger, and, upon leaving such place, he shall place some plain warning at the entrance thereto, to warn others from entering into the danger, and shall not return until ordered to do so by the mine-foreman, or assistant mine-foreman. (sec. .) [=shall prop roof, etc.=] each miner, or other person employed in a mine, shall securely prop the roof of the working place therein under his control, and shall obey any order, or orders, given by the superintendent or mine-foreman relating to the width of working places, and to the security of the mine in the part thereof where he is at work, and for fifteen feet back from the face of his working place. such miner, or other person, shall not be held to have violated the provisions of this clause if the owner, lessee or agent fails to supply the necessary props, caps, and timbers, as provided for in this act. (sec. , .) [=shall not waste props, etc.=] each miner, or other person shall avoid waste of props, caps, timber, or other material. when he has props, caps, timber, or other material unsuited for his purpose, he shall not cover up or destroy same, but shall place it near the track where it can be readily seen. (sec. , .) [=blasting when fire-damp is generating.=] he shall not fire a blast in any working place which is likely to generate sudden volumes of fire-damp, or where locked safety lamps are used, except with the consent of the mine-foreman, or other competent person designated by the mine-foreman for that purpose. (sec. .) [=blasting when restricted to specific times.=] at a mine where the firing of shots is restricted to specific times, no miner shall fire a shot until the time appointed for him to do so, and then only in such rotation as designated. (sec. .) [=examination after blasting.=] after each blast, he shall exercise great care in examining the roof and coal, and shall secure them safely before beginning to load coal. (sec. .) [=shall post after undermining.=] after the coal is undermined, he shall, before shooting the coal, properly post the roof of his working place. [=must not go under draw-slate.=] when draw-slate is over the coal, he shall not go underneath the draw-slate until it is made safe from falling, by securely posting it, and he shall not remove the posts until the coal is removed and he is ready to take down the draw-slate. [=shall load fine coal.=] he shall not place in the gob or refuse pile, or cover up, any fine coal or coal dust, but shall load same into cars. (sec. ; penalty, sec. .) sec. . [=duties of machine men.=] machine runners and helpers shall use care while operating mining machines. they shall not operate a machine unless the shields are in place, and shall warn persons not engaged in the operating of a machine of the danger in going near the machine while it is in operation, and shall not permit such persons to remain near the machine while it is in operation. they shall examine the roof of the working place and see that it is safe before starting to operate the machine. they shall not move the machine while the cutter chain is in motion. when connecting the power cable to the electric wires, they shall make the negative or grounded connections before connecting to the positive, and when disconnecting the power cable, shall disconnect from the positive line before disconnecting the negative or grounded. when positive feed wires extend into rooms, they shall connect such wires to the positive wire on the entry before connecting the power cable, and as soon as the power cable is disconnected shall disconnect such wire from the wire on the entry. they shall use care that the cable does not make contact with metallic rails of the track, and shall avoid, where possible, leaving the cable in water. if they remove props which have been placed by the miner for the security of the roof, they shall reset such props as promptly as possible. (sec. ; penalty, sec. .) sec. . [=duties of motormen and trip-riders.=] motormen and trip-riders shall use care in handling the locomotive and cars, and shall see that the signal or marker, as provided for, is used as provided, and shall be governed by the speed provided for in this act in handling cars. they shall not run the locomotive with the trolley ahead of the locomotive, except in cases where they cannot do otherwise, and then only at a speed of two miles per hour. they shall warn persons forbidden to ride on the locomotive or cars, and shall not permit such persons to ride on locomotive or cars contrary to the provisions of this act. [=duties of trip-rider, rope haulage.=] the trip-rider in charge of rope haulage trips shall see that the signal light, as provided for in this act, is in place and in proper condition before starting trip. [=drivers.=] drivers shall use care in handling cars, especially going down extreme grades, and at junction points. [=those in charge of trips of cars shall see that doors are closed.=] motormen, trip-riders and drivers in charge of haulage trips passing through doors used as a means of directing the ventilation, shall see that such doors are closed promptly after the trip passes through. (sec. , , ; penalty, sec. .) sec. . [=persons must not enter mine until fire-boss reports.=] no person shall enter a mine generating fire-damp so as to be detected by a safety lamp, until the fire-boss makes a report outside the mine on a blackboard provided for that purpose, and arranged where the men can conveniently inspect it. no person shall go beyond a danger signal, until all standing gas discovered has been removed or diluted and rendered harmless by a current of air. (sec. , .) [=persons ordered to withdraw must not re-enter without permission.=] any person being ordered by the mine-foreman to withdraw from the mine on account of the interruption of the ventilation shall not re-enter the mine until given permission to do so by the mine-foreman. (sec. .) [=not more than ten persons on a cage.=] when more than ten persons get on a cage or elevator to be lowered into a mine, or to be hoisted out of a mine, the person in charge of the lowering and hoisting of such persons shall order a sufficient number to get off to reduce the number to ten persons, and the persons so ordered shall immediately comply. (sec. .) [=employes shall not loiter.=] each employe of a mine shall go to and from his place of duty by the traveling ways provided; shall not travel around the mine, or the buildings, tracks or machinery connected therewith, where duty does not require, and when not on duty, shall not loiter at, in, or around the mine, the buildings, tracks or machinery connected therewith. [=intoxicants.=] no person shall go into, at, or around a mine, or the buildings, tracks or machinery connected therewith, while under the influence of intoxicants. no person shall use, carry, or have in his possession, at, in, or around a mine, or the buildings, tracks or machinery connected therewith, any intoxicants. [=must not go beyond danger signal.=] no person other than the fire-boss shall remove or go beyond any caution board or danger signal placed at the entrance to any working place, or to the entrance to any old workings in a mine. sec. . [=intent to defraud.=] no person shall erase or change a mark of reference or monument made in connection with measurements; change the checks on cars; wrongfully check a car, or do any act with intent to defraud. [=fire must not be taken into stable.=] no person shall take a lighted pipe, or other thing containing fire, except lanterns as provided for, into any stable or barn. (sec. - .) [=must not obstruct airway.=] no person shall place refuse in, or obstruct any airway or breakthrough used as an airway. [=injuries to mine by workmen and others.=] no workman, or other person, shall knowingly injure a water gauge, barometer, air-course, brattice, equipment, machinery, or live stock; obstruct or throw open an airway; handle or disturb any part of the machinery of the hoisting engine of a mine; open a door of a mine and neglect to close it; endanger the mine or those working therein; disobey an order given in pursuance of law, or do a wilful act whereby the lives and health of persons working therein, or the security of a mine, or the machinery connected therewith may be endangered. (penalty, sec. .) sec. . [=persons not permitted to ride on haulage trips.=] no person or persons except those in charge of trips, superintendents, mine-foremen, electricians, machinists and blacksmiths, when required by their duty, shall ride on haulage trips, except where by mutual agreement in writing, between the owner, lessee or agent, and the employes, a special trip of empty cars is run for the purpose of taking employes into and out of the mine, or empty cars are attached to loaded trips, which shall not be run at a speed exceeding eight miles per hour. no person except a trip rider shall ride on loaded car or cars, and he shall ride only the front or rear end of the trip. (sec. .) [=size of lamps for open lights.=] no person, except as hereinafter provided for, shall use in any coal mine, any oil lamp for the purpose of maintaining an open light, more than two and one-half inches in height, with spout not more than three inches long, with opening not more than three-eights inch in diameter; provided, however, that mine-foreman, electricians, machinists, motormen, trip-riders, drivers, and other persons whose duties require them to ride on moving trips, works in main air current, or travel frequently from place to place, may use lamps not exceeding three and one-half inches in height, with spout not more than four and one-half inches long, with opening not more than five-eights of an inch in diameter. (sec. ; penalty, sec. .) sec. . [=handling and storing of explosives.=] no workman shall have at any one time more than one twenty-five pound keg of blasting powder in the mine, nor more than three pounds of high explosives, and no person shall keep blasting powder or explosives dangerously near the electric wire or power cable in any part of the mine where electric wires are in use. no blasting powder, or other explosive, shall be stored in any mine except as above provided. [=explosives kept in boxes.=] every person who has powder or other explosives in a mine shall keep same in a wooden box, or boxes, securely locked, and said boxes shall be kept at least five feet from the track, and no two powder boxes shall be kept within twenty-five feet of each other, nor shall blasting powder and high explosives be kept in the same box, and in no case shall detonating caps be kept in a box with blasting powder or high explosives. [=fire must be kept from explosives.=] whenever a workman is about to open a box, package or keg containing powder or other explosives, and while handling the same, he shall place and keep his lamp at least five feet distant from said explosives, and in such position that the air current cannot convey sparks to it; and no person shall approach nearer than five feet to any open box, keg or package containing powder or other explosives, or within five feet of another person handling such explosives, with a lighted lamp, lighted pipe, or other thing containing fire. [=conveying of explosives.=] blasting powder or explosives must not be taken into or out of a mine, or moved from place to place in a mine along any entry or haulway where there are electric wires, while the power is on such wires, except when such powder or explosive is conveyed in insulated cars or packages. [=explosives and tools on cages or stairways.=] powder, explosives and working tools shall not be taken down or up a hoisting shaft in a cage when men are going down or up; nor shall they be taken down or up a stairway used for ingress and egress of persons. (sec. , ; penalty, sec. .) sec. . [=squibs and fuses; missed shots.=] any workman who is about to fire a shot with a squib, shall not shorten the fuse, saturate it with oil, or ignite it except at the extreme end; he shall see that all persons are out of danger from the probable effects of such shot, and if it be a rib shot, he shall notify the person or persons working next to him on said rib before firing said shot, and shall take measures to prevent any one approaching by shouting "fire" immediately before lighting the fuse. when a squib is used and a shot misses fire, no person shall return until five minutes shall have elapsed. when a fuse is used and a shot misses fire, no person shall return until one hour for each foot of fuse used shall have elapsed. the needle used in preparing a blast shall be made of copper, and the tamping bar shall be made of wood, or shall be tipped with at least five inches of solid copper. no inflammable material, or any material that may create a spark, shall be used for tamping, and some soft material must always be placed next to the cartridge or explosive. when it is necessary to tamp dynamite, nothing but a wooden tamper shall be used. (sec. , ; penalty, sec. .) =relating to persons not employes.= sec. . [=persons not employes of a mine.=] persons not employes of a mine, except those permitted by law, shall not enter such mine or go upon the property connected therewith, unless consent of the owner, lessee or agent has been secured, and then only when accompanied by a guide furnished by such owner, lessee or agent. this, however, shall not prohibit persons seeking employment at such mine, or the duly authorized representatives of the employes, from entering upon the property as may be necessary to make such application to the proper authority or to transact business, provided such persons do not enter the mine until given permission to do so, and do not stand on the tracks, go near the machinery, or other place of danger. (penalty, sec. .) =general provisions.= sec. . [=qualifications of miner.=] each person desiring to work by himself at mining or loading, shall first produce satisfactory evidence, in writing, to the mine-foreman of the mine in which he is employed, or to be employed, that he has worked at least nine months with, under the direction of, or as a practical miner; provided, however, if the mine in which such person is to be employed generates explosive gas, or fire-damp, he shall have worked not less than twelve months with, under the direction of, or as a practical miner. except as hereinafter provided, until a person has so satisfied the mine-foreman of his competency, he shall not work, or be permitted to work at mining or loading unless accompanied by a competent miner. [=inexperienced miner.=] the provisions of this section shall not prohibit a person not so qualified from working in a mine by himself, or with another inexperienced person, when such person or persons work under the direction of a competent overseer, as hereinafter prescribed. until such person or persons have been employed in a mine for a period of not less than three months, the overseer shall visit the working place of such persons not less frequently than once in each four hours that such persons are in the mine, and instruct them as to their work and safety, and assist them in caring for their safety. after such persons have been employed in a mine for a period of three months, and until they have been employed not less than six months, the overseer shall examine the working place not less frequently than once during each six hours that such persons are in the mine, and shall instruct them as to their work and safety, and assist them in caring for their safety. after such persons have been employed in a mine for a period of not less than six months, the overseer shall examine the working place not less than once each day until such persons become qualified by having worked the period of time hereinbefore provided. the overseer shall instruct such persons not to handle or use any explosives, except in his presence, until they have been employed in a mine not less than three months, and not then until he is satisfied that such persons are fully competent to handle and use same with safety. the overseer shall visit the working place of such persons oftener than required herein, when, in his judgment, it is necessary to do so for the proper safety of such persons. (sec. ; penalty, sec. .) sec. . [=oath and bond of weigh-master.=] any person employed to weigh coal at a mine in which ten or more miners are employed, and upon the weight of which the earnings of the miners depend, shall take and subscribe to an oath before an officer authorized to administer the same, that he will correctly weigh all coal taken from such mine under existing contracts between the owner, lessee or agent, and the miners, and give due credit for same; and when required by existing contracts between the lessor and lessee, he shall give due credit to such lessor. he shall also give a bond in the sum of three hundred dollars, with two sureties approved by the clerk of the township in which such mine is situated, conditioned for the faithful discharge of his duties, and payable to the state, with the oath indorsed thereon, which shall be deposited with such township clerk. (penalty, sec. .) sec. . [=examination of machinery, ventilating current, etc., by miner or owner.=] the miners employed in a mine may appoint two of their number to act as a committee to inspect, not oftener than once in every month, the mine and the machinery connected therewith, and to measure the ventilating current. if the owner, lessee or agent so desires, he may accompany such committee or appoint two or more persons for that purpose. the owner, lessee or agent shall afford every necessary facility for making such inspection and measurement, but the committee shall not in any way interrupt or impede the work in the mine at the time of such inspection and measurement. within ten days after the inspection and measurement, such committee shall make a correct report thereof to the chief inspector of mines, on blanks furnished by him. (sec. ; penalty, sec. .) sec. . [=appropriation of land for mines, how made.=] the owner, lessee or agent of a coal mine, may, when such owner, lessee or agent does not own or control suitable surface ground for openings for the ingress and egress of persons employed therein, for the means of ventilation as provided for in this act, for the means of draining said mine as may best protect the lives and health of the persons employed therein, for the protection of the employes and property, for conducting the water from the mine to any natural water course, or for suitable roadway from any opening to a public highway, appropriate as hereinafter provided, for any one or more of such purposes any required intervening or adjoining lands, and make openings, lay pipe for conducting water, and maintain roadways into, upon, over, under or through same, provided that no land shall be appropriated for a roadway more than twenty feet in width, and no land for any other one of such purposes in excess of one-quarter of an acre. such owner, lessee or agent, whether a corporation, firm or individual, shall be governed in proceedings to appropriate such land by the laws relating to the appropriation of private property by corporation; but no land shall be so appropriated unless the court is satisfied that suitable land cannot be obtained upon reasonable terms. sec. . [=examination and survey of mine by owner of land adjoining.=] each person owning land adjoining a mine worked for the production of coal, and each person interested in such mine, who has reason to believe that the protection of his interests therein or in the coal on his adjoining land requires it, upon making affidavit to that effect before a justice of the peace or other proper officer, may enter such mine and have an examination or survey of it made, after giving three days' notice, in writing, to the owner, lessee or agent of such mine. such examination shall be made at such time, and in such manner, as will least interfere with the working of the mine. [=transportation of surveying party.=] when the affidavit has been made, and notice given, as provided in the foregoing, upon the application of the person giving the notice, the person in charge of such mine shall transport, by the ordinary method for entrance and exit in use at such mine, a surveying party of not more than three persons, furnish them a competent guide, and supply them with necessary and proper lamps. the person in charge of the mine shall be paid by the person requesting the survey, fifty cents for each person so transported, and five dollars per day for guide; but, if the shaft, (if such mine be a shaft mine), exceed two hundred and fifty feet in depth, he shall be paid one dollar for each person so transported. [=liability for damages caused by examination.=] if the owner or lessee of such mine sustain damage for which compensation should be made because such examination or survey was made at unreasonable times, or in an improper or unwarrantable manner, the person making, such examination or survey, or causing it to be made, shall be liable therefor to such owner or lessee. [=forfeiture.=] the persons owning or operating a mine shall not hinder or obstruct such examination or survey, if made at a reasonable time, and in a reasonable manner, and as provided by law. [=to whom provisions concerning examination and survey available.=] the preceding provisions for examination and survey shall be available to any person, who, on his oath, states that he is the owner, or authorized agent of an owner, of land which he believes contains coal or commercial products adjacent to the underground working of a mine, although it does not adjoin the property of such mine. [=action for refusal to permit examination.=] upon the refusal of the owner, lessee or agent of a mine to comply with the provisions of this section, the person who makes the application for the survey may recover judgment as upon default, in a court of competent jurisdiction, against the owner, lessee or agent, in such sum as he declares under oath that he believes to be justly due him for coal belonging to him taken by the owner, lessee or agent of the mine without his permission, and the statute of limitations shall not run against such claim, but the demand, and refusal of permission to enter such mine, must be first proven to the satisfaction of the court or jury. sec. . [=checkweighman for miners.=] the miners employed at a mine where the earnings of such miners depend upon the weight of coal mined, may, at their own cost, designate or appoint a competent person as checkweighman, who, at all proper times, shall have full right of access to and examination of the scales, machinery or apparatus used at such mine to determine the correct weight of coal mined, and whose duty shall be to see the coal weighed and to make a correct record of such weights. not more than one person, however, on behalf of the miners collectively shall have such right at the same time. [=checkweighman for landowners.=] the landowners, or other persons interested in the rental or royalty at such mine, may, at their own cost, designate or appoint a competent person to act as checkweighman for them, who shall have the same rights as the checkweighman for the miners. not more than one person, however, on behalf of the landowners, or other persons interested in the rental or royalty, jointly, shall have such right at the same time. checkweighmen shall not interfere with the use of or tamper with such scales, machinery or apparatus, nor make any false entry of any weight, or in any manner exceed the duties prescribed herein. [=check-measurer.=] the miners employed at a mine where the earnings of such miners depend upon measurements, may, at their own cost, designate or employ, not more than one of their number as check-measurer to accompany each mine-foreman or other person making the measurements and see them make such measurements, and make a correct record of same. each mine-foreman or other person making measurements may have a helper, but such helper shall not be regarded as a person making measurements. the person or persons designated as check-measurer shall not in any manner interfere with or interrupt the work of the mine-foreman, or other person, while making such measurements. (penalty, sec. .) sec. . [=crossing public highway.=] any person, firm or corporation now or hereafter owning any land containing mineral, coal, stone or clay, and over any portion of which shall pass any state, county or township road or public highway, shall have the right and are hereby authorized to drill, excavate, mine or quarry through or under any such road; provided, however, that when any excavation is to be made in such manner that the top or highest level of such excavation will be extended within thirty feet vertical distance of such road, then and in that case before said work shall be commenced, such person, firm or corporation shall execute and deliver to the board of county commissioners in case of state or county roads, or to the township trustee in case of township roads, a bond, with good and sufficient surety in such amounts as shall be considered by said commission or trustees sufficient to cover any damages that may accrue by reason of excavating, mining or quarrying through or under any such road, the same to be approved by said commissioners or trustees; conditioned that while crossing over or mining or quarrying under any such road, a safe and unobstructed passageway or road shall be kept open by such person, firm or corporation for public use, and as soon as practicable such road shall be fully restored to its original safe and passable condition. when such crossing is made by excavation at a depth of more than thirty feet below the surface of such road, the person, firm or corporation making same shall be liable to the county commissioners or township trustees for any damage that may accrue by reason of such excavation, and shall be held to fully repair any such damage and to restore such road to its original safe and passable condition. the right to mine or quarry across or under public highways as hereinbefore provided shall accrue to the owner, lessee or agent of the land upon or through which such highway passes. (penalty, sec. .) =right of action in case of accident.= sec. . in case of an injury to persons or property, occasioned by a violation of any of the provisions of this act or any willful failure to comply with any provisions of this act any owner, lessee or agent of a mine, a right of action shall accrue to the person injured, for any direct damage he may have sustained thereby. in case of loss of life, by reason of such failure or willful neglect, a right of action shall accrue to the widow, and children, or if there be none such, then to the parents and next of kin, of the person whose death was so caused, for like recovery of damages for the injury they shall have sustained. each person who performs labor in opening or developing any coal mine, mining coal, and labor connected therewith, shall have a lien upon all the property of the person, firm or corporation owning, constructing or operating such mine, for the value of such labor for the full amount thereof, upon the same terms, as mechanic's liens are secured and enforced. ( o. laws .) =relating to oil and gas wells through coal measures.= =owner of well shall make and file map.= sec. . any person, firm or corporation holding property in any coal bearing or coal producing township, in any county of the state of ohio, either in fee, by virtue of a lease for oil or gas, mining purposes since january first, , or otherwise, whereon wells have been drilled for oil, gas or test purposes, shall cause to be made by a competent engineer, an accurate map on a scale of not less than one inch to four hundred feet, showing on said map the location and number of wells as near as the same can be located, that have been drilled, whether or not any of such wells have been previously abandoned, or were drilled and abandoned by former operators, who have ever held the said property for oil, gas or mining purposes. said map shall show the name and address of the person, firm or corporation owning said well or wells, the county and township, the names of the adjoining property owners, and lines of the property operated with the distances of the wells properly measured therefrom and checked from the section and quarter section lines, as will be necessary for an accurate survey. the map shall show all the engineer's notations of angles, distances, starting point, or corner stones, together with the numbers given the respective wells, giving a legend as to the manner in which various abandoned or producing wells, are designated. the original map shall be retained by the owner or his agent, and one copy filed with the industrial commission of ohio, division of mines, said copy showing thereon the sworn statement of the engineer making the map that same is correct. =well shall not be near mine opening.= no oil well, gas well or test well shall be drilled nearer than three hundred feet to any opening to a mine used as a means of ingress or egress for persons employed therein, nor nearer than one hundred feet to any building or inflammable structure connected therewith, and actually used as a part of the operating equipment of said mine. =persons drilling oil and gas wells in coal bearing or coal producing townships.= any person, firm or corporation before drilling or causing to be drilled any oil well, gas well or test well within the limits of any coal producing township in any county of the state of ohio, shall first file an application with, the industrial commission of ohio, division of mines, on blanks to be furnished by said commission for such purpose, and shall show the following: the name and address of the applicant, the proper date, location of the proposed well--giving the name of the property owner, section number, township and county, the number of the proposed well, and signed by an officer or agent of such operator. no well shall be commenced until the applicant or operator has been granted a permit, which shall be granted by the industrial commission of ohio, division of mines, under the following conditions: =when well is adjacent to mine.= if such proposed well is located within the limits directly adjacent to mining operations, such limits to be determined by the industrial commission of ohio, division of mines, the application for permit must be accompanied by a map showing the location of the proposed well and answering the requirements in the preceding regulations for mapping. =when well is not adjacent to mine.= if such proposed well is not located within the limits directly adjacent to mining operations, but within the limits of any coal producing or coal bearing township, the industrial commission of ohio, division of mines, shall grant a permit immediately upon receipt of the application, providing the applicant is a responsible person, firm or corporation. the industrial commission of ohio, division of mines, may at any time after the well is commenced, if the responsibility of the applicant or operator is considered doubtful, cause such operator or applicant to show proper guaranty of his intention to fulfill the requirements of the section, or cause all operations to cease forthwith. if any person, firm or corporation continue drilling on property already surveyed in accordance with the preceding requirements, a complete blue print or copy of map shall be made at the end of each year ending june th, showing the additional wells properly surveyed by a competent engineer as above mentioned, and filed with the industrial commission of ohio, division of mines, not later than the following first of september. =when well is to be abandoned owner shall give notice.= when any oil well, gas well or test well is to be abandoned, the person, firm or corporation owning such well shall notify the industrial commission of ohio, division of mines, or the deputy oil and gas well inspector of the district in which the well is located, as many days in advance as will be necessary for the inspector to arrange to be present at such abandonment. no well shall be abandoned without an inspector being present, unless permission has been first granted upon good cause shown, by the industrial commission of ohio, division of mines. =method of plugging well.= when any oil well, gas well or test well is to be abandoned, it must first be plugged in some secure manner above the oil or gas sand or rock formation, either by placing or driving one or more good seasoned wooden plugs, or a lead plug, as the case may require, so that no gas or oil may escape, or any water or destructive matter force itself into the oil or gas sand, or rock formation. upon such seasoned wooden plug or plugging material shall be filled at least thirty feet of cement properly mixed with sand, or thirty feet of good clay or rock sediment properly prepared. if any well has passed through a workable vein or seam of coal, it shall when it is abandoned be plugged in the following manner: a seasoned wooden plug shall be driven to a point thirty feet below the lowest workable seam of coal and the hole filled with cement to a point at least twenty feet above this seam of coal, at which point another wooden plug shall be placed and the hole filled for a distance of twenty feet with cement or properly prepared clay, or rock sediment. if there is more than one seam of coal the next seam above must be plugged off in like manner. =when well penetrates the excavations of any mine.= in the event that a well being drilled penetrates the excavations of any mine, it must be cased with casing of approximately the same diameter as the diameter of the hole, the hole to be drilled thirty feet or to solid slate or rock and not less than ten feet below the floor of such mine, and the casing shall be placed in the following manner: one string of casing shall be placed at a point above the roof of said mine so as to shut off all of the surface water; then the hole drilled through said mine and another string of casing put in. the bottom of the second string of casing, or the one passing through said mine, shall not be nearer than ten feet, or more than thirty feet from the floor of the mine where it passes through the same. when any well which has been drilled is to be abandoned and has passed through the excavations of any coal mine from which the minable coal has not all been removed, the person, firm or corporation owning said well shall leave in said well the casing passing through said mine from a point not less than ten feet, nor more than thirty feet below the floor of said mine, and extending above the roof of said mine at least five feet. a seasoned wooden plug shall be driven to a point at least forty feet below the floor of the mine and the hole above said plug together with the casing left in, which extends through the coal, shall be filled with cement; then a seasoned wooden plug shall be driven on the top of said casing, and the hole filled with cement for a distance of not less than twenty feet. =interpretation--"coal bearing and coal producing township."= a coal bearing or coal producing township of any county shall be interpreted to mean any, township as a unit, in which coal is found that, is being mined, or is of such thickness as to make it likely to be mined at some future time. any well drilled in such township, whether or not it passes through any coal, the same being barren in certain sections of such township, or the well being commenced below the line of outcrop of the coal, will nevertheless be required to be mapped and abandoned in accordance with the regulations and provisions of this section as given above, which shall apply uniformly throughout any coal bearing or coal producing township of any county. =relating to illuminating oil for mines.= =composition of illuminating oil for use in mines.= sec. . no person, firm or corporation shall compound, sell or offer for sale for illuminating purposes in any mine any oil other than oil composed of not less than eighty-two per cent, of pure animal or vegetable oil, or both, and not more than eighteen per cent, pure mineral oil. the gravity of such animal or vegetable oil shall not be less than twenty-one and one-half, and not more than twenty-two and one-half degrees baume scale, measured by tagliabue or other standard hydrometer, at a temperature of sixty degrees fahrenheit; the gravity of such mineral oil shall not be less than thirty-four and not more than thirty-six degrees baume scale, measured by tagliabue or other standard hydrometer at a temperature of sixty degrees fahrenheit, and the gravity of the mixture shall not exceed twenty-five degrees baume scale measured by tagliabue or other standard hydrometer at a temperature of sixty degrees fahrenheit. each person, firm or corporation compounding oil for illuminating purposes in any mine or mines, shall, before shipment thereof is made, securely brand, stencil or paste upon the head of each barrel or package, a label which shall have plainly printed, marked or written thereon, the name and address of the person, firm or corporation, having purchased same, the date of shipment, the percentage and the gravity in degrees baume scale, at a temperature of sixty degrees fahrenheit, of each of the component parts of animal, vegetable and mineral oil contained in the mixture, and the gravity in degrees baume scale at a temperature sixty degrees fahrenheit of the mixture. each label shall have printed thereon, over the fac-simile signature of the person, firm or corporation having compounded the oil, the following: "this package contains oil for illuminating purposes in mines in the state of ohio, and the composition thereof as shown hereon is correct." each person, firm or corporation, manufacturing paraffine wax for illuminating purposes in any mine, or mines, shall, before shipment thereof is made, securely brand, stencil, or paste, upon the head of each barrel, box, or case, containing small packages, the name and address of the person, firm or corporation, manufacturing paraffine wax therein contained, the name and address of the person, firm or corporation, having purchased the same, and the date of shipment. and each individual package contained within each barrel, box or case, shall have plainly printed thereon the name of the product, the name and address of the manufacturer thereof, together with the melting point, fire test, and the percentage of oil and moisture of the paraffine wax herein contained. but nothing herein contained shall prohibit the manufacture, sale or use for illuminating purposes in mines in this state, of paraffine wax with melting point at from one hundred five to one hundred twenty-four degrees of heat and minimum fire test not less than three hundred degrees fahrenheit, with not over four per cent, oil and moisture. =acetylene gas in mines.= sec. - . it shall be lawful to use acetylene gas in lamps in mines subject to the following conditions and restrictions: first, no person or persons shall take into a mine a greater quantity of calcium carbide than will be a reasonable supply for his own lamp for one day's work. second, no person shall deposit, or keep in his possession in a mine any calcium carbide, or refuse from calcium carbide, in anything except air-tight containers, and these containers with their contents must be taken out of the mine at the end of each day's work, or sooner, if possible. third, no person or persons, shall be allowed to use acetylene gas in lamps where there are old or abandoned workings where large quantities of black damp or other poisonous gases are liable to accumulate until such places have been examined by a competent person and pronounced to be free from foul or poisonous atmosphere. =other illuminants.= sec. - . no person shall use in any mine any other illuminant than those provided for in sections and - of the general code, unless with the consent of the chief inspector of mines. =penalty.= sec. - . any person who knowingly uses, or any owner, lessee or agent, who permits the use of any illuminant contrary to the provisions of sections , - and - , or any owner, lessee or agent who permits any person to deposit, or keep in his possession, in a mine any calcium carbide, or refuse from calcium carbide, except as provided in said sections and - , upon conviction, shall be fined not less than five nor more than ten dollars, and for a second or any subsequent offense shall be fined not less than twenty-five dollars nor more than one hundred dollars. ( o.l. .) sec. . [=no oil for illuminating purposes in mines shall be sold except oil prescribed in this act.=] no person, firm or corporation shall sell or offer for sale, any oil for illuminating purposes in any coal mine unless the barrel or package in which such oil was received bears the label of the compounder as provided for in this act. each person, firm or corporation selling or offering for sale any oil for illuminating purposes in any coal mine, shall, upon request of any district inspector of mines, or of any officer or duly authorized agent of any owner or lessee of a coal mine located within two miles of the point where such oil is offered for sale, submit such oil and the original containers for examination, and upon request, give a sample of such oil from one or more original containers selected by such inspector, officer or agent, for the purpose of making a test thereof. [=adulteration of illuminating oil forbidden.=] no person shall adulterate any oil either before or after taking same from the original containers, and shall not alter, transfer, or re-use any label placed upon any container. [=persons forbidden to use oil other than prescribed in this act.=] no person shall use for illuminating purposes in any coal mine, any oil other than the oil specifically provided for in this act. each person, while in a coal mine, shall, upon request of any district inspector of mines, or any officer or duly authorized agent of the owner or lessee, submit his lamp and supply of oil for examination, and upon request, give sample of oil for purpose of making test thereof, and state from whom purchased. [=provisions of this act shall apply only to oil used for open lights.=] the provisions of this act relating to the compounding, sale and use of oil for illuminating purposes in coal mines, shall apply to oil used in lamps for open lights. the oil used in safety lamps may be of such composition as will best serve the purpose. (sec. , ; penalty, sec. .) =relating to penalties.= =county coroner.= sec. . any county coroner who, after receiving notice of a fatal accident, or of an accident, which has resulted in the death of a person, at, in, or around a mine, from the owner, lessee or agent of such mine, or the chief inspector of mines, willfully refuses or neglects to comply, so far as such provisions relate to him, with the provisions of section nine hundred and twenty-one of the general code, shall, upon conviction thereof, be fined not less than twenty-five dollars nor more than fifty dollars, at the discretion of the court. =owner, lessee or agent.= any owner, lessee or agent of a mine, or any person, firm or corporation opening a new mine, having written knowledge of a violation of this act, who willfully refuses or neglects to comply with the provisions of section nine hundred and twenty-two, nine hundred and twenty-three, nine hundred and twenty-four, nine hundred and twenty-five, nine hundred and twenty-six, nine hundred and twenty-seven, nine hundred and twenty-eight, nine hundred twenty-nine, nine hundred and thirty, nine hundred and thirty-one, nine hundred and thirty-two, nine hundred and thirty-three, nine hundred and thirty-four, nine hundred and thirty-seven, nine hundred and thirty-eight, nine hundred and thirty-nine, nine hundred and forty, nine hundred and forty-one, nine hundred and forty-two, nine hundred and forty-three, nine hundred and forty-four, nine hundred and forty-five, nine hundred and forty-six, nine hundred and forty-seven, nine hundred and forty-eight, nine hundred and forty-nine, nine hundred and fifty, or nine hundred and seventy-one of the general code, shall, upon conviction thereof, be fined not less than twenty-five dollars nor more than fifty dollars, and for a second or any subsequent offense shall be fined not less than fifty dollars, nor more than one hundred dollars, at the discretion of the court. =superintendent, mine-foreman or over-seer.= any superintendent, mine-foreman, foreman or overseer, who willfully refuses or neglects to comply, so far as such provisions relate to each of them with the provisions of section nine hundred and fifty-one, nine hundred and fifty-two, nine hundred and fifty-three, and nine hundred and fifty-four of the general code, shall upon conviction thereof, be fined not less than ten dollars nor more than twenty-five dollars, and for a second or subsequent offense, shall be fined not less than ten dollars nor more than twenty-five dollars, or imprisoned not less than ten days nor more than twenty days, or both, at the discretion of the court. =stableman; fire-boss; entering mine generating fire-damp before reported safe, or going beyond danger signal.= any person or persons who willfully refuses or neglects to comply with the provisions of section nine hundred and fifty-five of the general code, or enters a mine generating fire damp before it is reported by the fire boss that it is safe for persons to enter, or goes beyond a danger signal indicating an accumulation of fire damp, as forbidden by the provisions of section nine hundred and fifty-nine of the general code, shall, upon conviction thereof, be fined not less than twenty-five dollars nor more than fifty dollars, and for a second or any subsequent offense shall be fined not less than twenty-five dollars nor more than fifty dollars, or imprisoned not less than ten days nor more than twenty days, or both, at the discretion of the court. =employes of mines.= any person, or persons, who violates the provisions of sections nine hundred and fifty-six, nine hundred and fifty-seven, nine hundred and fifty-eight, nine hundred and sixty, nine hundred and sixty-one, or nine hundred and sixty-two of the general code, or violates the provisions of section nine hundred and fifty-nine of the general code other than to enter a mine generating fire-damp before the fire boss reports it safe, or to go beyond a danger signal indicating an accumulation of fire-damp, shall, upon conviction thereof, be fined not less than five dollars, nor more than ten dollars, and for a second or any subsequent offense shall be fined not less than five dollars nor more than ten dollars, or imprisoned not less than five days nor more than ten days, or both, at the discretion of the court. =persons not employes, qualification of miners, check-weighman, check-measurer.= any person who willfully violates the provisions of sections nine hundred and sixty-four, nine hundred and sixty-five, nine hundred and sixty-six, nine hundred and sixty-seven, or nine hundred and seventy of the general code, or violates the provisions of section nine hundred and fifty-nine of the general code relating to loitering and intoxicants, at, in or around a mine, shall, upon conviction thereof, be fined not less than five dollars, nor more than ten dollars, and for a second or any subsequent offense shall be fined not less than five dollars nor more than ten dollars, or imprisoned not less than five days nor more than ten days, or both, at the discretion of the court. =drilling and operating oil and gas wells.= any person, firm or corporation who violates or willfully refuses or neglects to comply with the provisions of section , shall, upon conviction thereof, be fined not less than one hundred dollars, nor more than five hundred dollars, and for a second or any subsequent offense shall be fined not less than two hundred dollars and not more than one thousand dollars, or imprisoned not less than thirty days nor more than six months, at the discretion of the court. in addition, if the material is pulled out of a well which was not plugged in accordance with the provisions of section , the person, firm or corporation causing such offense may be made to clean out such well and properly plug the same, or pay the entire reasonable cost of such work being done under orders of the industrial commission of ohio, division of mines, within thirty days. =compounding oil for illuminating purposes in mines.= any person, firm or corporation who compounds, sells or offers for sale to dealers any oil or paraffine wax; fish oil or any other illuminant whatever, other than those specifically provided for in section , general code, unless with the consent and approval of the chief inspector of mines, for illuminating purposes in any mine in this state contrary to the provisions of sections nine hundred and seventy-four and nine hundred and seventy-five of the general code, shall upon conviction thereof, be fined not less than fifty dollars nor more than one hundred dollars and for a second or any subsequent offense shall be fined not less than one hundred dollars nor more than two hundred dollars, or imprisoned not less than thirty days nor more than sixty days, or both, at the discretion of the court. =sale of oil for illuminating purposes in mines.= any person, firm or corporation who sells, or offers for sale to any employe of a mine for illuminating purposes in a mine any oil or paraffine wax, fish oil or any other illuminant, other than those specially provided for in section nine hundred and seventy-four of the general code, unless with the consent and approval of the chief inspector of mines contrary to the provisions of section nine hundred and seventy-four and nine hundred and seventy-five of the general code, shall upon conviction thereof, be fined not less than twenty-five dollars nor more than fifty dollars, and for a second or any subsequent offense shall be fined not less than twenty-five dollars nor more than fifty dollars, or imprisoned not less than ten days nor more than twenty days, or both, at the discretion of the court. =using oil for illuminating purposes in mines.= any person who knowingly uses for illuminating purposes in a mine, any oil or paraffine wax, fish oil or any other illuminant whatever other than those specially provided for in section nine hundred and seventy-four of the general code, unless with the consent and approval of the chief inspector of mines, contrary to the provisions of sections nine hundred and seventy-four and nine hundred and seventy-five of the general code, shall, upon conviction thereof, be fined not less than five dollars nor more than ten dollars, and for a second or any subsequent offense shall be fined not less than five dollars nor more than ten dollars, or imprisoned not less than five days nor more than ten days, or both, at the discretion of the court. ( - a.) =regulating and prohibiting solid shooting.= =failure to obtain permit; penalty.= sec. - . whoever being engaged in the operation of a coal mine causes or permits any solid shooting to be done therein without having first obtained a permit to do so from the industrial commission of ohio shall be fined in a sum not exceeding one hundred dollars. =permit must be obtained.= sec. - . a permit to do solid shooting may be issued by the industrial commission of ohio in the case of any mine when application shall be made therefor by the owner, lessee or person engaged in the operation thereof and by a majority of the miners employed therein, and when such industrial commission shall be satisfied that such method of blasting is necessary for the just and reasonably profitable operation of such mine. such permit may be revoked at any time by said commission after sixty days' notice in writing to such owner, lessee or person operating such mine. any person in interest who is dissatisfied with any order of said industrial commission made under the power conferred upon it by this section, may commence an action to set aside, vacate or amend such order in the same manner and for the same reason as other orders of such commission may be set aside, vacated or amended. =each section declared to be independent section.= sec. - . each section of this act is hereby declared to be an independent section and the holding of any section to be void or ineffective for any cause shall not be deemed to affect any other section thereof. =relating to fines collected, prosecutions, when act shall take effect, and repeals.= sec. . [=fines collected.=] all fines collected by reason of prosecutions begun under the provisions of this act, shall be paid to the chief inspector of mines, and by him paid into the state treasury. sec. . [=prosecutions; how controlled.=] any prosecutions begun under the provisions of this act shall be controlled by sections thirteen thousand four hundred and twenty-three and thirteen thousand four hundred and thirty-two to thirteen thousand four hundred and thirty-nine inclusive of the general code. =regulation of weighing of coal.= =miner to be paid for all coal contained within car.= sec. - . every miner and every loader of coal in any mine in this state who under the terms of his employment is to be paid for mining or loading such coal on the basis of the ton or other weight shall be paid for such mining or loading according to the total weight of all such coal contained within the car (hereinafter referred to as mine car) in which the same shall have been removed out of the mine unless otherwise agreed between employer and miner or loader. =department of industrial relations to determine percentage of impurity.= sec. - . said industrial commission shall ascertain and determine the percentage of slate, sulphur, rock, dirt, or other impurity unavoidable in the proper mining or loading of the contents of mine cars or coal in the several operating mines within this state subject, however, to the right of the employer and miner or loader in any of such mines to make an agreement with reference thereto. =percentage of fine coal.= sec. - . when there is no agreement between the miner or loader of coal in any mine in this state and the operator thereof whereby the miner or loader is to be paid for mining or loading coal other than on the basis of the ton or other weight according to the total weight of all such coal contained within the car it shall be the duty of such miner or loader of coal and his employer to agree upon and fix, for stipulated periods, the percentage of fine coal commonly known as nut, pea, dust and slack allowable in the output of the mine wherein such miner or loader is employed. at any time when there shall not be in effect such agreed and fixed percentages of fine coal allowable in the output of any mine, said industrial commission shall forthwith upon request of such miner or loader or his employer, fix, such allowable percentage of fine coal, which percentage so fixed by said industrial commission shall continue in force until otherwise agreed and fixed by such miner or loader and his employer. whenever said industrial commission shall find that the total output of such fine coal at any mine for a period of one month during which such mine shall have been operating while the percentage of fine coal so fixed by said industrial commission has been in force, exceeds the percentage so fixed by it, said industrial commission shall at once make, enter and cause to be enforced such order or orders relative to the production of coal at such mine, as will result in reducing the percentage of such fine coal, to the amount so fixed by said industrial commission. sec. - . said industrial commission shall, as to all coal mines in this state, which have not been in operation heretofore, perform the duties imposed upon it by the provisions hereof. =department of industrial relations may change percentage.= sec. - . said industrial commission shall have full power from time to time, to change, upon investigation, any percentage by it ascertained and determined or fixed, as provided in the preceding sections hereof. =unlawful to use screen.= sec. - . it shall be unlawful for the employer of a miner or loader of the contents of any car of coal to pass any part of such contents over a screen or other device, for the purpose of ascertaining or calculating the amount to be paid such miner or loader for mining or loading such contents, whereby the total weight of such contents shall be reduced or diminished unless otherwise agreed between employer and miner or loader. any person, firm or corporation violating the provisions of this section shall be deemed guilty of a misdemeanor and upon conviction, shall be fined for each separate offense not less than three hundred dollars nor more than six hundred dollars. =loading impurity; penalty.= sec. - . a miner or loader of the contents of a mine car, containing a greater percentage of slate, sulphur, rock, dirt or other impurity, than that ascertained and determined by said industrial commission, as hereinbefore provided, shall be guilty of a misdemeanor and upon conviction shall be punished as follows: for the first offense within a period of three days he shall be fined fifty cents; for a second offense within such period of three days he shall be fined one dollar; and for the third offense within such period of three days he shall be fined not less than two dollars nor more than four dollars. provided, that nothing contained in this section shall affect the right of a miner or loader and his employer to agree upon deductions by the system known as docking, on account of such slate, sulphur, rock, dirt or other impurity. =jurisdiction.= the following are the sections of the general code referred to in various sections of the mining law, and under which prosecutions will be made. =jurisdiction.= sec. . justices of the peace, police judges and mayors of cities and villages shall have jurisdiction, within their respective counties, in all cases of violation of any law relating to: . adulteration or deception in the sale of dairy products and other food, drink, drugs and medicines. . the prevention of cruelty to animals and children. . the abandonment, non-support or ill treatment of a child by its parent. . the abandonment or ill treatment of a child under sixteen years of age by its guardian. . the employment of a child under fourteen years of age in public exhibitions or vocations injurious to health, life or morals, or which cause or permit it to suffer unnecessary physical or mental pain. . the regulation, restriction or prohibition of the employment of minors. . the torturing, unlawfully punishing, ill treating, or depriving anyone of necessary food, clothing or shelter. * * * * * . the prevention of short weighing and measuring and all violations of the weights and measures laws. ( o.l., .) =justices, police judges and mayors.= sec. . [=when imprisonment is a part of the punishment a jury shall be impaneled.=] in prosecutions before a justice, police judge or mayor, when imprisonment is a part of the punishment if a trial by jury is not waived the magistrate, not less than three days nor more than five days before the time fixed for trial, shall certify to the clerk of the court of common pleas of the county that such prosecution is pending before him. (r.s. sec. a.) sec. . [=clerk's duties.=] thereupon the clerk, in the presence of representatives of both parties, shall draw from the jury wheel or box containing the names of persons selected to serve as petit jurors in the court of common pleas in such county, twenty names which shall be drawn and counted in a like manner as for jurors in the court of common pleas. the clerk shall forthwith certify the names so drawn to the magistrate, who, thereupon, shall issue to any constable, chief of police or marshal in the county a venire containing the names of the persons to serve as jurors in the case and make due return thereof. (r.s. sec. a.) sec. . [=jurors.=] the jurors shall be subject to like challenges as jurors in criminal cases, except capital cases in the court of common pleas. if the venire is exhausted without obtaining the number required to fill the panel, the magistrate shall fill the panel with talesmen in the manner provided for criminal cases in the court of common pleas. (r.s. sec. a.) sec. . [=second or subsequent offense.=] in such prosecutions, where a different punishment is provided for a second or subsequent offense, the information or affidavit upon which the prosecution is based, must charge that it is the second or subsequent offense or the punishment shall be as for the first offense. (r.s. sec. a.) sec. . repealed. ( o.l., .) sec. . [=new trial.=] in such prosecutions, if there is a verdict for conviction, a new trial may be granted for like reasons and subject to like conditions as a new trial in criminal cases in the court of common pleas. (r.s. sec. a.) sec. . [=fees of jurors and witnesses.=] in such prosecutions, the jurors shall be entitled to the same mileage and fees as in the criminal cases in the court of common pleas. (r.s. sec. a; am. o.l., .) sec. . [=costs.=] in such prosecutions, no costs shall be required to be advanced or secured by a person authorized by law to prosecute. (r.s. sec. a; am. o.l., .) =relative to employment of minors.= =sixteen years: age limit for following occupations.= sec. . no child under the age of sixteen years shall be employed, permitted or suffered to work at any of the following occupations or any of the following positions: ( ) adjusting any belt to any machinery; ( ) sewing or lacing machine belts in any workshop or factory; ( ) oiling, wiping or cleaning machinery or assisting therein; ( ) operating or assisting in operating any of the following machines (a) circular or band saws; (b) wood shapers; (c) wood jointers; (d) planers; (e) sandpaper or woodpolishing machinery; (f) woodturning or boring machinery; (g) picker machines or machines used in picking wool, cotton, hair or any other material; (h) carding machines; (i) paper-lace machines; (j) leather-burnishing machines; (k) job or cylinder printing presses operated by power other than foot power; (l) boring or drill presses; (m) stamping machines used in sheetmetal and tinware, or in paper and leather manufacturing, or in washer and nut factories; (n) metal or paper cutting machines; (o) corner staying machines in paper box factories; (p) corrugating rolls, such as are used in corrugated paper, roofing or washboard factories; (q) steam boilers; (r) dough brakes or cracker machinery of any description; (s) wire or iron straightening or drawing machinery; (t) rolling mill machinery; (u) power punches or shears; (v) washing, grinding or mixing machinery; (w) calendar rolls in paper and rubber manufacturing; (x) laundering machines; (y) burring machinery; ( ) or in proximity to any hazardous or unguarded belts, machinery or gearing; ( ) or upon any railroad, whether steam, electric or hydraulic; ( ) or upon any vessel or boat engaged in navigation or commerce within the jurisdiction of this state. =sixteen years: age limit for following industries.= sec. . no child under the age of sixteen years shall be employed, permitted or suffered to work in any capacity ( ) in, about or in connection with any processes in which dangerous or poisonous acids are used; ( ) nor in the manufacture or packing of paints, colors, white or red lead; ( ) nor in soldering; ( ) nor in occupation causing dust in injurious quantities; ( ) nor in the manufacture or use of dangerous or poisonous dyes; ( ) nor in the manufacture or preparation of compositions with dangerous or poisonous gases; ( ) nor in the manufacture or use of compositions of lye in which the quantity thereof is injurious to health; ( ) nor on scaffolding; ( ) nor in heavy work in the building trades; ( ) nor in any tunnel or excavation; ( ) nor in, about or in connection with _any mine, coal breaker, coke oven, or quarry_; ( ) nor in assorting, manufacturing or packing tobacco; ( ) nor in operating any automobile, motor car or truck; ( ) nor in a bowling alley; ( ) nor in a pool or billiard room; ( ) nor in any other occupation dangerous to the life and limb or injurious to the health or morals of such child. =employer to furnish satisfactory evidence of age.= sec. - . an inspector of factories, attendance officer, or other officer charged with the enforcement of the laws relating to the employment of minors or school attendance may make demand on any employer in or about whose place or establishment or material or equipment a person apparently under the age of eighteen years is employed or permitted or suffered to work, and whose employment certificate is not filed as required by this act, that such employer shall furnish him satisfactory evidence that such person is in fact over eighteen years of age. the inspector of factories, attendance officer, or other officer charged with the enforcement of such laws, shall require from such employer unless an overage certificate is held by the employe the same evidence of age of such child as is required upon the issuance of an age and schooling certificate. failure of such employer to produce such evidence shall be deemed a violation of the laws relating to the employment of minors. =failure to produce satisfactory evidence of age.= sec. - . in case any employer shall fail to produce and deliver to a factory inspector, truant officer, or other officer charged with the enforcement of this act, within ten days after demand made pursuant to section - of this act, the evidence of age therein required, proof of the making of such demand and of such failure to produce and file such evidence shall be prima facie evidence of the illegal employment of such child in any prosecution brought therefor. =age and schooling certificate; by whom approved.= sec. . an age and schooling certificate may be issued only by the superintendent of schools and only upon satisfactory proof that the child to whom the certificate is issued is over sixteen years of age and has satisfactorily passed a test for the completion of the work of the seventh grade, provided that residents of other states who work in ohio must qualify as aforesaid with the proper school authority in the school district in which the establishment is located, as a condition of employment or service. any such age and schooling certificate may be issued only upon satisfactory proof that the employment contemplated by the child is not prohibited by any law regulating the employment of such children; and when the employer of any minor for whom such age and schooling certificate shall have been issued shall keep such age and schooling certificate on file as provided by law, the provisions of section - , general code, shall not apply to such employer in respect to such child while engaged in an employment legal for a child of the given sex and of the age stated therein. age and schooling certificate forms shall be formulated by the superintendent of public instruction, and except in cases otherwise specified by law must be printed on white paper. every such certificate must be signed in the presence of the officer issuing it by the child in whose name it is issued. blank certificates shall be furnished by the superintendent of public instruction upon request. sec. - . the superintendent of schools shall not issue such certificate until he has received, examined, approved and filed the following papers duly executed: ( ) the written pledge or promise of the person, partnership or corporation to legally employ the child, to permit him to attend school as provided in section , general code, and to return to the superintendent of schools the age and schooling certificate of the child or give notice of the non-use thereof within two days from the date of the child's withdrawal or dismissal from the service of that person, partnership or corporation, giving the reasons for such withdrawal or dismissal. ( ) the school record of the child, properly filled out and signed by the person in charge of the school which the child last attended; giving the recorded age of the child, his address, standing in studies, rating in conduct, and attendance in days during the school year of his last attendance, and if that was not a full year, during the preceding school year. ( ) evidence of the age of the child as follows: (a) the birth certificate of the child (or duly attested transcript thereof) issued near the date of the birth of the child by the registrar of vital statistics of ohio, or by a similar officer charged with the duty of recording births in another state or country, shall be conclusive evidence of the age of the child. (b) in the absence of such certificate, a passport (or duly attested transcript thereof) showing the date and place of birth of the child, filed with a register of passports at a port of entry of the united states; or a duly attested transcript of the certificate of birth or baptism or other religious record, showing the date and place of birth of the child, shall be conclusive evidence of the age of the child. (c) in case no one of the above proofs of age can be produced, other documentary evidence (except the affidavit of the parent, guardian or custodian) satisfactory to the superintendent of schools may be accepted in lieu thereof. (d) in case no documentary proof of age can be procured, the superintendent may receive and file an application signed by the parent, guardian or custodian of the child that a physician's certificate be secured to establish the sufficiency of the age of the child. such application shall state the alleged age of the child, the place and date of birth, his present residence, and such further facts as may be of assistance in determining the age of the child, and shall certify that the person signing the application is unable to obtain any of the documentary proofs specified in (a), (b) and (c) above. if the superintendent of schools is satisfied that a reasonable effort to procure such documentary proof has been without success such application shall be granted and the certificate of the school physician or if there be none, of a physician employed by the board of education, that said physician is satisfied that the child is above the age required for an age and schooling certificate as stated in section , general code, shall be accepted as sufficient evidence of age. ( ) a certificate from the school physician or physician designated by him, or if there be no school physician from the district health commissioner, or physician designated by him, showing after a thorough examination that the child is physically fit to be employed in such occupations as are not prohibited by law for a boy or girl, as the case may be, under eighteen years of age. but a certificate with the word limited written, printed or stamped diagonally across its face may be furnished by the school physician or other person indicated in the above sentence, and accepted by the superintendent of schools in issuing a "limited" age and schooling certificate provided in section - , general code, showing that the child is physically fit to be employed in some particular occupation not prohibited by law for a boy or girl as the case may be of the child's age which the child contemplates entering even if the child's complete physical ability to engage in any occupation as required in the preceding sentence cannot be vouched for. sec. - . when an age and schooling certificate, returned according to section - , general code, is reissued, the pledge of the new employer and certificate from the school physician or other person in his stead shall be secured and filed. sec. - . the age and schooling certificate provided in section , general code, shall be issued only with the word "limited" printed or stamped diagonally across its face if the certificate of the physician provided in section - or - , general code, is a limited certificate and in that case the particular employment to which it is limited shall be stated in the certificate, and the certificate cannot serve as the legal age and schooling certificate for employment in another occupation. such limited certificate shall be printed on pink paper. sec. - . in order to ascertain whether applicants for age and schooling certificates have satisfactorily completed the school work prescribed in section , general code, the board of education of any city school district may appoint a juvenile examiner who shall receive such compensation as may be fixed by the board of education. when such a juvenile examiner is employed no such certificate shall be granted by the superintendent of schools of the district unless the juvenile examiner has certified that he has examined the child and that the child has passed to his satisfaction the grade test as provided by section , general code, provided, however, that if a child in the opinion of said juvenile examiner is below the normal in mental development so that he cannot with further schooling and due industry pass such test, such fact shall be certified to by said examiner and the superintendent of schools shall grant the child an age and school certificate printed on yellow paper with the words "retarded-schooling not standard" written, printed or stamped diagonally across the face; and provided, further, that if the juvenile examiner is satisfied that the standard of any school is sufficiently high, he may accept the records thereof as showing that a child has passed the required test. in case no juvenile examiner is employed the superintendent of schools may proceed and determine in like manner; if after proper tests he determines that a child is below normal in mental development to the extent specified above, he shall grant such a "retarded" age and schooling certificate. if a child who desires an age and schooling certificate is granted a "retarded" certificate but secures only a limited health certificate; the word "limited" shall be written or stamped across the face of the "retarded" certificate and the limited "retarded" certificate shall be on yellow paper; in which case the certificate shall show to what employment it is limited. sec. - . a record giving all the facts contained in every age and schooling certificate issued shall be kept on file in the office issuing the same; and also a record of the names and addresses of the children to whom certificates have been refused, together with the names of the schools and grades which such children should attend and the reasons for the refusals; and also a record of all certificates returned or no longer used, as provided in sections - , ( ), - or - , general code, with the reasons therefor, and the subsequent assignment of the child to a school, if any; and also a record of the conditions on which any certificates were issued, and there shall be kept on file also the pledges given in connection therewith; and also a record of the special facts connected with the issuing of "retarded" or limited certificates. the superintendent of public instruction shall have the power to prescribe methods of filing of all such facts, records and papers, for purposes of effective reference. the above-named record is nevertheless not required in the cases of certificates denied to those determined immediately at the time of inquiry to be of insufficient age. sec. - . the superintendent of schools may issue a vacation certificate to a boy or girl under eighteen years of age and over fourteen years of age which shall permit him to be employed within the restrictions of other statutes during the summer school vacation up to august th, in occupations not forbidden by sections , or - , general code, to children of his age and sex, regardless of what schooling he has completed, but before such certificate is issued the requirements prescribed in section - with relation to health, written pledge of employment, and proof of age must be complied with. such vacation certificate shall be printed on blue or blue-tinted paper and the word "vacation" shall be printed or stamped across its face; such certificate shall include a statement of the school and grade in which the child is enrolled. such certificates must be returned to the superintendent of schools by employers within the same period and under the same penalties as regular age and schooling certificates and may be revoked by the superintendent of schools at any time because of the physical condition of the child or other sufficient cause. if a child who desires a vacation age and schooling certificate secures only a limited health certificate the word "limited" shall be written or stamped across the face of the vacation certificate and the limited vacation certificate shall be on blue or blue-tinted paper; in which case the certificate shall show to what employment it is limited. sec. - . whenever the school record of a child as specified in section - , general code, is required for the purpose of determining his eligibility to an age and schooling certificate, such record shall be furnished by the superintendent, principal, teacher or other official in charge of the public, private or parochial school attended by the child within two days after a request for the same is made by the parent, guardian or custodian of the child. sec. - . whenever an age and schooling certificate is applied for by a child over sixteen years of age who is unable to satisfactorily pass a test for the completion of the work of the seventh grade and who is not so below the normal in mental development that he cannot with further schooling and due industry pass such a test, an age and schooling certificate with the words "conditional--schooling not standard" printed or stamped across its face may be issued by the superintendent of schools to such child upon proof acceptable to such superintendent of schools of the following facts and upon agreement to the respective conditions made in writing by the child and by the parent, guardian or custodian in charge of such child: (a) facts to be proved: that the child is addicted to no habit which is likely to detract from his reliability or effectiveness as a worker, or proper use of his earnings or leisure, or the probability of his faithfully carrying out the conditions to which he agrees as specified in (b) below, and in addition any one of the following groups of facts-- ( ) that the child has been a resident of the school district for the last two or more years, has diligently attended upon instruction at school for the last two years or more, and is able to read, write and perform the fundamental operations of arithmetic. these abilities shall be judged by the juvenile examiner or if there be none, by the superintendent of schools. ( ) that the child having been a resident of the school district less than two years, diligently attended upon instruction in school in the district or districts in which the child was a resident next preceding his residence in the present district for the last school year preceding his removal to the present district, and has diligently attended upon instruction in the schools of the present school district for the period that he has been a resident thereof. ( ) that the child has removed to the present school district since the beginning of the last annual school session, and that instruction adapted to his needs is not provided in the regular day schools in the school district. ( ) that the child is not sufficiently familiar with the english language to be properly instructed in the full-time day schools of the district. ( ) that the child is needed for the support or care of a parent or parents or for the support or care of brothers or sisters for whom the parents are unable to provide and that the child is desirous of working for the support or care of such parents or siblings and that such child cannot render such needed support or care by a reasonable effort outside of school hours. but no age and schooling certificate shall be granted to a child upon proof of the facts in the preceding sentence without written consent given to the superintendent of schools by the judge of the juvenile court and by the board of state charities. (b) conditions to be agreed to:-- ( ) in case the certificate is granted under facts ( ), ( ), ( ) or ( ) above, that until reaching the age of eighteen years the child will diligently attend in addition to part-time classes, such evening classes as will add to his education for literacy, citizenship or vocational preparation which may be made available to him in the school district and which he may be directed to attend by the superintendent of schools, or in case no such classes are available, that he will pursue such reading and study and report monthly thereon as may be directed by the superintendent of schools. ( ) in case the certificate is granted under fact ( ) above, that until the age of twenty-one years or until the person is eighteen years of age and has learned to read, write and speak the english language, the said person will attend in addition to part-time classes, such evening classes as will assist the person to learn the american language or advance in americanization which may be made available to him in the school district and which he may be directed to attend by the superintendent of schools. such conditional age and school certificate shall be printed on green paper. if a conditional age and schooling certificate is at the same time a limited certificate, the word "limited" shall be written or stamped diagonally across the face and the provisions of section - , general code, shall apply except as to the color of the certificate. sec. - . a special age and schooling certificate which shall permit a child to be employed during the hours that the school to which the holder is assigned is not in session, other than the summer vacation, or, where cooperative part-time classes approved by the state board of education have been established, shall permit a child to be employed on the alternate days, weeks, or periods, on which his division is assigned to such part-time employment may be issued to a child above fourteen years of age under all of the conditions other than age and education which apply to a regular age and schooling certificate and such additional conditions as the superintendent of schools may deem necessary. such special age and schooling certificate shall entitle such child to engage in occupations not forbidden to such children by section , or - , general code. provided, however, that said sections , and - , shall not be interpreted in such a way as to prevent any pupil from working on any properly guarded machine in the manual training department of any school when such work is performed under the personal supervision of an instructor. no child under sixteen years of age shall be engaged in school and employment above nine hours altogether in any one day. every special age and schooling certificate shall be limited and specific and shall be in such form as will show all essential facts, and the form thereof or directions for recording the facts thereon may be prescribed by the superintendent of public instruction. such certificate shall be printed on light brown paper. such certificate shall be returned to the superintendent of schools on or before the day that school adjourns for the summer vacation except when the co-operative part-time classes continue during the summer vacation. they shall be filed and returned by employers under the same conditions and penalties as apply to regular age and schooling certificates. (h.b. no. -- o.l., .) =creating the department of industrial relations.= sec. - . in order that the governor may exercise the supreme executive power of the state vested in him by the constitution and adequately perform his constitutional duty to see that the laws are faithfully executed, the administrative functions of the state are organized as provided in this chapter. all powers vested in and duties imposed upon the lieutenant governor, the secretary of state, the auditor of state, the treasurer of state and the attorney general by the constitution and the laws shall continue except as otherwise provided by this chapter. sec. - . as used in this chapter: "department" means the several departments of state administration enumerated in section - of the general code. "division" means a part of a department established as provided in section - of the general code, for the convenient performance of one or more of the functions committed to a department by this chapter. the phrase "departments, offices and institutions" includes every organized body, office and agency established by the constitution and laws of the state for the exercise of any function of the state government, and every institution or organization which receives any support from the state. sec. - . the following administrative departments are created: the department of industrial relations, which shall be administered by the director of industrial relations, hereby created; * * * * * the director of each department shall, subject to the provisions of this chapter, exercise the powers and perform the duties vested by law in such department. sec. - . each director whose office is created by section - of the general code shall be appointed by the governor by and with the advice and consent of the senate, and shall hold his office during the pleasure of the governor. sec. - . in each department there shall be an assistant director, who shall be designated by the director to fill one of the offices within such department, enumerated in section - of the general code, or as the head of one of the divisions created within such department as authorized by section - of the general code. when a vacancy occurs in the office of director of any department, the assistant director thereof shall act as director of the department until such vacancy is filled. sec. - . offices are created within the several departments as follows: * * * * * in the department of industrial relations chiefs of divisions as follows: factory inspection labor statistics mines * * * * * sec. - . the officers mentioned in sections - and - of the general code shall be appointed by the director of the department in which their offices are respectively created, and shall hold office during the pleasure of such director. sec. - . the officers mentioned in sections - and - of the general code shall be under the direction, supervision and control of the directors of their respective departments, and shall perform such duties as such directors shall prescribe. with the approval of the governor, the director of each department shall establish divisions within his department, and distribute the work of the department among such divisions. each officer created by section - of the general code shall be the head of such a division. with the approval of the governor, the director of each department shall have authority to consolidate any two or more of the offices created in his department by section - of the general code, or to reduce the number of or create new divisions therein. the director of each department may prescribe regulations, not inconsistent with law, for the government of his department, the conduct of its employes, the performance of its business and the custody, use and preservation of the records, papers, books, documents and property pertaining thereto. * * * * * sec. - . each officer whose office is created by sections - , - and - of the general code shall, before entering upon the duties of his office, take and subscribe an oath of office as provided by law and give bond, conditioned according to law, with security to be approved by the governor in such penal sum as shall be fixed by the governor, not less in any case than ten thousand dollars. such bond and oath shall be filed in the office of the secretary of state. the director of each department may, with the approval of the governor, require any chief of a division created under the authority of this chapter, or any officer or employe in his department, to give like bond in such amount as the governor may prescribe. the premium, if any, on any bond required or authorized by this section may be paid from the state treasury. sec. - . the director of each department may, with the approval of the governor, establish and appoint advisory boards to aid in the conduct of the work of his department or any division or divisions thereof. such advisory boards shall exercise no administrative function, and their members shall receive no compensation, but may receive their actual and necessary expenses. sec. - . each officer whose office is created by sections - , - and - of the general code shall devote his entire time to the duties of his office, and shall hold no other office or position of profit. in addition to his salary provided by law, each such officer and each member of the boards and commissions in the departments created by this chapter shall be entitled to his actual and necessary expenses incurred in the performance of his official duties. sec. - . each department shall maintain a central office in the city of columbus. the director of each department may, in his discretion and with the approval of the governor, establish and maintain, at places other than the seat of government, branch offices for the conduct of any one or more functions of his department. sec. - . each department shall adopt and keep an official seal, which shall have engraved thereon the coat of arms of the state as described in section thirty of the general. code, shall be one and three-fourths inches in diameter, and shall be surrounded by the proper name of the department, to which may be added the title of any division, board or commission within the department, if the director of the department shall so prescribe. such seal may be affixed to any writs and authentications of copies of records and official papers, and to such other instruments as may be authorized by law or prescribed by the proper authority in any department to be executed. when so authenticated, any copy of such record, official paper, or other instrument shall be received in evidence in any court in lieu of the original. each department shall provide for the keeping, within such department, of such records and journals as may be necessary to exhibit its official actions and proceedings. sec. - . each department is empowered to employ, subject to the civil service laws in force at the time the employment is made, the necessary employes, and, if the rate of compensation is not otherwise fixed by law, to fix their compensation. nothing in this chapter shall be construed to amend, modify or repeal the civil service laws of the state, except as herein expressly provided. all offices created by sections - and - of the general code shall be in the unclassified civil service of the state. sec. - . all employes in the several departments shall render not less than eight hours, of labor each day, saturday afternoons, sundays and days declared by law to be holidays excepted in cases in which, in the judgment of the director, the public service will not thereby be impaired. each employe in the several departments shall be entitled during each calendar year to fourteen days leave of absence with full pay. in special and meritorious cases where to limit the annual leave to fourteen days in any one calendar year would work peculiar hardship, it may, in the discretion of the of the department, be extended. no employe in the several departments, employed at a fixed compensation, shall be paid for any extra services, unless expressly authorized by law. sec. - . under the direction of the governor, the directors of departments shall devise a practical and working basis for cooperation and coordination of work and for the elimination of duplication and overlapping functions. they shall, so far as practicable, cooperate with each other in the employment of services and the use of quarters and equipment. the director of any department may empower or require an employe of another department, subject to the consent of the superior officer of the employe, to perform any duty which he might require of his own subordinates. sec. - . each department shall make and file a report of its transactions, and proceedings at the time and in the manner prescribed by section - of the general code. sec. - . whenever power is vested in any of the departments created by this chapter, or in any other state department, board or commission, to inspect, examine, secure data or information, or to procure assistance from another department, office or institution, a duty is hereby imposed upon the department, office or institution, upon which demand is made, whether created by this chapter or otherwise, to make such power effective. sec. - . whenever rights, powers or duties which have heretofore been vested in or exercised by any officer, board, commission, institution or department, or any deputy, inspector or subordinate officer thereof, are, by this chapter, transferred, either in whole or in part, to or vested in a department created by this chapter, or any other department, office or institution, such rights, powers and duties shall be vested in, and shall be exercised by the department, office or institution to which the same are hereby transferred, and not otherwise; and every act done in the exercise of such rights, powers and duties shall have the same legal effect as if done by the former officer, board, commission, institution or department, or any deputy, inspector, or subordinate officer thereof. every person, firm and corporation shall be subject to the same obligations and duties and shall have the same rights arising from the exercise of such rights, powers and duties as if such rights, powers and duties were exercised by the officer, board, commission, department or institution, or deputy, inspector or subordinate thereof, designated in the respective laws which are to be administered by departments created by this chapter. every person, firm and corporation shall be subject to the same penalty or penalties, civil or criminal, for failure to perform any such obligation or duty, or for doing a prohibited act, as if such obligation or duty arose from, or such act were prohibited in, the exercise of such right, power or duty by the officer, board, commission or institution, or deputy, inspector or subordinate thereof, designated in the respective laws which are to be administered by departments created by this chapter. every officer and employe shall, for any offense, be subject to the same penalty or penalties, civil or criminal, as are prescribed by existing law for the same offense by any officer or employe whose powers or duties devolve upon him under this chapter. * * * * * =department of industrial relations.= sec. - . the department of industrial relations shall have all powers and perform all duties vested by law in the industrial commission of ohio, excepting the following: those powers and duties of the commission which it exercises as successor of the state liability board of awards, the state board of arbitration, the board of boiler rules, and in the investigation, ascertainment and determination of standards, devices, safeguards, and means of protection, being all powers and duties mentioned in paragraphs to , both inclusive, of section - of the general code, sections - , - , - , - , - , - , - , - and - , sections - to - , both inclusive, - , to , both inclusive, and sections - to - , both inclusive, of the general code, and the powers of the commission as successor of the board of boiler rules under section - of the general code, which shall continue to be exercised and performed by the industrial commission of ohio in the manner provided by law for the exercise of such powers and the performance of such duties. the industrial commission of ohio shall be a part of the department of industrial relations for administrative purposes in the following respects: the director of industrial relations shall be ex-officio the secretary of said commission, shall succeed to and perform all of the duties of the secretary of said commission, and shall exercise all powers of said secretary as provided by law; but such director may designate any employe of the department as acting secretary to perform the duties and exercise the powers of secretary of the commission. all clerical, inspection and other agencies for the execution of the powers and duties vested in the said industrial commission shall be deemed to be in the department of industrial relations, and the employes thereof shall be deemed to be employes of said department and shall have and exercise all authority vested by law in the employes of such commission. but the industrial commission of ohio shall have direct supervision and control over, and power of appointment and removal of, such employes whose position shall be designated by the governor as fully subject to the authority of such commission. the commission may appoint advisers, who shall without compensation assist the commission in the execution of the powers and duties retained by it under this section. * * * * * sec. . the annual salaries of the appointive state officers and employes herein enumerated shall be as follows: * * * * * department of industrial relations: director of industrial relations, six thousand five hundred dollars. chief of division of factory inspection, three thousand six hundred dollars. chief of division of labor statistics, three thousand dollars. chief of division of mines, three thousand six hundred dollars. * * * * * section . said original sections , , , - , , , (enacted as section of an act entitled "an act to create the agricultural commission of ohio and to prescribe its organization", etc., approved may , , ( ohio laws )), , (enacted as section of an act entitled "an act to create a board of control for the ohio agricultural experiment station", etc., approved april , , ( ohio laws, )), , , (enacted as section of an act entitled "an act to create the agricultural commission of ohio and to prescribe its organization", etc., approved may , ( ohio laws, )), , (enacted as section of an act entitled "an act to create a board of control for ohio agricultural experiment station", etc., approved april , , ( ohio laws, )), , (enacted as section of an act entitled "an act to create the agricultural commission of ohio and to prescribe its organization", etc., approved may , , ( ohio laws, )), , (enacted as section of an act entitled "an act to create a board of control for the ohio agricultural experiment station", etc., approved april , , ( ohio laws, )), , , - , , , - , , , - as enacted by the act approved march , ( o.l. ), , and of the general code, and sections , , , , , , , , , , , , , , - , - , - , - , - , , - , - , - , - , - , - , - , - , , , , , , , , , , , , - , - , - , - , - , - , - , , , , , , , , - , - , - , , , , , , , , , , , , - , - , , , , - , , , , , , - , , , - , , , - , - , - , - , - , - , , , , - , - , - , - , , - , - , , , , , , , - , and of the general code are hereby repealed. section . every officer and employe in the classified civil service of the state civil service at the time this act takes effect shall be assigned to a position in the proper department created by this act, and, so far as possible, to duties equivalent to his former office or employment; and such officers and employes shall be employes of the state in the classified civil service of the state of the same standing, grade and privileges which they respectively had in the office, board, department, commission or institution from which they were transferred, subject, however, to existing and future civil service laws. this section shall not be construed to require the retention of more employes than are necessary to the proper performance of the functions of such departments. all books, records, papers, documents, property, real and personal, and pending business in any way pertaining to the rights, powers and duties by this act transferred to or vested in a department created by this act, or to or in any other office, department or institution, at the time this act takes effect shall be delivered and transferred to the department, office or institution succeeding to such rights, powers and duties. this act shall not affect any act done, ratified or affirmed, or any right accrued or established, or any pending action, prosecution or proceedings, civil or criminal, at the time it takes effect; nor shall this act effect causes of such action, prosecution or proceeding existing at the time it takes effect; but such actions, prosecutions or proceedings may be prosecuted and continued, or instituted and prosecuted, by or before the department having jurisdiction or power under this act of the subject matter to which such action, prosecution or proceeding pertains. if the senate is not in session at the time initial appointments are to be made under this act, the governor shall make temporary appointments as in case of a vacancy, to all offices required by this act to be filled by appointment by the governor by and with the advice and consent of the senate, unless the initial appointments are otherwise provided for in this act. if this act shall go into effect prior to the expiration of the present fiscal year, the present existing departments, bureaus, offices, boards, commissions, and other organizations of the state government affected by this act shall continue, and the officers and employes therein shall continue to serve until the expiration of the present fiscal year for which appropriations have been made, unless their terms of office expire prior thereto; and the reorganization herein provided for shall be put into effect and the officers whose positions are hereby created shall assume their duties at the commencement of the succeeding fiscal year. section . this act is hereby declared to be an emergency law necessary for the immediate preservation of the public peace, health and safety. the reasons for such necessity lie in facts, which two-thirds of all the members elected to each branch of the general assembly have considered, found and determined and which are separately set forth herein, as follows: the eighty-third general assembly created a joint legislative committee to "investigate all of the * * * offices which have been created by the general assembly * * * with a view of * * * combining and centralizing the duties of the various departments, eliminating such as are useless and securing for the state of ohio such a reorganization of its governmental activities as will promote greater efficiency and greater economy therein." said committee made exhaustive investigations and published numerous reports, declaring the necessity of reorganizing fundamentally the executive branch of the state government in order to promote efficiency and conserve the public funds. upon the organization of the eighty-fourth general assembly, special committees were appointed in each house thereof to consider the recommendations of the former joint committee. the governor, in his message to the general assembly, recommended action along the general lines indicated by the former committee's report. wide publicity has been given to various projected plans of reorganization. according to the annual reports of the auditor of state, the balances subject to draft in the general revenue fund of the state, from which many of the activities of the state government are supported, had shrunk from more than two million dollars on june th, , to less than one million dollars on june th, , (all of which, and more, was covered by unlapsed appropriations for the preceding fiscal year), clearly indicating the immediate necessity either for increasing the revenues of the state, or for effecting such a reorganization of the state administration as would tend to conserve the present revenues. general economic conditions make increased taxes highly undesirable at the present time. at the convening of the eighty-fourth general assembly numerous vacancies existed in various state offices and in various state boards, and other like vacancies have occurred since that time. by reason of the known probability of a reorganization such as is embodied in this act, persons appointed to fill such vacancies have uncertain tenure and are thereby deterred from initiating and carrying through definite administrative policies; and in several instances such appointments have been accepted temporarily only, pending early reorganization. as a result of all the foregoing, the state service in the appointive state departments, shown by said investigations to be wasteful and inefficient, is becoming increasingly demoralized. all of these departments exercise functions pertaining to the protection of the public health, the conservation of the public peace and morals, or the promotion of the public safety. the necessity of placing their functions upon a sound, economical, permanent and secure basis is great and immediate. the appropriations for the current expenses of the state government and institutions which must be made by the eighty-fourth general assembly for the fiscal biennium beginning july st, , cannot be effectually apportioned nor their amounts fixed unless the reorganization effected by this act is operative during the period to be covered by such appropriations, so that the departments and offices of the state government are definitely determined; and such determination must be made and the framework of the executive branch of the state government must be definitely established and known at the time the general assembly is considering such appropriations. therefore, this act shall go into immediate effect. passed april , . approved april , . rupert beetham, _speaker of the house of representatives_. clarence j. brown, _president of the senate_. harry l. davis, _governor_. filed in office of secretary of state, april , . ( o.l., .) =index.= index sections. =a.= abandoned mines--precautions when approaching accidents-- fatal--duty of inspectors fatal--notice to chief inspector and coroner fatal--coroner's duty superintendent's duty provisions for persons injured action in case of access to mines by inspectors acetylene gas in mines - penalty of - action for non-compliance with statutes act shall not create new office, etc. additional openings airway obstruction alternating current annual report of owner, lessee or agent to chief inspector appliances--safe - appointments-- chief inspector and qualifications district inspectors and qualifications - appropriation of land assistant mine-foreman-- duties of , , penalty for non-compliance attendant--rescue car automatic doors , , =b.= blasting blasting powder - boilers--location of bonds-- weighmaster board of examiners breakthroughs brattices =c.= cages-- safe appliances protection of, etc. lowering and hoisting, no. persons, etc. , caution board checkweighmen-- duties of penalty for non-compliance check-measurer-- duties of penalty for non-compliance child labor , , - - , circuit breakers closing of doors , , committee of miners-- report of - code of signals conveying of explosives construction of new mines copper tools coroner-- duties of penalty for non-compliance coal dust-- duty of owner, lessee or agent duty of miner combustible matter--removal of , complaint against chief and district inspectors - crossing public highway controversy or disagreement between district inspector and owner, lessee or agent =d.= damages caused by examination dangerous places fenced-- duty of owner, lessee or agent duty of superintendent and mine-foreman duty of miner danger signal , defraud--intent to department of industrial relations - detaching locomotive--traveling ways disagreement between district inspector and owner, lessee or agent district inspectors-- duties of district inspectors as sealers of weights and measures discretionary power of mining department doors , , drivers dust and fine coal-- duties of owner, lessee or agent duty of miner duties of assistant mine-foreman , , duties of chief and district inspectors , duties of chief and oil and gas well inspector relating to oil and gas wells duties of coroner duties of check-weighman duties of check-measurer duties of employes duties of fire-boss , , duties of machine-men duties of miners duties of mine-foreman , , duties of over-seer , duties of recorder - duties of superintendent duties of stableman duties of trip-riders and motormen , , duties of weighmaster (for penalties, see section .) =e.= egress when inundation is probable electricity-- application of - discretionary power of chief and district inspectors emergency appliances engineers employes--duties of - employment of minors examination of mine--damages caused by examination and survey of mine examination of working places-- duty of owner, lessee or agent duty of mine-foreman duty of fire-boss duty of miner when unsafe examination of other than working places examination of machinery, ventilating current examination of mine by fire-boss , , examination of mine--right of employes , examiners--board of - explosives - =f.= fatal accidents-- duty of inspectors notice to chief inspector and coroner coroner's duty superintendent's duty provisions for action in case of fire-boss--duties of , , fire in stable--must not be taken into fire protection fine coal or coal dust-- duty of owner, lessee or agent duty of miner fines collected =g.= gauges--pressure gasoline in mines =h.= haulage--rope , haulage trips--persons not permitted to ride hoisting and lowering of persons , , =i.= illuminating oil - illuminants - industrial relations department - injured persons--provisions for inundation , inexperienced miners injuries to mine intoxicants--prohibition of intent to defraud injury to persons or property--right of action =j.= justices of peace, etc. =l.= lamps--size of land--appropriation of lien on property for labor light in mines light or signal on locomotive and train loitering lowering and hoisting of persons , locomotives in mines , locomotives in mines--detaching =m.= maps-- duty of chief inspector duty of owner, lessee or agent addition to previous abandoned mine map persons entitled to examine machine men--duties of machine shields-- duty of owner, lessee or agent duty of machine men machinery--examination of miners--duties of mine-foreman--duties of , , miner--qualifications of miner--inexperienced minors employed , , - - , duty of inspectors duty of owner, lessee or agent duty of mine-foreman mines, new--construction of mine lamps mine committee report , motormen and trip riders--duties of , , monthly report of mine-foreman to chief inspector =n.= new mines--construction of new office--shall not create notice to chief inspector--when must be given notice to chief inspector and coroner of accidents non-compliance with statutes--action for =o.= office--shall not create new office--chief deputy oil-- illuminating , quantity allowed in mine oil lamp--size of oil and gas wells oil and gas wells--duty of chief oil and gas well inspector openings-- additional second over-seer--duties of , =p.= penalties-- acetylene - county coroner check-weighman check-measurer employes fire-boss foreman mine-foreman non-employes owner, lessee or agent over-seer oil and gas well companies oil manufacturers oil dealers oil (persons using illegal) superintendent stableman weighmaster persons injured--provision for persons on cage--number allowed , persons not permitted to ride haulage trips persons not employes--relating to powder - pressure gauges precautions approaching abandoned mines props--supplying of prosecutions =q.= quantity of hay allowed in mine quantity of oil allowed in mine quantity of gasoline allowed in mine quantity of powder allowed in mine qualifications of miner qualifications and appointment of chief inspector qualifications and appointment of district inspectors =r.= recorder's duty , records--who entitled to examine regulations of weighing coal - - repeals report of fire-boss , , report of owner, lessee or agent to chief inspector , report of district inspector to chief inspector right of action reorganization of state departments - report of mine committee , report of mine-foreman to chief inspector, monthly rescue apparatus rescue stations - refuge holes rope haulage , roof--miner shall prop, etc. =s.= safe appliances for hoisting persons safety appliances speaking tube safety lamps-- when owner shall provide oil for use in scales , second opening shafts--fire protection shields--machine-- duty of owner, lessee or agent duty of machine men signals-- code of locomotive danger , , persons designated to give and receive solid shooting - - speaking tube squibs stables--underground-- construction of fire must not be taken into stablemen--duties of superintendent's duties surveying party--transportation of survey of mine and examination switches =t.= tamping tools--kind permitted telephones - test weights timber-- duty of owner, lessee or agent duty of mine-foreman duty of miners trip riders and motormen--duties of , , traveling ways and refuge holes traveling ways--duty of employes transportation of surveying party trolley wires =u.= underground stables-- construction of fire must not be taken into stablemen--duties of voltage =v.= ventilation-- duty of owner, lessee or agent , , duty of mine-foreman , report of mine committee , voltage =w.= wash room - weigh scales , weighing of coal - - weighmaster--duties of weights and measures--sealers of withdrawal of persons from mine when act takes effect who entitled to examine maps, records, etc. wires working places--examination of-- duty of owner, lessee or agent duty of mine-foreman duty of fire-boss duty of miner trancriber's note text emphasis is displayed as _italic_ and =bold=. whole and fractional parts are displayed as - / . although in general, subscripts are denoted _{#}. the formulae for the minerals are presented as k oal o · sio (orthoclase) where the number following the element would normally be subscripted. the cambridge manuals of science and literature the natural history of clay cambridge university press london: fetter lane, e.c. c. f. clay, manager [illustration] edinburgh: , princes street london: william wesley and son, , essex street, strand berlin: a. asher and co. leipzig: f. a. brockhaus new york: g. p. putnam's sons bombay and calcutta: macmillan and co., ltd. _all rights reserved_ [illustration] the natural history of clay by alfred b. searle cantor lecturer on brickmaking, author of _british clays, shales and sands_; _the clayworker's handbook_, etc., etc. cambridge: at the university press new york: g. p. putnam's sons cambridge: printed by john clay, m.a. at the university press _with the exception of the coat of arms at the foot, the design on the title page is a reproduction of one used by the earliest known cambridge printer, john siberch, _ preface both as raw materials and in the form of pottery, bricks, tiles, terra-cotta and many other articles of use and ornament, clays are amongst the most important rock products. yet the origin of the substances we know as 'clay,' the processes occurring in its formation and the causes of some of the most important of its characteristics are of such a nature that it is remarkable that its use should have become so extended in the arts and sciences, while we know so little of its properties when in a pure state. in the following pages an attempt has been made to state in a simple form an outline of our present knowledge of the subject and to indicate the problems which still lie before us. the experimental solution of these problems is rendered peculiarly difficult by the inertness of the materials at ordinary temperatures and the ease with which the clay molecule appears to break down into its constituent oxides at temperatures approaching red heat or as soon as it begins to react with alkaline or basic materials. another serious difficulty is the highly complex nature of that property known as 'plasticity' to which many clays owe their chief value. for many years this has been regarded as an elementary property such as hardness, cohesion or colour, but it is now known to be of so elusive a nature as almost to defy measurement with any degree of accuracy. the thoroughness with which the methods of physical chemistry have been applied to geological and mineralogical problems during recent years has been of very great assistance to the student of clay problems, as will be seen on studying some of the works mentioned in the short bibliography at the end of the present volume. when the principles of hydrolysis, ionization, mass reaction and reactional velocity have been applied in still further detail to the study of clays, our knowledge of their natural history will increase even more rapidly than it has done during the past few years. no industry exercises so great a fascination over those engaged in it as do the various branches of clayworking; no other substance offers so many problems of such absorbing interest to the artist, the craftsman, the geologist, the chemist and the general student of nature, whilst the differences in legal opinion as to the nature of clay could themselves occupy a volume far larger than the present one. a. b. s. the white building, sheffield. _november ._ contents chap. page table of clay rocks viii i introduction. the chemical and physical properties of clays ii clay and associated rocks iii the origins of clays iv the modes of accumulation of clays v some clays of commercial importance vi clay-substance: theoretical and actual bibliography index list of illustrations fig. quartz crystals pyrite marcasite illustrating the structure of a 'clay crumb' chart showing rates of drying seger cones indicating a temperature of ° c. ludwig's chart coal measures sequence in north staffordshire lias clay being worked for the manufacture of hand-made sand-faced roofing tiles oxford clay near peterborough cliffs of boulder clay at filey lying on calcareous crag china clay pit belonging to the north cornwall china clay co. orthoclase felspar illustrating the successive deposition of different strata lacustrine clay at skipsea clay at nostel, showing marine band kaolinite and mica mining best potter's clay in devonshire the chief clay rocks (arranged geologically) +--------------------------------------------------------+ {|recent (_alluvial clay_, _silt_, _brick earths_, | {| _boulder clay_) | {|--------------------------------------------------------| tertiary {|pliocene } | {|miocene } (_brick earths_, _ball clays_, | {|oligocene } _coarse pottery clays_) | {|eocene } | |--------------------------------------------------------| {|cretaceous (_cement clays_, _brick clays_) | {|--------------------------------------------------------| secondary {|oolitic (_brick and tile clays_) | {|--------------------------------------------------------| {|triassic (_brick, tile and terra-cotta clays_) | |--------------------------------------------------------| {|permian (_brick, tile and flower-pot clays_) | {|--------------------------------------------------------| {|carboniferous (_brick clays_, _fireclays_, _ganister_) | {|--------------------------------------------------------| primary {|devonian } | {|silurian } | {|ordovician } (_clay schists, slates and clay shales_) | {|cambrian } | {|pre-cambrian } | |--------------------------------------------------------| |igneous rocks occur on several horizons (_china clays_ | | _and kaolins_) | +--------------------------------------------------------+ (in the above table only the clay-bearing strata are mentioned. the formations named consist chiefly of other rocks in which the clays form strata of variable thickness.) chapter i introduction. the chemical and physical properties of clay the chief uses of clay have been recognized since the earliest periods of civilization; the ancient assyrian and egyptian records contain numerous references to the employment of clay for the manufacture of bricks and for fulling or whitening cloth. clays are distributed so widely and in many cases are so readily accessible that their existence and some of their characteristics are known in entirely uncivilized regions. the use of certain white clays as a food, or at any rate as a means of staving off hunger, is common among some tribes of very primitive peoples. the more important uses of clays for building and other purposes are naturally confined to the more civilized nations. the term _clay_ (a.s. _cloeg_; welsh _clai_; dutch _kley_) although used in a scientific sense to include a variety of argillaceous earths (fr. _argile_ = clay) used in the manufacture of bricks, tiles, pottery and ceramic products (gr. _keramos_ = potter's earth) generally, is really a word of popular origin and use. consequently, it is necessary to bear in mind, when considering geological or other problems of a scientific nature, that this term has been incorporated into scientific terminology and that its use in this connection not infrequently leads to confusion. in short, whilst almost every dictionary includes one or more definitions of clay, and most text-books on geology, mineralogy, and allied sciences either attempt a definition or assume the reader's knowledge of one, there is no entirely satisfactory limitation in regard to the substances which may or may not be included under the term. _clay_ is a popular term for a variety of substances of very varied origins, of great dissimilarity in their composition and in many of their chemical and physical properties, and differing greatly in almost every conceivable respect. it is commonly supposed that all clays are plastic, but some of the purest china clays are almost devoid of this property and some of the most impure earths used for brickmaking possess it in a striking degree. shales, on the one hand--whilst clearly a variety of clay--are hard and rock-like, requiring to be reduced to powder and very thoroughly mixed with water before they become plastic; many impure surface deposits, on the other hand, are so highly plastic as to necessitate the addition of other (sandy) materials before they can be used for the manufacture of bricks and tiles. attempts have been made to include in the term clay 'all minerals capable of becoming plastic when moistened or mixed with a suitable quantity of water,' but this definition is so wide as to be almost impracticable, and leads to the inclusion of many substances which have no real connection with clays. the limitation of the use of the word 'clay' to the plastic or potentially plastic materials of any single geological epoch is also impracticable, for clays appear to have been deposited in almost every geological period, though there is some difference of opinion as to the time of the formation of certain clays known as _kaolins_. clay is not infrequently termed a _mineral_, but this does not apply at all accurately to the many varieties of earths known as 'common clays,' which, together with the 'boulder clays,' contain many minerals and so cannot, as a whole, be included under this term. whatever may be the legal significance of the term 'mineral'--which has an important economic bearing on account of minerals being taxed or 'reserved' in some instances where non-minerals (including brick clay) are exempt--there can be no doubt that, scientifically, clay is _not a mineral but a rock_. whatever mineral (if any) may give the chief characteristic property to the clays as a class must be designated by a special title, for the general term 'clay' will not serve for this purpose. geologically, the clays are sedimentary rocks, some being unaltered, whilst others--the slates--are notably metamorphosed and can seldom be used for the purposes for which clays are employed. most clays may be regarded as a mixture of quartz grains, undecomposed rock débris and various decomposition products of rocks; if the last-named consists chiefly of certain hydrous alumino-silicates, they may be termed 'clay substance' (see chapter vi. the imperfections of this statement as a definition are obvious when it is remembered that it may include a mixture of fine sand and clay containing only per cent. of the latter substance. it is, at the present time, quite impossible to construct an accurate definition of the term 'clay.' the most satisfactory hitherto published defines 'clay' as 'a solid rock composed mainly of hydro-alumino-silicates or alumino-silicic acids, but often containing large proportions of other materials; the whole possessing the property of becoming plastic when treated with water, and of hardening to a stone-like mass when heated to redness.' from what has already been written, it will be understood that there is no such entity as a standard clay, for the varieties are almost endless, and the differences between them are sometimes so slight as to be scarcely distinguishable. a further consideration of this branch of the subject may, however, conveniently be deferred to a subsequent chapter. the best-known clays are the surface clays, loams and marls, the shales and other sub-surface clays, and the pottery and china clays. the values of these different materials vary enormously, some being almost worthless whilst others are highly valued. the _surface clays_ are chiefly used for the manufacture of bricks and tiles (though some are quite unsuitable for this purpose) and form the soil employed in agriculture in many districts. the _sub-surface clays_ and _shales_ are harder, and usually require mechanical treatment before they can be used for brick and terra-cotta manufacture, or for the production of refractory and sanitary articles. the _pottery and china clays_ are usually more free from accessory constituents, and are regarded as the 'purest' clays on the market, though a considerable amount of latitude must be allowed in interpreting the term 'pure.' china clays are by no means pure in the state in which they occur, and require careful treatment before they can be sold. further information with regard to the characteristics of certain clays will be found in chapter v. the chemical properties of clay. the chief constituents of all clays are alumina and silica, the latter being always in excess of the former. these two oxides are, apparently, combined to form a hydro-alumino-silicate or alumino-silicic acid corresponding to the formula h al si o [ ], but many clays contain a much larger proportion of silica than is required to form this compound, and other alumino-silicates also occur in them in varying proportions (see chapters v and vi). all clays may, apparently, be regarded as consisting of a mixture of one or more hydrous alumino-silicates with free silica and other non-plastic minerals or rock granules, and their chemical properties are largely dependent on the nature and proportion of these accessory ingredients. the purest forms of clay (china clays and ball clays) approximate to the formula above-mentioned, but others differ widely from it, as will be seen from the analyses on p. . the chemical properties of pure clay are described more fully in chapter vi. [footnote : this formula is commonly written al o · sio · h o, but although this is a convenient arrangement, it must not be understood to mean that clays contain water in a state of combination similar to that in such substances as washing soda--na co · h o, or zinc sulphate crystals--znso · h o (see chapter vi).] taking china clay, which has been carefully purified by levigation, as representative of the composition of a 'pure' clay, it will be found that the chief impurities in clays are (_a_) stones, gravel and sand--removable by washing or sifting; (_b_) felspar, mica and other silicates and free silica--which cannot be completely removed without affecting the clay and (_c_) lime, magnesia, iron, potash and soda compounds, together with minute quantities of other oxides, all of which appear to be so closely connected with the clay as to be incapable of removal from it by any mechanical methods of purification. to give a detailed description of the effect of each of the impurities just referred to would necessitate a much larger volume than the present, but a few brief notes on the more important ones are essential to a further consideration of the natural history of clay. _stones_, _gravel_ and _sand_ are most noticeable in the boulder clays, but they occur in clays of most geological ages, though in very varying proportions. sometimes the stones are so large that they may be readily picked out by hand; in any case the stones, gravel and most of the sand may be removed by mixing the material with a sufficient quantity of water and passing the 'slip' through a fine sieve, or by allowing it to remain stationary for a few moments and then allowing the supernatant liquid to run off into a settling tank. some clays contain sand grains which are so fine that they cannot be removed in this manner and the clay must then be washed out by a stream of water with a velocity not exceeding ft. per hour. even then, the clay so removed may be found to contain minute grains of silt, much of which may be removed by a series of sedimentations for various periods, though a material perfectly free from non-plastic granules may be unattainable. most of the sand found associated with clays is in the form of fragments of _quartz_ crystals (fig. ), though it may be composed of irregular particles of other minerals or of amorphous silica. _felspar_, _mica_ and other adventitious silicates occur in many natural clays in so fine a state of division that their removal would be unremunerative. in addition to this they act as fluxes when the clays are heated in kilns, binding the less fusible particles together and forming a far stronger mass than would otherwise be produced. consequently, they are valuable constituents in clays used for the manufacture of articles in which strength or imperviousness is important. if these minerals are present in the form of particles which are sufficiently large to be removed by elutriation in the manner described on the previous page, the purification of the clay is not difficult. usually, however, the most careful treatment fails to remove all these minerals; their presence may then be detected by microscopical examination and by chemical analysis. for most of the purposes for which clays are used, small proportions of these silicates are unimportant, but where clays of a highly refractory nature are required; and for most of the purposes for which china clays (kaolins) are employed, they must not be present to the extent of more than per cent., smaller proportions being preferable. [illustration: fig. . quartz crystals, natural size. (from miers' mineralogy _by permission of macmillan & co._)] _oxides_, _sulphides_, _sulphates_ and _carbonates_ of various metals form the third class of impurities in clays. of these, the most important are calcium oxide (lime), calcium carbonate (chalk and limestone), calcium sulphate (gypsum and selenite), the corresponding magnesia, magnesium carbonate, and sulphate, the various iron oxides, ferrous carbonate and iron sulphides (pyrite and marcasite) (p. ). potash and soda compounds are commonly present as constituents of the felspar, mica, or other silicates present, and need no further description, though small proportions of _soluble salts_--chiefly sodium, potassium, calcium and magnesium sulphates--occur in most clays and may cause a white scum on bricks and terra-cotta made from them. _lime and magnesia compounds_ may occur as silicates (varieties of felspar, mica, etc.), but their most important occurrence is as chalk or limestone. _chalk_ is a constant constituent of malms[ ] and of many marls, but the latter may contain limestone particles. _limestone_ occurs in many marls and to a smaller extent in other clays. in the boulder clays it frequently forms a large portion of the stony material. if the grains are very small (as in chalk), the lime compounds act as a flux, reducing the heat-resisting power of the clay and increasing the amount of vitrification; they produce in extreme cases a slag-like mass when the clay is intensely heated. if, on the contrary, the grains are larger (as frequently occurs with limestone), they are converted into lime or magnesia when the clay is 'burned' in a kiln, and the lime, on exposure to weather, absorbs moisture (_i.e. slakes_), swells, and may disintegrate the articles made from the clay. limestone (except when in a very finely divided state) is almost invariably objectionable in clays, but chalk is frequently a valuable constituent. [footnote : a _malm_ is a natural mixture of clay and chalk (p. ).] chalk is added to clay in the manufacture of malm-bricks to produce a more pleasing colour than would be obtained from the clay alone, to reduce the shrinkage of the clay to convenient limits and, less frequently, to form a more vitrifiable material. chalk, on heating, combines with iron oxide and clay, forming a white silicate, so that some clays which would, alone, form a red brick, will, if mixed with chalk, form a white one. lime compounds have the serious objection of acting as very rapid and powerful fluxes, so that when clays containing them are heated sufficiently to start partial fusion, a very slight additional rise in temperature may easily reduce the whole to a shapeless, slag-like mass. magnesia compounds act much more slowly in this respect and so are less harmful. _gypsum_--a calcium sulphate--occurs naturally in many sub-surface clays, often in well-defined crystalline masses. it reduces the heat-resisting power of the clays containing it and may, under some conditions, rise to the surface of the articles made from the clay, in the form of a white efflorescence or scum, such as is seen on some brick walls. _iron compounds_ are highly important because they exercise a powerful influence on the colour of the burned clays. the red oxide (ferric oxide) is the most useful form in burned clay, but in the raw material ferrous oxide and ferrous carbonate may also occur, though they are converted into the red oxide on heating. the red iron oxide, which is closely related to 'iron rust,' occurs in so finely divided a state that its particles appear to be almost as small as those of the finest clays. hence attempts to improve the colour of terra-cotta and bricks by the addition of commercial 'iron oxide' are seldom satisfactory, the finest material obtainable being far coarser than that occurring in clays. it is a curious fact that red iron oxide does not appear to form any compound with the other constituents of clay under ordinary conditions of firing, and although a 'base' and capable of reducing the heat-resisting power of clays, it does not appear to do so as long as the conditions in the kiln are sufficiently oxidizing. it is this which enables red bricks and other articles to be obtained with remarkable uniformity of colour combined with great physical strength. in a reducing atmosphere, on the contrary, ferrous oxide readily forms and attacks the clay, forming a dark grey vitreous mass. if the iron particles are separated from each other they will, on reduction, form small slag-like spots, but if they are in an extremely fine state of division and well distributed, the brick or other article will become slightly glossy and of an uniform black-grey tint. the famous staffordshire 'blue' bricks owe their colour to this characteristic; they are not really 'blue' in colour. the effect of chalk on the colour of red-burning clays has already been mentioned. _iron pyrite_ (fig. ) and _marcasite_ (fig. )--both of which are forms of iron sulphide--occur in many clays, particularly those of the coal measures. _mundic_ is another form of pyrites which resembles roots or twigs, but when broken show a brassy fracture. when in pieces of observable size the pyrite may be readily distinguished by its resemblance to polished brass and the marcasite by its tin-white metallic lustre and both by their characteristic cubic, root-like and spherical forms; the latter only show a brass-like sheen when broken. even when only a small proportion of mundic, pyrite or marcasite is present, it is highly objectionable for several reasons. in the first place, half the sulphur present is given off at a dark red heat and is liable to cause troublesome defects on the goods. secondly, because the remaining sulphur and iron are not readily oxidized, so that there is a great tendency to form slag-spots of ferrous silicate, owing to the iron attacking the clay at the same moment as it parts with its remaining sulphur. for this reason, clays containing any iron sulphide seldom burn red, but form products of a buff colour with black spots scattered irregularly over their surface and throughout the mass--an appearance readily observable on most hard-fired firebricks. if chalcopyrite (copper-iron sulphide) is present the spots may be bright green in colour. [illustration: fig. . pyrite.] [illustration: fig. . marcasite.] slightly magnified. (_from miers'_ mineralogy _by permission of macmillan & co._) _carbon_, either free or as hydrocarbons (chiefly vegetable matter) or in other forms, is a constituent of most clays, though seldom reported in analyses. its presence exercises an important influence in several respects. on heating the clay, with an ample supply of air, the carbonaceous matter may distil off (as shale oil), but more usually it decomposes and burns out leaving pores in the material. if the air-supply is insufficient and the heating is so rapid and intense that vitrification commences before the carbon is all burned away, the pores become filled with the fused ingredients of the clay, air can no longer reach the carbon particles and a black 'core' or heart is produced. under peculiarly disadvantageous conditions the material may also swell greatly. this is a serious defect in many classes of clay used for brickmaking, and its causes and prevention have been exhaustively studied by orton and griffiths ( )[ ] but, beyond the brief summary given above, these are beyond the scope of the present work. _water_ is an essential constituent of all unburned clays, though the proportion in which it occurs varies within such wide limits that no definite standard can be stated. this water is found in two conditions: (_a_) as moisture or mechanically mixed with the clay particles and (_b_) in a state of chemical combination. [footnote : references to original papers, etc. will be found in the appendix.] analyses of typical clays _the samples were all dried at ° c._ +-------------------+--------+-------+---------+--------+-------+-------+ | clay | china | ball |fireclay | brick |boulder| marl | | | clay | clay | | clay | clay | | +-------------------+--------+-------+---------+--------+-------+-------+ | locality |cornwall| dorset|yorkshire|midlands| lancs.|suffolk| +-------------------+--------+-------+---------+--------+-------+-------+ |ultimate analysis: | | | | | | | | silica | · | · | · | · | · | · | | alumina | · | · | · | · | · | · | | ferric oxide | · | · | · | · | · | · | | titanium oxide | -- | · | · | · | · | -- | | lime | · | · | · | · | · | · | | magnesia | · | · | · | · | · | · | | potash and soda | · | · | · | · | · | · | | carbon | · | · | · | · | · | · | | water | · | · | · | · | · | · | | other matter | · | · | · | · | · | · | +-------------------+--------+-------+---------+--------+-------+-------+ | total | · | · | · | · | · | · | +-------------------+--------+-------+---------+--------+-------+-------+ |proximate analysis:| | | | | | | | gravel and sand | -- | · | · | · | · | · | | silt | -- | · | · | · | · | · | | felspar- and mica-| | | | | | | | dust | · | · | · | · | · | · | | silica-dust | · | · | · | · | · | · | | free calcium | | | | | | | | carbonate | -- | -- | -- | · | · | · | | free iron oxide | | | | | | | | and pyrites | · | · | · | · | · | · | | 'true clay' | · | · | · | · | · | · | +-------------------+--------+-------+---------+--------+-------+-------+ | total | · | · | · | · | · | · | +-------------------+--------+-------+---------+--------+-------+-------+ for other analyses the books in the bibliography at the end of the present volume should be consulted, particularly no. , _i.e._ _british clays, shales and sands_. the amount of mechanically mixed water will naturally vary with the conditions to which the clay has been subjected; it will be greatest in wet situations and will diminish as the clay is allowed to dry. the 'combined water,' on the contrary, appears to be a function of the true clay present in the material, and reaches its highest proportions in the china clays and kaolins, which contain approximately per cent. on heating a clay to ° c. the moisture or mechanically mixed water is evaporated, but the combined water remains unaffected[ ] until the temperature is raised to more than ° c., when it is driven off and the clay is converted into a hard stone-like mass with properties entirely different from those it previously possessed (see chapter vi). [footnote : strictly, there is a slight loss at lower temperatures, but it is too small to be important.] the physical characters of clays. the physical characters of clays are of far more interest and importance than their chemical ones, though the two are naturally connected in many ways, and just as the chemical composition of clays is a subject of extreme complexity so is a study of many of their physical properties. hence only a few of the more important characteristics can be mentioned here: for further details the reader must consult a larger treatise ( ). clays are moderately soft, solid bodies, particularly when moistened, and can usually be cut with a knife, though some indurated clays and shales are almost as hard as felspar. their apparent specific gravity varies greatly, some clays being much more porous than others, but the true specific gravity is usually between · and · ; it is similar to that of quartz and slightly lower than that of felspar and mica. many clays appear to be devoid of structure, but those obtained from a considerable depth below the surface are frequently laminated and have a structure not unlike that of mica. this will be discussed later. examined under a microscope, clays are seen to consist of grains of a variety of sizes, the largest of which will usually be found to be composed of adventitious materials such as sand, quartz, felspar, mica, chalk and limestone. the smallest particles--to which clays owe their chief characteristics--are so minute as to make any examination of their shape very difficult, but they are usually composed of minute crystalline plates together with a much larger proportion of apparently amorphous material. the exact nature of both the crystals and the amorphous material is still unknown in spite of many investigations; in the purer clays both forms of substance appear to have the same chemical composition, viz. that of _kaolinite_ (h al si o ), which the crystalline portion closely resembles. clays emit a characteristic yet indefinable odour when moist; the cause of this is very imperfectly understood, though it is not improbably due to decomposing organic matter, as this occurs in most clays. the colours of freshly-dug clays are extremely varied and range from an almost pure white through all shades of yellow, red and brown to black. the predominating colours are grey or greyish brown and a peculiar yellow characteristic of some surface clays. the natural colour of a clay is no criterion as to its purity, for some of the darkest ball clays produce perfectly white ware on burning, whilst some of the paler clays are useless to the potter on account of the intensity of their colour when they come out of the kiln. the colour of raw clays is largely due to the carbonaceous matter they contain, and as this burns away in the kiln, the final colour of the ware bears no relation whatever to that of the original clay. the colour of burned ware depends upon the iron compounds in the clay--these producing buff, red, brown or black (usually termed 'blue') articles--on the presence of finely divided calcium carbonate (chalk) which can destroy the colouring power of iron compounds and produce white ware, and on the treatment the clay has received in the kiln. a clay which is white when underfired will usually darken in colour if heated to vitrification, and one which burns red in an oxidizing atmosphere may turn blue-grey or black under reducing conditions. the extent to which the carbonaceous matter is burned out also determines the colour of the fired ware. the presence of adventitious minerals in the clay may also affect its colour, particularly when fired. the most obvious feature in a piece of moist clay is its _plasticity_[ ] or ability to alter its shape when kneaded or put under slight pressure and to retain its new shape after the pressure has been removed. it is this property which enables the production of ornaments, vessels of various kinds, and the many other articles which are the result of the application of modelling tools, of moulding or of the action of a potter's wheel. so long as clay contains a suitable proportion of moisture it is plastic and may be made into articles of any desired shape, but if the amount of moisture in it is reduced or removed completely, the material is no longer plastic. it may become so, however, on adding a further suitable quantity of water and mixing, provided that it has not been excessively heated. if, in the removal of the moisture, the clay has been heated to ° c. or more, it loses its power of becoming plastic and is converted into a material more closely resembling stone. [footnote : a plastic substance is one with the characteristics of 'a fluid of so great a viscosity that it does not lose its shape under the influence of gravitation.'] the causes of plasticity appear to be somewhat numerous, though there is no generally accepted explanation of this remarkable quality which distinguishes clays from most other substances. it is true that wet sand, soap, wax, lead and some other materials possess a certain amount of plasticity, but not to anything like the same extent as clay. so far as clays are concerned, their plasticity appears to be connected with the presence of combined water as well as of mechanically mixed water, for if either of these are removed, plasticity--both actual and potential--is destroyed. the part played by water is not, however, completely known, for the many theories which have been advanced only cover some of the conditions and facts. a number of observers agree that the molecular constitution of clay is peculiar and that it is to this that plasticity is due. yet the curious fact that the purest clays--the kaolins--are remarkably deficient in plasticity shows that molecular constitution is not, alone, sufficient. others hold that the remarkably small size of clay particles enables them to pack together more closely than do particles of other materials and to retain around them a film of water which acts partly as a lubricant, facilitating the change of shape of the mass when under pressure, and partly as an adhesive, causing the particles to adhere to each other when the pressure is removed. zschokke has laid much emphasis on the importance of molecular attraction between clay and water as a cause of plasticity, and has suggested that the absorption of the water effects a change in the surfaces of the clay particles, giving them a gelatinous nature and enabling them to change their form and yet keep in close contact. the fact that mica, fluorspar and quartz, when in a sufficiently finely divided state, are also slightly plastic, appears to be opposed to the molecular constitution theory. smallness of grain undoubtedly has an influence on the plasticity of clay, coarse-grained clays being notably less plastic than others. daubrée pointed out that felspar, when ground with water, develops plasticity to a small extent, and olschewsky carried this observation further and has suggested that clays owe their plasticity to prolonged contact with water during their removal from their place of formation and previous to or during their deposition. a further confirmation of this theory is due to mellor ( ) who showed that on heating china clay with water under very considerable pressure its plasticity was increased and that felspar and some other non-plastic materials developed plasticity under these conditions. johnson and blake ( ) supposed that plasticity is due to the clay being composed of extremely minute plates 'bunched together,' a view which was also held by biedermann and herzfield, le chatelier and others. olschewsky enlarged this theory by suggesting that the plasticity of certain clays is dependent on the large surface and the interlocking of irregular particles with the plates just mentioned. these theories of interlocking are, however, incomplete, because the tensile strength of clays should accurately represent the plasticity if interlocking were the sole cause. zschokke has shown that tensile strength is only one factor which must be determined in any attempt to measure plasticity. e. h. l. schwarz ( ) has suggested that many clays are composed of small globular masses of plates so arranged as to form an open network (fig. ) which is sufficiently strong not to be destroyed by pressure. in the presence of water and much rubbing the plates are separated and are made to lie flat on each other, thereby giving a plastic and impermeable mass. if this is really the case it would explain the porosity and large surface of some clays and might account for their adsorptive power. [illustration: fig. . illustrating the structure of a 'clay crumb.' (_after schwarz._)] a theory which was first promulgated in by way ( ), but which has only received detailed attention during the last few years, attributes plasticity to the presence of colloid substances in clay or to the fact that clay particles possess physical characters analogous to those of glue and other colloids. these colloid substances have a submicroscopic or micellian structure; they are web-like, porous and absorb water eagerly. this water may be removed by drying, only to be re-absorbed on cooling, but if the heating temperature is excessive the structure of the colloids is destroyed. this colloid theory explains many of the facts noted by earlier investigators such as aron, bischof, seger, olschewsky, etc., but it is not entirely satisfactory, though rohland ( )--to whom the present prominence of this theory in europe is largely due--persistently maintains the contrary. one great objection is the fact that no characteristic _inorganic_ colloid substance has been isolated from pure clay. it is possible that some of the so-called 'colloidal' properties of clay may be due to the smallness of its particles and to their great porosity, as suggested by olschewsky. despite the present impossibility of producing a plastic material from artificially prepared colloidal hydro-alumino-silicates of the same ultimate composition as clay, and the fact that the addition of colloidal substances does not necessarily increase the true plasticity of clay, it cannot be denied that the presence of colloids has an important influence on it. the addition of starches, glue, gums and similar substances whilst apparently increasing the plasticity of clay does not do so in reality. the addition of per cent. of tannin, on the contrary, has been found by ries ( ) to increase both plasticity and binding power. plasticity appears to be composed of a number of characteristics so that it is scarcely likely that any single cause can be assigned to it. on the contrary, a study of the binding power, tensile strength, extensibility, adsorption, texture and molecular constitution of clays suggests very strongly that all these properties are involved in the production of plasticity and that it is due to the chemical as well as the physical nature of clay. no clay is entirely colloidal--or it would be elastic and not plastic--but all appear to contain both colloidal and non-colloidal (including plate-like) particles, and it is not improbable that materials in both these states are required, the colloidal matter acting as a cement. ries ( ) has, in fact, pointed out that colloids alone lack cohesiveness and solidity, and a fine mineral aggregate is necessary to change them into a plastic mass resembling clay. the relative proportions of the colloidal material and the sizes of the non-plastic grains will exercise an important influence on all the physical characteristics mentioned above, and therefore on the plasticity. the manner in which slightly plastic clays become highly plastic in nature is by no means certainly known. it has long been understood that the increase of plasticity is due to changes undergone by the clay during transportation. the most illuminating suggestion is that made by acheson in , who concluded that it is due to impurities in the water used in transporting the clay or remaining in contact with it during and after its deposition. these impurities may be considered as derived from the washings of forests, and after many experiments with plant extracts acheson believed the most important substance in this connection to be tannin or gallo-tannic acid, a dilute solution of which he found increased the plasticity of china clay by per cent. from this he further argued that the use of chopped straw by the israelites in egypt in the manufacture of bricks was unconsciously based on the tannin content of the straw increasing the plasticity of the material. [illustration: fig. . chart showing rates of drying. (_after bleininger._)] beadle has stated that per cent. of dissolved cellulose will increase the plasticity of china clay and make it equal to that of ordinary clay. plasticity is diminished by heating clays, and whilst much of it may be recovered if the temperature has not risen above ° c. it cannot be completely restored. moreover, a clay which has once been heated to a temperature above ° c. dries in a somewhat different manner to a raw clay. this is well shown in fig. in which are summarized the results obtained by a. v. bleininger on a sample of ball clay from dorset before heating and after portions of it had been heated for hours to °, °, °, ° and ° c. respectively. it is not impossible that if subjected to the influence of water for a sufficiently long time the whole of the plasticity of a heated clay may be restored, providing that the temperature has not been sufficient to cause a destruction of the clay molecule, but as this resumption requires a certain amount of time, bleininger has proposed to use the reduction in plasticity effected by the heating to enable excessively plastic clays to be worked without the necessity of adding non-plastic material to them. if any destruction of the clay-molecules has occurred, the plasticity of that portion of the clay can never be restored. the _binding power_ of clays is a characteristic closely connected with plasticity and occasionally confused with it. all plastic clays have the power of remaining plastic when mixed with materials such as sand, brick-dust ('grog') and other materials which are quite devoid of plasticity. the extent to which a clay can thus bind other materials together into a plastic mass depends, apparently, on the plasticity of the clay itself and on the size and nature of the particles of the added material; the more plastic the clay the larger will be the amount of material it can thus 'bind,' and the finer the latter the more easily will it form a strong material when mixed with a plastic clay. rohland ( ) has shown that the binding power of clay is not alone due to its cohesion, but that it is closely associated with the colloidal nature of plastic clays: 'fat' clays being those which are highly colloidal, highly plastic and possessing great binding power, whilst 'lean' clays are those deficient in these characteristics. the fact that, as a general rule, the dark coloured clays possess the most binding power, confirms this suggestion, as the dark colour is largely due to organic materials, probably in a colloidal state. the _shrinkage_ which all clays undergo on drying and when heated is another important characteristic. it is due to the fact that as water is removed the solid particles approach closer to each other, the volume of the whole mass being thereby reduced. in a wet piece of clay each particle is surrounded by a film of water, the thickness of which depends on the nature of the clay. as this water evaporates from the surface of the clay its place is taken by water from the interior which rises to the surface by capillary attraction. so long as there is any water between the particles of clay there will be shrinkage when this water is removed, but a stage is eventually reached when the particles of clay are in contact with each other and no more shrinkage can occur. that this cessation of shrinkage may take place before all the water has been removed from the clay is easily understood when it is remembered that whilst the clay particles may be in contact, yet there are still places (pores) where the contact is incomplete, and in these pores water may be retained. the amount of shrinkage clays undergo on drying depends partly on the proportion of water added to them and partly on the sizes of the different particles of clay, sand, etc. present. an average reduction in volume of to per cent. may be regarded as normal, but coarse loams may shrink only per cent. and very finely ground, highly plastic ball clays may shrink as much as per cent., though this is unusual. as all coagulated colloids, which have absorbed water, shrink on drying, this behaviour of clay appears to confirm the view as to its partially colloidal nature held by some investigators. when a piece of dry clay is heated sufficiently a further shrinkage (technically known as _kiln shrinkage_) occurs. this begins somewhat below a red heat and increases in rough proportion to the temperature and the duration of the heating. prolonged heating at a lower temperature will effect the same amount of shrinkage as a short exposure to a higher temperature, but though the greater part of the shrinkage occurs in a comparatively short time, continued heating will be accompanied by a further reduction in volume. this is due to the fact that clays have no definite melting point, but undergo partial fusion at all temperatures above ° c. or, in some cases, at even lower ones. as a portion of the material fuses, it fills up the pores in the mass and attacks the unfused material, this process being continued until either the heating is stopped or the whole material is reduced to a viscous slag. the reduction in the volume of commercial articles made of clay and placed in kilns varies greatly. with bricks, terra-cotta and pottery it must not, usually, exceed per cent. or the warping and cracking which occur will be so great as to make the articles useless. the fineness of the particles exercises an important influence on the kiln shrinkage of a clay, and the latter is frequently reduced in commercial clayworking by adding burned clay ground to a coarse powder to the plastic clay before it is used. sand is sometimes added for the same purpose, though its more frequent use is to reduce the shrinkage in drying. quartz and other forms of free silica expand on heating, so that clays containing them in large quantities shrink very slightly or may even expand. as clays shrink equally in all directions it is usual to state the contraction in linear instead of volume form. thus instead of stating that a certain clay when moulded into bricks, dried and burned, shrinks per cent. by volume, it is customary to state that it shrinks / in. per (linear) foot. for many purposes, it is sufficient to regard the linear shrinkage as one-third the volume-shrinkage, but this is not strictly accurate. the _fusibility_ of clays is a characteristic which has been very imperfectly studied. most clayworkers and investigators employ the term 'fusibility' in a special sense which is apt to be misleading. owing to the extremely high temperatures to which refractory clays can be heated without even losing their shape, it is almost impossible to fuse them completely. in addition to this, clays are not perfectly homogeneous materials and some of their constituents melt at lower temperatures than others. for this reason a clay may show signs of fusion at ° c., but it may be heated for some hours at ° c. and yet not be completely melted! consequently no single 'fusing point' can be stated. in practice, a suggestion made many years ago by seger ( ) is used; the clay to be tested is made into a small tetrahedron (fig. ), heated slowly until it bends over and the point of the test-piece is almost on a level with the base. the temperature at which this occurs is termed the 'fusing point' though it really only indicates the heat-treatment which is sufficient to soften the material sufficiently to cause it to bend in the manner described. in spite of the apparent crudeness of the test this 'softening point' appears to be fairly constant for most refractory clays. the bending of a test-piece in this manner is the result of the action of all fluxes[ ] in the clay, and as this depends on the size of grain and the duration of the heating above incipient fusion and does not give a direct measure of temperature, nor is the softening effect under one rate of rise in temperature the same as that at another rate. nevertheless a study of the behaviour of various clays heated simultaneously is valuable and the method forms a convenient means of comparing different materials. [footnote : for fluxing materials see p. .] the temperature may be measured by means of a pyrometer, but for the reason just stated it is more convenient and in some respects more accurate to use standard mixtures known as seger cones (fig. ), and to state the softening point in terms of the 'cone' which behaves like the clay being tested. a medium fireclay will not soften below seger cone ( ° c.) and a really good one will have a softening point of cone or ( ° to ° c.). [illustration: fig. . seger cones indicating a temperature of ° c.] the _refractoriness_ of a clay, or its resistance to high temperatures, is an important requirement in bricks required for furnace linings, in crucibles, gas retorts and other articles used in the metallurgical and other industries. the term is much abused and is frequently understood to mean resistance to the cutting action of flue gases and flame, the corrosive action of slags, and the strains set up by the repeated changes in temperature. this is unfortunate, for the term refractoriness has a perfectly definite meaning and should be employed exclusively to denote that a given clay is capable of retaining its shape at a given temperature or under given conditions when heated alone and without being subjected to any pressure. in great britain there is no officially recognized standard of minimum refractoriness[ ], but where one is required the suggested minimum of seger cone ( ° c.) made by e. cramer ( ) is usually employed. this is the recognized minimum in germany for fireclays, and though objections may be urged against the use of seger cones as a standard, equally forcible ones may be brought against making a temperature-scale the basis of measurement. under present circumstances, however, it is necessary to adopt one or other of these. [footnote : see _refractory clays_, chapter v.] various attempts have been made to ascertain the relationship (if any) between the refractoriness of clays and their chemical composition. if attention is confined strictly to the more refractory clays, some kind of relationship does appear to exist. thus richter found that the refractoriness of clay is influenced by certain oxides in the following order: magnesia, lime, ferrous oxide, soda and potash, but this only applies to clays containing less than per cent. of all these oxides. cramer, in , found that free silica also interfered with the action of these oxides and more recently ludwig ( ) has devised a chart (fig. ), on the upright sides of which are plotted the equivalents of the lime, magnesia and alkalies, whilst the silica equivalents are plotted on the horizontal base. in each case the 'molecular formula' of the clay is calculated from its percentage composition, and this 'formula' is reduced so as to have one 'molecule' of alumina, thereby fixing the alumina as a constant and reducing the number of variables to two--the metallic oxides and the silica. unfortunately ludwig's chart is only applicable to the more refractory clays and cannot be relied upon even for these, though it is extremely useful for comparing clays from identical or similar geological formations. [illustration: fig. . ludwig's chart.] attempts to express the refractoriness of clays by means of formulae proving abortive, there only remains the direct test of heating a clay under definite conditions in the manner previously described. _vitrification_ is closely connected with the fusibility and refractoriness of clays, and, as a term, indicates the amount of fusion which has occurred under certain conditions of heating. as already mentioned, all clays, on being subjected to a high temperature, undergo partial fusion, the more powerful bases attacking the finest particles of clay and silica, forming molten silicates, and then slowly attacking the more refractory portion; this slow fusion and solution continues until the whole of the material is melted. if the heating is stopped before the fusion has begun, the clay will be porous and comparatively soft, but as more and more material fuses, the mass (on cooling) becomes harder and less porous, as the fused material occupies the pores and sets to a dense, firm glassy mass. the amount of vitrification, or partial fusion, which occurs is, therefore, of great importance in some industries, as by stopping it at an appropriate stage articles of any desired degree of porosity, translucency or strength may be obtained. thus for common bricks, only sufficient vitrification is permitted to bind the particles firmly together, but in engineering bricks--where much greater strength is required--the vitrification is more complete. porcelain and earthenware may be similarly distinguished. the extent to which a given clay will vitrify depends on the amount of fluxing material (metallic compounds, and oxides other than ferric oxide and alumina) it contains, on the smallness of its particles and on the duration and intensity of the heating. clays containing alkalies and lime compounds vitrify with great rapidity when once the necessary temperature has been reached, so that unless great care is exercised the action will proceed too far and the goods will be warped and twisted or may even form a rough slag. refractory clays, on the contrary, vitrify more slowly and at much higher temperatures so that accidental overheatings of them are far less common. the difference between the temperature at which sintering or vitrification occurs and that at which the clay melts completely--usually termed the 'vitrification range'--varies with the nature of the clay. in some cases the clay melts as soon as vitrification becomes noticeable, in others the vitrification occurs at a dull red heat, but the material does not lose its shape until after a prolonged heating at the highest temperature of a firebrick kiln or testing furnace. calcareous clays have the melting and sintering points close together, so that it is almost impossible to produce vitrified and impervious ware from them, as they lose their shape too readily. if, however, the difference between the sintering and fusing temperatures can be enlarged--that is, if the vitrification range can be extended--more impervious ware can be made. the easiest means of extending the vitrification range consists in regulating the proportion of large and small particles. the former increase and the latter diminish the range. basic compounds and fluxes cause a lowering of the melting-point and a shortening of the vitrification range. the _porosity_ of raw clay is usually of small importance, but the porosity of fired clay or ware is often a serious factor in determining the suitability of certain articles for their intended purposes. in its natural state, clay does not readily absorb much water; on the contrary it becomes pasty and impervious unless it is disturbed and its texture destroyed, when it may be mixed with water to form a paste or, with more water, a thin 'cream' or 'slurry.' when heated moderately, clay forms a porous material and, unless the heating is excessive, it will absorb about one-eighth of its weight of water. further heating at a higher temperature reduces its porosity--the more easily fused material filling some of the pores--until a stage is reached when the material is completely vitrified and is no longer porous. porosity may thus be regarded as the opposite of vitrification; porous goods being relatively light and soft whilst vitrified ones are dense and hard. for some purposes, porosity is an important characteristic: for example, building bricks which are moderately porous are preferable to those which are vitrified. the manufacture of porous blocks for the construction of light, sound-proof partitions, etc. has increased rapidly of late. they are made by adding sawdust or other combustible material to the clay. the added substances burn out on firing the goods in a kiln. clays which are porous can be dried more readily and with less risk of cracking than those which are more dense. for this reason, some clayworkers mix non-plastic material such as sand or burned clay with their raw material. the _impermeability_ of plastic clay to water is a characteristic which is important for many purposes. the _absorptive power_ of clays is closely related to their porosity so far as pure water is concerned, but if the water contains certain salts in solution a selective absorption occurs, the bases being retained by the clay in such a manner that they cannot be removed by washing. the selective action is known as _adsorption_ and is most noticeable in highly plastic clays. bourry ( ) has shown that the slightly plastic china clays only exercise a small power of adsorbing calcium carbonate from solution, but highly plastic clays may adsorb per cent. of it. the alkaline chlorides and sulphates do not appear to be adsorbed in this manner, but the carbonates are readily removed from solution. all calcium and magnesium compounds appear to be adsorbed, though in variable quantities, the reaction being complicated when several soluble salts are present. ries ( ) has found that gallo-tannic acid is adsorbed readily and increases the plasticity of clay. ashley ( ) has endeavoured to measure the plasticity of clays by determining their adsorption capacity for various aniline dyes, but his untimely decease prevented the investigation being completed. there is reason to suppose that the relation between adsorption and plasticity is extremely close in many clays and that the former may, to an important extent, be used as a measure of the latter. in some clays, however, this relationship does not exist. sand and burned clay only show faint adsorption phenomena; felspar shows them to a slight and almost negligible extent and most of the other non-plastic ingredients of clays are non-adsorptive. selective adsorption being an important characteristic of colloidal substances, the possession of this power by plastic clays supports the claim that plasticity is due, at least in part, to the presence of colloids. the addition of small quantities of a solution of certain substances to a stiff clay paste usually reduces its stiffness, and in some cases turns it into a liquid. the alkalies are particularly powerful in this respect and their action may be strikingly illustrated by mixing a few drops of caustic soda with a stiff clay paste. in a few moments the mixture will be sufficiently liquid to pour readily, but it may be rendered quite stiff again by adding sufficient acid to neutralize the alkali previously used. weber ( ) has utilized this characteristic to great advantage in the production of sanitary ware and crucibles for glass-making by a process of casting which he has patented. the effect of adding water to a dry clay is curious. at first the particles in contact with the water become sticky and plastic, and if the proportion of water added is suitable and the mixing is sufficiently thorough a plastic mass will be produced, the characteristics of which will depend on the nature of the clay used. this process of mixing clay with a limited amount of water is known as 'tempering.' the proportion of water required to make a paste of suitable consistency for modelling appears to be constant for each clay. if, however, a larger proportion of water is added the particles of clay will be separated so widely from each other that they lose their cohesion, and instead of a plastic mass, the material will form a liquid of cream-like consistency. if a piece of stiff clay paste is suspended in a large volume of water without stirring, disintegration will still occur (though a much longer time will be required) and the clay will be deposited as a sediment at the bottom of the vessel. the leaner the clay or the larger the proportion of non-plastic material it contains, the more rapidly will this disintegration take place. a highly plastic clay will become almost impervious and will retain its shape indefinitely. if a mixture of clay and water in the form of a cream or slurry be allowed to rest, the larger and less plastic particles will settle, but many of the particles of true clay will remain suspended for several hours and some of them for several days. some particles of clay are so small that it is doubtful if they would ever settle completely unless some coagulant were added, and as they readily pass through all ordinary filtering media it is extremely difficult to collect them in a pure state. these turbid suspensions of clay may be rapidly cleared by the addition of sodium chloride which increases the surface tension of the solution. the fine particles behave in the same way as colloidal substances, _i.e._ as if they possessed an electrostatic charge. hence the addition of a salt (electrolyte), whose ions annul the opposite charges of the electric double layer assumed by helmholtz to be present, enables the particles to coagulate in accordance with the ordinary laws of surface tension ( ). _exposure_ to the action of air and frost has a marked effect on many clays. when freshly dug these may be hard and difficult to crush, but after exposure they break up readily into small fragments. clays differ greatly in the extent to which they are affected by exposure; some are completely disintegrated by standing hours in the open air, whilst others are scarcely affected by exposure in bleak places through several years of storm, sunshine and frost. usually, however, the effect of a couple of nights exposure to hard frost will produce a marked disintegration of the material. this process of exposure is known as 'weathering' and its effects are so important that it is employed whenever possible for clays requiring to be crushed before use. all clays are rendered more workable by exposure, but some of them are damaged by the oxidation of some impurities (_e.g._ pyrites) in them, though in other clays this very oxidation, if followed by the leaching action of rain, effects an important purification of the material. weathering appears to have no effect on the chemical composition of the particles of true clay in the material, though it may decompose the impurities present. on the clay itself its action is largely physical and consists chiefly in separating the particles slightly from each other, thereby enabling water to penetrate the material more readily and facilitating the production of a plastic paste. the disintegrating action of the weather on some 'clays' is so complete that they require no crushing but can be converted into a homogeneous paste by simply kneading them with a suitable proportion of water. it is possible that on exposure to the heat of the sun's rays--particularly in tropical climates--some chemical decomposition of the clay may occur, but compared with the purely physical action of weathering the amount of such chemical decomposition must be relatively unimportant in most cases. it may, however, account for the presence of free silica and free alumina in some clays. the action of the weather on rocks, resulting in the formation of clays, is described in chapter iii. _heat_ effects remarkable changes in the physical character of clays; the most important of these have already been noted. at a gentle heat, the clay is dried and retains most of its power of becoming plastic when moistened; very little, if any, decomposition occurs. at a higher temperature it loses its 'combined water,' the clay molecule apparently dissociating, and a hard stony mass--consisting of particles of free silica and free alumina cemented together by the more easily fusible impurities present--is formed. if the heating is continued the hardness of the material is increased owing to more molten silicate having been produced from the impurities present, and on cooling, its tensile strength and resistance to crushing will be found to be enormously greater than those of the original clay. all potential plasticity is destroyed by heating to ° c. and no method of restoring it has yet been devised. as clays are abundant, this is not a serious disadvantage for the specially desired characteristics of bricks, terra-cotta, pottery and porcelain are all such as to be incompatible with plasticity. the latter is extremely valuable in the shaping of the wares mentioned, but after the manufacture is completed, the destruction of the plasticity is an essential feature of their usefulness. if the heating is very prolonged or is repeated several times, clays change other of their physical characters and become brittle and liable to crack under sudden changes of temperature. this is partly due to the further fusion (vitrification) which occurs and partly to the formation of crystalline silicates, notably _sillimanite_ ( ). the extent to which clays are ordinarily heated and the conditions under which they are cooled do not usually induce the formation of crystals; the object of the clayworker being to produce a homogeneous mass, the particles of which are securely held together. the result is that burned clay products are usually composed of amorphous particles cemented by a glass-like material formed by the fusion of some of the mineral ingredients of the original substance. the silicates formed are, therefore, in a condition of solid, super-cooled solution in which the tendency to crystallize is restrained by viscosity. on raising the temperature of firing or on prolonging the heating at the previous maximum temperature the viscosity of the fused portion is diminished and crystallization may then occur. the facility with which crystallization occurs varies greatly with the composition of the fused material, those silicates which are rich in lime and magnesia crystallizing more readily than those containing potash or soda. vogt has stated that small quantities of alumina promote the formation of a glassy structure, and morozewicz has shown that a large excess of this substance must be present if crystallization is to occur. the study of the reactions which occur when clays are heated is, however, extremely complex, not only on account of the variety of substances present, but also on account of the high temperatures at which it is necessary to work, so that for a further consideration of it the reader should consult special treatises on the fusion of silicates. this subject has now become an important branch of physical chemistry. chapter ii clay and associated rocks clay, as already mentioned, is geologically a rock and not a mineral, and belongs to the important group of sedimentary rocks which have been derived from the igneous or primary ones by processes of weathering, suspension in water and subsequent deposition or sedimentation. whatever may be the primary origin of clay, its chief occurrence is in geological formations which have undoubtedly been formed by aqueous action. the materials resulting from the exposure of primary rocks to the action of the elements have been carried away by water--often for long distances--and after undergoing various purifications have been deposited where the speed of the water has been sufficiently reduced. in some cases they have again been transported and re-deposited and not infrequently clay deposits are found which show signs of subsequent immersion at considerable depths and have every appearance of having been subjected to enormous pressures and possibly to high temperatures. some clays have only been carried by small streams and for short distances; these are seldom highly plastic and resemble the lean china clays and kaolins. others have been carried by rapidly moving rivers and have been discharged into lakes or into the sea; they have thus undergone a process of gradual purification by elutriation, the sand and other heavier particles being first deposited and the far smaller particles of clay being carried a greater distance towards the centre of the lake or the quieter portions of the ocean. the nature of such deposits will, naturally, differ greatly from each other, the materials at first associated with the clay, or becoming mixed with it at a later stage, exercising an important influence on its texture, composition and properties. if the transporting stream flows through valleys whose sides are formed of limestone, chalk, sandstone or other materials, these will become mixed with the clay, and to so great an extent has the mixing occurred that very few clays occur in a state even approximating to purity. the majority of clays are contaminated with iron oxide, lime compounds and free silica in such a fine state of division that it is impossible to purify them completely without destroying the nature of the clay. in addition to this it must be remembered that the land is continually rising or sinking owing to internal changes in the interior of the earth, and that these subterranean changes bring about tilting, folding, overturning and other secondary changes, which, later, cause a fresh set of materials to be mixed with the clays. further than this, the action of the weather, of rivers and of the sea never ceases, so that a process of re-mixing and re-sorting of materials is continuously taking place, and has been doing so for countless ages. it is, therefore, a legitimate cause for wonder that such enormous deposits of clays of so uniform a character should occur throughout the length and breadth of europe, and practically throughout the world. for although the composition of many of these beds is of a most highly complex nature, the general properties such as plasticity, behaviour on heating, etc., remain remarkably constant over large areas of country, and the clays of each geological formation are so much alike in different parts of the world as to be readily recognized by anyone familiar with the material of the same formations in this country. considerable differences undoubtedly exist, but these are insignificant in comparison with the vastly different circumstances under which the deposits were accumulated. leaving the consideration of the modes of formation of the various clay deposits to later chapters (iii and iv), it is convenient here to enumerate some of the chief characteristics of the different clay deposits and their associated rocks. in this connection it is not proposed to enter into minute details, but rather to indicate in broad outline the chief characteristics of the clays from the different deposits. this general view is the more necessary as clay occurs in each main geological division of the sedimentary rocks and in almost every sub-division in various parts of the world. the =precambrian, cambrian, silurian and devonian= 'clays' are chiefly in the form of shales or slates, the latter being clays which have undergone a metamorphic change; the latter resulted in the production of a hard and partially crystalline material with but little potential plasticity and therefore of small importance for the ordinary purposes of clay working. _slates_ are distinguished from shales by their splitting into thin leaves which are not in the plane of original deposition, but are due to the deposited material being subjected to great lateral pressure. the re-arrangement of the particles thus produced has imparted to the material a cleavage quite independent of the original lamination. the shales in these formations are occasionally soft and friable and are then termed _marls_, but this name is misleading as they contain no appreciable proportion of finely divided calcium carbonate as do the true marls[ ]. [footnote : readers desiring more detailed information on the occurrence of the clays mentioned in this chapter should refer to the author's _british clays_ (no. in bibliography).] the clays in the =carboniferous limestone= are not, as a whole, of much importance, but the occurrence in this formation of pockets of white refractory clays in staffordshire, north wales (mold) and derbyshire is interesting, especially as these are used for the manufacture of firebricks and furnace linings. these clays are highly silicious and in composition are intermediate between the yorkshire fireclays and ganister. their origin is uncertain, but it is generally considered that they have been produced by the action of the weather and streams on the shales and grits of the coal measures which formerly occupied the higher ground around them, though maw ( ) states that 'it is scarcely open to question that they are the remnants of the subaerial dissolution of the limestone' (see 'fireclays,' chapter v). in the =upper carboniferous system= the clays are highly important because of their general refractory nature, though they differ greatly in this respect, some red-burning shales of this formation having no greater power to resist heat than have some of the surface clays. those of the coal measures are of two main kinds--shales, or laminated rocks which readily split along the planes of deposition, and unstratified underclays. the _shales_ usually occur above the seams of coal and are either of lacustrine or marine origin, differences in their fossils and lithological character supporting one origin for some deposits and the other for the remainder. some of them are fairly uniform in composition, but others vary so greatly in their physical characters, that they are divided by miners into 'binds' or relatively pure shales, 'rock-binds,' or sandy shales, and sandstones. they also vary greatly in thickness in different localities, and whilst they form the main feature in some districts, in others they are replaced by sandstones. the _underclays_ are so called from their usually lying beneath the coal seams. they are not noticeably stratified and vary greatly in character from soft unctuous materials to hard, sandy rocks. in composition they vary enormously, the percentage of silica ranging from per cent., or less, to as high as per cent. the mode of formation of the underclays is not certainly known. they do not appear to be soils or of terrestrial origin, but according to arber ( ) correspond closely to the black oozes of marine and semi-marine estuarine deposits of tropical swamps, or to the muds surrounding the stumps of trees in the buried forests of our coast-lines. they thus appear to be quite distinct from the shales above them, both in origin and physical characters. the more silicious portions, known as _ganister_[ ], possess comparatively few of the characteristics of clay though used, like all the more refractory clays of the coal measures, for all purposes for which fireclay is employed. the term _fireclay_ is, in fact, frequently applied to all the refractory deposits in the coal measures, without much regard to their composition (see chapter v). [footnote : the dinas rock used in the vale of neath (wales) is an even more silicious material found in the millstone grit immediately below the coal measures. it is largely employed for firebricks.] valuable coal measure clays occur in enormous quantities in northumberland, durham, yorkshire, nottinghamshire, derbyshire, staffordshire, near stourbridge, in warwickshire, shropshire, north and south wales and south west scotland. in ireland, on the contrary, the coal measure clays are of little value except in the neighbourhood of coal island, co. tyrone. the position of the 'sagger marls' of north staffordshire (keele series and etruria marls), relative to the 'farewell rock' or millstone grit, is shown in fig. in which the horizontal lines represent coal-seams and ironstone veins. [illustration: +---------------------+ | _keele series_ | | | +---------------------+ newcastle | | +---------------------+ coal | | | | | _etruria | | marls_ | | | top red mine +---------------------+ | | | | gubbin ironstone +---------------------+ | | | | | | | | +---------------------+ knowles coal | | | | burnwood ironstone +---------------------+ | | | | +---------------------+ mossfield coal +---------------------+ ft. coal | | | | | | | | +---------------------+ hard mine coal | | | | +---------------------+ cockshead coal | | | | +---------------------+ crabtree coal +---------------------+ | _millstone grit_ | | | +---------------------+ fig. . coal measures sequence in north staffordshire.] the dissimilarities in the fossils of the coal measure clays and shales in the northern and southern hemispheres suggest that there is a considerable difference in their formation, but the number of clays and shales which have been examined is too small for any accurate conclusion to be drawn. for many industrial purposes, particularly for the manufacture of refractory goods, the clays and shales of the carboniferous system are highly important. the less valuable burn to a reddish colour, often spoiled with many grey spots of ferrous silicate derived from the pyrites in the clay, but the purer varieties burn to a delicate primrose or pale buff tint and are amongst the most heat-resisting materials known. the coal measure clays of yorkshire are particularly esteemed for their refractory properties; for the manufacture of glazed bricks and for blocks for architectural purposes somewhat ambiguously termed 'glazed terra-cotta.' the inferior qualities are largely used for the manufacture of red engineering bricks, some of them competing successfully with the more widely known 'blue bricks' of staffordshire. the coal measure clays of shropshire are noted for the manufacture of red roofing tiles, especially in the neighbourhood of broseley. agriculturally, the coal measure clays are usually poor, but are occasionally of good quality. the shales produce heavy, cold clays and the yellow subsoil produces soils of a light, hungry character so that the two should, if possible, be mixed together. =permian clays= are of little value except for the manufacture of red building bricks. the nottinghamshire permian clays make excellent roofing tiles, flower pots and red bricks. agriculturally, the permian clays are a free working loam yielding large crops of most of the ordinary farm products. =triassic clays= are of great importance in the midlands, those upper portions of them known as the keuper marls being much used for the manufacture of bricks. they are specially known amongst clayworkers as the material from which the midland red bricks of nottinghamshire and leicestershire and the somersetshire tiles are prepared. =jurassic clays= are an important group, of marine origin, occurring in close association with limestone. for this reason they form a valuable source of material for the manufacture of portland cement, but are of less value to the brick and tile manufacturer. the jurassic system contains so large a variety of clays, of such widely different ages and characteristics, that no general description of them can be given in the present volume. [illustration: fig. . lias clay being worked for the manufacture of hand-made sand-faced roofing tiles. (_by courtesy of messrs webb bros. ltd., cheltenham._)] the '_lias clays_'--the lowest of the jurassic formation--are chiefly dark, bituminous shales, including the 'alum shales,' and are often seriously contaminated with pyrites and ironstone. when carefully selected they may be used to advantage in the production of most red articles such as bricks, tiles, chimney pots, etc. they shrink less in the kiln than do most clays, and are easily fusible on account of the lime they contain, but on the whole this formation is of great value for the manufacture of the articles just mentioned. agriculturally, the lias clays are laid down for grass, but the lighter soils are useful for arable purposes. the '_oolitic clays_,' which are also jurassic, usually contain limestone in the form of nodules, but are nevertheless important. they form a broad belt above the lias from dorset to yorkshire, and include the blue clays of the purbeck beds, stiff blue bituminous kimeridge clays, the irregular, sandy coral rag clays, the famous oxford clay (from which the peterborough and fletton bricks are made), the kellaways blue clay, and the fuller's earth deposits. the '_kimeridge clays_' are dark, stiff laminated clays, closely resembling gault, and are much used in the west and midlands for brickmaking. a well-known deposit of this character has long been used at pickering in yorkshire, but the most typical deposits are in huntingdonshire. the kimeridge clays contain a bituminous shale, or sapropelic coal, which evolves a characteristic odour on burning. agriculturally, the kimeridge clays resemble gault and are difficult to work as arable land, though they form first-rate pasturage. [illustration: fig. . oxford clay near peterborough. (_by courtesy of messrs ruston, proctor & co. ltd._)] the '_oxford clays_' are valuable for brickmaking when their use is understood, but to the uninitiated they are very troublesome. their colour is dark blue or grey and they are usually stiff or somewhat shaly in texture with layers of variable composition. the closely associated cornbrash (limestone) is a source of trouble unless great care is taken in the selection of the material. 'oxford clays' are not infrequently traversed by seams of poor coal or by oil-shales. agriculturally, oxford clay is difficult to work and, while much of it is valuable, large portions are poor and cold. when well exposed to frost it is made much lighter, but even then is not very suitable for wheat and autumn sown crops. the '_kellaway blue clays_' are often included in the oxford clays, though they form irregular bands above them and are of fresh-water origin, whilst the oxford clays are marine deposits. they are chiefly used commercially for domestic firebricks near oundle and stamford. =cretaceous clays= occur, as their name implies, in association with chalk. the chief clay in this system is the _gault_, a stiff, black, calcareous clay of marine origin chiefly used for brickmaking. when used alone, gault burns to a reddish colour, due to the iron present, but if, as is more usual, it is mixed with chalk, it burns perfectly white. some gaults contain sufficient chalk to render the addition of a further quantity unnecessary. agriculturally, the cretaceous clays form good arable soil where they are not too exposed, but they suffer from drought. the '_wealden clay_' is a stiff yellowish grey or blue clay extensively used for brickmaking in kent, sussex and surrey. it has been subdivided by geologists into a number of other clays, such as the wadhurst, fairlight, etc., but the differences between them lie more in the fossils occurring in them than in the characters of the clays themselves. they are usually contaminated with ironstone, gypsum and some limestone. agriculturally, the wealden clay produces stiff, yellowish soils of a wet and poor character, but sometimes loams of a highly productive nature occur. the =tertiary clays= include all those deposited after the chalk and previous to the close of the glacial period. they are usually mixed with sand and gravel, and though the deposits are often thin and irregular they are the most generally important of all clays. they vary greatly in character; some, like the london clay, being almost useless unless mixed with other materials, whilst others like the ball clays of devonshire and dorset are amongst the purest and most valuable of the plastic clays. the tertiary clays are divided by geologists into pliocene, miocene and eocene formations; of these the first are commercially unimportant and the second do not exist in great britain. at one time the bovey tracey clays were considered to be miocene, but they have recently been classed as oligocene by clement reid. agriculturally, the most important of the tertiary formations is the eocene, particularly near london, though it is much covered by sand or gravel. the _london clay_, which produces a heavy brown soil, is of slight value, though when properly drained it produces good crops of wheat, beans, and cabbages and other market-garden produce. for this purpose it is greatly improved by the addition of lime and of town manure. the south hampshire eocene beds of clay are cold, wet and of small agricultural value. the eocene clays are composed of a variety of clays, many of which are only distinguishable by the different fossils they contain. the most important are the reading clays, the london clay and the bagshot clays. the _reading clays_ extend over a considerable area in the south of england and are most valuable near the town from which they derive their name. the best qualities are mottled in a characteristic manner and are particularly suitable for the manufacture of roofing tiles and small terra-cotta--an industry for which reading is famous. the _london clay_ is always a treacherous material and is best avoided in the manufacture of bricks and other articles except under highly skilled technical advice. the _bagshot clays_ in dorsetshire are famous for the ball and pipe clays shipped from poole, whilst at bovey tracey and in several parts of devonshire equally valuable ball clays are found and are shipped from teignmouth. these _ball clays_ are of variable composition and colour and require careful selection and testing. they are closely associated with sands, but the lower beds of clay are remarkably stiff, plastic and white-burning. the colour of the raw clay varies from a pale yellow to a dark brown or even to black, but this is little or no criterion of the colour of goods made therefrom, as the colour is due to carbonaceous matters, per cent. or more carbon being usually present. the 'blue' and 'black' ball clays are the most valued by potters, but the quality is usually ascertained by a burning test. the value of these ball clays both in devonshire and dorset is due to their comparative freedom from iron and alkalies and to their remarkable unctuousness and plasticity. they are, therefore, largely used in the manufacture of all kinds of earthenware of which they form the foundation material. in composition, ball clays appear to consist chiefly of a hydro-alumino-silicate corresponding to the formula h al si o , and in this they very closely resemble the china clays (kaolins). the latter are, however, but slightly plastic whilst the ball clays are amongst the most plastic clays known. the china clays are also much more refractory than the ball clays owing to the somewhat larger proportion of alkalies in the latter. _pipe clays_ are an inferior quality of ball clay; they contain rather more iron and alkalies and considerably more silica. for this reason they can only be used for cheaper wares where colour is of less importance and where their excessive contraction can be neutralized by the addition of other substances such as flint. the =boulder clays= occur in a blanket-like covering of drift which lies over the greater part of northern and central england, and over a considerable portion of scotland and ireland. they are a product of the ice age and, whilst varying greatly in character, may usually be distinguished by the occurrence in them of rounded stones and gravel, some of the former bearing clear indications of glacial action. the boulder clays are largely used for the manufacture of building bricks, but the strata in which they occur are so irregular that very careful supervision of the digging is necessary. in some localities these clays form beds ft. or more in thickness and relatively free from gravel; in other districts the clay is interspersed with lenticular deposits of gravel or sand (commonly known as 'pockets'), and if these are mixed with the clay considerable difficulty in manufacture may be experienced. the total thickness of the drift deposits is often very great, as in the cliffs at filey (fig. ) which are ft. high. [illustration: fig. . cliffs of boulder clay at filey lying on calcareous crag.] the boulder clays--considered apart from the stones, gravel and sandy materials occurring with them--are usually red-burning, stiff and very plastic, but the gravel, sand and crushed stones mixed with them in the formation of the material usually render them of medium plasticity. by careful washing, most boulder clays may be purified sufficiently to enable coarse brown pottery to be made from them. clean deposits of sufficient size to be worked without any purification are occasionally found. usually, however, the boulder clay formation is somewhat treacherous as it is difficult to ascertain its nature; boreholes are apt to be quite misleading as the formation is so irregular in character. agriculturally, drift or boulder clays are poor soils, but by judicious management and careful mixing they may be made more fertile. where it contains chalk--as in norfolk and suffolk--boulder drift forms an excellent arable soil. =pleistocene or recent clays= are amongst the most important brickmaking materials in the south of england. they are of remarkably varied character, having been derived from a number of other formations. usually the deposits are somewhat shallow and irregular in form, but beds of considerable thickness occur in some localities. agriculturally, they are of considerable importance. most of the =brick earths= used in the south-east of england are of recent formation, those of the thames valley being of special importance in this connection, particularly where they are associated with chalk; thus forming natural _marls_ or enabling artificial marls to be produced. the brick earths--in the sense in which this term is used in the south--comprise three important types of clay: (_a_) _plastic clays_ not particularly differentiated from those already described, (_b_) _loams_ or sandy clays which are sufficiently plastic for satisfactory use, have the advantage of shrinking but slightly in drying, and are largely used in the manufacture of red facing bricks and as light soils, and (_c_) _marls_ or calcareous clays, used for the production of light coloured or white bricks, the chalk they contain combining with any iron compounds present and, at the same time, reducing the contractility of the clay. on burning, they form a cement which binds the particles into a strong mass. these are the 'true marls' or 'malms' composed of clay and chalk and must not be confused with the so-called marls of staffordshire and elsewhere which are almost free from lime compounds. there is, at present, no definition of 'marl' which is quite satisfactory; a maker of london stock bricks understanding by this term a clay containing at least per cent. of chalk; a maker of white suffolk bricks a material containing at least twice this amount; an agriculturalist any soil, not obviously sandy, which will make his clay land less sticky; and many geologists any friable argillaceous earths. a general consensus of opinion is, however, being gradually reached that the term 'marl' should be limited, as far as possible, to clays containing calcium carbonate in a finely divided state. =alluvial deposits=--which are also of recent formation, though still of sufficient age for skeletons of mammoths to be found in them--are of so variable a nature as to render any brief, general description impossible. many of them are so contaminated with sand and crushed limestone as to be useless for manufacturing purposes and of small value agriculturally, but others are important in both these respects. further details of the occurrence of clays in the various formations described will be found in the _maps and memoirs of the geological survey_ and in the author's _british clays_ ( ). chapter iii the origins of clays the terms 'primary' and 'residual' are applied to those clays which are found overlying or in close association with the rocks from which they have been derived, and distinguish them from the 'secondary' or 'transported' clays which have been carried some distance away from their place of origin. =residual clays= may be formed by the simple removal of other materials, the clay remaining behind, as in the decomposition of some argillaceous limestones, in which the calcareous matter has been removed by solution whilst the clay is unaffected. such a clay is not a primary one as it has probably been derived from some distant source and, having been deposited along with the limestone ooze, has formed an intimate mixture from which the limestone has, at a later geological epoch, been removed in the manner indicated. residual clays are seldom pure, being often rich in iron compounds, though the white clays of staffordshire and derbyshire are highly refractory. it is seldom necessary to distinguish residual clays from other secondary or transported ones (chapters ii and iv). =primary clays=, on the contrary, have been derived from rocks which have undergone chemical decomposition, one of the products being clay. the most important primary clays are the kaolins, which are derived from the decomposition of felspar, but other primary clays derived from other minerals are known, though less frequently mentioned. the _kaolins_ are primary clays[ ] formed by the decomposition of felspar and occur in many parts of the world. in great britain the most important are the china clays found in devon and cornwall, which occur in association with the granite from which they have been formed. the kaolins in germany are, apparently, of similar origin, though some are derived from porphyry and not from granite; they are the chief material used in the manufacture of dresden, meissen, berlin and other porcelains. the french kaolins from st yrieux and limousin are said by granger ( ) to be derived from gneiss amphibole. the american kaolins have, according to ries ( ), been chiefly formed from the weathering of pegmatite veins, but the origin of some important deposits in texas and indiana has not yet been fully explained. [footnote : some kaolins in central europe appear to have been transported and of secondary origin.] [illustration: fig. . china clay pit belonging to the north cornwall china clay co. (_by courtesy of w. h. patchell esq._)] the corresponding material used by the chinese for the manufacture of porcelain bears a name which is really that of the place from whence it was originally obtained; the term _kao-ling_ indicates merely a high ridge. according to richthofen ( ) the rock from which chinese porcelain is made is not a true kaolin, but is allied to the _jades_. the term 'kaolin' is therefore a misnomer when applied to white-burning, primary clays generally, but its use has become so firmly established as to render it permanent. kaolins are seldom found in a sufficiently pure state to be used direct, but must be freed from large amounts of undecomposed rock, quartz, mica, etc., by a process of washing and sedimentation. when purified in this manner, the best qualities of china clay yield, on analysis, alumina, silica and water in the proportions indicated by the formula h al si o together with about per cent. of mica and other impurities. some high class commercial kaolins contain over per cent. of mica and per cent. of quartz. the chief constituents of rocks which take part in the production of kaolins appear to be the felspars, but the natural processes by which these felspars are decomposed are by no means perfectly understood. some kaolins appear to have been formed by weathering and others by subaerial action. thus collins ( ) has stated very emphatically that the kaolinization of cornish felspar has been chiefly effected by fluorine and other substances rising from below and not by carbonic acid and water acting from above. ries ( ) and other american observers are equally convinced that certain kaolins they have examined are the result of 'weathering.' german and french investigators are divided in their opinions, and fuchs has found that the passau (saxony) kaolin is derived from a special mineral, not unlike a soda-lime felspar deficient in silica, to which he has given the name 'porcelain spar.' the _felspars_ form a class of minerals whose chief characteristic is the combination of an alkaline or alkaline-earth base with silica and alumina. orthoclase (k oal o · sio )--the chief potassium felspar--is typical of the whole class. when treated with water under suitable conditions, the felspar appears to become hydrolysed and some of the water enters into combination, the potash being removed by solution. attempts to effect this decomposition artificially have proved abortive though several investigators appear to have effected it to a limited extent by electrolysis or by heating under great pressure ( ). the effect on felspars of waters containing carbon dioxide in solution has been studied by forschammer, vogt, and others, and they have concluded that kaolinization may occur with this agent though it does not appear to be the chief cause in the formation of cornish china clays. [illustration: fig. . orthoclase felspar, natural size. (_from miers_' mineralogy _by permission of macmillan & co._)] the probable effect of fluoric vapours has been studied by collins ( ) who confirmed von buch's observation that fluorides (particularly lepidolite and tourmaline) are constantly associated with china clay; he found by direct experiment that felspar is decomposed by hydrofluoric acid at the ordinary temperature without the other constituents of the granite in which it occurs being affected. this theory is confirmed by the great depths of the kaolin deposits in cornwall and in zettlitz (bohemia) which appear to be too great to render satisfactory any theory of simple weathering though kaolins in other localities, especially in america, appear to be largely the result of weathering. according to hickling ( ) the product of the action of hydrofluoric acid 'has not the remotest resemblance to china clay.' kaolin, when carefully freed from its impurities, as far as this is possible, is peculiarly resistant to the action of water. this resistance may be due to its highly complex constitution, as the simpler hydro-alumino-silicates, such as collyrite, show an acid reaction when ground with water. rohland ( ), therefore, suggests that kaolinization is effected by water first hydrolysing the felspar and forming colloidal silica and sodium or potassium hydroxides which are removed whilst the complex alumino-silicate remains in the form of kaolin. hickling ( ), on the contrary, believes that the action of the weather on felspar produces secondary muscovite--a form of mica--and that this is, later, converted into kaolinite or china clay (fig. , p. ). the various theories which have been propounded may be summarized into three main classes, and whilst it is probable that any one of them, or any one combination, may be true for a particular kaolin, yet the whole process of kaolinization is so complex and the conditions under which it has occurred appear to be so diverse that it is doubtful if any simple theory can be devised which will satisfactorily meet all cases. (_a_) the decomposition of the granite, and particularly of the felspar within it, may be ascribed to purely chemical reactions in which the chief agents are water and carbon dioxide. (_b_) other substances--possibly of an organic nature and derived from the soil--may have played an important part. (_c_) wet steam and hot solutions of fluorine, boron or sulphur compounds may have effected the decomposition. the recent progress made in the application of the laws of physical chemistry to geological problems is continually throwing fresh light on this interesting subject. thus, studies of the dissociation pressures and transition points between the anhydrous and the hydrous states of various substances and the effect of water as a powerful agent of decomposition (hydrolysis) have shown that hydration is a characteristic result of decompositions occurring in the upper portions of the earth's crust and not in the lower ones, and that it is usually checked, or even reversed, when the substance is under great pressure. at great depths kaolins and other complex hydrous silicates give place to anhydrous ones such as muscovite, andalusite and staurolite. there is, therefore, good reason to believe that the kaolinization of cornish felspar has occurred at only moderate depths from the surface and that it has been chiefly produced by the action of water containing acid gases in solution. the acid in the water may have been absorbed from the atmosphere, or it may be due to vapours rising from below through the felspathic material. in great britain, china clay occurs in the form of powdery particles apparently amorphous, but containing some crystals, scattered through a mass of harder rock, the whole being known as china clay rock or 'carclazite.' the softer portions of this china clay rock are known as 'growan' and the china clay in it represents only a small proportion of the whole material. the finer particles of clay and other materials are removed by treatment with water, whereby one-third to one-eighth of the material is separated. this small proportion is then subjected to further washing and sedimentation in order to obtain the china clay in a state of commercial purity. it will thus be understood that the cornish china clays are not 'deposits' in the usual acceptation of that term, the soft growan from which they are obtained being almost invariably the result of decomposition _in situ_ of some species of felspar in disintegrated granite. the commercial kaolins of france, germany, america and china very closely resemble the cornish china clays in composition, but when used in the manufacture of porcelain they create differences in the finished material which are clearly noticeable, though microscopical examination and chemical analysis, at present, fail to distinguish between them in the raw state on account of their great resistance to ordinary chemical and physical forces. in addition to the breaking up of felspathic rocks with the formation of china clay or kaolin (kaolinization), other decompositions which occur may result in the formation of clays, and an examination of a considerable number of clays by j. m. van bemmelen ( ) has led him to suppose that several different clay-forming forces have been at work in the production of clays. he classifies these under four heads: ( ) _kaolinization_, or the decomposition of felspathic and similar rocks by the action of telluric water containing active gases in solution. ( ) _ordinary weathering_ in which the action is largely mechanical, but is accompanied by some hydrolysis owing to the impurities contained in the water which is an essential factor. ( ) _lateritic action_--or simple decomposition by heat--which occurs chiefly under tropical conditions, but may also occur in temperate climates, and has for its main product a mixture of free silica and alumina, the latter being in the form of (amorphous) 'laterite.' it may not improbably be a result of the decomposition of the clay molecule similar to that which occurs when china clay is heated, as there is no temperature below which it can be said that china clay does not decompose into free silica and alumina ( ). ( ) _secondary reactions_ in which the products of one of the reactions previously described may undergo further changes, as the conversion of amorphous clayite into crystalline kaolinite, or amorphous laterite into crystalline hydrargillite. weathering. the action of the forces conveniently classed under the term _weathering_ are of two main kinds: (_a_) the _mechanical grinding_ of sandstone, quartzite, limestone, and other rocks, causes an addition of adventitious material to clay, the proportions being sometimes so large as to render it necessary to term the material an argillaceous sand, rather than a sandy clay. some of these grains of mineral matter are so minute and so resistant to the ordinary chemical reagents as to make it extremely difficult to distinguish them from clay. (_b_) the _chemical decomposition_ due to the action of very dilute solutions. by this means simple silicates are decomposed with the formation of colloidal silica which may either remain in solution or may be deposited in a coagulated form. at the same time, some alumino-silicates will be similarly decomposed into colloidal alumino-silicic acids or clays. the ultimate results of the action of ordinary weathering on silicate rocks are, therefore, sands and clays, the latter being in some ways quite distinct in their origin and physical properties from the china clays. according to j. m. van bemmelen ( ) such clays also contain an alumino-silicate soluble in boiling hydrochloric acid followed by caustic soda, whereas pure china clays are unaffected by this treatment. the variety of silicates and other minerals which--in a partially decomposed condition--go to form 'clays' is so great that the complete separation of the smallest particles of them from those of the true clay present has never been accomplished and our knowledge of the mineralogical constitution of many of the best known clays is far from complete. it is highly probable that the action of water does not cease with the formation of clay, but that it slowly effects an increase in the plasticity of the clay. there thus appear to be at least three kinds of primary clay, viz.: _kaolinic_ or _china clays_ which are chiefly derived from felspar and can be isolated in a relatively pure state. they are highly refractory, but only slightly plastic. _epigenic_ or _colloidal clays_ derived from kaolinic clays, as a secondary product, or directly from felspar, mica, augite and other alumino-silicates by 'weathering.' they are usually less refractory and much more plastic than the china clays and contain a large percentage of impurities--sometimes in the form of free silica (sand) or of metallic oxides, carbonates, sulphides, sulphates, silicates, or other compounds. many so-called secondary clays such as pipe clays, ball clays and fireclays may be of this type, though their origin is difficult to trace owing to their subsequent transportation and deposition. _lateritic_ or _highly aluminous clays_, of a highly refractory character, but low plasticity. they are usually somewhat rich in iron oxide which materially affects their plasticity. unlike the china clays, pure lateritic clays are completely decomposed by hydrochloric acid. bauxite and some of the highly aluminous clays of the coal measures appear to be of this type. unfortunately these different types of clay are extremely difficult to distinguish and in many instances they have become mixed with each other and with other materials during the actions to be described in the next chapter, that it is often almost impossible to decide whether the true clay in a given specimen possessed its characteristics _ab initio_ or whether it has gained them since the time when it ceased to be a primary clay. =secondary clays= are those which have been produced by the action of the weather and other natural forces on primary clays, the changes effected being of a physical rather than a chemical nature (see chapter iv). the essential constituent of secondary clays has not been positively identified. in so far as it has been isolated it differs from the true clay in the primary clays in several important respects, and until its nature has been more fully investigated great caution must be exercised in assigning a definite name to it. for many purposes the term _pelinite_ (p. ) is convenient, being analogous to the corresponding one used for material in china clays (_clayite_, p. ). these terms are purely provisional and must be discarded when the true mineralogical identities of the substances they represent have been established. chapter iv the modes of accumulation of clays from whatever sources clays may have been originally derived, the manner in which they have been accumulated in their present positions is a factor of great importance both in regard to their chemical and physical characters and their suitability for various purposes. as explained in chapter iii, the china clays or kaolins may usually be regarded as primary clays derived from granitic or other felspathic or felsitic rocks by chemical decomposition. such clays are found near to their place of origin, are usually obtainable in a comparatively pure state and are generally deficient in plasticity. they may occur in beds of small or great depth, but these are not 'accumulations' in the ordinary meaning of that term. residual clays (p. ) also form a distinct class, as unlike the majority of argillaceous materials they are left behind when other substances are removed, usually by some process of solution. in many cases, however, the residual clays are really secondary in character, having been transported from their place of origin, together with limestone or other minerals, the mixture deposited and subjected to pressure and possibly to heat, whereby a rock-like mass is formed. this mass has then been subjected to the solvent action of water containing carbon dioxide or other substances which dissolve out the bulk of the associated minerals and leave the residual clay behind. the chief agents in the transport and accumulation of clays are the _air_, in the form of wind; _water_, in the form of rain, streams, rivers, floods, lakes and seas, or in the form of ice and snow as in glaciers and avalanches; _earth-movements_ such as the changes wrought by volcanoes, earthquakes and the less clearly marked rising and falling of various portions of the earth's crust which result in folded, twisted, sheared, cracked, inclined, laminated and other strata. these agents have first moved the clay from its original site and have later deposited it with other materials in the form of strata of widely varying area and thickness, some 'clay' beds being several hundred feet in depth and occupying many square miles in area, whilst others are in the form of thin 'veins' only a few inches thick or in 'pockets' of small area and depth. these deposits have in many places been displaced by subsequent earth-movements and have been overlain by other deposits so as to render them quite inaccessible. others have been covered by deposits several miles thick; but the greater part of the covering has since been removed by glacial or other forces, so that clays of practically all geological ages may be found within the relatively small area of great britain. the transportation of clays. by the action of wind or rain, or of rain following frost, the finer of particles clay are removed from their primary site and as the rain drops collect into streamlets, these unite to form streams and rivers and the clay with its associated minerals is carried along by the water. as it travels over other rocks or through valleys composed of sandstone, limestone and other materials, some of these substances are dislodged, broken into fragments of various sizes and with the clay are carried still further. in their journey these materials rub against each other and against the banks and bed of the stream, thereby undergoing a prolonged process of grinding whereby the softer rocks are reduced to very fine sand and silt which becomes, in time, very intimately mixed with the clay. if the velocity of the stream were sufficiently great, the mixed materials--derived from as many sources as there are rocks of the districts through which they have passed--would be discharged into a lake or into the sea. here the velocity of the water would be so greatly reduced that the materials would gradually settle, the largest and heaviest fragments being first deposited and the finer ones at a greater distance. with most streams and rivers, however, the velocity of the water is very variable, and a certain amount of deposition therefore occurs along the course, the heavier particles only travelling a short distance, whilst the finer ones are readily transported. if the velocity of the stream increases, these finer particles (which include the clay) may become mixed with other particles of various sizes and the materials thus undergo a series of mixings and partial sortings until they are discharged at the river mouth or are left along its sides by a gradual sinking of the water level. the clay will be carried the whole course of the river, unless it is deposited at some place where the velocity of the water is reduced sufficiently to permit it to settle. if floods arise, the area affected by the water will be increased. the _alluvial clays_ have, apparently, been formed by overflowing streams and rivers, the material in suspension in the water being deposited as the rate of flow diminished. such alluvial deposits contain a variety of minerals--usually in a very finely divided state--clay, limestone-dust or chalk, and sand being those most usually found. _river-deposited clays_, _i.e._, those which have accumulated along the banks, are characterized by their irregularity in thickness, their variable composition and the extent to which various materials are mixed together. this renders them difficult to work and greatly increases the risks of manufacture as the whole character of a fluviatile clay may change completely in the course of a few yards. according to the districts traversed by the water, the extent to which the materials have been deposited and re-transported and the fresh materials introduced by earth-movements, river-deposited clays may be (_a_) _plastic_ and sufficiently pure to be classified as 'clays,' (_b_) _marls_ or clays containing limestone-dust or chalk thoroughly mixed with the clay, and (_c_) _loams_ or clays containing so much sand that they may be distinguished by the touch from the clays in class (_a_). intermediate to these well-defined classes there are numerous mixtures bearing compound names such as sandy loams, sandy marls, argillaceous limestone, calcareous sands, and calcareous arenaceous clays, to which no definite characteristics can be assigned. to some extent a transportation of clays and associated materials occurs in _lakes_, but the chief processes there are of the nature of sedimentation accompanied by some amount of separation. on the shores of lakes, and to a much larger extent on the sea coasts, extensive erosion followed by transportation occurs continuously, enormous quantities of land being annually removed and deposited in some portion of the ocean bed. the erosion of cliffs and the corresponding formation of sand and pebbles are too well known to need further description. it should, however, be noticed that the clay particles, being much finer, are carried so far away from the shore that only pebbles and sand remain to form the beaches, the finer particles forming 'ocean ooze.' the action of the _sea_ in the transport of rock-materials is more intense than that of rivers, the coasts being worn away by repeated blows from the waves and the pebbles and sand grains the latter contain. the ocean currents carry the materials dislodged by the waves and transport them, sometimes to enormous distances, usually allowing a considerable amount of separation to take place during the transit. in this way they act in a similar manner to rivers and streams. _glaciers_ may be regarded as rivers of ice which erode their banks and bed in a manner similar to, but more rapidly than, streams of water. owing to their much greater viscosity, glaciers are able to carry large boulders as well as gravel, sand and clay, so that the materials transported by them are far more complex in composition and size than are those carried by flowing water. [illustration: fig. . illustrating the successive deposition of different strata.] separation and sedimentation. the clay and other particles having been placed in suspension in water by one or more of the natural forces already mentioned, they soon undergo a process of sorting or separation, previous to their deposition. the power of water for carrying matter in suspension depends largely on its velocity, and when this is reduced, as when a river discharges into a lake or sea, the larger and denser particles at once commence to settle, the smaller ones remaining longer in suspension, though if the velocity of the water is reduced sufficiently all the particles will be deposited. hence, the deposits in lakes (_lacustrine_) and at the mouths of rivers (_estuarine_) increase more or less regularly in fineness according to their distance from the point at which the water enters, the gravel and stones being deposited first, then the coarse sand, next the finer sand and finally the silt and clay (fig. ). if cross-currents are present, the deposits will, naturally, be made more irregular, and in some cases variations in the flow of the transporting water may cause the coarser particles to be carried further than usual so that they may cover some of the finer deposits previously formed; but as the clay and silt particles are so much finer than sand and gravel they usually travel so far before settling that their deposits are very uniform if the area over which they are spread is sufficiently large. lake-deposited clays are for this reason more uniform than estuarine beds, whilst beds deposited at considerable depths in the sea and at a great distance from land are still more uniform. a _lacustrine clay_ is usually more persistent and uniform than fluviatile beds though sometimes difficult to distinguish from the latter. some of the most valuable clay deposits are of lacustrine formation; their comparative purity and great uniformity enabling ware of excellent colour and texture to be produced without much difficulty. thus the reading mottled clays of the hampshire basin, on the outskirts of the london basin and in northern france are well known for the admirable red bricks, tiles and terra-cotta produced from them. still purer clays deposited at bovey heathfield in devonshire are also of lacustrine origin, though they differ in many respects from the ordinary lake-deposited clays and are of unusual thickness for deposits formed in this manner. [illustration: fig. . lacustrine clay at skipsea. (_by courtesy of t. sheppard esq._)] the greater purity of lacustrine clays, as compared with fluviatile ones, is attributed to the much larger area over which the deposit is spread,--enabling variations in the deposits to be much less noticeable than when a smaller area is covered--and to the very small velocity of the water in lakes, whereby all the coarser particles are deposited a considerable distance away from the clays and silts. ries ( ) has pointed out that many (american) lake-clays are of glacial origin, having been laid in basins or hollows along the margin of the ice-sheet or in valleys which have been dammed by an accumulation of drift across them. such clay beds are usually surface deposits of variable thickness and frequently impure. like all lacustrine deposits they show (though in a more marked degree than in the older and larger lakes) alternate layers of sand and clay, though the former are usually too thin to be noticeable except for their action in enabling the deposited material to be easily split along the lines of bedding. _estuarine deposits_ partake of the nature of both fluviatile and marine beds, according to their position relative to the river from which they originate. they are usually uncertain in character and are often irregular in composition owing to the variations in the flow of the water. the estuarine clays of great britain--with the possible exception of the jurassic deposits in northamptonshire and lincolnshire--are of minor importance, but in some countries they form a valuable source of clay. [illustration: fig. . clay at nostel, showing marine band. (_by courtesy of t. sheppard esq._)] _marine clays_ are, as their name implies, those deposited from sea water. they are frequently found at a considerable distance from the shores of the ocean in which they were laid down, and subsequent risings and fallings of the surface of the earth have so altered the areas occupied by sea water, that a large number of marine deposits now form dry land. though usually of enormous size and of generally persistent character, marine clay deposits vary considerably in the composition of the material at different depths, as well as in different areas. this is only to be expected from the manner of their deposition, from the varied sources of the material and from the numerous river- and ocean-currents taking part in their formation. for this reason it is generally necessary to mix together portions of the deposit drawn from various depths in order to secure a greater uniformity than would be obtained if a larger area were to be worked to a smaller depth. the oxford clay which extends from the centre of england to the centre of france is a typical marine clay. at the bottom of all oceans at the present day is a deposit, of unknown thickness, of red calcareous clay or _ooze_ which is steadily increasing in amount and is thereby forming a fresh marine deposit, though at present its inaccessibility deprives it of all economic value. it is important not to overlook the enormous part played by variations in the level of the land relative to that of the ocean in past ages. for instance, there is abundant evidence to show that practically the whole of great britain has been repeatedly submerged to great depths and has been raised to heights far greater than its present average. these oft-repeated risings and settlings have caused great changes in the nature of the deposited materials so that in the coal measures, for example, there are deposits of obviously fresh-water origin sandwiched in between others undoubtedly marine. it can readily be understood, as stated by arber ( ), that if, at a given period, the dry land during the formation of the coal measures gradually subsided, it would first be covered with clear water, whilst from those portions of the area which occupied the higher ground the rivers and streams continued to pour into their estuary a large amount of fresh-water material. later, a stage would be reached when mud of marine origin invaded the area and covered the previous deposits. when, after an indefinitely long period, the ground again rose, fresh-water deposits might again form, and this alternation of marine and fluviatile deposits appears to have been repeated with great frequency during the carboniferous period. in the lower coal measures of yorkshire and lancashire, stopes and watson ( ) have shown that the shales forming the roof of the upper foot coal were derived from drifted sediments of marine origin. precipitated clays. if the plasticity of some clays is really due to the colloidal nature of their particles, it is obvious that they must have been formed by a process of coagulation or precipitation at a distance from the site of the minerals from which they have been derived. according to the 'colloid theory,' felspar and other alumino-silicates are decomposed by 'weathering,' the chief effect of which is the formation (by hydrolysis) of a colloidal solution of 'clay.' this apparently clear solution flows along in the form of a small streamlet, joins other streamlets and continues its journey. so long as it is quite neutral or contains free alkali the solution will remain practically clear, but as soon as acids enter the stream, or are formed in it by the decomposition of organic matter, a coagulation of the colloidal matter will commence and the amount of 'clay' thus thrown out of solution will depend on the amount of such free acid. if the coagulation or precipitation occurs in still water, the 'clay' will be deposited almost immediately, otherwise it will be carried forward until it reaches a place where it can be deposited in the manner already described. such precipitated clays need not necessarily be pure, as other substances may be present in colloidal form and may be coagulated at the same time as the clay. in addition to these, the admixture of sand and other minerals present in suspension in the solution may become mixed with the particles during coagulation and be deposited with them. clays formed in this manner are extremely difficult to identify on account of the highly complex nature of the reactions occurring in their vicinity both during and subsequent to their formation. re-deposited clays. although many clays and other materials have been transported and accumulated in the manner described, the majority of those now available have been subjected to repeated transportation and deposition, owing to the frequent and enormous changes in the relative levels of land and water during the various geological epochs. so far as can be ascertained, it is during these changes of position and the recurrent exposure to air and to water containing various substances in solution, together with the almost incessant grinding which took place during the transportation and deposition, that most secondary clays became plastic. if this is the case, it explains the impossibility of increasing the plasticity of clay by artificial means, at any rate on a large scale. the simplest of the agents of re-deposition are rain-storms and floods which, forming suddenly, may cause the water of a stream or river to flow with unwonted velocity and so carry away previously formed deposits of various kinds. clays transported in this way are termed by ries ( ) _colluvial_ clays, the term 'diluvial' is generally employed in this country. if these are derived from a primary clay which has not travelled far since it left the original granite from which it was formed, they will usually be white-burning and of only slight plasticity, but if the flood affects materials which have already been re-deposited several times, the colluvial clays may be of almost any imaginable composition. floods of a different character--due to the subsidence of the land so that it is partially covered with lake- or sea-water, which beats on its shores and erodes it in the manner already described--are also important factors in the transportation of clays. so far as clays are concerned, the action of the sea is both erosive and depository, though the sedimentation in it being that of the pelagic ooze at great depths the clayey material is quite inaccessible. under certain conditions, however, the sea may erode land in one area and may return the transported material to the land in another area. the diluvial clay-silt known as _warp_ in the valley of the humber is of this character. quite apart from the action of water, however, much denudation, transportation and re-deposition of clays and associated materials has been due to the action of ice in the form of glaciers, though these do not appear to have had much effect in increasing the plasticity of the clays concerned. _glacially deposited clays_ are characterised by their heterogeneous composition, some of them containing far more sand than true clay, whilst yet retaining a sufficient amount of plasticity to enable them to be used for rendering embankments impervious and for the manufacture of common bricks, and, occasionally, of coarse pottery; others contain so much sand as to be useless for these purposes. most glacial deposits contain a considerable proportion of stones and gravel which must be removed before the clay can be used. the large proportion of adventitious matter is due in great part to the much greater erosive force and carrying power of ice as compared with water, resulting in much larger pieces of material being carried, and as the whole of the ice-borne material is deposited almost simultaneously when the glacier melts, only a very small amount of separation of the material into different grades takes place. the comparative freedom from coarse sand of some glacial clays shows that some sorting does occur, but it is very limited in extent as compared with that wrought in materials which have been exclusively transported by water. for the manufacture of bricks, tiles and coarse pottery in yorkshire, lancashire and some of the more northern counties of great britain, glacially deposited clays are of great importance in spite of their irregular composition. they are frequently termed 'boulder clays' or 'drift clays' (p. ), but in using these or any other terms for clays transported by glacial action it is important that they should not be understood to refer to the whole of the deposited matter. large 'pockets' of coarse sand and gravel frequently occur in deposits of this character and veins of the same materials are by no means uncommon. the custom of some geologists of referring to the _whole_ of a glacial deposit as 'boulder clay' has, in a number of cases, led to serious financial loss to clayworkers who have erroneously assumed that, because some 'boulder clays' are used for brick and tile manufacture, all deposits bearing a similar title would be equally suitable. this difficulty would largely be avoided if, as is now increasingly the case, the term 'drift' or 'glacial deposit' were used for the deposits as a whole, the term 'boulder clay' being restricted to the plastic portions and not including pockets of sand, gravel and other non-plastic materials. _boulder clays_--using this term in the limited sense just mentioned--consist of variable quantities of sand and clay, stones and gravel being generally associated with them. the stones may usually be removed by careful picking, and the gravel by means of a 'clay cleaner' which forces the plastic material through apertures too small to allow the gravel to pass. the plastic material so separated is far from being a pure clay and may contain almost half its weight of sand, the greater part of which is readily separated by washing the material. boulder clays, when freed from stones and gravel, are sufficiently plastic to meet the needs of most users, without being so highly plastic and contractile as to necessitate admixture with sand or similar material. some boulder clays contain limestone in the form of gravel or as a coarse powder produced by the crushing of larger fragments. these are less suitable for manufacturing purposes as the lime produced when the articles are burned in the kilns is liable to swell and to disintegrate them on exposure. owing to their origin and the nature of the impurities they contain, boulder clays are never pure and when burned are irregular in colour and somewhat fusible unless subjected to some process of purification. chapter v some clays of commercial importance although clays occur in deposits of almost all geological periods, many of them are of little or no commercial value. this may be due to their situation or to their composition and other characteristics. thus, a coal measure clay is ordinarily quite inaccessible, and to sink a shaft specially to obtain it may be an unprofitable undertaking; if, however, a shaft is sunk for coal the clays in the neighbourhood of the coal seams are rendered accessible and, usually, a certain amount of such clays is brought to the surface in order to remove it out of the way of the coal miners. again, a clay deposit may be so far removed from human habitations as to make it practically valueless, but if, for any reason, the population of the district in which the clay is situated grows sufficiently, the clay may become of considerable value. it not infrequently happens, therefore, that the commercial importance of a clay deposit is one which fluctuates considerably, yet, in spite of this fact, there are certain kinds of clay which are nearly always of some commercial value. the most important of these are the kaolins (china clays), the pottery and stoneware clays, the refractory clays (fireclays), the brick and terra-cotta clays and shales, and the clays used in the manufacture of portland cement. the origin and manner in which these clays have been accumulated have been described in the previous chapters; it now remains to indicate their characteristics from the point of view of their commercial value. =commercial china clays and kaolins= in the united kingdom are not simple natural products but, in the state in which they are sold commercially, have all been subjected to a careful treatment with water, followed by a process of sedimentation whereby the bulk of the impurities have been removed. according to the extent to which this treatment has been carried out, they will contain per cent. or more mica and quartz, with little or no tourmaline, felspar and undecomposed granite. in some parts of europe and america, kaolins are found in a state of sufficient purity to need no treatment of this kind unless they are to be used for the very highest class of wares. [illustration: _magnified diameters_ _magnified diameters_ _magnified diameters_ _magnified diameters_ crystals of kaolinite _magnified diameters_ crystals of secondary muscovite. fig. . kaolinite and mica. (_after g. hickling_ ( ).)] mica is usually the chief impurity as its particles are so small and their density resembles that of the purified china clay more closely than do the other minerals. in commerce the term _china clay_ is almost invariably used to denote the washed material obtained from the 'china clay rock,' but at the pits the word 'clay' is used indiscriminately for the carclazite (p. ) and for the material obtained from it. as the term 'kaolin' is used indifferently abroad for the crude 'deposit' and for the purified commercial article, it should be understood that the following information relates solely to the substance as usually sold and not to the crude material. commercial china clay or kaolin is a soft white or faintly yellowish substance, easily reduced to an extremely fine powder, which when mixed with twice its weight of water will pass completely through a no. sieve. its specific gravity is · , but the minuteness and nature of its smallest particles and their character are such that it will remain in suspension in water for several days; it thus appears to possess colloidal properties, at any rate so far as the smaller particles are concerned. it is almost infusible, but shows signs of softening at ° c. (seger cone ) or at a somewhat lower temperature, according to the proportion of impurities present. when heated with silica or with various metallic oxides it fuses more readily owing to the formation of silicates. china clays and kaolins are not appreciably affected by dilute acids, but some specimens are partially decomposed by boiling concentrated hydrochloric acid ( ) and all are decomposed by boiling sulphuric acid, the alumina being dissolved and the silica liberated in a form easily soluble in solutions of caustic soda or potash. this has led to the conclusion that some kaolins may have been produced by weathering, as the bulk of true kaolinitic clays (such as cornish china clay) is not affected by boiling hydrochloric acid (p. ). owing to the exceptional minuteness of its particles, it is extremely difficult to ascertain whether pure china clay or kaolin is crystalline or amorphous. johnson and blake ( ) found that all the specimens they examined 'consisted largely of hexagonal plates' and that in most kaolins 'these plates are abundant--evidently constituting the bulk of the substance.' this observation is contrary to the experience of most investigators, the majority of whom have found the bulk of the material to be amorphous and sponge-like, but a small portion of it to consist of hexagonal or rhombic crystals. mellor ( ) has proposed the name _clayite_ for this amorphous material, the crystalline portion being termed _kaolinite_ as suggested by johnson and blake. both kaolinite (crystalline) and clayite (amorphous) yield the same results on analysis and correspond very closely to the formula h al si o or al o · sio · h o, so that it is most probable that they are the same substance in different physical states. according to hickling ( ) the general impression that the particles of china clay are amorphous is due to the use of microscopes of insufficient power. with an improved instrument, hickling claims to have identified the 'amorphous' portion of china clay with crystalline kaolinite, the clay particles (fig. ) being in the form of irregular, curved, hexagonal prisms or in isolated plates. the former show strong transverse cleavages. the index of refraction and that of double refraction agree with those of anglesea kaolinite crystals, as does the specific gravity. in spite of their great purity, commercial china clays and kaolins are almost devoid of plasticity, nor can this property be greatly increased by any artificial treatment. this has led to the conclusion that plasticity is not an essential characteristic of the clayite or kaolinite molecules, but is due to physical causes not shown by any investigation of the chemical composition of the material. in addition to the specially purified kaolins just described, alkaline kaolins, siliceous kaolins and ferruginous kaolins are obtained from less pure rocks and do not undergo so thorough a treatment with water. some of these varieties are not improbably derived from transported kaolins, as they occur in tertiary strata, and so bear some resemblance to the white fireclays on the carboniferous limestone of staffordshire, derbyshire and north wales, though the latter are far more plastic. to be of value, a china clay or kaolin must be as white as possible and must be free from more than an insignificant percentage of metallic oxides which will produce a colour when the clay is heated to bright redness. if the material is to be used in the manufacture of paper, paint or ultra-marine, these colour-producing oxides are of less importance providing that the clay is sufficiently white in its commercial state. the manufacturer of china-ware and porcelain requires china clay or kaolin which, in addition to the foregoing characteristics, shall be highly refractory. it must, therefore, be free from more than about per cent. of lime, magnesia, soda, potash, titanic acid and other fluxes. it is a mistake to suppose that all white clays of slight plasticity are china clays or kaolins. some _pipe clays_ have these characteristics, but they contain so large a proportion of impurities as to be useless for the purposes for which china clay is employed and are consequently of small value. users of china clays and kaolins generally find it necessary to carry out a lengthy series of tests before accepting material from a new source, as such a material may possess characteristics not readily shown by ordinary methods of analysis, but which are sufficiently active to make it useless for certain purposes (see p. ). =pottery clays= are, as their name implies, those used in the manufacture of pottery, and comprise the china clays already mentioned (p. ), the ball clays and the less pure clays used in the manufacture of coarse red ware, flower pots, etc. the _china clays_ (p. ) are not used alone in pottery manufacture as they lack plasticity and cohesion. in the production of china-ware or porcelain they are mixed with a fluxing material such as cornish stone, pegmatite, or felspar, together with quartz or bone ash. thus, english china ware is produced from a mixture of approximately equal parts of bone ash, china clay and cornish stone, whilst felspathic or hard porcelain is made from a mixture of kaolin, felspar and quartz, a little chalk being sometimes added. the _ball clays_ (p. ) form the basis of most ordinary pottery, though some china clay is usually added in order to produce a whiter ware. flint is added to reduce the shrinkage--which would otherwise be inconveniently great--and the strength of the finished ware is increased, its texture is rendered closer and its capability of emitting a ringing sound when struck are produced by the inclusion of cornish stone or felspar in the mixture. small quantities of cobalt oxide are also added to improve the whiteness in the better classes of ware. [illustration: fig. . mining best potter's clay in devonshire. (_photo by mr g. bishop._)] the ball clays are characterised by their remarkably high plasticity, their fine texture and their freedom from grit. they are by no means so pure as the china clays, and unless carefully selected can only be used for common ware. the better qualities burn to a vitrified mass of a light brownish tint, but when mixed with the other materials used in earthenware manufacture they should produce a perfectly white ware. the inferior qualities are used for stoneware, drain pipes, etc. it should be noted that the term 'ball clay' is used for clays of widely differing characteristics though all obtained from one geological formation; when ordering it is necessary to state the purpose for which the clay is required or an entirely unsuitable material may be supplied. for the same reason, great care is needed in any endeavour to sell a ball clay from an hitherto unworked deposit. _coarse pottery clays_[ ] are usually found near the surface and whilst they may be derived from any geological formation, those most used in england are of triassic or permian origin, though some small potteries use material of other periods, including alluvial or surface clays. these clays are closely allied to those used for brickmaking, but are somewhat finer in texture and more plastic. in some cases they are prepared from brick clays by treating the latter in a wash-mill, the coarser particles being then removed, whilst the finer ones, in the state of a slip or slurry, are run into a settling tank and are there deposited. [footnote : coarse pottery has been defined as that made from natural clay without the addition of any material other than sand and water.] the presence of a considerable proportion of iron oxide results in the formation of red ware, which is necessarily of a porous nature, as the fluxes in the clay are such that they will not permit of its being heated to complete vitrification without loss of shape. to render it impervious the ware is covered with a glaze, usually producing red, brown or black ware (rockingham ware). the _stoneware_ or _drain-pipe clays_, are the most important of the _vitrifiable clays_ and owe their value to the fact that they can be readily used for the manufacture of impervious ware without the necessity of employing a glaze. they are, therefore, used in the manufacture of vessels for holding corrosive liquids such as acids and other chemicals, for sanitary appliances, sewerage pipes and in many other instances where an impervious material is required. owing to the lime, magnesia, potash and soda they contain, the stoneware clays undergo partial fusion at a much lower temperature than is required by some of the purer clays. the fused portion fills the pores or interstices of the material, making--when cold--a ware of great strength and impermeability. the chief difficulty experienced in the manufacture of stoneware is the liability of the articles to twist and warp when heated. for this reason it is necessary to burn them very carefully and to select the clays with circumspection. some clays are quite unsuitable for this branch of pottery manufacture because of the practical impossibility of producing ware which is correct in shape and is free from warping. what is required are clays in which the partial fusion will commence at a moderate temperature and will continue until all the pores are filled with the fused material without the remaining ingredients being attacked or corroded sufficiently to cause the ware to lose its shape. as the temperature inside a potter's kiln is continually rising, the great tendency is for the production of fused material to take place at an ever-increasing rate, so that the danger of warping becomes greater as the firing nears completion. some clays commence to vitrify at a moderate temperature and can be heated through a long range of temperature before an appreciable amount of warping occurs; such clays are said to possess a 'long range of vitrification' (p. ). in other clays the difference between the temperature at which vitrification commences and that at which loss of shape occurs is only a few degrees; such clays are useless for the manufacture of stoneware, as their vitrification range is too short. it is therefore essential that, for the manufacture of stoneware, a clay should contain a large proportion of refractory material which will form a 'skeleton,' the interstices of which will be filled by the more fusible silicates produced by the firing. it is generally found that of all the fluxes present in vitrifiable clays, soda and potash compounds--the so-called 'alkalies'--and all lime compounds are the most detrimental, as in association with clay they form a material with a very short range of vitrification. magnesia, on the contrary, accompanies a long vitrification range. the clays used in great britain for the manufacture of the best stoneware are the devonshire and dorset ball clays, the upper portions of these deposits being used for this purpose as they are somewhat less pure than the lower portions used in the manufacture of white ware. for coarser grades of stoneware, clays of other geological formations are employed, especially where the finished ware may be coloured, as the purity of the clay is of less importance. providing a clay has a sufficiently long vitrification range, a suitable colour when burned, and that it is capable of being readily formed into the desired shapes, its composition and origin are of small importance to the stoneware manufacturer. in actual practice, however, the number of sources of good stoneware clay is distinctly limited, and many manufacturers are thus compelled to add suitable fluxes to refractory clays in order to meet some of their customers' requirements. for this purpose a mixture of fireclay with finely powdered felspar or cornish stone is used. chalk--which is a cheaper and more powerful flux--or powdered glass cannot be used as the range of vitrification of the mixture would be too short. some manufacturers take the opposite course and add fireclay, flint, or other refractory material to a readily fusible clay. this is satisfactory if the latter clay is relatively low in lime and owes its fusibility to potash, soda or magnesia in the form of mica or felspar. the mica and felspar grains enter so slowly into combination with the clay that a long range of vitrification occurs, whereas with lime, or with some other soda and potash compounds, the combination occurs with great rapidity and the shape of the ware is spoiled. the =refractory clays= are commonly known as _fireclays_ on account of their resistance to heat. the china clays and kaolins are also refractory, but are too expensive and are not sufficiently plastic to be used commercially in the same manner as fireclays, except to a very limited extent, though bricks have been made for many years from the inferior portions of china clay rock at tregoning hill in cornwall. the geological occurrence of the fireclays of the coal measures has already been described on p. . in addition, there are the refractory clays occurring in pockets or depressions in the mountain limestone of north wales, staffordshire, derbyshire and ireland, which consist of siliceous clays and sands, the insoluble residue of the local dissolution of the limestone, intermixed with the débris of the overlying millstone grit (see p. ). these clays and sands can be mixed to produce bricks of remarkably low shrinkage, but the pockets are only large enough to enable comparatively small works to be erected and the clays are so irregular both in composition and distribution as to render their use somewhat speculative. a third type of refractory clay--termed _flint clay_--is used in large quantities in the united states, but is seldom found in great britain. when moistened, flint clays do not soften, but remain hard and flint-like with a smooth shell-like fracture. for use they are ground extremely fine, but even then they develop little plasticity. they are considered by ries ( ) to have been formed by solution and re-precipitation of the clay subsequent to its primary formation, in a manner similar to flint. they are somewhat rich in alumina and many contain crystals of pholerite (al o · sio · h o). the coal measure fireclays (p. )--which are by far the most important--are divided into two sections by the coal seams, those above the coal being shaly and fissile in structure whilst those below (_underclays_) are without any distinct lamination. both these clays may be equally refractory, but the underclays are those to which the term fireclay is usually applied. the lowest portions are usually more silicious and in some areas are so rich in silica as to be more appropriately termed silica rock or _ganister_. fireclays may, in fact, be looked upon as a special term for the grey clays of the coal measures, interstratified with and generally in close proximity to the seams of coal. they are known locally as _clunches_ and _underclays_ and were at one time supposed to represent the soil that produced the vegetation from which the coal was formed, but are now considered by many authorities to be of estuarine origin. it is important to notice that whilst the coals almost invariably occur in association with underclays, some fireclays are found at a considerable distance from coal. the fireclays of the coal measures have a composition varying within comparatively wide limits even in contiguous strata; those chiefly used having an average of to per cent. of alumina and to per cent. of silica. they appear to consist of a mixture of clay and quartz with a small proportion of other minerals, but in some of them a portion of the clay is replaced by halloysite--another hydro-alumino-silicate with the formula h al si o or al o . sio . h o. their grey colour is largely due to vegetable (carbonaceous) matter and to iron compounds. the latter--usually in the form of pyrites--is detrimental to the quality of the goods as it forms a readily fusible slag. unlike the iron in red-burning clays it can seldom be completely oxidized and so rendered harmless. the fireclays must therefore be carefully selected by the miners. on the continent, and to a much smaller extent in great britain, refractory articles are made from mixtures of grog or burned fireclay with just sufficient raw clay to form a mass of the required strength. for this purpose a highly plastic, refractory clay is required and the tertiary ball clays of devon and dorset (p. ) are particularly suitable. the most important characteristics of a fireclay are that it shall be able to resist any temperature to which it may be exposed and that the articles into which it is made shall not be affected by rapid changes in temperature. other characteristics of importance in some industries are the resistance to corrosive action of slags and vapours, to cutting and abrasion by dust in flue-gases or by the implements used in cleaning the fires. for those purposes it is necessary that a fireclay should possess high infusibility (p. ), a low burning shrinkage (p. ) and a high degree of refractoriness (p. ), and before it is used these characteristics should be ascertained by means of definite tests, as they cannot be determined by inspection of a sample or from a study of its chemical analysis. several grades of fireclay have long been recognized on the continent and in the united states of america, but the recent specification of the institution of gas engineers is the only official recognition in great britain of definite grades. this specification defines as no. grade a fireclay which shows no signs of fusion when heated to ° c. or cone at the rate of ° c. per minute, and as no. grade fireclay those which show no signs of fusion when similarly heated to ° c. or cone . it is regarded as a sign of fusion if a test piece with sharp angles loses its angularity after heating to a predetermined temperature (see p. ). it is customary to regard as 'fireclay' all clays which, when formed into the shape of a seger cone (fig. ) do not bend on heating slowly until a temperature of ° c. (cone ) is reached. any clays comprised within this definition and yet not sufficiently refractory to be of the no. grade just mentioned may be regarded as no. grade fireclays. many of the last named are well suited for the manufacture of blocks for domestic fireplaces, for glazed bricks and for firebricks not intended to resist furnace temperatures. to resist sudden changes in temperature the material must be very porous--the article being capable of absorbing at least one-sixth of its volume of water. for this reason it is customary to mix fireclays with a large proportion of non-plastic material of a somewhat coarse texture, the substance most generally employed being fireclay which has been previously burned and then crushed. this material is known as _grog_ or _chamotte_ and has the advantage over other substances of not affecting the composition of the fireclay to which it is added, whilst greatly increasing its technical usefulness. the addition of grog also reduces the shrinkage of the clay during drying and ensures a sounder article being produced. the most serious impurities in refractory clays are lime, magnesia, soda, potash and titanium and their compounds as they lower the refractoriness of the material. iron, in the state of ferric oxide is of less importance, but pyrites and all ferrous compounds are particularly objectionable. pyritic and calcareous nodules may, to a large extent, be removed by picking, and by throwing away lumps in which they are seen to occur. there is, at present, no other means of removing them. fireclays may be ground directly they come from the mine, but it is usually better to expose them to the action of the weather as this effects various chemical and physical changes within the material, which improves its quality as well as reduces the power required to crush it. to take full advantage of the refractory qualities of a clay it is necessary to select it with skill, prepare and mould it with care, to burn it slowly and steadily, to finish the heating at a sufficiently high temperature and to cool the ware slowly. rapidly heated fireclay is seldom so resistant to heat under commercial conditions as that which has been more steadily fired. rapid or irregular heating causes an irregular formation and distribution of the fused material during the process of vitrification (p. ) and so produces goods which are too tender to be durable. it is, therefore, necessary to exercise great care in the firing. =shales= are rocks which have been subjected to considerable pressure subsequent to their deposition and are, consequently, laminated and more readily split in one direction than in others. some shales are almost entirely composed of silica or calcareous matter, but many others are rich in clay, the term referring to physical structure and not to chemical composition. the clay-shales occur chiefly in the silurian and carboniferous formations, the latter being more generally used by clayworkers. clay-shales are valued according to (_a_) the proportion of oil which can be distilled from them, those rich in this respect being termed _oil shales_; (_b_) the colour when burned, as in _brickmaking and terra-cotta shales_; (_c_) the refractoriness, as in _fireclay shales_ and (_d_) the facility with which they are decomposed on exposure or on heating and form sulphuric acid as in _alum shales_. _oil shales_ contain so much carbonaceous matter that on distillation at a low red heat they yield commercially remunerative quantities of a crude oil termed _shale tar_. in composition they are intermediate between cannel coal and a purely mineral shale. to be of value they should not yield less than gallons of crude oil per ton of shale, with ammonia and illuminating gas as by-products. they are of silurian, carboniferous or oolitic origin, the kimeridge shale associated with the last-named being very valuable in this respect. the most important oil shales occur in scotland. the _fireclay shales_ have already been described on pages and . the _brickmaking shales_ are those which are sufficiently rich in clay to form a plastic paste when ground and mixed with water. they can be made into bricks of excellent colour and great strength, but for this purpose require the use of powerful crushing and mixing machinery. they are usually converted into a stiff paste of only moderate plasticity and are then moulded by machinery in specially designed presses, though some firebricks are made from crushed shale mixed into a soft paste with water and afterwards moulded by hand. some shales, such as the _knotts_ at fletton near peterborough are not made into a paste, the moist powdered shale being pressed into bricks by very powerful machinery. brickmaking shales may be found in any of the older geological formations, though they occur chiefly in the silurian, permian, carboniferous and jurassic systems. the purer shales of the coal measures burn to an agreeable cream or buff colour, the less pure ones and those of the other formations mentioned produce articles of a brick-red or blue-grey colour. where the shales are of exceptionally fine grain and their colour when burned is very uniform and of a pleasing tint they are known as _terra-cotta_ shales, the red terra-cottas being chiefly made from those occurring in wales and the buff ones from the lower grade fireclays of the coal measures. _alum shales_ are characterised by a high proportion of pyrites, which, on roasting, form ferrous sulphate and sulphuric acid. the latter combines with the alumina in the shale and when the roasted ore is extracted with water a solution of iron sulphate and aluminium sulphate is obtained. from this solution (after partial evaporation) alum crystals are obtained by the addition of potassium or ammonium sulphate. the chief alum shales are those of the silurian formation in scotland and scandinavia. the liassic shales of whitby were at one time an equally important source of alum. during recent years a large amount of alum has been obtained from other sources or has been made from the lower grade dorset and devonshire ball clays by calcining them and then treating them with sulphuric acid. these clays being almost free from iron compounds yield a much purer alum at a lower cost. =brick clays= are those which are not suitable--either from nature or situation--for the manufacture of pottery or porcelain and yet possess sufficient plasticity to enable them to be made into bricks. the term is used somewhat loosely, and geologists not infrequently apply it to clays which are quite unsuitable for brickmaking on account of excessive shrinkage and the absence of any suitable non-plastic medium. large portions of the 'london clay' are of this nature and can only be regarded as of use to brick- and roofing-tile-manufacturers when the associated bagshot sands are readily accessible. similarly, some of the very tough surface clays of the northern and midland counties are equally valueless, though designated 'brick clays' in numerous geological and other reports. it is, therefore, necessary to remember that, as ordinarily used, the term 'brick clay' merely indicates a material which appears at first sight to be suitable for brickmaking, but that more detailed investigations are necessary before it can be ascertained whether a material so designated is actually suitable for the purpose. it is also important to observe that local industrial conditions may be such that a valuable clay may be used for brickmaking because there is a demand for bricks, but not for the other articles for which the clay is equally suitable. for instance, a considerable number of houses in northumberland and durham were built of firebricks at a time when it was more profitable to sell these articles for domestic buildings than for furnaces. in many ways the bricks used for internal structural work form the simplest and most easily manufactured of all articles made from clay. the colour of the finished product is of minor importance and so long as a brick of reasonably accurate shape and of sufficient strength is produced at a cheap rate, little else is expected. impurities--unless in excessively large proportions--are of small importance and, indeed, sand may almost be considered an essential constituent of a material to be used for making ordinary bricks. it is, therefore, possible to utilize for this purpose some materials containing so little 'clay' as to make them scarcely fit to be included in this term. so long as the adventitious materials consist chiefly of silica and chalk and the mixture is sufficiently plastic to make strong bricks, it may be used satisfactorily in spite of its low content of clay, but if the so-called 'brick clay' contains limestone, either in large grains or nodules, it will be liable to burst the bricks or to produce unsightly 'blow-holes' on their surfaces. if too much sand or other non-plastic material is present, the resulting bricks will be too weak to be satisfactory. no brick clay can be regarded as 'safe' if it contains nodules of limestone--unless these can be removed during the preparation of the material--or if the resulting bricks will not show a crushing strength of at least tons per square foot. the introduction of machinery in place of hand-moulding and of kilns instead of clamps has greatly raised the standard of strength, accuracy in shape and uniformity in colour in many districts, and many builders in the midlands now expect to sort out from the 'common bricks' purchased, a sufficient number of superior quality to furnish all the 'facing bricks' they require. apart from this, and in districts where buildings are faced with stone or with bricks of a superior quality, the 'stock' or 'common brick' may be made from almost any clay which will bear drying and heating to redness without shrinking excessively or cracking. a linear shrinkage of in. per foot (= - / per cent.) may be regarded as the maximum with most materials used for brickmaking. clays which shrink more than this must have a suitable quantity of grog, sand, chalk, ashes or other suitable non-plastic material added. if the clay contains much ferric oxide it will produce red or brown bricks according to the temperature reached in the kiln, but if much chalk is also present (or is added purposely) a combined lime-iron-silicate is produced and the bricks will be white in colour. if only a small percentage of ferric oxide is present a clay will produce buff bricks, which will be spotted with minute black specks or larger masses of a greyish black slag if pyrites are also present or if ferrous silicate has been produced by the reduction of the iron compounds and their subsequent combination with silica. further information on brick earths will be found on page . a description of the processes used in the manufacture of bricks being outside the scope of the present work, the reader requiring information on this subject should consult _modern brickmaking_ ( ) or some similar treatise. _roofing tiles_ require clays of finer texture than those which may be made into bricks. stones, if present, must be removed by washing or other treatment, as it is seldom that they can be crushed to a sufficiently fine powder, unless only rough work is required. if sufficiently fine, the clay used for roofing tiles may be precisely the same as that used for bricks and is treated in a similar manner. it must, however, be of such a nature that it will not warp or twist during the burning; it must, therefore, have a long range of vitrification (p. ). _terra-cotta_ is an italian term signifying baked earth, but its meaning is now limited to those articles made of clay which are not classed as pottery, such as statues, large vases, pillars, etc., modelled work used in architecture, or for external decoration. although the distinction cannot be rigidly maintained, articles made of clay may be roughly divided into (_a_) pottery (_faience_) and porcelain (glazed), (_b_) terra-cotta (unglazed), (_c_) bricks and unglazed tiles devoid of decoration. in this sense, terra-cotta occupies an intermediate position between pottery and bricks, but no satisfactory definition has yet been found for it. thus, bricks with a modelled or moulded ornament are, strictly, terra-cotta, yet are not so named, and some pottery is unglazed and yet is never classed as terra-cotta, whilst glazed bricks are never regarded as pottery. again during the past few years, what is termed 'glazed terra-cotta' has been largely used for architectural purposes, yet this is really 'faience.' although this overlapping of terms may appear confusing to the reader, it does not cause any appreciable amount of inconvenience to the manufacturers or users, as it is not difficult for a practical clayworker to decide in which of the three classes mentioned a given article should be placed. partly on account of the lesser weight, but chiefly in order to reduce the tendency to crack and to facilitate drying and burning, terra-cotta articles are usually made hollow. it is necessary that clays used in the manufacture of terra-cotta should be of so fine a texture that the finest modelling can be executed. such clays occur naturally in several geological formations, and some may be prepared from coarser materials by careful washing, whereby the larger grains of sand, stones, etc., are removed. some shales, when finely ground, make excellent clays for architectural terra-cotta, portions of all the better known fireclay deposits being used for this purpose. it is, however, necessary to use only those shales which are naturally of fine texture, as mechanical grinding cannot effect a sufficient sub-division of the particles of some of the coarser shales. the finer triassic 'marls' are also admirable for terra-cotta work, the most famous deposit being the etruria marl series in the upper coal measures near ruabon. the most important characteristics required in terra-cotta clays are (_a_) fine texture, or at any rate the ability to yield a fine, dense surface, (_b_) small shrinkage with little tendency to twist, warp or crack in firing, (_c_) pleasing and uniform colour when fired, and (_d_) a sufficient proportion of fluxes to make it resistant to weather without giving a glossy appearance to the finished product. in large pieces of terra-cotta some irregularity of shape is almost unavoidable, but, if care is taken in the selection and manipulation of the material, this need not be unsightly. the durability of terra-cotta is largely dependent on the nature of the surface. the most suitable clays, when fired, have a thin 'skin' of vitrified material which is very resistant to climatic influences, and so long as this remains intact the ware will continue in perfect condition. if this 'skin' is removed, rain will penetrate the material and under the influence of frost may cause rapid disintegration. in the manufacture of very large pieces of terra-cotta a coarse, porous clay is used for the foundation and interior, and this is covered with the finer clay. by this means a greater resistance to changes in temperature is secured, the drying and the burning of the material in the kiln are facilitated and the risks of damage in manufacture are materially reduced. =cement clays= are those used in the manufacture of portland cement and of so-called natural cements. they are largely of an alluvial character and are of two chief classes: (_a_) those which contain chalk or limestone dust and clay in proportions suitable for the manufacture of cement and (_b_) those to which chalk or ground limestone must be added. they vary in composition from argillaceous limestones containing only a small proportion of clay to almost pure clays. the manufacture of portland cement has assumed a great importance and owing to the large amount of investigations made in connection with it, it may be said to represent the chief cement made from argillaceous materials, the others being convenient though crude modifications of it. the essential constituents are calcium carbonate (introduced in the form of chalk or powdered limestone) and clay, the composition of the naturally occurring materials being modified by the addition of a suitable proportion of one or other of these ingredients. the material is then heated until it undergoes partial fusion and a 'clinker' is formed. this clinker, when ground, forms the cement. in kent, the medway mud is mixed with chalk; in sussex, a mixture of gault clay and chalk is employed; in the midlands and south wales, liassic shales and limestone are used; in northumberland a mixture of kentish chalk and a local clay is preferred, and in cambridgeshire a special marl lying between the chalk and the greensand is found to be admirable for the purpose because it contains the ingredients in almost exactly the required proportions. for cement manufacture, clays should be as free as possible from material which, in slip form, will not pass through a no. sieve, as coarse sand and other rock débris are practically inert. the proportion of alumina and iron should be about one-third, but not more than one-half, that of the silica, and in countries where the proportion of magnesia in a cement is limited by standard specifications, it will be found undesirable to use clays containing more than per cent. of magnesia and alkalies. whilst calcareous clays usually prove the most convenient in the manufacture of cement, it is by no means essential to use them, and where a clay almost free from lime occurs in convenient proximity to a suitable chalk or limestone deposit an excellent cement may usually be manufactured. the 'clays' from which the so-called 'natural' or 'roman cements' are made by simple calcination and crushing, usually fuse at a lower temperature than do the mixtures used for portland cement, and unless their composition is accurately adjusted they yield a product of such variable quality as to be unsuitable for high class work. =fuller's earth= is a term used to indicate any earthy material which can be employed for fulling or degreasing wool and bleaching oil. true fuller's earth is obtained chiefly from the neighbourhood of reigate, surrey, woburn sands, bedfordshire and from below the oolite formation near bath, but owing to the scarcity of the material and the irregularity of its behaviour, china clay is now largely used for the same purpose. true fuller's earth is much more fusible than the white clays usually substituted for it, and when mixed with water it does not form a plastic paste but falls to powder. as the chief requirement of the fuller is the grease-absorbing power of the material there is no objection to the substitution of other earths of equal efficiency. fuller's earth does not appear to be a true clay, though its constitution and mineralogical composition are by no means clearly known. t. j. porter considers that it is chiefly composed of montmorillonite (al o · sio h o), anauxite, ( al o · sio · h o), and chalk with some colloidal silica and a little quartz. it therefore appears to resemble the less pure kaolins, but to contain little or no true clay, though in many respects it behaves in a manner similar to a kaolin of unusually low plasticity. =other clays= of commercial importance, with further details of the ones just mentioned, are described in the author's _british clays, shales and sands_ ( ). chapter vi clay substance: theoretical and actual having indicated the origin, modes of accumulation and general characteristics of the numerous materials known as 'clay,' it now remains to ascertain what substance, if any, is contained in all of them and may be regarded as their essential constituent, to which their properties are largely due. just as the value of an ore is dependent to a very large extent on the proportion of the desired metal which it contains, and just as coal is largely, though not entirely, esteemed in proportion to the percentage of carbon and hydrogen in it, so there may be an essential substance in clays to which they owe the most important of their characteristics. the proportion of metal in an ore or of hydrocarbon in a coal can be ascertained without serious difficulty by some means of analysis, but with clay the difficulties are so great that, to some extent at least, they must be regarded as being, for the present, insurmountable. this is in no small measure due to the general recognition of all minerals or rocks which become plastic when kneaded with water as 'clays' without much regard being paid to their composition. consequently materials of the most diverse nature in other respects are termed clays if they are known to become plastic under certain conditions. there is, in fact, at the present time, no generally accepted definition of clay which distinguishes it from mixtures of clay and sand or other fine mineral particles. the usual geological definitions are so broad as to include many mixtures containing considerably less than half their weight of true clay or they avoid the composition of the material altogether and describe it as a finely divided product of the decomposition of rocks. many attempts have been made to avoid this unfortunate position, which is alike unsatisfactory to the geologist, the mineralogist and the chemist as well as to the large number of people engaged in the purchase and use of various clays; and, whilst the end sought has not been reached as completely as is desirable, great progress has been made and much has been accomplished during the last twenty years. one of the earliest attempts to ascertain whether there is an essential constituent of all clays was made by seger ( ) who used two methods of separating some of the ingredients of natural clays from the remaining constituents. the first of these methods consists in an application of the investigations of schulze, schloesing and schoene on soils, viz. the removal of the finest particles by elutriation; the second is an extension of the method of forschammer and fresenius, viz. the treatment of the material with sulphuric acid. to the product containing the clay when either of these methods is used seger gave the name _clay substance_, but the material so separated is by no means pure clay. the term clay substance must, therefore, be confined to the crude product containing the clay together with such other impurities as are in the form of extremely small particles or are soluble in sulphuric acid. it has not yet been found possible to isolate pure clay from ordinary clays, so that in investigating the nature of what seger was endeavouring to produce when he obtained the crude clay substance, indirect methods are necessary. it has long been known that if a sample of 'clay'--using this word in the broadest sense--is rubbed in a considerable quantity of water so as to form a thin slip or slurry, it may readily be divided into a number of fractions each of which will consist of grains of different sizes. this separation may be effected by means of a series of sieves through which the slurry is poured, or the slurry may be caused to flow at a series of different speeds, the material left behind at each rate of speed being kept separate; or, finally, the slurry may be allowed to stand for a few seconds and may then be carefully decanted into another vessel in which it may remain at rest for a somewhat longer period, these times of resting and decantation, if repeated, providing a series of fractions the materials in which are more or less different in their nature. 'clays' containing a considerable proportion of coarse material are most conveniently separated into a series of fractions by means of sieves, whereby they are divided into (i) stones, (ii) gravel, (iii) coarse sand, (iv) medium sand, (v) fine sand and (vi) a slurry consisting of such small particles that they can no longer be separated by sifting. if the residues on the sieves are carefully washed free from any adhering fine material and are then dried, they will be found on examination to be quite distinct from anything definable as clay. they may consist of a considerable variety of minerals or may be almost entirely composed of quartz, but with the possible exception of some shales of great hardness, they are undoubtedly not clay. this simple process therefore serves to remove a proportion of material which in the case of some 'clays' is very large but in others is insignificant; thus per cent. of sand-like material may be removed from some brick-clays whilst a ball clay used for the manufacture of stoneware or pottery may pass completely through a sieve having meshes per linear inch. the material which passes through the finest sieve employed will contain all the true clay in the material; that is to say, the coarser portion will, as already mentioned, be devoid of the ordinary characteristics of clay. at the same time, this very fine material will seldom consist exclusively of clay, but will usually contain a considerable proportion of silt, extremely fine mineral particles and, in the case of calcareous clays, a notable proportion of calcium carbonate in the form of chalk or limestone particles. only in the case of the purest clays will the material now under consideration consist entirely of clay, so that it must be again separated into its constituents. this is best accomplished, as first suggested by schoene, by exposing the material to the action of a stream of water of definite speed. h. seger ( ) investigated this method very thoroughly and his recommendations as to the manner in which this separation by elutriation should be carried out remain in use at the present time. briefly, all material sufficiently fine to be carried away by a stream of water flowing at the rate of · in. per minute was found by seger to include the whole of the clay in the samples he examined, but, as was later pointed out by bischof, it is not correct to term the whole of this material 'clay substance,' as when examined under the microscope, it contains material which is clearly not clay. processes of decantation of the finest material obtained after elutriation still fail to separate all the non-clay material, and vogt has found that when the material has been allowed to stand in suspension for nine days some particles of mica are still associated with the clay. it would thus appear that no process of mechanical separation will serve for a complete purification of a clay; indeed, there are good reasons for supposing that extremely fine particles of quartz and mica render physical characteristics an uncertain means of accurately distinguishing clays from other rock dust. when chemical methods of investigation are employed the problem is not materially altered, nor is its solution fully attained. it is, of course, obvious that any chemical method should be applied to the product obtained by treating the raw material mechanically as above described, for to do otherwise is to create needless confusion. yet by far the greater number of published analyses of 'clays' report the ultimate composition of the whole material, no attempt being made to show how much of the various constituents is in the form of sand, stones or other coarse particles of an entirely non-argillaceous character. if the particles of a 'clay' which are sufficiently small to be carried away by a stream of water with a velocity of only · in. per minute are analysed, it will be found that their composition will vary according to the origin of the clay and the subsequent treatment to which it has been subjected during its transport and deposition. if the clay is fairly free from calcareous material and is of a white-burning nature it may be found to have a composition like china clays. red-burning clays, on the contrary, will vary greatly in composition, so that it becomes difficult to find any close analogy between these kinds of clay. this difference is partly due to the extremely fine state of division in which ferric oxide occurs in clays, the particles of this material corresponding in minuteness to those of the purest clays and so being inseparable by any mechanical process. in h. seger ( ) published what he termed a method of 'rational analysis,' which consisted in treating the clay with boiling sulphuric acid followed by a treatment with caustic soda. he found that the purer china clays (kaolins) and ball clays were made soluble by this means and that felspar, mica and quartz were to a large extent unaffected. later investigators have found that this method is only applicable to a limited extent and that its indications are only reliable when applied to the clays just named, but the principle introduced by seger has proved invaluable in increasing our knowledge of the composition of clays. by means of this so-called rational analysis seger found that the purer clays yielded results of remarkable similarity and uniformity, the material entering into solution having a composition agreeing very closely with the formula al o · sio · h o which is generally recognized as that of the chief constituent or constituents of china clay (kaolin) and the purer ball clays. this crude substance, obtainable from a large number of clays by the treatment just described, was named _clay substance_ by seger, who regarded it as the essential constituent of all clays. red-burning clays when similarly treated do not yield so uniform a product, and the ferric oxide entering into solution makes the results very discordant. moreover, even with the china clays or kaolins a small proportion of alkalies, lime and other oxides enter into solution and a number of minerals analogous to clay, but quite distinct from it, are also decomposed and dissolved. for these reasons the 'rational analysis' has been found insufficient; it is now considered necessary to make an analysis of the portion rendered soluble by treatment with sulphuric acid in order to ascertain what other ingredients it may contain in addition to the true clay present. as the china clays (kaolins) and ball clays on very careful elutriation all yield a product of the same ultimate composition, viz. per cent. of alumina, per cent. of silica, per cent. of water, and per cent. of other oxides, they are generally regarded as consisting of practically pure clay with a variable amount of impurities. many years ago fresenius suggested that these non-clayey constituents of clays should be calculated into the minerals to which they appeared likely to correspond so as to obtain a result similar to that obtained by seger without the disadvantages of the treatment with sulphuric acid and as supplementary to such treatment in the case of red-burning and some other clays. more recent investigators have found that if a careful microscopic examination of the clay is made the results of estimating the composition from the proportion of the different minerals recognizable under the microscope and by calculation from the analysis of the material agree very closely and are, as bischof ( ) and, more recently, mellor have pointed out, more reliable than the 'rational analysis' in the case of impure clays. if care is taken to make a microscopical examination identifying the chief impurities present the calculation from the analysis may usually be accepted as sufficiently accurate, but it is very unsatisfactory to assume, as some chemists do, that the alkalies and lime in the clay are all in the form of felspar and that the silica remaining in excess of that required to combine with the alkalies, lime and alumina is free quartz. some clays are almost destitute of felspar but comparatively rich in mica, whilst others are the reverse, so that some means of identifying the extraneous minerals is essential. when this is not used, the curious result is obtained that german chemists calculate the alkalies, etc. to felspar whilst the french chemists, following vogt, calculate them to mica; english ceramic chemists appear undecided as to which course to follow, and some of them occasionally report notable amounts of felspar in clays quite destitute of this mineral! a statement of the composition of a 'clay' based on a mechanical separation of the coarser ingredients followed by an analysis of the finer ones and a calculation of the probable constituents of the latter, as already described, is known as a _proximate analysis_ in order to distinguish it from an _ultimate analysis_ which states the composition of the whole material in terms of its ultimate oxides. a proximate analysis therefore shows the various materials entering into the composition of the clay in the following or similar terms: stones per cent. gravel " coarse sand " medium sand " fine sand " silt " felspar or mica dust " silica dust " 'true clay[ ]' " moisture " carbon " other volatile matter " [footnote : in analytical reports a note should be appended stating that the figure under this term shows the proportion of the nearest approximation to true clay at present attainable.] for some purposes it is necessary to show the proportion of calcium, iron and other compounds as in an ordinary ultimate analysis. a comparison of the foregoing with an ultimate or 'ordinary' analysis of a clay (p. ) will show at once the advantage of the former in increasing our knowledge of the essential constituent of all clays, if such a substance really exists. its absolute existence is by no means proved, for, as will have been noticed, its composition is largely based on assumption even in the most thorough investigations, particularly of the admittedly less pure clays. in the purer clays the problem is much simpler and in their case an answer of at least approximate accuracy can be given to the question 'what is clay?' even with these purer clays it is not sufficient to study an analysis showing the total amount of the silica, alumina and other oxides present; it is still necessary to effect some kind of separation into the various minerals of which they are composed. when, however, the accessory minerals do not exceed per cent. of the total ingredients their influence is less important and the nature and characteristics of the 'clay substance' itself can be more accurately studied. by careful treatment of well selected china clays, for example, it is possible to obtain a material corresponding to the formula al o · sio · h o within a total error of per cent., the small amount of impurity being, as far as can be ascertained, composed of mica. so pure a specimen of clay is found on microscopical examination to consist of minute irregular grains of no definite form, together with a few crystals of the same composition and identifiable as the mineral 'kaolinite' (p. ). this 'amorphous' material, which appears to be the chief constituent of all china clays and kaolins, has been termed _clayite_ by mellor ( ). johnson and blake, aron and other observers have stated that the majority of the particles in china clays and kaolins are crystalline in form. owing to their extreme smallness it is exceedingly difficult to prove that they are not so, though for all ordinary purposes they may be regarded as amorphous, the proportion of obviously crystalline matter present in british china clay of the highest qualities being so small as to be negligible. hickling ( ), using an exceptionally powerful microscope, claims to have identified this 'amorphous' substance in china clay as 'worn and fragmental crystals of kaolinite,' and recently mellor and holdcroft and rieke have shown that the apparently amorphous material shows the same endo- and exothermal reactions as crystalline kaolinite. so far as china clays or kaolins are concerned, kaolinite or an amorphous substance of the same composition appears to be identical with the 'ideal clay' or 'true clay' whose characters have so long been sought. this term--clayite--is very convenient when confined to china clays and kaolins, but it is scarcely legitimate to apply it, as has been suggested, to material in other clays until it has been isolated in a sufficiently pure form to enable its properties to be accurately studied. this restriction is the more necessary as in one very important respect clayite obtained from china clay and some kaolins differs noticeably from the nearest approach to it obtainable from the more plastic clays: namely, in its very low plasticity. this may be explained by the fact that it is only obtainable in a reasonably pure form in clays of a primary character, whilst the plastic clays have usually been transported over considerable areas and have been subjected to a variety of treatments which have had a marked effect on their physical character. moreover, the fact that the purest 'clay' which can be isolated from plastic clays appears to be amorphous and to some extent colloidal greatly increases the difficulty of obtaining it in a pure state, especially as no liquid is known which will dissolve it without decomposing it. the fact that it is not an elementary substance, but a complex compound of silica, alumina and the elements of water, also increases the intricacy of the problem, for these substances occur in other combinations in a variety of other minerals which are clearly distinct from clay. ever since the publication of seger's memorable papers ( ), and to a small extent before that time, it has been generally understood that china clay or kaolin represented the true essential constituent of clays, but several investigators have been so imbued with the idea that all true clay substance must have a crystalline form that they have frequently used the term 'kaolinite' to include the 'amorphous' substance in plastic clays. this is unfortunate as it is by no means proved that the latter is identical with kaolinite, and a distinctive term would be of value in preventing confusion. other investigators have used the word 'kaolin' with equal freeness, so that whilst it originally referred to material from a particular hill or ridge in china[ ] it has now entered into general use for all clays whose composition approximates to that of china clay (p. ) in which the plasticity is not well developed. thus, in spite of the difference in origin between many german and french kaolins and the china clays of cornwall, it is the custom in europe generally to term all these materials 'kaolin.' yet they are very different in many respects from the material originally imported from china. [footnote : _kao-ling_ is chinese for a high ridge or hill.] as the essential clay substance has not yet been isolated in a pure form from the most widely spread plastic clays, but is largely hypothetical as far as they are concerned, the author prefers the term _pelinite_[ ] when referring to that portion of any plastic clays or mixtures of clays with other minerals which may be regarded as being the constituent to which the argillaceous portion of the material owes its chief properties. in china clay and kaolin the 'true clay' is identical with clayite--or even with kaolinite (p. )--and there is great probability that this identity also holds in the case of the more plastic clays of other geological formations, but until it is established it appears wisest to distinguish the hypothetical or ideal clay common to all clays (if there is such a substance) by different terms according to the extent to which its composition and characters of the materials most closely resembling it are experimentally known. [footnote : from the [greek: pêlinos] = made of clay.] the substances most resembling this 'ideal clay' which have, up to the present been isolated, are: (_a_) _kaolinite._ found in a crystalline form in china clays and kaolins (p. ). (_b_) _clayite._ a material of the same chemical composition as kaolinite, but whose crystalline nature (if it be crystalline) has not been identified--chiefly obtained from china clays and kaolins. (_c_) _pelinite._ a material similar to clayite, but differing from it in being highly plastic and, to some extent, of a colloidal nature--obtained from plastic clays. (_d_) _laterite._ a material resembling clayite in physical appearance, but containing free alumina and free silica (p. ). (_e_) _clay substance._ a general term indicating any of the foregoing or a mixture of them; it is also applied (unwisely) to the material obtained when a natural clay is freed from its coarser impurities by elutriation (p. ). the chief characteristics of 'true clay' from different sources. in so far as it can be isolated _true clay_ appears to be an amorphous, or practically amorphous, material which may under suitable conditions crystallize into rhombic plates of kaolinite. the particles of which it is composed are extremely small, being always less than · in. in diameter. they adsorb dyes from solutions and show other properties characteristic of colloid substances though in a very variable degree, some clays appearing to contain a much larger proportion of colloidal matter than do others. to some extent the power of adsorption of salts and colouring matters appears to be connected with the plasticity (p. ) of the material, but this latter property varies so greatly in clayite or pelinite from different sources as to make any generalization impossible. true clay substance appears to be quite white, any colour present being almost invariably traceable to ferric compounds or to carbonaceous matter. the latter is of small importance to potters as it burns away in the kiln. the specific gravity of clay substance is · according to hecht, the lower figures sometimes reported being too low. its hardness is usually less than that of talc--the softest substance on mohs' scale--but some shales are so indurated as to scratch quartz. it is quite insoluble in water and in dilute solutions of acids or alkalies, but is decomposed by hydrofluoric acid and by concentrated sulphuric acid when heated, alumina entering into solution and silica being precipitated in a colloidal condition. it absorbs water easily until a definite state of saturation has been reached, after which it becomes impervious unless the proportion of water is so large and the time of exposure so great that the material falls to an irregular mass which may be converted into a slurry of uniform consistency by gently stirring it. with a moderate amount of water, pelinite develops sufficient plasticity to enable it to be modelled with facility, but clayite and some specimens of pelinite are somewhat deficient in this respect. the pelinitic particles usually possess the capacity to retain their plasticity after being mixed with considerable proportions of sand or other non-plastic material and are then said to possess a high binding power (p. ). if a large proportion of water is added to a sample of clayite or pelinite and the mixture is stirred into a slurry it will be found to remain turbid for a considerable time and will not become perfectly clear even after the lapse of several days. its power of remaining in suspension is much influenced by the presence of even small amounts of soluble salts in either the water or the clay substance, its precipitation being hastened by the addition of such salts as cause a partial coagulation of the colloidal matter present. some specimens of clayite and pelinite retain their suspensibility even in the presence of salts, but this is only true of a very limited proportion of the substance. in most cases the presence of soluble salts causes the larger particles to sink somewhat rapidly and to carry the finer particles with them. the rate at which a slip or 'cream' made of elutriated clay and water will flow through a small orifice is dependent on the viscosity of the liquid and this in turn depends on the amount of colloidal material present, _i.e._ on how much of the clay (pelinite) is in a colloidal form. its viscosity is greatly affected by the addition or presence of small quantities of acid or alkali or of acidic or basic salts. acids increase the viscosity; alkalies and basic salts, on the contrary, make the slip more fluid. neutral salts behave in different ways according to the concentration of the solution and to the amount of clay (pelinite) present in the slip. if the slip contains so little water as to be in the form of a thin paste, neutral salts usually have but a small action, but when the slip contains only a small proportion of clay (pelinite) the presence of neutral salts will tend to cause the precipitation of the clay. in this way salts act in two quite different directions according to the concentration of the slip. on drying a paste made of clay and water the volume gradually diminishes until the greater part of the water has been removed; after this the remainder of the water may be driven off without any further reduction in volume of the material. this is another characteristic common to colloidal substances such as gelatin. the material when drying attains a leathery consistency which is at a maximum at the moment when the shrinkage is about to cease; on further drying the material becomes harder and more closely resembles stone. providing that wet clay is not heated to a temperature higher than that of boiling water it appears to undergo no chemical change and on cooling it will again take up water[ ] and be restored to its original condition except in so far as its colloidal nature may have been affected by the heating. if, however, the temperature is raised to about ° c. a decomposition of the material commences and water is evolved. this water--which is commonly termed 'combined water'--is apparently an essential part of the clay-molecule and when once it has been removed the most important characteristics of the clay are destroyed and cannot be restored. the reactions which occur when clay is heated are complex and are rendered still more difficult to study by the apparent polymerization of the alumina formed. mellor and holdcroft ( ) have recently investigated the heat reactions of the purest china clay obtainable and confirm le chatelier's view ( ) that on heating to temperatures above ° c. clay substance decomposes into free silica, free alumina and water, the two former undergoing a partial re-combination with formation of sillimanite (al o sio ) if a temperature of ° c. is reached. mellor and holdcroft point out that there is no critical point of decomposition for clay substance obtained from china clay, as it appears to lose water at all temperatures, though its decomposition proceeds at so slow a rate below ° c. as to be scarcely appreciable. [footnote : some clays are highly hygroscopic and absorb moisture readily from the atmosphere. according to seger ( ) this hygroscopicity distinguishes true clay from silt and dust.] after the whole of the 'combined water' has been driven off, if the temperature continues to rise, it is found that at a temperature of ° c. an evolution of heat occurs. this exothermal point, together with the endothermal one occurring at the temperature at which the decomposition of the clay seems to be most rapid, has been found by le chatelier, confirmed by mellor and holdcroft, to be characteristic of clay substance derived from kaolin and china clay, and the two last-named investigators state that it serves as a means of distinguishing kaolinite or clayite from other alumino-silicates of similar composition. these thermal reactions have not, as yet, been fully studied in connection with plastic clays; with china clay, as already noted, they probably indicate a polymerization of the alumina set free by the decomposition of the clay substance, as pure alumina from a variety of sources has been found by mellor and holdcroft to behave similarly. on still further raising the temperature of pure clay (pelinite or clayite) no further reactions of importance occur, the material being practically infusible. if, however, any silica, lime, magnesia, alkalies, iron oxide or other material capable of combining with the alumina and silica is present as impurities in the clay substance, combination begins at temperatures above ° c. this causes a reduction of the heat-resisting power of the material; the silicates and alumino-silicates produced fuse and begin to react on the remaining silica and alumina, first forming an impermeable mass in place of the porous one produced with pure clay substance, and gradually, as the material loses its shape, producing a molten slag if the 'clay' is sufficiently impure. as ordinary clays are never quite free from metallic compounds other than alumina, this formation of a fused portion--technically known as _vitrification_ (p. )--occurs at temperatures depending on the nature of the materials present, so that a wide range of products is obtained, the series commencing with the entirely unfused pure clay (china clay), passing through the slightly vitrified fireclays, the more completely vitrified ball clays to the vitrifiable stoneware clays and ending with materials so rich in easily fusible matter as scarcely to be worthy of the name of clays. the constitution of the clay molecule is a subject which has attracted the attention of many investigators and is being closely studied at the present time. it is a subject of peculiar difficulty owing to the inertness of clay substance at all but high temperatures, and to the complexity of reactions which take place as soon as any reagent is brought into active connection with it. without entering into details regarding the various graphic formulae which have been suggested, it is sufficient to state that the one which is most probably correct, as far as present knowledge goes, is mellor's and holdcroft's re-arrangement of groth's formula ( ) ho\ /osio\ \al / \o / \ / ho/ /\ \osio/ / \ ho oh which on removal of the hydroxyl groups might be expected to give the anhydride o\\ /osio\ \\al / \ // \ / o// \osio/ though in practice this substance--if formed at all--appears to be instantly split up into al o and sio . by regarding the aluminium as a nucleus, as above, and some aluminium silicates as hypothetical alumino-silicic acids, as suggested by ulffers, scharizer, morozewicz ( ) and others, clay substance may be conveniently considered, along with analogous substances, as forming a special group quite distinct from the ordinary silicates. in this way mellor and holdcroft ( ) consider that clay substance is not a hydrated aluminium silicate--as is usually stated in the text-books--but an alumino-silicic acid, the salts of which are the zeolites and related compounds. from this hypothesis it naturally follows that clay substance is analogous to colloidal silica which has been formed by the decomposition of a silicate by means of water and an acid. if this view be correct, pure clay substance or true clay is a tetra-basic alumino-silicic acid h al sio or al si o ( h ). that its acid properties are not readily recognizable at ordinary temperatures is due to its inertness; at higher temperatures its power of combination with lime, soda potash and other bases is well recognized, though the reactions which occur are often complicated by decompositions and molecular re-arrangements which occur in consequence of the elevated temperature. there are a number of minerals which closely resemble clayite or pure clay substance in composition, the chief difference being in the proportion of water they evolve on being heated. thus _rectorite_ h al si o , _kaolinite_ h al si o , _halloysite_ h al si o and _newtonite_ h al si o . in the crystalline form these minerals may be distinguished from each other by means of the microscope, but as the chief materials of which clays are composed appears to be amorphous it is impossible to ascertain with certainty whether a given specimen of clay substance is composed of a mixture of these analogous minerals in an amorphous form or whether it consists entirely of clayite, _i.e._ the clay substance obtained from china clay. as already stated, the thermal reactions which occur on heating clayite appear to be characteristic of kaolinite whilst halloysite is completely decomposed at a temperature somewhat below ° c.; but the not improbable presence of two or more of these alumino-silicic acids in clays of secondary or multary origin makes it almost impossible to determine whether clayite is an essential constituent of all clays or whether the purest clay substance (pelinite) obtained from some of the more plastic clays does not possess a different chemical composition as well as different physical properties. the view that clays may be regarded as impure varieties of clayite is considered erroneous by several investigators for various reasons. for instance, felspar is rarely found in china clays, but is a common constituent of secondary (plastic) clays. j. m. van bemmelen ( ), who has found that the alumina-silica ratio of clays produced by weathering is always higher than that in clays of the china clay type produced by hypogenic action. in a number of clays examined he found that a portion was soluble in boiling hydrochloric acid whereas clayite is scarcely affected by this treatment. he also found a varying proportion of alumino-silicate insoluble in hydrochloric acid but dissolved on treatment with boiling sulphuric acid and subsequently with caustic soda solution; this latter he considers to be true clayite. unfortunately, his results were obtained by treating the crude clay with acid, instead of first removing such non-plastic materials as can be separated by washing, so that all that they show is that some clays contain alumino-silicates of a nature distinct from clayite in addition to any clayite which may be found in them. the fact that all clays when heated to or ° c. readily react with lime-water to form the same calcium silicates and aluminates indicates so close a resemblance between the clay substance obtainable from different sources as to constitute strong evidence of the identity of this substance with clayite or with materials so analogous to it as to be indistinguishable from it under present conditions. in all probability, the plastic clays have been derived from a somewhat greater variety of minerals than the primary clays (p. ) and under conditions of decomposition which differ in details, though broadly of the same nature as those producing china clays. the presence of colloidal matter suggests a more vigorous action--or even a precipitation from solution--instead of the slower reactions which result in the formation of the kaolinite crystals. the much smaller particles present in plastic clays also indicate a more complete grinding during the transportation of the material or some form of precipitation. if, as hickling suggests, all clays are direct products of the decomposition of _mica_, the fact that several varieties of mica are known and that the conditions under which these decompose must vary considerably, afford a good, if incomplete, explanation of some of the widely diverse characteristics observed in different clays. notwithstanding the great complexities of the whole subject and the apparently contradictory evidence concerning some clays, there is a wide-spread feeling that whatever may be the mineral from which a given clay has been derived, the _true clay substance_, which is its essential constituent, would (if it could be isolated in a pure state) prove to be of the same composition as kaolinite obtainable from china clay of exceptional purity. the purest clay substances (pelinite) yet obtained from some of the most plastic clays are, however, so impure as to make any detailed investigation of their composition by present methods abortive. the methods of synthesis which have proved so successful in organic chemistry have hitherto yielded few intelligible results with clays, on account of the complexity of the accessory reactions which occur. the difference between pure clay substance and ordinary clays. the properties and characteristics of _true clay_ are very seriously modified by other materials which may be associated with it. this may be perceived by comparing the properties of clays mentioned in chapter i with those of various forms of true clay just given. moreover, as true clay never occurs in a perfectly pure state in nature, the properties of clays must be largely dependent on the accessory ingredients. silica, for example, when alone is a highly refractory material, but in the presence of true clay it reduces the refractoriness of the latter. lime has a similar effect though its chemical action on the clay is entirely different. a very small proportion of some substances--notably the oxides of sodium and potassium--will greatly alter the behaviour of true clay when heated and will produce an impervious mass in place of a porous one. for these reasons, it is necessary in studying clays to pay attention to both their physical and chemical properties and to separate the material into fractions so that each of these may be studied separately and their individual as well as their collective characteristics ascertained. failure to do this has been the cause of much obscurity and confusion in investigations on certain clays composed of a considerable proportion of non-argillaceous material which ought to have been separated before any attempt was made to study the true clay present. there is, therefore, a considerable difference between a natural clay and the pure clay substance theoretically obtainable from it; this difference being most marked in the case of low-grade brick clays of glacial origin, which may contain per cent. or more of adventitious materials. if used in a natural state they would be found to be valueless on account of their impurities giving them characteristics of a highly undesirable character, whereas the true clay in them is found--in so far as it can be separated--to bear a close resemblance to that obtained from a high grade, plastic, pottery clay. unfortunately, it is, at present, impossible to isolate this clay substance in anything approaching a pure form, and many clays are without commercial value because of comparatively small proportions of impurities which cannot be separated from the clay substance without destroying the latter. classification of clays. owing to the widely differing substances from which clays can, apparently, be formed and the peculiar difficulties which are experienced in investigating the nature of clay substance from different sources, it is by no means easy to devise a scheme of classification of clays, though many of these have been attempted by different scientists. the classification adopted by geologists is based on the fossil remains and on the stratigraphical position of clays relative to other rocks, as described in chapter ii. this is of great value for some purposes, but the composition of the substances termed 'clay' by geologists differs so greatly, even when only one formation is considered, as to make their classification of little or no use where the value or worthlessness of the material depends upon its composition. thus the so-called oxford clay ranges from a hard silicious shale to a comparatively pure clay; some portions of it are so contaminated with calcareous and ferruginous matter as to make the material quite useless for the potter or clayworker. a geological classification of clays is chiefly of value as indicating probable origins, impurities and certain physical properties; but the limits of composition and general characteristics are so wide as to make it of very limited usefulness. the classification of clays on a basis of chemical composition is rendered of comparatively little value by the large number of clays which occupy ill-defined borders between the more clearly marked classes. moreover, attempts to predict the value and uses of clays from their chemical composition are generally so misleading as to be worse than useless, unless a knowledge of some of the physical characters of the clays is available. it is, of course, possible to differentiate some clays from others by their composition, but not with sufficient accuracy to permit of definite and accurate classification. a classification based exclusively on the composition of clays is equally unsatisfactory for other reasons, the chief of which is the placing together of clays of widely differing physical character, and the separation of clays capable of being used for a particular purpose. to some extent the latter objection may be disregarded, though it is of great importance in considering the commercial value of a clay. classification based on the uses of clays of different kinds has been suggested by several eminent ceramists, but is obviously unsatisfactory, particularly as it is by no means uncommon to use mixtures of clays and other minerals for some purposes. thus stoneware clays must be vitrifiable under conditions which may be defined with sufficient accuracy, but many manufacturers of stoneware do not use clays which are naturally vitrifiable; they employ a mixture of refractory clay and other minerals to obtain the material they require. a classification based on the origin of clays regarded from the petrological point of view offers some advantages, but is too cumbersome for ordinary purposes and suffers from the disadvantage that the origin of some important clays is by no means clearly known. the author prefers a modification of grimsley's and grout's classification ( ) as follows: i. primary clays. (_a_) clays produced by 'weathering' silicates--as some kaolins. (_b_) clays produced by lateritic action--very rich in alumina, some of which is apparently in a free state. (_c_) clays produced by telluric water containing active gases (hypogenically formed clays)--as cornish china clay. ii. secondary clays. (_d_) refractory[ ] secondary clays--as fireclays and some pipe clays. (_e_) pale-burning non-refractory clays--as pottery clays, ball clays and some shales. (_f_) vitrifiable clays--as stoneware clays, paving brick clays. (_g_) red-burning and non-refractory clays--as brick and terra-cotta clays and shales. (_h_) calcareous clays or marls, including all clays containing more than per cent. of calcium carbonate. iii. residual clays. (_i_) clays which have been formed by one of the foregoing actions and have been deposited along with calcareous or other matter but, on the latter being removed by subsequent solution, the clay has remained behind--as the white clays of the derbyshire hills. [footnote : a refractory clay is one which does not soften sufficiently to commence losing its shape at any temperature below that needed to bend seger cone (approximately °c.) (see p. ).] some further sub-division is necessary for special purposes, particularly in sections _e_, _f_ and _h_, but to include further details would only obscure the general scheme. some clays will, apparently, be capable of classification in more than one section, thus a vitrifiable clay may owe its characteristic to a high proportion of calcium carbonate and so be capable of inclusion as a calcareous clay. broadly speaking, however, if the clay is tested as to its inclusion in each section of the scheme in turn it will be found that its highest value will be in the section which is nearest to the first in which the clay can legitimately be placed. from a consideration of a classification such as the foregoing, together with a detailed study of the physical and chemical properties of the material as a whole, and also of the various portions into which it may be divided--particularly that which has been isolated by mechanical methods of purification and separation--it is not difficult to gain a fairly accurate idea of the nature of any clay. although the present state of knowledge does not permit them to be classified with such detail as is the case with plants, animals, or simple chemical compounds, the study of clays and the allied materials has a fascination peculiarly its own, not the least interesting features of which are those properties of the clay after it has been made into articles of use or ornament. these are, however, beyond the scope of what is commonly understood by the term 'the natural history of clay.' bibliography a complete bibliography of clay would occupy several volumes. the following list only includes the more accessible of the works quoted in the text. . "second report of the committee on technical investigation--rôle of iron in burning clays." orton and griffith. indianapolis. . . "british clays, shales and sands." alfred b. searle. charles griffin and co. ltd. london. . . "transactions of the english ceramic society." v. p. . hughes and harber. longton, staffs. . . "royal agricultural society's journal." xi. . "die tone." p. rohland. hartleben's verlag. vienna. . . "clays: their occurrence, properties and uses." h. ries. chapman and hall. london. . . "gesammelte schriften." h. seger. tonindustrie zeitung verlag. berlin. . . "tonindustrie zeitung." . p. . . "tonindustrie zeitung." . p. . . "treatise on ceramic industries." e. bourry (revised translation by a. b. searle). scott, greenwood and son. london. . . "the colloid matter of clay." h. e. ashley. u.s.a. geological survey bulletin . washington. . . "sprechsaal." . p. . . "action of heat on refractory materials." j. w. mellor and f. j. austen. trans. eng. cer. soc. vi. hughes and harber. longton, staffs. . . "wiedermann's annalen." vii. p. . . "geological contemporaneity." . . "geological magazine." iv. pp. , . . "la céramique industrielle." a. granger. gauthier frères. paris. . . "american journal of science." . p. . . "the hensbarrow district." j. h. collins. geological survey. . . "monographs of the u.s.a. geological survey." xxviii. c. r. van hise. . . "on kaolinite and pholerite." american journal of science. xliii. . . "the nomenclature of clays." j. w. mellor. eng. cer. soc. viii. hughes and harber. longton, staffs. . . "on the present distribution of coal balls." m. c. stopes and d. m. s. watson. phil. trans. royal society. b. vol. cc. . . "natural history of coal." e. a. n. arber. cambridge university press. . . "modern brickmaking." a. b. searle. scott, greenwood and son. london. . . "die verschiedene arten der verwitterung." j. m. van bemmelen. zeits. angewandte chemie. lxvi. leopold voss verlag. hamburg. . . "pyrometrische beleuchtung." carl bischof. tonindustrie zeitung. . . "die feuerfeste tone." carl bischof. quandt and haendler. leipzig. . . "the chemical constitution of the kaolinite molecule." trans. eng. cer. soc. x. hughes and harber. longton, staffs. . . "tabellarische uebersicht der mineralien." p. groth. brunswick. . . "west virginia geological survey." iii. . . "memoirs of the geological survey." london. . "the publications of stanford's geographical institute." london. . "handbuch der gesam. tonwarenindustrie." b. kerl. verlag der tonindustrie zeitung. . . "causal geology." e. h. l. schwarz. blackie and sons, ltd. . . "china clay: its nature and origin." g. hickling. trans. inst. mining engineers. . index absorption, , absorptive power of clays, accumulation of clays, acid-proof ware, acids, effect of, , , adsorption, , agriculture, clays in, , , , , , , , air, , alkalies in clay, , , , , , alluvial deposits, , , , alum clays and shales, , , alum manufacture, clays for, alumina, alumina, free, , , alumina-silica ratio, , alumino-silicic acid, , , , , , aluminous clays, , 'amorphous' clay, , analyses of clays, , , anauxite, architectural ware, , argillaceous earths, argillaceous limestone, , associated rocks, bagshot clays and sands, , ball clays, , , , , , , , , , , , , , bending of clay, bibliography, binding power, , binds, bituminous shales, , black spots, , black ware, bleaching oil, blue bricks, , bone-ash, boulder clays, , , , , bovey tracey clay, brick clays, earths and shales, , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , brittleness, brown ware, buff bricks, burned clay, , , , , calcareous clays, , , , , , , calcareous sands, calcium, see _lime compounds_ cambrian clays, carbon in clay, , , carbonates in clay, , carboniferous clays and shales, , carboniferous limestone, , carclazite, , cellulose in clays, cement clays, , , chalcopyrite, chalk, , , , , , , , , , , , chamotte, chemical properties of clay, china clay rock, , , china clays, , , , , , , , , , , , , , , , , , , , , , , , china-ware, , chinese clay, classification of clays, clay molecule, clay-shales, clay substance, _et seq._ clay substance, defined, clayite, , , , clinker, clunches, coagulated clays, coagulation, , coal measure clays and shales, , , , , , coarse pottery, cobalt, colloid theory, colloidal properties of clay, , , , , , , , colloidal silica, , , colloids, , , , , colluvial clays, colours of burned ware, , , colours of clays and shales, , , , , , combined water, , common clays, composition of clays, , , , , , , , , , , , , , composition of clays (burned), cornish stone, , cracked ware, , , , 'cream,' , , cretaceous clays, 'crumb' of clay, crushing clay, 'crystalline' clay, , , crystals in clay-ware, decantation, decomposition of clay, definitions of clay, - , , , , de-greasing wool, deposition of clays, , , , devonian clays, diluvial clays, dinas rock, disintegration, distribution of clays, drain-pipe clays, , drift, , drift clays, drying clays, , , durability, dyes, , earth movements, , earthenware, , earths for bricks, see _brick clays_ electrolytes, elutriation, , , eocene clays, epigenic clays, erosion, , , estuarine clays, , , etruria marls, , expansion, exposure, faience, farewell rock, fat clays, felspar, , , , , , , , , , ferric and ferrous compounds, , , see _iron_ fine clays, fineness, see _texture_ firebricks, , , , fireclay, , , , , , , , , , , fissile clays, flint, , flint clays, floods, , , flower-pot clays, , fluoric vapours, , , fluviatile clays, , fluxes, , , , , , , food-clays, formation of clays, , formula of clay, free alumina, , free silica, , , , frost, , fuller's earth, , fulling cloth, , fusibility, , , , fusible clays, fusing point, fusion, , , , , ganister, , , gault, , geological classification, geological nature of clay, , glacial clays, , , glaciers, , , glass, glassy structure, glazed bricks, glazed pottery, glazed terra-cotta, , grades of fireclay, gravel, , , , , , , , , green colour, greensand, grinding, , grit, , see also _millstone grit_ grog, , , , , growan, gypsum, , , halloysite, , hardness, heat, effects of, , , , , , , , , , , hydrargillite, hydro-alumino-silicates, hydrocarbons in clay, hydrolysis, , hygroscopic clays, hypogenic clays, ice-action, , ideal clay, impermeability, , impervious articles, , impurities in clays, , , , , , , , , , , , , ions, indurated clays, infusibility, , , see _refractoriness_ iron compounds, , , , , , , , , , , , , , ironstone, irregularity in shape, jurassic clays and shales, , kao-ling, kaolinite, , , , , , , kaolinization, , , kaolins, , , , , , , , , , , , , , , , , keele series, kellaways clay, , keuper marls, kiln shrinkage, kimeridge clays, knotts, lacustrine clays, , lake-deposited clays, , , lakes, , laminated clays, , , laterite, , lateritic action, , lateritic clays, lean clays, liassic clays and shales, , , lime, , , , lime compounds, , , , , , , , , , , , , , , , , , limestone, , , , , , , , , , , , lime troubles, loam, , , london clay, , , ludwig's chart, magnesium compounds, , , , , , , , , , , malm-bricks, malms, , marcasite, , marine clays, , marls, , , , , , , , , , , mechanical analysis, medway mud, melting point, , mica, , , , , , , , , , microscopical examination, , , , millstone grit, , , mineral nature of clay, minerals resembling clay, mining ball clay, modelling clays, moisture, , molecular attraction, molecular constitution of clay, , montmorillonite, mundic, muscovite, newtonite, nodules, , non-plastic material, , , non-refractory clays, occurrence of clays, , ocean currents, action of, odour of clay, oil, bleaching, oil shales, , , oolite clays, , ooze, , organic matter, , origins of clays, , , , oxford clay, , , oxides in clay, , paint, clays for, paper, clays for, particles, nature of, , , , , paving brick clays, pelagic ooze, , pelinite, , , permian clays and shales, , , pholerite, physical characters of clays, picking clay, pipe clays, , , , , plant-extracts in clays, plastic clays, , , , , , , , , , , , plasticity, - , , , , , , , , , , , , , , pleistocene clays, pockets, , , , , porcelain, , , , , , , pores in clay, , porosity, , , , , portland cement, potash compounds, , , , , , , , see _alkalies_ pottery clays, , , , , , , , , , , , , , , precambrian clays, precipitated clays, , primary clays, , , , proximate analysis, , purbeck clays, pure clays, , , , , , purification of clay, , , , , , , pyrites, , , , , , , , quartz, , , , , , , rain, , , rational analysis, reading clays, recent clays, rectorite, re-deposited clays, red bricks, red burning clays, , , red iron oxide, red ware, reduction in volume, refractoriness, , , , , refractory articles, , refractory clays, , , , , , , , , , , , residual clays, , , resistance to abrasion, resistance to corrosion, resistance to crushing, resistance to cutting, resistance to temperature, see _refractoriness_ resistance to weathering, ringing sound, river-deposited clays, rivers, , rock binds, rockingham, rock-like clays, rocks associated with clay, roman cements, roofing tiles, , , , sagger marls, sand, , , , , , , , , , , , sandstones, sandy clays, sandy loams, sandy marls, sanitary articles, , sawdust, scum, sea, action of, , , sea-deposited clays, secondary clays, , , , sedimentary rocks, sedimentation of clay, , , , seger cones, , selection of clay, selenite, separation of clays, , settling, sewerage pipes, shale oil, , shale tar, shales, , , , , , , , , , , , , , , , shrinkage, , , , , , , , , , , , sifting, , silica, , , , , , silica rock, silicates, , siliceous clays, sillimanite, , silt, , , , , silurian clays and shales, , sintering, size of particles, , , , , , 'skeleton,' 'skin' on ware, slag in bricks, etc., , , , slates, slurry, , , snow, soda compounds, , , , , , , , see _alkalies_ softening point, soil, see _agriculture_ solubility of clay, , soluble salts, sorting, sources of clays, specification of fire clays, specific gravity, , , staffordshire bricks, , standard clay, stone, cornish, , stoneware clays, , , , , , stones, , , , , , , streams, , strength, , , sub-surface clays, sulphates in clay, , , sulphides in clay, , sulphuric acid, sunlight, surface clays, , , , suspension of clay, , , , swelling, , tannin in clay, , , telluric water, temperature, resistance to, , tensile strength, , terra-cotta clays and shales, , , , , , , , , , , , , tertiary clays, texture, , thermal reactions, , , tiles, , , , , , titanium compounds, tourmaline, , transportation of clays, , , , , transported clays, triassic clays, , , true clay, , , , , twisted ware, , , types of clay, ultimate analysis, , ultra-marine, clays for, underclays, , , uses of clay, , valuation of clay, , , , , , vegetable matter, , veins, viscosity, verifiable clays, , , vitrification, , , , , , , vitrification range, , , , , volcanoes, warp, warped ware, , , washing, , water, effect of, , , , , , water in clays, , , , , , wealden clay, weathering, , , , , , , , white bricks, , white clays, , wind, zeolites, cambridge: printed by john clay, m.a. at the university press none note: project gutenberg also has an html version of this file which includes the original illustrations and in which the chemical equations are easier to read. see -h.htm or -h.zip: (http://www.gutenberg.net/dirs/ / / / / / -h/ -h.htm) or (http://www.gutenberg.net/dirs/ / / / / / -h.zip) transcriber's note: text: words surrounded by a tilde such as ~this~ means the word is in bold face. words surrounded by underscores like _this_ means the word is in italics in the text. letters in brackets with an = sign before it means that the letters have a macron over them, e.g. h[=a=c] signifies that the ac has a macron over it. numbers and equations: parentheses have been added to clarify fractions. underscores before bracketed numbers in equations denote a subscript. superscripts are designated with a caret and brackets, e.g. . ^{ } is . to the third power. the symbol .'. designates the symbol usually used for therefore (three periods in a triangle shape). a down arrow is represented by a vertical line over a capital v. like this: | v minor typographical errors have been corrected. footnotes have been moved to the end of the chapter, and all advertisements have been moved to the end of the book. a text-book of assaying: for the use of those connected with mines. by c. and j. j. beringer. revised by j. j. beringer, assoc. of the royal school of mines; fellow of the chemical society and of the inst. of chemistry; principal of the camborne mining school; and late public analyst for the county of cornwall. with numerous diagrams and tables. ninth edition. london: charles griffin and company, limited, exeter street, strand. . [all rights reserved.] publisher's note to the ninth edition the continued popularity of the present work, the last edition of which was published only a little over a year ago, continues to be a source of gratification to the publishers, who have much pleasure in issuing the present edition. _january ._ preface to the sixth edition the principal changes in this edition are additions to the articles on gold, cyanides, and nickel, and a much enlarged index. the additional matter covers more than forty pages. j. j. beringer. camborne, _january ._ preface. the text-book now offered to the public has been prepared to meet the existing want of a practical "handy book" for the assayer. to mining men the word "assaying" conveys a sufficiently clear meaning, but it is difficult to define. some writers limit it to the determination of silver and gold, and others imagine that it has only to do with "furnace-work." these limitations are not recognised in practice. in fact, assaying is becoming wider in its scope, and the distinction between "assayers" and "analysts" will in time be difficult to detect. we have endeavoured rather to give what will be of use to the assayer than to cover the ground within the limits of a faulty definition. at first our intention was to supply a description of those substances only which have a commercial value, but on consideration we have added short accounts of the rarer elements, since they are frequently met with, and occasionally affect the accuracy of an assay. under the more important methods we have given the results of a series of experiments showing the effect of varying conditions on the accuracy of the process. such experiments are often made by assayers, but seldom recorded. statements like those generally made--that "this or that substance interferes"--are insufficient. it is necessary to know under what conditions and to what extent. students learning any particular process cannot do better than repeat such a series of experiments. by this means they will, at the same time, acquire the skill necessary for performing an assay and a confidence in their results based upon work under different conditions. the electrolytic method of copper assaying given under _copper_ is a modification of luckow's; it was introduced by us into the offices of the rio tinto copper company, and has been in use for many years with success. this modification is now employed in copper-works in spain, germany, and england, and is used in place of the dry assay for the commercial valuation of copper ores. we have adhered to the gram and the "c.c." as the units of weight and volume. those who prefer working with grains and grain-measures can use the figures given, multiplied by ten. for example:--when gram is mentioned, grains should be used, and grain-measures take the place of "c.c." it is not advisable to mix the two systems, as by using gram weights and grain-measures. we have intentionally to a large extent omitted to mention the names of those who have originated or modified the various processes. the practice of naming a process after its discoverer has developed of late years, and is becoming objectionable. it is a graceful thing to name a gas-burner after bunsen, or a condenser after liebig; but when the practice has developed so far that one is directed to "finkenerise" a residue, or to use the "reichert-meissl-wollny" process, it is time to stop. we are indebted to the standard works of allen, crookes, fresenius, lunge, michell, percy, and sutton, and wish to express our sense of special indebtedness to mr. richard smith, of the royal school of mines. one or two of the illustrations are taken from mr. sexton's excellent little book on _qualitative analysis_. our obligation to some others is mentioned in the text. finally, we have to thank for assistance in the experimental work messrs. bailey, beswick, clarke, grant, higgins, and smith. the authors. camborne, _nov. _. contents. part i. chapter i. introductory. page object of assaying sampling drying: determination of moisture calculation and statement of results laboratory books and report forms quantity to be taken for an assay exercises chapter ii. methods of assaying.--dry gravimetric methods. methods of assaying gravimetric methods mechanical separations dry assays (a) fluxes (b) reducing agents (c) oxidising agents (c) apparatus chapter iii. wet gravimetric methods. wet gravimetric methods (a) solution (b) precipitation (c) filtration (c) drying and igniting chapter iv. volumetric assays. titrometric assays (a) standard solutions (b) standardising (c) methods of working (c) indirect titration colorimetric assays gasometric assays chapter v. weighing and measuring. weighing measuring liquids (a) graduated flasks (b) pipettes (c) burettes measuring gases chapter vi. reagents. acids, &c. bases, salts, &c. chapter vii. formulæ, equations, &c. chapter viii. specific gravity. introductory determination of specific gravity-- (a) hydrometers (b) specific gravity bottles calculations depending on specific gravity part ii. chapter ix. silver, gold, platinum, cyanides, mercury. silver--detection dry assay ( ) scorification ( ) pot assays, average ores " ores with metallic oxides " ores with metallic sulphides explanatory notes on the fusion the effect of charcoal, flour, &c. the effect of nitre the effect of mineral sulphides ( ) cupellation the loss of silver condition affecting the loss methods of correction lead required for cupellation ( ) calculation of the results in ounces to the ton of lbs. table ores with metallic particles ( ) explanatory notes ( ) examples of dry silver assays wet assays gravimetric method gay-lussac's method volhard's method a modified gay-lussac volhard's method applied to arsenic gold--detection amalgamation assay dry assay ( ) size of charges ( ) sampling ( ) assay tons ( ) small buttons, weighing " " measuring ( ) concentration in lead quartz ores ores with oxide of iron ores with metallic sulphides ( ) cyanide charges, residues, &c. ( ) cupellation cupels cupellation temperature cupellation loss ( ) inquartation ( ) flatting ( ) parting, in flasks " in test tubes " in glazed crucibles " loss, &c. ( ) check assays, surcharge ( ) bullion assays in special apparatus silver, &c., in gold bullion ( ) sampling of base bullion, &c. cyanides--commercial cyanides double cyanides prussic acid gold-dissolving power of cyanide liquor assay for cyanide strength , assay of commercial cyanide alkalinity of cyanides acidity of ores metals in cyanide liquors cyanicides platinum iridium mercury dry assay wet method chapter x. copper, lead, thallium, bismuth, antimony. copper--introductory dry assay valuation of copper ores wet methods ( ) electrolytic assay volumetric methods ( ) cyanide method ( ) iodide method ( ) colorimetric method examination of commercial copper lead dry assay wet assay ( ) gravimetric method ( ) volumetric method ( ) colorimetric method thallium bismuth dry assay wet method ( ) gravimetric determination ( ) colorimetric assay antimony dry assay wet method ( ) gravimetric assay ( ) volumetric method chapter xi. iron, nickel, cobalt, zinc, cadmium. iron gravimetric determination permanganate and bichromate methods stannous chloride method colorimetric determination nickel dry assay electrolytic assay titration by cyanide cobalt zinc gravimetric method volumetric method gasometric method cadmium chapter xii. tin, tungsten, titanium. tin vanning dry assay detection, &c. gravimetric determination volumetric determination examples titanium tungsten niobic and tantalic oxides chapter xiii. manganese, chromium, etc. manganese gravimetric determination volumetric determination ferrous sulphate assay iodine assay colorimetric determination chromium vanadium molybdenum uranium chapter xiv. earths, alkaline earths, alkalies. alumina thoria zirconia cerium lanthanum and didymium yttria beryllia lime strontia baryta magnesia the alkalies sodium potassium lithium cÆsium rubidium ammonium part iii. chapter xv. oxygen and oxides--the halogens. oxygen oxides water the halogens chlorine bromine iodine fluorine chapter xvi. sulphur and sulphates. sulphur gravimetric determination volumetric determination sulphates selenium tellurium chapter xvii. arsenic, phosphorus, nitrogen. arsenic gravimetric determination volumetric method, "iodine" " " "uranic acetate" phosphorus gravimetric determination volumetric determination nitrogen and nitrates chapter xviii. silicon, carbon, boron. silicon and silicates carbon and carbonates coals shales carbonates boron and borates appendix a. table of atomic weights and other constants table for converting degrees of the centigrade thermometer into degrees of fahrenheit's scale tables showing strengths of aqueous solutions of nitric and hydrochloric acids, of ammonia and of sulphuric acid appendix b. estimation of small quantities of gold practical notes on the iodide process of copper assaying method of separating cobalt and nickel appendix c. a lecture on the theory of sampling index a text-book of assaying. chapter i. introductory. assaying has for its object the determination of the quantities of those constituents of a material which add to or detract from its value in the arts and manufactures. the methods of assaying are mainly those of analytical chemistry, and are limited by various practical considerations to the determination of the constituents of a small parcel, which is frequently only a few grains, and rarely more than a few ounces, in weight. from these determinations calculations are made, which have reference to a mass of material of, perhaps, hundreds of tons. but in all cases, whether the mass under consideration be large or small, whether the material be obtained by mining, grown, or manufactured, the assayer is supposed to receive a small quantity, called "the sample," which is, or ought to be, the exact counterpart of the mass of material that is being dealt with. the taking and making of this sample is termed "sampling"; and the men whose special work it is to select such samples are "the samplers." but although "sampling" is thus distinct from "assaying," the assayer should be familiar with the principles of sampling, and rigorous in the application of these principles in the selecting, from the sample sent him, that smaller portion upon which he performs his operations. ~sampling.~--_in the case of gases_, there is absolutely no trouble in mixing. the only difficulty is in drawing off a fair sample where, as in flues, the body of the gas is in motion, and varies a little in composition from time to time. in this case, care must be taken to draw off uniformly a sufficient volume of the gas during a prolonged period; any portion of this larger volume may then be taken for the analytical operation. _in the case of liquids_, which mix more or less easily--and this class includes metals, &c., in the state of fusion--more or less severe agitation, followed by the immediate withdrawal of a portion, will yield a fairly representative sample. _in the case of solids_, the whole mass must be crushed, and, if not already of fairly uniform quality, mixed, before sampling can take place. most of the material which a sampler is called upon to deal with, is, however, in a more or less divided state and fairly uniform. in practice it is assumed that per cent. of the whole (= / th), if taken in portions of equal weight and at frequent and regular intervals, will represent the mass from which it was taken. taking a heap of ore, a, and selecting one out of every twenty spade-, bag-, barrow-, or wagon-fuls, according to the quantity of stuff in the heap, there is obtained a second heap, b, containing one-twentieth of the stuff of the heap a. if we crush the stuff in b until this heap contains approximately the same number of stones as a did--which means, crushing every stone in b into about twenty pieces--b will become the counterpart of a. selecting in the same manner per cent. of b, there is got a third heap, c. this alternate reduction and pulverising must be carried on until a sample of suitable size is obtained. this may be expressed very clearly thus:-- a = tons of rocks and lumpy ore. b = " " rough stones, / th of a. c = . " " small stones, / th of b. d = . " " coarse powder, / th of c. [illustration: fig. . cone partly reduced cone plan of frustrum divided. elevation of frustrum divided.] if the material to be sampled is already a dry powder, per cent. of it should be heaped in a cone; each lot being added on the apex of the cone already formed, so that it may distribute itself by falling evenly in all directions. when the cone is completed, convert it into a low frustrum of a cone by drawing stuff uniformly and in a direct line from the centre to the circumference. draw two diameters at right angles to each other, and reserving any two alternate quarters, reject the others. mix; and form another cone, and proceed until a sample is got of the bulk required. this is the usual plan, and all samples should be treated in this way when the stuff is fine enough to fall evenly down the sides of a cone. samples as they reach the assay office are seldom in a fit state for the work of the assayer; they are generally too coarse, and ought always to be more than he wants for any particular determination. the portion he requires should never be taken at hap-hazard; the sample must be reduced systematically to the quantity required. . _if the sample is a liquid:_ it is sufficient to shake the bottle, and take out a measured or weighed quantity for the assay. . _if a liquid with a solid in suspension:_ measure the whole of it. filter. make up the filtrate with the wash-water or water to the original bulk. assay it. dry and weigh the residue, and make a separate assay of it. . _if of a creamy consistency, free from heavy particles:_ mix well; spread out evenly on a glazed tile. take up equal portions at equal distances. mix and assay. . _if a mud of coarse and fine particles, or of particles of unequal density:_ weigh and transfer to a porcelain dish, or weigh in the dish. dry at ° c., weigh. treat the residue as a solid capable of being powdered. . _if a solid capable of being powdered, or already powdered:_ heap up into a cone; flatten with a spatula; divide along two diameters at right angles, and carefully reject the whole of two alternate quarters, brushing away any fine powder. mix the other quarters, and repeat (if necessary). for small quantities a fine state of division is essential. . _if a solid with metallic particles:_ powder and pass through a sieve; the metallic particles will not pass through. weigh both portions and assay separately. _sifting should be followed by a very thorough mixing._ . _if a metal or alloy in bar or ingot:_ clean the upper surface of the bar, and bore through the bar. use the borings. if the ingot or bar is small, cut it through and file the section. filings must be freed from fragments of the file by means of a magnet; and from oil, if any be present, by washing with a suitable solvent.[ ] where practicable, metals and alloys are best sampled by melting and granulating. the student must carefully avoid any chance of mixing dirt or particles of other samples with the particular sample which he is preparing. one ore should be done at a time, and when finished, it should be labelled and wrapped up, or bottled, before starting on a fresh sample. when an ore requires to be very finely ground in an agate mortar, it is often advisable to mix with a little pure alcohol and rub until free from grit; dry at ° c. and mix well before weighing. when an assay is required of a quantity of ore made up of parcels of different weight and quality, each parcel should be separately sampled and parts of each sample, bearing to each other the same proportion by weight as the original parcels, should be taken and mixed. for example, a lot of ore is made up of one parcel of a, tons, one of b, tons, and another of c, tons; a sample representing the whole may be got by mixing parts of a sample of a with parts of a sample of b, and parts of a sample of c. [illustration: fig. .] a bruising plate, like that in fig. , is convenient for general office work. the slab is of cast iron, about an inch thick. it is firmly supported on a solid block of wood, and pivoted for convenience in emptying. the bruising-hammer is steel-faced, about inches square, and - / inch thick. the block is firmly fixed to a small table or tressel, so that the slab is about feet inches from the ground. the slab is cleaned, and the sample collected with the help of a stiff-haired brush. ~drying: determination of moisture.~--in practice, the moisture is generally determined by the samplers, and the proportion is specified in grains per pound on the label attached to the sample when it reaches the assay office. the method adopted is usually to dry lb. = grs. of the ore in a frying-pan heated over a gas flame, or in an ordinary oven, until a cold bright piece of metal or glass is no longer damped when held over it. the loss of weight in grains = moisture. properly, however, this work should be done by the assayer, if only for the following reason. it is assumed that the dry ore of the sampler and of the assayer are the same thing; according to the nature of the ore, this may or may not be the case. the assayer, however, uses the sample which he has dried for his moisture-determination, as the dry ore on which he makes his other assays, and no variation in moisture would influence the other and more important determinations. some ores are sent to the smelter with from to per cent. of adherent water. in these cases it is best to spread out the sample, and taking equal portions fairly at regular intervals, weigh into a berlin dish grams. this should then be dried over a sand-bath, or if the ore is likely to be injured by excess of heat, over a water-bath until the weight is constant. the loss of weight multiplied by gives the percentage of water present. example:-- weight of dish + wolfram . grms. " " dish . " ----- " " wolfram . " " " dish + wolfram . " " " " dried . " ----- " " water . " . × = . ~ . %.~ there are other ores which are not apparently wet, but in the state called "air-dried." it is easier to take fair samples of these, and, consequently, it is not necessary to use so large a quantity as grams. but with a smaller quantity, extra precautions must be taken. all dry solids at ordinary temperatures absorb moisture from the air. the amount varies with the nature of the material and with the quantity of surface exposed. light bulky powders absorb more than heavy ones, because of the greater condensing surface. it is on this account that it is well to weigh substances, which have been dried, between close-fitting watch-glasses. the method of determining moisture is to weigh out into the glasses grams of ore, and dry in the water-oven until there is no further loss of weight. on taking the glasses out of the oven, they should be at once closed, the clip put on, and after cooling in a desiccator weighed. if after a second trial the loss is the same, or only increased by a milligram, the determination is finished. example:-- weight of glasses + pyrites . grms. " " glasses . " ------- " " pyrites . " " " glasses + pyrites, dried hour . " " " " " dried - / " . " " " " " . " " " " " dried . " ------- " " moisture . " . × = . ~ . %.~ [illustration: fig. .] sometimes it may be advisable to dry grams, in which case multiplying the loss by will give the percentage. the dried ore should be transferred to a weighing-tube (fig. ), and reserved for the subsequent determinations. the weighing-tube with the ore must be marked, and kept in a desiccator. most ores and inorganic substances can be dried, and their moisture determined by the loss in this way. when, however, the substance contains another somewhat volatile ingredient, it is exposed over sulphuric acid in a desiccator for two days (if _in vacuo_, all the better), and the loss determined. moisture in dynamite should be determined in this way. when water is simply mechanically mixed with a substance it presents but little difficulty. the combined water is a different matter. slaked lime, even when perfectly dry, contains much water; and if the water of soda crystals were separated and frozen, it would occupy a volume equal to that of the original crystals. perfectly dry substances may contain much water, and this combined water is retained by different materials with very unequal vigour. sodium sulphate and sodium phosphate crystals lose water even when exposed under ordinary conditions to dry air. soda crystals when heated melt, and at a moderate temperature give off their water with ebullition. the temperature at which all the water is given up varies with each particular salt; the actual determination of the water in each case will require somewhat different treatment. such determinations, however, are seldom required; and from a practical point of view this combined water causes no trouble. _in assaying ores_, we term "moisture" all water which is lost by exposure in a water-oven at ° c., and the "dry ore" is the ore which has been dried at this temperature. no advantage, but rather endless confusion, would be caused by varying the temperature with the object of estimating the whole of the water which a hydrated salt may contain. the results of the assay of the other components should be calculated on the "dry ore." one advantage of this is obvious:--the dry ore has a constant composition, and the results of all assays of it will be the same, no matter when made; the moisture, however, may vary from day to day, and would be influenced by a passing shower of rain. it is well to limit this variability to the moisture by considering it apart, and thus avoid having the percentage, say, of copper rising and falling under the influence of the weather. in the case of certain salts, however, such as soda crystals and hydrated sulphate of copper (when these constitute the bulk of the substance to be assayed), it is as well to perform the assay on the moist, or at any rate air-dried, substance.[ ] it would be equally convenient to calculate on the substance dried at ° c.; but in this case it would be well, in order to avoid a somewhat shallow criticism, to replace the term "moisture" by the longer but equivalent phrase "water lost at ° c." ~calculation and statement of results.~--by far the most generally convenient method of stating the results of an assay is that of the percentage or parts in a hundred, and to avoid a needlessly troublesome calculation it is well to take such a quantity of ore for each assay as by a simple multiplication will yield the percentage. in these calculations decimals are freely employed, and students should make themselves familiar with the methods of using them. other methods of statement are in use, and have advantages in certain special cases. with bullion the parts in a thousand are given, and in those cases in which the percentage is very small, as in water analysis, it is convenient to report on parts in , , or even on parts per , , . these are easily got from the corresponding percentages by shifting the decimal point one, three, or four places to the right. thus . per cent. is per thousand; and . per cent. is . per , , or per million. with ores of tin, silver, and gold, the result is stated as so many cwts., lbs., or ozs., in the ton. with dressed tin ores as they are sent to the smelter, the produce is given in cwts. and quarters to the ton. the corresponding percentage may be obtained by multiplying by five; or, inversely, if the percentage is given, the produce may be got by dividing by five. a produce of - / equals a percentage of . × = . ; and a percentage of . equals a produce of / = . with tin ores as raised (in which the percentage is small) the reduction must be carried to pounds per ton. one per cent. equals . lbs. to the ton; consequently, if we multiply the percentage by . , the produce will be given. thus, if an ore contains . per cent. of oxide of tin, the produce is . × . = lbs. (or cwt., quarter, and lbs.) to the ton. with gold and silver ores, the proportion of precious metal is small, and it is necessary to carry the reduction to ozs. and dwts. to the ton; and since gold and silver are sold by troy weight, whilst the ton is avoirdupois, it is of importance to remember that the ounces in the two systems are not the same. a ton contains , , grains, which equal , . dwts. or , . ozs. (troy). the following rules are useful:-- to get ozs. (troy) per ton, multiply parts per , by . ; to get dwts. per ton, multiply parts per , by . ; to get grains per ton, multiply parts per , by . . where liquids are being assayed, cubic centimetres are held to be equivalent to grams, and the usual method of statement is, "so many parts by weight in so many by measure." where the statement is made as grams per litre or grains per gallon, there can be no doubt as to what is meant; and even if it be expressed in parts per , , parts by weight in a measured volume must be understood unless the contrary is expressly stated. in some cases, where the density of the solution differs greatly from that of water, the percentage by weight may be given; and in others, mixtures of two or more liquids, the percentages may be given by volume or by weight; as so many c.c. in c.c., or as so many grams in grams, or even as so many grams in c.c. in such cases it must be distinctly shown which method of statement is adopted. one grain per gallon means grain in , grain-measures, or one part in , . dividing by and multiplying by will convert grains per gallon into parts per , . inversely, dividing by and multiplying by , will convert parts per , into grains per gallon. grams per litre are parts per ; multiplying by will give parts per , , and multiplying by will give grains per gallon. among foreign systems of weights, the french is by far the best. kilograms ( . lbs.) per quintal ( . lbs.) are parts per cent.; and grams ( . grs.) per quintal are parts per , . from the rule already given, grams per quintal may be converted into ounces to the ton by multiplying by . . the german loths per centner ( / oz. (avoirdupois) to lbs.) equal parts per ; they are converted into parts per cent. by dividing by , or into ounces (troy) per ton by multiplying by . . in the united states, as a sort of compromise between the avoirdupois and metric systems, a ton is taken as lbs. there, too, the custom is adopted of reporting the gold and silver contents of an ore as so many dollars and cents to the ton. in the case of gold, an ounce is considered to be worth . dollars. with silver, the _nominal_ value is . dollars per ounce, but frequently in assay reports it is taken as one dollar. the practice is objectionable. the prices of metals vary with the fluctuations of the market, and if the assayer fixed the price, the _date_ of his report would be all important; if, on the other hand, he takes a fixed price which does not at all times agree with the market one, it leaves a path open for the deception of those unacquainted with the custom. american "dollars on the ton of lbs." may be converted into "ounces in the ton of lbs." by dividing by . in the case of silver, and by . in the case of gold. ~laboratory books and report forms.~--the record which the assayer makes of his work must be clear and neat, so that reference, even after an interval of years, should be certain and easy. one method should be adopted and adhered to. where there are a large number of samples, three books are required. _sample book._--this contains particulars of the samples (marks, &c.), which are entered by the office-clerk as they arrive. he at the same time puts on each sample the distinguishing number. example of page of sample book. +----------+----------+--------------------------+----------------+ | date. | number. | sample. | remarks. | +----------+----------+--------------------------+----------------+ | feb. | | tough copper | for arsenic. | | " | x | piece of metal | for ni and cu. | | " | | tough copper. | | | " | | silver precipitate, | with letter. | | | | casks, cwt. qr. | | | " | | purple ore, tons. | | | " | j.t. | lead ore, j.t. | from corsica. | | " | j.t. | " j.t. | | +----------+----------+--------------------------+----------------+ _laboratory book._ this is the assayer's note-book, in which he enters clearly the particulars of his work--the results obtained, as well as how these results were arrived at. the calculations should be done on scrap-paper, and should not be entered, although, of course, detail enough must be shown to enable the results to be recalculated. example of page of laboratory book. ______________________________________________________________ purple ore grams / / . grm. . " ------ colorimetric . × = . % copper ______________________________________________________________ tough copper grams feb. / . c.c. uranium. = . % arsenic ______________________________________________________________ tough copper grams . c.c. uranium. = . % arsenic ______________________________________________________________ grams tough copper . c.c. uranium feb. / = . % arsenic ______________________________________________________________ standard of uranium acetate. . gram as_{ }o_{ } = . c.c. uranium. .'. cc. uranium = . gram as. ______________________________________________________________ grams tin ore cruc. and sno_{ } . grms. feb. / cruc. and ash . " ------ sno_{ } = . = . % tin ______________________________________________________________ _the assay book._--this is the official book, and is a combination of the sample and laboratory books. it corresponds with the report-forms. without being loaded with detail, it should contain sufficient to characterise each sample. key to following example page of assay book: dr = date reported. not det. = not detected example of page of assay book. -------------------------------------------+----+-------+---------------+---- description of sample. | | water | assay on | ------+--------------------+---------------| |lost at| the dry | date. | material. | weight. |no. | ° c.|material. | dr ------+--------------------+---+---+---+---+----+-------+---------------+---- | |ton|cwt|qrs|lbs| | | | feb. |tough cake copper | | | | | | |arsenic, . % | " |tough cake copper | | | | | | |arsenic, . % | " |tough cake copper | | | | | | |arsenic, . % | | | | | | | | | | feb. |nickel disc for c.r.| | | | | x | |copper, . | | | | | | | | |nickel, . | | | | | | | | |iron, . | | | | | | | | | ----- | | | | | | | | | . | | | | | | | | | ------ | " |silver precipitate, | | | | | | not | | | casks | | | | | | det. |silver, . | | | | | | | | |gold, . | | | | | | | | |lead, . | | | | | | | | |zinc, . | | | | | | | | |silver, . | | | | | | | | | ozs. per ton | | | | | | | | |gold, . | | | | | | | | | ozs. per ton | " |purple ore | | | | | | not |copper, . % | | | | | | | | det. |sulphur . % | ------+--------------------+---+---+---+---+----+-------+---------------+---- when the number of samples is small, the sample book may be omitted, and the entries made in the assay book as the samples arrive. _report-forms._ these should entail as little writing as possible in making out the report. for general purposes the form given on p. is useful. ~the quantity of substance~ to be taken for any particular assay depends largely upon the method of assay adopted. there are, however, some general considerations which should be remembered, and some devices for simplifying the calculations which should be discussed. the smaller the percentage of the substance to be determined, the larger should be the amount of the ore taken. the following table will give a general idea as to this:-- percentage of the substance amount of ore, &c. to to be determined. be weighed. - gram. - grams. - " - . " . - . " [illustration: assay note] the rougher the method of assay adopted, the larger should be the quantity of ore taken. if the degree of accuracy attainable with the methods and instruments at the assayer's service is known, it is easy to calculate what quantity should be taken for any particular case. if the results are good within . gram, then, taking gram of ore we can report within . per cent., or if they are good within . gram, taking grams of ore, we can report within part per , , or very closely within - / dwt. to the ton. if it is wished to be yet more particular in reporting, larger quantities must be taken. the difficulty of manipulating very small or very large precipitates, &c., must be borne in mind. so, too, must the fact that the greater the weight of the final product of an assay, the less, as a rule, is the percentage error. the distinction between absolute and percentage error, often overlooked, is important. if . gram of silver be cupelled with grams of lead, there may be obtained a button of . gram; the absolute loss is . gram, and this equals per cent. of the silver present. similarly, cupelling . gram, the resulting button may be . ; the absolute loss is only . gram, but this equals per cent. of the silver present. in the same way the student should see that the two results, . per cent. and . per cent., are really more concordant than the results . per cent. and . per cent. a device often adopted in practice where a large number of assays of one kind are made, and the report is given as so many ounces or pounds to the ton, is that known as the _assay ton_. the assay ton may be any arbitrary and convenient weight, but its subdivisions must bear to it the same relations as pounds and ounces bear to the actual ton. on the other hand, in a laboratory where many kinds of work are performed, different sets of weights of this kind would only tend to confusion, even if they were not unnecessary. with a set of gram weights and its subdivisions anything may be done. if it is desired to report as pounds to the ton, then, since there are lbs. to the ton, a weight of . grams may be taken as the assay ton, and each . gram yielded will equal lb., or . grams may represent the ton, and each . gram a pound. similarly, since there are , . ozs. troy to the ton; if we take . grams as the assay ton, each . gram will equal oz. to the ton. in some cases it may be convenient to have, in addition to the usual gram weights, one or other of the "assay tons" mentioned above, but generally it is better to work on a purely decimal system, and convert when required into ounces per ton, &c., either by actual calculation or by reference to a set of tables. practical exercises. the student should practise such calculations as the following:-- . calculate the percentages in the following cases:-- (a) ore taken, grams; copper found, . . (b) " . gram; iron found, . . (c) " grams; lead found, . . . calculate the parts per thousand in the following:-- (a) bullion taken, . gram; silver found, . . (b) " . gram; silver found, . . (c) " . gram; gold found, . . . calculate parts per , in the following:-- (a) ore taken, grams; silver found, . . (b) " grams; gold found, . . (c) water taken, c.c.; solids found, . . . calculate cwts. to the ton in the following:-- (a) ore taken, grams; tin found, . . (b) " grams; tin found, . . (c) an ore with . per cent. of tin. . calculate lbs. to the ton in the following:-- (a) an ore with . per cent. oxide of tin. (b) ore taken, grams; oxide of tin found, . . . calculate ozs. (troy) to the ton in the following:-- (a) ore taken, grams; gold found, . . (b) " grams; silver found, . . (c) " grains; silver found, . . . calculate in grains per gallon:-- (a) . gram per litre. (b) . parts per , . (c) solution taken, c.c.; copper found, . gram. (c) " c.c.; iron found, . gram. . convert into ozs. (troy) per ton:-- (a) loths per centner. (b) grams per quintal. (c) parts per , . footnotes: [ ] ether or carbon bisulphide. [ ] such substances are best dried by pressing between folds of dry filter-paper. chapter ii. methods of assaying.--dry gravimetric methods. the methods of assaying are best classed under two heads, gravimetric and volumetric, in the former of which the final results are weighed, whilst in the latter they are measured. a commoner and older division is expressed in the terms much used in practice--wet assays and dry assays. wet assays include all those in which solvents, &c. (liquid at the ordinary temperature), are mainly used; and dry assays, those in which solid re-agents are almost exclusively employed. dry assays form a branch of gravimetric work, and we shall include under this head all those assays requiring the help of a wind furnace. wet assays, as generally understood, would include not only those which we class as wet gravimetric assays, but also all the volumetric processes. ~gravimetric methods~ aim at the separation of the substance from the other matters present in the ore, so that it may be weighed; and, therefore, they must yield the _whole_ of the substance in a pure state. it is not necessary that a metal should be weighed as metal; it may be weighed in the form of a compound of definite and well known composition. for example, one part by weight of silver chloride contains (and, if pure, always contains) . part of silver; and a quantity of this metal can be as exactly determined by weighing it as chloride as by weighing it in the metallic state. but in either case the metal or its chloride must be pure. exact purity and complete separation are not easily obtained; and methods are used which are defective in one or both of these respects. it is well to note that an impure product increases the result, whilst a loss of the substance decreases it; so that if both defects exist in a process they tend to neutralise each other. of dry methods generally, it may be said that they neither give the whole of the substance nor give it pure; so that they are only calculated to show the amount of metal that can be extracted on a manufacturing scale, and not the actual quantity of it present. their determinations are generally rough and always low. the gold and silver determinations, however, will compare very favourably with any of the other processes for the estimation of these metals in their ores. the calculation of the results of a gravimetric assay has already been referred to. if the result is to be stated as percentage, it may always be done by the following rule:--_multiply the weight of the substance got by the percentage of metal it contains, and divide by the weight of ore taken._ gravimetric methods are divided into three groups: ( ) mechanical separations; ( ) dry methods; and ( ) wet methods. ~mechanical separations.~--under this head are classed the method of assaying tin ores, known as vanning, and the amalgamation assay for gold. a set of sieves to determine the relative proportion of powders of different degrees of fineness is sometimes useful. a set with , , and meshes to the inch is convenient. ~dry assays.~--an important distinction between wet and dry methods of assaying is, that in the former the substance is got into the liquid state by solution, whilst in the latter fusion is taken advantage of. the difference between solution and fusion is easily illustrated: a lump of sugar heated over a candle-flame melts or fuses; suspended in water it dissolves. many substances which are insoluble or infusible of themselves, become soluble or fusible when mixed with certain others; thus, in this way, solution is got with the aid of reagents, and fusion with the help of fluxes. for example, lead is insoluble in water, but if nitric acid be added, the metal rapidly disappears. it is convenient, but somewhat inaccurate, to say that the acid dissolves the lead. if the lead be acted on by nitric acid alone, without water, it is converted into a white powder, which does not dissolve until water is added; in this case it is obvious that the water is the solvent. the function of the acid is to convert the lead into a soluble compound. ~fluxes~ may act as true solvents. fused carbonate of soda dissolves baric carbonate, and perhaps in many slags true solution occurs; but in the great majority of cases a flux is a solid reagent added for the purpose of forming a fusible _compound_ with the earthy or stony minerals of the ore. few of the minerals which occur in the gangue of an ore are fusible; and still fewer are sufficiently fusible for the purposes of the assayer, consequently the subject is one of importance, and it ought to be treated on chemical principles. an idea of the composition of some of the more frequently occurring rocks may be gathered from the following table, which represents rough averages:-- ----------------------------------------------------------------- | | |oxide|lime and | |silica.|alumina.| of |magnesia.|alkalies. | | |iron | | ----------------------------------------------------------------- | % | % | % | % | % sandstone, grit, | | | | | quartzite, &c. | - | -- | -- | -- | -- granite, gneiss, | | | | | quartz-porphyry, | | | | | fire-clay, &c. | - | - | | | - | | | | |less in | | | | |fire-clay. mica-schist | | | | | trachyte, syenite | | | | - | - clay-slate | | | | | diorite | | | | | - horneblende-rock | | | | | - brick-clay | | | | | -- china-clay | | | -- | -- | -- basalt, dolerite, &c.| | | | | serpentine | | -- | -- | | -- chalk, limestone, | | | | | dolomite, &c. | -- | -- | -- | - | -- ----------------------------------------------------------------- silica itself, and the silicates of alumina, of lime, and of magnesia, are practically infusible; the silicates of soda, of potash, and of iron are easily fusible if the base (soda, potash, or oxide of iron) be present in sufficient quantity, and if, in the case of the iron, it is present mainly as lower oxide (ferrous silicate). the addition of lime, oxide of iron, or alkali to silicate of alumina results in the formation of a double silicate of alumina and lime, or of alumina and iron, &c., all of which are easily fusible. similarly, if to a silicate of lime we add oxide of iron, or soda, or even alumina, a fusible double silicate will be formed. thus lime, soda, oxide of iron, and clay, are _fluxes_ when properly used; but since lime, clay (and oxide of iron if there be any tendency to form peroxide), are of themselves infusible, any excess of these fluxes would tend to stiffen and render pasty the resulting slag. so, too, soda, which is a very strong base, may act prejudicially if it be in sufficient excess to set free notable quantities of lime and magnesia, which but for that excess would exist in combination as complex fusible silicates. there are many minerals which with but little soda form a glass, but with more yield a lumpy scoriacious mass. there are many minerals, too, which are already basic (for example, calcite), and which, when present, demand either a less basic or an acid flux according to the proportions in which they exist. for purposes of this kind borax, or glass, or clay with more or less soda may be used, and of these borax is by far the most generally useful. an objection to too basic a slag (and a very important one) is the speed with which it corrodes ordinary crucibles. these crucibles, consisting of quartz and clay, are rapidly attacked by lime, soda and bases generally. [illustration: fig. .] in considering what is and what is not a good slag, certain chemical properties are of importance. if a mixture of many substances be fused and allowed to solidify in a crucible, there will be found some or all of the following. at the bottom of the crucible (fig. ) a button of metal, resting on this a speise; then a regulus, next a slag made up of silicates and borates and metallic oxides, and lastly, on the top another layer of slag, mainly made up of fusible chlorides and sulphates. in assaying operations the object is generally to concentrate the metal sought for in a button of metal, speise or regulus, and to leave the earthy and other impurities as far as possible in the slag; whether there be one or two layers of slag is a matter of indifference;[ ] but the chemical action of the lower layer upon the speise, or regulus, or metal, is of great importance. a _regulus_ is a compound of one or more of the metals with sulphur; it is usually brittle, often crystalline, and of a dull somewhat greasy lustre. it is essential that the slag, when solid, shall be so much more brittle than the regulus, that it shall be easy to crumble, and remove it without breaking the latter; and it must not be basic. the effect of fusing a regulus with a basic slag is well seen when _sulphide of lead_ is fused with _carbonate of soda_; the result is a button of metal (more or less pure), and a slag containing sulphides of lead and sodium; and again, if sulphide of lead be fused with an excess of oxide of lead, a button of lead will be got, and a slag which is simply oxide of lead (with whatever it may have taken up from the crucible), or if a sufficient excess has not been used, oxide of lead mixed with some sulphide. when (as is most frequently the case) the desire is to prevent the formation of regulus, these reactions may be taken advantage of, but otherwise the use of a flux having any such tendency must be avoided. a good slag (from which a regulus may be easily separated) may be obtained by fusing, say, grams of ore with borax grams, powdered glass grams, fluor spar, grams, and lime grams; by quenching the slag in water as soon as it has solidified, it is rendered very brittle. sulphide of iron formed during an assay will remain diffused through the slag, instead of fusing into a button of regulus, if the slag contain sulphide of sodium. the same is true of other sulphides if not present in too great a quantity, and if the temperature is not too high. _speises_ are compounds of a metal or metals with arsenic. they are chiefly of interest in the metallurgy of nickel, cobalt, and tin. they are formed by heating the metal or ore in covered crucibles with arsenic and, if necessary, a reducing agent. the product is fused with more arsenic under a slag, consisting mainly of borax. they are very fusible, brittle compounds. on exposure to the air at a red heat the arsenic and the metal simultaneously oxidize. when iron, cobalt, nickel, and copper are present in the same speise, they are eliminated in the order mentioned. _slags_ from which metals are to be separated should not be too acid; at least, in those cases in which the metal is to be reduced from a compound, as well as separated from earthy impurities. where the object is simply to get a button of metal from a substance in which it is already in the metallic state, but mixed with dross (made up of metallic oxides, such as those of zinc or iron), from which it is desired to separate it, an acid flux like borax is best; or, if the metal is easily fusible, and there would be danger of loss of metal by oxidation or volatilising, it may be melted under a layer of resin or fat. common salt is sometimes used with a similar object, and is often useful. under certain conditions, however, it has a tendency to cause the formation of volatile chlorides with a consequent loss of metal. in the great majority of cases, the fusion of the metal is accompanied by reduction from the state of oxide; in these the slag should be basic. it is not easy to reduce the whole of a reducible oxide (say oxide of copper or of iron) from a slag in which it exists as a borate or silicate; there should be at least enough soda present to liberate it. when the object is to separate one metal, say copper, without reducing an unnecessary amount of another (iron) at the same time, a slag with a good deal of borax is a distinct advantage. the slag then will probably not be free from copper, so that it will be necessary to powder and mix the slag with some soda and a reducing agent, and to again fuse the slag in order to separate this residual metal. in all those cases in which the slag retains an oxide of a heavy metal, this cleaning of the slag is advisable, and in the case of rich ores necessary. slags containing sulphides are especially apt to retain the more easily reducible metals. the following are the ordinary and most useful fluxes:-- ~soda.~--the powdered bicarbonate, sold by druggists as "carbonate of soda," is generally used. it gives off its water and excess of carbonic acid readily and without fusion. where the melting down is performed rapidly, the escaping gas is apt to cause trouble by frothing, and so causing waste of the material. ordinary carbonate of soda, when hydrated (soda crystals), melts easily, and gives off its water with ebullition. it is unfit for use in assaying, but when dried it can be used instead of the bicarbonate. one part of the dried carbonate is equivalent to rather more than one and a half parts of the bicarbonate. from two to four parts of the flux are amply sufficient to yield a fluid slag with one part of earthy matter. this statement is also true of the fluxes which follow. ~borax~ is a hydrated biborate of soda, containing nearly half its weight of water. when heated it swells up, loses its water, and fuses into a glass. the swelling up may become a source of loss in the assay by pushing some of the contents out of the crucible. to avoid this, _fused_ or _dried borax_ may be used, in which case a little more than half the amount of borax indicated will suffice. borax will flux almost anything, but it is especially valuable in fluxing lime, &c., and metallic oxides; as also in those cases in which it is desired to keep certain of the latter in the slag and out of the button of metal. ~oxide of lead~, in the form of red lead or litharge, is a valuable flux; it easily dissolves those metallic oxides which are either infusible or difficultly fusible of themselves, such as oxides of iron or copper. the resulting slag is strongly basic and very corrosive; no crucible will long withstand the attack of a fused mixture of oxides of lead and copper. with silicates, also, it forms very fusible double silicates; but in the absence of silicates and borates it has no action upon lime or magnesia. whether the lead be added as litharge or as red lead, it will exist in the slag as monoxide (litharge); the excess of oxygen of the red lead is thus available for oxidising purposes. if this oxidising power is prejudicial, it may be neutralised by mixing the red lead with per cent. of charcoal. ~glass~: broken beakers and flasks, cleaned, dried, and powdered will do. it should be free from lead. ~fluor~: fluor-spar as free as possible from other minerals, powdered. it helps to flux phosphate of lime, &c., and infusible silicates. ~lime~: should be fresh and powdered. it must not be slaked. powdered white marble (carbonate of lime) will do; but nearly double the quantity must be taken. one part of lime produces the same effect as . parts of the carbonate of lime. ~tartar~ and "black flux," are reducing agents as well as fluxes. the "black flux," which may be obtained by heating tartar, is a mixture of carbonate of potash and charcoal. reducing agents.--the distinction between reducing agents and fluxes (too often ignored) is an important one. fluxes yield slags; reducing agents give buttons of regulus or of metal. the action of a reducing agent is the separation of the oxygen or sulphur from the metal with which it is combined. for example, the mineral anglesite (lead sulphate) is a compound of lead, sulphur, and oxygen; by carefully heating it with charcoal the oxygen is taken away by the charcoal, and a regulus of lead sulphide remains. if the regulus be then fused with metallic iron the sulphur is removed by the iron, and metallic lead is left. the charcoal and the iron are reducing agents. but in defining a reducing agent as one which removes oxygen, or sulphur, from a metallic compound so as to set the metal free, it must be remembered that sulphur itself will reduce metallic lead from fused litharge, and that oxygen will similarly set free the metal in fused lead sulphide. there is no impropriety in describing sulphur as a reducing agent; but it is absurd to call oxygen one. some confusion will be avoided if these substances and those which are opposite to them in property be classed as oxidising and de-oxidising, sulphurising, and de-sulphurising agents. most oxidising agents also act as de-sulphurisers. _the de-oxidising agents_ most in use are the following:-- ~charcoal.~--powdered wood charcoal; it contains more or less hygroscopic moisture and about or per cent. of ash. the rest may be considered carbon. carbon heated with metallic oxides takes the oxygen; at low temperatures it forms carbon dioxide, and at higher ones, carbon monoxide. other conditions besides that of temperature have an influence in producing these results; and as the quantity of charcoal required to complete a definite reaction varies with these, it should be calculated from the results of immediate experience rather than from theoretical considerations. ~flour.~--ordinary wheat flour is convenient in use. on being heated it gives off inflammable gases which have a certain reducing effect, and a residue of finely divided carbon is left. it is likely to vary in the quantity of moisture it contains. two parts of flour should be used where one part of charcoal would be otherwise required. ~tartar.~--this is crude hydric potassic tartrate; the purified salt, cream of tartar, may be used. on being heated it gives off inflammable gases, and leaves a residue formed of potassic carbonate mixed with finely divided carbon. five parts of tartar should be used in the place of one of charcoal. ~anthracite~ or ~culm~ is a kind of coal containing per cent. or more of carbon. it gives off no inflammable gas. it is denser, and takes longer in burning, than charcoal. its reducing effect is little inferior to that of charcoal. almost any organic substance can be used as a reducing agent, but it is well not to select one which melts, swells up, or gives off much water and gas when heated in the furnace. ~potassic cyanide~ is an easily fusible and somewhat volatile salt, which, when fused, readily removes oxygen and sulphur from metallic compounds, and forms potassic cyanate or sulphocyanate as the case may be. commercial samples vary much in purity; some contain less than per cent. of the salt. for assaying, only the better qualities should be used. ~iron~ is a de-sulphurising rather than a de-oxidising agent. iron is used in the form of rods, / -inch in diameter, or of nails, or of hoop iron. in the last case it should be thin enough to be bent without difficulty. wrought iron crucibles are very useful in the processes required for making galena assays. _the chief oxidising agents (which are also de-sulphurisers)_ are the following:-- ~nitre~, or potassic nitrate.--this salt fuses very easily to a watery liquid. it oxidises most combustible substances with deflagration, and thereby converts sulphides into sulphates, arsenides into arsenates, and most metals into oxides. in the presence of strong bases, such as soda, the whole of the sulphur is fully oxidised; but in many cases some arsenic is apt to escape, and to give rise to a peculiar garlic-like odour. the sulphates of soda and potash are thus formed, and float as a watery liquid on the surface of the slag. ~red lead~ is an oxide of lead. about one-quarter of its oxygen is very loosely held, and, hence, is available for oxidising purposes, without any separation of metallic lead. the rest of the oxygen is also available; but for each part of oxygen given off, about parts of metallic lead are deposited. in silver assays this power of readily giving up oxygen is made use of. the residual oxide (litharge) acts as a flux. ~hot air~ is the oxidising agent in roasting operations. the sulphur and arsenic of such minerals as mispickel and pyrites are oxidised by the hot air and pass off as sulphur dioxide and "white arsenic." the metals generally remain in the form of oxide, mixed with more or less sulphate and arsenate. the residue may remain as a powdery substance (a calx), in which case the process of roasting is termed calcination; or it may be a pasty mass or liquid. in the calcination of somewhat fusible minerals, the roasting should be done at a low temperature to avoid clotting; arsenic and sulphur being with difficulty burnt off from the clotted mineral. a low temperature, however, favours the formation of sulphates; and these (if not removed) would reappear in a subsequent reduction as sulphides. these sulphates may be decomposed by a higher temperature towards the end of the operation; their removal is rendered more certain by rubbing up the calx with some culm and re-roasting, or by strongly heating the calx after the addition of solid ammonic carbonate. in roasting operations, as large a surface of the substance as possible should be exposed to the air. if done in a crucible, the crucible should be of the cornish type, short and open, not long and narrow. for calcinations, _roasting dishes_ are useful: these are broad and shallow, not unlike saucers, but unglazed. in those cases in which the products of the roasting are liquid at the temperature used, a _scorifier_ (fig. ) is suitable if it is desired to keep the liquid; but if the liquid is best drained off as quickly as it is formed, a _cupel_ (fig. ) should be used. [illustration: fig. .] a scorifier is essentially a roasting dish sufficiently thick to resist, for a time, the corrosive action of the fused metallic oxides it is to contain. the essential property of a cupel is, that it is sufficiently porous to allow the fused oxide to drain into it as fast as it is formed. it should be large enough to absorb the whole of the liquid; and of course must be made of a material upon which the liquid has no corrosive action. cupels do not bear transport well; hence the assayer generally has to make them, or to supervise their making. a quantity of bone ash is carefully mixed with water so that no lumps are formed, and the mixture is then worked up by rubbing between the hands. the bone ash is sufficiently wet when its cohesion is such that it can be pressed into a lump, and yet be easily crumbled into powder. cupel moulds should be purchased. they are generally made of turned iron or brass. they consist of three parts ( ) a hollow cylinder; ( ) a disc of metal; and ( ) a piston for compressing the bone ash and shaping the top of the cupel. the disc forms a false bottom for the cylinder. this is put in its place, and the cylinder filled (or nearly so) with the moistened bone ash. the bone ash is then pressed into shape with the piston, and the cupel finished with the help of three or four smart blows from a mallet. before removing the piston, turn it half-way round upon its axis so as to loosen and smooth the face of the cupel. the cupel is got out by pressing up the disc of metal forming the false bottom; the removal is more easily effected if the mould is somewhat conical, instead of cylindrical, in form. the cupels are put in a warm place to dry for two or three days. a conveniently sized cupel is - / inches in diameter and about / inch high. the cavity of the cupel is about / inch deep, and something of the shape shown in fig. . [illustration: fig. .] [illustration: fig. .] [illustration: fig. .] there are two kinds of furnaces required, the "wind" and "muffle" furnaces. these are built of brick, fire-brick, of course, being used for the lining. they are connected with a chimney that will provide a good draught. figure shows a section of the wind furnace, fig. a section of the muffle furnace, and fig. a general view of a group comprising a muffle and two wind furnaces suitable for general work. when in operation, the furnaces are covered with iron-bound tiles. the opening under the door of the muffle is closed with a loosely fitting brick. the floor of the muffle is protected with a layer of bone-ash, which absorbs any oxide of lead that may be accidentally spilt. the fire bars should be easily removable. few tools are wanted; the most important are some cast-iron moulds, tongs (fig. ), stirrers for calcining (fig. ), and light tongs of a special form for handling scorifiers and cupels (_see_ silver). [illustration: fig. .] [illustration: fig. .] the coke used should be of good quality; the formation of a fused ash (clinker), in any quantity, causes ceaseless trouble, and requires frequent removal. the coke should be broken into lumps of a uniform size (about in. across) before being brought into the office. the furnace should be well packed by stirring, raising the coke and not ramming it, and it should be uniformly heated, not hot below and cold above. in lighting a furnace, a start is made with wood and charcoal, this readily ignites and sets fire to the coke, which of itself does not kindle easily. in commencing work, add (if necessary) fresh coke, and mix well; make hollows, and into these put old crucibles; pack around with coke, so that the surface shall be concave, sloping upwards from the mouths of the crucibles to the sides of the furnace; close the furnace, and, when uniformly heated, substitute for the empty crucibles those which contain the assays. it is rarely advisable to have a very hot fire at first, because with a gradual heat the gases and steam quietly escape through the unfused mass, while with too strong a heat these might make some of the matter in the crucible overflow. moreover, if the heat should be too strong at first, the flux might melt and run to the bottom of the crucible, leaving the quartz, &c., as a pasty mass above; with a gentler heat combination is completed, and the subsequent fiercer heat simply melts the fusible compound into homogeneous slag. the fused material may be left in the crucible and separated from it by breaking when cold. it is generally more convenient to pour it into cast-iron moulds. these moulds should be dry and smooth. they act best when warmed and oiled or black-leaded. air entering through the fire-bars of a furnace and coming in contact with hot coke combines with it, forming a very hot mixture of carbonic acid and nitrogen; this ascending, comes in contact with more coke, and the carbonic acid is reduced to carbonic oxide; at the top of the furnace, or in the flue, the carbonic oxide meeting fresh air, combines with the oxygen therein and re-forms carbonic acid. in the first and third of these reactions, much heat is evolved; in the second, the furnace is cooled a little. it must always be remembered, that the carbonic oxide of the furnace gases is a reducing agent. when these gases are likely to exert a prejudicial effect, and a strongly oxidising atmosphere is required, the work is best done in a _muffle_. footnotes: [ ] there is an exception to this, as when the slag is liable to be acted on when exposed to the air and to the gases of the furnace. in this case a layer of fused common salt floating on the slag, so as to protect it from the air and furnace gases, is a distinct advantage. chapter iii. wet gravimetric methods. in _dry assays_ the metal is almost always separated and weighed as metal; in _wet_ gravimetric assays the metal is more usually weighed in the form of a definite compound of known composition. the general methods of working resemble those of ordinary chemical analysis, and their successful working is greatly helped by a knowledge of, at any rate, those compounds of the metal which enable it to be separated, and of those which are the most convenient forms in which it can be weighed. but the work of the assayer differs from that of the analyst, inasmuch as the bulk of his estimations are made upon material of practically the same kind, varying only in richness; consequently in assaying, it is possible (and necessary) to work on such a definite plan as will involve the least amount of labour in weighing and calculating. the assayer connected with mining has generally two classes of material to deal with: those comparatively rich and those comparatively poor. for example, silver in bullion and in ores; copper precipitates or regulus, and copper ores and slags; and "black tin" and tin ores. he is only occasionally called on to assay the intermediate products. it is indispensable that he should have an approximate knowledge of the substance to be determined. with new ores this information is best got by a qualitative testing. knowing that only certain bodies are present, it is evident that the number of separations can be reduced, and that simple methods can be devised for arriving at the results sought for. the best method is that which involves the least number of separations. the reactions must be sharp and complete, and yet not be liable to error under varying conditions. to bring the richer and poorer materials under the same conditions for the assay, a small weight, say gram of the richer, and a larger weight ( or grams) of the poorer, substance is weighed up. a method is then adopted which will concentrate the whole of the metal (either during or after solution) in a product which need not necessarily be pure. the work on this product is comparatively easy. in separating small quantities of a substance from a large bulk of impurities, the group separations must not as a rule be too much relied on. very large precipitates carry down small quantities of bodies not belonging to the group, more especially when there is a tendency to form weak double compounds. the re-dissolving and re-precipitating of bulky precipitates should be avoided. when a large number of assays of the same kind have to be carried out, a plan something like the following is adopted:--the samples, after having been dried, are placed in order on a table at the left hand of the assayer. he takes the first, marks it with a number, samples and weighs up the quantity required, and transfers it to a flask, which is similarly marked. as the weighings are finished, the samples are placed in the same order on his right hand. the assistant takes the flasks in batches of four or five at a time to the fume cupboard, where he adds a measured quantity of acid. when solution has been effected, dilution with a measured volume is generally necessary. the assayer sees to this and (whilst the funnels and filters are being prepared) makes any separation that is necessary. the filters are arranged in order on a rack (fig. ), and need not be marked unless the precipitates or residues have subsequently to be dried. the filters are washed with hot water, and if the filtrates are wanted flasks are placed beneath, if not, the solution is drained off down the sink. precipitation or reduction (or whatever it may be) is now made; the assistant filters the prepared samples, one at a time, whilst the assayer is engaged with the others. the same style of work is continued until the assays are completed. if one should be spoiled, it is better to allow it to stand over for assaying along with the next batch. if one filters slowly or is in any way less forward than the rest, it may lessen the accuracy of the other assays, owing to oxidation, &c., it should, therefore, be put on one side. the assays are dealt with in batches of ten or twenty, so that a large quantity of work can be quickly finished. [illustration: fig. .] when the assays are finished, it is the duty of the assistant to clean the apparatus (with reagents, if necessary), and to put the vessels in the place set apart for them. flasks are best kept inverted on a rack, so that they may be dry and clean by the next morning. berlin crucibles must be cleaned and ignited. the amount of apparatus employed should be as little as is feasible. the assay should be carried out as much as possible in the same flask. the bench must be clean, and altogether free from apparatus not in actual use. crucibles and dishes in which weighings are made should be marked with numbers or letters; and their weights recorded, together with the date of weighing, in a small ledger, which is kept in the drawer of the balance. by this means a record of the "wear" of each piece of apparatus is obtained, and, what is more important, much weighing is saved, and increased confidence is gained. the weight of each piece of apparatus need not be taken daily. it will be seen from the record in the book and a knowledge of the use it has been put to how often a checking of the weight is necessary. the entries are made in black lead as follows:-- dish, a. feb. . grams. . . . platinum vessels and apparatus lose, and porcelain ones slightly gain, weight with continued use. the special details of the work is given under each assay; certain general instructions will be given here. ~solution.~--it is not always necessary to get the whole of the mineral in solution, provided the body sought for is either completely dissolved or altogether left in the residue. it is often only by a qualitative examination of the solution (or residue, as the case may be) that the assayer can satisfy himself that it is free from the substance sought. but previous experience with the same kind of ore will show to what extent this testing is necessary. solution is generally best effected in flasks; but where the resulting liquid has afterwards to be evaporated to dryness and ignited, evaporating dishes (fig. ) are used. with them clock glasses are used as covers during solution to avoid loss through effervescence. evaporating dishes are also best when an insoluble residue has to be collected, since it is difficult to wash out most residues from a flask. bumping occurs less frequently in dishes than in flasks. [illustration: fig. .] after the addition of the acid, and mixing by agitation, the vessel containing the substance is heated. this is best done on the "hot plate" (fig. ). this consists of a slab of cast iron about half or three-quarters of an inch thick, supported on loose fire bricks, and heated by two or three ring burners (figs. and ). the burners are connected to the gas supply by means of _lead_ tubing, to which they are soldered. flasks and dishes after being put on the plate are not further handled until solution is complete or the evaporation is carried to dryness. the hot plate is contained in a cupboard so as to be out of the reach of cold draughts. [illustration: fig. .] [illustration: fig. .] [illustration: fig. .] the action of the acids and other solvents is described in the chapter on reagents. ~precipitation.~--in precipitating add sufficient of the reagent to complete the reaction. the student must be on his guard against adding a very large excess, which is the commoner error. in some reactions the finishing point is obvious enough; either no more precipitate is formed, or a precipitate is completely dissolved, or some well-marked colour or odour is developed or removed. in those cases in which there is no such indication, theoretical considerations should keep the use of reagents within reasonable limits. the solutions of the reagents (_see_ reagents) are generally of five or ten per cent. strength. a small excess over that demanded by theory should be sufficient. [illustration: fig. .] [illustration: fig. .] [illustration: fig. .] [illustration: fig. .] ~filtration.~--solutions are best filtered hot whenever the assay allows of this being so done. the precipitate should be allowed to settle, and the clear liquid decanted on the filter with the aid of a glass rod if necessary. the filter-paper must not be too large, but at the same time it must not be overloaded with the precipitate. there should be ample room for washing. for general use three sizes of filter-paper are sufficient. common quick filtering-paper (english) is best for most work in assaying. the specially prepared paper (swedish or rhenish) is used for collecting those precipitates which have to be weighed. the papers are folded as shown in fig. , and should not project above the funnel. the filter-paper works better if damped with hot water. in special cases filtering is hastened by means of an air-pump. the apparatus used consists of a water-jet (fig. ), which is connected with the tap, as also with a bottle fitted as shown in fig. . the pump draws the air out from the bottle, and atmospheric pressure forces the liquid through the filter-paper. the bottom of the funnel is provided with a platinum cone, which supports the filter-paper, and prevents its breaking. the pump is only used in exceptional cases; nearly all the filtrations required by the assayer can be made without it. the usual methods of supporting the funnel during filtration are shown in fig. . where the filtrate is not wanted, pickle bottles make convenient supports. after the precipitate has been thrown on the filter, it is washed. in washing, several washings with a small quantity of water are more effective than a few with a larger quantity of that fluid. the upper edge of the filter-paper is specially liable to escape complete washing. excessive washing must be avoided; the point at which the washing is complete is found by collecting a little of the filtrate and testing it. the precipitate is removed from the filter-paper for further treatment by opening out the paper and by washing the precipitate with a jet of water from a wash-bottle into a beaker, or back through the funnel into the flask. in some cases, when the precipitate has to be dissolved in anything in which it is readily soluble, solution is effected in the filter itself allowing the liquid to run through as it is formed. ~drying and igniting.~--precipitates, as a rule, require drying before being ignited. with small precipitates the filter-paper may be opened out, and placed on a warm asbestos slab till dry; or the funnel and the filter with the precipitate is placed in a warm place, and supported by any convenient means. the heat must never be sufficient to char the paper. some precipitates must be dried at a temperature not higher than ° c. these are placed in the water-oven (fig. ), and, when apparently dry, they are taken from the funnel, placed between glasses, and then left in the oven till they cease to lose weight. such precipitates are collected on tared filters. those precipitates which will stand a higher temperature are dried in the hot-air oven at a temperature of from ° to °. the drying is continued until they appear to be free from moisture, and until the precipitate ceases to adhere to the filter. in drying sulphides the heat must not be raised to the melting point of sulphur, since, if there is any free sulphur present, it fuses and filters through. [illustration: fig. .] the precipitate, having been dried, is transferred to a watch-glass. the filter-paper is opened out over a sheet of note-paper, and, with a camel-hair brush, the precipitate is gently brought into the glass. most precipitates come away easily, and the transfer can be made without apparent loss. the watch-glass is covered by the funnel, and the filter-paper (folded into a quadrant) held by the tweezers and set fire to with the flame of a bunsen burner. it is allowed to burn over the crucible, into which the black bulky ash is allowed to drop, and two or three drops of nitric acid are then added. the crucible is placed on a pipe-stem triangle (fig. ), supported on a tripod. it is at first heated gently with a bunsen burner, and afterwards more strongly, until the residue is free from carbon. it is cooled, and treated with any acid necessary to convert the small amount of precipitate into the state in which it is to be weighed; heated again, and cooled. the main precipitate is transferred to the crucible, and the heating repeated very gently at first, but more strongly towards the end of the operation. it is next placed in the muffle, and, after two or three minutes at a red heat, it is removed and allowed to cool in the desiccator before weighing. this is for bodies that will bear a red heat; for those compounds that require a lower temperature the heating in the muffle is omitted. the muffle used for this purpose must not be used at the same time for cupelling; a gas muffle (fig. ), such as one of fletcher's, is best. a desiccator (fig. ) is an air-tight vessel which prevents access of moisture, &c., to the substance. usually the air in it is kept dry by means of a basin containing sulphuric acid. [illustration: fig. .] [illustration: fig. .] [illustration: fig. .] the crucible is removed from the muffle with the tongs and carried to the desiccator. it is best, in an office, to have a large desiccator permanently fixed alongside the balance, into which all substances may be put before being weighed. the substance is removed from the bench or muffle in the small hand apparatus generally sold, and carried to the balance room to be transferred to the large desiccator, where it is allowed to become thoroughly cold before being weighed. twenty minutes is generally the time allowed after ignition before it is advisable to weigh. bodies allowed to cool in the air after they have been ignited will absorb moisture, and hot bodies placed in the balance-pan will disturb the equilibrium and show false results. compounds that absorb moisture must be weighed quickly; they should, therefore, be weighed in covered vessels. such compounds are detected by their continually-increasing weight. they should be ignited and weighed again in a well-covered dish. substances that have been washed with alcohol, ether, or any readily volatile liquid are dried in the water oven. they quickly dry if there is no water present, and are generally fit for weighing in less than one hour. sometimes drying for a few minutes only will be sufficient. the weight of the crucible and precipitate having been obtained, the weight of the crucible and ash is deducted; for example-- crucible and precipitate . grams. crucible and ash . " ------ . " the weight of the ash is best added to that of the crucible. the amount of ash in filter-papers must not be neglected, although papers are now made almost free from ash, and the amount to be deducted is found by taking eight or ten papers and burning them until they become white, and then weighing the ash. the amount varies from . to . gram for different papers. having determined the ash, place in the balance-drawer three of the filter-papers pinned together, with the weights marked on them in the way shown in fig. , so as to be readily seen when there is occasion to refer to them. [illustration: fig. .] it must be remembered that the determination of small quantities of substances generally involves the use of reagents which are often contaminated, as an impurity, with the body sought for. thus, in assaying silver, the oxide of lead or metallic lead used is rarely free from silver; and in the case of arsenic, the acids, zinc or ferric chloride are sure to contain arsenic. the same observation applies to the precipitation of lead by zinc, &c. the errors caused by these impurities are more marked in the determination of material having small quantities of metal than in that of ores which contain larger quantities. errors of this kind are counteracted or neutralised by "blank" or "blind" determinations. these consist in carrying out by the side of and during the assay a duplicate experiment with the reagents only, which are thereby subjected to the same processes of solution, evaporation, filtration, &c. the final result thus obtained is deducted from that given by the assay, the difference gives the corrected result. in some cases, where it is desired or necessary to have a tangible residue or precipitate, some _pure_ inert material is added. chapter iv. volumetric assays. these have been already described as those in which the results are got by measuring, either--( ) the volume of a reagent required to complete some reaction, or ( ) the volume of the resulting product. for example, if a permanganate of potash solution be added to a solution containing a weighed amount of iron, dissolved in sulphuric acid, the strong colour of the permanganate of potash will be removed until a certain quantity of it has been added. repeating the experiment, it will be found that the same amount of iron decolorises the same volume of the permanganate solution within certain narrow limits of variation, known as "error of experiment." this error is due to variation in the method of working and to slight differences in the weighings and measurings; it is present in all experimental methods, although the limits of variation are wider in some than in others. apart from this error of experiment, however, it is certain that a given volume of the permanganate of potash solution corresponds to a definite weight of iron, so that if either is known the other may be calculated. similarly, if a known weight of zinc (or of carbonate of lime) be dissolved in hydrochloric acid, a gas will be given off which can be measured, and so long as the conditions of the experiment do not vary, the same weight of zinc (or of carbonate of lime) gives off the same volume of gas. the weight of the one can be determined from the volume of the other. or, again, the quantity of some substances may be measured by the colour of their solutions, on the principle that, other things being equal, the colour of a solution depends upon the quantity of colouring matter present. so that if two solutions of the same substance are equally coloured they are of equal strength. in this way an unknown may be compared with a known strength, and a fairly accurate determination may be made. these three illustrations serve as types of the three chief classes of volumetric assays--titrometric, gasometric, and colorimetric. ~titrometric assays.~--within the limits of the error of experiment, a definite volume of a solution or gas represents a certain weight of metal or other substance, hence the exact weight may be determined by experiment. the error of experiment may be reduced to insignificant dimensions by repeating the experiment, and taking the mean of three or four determinations. this will at the same time show the amount of variation. thus, if . gram of iron were dissolved and found to require . cubic centimetres of the solution of permanganate of potash, and if on repeating, . , . , and . c.c. were required, the experimenter would be justified in saying that . c.c. of the permanganate solution represent . gram of iron, and that his results were good within . c.c. of the permanganate solution. so that if in an unknown solution of iron, . c.c. of the permanganate solution were used up, he could state with confidence that it contained a little more than . gram of iron. with a larger experience the confidence would increase, and with practice the experimental error will diminish. but supposing that the unknown solution required, say, . instead of . c.c., he would not be justified in saying that, since . c.c. are equivalent to . gram, . c.c. are equivalent to twice that amount; and that, consequently, the unknown solution contained a little less than gram of iron; or, at least, he could not say it except he (or some one else) had determined it by experiment. but if on dissolving gram of iron, he found it to require . c.c. of the solution, and in another experiment with . gram of iron that . c.c. of the solution were required, he would be justified in stating that _the volume of solution required is proportional to the quantity of metal present_. there are a large number of volumetric assays of which this is true, but that it is true in any particular case can only be proved by experiment. even where true it is well not to rest too much weight upon it, and in all cases the quantity of metal taken, to determine the strength of the solution used, should not differ widely from that present in the assay. there are certain terms which should be explained here. when the solution of a reagent is applied under such conditions that the volume added can be correctly determined, the operation is called "titrating," the solution of the reagent used the "standard solution," and the process of determining the strength of the standard solution is "standardising." the "standard" is the quantity of metal equivalent to c.c. of the standard solution. ~standard solutions.~--in making these the salt is accurately weighed and transferred to a litre flask, or to the graduated cylinder, and dissolved. the method of dissolving it varies in special cases, and instructions for these will be found under the respective assays. generally it is dissolved in a small quantity of liquid, and then diluted to the mark. for those substances that require the aid of heat, the solution is made in a pint flask, cooled, and transferred; after which the flask is well washed out. after dilution, the liquids in the measuring vessel must be thoroughly mixed by shaking. this is more easily and better done in the cylinder than in the litre flask. the solution is next transferred to a dry "winchester" bottle and labelled. the label may be rendered permanent by waxing it. standard solutions should not be kept in a place exposed to direct sunlight. oxidising and reducing solutions, such as those of permanganate of potash, ferrous sulphate, iodine, hyposulphite of soda, &c., gradually weaken in strength; the solutions of other salts are more stable; while those of potassium bichromate and baric chloride are almost permanent. solutions of potassium permanganate may be kept for a month or so without much change. the solutions of hyposulphite of soda and of iodine should be examined weekly. ferrous sulphate solutions, if acidulated with sulphuric acid, may be depended on for two or three weeks without fresh standardising. before filling the burette, the "winchester" bottle should be well shaken and a portion of about or c.c. poured into a dry beaker or test-glass. besides the standard solutions, which are required for titrating an assay, permanent solutions of the metal or acid of equivalent strength are very useful. when the finishing point of a titration has been overstepped (_i.e._, the assay has been "overdone"), a measured volume, say or c.c., of a solution containing the same metal may be added. the titration can then be continued, but more cautiously, and the value in "c.c." for the quantity added be deducted from the final reading. ~standardising.~--suppose the object is to standardise a solution of permanganate similar to that referred to above. a convenient quantity of iron (say . gram) would be weighed out, dissolved in dilute sulphuric acid, and the solution titrated. suppose . c.c. of the permanganate solution are required, then . : . :: : _x_ _x_ = . gram. this result, . gram, is the "_standard_." when a gas is measured, the standard may be calculated in the same way. for example: with . gram of zinc, . c.c. of gas were obtained. then the quantity of zinc equivalent to c.c. of the gas is got by the proportion. . : . :: : _x_ _x_ = . gram. using the term "standard" in this sense, the following rules hold good:-- to find the weight of metal in a given substance:--_multiply the standard by the number of c.c. used and divide by ._ for example: a piece of zinc was dissolved and the gas evolved measured . c.c. then by the rule, . × . / should give the weight of the piece of zinc. this gives . gram. to find the percentage of metal in a given substance:--_multiply the standard by the number of c.c. used and divide by the weight of substance taken._ for example: if grams of a mineral were taken, and if on titrating with the permanganate solution (standard . ) . c.c. were required, then ( . × . )/ = . . this is the percentage. if the standard is exactly gram, and gram of ore is always taken, these calculations become very simple. the "c.c." used give at once the percentage, or divided by give the weight of metal. if it is desired to have a solution with a standard exactly . gram, it is best first to make one rather stronger than this, and then to standardise carefully. divide by the standard thus obtained and the result will be the number of c.c. which must be taken and be diluted with water to litre. for example: suppose the standard is . , then / . gives , and if c.c. be taken and diluted with water to c.c. a solution of the desired strength will be obtained. the standard of this should be confirmed. a simpler calculation for the same purpose is to multiply the standard by ; this will give the number of c.c. to which litre of the solution should be diluted. in the above example a litre should be diluted to c.c. it has been assumed in these rules that the titration has yielded proportional results; but these are not always obtained. there can be no doubt that in any actual re-action the proportion between any two re-agents is a fixed one, and that if we double one of these then exactly twice as much of the other will enter into the re-action; but in the working it may very well be that no re-action at all will take place until after a certain excess of one or of both of the re-agents is present. in titrating lead with a chromate of potash solution, for example, it is possible that at the end of the titration a small quantity of the lead may remain unacted on; and it is certain that a small excess of the chromate is present in the solution. so, too, in precipitating a solution of silver with a standard solution of common salt, a point is reached at which a small quantity of each remains in solution; a further addition either of silver or of salt will cause a precipitate, and a similar phenomenon has been observed in precipitating a hydrochloric acid solution of a sulphate with baric chloride. the excess of one or other of the re-agents may be large or small; or, in some cases, they may neutralise each other. considerations like these emphasise the necessity for uniformity in the mode of working. whether a process yields proportional results, or not, will be seen from a series of standardisings. having obtained these, the results should be arranged as in the table, placing the quantities of metal used in the order of weight in the first column, the volumes measured in the second, and the standards calculated in the third. if the results are proportional, these standards will vary more or less, according to the delicacy of the process, but there will be no apparent order in the variation. the average of the standards should then be taken. +-------------+---------------+----------+ | weight. | volume found. | standard | +-------------+---------------+----------+ | . gram | . c.c. | . | | . " | . " | . | | . " | . " | . | | . " | . " | . | | . " | . " | . | +-------------+---------------+----------+ any inclination that may be felt for obtaining an appearance of greater accuracy by ignoring the last result must be resisted. for, although it would make no practical difference whether the mean standard is taken as . or . , it is well not to ignore the possibility that an error of . c.c. may arise. a result should only be ignored when the cause of its variation is known. in this series the results are proportional, but the range of weights ( . - . gram) is small. all processes yield fairly proportional results if the quantities vary within narrow limits. as to results which are not proportional, it is best to take some imaginary examples, and then to apply the lesson to an actual one. a series of titrations of a copper solution by means of a solution of potassic cyanide gave the following results:-- +---------------+---------------+-----------+ | copper taken. | cyanide used. | standard. | +---------------+---------------+-----------+ | . gram | . c.c. | . | | . " | . " | . | | . " | . " | . | | . " | . " | . | +---------------+---------------+-----------+ these are proportional, but by using a larger quantity of acid and ammonia in the work preliminary to titration, we might have had to use c.c. of cyanide solution more in each case before the finishing point was reached. the results would then have been: +---------------+---------------+-----------+ | copper taken. | cyanide used. | standard. | +---------------+---------------+-----------| | . gram | . c.c. | . | | . " | . " | . | | . " | . " | . | | . " | . " | . | +---------------+---------------+-----------+ it will be noted that the value of the standard increases with the weight of metal used; and calculations from the mean standard will be incorrect. by subtracting the lowest standardising from the highest, a third result is got free from any error common to the other two; thus:-- . gram = . c.c. "cyanide." . " = . " " --- ---- . " = . " " and the standard calculated from this corrected result is . . further, if . gram requires . c.c., then . gram should require . c.c., or . c.c. less than that actually found. we may therefore use the following rules for working processes which do not yield proportional results. make a series of two or three titrations, using very different quantities of metal in each. subtract the lowest of these from the highest, and calculate the standard with the remainder. calculate the volume required by this standard in any case, and find the excess or deficit, as the case may be. if an excess, subtract it from the result of each titration; if a deficit, add it; and use the standard in the usual way. the following table shows an actual example:-- +--------------+---------------+-----------+ | chalk taken. | gas obtained. | standard. | +--------------+---------------+-----------+ | . gram | . c.c. | . | | . " | . " | . | | . " | . " | . | | . " | . " | . | | . " | . " | . | | . " | . " | . | +--------------+---------------+-----------+ it will be seen that the standard decreases as the quantity of chalk increases; this points to a deficiency in the quantity of gas evolved. then . = . c.c. . = . " ------ = ---- . = . " and . × / . = . . then, multiplying the weight of chalk taken by , and dividing by . , we get the calculated results of the following table:-- +--------------+------------+-----------------+-------------+ | chalk taken. | gas found. | gas calculated. | difference. | +--------------+------------+-----------------+-------------+ | . gram | . c.c. | . c.c. | - . c.c. | | . " | . " | . " | - . " | | . " | . " | . " | - . " | | . " | . " | . " | - . " | | . " | . " | . " | - . " | | . " | . " | . " | - . " | +--------------+------------+-----------------+-------------+ by adding c.c. to the quantity of gas obtained, and taking . as the standard, the calculated results will agree with those found with a variation of . c.c. when a large number of assays of the same kind are being made, this method of calculation is convenient; when, however, only one or two determinations are in question, it is easier to make a couple of standardisings, taking quantities as nearly as possible the same as those present in the assays. sometimes it is necessary to draw up a table which will show, without calculation, the weight of substance equivalent to a given volume of gas or of solution. the substance used for standardising should be, whenever possible, a pure sample of the substance to be determined--that is, for copper assays pure copper should be used, for iron assays pure iron, and so on; but when this cannot be got an impure substance may be used, provided it contains a known percentage of the metal, and that the impurities present are not such as will interfere with the accuracy of the assay. including compounds with these, the standard may be calculated by multiplying the standard got in the usual way, by the percentage of metal in the compound or impure substance, and dividing by . if, for example, the standard . gram was obtained by using a sample of iron containing . per cent. of metal, the corrected standard would be . × . / = . . in volumetric analysis the change brought about must be one in which the end of the reaction is rendered prominent either by a change of colour or by the presence or absence of a precipitate. if the end of the reaction or finishing-point is not of itself visible, then it must be rendered visible by the use of a third reagent called an indicator. for example, the action of sulphuric acid upon soda results in nothing which makes the action conspicuous; if, however, litmus or phenolphthalein be added the change from blue to red in the first case, or from red to colourless in the second, renders the finishing-point evident. some indicators cannot be added to the assay solution without spoiling the result; in which case portions of the assay solution must be withdrawn from time to time and tested. this withdrawal of portions of the assay solution, if rashly done, must result in loss; if, however, the solution is not concentrated, and if the portions are only withdrawn towards the end of the titration, the loss is very trifling, and will not show-up on the result. the usual plan adopted is to have a solution of the indicator placed in drops at fairly equal intervals distributed over a clean and dry white porcelain-plate: a drop or two of the solution to be tested is then brought in contact with one of these and the effect noted. another plan is to have thin blotting-paper, moistened with a solution of the indicator and dried; a drop of the solution to be tested placed on this shows the characteristic change. when the assay solution contains a suspended solid which interferes with the test, a prepared paper covered with an ordinary filter-paper answers very well; a drop of the solution to be tested is placed on the filter-paper, and, sinking through, shows its effect on the paper below. except when otherwise stated, all titrations should be made at the ordinary temperature; cooling, if necessary, by holding the flask under the tap. when a titration is directed to be made in a boiling solution, it must be remembered that the standard solution is cold, and that every addition lowers the temperature of the assay. on running the solution from the burette into the assay, do not let it run down the side of the flask. if a portion of the assay has to be withdrawn for testing, shake the flask to ensure mixing, and then take out a drop with the test-rod; the neglect of these precautions may give a finishing-point too early. this is generally indicated by a sudden finish, in which case on shaking the flask and again testing no reaction is got. do not remove the drop on the point of the burette with the test-rod; let it remain where it is or drop it into the solution by carefully opening the clip. generally the methods of working are as follows:-- ( ) _when the finishing-point depends on a change of colour in the solution._--increase the bulk of the assay up to from to c.c. with water. boil or cool, as the case may be. run in the standard solution from a burette speedily, until the re-agent appears to have a slower action, and shake or stir all the time. then run c.c. or so at a time, still stirring, and finally add drops until the colour change is got. ( ) _when an outside-indicator is used._--pour the standard solution from a burette into the assay until or c.c. from the finishing-point; then run in c.c. at a time (stirring and testing on the plate between each) until the indicator shows the change wanted, and deduct . c.c. for excess. when greater accuracy is sought for a duplicate assay is made. in this case the standard solution is run in close up to the end, and the operation is finished off with a few drops at a time. ( ) _where the finishing-point depends upon the absence of a precipitate and no outside-indicator is used._--as in the last case, run in the standard solution up to within a few c.c. of the end, then run in c.c. at a time until a precipitate is no longer formed, but here . c.c. must be deducted for excess, since it is evident that the whole of the last "c.c." must have been, and a portion of the previous one may have been, in excess. ~indirect titration.~--the action of permanganate of potash upon a ferrous solution is one of oxidation, hence it is evident that if any other oxidising agent is present it will count as permanganate. in such a case the titration can be used (indirectly) to estimate the quantity of such oxidising agent, by determining how much less of the permanganate is used. for example, suppose that gram of iron dissolved in sulphuric acid requires c.c. of standard permanganate to fully oxidise it, but that the same amount of iron only requires . c.c. of the same standard permanganate if it has been previously heated with . gram of black oxide of manganese. here it is evident that . gram of black oxide does the work of . c.c.[ ] of the permanganate solution, and that these quantities are equivalent; moreover, if . c.c. correspond with . gram, then c.c. correspond with . which is the standard. on theoretical grounds, and by a method of calculation which will be explained further on (under the heading "calculations from formulæ"), it can be found that if the standard for iron is gram, that for the black oxide will be . gram. the principles of these indirect titrations become clearer when expressed in a condensed form. thus, in the example selected, and using the formulæ fe = iron, kmno_{ } = permanganate of potash, and mno_{ } = oxide of manganese, we have:-- ( ) gram fe = c.c. kmno_{ } ( ) gram fe = . c.c. kmno_{ } + . gram mno_{ } .'. c.c. kmno_{ } = . c.c. kmno_{ } + . gram mno_{ } ( - . ) c.c. kmno_{ } = . gram mno_{ } . c.c. kmno_{ } = . gram mno_{ } the iron does not enter into the calculation if the same quantity is present in the two experiments. an indirect titration thus requires three determinations, but if more than one assay is to be carried on, two of these need not be repeated. the standard is calculated in the usual way. ~colorimetric assays.~--these are assays in which the colour imparted to a solution by some compound of the metal to be determined is taken advantage of; the depth of colour depending on the quantity of metal present. they are generally used for the determination of such small quantities as are too minute to be weighed. the method of working is as follows:--a measured portion of the assay solution (generally / , / , / , or / of the whole), coloured by the substance to be estimated, is placed in a white glass cylinder standing on a sheet of white paper or glazed porcelain. into an exactly similar cylinder is placed the same amount of re-agents, &c., as the portion of the assay solution contains, and then water is added until the solutions are of nearly equal bulk. next, a standard solution of the metal being estimated is run in from a burette, the mixture being stirred after each addition until the colour approaches that of the assay. the bulk of the two solutions is equalised by adding water. then more standard solution is added until the tints are very nearly alike. next, the amount added is read off from the burette, still more is poured in until the colour is slightly darker than that of the assay, and the burette read off again. the mean of the readings is taken, and gives the quantity of metal added. it equals the quantity of metal in the portion of the assay. if this portion was one-half of the whole, multiply by two; if one-third, multiply by three, and so on. when the quantity of metal in very dilute solutions is to be determined, it is sometimes necessary to concentrate the solutions by boiling them down before applying the re-agent which produces the coloured compound. such concentration does not affect the calculations. ~gasometric assays.~--gasometric methods are not much used by assayers, and, therefore, those students who wish to study them more fully than the limits of this work will permit, are recommended to consult winkler and lunge's text-book on the subject. the methods are without doubt capable of a more extended application. in measuring liquids, ordinary variations of temperature have but little effect, and variations of atmospheric pressure have none at all, whereas with gases it is different. thus, c.c. of an ordinary aqueous solution would, if heated from ° c. to ° c., expand to about . c.c. c.c. of a gas similarly warmed would expand to about . c.c., and a fall of one inch in the barometer would have a very similar effect. and in measuring gases we have not only to take into account variations in volume due to changes in temperature and atmospheric pressure, but also that which is observed when a gas is measured wet and dry. water gives off vapour at all temperatures, but the amount of vapour is larger as the temperature increases. by ignoring these considerations, errors of or per cent. are easily made; but, fortunately, the corrections are simple, and it is easy to construct a piece of apparatus by means of which they may be reduced to a simple calculation by the rule of three. the volume of a gas is, in practice, usually reduced to that which it would be at a temperature of ° c., when the column of mercury in the barometer is mm. high. but, although convenient, this practice is not always necessary. the only thing required is some way of checking the variations in volume, and of calculating what the corrected volume would be under certain fixed conditions. suppose that at the time a series of standardisings is being made, c.c. of air were confined in a graduated tube over moist mercury. these c.c. would vary in volume from day to day, but it would always be true of them that they would measure c.c. under the same conditions as those under which the standardisings were made. if, then, in making an actual assay, . c.c. of gas were obtained, and the air in the tube measured c.c., we should be justified in saying, that if the conditions had been those of the standardising, the c.c. would have measured c.c., and the . c.c. would have been . ; for : :: . : . . the rule for using such a piece of apparatus for correcting volumes is:--_multiply the c.c. of gas obtained by , and divide by the number of c.c. of air in the apparatus._ if it is desired to calculate the volumes under standard conditions (that is, the gas dry, at ° c. and mm. barometric pressure) the calculations are easily performed, but the temperature and pressure must be known. _correction for moisture._--the "vapour tension" of water has been accurately determined for various temperatures, and it may be looked upon as counteracting the barometric pressure. for example, at ° c. the vapour tension equals . millimetres of mercury; if the barometer stood at mm., the correction for moisture would be made by subtracting . from , and taking . mm. to be the true barometric pressure. the vapour tensions for temperatures from ° c. to ° c. are as follows:-- -------+----------++-------+----------++-------+---------- temp. | tension. || temp. | tension. || temp. | tension. -------+----------++-------+----------++-------+---------- ° | . mm. || ° | . mm. || ° | . mm. ° | . mm. || ° | . mm. || ° | . mm. ° | . mm. || ° | . mm. || ° | . mm. ° | . mm. || ° | . mm. || ° | . mm. ° | . mm. || ° | . mm. || ° | . mm. ° | . mm. || ° | . mm. || ° | . mm. ° | . mm. || ° | . mm. || ° | . mm. -------+----------++-------+----------++-------+----------- the _correction for pressure_ is:--multiply the volume by the actual pressure and divide by . the _correction for temperature_:--multiply the volume by and divide by the temperature (in degrees centigrade) added to . for all three corrections the following rules hold good. _to reduce to ° c. and mm. dry._ volume × . × (pressure-tension) corrected volume = -------------------------------------- temperature + to find the volume, which a given volume under standard conditions would assume, if those conditions are altered. volume × . × (temperature + ) resulting volume = ------------------------------------ pressure - tension as an example, we will suppose that it is desired to enclose in the apparatus referred to on p. , a volume of air, which, when dry (at ° c. and mm.), shall measure c.c., whilst the actual temperature is ° c., and the pressure mm. the second formula is the one to be used, and we get . c.c. c.c.× . × required volume = ---------------------- - . . = ------- . = . c.c. footnotes: [ ] - . = . . chapter v. weighing and measuring. ~weighing.~--the system of weights and measures which we have adopted is the french or metric system; in this the gram ( . grains) is the unit of weight; the only other weight frequently referred to is the milligram, which is . , or / gram. the unit of volume is the cubic centimetre, which is approximately the volume of gram of water, and which thus bears to the gram the same relation as grain-measures bear to grains. it is usual to write and even pronounce cubic centimetre shortly as c.c., and the only other denomination of volume we shall have occasion to use is the "litre," which measures c.c., and is roughly - / pints. the weights used are kept in boxes in a definite order, so that the weights on the balance can be counted as well by noting those which are absent from the box as by counting those present on the scale-pan. the weights run , , , , , , , and grams, and are formed of brass. the fractions of the gram are generally made of platinum or of aluminium, and are arranged in the following order:-- . , . , . , . , and . , . , . , . . these may be marked in this way, or they may be marked , , , , , , , ; the meaning milligrams. some makers send out weights in the series , , , , &c. weights of less than . gram are generally present in a box, but it is much more convenient to work with a rider. this is a piece of wire which in the pan weighs . gram; it is made in such a form that it will ride on the beam, and its effective weight decreases as it approaches the centre. if the arm of the beam is divided into tenths, then each tenth counting from the centre outward equals . gram or milligram, and if these tenths be further subdivided the fractions of a milligram are obtained; and these give figures in the fourth place of decimals. a fairly good balance should be sensitive to . gram. the weights must never be touched with the fingers, and the forceps for moving them is used for no other purpose. when not in actual use the box is kept closed. the weights must not be allowed to remain on the pan of the balance. the balance-case must not be open without some reason. it must be fixed level, and, once fixed, must not be needlessly moved. the bench on which it stands should be used for no other purpose, and no one should be allowed to lean upon it. [illustration: fig. .] when using a balance sit directly in front of it. ordinarily the substance to be weighed is best put on the pan to the user's left; the weights and the rider are then easily manipulated. powders, &c., should not be weighed directly on the balance; a counterpoised watch-glass or metal scoop (fig. ) should be used. in some cases it is advisable to use a weighing-bottle. this is a light, well-stoppered bottle (fig. ) containing the powdered ore. it is first filled and weighed; then some of the substance is carefully poured from it into a beaker or other vessel, and it is weighed again; the difference in the two weighings gives the weight of substance taken. a substance must always be cold when weighed, and large glass vessels should be allowed to stand in the balance-box a little while before being weighed. always have the balance at rest when putting on or taking off anything from the pans. put the weights on systematically. in using the rider (except you have a reason to the contrary), put it on at the ; if this is too much, then try it at the ; if then the weights are too little, try at the , if still not enough, the correct weight must be between the and ; try half-way between. it is best to work with the balance vibrating; equilibrium is established when the vibration to the left is the mean of the preceding and succeeding vibrations to the right. for example, if it vibrates divisions to the right on one swing, and divisions on the next, the intermediate vibration to the left should have been - / . note whether the substance increases in weight whilst on the balance. if it does it may be because it was put on warm, and is cooling, or it may be because it is taking up moisture from the air. substances which take up moisture rapidly should be weighed in clipped watch-glasses or in light-weighing bottles or tubes. students, in recording the weights, should first read off those missing from the box, writing down each order of figures as determined; first tens, then units, and so on. remember that the first four platinum weights give the figures of the first place of decimals, the second four give the second place, and that the third and fourth places are given by the rider. having taken down the figures, confirm them by reading off the weights as you put them back into the box. do not rest a weight on the palm of your hand for convenience in reading the mark upon it. remember one weight lost from a box spoils the set. do not take it for granted that the balance is in equilibrium before you start weighing: try it. [illustration: fig. .] ~measuring liquids.~--for coarse work, such as measuring acids for dissolving ores, graduated glasses similar to those used by druggists may be used. it is well to have two sizes--a smaller graduated into divisions of c.c. (fig. ), and a larger with divisions equal to c.c. no measurement of importance should be made in a vessel of this kind, as a slight variation in level causes a serious error. ~graduated flasks~ must be used when anything has to be made up to a definite bulk, or when a fixed volume has to be collected. if, for example, a certain weight of substance has to be dissolved and diluted to a litre, or if the first c.c. of a distillate has to be collected, a flask should be used. each flask is graduated for one particular quantity; the most useful sizes are c.c., c.c., c.c., c.c., and c.c. the mark should be in the narrowest part of the neck, and should be tangential to the curved surface of the liquid when the flask _contains_ the exact volume specified. the level of a curved surface of liquid is at first somewhat difficult to read: the beginner is in doubt whether the surface should be taken at a, b, or c (fig. ). it is best to take the lowest reading c. in some lights it is difficult to find this; in such cases a piece of white paper or card held behind and a little below, so as to throw light up and against the curved surface, will render it clear. in reading, one should look neither up at nor down upon the surface, but the eye should be on the same level with it. it must be kept in mind that flasks _contain_ the quantity specified, but deliver less than this by the amount remaining in them and damping the sides. if it is desired to transfer the contents say of a c.c. flask to a beaker, it will be necessary to complete the transfer by rinsing out the flask and adding the washings; otherwise there will be a sensible loss. graduated cylinders (fig. ) are convenient for preparing standard solutions. [illustration: fig. .] [illustration: fig. .] [illustration: fig. .] ~pipettes~ and burettes are graduated to _deliver_ the quantities specified. the principle of the pipette, and the advantages and disadvantages of its various forms, may be understood by considering the first form shown in fig. . it is essentially a bulbed tube drawn out to a jet at its lower end, and having on each side of the bulb a mark so placed that when the surface of the liquid falls from the upper to the lower mark the instrument shall deliver exactly c.c. the bore of the jet should be of such a size as will allow the level of the liquid to fall at the rate of about one foot in two minutes. if it runs more quickly than this, an appreciable error arises from the varying amount of liquid remaining, and damping the sides of the bulb. the flow of liquid from a pipette must not be hastened by blowing into it. the lower tube or nose of the pipette should be long enough to reach into the bottle or flask containing the liquid about to be measured. the pipette is filled by sucking at the open end with the mouth; this method of filling renders the use of the instrument dangerous for such liquids as strong acids, ammonia, and such poisonous solutions as that of potassic cyanide. one attempt with a fairly strong solution of ammonia will teach the beginner a very useful lesson. as soon as the liquid rises above the upper mark in the pipette, the mouth is withdrawn, and the pipette quickly closed by pressing the upper aperture with the index finger of the right hand; it is well to have the finger slightly moist, but not damp. the neck of the pipette should be long enough to allow its being firmly grasped by the fingers and thumb of the right hand without inconvenience. the pipette is first held in a vertical position long enough to allow any moisture outside the tube to run down, and then the liquid is allowed to run out to the level of the upper mark; this is easily effected by lessening the pressure. if the finger is wet, the flow will be jerky, and good work impossible. the pipette is next held over the vessel into which the c.c. are to be put, and the liquid allowed to run out. when the bulb is nearly empty, the flow should be checked by replacing the finger, and the liquid allowed to escape slowly until the lower mark is reached. the pipette is then withdrawn; it is in the withdrawing that the disadvantage of this particular form[ ] makes itself felt. it must be withdrawn very steadily, as the slightest shock causes the remaining column of liquid to vibrate, whereby air is drawn in and the liquid is forced out. this disadvantage is got rid of by making the mouth of the jet the lower limit, or, in other words, allowing the instrument to empty itself. there are two forms of such pipettes; in the one generally recommended in gay-lussac's silver assay (the last shown in fig. ) the nose is replaced by a jet. this is most conveniently filled by stopping the jet with the finger, and allowing the liquid to flow in a fine stream into the neck until the pipette is filled, and then working as just described. the other form is the one in general use; in fact, a long nose to a pipette is so convenient that it may almost be said to be necessary. but the accuracy is slightly diminished; a long narrow tube makes a poor measuring instrument because of the amount of liquid it finally retains. a defect possessed by both forms is the retention of a drop of varying size in the nozzle. whatever method is adopted for removing this drop must be always adhered to. the most convenient form is the one last described, and the most useful sizes are c.c., c.c., c.c., c.c., and c.c. ten c.c. pipettes graduated into tenths of a cubic centimetre are very useful: those are best in which the graduation stops short of the bottom. all measurements should be made at the ordinary temperature; and, before being used, the pipette should be rinsed out with a cubic centimetre or so of the solution to be measured. after using, it should be washed out with water. ~burettes~ differ mainly from pipettes in having the flow of liquid controlled from below instead of from above. the best form is that known as mohr's, one kind of which is provided with a glass stopcock, while the other has a piece of india-rubber tube compressed by a clip. the latter cannot be used for solutions of permanganate of potash or of iodine, or of any substance which acts on india-rubber; but in other respects there is little to choose between the two kinds. a burette delivering c.c., and graduated into fifths (_i.e._, each division = . c.c.), is a very convenient size. for some kinds of work, c.c. divided into tenths (_i.e._, each division = . c.c.) may be selected. burettes may be fixed in any convenient stand; they must be vertical and should be so placed that the assayer can read any part of the graduated scale without straining. when not in use, they should be kept full of water. when using a burette, the water must be run out; the burette is next rinsed with some of the solution to be used, and drained; and then it is filled with the solution. next squeeze the india-rubber tube so as to disentangle air-bubbles and, by smartly opening the clip, allow the tube and jet to be filled; see that no bubbles of air are left. then run out cautiously until the level of the liquid in the burette stands at zero. in reading the level with very dark-coloured liquids it is convenient to read from the level a (fig. ), and, provided it is done in each reading, there is no objection to this. the accuracy of the reading of a burette is sensibly increased by the use of an erdmann float. this is an elongated bulb, weighted with mercury, and fitting (somewhat loosely) the tube of the burette. it floats in the solution, and is marked with a horizontal line; this line is taken as the level of the liquid. if the burette is filled from the top, the float rises with aggravating slowness, and this is its chief disadvantage. the float must come to rest before any reading is made. [illustration: fig. .] a convenient plan for filling a burette from below is shown in fig. . the diagram explains itself. the bottle containing the standard solution is connected with the burette by a syphon arrangement through the glass tube and t-piece. the flow of liquid into the burette is controlled by the clip. when this clip is opened, the burette fills; and when it is closed, the burette is ready for use in the ordinary way. ~measuring gases.~--lange's nitrometer (fig. ) is a very convenient instrument for many gasometric methods. it requires the use of a fair quantity of mercury. in fig. , there is a representation of a piece of apparatus easily fitted up from the ordinary material of a laboratory. it is one which will serve some useful purposes. it consists of a wide-mouthed bottle fitted (by preference) with a rubber cork. the cork is perforated, and in the perforation is placed a glass tube which communicates with the burette. the burette is connected by a rubber tube and a y-piece, either with another burette or with a piece of ordinary combustion-tube of about the same size. the wide-mouthed bottle contains either a short test-tube or an ordinary phial with its neck cut off. in working the apparatus the weighed substance is put in the bottle and the re-agent which is to act on it, in the test-tube; the cork is then inserted. the liquid in the two burettes is next brought to the same level, either by pouring it in at a or running it out at b. the level of the liquid in the apparatus for correcting variation in volume is then read and noted. next, after seeing that the level of the liquid in the burette has not changed, turn the bottle over on its side so that the re-agent in the test-tube shall be upset into the bottle. then, as the volume of the gas increases, lower the liquid in the burette by running it out at b, and at the same time keep the level in a half an inch or so lower than that in the burette. when the action has finished bring the liquid in the two vessels to the same level and read off the burette. this part of the work must always be done in the same manner. [illustration: fig. .] _the volume corrector for gas analysis_ is a graduated glass tube of c.c. capacity inverted over a narrow glass cylinder of mercury. it contains . or . c.c. of water and a volume of air, which, if dry and under standard conditions, would measure c.c. the actual volume varies from day to day, and is read off at any time by bringing the mercury inside and outside to the same level. this is done by raising or lowering the tube, as may be required. any volume of gas obtained in an assay can be corrected to standard temperature and pressure by multiplying by and dividing by the number of c.c. in the corrector at the time the assay is made. footnotes: [ ] it is best to use this form with a glass stopcock, or with an india-rubber tube and clip, after the manner of a mohr's burette. chapter vi. re-agents.--acids, etc. ~acetic acid~, h[=a=c] or c_{ }h_{ }o_{ }. (sp. gr. . , containing per cent. real acid).--an organic acid, forming a class of salts, acetates, which are for the most part soluble in water, and which, on ignition, leave the oxide or carbonate of the metal. it is almost always used in those cases where mineral acids are objectionable. to convert, for example, a solution of a substance in hydrochloric acid into a solution of the same in acetic acid, alkali should be added in excess and then acetic acid. many compounds are insoluble in acetic acid, which are soluble in mineral acids, such as ferric phosphate, ferric arsenate, zinc sulphide, calcium oxalate, &c., so that the use of acetic acid is valuable in some separations. the commercial acid is strong enough for most purposes, and is used without dilution. ~"aqua regia"~ is a mixture of part by measure of nitric acid and parts of hydrochloric acid. the acids react forming what is practically a solution of chlorine.[ ] the mixture is best made when wanted, and is chiefly used for the solution of gold and platinum and for "opening up" sulphides. when solutions in aqua regia are evaporated, chlorides are left. ~bromine~, br. (sp. gr. . ). practically pure bromine.--it is a heavy reddish-brown liquid and very volatile. it boils at ° c., and, consequently, must be kept in a cool place. it gives off brown irritating vapours, which render its use very objectionable. generally it answers the same purpose as aqua regia, and is employed where the addition of nitric acid to a solution has to be specially avoided. it is also used for dissolving metals only from ores which contain metallic oxides not desired in the solution. ~"bromine water"~ is simply bromine shaken up with water till no more is dissolved. ~carbonic acid~, co_{ }.--a heavy gas, somewhat soluble in water; it is mainly used for providing an atmosphere in which substances may be dissolved, titrated, &c., without fear of oxidation. it is also used in titrating arsenic assays with "iodine" when a feeble acid is required to prevent the absorption of iodine by the alkaline carbonate. it is prepared when wanted in solution, by adding a gram or so of bicarbonate of soda and then as much acid as will decompose the bicarbonate mentioned. when a quantity of the gas is wanted, it is prepared, in an apparatus like that used for sulphuretted hydrogen, by acting on fragments of marble or limestone with dilute hydrochloric acid. ~citric acid~ (h_{ }[=c=i] or c_{ }h_{ }o_{ }.h_{ }o) is an organic acid which occurs in colourless crystals, soluble in less than their weight of water. the solution must be freshly prepared, as it gets mouldy when kept. it forms a comparatively unimportant class of salts (citrates). it is used in the determination of phosphoric acid, chiefly for the purpose of preventing the precipitation of phosphates of iron and alumina by ammonia, and in a few similar cases. the commercial crystals are used; they should be free from sulphuric acid and leave no ash on ignition. ~hydrochloric acid~, hcl in water, (sp. gr. . . it contains per cent. of hydrogen chloride).--it is sometimes called "muriatic acid," and when impure, "spirit of salt." the acid solution should be colourless and free from arsenic, iron, and sulphuric acid. it forms an important family of salts, the chlorides. it is the best acid for dissolving metallic oxides and carbonates, and is always used by the assayer when oxidising agents are to be avoided. the acid is used without dilution when no directions are expressly given to dilute it. it has no action on the following metals: gold, platinum, arsenic, and mercury; it very slightly attacks antimony, bismuth, lead, silver, and copper. tin is more soluble in it, but with difficulty; whilst iron, zinc, nickel, cobalt, cadmium, and aluminium easily dissolve with evolution of hydrogen and the formation of the lower chloride if the metal forms more than one class of salts. all the metallic oxides, except a few of the native and rarer oxides, are dissolved by it with the formation of chlorides of the metal and water. ~dilute hydrochloric acid~ is made by diluting the strong acid with an equal volume of water. this is used for dissolving precipitates obtained in the general course of analysis and the more easily soluble metals. ~hydrofluoric acid, hf.~--a solution in water may be purchased in gutta-percha or lead bottles. it is of variable strength and doubtful purity. it must always be examined quantitatively for the residue left on evaporation. it is used occasionally for the examination of silicates. it attacks silica, forming fluoride of silicon, which is a gas. when the introduction of another base will not interfere with the assay, the substance may be mixed in the platinum dish with fluoride of ammonium, or of potassium, or of calcium, and hydrochloric acid, instead of treating it with the commercial acid. it is only required in special work. the fumes and acid are dangerous, and, of course, glass or porcelain vessels cannot be used with it. ~iodine, i.~--this can be obtained in commerce quite pure, and is often used for standardising. it is very slightly soluble in water, but readily dissolves in potassium iodide solution. it closely resembles chlorine and bromine in its properties, and can be used for dissolving metals without, at the same time, attacking any oxide which may be present. it is chiefly used as an oxidizing agent in volumetric work, being sharp in its reactions and easily detected in minute quantities. it cannot be used in alkaline solutions, since it reacts with the hydrates, and even with the carbonates, to form iodides and iodates. iodine is soluble in alcohol. ~nitric acid, hno_{ }.~ (sp. gr. . ; boiling point ° c.; contains per cent. by weight of hydrogen nitrate).--it is convenient to remember that one c.c. of this contains gram of real acid. it combines the properties of an acid and of an oxidising agent. one c.c. contains . gram of oxygen, most of which is very loosely held, and easily given up to metals and other oxidisable substances. consequently it will dissolve many metals, &c., upon which hydrochloric acid has no action. all sulphides (that of mercury excepted) are attacked by it, and for the most part rendered soluble. it has no action on gold or platinum, and very little on aluminium. the strong acid at the ordinary temperature does not act on iron or tin; and in most cases it acts better when diluted. some nitrates being insoluble in nitric acid, form a protecting coat to the metal which hinders further action. where the strong acid does act the action is very violent, so that generally it is better to use the dilute acid. when iron has been immersed in strong nitric acid it not only remains unacted on, but assumes a _passive_ state; so that if, after being wiped, it is then placed in the dilute acid, it will not dissolve. tin and antimony are converted into insoluble oxides, while the other metals (with the exception of those already mentioned) dissolve as nitrates. during the solution of the metal red fumes are given off, which mainly consist of nitrogen peroxide. the solution is often coloured brown or green because of dissolved oxides of nitrogen, which must be got rid of by boiling. generally some ammonium nitrate is formed, especially in the cases of zinc, iron, and tin, when these are acted on by cold dilute acid. sulphur, phosphorus, and arsenic are converted into sulphuric, phosphoric, and arsenic acids respectively, when boiled with the strong acid. ~dilute nitric acid.~--dilute volume of the strong acid with of water. ~oxalic acid~, h_{ }[=o] or (h_{ }c_{ }o_{ }. h_{ }o.)--this is an organic acid in colourless crystals. it forms a family of salts--the oxalates. it is used in standardising; being a crystallised and permanent acid, it can be readily weighed. it is also used in separations, many of the oxalates being insoluble. for general use make a per cent. solution. use the commercially pure acid. on ignition the acid should leave no residue. [illustration: fig. .] ~sulphuretted hydrogen.~ hydrosulphuric acid, sh_{ }.--a gas largely used in assaying, since by its action it allows of the metals being conveniently classed into groups. it is soluble in water, this liquid dissolving at the ordinary temperature about three times its volume of the gas. the solution is only useful for testing. in separations, a current of the gas must always be used. it is best prepared in an apparatus like that shown in fig. , by acting on ferrous sulphide with dilute hydrochloric acid. when iron has to be subsequently determined in the assay solution, the gas should be washed by bubbling it through water in the smaller bottle; but for most purposes washing can be dispensed with. the gas is very objectionable, and operations with it must be carried out in a cupboard with a good draught. when the precipitation has been completed, the apparatus should always be washed out. the effect of this acid on solutions of the metals is to form sulphides. all the metallic sulphides are insoluble in water; but some are soluble in alkaline, and some in acid, solutions. if sulphuretted hydrogen is passed through an acid solution containing the metals till no further precipitation takes place, a precipitate will be formed containing sulphides insoluble in the acid. on filtering, adding ammonia (to render the filtrate alkaline), and again passing the gas, a further precipitate will be obtained, consisting of sulphides insoluble in an alkaline solution, but not precipitable in an acid one; the filtrate may also contain sulphides not precipitable in an acid solution, which are soluble in an alkaline one; these will be thrown down on neutralising. again, the metals precipitated in the acid solution form sulphides which may be divided into groups, the one consisting of those which are soluble, and the other of those which are not soluble, in alkalies. this classification is shown in the following summary:-- . _precipitable in an acid solution._ (a) soluble in alkalies.--sulphides of as, sb, sn, au, pt, ir, mo, te, and se. (b) insoluble in alkalies.--sulphides of ag, pb, hg, bi, cu, cd, pd, rh, os, and ru. . _not precipitated in an acid solution, but thrown down in an alkaline one._ sulphides of mn, zn, fe, ni, co, in, tl, and ga. these can again be divided into those which are dissolved by dilute acids and those which are not. . _not precipitated in an acid or alkaline solution, but thrown down on neutralising the latter._ sulphides of v and w. sulphuretted hydrogen is a strong reducing agent. ferric salts are thereby quickly reduced to ferrous; in hot solutions nitric acid is decomposed. these changes are marked by a precipitation of sulphur, and the student must be careful to pass the gas sufficiently long, and not be too hasty in concluding that no sulphide will form because it does not at once make its appearance. the best indication that it has been passed long enough is the smell of the gas in the solution after shaking. ~sulphurous acid~, h_{ }so_{ }.--the reagent used may be regarded as a saturated solution of sulphur dioxide in water. it may be purchased, and keeps for a long time. it may be made by heating copper with sulphuric acid and passing the gas formed into water. the heat should be withdrawn when the gas is coming off freely. it is used as a reducing agent, and should not be diluted. ~sulphuric acid~, h_{ }so_{ }. (sp. gr. . , containing per cent. of real acid, h_{ }so_{ }.)--this acid forms insoluble sulphates with salts of lead, strontium, and barium. it has a high boiling point, ° c., and, when evaporated with salts of the more volatile acids, converts them into sulphates. when nitrates or chlorides are objectionable in a solution, evaporation with sulphuric acid removes them. in working with this acid caution is necessary, since, on mixing with water, great heat is evolved; and, if either the acid or water has been previously heated, a serious accident may result. in diluting the acid it should be poured into cold water. glass vessels containing boiling sulphuric acid should be handled as little as possible, and should not be cooled under the tap. the action of diluted sulphuric acid on metals closely resembles that of dilute hydrochloric acid. magnesium, aluminium, iron, zinc, nickel, cobalt, manganese, and cadmium dissolve, with evolution of hydrogen, in the cold acid, or when warmed. the action of hot and strong sulphuric acid is altogether different; it acts as an oxidising agent, and is itself reduced to sulphur dioxide or even to sulphur. the following metals are attacked in this way:--copper, bismuth, mercury, silver, antimony, tin, and lead. gold, platinum, and arsenic are not affected. this property is made use of in parting silver from gold and platinum. metallic sulphides are similarly attacked; but this method of opening up minerals has the disadvantage of giving rise to the formation of anhydrous sulphates of iron, &c., which are not readily dissolved when afterwards diluted. the use of sulphuric acid in assaying is (for these reasons) to be avoided. its chief use is as a drying agent, since it has a strong affinity for water. air under a bell jar may be kept dry by means of a basin of sulphuric acid, and gases bubbled through it are freed from water-vapour. ~dilute sulphuric acid.~--this is made by diluting volume of the strong acid with of water. ~tartaric acid~, h_{ }[=t] or c_{ }h_{ }o_{ }.--a crystallised organic acid, soluble in less than its own weight of water, or in less than three parts of alcohol. it is used for the same purposes as citric acid is. the solution is made when required. bases, salts, &c. ~alcohol~, c_{ }h_{ }o. (commercial alcohol of sp. gr. . ; it contains per cent. by weight of alcohol.)--it should burn with a non-luminous flame and leave no residue. it is used for washing precipitates where water is inapplicable, and for facilitating drying. ~ammonia~, nh_{ }. (commercial ammonia, a solution having a sp. gr. of . to . , and containing about per cent. of ammonia.)--it is used as an alkali (more commonly than soda or potash), since an excess of it is easily removed by boiling. the salts of ammonium formed by it may be removed by igniting, or by evaporating in a porcelain dish with an excess of nitric acid. it differs in a marked way from soda or potash in its solvent action on the oxides or hydrates of the metals. salts of the following metals are soluble in an ammoniacal solution in the presence of ammonic chloride:--copper, cadmium, silver, nickel, cobalt, manganese, zinc, magnesium, sodium, potassium, and the alkaline earths. ~dilute ammonia~ is made by diluting vol. of commercial ammonia with of water. the dilute ammonia is always used; but in assays for copper a stronger solution ( of strong ammonia to of water) is required. ~ammonic carbonate~ (am_{ }co_{ }) is prepared by dissolving one part of the commercial sesquicarbonate of ammonia in four parts of water, and adding one part of strong ammonia. ~ammonic bicarbonate~ (hamco_{ }) is prepared by saturating a solution of the sesquicarbonate of ammonia with carbon dioxide. ~ammonic chloride~, amcl.--use the commercial salt in a per cent. solution in water. the salt should leave no residue on ignition. ~ammonic molybdate.~--the solution is prepared as follows:--dissolve grams of the powdered commercial salt in c.c. of dilute ammonia, and pour the solution in a slow stream into c.c. of dilute nitric acid; make up to litre, and allow the mixture to settle before using. it is used for the purpose of separating phosphoric oxide from bases and from other acids, and also as a test for phosphates and arsenates. in using this solution the substance must be dissolved in nitric acid, and a considerable excess of the reagent added ( c.c. is sufficient to precipitate . gram p_{ }o_{ }); when the phosphate is in excess no precipitate will be got. the precipitate is phospho-molybdate of ammonia. ~ammonic nitrate~ (amno_{ }) is used in the separation of phosphoric oxide by the molybdate method, and occasionally for destroying organic matter. it is soluble in less than its own weight of water. the solution is made when wanted. ~ammonic oxalate~ (am_{ }c_{ }o_{ }. h_{ }o) is used chiefly for the separation of lime. the solution is made by dissolving grams of the salt in c.c. of water. ~ammonic sulphide~ may be purchased in the state of a strong solution. it is yellow, and contains the disulphide, s_{ }am_{ }. it serves the same purpose as is obtained by passing a current of sulphuretted hydrogen through an ammoniacal solution; but has the disadvantage of loading the solution with sulphur, which is precipitated when the solution is subsequently acidified. it is useful for dissolving the lower sulphide of tin (sns). ~baric carbonate~ (baco_{ }) is sometimes used for precipitating the weaker bases. it should be prepared when wanted by precipitating a solution of baric chloride with ammonic carbonate and washing. the moist precipitate is used without drying. ~baric chloride~, bacl_{ }. h_{ }o.--a crystallised salt, soluble in - / parts of water. it is used for the detection and separation of sulphates. make a per cent. solution. "~black flux.~"--a mixture of finely divided carbon with carbonate of potash or with carbonates of potash and soda. it is prepared by heating tartar or "rochelle salt" until no more combustible gas is given off. one gram will reduce about grams of lead from litharge. ~borax~, na_{ }b_{ }o_{ }. h_{ }o.--it is chiefly used as a flux in dry assaying, as already described. it is also used in testing before the blowpipe; many metallic oxides impart a characteristic colour to a bead of borax in which they have been fused. ~calcium chloride.~--the crystallised salt is cacl_{ }. h_{ }o; dried at ° c. it becomes cacl_{ }. h_{ }o, and when fused it becomes dehydrated. the fused salt, broken into small lumps, is used for drying gases. it combines with water, giving off much heat; and dissolves in a little more than its own weight of water. strong solutions may be used in baths in which temperatures above the boiling-point of water are required. one part of the salt and of water give a solution boiling at °, and a solution of parts of the salt in of water boils at °. the salt is very little used as a reagent. ~calcium fluoride~ or "~fluor spar~," caf_{ }.--the mineral is used as a flux in dry assaying; it renders slags which are thick from the presence of phosphates, &c., very fluid. mixed with hydrochloric acid it may sometimes be used instead of hydrofluoric acid. ~calcium carbonate~, caco_{ }.--it is precipitated in a pure state by ammonic carbonate from a solution of calcium chloride. it is used for standardising. in the impure state, as marble or limestone, it is used in the preparation of carbonic acid. ~calcium hydrate~ or ~"lime water."~--this is used in testing for carbon dioxide and in estimating the amount of that gas present in air. it may be made by slaking quicklime and digesting the slaked lime with water. one hundred c.c. of water at ° c. dissolves . grams of the hydrate (cah_{ }o_{ }), and hot water dissolves still less. "_milk of lime_" is slaked lime suspended in water. ~cobalt nitrate~ (co(no_{ })_{ }. h_{ }o) is used in a per cent. solution for the detection of oxides of zinc, aluminium, &c.; on ignition with which it forms characteristically coloured compounds. ~copper~, cu.--pure copper, as obtained by electrolysis, can be purchased. this only should be used. ~copper oxide~, cuo.--it occurs as a black, heavy, and gritty power, and is used for the oxidation of carbon and hydrogen in organic substances. it should be ignited and cooled out of contact with air just before using, since it is hygroscopic. oxide of copper which has been used may be again utilised after calcination. ~copper sulphate~ (cuso_{ }. h_{ }o) contains . per cent. of copper. it is used in the outer cell of a daniell-battery. the commercial salt is used for this purpose. the re-crystallised and pure salt is used for preparing the anhydrous sulphate, which is used for detecting moisture in gases. for this purpose it is dried at ° c. till no trace of green or blue colour remains. it must be prepared when wanted. it may be conveniently used in the form of pumice-stone, saturated with a solution of the salt and dried. traces of moisture develop a green colour. ~ferric chloride~, fe_{ }cl_{ }. (when crystallised, fe_{ }cl_{ }. h_{ }o.)--the solution is prepared as described under iron. the commercial salt contains arsenic, and, since the chief use of ferric chloride is for the determination of this substance, it must be purified (_see_ under arsenic). ~ferric sulphate~ (fe_{ }(so_{ })_{ }) is a yellowish white deliquescent salt. it is used as an indicator in volumetric silver assaying, and for the separation of iodine from bromine. it may be purchased as iron alum, am_{ }fe_{ }(so_{ })_{ }. h_{ }o. but it is best prepared by adding strong sulphuric acid to ferric hydrate in equivalent proportions. use it as a solution containing or per cent. of iron. ~ferrous sulphate~, feso_{ }. h_{ }o.--the granulated form is best, and can be purchased pure. it is used for standardising. it keeps better in crystals than in solution. it is readily soluble in water, but the solution is best made with the help of a little free acid. as a re-agent use a per cent. solution. the crystals should be clear bluish-green; if their colour is dark green, brown, or blue, they should be rejected. ~ferrous sulphide~ (fes) is used for the preparation of sulphuretted hydrogen. it may be purchased and broken in small lumps, nut-size, for use. "~fusion mixture~" (k_{ }co_{ }.na_{ }co_{ }) is a mixture of potassic and sodic carbonates in the proportions of of the former to of the latter, by weight. it is hygroscopic. a mixture of the bicarbonates is better, being purer and less apt to get damp. ~gallic acid~ (c_{ }h_{ }o_{ }.h_{ }o) is an organic acid, occurring as a pale fawn-coloured crystalline powder, soluble in parts of cold water, or in parts of boiling water. it is used for the determination of antimony. a per cent. solution in warm water is made when required. ~hydrogen~ (h) is a gas. it is obtained by acting on zinc with dilute hydrochloric or sulphuric acid. it is used as a reducing agent, and for providing an atmosphere free from oxygen. it reduces metallic oxides at a high temperature. it must be freed from water; and special precautions should be taken to prevent an admixture with air. it is generally required in a current which can be continued for an hour or more without interruption. the preparation can be conveniently carried out in the apparatus shown (fig. ). a quart bottle is half filled with sheet zinc, and connected with bulbs filled with sulphuric acid, and with a calcium chloride tube. the last is connected with the apparatus through which the gas has to be passed. dilute hydrochloric acid mixed with a few cubic centimetres ( c.c. to pint) of stannous chloride sol. to fix any dissolved oxygen, is placed in the funnel, and let into the bottle by opening the stopcock when required. care must be taken to let the hydrogen escape for some time before starting the reduction. [illustration: fig. .] ~gold~, au.--gold, obtained by cupelling and "parting," is for most purposes sufficiently pure. it is best kept in the shape of foil. when the purer metal is required, gold should be dissolved in aqua regia, the solution evaporated to a paste, diluted, allowed to stand, and filtered. the filtered solution is acidified with hydrochloric acid, warmed, and precipitated with sodium sulphite. the precipitate is collected, washed, and fused on charcoal. ~iron~, fe.--the soft wire (thin) is used for standardising. rods are used in dry assays as a desulphurising agent. steel must not be used, since it is not pure, and contains a variable amount of iron. ~lead~, pb.--granulated lead or lead-foil is used in the dry assay for silver and gold, and in the preparation of lead salts. it can be obtained very pure, but always contains more or less silver, or milligrams in grams. the amount of silver it contains must be determined and recorded. ~lead acetate~ (pb[=a=c]_{ }. h_{ }o, or pb(c_{ }h_{ }o_{ })_{ }. h_{ }o) is used as a test, specially for the detection and estimation of sulphuretted hydrogen. prepare a per cent. solution for use. ~lead nitrate~ (pb(no_{ })_{ }) can be purchased pure. it is used for standardising. ~lead dioxide~ (pbo_{ }) occurs as a dark-brown powder. it is used as an oxidizing agent and for absorbing sulphurous oxide. it can be prepared by digesting red lead with warm dilute nitric acid; washing and drying the residue. "~litharge~," pbo.--it can be purchased as a yellow heavy powder. it is used in dry assaying as a flux, as a desulphurising agent, and also as a source of lead. it always contains some silver, the amount of which must be determined. ~litmus.~--this is an organic colouring matter which is turned red by acids and blue by alkalies. for ordinary purposes it is best used as litmus paper, which may be purchased in small books. a solution is prepared by digesting or grams of the commercial litmus in c.c. of water on the water bath. after being allowed to settle, it is filtered and made just faintly red with acetic acid. then there is added a drop or two of a solution of soda and c.c. of alcohol. it should be kept in a loosely-covered bottle. ~magnesia~, mgo.--it may be purchased as "calcined magnesia." it is used for making "magnesia mixture," and should be kept in a corked wide-mouthed bottle. "~magnesia mixture.~"--dissolve grams of magnesia in about a quarter of a litre of dilute hydrochloric acid, avoiding excess. add grams of magnesia, boil, and filter. add grams of ammonic chloride, and c.c. of strong ammonia; and dilute with water to litres. it should be kept in a stoppered winchester. ~magnesium sulphate~, mgso_{ }. h_{ }o.--it can be purchased very pure, and is occasionally used as a standard salt. ~manganese dioxide~, mno_{ }.--it is used in the preparation of chlorine. the commercial article is not pure, but is sufficiently so for this purpose. ~marble~, caco_{ }.--fragments of the white crystalline variety only should be used. it is used as a source of lime and of carbon dioxide. ~mercury~, hg.--this can be purchased pure. it should have a bright surface, flow without a tail, and leave no residue on ignition. it is used as a standard; for amalgamation; and as a confining liquid in gas analysis. ~mercuric chloride~ (hgcl_{ }) may be purchased pure. make a per cent. solution in water. it is used for destroying an excess of stannous chloride; for removing sulphuretted hydrogen from solution; and as a test for stannous salts. ~microcosmic salt~, hamnapo_{ }. h_{ }o.--when fused napo_{ } is formed. it is used in testing for metallic oxides and silica before the blowpipe. the crystals are sometimes used as a standard for phosphoric acid. "~nessler's solution.~"--mode of preparation: dissolve grams of potassium iodide in c.c. of water; dissolve grams of mercuric chloride in c.c. of water, and pour this solution into that of the iodide till a permanent precipitate is produced; make up to litre with a per cent. solution of potash; add mercuric chloride till a precipitate is again formed; allow to settle and decant. it is used for detecting ammonia. ~nitre.~--this is potassium nitrate. ~platinum chloride~, hcl.ptcl_{ }. (in the crystallised form it has h_{ }o).--it may be made as follows:--take grams of clean platinum scrap and dissolve in a flask at a gentle heat in c.c. of hydrochloric acid with the occasional addition of some nitric acid; evaporate to a paste; and then dissolve in c.c. of water. it is used for separating and determining potassium. ~phenolphthalein~ is an organic compound used as an indicator; more especially in determining the weaker acids, it cannot be used in the presence of ammonia. dissolve half a gram in c.c. of dilute alcohol. ~potassium bicarbonate~, khco_{ }.--it may be purchased pure; on ignition it leaves the carbonate, k_{ }co_{ }, which may be used as a standard. ~potassium cyanide~, kcn.--it is used in the dry assay as a reducing agent. the commercial salt is very impure. purchase that sold as potassic cyanide (gold) which contains about per cent. of kcn. it is used for copper assaying and occasionally in separation. make a per cent. solution when wanted. ~potassium bichromate~, k_{ }cr_{ }o_{ }. it may be purchased nearly pure. it is used as an oxidising agent, for determining iron; and as a test solution. for this last purpose a per cent. solution is prepared. ~potassium chlorate~ (kclo_{ }) can be purchased pure. it is used with hydrochloric acid as a substitute for aqua regia. ~potassium ferrocyanide~ (k_{ }fe(cn)_{ }. h_{ }o), or "yellow prussiate of potash," is used as a test; as an indicator; and for the determination of zinc. make a per cent. solution. ~potassium ferricyanide~ (k_{ }fe_{ }(cn)_{ }), or "red prussiate of potash," is used for testing; and as an indicator. make a per cent. solution when wanted, as it decomposes on keeping. ~potassium hydrate~, kho. purchase that purified with alcohol. it is an alkali, and is used for absorbing carbonic acid, &c. ~potassium iodide~, ki. it may be purchased nearly pure. it is used as a test and for dissolving iodine. it should be used in a per cent. solution freshly made. the solution decomposes on exposure to light, with separation of iodine. ~potassium nitrate~ (kno_{ }) can be purchased pure. it is used in the dry way as an oxidizing agent. it is very fusible. it decomposes at a low temperature into potassium nitrite (kno_{ }) and free oxygen; and at a higher temperature leaves potash (k_{ }o). it oxidizes sulphur and carbon with explosive violence. this action may be moderated by mixing the nitre with carbonate of soda, common salt, or some other inert body. ~potassium nitrite~, kno_{ }.--the commercial article is not pure, but is sufficiently so for the purpose required. a saturated solution is used in the separation of cobalt; the solution is made when wanted. ~potassium permanganate~, kmno_{ }.--this salt can be purchased sufficiently pure. it is much used as an oxidizing agent. ~potassium bisulphate~ (khso_{ }) is used as a dry reagent for opening up minerals. it fuses; and at a much higher temperature is converted into potassium sulphate with loss of sulphuric acid. ~potassium sulphocyanate~ (kcns) is used for the detection and determination of traces of ferric iron; as also in the separation of silver and copper from some of the other metals. make a per cent. solution. it should show no colour on the addition of hydrochloric acid. "~red lead~" (pb_{ }o_{ }) is used in the dry assay as a flux instead of litharge, from which it differs in containing a little more oxygen. when acted on by nitric acid a brown residue of lead dioxide is left, nitrate of lead going into solution. like litharge it always carries silver; about milligrams in grams. ~silver~, ag.--pure silver in foil is required as a standard. it may be prepared as follows:--dissolve scrap silver in dilute nitric acid and decant off from any residue; dilute the solution with hot water and add hydrochloric acid until there is no further precipitate, stir; allow the precipitate to settle; decant and wash; dry the precipitate, mix it with twice its bulk of carbonate of soda and fuse the mixture in a crucible until tranquil; clean the button and roll or hammer it into foil. ~sodium acetate~, nac_{ }h_{ }o_{ }. h_{ }o.--the crystals may be purchased sufficiently pure. make a per cent. solution in water. it is used for replacing mineral acids by acetic acid.[ ] ~sodium acetate and acetic acid.~--a solution is used in the determination of phosphates and arsenates; grams of the salt is dissolved in c.c. of acetic acid, and diluted with water to one litre. ~sodium bicarbonate~ (nahco_{ })is used as a flux in dry methods. on ignition it leaves the carbonate (na_{ }co_{ }), which is used as a standard reagent. make a per cent. solution of the carbonate for use. it should be free from chlorides or sulphates, or if impure the amount of impurities must be determined. ~sodium hydrate~, naho. it may be purchased in sticks, which should be kept in a well-corked bottle. it is sometimes called "caustic soda." it is a strong alkali. it is used for neutralizing acid solutions and for separations where ammonia is unsuitable. make a per cent. solution for use. ~sodium hyposulphite~, na_{ }s_{ }o_{ }. h_{ }o.--it may be purchased pure. it is generally known as "hypo." it is used as a standard. ~sodium sulphite~ (na_{ }so_{ }. h_{ }o) is used as a reducing agent. ~sodium phosphate~, na_{ }hpo_{ }. h_{ }o. the crystals may be purchased pure, but they effloresce in dry air with loss of water. it is used as a standard and for precipitating magnesia, &c. make a per cent. solution. ~stannous chloride~, sncl_{ }. h_{ }o.--the crystals are best purchased. if kept dry and free from air they are fairly permanent. a solution is made by dissolving grams in c.c. of hydrochloric acid and diluting to litre. the solution is not permanent. it is a strong reducing agent, and is chiefly used in solution for this purpose. ~tin~, sn.--grain tin should be purchased. it is not pure, but contains . per cent. of the metal. the chief impurity is copper. it can be used as a standard. when acted on with hot hydrochloric acid it slowly dissolves (more rapidly in contact with platinum) and forms stannous chloride. ~uranium acetate~, uo_{ }(c_{ }h_{ }o_{ })_{ }.h_{ }o.--it is best purchased in crystals. the solution is used for the determination of phosphates and arsenates. a solution of per cent. strength is occasionally used as an indicator. ~uranium nitrate~, uo_{ }(no_{ })_{ }. h_{ }o.--this salt is very soluble in water and is sometimes used instead of the acetate, which is somewhat difficult to dissolve. "~water~," h_{ }o.--spring or well water is sufficiently pure for most purposes, c.c. will leave a residue of from to milligrams, so that where a salt has to be dissolved out, evaporated, and weighed it should be replaced by distilled water. rain water, melted snow, &c., always leave less residue than spring water; but in other respects they are often dirtier. distilled water is best prepared in the office, a glass or tin condenser being used. ~zinc~, zn.--it is sold in a granulated form or in sticks. it generally contains over per cent. of lead, with a little iron and arsenic. it is used for separating metals from their solutions, and generally as a reducing agent. for the preparation of hydrogen, and in most other cases, scrap sheet zinc may be used. ~zinc oxide~, zno.--the commercial oxide sometimes contains carbonate. ~zinc sulphate~, znso_{ }. h_{ }o.--it is occasionally used as a standard, and can be purchased nearly pure. footnotes: [ ] hcl + hno_{ } = cl_{ } + nocl + h_{ }o. [ ] nac_{ }h_{ }o_{ } + hcl = h_{ }c_{ }o_{ } + nacl. chapter vii. formulÆ, equations, etc. formulæ and equations are a kind of short hand for expressing briefly and in the language of the atomic theory the facts of chemical composition and reaction. the convenience of this method of expressing the facts justifies a short description of it here. on comparing the percentage composition of a series of compounds the proportions in which the elements combine appears to be regulated by no simple law. for example: realgar. orpiment. mispickel. pyrites. arsenic . . . -- sulphur . . . . iron -- -- . . ------ ------ ------ ------ . . . . but if in these examples the composition is calculated, not on parts, but on , , , and parts respectively, evidence of a simple law becomes apparent. realgar. orpiment. mispickel. pyrites. arsenic . . . -- sulphur . . . . iron -- -- . . ------ ------ ------ ------ . . . . it will be seen that the proportion of arsenic is or twice , that of iron is , and that of sulphur or some simple multiple of . the series of examples might be extended indefinitely, and it would still be found that the "combining proportions" held good. the number is spoken of as the "combining weight," or, more frequently, as the "atomic weight" of arsenic. similarly is the atomic weight of iron, and the atomic weight of sulphur. the importance of this law of chemical combination is altogether independent of the atomic theory; but this theory furnishes the simplest explanation of the facts. according to it a chemical compound is made up of exactly similar groups of particles. the particles of each elementary substance are all alike, but differ from those of other elements in weight. ultimate particles are called _atoms_, and the groups of atoms are called _molecules_. the atomic weight of any particular element is the weight of its atom compared with the weight of an atom of hydrogen. the atom of sulphur, for instance, is times as heavy as the atom of hydrogen, and the atomic weight of sulphur is . the _molecular weight_ is the sum of the atomic weights of the group. the molecule of pyrites contains two atoms of sulphur and one of iron: on referring to the table of atomic weights it will be seen that the atomic weights are--sulphur , and iron . the molecular weight, therefore, is + + --that is, . the meaning of this is, parts by weight of iron pyrites contain parts of sulphur and parts of iron; and this is true whether the "parts by weight" be grains or tons. _the symbol or formula of an atom_ is generally the initial letter or letters of the latin or english name of the substance. the atom of hydrogen is written h, that of oxygen o, of sulphur s, of iron (ferrum) fe, and so on. a list of these symbols is given in the table of atomic weights. _the formula of a molecule_ is obtained by placing together the symbols of the contained atoms. thus, fe represents an atom of iron, s an atom of sulphur, while fes represents the molecule of sulphide of iron as containing one atom of each element. when more than one atom of an element is present this is shown by writing a figure under and after the symbol; thus, fes_{ } represents a molecule with one atom of iron and two atoms of sulphur, fe_{ }s_{ } similarly shows one with two atoms of iron and three of sulphur. when a group of atoms is enclosed in brackets, a figure after and under the bracket multiplies all within it; for example, pb(no_{ })_{ } is another way of writing pbn_{ }o_{ }. sometimes it is convenient to represent the atoms of a molecule as divided into two or more groups; this may be done by writing the formulæ of the groups, and separating each simple formula by a full stop. slaked lime, for instance, has the formula cah_{ }o_{ }; or, as already explained, we may write it ca(ho)_{ }; or, if for purposes of explanation we wished to look on it as lime (cao) and water (h_{ }o), we could write it cao.h_{ }o. a plus sign (+) has a different meaning; cao + h_{ }o indicates quantities of two substances, water and lime, which are separate from each other. the sign of equality (=) is generally used to separate a statement of the reagents used from another statement of the products of the reaction; it may be translated into the word "yields" or "becomes." the two statements form an equation. ignoring the quantitative relation, the meaning of the equation cao + h_{ }o = cao.h_{ }o is: "lime and water yield slaked lime." by referring to a table of atomic weights we can elicit the quantitative relations thus:-- cao + h_{ }o = cah_{ }o_{ } | | | v v v ca = h_{ } = = × ca = o = o = h_{ } = = × -- -- o_{ } = = × -- or, putting it in words, parts of lime combine with parts of water to form parts of slaked lime. this equation enables one to answer such a question as this:--how much lime must be used to produce cwt. of slaked lime? for, if lbs. of slaked lime require lbs. of lime, lbs. will require ( × )/ , or about - / lbs. as another example having a closer bearing on assaying take the following question:--"in order to assay grams of 'black tin' (sno_{ }) by the cyanide process, how much potassic cyanide (kcn) will be required?" the reaction is sno_{ } + kcn = sn + kcno | | v v sn = k = o_{ } = c = --- n = -- × = what is sought for here is the relation between the quantities of sno_{ } and kcn. note that a figure before a formula multiplies all that follows up to the next stop or plus or equality sign. the question is now resolved to this: if grams of oxide of tin require grams of cyanide, how much will grams require? : :: : _x_ _x_ = . grams. a problem of frequent occurrence is to find the percentage composition of a substance when its formula has been given. for example: "what percentage of iron is contained in a mineral having the formula fe_{ }o_{ }. h_{ }o?" bringing this formula together we have fe_{ }h_{ }o_{ }. find the molecular weight. fe_{ } = = × h_{ } = = × o_{ } = = × --- then we get: parts of the mineral contain of iron. how much will contain? : :: : _x_ _x_ = . . and the answer to the question is . per cent. again, suppose the question is of this kind:--"how much crystallised copper sulphate (cuso_{ }. h_{ }o) will be required to make litres of a solution, c.c. of which shall contain . gram of copper?" a litre is c.c., so, therefore, litres of the solution must contain . gram × , or grams. how much crystallised copper sulphate will contain this amount of metal? cu = . s = . o_{ } = . = × h_{ }o = . = × ----- . if . grams of copper are contained in . grams of sulphate, in how much is grams contained. . : . :: grams : _x_ _x_ = . grams. the answer is, . grams must be taken. as a sample of another class of problem similar in nature to the last (but a little more complicated) take the following:--"what weight of permanganate of potash must be taken to make litres of a solution, c.c. of which shall be equivalent to gram of iron?" in the first place the litres must be equivalent to grams of iron, for there are × c.c. in two litres. in the titration of iron by permanganate solution there are two reactions. first in dissolving the iron fe + h_{ }so_{ } = feso_{ } + h_{ } | v and second, in the actual titration, feso_{ } + kmno_{ } + h_{ }so_{ }= mnso_{ } | + fe_{ }(so_{ })_{ } + khso_{ } + h_{ }o v k = mn = o_{ }= --- × = as before, attention is confined to the two substances under consideration--viz., fe and kmno_{ }. in the second equation, we find parts of the permanganate are required for molecules of feso_{ }; and in the first equation parts of iron are equivalent to one molecule of feso_{ }, therefore of iron are equivalent to of permanganate; and the question is, how much of the permanganate will be equivalent to grams of iron? : :: grams : _x_. _x_= . grams. the answer is . grams. very similar to this last problem is the question suggested under the head "indirect titration" (p. ). "if c.c. of the standard permanganate solution are equivalent to gram of iron, how much peroxide of manganese will they be equivalent to?" the equation for dissolving the iron is already given; the second equation is feso_{ } + mno_{ } + h_{ }so_{ } | = fe_{ }(so_{ })_{ } + mnso_{ } + h_{ }o | v mn = o_{ } = -- it will be seen that grams of peroxide of manganese are equivalent to grams of iron. how much then is equivalent to gram of iron? : :: gram : _x_ _x_ = . gram. it is sometimes convenient to calculate the formula of a substance from its analysis. the method of calculating is shown by the following example. required the formula of a mineral which gave the following figures on analysis:-- cupric oxide (cuo) . ferrous oxide (feo) . zinc oxide (zno) . sulphuric oxide (so_{ }) . water (h_{ }o) . ------ . first find the molecular weights of cuo, feo, &c., and divide the corresponding percentages by these figures. thus, cuo = . + = . and . divided by . gives . . similarly feo = + = and . divided by gives . . treated in the same way the oxide of zinc, sulphuric oxide and water give as results . , . and . . classify the results as follows:-- bases. acids. water. cuo . so_{ } . h_{ }o . feo . zno . ---------- ------------- ------------ ro . ro_{ } . r_{ }o . the figures . , . and . should be then divided by the lowest of them--_i.e._, . ; or where, as in this case, two of the figures are very near each other the mean of these may be taken--_i.e._, . . whichever is taken the figures got will be approximately , and . the formula is then ro.so_{ }. h_{ }o in which r is nearly / ths copper, / ths iron and a little zinc. this formula requires the following percentage composition, which for the sake of comparison is placed side by side with the actual results. calculated. found. cupric oxide . . ferrous oxide . . zinc oxide nil . sulphuric oxide . . water . . ----- ------ . . trimming the results of an analysis to make them fit in more closely with the calculations from the formula would be foolish as well as dishonest. there can be no doubt that the actual analytical results represent the composition of the specimen much more closely than the formula does; although perhaps other specimens of the same mineral would yield results which would group themselves better around the calculated results than around those of the first specimen analysed. it must be remembered that substances are rarely found pure either in nature or in the arts; so that in most cases the formula only gives an approximation to the truth. in the case of hydrated salts there is generally a difficulty in getting the salt with exactly the right proportion of water. practical exercises. the following calculations may be made:-- . calculate standards in the following cases-- (a) silver taken, . gram. standard salt used, . c.c. (b) iron taken, . gram. bichromate used, . c.c. . calculate percentages:-- (a) ore taken, gram. solution used, . c.c. standard, . gram. (b) ore taken, gram. barium sulphate got, . gram. barium sulphate contains . per cent. of sulphur, and the percentage of sulphur in the ore is wanted. (c) barium sulphate is baso_{ }. calculate the percentage of sulphur it contains, for use in the preceding question. . a method of estimating the quantity of peroxide in a manganese ore is based on the following reactions:-- ( ) mno_{ } + hcl = mncl_{ } + cl_{ } + h_{ }o. ( ) cl + ki = kcl + i. to how much mno_{ } is gram of iodine (i) equivalent? . a mineral has the following composition:-- carbonic acid (co_{ }) . copper oxide (cuo) . water (h_{ }o) . what is its formula? . how much copper is contained in . gram of crystallized copper sulphate (cuso_{ }. h_{ }o)? how much of these crystals must be taken to give . gram of copper? . how much ferrous sulphate crystals (feso_{ }. h_{ }o) must be taken to yield litres of a solution, c.c. of which shall contain . gram of iron? . galena is pbs, and hæmatite fe_{ }o_{ }. what percentages of metal do these minerals contain? chapter viii. specific gravity. the relation of the weight of a substance to its volume should be kept in mind in all cases where both weight and volume are dealt with. students are apt to imagine that on mixing equal volumes of, say, sulphuric acid and water, an acid of half the strength must be obtained. if the statement of strength is in parts by weight this will lead to considerable error. for example, c.c. of sulphuric acid containing per cent. by weight of real acid, will, if diluted with c.c. of water, yield a solution containing not per cent. by weight, but about . per cent. of the acid. the reason is this: the c.c. of sulphuric acid weighs grams, and contains . grams of real acid, while the c.c. of water weighs only grams; the mixed water and acid weighs grams, and contains . of real acid, which is equivalent to nearly . per cent. by weight. if, however, the method of statement be volumetric, it would be correct to say that doubling the volume halves the strength: if c.c. of brine contains grams of salt, and is diluted with water to c.c., it would be of one-half the former strength, that is, c.c. of the solution would contain grams of salt. this confusion is avoided by always stating the strengths as so many grams or "c.c." in c.c. of the liquid. but obviously it would be advantageous to be able to determine quickly the weight of any particular substance corresponding to c.c. or some other given volume. moreover, in descriptions of processes the strengths of acids and solutions are frequently defined neither by their gravimetric nor volumetric composition, but by a statement either of specific gravity or of the degrees registered by twaddell's or beaumé's hydrometer. thus, in the description of the process of gold parting, one writer gives: "the acid should be of . specific gravity"; and another says: "the acid must not be stronger than ° beaumé." these considerations justify an account of the subject in such a work as this. and on other grounds the determination of a specific gravity is one of the operations with which an assayer should be familiar. the meaning of "specific gravity" is present in the mind of every one who uses the sentence "lead is heavier than water." this is meaningless except some such phrase as "bulk for bulk" be added. make the sentence quantitative by saying: "bulk for bulk lead is . times heavier than water," and one has the exact meaning of: "the specific gravity of lead is . ." a table of the specific gravities of liquids and solids shows how many times heavier the substances are than water. it is better, however, to look upon the specific gravity (written shortly, sp. g.) as the weight of a substance divided by its volume. in the metric system, c.c. of water at ° c. weighs with sufficient exactness gram; consequently, the sp. g., which states how many times heavier than water the substance is, also expresses the weight in grams of one c.c. of it. so that if a c.c. flask of nitric acid weighs, after the weight of the flask has been deducted, grams, c.c. of the acid weighs . gram, and the sp. g. is . . the specific gravity, then, may be determined by dividing the weight of a substance in grams by its volume in c.c.; but it is more convenient in practice to determine it by dividing _the weight of the substance by the weight of an equal volume of water_. and since the volumes of all substances, water included, vary with the temperature, the temperature at which the sp. g. is determined should be recorded. even then there is room for ambiguity to the extent that such a statement as the following, "the specific gravity of the substance at ° c. is . ," may mean when compared with water at ° c. or ° c., or even . ° c. for practical purposes it should mean the first of these, for in the actual experiments the water and the substance are compared at the same temperature, and it is well to give the statement of results without any superfluous calculation. in the metric system the standard temperature is ° c., for it is at this point that c.c. of water weighs exactly gram. in england, the standard temperature is ° f. ( . ° c.), which is supposed to be an average temperature of the balance-room. the convenience of the english standard, however, is merely apparent; it demands warming sometimes and sometimes cooling. for most purposes it is more convenient to select a temperature sufficiently high to avoid the necessity of cooling at any time. warming to the required temperature gives very little trouble. ~determination of specific gravity.~--there is a quick and easy method of determining the density or sp. g. of a liquid, based upon the fact that a floating body is buoyed up more by a heavy liquid than by a light one. the method is more remarkable for speed than accuracy, but still is sufficiently exact. the piece of apparatus used for the purpose is endowed with a variety of names--sp. g. spindle, hydrometer, areometer, salimeter, alcoholimeter, lactometer, and so on, according to the special liquid upon which it is intended to be used. it consists of a float with a sinker at one end and a graduated tube or rod at the other. it is made of metal or glass. generally two are required, one for liquids ranging in sp. g. from . to . , and another, which will indicate a sp. g. between . and . . the range depends on the size of the instrument. for special work, in which variations within narrow limits are to be determined, more delicate instruments with a narrower range are made. [illustration: fig. .] in using a hydrometer, the liquid to be tested is placed in a cylinder (fig. ) tall enough to allow the instrument to float, and not too narrow. the temperature is taken, and the hydrometer is immersed in the fluid. the mark on the hydrometer stem, level with the surface of the liquid, is read off. with transparent liquids it is best to read the mark under and over the water surface and take the mean. the graduation of hydrometers is not made to any uniform system. those marked in degrees baumé or twaddell, or according to specific gravity, are most commonly used. the degrees on baumé's hydrometer agree among themselves in being at equal distances along the stem; but they are proportional neither to the specific gravity, nor to the percentage of salt in the solution. they may be converted into an ordinary statement of specific gravity by the following formulæ:-- sp. g. = . /( . -degrees baumé.) or putting the rule in words, subtract the degrees baumé from . , and divide . with the number thus obtained. for example: ° baumé equals a sp. g. of . . . /( . - ) = . /( . ) = . this rule is for liquids heavier than water; for the lighter liquids the rule is as follows:-- sp. g. = /( + degrees baumé.) or in words divide by the number of degrees baumé added to . for example: ammonia of ° beaumé has a sp. g. of . (nearly). /( + ) = / = . a simple series of calculations enables one to convert a beaumé hydrometer into one showing the actual sp. g. graduation, according to sp. g. is the most convenient for general purposes. in these instruments the distances between the divisions become less as the densities increase. twaddell's hydrometer is graduated in this way: each degree twaddell is . in excess of unity. to convert into sp. g. multiply the degrees twaddell by . , and add . for example: ° twaddell equals a sp. g. of . . ×. = . ; + . = . . there is a practice which ignores the decimal point and speaks of a sp. g. of instead of . . in some cases it is convenient, and inasmuch as no substance has a real sp. g. of much over , it can lead to no confusion. the figures expressed in this way represent the weight of a litre in grams. some hydrometers are graduated so as to show at a glance the percentage composition of the liquid they are intended to be used with. gay-lussac designed one to show the alcoholic strength of mixtures of alcohol and water; the construction of others upon the same principle is easy and perhaps useful. but when the principle is applied to complex liquids and mixed solutions, it is misleading. the various methods of graduation ought all to give place to one showing a simple statement of the sp. g. the method of determining sp. g. with the hydrometer is obviously inapplicable to the case of solids, and in the case of liquids it should not be used where exact figures are required. there are several other methods which may be used, but on the whole those with the specific gravity bottle are most convenient. [illustration: fig. .] ~the specific gravity bottle~ (fig. ) is a light flask of about c.c. capacity, provided with a well-fitting perforated stopper. it is essentially a graduated flask, which measures a constant volume, but it does not much matter what the volume is. _in taking the sp. g. of a liquid_ (_or, what is the same thing, a fused solid_) there is wanted the weights ( ) of the flaskful of water and ( ) of the flaskful of the liquid. dividing the second by the first gives the required sp. g. the actual weighings required are-- ( ) of the dry and empty flask, ( ) of the flask filled with water, and ( ) of the flask filled with the liquid. the weighing of the flask once made need not be often repeated. it is well to do so now and then for safety's sake; but one weighing will serve for a large number of determinations. the same remarks apply to the weighing of the bottle filled with water. the bottle is dried by rinsing out first with alcohol and afterwards with ether; ether is very volatile, and a short exposure in a warm place will soon drive off the little remaining about the sides. the ether vapour should be sucked out through a glass tube. see that the bore of the stopper is dry as well as the bottle. let the dry bottle stand in the box of the balance for a minute or two before weighing. the weight is, strictly speaking, not that of the empty bottle, but of the bottle filled with air. the empty bottle would weigh from to milligrams less. correcting for this would, in most cases, only make a difference in the fourth place of decimals,[ ] so that it is better to ignore the error. the weight of the flask filled with water is got by filling it with distilled water, and inserting the stopper. the excess of water will overflow at the margin and through the bore. the bottle is wiped with a soft, dry cloth, taking care not to squeeze or warm the bottle. the bottle will remain filled to the top of the stopper. it is allowed to stand in the balance box for a minute or two, and then weighed. distilled water, as stated, should be used; the use of ordinary water may increase the weight by or milligrams. many waters, if they have not previously been boiled, give off bubbles of air which render the weighing worthless. the temperature of the water is of greater importance; lowering the temperature ° will increase the weight by or milligrams. a beaker of water may be warmed or cooled to the required temperature; then the bottle is filled from it, and quickly weighed. if the balance-room is cooler than the water, the latter will draw back into the bottle, and a few small bubbles of air will enter; but even in extreme cases this will only increase the weight by a very small fraction of a milligram. there is more trouble caused when the room is warmer, for the liquid then expands and protrudes as a drop resting on the top of the stopper. there will in this case be loss by evaporation, which in the case of the more volatile liquids, such as alcohol, is serious. to prevent this loss, as well as any that may arise by overflow, the stopper should be dilated above into a small cup, a (fig. ), which may itself be stoppered. in a bottle of this kind the neck of the stopper is graduated, and the bottle is considered full when the liquid stands at the level of the mark in the neck. on inserting the stopper, the liquid rises into the cup, and is reduced to the level of the mark by absorption with pieces of filter-paper. [illustration: fig. .] for most purposes, however, there is no need for cooling and allowing room for subsequent expansion. the assayer, as a rule, can select his own standard temperature, and may choose one which will always necessitate warming. it will be handier in this case to have a bottle with a thermometer stopper. of the two types shown in fig. , that with the external thermometer tube (a) is more generally useful. [illustration: fig. .] the bottle is filled at a lower temperature, and is then gently warmed so as to slowly raise the temperature to the required degree. the superfluous liquid is then at once wiped off, and the bottle cooled and weighed. the weight of the flask filled with the liquid whose sp. g. has to be determined is ascertained in a similar way. of course the temperature must be the same. if the liquid does not mix with water, the bottle should be dried before filling, but otherwise the flask need only be rinsed out two or three times with the liquid. having obtained the three weighings, deduct the weight of the bottle from each of the others to get the weights of the water and liquid respectively. divide the latter by the former, the result shows the sp. g. as an example, take the following, in which a rather large sp. g. bottle was used:-- . weight of bottle . gram . weight of bottle and water . " . weight of bottle and paraffin . " by subtracting from and the result is as follows:-- . grams . grams . " . " ------ ------ . of water. . of paraffin. divide the weight of the paraffin by that of the water-- . ) . ( . . ------- ....... the sp. g. of the paraffin is . . _the sp. g. of a fusible solid_ may be obtained in the same way at a temperature some degrees above its fusing point. _the sp. g. of a solid in powder or gravel sufficiently fine to pass through the neck of the bottle_ is easily determined. if the bottle filled with water weighs grams, and there is placed on the pan alongside of it grams of a sand, the weight of the two together will of course be grams. but if the sand is put in the bottle, it evidently displaces its own bulk of water; and if, on again weighing, the weight is found to be instead of grams, it is because the grams of sand has displaced grams of water. bulk for bulk, the sand is - / times as heavy. in practice, the weight of the bottle filled with water will probably be already known; if not, it must be determined. a certain quantity, say grams, of the powdered substance is then transferred carefully to the bottle. the bottle need not be dry inside, but its neck and outside must be. in making this transference a careful worker will make no loss, and the mode of working saves a little time. but it is better to weigh the dry flask; put into it to grams of the powder, and weigh again. the increase in weight gives accurately the weight of powder in the bottle. about two-thirds fill the bottle with distilled water, and mix with the powder by gentle shaking. air bubbles will disentangle themselves, and rise to the surface of the water. wash back anything adhering to the stopper with a jet of water, and fill the bottle almost to overflowing. allow it to stand for a minute or so; replace the stopper; warm to the required temperature; take off the superfluous moisture; wipe and weigh. as an example, take the following:-- . weight of bottle . grams . " " bottle filled with water . " . " " bottle with wolfram . " . " " bottle with wolfram and water . " subtract ( ) from ( ) to get the weight of wolfram taken: . grams . " ------ . " add the weight of the wolfram to the weight of the bottle filled with water: . grams . " ------ . " subtract ( ) from this to get the weight of water displaced: . grams . " ------ . " divide the weight of the wolfram by the weight of the water displaced to get sp. g.: . ) . ( . . ------ ...... _if the solid is soluble in water, or has a tendency to float_, some liquid other than water is used. paraffin oil or oil of turpentine will do. the process is as follows:--the weight of the dry and empty bottle having been determined, add a sufficiency of the substance and weigh again to find how much has been added. fill up with paraffin oil and weigh again. clean out the substance by rinsing with paraffin; fill up and weigh. calculate the sp. g. as if water had been used, and multiply by the sp. g. of the paraffin. for example: . weight of bottle . grams . " " bottle and nitre . " . " " bottle and paraffin . " . " " bottle and paraffin and nitre . " . " " bottle and water . " first from ( ),( ), and ( ), calculate the sp. g. of the paraffin as already shown. it will be . . deduct ( ) from ( ) to get the weight of the nitre: . grams . " ------ . " add this to ( ): . grams . " ------ . " and deduct ( ) to find the weight of the equal bulk of paraffin. . grams . " ------ . " divide the weight of the nitre by the weight of the paraffin: . ) . ( . ------ ...... the sp. g., taking paraffin as the standard instead of water, is . . multiply this by the sp. g. of paraffin, . , and the result is . as the sp. g. of nitre compared with water. similarly, a sp. g. compared with water at say ° c. can be converted into one compared with water at standard temperature, by multiplying by the sp. g. of water at ° c. the following table gives the sp. g. of water at various temperatures:-- -----------+------++-----------+------++-----------+------- degrees | || degrees | || degrees | centigrade.|sp. g.||centigrade.|sp. g.||centigrade.|sp. g. -----------+------++-----------+------++-----------+------- ° | . || ° | . || ° | . ° | . || ° | . || ° | . ° | . || ° | . || ° | . -----------+------++-----------+------++-----------+------- if, for example, a substance at ° c. has a sp. g. of . as compared with water at ° c., it will have (compared with water at ° c.) a sp. g. of . × . ; or . . the figures . represent the sp. g. of the substance at ° c. compared with water at ° c. except in comparing the sp. gravities of the same substance at different temperatures, a calculation of this kind serves no useful purpose. _in taking the specific gravity of a solid not in powder_, a lump of it is freed from loose particles and its exact weight determined. by means of a horse hair with a slip knot it is suspended to the balance, and beneath it is placed, out of contact with the balance pan, a beaker of distilled water. the horse hair must be long enough to keep the mineral well beneath the surface of the water so as to allow the balance to vibrate. air bubbles are removed by touching with a camel-hair pencil. whilst the mineral is suspended in water the weight is again taken. it will weigh less than before, and the difference between the two weighings gives the weight of water (and consequently the volume) displaced by the mineral. the weight in air divided by the difference is the specific gravity. thus weight in air . grams weight in water . " ------ difference . gram . / . equals . , the sp. g. the sp. g. of a substance depends mainly on its composition, but is affected by certain conditions. the effect of temperature has been already considered. air holes and empty spaces lessen the specific gravity of otherwise solid bodies; and metals, which after fusion become imperfect solids, have their density increased by hammering or rolling. but metals when free from pores have their density diminished when rolled, without annealing. the effects of these conditions are slight when compared with those due to the presence of impurities. for simple substances, or mixtures of only two substances, a determination of sp. g. is a sufficient check on the composition for many practical purposes; and with more complex mixtures, such as slags and some of the products of dressing operations in which the material does not differ much in its nature from time to time, such a determination will yield information of considerable value, and afford a check upon the proper working of a process. when the mixing of two substances is accompanied by a change in volume, the sp. g. of the mixture can only be learnt by experiment. but when the substances have no such action on each other the resulting sp. g. can be calculated. some of these calculations have a practical interest as well as an educational value. students should practise them so as to become familiar with the relations between weight and volume. _when substances are mixed by volume_, the sp. g. of the mixture is the mean of those of its constituents, and may be calculated in the usual way for obtaining averages. c.c. of a substance having a sp. g. of . mixed with c.c. of another having a sp. g. of . will yield c.c. of a substance having a sp. g. of . . if, however, we write gram instead of c.c. in the above statement, the resulting sp. g. will be . . the simplest plan is to remember that the sp. g. is the weight divided by the volume (sp. g. = w/v) and the sp. g. of a mixture is the sum of the weights divided by the sum of the volumes (sp. g. = (w + w' + w", &c.)/(v + v' + v", &c.)). in the above example the sum of the volumes is c.c.; the weights (got by multiplying each volume by its corresponding sp. g.) are . gram and gram. the sum of the weights divided by the sum of the volumes is . / or . . the sp. g. of a mixture of c.c. of a substance having a sp. g. of . , with c.c. of another having a sp. g. of . may be thus found:-- sp. g. = ( + . )/( + ) = . multiply each volume by its sp. g. to get its weight: × . = × . = . add these together ( + . = . ) and divide by the sum of the volumes ( + = ): ) . ( . -- , &c. the sp. g. will be . , provided the mixture is not accompanied by any change of volume. the same formula will serve when the proportion of the ingredients is given by weight. a mixture of parts by weight of galena (sp. g. . ) with parts of blende (sp. g. ) will have a sp. g. of . : sp. g. = ( + )/( . + . ) = / . = . it is necessary in this case to calculate the volumes of the galena and of the blende, which is done by dividing the weights by the sp. gravities: thus, divided by . gives . and divided by gives . . the converse problem is a little more difficult. given the sp. g. of a mixture and of each of the two ingredients, the percentage by weight of the heavier ingredient may be ascertained by the following rule, which is best expressed as a formula. there are three sp. gravities given; if the highest be written h, the lowest l and that of the mixture m, then: percentage of heavier mineral = ( ×h×(m-l))/(m×(h-l)) suppose a sample of tailings has a sp. g. of . , and is made up of quartz (sp. g. . ) and pyrites (sp. g. . ): then the percentage of pyrites is : ( × . ×( - . ))/( ×( . - . )) = ( × . )/( × . ) = / . = . the same problem could be solved with the help of a little algebra by the rule already given, as thus: the sp. g. of a mixture equals the sum of the _weights_ of the constituents divided by the sum of the _volumes_. then grams of the tailings with _x_ per cent. of pyrites contain -_x_ per cent. of quartz. the sum of the weights is . the volume of the pyrites is _x_/ . and of the quartz ( -_x_)/ . . then we have by the rule = /((_x_/ . )+( -_x_)/ . ) = /( - . _x_) = . _x_ and _x_ = . if the percentage (p) and sp. g. (h) of one constituent and the sp. g. (m) of the mixture are known, the sp. g. of the other constituent may be calculated by the following formula, in which _x_ is the required sp. g.: _x_ = (( -p)×m×h)/(( ×h)-(p×m)) for example, "tailings" (sp. g. . ) containing . per cent. of pyrites (sp. g. . ) will contain ( - . ), . per cent. of earthy matter having a mean sp. g. of _x_: _x_ = (( - . )× × . )/(( × . )-( . × )) = . / . = . the differences in sp. g. corresponding to differences in strength have been carefully determined and tabulated in the case of the stronger acids and of many other liquids. such tables are given at the end of this book. _to calculate the weight of a measured volume of mineral or rock._--multiply the cubic feet by . and then multiply by the sp. g. of the stuff, the answer gives the weight in pounds. for example, cubic feet of quartz weighs × . × . = , lbs. the weight of any mass of mineral of known extent and sp. g. is ascertained in this way. the following table gives the specific gravities of some of the commoner minerals. barytes . blende . calcite . cassiterite . chalybite . copper pyrites . fluor . galena . hæmatite . mispickel . pyrites . quartz . footnotes: [ ] the difference of or milligrams is disregarded here because it detracts equally from the actual weight of the water and liquid to be determined. if the liquid is a heavy one the difference shows itself in the third or second place of decimals. the correction may be made by deducting from the weight of the flask . grams for each gram of water it holds. part ii.--the metals. chapter ix. silver, gold, cyanides, platinum, mercury. silver. silver is widely diffused, and has been found in most mining districts. it occurs native in sufficient quantity to constitute one of the chief ores of the metal. it also occurs combined with sulphur (as in argentite), with sulphur and antimony (as in stephanite or brittle silver ore, and in pyrargyrite or ruby silver), and with copper, sulphur, antimony, and arsenic, as in polybasite. chloride of silver occurs native as horn silver or kerargyrite. silver is found in the ores of other metals, such as fahlerz, which sometimes contains from two to ten per cent. of the metal, and galena, which is an important source of it; in fact, galena is never found entirely free from silver. it is present also in greater or less quantity in the ores of copper and zinc. silver dissolves readily in nitric acid, forming silver nitrate. it only forms one family of salts, and of these the chloride and nitrate are of chief importance to the assayer. the formation of the chloride of silver on the addition of hydrochloric acid or a soluble chloride to the nitric acid solution, serves for the recognition and separation of silver. the precipitated chloride is white (becoming violet on exposure to light), insoluble in nitric acid, soluble in ammonia, hyposulphite of soda, or concentrated solutions of chlorides. the best confirmatory test is made by wrapping the precipitate in a little sheet lead, and cupelling, when the silver will be left in the metallic state, and is easily recognized. ~dry assay.~--this assay is made up of two parts: ( ) the concentration of the silver in a button of lead; and ( ) the cupellation of the resulting alloy. the concentration of the button of lead may be effected either by scorification or by fusion in a crucible. the scorification assay is performed in a scorifier, which is a shallow open-mouthed dish about - / inches across, with a very thick bottom to enable it to withstand the corrosive action of the slag. a charge of more than or grams of the ore cannot be worked in one, and with such small charges the unavoidable variations have a serious effect on the figures reported. a difference of one milligram on the weight of the button of silver got represents a difference of or ounces per ton. with rich ores such variation is unavoidable under any conditions, and the only safe plan is to take the mean of several assays. but with poorer ores the accuracy of the assay, as well as convenience in working, is much increased by working in a crucible with larger charges. in scorification the proportion of lead required for scorifying gram of ore is in average cases from to grams, sinking in the case of galena to grams, and rising with earthy and refractory substances to from to grams. but by fusing in a crucible with well-selected fluxes, a proportion of of flux to of ore is generally sufficient; and not only is the proportion of added matter less, but it is also easier to manipulate large quantities in crucibles, so that, although in some cases the crucible assay is more troublesome and less satisfactory, yet with poor and earthy ores it is the best method of dealing with them; while when properly worked it yields results as accurate as scorification does. as a general rule, if more than grams of ore must be taken, the crucible assay should be adopted. [illustration: fig. .] ~scorification assay.~--the charge of ore is usually grams, sometimes ; the lead varies from to grams, and the quantity of soda, borax, or powdered glass added varies from . to or grams. it is generally recommended to have the lead granulated,[ ] and to mix the ore with about half of it in the scorifier; then to put on the rest of the lead; and finally to sprinkle the borax or glass on the top. it answers just as well, however, to use the lead in the shape of foil, and wrap the ore up in it; and if the ore contains much sulphur, the borax may with advantage be added (wrapped in a little tissue paper) some five or ten minutes after the operation has started. [illustration: fig. .] the process of scorification is as follows:--a scorifier (fig. ) of convenient size having been selected (one - / inches across is most generally useful), it is dried at a gentle heat for about ten minutes. the charge is then put into it, and it is introduced, with the help of a scorifier tongs (fig. ), into a muffle heated considerably above redness. the muffle is then closed, and when the metal has melted down, it is opened, but the temperature is kept up. a ring of slag will, after a time, form around the metal, and when this appearance (known as the eye) presents itself, the temperature may be lowered. when the eye has disappeared--that is, when the layer of slag has quite closed in--a pinch of powdered culm wrapped in tissue paper is added. as soon as the slag has again become tranquil, the scorifier is taken out, and its contents are poured into a mould (fig. ), the slag is detached, and saved. if the button of metal weighs more than grams, its size is reduced by another scorification in the same scorifier, which should have been replaced in the muffle immediately after the contents had been poured out. if the ore is not a very rich one, the button of lead will carry practically all the silver; but with rich ores it is more satisfactory to save the slag, and subsequently to melt it down with the cupel on which the lead has been treated, so as to recover the silver lost in the slag, together with that absorbed in the cupel, at one operation. or, if the cupellation loss is neglected or calculated in some other manner, the slag or slags from the scorifier may be powdered and mixed with grams of oxide of lead, grams of borax, and gram of charcoal. this should be melted down in a small crucible, and the resulting button of lead cupelled. [illustration: fig. .] if the scorification has been unsatisfactory, the quantity of silver obtained from the slag will be by no means inconsiderable. the usual explanation is that with sulphury ores compounds of metallic oxides and sulphides (oxysulphides) are formed, which remain in the slag, retaining considerable quantities of the precious metal. it is said that under certain conditions such a slag may contain as much as per cent. of silver. an excess of lead and a high temperature prevents the formation of these oxysulphides. but if much silver is present in the ore, the slag cannot be safely thrown away, even if sulphur is absent, and the process has been satisfactorily performed. if the crust which appears on the surface of the lead does not clear, add a small lump of borax and grams more lead; then close the muffle, and keep the temperature as high as possible. if the slag forms properly, but shows unfused or only half-fused lumps, even when the scorification has proceeded for some time, add more borax, and stir with an iron rod. the slag adhering to the rod must be detached by hammering, and replaced in the scorifier. if the ore consists largely of quartz, soda should be added instead of borax; or, if it contains much copper, powdered quartz may be used. if the scorifier at the end of an operation is more than usually corroded, the borax should be replaced in subsequent assays on similar ores by powdered glass or quartz. if a fairly fluid slag is formed which does not clear from the metal and show the eye, more lead and a higher temperature is wanted. as a general rule, it may be stated that when a scorification is unsatisfactory, what is wanted is more heat, more lead, or more borax. it is a safe plan when work has to be done on a strange ore, to make three or four assays with varying quantities of lead. the proportion of lead is right when a further addition does not yield a higher result. the proper proportion having been found, a note of it should be made for future use. pot assays. the object of the fusion in a crucible, like that of scorification, is to concentrate the silver in a button of lead which is to be subsequently cupelled; and to retain the earthy and waste matters in the slag. it is necessary to consider the quality of the slag and the weight and quality of the lead. the slag when fused should be liquid and homogeneous, and not too corrosive on the crucible. the button of lead should be soft, malleable, and free from a coating of regulus.[ ] in weight it should not differ much from the ore taken. with grams of ore, for example, a button of lead weighing from to grams will be satisfactory: less than this would leave an undue proportion of silver in the slag; and more would be unnecessarily large for cupelling, and would increase the loss in that operation. with average ores, take grams of the powdered ore and mix with grams of "soda," grams of red-lead or litharge, grams of borax, and from to . grams of flour, and place in an e crucible (battersea round). put these in the furnace at a red heat, cover the crucible, and gradually raise the temperature until the whole charge has melted down and is in a state of tranquil fusion. pour into a mould, and replace the crucible in the furnace. as soon as the lead is solid, detach the slag and put it back into the crucible; and when it is again fluid, charge on to it with a copper scoop a mixture of grams of oxide of lead, and gram of charcoal: when fusion has again become tranquil, pour and detach the button of lead. the lead buttons should be hammered into discs with rounded edges, and be freed from slag; if too big for a cupel they may be scorified together in a small scorifier, but it is better to cupel them separately. ~ores containing metallic oxides.~--peroxides of iron, manganese, and copper interfere by counteracting the effect of the charcoal or flour, and thus reducing the size of the lead button. peroxide of iron will reduce the weight of lead by a little more than its own weight; and peroxide of manganese has about twice this effect. when these oxides are present an additional quantity of flour must be used, and precautions must be taken to prevent reoxidation of the slag by the furnace gases. this may best be prevented by using a layer of common salt as a cover to the charge. when the ores contain a good deal of quartz or stony matter, the fluxes just given (for average ores) will do; but the proportion of soda should be diminished, and that of the borax, oxide of lead, and flour increased as the quantity of metallic oxides become greater. if the ore contains practically no quartz, the soda may be altogether omitted, and some glass or powdered quartz added. the following charge may be taken as an example: weigh up grams of the powdered ore, grams each of "soda" and borax, grams of oxide of lead, and grams of flour. mix and place them in an e crucible, and cover with a layer of from a quarter to half an inch of common salt. place in the furnace as before. the salt will give off a considerable amount of fume, which will, to a certain extent, conceal the state of the charge: when the crucible has been in the furnace for about minutes remove it and pour out the contents immediately. with ores that produce a thick slag the addition of grams of fluor spar will be an advantage. it may happen that with an unknown ore the first assay will be more or less unsatisfactory: but from it the necessity for adding more or less flour will be learnt, and a second assay, with the necessary modification of the charge, should give a good result. ~ores containing much sulphides.~--ores of this class may be easily recognized, either by the appearance of the minerals they contain or by the odour of sulphurous oxide (so_{ }) which they evolve when roasted on a spatula. the sulphides most commonly present, in addition to the sulphurized minerals of silver, are pyrites, galena, blende, and mispickel. when they are present in only a moderate amount, their effect is simply to increase the weight of the button of lead; and this is easily counteracted by reducing the amount of flour, or by omitting it. when in larger amounts, they not only yield large buttons, but also render the metal sulphury, sometimes even giving a button of regulus instead of lead. this last evil may be remedied ( ) by putting in a rod of iron as soon as the charge has fused, or ( ) it may be counteracted by a proper addition of nitre, or ( ) when the sulphides present are only those of iron or copper the sulphur may be removed by calcining, and the ore converted into one of the class containing metallic oxides. the calcination is effected as follows:--weigh up grams of the powdered ore and place it in a wide-mouthed crucible sufficiently large to perform the subsequent melting down in. the roasting must be done at a gentle heat at first, so as to avoid clotting: the mouth of the crucible should project considerably above the coke, and should slope forward towards the worker. the charge must be occasionally stirred with the stirrer (fig. ) so as to expose fresh surfaces to the action of the air, and to prevent adhesion to the sides of the crucible. the stirrer should not be removed till the calcination is finished. the temperature should be raised at the end to a good red heat; and (to ensure the decomposition of any sulphate that may be formed) the roasted ore should be rubbed up in a mortar with a pinch of anthracite, and again calcined. it is then mixed with fluxes as described, and fused in the same crucible. the calcination of an ore is a work occupying a good deal of time, and, in most cases, it is better to take advantage of the desulphurizing power of red lead or nitre. red lead by itself will do, but a large quantity of it will be required; part of a metallic sulphide needs from to parts of red lead to yield a button free from sulphur; whereas at most from to - / parts of nitre are sufficient. there is sometimes an advantage in having a considerable excess of oxide of lead in the slag, but where there is no such reason, parts of red lead to of ore is enough. a charge which will do for most sulphides is the following: grams of ore, to grams of red lead, grams of "soda," of borax, and sufficient nitre (or perhaps flour) to give a button of about grams of lead. how much this must be (if not already known) may be approximately determined by fusing grams of the ore and grams of "soda" in a small crucible (c) with grams of litharge (not red lead) under a cover of salt, and weighing the resulting button of lead. subtract from the weight of lead obtained, and the difference multiplied by . will give the quantity in grams of nitre required. if the button of lead weighs less than grams flour must be added. if this is not satisfactory repeat the assay, adding an extra gram of nitre for each grams of lead in excess of that required, or gram of flour for a -gram deficiency. in the method in which iron is used as a de-sulphurising agent, only as much oxide of lead should be added as will give a button of lead of the required size. rather a large button of lead should be got, and the slag should be strongly alkaline; if the ore does not already carry a large amount of sulphur some should be added. the fusion should be performed at a low temperature (similar to that for a galena assay), and should be continued for some time after it has become tranquil. take grams of the ore, grams of "soda," grams of oxide of lead, and or grams of borax; place this mixture in a crucible (with a rod of iron, as in the galena assay), cover, and fuse for about half an hour. take out the rod, washing it in the slag, and, in a minute or two, pour. clean and cupel the button of lead. ~general remarks on the fusion.~--other things being equal, the smaller the quantity of the slag the better, provided there is sufficient to cover the metal. the presence of peroxides of the heavy metals is prejudicial, since they tend to increase the quantity of silver retained in the slag. it may be given as a general rule that when iron, copper, manganese, &c., are present, there is a more than ordinary need for cleaning the slags, and care must be taken to keep these metals in the state of lower oxide. in selecting the fluxes, it should be remembered that soda is the best for quartz, and borax for lime and metallic oxides. and that with ores almost free from gangue some quartz or glass should be added to protect the crucible. two parts of soda are enough to flux part of quartz; whilst of borax, or oxide of lead, parts are barely sufficient. oxide of lead has the advantage of being heavy and so does not occupy much space in the crucible; on the other hand, if the melting down be performed too quickly, or if oxide of lead only is used, this high specific gravity is a disadvantage, for the lighter earthy matter floats as a pasty mass on the more fluid oxide of lead, and thus escapes its action. when metallic sulphides are present in the ore, an excess of oxide of lead helps to keep the sulphur out of the button of metal. in addition to the oxide of lead required as a flux, some will be required to provide the lead in which the silver is to be collected. oxide of lead, mixed with charcoal or flour, yields, when heated, a multitude of minute buttons of metal uniformly distributed through the mass of the charge; as the charge melts down these run together and fall to the bottom; this shower of lead collects the silver more easily than a single button at the bottom of the crucible could do. only that portion of the oxide of lead which remains in the slag can be considered as a flux; very often the first indication of an excessive reduction of lead is the pastiness of the slag rendered thick by the withdrawal of the oxide of lead which would have kept it fluid. if, in an assay, it is found that parts of flux are not sufficient for part of ore, the remedy lies in using a different flux rather than in taking a larger quantity. _on the reducing effect of charcoal, flour, and tartar._--the weight to be got from a given charge will depend (provided sufficient oxide of lead is present) upon the proportion of the reducing agents in it. we have thought it well to illustrate this part of the subject by a series of experiments which the learner will do well to practise for himself before proceeding to the assay of actual ores. take grams of litharge and grams of a mixture of borax and soda. fuse three lots ( ) with . gram of charcoal, ( ) with grams of flour, and ( ) with . grams of tartar. weigh the buttons of lead obtained, and divide each by the weight of reducing agent used. the results will differ somewhat with the dryness and quality of the flour, etc., used; in one series of experiments they were as follows:-- gram. grams. gram. grams. . charcoal gave . lead .'. charcoal = . lead. . flour " . " .'. flour = . " . tartar " . " .'. tartar = . " the use of flour as a reducing agent has many advantages, and it is well to remember that _ gram of flour reduces about grams of lead_; and that charcoal has twice, and tartar one-half, this reducing effect. _on the reducing effect of charcoal, &c., on red lead._--it is often easier to obtain red lead of good quality than it is litharge, and by a large number of assayers red lead is the form of oxide of lead always used. red lead, however, contains an excess of oxygen which will use up some of the reducing agent before lead separates out. on making a series of experiments (similar to the last, but using grams of red lead instead of the litharge) the results were, with the same quantities of the reducing agents:-- with charcoal, grams of lead. " flour, " " " tartar, " " comparing these with the results with litharge, in the previous table it will be seen that the same quantity of reducing agent has in each case brought down grams less of lead, so that a larger amount of the reducing agent must be added to get a button of the same weight as that obtained with litharge. to get a button of a desired weight, say grams, we must add reducing agent sufficient to throw down + or grams of lead, which would require . grams of flour. if this amount of flour is fused with grams of red lead, a button of lead weighing grams will be formed, the other grams being kept up by the oxygen of the red lead. if the quantity of red lead differs from grams, this rule must be modified. with grams of red lead, for example, we should add an excess of reducing agent sufficient to throw down grams of lead instead of . similarly, with grams of red lead, we should add enough to throw down grams. the following rule will enable one to calculate the weight of flour required to produce a button of lead of any desired weight from any given quantity of red lead. each grams of red lead present diminishes the weight of the lead by gram. if then we _divide the weight of red lead in a charge by , and add this to the weight of lead required, the sum divided by will give the weight of flour which must be added_. using grams of red lead and wanting a button of grams, we should add . grams of flour. / = ; + = ; / = . nearly. the following are some results obtained which will illustrate the rule:-- red lead used. flour used. lead got. grams grams . grams " " . " " " . " " " . " _on the reducing effect of metallic sulphides, and the counteracting effect of nitre._--the sulphides found in ores will reduce a button of lead from oxide of lead just as flour does; and, as charcoal, flour and tartar differ in their reducing power, so equal weights of the different mineral sulphides throw down different weights of lead. one gram of iron pyrites yields about grams of lead. one gram of copper pyrites, blende, fahlerz, or mispickel, yields or grams of lead, whilst gram of antimonite will give , and gram of galena only a little over grams. it is evident that if an ore carries much of these sulphides, the quantity of lead reduced will be very much larger than that required for an assay. to counteract this effect nitre is added; _ gram is added for each grams of lead in excess of that required_. for example: with a -gram charge of an ore containing per cent. of pyrites, if no nitre were added, grams of lead would be got; or, if there was not sufficient oxide of lead to yield this quantity of metal, the button would be sulphury. to reduce the weight of the button by grammes, we should add grams of nitre, if litharge were used; or if red lead were used, we should add grams of nitre, _since the oxidizing effect of grams of red lead is equivalent to that of of nitre_, and since grams of red lead are generally used in a charge. two assays of an ore of this kind with these quantities of nitre gave . grams of lead with litharge, and . grams with red lead. it is best to use in these assays grams of red lead, of soda, and of borax, with grams of the ore. if the lead got by the preliminary fusion in a small crucible with litharge (described under "_ores containing much sulphides_") is known, the following table will indicate the quantity of nitre, or flour, to be added with this charge:-- -------------------------------+-------------------+------------------ lead got in preliminary fusion | flour to be added | nitre to be added with grams of ore. | to the assay. | to the assay. -------------------------------+-------------------+------------------ . gram | . grams | none . grams | . gram | -- . " | none | . grams . " | -- | . " . " | -- | . " . " | -- | . " . " | -- | . " . " | -- | . " -------------------------------+-------------------+------------------ if litharge is used in the assay instead of red lead grams more nitre, or . gram less flour must be used. when more than a few grams of nitre are added to a charge the proportion of "soda" and borax should be increased, because one of the products of the reaction of nitre upon sulphides in the presence of soda is sulphate of soda, and because the "soda" thus used up no longer serves as a flux; more borax should be added, as it is the best flux for the metallic oxides which are formed in the process. if in an assay too large a button of lead is got, even after this calculation has been made, and the assay is repeated, add gram more nitre for each grams of lead in excess. sometimes the assay appears tranquil before the nitre has produced its full effect; in such cases it is well to seize the crucible with the tongs and mix its fused contents by rotating them; if this causes an effervescence, the crucible should be replaced in the fire and the fusion continued. the following experiments will illustrate the extent to which the above rules may be relied on. in all of them the standard flux was used, viz.:-- grams of red lead, of soda, and of borax. _pyrites_ . quartz -- -- . nitre -- -- -- . lead got . . . . . . . . . _copper pyrites_ quartz -- -- nitre -- -- lead got . . . . _antimonite_ quartz -- -- nitre -- -- lead got . . . . _galena_ quartz. -- -- -- nitre -- -- . lead got . . . . . . a similar set of experiments, with grams of litharge instead of grams of red lead, gave:-- _pyrites_ quartz -- -- nitre -- -- . lead got . . . . . . _copper pyrites_ quartz -- -- nitre -- -- lead got . . . . _blende_ quartz -- -- nitre -- -- lead got . . . . . _antimonite_ quartz -- -- nitre -- -- lead got . . . . . _galena_ quartz -- -- -- nitre -- -- . lead got . . . . . . the variation in some of these experiments, in which we might have expected similar results, is due to the fact that the sulphur, and in some cases the metals, are capable of two degrees of oxidation. for example: theoretically gram of iron pyrites (fes_{ }) would yield . grams of lead if the sulphur were oxidised to sulphurous oxide (so_{ }), and the iron to ferrous oxide (feo); whilst if the sulphur were oxidised to sulphate (so_{ }), and the iron to ferric oxide, . grams of lead will be thrown down. similarly the yield with copper pyrites would be . or . ; with blende, . or . ; with antimonite, . or ; and with galena, . or . . as regards the metals, the lower oxide will always be formed if the assay is carried out properly (fused under a cover, and with a sufficiency of reducing agent). but the proportion of sulphur oxidised completely will vary with the conditions of the assay. with a slag containing much soda the tendency will be to form sulphate, and, in consequence, a big reduction of lead; whilst with an acid slag containing much quartz the tendency will be for the sulphur to go off as sulphurous oxide (so_{ }). in a fusion with litharge alone all the sulphur will be liberated as the lower oxide, whilst with much soda it will be wholly converted into sulphate. for example: grams of an ore containing a good deal of pyrites and a little galena, gave, when fused with litharge, . grams of lead. a similar charge, containing in addition . grams of soda, gave . grams of lead. it will be noted from the experiments that gram of nitre kept up on the average grams of lead; the range being from . with acid slags to . with very basic ones. these facts serve to explain some apparently irregular results got in practice. cupellation. the process is as follows:--the cupels, which should have been made some time before and stored in a dry place, are first cleaned by gentle rubbing with the finger and blowing off the loose dust; and then placed in a hot muffle and heated to redness for from to minutes before the alloy to be cupelled is placed on them. the reasons for this are sufficiently obvious: the sudden evolution of much steam will blow a cupel to pieces; and, if the whole of the water has not been removed before the cupel is filled with molten lead, the escaping steam will bubble through, and scatter about particles of the metal. if some particles of unburnt carbon remain in the bone ash, a similar result will be produced by the escape of bubbles of carbonic acid as soon as the fused litharge comes in contact with them. the cupels having been prepared are arranged in a definite order in the muffle, and the assay buttons are arranged in a corresponding order on some suitable tray (cupel tray, fig. ); the heat of the muffle being at bright redness. then with the help of the tongs (fig. ) the assay buttons should be placed each in its proper cupel; a note having been previously made of the position it is to occupy, and the door of the muffle closed. [illustration: fig. .] this part of the work should be done promptly, so as not to unduly cool the muffle: the start requires a fairly high temperature, and is a critical part of the process. a black crust forms at once on the surface of the lead; but this ought soon to fuse and flow in greasy drops from off the face of the metal, so as to leave the latter fluid with a well-defined outline, and much brighter than the cupel. if this clearing does not take place, the buttons are said to be frozen; in which case the temperature must be raised, some pieces of charcoal put in the muffle, and the door closed. if they still do not clear, the heat must have been much too low, and it is best to reject them and repeat the assays. [illustration: fig. .] when the buttons have cleared it is well to check the draught of the furnace, and to partly open the door of the muffle, so as to work at as low a temperature as is compatible with the continuation of the process.[ ] too low a temperature is indicated by the freezing of the buttons and the consequent spoiling of the assays. experience soon enables one to judge when the heat is getting too low. a commoner error is to have the heat too high: it should be remembered that that which was high enough to clear the buttons at starting is more than sufficient to keep the process going. at the finish a higher temperature is again required: therefore the door of the muffle should be closed and the furnace urged. the finish is easily recognised. the drops of litharge which in the earlier stages flow steadily from the surface of the alloy, thin off later to a luminous film. at the end this film appears in commotion, then presents a brilliant play of colours, and, with a sudden extinction, the operation is finished. the metal again glows for an instant whilst becoming solid. if the button is a small one the cupel is withdrawn at once and placed on that square of the cupel tray which corresponds to the position it occupied in the muffle. if, however, it is fairly large precautions must be taken to prevent spirting. molten silver dissolves oxygen from the air and gives it off on solidifying; the escape of the gas on sudden cooling is violent and, by throwing off particles of the metal, may cause loss. this is called "vegetation" or "spirting." the silver is apparently solid when spirting takes place; the crust breaks suddenly and some of the metal is forced out. the evil is best guarded against by slow cooling and avoiding draughts. with large buttons of silver precautions should never be omitted. one plan is to allow the cupels to cool in the muffle itself, the mouth being closed with hot charcoal. another is to cover the cupel with another cupel previously heated to redness; in this case the silver cools between two hot cupels, and, of course, cools slowly. a third plan is to withdraw the cupel to the door of the muffle, holding it until it begins to get solid and then immediately to put it back into the hotter part of the muffle. silver remains after cupellation in flattened elliptical buttons, adhering but only slightly to the cupel. its upper surface should show faint markings as if it were crystalline. the presence of platinum renders it still more crystalline, but removes the characteristic lustre and renders the metal dull and grey. copper, if not completely removed, has a very marked effect on the appearance of the button: the metal is spread out, damping, as it were, and firmly adhering to the cupel, which latter in the neighbourhood of the metal is almost black with oxide of copper. sometimes the silver button is globular, or even more sharply rounded on its under than on its upper surface; it is said that this is due to the presence of lead. gold may be present even to the extent of per cent. without showing any yellow colour. the appearance of the cupel affords some useful information. the presence of cracks evidently due to shrinkage indicates a badly made cupel. if, however, they are accompanied by a peculiar unfolding of the cupel, the margin losing its distinctness, it is because of the presence of antimony. when lead is the only easily oxidisable metal present, the stained portion of cupel is yellow when cold. a greenish tint may be due to small quantities of copper or, perhaps, nickel, cobalt, or platinum. larger quantities of copper give a greenish grey or almost black colour. a dark green and corroded cupel may be due to iron. rings of pale-coloured scoria may be due to tin, zinc, antimony, or arsenic. when the cupel shows signs of the presence of these metals in objectionable quantity, it is well to repeat the assay and scorify so as to remove them before cupellation. the button should be detached from the cold cupel by seizing with a pair of pliers: the under surface should be distorted by squeezing or hammering the button so as to loosen the adhering bone ash. the cleaning is easily completed by rubbing with a clean hard brush. after cleaning the buttons are best put on a tray of marked watch-glasses, and then taken to the balance and weighed. the weight of silver got needs a small correction; ( ) by deducting for the amount of silver introduced by the lead or oxide of lead used in the assay;[ ] and ( ) by adding for the cupellation loss. ~loss in cupellation.~--during the whole process of cupelling a silver lead alloy a more or less abundant fume may be observed rising from the cupel. this furnishes an evident loss of lead and a possible loss of silver; for although silver at the temperature of cupellation gives off no appreciable vapour, it is known that such fume formed on a large scale contains silver. it is, however, difficult to believe that the small amount of lead vapourised carries with it a weighable amount of silver. that it does not do so in the ordinary way of working is shown by the fact that a button of silver equal in weight to the silver lost in cupelling may be got by smelting the cupel and cupelling the resulting button of lead. the loss of silver by volatilisation is altogether inconsiderable, unless the temperature at which the operation is performed is much too high. another possible source of loss is the infiltration of small particles of alloy into the cupel. the cupel is necessarily porous, and particles of metal may perhaps drain into it, more especially if the bone ash is not in fine powder; but if this is the main source of loss it is hard to see why, in cupelling equal weights of silver and gold, the loss is not equal in each case. it is not easy to believe that the mere filtration of the fused alloy will effect such a change in the proportion of the metals as that which actually occurs. for example: a cupel on which an alloy consisting of . gram of silver, . gram of gold, and grams of lead had been cupelled, was found to contain - / milligrams of silver, and rather less than half a milligram of gold. assuming, for the sake of argument, that the gold present had filtered into the cupel in the form of small drops of alloy, it would have been accompanied by less than a milligram of silver, and the presence of the extra or milligrams of silver must have been due to a different cause. there can, thus, be little doubt that the cause of the greater part of the "cupellation loss" is a chemical one and cannot be counteracted by a mechanical contrivance.[ ] in cupellation, then, there is a loss, apart from imperfect working, inherent in the process itself; and as the amount of this loss varies under different conditions, it is necessary to study it somewhat in detail. the following experiments are taken without selection from the work of one student. three experiments were made for each determination, and the mean result is given. by "range" is meant the difference between the highest and lowest result and the percentage loss is calculated on the silver present. the silver added in the lead used has been deducted. ~effect of varying lead.~--in each experiment . gram of silver was taken and cupelled with the lead. the silver loss and "range" are expressed in milligrams. ------------+--------------+--------+------------------ lead used. | silver lost. | range. | percentage loss. ------------+--------------+--------+------------------ grams. | | | | . | . | . | . | . | . | . | . | . | . | . | . ------------+--------------+--------+------------------ the loss increases with the lead used. ~effect of varying temperature.~-- . gram of silver was cupelled with grams of lead. temperature. silver lost. range. percentage loss. bright red . . . clear yellow . . . the difference in temperature in these experiments was much greater than would occur even with careless work. ~effect of varying silver.~-- grams of lead were used in each cupellation. ---------------+--------------+--------+------------------ silver taken. | silver lost. | range. | percentage loss. ---------------------------------------------------------- milligrams. | | | . | . | . | . . | . | . | . . | . | . | . . | . | . | . . | . | . | . . | . | . | . . | . | . | . ---------------+--------------+--------+------------------ it will be seen that, although the quantity of silver lost increases with the silver present, the percentage loss is greater on the smaller buttons. the following results are often quoted:--cupelling grain of silver with grains of lead, the loss was . per cent.; grains of silver with grains of lead, loss . per cent.; grains of silver cupelled with grains of lead, lost . per cent. the proportion of silver to lead was the same in the three experiments, and the largest button gave the best result. evidently, if the quantities of lead had been the same in the three experiments (say, grains in each case), the loss on the smaller quantities of silver would appear worse in the comparison. in judging these results, it must be borne in mind that it is difficult to regulate the temperature, &c., in consecutive experiments so as to get exactly similar results, so that the range in consecutive cupellations is greater than that in a batch cupelled side by side. ~effect of copper and antimony.~-- . gram of silver was cupelled with grams of lead, and to one batch . gram of antimony, and to another . gram of copper was added. loss in silver lost. range. percentage. without addition . . . with antimony . . . with copper . . . perhaps the antimony has so small an effect because it is eliminated in the earlier part of the process, while the silver is still alloyed with, and protected by, a large proportion of lead; whilst the copper on the other hand makes its fiercest attack towards the close, when the silver is least capable of resisting it. the ill effects of copper are most strongly felt when the quantity of lead present is not sufficient to remove it: the coppery button of silver got under these conditions is very considerably less than the weight of silver originally taken. although the above is a fair statement of the loss attending average work, it will not do in very important and exact work to place too much reliance on the figures given, or, indeed, on any other set of figures, with the object of correcting the result of an assay. each man must rely on his own work. it is easy to determine what allowance must be made for the loss in cupellation by cupelling side by side with the assay piece an alloy of similar and _known_ composition. for, if the two pieces are very nearly alike, we may justly conclude that the loss on each will be the same; and if, further, we take the average of three or four such determinations we shall get results accurate within . per cent. the method of getting such results may be best explained by one or two illustrations. this method of working is termed "assaying by checks." suppose we have an alloy of silver and lead in unknown proportions and that by cupelling two lots of grams each there is got from i. . gram of silver, and from ii. . gram. we should know from general experience that the actual quantity of silver present was from to milligrams more than this. to determine more exactly what the loss is, the following plan is recommended:--the two silver buttons are wrapped up each in grams of lead, and cupelled side by side with two other lots of grams of the original alloy. if now the two buttons i. and ii. weigh . and . , they will have suffered in this second cupellation an average loss of . milligrams. suppose the two fresh lots of alloy gave . and . of silver, the average loss on these would also be . milligrams. add this loss to each result, and take the mean; which is in this case . . if copper is present in the alloy as well as silver, it is necessary to add about the same quantity of copper to the checks as is supposed, or known, to be present in the assays. if the substance to be assayed is an alloy of silver and copper, first cupel . gram of it, with, say, grams of lead, and weigh the resulting button of silver, in order to get an approximate knowledge of its composition. suppose the button weighs . gram. we know that this is below the truth: for the sake of round numbers take it as . , and assume that the rest of the alloy ( . gram) was copper. two check pieces are then weighed out, each containing . gram silver and . gram of copper wrapped in grams of lead. of course the silver must be pure. and there is also weighed out two (or better, four) assay pieces each containing half a gram of the alloy wrapped in grams of lead. the whole lot are then cupelled as nearly as possible under the same conditions. with four assay pieces, the cupels should be placed close together in two rows of three across the muffle; the two check pieces are put in the middle cupels. suppose the buttons of silver got weighed as follows:-- check pieces i. . ii. . assay pieces i. . ii. . iii. . iv. . the average loss on the two check pieces is . milligrams, and the average result of the four assay pieces is . . add the average loss to the average result, and there is got the corrected result, . . and if . gram of alloy contain . of silver, will contain . of silver, and this is the degree of fineness. a correction for the loss in cupellation is always made in this way when rich alloys are being assayed; and in the case of rich ores it may be done after the manner of the first of the above illustrations. there is another method of working which relies more on experiment. this is to smelt the cupel as described further on (p. ), and to again cupel the resulting button of lead. the button of silver got in this second cupellation is added to that first obtained. it will sometimes, but not often, happen that the two buttons together will slightly exceed in weight the silver which was actually present. this is because of the retention in the buttons of a small quantity of lead. it has been stated that the proportion of lead thus retained may be as much as % of the silver present; this, however, can only be under exceptional conditions. a determination of the actual silver in the buttons got in the series of cupellations quoted on pages , , gave an average percentage of . , so that even with the larger buttons the effect of the retained lead would be only to increase the weight by about milligram. in the method of working with checks, the retained lead has no disturbing influence. ~the proportion of lead required~ for the cupellation of any particular alloy requires consideration. with too much lead the time occupied in the process is increased, and so is the loss of silver; on the other hand, too little lead is of greater disadvantage than too much. from to parts of lead are required for each part of silver alloy, or, if gold is present, about twice as much as this must be used. for the cupellation of gram of a silver copper alloy containing different percentages of copper, the following quantities of lead should be used:-- percentage of copper in alloy. lead required. grams " " " " - - " the alloy, in not too large pieces, is wrapped in the required weight of lead foil and charged into the cupel at once; or the lead may be put in first, and, when the cupellation has fairly started, the alloy may be added wrapped in tissue paper; or a portion of the lead may be first started and the alloy wrapped in the remaining lead and subsequently added. the cupellation of large quantities of alloy or of alloys which contain tin, antimony, iron, or any substance which produces a scoria, or corrodes the cupel, must be preceded by a scorification. the advantages of this are that the slag is poorer in precious metal than that found on a cupel and is more easily collected and cleaned; that larger quantities of metal can be treated, and that, even if the substance is in part infusible, or produces at the start a clinkery mass or scoria, the oxide of lead gradually accumulates, fluxes the solid matters, and produces a good final result; but if the oxide of lead by itself is not sufficient for the purpose, borax or some other flux can be easily added. if the button of silver got is very small its weight may be estimated from its size; but it must be remembered that the weight varies as the cube of the diameter. if one button has twice the diameter of another it is eight times as heavy and so on. scales specially constructed for measuring silver and gold buttons may be purchased; but it is much better to make the measurement with the help of a microscope provided with an eyepiece micrometer. if the length of the long diameter of a silver button be taken the following table will give the corresponding weight in milligrams:-- ------------+-----------++------------+--------- diameter. | weight. || diameter. | weight. ------------------------------------------------ . inch | . || . inch | . . " | . || . " | . . " | . || . " | . . " | . || . " | . . " | . || . " | . . " | . || . " | . . " | . || . " | . . " | . || . " | . . " | . || . " | . ------------+-----------++------------+--------- the weight of a corresponding button of gold is got by multiplying by . . these figures are based on those given by plattner, and apply only to buttons of such shape as those left after cupellation. a sphere of silver . inch in diameter would weigh . milligram, and a similar sphere of gold weighs . milligram. it is safer, however, to compare with a micrometer the diameter of the button whose weight has to be determined with that of a standard button of nearly equal size whose weight is known. the weights of the two buttons are proportional to the cubes of their diameters. this plan of working is described more fully in appendix b., page . ~calculation of the results.~--after deducting for the silver added, and correcting for the cupellation loss, the calculation is made in the usual way; reporting as so many parts per thousand in the case of rich alloys and as so many ounces and pennyweights, or better as ounces and decimals of an ounce, in the case of poor alloys and ores. in this last case, however, it is less fatiguing to refer to a set of tables which give, either directly or by means of simple addition, the produce corresponding to any weight obtained from certain given weights of the substance. the following table gives the produce in ounces and decimals of an ounce per ton of pounds:-- ------------+---------------------------------------------------------- | weight of ore taken. weight of |----------+----------+-----------+-----------+------------ metal got. | grams. | grams. | grams. | grams. | grams. ------------+----------+----------+-----------+-----------+------------ . | . | . | . | . | . . | . | . | . | . | . . | . | . | . | . | . . | . | . | . | . | . . | . | . | . | . | . . | . | . | . | . | . . | . | . | . | . | . . | . | . | . | . | . . | . | . | . | . | . . | . | . | . | . | . . | . | . | . | . | . . | . | . | . | . | . . | . | . | . | . | . . | . | . | . | . | . . | . | . | . | . | . . | . | . | . | . | . . | . | . | . | . | . . | . | . | . | . | . . | . | . | . | . | . . | . | . | . | . | . . | . | . | . | . | . . | . | . | . | . | . . | . | . | . | . | . . | . | . | . | . | . . | . | . | . | . | . . | . | . | . | . | . . | . | . | . | . | . . | . | . | . | . | . . | . | . | . | . | . . | . | . | . | . | . . | . | . | . | . | . . | . | . | . | . | . . | . | . | . | . | . . | . | . | . | . | . . | . | . | . | . | . . | . | . | . | . | . . | . | . | . | . | . ------------+----------+----------+-----------+-----------+------------ when, as in this table, the fraction of an ounce is expressed by two places of decimals, it may be reduced to pennyweights (dwts.) by dividing by . for example, . of an ounce is dwts. the fraction of a dwt. similarly expressed may be converted into grains with sufficient exactness by dividing by . thus, . ozs. equal oz. . dwts., or oz. dwts. grains. in england it is usual to report in ounces and decimals of an ounce. the way to use the table is best shown by an example. suppose a button of silver weighing . gram was obtained from grams of ore. look down the -gram column of the table, and select the values corresponding to each figure of the weight, thus:-- . = . ozs. to the ton . = . " . = . " ------ ----- . = . " add these together. the produce is . ozs., or ozs. dwt. to the ton. or, suppose an ore is known to contain . per cent. of silver. look down the -gram column, select the values, and add them together as before. . = . ozs. per ton . = . " . = . " ---- ------ . = . " this gives ozs. dwt. grains to the ton. the calculation becomes more complicated when, as is frequently the case, the ore contains metallic particles. these show themselves by refusing to pass through the sieve when the ore is powdered. when they are present, a large portion, or if feasible the whole, of the sample is powdered and sifted. the weights of the sifted portion and of the "metallics," or prills, are taken; the sum of these weights gives that of the whole of the sample taken. it is very important that nothing be lost during the operation of powdering. each portion has to be assayed separately. it is usual to assay a portion of the sifted sample, say, or grams, and to add to the produce of this its share of the "metallics." this way of calculating, which is more convenient than correct, is illustrated by the following example:-- weight of whole sample grams made up of sifted portions " " "metallics" " --- " twenty grams of the sifted portion, when assayed, gave . gram of silver. the whole of the "metallics" scorified and cupelled gave . gram of silver. since the grams assayed was - th of the whole, - th part of the . gram of silver (from the metallics) must be added to its produce. we thus get . gram ( . + . ). referring to the gram column, we get-- . = . . = . . = . . = . ------ ------ . = . ounces per ton. a more legitimate method of calculation is as follows:--calculate separately the produce of each fraction as if they were from different ores. multiply each produce (best stated in per cents.) by the weight of the corresponding fraction. add together the products, and divide by the weight of the whole sample. taking the same example for illustration, we have:-- _metallics._--weight gram. gram of it yielded . grams of silver. .'. produce = . per cent. produce multiplied by the weight is still ~ . ~. _sifted portion._--weight grams. grams of it yielded . gram of silver. .'. produce = . per cent. produce multiplied by weight ( . × ) is ~ . ~. add together; and divide by , the weight of the whole sample-- . . ------- ) . ( . . is the total produce of the ore in per cents. referring to the -gram column in the table we find . ounces to the ton as the produce. . = . . = . . = . . = . ------ . comparing this with the result calculated by the first method--viz., . , we see that that was . oz., or between and dwts. too high. with ores containing "metallics" it is of great importance to powder the whole of the selected sample without loss during the process; and of even greater importance to well mix the sifted portion, of which the last portions to come through the sieve are apt to be more than ordinarily rich through the grinding down of some portions of the metallic prills. ~remarks on cupellation.~--cupellation is at once the neatest and the most important of the dry methods of assaying. its purpose is to remove easily oxidisable metals, such as lead and copper, from silver and gold, which are oxidisable with difficulty. metals of the first class are often spoken of as _base_, and gold and silver as _noble_ metals. when lead is exposed to the action of air at a temperature a little above redness, it combines with the oxygen of the air to form litharge, an oxide of lead, which at the temperature of its formation is a _liquid_. consequently, if the lead rests on a porous support, which allows the fused litharge to drain away as fast as it is formed, a fresh surface of the lead will be continually exposed to the action of the air, and the operation goes on until the whole of the lead has been removed. silver or gold exposed to similar treatment does not oxidise, but retains its metallic condition; so that an alloy of lead and silver similarly treated would yield its lead as oxide, which would sink into the support, while the silver would remain as a button of metal. the porous support, which is called _a cupel_(fig. ), should absorb the slag (oxide of lead, etc.) just as a sponge absorbs water, but must be sufficiently fine-grained to be impervious to the molten metal. at first sight it appears difficult to filter, as it were, a fluid slag from a fluid metal; but an ordinary filter-paper damped with oil will allow oils to run through and yet retain the water; but damped with water it will allow water to run through and retain oils. similarly, fused slags damp and filter through a cupel, but the molten metal not damping it withdraws itself into a button, which is retained. although, of course, if the cupel is very coarse-grained the metal may sink into the hollows. copper, antimony, tin, and most other metals, form powdery oxides, which are not of themselves easily fusible, and it is necessary when these are present to add some solvent or flux to render the oxide sufficiently fluid. fortunately, oxide of lead is sufficient for the purpose; hence, mixed oxides of copper and lead, provided the lead is present in proper proportion, form a fluid slag. in separating copper from silver or gold, advantage is taken of this fact; for, although we cannot cupel an alloy of copper and silver, it is easy to cupel an alloy of copper, silver and lead. if, however, the lead is not present in sufficient quantity, the whole of the copper will not be removed, and the button of silver, still retaining copper, will be found embedded in a coating of black oxide of copper. copper oxidises less easily than lead does; and, consequently, the alloy which is being cupelled becomes relatively richer in copper as the operation proceeds. it is on this account that the ill-effects of the copper make themselves felt at the close of the operation, and that the oxide of copper is found accumulated around the button of silver. tin and antimony, on the other hand, are more easily oxidised; and the tendency of their oxides to thicken the slag makes itself felt at the commencement: if the button of alloy once frees itself from the ring or crust of unfused oxide first formed, the cupellation proceeds quietly, and leaves a clean button of silver in the centre. but in either case the cupellation is imperfect, and should be repeated with a larger proportion of lead. an unfused and, consequently, unabsorbed slag tends to retain small buttons of alloy or metal, and thus cause serious loss. there is a principle underlying many of the phenomena of dry silver assaying which the student should endeavour to understand; and which serves to emphasise and explain some facts which without an explanation may present difficulties. if a button of melted lead be covered with a layer of slag rich in oxide of lead, and a second metal be added, this other metal distributes itself between the metal and slag in proportions which depend mainly upon the ease with which it is oxidised, and to a large extent upon the relative quantities of material present. easily oxidisable metals such as zinc, iron, antimony and tin, will go mainly into the slag, and, if the proportion of the slag is large, very little will go into the metal. on the other hand, with metals oxidisable with difficulty, such as silver, gold, and platinum, the reverse holds true; nearly the whole of the metals will go into the lead, and very little into the slag. if, however, the slag be very rich, say in antimony, the lead will contain antimony; and, on the other hand, if the lead be very rich in silver, the slag will contain silver in appreciable quantity. copper, which is near lead in the facility with which it is oxidised, will serve for the purpose of a detailed example. the results of actual analyses of metal and slag formed in contact with each other are shown in the following table:-- ---------------------------+-------------------------- percentage composition | percentage composition of the metal. | of the slag. ----------+----------------+-----------+-------------- lead. | copper. | lead. | copper. . | . | . | . . | . | . | . . | . | . | . . | . | . | . . | . | . | . ----------+----------------+-----------+-------------- it will be seen from this table that the slag is always much richer in lead and poorer in copper than the metal with which it is in contact. the ratio of lead to copper in these five samples is:-- in the metal. in the slag. : : . : : . : . : . : : . : . : . assuming these figures to be correct, the following statement is approximately true. on oxidising an alloy of grams of copper and grams of lead, and pouring off the slag when grams of lead have gone into it, there will be a loss of (owing to the slag carrying it off) about . gram of copper. on repeating the operation, the next grams of lead will carry with them about . gram of copper; and on again repeating, grams of lead will remove . gram of copper. finally, the last gram of lead will carry with it . gram of copper, and there will be left a button of copper weighing . grams. the slag will have carried off altogether . gram of copper, which is per cent. of the metal originally present. with the more perfect exposure to the air, and quicker removal of the slag, which results from heating on a cupel, the loss would be heavier. karsten got by actual experiment on cupelling copper and lead in equal proportions, a loss of . per cent. going back to the example: if the slag were collected and fused with a suitable reducing agent so as to convert, say, half of it into metal, that half would contain nearly the whole of the copper (such a reduction is called "cleaning the slag"). on reoxidising this metal, another button of copper is formed which, added to the first, would reduce the loss from per cent. to, say, or per cent. and it is conceivable that by a series of similar operations, almost the whole of the grams of copper originally taken might be recovered. in practice the problem is (as far as the copper is concerned) not how to save, but how most easily to remove it; and since the removal of this metal is quicker from an alloy containing not too much lead, it is evident that two or three operations with small quantities of lead will be more effectual than a single treatment with a larger quantity. with those metals (tin, antimony, &c.) which pass quickly into the slag, the contrary is true; hence with these it is necessary to have enough lead present, so that the slag formed at the outset shall contain enough oxide of lead to make it fluid. as silver is so much less easily oxidised than copper, we should reasonably expect that the proportion of silver carried off in the oxide of lead would be considerably less than that of the copper indicated in the above example. indeed, there are one or two facts which tend to encourage the hope that the operation may be conducted without any loss. if a piece of pure silver foil is exposed on a cupel to air at the usual temperature of cupellation, it undergoes very little change; it does not even fuse; it loses nothing in weight, and does not oxidise. in fact, even if oxide of silver were formed under these conditions, it could not continue to exist, for it is decomposed into silver and oxygen at a temperature considerably below redness. on the other hand, oxide of silver is not reduced to metal by heat alone, when mixed with an excess of oxide of lead; while metallic silver is converted into oxide when heated with the higher oxides of lead, copper, and some other metals. that silver, and even gold (which is more difficult to oxidise than silver), may be carried off in the slag in this way, is in agreement with general experience. if grams of silver are cupelled with grams of lead, there will be a loss of about milligrams of silver, which is in round numbers - th of the corresponding copper loss; with grams of gold and grams of lead, the loss will be or milligrams, which is about - th of the corresponding silver loss. ~determination of silver in assay lead.~--scorify grams of the lead with . gram of powdered quartz or glass at not too high a temperature. when the eye has "closed in," pour; reject the slag, and cupel the button of lead. remove the cupel from the muffle immediately the operation is finished. weigh, and make a prominent note of the result in the assay book, as so many milligrams of silver contained in grams of lead. ~determination of silver in red lead or litharge.~--fuse grams of the oxide with from to grams of borax; and in the case of litharge with grams or with red lead grams of flour. cupel the lead, and weigh the button of silver. note the result as in the last case. ~determination of silver in argentiferous lead.~--be careful in taking the sample, since with rich silver lead alloys the error from bad sampling may amount to several parts per cent. cupel two lots of grams each, and weigh the buttons of silver. add to these the estimated cupel loss, and calculate the result. or wrap each button of silver in grams of assay lead, and re-cupel side by side with two fresh lots of grams each of the alloy. calculate the loss incurred, and add on to the weight of the two fresh buttons got. ~determination of silver in bullion.~--the remarks made under the last heading as to the importance of correct sampling apply with equal force here. make a preliminary assay by cupelling . gram of the alloy with gram of assay lead; calculate the percentage composition. refer to the table on page to find what weight of lead is required for cupelling gram of alloy. weigh out four lots of gram each, and wrap them in the required quantity of lead. make two check pieces by weighing up two lots of fine silver equal to that which you believe to be present in the assay pieces; add copper to make up the weight to gram, and wrap in the same quantity of lead as was used for the assays. [illustration: fig. .] prepare six cupels and charge them in the annexed order (fig. ), and cupel. guard against spirting. clean and weigh the buttons of silver. add the mean loss on the two check pieces to the mean weight of the four assay pieces; this multiplied by will give the degree of fineness. ~determination of silver in copper.~--the silver is best separated in the wet way before cupelling, but if the proportion is not too small, it can be found by cupellation. weigh up grams of the metal, wrap in grams of sheet lead, and cupel; when the cupellation has proceeded for fifteen minutes, add grams more lead, and continue till finished. weigh the button of silver. the cupellation loss will be five or six per cent. of the silver present. determine it by powdering the saturated portion of the cupel and fusing in a large cornish crucible with grams each of soda and borax, grams of fluor spar, and - / gram of charcoal. cupel the resulting button of lead, and add grams more of lead towards the close of the operation. deduct the weight of silver contained in the lead used from the weight of the two buttons, and calculate to ounces to the ton. in an experiment in which . gram of silver was present, the weight of the button from the first cupellation was . , and that of the button from the second, after correcting for the lead added, was . gram. ~determination of silver in galena.~ _by pot assay._--mix grams of the powdered ore with grams of red lead, grams of soda, and grams of borax, as also with from to grams of nitre. fuse and pour. clean the slag if the ore is rich. cupel the buttons of lead. make the usual corrections and calculate in ounces to the ton. _by scorification._--take grams of the ore, grams of lead, and . gram of borax. scorify, clean the slag by adding anthracite after the "eye" has closed in: cupel the button of lead. weigh the button of silver, make the necessary corrections, and calculate to ounces to the ton. the determination may also be made by cupelling the button of lead got in the dry lead assay. a sample of galena determined by the three methods gave the following results:-- by pot assay . ozs. per ton. " scorification . " " lead assay . " ~determination of silver in an ore.~ _by pot assay._--take grams of the powdered ore and mix with grams of soda, grams of red lead, and grams of borax, as also with from to grams of flour. fuse: pour. clean the slag by fusing with grams of red lead and two grams of flour. cupel the buttons of lead; weigh; make the necessary corrections, and calculate to ounces to the ton. _by scorification._--take grams of the powdered ore, grams of lead, and . gram of "soda" or borax. scorify. clean the slag by fusing in a crucible as in the pot assay. cupel, &c. _examples._--_by pot assay._--ore taken grams. silver got . gram silver from slag . " silver lost in cupellation . " ------ . " deduct silver in red lead . " ------ silver in ore . " = . ozs. per ton. _by scorification._--ore taken, grams. silver got. . gram silver from slag . " silver lost in cupellation . " ------ . " deduct silver in lead . " ------ silver in ore . " = . ozs. per ton. ~determination of silver in silver precipitate.~--this substance contains, in addition to metallic silver and gold, sulphates of lead and lime; oxides of zinc, copper, and iron; and more or less organic matter. the sample as received is generally free from "water at ° c."; and, since it rapidly absorbs water, care should be taken in weighing it. since it contains combined water it is not suited for scorifying; therefore the determination of silver and gold (fine metal) is made by pot assay. weigh up grams of the precipitate, mix with grams of litharge and gram of charcoal. melt in a crucible at a moderate heat and pour. detach the slag, replace in the crucible, and, when fused, add a mixture of grams of litharge and gram of charcoal. when the fusion is again tranquil, pour; and cupel the two buttons of lead. in a sample worked in this manner the mean of four determinations gave . gram of "fine metal"; deducting milligram for the silver contained in the oxide of lead, and adding milligrams for the cupellation loss, there is got . gram or . per cent. of silver (and gold) in the sample. ~determination of silver in burnt ores.~ _by pot assay._--roasted cupriferous pyrites containing small quantities of gold and silver comes under this heading. the following mixture will give a fluid slag which is heavy and tough when cold:-- ore. borax. sand. litharge. charcoal. mix; place in a large crucible; cover with salt; and melt down under cover. when fused drop in an iron rod for a few minutes, and about a couple of minutes after its withdrawal, pour the charge quickly into a large conical mould. the button of lead should weigh about grams. cupel and weigh the silver. the litharge may be replaced by red lead, in which case another gram of charcoal powder must be added. in our experience the results obtained by this method are about per cent. less than the actual content of the ore. the results of two assays, after deducting for the silver in the litharge used, were . and . milligrams; and a third assay, in which . milligrams of silver had been added, gave . , which, after deducting the added silver, leaves . milligrams. the average of the three results is . milligrams from the grams of ore. two lots of grams of the same ore treated in the wet way gave . and . milligrams of silver. burnt ores from spanish pyrites carry about . per cent. of silver. wet methods. silver is got into solution from its ores by attacking with nitric acid, but it is best, after dissolving, to cautiously add dilute hydrochloric acid, and to carefully avoid excess. if the quantity of silver is very small the solution is allowed to stand twenty-four hours, but, otherwise, it is warmed and filtered as soon as it clears. dry the residue and concentrate the silver in a button of lead by pot method or scorification, according to the amount of stony matter present. cupel the lead, and the resulting button will be free from all metals, except perhaps gold. it may be weighed; or dissolved in nitric acid, and the silver determined gravimetrically in the diluted and filtered solution. it is better to weigh the metal and afterwards to determine the gold in it, estimating the silver by difference. silver alloys are dissolved in dilute nitric acid (free from chlorides), diluted, and filtered. the solution is then ready for gravimetric determination. sulphuretted hydrogen precipitates silver (like copper), completely, even from fairly acid solutions. gravimetric determination. add dilute hydrochloric acid in small excess to the hot dilute solution, which must contain free nitric acid. heat and stir until the solution clears. decant through a small filter, and wash with hot water, acidulated at first with a little nitric acid if bismuth is suspected to be present. dry quickly, transfer as much as possible of the precipitate to a watch-glass; burn and ignite the filter paper, treating the ash first with two drops of nitric acid and then with one of hydrochloric, and again dry. add the rest of the silver chloride and heat slowly over a bunsen burner until it begins to fuse. cool and weigh. the precipitate is silver chloride (agcl) and contains . per cent. of silver. the moist precipitate is heavy and curdy; it is decomposed by direct sunlight, becoming violet under its influence. when heated it is yellowish; and, since it is volatile at a high temperature, it must not, in drying, be heated above its fusing point. the fused chloride can be removed from the crucible (to which it adheres strongly) by digesting with dilute acid and zinc. for the determination of silver in nearly pure bullion the following process is used:--weigh up . gram of the alloy. with this amount of alloy each milligrams of silver chloride formed is equivalent to degree of fineness, so that the weight of the silver chloride obtained (stated in milligrams and divided by ) will give the degree of fineness. transfer to a bottle (known as "bottles for the indian mint assay") and dissolve in c.c. of dilute nitric acid, then make up with water to c.c. and add c.c. of dilute hydrochloric acid. allow to stand a few minutes and then shake. fill the bottle completely with water, allow to settle, and syphon off the clear liquid; pour on more water, shake gently to break up the lumps, and again fill the bottle with water. invert over the mouth of the bottle a porous wedgwood crucible, somewhat similar to those used in gold parting. take firm hold of the crucible and bottle, and invert promptly so that the silver chloride may be collected in the crucible. allow to stand a little while for the precipitate to settle, and then carefully remove the crucible under water.[ ] drain off most of the water and break up the silver chloride with the help of a well-rounded glass rod. this greatly facilitates the subsequent drying. dry first on the water bath and then on the iron plate. remove the dried silver chloride, by inverting the crucible, and weigh it. as an example, determinations of silver in a coin carried out in this way gave:-- ( ) . gram agcl = . fineness. ( ) . " = . " ( ) . " = . " ~determination of silver in burnt ores.~--take grams of the ore and place in a large beaker of - / litres capacity, and cover with c.c. of hydrochloric acid. boil for half an hour until the oxides are dissolved and the residue looks like sand and pyrites; then add c.c. of nitric acid, and boil till free from nitrous fumes. dilute to litres with water, and pass a current of sulphuretted hydrogen till the iron is reduced, the copper and silver precipitated, and the liquor smells of the gas. this takes about one hour and a half. filter off the precipitate (rejecting the solution) and wash with warm water. dry and transfer to an evaporating dish, adding the ashes of the filter paper. heat gently with a bunsen burner until the sulphur burns, and then calcine until no more sulphurous oxide comes off. when cold add c.c. of nitric acid, boil and dilute to c.c. add c.c. of very dilute hydrochloric acid ( to ),[ ] stir well, and allow to stand overnight. decant on to a swedish filter paper, dry and calcine. mix the ashes with grams of litharge and gram of charcoal, and fuse in a small crucible. detach the button of lead and cupel. weigh and make the usual corrections. as an example, grams of ore treated in this way gave . milligrams of silver; deducting . for the silver added in the oxide of lead leaves milligrams obtained from the ore. another experiment on grams of the same ore to which milligrams of silver had been added gave . milligrams. deduct . for the silver added; this leaves . milligrams as the silver obtained from the ore. these give, as a mean result, . per cent., or . ounce per ton. ~determination of silver in commercial copper.~--for the method of doing this, with an example and experiment, see under the heading of _examination of commercial copper_. volumetric methods. there are two of these, one adapted for the determination of silver in alloys of approximately known composition, and the other of more general application. the first of these, generally known as "gay-lussac's" method is, as regards its working, perfect in principle; but it requires a practically constant quantity of silver, that is, one which varies by a few milligrams only in each determination. it is a confirmatory method rather than a determinative one. the other is known as "volhard's," and resembles in principle and method an ordinary volumetric process. ~gay-lussac's method~ is based on the precipitation of silver from a nitric acid solution by a solution of sodium chloride. the point at which the whole of the silver is precipitated being recognised by the standard solution ceasing to give a precipitate. the process depends for its success upon, ( ) the ease which silver chloride separates out from the solution leaving it clear after shaking, and, ( ), the cloudiness produced by the reaction of very small quantities of silver nitrate and sodium chloride. in working, a quantity of the sodium chloride solution equal to gram of silver is added at once to the assay; and, when the solution has been rendered clear by shaking, the residual silver (which should not exceed a few milligrams) is estimated with the help of a weaker solution of sodium chloride. the success in working evidently depends upon the accuracy with which the first addition of the salt solution is made. on this account the standard solution is run in from a special pipette capable of delivering a practically invariable volume of solution. it is not so important that this shall deliver exactly c.c. as that in two consecutive deliveries the volume shall not differ by more than . c.c. the dilute salt solution is one-tenth of the strength of that first run in, and c.c. of it is equivalent to milligram of silver. ordinarily it is run in c.c. at a time (and an ordinary burette may be used for this purpose), shaking between each addition until it ceases to give a precipitate. if many such additions have to be made the operation not only becomes tedious, but the solution also ceases to clear after shaking, so that it becomes impossible to determine the finishing point. if the assay contains less than one gram of silver the first addition of the dilute salt solution of course produces no precipitate. five milligrams of silver in solution ( c.c.) is then added, and the assay proceeded with in the usual way; milligrams of silver being deducted from the amount found. there is required for the assay a _standard solution of sodium chloride_, which is prepared by dissolving . grams of the salt (made by neutralizing carbonate of soda with hydrochloric acid) in water and diluting to one litre. c.c. of this is equivalent to gram of silver. the weaker solution of salt is made by diluting c.c. of the stronger one to one litre. one c.c. of this will equal milligram of silver, or . c.c. of the stronger solution. a _standard solution of silver_ equivalent to the dilute salt solution is made by dissolving gram of fine silver in c.c. of dilute nitric acid, and diluting with water to one litre. [illustration: fig. .] the solution of salt is standardised as follows:--weigh up . gram of fine silver and dissolve in c.c. of dilute nitric acid in a bottle provided with a well-fitting flat-headed stopper. heat on the water bath to assist solution, resting the bottle in an inclined position. when dissolved blow out the nitrous fumes with the help of a glass tube bent at right angles. run in from a stoppered pipette (as shown in fig. ) c.c. of the standard salt solution, and shake vigorously until the solution clears. fill an ordinary burette with the weaker standard salt solution, and run c.c. into the assay bottle, letting it run down the side so that it forms a layer resting on the assay solution. if any silver remains in solution a cloudy layer will be formed at the junction where the two liquids meet. this is best observed against a black background if a cloudiness is seen, shake, to clear the liquid, and run in another c.c. of salt, and continue this until a cloudiness is no longer visible. deduct . c.c. from the amount of the weaker sodium chloride solution run in. divide the corrected reading by , and add to the c.c. this will give the volume of strong salt solution equivalent to the silver taken. if the first addition of the weaker salt solution causes no cloudiness add c.c. of the silver solution from an ordinary pipette, shake, and then run in the weaker salt solution, working as before. these milligrams of silver added must be allowed for before calculating. as an example:-- . gram of fine silver was taken for standardising a solution and c.c. of the weaker salt solution were run in. deducting . and dividing by gives . c.c. to be added to the c.c. . : . :: : _x_ _x_ = . which is the standard of the salt solution. the method of working an assay may be gathered from the following example:--in the determination of silver in some buttons left after cupellation, it was assumed that these would contain . per cent. of silver. for the assay it was necessary to take a quantity that should contain a little more than . grams of silver; then . : :: . : _x_ _x_ = . to ensure a slight excess, there was taken . gram of the buttons, which was treated in exactly the same way as for the standardising. the quantity of the weaker salt solution required was c.c.; deducting . c.c., and dividing by , gives . c.c. of strong salt solution, which is equivalent to . gram of silver. this being obtained from . gram of alloy, is equal to . per cent., or . fine. ~the effect of temperature.~--the standardising and the assay must be done at the same time, since a difference of ° c. makes a difference of . c.c. in measuring the c.c. of strong solution of salt. it is always best to prepare a standard with each batch of assays. ~sulphocyanate method.~--volhard's process is based upon the precipitation of silver in nitric acid solutions with potassium sulphocyanate, the finishing point being the development of a reddish-brown colour, produced by the action of the excess of sulphocyanate upon ferric sulphate. the white sulphocyanate settles readily, leaving the liquor clear; and a persistent brown coloration in the liquid indicates the finish. the assay must be carried out in the cold; and water free from chlorides[ ] must be used. _the standard sulphocyanate of potassium_ solution is made by dissolving - / or grams of the salt (kcys) in water, and diluting to litre. c.c. are about equivalent to . gram of silver. _the standard silver nitrate solution_ is made by dissolving grams of fine silver in c.c. of dilute nitric acid, boiling off nitrous fumes, and diluting to litre. the _indicator_ is a saturated solution of iron alum, or a solution of ferric sulphate of equivalent strength made by titrating acid ferrous sulphate with potassium permanganate. use c.c. for each assay. the sulphocyanate solution is standardised by placing c.c. of the silver nitrate solution in a flask with c.c. of dilute nitric acid, diluting to c.c. with water, and running in the sulphocyanate until the greater part of the silver is precipitated; then adding c.c. of the ferric indicator, and continuing the titration until a reddish-brown colour is developed, and remains permanent after shaking continuously. the assay is similarly performed, the silver being used in the state of a nitric acid solution. the effect of variations in the conditions of the assay may be seen from the following experiments, in which c.c. of standard silver nitrate were used:-- ~effect of varying temperature~:-- temperature ° c. ° c. ° c. ° c. sulphocyanate reqd. . c.c. . c.c. . c.c. . c.c. ~effect of varying nitric acid~:--varying nitric acid has no effect, except that with a fairly acid solution the finishing point is somewhat sharper. nitric acid added c.c. c.c. c.c. c.c. sulphocyanate reqd. . c.c. . c.c. . c.c. . c.c. ~effect of varying bulk~:-- bulk c.c. c.c. c.c. c.c. sulphocyanate reqd. . c.c. . c.c. . c.c. . c.c. ~effect of varying ammonic nitrate~:-- ammonic nitrate gram gram grams grams sulphocyanate reqd. . c.c. . c.c. . c.c. . c.c. ~effect of varying silver~:-- silver added c.c. c.c. c.c. c.c. c.c. sulphocyanate reqd. . c.c. . c.c. . c.c. . c.c. . c.c. this method is valuable for determining silver in salts, alloys, and solutions, where no more than an ordinary degree of accuracy is demanded. it is easy, and applicable under most of the usual conditions. its greatest disadvantage is the brown coloration produced by the sulphocyanate when the assay is nearly, but not quite, finished; and the slowness with which this is removed on shaking up with the precipitate. this is worse with large quantities of precipitate, and if about gram of silver is present, it gives an indefiniteness to the finish which lowers the precision of the process to about in ; this is useless for the assays of bullion. one writer states that this inconvenience is due to portions of liquid being entangled in the precipitate, but it appears much more likely to be due to the action of the precipitate itself. in attempting to apply the process to the assay of bullion by working it on the principle of a gay-lussac assay, it was found that a very considerable excess of silver was required to complete the reaction. in these experiments c.c. of "sulphocyanate" (very accurately measured) was run into the solution containing the weighed portion of bullion (fine silver) and, after shaking the solution, was filtered. in the filtrate the remaining silver, if there should be any, was determined by the ordinary titration, but with "sulphocyanate" of one-tenth the strength. this final titration was quite satisfactory. the amount of silver precipitated by the first c.c., however, varied with the quantity of silver present as in the following series.[ ] silver present. silver precipitated. . gram. . gram. . " . " . " . " . " . " these, of course, preclude a method of the kind aimed at, and at the same time emphasise the importance of uniformity of work in the ordinary process. in the determination of chlorides in sea-water, dittmar used a combined method: precipitating the bulk of the silver as chloride, and after filtering, determining the small excess of silver by sulphocyanate. this modification answers admirably when applied to the assay of bullion. in the ordinary gay-lussac method, the precipitation of the bulk of the silver by the c.c. of salt solution leaves nothing to be desired, either as to ease in working or accuracy of result; the silver precipitate settles quickly, and leaves a clear liquor admirably fitted for the determination of the few milligrams of silver remaining in solution. but the method of determining this residual silver by adding successive small quantities of salt so long as they continue to give a precipitate is unsatisfactory, and, judged on its own merits apart from the rest of the process, could hardly escape condemnation. it is clumsy in practice, for the continued adding of small portions of salt solution is laborious and becomes impossible with more than a few milligrams of silver in solution. the proposed modification is simple; having precipitated the silver with the c.c. of salt solution, as described under gay-lussac's method (page ), shake till the liquor clears, and filter into a flask, washing with a little distilled water. add c.c. of "ferric indicator" to the filtrate and titrate with a standard "sulphocyanate solution" made by diluting the ordinary standard solution to such an extent that c.c. after diluting shall be equivalent to . gram of silver.[ ] calculate the weight of silver found by "sulphocyanate" and add it to the weight which c.c. of the salt solution will precipitate. an advantage of this modification is that an excess of milligrams may be determined as easily and exactly as . in standardising the salt solution, then, weigh up, say . gram of pure silver, dissolve and titrate. suppose . c.c. of "sulphocyanate" required; then these are equivalent to . gram of silver, ( c.c. = . ); the silver precipitated by the salt is . -. --_i.e._, . gram, which is the standard. ~application of the method to assays for arsenic.~--if silver nitrate be added to a neutral solution of an arsenate of one of the alkali metals, silver arsenate (ag_{ }aso_{ }), is thrown down as a dark-red precipitate. if, after adding excess of silver nitrate to insure a complete precipitation, the arsenate of silver be filtered off, the weight of the arsenic could be estimated from the weight of silver arsenate formed. but this may be done much more conveniently by dissolving the precipitate in nitric acid, and titrating with sulphocyanate; the silver found will be to the arsenic present as ( × ) is to . the mineral is best treated by the method given in the third paragraph on page ; but the solution, after being acidified with nitric acid, should be made exactly neutral with ammonia. a small excess of silver nitrate should then be added, and since acid is liberated in the reaction, the liquor must again be neutralised.[ ] the precipitate must then be filtered off, and washed with distilled water. then dissolve it in the paper by slowly running over it c.c. of dilute nitric acid. wash the filter with distilled water, collecting with the filtrate in a small flask. add c.c. of "ferric indicator" and titrate. if the sulphocyanate solution be made up with or grams of the potassium salt to the litre, and be then standardised and diluted, so that for c.c. it shall equal . gram of silver, (see p. ), then it will also equal . gram of arsenic (as). except for ores rich in arsenic, it will be better to work with a solution one half this strength. the standard as calculated from an experiment with pure silver should be checked by another using pure resublimed white arsenic, as_{ }o_{ }, which contains . % of the metal. the quantity of white arsenic taken, . or . gram, should contain about as much arsenic as will be present in the assays. it is converted into sodium arsenate by evaporating to a small bulk with nitric acid and neutralising with soda. the precipitation and titration of the silver arsenate should be exactly as in the assays. the difficulty of the method is in the neutralising; which has to be very carefully done since silver arsenate is soluble in even faintly acid solutions; one drop of nitric acid in c.c. of water is enough to produce an absolutely worthless result; and an excess of acid much less than this is still very prejudicial. the addition of a little sodium acetate to the solution after the final neutralising has a good effect. ~arsenic in mispickel.~--weigh up . gram of the finely-powdered ore, and place in a berlin crucible about - / or - / inch in diameter. treat with or drops, one drop at a time, of strong nitric acid, warm very gently, but avoid much heating. put on a thin layer of nitre, and rather more than half fill the crucible with a mixture of equal parts of soda and nitre. heat quickly in the blow-pipe flame, and when the mass is fused and effervescing, withdraw and allow to cool. boil out with water, filter and wash. insert a piece of litmus paper and cautiously neutralise with nitric acid, using ammonia to neutralise any accidental excess of the acid. add a gram or so of ammonium nitrate and silver nitrate in excess, neutralise again with ammonia and add two or three grams of sodium acetate. filter off the precipitate, wash and titrate. in the fusion care should be taken to avoid much effervescence (an excess of the soda mitigates this) and the operation should be stopped as soon as the whole has entered into fusion. colorimetric determination. there is, properly speaking, no colorimetric method, but the following, which is sometimes used, is based on similar principles. it is useful for the determination of small quantities of silver in substances which yield clear solutions with nitric acid. dissolve a weighed quantity of the substance in nitric acid, and dilute to a definite bulk. divide into two equal parts. to one, add a drop or two of dilute hydrochloric acid, stir and filter. to the other, add a similar amount of dilute acid, and then to the filtered portion run in from a burette standard silver nitrate ( c.c. = . milligram silver) until the solutions are equally turbid. calculate in the usual way. gold. gold occurs in nature chiefly as metal. it always contains more or less silver, and, in alluvial sands, &c., may be associated with platinum and iridium. gold is insoluble in hydrochloric or nitric acid, but is dissolved by aqua regia or by solutions of iodine, bromine, or chlorine. it is taken up by mercury, forming an amalgam, from which the mercury may be driven off by heat. when gold occurs in particles of any size, it is readily detected by its appearance, but when finely disseminated through a large quantity of rock, it is separated and detected by the amalgamation assay--described below--or by a process of washing somewhat similar to vanning, or by the following test:--powder and, if necessary, roast to grams of the ore, put on it three or four crystals of iodine and enough alcohol to cover it; allow to stand for half an hour; a piece of filter paper moistened with the liquid and burnt leaves an ash with a distinctly purple tint if any gold is present. it is better, however, to filter off the solution, evaporate, and ignite. then, either take up with mercury, and ignite the amalgam so as to get a speck of the metallic gold; or treat with a few drops of aqua regia, and test the solution with stannous chloride: a purple coloration indicates gold. ~amalgamation assay.~--this does not attempt to give the total produce of gold, but rather the quantity which can be extracted on a large scale; therefore it should imitate as closely as possible the process adopted in the mine or district for extracting the metal. take lbs of the ore in powder and roast; make into a stiff paste with hot water and rub up for an hour or so with a little mercury. wash off the sand carefully, and collect the amalgam. drive off the mercury by heat, and weigh the residual gold. it is best to cupel it with lead before weighing. in an experiment on a lot of ore which contained . gram of gold, . gram was obtained by the above process, equal to about - / per cent. recovered. with ores generally, the yield may be from to per cent. of the actual gold present. dry assay. the dry assay of gold ores resembles in its main particulars the dry assay for silver by the crucible method; and for much that is of importance in its discussion the student is referred to what is written under silver on pp. - . ~size of assay charges.~--gold ores rarely contain more than a few ounces, often only a few pennyweights of gold to the ton; consequently, the button of gold obtainable from such quantities of ore as may be conveniently worked by assaying methods is often so small as to require more than ordinary care in its manipulation. one milligram of gold forms a button of about the size of one of the full-stops on this page, and compared with a million similar particles of quartz (about four ounces), represents a produce of a quarter of an ounce to the ton: a proportion such as the assayer is frequently called on to determine. it is evident, therefore, that a charge of half an ounce or less of the ore, such as is usual with silver ores, would demand of the worker both skill and care in the handling of the minute quantity of gold to be obtained from it. fortunately the work is simple and precise, so that in practised hands and with only a -gram charge the assay of a -dwt. ore is practicable; with so small a charge, however, the result is barely perceptible on a sensitive balance: the button of gold should be measured under a microscope. it follows, therefore, that larger charges of say , , or even grams, have an advantage in that they lessen the strain on the worker's attention, and, except in the case of the poorest mineral, bring the button of gold within the scope of the balance. on the other hand, the inconvenience of the larger charges lies in the amount of fluxes and consequent size of the crucibles required to flux them. ~sampling.~--a further consideration in favour of the larger charges is the matter of sampling. in preparing his ore, the student should ask himself what reasonable expectation he has that the portion he puts in the furnace will be of average richness. the larger charges are likely to be nearer than the smaller ones to the average of the parcel of ore from which they are taken. in explanation of this, let us suppose a large heap of -dwt. ore, in sand of the coarseness of full-stops, and containing all its gold in particles of milligram, as uniformly distributed as care and labour in the mixing can accomplish. such a heap could not possibly occur in practice, but it will serve for purposes of illustration. now, one ton of the sand, however taken, would contain appreciably the same quantity of gold as any other ton. for a ton would contain about particles of gold; and even if two separate tons differed by as much as particles (which they are just likely to do), this would mean only a difference of or grains to the ton. on the other hand, two portions of lbs., which should contain on the average particles of gold, are likely enough to differ by particles, and this, calculated on a ton, means a difference of dwt. it is easy to see that something like this should be true; for on calculating the -lb. lot up to a ton, the deviation from the average, whatever it may be, is multiplied by ; whereas, if the ton were made up by adding -lb. lot to -lb. lot, up to the full tale, then a large proportion of the errors (some being in excess and some in defect) would neutralise each other. an average which is practically true when dealing with thousands, and perhaps sufficiently exact with hundreds, would be merely misleading when applied to tens and units. reasonable safety in sampling, then, is dependent largely on the number of particles of gold in the charge taken, and the risk of an abnormal result is less, the larger the charge taken. by doubling the charge, however, we merely double the number of particles. powdering finely is much more effective; for, since the weight of a particle varies as the cube of the diameter, halving the diameter of the particles increases their number eight-fold. if, now, we modify our illustration by assuming the particles to have only one-sixth the diameter of a full-stop (which would represent a powder of a fineness not unusual in ores prepared for assaying), we should multiply the number of particles by ( × × = ). we should then reasonably expect a -lb. parcel of the powder to give as safe a sample as a ton of the sand would give; and portions of a size fit for crucible work, say or grams, would be as safe as or -lb. samples of the coarser stuff. for example, grams of such powder would contain, for a -dwt. ore, about particles; and in the majority of cases the error due to sampling would be less than or grains to the ton, and would only occasionally exceed a pennyweight. with richer ores the actual deviation stated as so much to the ton of ore might be greater, but it would represent a smaller proportion, stated in percentage of the gold actually present, and would ultimately fall within the limits of unavoidable error. it will be seen that the size of the quartz particles has no direct bearing on the argument; and, in fact, the coarseness of the quartz only interferes by preventing the uniform mixing of the sand and by binding together several particles of gold; in this last case, particles so united must, of course, count as one larger particle. now, there are some natural ores in which the gold particles are all very small; with these fine powdering and mixing yields a product from which a sample may be safely taken. then, again, in "tailings," before or after treatment with cyanide, we have a similar material, inasmuch as the coarser gold has been removed by previous amalgamation. with these, it is not unusual to take the portion for assay without any further powdering, since they are poor in gold, and have already been stamped and passed through a sieve of say thirty holes to the inch (linear). but there are other ores, in lump showing no visible gold, which contain the gold in all possible degrees of fineness, from say prills of a milligram or so down to a most impalpable powder. the treatment of these cannot be so simple and straightforward. suppose a parcel of grams (say lbs.) of such ore in fine powder, containing on an average particle of milligram (the presence or absence of which makes a difference of . dwt. on the ton), others of about . milligram (each representing . dwt.), and others, which are too coarse to pass through an sieve, and having an average weight of . milligram (each . dwt.), and that the rest of the gold, equivalent altogether to ounces to the ton, is so finely divided that a charge of grams may be taken without any considerable risk of its interfering with the sampling. then in a -gram charge there would be one chance in twenty of getting the milligram particle, in which case the result would be . dwts. too high; on the other hand, if it were not present the result would on this account be . dwt. too low. of the ten . -milligram particles, it is as likely as not that one will be present, and its presence or absence would cause an error of . dwts., more or less. of the particles of . milligram, there would probably be from to , instead of , the proper number; this would mean a variation of . dwts. from the true proportion. so that the probable result would range about dwts. more or less than the - / ozs., which is the true produce, and there are possibilities of astounding results. it is true that the majority of the results would be well within these limits, and now and again the heart of the student would be gladdened by a beautiful concordance in duplicate assays; nevertheless, there can be no reasonable expectation of a good assay, and to work in this way, on a -gram charge, would be to court failure. the coarse gold must ruin the assay. the difficulty may be met by concentrating the whole of the coarse gold in a small fraction of the ore, by sifting and making a separate assay of this fraction. a portion of the ore, of about grams, is ground to a very fine powder and passed through an sieve, re-grinding when necessary, until only or grams is left of the coarser powder. this is mixed with fluxes and carried through as a separate assay. the sifted portion is _thoroughly mixed_, and a portion of it, say or grams, taken for assay. the weights of the two portions must be known, and care must be taken that nothing is lost in the powdering. the method of calculating the mean result from the two assays is shown on page . in this way of working there is no advantage in continuing the grinding until the coarser fraction is reduced to a gram or so--rather the contrary; and rubbing on until all the gold is sent through the sieve is to be distinctly avoided. the student must bear in mind that what he is aiming at is the exclusion of all coarse gold from the portion of ore of which he is going to take only a fraction. the question of the smaller sampling of gold ores has been dwelt on at considerable length, as befits its importance, in order that the student may be impressed with a sense of its true meaning. sampling is not a mystery, nor does the art lie in any subtle manner of division. it is, of course, absolutely necessary that the stuff to be sampled shall be well mixed, and the fractions taken, so that each part of the little heap shall contribute its share to the sample. moreover, it must be remembered that tossing about is a poor sort of mixing, and that everything tending to separate the large from the small, the light from the heavy, or the soft from the hard (as happens in sifting), must be avoided, or, if unavoidable, must be remedied by subsequent mixing. with a well-taken sample, we may rely on a great majority of our results falling within normal limits of error; but nothing can be more certain than that, in a moderately large experience we shall get, now and again, deviations much more considerable. these erratic assays can only be met by the method of working duplicates, which call attention to the fault by discordant results. such faulty assays should be repeated in duplicate, so that we may rest the decision on three out of four determinations. the likelihood of two very faulty assays being concordant is remote; but with very important work, as in selling parcels of ore, even this risk should be avoided, as concordance in these cases is demanded in the reports of two or more assayers. the following actual reports on a disputed assay will illustrate this: (a) ozs. dwt.; (b) ozs. dwts. grains; (c) ozs. dwts.; (c) ozs. dwts. grs. the mean result of several assays, unless there be some fault in the method, will be very fairly exact; and individual assays, with an uncertainty of in , may, by repetition, have this reduced to in or less. ~assay tons, etc.~--having decided on taking a larger or smaller portion, the exact quantity to be used will be either some round number of grams, such as or , easily calculable into percentage; or it will be that known as the "assay ton" (see page ) or some simple multiple or fraction of it, which is easily calculable into ounces. the reports, too, are at least as often made as ounces in the short ton of lbs., as on the more orthodox ton of lbs. now the short ton is equal to , . troy ounces; and the corresponding "assay ton" is got from it by replacing ounces by milligrams. the advantage of its use is that if one assay ton of ore has been taken, the number of milligrams of gold obtained is also the number of ounces of gold in a ton of the ore, and there is absolutely no calculation. even if half an assay ton has been taken the only calculation needed is multiplying the milligrams by two. on the other hand with a charge of two assay tons the milligrams need halving. where weights of this kind (_i.e._, assay tons) are not at hand they may be easily extemporised out of buttons of tin or some suitable metal, and it is better to do this than to array out the grams and its fractions at each weighing. the sets of "assay tons," however, are easily purchased. as stated on page , the assay ton for lbs. is . grams; and for the short ton, . grams. if, however, the round number of grams be used and the result brought by calculation to the produce on grams, the conversion to ounces to the ton may be quickly effected by the help of the table on page . as this table only deals with the ton of lbs., it is supplemented here by a shortened one dealing only with _the produce of grams_ and stating the result in _ounces troy to the short ton of lbs_. ~estimation of small quantities of gold.~--_by the balance._ in estimating minute quantities of gold there are one or two points, of importance to an assayer only in this assay, where they will often allow one to avoid the working of inconveniently large charges. one of these is known as "weighing by the method of vibrations." table for calculating ounces to the short ton from the yield of gold from grams of ore. ----------+---------+-----------+---------+-----------+--------- milligram.|ounces to|milligrams.|ounces to|milligrams.|ounces to | the ton.| | the ton.| | the ton. ----------+---------+-----------+---------+-----------+--------- . | . | . | . | . | . . | . | . | . | . | . . | . | . | . | . | . . | . | . | . | . | . . | . | . | . | . | . . | . | . | . | . | . . | . | . | . | . | . . | . | . | . | . | . . | . | . | . | . | . . | . | . | . | . | . . | . | . | . | . | . . | . | . | . | . | . ----------+---------+-----------+---------+-----------+--------- suppose a balance at rest in perfect equilibrium, with the pointer exactly over the middle point of the scale. let the scale be a series of points at equal distances along a horizontal line; then, if a small weight be placed on one pan, the pointer will deviate from its vertical position and come to rest opposite some definite part of the scale, which will depend upon the magnitude of the weight added. the law determining this position is a very simple one; the deviation as measured along the points of the scale varies directly as the weight added. for example, with an ordinarily sensitive balance, such as is used for general purposes, one milligram will move the pointer along, say, three divisions of the scale; then two milligrams will move it six divisions; half a milligram, one and a half divisions; and so on. of course, with a more sensitive balance the deviations will be greater. now the point at which the needle comes to rest is also the middle point about which it vibrates when swinging. for example, if the needle swings from the third to the seventh division on the right then [( + )/ ] it will come to rest on the fifth. in working by this method the following conventions are useful: always place the button to be weighed on the left pan of the balance, the weights on the right; count the divisions of the scale from the centre to right and left, marking the former + and the latter -; thus - is the fifth division to the left. then the position of rest is half the algebraic sum of two readings. for example, let the readings be to the right and to the left, then (+ - )/ = + . the mean division is the second division to the right. if the student will place himself in front of a balance and repeat the following observations and replace the figures here given by his own, he will have no difficulty in grasping the method. first determine the _bias_ of the balance; suppose the unloaded balance swings + . and - ; the bias then is ( . - )/ = +. or one-eighth of a division to the right. now having put on the button to be weighed let the readings be + . and + . , and ( . + . )/ = + . . then the effect of the button has been to move the pointer from +. to + . , or . divisions to the right; we should, therefore, add the weight equivalent of . divisions to the weights, whatever they may be on the right hand pan of the balance; if the divisions were to the left (- divisions) we should subtract. the value of division is easily determined. suppose the button in the example were a milligram weight, then we should have found that milligram = . divisions .'. division = . milligram. this method of working adds very considerably to the power of a balance in distinguishing small quantities. [illustration: fig. _a._] _by the microscope_.--the use of the microscope also is a real advantage in estimating the weights of minute buttons of gold where there is no undue risk in sampling, and where an error of say in on the quantity of gold is tolerable. for ores with copper, lead, zinc, &c., as well as for tailings rather poor in gold, this leaves a wide field of usefulness. the method is described on page , but the description needs supplementing for those who are not accustomed to the use of a microscope. the eye-piece of a microscope (fig. _a_, a) unscrews at _a_, showing a diaphragm at _b_, which will serve as a support for an eye-piece micrometer. this last, b, is a scale engraved on glass, and may be purchased of any optical instrument maker, though it may be necessary to send the eye-piece to have it properly fitted. when resting on the diaphragm it is in focus for the upper lens, so that on looking through the microscope, the scale is clearly seen in whatever position the instrument may be as regards the object being looked at. suppose this to be a small button of gold on a shallow, flat watch-glass, on the stage of the microscope. bring the button under the "objective" (_i.e._, the nose of the microscope), which should be about a quarter of an inch above the watch-glass; then looking through the instrument, raise the tube until the button of gold, or at least some dust on the glass, comes into focus. if the button is not in the field, rest the thumbs and index fingers, using both hands, on the edge of the watch-glass, pressing lightly but steadily, and give the glass a slow, short, sweeping motion; the button will perhaps appear as an ill-defined blackness, because not quite in focus. bring this into the centre of the field. raise or lower the microscope until the button appears with sharp outlines. if the scale does not cover the button, rotate the eye-piece; this will bring the scale into a new position. since the divisions over the button are less distinct than the others, it is best to read the latter. thus, in fig. _b_, there are divisions on one side of the button, and on the other, making altogether . the whole scale is , therefore the diameter of the button is divisions. the value of each division obviously varies with the magnifying power employed. with most microscopes there is a telescopic arrangement whereby the tube may be lengthened; if this be done and the button again brought in focus, it will be seen that, as measured on the scale, the button is much larger than before. it is evident, therefore, the micrometer must always be used in the same way. the method given in the appendix (page ), for finding the value of the scale when gold buttons are to be measured is easy and satisfactory. when the button of gold is so small that there is considerable risk of losing it in transferring to a watch-glass, it may be measured on the cupel, but for this purpose it must be well illuminated; this is best done by concentrating light on it with a lens, or with what comes to the same thing, a clean flask filled with water. [illustration: fig. _b._] most assayers, however, using a micrometer in this way, would like to know its absolute value. to do this, a stage micrometer must be purchased. this is like an ordinary microscope slide (fig. _a_, c), and when looked at through a microscope it shows (fig. _c_) lines ruled on the glass at distances of tenths and hundredths of a millimetre, ten of each, so that the full scale is . mm. in the case illustrated, divisions of the scale in the eye-piece are just equal to the . mm., therefore division equals . mm. a cube of this diameter would contain (. ×. ×. ) . cubic mm. the corresponding sphere is got by multiplying by . ; this gives . cb. mm. the weight of cb. mm. of water is milligram; and, since gold is . times as heavy as water (sp. g. = . ), the contents in cb. mm. must be multiplied by . . this gives . milligram as the weight of a sphere of gold measuring division. [illustration: fig. _c._] if every result had to be calculated in this way the method would be very laborious; but, having the figures for the first division, those of the others may be calculated by multiplying by the cube of the corresponding number. thus, for the third division ( × × = ), the content of the cube (. × ) is . cb. mm.; the content of the sphere (. × ) is . cb. mm.; and the corresponding sphere of gold (. × ) is . milligram. with the help of a table of cubes the whole calculation for or divisions may be made in half an hour, and the results preserved in the form of a table will simplify all future work. ~assay operations.~--the actual work of the assay resolves itself into three operations:--( ) the fusion of the ore and concentration of the "fine metal" (_i.e._, gold and silver) in a button of lead; ( ) the cupellation of the lead, whereby a button of fine metal is obtained; and ( ) the "parting" of the gold which separates it from the accompanying silver. the following description takes the order as here given, but the student, in learning the method, should first practise cupellation if he has not already done so; next he should practise the separation of gold from silver, taking known weights of fine gold (p. ), varying from . or . gram down to quite minute quantities, and not resting satisfied until a sensitive balance can barely distinguish between the weights of gold taken and found. it may be noted here that if he has not a flatting mill at his disposal, then for large buttons it is better to make an alloy with eight or nine parts of silver to one of gold, and attack it with acid without previous flattening, rather than accept the risk and labour of beating out a less easily attacked alloy to the necessary thinness with a hammer. it is only after a sense of security in gold parting has been acquired, that the attack of an ore can be profitably accomplished, and even then simple and easy ores should be first taken, passing on to others more difficult, either because of a more complex mineral composition or a difficulty in sampling. ~concentration of the fine metal in lead.~--the best flux for quartz, which makes up the earthy matter of most gold ores, is soda, and this is best added as carbonate or bicarbonate. by theory,[ ] grams of quartz will require . grams of the carbonate, or grams of the bicarbonate, to form sodium silicate, which is a glassy, easily-fusible substance, making a good slag. if the bicarbonate is used, and heat is applied gradually, steam and carbonic acid are given off at a comparatively low temperature, and the carbonate is left; at a higher temperature (about ° c., or a cherry-red heat) the carbonate fuses attacking the quartz, and giving off more carbonic acid; as the heat increases, and the attack on the quartz (which of itself is infusible) becomes complete, the whole mass settles down to a liquid sodium silicate, which is sufficiently fluid to allow the gold and lead to settle to the bottom. the fluid slag does to a certain extent dissolve some of the crucible, but not seriously. in a perfect working of this experiment, the first evolution of gases (steam and carbonic acid) should be gentle, so as to run no risk of its blowing the fine powder out of the crucible; and the heat at which the second evolution of carbonic acid is produced should be maintained until the reaction is completed, so that there may be little or no formation of gas in the fused mass to cause an effervescence which may force some of the charge over the edges of the crucible. of course, in practice the ideal fusion is not attained, but there is no difficulty in approaching it closely enough to prevent the charge at any time rising above the level it reached at first in the crucible, and this should be accomplished. it is usual with quartzose ores to rely mainly on the action of carbonate of soda, but not entirely. litharge is also used; it forms, on fusion with quartz, a silicate of lead, which is a yellow glass, easily fusible, and more fluid in the furnace than silicate of soda is. by theory, grams of quartz would require grams of litharge.[ ] the reaction takes place without evolution of gas, and in its working the only point is to so regulate the heat that the litharge shall not fuse and drain under the unattacked quartz, leaving it as a pasty mass on the surface. now, if in making up a charge for grams of ore, we took grams of bicarbonate of soda (equivalent to about grams of the carbonate), this being five-sevenths of grams (which by itself would be sufficient), leaves two-sevenths of the quartz to be fluxed by other reagents: two-sevenths of grams (say grams) of litharge would serve for this purpose. but if we used grams of borax, which has a fluxing action about equal to that of the litharge, then grams of the latter, or (making an allowance for the quartz being not quite pure) say grams, will suffice. the fluxes, then, for the grams of ore would be: bicarbonate of soda grams, litharge grams, and borax grams; we could decrease any of these, and proportionately increase either or both of the others, and still rely on getting a fusible slag, which is the whole of the function of a flux, considered simply as a flux. it should be remembered, however, that the slag is a bi-silicate or acid slag, and that its acid character is increased by increasing the proportion of borax. but in addition to the fluxes there is required about or grams of lead to collect the silver and gold. this is best added as litharge (say grams) and flour ( grams), or charcoal powder ( grams). see pages and . the full charge, then, would be: ore grams. bicarbonate of soda " litharge " borax " flour " these should be mixed, placed in a suitable crucible (a g battersea, round, will do), and heated, at first at a red heat, but finally much hotter, so as to get a fluid and clean slag. when the charge has been in tranquil fusion for some little time, take it out and pour it into an iron mould. when cold, detach the button of lead. the slag should be glassy, all through alike, and easily separable from the metal. with ordinary ores, this slag may be considered as free from gold. in an experiment in which milligrams of gold were added, the full amount was obtained from the lead produced by the first fusion. but in certain cases, more especially where large amounts of metallic oxides are present, the slag is not so clean, and with these the slag should be powdered, mixed with grams of litharge and of flour, and melted again; it is an advantage to add a small prill of say or milligrams of silver to the charge, as it insures a visible product in the cupellation. indeed, this last precaution is a good one to be taken wherever there is reason to expect very small buttons. it has the further advantage, that, if the quantity of silver necessary for inquartation is known, the right quantity may be added here, so as to save a subsequent operation. ~ores containing oxides of iron.~--of the metallic oxides likely to be present in a slag, oxide of iron is the most important. gold is occasionally found in a matrix of this substance, and in the assay of "concentrates" largely made up of pyrites, this oxide will be formed in the preliminary calcination. now, the lower oxide of iron (ferrous oxide, feo) is easy to deal with; fused borax will dissolve about its own weight of it, and a silicate of soda (such as makes up the bulk of a slag in a gold assay) will take up at least half as much. but the higher oxide (ferric oxide, fe_{ }o_{ }) is more refractory; even parts of borax yields a poor product, and slags with any considerable percentage of it are not satisfactory. a student attempting to recover gold from some hæmatite (in which there was about half an ounce of the metal), found in the slag nearly a gram of gold, although in the first fusion the slag appeared perfectly fluid. there is, however, no difficulty in getting good slags, even with large quantities of iron. for example, with grams of ferric oxide, of quartz, of borax, of soda,[ ] of litharge, and of flour, the result was quite satisfactory. so, too, was of quartz, of soda, of litharge, and of flour. it is well, however, in such cases to have an ample proportion of flux and to aim at a larger button of lead than usual by increasing the proportion of flour or charcoal (see also page ). a charge used on the randt for roasted "concentrates" (which we may roughly speak of as quartz and ferric oxide), is one assay ton (about grams) each of ore, soda, and borax, and one and a half assay ton of litharge and grams of charcoal. whilst, for the same material, from which most of the gold has been extracted by "chloridising," . tons each of ore, borax, and soda, of litharge, and grams of charcoal are needed. this quantity requires a large crucible (i battersea, round). in this the proportion of silicate of soda and borax counted together is to the oxide of iron as to , on the supposition that the quartz and oxide of iron of the ore are in about equal quantities; but, in the larger charge especially, much oxide of lead would also remain as a flux. ~ores containing sulphides.~--in assaying ores containing a large proportion of pyrites or mispickel, or both, the best plan is to take a portion and calcine so as to convert it into a product of the kind just considered. the weighed portion of ore should be placed in a clean crucible and be heated to incipient redness: with pyrites the first effect is to drive off about half the sulphur as vapour which burns as flame over the ore. at this stage care should be taken that there is no great increase of temperature, otherwise there may be more or less fusion, which would spoil the operation. when the sulphur flame ceases the solid sulphide of iron burns with visible incandescence and the charge should now be stirred with a flattened iron rod so as to expose fresh portions to the air. the top of the furnace must be open, so that air may have free access to the crucible. when stirring is no longer followed by visible burning the heat may be raised to full redness. the crucible is then lifted out (the stirrer still resting in it) and if the charge gives off no odour of burning sulphur it is shaken out into an iron mortar and mixed with the fluxes, taking care to clean the stirrer in the mixture. the charge is then replaced in the crucible in which the roasting was done and fused in the furnace. the resulting button of lead is cupelled for fine metal. ores rich in sulphides requiring this treatment are frequently "concentrates." for their assay take assay ton ( grams), calcine and mix with an equal weight of soda and of borax ( grams each), and half as much again of litharge ( . tons or grams), and with grams of charcoal or grams of flour. where the sulphides are present in smaller proportion ( per cent. or less), they may be taken as serving the purpose of flour or charcoal (see page ); the sulphur and iron are oxidised at the expense of the litharge with a consequent separation of lead as metal. if the proportion of sulphides is not sufficient to give a large enough button of lead, some charcoal or flour should be added. on the other hand, if they are in small excess and give a button of lead somewhat sulphury, _i.e._, hard and brittle, it may be remedied by the judicious addition of nitre; this last reagent, however, should not be used in large quantity. a plan much used to prevent sulphury buttons is to insert an iron rod or a nail in the charge in the crucible; the iron takes the sulphur forming sulphide of iron which in moderate quantity does not form a separate layer of matte but dissolves in the slag. a slag formed of grams of quartz, soda, and some borax, may take up in this way some or grams of sulphide of iron. if, however, an ore gives a layer of matte or speise, it is best to repeat the assay by the method of calcining before fusion. ~cyanide charges, etc.~--in assaying the "tailings" which are to be treated in a cyaniding plant the following charge is used: tailings assay tons or grams. litharge . " " soda . " " borax . " " the sand is assayed without any further crushing and the assay is made in duplicate. the residues after treatment with cyanide, differing from the tailings merely in being poorer in gold because of the extraction by the solution of cyanide, are run down with the same fluxes in the same relative proportions. but four charges of . assay tons (say grams) are worked, and two of the resulting buttons are scorified together and then cupelled, etc., so as to give duplicate assays on charges of assay tons. this is one of the cases in which it is desirable to add a small portion of silver before cupelling. in assaying the "cyanide liquors" for gold, assay tons of the liquor are measured out ( . c.c. for the ton of lbs., . c.c. for the other) and are evaporated to dryness in a lead dish weighing about grams. such a dish is easily extemporised out of a piece of lead foil, if the ordinary vessel is not at hand; but care must be taken that the lead is free from gold. the dish with the dried residue is then scorified and the resulting button of lead is cupelled. [illustration: fig. c.] in some cases the fusion of the ore may be replaced by a treatment with solution of cyanide of potassium and the gold recovered from the solution in the way just described. for this purpose the ore should be in not too fine powder, otherwise there will be great difficulty in filtering; a sand which will pass a sieve and having no large proportion of very fine stuff will do. not less than grams should be taken; and as an extraction apparatus a bell jar capable of holding half as much again may be used. such a jar may be extemporised by cutting off the bottom of a bottle by leading a crack around it with a red hot poker; or a lamp chimney will serve the purpose. the smaller mouth of the jar is closed by a perforated cork provided with a clipped tube after the manner of a burette (see fig. c). in the jar, just over the cork, put a plug of loose asbestos or glass wool, or a piece of sponge to act as a filter; a layer of broken glass, coarse at the bottom and fine at the top, will serve the same purpose. on this, place the charge of ore to be extracted. prepare a solution of cyanide of potassium in water, with or grams of the salt to the litre. it may be that the whole point of the assay depends on the solution being of a definite strength; as, for example, where the relative efficiency of solutions of different strengths is being determined, when it will be best to estimate the quantity of cyanide of potassium in the dilute solution by the method given at the end of this article (page ). pour the cyanide solution on to the ore, letting the first portions to come through run into the beaker, but as soon as the ore is thoroughly wetted close the clip and allow to stand for several hours. then, opening the clip, run through more cyanide solution and then water, so as to wash the gold-carrying liquor thoroughly into the beaker. it is no matter if the liquor is a little bit turbid; transfer it to a lead dish, evaporate, scorify, and cupel in the usual fashion. the assay of gold-zinc slimes, which is the precipitate formed by zinc acting on cyanide solutions of gold, may be made by wrapping or grams in grams of sheet lead and scorifying, cupelling, &c. the amount of impurity in the stuff varies greatly; it is usually calcined and mixed thoroughly with soda per cent., borax per cent., and sand per cent., and melted in graphite pots. the buttons of bullion obtained are afterwards remelted with borax and run into bars, the fineness of which varies from to thousandths. the bars are sampled by chipping off diagonally opposite corners: or better, by drilling, the drillings being freed from pieces of steel with the help of a magnet. ~cupellation.~[ ]--the cupellation of lead for gold differs very little from that of lead carrying silver. when the gold is accompanied by a larger proportion of silver, and both have to be determined, the cupellation must be conducted exactly as in a silver assay, the usual precautions being taken to moderate the temperature so as to lessen the cupellation loss and to promote a slow and undisturbed solidification in order to avoid spirting. if, however, the gold predominates the finish should be effected at a higher heat, as the melting-point of gold is ° higher than that of silver. the bad effect of a higher temperature in increasing the cupellation loss need hardly be considered in the case of such small buttons of gold as are obtained in assaying gold ores, as any loss there may be is hardly appreciable by the balance. with larger quantities of gold, however (as in assaying gold bullion), this loss becomes important; and it is therefore necessary to very carefully regulate the temperature of the muffle so as to minimise the loss. ~the cupels~ are made of well-burnt bone-ash, of the fineness of coarse wheat flour, moistened with one-twelfth its weight of water and compressed into shape in suitable moulds. the moulds sold for this purpose are often of unsuitable shape. since lead has a specific gravity of over , a cup to hold from to grams of molten lead need not have a capacity of more than about c.c. a hollow about inch across and / inch deep is sufficient; and the body of the cupel to absorb this weight of lead should itself weigh from to grams. the button of lead in a gold assay may be twice as heavy as this. for these larger buttons a hollow - / inch across and / inch deep will be sufficient. if these larger cupels are not at hand the larger buttons will have to be reduced in size by a scorification before cupelling. in some cases this preliminary scorification is advantageous or even necessary: this may be because the lead is hard and impure, or it may be that a very small button of gold is expected. in the latter case it is best to scorify the lead down to something less than gram, and to perform the cupellation on a specially prepared small fine cupel. these small cupels are best made by grinding the unsaturated portion of a used cupel to a fine powder, and compressing the dry powder into a small berlin crucible or scorifier; the face should be made quite smooth by pressure from a pestle. on such cupels a small speck of gold (less than . milligram) will be left in a good shape and easily visible; but the cupel must be withdrawn from the muffle as soon as the cupellation is finished to make sure of always getting the button in good condition. in places, such as mints, where large numbers of bullion assays are regularly made a special form of cupel is used so that not less than six dozen assays may all be cupelled at the same time in a muffle of ordinary size. these cupels are square blocks, a little less than inches across, and a little more than three quarters of an inch deep. each block carries four hollows of about . inch across and . inch deep. a muffle, on a floor space of inches by , would take of these blocks abreast and deep, and thus provide the means for assays.[ ] cupels made with wet bone-ash should be slowly dried; and if in the muffle they can be slowly brought to an orange-red heat it is all the better. under no circumstances must the lead be placed on the cupel before the latter has been so thoroughly heated that it can no longer give off steam or gas of any kind. for this gas bubbling through the molten metal spatters it, thus spoiling one assay and throwing doubt on all the rest. again, the risk of freezing at the start is much greater with a cupel which has not been properly heated. the best plan is to do all the cupellations in batches. after the muffle has cooled down for the withdrawal of the last batch, and the old cupels have been taken out, the new cupels for the next batch should be put in their place. the furnace should then be stoked and made ready for the next cupellations; by the time the furnace is ready the cupels will be ready also. there should be no unnecessary handling of the cupels once they have been placed in the muffle. ~the cupellation temperature for gold~ is an orange-red heat or perhaps a little hotter. beginners, who are apt to overheat their furnace, should avoid a heat which can properly be called yellow. dr. t.k. rose[ ] has determined the temperature of a muffle during the cupellation of gold-silver alloys at the royal mint. in one muffle the temperature ranged from ° to ° c.; the lower temperature was of course in the front of the muffle. in another it ranged from ° to °, and here the muffle appeared to the eye "decidedly cooler than usual." the alloy left after cupelling was made up of part of gold to - / parts of silver, and was fused at °; hence the usual temperature of cupellation was, say, ° or ° above the melting-point of the residual metal. to obtain some real knowledge as to the meaning of these figures, the student should prepare pointed pieces of the following metals: silver, which melts at °; gold, which melts at °; and an alloy, half silver, half gold, which melts at °. these should be placed on clean cupels in a muffle almost entirely closed; the temperature should be very slowly raised, and the appearance of the muffle when each metal begins to melt should be carefully noted. the cupelling temperature in dr. rose's experiment was as much above the melting-point of gold as this is above that of the silver-gold alloy. the _finish of the cupellation_ of gold or gold-silver alloys is practically the same as with pure silver; there is the same thinning out of the litharge into a luminous film which becomes iridescent before the brightening. but the danger of spirting decreases as the proportion of gold becomes greater, and disappears when the gold is much over per cent. nevertheless it is well to let such buttons become solid undisturbed and protected from draughts in the body of the muffle. this means closing the muffle and allowing the furnace to cool down somewhat before withdrawing the cupels. buttons solidified in this way are more malleable than when they are withdrawn promptly on the finish of the cupellation. this is important with large buttons, as in a bullion assay. on the other hand, very small buttons, especially such as have to be measured rather than weighed, should be withdrawn as soon as the luminous film has disappeared. for when this is done the button can be loosened from the cupel by merely touching it with the point of a pin, and is then safely and easily transferred to a watch glass by touching it with the head of a pin which has been moistened. it adheres to this, and if the pin is not too wet comes off at once on touching the glass, or in any case will do so on gentle warming. molten gold, with little or no silver, has a peculiar colour which is easy to recognise; it is more globular than a button of silver of the same size would be, and it shows less adhesion to the cupel. just after becoming solid it glows beautifully, and this is so marked that it is a valuable help in finding the position of a button when it is more than ordinarily minute. if the button left from cupellation is yellow it is at least half gold, and a rough guess as to the proportion of gold may be made from its yellowness; the rest of the metal is generally silver. the presence of platinum or one of the platinum group of metals makes the surface of the button dull and crystalline. the native alloy of osmium and iridium does not alloy with gold, however, but falls to the bottom of the molten metal. it shows itself in the subsequent parting as a black spot or streak on the under surface. the buttons are removed from the cupel with a pair of pliers and then brushed to remove adherent litharge and bone-ash. some assayers advise cleaning by dipping in warm dilute hydrochloric acid followed by washing in water and drying. the button is next weighed. when the quantity of silver obtained is not required to be known the weighing may sometimes be omitted. the next operation in either case is parting either with or without a previous inquartation. _the loss of gold in cupellation_ is by no means always inconsiderable. in three cupellations of gram of gold with grams of lead made purposely at a very high temperature the cupel absorbed . , . , and . milligrams of gold. hence at a high temperature there may easily be a loss of more than half a per cent. of the gold. in ten cupellations with the same quantities of gold and lead, but at an ordinary temperature, the gold recovered from the cupels varied from . to . milligrams, and gave an average of . milligrams. in round numbers the cupellation loss of pure gold is . per cent. but if the gold be alloyed with _silver_ the loss is diminished, as is shown by the following experiments. gold, . gram, was cupelled with grams of lead and varying amounts of silver, and the cupels were assayed for gold with the following results: silver in the alloy . gram . gram . gram gold in the cupel . milligram . milligram . milligram these, calculated on the . gram of gold, give the loss as . , . and . per cent. respectively. the effect of _copper_, on the other hand, is to increase the cupellation loss, which, silver being absent, may from this cause rise to . per cent., even when the temperature is not excessive. in the ordinary assay of gold-copper alloys a constant weight of the alloy is always taken; hence as the weight of copper in a cupel charge increases, the weight of gold decreases. the silver, on the other hand, is always very nearly two and a half times as much as the gold, whatever its quantity may be. but the cupellation loss is smaller with less gold and greater with more copper, and it so happens in these assays that these two opposites nearly neutralise one another. mr. w.f. lowe[ ] found the gold recoverable from the cupels on which grains of gold bullion had been treated varied only between . and . grain (_i.e._ from . to . per cent. of the bullion treated), although the quality of the bullion varied from to carat.[ ] but in the poorest bullion there was only . grains of pure gold, while in the richest there were . grains; yet each lost on the cupel the same weight of gold, viz., . grain. when reckoned in percentages of the actual gold present the losses are . per cent. and . per cent. respectively. the heavier percentage loss is mainly due to the increased quantity of copper. as with silver so with gold the predominant cause of the cupellation loss is the solution of the metal in the molten litharge which passes into the cupel. three lots of gram of gold cupelled each with grams of lead repeatedly, so as to make cupellations in all, lost in actual weight . milligrams. the gold recovered from the cupels amounted altogether to . milligrams. this shows that, compared with the absorption by the cupel, the other causes of loss are inconsiderable. the loss of gold by _volatilisation_ is, however, a real one. the dust from the flues of assay furnaces has been tested on several occasions and found to contain gold, though in small quantity. thus mr. lowe found . per cent. of silver and . per cent. of gold in such a material. the lead volatilised from a gold bullion assay would need to be ten times as rich as this to account for a loss of gold equal to the hundredth part of a milligram. dr. rose, in the paper already quoted, believes that on a . gram charge of standard bullion the loss from volatilisation is not less than . nor more than . milligram of gold. by way of conclusion it may be said that the cupellation loss of gold is about . per cent., and that it is largely met or even over corrected by a compensating error due to silver retained in the gold after parting. ~inquartation.~--the method of separating the gold from the silver in gold-silver alloys by boiling with nitric acid does not act equally well in all cases. an alloy half silver half gold, rolled to thin sheet and boiled for half an hour with nitric acid, may still retain more than two-thirds of its silver. an alloy of part gold and . parts of silver gives up practically the whole of its silver under similar treatment. the gold is left in a coherent, though easily broken, sheet retaining the shape of the original alloy. the gold thus left is quite spongy and porous, so that the acid can penetrate into its innermost portions. but if the silver is in large excess in the alloy, the removal of the silver is less complete, and the residual gold, instead of holding together in a form easy to manipulate, falls to a powder which requires care and time in its treatment. the older assayers, therefore, added silver to their gold in such proportion that the alloy for parting should be one quarter gold to three quarters silver. this operation they called _inquartation_. the modern practice is to aim at getting an alloy with - / parts of silver and part of gold. in gold bullion assays this proportion should be obtained with fair exactness. and in the parting of such gold buttons as are obtained in assaying ores it is well to aim at this proportion, though absolute precision is not a matter of importance. if the button left on cupelling the lead from an assay of an ore appears white, it is best to assume that it already contains at least a sufficiency of silver, in the absence of any knowledge to the contrary. this will be true in almost all cases. but if, on parting, it does not lose at least two-thirds of its weight, this indicates that the assumption was not justified; and also what quantity of silver must be added to the button before again attempting to part. generally the fault will be in the other direction; the silver will be in excess and the gold will break up and demand very careful treatment. if, however, such a button is yellow, then, from its weight and depth of colour, a rough estimate can be made of how much gold is contained in it. silver must be added to make the total weight - / times as much as that of the gold supposed to be present. thus, if the button weighs milligrams and is supposed to contain milligrams of gold, then multiplied by - / is ; the button must, in such case, be made up to milligrams by adding milligrams of silver. in judging of the quality of the gold button, no ordinary error will very seriously affect the result. if, in the example just given, the quantity of gold present was really or even milligrams of gold, the resulting alloy would still have been suitable for such partings. in fact, in routine assays, where the quantity as well as the quality of the gold is known within fair limits, it is often the custom to add the silver for inquartation to the lead during the first cupellation. but in the assay of rich gold alloys such approximate work will not do. if the composition is not already known with a fair degree of accuracy _preliminary assays_ must be made. weigh up two lots of milligrams of the alloy and wrap each in grams of lead. to one add milligrams of silver. cupel both. the button containing the added silver must be flattened and boiled with c.c. of nitric acid; and the resulting gold must be washed, dried, ignited and weighed. this, in milligrams, gives directly the percentage of gold. the weight of the other button gives the percentage of gold and silver; the difference between the two gives the percentage of silver. the rest will, perhaps, be copper. the composition of the alloy being known, or having been determined as just described, the calculation of how much silver must be added is fairly simple. the following is an example. suppose the bullion contains per cent. of gold, per cent. of silver and per cent. of copper, and that . gram of it is to be taken for an assay. the . gram, then, will contain gold . gram silver . " copper . " but the total silver required is . gram × . . this equals . . allowing for the . gram of silver already present, . gram of silver must be added. the silver is incorporated with the gold, and at the same time the copper is eliminated, by cupelling with sheet lead. how much sheet lead must be used will depend partly on how much bullion is taken, partly on how much copper it contains. four grams of lead will do for a . gram charge; and for a . gram charge, grams may be used. but with per cent. of copper these amounts should be doubled; with per cent. of copper they should be trebled; and with over per cent. of copper four times as much lead should be used. for small buttons of gold as little lead as may be relied on to start cupelling may be taken; the lead may conveniently be in the form of little cups made by folding lead foil on a piece of glass rod. with a large number of bullion assays systematically worked and checked a simple plan would be to always use the quantity of lead required by the alloy containing most copper which turns up for assay. this weight, cut out of lead foil, would be kept in stock folded into little bags ready to receive the bullion and silver. the silver used for inquartation must, of course, be free from gold and is best prepared by the assayer who is to use it (see p. ). it should not be in long strips or angular pieces likely to perforate the lead in which it is folded. when wrapped in the lead it should be in the middle and should make as compact a parcel as possible. each little parcel, as completed, should be placed on a tray in its properly numbered compartment. its position here should correspond to that it will occupy in the muffle and eventually in the cupel tray. the cupellation must be made with all the requisite precautions. a good smooth malleable button is needed for the next operation, which is known as flatting. [illustration: fig. .] ~flatting.~--small buttons, such as are got in assaying most gold ores, are placed on a polished steel anvil and flattened by one or two blows with a hammer. the flattened discs are heated to dull redness on a clean cupel and are then ready for parting. somewhat larger buttons may be similarly treated, but they should be annealed (_i.e._ heated to redness and allowed to cool) during the flattening. the silver-gold alloy left from the cupellation is soft and bends like lead; but after hammering or rolling it becomes harder, gets a spring in it like a piece of mainspring and cracks or splits somewhat easily. there should be no cracks or stripping or even roughness on the flattened metal, since such defects may cause the loss of small particles either during the flattening or in the subsequent treatment with acid. the softness of the metal is restored by heating. in bullion assays the flatting of the buttons requires care and practice for its skilful working. the strips of alloy for parting should be of uniform thickness and condition so that the action of the acid shall be equal in all cases. the button is taken from the cupel, cleaned and placed on the anvil: it is then struck a heavy blow which widens it to about / inch in diameter; this blow is followed by two others, one a little in front, the other behind, which lengthen the disc and give a very blunt roof-like slope to its upper face. it should then be annealed. this may be done by putting it in a just red-hot scorifier heated in a muffle: it very soon attains the right heat and may then be transferred to a cold scorifier; the hot scorifier should be put back into the muffle. the softened disc is then taken to the rolls (fig. ). the rolls are loosened until the disc can be pressed between them. looking through the interval between them the rolls should appear exactly parallel; if they are not, one adjusting screw should be loosened and the other tightened until parallelism is obtained. the rolls are now turned and the disc should be drawn through without any great effort. beginners are apt to err by trying to do too much with one turn of the handle. it is easy to stop whilst the rolls are only just gripping the metal and then to bring the disc back by reversing the action. if the disc was originally level and the rolls are parallel, the metal will appear as a strip which has been merely lengthened. if the rolls are tighter on one side the strip will be bowed; the tighter side will correspond with the outer curve of the crescent. a mistake of this kind may be amended by passing the strip through the rolls the other way, so as to reverse the irregularity and so straighten the strip. the screw on the looser side should then be tightened until parallelism is obtained; after which more care should be taken to tighten the two screws equally. the rolling should be stopped when the strip is or inches long and of the thickness of an ordinary visiting card. the strip should be annealed during the rolling and again at the finish. ~parting.~--the thin sheet of metal is dropped into hot dilute nitric acid and boiled for five or six minutes after the brisk action of the acid on the metal has ceased. at this stage nearly all the silver has gone into solution as nitrate of silver and the acid is charged with this salt. this acid is poured off and the residual metal is again boiled for from to minutes with a second lot of stronger acid. this leaves the gold almost pure, though it may still retain from . to . per cent. of silver. treatment with the first acid only would probably leave three or four times as much. the _nitric acid_ used should be free from hydrochloric, sulphuric, iodic and telluric acids. in testing it for the first of these add nitrate of silver and dilute with distilled water; there should be no turbidity. in testing for the others evaporate three lots in dishes over a water-bath. test one for sulphates by adding water and barium chloride. test another for iodates by taking up with a little water, adding a few drops of starch paste and then dilute sulphurous acid solution a little at a time; there should be no blue colour. test the third for tellurium by heating with c.c. of strong sulphuric acid until dense fumes come off; allow to cool considerably; a piece of tin foil added to the warm acid develops a fine purple colour if only a trace of tellurium is present. the presence of lower oxides of nitrogen, which impart a brown colour to the acid, is objectionable; they, however, are removed by boiling the diluted acid before using it for parting. it is usual to keep a stock of the acid suitably diluted to the two strengths required for the parting. these are known as the parting acids. the _first parting acid_ is the weaker and is used in the first attack on the metal. the specific gravity generally recommended for it is about . . it may be prepared either by diluting the strong acid with about its own volume of distilled water, or by suitably diluting the second parting acid which has been already used in an assay; the small proportion of silver this contains is not harmful for this purpose. the _second parting acid_ has a specific gravity of about . , and may be made by diluting the strong acid with half its volume of distilled water. _parting in flasks._--flasks are most convenient for the larger partings, as in bullion assays; and should always be used for this purpose unless some of the special parting apparatus, like that used in mints, is available. many assayers use flasks, though of a smaller size, for the ordinary partings in assaying gold ores. the flasks are either bulbs with long necks (fig. ) which ought to be heated on rose burners of special construction; or they are small flat-bottomed conical flasks which may be conveniently heated on a hot-plate and are, in this respect, much easier to deal with in general work. the following instructions apply to the parting of an alloy containing a few decigrams of gold together with the proper proportion of silver. [illustration: fig. .] the strip from the rolls, after being softened by annealing, is folded on itself on a glass rod into a roll or cornet. it should be so plastic that it will retain the shape thus given it and not spring open on removing the pressure of the fingers. about c.c. of the first parting acid are placed in a -ounce conical flask and heated to boiling; the flask is then withdrawn, and tilted a little to one side, whilst the cornet is cautiously dropped into it; there will be a sudden issue of hot vapours and a prompt withdrawal of the hand is advisable. the flask is replaced on the hot plate and the acid is kept boiling for or minutes. the flask is then withdrawn and the acid diluted with about an equal volume of distilled water. if the flask has a thick glass band around its neck, a little way down,[ ] care must be taken to use hot water, for any sudden chill will certainly crack the flask where it is thus thickened. the liquor is carefully decanted into a clean beaker and is then thrown into a jar marked "waste silver." about c.c. of the second parting acid, heated to boiling, is then poured into the flask, which is then replaced on the hot plate. the boiling is continued for or minutes or even longer. at this stage bumping has to be specially guarded against; after a little experience it is easy to see when this is imminent and the flask should be withdrawn to a cooler part of the plate; it is better to prolong the heating at a temperature below boiling than to run the risk of disaster. some of the older writers, however, are rather insistent on vigorous boiling with large bubbles. the addition of a small ball of well-burnt clay of about the size of a pea has been recommended, as it lessens the tendency to irregular and dangerous boiling. at the end of the treatment with the second acid the flask is withdrawn from the plate and the acid is diluted with an equal volume of distilled water. the liquor is carefully decanted into a beaker, and then poured into a jar or winchester marked "acid waste"; it serves for making the first parting acid. the flask is then washed twice with hot distilled water; the washings must be carefully decanted from the gold. the flask is then filled with water. a parting cup (size b) is then placed over its mouth, like a thimble on the tip of a finger. this cup is of unglazed porous earthenware of such texture that it absorbs the last few drops of water left on drying; and with a surface to which the gold does not adhere even on ignition. the gold should fall out cleanly and completely on merely inverting the cup over the pan of the balance. the flask and cup are then inverted so that the flask stands mouth down in the cup; a little of the water from the flask flows into the cup, but only a little. the gold falls steadily through the water into the cup. when time has been allowed for even the finest of the gold to have settled into the cup, the flask is removed. this is easiest done under water. the cup, with the flask still resting in it, is dipped under water in a basin; as soon as the neck of the flask is immersed the crucible can safely be drawn away from under it and then lifted out of the water. the flask should not be taken away first, for the rush of water from it may easily sweep the gold out of the cup. the water in the cup is then drained off and the cup is dried at not too high a temperature; for if the last drop or two of water should boil there is danger of spattering the gold out of the crucible. when it is dry, the cup is heated on a pipe-clay triangle over a bunsen burner, or on a slab of asbestos in a muffle, to a dull-red heat. this brings the gold to "colour"; that is, the loose tender dark coloured gold becomes bright yellow and coherent; and is in a state fit to be transferred to the balance and weighed. all unnecessary transferences must be avoided. as soon as the cup is cool it may be inverted over the pan of the balance, when the gold will fall out cleanly or, at the worst, a gentle tap with the finger will be sufficient to detach it. _parting in test-tubes_, or in the smaller conical flasks, is used in the assay of gold ores of ordinary richness. the work is exactly like that just described in all its main features. generally speaking much less acid will be used; for example, in test-tubes and for small buttons, or c.c. of each acid is quite enough. again, the action need not be so prolonged; or minutes in each acid is sufficient. so, too, the heating may be less; it is very convenient to support the test-tubes in a water-bath, or merely to rest them in a beaker of boiling water; and there is no serious objection to doing this. a smaller parting cup should be used; the a size is suitable. the button, on the other hand, should be beaten thinner than is needed for the larger partings. if the silver should be in excess and the gold becomes much broken up, ample time should be given for subsidence from the test-tube or flask into the parting cup. _parting in glazed crucibles or dishes._--this method of working has the advantage that there is no transference of the gold until it is placed on the pan of the balance. on the other hand, in the boiling more care is required in adjusting the temperature. the following instructions apply to the treatment of very small buttons, to which the method is more particularly applicable; but very little modification is needed for the treatment of larger buttons. the smallest sized berlin crucibles answer admirably. they should be cleaned by treatment with hot and strong sulphuric acid, followed by washing in distilled water; the comfort and ease of working mainly depends on the thoroughness of this cleaning. the crucible, one-third full with the first parting acid, is heated on the hot plate until the acid is almost boiling. the flattened and annealed button is dropped into it and the heating continued with, at most, gentle boiling for a few minutes. the crucible is then filled with distilled water, which cools it enough for easy handling; and when the gold has settled the liquor is poured off along a glass rod into a clean beaker. any greasiness of the crucible makes itself felt here and is very objectionable. the crucible is then one-third filled with the second parting acid and the heating resumed, care being taken not to raise the temperature too high; this should be continued much longer than before, say for five or ten minutes or even longer according to the size of the button. distilled water is again added and, when it is drained off, the washing with distilled water is twice repeated. it will not be possible to drain off the last drop of water; but if the gold is coherent, the crucible can be so inclined that this drop drains away from the gold, in which case the drying can be done rapidly; the boiling of the water will do no harm. but when the gold is much broken up, it will collect in the middle of this drop and the drying must be done gently; best by putting the crucible in a warm place. when dry, the crucible is heated till the gold changes colour, but the heat must be kept well below redness. when cold, the gold is transferred directly to the pan of the balance. with minute specks of gold which will require measuring, it is best to put a small piece of lead foil (say . gram) in the crucible over the gold, and then heat the crucible to above redness over a blowpipe. whilst the lead is oxidising it is easily swept round in a bath of molten litharge by merely tilting the crucible. in this way any separated specks of gold can be taken up with certainty. when the worker is satisfied that the lead has had ample opportunity for taking up the gold, the lead must be kept in one place and the heat slowly lowered. by this means the button becomes supported in comparatively pure litharge and when solid can be picked out quite easily with a pair of pliers and in a very clean condition. the lead button is then cupelled on a very fine cupel, as already described. the method of working last described destroys the crucible. if the gold is not quite so small this may be avoided. a small piece of lead foil should be hammered out until it is perfectly flexible. it is then shaped into a tray and the gold is transferred to it. the lead is then folded over, with the help of two pins; and cupelled. if the crucible shows a black stain on heating it is because some silver remains through bad washing. it shows poor work and the assay should be repeated. _the silver retained in the gold after parting_ is, in bullion assays, an important matter; it is roughly equal to the loss of gold due to absorption by the cupel. mr. lowe working on . oz. of gold, obtained by parting in assaying bullion, found it to contain . per cent. of silver. dr. rose in some special assay pieces found by a less direct method of assaying, from . to . per cent. of silver. the proportion of silver retained varies in a marked way with the proportion of gold to silver in the alloy before parting. it is generally stated that the retained silver is least when this proportion is to - / , and more or less silver than this leads to a less pure gold after parting. _platinum_ in an alloy being parted is dissolved along with the silver either altogether or in part. it imparts a straw yellow colour to the parting acid. _palladium_ gives an orange colour to the acid. _the loss of gold by solution in the acid during parting_ is small, but easily demonstrable. on a -milligram charge of bullion it may amount to from . to . milligram; _i.e._ from . to . per cent. it is due to gold actually dissolved and not merely held in suspension. ~assaying with checks. surcharge.~--it will be seen from what has been stated that the errors in gold parting are of two kinds: viz. ( ) a loss of gold on the cupel and to a less extent by solution in the acid, and ( ) an apparent gain of gold due to the retention of silver in the parted material. both errors are small, and as they are of an opposite character they tend to neutralise each other. hence they are altogether without effect on the accuracy of the assays of ores when the total gold is reckoned in milligrams. and even with the larger amounts present in bullion assays their influence is so small that an uncorrected result is still fairly accurate; the resultant error would not be more than one part in two or three thousand. it is customary to report the purity of bullion, or its fineness as it is called, in parts per thousand of bullion. the sum of the errors of an assay, which is called the _surcharge_, is reported in the same way. thus a surcharge of + . means that the gold as weighed was . part per more than the gold actually present. but a surcharge - . means that on the whole there was a loss of . part per in the assay. speaking roughly the retained silver will vary with the weight of gold present; if one alloy contains twice as much gold as another the retained silver will be about twice as much also. on the other hand, as already explained, the cupellation loss on the poorer alloy is as much as, or even more than, with the richer one, because of the copper, &c. present. with rich gold alloys the silver more than compensates for the loss and the surcharge is positive; but with poorer alloys the loss is greater and the surcharge is negative. in mints and places where bullion assays must be made with the highest attainable accuracy, the surcharge is determined by experiment, and the proper correction is made in the reports on the bullion. this is done by making assays of gold of the highest degree of purity alongside of those of the bullion whose quality has to be determined. these "checks" are so made that they do not differ from the actual assays in any material point. thus, being of the same quality and weight and undergoing exactly the same treatment, they may reasonably be expected to have the same surcharge as the assays they imitate. suppose the bullion being assayed varies only a little, up or down, from gold and copper in the thousand, and that . gram of it is used in each assay. a quantity of gold differing only a little from . gram would be very exactly weighed and placed with . gram of copper in the same weight of lead as is being used in the other assays. it would be cupelled, parted, &c., as nearly as possible under the same conditions as the actual assays. suppose the pure gold weighed . gram and the parted gold weighed . gram, the gain in weight, . gram, would be deducted from the actual assays. a surcharge correction is never applied except to bullion of the same quality as that represented by the "check assay" it was calculated from. it is evident that unless the gold is of the highest degree of purity these check assays will introduce an error almost equal to that which it is designed to remedy. moreover, to work the checks to the greatest advantage, a very systematic and uniform method of working must be adopted. ~parting in special apparatus.~--one plan for obtaining greater uniformity is to stamp each cornet with a number for purposes of identification, and to treat several, including one or more check assays in the same acid contained in a beaker; all the assays under these conditions evidently receive precisely the same acid treatment. such a plan can of course only be adopted where there is no risk of the gold breaking up during the parting. an improvement on this is to have a porcelain basin[ ] about - / inches in diameter and with a capacity of about - / litres. it is provided with a porcelain cover with numbered holes through which tubes dip into the acid. the cover is removable. the tubes are like test-tubes and are supported by the cover; their bottoms are perforated with holes or slits. the acid is placed in the basin and boiled over a flat burner; it enters the tubes through the slits. the cornets are placed each in its proper tube. when the boiling is finished, the cover with the tubes is lifted and at the same time the acid drains back into the basin. a dip into a basin of distilled water washes at one operation all assays. the cover is then put on a basin containing the stronger parting acid which is already boiling. this boiling is continued for half an hour. the cover with the cornets is then lifted out from the acid and dipped two or three times in distilled water to wash off the last traces of acid. to transfer the cornets from the tubes to the porous cups the whole of the tube must be dipped under the water; otherwise the operation is exactly as when working with test-tubes. a still simpler method of working is to use small platinum cups[ ] provided with fine slits which admit the acid but retain the gold. a number of these, say , are supported on a platinum tray. the parting acids are boiled in platinum dishes under a hood; and the cornets (each in its proper cup) are placed in the acid all at once: the tray carrying the cups is provided with a handle suitable for this purpose. after a proper boiling the tray is lifted out of the weaker acid into the stronger one, where it undergoes the second boiling. it is next dipped several times in distilled water and lastly, after a gentle drying, it is raised to an annealing temperature which must not be too high for fear of the gold sticking to the platinum. after cooling, the cornets are transferred from the platinum cups directly to the pan of the balance. here all cornets have exactly the same treatment and the "checks" may be compared with great exactness with the other assays accompanying them. there is, too, a great saving of labour.[ ] ~silver, &c., in gold bullion.~--the base metals are generally determined by cupelling . gram of the alloy with grams of lead. the loss in cupellation having been allowed for by any of the usual methods (see p. ) the gold and silver contents are given. by deducting the gold the proportion of silver is obtained. the silver is generally determined by difference in this way. if it is desired to dissolve out the copper, silver, &c., and to determine them in the wet way, the gold must first be alloyed with a sufficiency of some other metal to render it amenable to the attack by acid. cadmium is the metal generally recommended, and the alloy is made by melting together a weighed portion of the gold with five or six times its weight of cadmium in a berlin crucible and under a thin layer of potassium cyanide. ~lead with gold or silver.~--large quantities of lead carrying gold and silver are sold to refiners in bars weighing about lbs. each. the assay of these alloys presents no special difficulties, but the sampling of them is a question which may be profitably discussed.[ ] a molten metal may be conceived to have all the physical states observed in ordinary liquids, although these cannot be actually seen owing to its opaqueness. there is no doubt that _pure_ lead at a temperature only a little above its melting-point can contain a large proportion of gold in such a manner that it may in a figurative way be spoken of as a clear solution. any small portion withdrawn from the molten metal would afford a perfect sample. the same would be true of any pure alloy of lead and silver in which the silver does not exceed the proportion of - / per cent.[ ] on the other hand, if the molten metal contains much more than . per cent. of zinc, more than . per cent. of copper, or a larger quantity of silver, it may be likened to a turbid liquor. the resemblance holds good so far that if the molten lead be further heated, whereby its solvent power on the added metal is increased, the turbidity will disappear, or at least be considerably diminished. a portion taken at random from such a molten metal may, or may not, give a good sample. the suspended insoluble matter will tend to concentrate itself in the upper or lower parts of the liquid according to whether it is heavier or lighter than it; and this separation may occur with extreme slowness or with fair rapidity. however, it is generally agreed that in the case of such alloys as occur in practice, samples taken in this way are quite satisfactory and are the best obtainable. the precautions insisted on are that the lead shall be made as hot as practicable; that it shall be stirred up at the time of taking the sample; and that the portion withdrawn shall be taken out with a ladle at least as hot as the molten metal. the further precaution that if any dross be on the surface of the metal it shall be skimmed off and separately sampled and assayed is almost too obvious to require mention. an alternative and, perhaps, better way of taking the sample is to withdraw portions at equal intervals from the stream of metal whilst the pot is being emptied; equal weights taken from these portions and mixed (by melting or in some other way) give a fair sample of the whole. in addition, separate assays of each portion will show to what extent the metal lacks uniformity in composition for example, samples taken at the beginning, middle, and end of a run gave the following results in ozs. of silver per ton: , , , showing an average result of ozs. fifteen fractions taken at regular intervals during the same pouring ranged from ozs. to ozs.: the average result was . ozs. the same lead cast into bars and sampled by sawing gave an average of ozs.[ ] in another case[ ] samples drawn at the beginning, middle, and end of a run gave ozs., ozs. and ozs. the mean result in such cases is always a reasonably safe one, but evidently where the metal varies a good deal it is safer to take more than three dips. imagine such lead run into moulds and allowed to become solid as bars; the difference between bar and bar would not be greater than that between corresponding dip samples. but in each bar the distribution of the silver and gold is very seriously affected during solidification. chips taken from the same bar of auriferous lead may show in one place ozs. of gold to the ton, in another ozs.; similarly with silver they may vary as much as from ozs. to ozs. to the ton. this rearrangement of the constituents of a bar takes place whilst the lead is partly solid, partly liquid. the most useful conception of such half-solidified metal is that of a felted spongy mass of skeleton crystals of comparatively pure lead saturated with a still fluid enriched alloy. if the solidification of an ingot of impure tin be watched it will be evident that the frosted appearance of the surface is due to the withdrawal of the fluid portion from a mat of crystals of purer tin which have been for some time solid and a contraction of the mass. the shrinking of the last part to become solid is further shown by the collapse of the surface of the ingot where weakest; that is, a furrow is formed on the flat surface. in other cases of fused metal there is expansion instead of contraction in this final stage of the solidification, and the enriched alloy then causes the upper face of the ingot to bulge outwards. there are other causes effecting the redistribution of the metals through the ingot. there can be no general rule of wide application showing which part of a bar is richest and which poorest in the precious metals. this will depend on the quantities of gold or silver, on the quantities and kinds of other metals present and on the manner of casting. the student is advised to consult mr. claudet's paper which has been already referred to. the best method of sampling such bars is to melt them all down and to take a dip sample of the molten metal in one or other of the methods already described. according to mr. claudet this should be done in all cases where the gold exceeds one or two ounces or where the silver exceeds ozs. to the ton. if during the melting down some dross has formed this must be skimmed off, weighed and separately sampled and assayed. the clean lead also must be weighed, sampled and assayed. the mean result must be calculated. thus tons cwts. of clean lead assaying ozs. to the ton will contain ozs. of silver; cwt. dross assaying ozs. to the ton will contain ozs. of silver. the tons of lead and dross will contain ozs. of silver or . ozs. per ton. of the methods of sampling which avoid melting the bars, that known as sawing is the only one which is thoroughly satisfactory. in it the bars are brought to a circular saw having fine teeth and are sawn across either completely or halfway through; in this way a quantity of lead sawdust is obtained (say lb. or so from a bar) which represents exactly the average of the bar along the particular cross section taken and approximately that of the whole bar. a bar of lead, which by dip assay gave ozs. to the ton, gave on three transverse sections ozs., ozs. and ozs. the variation may be greater than this, but with a large number of bars, where each bar is cut across in as far as possible a different place, these variations tend to neutralise each other and a good sample is obtained. two or three cwt. of sawdust may be obtained in this way; this is thoroughly mixed and reduced by quartering in the usual way or by a mechanical sampler. a sample of or lbs. is sent to the assayer. this being contaminated with the oil used in lubricating the saw is freed from it by washing with carbon bisulphide, ether or benzene and dried. then, after mixing, to grams of it are carefully weighed and placed in a hot crucible, the heat of which should be sufficient to melt all the lead. the molten lead should not be overheated and should show no loss due to the melting. the removal of the oil may have decreased the weight by perhaps one half per cent. if the lead gives dross on heating it may be melted under or grams of potassium cyanide, which prevents the formation of dross. samples are sometimes taken with a drill, gouge or chisel, though no method of this kind is quite satisfactory. one plan adopted is to use a punch which, when driven into the bar, gives a core or rod of metal about half as long as the bar is thick and about one-eighth of an inch across. with five bars side by side it is customary to drive in the punch at one end on the first bar, and at the opposite end on the last one, and on the others in intermediate positions in such a manner that all the holes will be along a diagonal of the rectangle enclosing the bars. the bars are then turned over and similar portions punched out through the bottoms of the bars and along the other diagonal. or one set of five may be sampled along the top and the next set along the bottom of the bars. silver and gold present in bars of copper are subject to the same irregularity of distribution as in lead. the sampling of such bars is guided by the same principles.[ ] cyanides. the cyanides ought perhaps to be considered along with chlorides, bromides and iodides in chapter xv. but they are treated here because they owe their importance to their use in the extraction of gold and because their determination has become a part of the ordinary work of an assayer of gold ores. formerly, the cyanide most easily obtained in commerce was potassium cyanide; and it was generally sold in cakes which might contain as little as per cent. or as much as per cent. of the pure salt. it became customary to express the quality of a sample of commercial cyanide by saying it contained so much per cent. of potassium cyanide. the commercial product now made by improved methods of manufacture is actually sodium cyanide, but is called "potassium cyanide" (probably with the words "double salt" on the label); it contains cyanide equivalent to something over per cent. of potassium cyanide in addition to a large proportion of sodium carbonate and other impurities. what is wanted in most cases is merely a soluble cyanide, and it is a matter of indifference whether the base be sodium or potassium. but since parts of sodium cyanide (nacn = ) are equivalent to parts of potassium cyanide (kcn = ) it is evident that a pure sample of sodium cyanide would contain cyanide equivalent to little less than per cent. of potassium cyanide. therefore a sample of cyanide reported on in this way may be rich in cyanide, and yet have much impurity. the commonest impurity in commercial cyanide is carbonate of sodium or potassium. this may be tested for by dissolving, say, grams in a little water and adding barium chloride. there may be formed a white precipitate of barium carbonate, which if filtered off, washed and treated with acid, will dissolve with effervescence. cyanate may be tested for in the solution from which the barium carbonate has been filtered by adding a little soda and boiling; if cyanates are present they decompose, giving off ammonia (which may be tested for in the steam) and yielding a further precipitate of barium carbonate.[ ] if the soda alone gave a further precipitate of barium carbonate, this may, perhaps, be due to the presence of bicarbonates. alkaline sulphides may be present in small quantity in commercial cyanide. their presence is shown at once when the sample is being tested for its strength in cyanide, inasmuch as the first few drops of silver nitrate solution produce at once a darkening of the liquor. a special test for sulphide may be made by adding a drop or two of solution of acetate of lead to four or five c.c. of soda solution and adding this to a clear solution of the suspected cyanide. this will cause a black precipitate or colour, if any sulphide is present. the cyanides of the heavier metals combine with the alkaline cyanides to form double cyanides. some of these, ferrocyanide and ferricyanide of potassium for example, have such characteristic properties that the fact that they are cyanides may be overlooked. others, such as potassium zinc cyanide (k_{ }zncy_{ }), have much less distinctiveness: they behave more or less as a mixture of two cyanides and are, moreover, so easily decomposed that it may be doubted if they can exist in dilute alkaline solutions. in reporting the cyanide strength of a cyanide liquor as equivalent to so much per cent. of potassium cyanide, there is a question as to whether the cyanide present in the form of any of these double cyanides should be taken into account. it must be remembered that the object of the assay is not to learn how much of the cyanide exists in the solution as actual potassium cyanide; reporting the strength in terms of this salt is a mere matter of convenience; what is really desired is to know how much of the cyanide present in the liquor is "free" or "available" for the purposes of dissolving gold. every one is agreed as to the exclusion of such cyanides as the following: potassium ferrocyanide (k_{ }fecy_{ }), potassium ferricyanide (k_{ }fecy_{ }), potassium silver cyanide (kagcy_{ }), and potassium aurocyanide (kaucy_{ }); and the double cyanides with copper or nickel. but with cyanide liquors containing zinc the position is less satisfactory. one method of assay gives a lower proportion of cyanide when this metal is present; and the loss of available cyanide thus reported depends, though in a fitful and uncertain way, upon the quantity of zinc present. the other method of assay reports as full a strength in cyanide as if no zinc were present. unfortunately, using both methods and accepting the difference in the results as a measure of the quantity of zinc present, or at any rate of the zinc present as cyanide, is not satisfactory. it appears best to use the method which ignores the zinc; and to determine the amount of zinc by a special assay of the liquor for this metal. the cyanide present as hydrogen cyanide or prussic acid (hcy) is practically useless as a gold solvent. hence any report on the strength of a cyanide liquor which assigned to this the same value as its equivalent of alkaline cyanide would be misleading. on the other hand, it is "available cyanide" inasmuch as a proper addition of sodium hydrate[ ] would restore its value. the question of the presence or absence of free prussic acid is involved in the larger one as to whether the cyanide solution has the right degree of alkalinity. the assay for "cyanide" should include the hydrogen cyanide with the rest. a rough test of the power of a cyanide liquor for dissolving gold may be made by floating a gold leaf on its surface and noting the time required for its solution. this test might, perhaps, be improved by taking, say, c.c. of the liquor and adding three or four gold leaves so that the gold shall always be in considerable excess. the liquor should not be diluted as this will affect the result. it should be allowed to stand for a definite time, say at least two or three hours, or better, that corresponding to the time the liquor is left in contact with the ore in actual practice. the liquor should then be filtered off and, with the washings, be evaporated in a lead dish as in the assay of cyanide liquors for gold (p. ). the gold obtained on cupelling, less any gold and silver originally present in the liquor, would be the measure of the gold dissolving power. the assay for cyanide by titration with silver nitrate. the determination of the quantity of a cyanide is made by finding how much silver nitrate is required to convert the whole of the cyanide into potassium silver cyanide[ ] or one of the allied compounds. it will be seen from the equation that parts by weight of silver nitrate are required for parts by weight of potassium cyanide. as already explained it is customary to report the cyanide-strength in terms of potassium cyanide, even when only the sodium salt is present. one gram of potassium cyanide will require . gram of silver nitrate. _the standard solution of silver nitrate_ is made by dissolving . grams of silver nitrate in distilled water and diluting to litre; c.c. of such a solution are equivalent to gram of potassium cyanide.[ ] the titration is performed in the usual way, running the standard solution of silver nitrate into a solution containing a known weight or volume of the material containing the cyanide. the _finishing point_ is determined in one of two ways, both of which are largely used. in the first place, as long as there remains any free cyanide in the solution the silver nitrate will combine with it forming the double cyanide and yielding a clear solution; but as soon as all the free cyanide is used up the silver nitrate will react with the double cyanide[ ] forming silver cyanide, which separates as a white precipitate and renders the solution turbid. but, in the second place, if potassium iodide is present in the solution the excess of silver nitrate will react with it,[ ] rather than with the double cyanide; and silver iodide will separate as a yellowish turbidity which is easily recognised. in working with pure solutions, the two finishing points give the same results; and this is true even when there is much difference in the degree of dilution. the finishing point with the iodide, however, has an advantage in precision. moreover, it is but little affected by variations in alkalinity, which render the other finishing point quite useless. the great difference between the two is shown when zinc is present in the solution. in this case, when working without the iodide, the first appearance of a turbidity is less distinct; the turbidity increases on standing and as a finishing point is unsatisfactory. it can be determined with precision only by very systematic working and after some experience. the turbidity is due to the separation of an insoluble zinc compound. a most important point (to which reference has already been made) is that less silver nitrate is required to give this turbidity and, consequently, a lower strength in cyanide is reported. on the other hand, as much silver nitrate is required to give the yellow turbidity due to silver iodide as would be required if no zinc were present. unfortunately the difference in the two titrations does not depend merely on the quantity of zinc present; as it is also influenced by the extent of dilution, the degree of alkalinity of the solution, and the quantity of cyanide present. in an experiment with . gram of zinc sulphate and . gram of potassium cyanide the difference in the two finishing points was only . c.c.; whereas with . gram of potassium cyanide, the other conditions being the same, the difference was . c.c. of standard silver nitrate. on the assumption that all the zinc was present as potassium zinc cyanide (k_{ }zncy_{ }) the difference should have been c.c. in each case. again, repeating the experiment with . gram of potassium cyanide, but with . gram of crystallised zinc sulphate, the difference was . c.c.: that is, merely doubling the quantity of zinc increased the difference by more than four times. hence it would appear better to use the method with the iodide and make a separate assay for the zinc. but since the student may be called on to use the other method, he is advised to practice it also. ~the assay without iodide.~--the standard solution of silver nitrate is placed in a small burette divided into tenths of a c.c. ten c.c. of the cyanide solution to be assayed is transferred to a small flask and diluted with water to about c.c. the silver solution is then run in from the burette (with constant shaking of the flask), a little at a time but somewhat rapidly, until a permanent turbidity appears. since c.c. of the silver nitrate solution corresponds to . gram of potassium cyanide, it also corresponds to . per cent. of this salt counted on the c.c. of cyanide solution taken. the titration should be performed in a fairly good uniform light. the learner should practice on a fairly pure solution of potassium cyanide at first, and this may conveniently have a strength of about per cent. for practice with solutions containing zinc make a solution containing . gram of crystallised zinc sulphate in c.c. and slowly add measured quantities of from to c.c. of this to the c.c. of cyanide liquor before diluting for the titration. if a cyanide solution blackens on the addition of the silver nitrate it contains sulphide. in this case, shake up a considerable bulk of the liquor with a few grams of lead carbonate, allow to settle and make the assay on c.c. of the clear liquor. if the cyanide liquor be suspected to contain free prussic acid, take c.c. for the assay as usual; but, before titrating, add . or . gram of sodium carbonate. on no condition must caustic soda or ammonia be added. the difference between the results, with and without the addition of carbonate of soda, is supposed to measure the quantity of free prussic acid. if this has to be reported it is best done as "prussic acid equivalent to ... per cent. of potassium cyanide." suppose, for example, the difference in the two titrations equals c.c. of standard silver nitrate; the prussic acid found would be equivalent to . per cent. of potassium cyanide. ~the assay with iodide.~--the standard solution of silver nitrate is placed in a burette divided into tenths of a c.c. take c.c. of the cyanide liquor, which should previously have been treated with white lead for the removal of sulphides if these happened to be present. transfer to a small flask, add or drops of a solution of potassium iodide and or c.c. of a solution of sodium hydrate; dilute to or c.c. with water. if much zinc is present the soda may be increased to or c.c. with advantage. the standard solution should be run in somewhat rapidly, but a little at a time, so that the precipitate at first formed shall be small and have only a momentary existence. the titration is continued until there is a permanent yellowish turbidity. the most satisfactory and exact finish is got by ignoring any faint suspicion of a turbidity and accepting the unmistakable turbidity which the next drop of silver nitrate is sure to produce. this finishing point gives results which are exactly proportional to the quantity of cyanide present; and it can be recognised with more than ordinary precision even in solutions which are not otherwise perfectly clear. each c.c. of the standard silver nitrate solution corresponds to . gram of potassium cyanide; and if c.c. of the liquor are taken for assay this corresponds to . per cent. or lbs. to the short ton or . lbs. to the long ton. as already explained the result should be reported as "cyanide equivalent to so much per cent. of potassium cyanide." the following experimental results were obtained with a solution of potassium cyanide made up to contain about . per cent. of the salt. ~effect of varying cyanide.~--the bulk before titration was in each case c.c.; c.c. of soda and drops of potassium iodide were used in each case. cyanide added c.c. c.c. c.c. c.c. c.c. c.c. silver required . c.c. . c.c. . c.c. . c.c. . c.c. . c.c. accepting the result for c.c. as correct, the others are in very satisfactory agreement. ~effect of varying dilution.~--the conditions were those of the c.c. experiment in the last series; but varying amounts of water were used in diluting. water added none c.c. c.c. c.c. silver required . c.c. . c.c. . c.c. . c.c. very considerable dilution therefore has no effect. ~effect of varying soda.~--the conditions were those of the c.c. experiment in the first series, except that varying amounts of soda solution were used. soda added none c.c. c.c. silver required . c.c. . c.c. . c.c. this alkali therefore has no prejudicial effect. ~effect of ammonia.~--soda causes turbidity in some cyanide liquors; with these it should be replaced by or c.c. of dilute ammonia with a gram or so of ammonium chloride. the following experiments with dilute ammonia show that larger quantities of this reagent must be avoided. ammonia added none c.c. c.c. c.c. silver required . c.c. . c.c. . c.c. . c.c. ~effect of sodium bicarbonate.~--in this experiment gram of bicarbonate of soda was used instead of the soda or ammonia of the other experiments. the silver nitrate required was only . c.c. instead of the . c.c. which is the normal result. this is probably due to the liberation of prussic acid and shows the importance of having the solution alkaline. ~effect of zinc.~--in each experiment c.c. of the cyanide solution and . gram of zinc sulphate crystals were used and the bulk was made up to c.c. before titrating. soda added c.c. c.c. c.c. c.c. silver required . c.c. . c.c. . c.c. . c.c. the work was easier with the more alkaline solutions. the titration in the presence of zinc is comparatively easy, but, in learning it, it is well to have a burette with cyanide so that if a titration be overdone it can be brought back by the addition of or c.c. more cyanide and the finish repeated; a quarter of an hour's work in this way will ensure confidence in the method. ~effect of other substances.~--it was found that an alkaline cyanate, sulphocyanate, ferrocyanide, nitrite, borate, silicate or carbonate has no effect. the ferricyanide had a small influence and, as might be expected, hyposulphite is fatal to the assay. the addition of salts of lead and cadmium was without effect. on the other hand, nickel produces its full effect; and the quantity of nickel added can be calculated with accuracy from the extent of its interference with the titration. ~assay of commercial cyanide of potassium.~--break off or grams of the cyanide in clean fresh pieces, weigh accurately to the nearest centigram. dissolve in water containing a little sodium hydroxide; transfer to a -litre flask: dilute to litres; add a few grams of white lead; shake up and allow to settle. run c.c. of the clear liquor from a burette into an oz. flask; add or c.c. of soda solution and drops of potassium iodide. titrate with the standard solution of silver nitrate. the percentage may be calculated by multiplying the number of c.c. used by ( c.c. is one fortieth of the litres) and dividing by the weight of commercial cyanide originally taken. ~alkalinity of commercial potassium cyanide and of cyanide solutions.~--hydrocyanic acid like carbonic acid has no action on methyl-orange;[ ] hence the alkaline cyanides may be titrated with "normal acid" as easily as the carbonates or hydrates. c.c. of normal acid will neutralise . grams of pure potassium cyanide.[ ] a solution of commercial cyanide prepared as for the assay last described, but best without the addition of white lead, may be used for the test. take c.c. of it; tint faintly yellow with methyl-orange and titrate with normal acid till the liquor acquires a permanent reddish tint. in the case of the purer samples of cyanide the quantity of acid used will correspond exactly with that required to neutralise the actual quantity of cyanide present as determined by the assay with nitrate of silver. the less pure samples will show an excess of alkalinity because of the presence of sodium carbonate or of potassium carbonate. in comparing the alkalinity and cyanide strength of a solution the simplest plan is to take c.c. of the solution and titrate with normal acid; for in this case each c.c. of normal acid corresponds to . per cent. of potassium cyanide. in systematic assays of this kind, the alkalinity would no doubt be generally in excess of that required by the cyanide present: there would be no inconvenience in recording such excess in terms of potassium cyanide. ~determination of the acidity of an ore.~--most ores have the power of destroying more or less of the alkalinity of a cyanide solution and in a proportionate degree of damaging its efficiency. an assay is needed to determine how much lime or soda must be added for each ton of ore in order to counteract this. whether this acidity should be reported in terms of the lime or of the soda required to neutralise it will depend on which of these reagents is to be used in the actual practice. again, if the ore is washed with water before treating with cyanide on the large scale, then the assay should be made of the acidity of the ore after a similar washing. the _standard solutions of acid and alkali_ used for this determination may be one-fifth normal. c.c. of the normal solution should be diluted to litre in each case, c.c. of the resulting solutions would be equivalent to milligrams of soda (naho) or . milligrams of lime, cao. it must be remembered this refers to the pure bases in each case. suppose it is desired to report as so many lbs. of lime to the short ton ( lbs.) of ore. since c.c. of the standard solution is equivalent to . milligrams of lime, if we take times this weight of ore (_i.e._ , milligrams or . grams) for the assay, each c.c. of standard solution will be equivalent to lb. of lime to the short ton.[ ] ~total acidity.~--weigh out . grams of the ore, place them in a four-inch evaporating dish and measure on to it from a burette or c.c. of the standard solution of soda. stir the soda solution into the ore and allow to stand for or minutes with occasional stirring. stir up with or c.c. of water, float a piece of litmus paper on the liquid and titrate with the standard solution of acid. if the ore is strictly neutral the quantity of "acid" required to redden the litmus will be the same as the quantity of "soda" originally used. if the ore is acid, less acid will be used. for example, if c.c. of soda were used and only c.c. of acid were required, the ore will have done the work of the remaining c.c. of acid. and the ton of ore will require lbs. of lime to neutralise its acidity. ~acidity after washing.~--take . grams of the ore; wash thoroughly with water and immediately treat the residue, without drying, exactly as just described. ~examination of cyanide solutions for metals, &c.~--take a measured quantity of the solution, say c.c.[ ] and evaporate in a small dish with, say, half a c.c. of strong sulphuric acid. evaporate at first, on a water-bath in a well ventilated place, but finish off with a naked bunsen flame, using a high temperature at the end in order to completely decompose the more refractory double cyanides. allow to cool; moisten with strong hydrochloric acid; warm with a little water and test for the metals in the solution by the ordinary methods. since the quantities of the metals likely to be present may be given in milligrams the work must be carefully performed. it may be worth while to determine the proportions of lime and magnesia as well as those of the metals proper. or the c.c. of cyanide liquor may be evaporated with c.c. of strong nitric acid to dryness and gently ignited and the residue taken up with or c.c. of strong hydrochloric acid. copper, iron, and zinc can be rapidly determined in such a solution, as follows. dilute with water to or c.c., add an excess of ammonia, and filter. the precipitate will contain the iron as ferric hydrate; dissolve it in a little hot dilute sulphuric acid: reduce with sulphuretted hydrogen; boil off the excess of gas, cool and titrate with standard potassium permanganate (p. ). determine the copper in the filtrate colorimetrically (p. ); but avoid further dilution. then add dilute hydrochloric acid, so as to have an excess of or c.c. after neutralising the ammonia; add some clean strips of lead foil, and boil until the solution has for some time become colourless. titrate with standard potassium ferrocyanide (p. ) without further dilution, and bearing in mind that at most only one or two c.c. will be required. ~examination of an ore for "cyanicides."~--place grams of the ore with c.c. of a cyanide solution of known strength (say . or . per cent.) in a bottle and agitate for a definite time, such as one or two days. filter off some of the liquor and assay for cyanide, using say c.c. calculate how much cyanide has been destroyed in the operation. evaporate c.c. with sulphuric or nitric acid and examine for metal. test another portion for sulphides, &c. the student who has mastered the methods of assaying can greatly improve himself by working out such problems as the above. platinum. platinum occurs in nature in alluvial deposits associated with gold and some rare metals, generally in fine metallic grains, and, occasionally, in nuggets. it is a grey metal with a high specific gravity, . when pure and about . in native specimens. it is fusible only at the highest temperature, and is not acted on by acids. it is dissolved by warm aqua regia, forming a solution of "platinic chloride," h_{ }ptcl_{ }. this substance on evaporation remains as a brownish red deliquescent mass; on drying at ° c. it is converted into platinous chloride, ptcl_{ }, and becomes insoluble, and at a higher temperature it is converted into platinum. all platinum compounds yield the metal in this way. platinic chloride combines with other chlorides to form double salts, of which the ammonic and potassic platino-chlorides are the most important. platinum alone is not soluble in nitric acid; but when alloyed with other metals which dissolve in this acid it too is dissolved; so that in gold parting, for example, if platinum was present, some, or perhaps the whole of it would go into solution with the silver. such alloys, however, when treated with hot sulphuric acid leave the platinum in the residue with the gold. platinum is detected when in the metallic state by its physical characters and insolubility in acids. in alloys it may be found by dissolving them in nitric acid or in aqua regia, evaporating with hydrochloric acid, and treating the filtrate with ammonic chloride and alcohol. a heavy yellow precipitate marks its presence. the assay of bullion, or of an alloy containing platinum, may be made as follows: take . gram of the alloy and an equal weight of fine silver, cupel with sheet lead, and weigh. the loss in weight, after deducting that of the silver added, gives the weight of the base metals, copper, lead, &c. flatten the button and part by boiling with strong sulphuric acid for several minutes. _when cold_, wash, anneal, and weigh. the weight is that of the platinum and gold. the silver may be got by difference. re-cupel the metal thus got with or times its weight of silver, flatten and part the gold with nitric acid in the usual way (see under _gold_), and the platinum will dissolve. the gold may contain an alloy of osmium and iridium; if so, it should be weighed and treated with aqua regia. the osmiridium will remain as an insoluble residue, which can be separated and weighed. its weight deducted from that previously ascertained will give the weight of the gold. when the platinum only is required, the alloy must be dissolved by prolonged treatment with aqua regia, the solution evaporated to dryness, and the residue extracted with water. the solution thus obtained is treated with ammonic chloride in large excess and with some alcohol. a sparingly soluble[ ] yellow ammonic platinum chloride is thrown down, mixed, perhaps, with the corresponding salts of other metals of the platinum group. gold will be in solution. the solution is allowed to stand for some time, and then the precipitate is filtered off, washed with alcohol, dried, and transferred (wrapped in the filter paper) to a weighed crucible. it is ignited, gently at first, as there is danger of volatilising some of the platinum chloride, and afterwards intensely. with large quantities of platinum the ignition should be performed in an atmosphere of hydrogen. cool and weigh as metallic platinum. iridium occurs in nature alloyed with osmium as osmiridium or iridosmine, which is "rather abundant in the auriferous beach sands of northern california" (dana). it occurs in bright metallic scales, which do not alloy with lead, and are insoluble in aqua regia. iridium also occurs in most platinum ores, and forms as much as two per cent. of some commercial platinum. in chemical properties it resembles platinum, but the ammonic irido-chloride has a dark red colour, and on ignition leaves metallic iridium, which does not dissolve in aqua regia diluted with four or five times its volume of water and heated to a temperature of ° or ° c. the other metals of the platinum group are palladium, rhodium, osmium, and ruthenium. they differ from gold, platinum, and iridium by the insolubility of their sulphides in a solution of sodium sulphide. palladium is distinguished by the insolubility of its iodide; and osmium by the volatility of its oxide on boiling with nitric acid. mercury. mercury occurs native and, occasionally, alloyed with gold or silver in natural amalgams; but its chief ore is the sulphide, cinnabar. it is comparatively rare, being mined for only in a few districts. it is chiefly used in the extraction of gold and silver from their ores (amalgamation); for silvering mirrors, &c. mercury forms two series of salts, mercurous and mercuric, but for the purposes of the assayer the most important property is the ease with which it can be reduced to the metallic state from either of these. mercury itself is soluble in nitric acid, forming, when the acid is hot and strong, mercuric nitrate. cinnabar is soluble only in aqua regia. mercurous salts are generally insoluble, and may be converted into mercuric salts by prolonged boiling with oxidising agents (nitric acid or aqua regia). the salts of mercury are volatile, and, if heated with a reducing agent or some body capable of fixing the acid, metallic mercury is given off, which may be condensed and collected. mercury is separated from its solutions by zinc or copper, or it may be thrown down by stannous chloride, which, when in excess, gives a grey powder of metallic mercury, or, if dilute, a white crystalline precipitate of mercurous chloride. nitric acid solutions of mercury yield the metal on electrolysis; and, if the pole on which the metal comes down be made of gold or copper, or is coated with these, the separated mercury will adhere thereto. it may then be washed and weighed. the best tests for mercury next to obtaining globules of the metal are: ( ) a black precipitate with sulphuretted hydrogen from acid solutions, which is insoluble in nitric acid; and ( ) a white precipitate with stannous chloride. dry method. [illustration: fig. .] weigh up grams, if the ore is rich, or grams, if a poorer mineral. take a piece of combustion tube from inches to feet long, closed at one end, and place in it some powdered magnesite, so as to fill it to a depth of or inches, and on that a layer of an equal quantity of powdered lime (not slaked). mix the weighed sample of ore in a mortar with grams of finely powdered lime and transfer to the tube; rinse out the mortar with a little more lime, and add the rinsings. cover with a layer of six or seven inches more lime and a loosely fitting plug of asbestos. draw out the tube before the blowpipe to the shape shown in fig. , avoiding the formation of a ridge or hollow at the bend which might collect the mercury. tap gently, holding the tube nearly horizontal, so as to allow sufficient space above the mixture for the passage of the gases and vapours which are formed. place the tube in a "tube furnace," and, when in position, place a small beaker of water so that it shall just close the opening of the tube. the point of the tube should not more than touch the surface of the water. bring the tube gradually to a red heat, commencing by heating the lime just behind the asbestos plug, and travelling slowly backwards. when the portion of the tube containing the ore has been heated to redness for some time the heat is carried back to the end of the tube. the magnesite readily gives up carbonic acid, which fills the tube and sweeps the mercury vapour before it. some of the mercury will have dropped into the beaker, and some will remain as drops adhering to the upper part of the neck. whilst the tube is still hot cut off the neck of the tube just in front of the asbestos plug (a drop of water from the wash bottle will do this), and wash the mercury from the neck into the beaker. the mercury easily collects into a globule, which must be transferred, after decanting off the bulk of the water, to a weighed berlin crucible. the water is removed from the crucible, first by the help of filter paper, and then by exposing in a desiccator over sulphuric acid, where it should be left until its weight remains constant. it should not be warmed. _example_:-- grams of an ore treated in this way gave . grams of mercury, equivalent to . per cent. pure cinnabar contains . per cent. wet methods. _solution._--since solutions of chloride of mercury cannot be boiled without risk of loss,[ ] nitric acid solutions should be used wherever possible. no mercury-containing minerals are insoluble in acids; but cinnabar requires aqua regia for solution. in dissolving this mineral nitric acid should be used, with just as much hydrochloric acid as will suffice to take it up. to separate the mercury, pass sulphuretted hydrogen in considerable excess through the somewhat dilute solution. the precipitate should be black, although it comes down at first very light coloured. it is filtered, washed, and transferred back to the beaker, and then digested with warm ammonic sulphide. the residue, filtered, washed, and boiled with dilute nitric acid, will, in the absence of much lead, be pure mercuric sulphide. if much lead is present, a portion may be precipitated as sulphate, but can be removed by washing with ammonic acetate. to get the mercury into solution, cover with nitric acid and a few drops of hydrochloric, and warm till solution is effected. dilute with water to or c.c. gravimetric determination. this may be made by _electrolysis_. the same apparatus as is used for the electrolytic copper assay may be employed, but instead of a cylinder of platinum one cut out of sheet copper should be taken, or the platinum one may be coated with an evenly deposited layer of copper. fix the spiral and weighed copper cylinder in position, couple up the battery, _and when this has been done_ put the nitric acid solution of the mercury in its place.[ ] the student had better refer to the description of the _electrolytic copper assay_. the mercury comes down readily, and the precipitation is complete in a few hours: it is better to leave it overnight to make sure of complete reduction. disconnect the apparatus, and wash the cylinder, first with cold water, then with alcohol. dry by placing in the water oven for two or three minutes. cool and weigh: the increase in weight gives the amount of metallic mercury. it must be remembered that copper will precipitate mercury without the aid of the battery; but in this case copper will go into solution with a consequent loss in the weight of the cylinder: this must be avoided by connecting the battery before immersing the electrodes in the assay solution. the electrolysed solution should be treated with an excess of ammonia, when a blue coloration will indicate copper, in which case the electrolysis is unsatisfactory. with a little care this need not happen. gold cylinders may preferably be used instead of copper; but on platinum the deposit of mercury is grey and non-adherent, so that it cannot be washed and weighed. volumetric methods. several methods have been devised: for the details of these the student is referred to sutton's "handbook of volumetric analysis." questions. . the specific gravity of mercury is . . what volume would grams occupy? . if . grams of cinnabar gave . grams of mercury, what would be the percentage of the metal in the ore? . pour solution of mercuric chloride on mercury and explain what happens. . on dissolving . gram of mercury in hot nitric acid, and passing sulphuretted hydrogen in excess through the diluted solution, what weight of precipitate will be got? footnotes: [ ] lead may be granulated by heating it to a little above the melting point, pouring it into a closed wooden box, and rapidly agitating it as it solidifies. [ ] a rod of iron placed in the crucible with the assays will decompose any regulus that may be formed. [ ] with buttons poor in silver the lowering of the temperature at this stage is not a matter of importance. [ ] grams of the lead, or of its oxide, will contain from . to . milligrams. [ ] still the precautions of having cupels well made from bone ash in fine powder, and of working the cupellation at as low a temperature as possible are very proper ones, provided they are not carried to an absurd excess. [ ] be careful to remove the crucible before taking the bottle out of the basin of water; if this is not done the chloride may be washed out of it. [ ] c.c. of this dilute acid will precipitate or milligrams of silver. [ ] chlorides interfere not merely by removing silver as insoluble silver chloride, but also by making it difficult to get a good finishing point, owing to the silver chloride removing the colour from the reddened solution. [ ] these results were obtained when using ammonium sulphocyanate, and cannot be explained by the presence of such impurities as chlorides, &c. [ ] multiply the _standard_ by , and dilute c.c. of the standard solution to the resulting number of c.c. thus, with a solution of a standard . , dilute c.c. to c.c., using, of course, distilled water. [ ] hna_{ }aso_{ } + agno_{ } = ag_{ }aso_{ } + hno_{ } + nano_{ }. [ ] sio_{ } + na_{ }co_{ } = co_{ } + na_{ }sio_{ } sio_{ } + nahco_{ } = co_{ } + na_{ }sio_{ } + h_{ }o. [ ] pbo + sio_{ } = pbsio_{ } [ ] here and elsewhere in this article when a flux is spoken of as soda the bicarbonate is meant. [ ] see the description of the process commencing on p. and the explanatory remarks on p. . [ ] percy, _metallurgy of silver and gold_, p. . [ ] "limits of accuracy attained in gold-bullion assay," _trans. chem. soc._, . [ ] "assaying and hall-marking at the chester assay office." w.f. lowe. _journ. soc. chem. industry_, sept. . [ ] fine or pure gold is carat. nine carat gold therefore contains parts of gold in of the alloy; eighteen carat gold contains parts of gold in ; and so on. [ ] the mouth of the flask must not have a rim around it. [ ] see "assaying and hall-marking at the chester assay office," by w.f. lowe. _journ. soc. chem. industry_, sept. . [ ] percy, _metallurgy of silver and gold_, p. . [ ] see also "the assaying of gold bullion," by c. whitehead and t. ulke. _eng. and mining journal_, new york, feb. , . [ ] consult percy's _metallurgy of silver and gold_, p. ; a.c. claudet, _trans. inst. mining and metallurgy_, vol. vi. p. ; g.m. roberts _trans. amer. inst. mining engineers_, buffalo meeting, ; j. and h.s. pattinson, _journ. soc. chem. industry_, vol. xi. p. . [ ] heycock and neville, _journ. chem. soc._, , p. . [ ] g.m. roberts. [ ] a.c. claudet. [ ] "the sampling of argentiferous and auriferous copper," by a.r. ledoux. _journ. canadian mining institute_, . [ ] nacno + bacl_{ } + naho + h_{ }o = nh_{ } + baco_{ } + nacl. [ ] hcy + naho = nacy + h_{ }o. [ ] kcn + agno_{ } = kag(cn)_{ } + kno_{ }. [ ] if it be desired to make a solution so that c.c. shall be equivalent to gram of sodium cyanide, then . grams of silver nitrate should be taken for each litre. [ ] agno_{ } + kagcy_{ } = agcy + kno_{ }. [ ] agno_{ } + ki = agi + kno_{ }. [ ] see pp. , , and for a description of the methods for measuring the quantity of acid or alkali. [ ] kcn + hcl = kcl + hcn [ ] taking . grams of ore, each c.c. = lb. of soda to the short ton. the corresponding figures for the long ton are . grams for lime and . grams for soda. [ ] in which case each . gram of metal found equals lb to the short ton of solution. [ ] c.c. of water dissolves . gram of the salt; it is almost insoluble in alcohol or in solutions of ammonic chloride. [ ] according to personne mercuric chloride is not volatilised from boiling solutions when alkaline chlorides are present. [ ] the solution should contain about . gram of mercury, and a large excess of nitric acid must be avoided. chapter x. copper--lead--thallium--bismuth--antimony. copper. copper occurs native in large quantities, especially in the lake superior district; in this state it is generally pure. more frequently it is found in combination. the ores of copper may be classed as oxides and sulphides. the most abundant oxidised ores are the carbonates, malachite and chessylite; the silicates, as also the red and black oxides, occur less abundantly. all these yield their copper in solution on boiling with hydrochloric acid. the sulphides are more abundant. copper pyrites (or yellow ore), erubescite (or purple ore), and chalcocite (or grey ore) are the most important. iron pyrites generally carries copper and is frequently associated with the above-mentioned minerals. these are all attacked by nitric acid. they nearly all contain a small quantity of organic matter, and frequently considerable quantities of lead, zinc, silver, gold, arsenic, bismuth, &c. the copper ores are often concentrated on the mine before being sent into the market, either by smelting, when the product is a regulus or matte, or by a wet method of extraction, yielding cement copper or precipitate. a regulus is a sulphide of copper and iron, carrying from to per cent. of copper. a precipitate, which is generally in the form of powder, consists mainly of metallic copper. either regulus or precipitate may be readily dissolved in nitric acid. copper forms two classes of salts, cuprous and cupric. the former are pale coloured and of little importance to the assayer. they are easily and completely converted into cupric by oxidising agents. cupric compounds are generally green or blue, and are soluble in ammonia, forming deep blue solutions. dry assay. that, for copper, next after those for gold and silver, holds a more important position than any other dry assay. the sale of copper ores has been regulated almost solely in the past by assays made on the cornish method. it is not pretended that this method gives the actual content of copper, but it gives the purchaser an idea of the quantity and quality of the metal that can be got by smelting. the process is itself one of smelting on a small scale. as might be expected, however, the assay produce and the smelting produce are not the same, there being a smaller loss of copper in the smelting. the method has worked very well, but when applied to the purchase of low class ores (from which the whole of the copper is extracted by wet methods) it is unsatisfactory. the following table, which embodies the results of several years' experience with copper assays, shows the loss of copper on ores of varying produce. the figures in the fourth column show how rapidly the proportion of copper lost increases as the percentage of copper in the ore falls below per cent. for material with more than per cent. the proportion lost is in inverse proportion to the copper present. loss of copper. -----------------+------------+-----------+------------------ copper present. | dry assay. | margin. | loss on | | | parts of copper. -----------------+------------+-----------+------------------ per cent. | per cent. | per cent. | | | . | . | - / | . | . | - / | . | . | - / | . | . | - / | . | . | - / | . | . | - / | . | . | - / | . | . | - / | . | . | - / | . | . | - / | . | . | | . | . | - / | . | . | - / | . | . | - / | . | . | - / | . | . | - / | . | . | - / | . | . | - / | . | . | - / | . | . | - / | . | . | - / | . | . | - / | . | . | | . | . | | . | . | | . | . . | - / | . | . . | - / | . | . . | - / | . | . . | - / | . | . . | - / | . | . . | - / | . | . . | - / | . | . . | - / | . | . -----------------+------------+-----------+------------------ the wet assay being known, the dry assay can be calculated with the help of the above table by deducting the amount in the column headed "margin" opposite the corresponding percentage. for example, if the wet assay gives a produce of . per cent., there should be deducted . ; the dry assay would then be . , or, since the fractions are always expressed in eighths, - / . with impure ores, containing from to per cent. of copper, the differences may be perhaps / greater. wet methods are gradually replacing the dry assay, and it is probable that in the future they will supersede it; for stock-taking, and the various determinations required in smelting works and on mines, they are generally adopted, because they give the actual copper contents, and since it is obvious that a knowledge of this is more valuable to the miner and smelter. moreover, the working of the dry method has been monopolised by a small ring of assayers, with the double result of exciting outside jealousy and, worse still, of retarding the development and improvement of the process. the principal stages of the dry assay are: ( ) the concentration of the copper in a regulus; ( ) the separation of the sulphur by calcining; ( ) the reduction of the copper by fusion; and ( ) the refining of the metal obtained. the whole of these operations are not necessary with all copper material. ores are worked through all the stages; with mattes, the preliminary fusion for regulus is omitted; precipitates are simply fused for coarse copper, and refined; and blister or bar coppers are refined, or, if very pure, subjected merely to washing. the quantity of ore generally taken is grains, and is known as "a full trial"; but for rich material, containing more than per cent. of copper, "a half trial," or grains, is used. ~fusion for regulus.~--the ore (either with or without a previous imperfect roasting to get rid of any excess of sulphur) is mixed with borax, glass, lime, and fluor spar; and, in some cases, with nitre, or iron pyrites, according to the quality of the ore. the mixture is placed in a large cornish crucible, and heated as uniformly as possible in the wind furnace, gradually raising the temperature so as to melt down the charge in from to minutes. the crucible is removed and its contents poured into an iron mould. when the slag is solid, it is taken up with tweezers and quenched in water. the regulus is easily detached from the slag. it should be convex above and easily broken, have a reddish brown colour, and contain from to per cent. of copper. a regulus with more than this is "too fine," and with less "too coarse." a regulus which is too fine is round, compact, hard, and of a dark bluish grey on the freshly broken surface. a coarse regulus is flat and coarse grained, and more nearly resembles sulphide of iron in fracture and colour. if an assay yields a regulus "too coarse," a fresh determination is made with more nitre added, or the roasting is carried further. with low class ores a somewhat coarse regulus is an advantage. if, on the other hand, the regulus is too fine, less nitre or less roasting is the remedy. with grey copper ores and the oxidised ores, iron pyrites is added. ~calcining the regulus.~--it is powdered in an iron mortar and transferred to a small cornish crucible, or (if the roasting is to be done in the muffle) to a roasting dish or scorifier. the calcining is carried out at a dull red heat, which is gradually increased. the charge requires constant stirring at first to prevent clotting, but towards the end it becomes sandy and requires less attention. if the temperature during calcination has been too low sulphates are formed, which are again reduced to sulphides in the subsequent fusion. to prevent this the roasted regulus is recalcined at a higher temperature, after being rubbed up with a little anthracite. the roasted substance must not smell of burning sulphur when hot. it is practically a mixture of the oxides of copper and iron. ~fusion for coarse copper.~--the calcined regulus is mixed with a flux consisting of borax and carbonate of soda, with more or less tartar according to its weight. some "assayers" use both tartar and nitre, the former of course being in excess. the charge is returned to the crucible in which it was calcined, and is melted down at a high temperature, and, as soon as tranquil, poured. when solid it is quenched and the button of metal separated. the slag is black and glassy. the small quantity of copper which it retains is recovered by a subsequent "cleaning," together with the slags from the next operation. the button of "coarse copper" obtained must be free from a coating of regulus. it will vary somewhat in appearance according to the nature and quantity of the impurities. ~refining the coarse copper.~--the same crucible is put back in the furnace, deep down and under the crevice between the two bricks. when it has attained the temperature of the furnace the coarse copper is dropped into it and the furnace closed. the copper will melt almost at once with a dull surface, which after a time clears, showing an "eye." some refining flux is then shot in from the scoop (fig. ), and, when the assay is again fluid, it is poured. when cold the button of metal is separated. [illustration: fig. .] the button of "fine" copper is flat or pitted on its upper surface, and is coated with a thin orange film; it must have the appearance of good copper. if it is covered with a red or purple film, it is overdone or "burnt." if, on the other hand, it has a rough, dull appearance, it is not sufficiently refined. assays that have been "burnt" are rejected. those not sufficiently fine are treated as "coarse copper," and again put through the refining operation. ~cleaning the slags.~--these are roughly powdered and re-fused with tartar, etc., as in the fusion for coarse copper. the button of metal got is separated (if big enough refined) and weighed. the details of the process are slightly varied by different assayers: the following will be good practice for the student. ~determination of copper in copper pyrites.~--powder, dry, and weigh up grams of the ore. mix with grams each of powdered lime and fluor, grams each of powdered glass and borax, and or grams of nitre. transfer to a large cornish crucible and fuse under a loose cover at a high temperature for from to minutes. when fluid and tranquil pour into a mould. when the slag has solidified, but whilst still hot, quench by dipping two or three times in cold water. avoid leaving it in the water so long that it does not dry after removal. when cold separate the button, or perhaps buttons, of regulus by crumbling the slag between the fingers. see that the slag is free from regulus. it should be light coloured when cold and very fluid when hot. reject the slag. powder the regulus in a mortar and transfer to a small crucible. calcine, with occasional stirring, until no odour of sulphurous oxide can be detected. shake back into the mortar, rub up with about gram of powdered anthracite, and re-calcine for minutes longer. mix the calcined regulus with grams of tartar, grams of soda, and grams of borax; and replace in the crucible used for calcining. fuse at a bright red heat for or minutes. pour, when tranquil. as soon as solid, quench in water, separate the button of copper, and save the slag. to refine the copper a very hot fire is wanted, and the fuel should not be too low down in the furnace. place the crucible well down in the fire and in the middle of the furnace. the same crucible is used, or, if a new one is taken, it must be glazed with a little borax. when the crucible is at a good red heat, above the fusing point of copper, drop the button of copper into it, and close the furnace. watch through the crevice, and, as soon as the button has melted and appears clear showing an eye, shoot in grams of refining flux, close the furnace, and, in a few minutes, pour; then separate the button of copper. add the slag to that from the coarse copper fusion, and powder. mix with grams of tartar, . gram of powdered charcoal, and grams of soda. fuse in the same crucible, and, when tranquil, pour; quench, and pick out the prills of metal. if the copper thus got from the slags is coarse looking and large in amount, it must be refined; but, if small in quantity, it may be taken as four-fifths copper. the combined results multiplied by five give the percentage of copper. the refining flux is made by mixing parts (by measure) of powdered nitre, - \ of tartar, and of salt. put in a large crucible, and stir with a red-hot iron until action has ceased. this operation should be carried out in a well-ventilated spot. for pure ores in which the copper is present, either as metal or oxide, and free from sulphur, arsenic, &c., the concentration of the copper in a regulus may be omitted, and the metal obtained in a pure state by a single fusion.[ ] it is necessary to get a fluid neutral slag with the addition of as small an amount of flux as possible. the fusion should be made at a high temperature, so as not to occupy more than from to minutes. thirty grams of ore is taken for a charge, mixed with grams of cream of tartar, and grams each of dried borax and soda. if the gangue of the ore is basic, carrying much oxide of iron or lime, silica is added, in quantity not exceeding grams. if, on the other hand, the gangue is mainly quartz, oxide of iron up to grams must be added. _example._--twenty grams of copper pyrites, known to contain . per cent. of copper, gave by the method first described . grams of copper, equalling - / per cent. another sample of grams of the same ore, calcined, fused with grams of nitre, and washed to ensure the removal of arsenic and sulphur, and treated according to the second method, gave a button weighing . grams, equalling - / per cent. the ore contained a considerable quantity of lead. lead renders the assay more difficult, since after calcination it remains as lead sulphate, and in the fusion for coarse copper reappears as a regulus on the button. ~the estimation of moisture.~--the cornish dry assayer very seldom makes a moisture determination. he dries the samples by placing the papers containing them on the iron plate of the furnace. it is well known that by buying the copper contents of pyrites by cornish assay, burning off the sulphur, and converting the copper into precipitate, a large excess is obtained. notes on the valuation of copper ores. closely bound up with the practice of dry copper assaying is that of valuing a parcel of copper ore. the methods by which the valuation is made have been described by mr. westmoreland,[ ] and are briefly as follows:--the produce of the parcel is settled by two assayers, one acting for the buyer, the other for the seller; with the help, in case of non-agreement, of a third, or referee, whose decision is final. the dry assayers who do this are in most cases helped, and sometimes, perhaps, controlled, by wet assays made for one or both of the parties in the transaction. in the case of "ticketing," the parcels are purchased by the smelters by tender, and the value of any particular parcel is calculated from the average price paid, as follows:--the "standard," or absolute value of each ton of fine copper in the ore, is the price the smelters have paid for it, plus the returning charges or cost of smelting the quantity of ore in which it is contained. the value of any particular parcel of ore is that of the quantity of fine copper it contains, calculated on this standard, minus the returning charges. the ton consists of cwts., and it is assumed that the "settled" produce is the actual yield of the ore. if at a ticketing in cornwall tons of ore containing . tons of fine copper (by dry assay) brought £ s., the standard would be £ s. this is calculated as follows:--the returning charge is fixed at s. per ton of ore. this on tons will amount to £ s. add this to the actual price paid, and there is got £ as the value of the fine copper present. the weight of copper in these tons being . tons, the standard is £ / . , or £ s. (nearly). the value of a parcel of tons of a per cent. ore on the same standard would be arrived at as follows:--the tons at per cent. would contain tons ( × / ) of fine copper. this, at £ s. per ton, would give £ s. from this must be deducted the returning charges on tons of ore at s. per ton, or £ s. this leaves £ s. as the value of the parcel. at swansea the returning charge is less than in cornwall, and varies with the quality of the ore. this appears equitable, since in smelting there are some costs which are dependent simply on the number of tons treated, and others which increase with the richness. the returning charge then is made up of two parts, one fixed at so much ( s. d.) per ton of ore treated, and the other so much ( s. d.) per unit of metal in the ore. in this way the returning charge on a ton of ore of - / produce would be ( s. d.)+( - / ×( s. d.)), or £ s. if, for example, chili bars, containing per cent. of copper, bring £ per ton, the standard is £ s. d. it is got at in this way. the returning charge on a per cent. ore is ( s. d.)+( ×( s. d.)), or £ s. d. this added to £ gives £ s. d., and this multiplied by and divided by ( tons of the bars will contain tons of fine copper) will give £ s. d. the price of tons of pyrites, containing - / per cent. of copper by dry assay, would be got on this standard as follows:--the parcel of ore would contain - / tons of copper. this multiplied by the standard gives £ s. d. from this must be deducted the returning charge, which for ton of ore of this produce would be ( s. d.) + ( - / ×( s. d.)) or £ s. d., and on the tons is £ s. d. this would leave £ s. d. as the price of the parcel, or s. d. per ton. this would be on the standard returning charge of s. (for - / per cent. ore); if a smaller returning charge was agreed on, say s., the difference in this case, s., would be added to the price per ton. wet methods. the solubility of the ores of copper in acid has already been described, but certain furnace products, such as slags, are best opened up by fusion with fusion mixture and a little nitre. the method of dissolving varies with the nature of the ore. with grams of pyrites, a single evaporation with c.c. of nitric acid will give a residue completely soluble in c.c. of hydrochloric acid. if the ore carries oxide of iron or similar bodies, these are first dissolved up by boiling with c.c. of hydrochloric acid, and the residue attacked by an addition of c.c. of nitric. when silicates decomposable by acid are present, the solution is evaporated to dryness to render the silica insoluble; the residue extracted with c.c. of hydrochloric acid, and diluted with water to c.c. it is advisable to have the copper in solution as chloride. to separate the copper, heat the solution nearly to boiling (best in a pint flask), and pass a rapid current of sulphuretted hydrogen for four or five minutes until the precipitate settles readily and the liquid smells of the gas. when iron is present it will be reduced to the ferrous state before the copper sulphide begins to separate. the copper appears as a brown coloration or black precipitate according to the quantity present. filter through a coarse filter, wash with hot water containing sulphuretted hydrogen, if necessary. wash the precipitate back into the flask, boil with c.c. of nitric acid, add soda till alkaline, and pass sulphuretted hydrogen again. warm and filter, wash and redissolve in nitric acid, neutralise with ammonia, add ammonic carbonate, boil and filter. the copper freed from impurities will be in the solution. acidulate and reprecipitate with sulphuretted hydrogen. when the nature of the impurities will allow it, this process may be shortened to first filtering off the gangue, then precipitating with sulphuretted hydrogen and washing the precipitate on the filter first with water and then with ammonium sulphide. having separated the copper as sulphide, its weight is determined as follows. dry and transfer to a weighed porcelain crucible, mix with a little pure sulphur, and ignite at a red heat for or minutes in a current of hydrogen. allow to cool while the hydrogen is still passing. weigh. the subsulphide of copper thus obtained contains . per cent. of copper; it is a greyish-black crystalline mass, which loses no weight on ignition if air is excluded. copper may be separated from its solutions by means of sodium hyposulphite. the solution is freed from hydrochloric and nitric acids by evaporation with sulphuric acid; diluted to about a quarter of a litre; heated nearly to boiling; and treated with a hot solution of sodium hyposulphite (added a little at a time) until the precipitate settles and leaves the solution free from colour. the solution contains suspended sulphur. the precipitate is easily washed, and under the proper conditions the separation is complete, but the separation with sulphuretted hydrogen is more satisfactory, since the conditions as to acidity, &c., need not be so exact. zinc or iron is sometimes used for separating copper from its solutions, but they are not to be recommended. electrolytic assay. the separation of copper by means of a current of electricity is largely made use of, and forms the basis of the most satisfactory method for the determination of this metal. if the wire closing an electric circuit be broken, and the two ends immersed in a beaker of acidulated water or solution of any salt, the electricity will pass through the liquid, bringing about some remarkable changes. hydrogen and the metals will be liberated around that part of the wire connected with the zinc end of the battery, and oxygen, chlorine, and the acid radicals will be set free around the other. different metals are deposited in this way with varying degrees of ease, and whether or not any particular metal will be deposited depends--( ) on the conditions of the solution as regards acid and other substances present, and ( ) on the _intensity_ of the current of electricity used. for analytical purposes the metal should be deposited not only free from the other metals present, but also as a firm coherent film, which may afterwards be manipulated without fear of loss. this is, in the case of copper and many other metals, effected by a simple control of the conditions. it is necessary that the electrodes, or wires which bring the electricity into the solution, should be made of a material to which the deposited metal will adhere, and which will not be attacked by substances originally present or set free in the solution. they are generally made of platinum. there are various arrangements of apparatus used for this purpose, but the following plan and method of working is simple and effective, and has been in daily use with very satisfactory results for the last five or six years. the battery used is made up of two daniell cells, coupled up for intensity as shown in fig. --that is, with the copper of one connected with the zinc of the other. for eight or ten assays daily the quart size should be used, but for four or five two pint cells will be sufficient. [illustration: fig. .] the outer pot of each cell is made of sheet copper, and must be clean and free from solder on the inside. it is provided near the top with a perforated copper shelf in the shape of a ring, into which the inner or porous cell loosely fits. it is charged with a saturated solution of copper sulphate, and crystals of this salt must be added, and always kept in excess. when the battery is at work copper is being deposited on the inner surface of this pot. the inner or porous pot contains the zinc rod, and is charged with a dilute acid, made by diluting one volume of sulphuric acid up to ten with water. the object of the porous pot is to prevent the mixing of the acid and copper sulphate solutions, without interrupting the flow of electricity. the copper sulphate solution will last for months, but the acid must be emptied out and recharged daily. the zinc rods must be well amalgamated by rubbing with mercury under dilute acid until they show a uniformly bright surface. they should not produce a brisk effervescence when placed in the acid in the porous pot before coupling up. the battery when working is apt to become dirty from the "creeping" of the copper and zinc sulphate solution. it must be kept away from the working bench, and is best kept in a box on the floor. [illustration: fig. .] the connection of the battery with, and the fixing of, the electrodes may be made by any suitable arrangement, but the following is a very convenient plan. the wire from the zinc is connected by means of a binding screw with a piece of stout copper wire, which, at a distance sufficiently great to allow of easy coupling with the battery, is led along the back of a piece of hard wood. this is fixed horizontally about one foot above the working bench. the general arrangement is shown in fig. , in which, however, for the sake of economy of space, the battery is placed on the working bench instead of on the floor. the piece of wood is one inch square and three or four feet long. it is perforated from front to back at distances of six inches by a number of small holes, in which are inserted screws like that shown in fig. . these are known as "terminals," and may be obtained of any electrician. the head of each screw is soldered to the wire mentioned above as running along the back and as being connected with the zinc end of the battery. these terminals serve to fix the electrodes on which the copper is to be deposited. the wire from the copper end of the battery is similarly connected by a connecting screw (fig. ) with another wire (h in fig. ), which runs along the top of the rod and has soldered to it, at distances of six inches, cylindrical spirals of copper wire. these should project from the rod at points about half-way between the terminals already described. they may be made by wrapping copper wire around a black-lead pencil for a length of about three inches. [illustration: fig. .] [illustration: fig. .] [illustration: fig. .] the rod is perforated from top to bottom with a series of small holes, one in advance of each terminal but as near it as possible. into these short pieces of glass tube are inserted to ensure insulation. these receive the other electrodes, which are connected with the wire leading to the copper end of the battery, through the spirals, with the help of a binding screw. the figure will make this clear. (fig. .) [illustration: fig. ] ~the electrodes~ consist of a platinum spiral and cylinder. the spiral should have the shape shown in a, fig. . when in work it is passed through one of the holes fitted with glass tubes and connected with the copper end of the battery. the thickness of the wire of which it is made is unimportant, provided it is stout enough to keep its form and does not easily bend. the spiral will weigh about grams. the cylinder (c, fig. ) will weigh about grams. it should have the shape shown in the figure. in working it is clamped to one of the terminals, and on it the copper is deposited. a cylinder will serve for the deposition of from to . gram of copper. it is made by rivetting a square piece of foil on to a stiff piece of wire, and then bending into shape over a glass tube or piece of rounded wood. each cylinder carries a distinctive number, and is marked by impressing roman numerals on the foil with the blade of a knife. the weight of each is carefully taken and recorded. they lose slightly in weight when in use, but the loss is uniform, and averages half a milligram per month when in daily use. the cylinders are cleaned from deposited copper by dissolving off with nitric acid and washing with water; and from grease by igniting. the ~beakers~, to contain the solution of copper to be electrolysed, are ordinary tall beakers of about c.c. capacity, and are marked off at c.c. and c.c. they are supported on movable stands, consisting of wooden blocks about six inches high and three inches across. the bar of wood which carries the connecting wires and electrodes is permanently fixed over the working bench, at such a height that, with the beakers resting on these blocks, the electrodes shall be in position for working. to fix the electrodes to the rod, remove the stand and beaker and pass the long limb of the spiral up through one of the glass tubes. connect it with the free end of the copper spiral by means of a connecting screw (fig. ), and then draw out and bend the copper spiral so that the platinum one may hang freely. screw the wire of the cylinder to the terminal, and, if necessary, bend it so that the cylinder itself may be brought to encircle the rod of the spiral in the manner shown in fig. . the ~general method of working~ is as follows:--the quantity of ore to be taken for an assay varies with the richness of the ore, as is shown in the following table:-- percentage of copper quantity of ore in the ore. to be taken. to grams to " to " to . " to " the weighed quantity of ore is dissolved by evaporating with nitric acid and taking up with hydrochloric, as already described. any coloured residue which may be left is generally organic matter: it is filtered off, calcined, and any copper it contains is estimated colorimetrically. nearly always, however, the residue is white and sandy. the copper is separated from the solution as sulphide by means of a rapid current of sulphuretted hydrogen. the liquid is decanted off through a filter, the precipitate washed once with hot water and then rinsed back into the flask (the filter paper being opened out) with a jet of water from a wash bottle. fifteen c.c. of nitric acid are added to the contents of the flask, which are then briskly boiled until the bulk is reduced to less than c.c. the boiling down is carried out in a cupboard free from cold draughts, so as to prevent the condensation of acid and steam in the neck of the flask. twenty c.c. of water are next added, and the solution is warmed, and filtered into one of the beakers for electrolysis. the filtrate and washings are diluted with water to the c.c. mark, and the solution is then ready for the battery. it must not contain more than per cent. by volume of nitric acid. the number and weight of the platinum cylinder having been recorded, both electrodes are fixed in position and the wooden block removed from under them. the beaker containing the copper solution is then brought up into its place with one hand, and the block replaced with the other so as to support it. all the assays having been got into position, the connecting wires are joined to the battery. if everything is right bubbles of oxygen at once stream off from the spiral, and the cylinder becomes tarnished by a deposit of copper. if the oxygen comes off but no copper is deposited, it is because the assay solution contains too much nitric acid. if no action whatever takes place, it is because the current is not passing. in this case examine the connections to see that they are clean and secure, and the connecting wires to see that they are not touching each other. the action is allowed to go on for sixteen or seventeen hours, so that it is best to let the current act overnight. in the morning the solutions will appear colourless, and a slow stream of oxygen will still be coming off from the spiral. a wash-bottle with cold distilled water and two beakers, one with distilled water and the other with alcohol, are got ready. the block is then removed, the spiral loosened and lowered with the beaker. the cylinder is next detached and washed with a stream of water from the wash-bottle, the washings being added to the original solution. the current from the battery is not stopped until all the cylinders are washed. after being dipped in the beaker of water and once or twice in that with the alcohol, it is dried in the water-oven for about three minutes, and then weighed. the increase in weight is due to deposited copper. this should be salmon-red in colour, satin-like or crystalline in appearance, and in an even coherent deposit, not removed by rubbing. it is permanent in air when dry, but sulphuretted hydrogen quickly tarnishes it, producing coloured films. with ores containing even very small proportions of bismuth, the deposited copper has a dark grey colour, and when much of this metal is present the copper is coated with a grey shaggy deposit. it still remains to determine any copper left undeposited in the solution. this does not generally exceed four or five milligrams, and is estimated colorimetrically. thirty c.c. of dilute ammonia (one of strong ammonia mixed with one of water) are added to the electrolysed solution, which is then diluted up to the c.c. mark with water. it is mixed, using the spiral as stirrer, and, after standing a few minutes to allow the precipitate to settle, c.c. of it are filtered off through a dry filter for the colorimetric determination. since only two-thirds of the solution are taken for this, the quantity of copper found must be increased by one-half to get the quantity actually present. [illustration: fig. .] the ~colorimetric determination~ may be made in the manner described under that head, but where a number of assays are being carried out it is more convenient to have a series of standard phials containing known amounts of copper in ammoniacal solution. by comparing the measured volume of the assay solution with these, the amount of copper present is determined at a glance. these standard bottles, however, can only be economically used where a large number of assays are being made daily. a convenient plan is to get a quantity of white glass four-ounce phials, like that in fig. , and to label them so that they shall contain c.c. when filled up to the bottom of the labels. the labels should be rendered permanent by coating with wax, and be marked with numbers indicating the milligrams of copper present. the bottles are stopped with new clean corks, and contain, in addition to the specified quantity of copper, c.c. of nitric acid and c.c. of strong ammonia, with sufficient water to make up the bulk to c.c. the copper is best added by running in the requisite amount of a standard solution of copper, each c.c. of which contains . gram of the metal. the standard bottles should be refilled once every three or four months, since their colorimetric value becomes slowly less on keeping. the following determinations of a set which had been in use for three months will illustrate this. the figures indicate milligrams of copper in c.c.: the first row gives the nominal and the second row the actual colorimetric value of the standards. the difference between the two shows the deterioration. . . . the amount of copper in the assay is got by increasing that found colorimetrically by one-half and adding to that found on the platinum cylinder. the percentage is calculated in the usual way. the following examples will illustrate this, as well as the method of recording the work in the laboratory book:-- --------------------------------------------- cylinder i. + cu . cylinder i. . ------ . by colour c.c. = . } . } . ------ ------ . . ix. sample. took grams. copper = . % --------------------------------------------- cylinder vi. + cu . cylinder vi. . ------- . by colour, c.c. = . } . } . ------ ------ . . matte, no. . took . gram. copper = . % --------------------------------------------- cylinder xiii. + cu . cylinder xiii. . ------- . by colour c.c. = . } . } . ------ ------ . . x. sample, cake copper. took . gram. copper = . % --------------------------------------------- in the electrolytic assay of metals, alloys, precipitates, and other bodies rich in copper, the preliminary separation of the copper by sulphuretted hydrogen is unnecessary. it is sufficient to dissolve the weighed sample in c.c. of nitric acid, boil off nitrous fumes, dilute to c.c. with water, and then electrolyse. ~general considerations.~--in the preliminary work with the copper sulphide there is a small loss owing to its imperfect removal in washing the filter paper, and another small loss in dissolving in nitric acid owing to the retention of particles in the fused globules of sulphur. to determine its amount the filter-papers and sulphur were collected from forty assays, and the copper in them determined. the average amount of copper in each assay was . gram; that left on the filter paper was . gram; and that retained by the sulphur . gram; thus showing an average loss from both sources of . gram. the determinations from another lot of forty-two similar assays gave on an average copper left on filter paper . gram copper retained by sulphur. . " the loss from these sources is trifling, and need only be considered when great accuracy is required. the deposition of the copper under the conditions given is satisfactory, but, as already stated, if the solution contain more than per cent. of nitric acid it is not thrown down at all; or if a stronger current is used, say that from three bunsen cells, it will be precipitated in an arborescent brittle form, ill adapted for weighing. it may be noted here that increasing the size of the cells does not necessarily increase the intensity of the current. in two determinations on pure electrotype copper the following results were obtained:-- copper taken. copper found. . gram . gram . " . " the presence of salts of ammonia, &c., somewhat retards the deposition, but has no other ill effect. the organic matter generally present in copper ores interferes more especially in the colorimetric determination of the residual copper. it can be detected on dissolving the ore as a light black residue insoluble in nitric acid. it is filtered off at once, or, if only present in small amount, it is carried on in the ordinary process of the assay and separated in the last filtration before electrolysis. the following experiments were made to test the effect of the presence of salts of foreign metals in the solution during the precipitation of copper by electrolysis:-- --------------+----------------------------------------+--------------- copper taken. | other metal added. | copper found. --------------+----------------------------------------+--------------- . gram | . gram of silver | . . " | . " " | . . " | . " mercury | . . " | . " " | . . " | . " lead | . . " | . " " | . . " | . " arsenic | . . " | . " " | . . " | . " antimony | . . " | . " " | . . " | . " tin | . . " | . " " | . . " | . " bismuth | . . " | . " cadmium | . . " | . " zinc | . . " | . " nickel | . . " | . " iron | . . " | . " chromium (cr_{ }o_{ }) | . . " | . " " (k_{ }cro_{ }) | . . " | . " aluminium | . . " | . " manganese | . --------------+----------------------------------------+--------------- it will be seen from these that mercury, silver, and bismuth are the only metals which are precipitable[ ] along with the copper under the conditions of the assay. mercury, which if present would interfere, is separated because of the insolubility of its sulphide in nitric acid. bismuth is precipitated only after the main portion of the copper is thrown down. it renders the copper obviously unsuitable for weighing. it darkens, or forms a greyish coating on, the copper; and this darkening is a delicate test for bismuth. in assaying ores containing about three and a half per cent. of copper, and known to contain bismuth in quantities scarcely detectable in ordinary analysis, the metal deposited was distinctly greyish in colour, and would not be mistaken for pure copper. ten grams of this impure copper were collected and analysed, with the following results:-- copper . per cent. bismuth . " iron . " arsenic . " ------ . the quantity of copper got in each assay was . gram, and consequently the bismuth averaged . gram. to separate the bismuth in such a case the deposit is dissolved off by warming it in the original solution. the bismuth is precipitated by the addition of ammonic carbonate, and the solution, after filtering and acidifying with nitric acid, is re-electrolysed. ~determination of copper in commercial copper.~--take from to . gram, weigh carefully, and transfer to a beaker; add c.c. of water and c.c. of nitric acid; cover with a clock glass, and allow to dissolve with moderate action; boil off nitrous fumes, dilute to c.c., and electrolyse. the cylinder must be carefully weighed, and the electrolysis allowed to proceed for hours. the weight found will be that of the copper and silver. the silver in it must be determined[ ] and deducted. ~determination of copper in brass, german silver, or bronze.~--treat in the same manner as commercial copper. if nickel is present, the few milligrams of copper remaining in the electrolysed solution should be separated with sulphuretted hydrogen, the precipitated sulphide dissolved in nitric acid, and determined colorimetrically. volumetric processes. there are two of these in use, one based on the decolorising effect of potassic cyanide upon an ammoniacal copper solution, and the other upon the measurement of the quantity of iodine liberated from potassic iodide by the copper salt. the cyanide process is the more generally used, and when carefully worked, "on certain understood and orthodox conditions," yields good results; but probably there is no method of assaying where a slight deviation from these conditions so surely leads to error. an operator has no difficulty in getting concordant results with duplicate assays; yet different assayers, working, without bias, on the same material, get results uniformly higher or lower; a difference evidently due to variations in the mode of working. where a large number of results are wanted quickly it is a very convenient method. the iodide process is very satisfactory when worked under the proper conditions. cyanide method. the process is based upon the facts--( ) that when ammonia is added in excess to a solution containing cupric salts, ammoniacal copper compounds are formed which give to the solution a deep blue colour; and ( ) that when potassic cyanide is added in sufficient quantity to such a solution the colour is removed, double cyanides of copper and potassium or ammonium being formed.[ ] in the explanation generally given the formation of cuprous cyanide is supposed[ ]; but in practice it is found that one part of copper requires rather more than four parts of cyanide, which agrees with the former, rather than the latter, explanation. reliance on the accuracy of the process cannot rest upon the supposition that the cyanide required for decoloration is proportional to the copper present, for varying quantities of ammonia salts, ammonia and water, and differences of temperature have an important effect. the results are concordant and exact only when the cyanide is standardised under the same conditions as it is used. it is best to have the assay solution and that used for standardising as nearly as possible alike, and to titrate the two solutions side by side. this demands an approximate knowledge of the quantity of copper contained in the ore and a separation of the bulk of the impurities. for the titration there is required a standard solution of potassium cyanide made by dissolving grams of the salt, known to dealers as potassium cyanide (gold), in water and diluting to one litre: c.c. of this will be about equivalent to one gram of copper. for poor ores the solution may conveniently be made half this strength. the solution of the ore and the separation of the copper as sulphide are effected in the same ways as have been already described for electrolysis. similarly, too, the sulphide is attacked with c.c. of nitric acid and the assay boiled down to c.c. add c.c. of water and warm, filter into a pint flask, wash well with water, and dilute to about c.c.; add c.c. of dilute ammonia, and cool. prepare a standard by dissolving a quantity of electrotype copper (judged to be about the same as that contained in the assay) in c.c. of water and c.c. of nitric acid, boil off the nitrous fumes, and dilute to c.c.: add c.c. of dilute ammonia and cool. fill a burette with the standard cyanide solution. the burette with syphon arrangement, figured on page , is used. a number of titrations can be carried on at the same time provided the quantity of copper present in each is about the same. this is regulated in weighing up the ore. the flasks must of course be marked, and should be arranged in series on a bench in front of a good light and at such a height that the liquid can be looked through without stooping. supposing about c.c. of cyanide will be required, c.c. should be run into each, and each addition be recorded as soon as made; then run c.c. into each. the solutions will now probably show marked differences of tint: add c.c. of cyanide to the lighter ones and more to the darker, so as to bring the colours to about the same depth of tint. they should all be of nearly equal tint just before finishing. at the end add half a c.c. at a time until the colours are completely discharged. a piece of damp filter paper held between the light and the flask assists in judging the colour when nearly finished. overdone assays show a straw yellow colour which deepens on standing. the following will illustrate the notes recorded of five such assays and one standard:-- ( ) c.c. c.c. c.c. c.c. c.c. / c.c. -- c.c. = - / c.c. ( ) " " " " " / " -- " = - / " ( ) " " " " " / " -- " = - / " ( ) " " " " " / " / " = " ( ) " " " " " / " -- " = - / " ( ) " " " " " / " / " = standard three grams of ore were taken, and the standard contained . gram of copper. in this series the difference of half a c.c. means about . per cent. on the ore; with a little practice it is easy to estimate whether the whole or half of the last addition should be counted. to get satisfactory results, the manner of finishing once adopted must be adhered to. the following experiments show the effect of variation in the conditions of the assay:--use _a solution of copper nitrate_, made by dissolving grams of copper in c.c. of water and c.c. of nitric acid, and diluting to a litre. c.c. = gram of copper. ~effect of varying temperature.~--in these experiments c.c. of copper nitrate were used, with c.c. of nitric acid, c.c. of dilute ammonia, and water to c.c. the results were-- temperature ° ° ° ° cyanide required . c.c. . c.c. . c.c. . c.c. the temperature is that of the solution _before_ titrating. these show the importance of always cooling before titrating, and of titrating the assay and standard at the same temperature. ~effect of varying bulk.~--the quantities of copper, acid, and ammonia were the same as in the last-mentioned experiments. the results were:-- bulk . c.c. . c.c. . c.c. . c.c. cyanide required . " . " . " . " these show that large variations in bulk must be avoided. ~effect of varying ammonia.~--the quantities of copper and acid were the same as in the series of experiments last noticed. the bulk was c.c. the results were:-- dilute ammonia . c.c. . c.c. . c.c. . c.c. cyanide required . " . " . " . " ~effect of varying acid.~--the quantities of copper and water were the same as in the last-noticed set of experiments: c.c. of dilute ammonia were used. nitric acid . c.c. . c.c. . c.c. cyanide required . " . " . " on adding nitric acid to the solution it combines with a portion of the ammonia to form ammonic nitrate; it will be seen from the last series of experiments that the lessening of the amount of free ammonia will decrease the quantity of cyanide required; but, on the other hand, the ammonic nitrate which is at the same time formed will increase the amount required; under the conditions of the assay these two effects neutralise each other, and such differences in the quantity of acid as are likely to occur are unimportant. ~effect of varying ammonic salts.~--the quantities of copper, water, and ammonia were the same as in the last mentioned set of experiments, but no nitric acid was used. ammonic nitrate added gram grams grams grams cyanide required . c.c. . c.c. . c.c. . c.c. these show that combined ammonia seriously affects the titration, and that the principle sometimes recommended of neutralising the acid with ammonia, and then adding a constant quantity of ammonia, is not a good one, because there is then an interference both by the ammonia and by the variable quantity of ammonic salts. the same quantity of combined ammonia has the same effect, whether it is present as sulphate, nitrate, chloride, or acetate, as the following experiments show. four lots of c.c. of "copper nitrate" were taken, and c.c. of dilute ammonia added to each. these were carefully neutralised with the respective acids, rendered alkaline with c.c. more of ammonia, cooled, diluted to bulk, and titrated. the results were:-- with sulphuric acid . c.c. of cyanide " nitric acid . " " " hydrochloric acid . " " " acetic acid . " " ~effect of foreign salts.~--sulphates, nitrates and chlorides of sodium or potassium have no action, whilst the hydrates, carbonates, bicarbonates, sulphites, and nitrites have an important effect. the interference of ammonic salts has already been shown. salts of silver, zinc, and nickel react with cyanide just as copper does, and consequently interfere. ferrous salts are sure to be absent, and ferric salts yield ferric hydrate with the ammonia, which is not acted on by the cyanide, but, owing to its bulkiness, it settles slowly; this lengthens the time required for titration, and so modifies the manner of working. _an assay should not be worked with ferric hydrate present, unless the standard contains about the same amount of it._ on mines it is often inconvenient to separate the copper by means of sulphuretted hydrogen; hence it is customary to titrate without previous separation. in this case, instead of standardising the cyanide with electrotype copper, a standard ore should be used. this should be an ore (of the same kind as those being assayed) in which the copper has been carefully determined. ~effect of varying copper.~--in these experiments c.c. of nitric acid, c.c. of ammonia, and water to c.c. were used. copper nitrate present . c.c. . c.c. . c.c. . c.c. . c.c. cyanide required . " . " . " . " . " these results show that under the conditions laid down the various causes of disturbance nearly neutralise one another, and the results within a fair range are practically proportional. ~determination of copper in copper pyrites.~--weigh up grams of the dried and powdered ore, and place in an evaporating dish about four inches in diameter. cover with c.c. of nitric acid and put on a hot plate. evaporate to dryness without further handling. allow to cool and take up with c.c. of hydrochloric acid, boil, dilute, and transfer to a pint flask, filtering if necessary. make up the bulk with the washings to about c.c. precipitate with sulphuretted hydrogen, filter, and wash back the precipitate into the flask. add c.c. of nitric acid, and boil down rapidly to c.c. dilute, add c.c. of dilute ammonia, make up to c.c., and cool. for the standard, weigh up . gram of copper, more or less, according to the quantity judged to be present in the assay. dissolve in c.c. of dilute nitric acid, boil off nitrous fumes, add c.c. of dilute ammonia, make up to the same bulk as that of the assay, and cool. titrate the two solutions side by side and as nearly as possible in the same manner. since the assay solution is often turbid from the presence of small quantities of lead and of iron from incomplete washing, and since this slight precipitate is very slow in settling, the standard can hardly be compared strictly with the assay. this can be counteracted by precipitating in both solutions a mixture of ferric and aluminic hydrates, which settles readily and leaves the supernatant liquor clear. to effect this, boil the nitric acid solutions with c.c. of a solution containing grams each of alum and ferrous sulphate to the litre. in an actual determination grams of the ore were taken and compared with . gram of copper. the assay required . c.c. of cyanide and the standard . c.c. . : . :: . : . this on grams of ore = . per cent.; the same sample by electrolysis gave . per cent. of copper. ~determination without previous separation.~--dissolve up grams as before, but, instead of passing sulphuretted hydrogen, add c.c. of dilute ammonia, shake well, and cool. prepare a standard by dissolving . gram of copper in c.c. of nitric acid, add . gram of iron in the form of ferric chloride and c.c. of hydrochloric acid, dilute to about c.c., add c.c. of dilute ammonia, and cool. titrate the two solutions side by side. in a determination on the sample last used, c.c. were required for the assay and c.c. for the standard, which indicates . per cent. of copper. this method of working is somewhat rough. iodide method. this is based upon the fact that when potassic iodide in excess is added to a strong solution of a cupric salt in a faintly acid solution, cuprous iodide is formed and an equivalent of iodine liberated.[ ] the iodine is measured by titrating with a solution of sodium hyposulphite,[ ] using starch paste as indicator. the iodine is soluble in the excess of potassium iodide, forming a deep brown solution; the hyposulphite is added until this brown colour is almost removed. starch paste is then added, and strikes with the remaining iodine a dirty blue colour. the addition of the "hypo" is continued until the blue colour is discharged. the end reaction is sharp; a drop is sufficient to complete it. as regards the titration, the process leaves little to be desired; the quantity of "hypo" required is strictly proportional to the copper present, and ordinary variations in the conditions of working are without effect. the presence of salts of bismuth masks the end reaction because of the strong colour imparted to the solution by the iodide of bismuth. under certain conditions there is a return of the blue colour in the assay solution after the finishing point has apparently been reached, which is a heavy tax on the patience and confidence of the operator. this is specially apt to occur when sodium acetate is present, although it may also be due to excessive dilution. ~the standard "hypo" solution~ is made by dissolving . grams of the crystallised salt (na_{ }s_{ }o_{ }. h_{ }o) in water and diluting to one litre. one hundred c.c. will equal one gram of copper. the starch solution is made by mixing gram of starch into a thin paste with cold water, pouring it into c.c. of boiling water, and continuing the boiling for a minute or so. the solution must be cold before use, and about c.c. is used for each assay. it should not be added until the bulk of the iodine has been reduced. to standardise the "hypo," weigh up . or . gram of pure copper, dissolve in c.c. of dilute nitric acid, boil off nitrous fumes, and dilute with an equal bulk of cold water. add "soda" solution until a permanent precipitate is obtained, and then c.c. of acetic acid. this should yield a clear solution. fill an ordinary burette with the "hypo." add grams of potassium iodide crystals to the copper solution, and, when these are dissolved, dilute to c.c. with water. run in the "hypo" solution rather quickly until the brown colour is nearly discharged--_i.e._, to within or c.c. of the finish. add c.c. of the starch solution, and continue the addition of the "hypo" a few drops at a time until the tint suddenly changes to a cream colour. the blue colour must not return on standing three or four minutes. calculate the standard in the usual way. in assaying ores, the copper is dissolved and separated with sulphuretted hydrogen as in the other processes, but the sulphide should be washed more completely to ensure the absence of iron salts. the following experiments show the effect of variation in the conditions of the assay. use a solution of copper sulphate containing . grams of copper sulphate crystals (cuso_{ }. h_{ }o) in the litre. c.c. equal . gram of copper. ~effect of varying temperature.~--the assay after the addition of the potassic iodide must be kept cold, else iodine may be volatilised. ~effect of varying potassium iodide.~--in various descriptions of the process the amount of iodide required is variously stated at from "a few crystals" to as much as grams. the proportion required by theory for gram of copper is a little over grams: an excess, however, is required to keep the liberated iodine in solution. on economic grounds this excess should not be extravagant; if the student uses parts of the iodide for each part of copper in the assay he will have sufficient. in the experiments there were used c.c. of the copper sulphate, with varying amounts of potassic iodide, and the following results were got:-- potassic iodide added . gram grams grams "hypo" required . c.c. . c.c. . c.c. in these the iodide was added direct to the solution containing the copper, which was afterwards diluted to c.c. and titrated. in another series the iodide was added after the dilution to c.c., and the results were:-- potassic iodide added . gram grams grams grams "hypo" required . c.c. . c.c. . c.c. . c.c. ~effect of varying bulk.~--in these experiments, c.c. of copper sulphate were taken, grams of potassic iodide added, and also water to the required bulk. bulk . c.c. . c.c. . c.c. . c.c. "hypo" required . " . " . " . " in the last of these experiments the colour was discharged at c.c., but gradually returned until . c.c. had been run in. it will be seen that considerable variation in bulk does not interfere. ~effect of acetic acid.~--these experiments were like the last series mentioned, but the bulk was c.c., and varying amounts of acetic acid were added. acetic acid added c.c. . c.c. . c.c. . c.c. . c.c. "hypo" required . " . " . " . " . " acetic acid, then, does not interfere to any serious extent. ~effect of varying sodium acetate.~--these experiments were like those last mentioned, but without acetic acid, and with varying amounts of sodium acetate. sodium acetate added gram gram grams grams grams "hypo" required . c.c. . c.c. . c.c. . c.c. . c.c. in the grams experiment, when the finishing point had been apparently reached the colour slowly returned; but as the results generally on titrating were not satisfactory a repetition of the experiment was made with the addition of c.c. of acetic acid, which gave an equally bad result. ~effect of foreign salts.~--the conditions of these experiments were the same as before. the salts were added and dissolved before the addition of the potassium iodide. using grams (or in the case of the acids, c.c.), the results were as follows:-- dilute acetic salt added -- h_{ }so_{ } acid naac nacl "hypo" required . c.c. . c.c. . c.c. . c.c. . c.c. salt added kno_{ } na_{ }so_{ } amcl am_{ }so_{ } "hypo" required . c.c. . c.c. . c.c. . c.c. the low result with the sulphate of soda was evidently due to the formation of a sparingly soluble double salt, which removed copper from the solution; on adding a little acetic acid the full amount of "hypo" was required. the effect of the presence of certain metals is important. the method of determining it was to add the substance to the solution containing the copper, and partly precipitate with soda solution; then treating with c.c. of acetic acid, adding the iodide, and proceeding as before. substance added. "hypo" required, - . c.c . gram arsenic as as_{ }o_{ } . " . " antimony as sbcl_{ } . " . " lead as pb(no_{ })_{ } . " a similar experiment with . gram of bismuth nitrate could not be determined, the end-reaction being masked. bismuth iodide is soluble in potassic iodide, forming a brown solution, the colour of which is very similar to that produced by iodine; and although it does not strike a blue colour with starch, "hypo" has an action on it. a similar experiment with . gram of iron as ferric chloride required . c.c. of "hypo," and the colour returned on standing. this shows that ferric acetate liberates iodine under the conditions of the assay. trying to counteract this, by adding to a similar solution . gram of phosphate of soda dissolved in a little water, . c.c. of "hypo" were required instead of . , but the assay showed signs of returning colour. in standardising, the same result was obtained, whether the copper was present as nitrate or sulphate before neutralising. ~effect of varying copper.~--with the same conditions as before, but with varying amounts of copper and a proportionally increasing quantity of iodide, the results were:-- copper present . c.c. . c.c. . c.c. . c.c. . c.c. "hypo" required . " . " . " . " . " showing the results to be exactly proportional.[ ] ~determination of copper in copper pyrites.~--take grams of the dried and powdered ore and treat in a porcelain dish with c.c. of nitric acid, and evaporate to dryness. take up with c.c. of hydrochloric acid, dilute, and transfer to a pint flask; make up with water to c.c., warm, and pass sulphuretted hydrogen to excess. filter, and wash the precipitate with water acidified with sulphuric acid. wash the precipitate back into the flask, and dissolve with c.c. of nitric acid. evaporate almost to dryness; add c.c. of water, and boil till free from nitrous fumes; filter off the sulphur and gangue; neutralise with soda, avoiding excess; add or c.c. of acetic acid, and shake till clear. add grams of potassium iodide, dilute to c.c., and titrate. the following is an example:-- . gram of copper required . c.c. "hypo." the assay required . " " which is equal to . per cent. of copper. colorimetric process. this is based on the blue coloration of ammoniacal copper solutions. the quantity of copper in c.c. of the assay solution should not be more than milligrams, or less than half a milligram. it is not so delicate as most other colorimetric methods, but nevertheless is a very useful one. the manner of working is the same as that described under iron. ~standard copper solution.~--weigh up . gram of electrotype copper, dissolve in c.c. of nitric acid, boil off nitrous fumes, and dilute to litre. c.c. = . milligram. in nearly all cases it will be necessary to separate the copper with sulphuretted hydrogen from a solution of about grams of the material to be assayed. the filter paper containing the sulphide (and, probably, much sulphur) is dried and burnt. the ashes are dissolved in c.c. of dilute nitric acid, c.c. of dilute ammonia added, and the solution filtered through a coarse filter into a nessler tube, washing the paper with a little dilute ammonia. the estimation of the colour and calculation of the result are made in the way described on page . the effect of varying conditions on the assay may be seen from the following experiments. ~effect of varying temperature.~--the effect of increased temperature is to slightly decrease the colour, but this can only be observed when a fair quantity of copper is present. . c.c. at ° showed the colour of . c.c. at ° . " " " " . " . " " " " . " . " " " " . " ~effect of varying ammonia.~--the solution must, of course, contain free ammonia; about c.c. of dilute ammonia in c.c. bulk is the quantity to be used in the experiments. a larger quantity affects the results, giving lower readings and altering the tint. with small quantities of ammonia the colour approaches a violet; with larger, a sky-blue. . c.c. with c.c. of strong ammonia read . c.c. . " " " " " . " . " " " " " . " ~effect of ammonic salts.~--the following table shows the results after addition of ammonic salts:-- --------------+-----------------+------------------+------------------ c.c. present.| with grams | with grams | with grams | ammonic nitrate.| ammonic chloride.| ammonic sulphate. --------------+-----------------+------------------+------------------ . | . | . | . . | . | . | . . | . | . | . --------------+-----------------+------------------+------------------ these show that sulphates should be avoided, and either nitrate or chloride solutions be used in the standard as well as in the assay. ~determination of copper in a manganese ore.~--treat grams of the ore with c.c. of hydrochloric acid, and evaporate to dryness. take up with c.c. of hydrochloric acid; dilute to about c.c., and pass sulphuretted hydrogen until the solution smells of the gas; filter, burn, take up with c.c. of dilute nitric acid, add c.c. of dilute ammonia, and filter into the nessler tube, and make up with the washings to c.c. into the "standard" tube put c.c. of dilute nitric acid and c.c. of dilute ammonia. make up to nearly c.c. with water, and run in the standard copper until the colours are equal. in a determination c.c. (= . milligrams of copper) were required; this in grams of ore = . per cent. ~determination of copper in "black tin."~--weigh up grams of the dried ore, boil with c.c. of hydrochloric acid, and afterwards add c.c. of nitric; boil off nitrous fumes, evaporate to about c.c., dilute to c.c., add c.c. of dilute ammonia; stir, and filter. if much iron is present, dissolve the precipitate of ferric hydrate in acid, and reprecipitate with ammonia. mix the two filtrates, and dilute to c.c. take c.c. for the test. a sample of grams of an ore treated in this way required . c.c. of standard copper to produce equality of tint. this gives . per cent. ~determination of copper in tin.~--weigh up gram of the sample, transfer to an evaporating dish, and cover with c.c. of aqua regia. warm until the metal has dissolved, then evaporate almost to dryness. take up with a few c.c. of hydrochloric acid and again evaporate. dissolve the residue in c.c. of dilute hydrochloric acid and transfer to a c.c. flask. add c.c. of dilute ammonia and make up with water to the containing mark. filter off c.c. of the solution into a nessler glass and determine the copper in it colorimetrically. examination of commercial copper. very pure copper can be obtained in commerce, owing to the demand for metal of "high conductivity" for electrical purposes, which practically means for metal free from impurities. much of the metal sold contains as much as one per cent. of foreign substances, of which arsenic is the most important. the other elements to be looked for are bismuth, lead, antimony, silver, gold, iron, nickel, cobalt, sulphur, and oxygen. in "blister copper" (which is the unrefined metal), aluminium, silicon, and phosphorus may be met with. ~oxygen.~--all commercial copper carries oxygen; most of it is present as cuprous oxide, which is dissolved by molten copper. the estimation of oxygen is often made "by difference." the copper and the other impurities being determined, the rest is assumed to be oxygen. probably this is nearly correct, but the whole of the oxygen should not be ascribed to cuprous oxide; for any arsenic the metal contained would be present as cuprous arsenite, since arsenide of copper and cuprous oxide could not exist together at the temperature of fusion without interacting. in the report of the analysis, it is best to state the proportion of oxygen thus:-- oxygen ---- per cent. by difference. there is a method of determination by fusing or grams in a brasqued crucible, and counting the loss as oxygen; and another method for the determination of cuprous oxide based on the reaction of this substance with nitrate of silver.[ ] about grams of silver nitrate, dissolved in c.c. of water, is allowed to act upon gram of the copper in the cold. the precipitate is filtered off, washed thoroughly with water, and the basic salt dissolved and determined colorimetrically. one part of copper found represents . part of cuprous oxide, or . part of oxygen. copper generally carries from . to . per cent. of oxygen. ~silver~ is found in most samples, but occurs in variable proportions; when it amounts to ounces per ton it has a commercial value. to determine its amount, dissolve grams of the copper in c.c. of nitric acid and c.c. of water, boil off nitrous fumes, and dilute to about c.c. one or two c.c. of dilute hydrochloric acid (one to of water) are added, stirred in, and the precipitate allowed to settle for twenty-four hours. filter through a double swedish paper, dry, burn, and cupel the ashes with one gram of sheet lead. ten grams of a sample of copper gave in this way . milligrams of silver. ten grams of the same copper, to which milligrams of silver had been added gave . milligrams. ~gold.~--to determine it, dissolve , , or grams of the sample in , , or c.c. of nitric acid and an equal volume of water, boil till free from nitrous fumes, and dilute to double its volume. allow to stand for some time, decant on to a filter, dry, burn, and cupel the ashes with gram of sheet lead. if silver is present, owing to traces of chlorides in the re-agents used, "parting" will be necessary. (see _gold_.) working in this way on grams of copper, to which . milligram of gold had been added, a button weighing . milligrams was obtained. ~antimony~ is not a frequent impurity of copper: it can be detected in quantities over . per cent. by a white residue of sb_{ }o_{ }, insoluble in nitric acid. with material containing only small quantities of antimony the white oxide does not show itself for some time, but on long-continued boiling it separates as a fine powder. it is best (when looking for it) to evaporate the nitric acid solution to the crystallising point, to add a little fresh nitric acid and water, and then to filter off the precipitate. after weighing it should be examined for arsenic and bismuth. ~lead.~--refined coppers are often free from lead, anything more than traces being seldom found; in coarse coppers it is sometimes present in considerable quantities. its presence may be detected in the estimation of the copper electrolytically, the platinum spiral becoming coated with a brown or black deposit of lead dioxide. the depth of colour varies with the lead present, and obviously could be made the basis of an approximate estimation. the colour shows itself within an hour or so, but is best observed when all the copper has been deposited. electrolysing a solution of one gram of pure copper, to which . milligram of lead had been added, the deposit was dark brown; in a similar solution with milligram of lead it was much darker, and with milligrams it was black. under the conditions of the assay the dioxide cannot be weighed, as it partly dissolves on breaking the current. when lead has been found, its quantity may be estimated by evaporating to dryness the nitric acid solution to which an excess of sulphuric acid has been added, taking up with water, and filtering off and weighing the lead sulphate. the separation of traces of lead as chromate is a fairly good one. dissolve grams of the copper in c.c. of nitric acid and an equal volume of water; boil off nitrous fumes, neutralise with soda, and afterwards acidulate with acetic acid; and dilute to a litre. add grams of sodium acetate, warm, and precipitate the lead with a dilute solution of potassium chromate. copper chromate (yellow) may be at the same time thrown down, but it is readily soluble on diluting. filter off the precipitate; wash it into a beaker and pass sulphuretted hydrogen; oxidise the sulphide and weigh as lead sulphate. treated in this way grams of copper yielded sulphate of lead equal to . milligrams of lead. five grams of the same sample to which milligrams of lead were added gave . milligrams. ~nickel and cobalt.~--nickel is always present in larger or smaller quantities in commercial copper, and, perhaps, has an influence on the properties of the metal. it is determined as follows:--dissolve grams of the copper in c.c. of nitric acid and an equal bulk of water, boil off nitrous fumes and neutralise with soda, add grams of carbonate of soda dissolved in water, boil, and filter. acidify the filtrate with or c.c. of dilute nitric acid and dilute to or - / litres. pass sulphuretted hydrogen through the cold solution till the copper is all down and the liquid smells of the gas. filter and evaporate the filtrate to a small bulk, and determine the nickel by electrolysing the solution rendered ammoniacal, or by precipitating as sulphide and weighing as sulphate. (see under _nickel_.) the precipitate, after weighing, should be tested for cobalt. if present it is separated with potassium nitrite as described under _cobalt_. ten grams of copper gave . milligrams of nickel; and another lot of grams of the same copper, to which . milligrams of nickel had been added, gave . milligrams. ~sulphur.~--the amount of sulphur in refined copper is very small, seldom exceeding . per cent. in coarse copper, as might be expected, it is found in larger quantities. in determining it, it is first converted into sulphuric acid, and then precipitated and weighed as barium sulphate. the precipitation cannot be effected from a nitric acid solution. ten grams of copper are dissolved in nitric acid, as for the other determinations, and then boiled with excess of hydrochloric acid till the nitric acid is completely removed. there is then added a few drops of a dilute solution of baric chloride, and the solution is allowed to stand for some hours. the baric sulphate is filtered off and weighed. the necessity for precipitating from a hydrochloric acid solution is seen from the following determinations. in each experiment grams of copper was used, and a known weight of sulphur, in the form of copper sulphate, added. --------------+---------------------------+--------------------- sulphur added.| sulphur found in | sulphur found in |hydrochloric acid solution.|nitric acid solution. --------------+---------------------------+--------------------- milligrams | milligrams | . milligrams " | " | . " " | " | . " --------------+---------------------------+--------------------- ~bismuth.~--nearly all samples of copper contain bismuth, but only in small quantities. it is best determined colorimetrically as described under _bismuth_. the method of concentrating and preparing the solution for colorimetric assay is as follows. dissolve grams of copper in nitric acid, as in the other determinations; neutralise with soda; add or . grams of bicarbonate of soda and boil for ten minutes; filter, dissolve the precipitate in hot dilute sulphuric acid; add sulphurous acid and potassium iodide in excess, and boil till free from iodine. filter and dilute to c.c. take c.c. of the yellow solution for the determination. a few c.c. of a dilute solution of sulphurous acid ( in ) will prevent the liberation of iodine. the following experiments test the method of separation. ten grams of copper were treated as above and precipitated with . gram of "soda;" the precipitate contained . milligram of bismuth (= . per cent.). the filtrate treated with another . gram of "soda" gave a precipitate which was free from bismuth. to the filtrate from this was added . milligram of bismuth, and another fraction was precipitated with . gram of "soda." in this precipitate was found . milligram of bismuth. to the filtrate another milligram of bismuth was added and the separation with "soda" repeated. the bismuth was separated from this precipitate with ammonic carbonate before determination, and . milligram was found. ~arsenic.~--the proportion of arsenic in copper varies from . to . per cent. whilst in coarse copper it may amount to or even per cent. to determine it, dissolve , , or grams of the copper (according to the amount of arsenic present) in c.c., c.c., or c.c. of nitric acid, and an equal volume of water. boil off the nitrous fumes, dilute to c.c. and neutralise with soda; add . or grams of carbonate of soda dissolved in a little water, and boil. filter (washing is unnecessary) and dissolve back into the flask with a little dilute hydrochloric acid; add c.c. of dilute ammonia and c.c. of "magnesia mixture," and allow to stand overnight. the whole of the arsenic is precipitated as ammonic-magnesic arsenate in one hour, but it is advisable to leave it longer. the precipitate may be dried and weighed, or, better, titrated with uranium acetate. (see _arsenic_.) to test this method of separation grams of pure copper were taken and . gram of arsenic dissolved with it. the arsenic was determined by titration with uranium acetate, and . gram was found. two other similar experiments with . and . gram of arsenic added, gave . and . gram respectively. antimony or bismuth may be present without interfering with the titration. with . gram of antimony and . gram of arsenic, . gram of arsenic was found; and in another case, with . gram of bismuth and . gram of arsenic, . gram was found. in these experiments the antimony and bismuth were present in the assay solution when titrated. for a gravimetric determination they would require to be removed before precipitating with "magnesia mixture." phosphorus, if present, counts as arsenic in the proportion of to . ; but, except in the case of coarse coppers, it is always absent. iron, if present, interferes by forming a white flocculent precipitate of ferric arsenate after the addition of the sodium acetate and preliminary to the titration. each milligram of iron abstracts, in this way, . milligrams of arsenic. ~iron.~--refined coppers carry traces of iron, varying from . to . per cent. it is best determined during the arsenic estimation. the precipitate of the ammonic-magnesic arsenate will contain the whole of the iron as ferric hydrate. on dissolving in hydrochloric acid, neutralising with ammonia, adding c.c. of sodic acetate, diluting, and boiling, it reappears as a white precipitate of ferric arsenate. it is filtered off (the arsenic being estimated in the filtrate), dissolved in warm hydrochloric acid, and determined colorimetrically as described under _iron_. a series of experiments testing the separation is there given. ~phosphorus.~--refined coppers do not carry phosphorus, although it may be present in "coarse copper" up to per cent. or more. in such samples the following method is adopted for the estimation of both phosphorus and arsenic. dissolve grams of copper and . , . , or . gram of iron wire (according to the amount of arsenic and phosphorus present) in c.c. of nitric acid and an equal volume of water. add soda till the free acid is nearly neutralised. next add a strong solution of sodium acetate, until the solution ceases to darken on further addition, then dilute with water to half a litre. the solution is best contained in a large beaker; it is next heated to the boiling point, and at once removed and allowed to settle. if the precipitate is light coloured it is evidence that sufficient iron has not been added, or, if it is green, from basic copper salts, it shows that the solution was not sufficiently acid. in either case start afresh. filter off the precipitate and wash with hot water containing a little sodium acetate, dissolve it off the filter with hot dilute hydrochloric acid, add ammonia in excess, and pass sulphuretted hydrogen for five minutes. warm at about ° c. for a quarter of an hour. filter. the clear yellow filtrate contains the arsenic and phosphorus. add dilute sulphuric acid in excess; filter off the yellow precipitate of sulphide of arsenic, dissolve it in nitric acid, and titrate with uranium acetate, as described under _arsenic_. the filtrate from the sulphide of arsenic is rendered alkaline with ammonia and "magnesia mixture" added. the solution is stirred, and allowed to stand overnight. the precipitate of ammonic-magnesic phosphate is filtered off, dissolved, and titrated with uranium acetate, using the same standard solution as is used in the arsenic assay: . gram of arsenic equals . gram of phosphorus. ~copper.~--the method of determining this has been described under _electrolytic assay_. in the method of concentration by fractional precipitation with sodic carbonate (which is adopted in most of these determinations) the precipitate will contain all the bismuth, iron, and alumina; the arsenic and phosphorus as cupric arsenate and phosphate; and the greater part of the lead, antimony, and silver. the nickel and cobalt, and the sulphur as sulphuric acid, will remain in solution with the greater part of the copper. practical exercises. . according to a wet assay grams of a certain ore contained . gram of copper. what would you expect the dry assay produce to be? . a standard solution is made by dissolving grams of potassic cyanide and diluting to a litre. assuming the salt to be per cent. real cyanide, what would c.c. of the solution be equivalent to in grams of copper? . how would you make a solution of "hypo" of such strength that c.c. shall equal . gram of copper? . what weight of ore, containing . per cent. of copper, would you take in order to get about . gram of copper in solution for electrolysis? . the solution of copper in nitric acid is effected by the following reaction:-- cu + hno_{ } = cu(no_{ })_{ } + h_{ }o + no. what volume of nitric acid will be required to dissolve gram of copper? lead. the chief ore of lead is galena, a sulphide of lead, common in most mining districts, and frequently associated with blende and copper-pyrites. it always carries more or less silver; so that in the assay of the ore a silver determination is always necessary. carbonate (cerussite), sulphate (anglesite), and phosphate (pyromorphite) of lead also occur as ores, but in much smaller quantities. lead ores are easily concentrated (owing to their high specific gravity, &c.) by mechanical operations, so that the mineral matter sent to the smelter is comparatively pure. lead is readily soluble in dilute nitric acid. the addition of sulphuric acid to this solution throws down heavy, white, and insoluble lead sulphate. galena is soluble in hot hydrochloric acid, sulphuretted hydrogen being evolved; but the action is retarded by the separation of the sparingly soluble lead chloride. if a rod of zinc is placed in this solution, metallic lead is precipitated on it as a spongy mass, the lead chloride being decomposed as fast as it is formed. the opening up of the ore is thus easily effected, the sulphur going off as sulphuretted hydrogen, and the lead remaining in a form easily soluble in dilute nitric acid. galena itself is readily attacked by nitric acid, part of the lead going into solution, and the rest remaining as insoluble lead sulphate. the sulphate is due to the oxidation of the sulphur by nitric acid; its amount will vary with the quantity and concentration of the acid used. sulphate of lead is soluble in solutions of ammonium or sodium acetate; or it may be converted into carbonate by boiling with carbonate of soda. the carbonate, after washing off the sulphate of soda, dissolves easily in nitric acid. the precipitation of lead from acid solutions with sulphuric acid, and the solubility of the precipitate in ammonium acetate, distinguishes it from all other metals. the addition of potassium chromate to the acetate solution reprecipitates the lead as a yellow chromate. dry assay. the dry assay of lead is largely used, but it is only applicable to rich or concentrated ores, and even with these only gives approximate results. both lead and lead sulphide are sensibly volatile at a moderately-high temperature; hence it is necessary to obtain a slag which is easily fusible. as a reducing agent iron is almost always used, and this is added either in the form of an iron rod, or the crucible itself is made of this metal. the flux used is carbonate of soda. when a clay crucible is used, the method of working is as follows:--weigh up grams of the dry and powdered ore, mix with an equal weight of "soda" and grams of tartar; place in a crucible (e. battersea round), and then insert a piece of iron rod about half an inch in diameter, and of such a length that it will just allow the crucible to be covered. the rod should be pushed down so as to touch the bottom of the crucible, and the mixture should be covered with a sprinkling of borax. place in a furnace heated to, but not above, redness, and cover the crucible. in about twenty minutes the charge will be fused: the fusion is complete when bubbles of gas are no longer being evolved; and then, but not till then, the iron is withdrawn, any adhering buttons of lead being washed off by dipping the rod a few times in the slag. cover the crucible, leave it for a minute or two, and then pour. detach the slag, when cold, by hammering. the weight of the button multiplied by gives the percentage. the commoner errors of students in working the process are too high a temperature and too quick a withdrawal. a sample of ore treated in this manner gave on duplicate assay . and . grams of lead, equalling . and . per cent. respectively. by wet assay the sample gave . per cent. using an iron crucible, the results will be per cent. or so higher. the crucible must be made of wrought iron; and, if it has been previously used, should be cleaned by heating to dull redness and scraping the scale off with a stirrer. take grams of the ore, mix with grams of "soda" and grams of tartar; put the mixture in the crucible, and cover with a sprinkling of borax; heat for about twenty minutes at not too high a temperature, and then scrape down the slag adhering to the side with a stirrer. leave in the furnace till action has ceased. before pouring, tap the pot gently, and then tilt it so as to make the slag wash over the part of the crucible along which the charge is to be poured. pour; and, when cold, clean and weigh the button of metal. a crucible may be used from ten to twenty times. these assays are for ores containing the lead chiefly as sulphide. for oxidised ores, charcoal or tartar is employed as the reducing agent. the student may practise on red lead as follows:--take grams of red lead; mix with grams each of borax and "soda" and about . gram of powdered charcoal; place in a small clay crucible with a cover (c. battersea round), fuse at a gentle heat, and pour when action ceases. this assay will only take a few minutes. where lead is present as phosphate (as in the case of pyromorphite), or mixed with phosphates (as sometimes happens), carbonate of soda is a suitable flux; but the phosphate of soda which is formed makes a thick tenacious slag, which is very apt to be carried out of the pot by the escaping gas. a wide-mouthed clay pot is taken and a little fluor spar added. for the assay of pyromorphite the following charge may be used:--ore, grams; "soda," grams; tartar, grams; and fluor spar, grams; and grams of borax as a cover. this will melt down in about ten minutes, and should be poured as soon as tranquil. wet assay. in the case of galena the best method of getting the lead into solution is to treat with hydrochloric acid and zinc. put gram of the ore in an evaporating dish inches across, and cover with c.c. of dilute hydrochloric acid. heat till the evolution of sulphuretted hydrogen becomes sluggish, and then drop in a piece of zinc rod. if the solution effervesces too strongly, dilute it. continue the heating until the sulphide is seen to be all dissolved; when the lead is all precipitated, pour off the liquid and wash twice with cold water. peel off the precipitated lead with the help of a glass rod, and then clean the zinc. cover the lead with c.c. of water and c.c. of dilute nitric acid, and heat gently till dissolved; all the lead will be in solution, and, when filtered off from the gangue, will be ready for a gravimetric determination. for volumetric work this filtering is unnecessary. the chief objection to this method is that commercial zinc carries considerable quantities of lead. although this can be determined and allowed for, the correction required is in most cases too large to be satisfactory. the following method is applicable in all cases, but is more troublesome:--treat gram of the ore with c.c. of dilute nitric acid in an evaporating dish covered with a clock-glass, and evaporate till nearly dry. take up with c.c. of water, and add c.c. of dilute sulphuric acid. filter. the residue contains the lead as sulphate, together with the insoluble matter of the ore and globules of sulphur. warm with a solution of ammonium acetate, and filter. the lead will be in the filtrate, and is recovered in a state fit for direct gravimetric estimation by the addition of dilute sulphuric acid. if the volumetric method is to be used, the lead sulphate should be dissolved out with a solution of sodium acetate instead of with the ammonium salt solution. gravimetric determination. the lead is separated and precipitated as sulphate, as already described. the solution must be allowed to stand, and the clear liquid be decanted through a filter. transfer the precipitate, and wash with very dilute sulphuric acid ( or c.c. in c.c. of water). the acid must be completely removed with one or two washes with cold water, and then with alcohol. the volume of liquid required for washing is small, as the precipitate is dense and easily cleaned; but the washing must be carefully done, since if any acid remains it will, on drying, char the paper, and render the subsequent work troublesome. dry, transfer to a watch-glass, and burn the filter paper, collecting its ash in a weighed porcelain crucible. the filter paper must be freed as much as possible from the lead sulphate before burning, and the ash treated with a drop or two of nitric and sulphuric acids. transfer the lead sulphate to the crucible; ignite gently, keeping the temperature below redness; cool, and weigh. the precipitate will contain . per cent. of lead oxide or . per cent. of lead. ~determination of lead in commercial zinc.~--take grams of zinc, and treat (without heating) with c.c. of dilute hydrochloric acid. when the zinc is nearly all dissolved, decant off the clear liquid, and dissolve the residue in c.c. of dilute nitric acid. evaporate till most of the acid is removed; dilute to or c.c. with water, and add c.c. of dilute sulphuric acid. filter off, and weigh the lead sulphate. ten grams treated in this way gave-- . gram of lead sulphate, equivalent to . per cent. of lead. volumetric method. this is based upon the reaction between chromate of potash and soluble lead salts in neutral solutions, whereby an insoluble yellow chromate of lead is produced.[ ] an excess of the chromate is required to complete the reaction, so that the point at which an indicator shows the presence of undecomposed chromate cannot be satisfactorily taken as the finish. therefore an excess of the standard chromate must be run in, and such excess determined. chromate of lead is not precipitated from strong nitric acid solutions, and only incompletely from dilute ones. acids generally are detrimental to the precipitation, and must be neutralised before titrating. if the lead is present as sulphate in sodic acetate solution, it is well to render it distinctly alkaline with ammonia. lead chromate precipitated in the cold is a lemon-yellow, light precipitate, very difficult to filter: on heating to ° c. the colour becomes orange; at ° c. it assumes a deeper hue, and becomes flocculent; and at a boiling temperature it still further darkens and settles readily. these changes in colour are not due to any chemical change, as will be seen by testing the filtrate for chromium or lead: this is an advantage to the assay, since it is only at the higher temperature that the precipitate can be easily filtered. the lead is not completely precipitated, but the amount remaining in solution is only or milligrams, which is just sufficient to give a dark coloration with sulphuretted hydrogen. _the standard chromate of potash solution_ is made by dissolving . grams of bichromate of potash and . grams of caustic soda in water, and diluting to litre; or . grams of the neutral chromate (k_{ }cro_{ }) may be dissolved and diluted to litre: c.c. will be equivalent to . gram of lead. _standard lead solution._-- grams of nitrate of lead (pb(no_{ })_{ }) are dissolved in water and diluted to litre; c.c. will contain . gram of lead. _acetate of soda solution._-- grams of the crystallised salt (naac. h_{ }o) are dissolved, and diluted to litre. use c.c. for each assay. in the titration the assay solution should measure to c.c., and should be boiling or nearly so. it is best contained in a pint flask, and the standard chromate solution used with an ordinary burette. run in the chromate solution in a steady stream until the whole of the lead has been precipitated. the amount required for this may be calculated: for example, gram of an per cent. ore would require c.c. a little of the assay may be filtered off, and if it does not show a yellow colour in the filtrate run in c.c. more of the standard solution and continue this addition till a colour is shown. after this run in another c.c. to ensure an excess, dilute to c.c., and heat to boiling; allow to settle for three or four minutes, filter off c.c. into a nessler glass, and determine the excess of chromate colorimetrically. the excess found in the c.c. must, of course, be multiplied by five, and then be deducted from the quantity of chromate originally run into the assay solution. the quantity to be deducted should not exceed c.c. where a number of determinations are made the colorimetric estimation is facilitated by using a series of standard phials similar to those described under the _electrolytic copper assay_. the determination is rendered sharper and less liable to error by the addition of a few drops of acetic acid to convert the chromate into bichromate. the same chromate solution must be used in this determination as was used in the precipitation. in standardising the chromate solution, the standard lead nitrate solution is used. a quantity containing about as much lead as the assay is supposed to contain is measured off, rendered alkaline with dilute ammonia, and then neutralised with acetic acid, using a small piece of litmus paper dropped into the solution as indicator. then dilute, boil, and titrate. when the lead in the assay has been separated as sulphate and dissolved in sodic acetate, less chromate is apparently required, and in this case it will be necessary to precipitate the lead in the standard with an equivalent of sodic sulphate and redissolve in sodic acetate just as in the assay. in these solutions (although there is considerable chromate in excess) a further addition of or c.c. of the chromate solution will cause a further precipitate. the following experiments show the effect of variation in the conditions of the assay:-- ~effect of varying temperature.~--twenty c.c. of lead nitrate solution and grams of sodium acetate were used; diluted to c.c., heated to the desired temperature, and titrated. the results were:-- temperature ° ° ° ° "chromate" required . c.c. . c.c. . c.c. . c.c. the first two of these filtered badly, the precipitate coming through the filter; the last was very satisfactory in the working. ~effect of varying bulk.~--using c.c. of lead nitrate, and grams of sodium acetate as before, diluting to the required bulk, heating to boiling, and titrating, the results were:-- bulk . c.c. . c.c. . c.c. . c.c. "chromate" required . " . " . " . " ~effect of varying acetic acid.~--since the experiments are carried out in the presence of sodic acetate, acetic acid is the only acid whose effect need be considered. working as before, but with c.c. bulk and varying amounts of the acid, the results were:-- acid present -- . c.c. . c.c. . c.c. "chromate" required . c.c. . " . " . " these experiments show that only slight quantities of acid are admissible. ~effect of varying sodium acetate.~--with the same conditions as before, but with varying weights of sodium acetate, the results were:-- sodium acetate present -- grams grams grams grams "chromate" required . c.c. . c.c. . c.c. . c.c. . c.c. these experiments show that excessive quantities of sodium acetate must be avoided. ammonium acetate interferes to a greater extent, and if both acetic acid and this salt are present, each exerts its disturbing influence. with grams of ammonium acetate, . c.c. of the chromate solution were required instead of . c.c. in the absence of this salt; with grams of the acetate and c.c. of acetic acid, only . c.c. were required. ~effect of foreign salts.~--as already stated, sulphates interfere. twenty c.c. of the lead nitrate solution were taken, precipitated with sulphate of soda, and the precipitate dissolved in grams of sodium acetate and titrated as before. duplicate experiments required . c.c. and . c.c. of the chromate solution. a similar experiment with c.c. of lead nitrate required . c.c. of chromate. if the sulphate had not been present, the results would have been . c.c. and . c.c. respectively. ~effect of varying lead.~--in these experiments the conditions were as before, but with varying amounts of lead. lead nitrate solution present . c.c. . c.c. . c.c. . c.c. chromate solution required. . " . " . " . " ~determination of lead in galena.~--weigh up gram of the powdered and dried ore, and boil in an evaporating dish with c.c. of dilute hydrochloric acid. when the action becomes sluggish, dilute with an equal bulk of water, and add a weighed piece of zinc rod about inch long and quarter-inch across. keep up a moderate action by warming till the ore is seen to be completely attacked and the lead precipitated. decant off the solution, wash once, strip off the lead, wash and weigh the remaining zinc. dissolve the lead in c.c. of dilute nitric acid, and c.c. of water with the aid of heat. dilute and transfer to a pint flask; add a slight excess of dilute ammonia, and render faintly acid with acetic acid. dilute to c.c., heat to boiling, and run in the standard chromate in slight excess, noting the amount required, and make up to c.c. with water. boil the solution, allow to settle for a minute or so, filter off c.c., and determine the excess of chromate colorimetrically. as an example, gram of an impure galena was precipitated with c.c. of standard chromate ( c.c. = . gram lead). the excess found in c.c. was . c.c., which, multiplied by , gives . c.c. as the excess in the whole solution. the remaining . c.c. of "chromate" required by the assay, are equivalent to . gram of lead. the zinc used up weighed . grams, and contained . gram of lead. thus we get-- lead in the assay . gram lead from the zinc . " ------ .'. lead in the galena . " equivalent to . per cent. another sample, in which the galena was accompanied with a large quantity of pyrites, gave the following results:--three grams were treated with c.c. of dilute hydrochloric acid and a rod of zinc. the zinc and lead were carefully transferred to another vessel, the zinc cleaned, and the lead (dissolved in c.c. of dilute nitric acid and c.c. of water) treated as before. . c.c. of the chromate were required = . gram lead lead in grams of zinc = . " ------ .'. lead in grams of the ore = . " equivalent to . per cent. the same ore gave by separation of the lead with sulphuretted hydrogen, and conversion into sulphate, . per cent. with fairly pure ores, free from sulphate, the assay may be made more quickly as follows: dissolve gram of the finely powdered ore by boiling gently with c.c. of dilute hydrochloric acid for minutes; cool; add a few drops of permanganate; neutralise with ammonia, add acetic acid and a little sodium acetate. titrate with standard chromate. colorimetric process. this is based upon the brown coloration produced in very dilute solutions of lead by the action of a solution of sulphuretted hydrogen. the quantity of lead in the c.c. of the assay solution must not much exceed . milligram, nor be less than . . the sulphuretted hydrogen is used in the form of a solution, and is not bubbled through the assay. the principle of working is the same as previously described. _standard lead solution._--each c.c. of this should contain . milligram of lead. it is made by diluting c.c. of the solution of lead nitrate, described under the volumetric process, to litre. _sulphuretted hydrogen water_ is made by passing a current of the washed gas into water till the latter is saturated. five c.c. of the sulphuretted hydrogen water are put into a nessler tube, the measured portion of the assay solution added, and the whole diluted with water to the c.c. mark. into the standard nessler tube the same amount of the sulphuretted hydrogen water is put, and diluted to nearly c.c. the standard lead solution is then run in till the tints are equal. the assay solution must not contain much free acid, and if the conditions will allow it, may with advantage be rendered alkaline with ammonia. the chief cause of disturbance is the precipitation of lead sulphide forming a black turbid solution instead of a brown clear one. this may be caused by using hot solutions or an excess of acid. other metals precipitable by sulphuretted hydrogen must be absent as well as strong oxidising agents. ~effect of varying temperature.~--the effect of increased temperature is to change the colour from brown to black, and to render the estimation difficult. c.c. at ° c. showed the colour of . c.c. at ° c. " " " " . " at ° c. " " " " . " at ° c. ~effect of varying time.~--the colour becomes lighter on standing: c.c. on standing , , and minutes became equal in colour to . c.c. ~effect of acids and ammonia.~--two c.c. of the solution with c.c. of dilute hydrochloric acid became cloudy and equivalent to about . c.c.; and a similar result was got with c.c. of dilute sulphuric acid. with c.c. of dilute ammonia the solution became somewhat darker, or equal to . c.c.; but gave a very clear solution easy to compare. ~determination of lead in commercial zinc.~--dissolve . gram of the metal in c.c. of dilute nitric acid evaporates till a solid separates out, dilute to c.c. with water, and take c.c. for assay. a sample treated in this way required . c.c.; this multiplied by gives . c.c., equivalent to . milligram of lead, or . per cent. by gravimetric assay the sample gave . per cent. practical exercises. . thirty grams of galena gave on dry assay grams of lead; and this, on cupellation, gave milligrams of silver. calculate the results in per cents. of lead and in ounces of silver to the ton of ore. . how many ounces of silver to the ton would be contained in the lead got from this ore if the loss in smelting is equal to that of the assay? . having given you a sample of white lead freed from oil by washing with ether, how would you proceed to determine the percentage of lead in it? thallium. thallium is a rare metal, found in small quantities in some varieties of iron and copper pyrites, and in some lithia micas. it resembles lead in appearance. its compounds resemble the salts of the alkalies in some respects; and, in others, those of the heavy metals. it is detected by the green colour which its salts impart to the flame. this, when examined with the spectroscope, shows only one bright green line. it is separated and estimated by dissolving in aqua regia; converting into sulphate by evaporation with sulphuric acid; separating the second group of metals with sulphuretted hydrogen in the acid solution, boiling off the excess of the gas; nearly neutralising with carbonate of soda; and precipitating the thallium with an excess of potassic iodide. on allowing the liquid to stand for some time a bright yellow precipitate of thallous iodide separates out. this is collected on a weighed filter; washed with cold water, finishing off with alcohol; dried at ° c., and weighed. the precipitate is thallous iodide tli, and contains . per cent. of thallium. bismuth. bismuth is nearly always found in nature in the metallic state; but occasionally it is met with as sulphide in bismuthine and as carbonate in bismutite. it is also found in some comparatively rare minerals, such as tetradymite, combined with tellurium, and associated with gold. in minute quantities it is widely distributed: it is a common constituent of most copper ores; hence it finds its way into refined copper, which is seldom free from it. it is occasionally met with in silver in sufficient quantity to interfere with the working qualities of that metal. bismuth compounds are used in medicine and in the manufacture of alloys. bismuth possesses many useful properties. it has considerable commercial value, and sells at a high price. the metal is brittle, breaks with a highly crystalline fracture, and has a characteristic reddish-yellow colour. it is almost insoluble in hydrochloric, but readily dissolves in nitric, acid; and gives, if the acid is in excess, a clear solution. bismuth salts have a strong tendency to separate out as insoluble basic compounds; this is more especially true of the chloride which, on diluting with a large volume of water, becomes milky; the whole of the bismuth separating out. the nitrate, carbonate, and hydrate yield the oxide (bi_{ }o_{ }) on ignition. this oxide closely resembles litharge. it combines with silica, forming fluid slags; and at a red heat is liquid enough to be absorbed by a cupel; in fact, bismuth may take the place of lead in cupellation. the metal itself is easily fusible, and may be separated from its ores by liquation. the assay of bismuth by wet methods presents little difficulty, and is fairly accurate. the price of the metal is such that only methods which yield good results should be adopted; and, since bismuth is volatile at the temperature of the furnace, and is found mixed with ores not easy to flux, as also with metals which are not easily separated by the dry method, the dry assay can only be considered as having a qualitative value. dry assay. ~by liquation.~--this is adapted to ores containing the bismuth as metal. take grams of the powdered ore and place in a crucible with a perforated bottom, put this crucible into another of about the same size and lute the joint. lute on a cover, place in the furnace and heat to redness. the bismuth melts readily and drains into the lower crucible from which, when cold, it is taken and weighed. ~by fusion.~--for fairly pure ores the process is as follows:--take grams of the ore and mix with grams of fusion mixture, grams of salt and or grams of potassium cyanide; place in a crucible, cover, and fuse at a moderate temperature for about fifteen minutes; pour; when cold detach the metal and weigh. for coppery ores in which the metals are present as sulphides use the fluxes just given with grams of charcoal (instead of the cyanide) and a little sulphur. for coppery ores in which the metals are present as oxides, mix grams of the ore with grams of fusion mixture, grams of salt, grams of sulphur and grams of charcoal; and fuse. a considerable percentage of bismuth is lost in these assays; it is stated as being nearly per cent. of the metal present. wet methods. ~detection.~--bismuth is detected by dissolving the substance in nitric or hydrochloric acid and precipitating the diluted solution with sulphuretted hydrogen. the precipitated sulphides, after digesting with soda and washing, are dissolved in nitric acid and the solution boiled with ammonium carbonate. the precipitate is washed and then warmed with dilute sulphuric acid. the solution will contain the bismuth. add a solution of potassium iodide in excess, and boil; a yellow or dark brown solution proves that bismuth is present. another good test for small quantities of bismuth is to add tartaric acid to the solution to be tested, and then to make it alkaline with potash. add a few c.c. of schneider's liquid,[ ] and heat. a brownish-black colour is produced by as little as one part of bismuth in , of solution. the test is not applicable in the presence of mercury, copper, or manganese. compounds of bismuth fused with cyanide of potassium in a berlin crucible readily give a globule of bismuth which is recognised by its appearance and fracture. ~solution and separation.~--the solution of bismuth compounds presents no difficulty. they are soluble in nitric acid or aqua regia, and, provided the solution is sufficiently acid, they remain dissolved. in separating it from other metals the solution is made up to about c.c. and treated with a current of sulphuretted hydrogen. the bismuth comes down in a tolerably strong acid solution. the sulphide is decanted on to a filter and washed. it is next digested with ammonic sulphide; or, better (especially when other metals are present), dissolved in nitric acid, and treated with an excess of ammonia and a current of sulphuretted hydrogen. the precipitate is filtered off and evaporated to dryness with nitric acid. it is taken up with a few drops of sulphuric acid and a little water; and warmed and filtered, if necessary. the filtrate is nearly neutralised with ammonia; ammonium carbonate added in slight excess; and the liquid heated to boiling and filtered. the bismuth will be contained in the precipitate with perhaps traces of lead, antimony, tin, or sometimes iron from incomplete separation or washing. when only traces of a precipitate are got it must be tested. the bismuth precipitate is readily soluble in dilute nitric acid. gravimetric determination. the bismuth having been separated and dissolved in nitric acid[ ] is precipitated (after dilution) by the addition of carbonate of ammonium in slight excess, and boiling. the precipitate is filtered off, washed with hot water, dried, ignited, and weighed. the ignition should be performed carefully at not above a low red heat. the oxide which is formed has, at this temperature, a dark yellow or brown colour, and becomes yellow on cooling. it is bismuthic oxide (bi_{ }o_{ }) and contains . per cent. of bismuth. fusion with potassium cyanide at a temperature just sufficient to melt the salt reduces it to the metal which falls to the bottom and runs into a globule. the button of metal may be weighed, but it often sticks tenaciously to the bottom of the crucible. the precipitation with ammonic carbonate must not be made in a sulphate or chloride solution; since basic compounds would then be thrown down, and the result on weighing would either be too low (because of the volatilisation of the chloride), or too high (because of the retention of sulphuric acid). bismuth compounds in a nitric acid solution are readily decomposed by the electric current, but the deposited bismuth is not coherent. it comes down in shaggy tufts which are difficult to wash and easy to oxidise. volumetric assay. there are two methods which have been proposed; one based on the precipitation as chromate and the estimation of the chromic acid; and the other on the precipitation as oxalate and subsequent titration with permanganate of potash. these offer little advantage over the easy gravimetric determination. colorimetric method. bismuth iodide dissolves in excess of potassium iodide, forming a yellow-coloured solution, indistinguishable in colour from that given by iodine. the colour, however, is not removed by boiling or by sulphurous acid. since none of the commoner metals give such a colour, and free iodine is easily separated by boiling, this method is specially suited for small determinations of bismuth. it requires a _solution of bismuth_, made by dissolving . gram of bismuth in a drop or so of nitric acid, evaporating with a little sulphuric acid and diluting with water to litre. c.c. will contain . milligram of bismuth. and a _solution of sulphurous acid_, made by diluting c.c. of the commercial acid to litre with water. the determination is made in the usual way: c.c. of the prepared solution, which should not carry more than . milligram nor less than . milligram of bismuth, are placed in a nessler tube and the colour compared with that observed in a similar tube containing water and potassium iodide on adding the standard solution of bismuth. the assay solution is prepared by separating the bismuth with sulphuretted hydrogen, boiling the precipitate with nitric acid, and evaporating with sulphuric acid. take up with water, add or c.c. of solution of potassium iodide, boil off any iodine liberated, dilute, filter, and make up to c.c. according to the depth of colour take , , or c.c. and transfer to the nessler tube. add a few c.c. of the solution of sulphurous acid. into the other nessler tube put as much potassium iodide solution as is contained in the assay tube, with sulphurous acid and water to within a few c.c. of the bulk. then add the standard bismuth solution till the tints are equal. the student must be careful not to confuse the colour of the bismuth iodide with that of free iodine. if the yellow colour is removed by boiling and returns on standing it is due altogether to iodine; if it is lessened by the addition of a few drops of the dilute sulphurous acid, it is in part due to it. hence the necessity of having a little free sulphurous acid in each tube. a strong solution must not be used, since it liberates iodine from potassium iodide. the following experiments illustrate the effect of variation in the conditions of the assay:-- ~effect of varying temperature.~--at a higher temperature the colour is somewhat lessened. . c.c. at ° c. showed the colour of . c.c. at ° c. . " " " " . " . " " " " . " ~effect of free acid.~-- . c.c. with c.c. of nitric acid equalled . c.c. . " " sulphuric acid " . " hydrochloric acid almost completely removes the colour, which, however, is restored by the addition of a few crystals of potassium iodide. ~effect of alkalies.~--ammonia, soda, or potash destroys the colour, but it is restored on acidifying with nitric or sulphuric acid. ~effect of ammonic salts.~--the following table shows the results after addition of ammonic salts:-- -------------+----------------+-----------------+----------------- c.c. present.|with grams |with grams |with grams |ammonic nitrate.|ammonic sulphate.|ammonic chloride. -------------+----------------+-----------------+----------------- . c.c. | . c.c. | . c.c. | -- . " | . " | . " | -- . " | . " | . " | -- -------------+----------------+-----------------+----------------- ammonic chloride, like hydrochloric acid, removes the colour, which may be restored on the addition of more potassium iodide. nitrates and sulphates do not thus interfere. ~effect of foreign salts.~--sodic hyposulphite almost completely removes the colour. copper salts liberate iodine; but when this has been removed by boiling and the cuprous iodide has been filtered off there is no further interference. dilute solutions of lead salts give no colour. practical exercises. . a fusible alloy is made up of parts of bismuth, of lead, and of tin. what weight of oxide of bismuth, bi_{ }o_{ }, would you get on the analysis of gram of it? . what weight of bismuth can be got from grams of the subnitrate biono_{ }.h_{ }o? . how would you detect and separate arsenic, lead, and copper in a sample of bismuth? antimony. antimony occurs in the native state, but is rare; its common ore is antimonite, the sulphide (sb_{ }s_{ }). jamesonite and other sulphides of lead and antimony are frequently met with. sulphide of antimony is also a constituent of fahlerz and of many silver ores. antimonite occurs generally in fibrous masses, has a lead-like metallic lustre, is easily cut with a knife, and melts in the flame of a candle. antimony itself has a very crystalline fracture, is brittle, and has a bluish-white colour. it is used in the preparation of alloys with lead and tin for the manufacture of type-metal. it is readily fusible, and imparts hardness and the property of taking a sharp cast to its alloys. it is practically insoluble in hydrochloric acid. on boiling with strong nitric acid it is converted into antimonic oxide (sb_{ }o_{ }), which is a powder almost insoluble in this acid or in water, but which may be got into solution with difficulty by the prolonged action of hydrochloric and tartaric acids. antimonic oxide is converted on ignition into the tetroxide (sb_{ }o_{ }) with loss of oxygen. antimony forms two series of salts, antimonious and antimonic; and advantage is taken of this in its determination volumetrically. either sulphide of antimony yields antimonious chloride on boiling with hydrochloric acid, sulphuretted hydrogen being given off; and, in the case of antimonic sulphide, sulphur is deposited. antimonious is converted into antimonic chloride by treatment with permanganate of potash in an acid solution. antimonic chloride and potassium iodide react, forming antimonious chloride and free iodine. this latter may be got rid of by boiling. sulphide of antimony is separated from the ore by liquation; this regulus is met with in commerce as "crude antimony." dry assay. an approximate determination of the amount of sulphide of antimony in an ore may be made by fusing and liquating in a luted double crucible in the manner described under bismuth. this is unsatisfactory. the determination of metallic antimony in an ore is made either by fusion with potassium cyanide or by fusion with iron, as in the galena assay. both methods yield poor results; and, where iron is used, it must be added in quantity only sufficient for desulphurising; this amounts to about per cent. in pure ores. if the iron is in excess it alloys with the reduced antimony. if, on the other hand, it is insufficient, the metal will contain sulphur; or sulphide of antimony will be lost in the slag. the following note, for which we are indebted to mr. bedford mcneill, a.r.s.m., gives a description of the method adopted in the commercial valuation of a parcel of antimony ore:-- the antimony smelter, when he wishes to determine the value of any parcel of ore--usually the sulphide--that may be offered for sale, practically has recourse to the smelting operation. that is, a quantity of or cwts. taken by his sampler having been obtained, he treats it under the immediate supervision of the foreman smelter as if it formed part of the ore in process of daily reduction at his works. he thus determines by actual trial the output which it may fairly be anticipated will be yielded by the bulk, and upon the result of this trial or assay, and the knowledge gained of the actual behaviour of the ore under treatment, he bases his tender, knowing that, should he secure the parcel, he may confidently expect a similar return. briefly, the process consists of the three ordinary operations of-- (a) singling or removing most of the antimony from the ore; (b) doubling; (c) refining or "starring." but in the assay sufficient information is generally given by the first two of these. a new pot having been taken and made hot in the furnace, or lbs. of the ore is weighed in (the mineral from the necessities of sampling not exceeding walnut size); to lbs. of salt cake is now added to render the separation of the resulting sulphide of iron more easy, as also to assist in the fusion of the gangue; to lbs. of tin-plate scrap, beaten more or less into ball shape, is weighed, placed on the top of the ore and salt cake, and the whole brought to a state of fusion. the foreman from time to time takes notice of the behaviour of the ore under the working conditions. ores that manifest a tendency to "boil" or "froth " require the admixture of other more sluggish mineral in order to render their reduction economically practicable. after - / to - / hours (the time depending mainly on the temperature), the contents of the crucible are usually in a state of tranquil fusion. the pot is now lifted from the fire, and its contents transferred to a conical iron mould, the empty pot being immediately put back into the fire, and the latter "mended" with sufficient coke for another run. the conical mould (when dealing with a "strange" ore, and the possibility of insufficient iron being present to satisfy the sulphur contents) is wiped inside with clay previous to pouring in the molten charge. otherwise the mould itself will be attacked, and the contents after solidifying will require to be chiselled out piecemeal. a further lbs. of the ore is now charged into the crucible with iron as above; but before this second charge is ready to be drawn an inspection of the first may suggest the addition of either or lbs. more iron, or or lbs. more ore. it is a good fault rather to aim at an excess of iron as tending to clean the ore from antimony, any of the latter that (from an insufficiency of iron) may be left in the slag from the first process being irretrievably lost; whereas, if the iron be in excess, that which is combined with the crude antimony resulting from the first process is easily got rid of by adding to lbs. or so of ore in the second process. this latter, as practised for the determination of the value of a parcel of ore, consists in selecting two of the best quality singles, resulting from perhaps four or five trials as above, and running them down with a few pounds of salt cake, or a mixture of salt cake with american potash, and (as is generally necessary) a small addition of ore. upon the final result (confirmed perhaps on another pair of singles, and, judging from the total weight or output of the metal as calculated from the ore used in "singling," plus any added in the "doubling," the crystalline fracture and face of the metal, its colour, etc.) the price to be offered for the parcel of ore is fixed. wet methods. ~detection.~--the antimony, if any, being got into solution by treating the ore with hydrochloric acid or aqua regia may be detected by evaporating with hydrochloric acid, diluting, and filtering into the cover of a platinum crucible or (better) a platinum dish. a small lump of zinc is then added, and, if antimony is present, _the dish_ will in a minute or so be stained black with a deposit of metallic antimony. this stain is removed by nitric, but not by hydrochloric, acid. the reaction is delicate and characteristic; arsenic under like conditions is evolved as arseniuretted hydrogen, and tin is deposited as metal _on the zinc_. ~solution.~--ores, &c., containing antimony are best opened up by boiling with hydrochloric acid or aqua regia; treatment with nitric acid should be avoided wherever possible, since it forms antimonic acid, which is subsequently dissolved only with difficulty. salts of antimony in solution have a tendency to form insoluble basic salts; so that care must be exercised in diluting. compounds such as antimonite which are soluble in hydrochloric should be dissolved at once in that acid. ~separation.~--to the solution add potash in excess and a little free sulphur, and pass a current of sulphuretted hydrogen for some minutes; allow to digest for an hour or so on a hot plate; filter; and wash the residue. acidulate the filtrate with hydrochloric acid: the precipitate will contain the antimony (as sb_{ }s_{ }), and possibly arsenic or tin. the precipitate is transferred to a beaker and boiled with hydrochloric acid; the solution is filtered off and diluted. add a few crystals of tartaric acid, and pass a current of sulphuretted hydrogen for some time. the first flocculent precipitate will become denser, and render the filtering more easy. transfer the precipitate (after washing free from chlorides) to a berlin dish, and treat cautiously with fuming nitric acid. the action of this acid on the sulphide is very violent. evaporate and ignite, transfer to a silver dish, and fuse with four or five times its weight of caustic soda, cool and extract with a little water, then add an equal volume of alcohol, and allow to stand overnight. filter, wash with dilute alcohol. (the filtrate will contain the tin.) the residue contains the antimony as antimonate of soda, and is dissolved off the filter with hot dilute hydrochloric, with the help of a little tartaric, acid. the filtrate is now ready for the gravimetric determination. gravimetric assay. pass a current of sulphuretted hydrogen through the solution containing the antimony to which a little tartaric acid has been previously added. pass the gas till the precipitate becomes dense, and the antimony is all down. the solution must not be too strongly acid. filter off the precipitate, wash with hot water, dry in the water oven, transfer to a weighed porcelain dish, and cautiously treat with fuming nitric acid. continue the action on the water bath till the sulphur and antimony are completely oxidised. evaporate; ignite, gently at first, then strongly over the blast; cool, and weigh. the residue is a white infusible powder, and consists of antimony tetroxide, sb_{ }o_{ }, containing . per cent. of the metal. ~determination of antimony as bigallate.~--what appears to be a very good method has been worked out by m.a. guyard, and is described in crookes' _select methods_, p. . the antimony must be in solution as antimonious chloride, and must not be accompanied by an excess of hydrochloric acid. to ensure these conditions, the solution is treated with potassium iodide until no more iodine is evolved, and is then evaporated to remove the excess of hydrochloric acid. to the concentrated, and nearly neutral, solution a freshly-prepared solution of gallic acid is added in slight excess. a bulky white precipitate is formed that settles rapidly. the solution is diluted with hot water and washed by decantation. then the precipitate is collected on a weighed double filter, washed once or twice with hot water, and dried at ° c. the dried substance is antimony bigallate, and contains . per cent. of antimony. it should be completely soluble in ammonium sulphide. the solution in which the antimony is precipitated need not be quite free from other metals. volumetric method. this is based on the reduction of antimonic chloride (sbcl_{ }) to antimonious (sbcl_{ }) by the action of potassium iodide in strong hydrochloric acid solution.[ ] iodine is at the same time liberated, and the amount of antimony reduced is got at by titrating with sodium hyposulphite, which measures the iodine set free. the standard solution of sodium hyposulphite is made by dissolving . grams of the salt (na_{ }s_{ }o_{ }. h_{ }o) in water, and diluting to litre. one hundred c.c. will be equivalent to about gram of antimony. it is standardised with the help of a solution of antimony made as follows:--weigh up grams of powdered antimony, transfer to a flask, and cover with c.c. of hydrochloric acid; boil, and add nitric acid ( or drops at a time) until the metal is dissolved. allow the action of the nitric acid to cease before adding more. boil down to a small bulk, add c.c. of hydrochloric acid, and dilute to nearly litre. warm until any precipitate which has formed is redissolved; allow to cool slowly, and run in from a pipette a weak solution of permanganate until a faint brown colour is produced. dilute to exactly litre; c.c. contain . gram of antimony as antimonic chloride. in standardising, take c.c. of the antimony solution, and transfer to a flask; add grams of potassium iodide crystals, and when dissolved, after standing a few minutes, run in the solution of "hypo" from an ordinary burette until the greater part of the iodine has been reduced. add a few drops of starch solution, and continue the addition of the "hypo" until the muddy-green colour changes to a clear brownish-yellow. the solution must be shaken after each addition of the "hypo." in determining antimony in ore, weigh up . to gram, and dissolve in hydrochloric acid with, if necessary, the help of chlorate of potash. the antimony is separated as sulphide, redissolved in hydrochloric acid, and oxidised with a crystal of chlorate of potash. chlorine is boiled off, and the solution diluted with an equal bulk of water. to the clear cold solution potassium iodide is added, and after a few minutes the liberated iodine is titrated with "hypo," as already described. the method only yields satisfactory results when the standard and assay are carried out alike. footnotes: [ ] "modern american methods of copper smelting" (dr. peters). [ ] "journal of the society of chemical industry," vol. v. no. . [ ] lead when present is precipitated on the _spiral_ in the form of a dark powder of dioxide (pbo_{ }). manganese is also thrown down on the spiral as dioxide (mno_{ }), the solution at the same time becomes violet from the formation of permanganic acid. [ ] see the method given under _examination of commercial copper_. [ ] cuso_{ } + kcy = kcy.cucy_{ } + k_{ }so_{ }. [ ] cuso_{ } + kcy + am_{ }o = cu_{ }cy_{ } + am_{ }so_( ) + k_{ }so_{ } + kcyo. [ ] cuso_{ } + ki = cn_{ }i_{ } + i + k_{ }so_{ }. [ ] na_{ }s_{ }o_{ } + i = nai + na_{ }s_{ }o_{ }. [ ] for further information, see appendix b., and a paper by j.w. westmoreland, _journal of the society of chemical industry_, vol. v. p. . [ ] cu_{ }o + agno_{ } + h_{ }o = cu_{ }h_{ }o_{ }no_{ } + cu(no_{ })_{ } + ag. (insoluble basic salt.) [ ] k_{ }cro_{ } + pb(no_{ })_{ } = pbcro_{ } + kno_{ } [ ] made by dissolving grams of tartaric acid and grams of stannous chloride in water, and adding potash solution till it is alkaline. the solution should remain clear on heating to ° or ° c. [ ] it must be remembered that arsenate of bismuth is completely insoluble in this acid. [ ] sbcl_{ } + ki = i_{ } + sbcl_{ } + kcl. chapter xi. iron--nickel--cobalt--zinc--cadmium. iron. iron rusts or oxidises very readily, and, consequently, is rarely found in the metallic state in nature; such native iron as is found being generally of meteoric origin or imbedded in basalt and other igneous rocks. it chiefly occurs as oxide, as in magnetite, hæmatite, and in the brown iron ores and ochres. chalybite, which is carbonate of iron, is an ore of great importance. iron is found combined with sulphur in pyrrhotine and pyrites, and together with arsenic in mispickel. it is a common constituent of most rocks, imparting to them a green, black, or brown colour; and is present, either as an essential part or as an impurity, in most substances. the chemistry of iron is somewhat complicated by the existence of two oxides, each of which gives rise to a well-marked series of compounds. those derived from the lower oxide, known as ferrous salts, are generally pale and greenish. ferric salts are derived from the higher oxide, and are generally red, brown, or yellow. the existence of these two well-marked families of salts renders the assay of iron comparatively easy, for the quantity of iron present in a solution can be readily measured by the amount of oxidising or reducing agent required to convert it from the one state into the other--that is, from ferrous to ferric, or from ferric to ferrous, as the case may be. in the red and brown iron ores and ochres ferric iron is present; in chalybite the iron is in the ferrous state; and in magnetite it is present in both forms. traces of iron in the ferrous state may be found (even in the presence of much ferric iron) by either of the following tests:-- . ferricyanide of potassium gives a blue precipitate or green coloration; with ferric salts a brown colour only is produced. . a solution of permanganate of potassium is decolorised by a ferrous salt, but not by a ferric one. traces of ferric iron can be detected (even in the presence of much ferrous iron) by the following tests:-- ( ) by the brown or yellow colour of the solution, especially when hot. ( ) by giving a pink or red coloration with sulphocyanide of potassium. substances containing oxide of iron yield the whole of the iron as metal when fused at a high temperature with charcoal and suitable fluxes. the metal, however, will contain varying proportions of carbon and other impurities, and its weight can only afford a rough knowledge of the proportion of the metal in the ore. there are two or three methods of dry assay for iron, but they are not only inexact, but more troublesome than the wet methods, and need not be further considered. chalybite and the hydrated oxides dissolve very readily in hydrochloric acid; hæmatite and magnetite dissolve with rather more difficulty. iron itself, when soft, is easily soluble in dilute hydrochloric, or sulphuric, acid. pyrites, mispickel, &c., are insoluble in hydrochloric acid, but they are readily attacked by nitric acid. certain minerals, such as chrome iron ore, titaniferous iron ore, and some silicates containing iron, remain in the residue insoluble in acids. some of these yield their iron when attacked with strong sulphuric acid, or when fused with the acid sulphate of potash. generally, however, it is better in such stubborn cases to fuse with carbonate of soda, and then attack the "melt" with hydrochloric acid. when nitric acid, or the fusion method, has been used, the metal will be in solution in the ferric state, no matter in what condition it existed in the ore. but with dilute hydrochloric or sulphuric acid it will retain its former degree of oxidation. hydrochloric acid, for example, with chalybite (ferrous carbonate) will give a solution of _ferrous_ chloride; with hæmatite (ferric oxide) it will yield _ferric_ chloride; and with magnetite (ferrous and ferric oxides) a mixture of ferrous and ferric chlorides. metallic iron yields solutions of _ferrous_ salts. it is convenient to speak of the iron in a ferrous salt as ferrous iron, and when in the ferric state as ferric iron. frequently it is required to determine how much of the iron exists in an ore in each condition. in such cases it is necessary to keep off the air whilst dissolving; the operation should, therefore, be performed in an atmosphere of carbonic acid. ~separation.~--the separation of the iron from the other substances is as follows:--silica is removed by evaporating the acid solution, and taking up with acid, as described under _silica_; the whole of the iron will be in solution. the metals of groups i. and ii. are removed by passing sulphuretted hydrogen, and at the same time the iron will be reduced to the ferrous state. the solution should be filtered into a oz. flask, boiled to get rid of the gas, and treated (whilst boiling) with a few drops of nitric acid, in order to convert the whole of the iron into the ferric state. when this condition is arrived at, an additional drop of nitric acid causes no dark coloration. the boiling must be continued to remove nitrous fumes. next add caustic soda solution until the colour of the solution changes from yellow to red. the solution must be free from a precipitate; if the soda be incautiously added a permanent precipitate will be formed, in which case it must be redissolved with hydrochloric acid, and soda again, but more cautiously, added. after cooling, a solution of sodium acetate is added until the colour of the solution is no longer darkened. the solution, diluted to two-thirds of the flaskful with water, is heated to boiling. long-continued boiling must be avoided. the precipitate is filtered quickly through a large filter, and washed with hot water containing a little acetate of soda. the precipitate will contain all the iron and may also contain alumina, chromium, titanium, as well as phosphoric, and, perhaps, arsenic acids.[ ] dissolve the precipitate off the filter with dilute sulphuric acid, avoiding excess, add tartaric acid and then ammonia in excess. pass sulphuretted hydrogen, warm, and allow the precipitate to settle. filter and wash with water containing a little ammonic sulphide. gravimetric method. dissolve the precipitate in dilute hydrochloric acid; peroxidise with a few drops of nitric acid and boil, dilute to about c.c., add ammonia (with constant stirring) till the liquid smells of it, and heat to boiling. wash as much as possible by decantation with hot water. transfer to the filter, and wash till the filtrate gives no indication of soluble salts coming through. the filtrate must be colourless and clear. the wet precipitate is very bulky, of a dark-brown colour and readily soluble in dilute acids, but insoluble in ammonia and dilute alkalies. when thrown down from a solution containing other metals it is very apt to carry portions of these with it, even when they are by themselves very soluble in ammoniacal solutions. it must be dried and ignited, the filter paper being burnt separately and its ash added. when further ignition ceases to cause a loss of weight, the residue is ferric oxide (fe_{ }o_{ }), which contains per cent. of iron. the weight of iron therefore can be calculated by multiplying the weight of oxide obtained by . . the presence of ammonic chloride causes loss of iron during the ignition, and organic matter causes an apparent loss by reducing the iron to a lower state of oxidation. when the iron in the solution much exceeds . gram the volumetric determination is generally adopted, as the bulkiness of the precipitate of ferric hydrate makes the gravimetric method very inconvenient. volumetric methods. as already explained these are based on the measurement of the volume of a reagent required to bring the whole of the iron from the ferrous to the ferric state (oxidation), or from the ferric to the ferrous (reduction). ferrous compounds are converted into ferric by the action of an oxidising agent in the presence of an acid. either permanganate or bichromate of potash is generally used for this purpose.[ ] ferric compounds are reduced to ferrous by the action of:-- ( ) stannous chloride; ( ) sulphuretted hydrogen; ( ) sodium sulphite; or ( ) zinc.[ ] the processes, then, may be divided into two kinds, one based on oxidation and the other on reduction. in each case the titration must be preceded by an exact preparation of the solution to be assayed in order that the iron may be in the right state of oxidation. ~permanganate and bichromate methods.~ these consist of three operations:-- ( ) solution of the ore; ( ) reduction of the iron to the ferrous state; and ( ) titration. ~solution.~--the only point to be noticed concerning the first operation (in addition to those already mentioned) is that nitric acid must be absent. if nitric acid has been used, evaporate to dryness, of course without previous dilution; add hydrochloric or sulphuric acid, and boil for five or ten minutes. dilute with water to about c.c., and warm until solution is complete. the reduction is performed by either of the following methods:-- . _with stannous chloride._--fill a burette with a solution of stannous chloride,[ ] and cautiously run the liquid into the hot assay solution (in which the iron is present as _chloride_) until the colour is discharged. a large excess of the stannous chloride must be avoided. then add c.c. of a - / per cent. solution of mercuric chloride, this will cause a white precipitate (or a grey one if too large an excess of the stannous chloride has been added). boil till the solution clears, cool, dilute, and titrate. . _with sulphuretted hydrogen._--cool the solution and pass through it a current of washed sulphuretted hydrogen till the liquid smells strongly of the gas after withdrawal and shaking. a white precipitate of sulphur will be formed, this will not interfere with the subsequent titration provided it is precipitated in the cold. if, however, the precipitate is coloured (showing the presence of the second group metals), or if the precipitation has been carried out in a hot solution, it should be filtered off. boil the solution until the sulphuretted hydrogen is driven off; this may be tested by holding a strip of filter paper dipped in lead acetate solution in the steam issuing from the flask. the presence of sulphuretted hydrogen should be looked for rather than its absence. it is well to continue the boiling for a few minutes after the gas has been driven off. cool and titrate. . _with sodium sulphite._--add ammonia (a few drops at a time) until the precipitate first formed redissolves with difficulty. if a permanent precipitate is formed, redissolve with a few drops of acid. to the warm solution add from to grams of sodium sulphite crystals. the solution will become strongly coloured, but the colour will fade away on standing for a few minutes in a warm place. when the colour is quite removed, add c.c. of dilute sulphuric acid, and boil until the steam is quite free from the odour of sulphurous acid. cool and titrate. . _with zinc._--add about grams of granulated zinc; if the hydrogen comes off violently add water; if, on the other hand, the action is very slow, add sufficient dilute sulphuric acid to keep up a brisk effervescence. the reduction is hastened by warming, and is complete when the solution is quite colourless and a drop of the liquid tested with sulphocyanate of potassium gives no reaction for ferric iron. filter through "glass wool" or quick filtering paper. the zinc should be still giving off gas rapidly, indicating a freely acid solution; if not, acid must be added. wash with water rendered acid. cool and titrate. with regard to the relative advantages of the different methods they may be roughly summed up as follows:--the stannous chloride method has the advantage of immediately reducing the ferric iron whether in hot or cold solution and under varied conditions in regard to acidity, but has the disadvantage of similarly reducing salts of copper and antimony, which, in a subsequent titration, count as iron. moreover, there is no convenient method of eliminating any large excess of the reagent that may have been used; and, consequently, it either leaves too much to the judgment of the operator, or entails as much care as a titration. students generally get good results by this method. the sulphuretted hydrogen method also has the advantage of quick reduction under varying conditions, and the further one of adding nothing objectionable to the solution; in fact it removes certain impurities. the disadvantages are the necessity for boiling off the excess of the gas, and of filtering off the precipitated sulphur, although this last is not necessary if precipitated cold. the tendency with students is to get high results. the sodium sulphite method has the advantages of being clean and neat, and of requiring no nitration. on the other hand it requires practice in obtaining the best conditions for complete reduction; and, as with sulphuretted hydrogen, there is the necessity for boiling off the gas, while there is no simple and delicate test for the residual sulphurous acid. in addition, if an excess of sodium sulphite has been used and enough acid not subsequently added, the excess will count as iron. students generally get low results by this method. the advantages of the zinc method are, that it is easily worked and that the excess of zinc is readily removed by simply filtering. the disadvantages are the slowness[ ] with which the last portions of ferric iron are reduced, the danger of loss by effervescence, the precipitation of basic salts, and, perhaps, of iron, and the loading of the solution with salts of zinc, which in the titration with bichromate have a prejudicial effect. the tendency in the hands of students is to get variable results, sometimes low and sometimes high. generally speaking, the sulphuretted hydrogen and sodium sulphite methods are to be preferred. carefully worked each method will yield good results. the titration may be done with a standard solution of ( ) permanganate of potash, or ( ) bichromate of potash. . _with permanganate of potash._--prepare a standard solution by dissolving . grams of the salt and diluting to one litre. the strength of this should be c.c. = . gram of iron, but it varies slightly, and should be determined (and afterwards checked every two or three weeks) by weighing up . gram of iron wire, dissolving in c.c. of dilute sulphuric acid, diluting to about c.c., and titrating. the standard solution must be put in a burette with a glass stopcock, as it attacks india-rubber. the assay should be contained in a pint flask, and be cooled before titrating. the standard solution must be run in until a pinkish tinge permeates the whole solution; this must be taken as the finishing point. when certain interfering bodies are present this colour quickly fades, but the fading must be ignored. with pure solutions the colour is fairly permanent, and a single drop of the potassium permanganate solution is sufficient to determine the finishing point. . _with bichromate of potash._--prepare a standard solution by dissolving . grams of the powdered and dried salt in water, and diluting to litre. this solution is permanent, its strength is determined by dissolving . gram of iron wire in c.c. of dilute sulphuric acid, diluting to about a quarter of a litre, and titrating. also prepare a test solution by dissolving . gram of ferricyanide of potassium in c.c. of water. this solution does not keep well and must be freshly prepared. an ordinary burette is used. the assay is best contained in a glazed earthenware dish, and may be titrated hot or cold. to determine the finishing point, place a series of drops of the ferricyanide solution on a dry white glazed plate. the drops should be of about the same size and be placed in lines at fairly equal distances. the bichromate is run in, in a steady stream, the assay solution being continuously stirred until the reaction is sensibly slackened. then bring a drop of the assay with the stirrer in contact with one of the test drops on the plate. the standard can be safely run in c.c. at a time, so long as the test drop shows signs of a precipitate. when only a coloration is produced run in cautiously a few drops at a time so long as two drops of the assay gives with the test a colour which is even faintly greener than two drops of the assay solution placed alongside. the finishing point is decided and practically permanent, although it demands a little practice to recognise it. the titration with permanganate of potassium has the advantage of a more distinct finishing point and easier mode of working; its application, however, is somewhat limited by the disturbing effects of hydrochloric acid. the bichromate method has the advantage of a standard solution which does not alter in strength, and the further one of being but little affected by altering conditions of assay. hydrochloric acid has practically no effect on it. both methods give accurate results and are good examples of volumetric methods. the following results illustrate the extent to which the methods may be relied on; and the influence which the various conditions of experiment have on the assay. solutions of ferrous sulphate and of ferrous chloride were made containing . gram of iron in each c.c., thus corresponding to the standard solutions of permanganate and bichromate of potassium. these last were prepared in the way already described. the solution of ferrous sulphate was made by dissolving . grams of iron wire in c.c. of dilute sulphuric acid and diluting to litre. a similar solution may be made by dissolving . grams of pure ferrous sulphate crystals in water, adding c.c. of dilute sulphuric acid, and diluting to litre. ~rate of oxidation by exposure to air.~--this is an important consideration, and if the rate were at all rapid would have a serious influence on the manner of working, since exclusion of air in the various operations would be troublesome. c.c. of the solution of ferrous sulphate were taken in each experiment, acidified with c.c. of dilute sulphuric acid, and diluted to c.c. the solution was exposed, cold, in an open beaker for varying lengths of time, and titrated with permanganate of potassium. time exposed hour day days days c.c. required . . . . these results show that the atmospheric oxidation in cold solutions is unimportant. with boiling solutions the results are somewhat different; a solution which at the outset required c.c. of permanganate of potassium, after boiling for an hour in an open beaker (without any precautions to prevent oxidation), water being added from time to time to replace that lost by evaporation, required . c.c. if the solution be evaporated to dryness the oxidising power of concentrated sulphuric acid comes into play, so that very little ferrous iron will be left. a solution evaporated in this way required only . c.c. of permanganate of potassium. ~effect of varying temperature.~--in these experiments the bulk was in each case c.c., and c.c. of dilute sulphuric acid were present. the permanganate required by c.c. of ferrous sulphate was, at ° . c.c., and at ° . c.c. " " " . " . " " " " . " . " the lower result with the c.c. may be due to oxidation from exposure. ~effect of varying bulk.~--the following experiments show that considerable variations in bulk have no practical effect. in each case c.c. of ferrous sulphate solution and c.c. of dilute acid were used. bulk of assay c.c. c.c. c.c. c.c. permanganate required . " . " . " . " ~effect of free sulphuric acid.~--free acid is necessary for these assays; if there is an insufficiency, the assay solution, instead of immediately decolorising the permanganate, assumes a brown colour. the addition of c.c. of dilute sulphuric acid suffices to meet requirements and keep the assay clear throughout. the following experiments show that a considerable excess of acid may be used without in the least affecting the results. in each case c.c. of ferrous sulphate were used. dilute sulphuric acid . c.c. . c.c. . c.c. . c.c. . c.c. . c.c. permanganate required . " . " . " . " . " . " ~effect of foreign salts.~--when the assay has been reduced with zinc varying quantities of salts of this metal pass into solution, the amount depending on the quantity of acid and iron present. salts of sodium or ammonium may similarly be introduced. it is essential to know by experiment that these salts do not exert any effect on the titration. the following series of experiments show that as much as grams of zinc sulphate may be present without interfering. zinc sulphate present gram gram grams grams permanganate required . c.c. . c.c. . c.c. . c.c. magnesium, sodium, and ammonium salts, are equally without effect. ammonic sulphate present gram gram grams permanganate required . c.c. . c.c. . c.c. sodic sulphate present gram gram grams permanganate required . c.c. . c.c. . c.c. magnesic sulphate present gram gram grams permanganate required . c.c. . c.c. . c.c. ~effect of varying amounts of iron.~--it is important to know within what limits the quantity of iron in an assay may safely vary from that used in standardising. in the following experiments the conditions as to bulk, acidity, and mode of working were the same as before:-- ferrous sulphate solution taken c.c. c.c. c.c. c.c. c.c. permanganate required . " . " . " . " . " the ferrous sulphate solution is here a little weaker than that of the permanganate of potassium, but the results show that the permanganate required is proportional to the iron present. ~titrations in hydrochloric solutions.~--these are less satisfactory than those in sulphuric solutions, since an excess of hydrochloric acid decomposes permanganate of potassium, evolving chlorine, and since the finishing point is indicated, not by the persistence of the pink colour of the permanganate, but by a brown coloration probably due to perchloride of manganese. nevertheless, if the solution contains only from to per cent. of free hydrochloric acid (sp. g. . ) the results are the same as those obtained in a sulphuric acid solution. equal weights ( . gram) of the same iron wire required exactly the same quantity of the permanganate of potassium solution ( c.c.) whether the iron was dissolved in dilute sulphuric or dilute hydrochloric acid. the following series of experiments are on the same plan as those given above with sulphuric acid solutions. a solution of ferrous chloride was made by dissolving . grams of iron wire in c.c. of dilute hydrochloric acid and diluting to litre. the dilute hydrochloric acid was made by mixing equal volumes of the acid (sp. g. . ) and water. ~rate of atmospheric oxidation.~-- c.c. of the ferrous chloride solution were acidified with c.c. of the dilute hydrochloric acid and diluted to c.c. this solution was exposed cold in open beakers. time exposed -- hour day days days permanganate required . c.c. . c.c. . c.c. . c.c. . c.c. similar solutions boiled required, before boiling, c.c.; after boiling for one hour, replacing the water as it evaporated, . c.c.; and after evaporation to a paste and redissolving, . c.c. ~effect of varying temperature.~--solutions similar to the last were titrated and gave the following results:-- temperature ° ° ° ° permanganate required . c.c. . c.c. . c.c. . c.c. ~effect of varying bulk.~--as before, c.c. of the iron solution, and c.c. of the dilute acid were diluted to the required volumes and titrated. bulk c.c. c.c. c.c. c.c. permanganate required . " . " . " . " the variation due to difference in bulk here, although only equal to an excess of . milligram of iron for each c.c. of dilution, are about three times as great as those observed in a sulphuric acid solution. ~effect of free hydrochloric acid.~--in these experiments c.c. of the ferrous chloride solution were used with varying quantities of acid, the bulk of the assay in each case being c.c. dilute acid present c.c. c.c. c.c. c.c. permanganate required . " . " . " . " the last had a very indistinct finishing point, the brown coloration being very evanescent. the effect of the acid is modified by the presence of alkaline and other sulphates, but not by sulphuric acid. repeating the last experiment we got-- without further addition . c.c. with c.c. of dilute sulphuric acid . " " grams ammonic sulphate . " " " sodic sulphate . " " " magnesium sulphate . " " " manganese sulphate . " the results with these salts, in counteracting the interference of the acid, however, were not a complete success, since the end-reactions were all indistinct, with the exception, perhaps, of that with the manganese sulphate. ~effect of varying amounts of iron.~--in these experiments the bulk of the assay was c.c., and c.c. of acid were present. ferrous chloride used c.c. c.c. c.c. c.c. c.c. permanganate required . " . " . " . " . " in making himself familiar with the permanganate of potassium titration, the student should practise by working out a series of experiments similar to the above, varying his conditions one at a time so as to be certain of the cause of any variation in his results. he may then proceed to experiment on the various methods of reduction. _a solution of ferric chloride_ is made by dissolving . grams of iron wire in c.c. of hydrochloric acid (sp. g. . ), and running from a burette nitric acid diluted with an equal volume of water into the boiling iron solution, until the liquid changes from a black to a reddish-yellow. about . c.c. of the nitric acid will be required, and the finishing point is marked by a brisk effervescence. the solution of iron should be contained in an evaporating dish, and boiled briskly, with constant stirring. there should be no excess of nitric acid. boil down to about half its bulk; then cool, and dilute to one litre with water. twenty c.c. of this solution diluted to c.c. with water, and acidified with c.c. of dilute hydrochloric acid, should not decolorise any of the permanganate of potassium solution; this shows the absence of ferrous salts. and c.c. of the same solution, boiled with c.c. of the ferrous sulphate solution, should not decrease the quantity of "permanganate" required for the titration of the ferrous sulphate added. in a series of experiments on the various methods of reduction, the following results were got. the modes of working were those already described. ( ) _with stannous chloride._--twenty c.c. of the ferric chloride solution required, after reduction with stannous chloride, c.c. of "permanganate." fifty c.c. of a solution of ferrous chloride, which required on titration . c.c. of "permanganate," required for re-titration (after subsequent reduction with stannous chloride) c.c. of the permanganate solution. ( ) _with sulphuretted hydrogen._--two experiments with this gas, using in each c.c. of the ferric chloride solution, and c.c. of hydrochloric acid, required (after reduction) . c.c. and . c.c. of "permanganate." repeating the experiments by passing the gas through a nearly boiling solution, but in other respects working in the same way, . c.c. and . c.c. of the permanganate solution were required. the sulphur was not filtered off in any of these. in another experiment, in which c.c. of the ferrous sulphate solution were titrated with "permanganate," c.c. of the latter were required. the titrated solution was next reduced with sulphuretted hydrogen, brought to the same bulk as before, and again titrated; . c.c. of the permanganate of potassium solution were required. ( ) _with sodium sulphite._--twenty c.c. of the ferric chloride solution, reduced with sodium sulphite, required . c.c. of "permanganate." in one experiment c.c. of the ferrous sulphate solution were titrated with "permanganate"; . c.c. of the last-mentioned solution were required. the titrated solution was reduced with sodium sulphite, and again titrated; it required . c.c. of the permanganate of potassium solution. ( ) _with zinc._--twenty c.c. of the ferric chloride solution, reduced with zinc and titrated, required . c.c. of "permanganate." fifty c.c. of a solution of ferrous sulphate which required . c.c. of "permanganate," required for re-titration, after reduction with zinc, . c.c. the student should next practise the titration with bichromate, which is more especially valuable in the estimation of hydrochloric acid solutions. the following experiments are on the same plan as those already given. in each experiment (except when otherwise stated) there were present c.c. of the ferrous chloride solution, and c.c. of dilute hydrochloric acid, and the bulk was c.c. ~effect of varying temperature.~--the quantities of the bichromate of potassium solution required were as follows:-- temperature ° ° ° ° bichromate required . c.c. . c.c. . c.c. . c.c. ~effect of varying bulk.~-- bulk c.c. c.c. c.c. c.c. c.c. bichromate required . " . " . " . " . " ~effect of varying acid.~--in these, variable quantities of dilute hydrochloric acid were used. acid present c.c. c.c. c.c. bichromate required . " . " . " ~effect of foreign salts.~--the effect of the addition of grams of crystallized zinc sulphate was to decrease the quantity of "bichromate" required from . c.c. to . c.c., but the colour produced with the test-drop was very slight at . c.c., and with incautious work the finishing point might have been taken anywhere between these extremes. zinc should not be used as a reducing agent preliminary to a "bichromate" titration. ten grams of ammonic sulphate had the effect of rendering the finishing point faint for about . c.c. before the titration was finished, but there was no doubt about the finishing point when allowed to stand for a minute. the student should note that a titration is not completed if a colour is developed on standing for five or ten minutes. ten grams of sodic sulphate had no effect; . c.c. were required. ~effect of varying iron.~--the results are proportional, as will be seen from the following details:-- ferrous chloride present . c.c. . c.c. . c.c. . c.c. . c.c. bichromate required . " . " . " . " . " the student may now apply these titrations to actual assays of minerals. the following examples will illustrate the mode of working and of calculating the results:-- ~determination of iron in chalybite.~--weigh up gram of the dry powdered ore, and dissolve in c.c. of dilute sulphuric acid and an equal volume of water with the aid of heat. avoid evaporating to dryness. dilute and titrate. the result will give the percentage of iron existing in the ore in the ferrous state. some ferric iron may be present. if it is wished to determine this also, add (in dissolving another portion) c.c. of dilute hydrochloric acid to the sulphuric acid already ordered, and reduce the resulting solution before titrating. by dissolving and titrating (without previous reduction) one has a measure of the ferrous iron present; by dissolving, reducing, and then titrating, one can measure the total iron; and as the iron exists in only two conditions, the total iron, less the ferrous iron, is the measure of the ferric iron. ~determination of iron in brown or red ores or magnetite.~--weigh up . gram of the ore (powdered and dried at ° c.), and dissolve in from to c.c. of strong hydrochloric acid, boiling until all is dissolved, or until no coloured particles are left. dilute, reduce, and titrate. ~determination of iron in pyrites.~--weigh up gram of the dry powdered ore, and place in a beaker. cover with c.c. of strong sulphuric acid, mix well by shaking, and place on the hot plate without further handling for an hour or so until the action has ceased. _allow to cool_, and dilute to c.c. warm until solution is complete. reduce and titrate. ~determination of iron in substances insoluble in acids.~--weigh up gram of the ore, mix with or grams of carbonate of soda and . gram of nitre by rubbing in a small mortar, and transfer to a platinum crucible. clean out the mortar by rubbing up another gram or so of soda, and add this to the contents of the crucible as a cover. fuse till tranquil. cool. extract with water. if the ore carries much silica, evaporate to dryness with hydrochloric acid to separate it. re-dissolve in hydrochloric acid, and separate the iron by precipitating with ammonia and filtering. if only a small quantity of silica is present, the aqueous extract of the "melt" must be filtered, and the insoluble residue washed and dissolved in dilute hydrochloric acid. reduce and titrate. a convenient method of at once separating iron from a solution and reducing it, is to add ammonia, pass sulphuretted hydrogen through it, filter, and dissolve the precipitate in dilute sulphuric acid. the solution, when boiled free from sulphuretted hydrogen, is ready for titrating. stannous chloride process. the colour imparted to hot hydrochloric acid solutions by a trace of a ferric compound is so strong, and the reducing action of stannous chloride is so rapid, that a method of titration is based upon the quantity of a standard solution of stannous chloride required to completely decolorise a solution containing ferric iron. this method is more especially adapted for the assay of liquors containing much ferric iron and of those oxidised ores which are completely soluble in hydrochloric acid. it must be remembered, however, that it only measures the ferric iron present, and when (as is generally the case) the total iron is wanted, it is well to calcine the weighed portion of ore previous to solution in order to get the whole of the iron into the higher state of oxidation, since many ores which are generally supposed to contain only ferric iron carry a considerable percentage of ferrous. _the stannous chloride solution_ is made by dissolving grams of the commercial salt (sncl_{ }. h_{ }o) in c.c. of water with the help of c.c. of dilute hydrochloric acid, and diluting to a litre. the solution may be slightly opalescent, but should show no signs of a precipitate. the strength of this is about equivalent to gram of iron for each c.c. of the solution, but it is apt to lessen on standing, taking up oxygen from the air, forming stannic chloride. a larger proportion of hydrochloric acid than is ordered above would remove the opalescence, but at the same time increase this tendency to atmospheric oxidation, as the following experiments show. the stannous chloride solution ( c.c.) was mixed with varying amounts of strong hydrochloric acid (sp. g. . ), diluted to c.c., and exposed in open beakers for varying lengths of time; and the residual stannous chloride measured by titration with permanganate. the quantities required were as follows:-- time exposed. per cent. acid. per cent. acid. per cent. acid. hour . c.c. . c.c. . c.c. day . " . " . " days . " . " . " these indicate very clearly the increased susceptibility to oxidation in strongly acid solutions. _a standard solution of ferric chloride_ is prepared in the same manner as that described under the experiments on the methods of reduction; but it should be of twice the strength, so that c.c. may contain gram of iron. this solution is used for standardising the stannous chloride when required; and must be carefully prepared; and tested for the presence of nitric acid. the titration is more limited in its application than either of the oxidising processes because of the restrictions as to bulk, quality and quantity of free acid present, and other conditions of the solution to be assayed. the following experiments show the conditions necessary for a successful titration. ~effect of varying temperature.~--twenty c.c. of ferric chloride solution with c.c. of strong hydrochloric acid, diluted to c.c., gave the following results when titrated:-- temperature ° ° ° ° stannous chloride required . c.c. . c.c. . c.c. . c.c. the finishing point, however, is more distinct the hotter the solution; so that it is best in all cases to run the standard into the boiling solution. ~effect of varying bulk.~--solutions containing the same quantity of iron and acid as the last, but diluted to various bulks, and titrated while boiling, gave the following results:-- bulk c.c. c.c. c.c. stannous chloride required . " . " . " ~effect of varying quantities of hydrochloric acid.~--in these experiments the bulk before titration was c.c. except in the last, in which it was c.c. with less than c.c. of strong hydrochloric acid the finishing point is indistinct and prolonged. strong hydrochloric acid present c.c. c.c. c.c. c.c. c.c. stannous chloride required . " . " . " . " . " ~effect of free sulphuric acid.~--in these experiments c.c. of hydrochloric acid were present, and the bulk was c.c. strong sulphuric acid present -- c.c. c.c. c.c. c.c. stannous chloride required . " . " . " . " this interference of strong sulphuric acid may be completely counteracted by somewhat modifying the mode of working. another experiment, like the last of this series, required . c.c. ~effect of foreign salts.~--experiments in which grams of various salts were added showed them to be without effect. the results were as follows:-- salt present -- amcl am_{ }so_{ } mgcl_{ } stannous chloride required . c.c. . c.c. . c.c. . c.c. salt present cacl_{ } fecl_{ } al_{ }cl_{ } stannous chloride required . c.c. . c.c. . c.c. ~effect of varying iron.~--titrating a solution (with c.c. of hydrochloric acid) measuring c.c., and kept boiling, the quantity of stannous chloride solution required is practically proportional to the iron present. ferric chloride added c.c. c.c. c.c. c.c. c.c. stannous chloride required . " . " . " . " . " the student, having practised some of the above experiments, may proceed to the assay of an iron ore. ~determination of iron in brown iron ore.~--weigh up gram of the dried and powdered ore, calcine in the cover of a platinum crucible, and dissolve up in an evaporating dish[ ] with c.c. of strong hydrochloric acid. when solution is complete, dilute to c.c. after replacing any acid that may have been evaporated. boil, and run in the stannous chloride solution until the colour is faintly yellow; boil again, and continue the addition of the stannous chloride solution, stirring continuously until the solution appears colourless. note the quantity of the stannous chloride solution required. suppose this to be c.c. take c.c. of the standard ferric chloride solution, add c.c. of hydrochloric acid, boil and titrate in the same way as before. suppose this to require c.c. then as is equivalent to of the iron solution, is equivalent to . .[ ] this gives the percentage. it is not necessary to standardise the stannous chloride solution in this way with each sample assayed, the ratio : would serve for a whole batch of samples; but the standardising should be repeated at least once each day. colorimetric method. this method is valuable for the determination of small quantities of iron present as impurities in other metals or ores. it is based on the red coloration developed by the action of potassic sulphocyanate on acid solutions of ferric salts. _standard ferric chloride solution._--take c.c. of the ferric chloride solution used for standardising the stannous chloride solution, add c.c. of dilute hydrochloric acid, and dilute to litre with water. c.c. = . milligram. _solution of potassic sulphocyanate._--dissolve grams of the salt in water, and dilute to a litre. it should be colourless. use c.c. for each test. the quantity of the substance to be weighed for the assay should not contain more than a milligram of iron; consequently, if the ore contain more than . per cent. of that metal, less than a gram of it must be taken. the method is as follows:--weigh up gram of the substance and dissolve in a suitable acid; dilute; and add permanganate of potash solution until tinted. boil for some time and dilute to c.c. take a couple of nessler tubes, holding over c.c., but marked at c.c.; label them " " and " "; and into each put c.c. of the potassic sulphocyanate solution and c.c. of dilute hydrochloric acid. the solutions should be colourless. to " " add c.c. of the assay solution, and dilute to the c.c. mark. to the other add water, but only to within or c.c. of this mark. now run in the standard ferric chloride solution from a small burette, c.c. at a time, stirring after each addition till the colour is nearly equal to that of the assay (no. ). at this stage bring the solution to the same level by diluting, and make a further addition of the standard ferric chloride solution till the colours correspond. the amount of iron will be the same in each tube; that in the standard may be known by reading off the volume from the burette and multiplying by . milligram. if the c.c. of the assay solution gave a colour requiring more than or c.c. of the standard ferric chloride solution, repeat the determination, taking a smaller proportion. the effect of varying conditions on the assay will be seen from the following experiments:-- ~effect of varying temperature.~--the effect of increase of temperature is to lessen the colour; in fact, by boiling, the colour can be entirely removed. all assays are best carried out in the cold. c.c. at ° would only show the colour of . c.c. at ° " " " " . " " " " " . " ~effect of time.~--the effect of increase of time is to increase the colour, as will be seen from the following experiments:-- c.c. on standing minutes became equal to . c.c. " " " " . " " " " " . " ~effect of free acid.~--if no acid at all be present, the sulphocyanate of potassium solution removes the colour it first produces, so that a certain amount of acid is necessary to develop the colour. the use of a large excess has a tendency to increase the colour produced. c.c. nitric acid (sp. g. . ) read . c.c. instead of c.c. with the dilute acid. c.c. sulphuric acid (sp. g. . ) read . c.c. instead of c.c. with the dilute acid. c.c. hydrochloric acid (sp. g. . ) read . c.c. instead of c.c. with the dilute acid. ~effect of foreign metals.~--lead, mercury, cadmium, bismuth, arsenic, tin, antimony, nickel, cobalt, manganese, aluminium, zinc, strontium, barium, calcium, magnesium, sodium, or potassium, when separately present in quantities of from to times the weight of iron present, do not interfere if they have previously been brought to their highest oxidised condition by boiling with nitric acid or by treating with permanganate. arsenic and phosphoric acids interfere unless an excess of free hydrochloric or other acid is present. oxalic acid (but not tartaric acid) in minute quantities destroys the colour. nitrous acid strikes a red colour with the sulphocyanate of potassium; consequently, when nitric acid has been used in excess, high results may be obtained. copper and some other metals interfere, so that in most cases it is advisable to concentrate the iron before estimating it. a blank experiment should always be made with the reagents used in order to determine the iron, if any, introduced during the solution, &c., of the substance assayed. ~determination of iron in metallic copper.~--this may be most conveniently done during the estimation of the arsenic. the small quantity of white flocculent precipitate which may be observed in the acetic acid solution before titrating, contains the whole of the iron as ferric arsenate. it should be filtered off, dissolved in c.c. of dilute hydrochloric acid, and diluted to c.c.; c.c. of this may be taken for the estimation. for example: grams of copper were taken, and the iron estimated; . c.c. of standard ferric chloride solution were used, equivalent to . milligram of iron; this multiplied by (because only / th of the sample was taken) gives . milligram as the iron in grams of copper. this equals . per cent. in a series of experiments with this method working on -gram lots of copper, to which known quantities of iron had been added, the following were the results:-- iron present . % . % . % . % iron found . " . " . " . " when no arsenic is present in the copper, the iron can be separated by fractionally precipitating with sodic carbonate, dissolving in ammonia, and filtering off the ferric hydrate. coppers generally carry more iron the less arsenic they contain. ~determination of iron in metallic zinc.~--dissolve gram of zinc in c.c. of dilute hydrochloric acid, adding a drop or two of nitric acid towards the end to effect complete solution. boil, dilute, and tint with the permanganate of potassium solution; boil till colourless, and dilute to c.c. take c.c. for the determination. make a blank experiment by boiling c.c. of dilute hydrochloric acid with a drop or two of nitric acid; add a similar quantity of the permanganate of potassium solution, boiling, &c., as before. the quantity of iron in zinc varies from less than . to more than . per cent. when gram is taken and worked as above, each c.c. of ferric chloride solution required indicates . per cent. of iron. ~determination of iron in metallic tin.~--cover gram of tin with c.c. of hydrochloric acid, add c.c. of nitric acid, and evaporate to dryness. take up with c.c. of dilute hydrochloric acid, add c.c. of the potassic sulphocyanate solution, and make up to c.c. probably the colour developed will be brown instead of red owing to the presence of copper; in this case, add to the standard as much copper as the assay is known to contain (which must have previously been determined; see _copper_); the titration is then carried out in the usual way. or the iron may be separated from the copper in the tin by the following process:--dissolve grams of metal in c.c. of hydrochloric acid and c.c. of nitric acid, and evaporate to dryness. take up with c.c. of dilute hydrochloric acid, add grams of potash dissolved in c.c. of water, and warm till the tin is dissolved. pass sulphuretted hydrogen, boil, cool, and filter. the iron and copper will be in the precipitate. they are separated in the ordinary manner. practical exercises. . calculate from the following determinations the percentages of ferrous, ferric, and total iron in the sample of ore used. gram of ore dissolved and titrated required . c.c. of bichromate of potassium solution. gram of ore dissolved, reduced, and titrated required . c.c. of bichromate of potassium solution. standard = . . . one gram of an ore contained . gram of ferrous iron and . gram of total iron. the iron existing as oxide, what are the percentages of ferrous oxide (feo) and ferric oxide (fe_{ }o_{ }) in the ore? . one gram of brown iron ore dissolved in hydrochloric acid required . c.c. of stannous chloride (standard = . ). another gram dissolved in acid and titrated with "permanganate" required . c.c. (standard = . ). calculate the percentages of ferrous, ferric, and total iron. . another gram of the same ore, roasted, dissolved and titrated with stannous chloride, required . c.c. to what extent does this result confirm the others? . two grams of a metal were dissolved and diluted to c.c. five c.c. were taken for a colorimetric determination, and required . c.c. of the standard ferric chloride solution. what is the percentage of iron in the metal? nickel. nickel and cobalt are closely related in their chemical properties, and may best be considered together. nickel is the commoner of the two, and is met with in commerce alloyed with copper and zinc as german silver; as also in the coinage of the united states and on the continent. it is used for plating polished iron and steel goods, forming a coating little liable to rust and taking a good polish. the ores of nickel are not very common. kupfernickel and chloanthite are arsenides of nickel with, generally, more or less iron and cobalt. noumeite and garnierite are hydrated silicates of nickel and magnesia. the chief sources of nickel are these silicates, which are found in large quantity in new caledonia; and a pyrites found in norway, containing three or four per cent. of the metal. in smaller quantities it is more widely distributed, being frequently met with in copper ores; consequently, commercial copper is rarely free from it. nickel is readily soluble in moderately concentrated nitric acid. its salts are mostly green, and soluble in excess of ammonia, forming blue solutions; in these respects it resembles copper. the acid solutions, however, are not precipitated by sulphuretted hydrogen, although in alkaline solutions a black sulphide is formed which is insoluble in dilute hydrochloric acid. if the sulphide is formed in a solution containing much free ammonia, the precipitation is incomplete, some sulphide remaining in the solution and colouring it dark brown. these reactions serve to distinguish and separate nickel from other metals, except cobalt. if the separated sulphide be heated in a borax bead, the colour obtained will be a sherry brown in the outer flame, and grey or colourless in the inner flame if nickel only is present. in the presence of cobalt these colours are masked by the intense and characteristic blue yielded in both flames by that metal. dry assay. the dry assay of nickel (cobalt being at the same time determined) is based on the formation of a speise which will carry the cobalt, nickel, copper, and some of the iron of the ore in combination with arsenic. a speise of this kind, fused and exposed at a red heat to air, first loses arsenide of iron by oxidation. it is only when the iron has been oxidised that the arsenide of cobalt begins to be attacked; and when the removal of the cobalt is complete, the nickel commences to pass into the slag, the copper being left till last. the changes are rendered evident by fusion in contact with borax. the process is as follows:--weigh up grams of the ore, and calcine thoroughly on a roasting dish in the muffle. rub up with some anthracite, and re-roast. mix intimately with from to grams of metallic arsenic, and heat in a small covered clay crucible at dull redness in a muffle until no more fumes of arsenic come off (about minutes). take out the crucible, and inject a mixture of grams of carbonate of soda, grams of flour, and grams of fused borax. place in the wind furnace, and raise the temperature gradually until the charge is in a state of tranquil fusion. pour; when cold, detach the button of speise, and weigh. weigh out carefully a portion of about gram of it. place a shallow clay dish in the muffle, and heat it to bright redness; then add about . gram of borax glass wrapped in a piece of tissue paper; when this has fused, drop the piece of speise into it. close the muffle until the speise has melted, which should be almost at once. the arsenide of iron will oxidise first, and when this has ceased the surface of the button brightens. remove it from the muffle, and quench in water as soon as the button has solidified. the borax should be coloured slightly blue. weigh: the loss is the arsenide of iron. repeat the operation with the weighed button on another dish, using rather less borax. continue the scorification until a film, green when cold, floating on the surface of the button shows that the nickel is beginning to oxidise. cool, separate, and weigh the button as before. the loss is the arsenide of cobalt. if copper is absent, the speise is now arsenide of nickel. the weight of nickel corresponding to the arsenide got is calculated by multiplying by . ; and, similarly, the weight of the cobalt is ascertained by multiplying the loss in the last scorification by . .[ ] it must be remembered that the nickel and cobalt so obtained are derived from a fraction only of the speise yielded by the ore taken, so that the results must be multiplied by the weight of the whole of the speise, and divided by the weight of the fragment used in the determination. as an example, suppose grams of ore gave . grams of speise, and . gram of this gave . gram of nickel arsenide. then-- . × . = . gram of nickel . × . / . = . gram of nickel and this being obtained from grams of ore is equivalent to . per cent. when copper is also present, weigh up accurately about . gram of gold, and place it on the scorifier with the button of nickel and copper arsenide, using borax as before. scorify until the button shows the bluish-green colour of a fused gold-copper alloy. then cool, and weigh the button of copper and gold. the increase in weight of the gold button gives the copper as metal. the weight of the copper multiplied by . is the weight of the copper arsenide (cu_{ }as) present. the difference will be the nickel arsenide. the student should enter the weighings in his book as follows: ore taken -- grams speise got -- " speise taken -- grams arsenides of cobalt, nickel, and copper -- " " nickel and copper -- " gold added -- " gold and copper got -- " showing cobalt -- per cent. nickel -- " copper -- " wet methods. ~solution and separation.~--two or three grams of a rich ore, or to grams if poor, are taken for the assay. if much arsenic is present (as is usually the case), the ore must be calcined before attacking with acids. transfer to a flask; and boil, first with hydrochloric acid until the oxides are dissolved, and then with the help of nitric acid, until nothing metalliferous is left. dilute, nearly neutralise with soda, and separate the iron as basic acetate,[ ] as described in page . through the filtrate pass sulphuretted hydrogen till saturated. allow to settle (best overnight), filter, and wash. transfer the precipitate to a beaker, and dissolve in nitric acid. dilute with water, pass sulphuretted hydrogen, and filter off the precipitate, if any. boil off the gas, add ammonia until a precipitate is formed, and then acidify somewhat strongly with acetic acid. pass sulphuretted hydrogen in a slow stream until any white precipitate of zinc sulphide, there may be, begins to darken. filter; to the filtrate add ammonia, and pass sulphuretted hydrogen. the precipitate will contain the nickel and cobalt as sulphides. where small quantities of nickel and cobalt are present, and an approximate determination is sufficient, they can be concentrated as follows:--remove the copper, &c., by passing sulphuretted hydrogen through the acid solution and filtering; add ammonia to the filtrate, and again pass sulphuretted hydrogen; then heat nearly to boiling, and filter. dissolve the precipitate off the filter with dilute hydrochloric acid; the residue will contain nearly all the nickel and cobalt as sulphides. ~separation of nickel and cobalt.~--dissolve the sulphides separated as above in nitric acid; render alkaline with a solution of potash, then acidify with acetic acid; add a concentrated solution of _nitrite_ of potash. the liquid after this addition must have an acid reaction. allow to stand for hours in a warm place. filter off the yellow precipitate of nitrite of potash and cobalt, and wash with a per cent. solution of acetate of potash. the cobalt is determined in the precipitate in the way described under _cobalt_. the nickel is separated from the solution by boiling with sodic hydrate, filtering, and dissolving the precipitate in nitric acid. the solution will contain the nickel. gravimetric determination. the solution, which contains the nickel free from other metals, is heated, and a solution of sodic hydrate added in slight excess. the precipitate is filtered off, washed with boiling water, dried, ignited at a red heat, and weighed when cold. the ignited substance is nickel oxide (nio), and contains . per cent. of nickel. the oxide is a green powder, readily and completely soluble in hydrochloric acid, and without action on litmus paper. it is very easily reduced by ignition in hydrogen to metallic nickel. [illustration: fig. .] nickel is also determined by electrolysis, as follows:--the nitric acid solution is rendered strongly ammoniacal, and placed under the electrolytic apparatus used for the copper assay. three cells (fig. ), however, must be used, coupled up for intensity, that is, with the zinc of one connected with the copper of the next. the electrolysis is allowed to go on overnight, and in the morning the nickel will be deposited as a bright and coherent film. a portion of the solution is drawn off with a pipette; if it smells of ammonia, has no blue colour, and gives no precipitate with ammonic sulphide, the separation is complete. wash the cylinder containing the deposited metal, first with water and then with alcohol, as in the copper assay. dry in the water oven, and weigh. the increase in weight is metallic nickel. as an example:--there was taken gram of a nickel alloy used for coinage. it was dissolved in c.c. of nitric acid, and diluted to c.c. with water. the copper was then precipitated by electrolysis. it weighed . gram. the solution, after electrolysis, was treated with sulphuretted hydrogen, and the remaining copper was thrown down as sulphide, and estimated colorimetrically. this amounted to - / milligrams. the filtrate was evaporated, treated with ammonia, warmed, and filtered. the ferric hydrate was dissolved in dilute acid, and reprecipitated, dried, ignited, and weighed. its weight was . gram. the two filtrates were mixed, and reduced in bulk to about c.c.; a considerable excess of ammonia was added, and the nickel precipitated by electrolysis. it weighed . gram. these quantities are equivalent to: copper . per cent. nickel . " iron . " ------ . volumetric determination. an alkaline solution of potassium cyanide, to which a little potassium iodide has been added, can be assayed for its strength in cyanide by titrating with a standard solution of silver nitrate. nickel interferes with this assay, doing the work of its equivalent of silver; and the quantity of nickel present can be calculated from the amount of its interference in the titration. a volumetric assay for nickel is based on this. it has the disadvantage of all indirect titrations in that it requires two standard solutions. on the other hand it gives good results even under unfavourable conditions, and is applicable in the presence of much zinc. small quantities of cobalt will count as so much nickel, but larger quantities make the assay unworkable. some of the other metals--lead for example--have no appreciable effect; but practically the solution demands a preliminary treatment which would result in their removal. nevertheless it is a very satisfactory method and makes the determination of nickel quick and comparatively easy in most cases. _the standard solution of silver nitrate_ is made by dissolving . grams of recrystallised silver nitrate in distilled water and diluting to litre: c.c. of this solution are equivalent to . gram of nickel.[ ] _the standard solution of potassium cyanide_ should be made so as to be exactly equal to the silver nitrate solution. this can be done as follows: weigh up grams of good potassium cyanide ( per cent.), dissolve in water, add c.c. of a per cent. solution of sodium hydrate and dilute to litre. fill one burette with this and another with the solution of silver nitrate. run c.c. of the cyanide into a flask; add a few drops of potassium iodide solution and titrate with the standard silver nitrate until there is a distinct permanent yellowish turbidity. the titration is more fully described under _cyanide_, p. . the cyanide solution will be found rather stronger than the silver nitrate; dilute it so as to get the two solutions of equal value. for example, . c.c. of silver nitrate may have been required: then add . c.c. of water to each c.c. of the cyanide solution remaining. if the full c.c. are available, then add to them . c.c. of water. after mixing, take another c.c. and titrate with the silver nitrate; the two solutions should now be exactly equal. the cyanide solution, being strongly alkaline with soda, keeps very well; but its strength should be checked from time to time by titrating with silver nitrate; should there be any slight inequality in the strengths of the two solutions it is easily allowed for in the calculations. ~the titration.~--the solution, containing not much more than . gram of nickel, and free from the interfering metals, must be cooled. it is next neutralised and then made strongly alkaline with a solution of soda (naho); an excess of or c.c. suffices. this will produce a precipitate. the cyanide solution is now run in from a burette until the solution clears, after which an excess of about c.c. is added. it is well to use some round number of c.c. to simplify the calculation. add a few drops of potassium iodide solution, and run in the standard solution of silver nitrate from a burette. this should be done a little at a time, though somewhat rapidly, and with constant shaking, till a permanent yellow precipitate appears. if the addition of the cyanide did not result in a perfectly clear solution, this is because something besides nickel is present. the residue may be filtered off, though with a little practice the finishing-point may be detected with certainty in the presence of a small precipitate. if the student has the slightest doubt about a finish he should run in another c.c. of the cyanide and again finish with silver nitrate. the second result will be the same as the first. for example, if c.c. of cyanide and c.c. of silver nitrate were required at the first titration, then the c.c. of cyanide in the second titration will require c.c. of silver nitrate. the difference between the quantities of the two solutions used in each case will be c.c. it is this difference in the readings of the two burettes which measures the quantity of nickel present. each c.c. of the difference is equal to . gram of nickel. but if the cyanide solution is not exactly equal in strength to the silver nitrate, the quantity of cyanide used should be calculated to its equivalent in silver nitrate before making the subtraction. the following experimental results illustrate the accuracy of the assay and the effect upon it of varying conditions. a solution containing gram of nickel sulphate (niso_{ }. h_{ }o) in c.c. was used. by a separate assay the sulphate was found to contain . per cent. of nickel. for the sake of simplicity the results of the experiments are stated in weights of nickel in grams. ~effect of varying excess of cyanide solution.~--in each experiment there was c.c. of the nickel solution, equal to . gram of nickel. there were also c.c. of soda solution, or drops of potassium iodide and sufficient water to bring the bulk to c.c. before titrating. cyanide in excess c.c. c.c. c.c. c.c. c.c. nickel found . . . . . although the difference between the highest and lowest of these results is only milligram, their meaning is quite obvious. the excess of cyanide should not be less than c.c. ~effect of varying the quantity of soda.~--there were two series of experiments, one with c.c. of nickel solution (= . gram of nickel), the other with c.c. the conditions were as before, except that the quantity of soda was varied. soda added c.c. c.c. c.c. nickel found, st series . . . " " nd series . . . these show that the presence of much soda, though it has only a small effect, is beneficial rather than otherwise. ammonia has a bad effect, if present in anything like the same quantities. ~effect of varying the nickel.~--in experiments with , , and c.c. of the nickel solution, the results were:-- nickel present . . . nickel found . . . ~effect of zinc.~--in these experiments c.c. of nickel solution (= . gram of nickel), c.c. of soda, drops of potassium iodide and water to c.c. were used. the excess of cyanide was purposely kept at from to c.c., which is hardly sufficient. zinc added . gram. . gram. nickel found . . . on increasing the excess of cyanide to over c.c. and doubling the quantity of soda, the experiment with . gram of zinc gave . gram of nickel. hence the titration is satisfactory in the presence of zinc provided that not fewer than or c.c. of soda are used, and that the excess of cyanide is such that not fewer than or c.c. of silver nitrate are required in the titration. moreover, these precautions should be taken whether zinc is present or not. ~effect of other metals.~--if metals of the first and second groups are present they should be removed by passing sulphuretted hydrogen and filtering. if _iron_ is present it must be removed, since ferrous salts use up much cyanide, forming ferrocyanides, and ferric salts yield ferric hydrate, which obscures the end reaction. hence the sulphuretted hydrogen must be boiled off and the iron removed as basic ferric acetate by the method described on p. . if the precipitate is bulky it should be dissolved in a little dilute acid, neutralised and again precipitated as basic acetate. the nickel will be in the two filtrates. in the absence of manganese and cobalt the titration may be made without further separation. _manganese_ does not directly interfere, but the precipitated hydrate, which rapidly darkens through atmospheric oxidation, obscures the end reaction. it may be removed by passing sulphuretted hydrogen through the filtrate from the acetate separation: sulphides of nickel, cobalt and zinc will be precipitated, whilst manganese remains in solution: the addition of more sodium acetate may assist the precipitation. the precipitate must be filtered off and dissolved in nitric acid: the solution should be evaporated to dryness. the filtrate may retain a little nickel; if so, add ammonia till alkaline, then acidify with acetic acid and again filter; any small precipitate obtained here should be added to that first obtained. it is only when _cobalt_ is present that any further separation is required. cobalt hydrate takes up oxygen from the air, and on adding potassium cyanide some may refuse to dissolve; and the solution itself acquires a brown colour, which becomes deeper on standing. at this stage the cobalt is easily separated. the solution containing the nickel and cobalt with no great excess of acid, is made alkaline by adding c.c. of soda exactly as in preparing for a titration. so, too, the solution of cyanide is added so as to have an excess of or c.c.; the solution may have a brown colour, but if it is not quite clear it _must_ be filtered. then warm (boiling is not needed) and add from to c.c. of bromine water. this throws down all the nickel as black peroxide in a condition easy to filter. filter it off and wash with water. the precipitate can be dissolved off the filter with the greatest ease by a little warm sulphurous acid. the filtrate and washings, boiled till free from sulphurous acid, yield the nickel as sulphate in a clean condition. ~determination of nickel in nickel sulphate crystals.~--take . gram of the salt, dissolve in c.c. of water and add c.c. of solution of soda. run in from a burette, say, c.c. "cyanide." add a few drops of potassium iodide and titrate back with "silver nitrate." suppose . c.c. of the latter is required. then . c.c. subtracted from c.c. leaves . c.c., and since c.c. = . gram of nickel, . c.c. will equal . gram of nickel. this in . gram of the salt equals . per cent. ~determination of nickel in german silver.~--weigh up . gram of the alloy, and dissolve in a dish with or c.c. of dilute nitric acid. add c.c. of dilute sulphuric acid and evaporate till all the nitric acid is removed. cool, take up with c.c. of water, and when dissolved pass sulphuretted hydrogen through the solution. filter off the precipitate and wash with water containing sulphuretted hydrogen and dilute sulphuric acid. boil down the filtrate and washings to get rid of the excess of the gas; add some nitric acid and continue the boiling. cool, neutralise the excess of acid with soda, add gram of sodium acetate and boil. filter off the precipitate which contains the iron. the filtrate, cooled and rendered alkaline with soda, is ready for the titration. cobalt occurs less abundantly than nickel. its chief ores are smaltite and cobaltite, which are arsenides of cobalt, with more or less iron, nickel, and copper. it also occurs as arseniate in erythrine, and as oxide in asbolan or earthy cobalt, which is essentially a wad carrying cobalt. it is mainly used in the manufacture of smalts for imparting a blue colour to glass and enamels. the oxide of cobalt forms coloured compounds with many other metallic oxides. with oxide of zinc it forms "rinman's green"; with aluminia, a blue; with magnesia, a pink. this property is taken advantage of in the detection of substances before the blow-pipe. the compounds of cobalt in most of their properties closely resemble those of nickel, and the remarks as to solution and separation given for the latter metal apply here. solutions of cobalt are pink, whilst those of nickel are green. the detection of cobalt, even in very small quantity, is rendered easy by the strong blue colour which it gives to the borax bead, both in the oxidising and in the reducing flame. it is concentrated from the ore in the same way as nickel, and should be separated from that metal by means of potassic nitrite in the way described. the dry assay of cobalt has been given under _nickel_. gravimetric method. the yellow precipitate from the potassium nitrite, after being washed with the acetate of potash, is washed with alcohol, dried, transferred to a weighed porcelain crucible, and cautiously ignited with an excess of strong sulphuric acid. the heat must not be sufficient to decompose the sulphate of cobalt, which decomposition is indicated by a blackening of the substance at the edges. the salt bears a low red heat without breaking up. if blackening has occurred, moisten with sulphuric acid, and ignite again. cool and weigh. the substance is a mixture of the sulphates of cobalt and potash ( coso_{ } + k_{ }so_{ }), and contains . per cent. of cobalt. cobalt is also gravimetrically determined, like nickel, by electrolysis, or by precipitation with sodic hydrate. in the latter case, the ignited oxide will be somewhat uncertain in composition, owing to its containing an excess of oxygen. consequently, it is better to reduce it by igniting at a red heat in a current of hydrogen and to weigh it as metallic cobalt. practical exercises. . in the dry assay of an ore containing cobalt, nickel, and copper, the following results were obtained. calculate the percentages. ore taken, grams. speise formed, . gram. speise taken. . gram. arsenides of cobalt, nickel, and copper got, . gram. arsenide of nickel and copper got, . gram. gold added, . gram. gold and copper got, . gram. . calculate the percentage composition of the following compounds: co_{ }as, ni_{ }as, and cu_{ }as. . a sample of mispickel contains per cent. cobalt. what weight of the mixed sulphates of potash and cobalt will be obtained in a gravimetric determination on gram of the ore? . . gram of metal was deposited by the electrolysis of a nickel and cobalt solution. on dissolving in nitric acid and determining the cobalt . gram of potassium and cobalt sulphates were got. find the weights of cobalt and nickel present in the deposit. . what should be the percentage composition of pure cobaltite, its formula being coass? zinc. zinc occurs in nature most commonly as sulphide (blende); it also occurs as carbonate (calamine) and silicate (smithsonite). each of these is sufficiently abundant to be a source of the metal. the metal is known in commerce as "spelter" when in ingots, and as sheet zinc when rolled. it is chiefly used in the form of alloys with copper, which are known as brasses. it is also used in the form of a thin film, to protect iron goods from rusting--galvanised iron. ores of zinc, more especially blende, are met with in most lead, copper, gold, and silver mines, in larger or small quantities scattered through the lodes. those ores which generally come under the notice of the assayer are fairly rich in zinc; but alloys and metallurgical products contain it in very varying proportions. zinc itself is readily soluble in dilute acids; any residue which is left after boiling with dilute hydrochloric or sulphuric acid consists simply of the impurities of the metal; this is generally lead. all zinc compounds are either soluble in, or are decomposed by, boiling with acids, the zinc going into solution. zinc forms only one series of salts, and these are colourless. their chief characteristic is solubility in an alkaline solution, from which sulphuretted hydrogen produces a white precipitate of zinc sulphide. zinc is detected by dissolving the substance in hydrochloric or nitric acid, boiling, and adding sodic hydrate in excess, filtering, and adding ammonic sulphide to the filtrate. the precipitate contains the zinc, which can be dissolved out by boiling with dilute sulphuric acid, and detected by the formation of a white precipitate on the addition of potassic ferrocyanide. the dry assay of zinc can only be made indirectly, and is unsatisfactory. zinc is volatile, and at the temperature of its reduction is a gas. it is impracticable to condense the vapour so as to weigh the metal, consequently its amount is determined by loss. the following method gives approximate results: take grams of the dried and powdered ore and roast, first at a low temperature and afterwards at a higher one, with the help of carbonate of ammonia to decompose the sulphates formed; cool and weigh. the metals will be present as oxides. mix with grams of powdered charcoal and charge into a black-lead crucible heated to whiteness, cover loosely, and leave in the furnace for about a quarter of an hour. uncover and calcine the residue, cool and weigh. the loss in weight multiplied by . gives the percentage of zinc in the ore. wet methods. solution and separation may be effected as follows: treat or grams of the substance with or c.c. of hydrochloric acid or aqua regia; evaporate to dryness; take up with c.c. of hydrochloric acid and dilute to c.c.; heat nearly to boiling; saturate with sulphuretted hydrogen; filter, and wash with water acidulated with hydrochloric acid. boil off the sulphuretted hydrogen and peroxidise with a few drops of nitric acid. cool; add caustic soda till nearly, but not quite, neutralised, and separate the iron as basic acetate by the method described under _iron_. to the filtrate add ammonia till alkaline, and pass sulphuretted hydrogen. allow to settle and decant on to a filter. dissolve off the precipitate from the filter with hot dilute hydrochloric acid. the solution will contain the zinc, together with any manganese the ore contained, and, perhaps, traces of nickel and cobalt. if the zinc is to be determined volumetrically, and manganese is present, this latter is separated with carbonate of ammonia, as described further on; but if a gravimetric method is used, and only small quantities of manganese are present, it is better to proceed as if it were absent, and to subsequently determine its amount, which should be deducted. gravimetric determination. the solution containing the zinc is contained in an evaporating dish, and freed from sulphuretted hydrogen by boiling, and, if necessary, from an excess of acid by evaporation. the evaporating dish must be a large one. cautiously add sodium carbonate to the hot, moderately dilute solution, until the liquid is distinctly alkaline, and boil. allow the precipitate to settle, decant on to a filter, and wash with hot water. dry, transfer to a porcelain crucible (cleaning the paper as much as possible), add the ash, ignite, and weigh. the substance weighed is oxide of zinc, which contains . per cent. of the metal. it is a white powder, becoming yellow when heated. it must not show an alkaline reaction when moistened. if it contains manganese this metal will be present as sesquioxide (mn_{ }o_{ }). its amount can be determined by dissolving in dilute acid and boiling with an excess of sodic hydrate. the oxide of manganese will be precipitated, and can be ignited and weighed. its weight multiplied by . must be deducted from the weight of oxide of zinc previously obtained. the results yielded by the gravimetric determination are likely to be high, since the basic carbonate of zinc frequently carries down with it more or less soda which is difficult to wash off. volumetric determination this method is based on the facts that zinc salts in an acid solution decompose potassium ferrocyanide, forming a white insoluble zinc compound; and that an excess of the ferrocyanide can be detected by the brown coloration it strikes with uranium acetate. the method resembles in its working the bichromate iron assay. the standard solution of potassium ferrocyanide is run into a hot hydrochloric acid solution of the zinc until a drop of the latter brought in contact with a drop of the indicator (uranium acetate) on a white plate strikes a brown colour. the quantity of zinc in the solution must be approximately known; run in a little less of the ferrocyanide than is expected will be necessary; test a drop or two of the assay, and then run in, one or two c.c. at a time, until the brown colour is obtained. add c.c. of a standard zinc solution, equivalent in strength to the standard "ferrocyanide," re-titrate, and finish off cautiously. of course c.c. must be deducted from the reading on the burette. the precipitate of zinc ferrocyanide formed in the assay solution is white; but if traces of iron are present, it becomes bluish. if the quantity of ferrocyanide required is known within a few c.c., the finishing point is exactly determined in the first titration without any addition of the standard zinc solution. unfortunately this titration serves simply to replace the gravimetric determination, and does not, as many volumetric processes do, lessen the necessity for a complete separation of any other metals which are present. most metals give precipitates with ferrocyanide of potassium in acid solutions. if the conditions are held to, the titration is a fairly good one, and differences in the results of an assay will be due to error in the separation. ferric hydrate precipitated in a fairly strong solution of zinc will carry with it perceptible quantities of that metal. similarly, large quantities of copper precipitated as sulphide by means of sulphuretted hydrogen will carry zinc with it, except under certain nicely drawn conditions. when much copper is present it is best separated in a nitric acid solution by electrolysis. the titration of the zinc takes less time, and, with ordinary working, is more trustworthy than the gravimetric method. _the standard ferrocyanide solution_ is made by dissolving . grams of potassium ferrocyanide (k_{ }fecy_{ }. h_{ }o) in water, and diluting to a litre. one hundred c.c. are equal to gram of zinc. _the standard zinc solution_ is made by dissolving grams of pure zinc in c.c. of hydrochloric acid and or c.c. of water, and diluting to litre, or by dissolving . grams of zinc sulphate (znso_{ }. h_{ }o) in water with c.c. of hydrochloric acid, and diluting to litre. one hundred c.c. will contain gram of zinc. _the uranium acetate solution_ is made by dissolving . gram of the salt in c.c. of water. to standardise the "ferrocyanide" measure off c.c. of the standard zinc solution into a oz. beaker, dilute to c.c., and heat to about ° c. (not to boiling). run in or c.c. of the "ferrocyanide" solution from an ordinary burette, and finish off cautiously. fifty divided by the quantity of "ferrocyanide" solution required gives the standard. in assaying ores, &c., take such quantity as shall contain from . to gram of zinc, separate the zinc as sulphide, as already directed. dissolve the sulphide off the filter with hot dilute hydrochloric acid, which is best done by a stream from a wash bottle. evaporate the filtrate to a paste, add c.c. of dilute hydrochloric acid, dilute to c.c. or c.c., heat to about ° c., and titrate. manganese, if present, counts as so much zinc, and must be specially separated, since it is not removed by the method already given. the following method will effect its removal. to the hydrochloric acid solution of the zinc and manganese add sodium acetate in large excess and pass sulphuretted hydrogen freely. allow to settle, filter off the zinc sulphide and wash with sulphuretted hydrogen water. the precipitate, freed from manganese, is then dissolved in hydrochloric acid and titrated. the following experiments show the effect of variation in the conditions of the assay:-- ~effect of varying temperature.~--using c.c. of the standard zinc solution, c.c. of dilute hydrochloric acid, and diluting to c.c. temperature ° c. ° c. ° c. ° c. "ferrocyanide" required . c.c. . c.c. . c.c. . c.c. the solution can be heated to boiling before titrating without interfering with the result; but it is more convenient to work with the solution at about ° c. cold solutions must not be used. ~effect of varying bulk.~--these were all titrated at about ° c., and were like the last, but with varying bulk. bulk . c.c. . c.c. . c.c. . c.c. "ferrocyanide" required . " . " . " . " any ordinary variation in bulk has no effect. ~effect of varying hydrochloric acid.~-- with c.c. bulk and varying dilute hydrochloric acid the results were:-- acid added . c.c. . c.c. . c.c. . c.c. . c.c. "ferrocyanide" required . " . " . " . " . " ~effect of foreign salts.~--the experiments were carried out under the same conditions as the others. five grams each of the following salts were added:-- salt added { ammonic ammonic sodium sodium { chloride. sulphate. chloride. sulphate. "ferrocyanide" required . c.c. . c.c. . c.c. . c.c. salt added { potassium magnesium nil. { nitrate. sulphate. "ferrocyanide" required . c.c. . c.c. . c.c. in a series of experiments in which foreign metals were present to the extent of . gram in each, with c.c. of zinc solution and c.c. of dilute hydrochloric acid, those in which copper sulphate, ferrous sulphate, and ferric chloride were used, gave (as might be expected) so strongly coloured precipitates that the end reaction could not be recognised. the other results were:-- "ferrocyanide" required. with nothing added. . c.c. " . gram lead (as chloride) . " " . " manganese (as sulphate) . " " . " cadmium (as sulphate) . " " . " nickel (as sulphate) . " ~effect of varying zinc.~--these were titrated under the usual conditions, and gave the following results:-- zinc added . c.c. . c.c. . c.c. . c.c. . c.c. "ferrocyanide" required . " . " . " . " . " ~determination of zinc in a sample of brass.~--take the solution from which the copper has been separated by electrolysis and pass sulphuretted hydrogen until the remaining traces of copper and the lead are precipitated, filter, boil the solution free from sulphuretted hydrogen, put in a piece of litmus paper, and add sodic hydrate solution in slight excess; add c.c. of dilute hydrochloric acid (which should render the solution acid and clear); warm, and titrate. a sample of . gram of brass treated in this manner required . c.c. of "ferrocyanide" (standard c.c. = . zinc), which equals . gram of zinc or . per cent. ~determination of zinc in blende.~--dissolve gram of the dried and powdered sample in c.c. of nitric acid with the help of two or three grams of potassium chlorate dissolved in the acid. evaporate to complete dryness, taking care to avoid spirting. add grams of powdered ammonium chloride, c.c. of strong ammonia and c.c. of boiling water; boil for one minute and see that the residue is all softened. filter through a small filter, and wash thoroughly with small quantities of a hot one per cent. solution of ammonium chloride. add c.c. of hydrochloric acid to the filtrate. place in the solution some clean lead foil, say or square inches. boil gently until the solution has been colourless for three or four minutes. filter, wash with a little hot water; and titrate with standard ferrocyanide. ~determination of zinc in silver precipitate.~--this precipitate contains lead sulphate, silver, copper, iron, zinc, lime, &c. weigh up grams of the sample, and extract with c.c. of dilute sulphuric acid with the aid of heat. separate the copper with sulphuretted hydrogen, peroxidise the iron with a drop or two of nitric acid, and separate as acetate. render the filtrate ammoniacal, pass sulphuretted hydrogen; warm, and filter. dissolve the precipitated zinc sulphide in dilute hydrochloric acid, evaporate, dilute, and titrate. silver precipitates carry about . per cent. of zinc. gasometric method. metallic zinc is readily soluble in dilute hydrochloric or sulphuric acid, hydrogen being at the same time evolved.[ ] the volume of the hydrogen evolved is obviously a measure of the amount of zinc present in the metallic state. the speed with which the reaction goes on (even in the cold) and the insolubility of hydrogen renders this method of assay a convenient one. it is especially applicable to the determination of the proportion of zinc in zinc dust. the apparatus described in the chapter on gasometric method is used. the method of working is as follows: fill the two burettes with cold water to a little above the zero mark, place in the bottle about . gram of the substance to be determined, and in the inner phial or test tube c.c. of dilute sulphuric acid; cork the apparatus tightly and allow to stand for a few minutes; then bring the water to the same level in the two burettes by running out through the clip at the bottom. read off the level of the liquid in the graduated burette. turn the bottle over sufficiently to spill the acid over the zinc, and then run water out of the apparatus so as to keep the liquid in the two burettes at the same level, taking care not to run it out more quickly than the hydrogen is being generated. when the volume of gas ceases to increase, read off the level of the liquid, deduct the reading which was started with; the difference gives the volume of hydrogen evolved. at the same time read off the volume of air in the "volume corrector," which must be fixed alongside the gas burettes. make the correction. for example: a piece of zinc weighing . gram was found to give . c.c. of gas at a time when the corrector read c.c.[ ] then the corrected volume is : :: . : _x_. _x_ = . c.c. c.c. of hydrogen at ° c. and mm. is equivalent to . gram of zinc; therefore the quantity of zinc found is : :: . : _x_. _x_ = . gram of zinc. this being contained in . gram of metal is equivalent to . per cent. as an example of a determination in which reducing the volume of liberated hydrogen to ° c. and mm. is avoided, the following may be taken:-- . gram of pure zinc gave . c.c. of gas; and the volume of air in the corrector was . c.c. . gram of the assay gave . c.c. of gas; and the volume of air in the corrector was . c.c.; : . :: . : _x_. _x_ = . c.c. this is the volume of gas got in the assay if measured under the same conditions as the standard, . : . :: . : _x_. _x_ = . . then . : . :: : _x_. _x_ = . per cent. as these assays can be made quickly, it is well for the sake of greater accuracy to make them in duplicate, and to take the mean of the readings. one set of standardisings will do for any number of assays. the student must carefully avoid unnecessary handling of the bottle in which the zinc is dissolved. ~colorimetric method.~--zinc salts being colourless, there is no colorimetric determination. examination of commercial zinc. take grams of zinc, and dissolve them in dilute nitric acid; boil, allow to settle; filter; wash, dry; ignite the precipitate, if any, and weigh as oxide of tin. examine this for arsenic. ~lead.~--add ammonia and carbonate of ammonia to the liquid, and boil, filter off the precipitate, wash with hot water. digest the precipitate with dilute sulphuric acid; filter, wash, and weigh the sulphate of lead. ~iron.~--to the filtrate from the sulphate of lead add ammonia, and pass sulphuretted hydrogen; digest, and filter. (save the filtrate.) dissolve the precipitate in hydrochloric acid, oxidise with nitric acid, and precipitate with ammonia. wash, ignite, and weigh as ferric oxide. calculate to iron. ~arsenic.~--to the filtrate from the sulphide of iron add hydrochloric acid in slight excess; filter off, and wash the precipitate. rinse it back into the beaker, dissolve in nitric acid, filter from the sulphur, and add ammonia, in excess, and magnesia mixture. filter off the ammonic-magnesic arsenate, and wash with dilute ammonia. dry, ignite with nitric acid, and weigh as magnesic pyrarsenate. calculate to arsenic, and add to that found with the tin. ~copper.~--to the filtrate from the ammonia and ammonic carbonate add sulphuric acid in small excess, and pass sulphuretted hydrogen. allow to settle, filter, and wash. rinse the precipitate into a beaker, boil with dilute sulphuric acid, and filter. (save the filtrate.) dry, burn the paper with the precipitate, treat with a drop or two of nitric acid, ignite, and weigh as copper oxide. calculate to copper. ~cadmium.~--to the filtrate from the sulphide of copper add ammonia, so as to nearly neutralise the excess of acid, and pass sulphuretted hydrogen. collect and weigh the precipitate as cadmium sulphide, as described under _cadmium_. practical exercises. . what weight of hydrogen will be evolved in dissolving gram of zinc in dilute sulphuric acid? . how many c.c. would this quantity of hydrogen measure at ° c. and m.m.? ( litre weighs . gram). . . gram of zinc are found to give . c.c. of hydrogen. in another experiment under the same conditions . c.c. are got. what weight of zinc was used for the second experiment? . a sample of blende is found to contain per cent. of zinc. what percentage of zinc sulphide did the sample contain? . how much metallic lead would be precipitated from a solution of lead acetate by gram of zinc? cadmium. cadmium occurs in nature as cadmium sulphide in greenockite, cds, which is very rare. it is widely diffused in calamine, blende, and other zinc ores, forming, in some cases, as much as or per cent. of the ore. oxide of cadmium forms the "brown blaze" of the zinc smelters. sulphide of cadmium is used as a pigment (cadmium yellow); and the metal and some of its salts are useful reagents. the salts of cadmium closely resemble those of zinc. the hydrate, however, is insoluble in excess of potash, and the sulphide is insoluble in dilute acids. it forms only one series of salts. cadmium is detected by giving with sulphuretted hydrogen in solutions, not too strongly acid, a yellow precipitate, which is insoluble in solutions of the alkalies, alkaline sulphides, or cyanide of potassium. ~solution and separation.~--substances containing cadmium are soluble in acids. the solution is evaporated to dryness (to render any silica that may be present insoluble) and taken up with c.c. of dilute hydrochloric acid. dilute to c.c., and pass sulphuretted hydrogen. filter, digest the precipitate with soda, wash, and boil with dilute sulphuric acid. filter; the filtrate contains the cadmium and, possibly, a small quantity of zinc, from which it is best separated by reprecipitating with sulphuretted hydrogen. gravimetric determination. the solution containing the cadmium freed from the other metals is precipitated with sulphuretted hydrogen in a moderately-acid solution. the precipitate is collected on a weighed filter, and washed, first with an acid solution of sulphuretted hydrogen, and afterwards with water. it is dried at ° c. and weighed. if free sulphur is suspected to be present, extract with bisulphide of carbon, and again weigh. the residue is cadmium sulphide, which contains . per cent. of cadmium. it is a yellow powder insoluble in solutions of the alkalies, alkaline sulphides, or cyanide of potassium. it dissolves readily in acid. it cannot be ignited in a current of hydrogen without loss. volumetric method. the solution containing the cadmium is concentrated by evaporation, and mixed with an excess of oxalic acid and alcohol. the precipitate is filtered, washed with alcohol, dissolved in hot hydrochloric acid, and titrated with permanganate of potassium. footnotes: [ ] when chromium is present some of the iron may escape precipitation but it can be recovered from the solution by means of ammonic sulphide. [ ] ( ) feso_{ } + kmno_{ } + h_{ }so_{ } = fe_{ }(so_{ })_{ } + mnso_{ } + k_{ }so_{ } + h_{ }o. ( ) fecl_{ } + k_{ }cr_{ }o_{ } + hcl = fe_{ }cl_{ } + cr_{ }cl_{ } + kcl + h_{ }o. [ ] ( ) fe_{ }cl_{ } + sncl_{ } = fecl_{ } + sncl_{ }. ( ) fe_{ }cl_{ } + sh_{ } = fecl_{ } + hcl + s. ( ) fe_{ }cl_{ } + na_{ }so_{ } + h_{ }o = fecl_{ } + na_{ }so_{ } + hcl. ( ) fe_{ }cl_{ } + zn = fecl_{ } + zncl_{ }. [ ] grams of stannous chloride and c.c. of dilute hydrochloric acid are diluted to one litre. [ ] the maximum reducing effect of zinc is obtained by exposing as large a surface as possible of the metal in a hot concentrated solution containing but little free acid (thorpe). [ ] about inches in diameter. [ ] : :: : . . the iron in the ore is, then, the same in amount as that in . c.c. of the ferric chloride solution; and since c.c. of the latter contain gram of iron, . c.c. of the same contains . gram of iron; and, further, if gram of ore carries this amount of iron, grams of ore will obviously give . grams of iron. [ ] these compounds are ni_{ }as and co_{ }as. [ ] with large quantities of iron the ferric precipitate should be re-dissolved and re-precipitated. the filtrate must be added to the original filtrate. [ ] kcy + niso_{ } = k_{ }nicy_{ } + k_{ }so_{ } kcy + agno_{ } = kagcy_{ } + kno_{ } .'. agno_{ } = ni [ ] zn + h_{ }so_{ } = h_{ } + znso_{ }. [ ] these c.c. are equivalent to c.c. of dry air at ° c. and mm. chapter xii. tin--tungsten--titanium. tin. tin occurs in nature as cassiterite (containing from to per cent. of oxide of tin), which mineral is the source from which the whole of the tin of commerce is derived. tin also occurs as sulphide combined with sulphides of copper and iron in the mineral stannine or bell-metal ore. it is a constituent of certain rare minerals, such as tantalite. the methods of assaying tin in actual use are remarkable when compared with those of other metals. the more strictly chemical methods are rendered troublesome by the oxide being insoluble in acids, resembling in this respect the gangue with which it is associated. moreover, it is not readily decomposed by fusion with alkalies. the oxide has first to be reduced to metal before the tin can be dissolved. the reduction may be performed by fusing with potassic cyanide, by heating to moderate redness in a current of hydrogen or coal gas, or by heating to a higher temperature with carbon. the reduced metal is only slowly dissolved by hydrochloric acid, and although it is readily soluble in aqua regia, the solution cannot be evaporated or freed from the excess of acids, by boiling, without loss of tin, because of the volatility of stannic chloride. there has long been a difficulty in getting a quick wet method. the process of assaying tin ores adopted in the mines of cornwall is a mechanical one known as "vanning," the object of which is to find the percentage of "black tin," which, it is well to remember, is not pure cassiterite, much less pure oxide of tin. tin ore, as taken from the lode, contains from to per cent. of cassiterite, and is mainly made up of quartz, felspar, chlorite, schorl, and other stony minerals, together with more or less mispickel, iron and copper pyrites, oxide of iron, and wolfram. the cassiterite has a specific gravity ( . to . ) considerably higher than that of the vein-stuff ( . to . ), and is concentrated by a series of washings till it is free from the lighter material. those minerals which have a specific gravity approaching that of the cassiterite are not completely removed. the mispickel and copper and iron pyrites are converted into oxides by roasting, and are in great part removed by a subsequent washing. the concentrated product is known as "black tin," and in this condition is sold to the smelter. the chief foreign matters in the black tin are silica, oxides of iron and copper, and wolfram, with traces of manganese and niobic acid; and in certain stream ores there may be as much as or per cent. of titaniferous iron. the black tin from the mines contains from to per cent. of water, and is sold and assayed wet. a series of typical samples of black tin ranged as follows:-- --------------------------+---------------------+----------------- source of material. | percentage of metal |specific gravity. | in dry ore. | --------------------------+---------------------+----------------- good mine ore | . | . inferior do. | . | . titaniferous stream ore | . | . mine ore with wolfram | . | . ore from stream works | . | . --------------------------+---------------------+----------------- it will be seen from these figures that black tin is a very variable substance; and that the specific gravity is largely influenced by the impurities; hence, it is only an indication of the percentage of metal when the same kind of ore is dealt with. as already pointed out, the object of vanning is to determine the proportion of black tin in the lode stuff. the relation between the actual content in oxide of tin and the produce got by vanning has been tested on several occasions with results which show a fair degree of approximation. the following are some published results of assays of the same batch of ore. the vanning results were obtained by a cornish vanner of recognised ability, and the wet assays by two london firms of the highest standing:-- vanning results: (average) lbs. of "black tin." wet assay results: a . lbs. of stannic oxide. b . lbs. " the vanner reported his black tin as containing per cent. of tin. this will bring his result, if calculated as stannic oxide, to . lbs. to the ton; which agrees with the others. according to our experience the "van" assay agrees fairly well with the "wet" one, if the black tin is assumed to contain . per cent. of stannic oxide (sno_{ }). vanners are, as a rule, skilful men, and show remarkable dexterity in separating the black tin, with the help of their apparatus, which consists simply of a shovel and a kieve of water. an account of the process is given below. but different vanners, all good men, will get different results working on material new to them. the black tin weighed by the vanner is supposed to correspond in quality with the black tin returned from the floors of the mine for which he is assaying, but this differs materially in different mines with the nature of the gangue. the process leaves too much to the judgment of the vanner. it is more than probable that in practice the returns from the dressing-floors check the assayer, instead of, as should properly be the case, the assayer checking the returns. it is only when this last is done that any control is had over the system of dressing. a correct assay of this ore is a matter of some importance, because of the high price of the metal. the method of assaying the black tin is a dry one, and consists of mixing it with "culm," and submitting it in a black-lead crucible to the highest temperature of a wind furnace. the sample is taken wet as it arrives at the smelting house, and is assayed direct. the product of the assay is examined, and a deduction of a considerable percentage is very properly made for impurities, since the assay really determines the percentage, not merely of tin, but of the bodies present which are reducible at a white heat. the judgment as to how much is to be deducted is assisted partly by an examination of the metal got from the assay, and partly by the experience acquired in smelting similar ores. the produce, which is that of the impure tin, is stated in parts in twenty; thus a produce of is equivalent to per cent., or to cwt. per ton. [illustration: fig. .] mechanical separation.--vanning. this process, which has already been referred to, is carried out as follows:--after sampling the ore in the ordinary way, a quantity (varying with its richness) is weighed out. special weights are generally used. the standard weight, marked , weighs about an ounce; with poor ores this quantity is taken for an assay, but with richer ores or even is sufficient. the unit of weight has no special name, but the parts in are spoken of as the produce; thus, if of ore were taken and . of black tin were separated, the produce would be - / : obviously half the "produce" will give the percentage. the weighed portion of the ore is placed on the vanning shovel. the vanner stands in front of a tub of water (kieve) and allows or c.c. of water to flow on to the ore. he then raises the shovel a little above the surface of the water, and, holding it nearly horizontal, briskly rotates the water by imparting to the shovel a slight circular motion, passing into an elliptical one (front to back). this causes the finer mud to be suspended in the liquid, which is then run off, leaving the body of the ore in the centre of the shovel. this is repeated until the water after standing a moment is fairly clear. about half as much water as before is brought on; then, with a motion which is similar to the previous one, but with a jerk added in one direction, the heavier minerals are thrown up, and the stony matter brought back. the jerk is produced just as the wave of water is returning. the descending wave of water draws with it the bulkier and lighter particles of the ore, whilst the heavier matter lying on the bottom is scarcely affected by it. the jerky motion, however, carries it to the front of the shovel. the lighter stuff is washed off, and the residue dried by holding the shovel over the furnace. it now corresponds, more or less, to the stuff which on the mine is sent to the calciner. it is swept from the shovel into a scoop, and transferred to a hot crucible; in which it is calcined until free from sulphur. some vanners calcine their samples before commencing to van. the calcined ore is shaken out of the crucible on to the shovel; rubbed up with a hammer; and washed (as at first) to get rid of the finer and lighter "waste." the separating motions are again gone through; and the "head" of the best of the black tin is thrown well up on one side of the shovel in the form of a crescent, so as to leave room on the shovel to work with the "tailings." the quantity of water used is kept low, to prevent this "crop" tin from being washed back again. the tailings are then crushed to free the tin from adherent oxide of iron; and again washed to throw up the remaining tin ore. as this tin is finely divided, it is more difficult to bring it up, so that a vigorous and rapid motion is required. the tailings are now washed off, and the whole of the black tin is brought into the centre of the shovel. it requires two or three washings more to free it from the waste it contains. very small quantities of water are used. the purity of the black tin can be seen by its appearance on the shovel. the cleaned ore is dried as before, freed from particles of iron with the aid of a magnet, and weighed. the weighings are carried to / th of the unit used. the following example illustrates the method of calculation adopted on the mine. a parcel of ton cwt. qrs. of tin ore with a produce of (equal to - / per cent.) contains cwt. qrs. lbs. of black tin. this result is obtained as follows:-- ton cwt. qrs. } ----------------- } } equivalent to multiplying by . } ---------------- } . strike off the first figure to the right. multiply by to reduce to quarters. --------- --------- multiply by to reduce to pounds. ----- ----- . strike off the first figure to the right. similarly, a parcel of tons cwt. with a produce of - / contains cwt. qr. lbs. of black tin. for the following information, as well as for much of that already given about vanning, we are indebted to captain reynolds, of cook's kitchen mine. "to have a complete set of tools for all vanning purposes, it will be necessary to get the following:--a vanning shovel inches long and inches wide, weighing not over - / pounds. it is made of hammered sheet iron of the shape shown in fig. . it must have a light wooden handle (preferably of deal) feet long. a bruising hammer, weighing - / pounds, with a handle foot long. a pair of tongs (furnace) - / feet long, made of / -inch round iron. and a set of ordinary clay crucibles for calcining. there ought to be two sets of scales and weights: the first should be confined to weighing the powdered tin stuff, and the second ought to be a much higher class one, for weighing the black tin obtained. the furnace for roasting the sample should be inches square and inches deep, with the fire-bars at the bottom three-quarters of an inch apart. the water-box for vanning in should be at least feet long, feet inches wide, and inches deep." dry methods. for the following description of the process adopted in cornwall we are indebted to mr. a.k. barnett, f.g.s., of chyandour. ~cornish method.~--_tin ore assay._--the ore to be smelted or assayed should be concentrated to say not less than per cent. of metallic tin; though to obtain satisfactory results it should be brought nearer per cent., as with ore containing less than to per cent. of metal there will be a considerable loss both in the assaying and in the smelting. if the ore to be operated on does not contain this quantity of metal, then the sample (if coarse) must be reduced to a fine state, the gangue being removed by vanning, and the ore saved for the fire assay. the method adopted for the determination of tin in the ore is as follows:--about - / ounces troy ( grains, or about grams) of the ore to be assayed is weighed out and mixed on a flat copper pan (shaped with a long lip) with one-fifth of its weight ( grains, or . grams) of powdered culm (anthracite). the mixture of ore and culm is either transferred to a black-lead crucible before the latter is put into the furnace, or, as some prefer, it is carefully swept into a crucible which has been imbedded in the fire. some assayers cover their pots with a flat cover placed loosely on, while others leave the mixture in the open pot. the furnace, which has been previously fired to a strong heat, is then covered, and the sample is subjected to a sharp fire for a period of from twelve to twenty minutes. no definite time can be stated, as, besides the strength of the fire, the quality and condition of the ore, and the impurities associated with it, greatly affects the time required for the complete reduction of the ore. as soon as the mixture in the crucible has settled down to a uniform white heat, and any very slight ebullition which may have taken place has subsided, the crucible is gently shaken, removed from the fire (the culm-ash or slag which covers the metal being carefully drawn aside with an iron scraper), and the metal is poured quickly into an iron ingot-mould, which is usually placed on a copper pan to save the culm-slag and the adherent metal which comes out with it. the crucible is then carefully scraped, and the scrapings, together with the contents of the mould and pan, are transferred to a mortar. there the ingot of tin is freed from slag and then taken to the scales. the rest, after being finely powdered, is passed through a sieve. the flattened particles of tin which remain on the sieve are weighed with the ingot (the _lump_, as it is called); whilst the siftings are vanned on a shovel, and (the slag being washed off) the fine tin is collected, dried, and weighed with the rest: the whole gives the produce or percentage of metal in the ore. the results of the assays are expressed in cwts. of metal in the ton of ore. the percentage is rarely given and never used in cornwall. thus--" - / produce" would mean that the assay yielded results at the rate of - / cwts. of metal for one ton of the ore. some assayers use a little powdered fluor-spar to assist the fusion of refractory slags. a small quantity of borax will also occasionally be of service for ores containing silica in excess of any iron that may be present. the borax renders the slag more fusible, and assists the formation of a larger lump (with less fine tin in the slag) than would be obtained by the use of culm alone. the quality and the percentage of _pure tin_ in the metal will vary considerably, according to the impurities that are associated with the ore to be assayed. the crude lump is then remelted in a small iron ladle at as low a temperature as possible, and the fused metal is poured into a shallow trench about inches long by / of an inch wide cut in a block of white marble. the metal will be silvery-white if the temperature employed be correct; if too hot, the surface will show a yellow, red, or blue colour (according to the heat employed); in such case the metal should be remelted at a lower temperature. if the metal on cooling remains perfectly clear and bright, then it may be assumed that the tin is of good quality and commercially pure. a crystallised or frosted appearance of the metal indicates the presence of some alloy, say of iron, copper, zinc, lead, antimony, &c. the assayer who has had much practice can readily distinguish the metal or metals that are associated with the ore by noting the appearance of the tin on cooling; and can fairly judge the quantity of impurity present by the amount of the crystallisation or stain. whilst the foregoing method of assaying cannot lay claim to scientific accuracy, it is by no means so imperfect as some writers would have us believe, who state that a loss of to per cent. arises in the operation. it is certainly the most ready and expeditious mode of determining the commercial value of a parcel of tin ore, which, after all, is the main object of all assaying operations. the difficulty which beginners find in obtaining satisfactory results, and any loss of metal which those not accustomed to the process may incur, will invariably occur in the vanning of the powdered slag for the fine tin, the rest of the operations being easy of execution, and requiring only the ordinary care necessary for all metallurgical work. there is no doubt that if low percentage ores containing silica are assayed in this manner, low results are obtained, as it is impossible to reduce the whole of the tin in the presence of free silica; with this class of ores, care should be taken to remove some of the silica by preliminary vanning, or some flux should be added which will combine with the silica, and so prevent its entering into combination with the tin. low quality tin ores containing iron, copper, lead, zinc, antimony, etc., combined with arsenic, sulphur, or oxygen, will give very much higher results than the actual percentage of tin in the sample. the other metals (being readily reduced in the presence of tin) alloy with it, and give a hard lump difficult to fuse in the iron ladle; where the quantity of foreign metals is large, the metal can only be melted to a stiff pasty mass; so that (in determining the value of a ton of tin ore, or even reporting on the percentage of tin it contains) not only must the weight of the assay be the basis for calculation, but the quality and character of the metal obtained must also be considered. thus two ores of tin might be assayed both yielding a similar _produce_, say - / ( - / per cent.), and yet one might contain per cent. less tin than the other. if it be required to obtain the pure metal from tin ores containing the ores of other metals associated with them, the latter must be removed by digesting in strong hydrochloric acid, and washing. the assay may then be conducted in the usual way, and a fairly pure lump will be obtained. if wolfram be present in any appreciable quantity in the ore, it considerably reduces the proportion of lump, and at the same time it increases the fine tin (or _prillion_, as it is termed) in the assay. this may be got rid of by boiling in aqua regia, and dissolving out the tungstic acid which has been liberated by means of ammonia. it will be seen that this method of assaying tin has its advantages and its drawbacks. it is quickly performed; with ores of good quality it gives results not to be excelled by any other process; and it gives the smelter the actual alloy and quality of metal he may expect to get in the smelting of the ore, which no other mode of assaying will do: against which may be set the skill required to obtain accurate results with the vanning shovel; the loss of metal in poor ores containing an excess of silica; and the high results from ores containing a large quantity of metallic impurities. ~cyanide method.~--weigh up grams of the ore and dry it on a scoop over the bunsen flame. when dry, weigh, and calculate the percentage of water from the loss in weight. transfer the dried ore to an evaporating dish, and cover with c.c. of hydrochloric acid; boil for or minutes, and then add c.c. of nitric acid and boil again. dilute with water, and filter. transfer the filter and its contents to an e battersea crucible, and calcine it for a few minutes. cool, and weigh the residue. the loss equals the oxides soluble in acid. transfer the residue to the crucible and mix it with its own weight of cyanide of potassium; add a similar amount of "cyanide" as a cover. place in the furnace, and when the charge has attained the temperature of the furnace (in from to minutes), remove it at once; tap the pot _vigorously_ several times, and then pour its contents quietly into a mould. dissolve the slag in water, clean, dry, and weigh the button of tin. wet methods. ~detection.~--tin ore is detected by its insolubility in acids, high specific gravity, and characteristic appearance in water. the powder is separated from the lighter gangue by washing. it is fused in a berlin crucible with five times its weight of potassic cyanide at a moderately high temperature in a muffle, or over the blowpipe. the slag is washed off with water, and the metallic buttons or residue treated with hydrochloric acid (not aqua regia), for some time. one portion of the solution strikes a purple colour with chloride of gold, another portion gives a white or grey precipitate or cloudiness with mercuric chloride. these reactions are characteristic of tin as stannous chloride. metallic tin treated with nitric acid becomes converted into a white insoluble powder (metastannic acid). aqua regia dissolves tin readily, forming stannic chloride, and in this solution the metal is detected by precipitation with sulphuretted hydrogen, which gives a yellow precipitate. tin in solution as stannic or stannous chloride is precipitated as metal by means of zinc. the fact that tin forms two well-defined series of compounds is taken advantage of in assaying (just as in the case of iron), by determining how much of an oxidising agent is required to convert it from the stannous into the stannic state. for example, on the addition of a solution of permanganate of potash to a solution of stannous chloride the oxidation goes on rapidly, and the finishing point is sharp and distinct; but acid solutions of stannous chloride quickly take up oxygen from that dissolved in the water used and from the air. unfortunately, there is no obvious sign that such oxidation has taken place, except that (fatal to the assay) a smaller volume of the permanganate is required. great care is required with such solutions, both before and during titration. the addition of an excess of ferric chloride to the stannous solution, as soon as the whole of the tin has been dissolved, will lessen this liability to oxidation. ~separation.~--if the tin is present in an alloy, the substance is boiled in an evaporating dish with dilute nitric acid until the whole of the material is attacked. evaporate nearly to dryness, dilute, boil for a few minutes, and filter off the white insoluble residue. under certain circumstances this residue will be nearly free from other metals, in which case it is ignited and weighed. if not known to be pure it must be ignited, reduced in a current of hydrogen, and treated as subsequently described. when the tin is present as insoluble oxide in an ore, the substance is finely powdered, and from to grams of it (according to its richness) boiled with c.c. of hydrochloric acid in an evaporating dish till the oxide of iron is seen to be dissolved. then add c.c. of nitric acid (or more if much pyrites, &c., is present) and continue the boiling till these are decomposed; dilute and filter off, washing first with dilute acid and afterwards with a little dilute ammonia, dry, ignite, and place in a combustion tube (together with the filter-ash) and heat to redness for about thirty minutes in a current of dried hydrogen. [illustration: fig. .] the oxide of tin is placed in a porcelain boat (fig. ), which is then introduced into a piece of combustion tube. the latter, wrapped in a piece of wire gauze, is supported on a couple of iron rings, and heated by one or two bunsen burners in a furnace fitted up with loose fire-brick tiles, as shown in fig. . [illustration: fig. .] when the reduction is complete the tube is allowed to cool; the boat is removed and the tin dissolved. add a rod of zinc to the freely-acid hot solution, and in a few minutes decant through a filter and wash with water, after having removed the zinc. wash the precipitated metal back into the beaker, and dissolve in c.c. of dilute nitric acid, evaporate off the excess of acid; dilute, boil, and filter. wash, dry, ignite strongly in a porcelain crucible, and weigh. in the absence of antimony the above separation works very well, but if this metal is present in quantity the metals precipitated on the zinc must be covered with hydrochloric acid and treated with a few drops of nitric. it is then warmed with iron wire until no more of the latter dissolves. the antimony is precipitated as metal, and the tin remains in solution as stannous chloride. the antimony is filtered off, and may be washed with alcohol, and weighed, whilst the tin in the filtrate is precipitated with zinc, and treated as already described. gravimetric method. if the tin is not already in the metallic state it is reduced to this condition by the method given (precipitation by zinc). treat the finely-divided metal (washed free from chlorides) in a four-inch evaporating dish with c.c. of dilute nitric acid, cover with a clock-glass, and apply a gentle heat until the precipitate appears of a white colour and the metal is completely attacked. evaporate nearly to dryness on a water-bath; then add c.c. of water, heat to boiling, and filter. wash with hot water, dry, transfer to a weighed porcelain crucible, add the filter-ash, ignite strongly, and weigh. the precipitate after ignition is stannic oxide (sno_{ }). it is a yellowish-white powder (darker whilst hot), insoluble in acids, and contains . per cent. of tin. cold dilute nitric acid dissolves tin to a clear solution, which becomes a white enamel-like jelly on heating; this (filtered off, washed, and dried) forms an opal-like substance, which is converted on ignition into stannic oxide with evolution of nitrous fumes. stannic oxide when ignited with chlorides is more or less completely converted into stannic chloride, which volatilises. the presence of chlorides during the evaporation with nitric acid causes a similar loss. ~determination of tin in an alloy.~--(_bronze._)--take grams, and attack with c.c. of dilute nitric acid in a covered beaker with the aid of heat. boil till the bulk is reduced by one-half, dilute with c.c. of water, allow to settle for a few minutes, and filter; wash well first with water acidulated with a little nitric acid, and afterwards with water; dry, ignite, and weigh as stannic oxide. ~determination of tin in tin ore.~--treat grams of the dried and finely-powdered ore with c.c. of hydrochloric acid in a four-inch evaporating dish. after the soluble oxides have been dissolved add or c.c. of nitric acid, boil off nitrous fumes, dilute, and filter. dry the filter, transfer the cleaned ore to a piece of combustion tube ten or twelve inches long and narrowed at one end. pass a current of hydrogen through the tube and heat to redness for minutes; cool whilst the gas is still passing. dissolve in c.c. of dilute hydrochloric acid and keep the solution tinted with permanganate of potassium. when the colour of the permanganate becomes permanent dilute to a bulk of c.c. with water, filter, and wash. heat; add a rod of zinc weighing about grams; allow to stand for a few minutes; decant through a filter; and wash, removing the remaining zinc and returning the tin to the beaker. treat with c.c. of dilute nitric acid, boil for some time, take up with water, filter, wash, dry, ignite, and weigh as stannic oxide. volumetric method. ~titration with solution of permanganate of potassium.~--this titration may be made either directly on the solution of stannous chloride (prepared by dissolving the precipitated metal in hydrochloric acid), or indirectly, on a solution of ferrous chloride (produced by the reducing action of the precipitated metal on ferric chloride). the standard solution of permanganate of potassium is made by dissolving . grams of the salt in water and diluting to one litre. c.c. are equivalent to . gram of tin. the precipitated tin is transferred to a flask; and dissolved in c.c. hydrochloric acid, with the aid of heat and in an atmosphere of carbonic acid. the acid and metal are placed in the flask; which is then filled with the gas, and stopped with a cork provided with a rubber valve. when solution is complete the flask is again filled with carbonic acid. fifty c.c. of water freed from air and saturated with carbonic acid are then added. this water is made by adding a gram of bicarbonate of soda and c.c. of hydrochloric acid to c.c. of water: the effervescence sweeps out the dissolved oxygen. the permanganate of potassium solution is then run in from a stop-cock burette in the usual way until a faint pink tinge is obtained. the following experiments show the effect of variations in the conditions of the assay. a solution of stannous chloride equivalent in strength to the "permanganate" was made by dissolving . grams of the crystallised salt (sncl_{ }. h_{ }o.) in c.c. of water and c.c. of hydrochloric acid and diluting to litre with water freed from dissolved oxygen. c.c. contain gram of tin. in the first experiments tap water was used and no precautions were taken for excluding air. except when otherwise stated, c.c. of the stannous chloride were used in each experiment with c.c. of hydrochloric acid, and were diluted to c.c. with water before titration. ~effect of varying hydrochloric acid.~ acid added . c.c. . c.c. . c.c. . c.c. "permanganate" required . " . " . " . " the only effect of the increase in quantity of acid was to give the brown of perchloride of manganese instead of the pink of permanganic acid to mark the finishing point. ~effect of varying temperature.~ temperature ° c. ° c. ° c. ° c. "permanganate" required . c.c. . c.c. . c.c. . c.c. ~rate of atmospheric oxidation.~--solutions ready for titration were exposed to air at the ordinary temperature for varying lengths of time and then titrated. time exposed min. min. min. min. min. "permanganate" required . c.c. . c.c. . c.c. . c.c. . c.c. it is best to titrate at once, although the loss by oxidation is only small after one hour's exposure. ~effect of varying tin.~ stannous chloride added . c.c. . c.c. . c.c. . c.c. . c.c. "permanganate" required . " . " . " . " . " ~effect of varying bulk.~ bulk . c.c. . c.c. . c.c. . c.c. "permanganate" required. . " . " . " . " the two last series show an interference, which is due to the oxygen dissolved in the water, as may be seen from the following similar experiments, which were, however, performed with water freed from oxygen and in which the titrations were effected in an atmosphere of carbonic acid. ~effect of varying tin.~--a new solution of stannous chloride was used. stannous chloride added . c.c. . c.c. . c.c. . c.c. . c.c. "permanganate" required . " . " . " . " . " ~effect of varying bulk.~ bulk . c.c. . c.c. . c.c. . c.c. . c.c. "permanganate" required . " . " . " . " . " it will be seen that in working under these conditions the results are proportional and the method satisfactory. ~examination of tin phosphide.~--(_phosphor tin_.)--this substance is used in the manufacture of "phosphor bronze" and similar alloys. it is a crystalline, imperfectly-malleable, metallic substance. it is soluble in hydrochloric acid with effervescence; phosphoretted hydrogen, which inflames on the addition of a drop or two of nitric acid, being evolved. it is attacked by nitric acid, yielding a white powder of stannic phosphate; this is not easily decomposed by ammonium sulphide or readily soluble in hydrochloric acid. "phosphor-tin" is made up only of tin and phosphorus. for the estimation weigh up gram. place in a weighed berlin dish; and cover with c.c. of nitric acid and or c.c. of water. let the reaction proceed (under a clock-glass) on the water-bath till complete. remove the glass; evaporate to dryness, and ignite, at first gently over a bunsen burner, and afterwards in the muffle at a red heat. cool in the desiccator, and weigh as quickly as possible when cold. the substance contains the tin as stannic oxide, sno_{ }, and the phosphorus as phosphoric oxide, p_{ }o_{ }. the increase in weight on the gram of substance taken gives the weight of the oxygen taken up by the phosphorus and tin, and since gram of tin takes up only . gram of oxygen, and gram of phosphorus takes up . gram, the proportion of tin to phosphorus can be calculated from the increase in weight. for example, gram of a sample gave . gram of mixed oxides, which is . gram in excess of that which would be got with pure tin. if the substance was all phosphorus the excess would be . gram; consequently the proportion of phosphorus in the substance is . / . , or . per cent. the tin is calculated by difference, . per cent. another method of separating and determining the phosphorus is as follows:--take gram of the substance and add to it c.c. of hot aqua regia. boil till dissolved, dilute, and precipitate the tin with sulphuretted hydrogen. to the filtrate add ammonia and "magnesia mixture." filter; wash the precipitate with dilute ammonia; dry, ignite, and weigh as magnesic pyrophosphate. calculate the phosphorus, and take the tin by difference. a sample of phosphor tin gave-- tin . per cent. (by difference) phosphorus . " ----- . ~tin arsenide.~--this is met with in tin-smelting; it closely resembles the phosphide, but the crystals have a duller grey appearance. it contains simply tin and arsenic. the determination is made by treating gram of the substance with nitric acid and weighing the mixed oxides of tin and arsenic in the same manner as in the case of the phosphide. one gram of arsenic will give . gram of arsenic oxide, as_{ }o_{ }; consequently the excess of weight of the mixed oxides over . gram must be divided by . ; the result multiplied by gives the percentage of arsenic. in consequence of the higher atomic weight of arsenic the results by this method are not so close as with the phosphide. each milligram of excess weight (over . ) represents . per cent. of arsenic, as. both in this and in the corresponding phosphide determination care must be taken to avoid absorption of moisture, by allowing the oxides to cool in a desiccator and weighing quickly. the percentage of arsenic is better determined as follows:--weigh up gram of the substance, dissolve in aqua regia, dilute, and pass sulphuretted hydrogen. render alkaline with ammonia, and add ammonium sulphide till the precipitate is dissolved. add "magnesia mixture." filter off the precipitate, wash with dilute ammonia, ignite with a few drops of nitric acid, and weigh as magnesic pyrarsenate. calculate the arsenic and take the tin by difference. a sample treated in this way gave-- tin . per cent. by difference arsenic . " ----- . ~examination of black tin.~--dry the ore, and reduce it to a fine powder. weigh up grams, and boil with c.c. of hydrochloric acid and c.c. of nitric for ten or fifteen minutes. filter, and reserve the filtrate. ~tungstic acid.~--digest the residue with about c.c. of water and a few c.c. of dilute ammonia for a few minutes, and filter; collect the filtrate in a weighed porcelain dish, evaporate to dryness, ignite, and weigh as tungstic acid, wo_{ }. ~stannic oxide.~--dry, ignite, and weigh the insoluble residue. transfer to a porcelain boat, and reduce in a current of hydrogen at a red heat for half an hour. allow to cool whilst the hydrogen is still passing. transfer the boat to a beaker, and dissolve up the tin in c.c. of hydrochloric acid and a c.c. or so of nitric. wash out the combustion tube with some acid and add the washing to the contents of the beaker. warm gently, dilute with water, and filter. collect, dry, ignite, and weigh the insoluble residue. through the filtrate pass a rapid current of sulphuretted hydrogen, allow to settle, and filter. wash the precipitate with hot water, dry, calcine gently; ignite with ammonium carbonate, and weigh as stannic oxide, sno_{ }. the insoluble residue will in most cases retain some tin. fuse it with fusion mixture, take up with hydrochloric acid, filter, pass sulphuretted hydrogen through the filtrate, collect and wash the sulphide of tin. ignite and weigh as stannic oxide, and add it to that previously obtained. ~copper.~--pass sulphuretted hydrogen through the acid filtrate obtained in the first cleaning of the ore, collect the precipitate, and wash first with soda solution and then with hot water. dry, ignite, and weigh as cupric oxide, cuo. mix the filtrate with that from the main portion of the sulphide of tin. ~ferric oxide.~--boil off the sulphuretted hydrogen from the mixed filtrates and peroxidise with nitric acid. add ammonia in slight excess, boil, filter, dry, ignite, and weigh the precipitate as ferric oxide. this will be practically pure, but the iron in it must be determined by dissolving and titrating. the filtrate from the iron may contain zinc, lime, and magnesia, but rarely in quantities sufficient to be determined. ~silica, &c.~---the silica may be calculated from the weight of the residue insoluble in acid, after the reduction of the tin in hydrogen, by deducting from it the weight of the oxide of tin subsequently found. or it may be determined as follows:--the insoluble portion is fused with fusion mixture, and taken up with hydrochloric acid, as already described. on filtering, the filter will retain a portion of the silica. the rest is recovered, after the removal of the stannous sulphide, by evaporating to dryness, taking up with hydrochloric acid, and filtering through the same filter. it is washed, dried, ignited, and weighed as silica. the filtrate from the silica is boiled with a little nitric acid and precipitated with ammonia. the precipitate is collected, washed, ignited, and weighed as ferric oxide and alumina (but it frequently contains oxide of titanium). when the last is present it is determined by fusing with bisulphate of potash and extracting with cold water. the solution is nearly neutralised with ammonia, charged with sulphurous acid, and boiled. the precipitate is collected, washed, dried, ignited, and weighed as oxide of titanium, tio_{ }. the difference between this weight and that of the combined oxides gives the ferric oxide and alumina. the filtrate from the mixed oxides is examined for lime and magnesia. ~sulphur.~--rub up grams of the ore with grams of nitre, transfer to a porcelain dish, and fuse over a bunsen burner for fifteen minutes. when cold, extract with water, and determine the sulphur volumetrically with standard barium chloride. the sulphur may be present as sulphide or sulphate. ~arsenic.~--take grams, and evaporate with nitric acid; dilute, add ammonia, pass sulphuretted hydrogen, and filter. to the filtrate add "magnesia mixture." collect the precipitate, ignite with nitric acid, and weigh as magnesic pyrarsenate. the following may be taken as an example of the composition of an impure black tin:-- tungstic acid . % stannic oxide . silica . titanic oxide . copper oxide . ferric oxide . sulphur . arsenic . ---- . ~examination of hardhead.~--in the smelting of tin ores a quantity of speise, known as "hardhead," is produced. it is essentially an arsenide of iron, carrying a considerable quantity of tin. much of this last is present in the form of small buttons of metal distributed through the mass. the buttons can be seen on careful inspection, and become evident on powdering. in assaying the substance, a variation in the usual method of sampling is required, because of the quantity of metal present which cannot be powdered. after powdering as finely as possible, the coarse particles are sifted off and weighed. the weight of the powder is also taken. the method of working is best illustrated by an example. a sample of hardhead weighed . grams, and gave . grams of coarse particles, equivalent to . per cent. of the whole. the fine portion weighed grams, which is equivalent to . per cent. thirteen and a half grams of the coarse material were dissolved in aqua regia, and diluted with water to litre. ten c.c. of this contain . gram of the metallic portion, which is the amount contained in gram of the original hardhead. if, in a determination, gram of the substance is wanted, weigh up . gram of the powdered portion, and add to it c.c. of the solution. it will be seen that these together make up gram of the original sample. the solution of the metallic portion must be saved until the analysis is finished. ~tin and copper.~--weigh up the portion of the powdered stuff equivalent to gram of the sample. transfer to a flask, and cover with c.c. of the solution of the metallic portion and c.c. of aqua regia. boil gently till oxidation is complete and the nitric acid for the greater part driven off. dilute to c.c. with water, and pass sulphuretted hydrogen for some time. filter, wash with hot water, and rinse through the funnel back into the flask. digest with yellow sodium sulphide until only a light, flocculent, black precipitate is left. filter this off, wash with hot water, dry, calcine, treat with a little nitric acid, ignite, and weigh as copper oxide, cuo. the weight multiplied by . gives the weight of copper. the filtrate containing the tin is rendered acid with hydrochloric acid, and filtered. the precipitate is rinsed into a half-pint beaker, covered with c.c. of hydrochloric acid, and boiled down to about c.c. the solution is filtered off from the sulphur and sulphide of arsenic, which, after washing with hot water, is transferred to a flask labelled "arsenic." a strip of sheet zinc ( in. by in.) is placed in the solution. the evolution of hydrogen should be brisk. in five or ten minutes decant off a few c.c. of the liquid, and test with sulphuretted hydrogen for tin. if no yellowish precipitate is formed, decant off the rest of the liquid, and wash the precipitated metal with hot water two or three times by decantation. the metal should be in a lump; if there are any floating particles they must be made to sink by compression with a glass rod. transfer the washed metal to an evaporating dish or in. across, and cover with a few c.c. of hot water. add nitric acid drop by drop till the tin is completely attacked. evaporate nearly to dryness, and add a drop or two more of nitric acid and c.c. of water. boil and filter. wash with hot water, dry, ignite, and weigh as stannic oxide, sno_{ }. calculate to metallic tin by multiplying by . .[ ] the filtrate from the first treatment with sulphuretted hydrogen will probably no longer smell of the gas. warm and pass the gas for a few minutes longer. filter off any precipitate of sulphide of arsenic, and transfer it to the flask for "arsenic." boil the filtrate (ignoring any signs of a further precipitation of arsenic) with a few c.c. of nitric acid, and separate the iron as basic acetate. wash; reserve the filtrate for cobalt. ~iron.~--rinse back the "basic acetate," precipitate into the flask, add ammonia, dilute with water to about c.c., and pass sulphuretted hydrogen for a few minutes. filter, and wash with hot water. collect the filtrate in the flask labelled "arsenic." boil the precipitate with dilute sulphuric acid, filter, and titrate the filtrate with the permanganate of potassium solution after boiling off the sulphuretted hydrogen. report the result as iron. the sulphuric acid will not effect complete solution, a light black residue will remain, chiefly sulphur; this must be rinsed into the filtrate from the acetate separation. it contains cobalt. ~cobalt.~--the filtrate from the acetate separation will have a pink colour. render it ammoniacal and pass sulphuretted hydrogen. collect the precipitate on a filter, dry, and ignite. dissolve in hydrochloric acid, and evaporate nearly to dryness with an excess of nitric acid. dilute with or c.c. of water and add potash solution in slight excess. add acetic acid until the solution is acid and the precipitate is quite dissolved. add or c.c. of a strong solution of potassium nitrite, and determine the cobalt, as described on pp. , . boil the filtrate from the cobalt, precipitate with hydrochloric acid, render ammoniacal, and test for zinc, nickel, and manganese. _the remainder of the tin_ will be contained in the flask labelled "arsenic." acidify with hydrochloric acid and filter. rinse into a beaker, and evaporate to a small bulk with c.c. of nitric acid. dilute and filter. dry the precipitate, consisting of stannic arsenate ( sno_{ }.as_{ }o_{ }), ignite, and weigh. calculate the tin it contains by multiplying by . , and add to that already found. ~arsenic.~--this is determined in a separate portion. weigh up a portion of the powder equivalent to gram of the hardhead, place in a pint flask, and boil with c.c. of nitric acid. when action has ceased add c.c. of the solution of the metallic portion and then hydrochloric acid (a few drops at a time) till solution is complete. warm gently in dissolving, but do not boil. dilute to about c.c., render alkaline with ammonia, and add c.c. of yellow ammonium sulphide. digest at a gentle heat for about thirty minutes, filter, and wash. add c.c. of magnesia mixture, shake well, allow to stand for an hour, filter, and wash with dilute ammonia. the precipitate is dissolved and then titrated with uranium acetate, or it is evaporated with nitric acid, ignited, and weighed as pyrarsenate of magnesia. calculate the result to arsenic, as. ~sulphur.~--weigh up a portion of the powder equivalent to or grams of the hardhead. rub up in a mortar with grams of nitre and fuse in a porcelain dish for ten minutes. extract with water, add or c.c. (as the case may be) of the solution of the "metallics." add grams of sodic acetate, and ferric chloride until the precipitate turns brown; dilute with water to half a litre, boil, and titrate with standard baric chloride, as described under _sulphur_. report as sulphur. a sample of hardhead examined in this way gave-- sulphur . % arsenic . tin . copper . iron . cobalt . ------ . ~examination of tin slags.~--in tin smelting works the term "slag" is applied to the unfused portion of the charge. it is made up of unburnt anthracite and small lumps of slag proper together with some buttons of metallic tin. this is rarely, if ever, assayed. the slag proper (or, as it is generally called, "glass") is a silicate of iron, alumina, and lime, containing from to per cent. of tin. it is thus examined:--the sample after bruising on an iron plate, is reduced to a very fine powder by grinding in an agate mortar. in this state it is in most cases readily decomposed by hydrochloric acid. ~determination of tin.~--where the percentage of tin only is required, take grams of the powdered slag and well mix with it c.c. of hydrochloric acid, and heat to boiling. add c.c. of nitric acid, allow to stand for fifteen minutes, dilute with water, and filter. pass a rapid current of sulphuretted hydrogen for some time. allow to settle, and filter. the precipitate, after washing with hot water, is dried, and gently calcined until the greater part of the sulphur is burnt off. it is then strongly ignited in the muffle (or over the blowpipe) with the addition of a small lump of ammonic carbonate. the residue is weighed as stannic oxide (sno_{ }); and is calculated to metallic tin by multiplying by . . the percentage on the slag is calculated in the usual way. the tin is always best determined in the examination of slags by a separate assay carried out in this way. the determination of the other constituents is thus made:-- ~silica.~--take grams of the powdered slag and cover them, in a small evaporating dish, with c.c. of hydrochloric acid; mix well by stirring with a glass rod; and evaporate to dryness. if (as is generally the case) tungsten is present the solution will be blue. take up with c.c. of hydrochloric acid. add c.c. of nitric acid; and reduce by boiling to about half the bulk. add about c.c. of water, boil, and filter. wash the residue with hot dilute hydrochloric acid. it consists of silica with the tungstic acid. wash it back into the dish; and digest with or c.c. of a cold solution of ammonic carbonate. filter; and collect the filtrate and washings in a weighed porcelain dish. dry the residue, ignite strongly, and weigh as silica, sio_{ }. in certain exceptional cases this may contain some unaltered cassiterite, which is easily recognised by its appearance. ~tungsten.~--the ammonic carbonate filtrate from the silica is evaporated to dryness, ignited strongly over the blowpipe, and weighed. the residue is tungstic acid, wo_{ }. the tungsten may be conveniently reported in this form, although it is probably present as a lower oxide. ~tin.~--the acid filtrate from the silica and tungstic acid is treated with sulphuretted hydrogen. the sulphide of tin is filtered off. since the percentage of tin has been already determined, this precipitate may be neglected; or may be treated in the same way as the previous one, so as to check the result. since some stannic chloride will have been lost in the evaporation, a low result may be expected. the tin should be reported as stannous oxide; and is calculated by multiplying the percentage of tin by . . the filtrate from the tin is boiled rapidly down to remove sulphuretted hydrogen; and then peroxidised with or c.c. of nitric acid. it is cooled, transferred to a graduated flask, and diluted with water to c.c. ~ferrous oxide and alumina.~--half the filtrate from the tin (that is, c.c.) is taken, nearly neutralised with soda, and treated with sodium acetate. the basic acetate precipitate obtained on boiling is filtered off and washed. reserve the filtrate. the precipitate is dissolved off the filter with hot dilute hydrochloric acid; and the solution thus formed is treated with a slight excess of ammonia, and boiled. the precipitate is filtered off, washed with hot water, dried, ignited, and weighed as mixed ferric oxide and alumina. the ignited precipitate is then dissolved with sulphuric and hydrochloric acids; and the iron determined in the solution by titration with the solution of stannous chloride. the iron found is calculated to and reported as ferrous oxide, feo (factor = . ). to find the alumina, which is best estimated by difference, multiply the iron by . to get the weight of ferric oxide, and deduct this from the weight of alumina and ferric oxide found. this, of course, gives the alumina. a direct determination may be made by removing the tin from the titrated solution with sulphuretted hydrogen, filtering, nearly neutralising with ammonia, and boiling with a few grams of hyposulphite of soda. the precipitate, filtered, washed, and ignited, is the alumina, which is weighed. the direct determination gives a slightly low result. ~oxides of zinc and manganese.~--these are determined in the filtrate from the basic acetate precipitate by rendering alkaline with ammonia, and passing a current of sulphuretted hydrogen. generally a small, but decided, precipitate of alumina comes down, together with sulphides of any zinc or manganese which is present. the precipitate is allowed to settle, dried, ignited, and weighed. the metals are separately determined in it; and the residue is counted as alumina, and added to that already found. the mixed precipitate amounts to from to per cent. of the sample. ~lime.~--the filtrate from the last is treated with ammonic oxalate, boiled for a few minutes, allowed to settle, and filtered. the precipitate is washed with hot water; dried; ignited; and weighed as carbonate, after gentle ignition; or as lime, after strong ignition in the muffle. ~magnesia.~--the filtrate from the lime is treated with sodic phosphate and ammonia. it is well mixed by stirring, and allowed to stand overnight. the precipitate is washed with dilute ammonia, dried, ignited, and weighed as pyrophosphate. ~soda and potash.~--these are determined in the remaining half of the filtrate from the tin. the solution is rendered ammoniacal with ammonia; and treated, first with sulphuretted hydrogen, and then with ammonium oxalate. the precipitate is filtered off and rejected. the filtrate is evaporated in a small porcelain dish over a bunsen burner, or on the sand bath; and towards the close (or earlier if the evaporation is not proceeding well) nitric acid is added. the evaporation is carried to dryness; and the residue heated nearly to redness. the residue, which consists of magnesia with carbonates and chlorides of the alkalies, is extracted with water; and filtered. the filtrate is evaporated with hydrochloric acid in a weighed platinum dish, ignited gently, and weighed. this gives the weight of the mixed chlorides of sodium and potassium; which are then separated and determined as described under _potash_. it must be remembered when calculating the percentage that (with the exception of the silica, tungstic acid, and tin) the determinations have been made on gram of the sample. the following analysis will illustrate the composition of such a slag:-- tungstic acid . % silica . stannous oxide . ferrous oxide . alumina . oxide of manganese traces lime . magnesia . alkalies calculated as soda . ----- . titanium. titanium only occurs as a mineral in its oxidised state, or as titanic oxide (tio_{ }). it is a substance which has little commercial value, and is generally recognised as one of the rare bodies; although, in small quantities, it is widely disseminated. it occurs in granite, basalt, and other igneous rocks in quantities up to as much as per cent. it is also met with in clays and iron ores, and in river sands, in which it is often associated with stream tin. the proper minerals of titanium are rutile (tio_{ }), titaniferous iron (titanate of iron), and sphene (titanate and silicate of lime). the oxide of titanium (like cassiterite and quartz) is undecomposed by hydrochloric or nitric acid; so that it is generally found in the residue insoluble in acids. the titanates, however, are attacked, and a portion of the titanium dissolves; so that it must be looked for in both the filtrate and residue. oxide of titanium in its native form, or after ignition, may be made soluble by fusing the finely-divided substance with fusion mixture in a platinum dish. the resulting titanate is dissolved out of the "melt" by cold hydrochloric acid. the method most commonly used is fusion with bisulphate of potash. this renders the oxide of titanium soluble in cold water. the process is as follows:--the substance is extracted with hydrochloric and nitric acids, and the solution reserved for further treatment; the residue is dried, moistened with sulphuric acid, and evaporated once or twice to dryness with hydrofluoric acid. it is then fused with bisulphate of potash, and the "melt" extracted with cold water until all soluble matter is removed. the solution is filtered. the residue may consist of unremoved silica, and oxides of tantalum, niobium, and, perhaps, chromium. on the prolonged boiling of the filtrate, the oxide of titanium (and oxide of zirconium, if any) is precipitated. any titanium dissolved by the first extraction with acids is recovered in the following way:--sulphuretted hydrogen is passed into the acid solution, and any precipitate that may be formed is filtered off. the filtrate is oxidised, and the iron, aluminium, and titanium are separated as basic acetates (see under _iron_). the precipitate is dried and fused with bisulphate of potash. the "melt" is extracted with cold water, filtered if necessary, and the solution rendered first faintly alkaline with ammonia, then very slightly acid with sulphuric acid. or c.c. of a saturated solution of sulphurous acid is added, and the oxide of titanium precipitated by prolonged boiling. it is filtered off, added to the precipitate previously got, ignited with ammonic carbonate towards the end, and then weighed. ~detection.~--titanium is detected in an insoluble residue by fusing the residue for some time in a bead of microcosmic salt. in the reducing flame it gives a violet colour, which becomes reddish-brown if much iron is present. in the oxidising flame it gives a colourless or whitish bead. it is best detected in acid solutions by the deep brown or iodine colour developed on adding hydroxyl. a solution of this can be prepared by pouring peroxide of barium (bao_{ }) diffused in water into dilute hydrochloric acid (a little at a time), and keeping the acid in excess. ~separation.~--in the usual course of an analytical separation the hydrate of titanium will be thrown down with ferric hydrate, &c., on the addition of ammonic chloride and ammonia. it is best separated from this precipitate by fusion with bisulphate of potash, as already described, but it must be remembered that the presence of much mineral acid prevents complete precipitation when the solution is boiled. further, if phosphates are present, the precipitate will contain phosphoric oxide; it may be freed from this by fusion with sodium carbonate. a very good method of separating titanium from iron is to add tartaric acid and ammonia to the solution, and then precipitate the iron (as sulphide) with sulphuretted hydrogen. the filtrate contains the titanium, which is recovered by evaporating and igniting. it may be separated from zirconia by the action of sodium carbonate, which precipitates both; but when concentrated, redissolves the zirconia. the separation from large quantities of silica is best effected by evaporating with hydrofluoric acid, which volatilises the silicon; but sulphuric acid must be present, otherwise some titanium also will be lost, as may be seen from the following experiments,[ ] in which oxide of titanium (pure, ignited) was evaporated to dryness with a quantity of hydrofluoric acid known by experiment to be sufficient to volatilise gram of silica. _without sulphuric acid_, . gram of titanic oxide left . gram, showing a loss of about per cent. _with sulphuric acid_ the following results were obtained:-- oxide taken. left after evaporation and ignition. . gram . gram . " . " . " . " . " . " gravimetric determination. the titanic hydrate thrown down by ammonia (or on boiling the solution from the bisulphate) is collected, washed, dried, ignited strongly with the addition of a little ammonic carbonate, and weighed. the substance is titanic oxide (tio_{ }), and is generally reported as such. it contains . per cent. of titanium. it should be white, if pure (holland), white, yellow, or brown (fresenius), or black (tidy). volumetric method. a method has been proposed based on the reduction of titanic oxide by zinc in hydrochloric acid solutions to the sesquioxide. the reduction is marked by the development of a violet or green colour, the former with chlorides and the latter when fluorides are present. the quantity of titanium reduced is measured by titrating with permanganate of potassium solution. the water used must be free from dissolved oxygen. tungsten and tungstates. tungsten occurs in nature only in the oxidised state, or as tungstic acid (wo_{ }), either free, as in wolframine, or combined with oxides of manganese and iron, as in wolfram, or with lime, as in scheelite. wolfram occurs associated with tin ores, the value of which is consequently lowered. both wolfram and scheelite are of considerable importance as a source of tungstic acid for the manufacture of sodium tungstate, which is used as a mordant and for some other purposes, and as a source of metallic tungsten, which is used in steel-making. the tungsten minerals have a high specific gravity ( to . ). on treatment with hydrochloric acid or aqua regia they are decomposed; the yellow tungstic acid separates and remains insoluble. tungsten itself is insoluble in nitric acid or aqua regia; but is converted into tungstic acid (wo_{ }) by prolonged and strong ignition in air. alloys containing tungsten leave tungstic acid after treatment with nitric acid or aqua regia. tungstic acid may be got into solution after fusion with alkalies or alkaline carbonates. this solution gives with hydrochloric acid a white precipitate of tungstic acid, which becomes yellow on boiling, but the separation is not complete. fusion with bisulphate of potash gives a residue, which does not dissolve in water, but is soluble in ammonic carbonate. for the assay of minerals containing tungsten these reactions are only occasionally taken advantage of for testing or purifying the separated tungstic acid. ~detection.~--the minerals are easily recognised by their physical characters, and the yellow tungstic acid separated by boiling with acids is the best test for its presence; this, after decanting and washing, immediately dissolves in a few drops of dilute ammonia. a solution of tungstate acidulated with hydrochloric acid becomes intensely blue on the addition of stannous chloride and warming. fused in a bead of microcosmic salt it gives a clear blue colour (reddish-brown if iron is also present) in the reducing flame, but is colourless in the oxidising flame. ~solution and separation.~--the decomposition and solution of natural tungstates is difficult to effect owing to the separation of tungstic acid; the method of treatment is as follows:--boil the finely-powdered substance with hydrochloric acid or aqua regia till it apparently ceases to be attacked; dilute, filter, and wash with dilute hydrochloric acid. cover with dilute ammonia, and filter the solution, which contains ammonic tungstate, into an evaporating dish. treat the residue again with acid, and again dissolve out the separated tungstic acid with ammonia, and repeat this operation until decomposition is complete. by this means there will be obtained--( ) a solution containing tungstate of ammonia; ( ) an insoluble residue with silicates, and oxides of tin, niobium, tantalum, &c.; and ( ) an acid solution containing the soluble bases. the tungstate of ammonia requires simple evaporation on the water-bath and gentle ignition in order to cause the tungstic acid to be left in an almost pure state; possibly, it may carry a little silica. gravimetric determination. the tungstic acid is dissolved, and separated as ammonic tungstate, and, after evaporation, is gently ignited, the heat being increased towards the end. the residual tungstic acid is fixed, so that when the ammonia has been driven off it may be strongly heated without loss. it is a dark yellow or brown powder whilst hot, which becomes a light yellow on cooling. if any reduction has taken place it will be more or less greenish. it is weighed when cold, and is the trioxide or "tungstic acid" (wo_{ }), which contains . per cent. of tungsten. after its weight has been taken its purity is checked by fusing with hydric potassic sulphate, extracting with water, and treating the residue with ammonic carbonate. any silica present will be left undissolved; it should be separated and weighed, and its weight deducted from that of the tungstic acid found. ~determination of tungstic acid in wolfram.~--take grams of the finely-powdered sample and boil with c.c. of hydrochloric acid for half an hour, adding c.c. of nitric acid towards the end. allow to stand overnight and boil again for or minutes; dilute with an equal volume of water, and filter. wash with dilute hydrochloric acid, dissolve in a few c.c. of warm dilute ammonia, and dilute to c.c. with distilled water; allow to settle, and filter. evaporate in a weighed dish, ignite, and weigh. the following analysis will illustrate the composition of a sample of cornish wolfram as brought into the market:-- tungstic acid . % cassiterite . ferrous oxide . manganous oxide . niobic oxide, alumina, &c. . silica . copper oxide . zinc oxide . arsenic . sulphur . ----- . niobic and tantalic oxides. these oxides are commonly met with in samples of wolfram and tinstone, especially niobic. they are probably present in the form of columbite, a niobate of iron and manganese; and tantalite, a tantalate of the same metals. on boiling with hydrochloric acid they are both liberated, and remain for the greater part (all the niobic) in the insoluble residue with the tungstic acid. on removing the latter with dilute ammonia they remain as a white insoluble precipitate, very prone to run through the filter on washing. they may be dissolved in hydrofluoric acid either at once or after fusion with bisulphate of potash, and extraction with cold water. to the solution in hydrofluoric acid gradually add a boiling solution of acid potassium fluoride (hf, kf.). potassic fluotantalate (soluble in parts of water) separates out first, and afterwards potassic fluoniobate (soluble in parts of water). the separated salts (after heating with sulphuric acid and washing out the potassium sulphate formed) are ignited with ammonic carbonate, and weighed as tantalic oxide (ta_{ }o_{ }) and niobic oxide (nb_{ }o_{ }) respectively. they are both white powders. the oxide of niobium dissolved in a bead of microcosmic salt gives a bluish colour in the reducing flame. the oxide of tantalum dissolves in the bead, but gives no colour. footnotes: [ ] this will give almost the whole of the tin; a further portion will be got in subsequent work, and must be added to this result. [ ] published by p. holland, in the _chemical news_, vol. lix. p. . chapter xiii. manganese, chromium, &c. manganese. manganese occurs mainly as black oxide (mno_{ }) in the mineral pyrolusite; and, in a less pure form, in psilomelane and wad. the value of the ore depends rather on the percentage of available oxygen than on the proportion of metal present. the results of assays are generally reported as so much per cent. of the dioxide (mno_{ }). in smaller quantities it is very widely distributed. manganese itself has a value for steel-making; or, rather, for the making of spiegeleisen and ferro-manganese, which are used in the bessemer and siemens processes. for this purpose the percentage of the metal (mn) is required. consequently the minerals of manganese may be considered in two aspects--( ) as a source of oxygen; and ( ) as a source of manganese. these will require separate consideration. the black oxide is mainly used in the preparation of chlorine, liberation of which it brings about when treated with hot hydrochloric acid, or with a mixture of common salt and sulphuric acid. the quantity of chlorine which is obtained depends upon the proportion of dioxide present;[ ] and in assaying may either be measured by its equivalent of iodine liberated, or by the oxidising effect on an acid solution of ferrous sulphate. when the ore also carries substances which have a reducing effect (such as ferrous compounds), such assays will give, not the total dioxide (mno_{ }), but less, by the amount required to oxidise these impurities; and this is exactly what is required in valuing such an ore for commercial purposes. manganese compounds are characterised by the readiness with which they may be converted into highly-oxidised bodies. solution of manganese in hydrochloric acid, rendered alkaline with ammonia, yields a clear solution,[ ] which rapidly takes up oxygen from the air, forming a brown precipitate of the oxide (mn_{ }o_{ }). the addition of bromine or chlorine to such a solution determines the precipitation of a still higher oxide (approximately mno_{ }). on treating a compound containing manganese with nitric acid and dioxide of lead (pbo_{ }), the oxidation is carried still further, a purple-coloured solution of permanganic acid (hmno_{ } or h_{ }o.mn_{ }o_{ }) being formed. on fusing minerals containing (even traces of) manganese with sodium carbonate in an open crucible, a green "melt" is obtained which owes its colour to sodium manganate (na_{ }mno_{ } or na_{ }o.mno_{ }). this salt is soluble in water, forming a green solution; which, when rendered acid, rapidly changes into the permanganate with the characteristic purple colour. permanganate of potash is a salt much used in assaying, with some properties of which the student will have already become familiar. compounds of manganese, on boiling with strong hydrochloric acid, yield manganous chloride[ ] (mncl_{ }). the properties given above serve for the detection of manganese; the higher oxides are distinguished by causing the evolution of chlorine (with its peculiarly suffocating smell) when acted on with hydrochloric acid; while the green "melt," with sodium carbonate, can be relied on for the recognition of manganese itself. there is no dry assay of manganese ores. wet methods. strong hydrochloric acid is the best solvent for ores of manganese; but where the proportion of dioxide (mno_{ }) is required, the solution is effected during the assay. the ore should be in a very fine state of division before treatment with acids. the separation of manganese from other metals is thus effected: ignite, in order to destroy any organic matter which may be present; dissolve in hydrochloric acid, and evaporate to dryness, to separate silica. take up with hydrochloric acid, dilute, pass sulphuretted hydrogen, and filter. boil off the excess of gas, peroxidise the iron with a drop or two of nitric acid, and separate the iron as basic acetate (as described under _iron_).[ ] if the iron precipitate is bulky, it is dissolved in a little hydrochloric acid, reprecipitated, and the filtrate added to the original one. neutralise with soda, and add bromine in excess; heat gradually to boiling, allow to settle, and filter. the precipitate is impure dioxide of manganese (containing alkalies and, possibly, cobalt or nickel). gravimetric determination. dissolve the precipitate in hydrochloric acid, and boil; add a slight excess of carbonate of soda, warm, and filter. wash with hot water, dry, carefully ignite in an open berlin crucible, and weigh. the substance is the brown oxide (mn_{ }o_{ }), and contains . per cent. of manganese. if the percentage of dioxide is required it may be calculated by multiplying the percentage of manganese by . . it must be borne in mind that the manganese should never be calculated to dioxide except when it is known to exist in the ore only in that form. volumetric methods. the two methods are based on the oxidising effect of manganese dioxide; and if the metal does not already exist in this form it will require a preliminary treatment to convert it. the following method due to mr. j. pattinson[ ] effects this: a quantity of the ore containing not more than . grams of the metal (mn), is dissolved in hydrochloric acid in a pint beaker, and, if necessary, or c.c. of nitric acid are added to peroxidise the iron, and ferric chloride is added if required, so that there may be at least as much iron as manganese. calcium carbonate is added till the solution is slightly red; and next the redness is removed by the cautious addition of acid; c.c. of zinc chloride solution (containing grams of zinc per litre) are added, the liquid is brought to boil and diluted to about c.c. with boiling water; c.c. of a solution of bleaching powder ( grams to the litre and filtered), rendered slightly greenish by acid, are then run in and are followed by grams of calcium carbonate suspended in c.c. of boiling water. during effervescence the beaker is covered, the precipitate is stirred, and c.c. of methylated spirit are mixed in. the precipitate is collected on a large filter, washed with cold water, and then with hot, till free from chlorine, which is tested for with starch and potassium iodide. the acid ferrous sulphate solution (presently described) is then measured into the beaker, and the precipitate, still in the paper, added; more acid is added (if necessary), and the solution is diluted and titrated. in place of bleaching powder solution, c.c. of bromine water (containing grams per litre) may be used. ferrous sulphate assay. this method, which is the one commonly used, is based on the determination of the amount of ferrous iron oxidised by a known weight of the ore. it is known that parts of the dioxide will oxidise parts of ferrous iron;[ ] therefore gram will oxidise . gram of ferrous iron, or gram of ferrous iron oxidised will be equivalent to . gram of the dioxide. the finely-divided substance containing the dioxide is digested in a solution of a known quantity of iron in sulphuric acid. the iron, of course, must be in excess, which excess is determined when the ore is dissolved by titrating with standard permanganate or bichromate of potash solution. the assay resolves itself into one for the determination of ferrous iron, for which the standard solutions and method of working described under _iron_ are used. the assay is as follows:--for rich ores, grams of clean soft iron wire are treated, in a pint flask, with c.c. of dilute sulphuric acid and warmed till dissolved. carefully sample the ore, and in one portion determine the "moisture at ° c.;" grind the rest in a wedgwood mortar with a little pure alcohol until free from grit. this reduces the substance to a finely-divided state and assists solution. evaporate off the alcohol and dry at ° c., mix well, and keep in a weighing-bottle. weigh up grams and add them to the solution of iron in the flask; carefully wash it all down into the acid liquid. on rotating the flask the ore will rapidly dissolve, but gentle heat may be used towards the end to complete the solution. when the residue is clean and sandy-looking, and free from black particles, the flask is cooled, and the residual ferrous iron is determined by titration with "permanganate." the iron thus found, deducted from the grams taken, will give the amount of iron peroxidised by the dioxide contained in the grams of ore. this divided by and multiplied by . will give the percentage of dioxide in the sample, or multiplied by . will give that of metallic manganese. when the quantity of manganese or of the dioxide to be determined is small, it is not necessary to use grams of iron; gram, or even less, may be taken. the iron may be used in the form of a standard solution of ferrous sulphate and portions measured off, thus saving the labour of weighing. ~determination of dioxide in a manganese ore.~--weigh up or grams of the finely-powdered ore[ ] and an equal weight of pure iron wire, dissolve the wire in or c.c. of dilute sulphuric acid, and, when solution is complete, add the ore and warm till it too is dissolved. cool and titrate the remaining ferrous iron with the permanganate or bichromate of potassium solution. for example, . gram of pyrolusite and . gram of iron were taken and treated as above; . c.c. of "permanganate" (standard c.c. = . gram iron) were required; this indicates that . gram of iron was left unoxidised by the ore. the iron oxidised, then, was . gram ( . - . ); multiplying this by . , we find that . gram is the quantity of manganese dioxide which was present. this is equivalent to . per cent.; . : . :: : . . iodine method. it has been already stated that when dioxide of manganese is boiled with strong hydrochloric acid chlorine is given off, and that the amount of chlorine so liberated is a measure of the dioxide present. if the chlorine is passed into a solution of potassium iodide, an equivalent of iodine will be set free.[ ] this is apparently a very indirect way of determining how much of the dioxide is present; but the reactions are very sharp, and the final determination of the iodine is an easy one. [illustration: fig. .] the finely-powdered sample of dioxide is placed in a small flask provided with an exit tube leading into a solution of potassic iodide (fig. ). on adding hydrochloric acid and boiling, the chlorine evolved is driven into the iodide solution and there absorbed; the boiling is continued till the steam and hydrochloric acid fumes have driven the last portions of the chlorine out of the flask and into the solution. in this experiment there is a strong tendency for the iodide solution to rush back into the flask. this tendency is overcome by avoiding draughts and regulating the heat; or by placing a lump of magnesite in the flask, which acts by evolving carbonic acid and so producing a steady outward pressure. when the distillation is finished the tube containing the iodine is detached and washed out into a beaker. if the solution is strongly acid it should be almost neutralised by the cautious addition of dilute ammonia. if crystals of iodine have separated, potassium iodide must be added in quantity sufficient to dissolve them. the condenser must be kept cool whilst the chlorine is passing into it. the solution, transferred to a beaker, is titrated with a standard solution of sodic hyposulphite ( c.c. = . gram iodine or . gram of dioxide of manganese). in titrating, the solution should be cold, or not warmer than ° c. the bulk may vary from to c.c.; but it is best always to work with the same volume. the "hypo" is run in with constant agitation until the brown colour has been reduced to a light yellow; c.c. of starch solution are then added and the titration cautiously continued until the end is reached; the finish is indicated by a change from blue to colourless. the assay solution may be acidified with acetic, sulphuric, or hydrochloric acid before titrating with "hypo;" but it must be only faintly so. an excess of acid may be nearly neutralised with ammonia without interference, but excess of alkali is fatal. bicarbonate of soda must not be used in excess; it is best to avoid it altogether. the assay solution should be titrated at once, as it weakens on standing; and the "hypo" solution should be standardised every two or three days, as its strength is not constant. _the standard solution of hyposulphite of soda_ is made by dissolving grams of the salt (na_{ }s_{ }o_{ }. h_{ }o) in water and diluting to litre. c.c. are equivalent to . gram of iodine. this solution is standardised by weighing, in a small beaker, about half a gram of iodine, to which is added a crystal or two of potassium iodide and a few drops of water. when dissolved, the solution is diluted to c.c., and titrated in the manner described. the starch solution is made in the manner described under the iodide copper assay. c.c. are used for each titration. in determining the effects of variations in the condition of the assay a solution of iodine was used, which was equivalent in strength to the "hypo" solution. it was made by dissolving . grams of iodine with grams of potassium iodide in a little water and diluting to litre. c.c. of this solution were found (at the time of the experiments) to be equivalent to . c.c. of the "hypo." ~effect of varying temperature.~--the bulk of the solution was c.c.; c.c. of iodine were taken, and c.c. of starch solution were added towards the end as indicator. these conditions are also those of the other experiments, except where otherwise stated. iodine being volatile, it is to be expected that with hot solutions low results will be obtained. temperature ° ° ° ° ° "hypo" required . c.c. . c.c. . c.c. . c.c. . c.c. these show that the temperature should not much exceed °. ~effect of exposure of the iodine solution.~--twenty c.c. of the iodine were diluted to c.c., and exposed for varying lengths of time in open beakers at the ordinary temperature, and then titrated. time exposed -- day days days "hypo" required . c.c. . c.c. . c.c. . c.c. ~effect of varying bulk.~--these experiments were carried out in the usual way, bulk only varying. bulk . c.c. . c.c. . c.c. . c.c. "hypo" required . " . " . " . " ~effect of varying acid.~--these experiments were under the usual conditions, the bulk being c.c. the results were-- acetic acid -- . c.c. . c.c. "hypo" required . c.c. . " . " hydrochloric acid -- . c.c. . c.c. "hypo" required . c.c. . " . " sulphuric acid -- . c.c. . c.c. "hypo" required . c.c. . " . "[ ] nitric acid -- . c.c. . c.c. "hypo" required . c.c. . " could not be titrated. in the application of this titration to the assay of manganese ores, hydrochloric and hydriodic acids are the only ones likely to be present. ~effect of alkalies.~--on theoretical grounds the presence of these is known to be inadmissible. a solution rendered faintly alkaline with ammonia required only . c.c. of "hypo;" and another, with . gram of caustic soda, required . c.c. instead of . c.c. as in neutral solutions. ~effect of nearly neutralising hydrochloric acid solutions with ammonia.~--provided care is taken not to add excess of ammonia, this has a good effect, counteracting the interference of excess of acid. thus c.c. of iodine (as before) required . c.c. of "hypo;" with c.c. of hydrochloric acid . c.c. were required, but with c.c. of acid, nearly neutralised with dilute ammonia . c.c. were used. ~effect of the addition of starch.~--the addition of varying quantities of starch has no effect, provided it is added when the titration is nearly finished, as the following experiments show:-- starch added . c.c. . c.c. . c.c. . c.c. "hypo" required . " . " . " . " but if the starch is added before the titration, the results are liable to error. starch added . c.c. . c.c. "hypo" required . " . " the starch should be used fresh, and is best made on the day it is used; after four days the finishing point is not so good. ~effect of varying potassium iodide.~--an excess of iodide is always required to keep the iodine in solution; a larger excess has little effect. iodide added -- gram grams "hypo" required . c.c. . c.c. . c.c. the c.c. of iodine used, itself contained . gram of potassium iodide. ~effect of foreign salts.~-- bicarbonate of soda added -- . gram . gram . grams "hypo" required . c.c. . c.c. . c.c. . c.c. the solution obviously must be free from bicarbonate of soda. this should be remembered, since when titrating arsenic assays with iodine it must be present; and students must avoid confounding the two titrations. in some other experiments, in which grams each of the salts were taken, the following results were obtained:-- salt added -- amcl amno_{ } am_{ }so_{ } "hypo" required . c.c. . c.c. . c.c. . c.c. salt added nacl nano_{ } na_{ }so_{ } "hypo" required . c.c. . c.c. . c.c. ~effect of varying iodine.~-- iodine added . c.c. . c.c. . c.c. . c.c. . c.c. "hypo" required . " . " . " . " . " ~determination of dioxide in a manganese ore.~--weigh up . to . gram of the powdered ore; place in a flask, cover with c.c. of hydrochloric acid, and close the flask with a paraffined cork, and bulbs (as shown in fig. ), having previously charged the bulb with grams of potassium iodide in strong solution. heat the flask, and boil cautiously for about fifteen minutes. wash the contents of the bulbs into a large beaker, nearly (but not quite) neutralise with dilute ammonia, and titrate with the standard "hypo." as an example, . gram of pyrolusite was taken, and required . c.c. of standard "hypo" ( c.c. equal . gram iodine, or . gram mno_{ }), which equals . gram of the dioxide or . per cent. colorimetric method. when compounds of manganese free from chlorides are boiled with nitric acid and dioxide of lead,[ ] the manganese is converted into permanganic acid, which is soluble and tints the solution violet. the depth of colour depends on the amount of manganese present, and this should not much exceed milligrams. a quantity of substance containing not more than this amount of manganese should be boiled for a few minutes with c.c. of a solution containing c.c. of nitric acid, and or c.c. of dilute sulphuric acid, with or grams of lead dioxide. filter through asbestos, wash by decantation with dilute sulphuric acid, make up with distilled water[ ] to a definite bulk, and take a measured portion for the colorimetric determination. the standard solution of manganese is made by dissolving . gram of permanganate of potash (kmno_{ }) in a little water acidulated with nitric acid, and diluting to litre. one c.c. will contain . milligram of manganese. practical exercises. . what percentage of manganese (mn) is contained in permanganate of potash (kmno_{ })? . ten c.c. of a solution of permanganate of potash is found to oxidise c.c. of an acid solution of ferrous sulphate. the manganese is determined in the titrated solution by precipitation as dioxide and titrating. how much of the ferrous solution will be oxidised in the second titration? . what weight of potassium iodide would be just sufficient to absorb the chlorine evolved by . gram of pure dioxide of manganese? . what weight of iron must be dissolved up so as to have an excess of . gram after oxidation by gram of pure dioxide? . what weight of the brown oxide, mn_{ }o_{ } will be left on igniting gram of the pure dioxide? chromium. chromium occurs in nature chiefly as chromite or chrome iron ore (feo_{ }cr_{ }o_{ }, with more or less mgo and al_{ }o_{ }), which is the chief ore. it is a constituent of some silicates, and is frequently met with in very small quantities in iron ores. it occurs as chromate in crocoisite (pbcro_{ }), and some other rare minerals. the metal is used in steel-making. steel containing about . per cent. of it is rendered very hard; but its chief value is in its salts, the chromates. these are highly-coloured compounds, generally red or yellow. some of the insoluble chromates are used as pigments; chromate of lead or chrome-yellow is the most important. the soluble chromates, those of soda and potash, are valuable chemicals, and are largely used in the preparation of pigments, dyeing and tanning, and as oxidising agents. chromium forms two important classes of compounds--chromic salts, corresponding to the oxide cr_{ }o_{ }, and chromates, which contain the trioxide cro_{ }. solutions of chromic salts are green, whilst those of the chromates are yellow. chromates are reduced to chromic salts by the action of most reducing agents in the presence of an acid; and this property is used in assaying for the volumetric determination of ferrous iron, &c. the chromates in solution are more stable than other similar oxidising agents, and consequently are generally used in the laboratory as one of the standard oxidising agents for volumetric analysis. they have the disadvantage of requiring an outside indicator. bichromate of potash (k_{ }cr_{ }o_{ }) is the salt generally used for this purpose. chromic salts are oxidised to chromate by fusion with "fusion mixture" and nitre, or by treating with chlorine in an alkaline solution. chromic salts closely resemble those of ferric iron, and in the ordinary course of analysis chromic hydrate (green) is precipitated together with ferric hydrate, alumina, &c., on the addition of ammonic chloride and ammonia. the ignited oxide, cr_{ }o_{ }, however, is not reduced on heating to redness in a current of hydrogen. ~detection.~--chromium is detected by fusing the powdered substance with "fusion mixture" and nitre. the melt is extracted with water and filtered. the filtrate is acidified with acetic acid, and treated with a few drops of a solution of lead acetate. a yellow precipitate indicates chromium. substances containing chromium impart a green colour to the borax bead in both flames. small quantities of chromate in neutral solution can be found by the dark or violet-red colouration imparted thereto on boiling with a dilute decoction of logwood. ~solution and separation.~--chromates and chromic salts are generally soluble in water or dilute acids. chrome iron ore, however, and ignited chromic oxide are insoluble; and the former presents considerable difficulty on attempting to open up by the usual methods. a large number of mixtures have been tried in order to get all the chromium in a soluble form. among these are the following. one part of the very finely-powdered ore is fused with any of these mixtures. ( ) parts of bisulphate of potash. ( ) parts of bisulphate of potash and parts of potassium fluoride. ( ) parts of hydric potassic fluoride. ( ) parts of bisulphate of potash; and, afterwards, with parts of carbonate of soda and parts of nitre. ( ) parts of borax; afterwards, with carbonate of soda till it ceases to effervesce; then, with parts of carbonate of soda and of nitre. ( ) parts of borax and parts of fusion mixture. ( ) parts of caustic potash. ( ) parts of caustic soda and of magnesia. ( ) parts of caustic soda and of magnesia. ( ) parts of carbonate of soda and of lime. ( ) parts of soda-lime and of chlorate of potash. ( ) sodium peroxide. of these, numbers , , and yield the chromium in a form soluble in dilute acids, as chromic salt. the rest in a form soluble in water, as potassium or sodium chromate. on boiling an insoluble chromium compound with chlorate of potash and nitric acid, the chromium passes into solution as chromate. this method, however, does not answer for chrome iron ore. in the fusion methods the ore must be very finely powdered, well mixed with the fluxes, and subjected to a prolonged fusion in a platinum vessel at a high temperature. undecomposed particles require re-fusion. the aqueous extract containing the chromate is ready for volumetric work, except in those cases where nitre has been used. for gravimetric work the solution is acidified with hydrochloric acid, then mixed with ammonia in slight excess, boiled, and filtered. the filtrate is acidified with hydrochloric acid, and treated with sulphuretted hydrogen, warmed, rendered slightly alkaline with ammonia, and the gas again passed. the chromium is precipitated as chromic hydrate mixed with sulphur from the reduction with sulphuretted hydrogen. it is filtered off, washed with hot water, and ignited. it is weighed as chromic oxide. gravimetric determination. the solution containing the chromium, freed from other metals and earths and in the form of (green) chromic salt, is heated to boiling. if any chromate is present reduce it with sodium sulphite or sulphuretted hydrogen. add ammonia in slight excess, boil till the liquid is free from a red tint, and allow to settle for a few minutes. filter, wash with hot water, dry, and ignite strongly in a loosely-covered crucible. cool, and weigh. the substance is chromic oxide, cr_{ }o_{ }, and contains . per cent. of chromium. it is a dark-green powder insoluble in acids. when, as is generally the case, the chromium exists altogether as chromate (phosphates and arsenates being absent) it is best to proceed as follows:--render the solution acid with acetic acid, then add sodium acetate to the solution and heat nearly to boiling; next treat with a slight excess of acetate of lead, and boil. allow to settle, and filter. wash the precipitate with hot water, dry in the water-oven or at a low temperature. transfer the precipitate to a weighed berlin crucible, burn the filter separately, ignite below redness, cool in the desiccator, and weigh. the substance is lead chromate, pbcro_{ }, and contains . per cent. of chromium, or . per cent. of chromic oxide (cr_{ }o_{ }). volumetric method. this is based on the oxidation of ferrous iron by the solution containing the chromium as chromate. a known weight of iron ( . , , or . gram, according to the quantity of chromate) is dissolved in c.c. of dilute sulphuric acid. the solution containing the chromate is added, and the remaining ferrous iron titrated with the permanganate or bichromate of potassium solution, as described under _iron_. the iron thus found is deducted from that taken, and the difference gives the iron oxidised by the chromate. this multiplied by . gives the chromium, cr, and when multiplied by . gives the chromic oxide, cr_{ }o_{ }. colorimetric method. small quantities of chromium may be determined, after conversion into chromate, colorimetrically. the solution, which should not contain more than a few milligrams in c.c., is acidified with acetic acid and compared against an equal volume of water rendered acid with acetic acid and tinted with a standard bichromate of potassium solution. this standard bichromate is made by dissolving . grams of the salt in water and diluting to litre. one c.c. will contain milligram of chromium, cr. the manner of working this assay is the same as that adopted in the other colorimetric processes. ~determination of chromium in steel.~[ ]--weigh up . grams, dissolve in hydrochloric acid, and evaporate to dryness. fuse with sodium carbonate and nitre, extract with water, and make up to c.c. take c.c. of the clear liquor, boil with hydrochloric acid, add sodium phosphate, and then ammonia in slight excess. heat till clear. filter off the precipitate, dissolve it in hydrochloric acid, and evaporate to dryness. take up with a little acid, filter, and precipitate with a slight excess of ammonia. wash, ignite, and weigh as chromium phosphate ( cr_{ }o_{ }, p_{ }o_{ }), which contains . per cent. of chromium. vanadium. vanadium occurs in certain rare minerals, such as vanadinite ( pb_{ }(vo_{ })_{ }.pbcl_{ }), a vanadate of lead; mottramite, a vanadate of copper and lead; and dechenite, a vanadate of lead and zinc. it is occasionally found in iron and copper ores and in the slags from them. in spanish copper-precipitates it is found along with chromium, and is probably derived from the iron used for precipitating. the vanadates, like the chromates, are coloured compounds, generally yellow or red. on reduction, blue solutions are got. in their general reactions vanadates resemble phosphates. vanadium is detected by the red colouration produced by passing sulphuretted hydrogen into ammoniacal solutions for some time. on adding an acid to the filtered solution a brown precipitate of the sulphide is produced. this gives with borax a colourless bead in the oxidising, and a green one in the reducing, flame. it is separated by fusing the ore with potassic nitrate, extracting with water and precipitating with baric chloride. the precipitate is boiled with dilute sulphuric acid, filtered, neutralised with ammonia, and saturated with ammonic chloride. ammonium vanadate separates out. it is filtered off, ignited, and weighed as vanadic oxide, v_{ }o_{ }, containing . per cent. of vanadium. molybdenum. molybdenum occurs in nature chiefly as molybdenite (mos_{ }); it also occurs in wulfenite, a molybdate of lead (pbmoo_{ }), and in molybdic ochre (moo_{ }). molybdate of ammonia is an important reagent in the determination of phosphates, the manufacture of which compound is the chief purpose to which molybdenum is applied. iron and copper ores frequently contain molybdenum, sometimes in quantity; consequently it is met with in slags and pig-iron. molybdenum forms several series of salts. in those corresponding to the lower oxides it is basic; but the trioxide (moo_{ }) is the acid oxide which forms a series of salts called the molybdates. all molybdenum compounds are converted into the trioxide by boiling with nitric acid. the trioxide is a white powder readily dissolved by ammonia. it fuses at a red heat, and volatilises freely in contact with air. it is slightly soluble in water. molybdates are easily reduced, with the production of coloured solutions, by most reducing agents. sulphuretted hydrogen first produces a blue tint, and then precipitates a brown sulphide. the precipitation as sulphide is only complete on prolonged treatment; a green colour indicates that some molybdenum still remains in solution. the precipitated sulphide is soluble in ammonium sulphide. ~detection.~--molybdenum is detected by its behaviour with sulphuretted hydrogen. molybdenite can only be mistaken for graphite, from which it is easily distinguished by yielding sulphur dioxide on roasting, and by giving, on charcoal, a yellowish white incrustation, which becomes blue on touching it for a moment with the reducing flame. the borax-bead is colourless in the oxidising, and dark-brown in the reducing, flame. gravimetric determination. the solution containing the molybdate is neutralised and treated with an excess of mercurous nitrate. the precipitate is allowed to settle for some time, filtered, and washed with a dilute solution of mercurous nitrate. then it is dried, transferred to a weighed berlin crucible containing ignited oxide of lead, mixed, ignited, and weighed. the increase in weight gives the amount of trioxide, moo_{ }. this contains . per cent. of molybdenum. uranium. uranium occurs chiefly as pitchblende, which is an impure oxide (u_{ }o_{ }). it is also found as sulphate in uranochre, johannite, &c.; and as phosphate in the uranites, torbernite (hydrated phosphate of uranium and copper), and autunite (hydrated phosphate of uranium and lime). it also occurs in some rarer minerals. the oxide is used for colouring glass; and the nitrate and acetate are used as reagents. "uranium yellow," used for enamel painting, is sodium uranate. the uranates, in which the oxide of uranium acts as an acid, are mostly insoluble and of secondary importance. uranium forms two families of salts, uranous and uranic; corresponding to the oxides uo_{ } and uo_{ } respectively. the former are generally green and the latter yellow. uranous salts are converted into uranic by boiling with nitric acid or other oxidising agents. uranic salts, on the other hand, are easily reduced by sulphuretted hydrogen, stannous chloride or zinc. this property is made use of in determining the quantity of uranium in pure solutions by titrating with permanganate of potassium solution as in the case with iron. ~detection.~--the most characteristic reaction of the uranium compounds is their behaviour in the presence of alkaline carbonates in which they are freely soluble; even ammonium sulphide will not precipitate uranium from these solutions. on neutralising the carbonate with an acid a uranate of the alkali is precipitated. ammonia or sodic hydrate (free from carbonates) give yellow precipitates, which are insoluble in excess of the reagent, but are soluble in acids. ferrocyanide of potassium gives a reddish-brown precipitate. uranium colours the borax-bead yellowish-green in the oxidising, and green in the reducing, flame. ~solution and separation.~--the compounds of uranium are soluble in acids. powder the substance and evaporate with an excess of nitric acid. take up with hydrochloric acid, dilute, pass sulphuretted hydrogen, and filter. peroxidise the filtrate with a little nitric acid, add an excess of ammonic carbonate and some ammonium sulphide, and filter. render the solution acid, boil; and precipitate the uranium by means of ammonia. filter off, and wash it with dilute ammonic chloride. ignite, and weigh as protosesqui-oxide, u_{ }o_{ }. gravimetric determination. the solution containing the uranium free from other metals is, if required, first peroxidised by boiling with nitric acid. ammonia in slight excess is added to the nearly-boiling solution. a yellow precipitate is formed, which is filtered off hot and washed with a dilute solution of ammonium chloride. the precipitate is dried and ignited; and weighed as u_{ }o_{ }, which contains . per cent. of uranium. volumetric method. this is based on the precipitation of uranium as phosphate from acetic acid solutions and the recognition of complete precipitation by testing with potassic ferrocyanide; it is the converse of the process for the volumetric determination of phosphate. _the standard solution of phosphate_ is prepared by dissolving . grams of hydric sodic phosphate (na_{ }hpo_{ }. h_{ }o) in water and diluting to litre. c.c. will be equivalent to grams of uranium. take gram of the sample (or, if poor in uranium, grams) and separate the uranium as described. dissolve the precipitate in nitric acid and evaporate to a small bulk, add grams of sodium acetate, dilute with water to c.c., and boil. titrate the boiling solution with the sodium phosphate till it ceases to give a brown colouration with potassium ferrocyanide. calculate the percentage in the usual way. footnotes: [ ] mno_{ } + hcl = mncl_{ } + cl_{ } + h_{ }o. [ ] provided a sufficiency of ammonic chloride is present. [ ] with some silicates, &c., a preliminary fusion with sodium carbonate will be necessary. [ ] instead of sodium acetate, ammonium succinate can be used. [ ] _journ. soc. chem. industry_, vol. x. p. . [ ] mno_{ } + feso_{ } + h_{ }so_{ } = fe_{ }(so_{ })_{ } + mnso_{ } + h_{ }o. [ ] if the ore is very rich, a smaller quantity ( . or . gram) must be taken; otherwise the iron will be insufficient. [ ] mno_{ } + hcl = mncl_{ } + h_{ }o + cl_{ }. cl_{ } + ki = kcl + i_{ }. [ ] iodine probably lost by volatilisation. [ ] obtained as a brown powder by digesting red lead with nitric acid and filtering. [ ] the water for dilution and the dilute sulphuric acid used for washing should be previously tested, to see they have no reducing action, with dilute permanganate of potassium solution. [ ] arnold and hardy, _chemical news_, vol. lvii. p. . chapter xiv. earths, alkaline earths, alkalies. alumina. alumina, the oxide of aluminium (al_{ }o_{ }), is found in nature fairly pure in the mineral corundum; transparent and coloured varieties of which form the gems sapphire and ruby. a coarser compact variety contaminated with oxide of iron constitutes emery. compounded with silica, alumina forms the base of clays and many rock-forming minerals. china clay (or kaolin) is used as a source of alumina. bauxite, hydrated alumina, is also used for the same purpose--that is, for the preparation of sulphate of alumina. the mineral cryolite is a fluoride of aluminium and sodium. corundum is characterised by a high specific gravity ( . ) and extreme hardness. by these it is distinguished from felspar and similar minerals, which it somewhat resembles in general appearance. aluminium is used for a variety of small purposes: it is white, light, and very tenacious; but owing to the difficulty of its reduction it is expensive. aluminium forms one series of salts which closely resemble those of ferric iron. it forms an interesting series of double sulphates, known as the alums. common potash alum is al_{ }(so_{ })_{ },k_{ }so_{ }, h_{ }o. ~detection.~--alumina is not precipitated from its acid solution by sulphuretted hydrogen, but it is thrown down by ammonia (with the other earths) as a white hydrate, soluble in soda and insoluble in ammonic carbonate. filtered off and ignited, it assumes, after treatment with nitrate of cobalt before the blowpipe, a blue colour which is characteristic. with natural compounds containing metallic oxides this colour is masked. it is more satisfactory to make a separation in the wet way and to test the ignited oxide. ~separation and solution.~--if the substance is insoluble in hydrochloric acid it is finely powdered and fused with "fusion mixture" with the help, in the case of corundum (which is very refractory) of a little caustic soda or potash. the method of working is the same as that described for opening up silicates. see under _silica_. corundum cannot be powdered in wedgwood, or even agate, mortars; since it rapidly wears these away and becomes contaminated with their powder. it is best to use a hard steel mortar and to extract the metallic particles from the bruised sample with a magnet or dilute acid. when the substance has been completely attacked and dissolved, it is evaporated to dryness with an excess of hydrochloric acid on the water-bath to render any silica present insoluble. the residue is extracted with hydrochloric acid and freed from the second group of metals by means of sulphuretted hydrogen. the filtrate from this (after removing the sulphuretted hydrogen by boiling) is nearly neutralised, and treated with or grams of hyposulphite of soda[ ] in solution. it is then boiled till the sulphurous oxide is driven off. the precipitate is filtered off, ignited, and weighed as alumina. it is sometimes more convenient to proceed as follows:--after boiling off the sulphuretted hydrogen peroxidise the iron with a little nitric acid, add a solution of ammonic chloride, and then ammonia in very slight excess; boil, filter, wash, ignite, and weigh the oxides. these generally consist of ferric oxide and alumina. it is a common practice to determine the iron, calculate it to ferric oxide, and so to estimate the alumina indirectly. this may be done either by igniting in a current of hydrogen and estimating the iron by the weight of oxygen lost; or, by dissolving with sulphuric and hydrochloric acids, and determining the iron volumetrically. it should be borne in mind that these oxides will also contain any phosphoric oxide that happened to be in the mineral. in general analyses of samples containing alumina, it may be contained in both the soluble and insoluble portions. in these cases it is better to fuse the sample with "fusion mixture" before treatment with acids. the alumina in the fused mass will exist in a state soluble in acids. gravimetric determination. solutions containing alumina free from the other metals are diluted to a convenient bulk and heated nearly to boiling. add chloride of ammonium, and then ammonia in slight excess; boil, allow to settle, filter, and wash with hot water. dry the precipitate, and ignite in a platinum or porcelain crucible at the strongest heat. cool, and weigh. the substance is alumina, al_{ }o_{ }, which contains . per cent. of aluminium. it is only in special cases, such as the analysis of metals and alloys, that it is reported as aluminium. the percentage of alumina is generally given. ignited alumina is difficultly soluble in acids; it is not reduced by hydrogen at a red heat. ignited with ammonium chloride portions are volatilised. ~direct determination of alumina in the presence of iron.~--the iron and alumina are precipitated as hydrates by ammonia. the precipitate is dissolved in hydrochloric acid and the iron reduced to the ferrous state. it is then added to a hot solution of potash or soda. the solution is boiled till the precipitate settles readily, filtered, and washed with hot water. the alumina is contained in the filtrate, which is acidified with hydrochloric acid and the alumina precipitated therefrom as hydrate with ammonia, as just described. ~determination of alumina in the presence of phosphates and iron.~--for details, see a paper by r.t. thomson in the "journal of the society of chemical industry," v. p. . the principles of the method are as follows:--if the substance does not already contain sufficient phosphoric oxide to saturate the alumina, some phosphate is added. the iron is reduced to the ferrous state and phosphate of alumina precipitated in an acetic acid solution. it is purified by reprecipitation, ignited, and weighed as phosphate (al_{ }o_{ },p_{ }o_{ }), which contains . per cent. of alumina, al_{ }o_{ }. examination of clays. ~moisture.~--take grams of the carefully-prepared sample and dry in the water-oven till the weight is constant. ~loss on ignition.~--weigh up grams of the sample used for the moisture determination, and ignite in a platinum-crucible to redness, cool, and weigh. ~silica and insoluble silicates.~--weigh up another grams of the dried sample, and place them in a platinum dish; moisten with water, and cover with c.c. of sulphuric acid. evaporate and heat gently to drive off the greater portion of the free acid. allow to cool; and repeat the operation. extract by boiling with dilute hydrochloric acid, filter, wash, dry, ignite, and weigh. the quantity of insoluble silicates is determined by dissolving out the separated silica with a strong boiling solution of sodium carbonate. the residue (washed, dried, and ignited) is weighed, and reported as "sand." ~alumina and ferrous oxide.~--to the filtrate from the silica add "soda" solution till nearly neutral, and then sodium acetate. boil and filter off the precipitate. reserve the filtrate. dissolve the precipitate in hydrochloric acid, and dilute to exactly c.c. divide into two parts of c.c. each. in one determine the iron by reducing and titrating in the way described under volumetric iron. calculate the percentage as ferrous oxide, unless there are reasons to the contrary, also calculate its weight as ferric oxide. to the other portion add ammonia in slight excess, and boil. filter, wash with hot water, dry, ignite, and weigh as mixed alumina and ferric oxide. the weight of the ferric oxide has already been determined in the first portion: deduct it, and the difference is the weight of alumina. ~lime.~--to the reserved filtrate, concentrated by evaporation, add ammonium oxalate and ammonia; boil, filter, ignite strongly, and weigh as lime. ~magnesia~ is separated from the filtrate by adding sodium phosphate. it is weighed as magnesium pyrophosphate. ~potash and soda.~--these are determined in a fresh portion of the sample by lawrence smith's method, as described on page . thoria. this is an oxide of thorium, tho_{ }. it is only found in a few rare minerals. it is a heavy oxide, having, when strongly ignited, a specific gravity of . . in the ordinary course of analysis it will be separated and weighed as alumina. it is separated from this and other earths by the following method. the solution in hydrochloric acid is nearly neutralised and then boiled with sodium hyposulphite. the thoria will be in the precipitate. it is dissolved, and the solution heated with ammonium oxalate in excess. the precipitate is thorium oxalate, which is washed with hot water, dried, and ignited. it is then weighed as thoria, tho_{ }. thoria which has been ignited is not readily soluble in acids. zirconia. the oxide of zirconium, zro_{ }, is found in the mineral zircon, a silicate of zirconia, zrsio_{ }. when heated intensely it becomes very luminous, and is used on this account for incandescent lights. in the ordinary course it is thrown down by ammonia with the other earths, from which it is thus separated:--the hydrates precipitated in the cold, and washed with cold water, are dissolved in hydrochloric acid, nearly neutralised with soda, and precipitated by boiling with hyposulphite of soda. dissolve; and from the hydrochloric acid solution precipitate the thoria (if any) with ammonium oxalate. to the filtrate add carbonate of ammonia, which will precipitate any titanium present. the zirconia will be in solution, and is recovered by precipitating with potassium sulphate, or by evaporating the solution and igniting. it is separated from alumina by taking advantage of its insolubility in potassic hydrate. it is estimated in zircons in the following way:--the powdered substance is fused with bisulphate of potash, and extracted with dilute sulphuric acid. the residue is fused with caustic soda and extracted with water. the portion not dissolved, consisting of zirconate of soda, is dissolved in hydrochloric acid. the solution is diluted, filtered if necessary, and treated with ammonia in excess. the precipitate is filtered off, washed with hot water, dried, ignited, and weighed as zirconia, zro_{ }. this is a white powder, which is insoluble in acids; even in hydrofluoric acid it is only slightly attacked. cerium. cerium occurs as silicate (together with the oxides of lanthanum, didymium, iron and calcium) in the mineral cerite, which is its chief source. it also occurs as phosphate in monazite, and as fluoride in fluocerite. the oxalate is used in medicine. cerium forms two classes of salts corresponding to the oxides, cerous oxide (ce_{ }o_{ }) and ceric oxide (ceo_{ }). compounds of cerium with volatile acids yield dioxide on ignition; and this, on solution in hydrochloric acid, yields cerous chloride and chlorine. in the ordinary course cerium is thrown down along with alumina and the other earths by ammonia. it is separated by dissolving the hydrates in hydrochloric acid, and oxidizing with chlorine water. on treating with oxalic acid, cerium, lanthanum, and didymium are precipitated as oxalates, which on ignition are converted into oxides. these are soluble in acids. their solution in hydrochloric acid is nearly neutralised; acetate of soda is then added, and an excess of sodium hypochlorite. on boiling, the cerium is precipitated as dioxide, which is filtered off, ignited, and weighed. cerium is detected by giving with borax a bead which is yellow in the oxidising, and colourless in the reducing flame. traces of cerium compounds boiled with dioxide of lead and nitric acid will give a yellow solution. lanthanum and didymium occur together with cerium in cerite, and are separated with that metal as oxalates, as described under _cerium_. didymium salts have a rose or violet colour, and impart (when in sufficient quantity) the same colour to the borax bead. solutions have a characteristic absorption-spectrum. the separation of lanthanum and didymium in the solution from which the cerium has been precipitated is effected by precipitating them together as oxalates, igniting, and dissolving in dilute nitric acid. this solution is then evaporated to dryness and ignited, for a few minutes, just below redness. a subnitrate of didymium is formed, and remains as an insoluble residue on extracting with hot water. the separated salts are treated with ammonia and ignited, and weighed as oxides (la_{ }o_{ } and di_{ }o_{ }). yttria. yttria is found in gadolinite and some other rare minerals. it is precipitated along with the other earths by ammonia. it is distinguished by the insolubility of its hydrate in potash, by the insolubility of its oxalate in oxalic acid, and by not being precipitated by hyposulphite of soda or potassium sulphate. further, it is precipitated by potash in the presence of tartaric acid as an insoluble tartrate. this reaction distinguishes the members of the yttria group from most of the other earths. the other members of the group closely resemble it, and amongst them are erbia, terbia, ytterbia, scandia, &c. beryllia. the oxide of beryllium, beo (also known as glucina), occurs in nature mainly as silicate. beryl, the green transparent variety of which is the emerald, is the best known of these. it is a silicate of alumina and beryllia.[ ] some other minerals in which it occurs are phenakite, euclase, and chrysoberyl. in the ordinary course of analysis, beryllia will be precipitated with alumina, &c., by ammonic hydrate. it is distinguished by the solubility of its hydrate in ammonic carbonate, by not being precipitated by boiling with sodium hyposulphite, and by not being precipitated by ammonic sulphide from an ammonic carbonate solution. the analysis of silicates containing beryllia is thus effected. the finely powdered substance is fused with twice its weight of potassium carbonate; and the "melt" is extracted with water, and evaporated with a slight excess of sulphuric acid to render the silica insoluble. treat with water, filter, and evaporate the filtrate until a crust is formed. potash alum crystallises out. the liquor is poured off into a warm strong solution of ammonium carbonate. ferric hydrate and alumina will be precipitated. they are filtered off, re-dissolved, and again precipitated in ammonic carbonate solution; the combined filtrates are boiled for some time, and acidified slightly with hydrochloric acid. the carbon dioxide is boiled off, and the beryllia is then precipitated as hydrate with ammonia. the hydrate is washed with hot water, dried, ignited, and weighed as beryllia, beo. beryllia has a specific gravity of . . it is white, infusible, and insoluble in water. after ignition, it is insoluble in acids, except sulphuric, but is rendered soluble by fusion with alkalies. beryllia, in a solution of carbonate of ammonia, is precipitated as carbonate on boiling in proportion as the carbonate of ammonia is volatilised. the hydrate is dissolved by a boiling solution of ammonic chloride, ammonia being evolved. the alkaline earths. lime. lime is an oxide of calcium, cao. it occurs abundantly in nature, but only in a state of combination. the carbonate (caco_{ }), found as limestone, chalk, and other rocks, and as the minerals calcite and arragonite, is the most commonly occurring compound. the hydrated sulphate, gypsum (caso_{ }. h_{ }o), is common, and is used in making "plaster of paris." anhydrite (caso_{ }) also occurs in rock masses, and is often associated with rock salt. phosphate of lime, in the forms of apatite, phosphorite, coprolite, &c., is largely mined. lime is a component of most natural silicates. calcium also occurs, combined with fluorine, in the mineral fluor (caf_{ }). in most of these the acid is the important part of the mineral; it is only the carbonate which is used as a source of lime. lime, in addition to its use in mortars and cements, is valuable as a flux in metallurgical operations, and as a base in chemical work on a large scale. a mixture of lime and magnesia is used in the manufacture of basic fire-bricks. carbonate of lime on ignition, especially when in contact with reducing substances, loses carbonic acid, and becomes lime. this is known as "quicklime"; on treatment with water it becomes hot, expands, and falls to a powder of "slaked lime" or calcium hydrate (cah_{ }o_{ }). the hydrate is slightly soluble in water ( . gram in c.c.), forming an alkaline solution known as lime-water. calcium hydrate is more generally used suspended in water as "milk of lime." as a flux it is used either as limestone or as quicklime. silica forms with lime a compound, calcium silicate, which is not very fusible; but when alumina and other oxides are present, as in clays and in most rocky substances, the addition of lime gives a very fusible slag. ~detection.~--calcium is detected by the reddish colour which its salts impart to the flame. it is best to moisten with hydrochloric acid (or, in the case of some silicates, to treat with ammonium fluoride) before bringing the substance into the flame. when seen through a spectroscope, it shows a large number of lines, of which a green and an orange are most intense and characteristic. calcium is detected in solution (after removal of the metals by treatment with sulphuretted hydrogen and ammonium sulphide) by boiling with ammonium oxalate and ammonia. the lime is completely thrown down as a white precipitate. lime is distinguished from the other alkaline earths by forming a sulphate insoluble in dilute alcohol, but completely soluble in a boiling solution of ammonium sulphate. lime compounds are for the most part soluble in water or in dilute hydrochloric acid. calcium fluoride must be first converted into sulphate by evaporation in a platinum dish with sulphuric acid. insoluble silicates are opened up by fusion with "fusion mixture," as described under _silica_. ~separation.~--the separation of lime is effected by evaporating with hydrochloric acid, to separate silica; and by treating with sulphuretted hydrogen, to remove the second group of metals. if the substance contains much iron, the solution is next oxidised by boiling with a little nitric acid; and the iron, alumina, &c., are removed as basic acetates. the filtrate is treated with ammonia and sulphuretted hydrogen, and allowed to settle. the filtrate from this is heated to boiling, treated with a solution of ammonium oxalate in excess, boiled for five or ten minutes, allowed to settle for half an hour, and filtered. the precipitate contains all the lime as calcium oxalate. gravimetric determination. the precipitate of calcium oxalate is washed with hot water, dried, transferred to a weighed platinum crucible, and ignited at a temperature not above incipient redness. this ignition converts the oxalate into carbonate, with evolution of carbonic oxide, which burns at the mouth of the crucible with a blue flame.[ ] generally a small quantity of the carbonate is at the same time converted into lime. to reconvert it into carbonate, moisten with a few drops of ammonic carbonate solution, and dry in a water-oven. heat gently over a bunsen burner, cool, and weigh. the substance is calcium carbonate (caco_{ }), and contains per cent. of lime (cao). it is a white powder, and should show no alkaline reaction with moistened litmus-paper. where the precipitate is small, it is better to ignite strongly over the blowpipe, and weigh directly as lime. with larger quantities, and when many determinations have to be made, it is easier to make the determination volumetrically. volumetric methods. these are carried out either by dissolving the oxalate at once in dilute sulphuric acid, and titrating with permanganate of potassium solution; or by calcining it to a mixture of lime and carbonate, and determining its neutralising power with the standard solutions of acid and alkali. ~titration with permanganate of potassium solution.~--this solution is made by dissolving . grams of the salt in water, and by diluting to litre; c.c. are equivalent to . gram of lime. the solution is standardised by titrating a quantity of oxalic acid about equivalent to the lime present in the assay; . gram of lime is equivalent to . gram of crystallised oxalic acid. the standardising may be done with iron. the standard found for iron multiplied by . gives that for lime. the process is as follows:--the calcium oxalate (having been precipitated and washed, as in the gravimetric process) is washed through the funnel into a flask with hot dilute sulphuric acid, boiled till dissolved, diluted to c.c. with water, and heated to about ° c. the standard solution of "permanganate" is then run in, (not too quickly, and with constant shaking) until a permanent pink tinge is produced. the c.c. used multiplied by the standard, and divided by the weight of the substance taken, will give the percentage of lime. ~estimation of lime by alkalimetry.~--the methods of determining the amount of an alkali or base by means of a standard acid solution, or, conversely, of determining an acid by means of a standard alkaline solution, are so closely related that they are best considered under one head. the same standard solution is applicable for many purposes, and, consequently, it is convenient to make it of such strength that one litre of it shall equal an equivalent in grams of any of the substances to be determined. such solutions are termed _normal_. for example, a solution of hydrochloric acid (hcl = . ) containing . grams of real acid per litre, would be normal and of equivalent strength to a solution containing either grams of ammonia (nh_{ } = ) or grams of sodic hydrate (naho = ) per litre. it will be seen in these cases that the normal solution contains the molecular weight in grams per litre; and, if solutions of these strengths be made, it will be found that they possess equal neutralising value. if, now, a solution containing grams of sulphuric acid (h_{ }so_{ } = ) per litre be made, it will be found to have twice the strength of the above solution, that is, c.c. of the soda would only require c.c. of the acid to neutralise it. the reason for this will be seen on inspecting the equations:-- naho + hcl = nacl + h_{ }o. naho + h_{ }so_{ } = na_{ }so_{ } + h_{ }o. acids like sulphuric acid are termed bibasic, and their equivalent is only half the molecular weight. thus, a normal solution of sulphuric acid would contain grams ( / ) of real acid per litre. similarly, lime and most of the bases are bibasic, as may be seen from the following equations; hence their equivalent will be half the molecular weight. hcl + cao = cacl_{ } + h_{ }o. hcl + mgo = mgcl_{ } + h_{ }o. _the standard normal solution of hydrochloric acid_ is made by diluting c.c. of the strong acid to one litre with water. this will be approximately normal. in order to determine its exact strength, weigh up grams of recently ignited pure sodium carbonate or of the ignited bicarbonate. transfer to a flask and dissolve in c.c. of water; when dissolved, cool, tint faintly yellow with a few drops of a solution of methyl orange, and run in the standard "acid " from a burette till the yellow changes to a pink. read off the number of c.c. used, and calculate to how much sodium carbonate c.c. of the "acid" are equivalent. if the "acid" is strictly normal, this will be . grams. it will probably be equivalent to more than this. now calculate how much strictly normal "acid" would be equivalent to the standard found. for example: suppose the standard found is . gram of sodium carbonate, then-- . : . :: : _x_ (where _x_ is the quantity of normal "acid" required). _x_ = . c.c. to get the "acid" of normal strength, we should then add . c.c. of water to each c.c. of the standard solution remaining. suppose there were left c.c. of the approximate "acid," . c.c. of water must be added and mixed. it should then be checked by another titration with pure sodium carbonate. _the standard solution of semi-normal "alkali."_ the best alkali for general purposes is ammonia, but, since it is volatile (especially in strong solutions), it is best to make it of half the usual strength, or _semi-normal_. one litre of this will contain . grams of ammonia (nh_{ }), and c.c. of it will just neutralise c.c. of the normal "acid." take c.c. of dilute ammonia and dilute with water to one litre. run into a flask c.c. of the standard "acid," tint with methyl orange, and run in from a burette the solution of ammonia till neutralised. less than c.c. will probably be used. suppose c.c. were required, there should have been , hence there is a deficiency of five. then, for each c.c. of standard "ammonia" left, add c.c. of water, and mix well. c.c. will now be equivalent to c.c. of the "acid." as an example of the application of this method, we may take the determination of lime in limestone, marble, and similar substances. ~determination of lime in limestone.~--weigh up gram of the dried sample, and dissolve in c.c. of normal acid, cool, dilute to c.c., and titrate with the semi-normal solution of alkali (using methyl-orange as an indicator). divide the c.c. of alkali used by , subtract from , and multiply by . to find the weight of lime. this method is not applicable in the presence of other carbonates or oxides, unless the weight of these substances be afterwards determined and due correction be made. strontia. strontia, the oxide of strontium (sro), occurs in nature as sulphate, in the mineral celestine (srso_{ }), and as carbonate in strontianite (srco_{ }). it is found in small quantities in limestones, chalk, &c. strontia is used in sugar-refining, and for the preparation of coloured lights. ~detection.~--it is detected by the crimson colour which its compounds (when moistened with hydrochloric acid) impart to the flame. the spectrum shows a large number of lines, of which a red, an orange, and a blue are most characteristic. it resembles lime in many of its compounds, but is distinguished by the insolubility of its sulphate in a boiling solution of ammonium sulphate, and by the insolubility of its nitrate in alcohol. from baryta, which it also resembles, it is distinguished by not yielding an insoluble chromate in an acetic acid solution, by the solubility of its chloride in alcohol, and by the fact that its sulphate is converted into carbonate on boiling with a solution formed of parts of potassium carbonate and of potassium sulphate. it is got into solution in the same manner as lime. the sulphate should be fused with "fusion mixture," extracted with water, and thoroughly washed. the residue will contain the strontia as carbonate, which is readily soluble in dilute hydrochloric or nitric acid. ~separation.~--it is separated (after removal of the silica and metals, as described under _lime_) by adding ammonia and ammonia carbonate, and allowing to stand for some hours in a warm place. in the absence of baryta or lime it is filtered off, and weighed as strontium carbonate, which contains . per cent. of strontia. it is separated from baryta by dissolving in a little hydrochloric acid, adding ammonia in excess, and then acidifying with acetic acid, and precipitating the baryta with potassium bichromate, as described under _baryta_. the strontia is precipitated from the filtrate by boiling for some time with a strong solution of ammonic sulphate and a little ammonia. fifty parts of ammonic sulphate are required for each part of strontia or lime present. the precipitate is filtered off, and washed first with a solution of ammonic sulphate, and then with alcohol. it is dried, ignited and weighed as strontium sulphate. gravimetric determination. the determination of strontia in pure solutions is best made by adding sulphuric acid in excess and alcohol in volume equal to that of the solution. allow to stand overnight, filter, wash with dilute alcohol, dry, ignite at a red heat, and weigh as sulphate (srso_{ }). this contains . per cent. of strontia (sro); or . per cent. of strontium. baryta. baryta, oxide of barium (bao), commonly occurs in combination with sulphuric oxide in the mineral barytes or heavy spar (baso_{ }), and in combination with carbon dioxide in witherite (baco_{ }). these minerals are not unfrequently found in large quantity (associated with galena and other metallic sulphides) in lodes. small isolated crystals of these are frequently found in mining districts. barium is a constituent of certain mineral waters. the minerals are recognised by their high specific gravity and their crystalline form. compounds of barium are often used by the assayer, more especially the chloride and hydrate. the salts are, with the exception of the sulphate, generally soluble in water or hydrochloric acid. in such solutions sulphuric acid produces a white precipitate of baric sulphate, which is practically insoluble in all acids. the dioxide (bao_{ }) is used for the preparation of oxygen. on strong ignition it gives up oxygen, and is converted into baryta (bao), which, at a lower temperature, takes up oxygen from the air, re-forming the dioxide. ~detection.~--barium is detected by the green colour its salts, especially the chloride, give to the flame. this, viewed through the spectroscope, shows a complicated spectrum, of which two lines in the green are most easily recognised and characteristic. the salts of barium give no precipitate with sulphuretted hydrogen in either acid or alkaline solution, but with sulphuric acid they at once give a precipitate, which is insoluble in acetate of soda. in solutions rendered faintly acid with acetic acid, they give a yellow precipitate with bichromate of potash. these reactions are characteristic of barium. baryta is got into solution in the manner described under _lime_; but in the case of the sulphate the substance is fused with three or four times its weight of "fusion mixture." the "melt" is extracted with water, washed, and the residue dissolved in dilute hydrochloric acid. ~separation.~--the separation is thus effected:--the solution in hydrochloric acid is evaporated to dryness, re-dissolved in hot dilute hydrochloric acid, and sulphuric acid is added to the solution till no further precipitate is formed. the precipitate is filtered off, and digested with a solution of ammonium acetate or of sodium hyposulphite at ° or ° c. to dissolve out any lead sulphate. the residue is filtered off, washed, dried, and ignited. the ignited substance is mixed with four or five times its weight of "fusion mixture," and fused in a platinum-dish over the blowpipe for a few minutes. when cold, it is extracted with cold water, filtered, and washed. the residue is dissolved in dilute hydrochloric acid, and (if necessary) filtered. the solution contains the barium as baric chloride mixed, perhaps, with salts of strontium or lime. to separate these, ammonia is added till the solution is alkaline, and then acetic acid in slight excess. chromate of baryta is then thrown down, by the addition of bichromate of potash, as a yellow precipitate. it is allowed to settle, filtered and washed with a solution of acetate or of nitrate of ammonia. it is dried, ignited gently, and weighed. it is bacro_{ }, and contains . per cent. of baryta. gravimetric determination. the gravimetric determination of baryta, when lime and strontia are absent, is as follows:--the solution, if it contains much free acid, is nearly neutralised with ammonia, and then diluted to or c.c. it is heated to boiling, and dilute sulphuric acid is added till no further precipitation takes place. the precipitate is allowed to settle for a few minutes, decanted through a filter, and washed with hot water; and, afterwards, dried, transferred to a porcelain crucible, and strongly ignited in the muffle or over the blowpipe for a few minutes. it is then cooled, and weighed as sulphate of baryta (baso_{ }). it contains . per cent. of baryta (bao). in determining the baryta in minerals which are soluble in acid, it is precipitated direct from the hydrochloric acid solution (nearly neutralised with ammonia) by means of sulphuric acid. the precipitated baric sulphate is digested with a solution of ammonic acetate; and filtered, washed, ignited, and weighed. volumetric determination. the principle and mode of working of this is the same as that given under the sulphur assay; but using a standard solution of sulphuric acid instead of one of barium chloride. the standard solution of sulphuric acid is made to contain . grams of sulphuric acid (h_{ }so_{ }), or an equivalent of a soluble alkaline sulphate, per litre. c.c. will be equal to grams of baryta. five grams of the substance are taken, and the baryta they contain converted into carbonate (if necessary). the carbonate is dissolved in dilute hydrochloric acid. ten grams of sodium acetate are added, and the solution, diluted to c.c., is boiled, and titrated in the manner described. lead salts must be absent in the titration, and so must strontia and lime. ferrous salts should be peroxidised by means of permanganate or chlorate of potash. other salts do not interfere. magnesia. magnesia, the oxide of magnesium (mgo) occurs in nature in the rare mineral periclase (mgo); and hydrated, as brucite (mgh_{ }o_{ }). as carbonate it occurs in large quantity as magnesite (mgco_{ }), which is the chief source of magnesia. mixed with carbonate of lime, it forms magnesian limestone and dolomite. it is present in larger or smaller quantity in most silicates; and the minerals, serpentine, talc, steatite and meerschaum are essentially hydrated silicates of magnesia. soluble magnesian salts occur in many natural waters; more especially the sulphate and the chloride. kieserite (mgso_{ }.h_{ }o) occurs in quantity at stassfurt, and is used in the manufacture of epsom salts. ~detection.~--magnesia is best detected in the wet way. its compounds give no colour to the flame, and the only characteristic dry reaction is its yielding a pink mass when ignited before the blowpipe (after treatment with a solution of cobalt nitrate). in solution, it is recognised by giving no precipitate with ammonia or ammonic carbonate in the presence of ammonic chloride, and by giving a white crystalline precipitate on adding sodium phosphate or arsenate to the ammoniacal solution. magnesia differs from the other alkaline earths by the solubility of its sulphate in water. magnesia is dissolved by boiling with moderately strong acids; the insoluble compounds are fused with "fusion mixture," and treated as described under _silicates_. ~separation.~--it is separated by evaporating the acid solution to dryness to render silica insoluble, and by taking up with dilute hydrochloric acid. the solution is freed from the second group of metals by means of sulphuretted hydrogen, and the iron, alumina, &c., are removed with ammonic chloride, ammonia, and ammonic sulphide. the somewhat diluted filtrate is treated, first, with ammonia, and then with carbonate of ammonia in slight excess. it is allowed to stand for an hour in a warm place, and then filtered. the magnesia is precipitated from the filtrate by the addition of an excess of sodium phosphate and ammonia. it is allowed to stand overnight, filtered, and washed with dilute ammonia. the precipitate contains the magnesia as ammonic-magnesic phosphate. in cases where it is not desirable to introduce sodium salts or phosphoric acid into the assay solution, the following method is adopted. the solution (freed from the other alkaline earths by ammonium carbonate) is evaporated in a small porcelain dish with nitric acid. the residue (after removing the ammonic salts by ignition) is taken up with a little water and a few crystals of oxalic acid, transferred to a platinum dish, evaporated to dryness, and ignited. the residue is extracted with small quantities of boiling water and filtered off; while the insoluble magnesia is washed. the filtrate contains the alkalies. the residue is ignited, and weighed as magnesia. it is mgo. gravimetric determination. the solution containing the magnesia is mixed with chloride of ammonium and ammonia in excess. if a precipitate should form, more ammonic chloride is required. add sodium phosphate solution in excess, stir and allow to stand overnight. filter and wash the precipitate with dilute ammonia. dry, transfer to a platinum or porcelain crucible, and ignite (finally at intense redness); cool, and weigh. the substance is magnesic pyrophosphate (mg_{ }p_{ }o_{ }), and contains . per cent. of magnesia. volumetric method. the magnesia having been precipitated as ammonic-magnesic phosphate, which is the usual separation, its weight can be determined volumetrically by the method of titration described under _phosphates_. the same standard solution of uranium acetate is used. its standard for magnesia is got by multiplying the standard for phosphoric oxide by . . for example, if one hundred c.c. are equivalent to . gram of phosphoric oxide, they will be equivalent to ( . × . ) . gram of magnesia. the method of working and the conditions of the titration are the same as for the phosphate titration. the quantity of substance taken for assay must not contain more than . or . gram of magnesia. after precipitating as ammonic-magnesic phosphate with sodium phosphate, and well washing with ammonia, it is dissolved in dilute hydrochloric acid, neutralised with ammonia, and sodic acetate and acetic acid are added in the usual quantity. the solution is boiled and titrated. examination of a limestone. ~silica and insoluble silicates.~--take one gram of the dried sample and dissolve it in c.c. of dilute hydrochloric acid; filter; wash, dry, and ignite the residue. ~organic matter.~--if the residue insoluble in hydrochloric acid shows the presence of organic matter, it must be collected on a weighed filter and dried at °. on weighing, it gives the combined weights of organic and insoluble matter. the latter is determined by igniting and weighing again. the organic matter is calculated by difference. ~lime.~--where but little magnesia is present, this is determined by titration with standard acid. take one gram, and dissolve it in c.c. of normal hydrochloric acid. tint with methyl-orange and titrate with semi-normal ammonia. divide the quantity of ammonia used by , deduct this from , and multiply the remainder by . . this gives the percentage of lime. where magnesia is present, the same method is adopted, and the magnesia (which is separately determined) is afterwards deducted. the percentage of magnesia found is multiplied by . , and the result is deducted from the apparent percentage of lime got by titrating. ~magnesia.~--dissolve grams of the limestone in hydrochloric acid, and separate the lime with ammonia and ammonium oxalate. the filtrate is treated with sodium phosphate, and the magnesia is weighed as pyrophosphate, or titrated with uranium acetate. ~iron.~--dissolve grams in hydrochloric acid, reduce, and titrate with standard permanganate of potassium solution. this gives the total iron. the ferrous iron is determined by dissolving another grams in hydrochloric acid and at once titrating with the permanganate of potassium solution. ~manganese.~--dissolve grams in hydrochloric acid, nearly neutralise with soda, add sodium acetate, boil, and filter. to the filtrate add bromine; boil, and determine the manganese in the precipitate. see page . ~phosphoric oxide.~--this is determined by dissolving the ferric acetate precipitate from the manganese separation in hydrochloric acid, adding ammonia in excess, and passing sulphuretted hydrogen. filter and add to the filtrate "magnesia mixture." the precipitate is collected, washed with ammonia, ignited, and weighed as pyrophosphate. the alkalies. the oxides of sodium, potassium, lithium, cæsium, and rubidium and ammonia are grouped under this head. of these cæsia and rubidia are rare, and lithia comparatively so. they are easily distinguished by their spectra. they are characterised by the solubility of almost all their salts in water, and, consequently, are found in the solutions from which the earths and oxides of the metals have been separated by the usual group re-agents. the solution from which the other substances have been separated is evaporated to dryness, and the product ignited to remove the ammonic salts added for the purpose of separation. the residue contains the alkali metals generally, as chlorides or sulphates. before determining the quantities of the particular alkali metals present, it is best to convert them altogether, either into chloride or sulphate, and to take the weight of the mixed salts. it is generally more convenient to weigh them as chlorides. they are converted into this form, if none of the stronger acids are present, by simply evaporating with an excess of hydrochloric acid. nitrates are converted into chlorides by this treatment. when sulphates or phosphates are present, the substance is dissolved in a little water, and the sulphuric or phosphoric acid precipitated with a slight excess of acetate of lead in the presence of alcohol. the solution is filtered, and the excess of lead precipitated with sulphuretted hydrogen. the filtrate from this is evaporated to dryness with an excess of hydrochloric acid, and the residue, consisting of the mixed chlorides, is gently ignited and weighed. in many cases (such as the analysis of slags and of some natural silicates where the percentage of alkalies is small) the percentage of soda and potash (which most commonly occur) need not be separately determined. it is sufficient to report the proportion of mixed alkalies; which is thus ascertained:--dissolve the ignited and weighed chlorides in c.c. of distilled water, and titrate with the standard solution of silver nitrate (using potassic chromate as indicator) in the manner described under _chlorine_. the c.c. of silver nitrate used gives the weight in milligrams of the chlorine present. multiply this by . , and deduct the product from the weight of the mixed chlorides. this will give the combined weight of the alkalies (na_{ }o and k_{ }o) present. for example, . gram of mixed chlorides required on titrating . c.c. of silver nitrate, which is equivalent to . gram of chlorine. this multiplied by . gives . to be deducted from the weight of the mixed chlorides. mixed chlorides . gram deduction . " ------ mixed alkalies . " assuming this to have been got from gram of a rock, it would amount to . per cent. of "potash and soda." the relative proportions of the potash and soda can be ascertained from the same determination. sodium and potassium chlorides have the following composition:-- sodium . potassium . chlorine . chlorine . ----- ----- . . the percentage of chlorine in the mixed chlorides is calculated. it necessarily falls somewhere between . and . per cent., and approaches the one or the other of these numbers as the proportion of the sodium or potassium preponderates. each per cent. of chlorine in excess of . represents . per cent. of sodium chloride in the mixed chlorides. the percentage of potash and soda in the substance can be calculated in the usual way. sodium chloride multiplied by . gives its equivalent of soda (na_{ }o), and potassium chloride multiplied by . gives its equivalent of potash (k_{ }o). the weight of sodium chloride in the mixed chlorides is also calculated thus:--take the same example for illustration. multiply the chlorine found by . . this gives-- ( . × . ) = . . from the product deduct the weight of the mixed chlorides found-- product . mixed chlorides . ------- difference . the difference multiplied by . gives the weight of sodium chloride in the mixture. in this case it equals . gram. the potassium chloride is indicated by the difference between this and the weight of the mixed chlorides. it equals . gram. we have now got-- sodium chloride . gram potassium chloride . " from gram of the rock taken. multiplying these by their factors we have (soda = . × . ; potash . × . )-- soda = . per cent. potash = . " ~concentration of the alkalies.~--with the exception of magnesia, all the other bases are separated from the alkalies in the ordinary course of work without the addition of any re-agent which cannot be removed by simple evaporation and ignition. consequently, with substances soluble in acids, successive treatment of the solution with sulphuretted hydrogen, ammonia, ammonic sulphide, and ammonic carbonate, filtering, where necessary, will yield a filtrate containing the whole of the alkalies with ammonic salts and, perhaps, magnesia. the filtrate is evaporated in a small porcelain dish, with the addition of nitric acid towards the finish. it is carried to dryness and ignited. the residue is taken up with a little water, treated with a few crystals of oxalic acid, and again evaporated and ignited. the alkaline salts are extracted with water, and filtered from the magnesia into a weighed platinum dish. the solution is then evaporated with an excess of hydrochloric acid, ignited at a low red heat, and weighed. the residue consists of the mixed alkaline chlorides. for substances (such as most silicates and similar bodies) not completely decomposed by acids, lawrence smith's method is generally used. this is as follows:--take from . to gram of the finely powdered mineral, and mix, by rubbing in the mortar, with an equal weight of ammonium chloride. then mix with eight times as much pure calcium carbonate, using a part of it to rinse out the mortar. transfer to a platinum crucible, and heat gently over a bunsen burner until the ammonic chloride is decomposed (five or ten minutes). raise the heat to redness, and continue at this temperature for about three quarters of an hour. the crucible must be kept covered. cool, and turn out the mass into a -inch evaporating dish; wash the crucible and cover with distilled water, and add the washings to the dish; dilute to or c.c., and heat to boiling. filter and wash. add to the filtrate about . gram of ammonium carbonate; evaporate to about c.c., and add a little more ammonic carbonate and some ammonia. filter into a weighed platinum dish, and evaporate to dryness. heat gently, to drive off the ammonic chloride, and ignite to a little below redness. cool and weigh. the residue consists of the mixed alkaline chlorides. ~separation of the alkali-metals from each other.~--sodium and lithium are separated from the other alkali-metals by taking advantage of the solubility of their chlorides in the presence of platinic chloride; and from one another by the formation of an almost insoluble lithic phosphate on boiling with a solution of sodium phosphate in a slightly alkaline solution. cæsium, rubidium, and potassium yield precipitates with platinic chloride, which are somewhat soluble, and must be precipitated from concentrated solutions. cæsium and rubidium are separated from potassium by fractional precipitation with platinum chloride. their platino-chlorides, being less soluble than that of potassium, are precipitated first. one hundred parts of boiling water dissolve . of the potassium platino-chloride, . of the rubidium salt, and . of the corresponding cæsium compound. the separation of lithium, cæsium, and rubidium is seldom called for, owing to their rarity. the details of the separation of potassium from sodium are described under _potassium_. ammonia compounds are sharply marked off from the rest by their volatility, and it is always assumed that they have been removed by ignition; if left in the solution, they would count as potassium compounds. they will be considered under _ammonia_. sodium. sodium is the commonest of the alkali metals. it is found in nature chiefly combined with chlorine as "common salt" (nacl). this mineral is the source from which the various compounds of sodium in use are prepared. sodium occurs abundantly as nitrate (nano_{ }) in chili saltpetre, and as silicate in various minerals, such as albite (or soda-felspar). it occurs as fluoride in cryolite (na_{ }alf_{ }), and as carbonate in natron, &c. sulphates are also found. sodium is very widely diffused, few substances being free from it. the detection of sodium is easy and certain, owing to the strong yellow colour its salts impart to the flame; this, when viewed by the spectroscope, shows a single yellow line.[ ] the extreme delicacy of this test limits its value, because of the wide diffusion of sodium salts. it is more satisfactory to separate the chloride, which may be recognised by its taste, flame coloration, fusibility, and negative action with reagents. the chloride dissolved in a few drops of water gives with potassium metantimoniate, a white precipitate of the corresponding sodium salt. sodium salts are dissolved out from most compounds on treatment with water or dilute acids. insoluble silicates are decomposed and the alkali rendered soluble by lawrence smith's method, which has just been described. the separation of the sodium from the mixed chlorides is effected in the following way:--the chlorides are dissolved in a little water and the potassium separated as platino-chloride. the soluble sodium platino-chloride, with the excess of platinum, is boiled, mixed with sulphuric acid, evaporated to dryness, and ignited. on extracting with water, filtering, evaporating, and igniting, sodium sulphate is left, and is weighed as such. it is more usual, and quite as satisfactory, to calculate the weight of the sodium chloride by difference from that of the mixed chlorides, by subtracting that of the potassium chloride, which is separately determined. for example, gram of a rock gave--mixed chlorides, . gram, and . gram of potassic platino-chloride. this last is equivalent to . gram of potassium chloride. mixed chlorides found . deduct potassium chloride . ------ leaves sodium chloride . the weight of sodium chloride found, multiplied by . , gives the weight of the soda (na_{ }o). gravimetric determination. the solution, which must contain no other metal than sodium, is evaporated in a weighed platinum crucible or dish. towards the finish an excess, not too great, of sulphuric acid is added, and the evaporation is continued under a loosely fitting cover. the residue is ignited over the blowpipe, a fragment of ammonic carbonate being added towards the end, when fumes of sulphuric acid cease to be evolved. this ensures the removal of the excess of acid. the crucible is cooled in the desiccator, and weighed. the substance is sulphate of soda (na_{ }so_{ }), and contains . per cent. of soda (na_{ }o), or . per cent. of sodium (na). volumetric methods. there are various methods used for the different compounds of sodium. there is no one method of general application. thus with "common salt" the chlorine is determined volumetrically; and the sodium, after deducting for the other impurities, is estimated by difference. with sodic carbonate and caustic soda, a given weight of the sample is titrated with standard acid, and the equivalent of soda estimated from the alkalinity of the solution. with sodium sulphate, a modification of the same method is used. to a solution of . grams of the salt contained in a half-litre flask, c.c. of a solution of baryta water is added. the volume is made up to c.c. with water. the solution is mixed and filtered. half of the filtrate is measured off, treated with a current of carbonic acid, and then boiled. it is transferred to a half-litre flask, diluted to the mark, shaken up, and filtered. c.c. of the filtrate, representing a quarter of the sample taken, is then titrated with standard acid. the standard acid is made by diluting c.c. of the normal acid to litre. the c.c. of acid used multiplied by gives the percentage. a correction must be made to counteract the effect of impurities in the baryta as well as errors inherent in the process. this is small, and its amount is determined by an experiment with . grams of pure sodium sulphate. examination of common salt. ~moisture.~--powder and weigh up grams of the sample into a platinum dish. dry in a water oven for an hour, and afterwards heat to bare redness over a bunsen burner. cool, and weigh. the loss gives the water. ~chlorine.~--weigh up two separate lots of gram each; dissolve in c.c. of water, and determine the chlorine by titrating with the standard silver nitrate solution, using chromate of potash as indicator. see _chlorine_. ~insoluble matter.~--dissolve grams of the salt in water with the help of a little hydrochloric acid. filter off the sediment, wash, ignite, and weigh. this residue is chiefly sand. dilute the nitrate to c.c. ~lime.~--take c.c. of the filtrate, render ammoniacal and add ammonium oxalate; wash, dry, and ignite the precipitate. weigh as lime (cao). ~magnesia.~--to the filtrate from the lime add phosphate of soda. allow to stand overnight, filter, wash with dilute ammonia, dry, ignite, and weigh as pyrophosphate. ~sulphuric oxide.~--to the remaining c.c. of the filtrate from the "insoluble," add an excess of barium chloride. collect, wash, dry, ignite, and weigh the barium sulphate. ~sodium.~--it is estimated by difference. the following may be taken as an example:-- moisture . insoluble matter . lime . magnesia . sulphuric oxide . chlorine . sodium . ------ . potassium. potassium occurs in nature as chloride, in the mineral sylvine (kcl), and more abundantly combined with magnesium chloride, in earnallite (kcl.mgcl_{ }. h_{ }o). it occurs as nitrate in nitre (kno_{ }), and as silicate in many minerals, such as orthoclase (or potash-felspar) and muscovite (or potash-mica). potassium compounds are detected by the characteristic violet colour they impart to the flame. the presence of sodium salts masks this tint, but the interference can be neutralised by viewing the flame through a piece of blue glass. viewed through the spectroscope, it shows a characteristic line in the red and another in the violet. these, however, are not so easy to recognise or obtain as the sodium one. concentrated solutions of potassium salts give a yellow crystalline precipitate with platinum chloride, and a white crystalline one with the acid tartrate of soda. for these tests the solution is best neutral. these tests are only applicable in the absence of compounds other than those of potassium and sodium. gravimetric determination. this process serves for its separation from sodium. take gram of the sample and dissolve it in an evaporating dish with c.c. of water. acidify with hydrochloric acid in quantity sufficient (if the metals are present as chlorides) to make it acid, or, if other acids are present, in at least such quantity as will provide the equivalent of chlorine. add grams of platinum, in solution as platinum chloride, and evaporate on a water-bath to a stiff paste, but not to dryness. moisten with a few drops of platinic chloride solution without breaking up the paste by stirring. cover with c.c. of strong alcohol, and wash the crystals as much as possible by rotating the dish. allow to settle for a few moments, and decant through a filter. wash in the same way two or three times until the colour of the filtrate shows that the excess of the platinum chloride used is removed. wash the precipitate on to the filter with a jet of alcohol from the wash-bottle; clean the filter-paper, using as little alcohol as possible. dry in the water-oven for an hour. brush the precipitate into a weighed dish, and weigh it. it is potassium platino-chloride (k_{ }ptcl_{ }), and contains . per cent. of potassium, or . per cent. of potassium chloride (kcl), which is equivalent to . per cent. of potash (k_{ }o). if the filter-paper is not free from precipitate, burn it and weigh separately. the excess of weight over that of the ash will be due to platinum and potassic chloride (pt and kcl). this multiplied by . will give the weight of the potassic platino-chloride from which it was formed. it must be added to the weight of the main precipitate. the mixed alkaline chlorides obtained in the usual course of analysis are treated in this manner; the quantity of platinum added must be about three times as much as the mixed chlorides weigh. volumetric methods. these are the same as with soda. ~examination of commercial carbonate of potash.~--the impurities to be determined are moisture, silica, and insoluble matter, chlorine, sulphuric oxide, and oxide of iron. these determinations are made in the ways described under the examination of common salt. the ~potassium~ is determined by converting it into chloride and precipitating with platinum chloride, &c., as just described. ~available alkali.~--weigh up . grams of the sample, dissolve in water, and make up to c.c. take c.c., tint with methyl orange, and titrate with the normal solution of acid. the c.c. of acid used multiplied by gives the percentage of available alkali calculated as potash (k_{ }o). ~soda.~--this is calculated indirectly in the following way:--deduct from the potassium found the quantity required for combination with the chlorine and sulphuric oxide present, and calculate the remainder to potash (k_{ }o). the apparent surplus excess of available alkali is the measure of the soda present. ~carbon dioxide.~--the c.c. of acid used in the available alkali determination, multiplied by . and divided by . , gives the percentage of carbon dioxide. lithium. lithia, the oxide of lithium (li_{ }o), occurs in quantities of or per cent. in various silicates, such as lepidolite (or lithia-mica), spodumene, and petalite. it also occurs as phosphate in triphyline. it is a constituent of the water of certain mineral springs. a spring at wheal clifford contained as much as . gram of lithium chloride per litre. in small quantities, lithia is very widely diffused. the ~detection~ of lithia is rendered easy by the spectroscope; its spectrum shows a red line lying about midway between the yellow sodium line and the red one of potassium. it also shows a faint yellow line. the colour of the flame (a crimson) is characteristic. the reactions of the lithium compounds lie between those of the alkalies and of the alkaline earths. solutions are not precipitated by tartaric acid nor by platinic chloride. the oxide is slowly soluble in water. the carbonate is not freely soluble. lithia is completely precipitated by sodic phosphate, especially in hot alkaline solutions. in its determination the mixed alkaline chlorides obtained in the separation of the alkalies are dissolved in water, a solution of soda is added in slight excess, and the lithia precipitated with _sodic_ phosphate. before filtering, it is evaporated to dryness and extracted with hot water rendered slightly ammoniacal. the residue is transferred to a filter, dried, ignited, and weighed. the precipitate is lithium phosphate ( li_{ }o, p_{ }o_{ }), and contains . per cent. of lithia. the separation of lithia from magnesia is not given by the usual authorities. wohler recommends evaporating the solution to dryness with carbonate of soda. on extracting the residue with water, the lithia dissolves out and is determined in the filtrate. one hundred parts of water dissolve, at the ordinary temperature, . parts of lithium carbonate (li_{ }co_{ }); the basic magnesia compound is almost insoluble in the absence of carbon dioxide and ammonium salts. caesium. the oxide of caesium, caesia (cs_{ }o), is found associated with lithia in lepidolite, &c., and, together with rubidium, in many mineral waters. the mineral pollux is essentially a silicate of alumina and caesia; it contains . per cent. of the latter oxide. caesium is best detected by the spectroscope, its spectrum being characterised by two lines in the blue and one in the red; the latter is about midway between the lithium and sodium lines. if not detected by the spectroscope, or specially looked for, caesia would, in the ordinary course of work, be separated with the potash and weighed as potassium platino-chloride. caesia is separated from all the other alkalies by adding to the acid solution of the mixed chlorides a strongly acid cold solution of antimonious chloride. the acid used must be hydrochloric. the caesium is precipitated as a white crystalline precipitate (cscl.sbcl_{ }), which is filtered off, and washed, when cold, with strong hydrochloric acid; since it is decomposed by water or on warming. the precipitate is washed into a beaker, and treated with sulphuretted hydrogen; after filtering off the sulphide of antimony, the solution leaves, on evaporation, the caesium as chloride. rubidium. rubidium occurs widely diffused in nature, but in very small quantities. it is generally associated with caesium. it is detected by the spectroscope, which shows two violet lines and two dark red ones. like caesium, it is precipitated with platinic chloride, and in the ordinary course of work would be weighed as potassium. it is separated from potassium by fractional precipitation with platinic chloride. rubidium platino-chloride is much less soluble than the potassium salt. ammonium. it is usual to look upon the salts of ammonia as containing a compound radical (nh_{ } = am), which resembles in many respects the metals of the alkalies. ammonium occurs in nature as chloride in sal ammoniac (amcl), as sulphate in mascagnine (am_{ }so_{ }), as phosphate in struvite (ammgpo_{ }. h_{ }o). minerals containing ammonium are rare, and are chiefly found either in volcanic districts or associated with guano. ammonia and ammonium sulphide occur in the waters of certain tuscan lagoons, which are largely worked for the boracic acid they contain. the crude boracic acid from this source contains from to per cent. of ammonium salts. it is from these that the purer forms of ammonium compounds of commerce known as "from volcanic ammonia" are derived. but the bulk of the ammonia of commerce is prepared from the ammoniacal liquors obtained as bye-products in the working of certain forms of blast furnaces and coke ovens, and more especially in gas-making. ammonia hardly comes within the objects of assaying; but it is largely used in the laboratory, and the assayer is not unfrequently called on to determine it. ammonium salts are mostly soluble in water. in strong solutions they give a yellow precipitate of ammonium platino-chloride on the addition of chloride of platinum; and with the acid tartrate of soda yield a white precipitate of hydric ammonic tartrate. these reactions are similar to those produced with potassium compounds. heated with a base, such as lime or sodic hydrate, ammonium salts are decomposed, yielding ammonia gas (nh_{ }), which is readily soluble in water. the solution of this substance is known as ammonic hydrate or "ammonia." they are volatilised on ignition; either with, or without, decomposition according to the acid present. this fact is of importance in analytical work; since it allows of the use of alkaline solutions and reagents which leave nothing behind on heating. it must be remembered, however, that, although ammonic chloride is volatile, it cannot be volatilised in the presence of substances which form volatile chlorides without loss of the latter. for example: ferric oxide and alumina are thus lost, volatilising as chlorides; and there are some other compounds (notably ammonic magnesic arsenate) which on heating to redness suffer reduction. the presence of ammonic chloride in such cases must be avoided. ~detection.~--compounds of ammonium are detected by their evolving ammonia when mixed or heated with any of the stronger bases. the ammonia is recognised by its odour, by its alkaline reaction with litmus paper, and by yielding white fumes, when brought in contact with fuming acid. in consequence of the use of ammonium salts and ammonia as reagents, it is necessary to make a special test for and determination of ammonium.[ ] in the ordinary course of work it will be "lost on ignition." the determination presents little difficulty, and is based on the method used for its detection. [illustration: fig. .] ~solution and separation.~--although ammonium salts are soluble in water, there is no necessity for dissolving them. the compound containing the ammonia is boiled with an alkaline solution; and the liberated ammonia condensed and collected. the substance is weighed out into a flask of about c.c. capacity. the flask is closed with a rubber cork perforated to carry a c.c. pipette and a bulb exit tube. the latter is connected with a receiver, which is a small flask containing dilute hydrochloric acid (fig. ). the flask containing the substance is corked, and the greater part of the soda solution is run in from the pipette. the solution is then boiled. the ammonia volatilises, and is carried over into the hydrochloric acid, with which it combines to form ammonic chloride. the distillation is carried on gently until the bulk of the liquid is driven over. the ammonia in the receiver will be mixed only with the excess of hydrochloric acid. this separation is used in all determinations. gravimetric determination. the contents of the flask are transferred to a weighed platinum dish, and evaporated on the water-bath. it is dried until the weight is constant. the chloride of ammonium remains as a white mass which, after cooling in a desiccator, is weighed. it contains . per cent. of ammonium (nh_{ }), or . per cent. of ammonia (nh_{ }). on heating over the bunsen burner it is completely volatilised, leaving no residue. volumetric determination. weigh up . gram of the substance and place it in the flask. measure off c.c. of the normal solution of acid, place them in the receiver, and dilute with an equal volume of water. run in through the pipette (by opening the clip) c.c. of a strong solution of soda, boil until the ammonia has passed over, and then aspirate a current of air through the apparatus. disconnect the receiver, and tint its contents with methyl orange. titrate the residual acid with a semi-normal solution of alkali. divide the c.c. of the "alkali" solution used by , and deduct from the c.c. the difference will give the number of c.c. of the normal acid solution neutralised by the ammonia distilled over. each c.c. of "acid" so neutralised, represents per cent. of ammonia in the sample. if the results are to be reported as ammonium, . gram of the sample is taken instead of . gram. colorimetric determination. this is effected by means of "nessler's" reagent, which strikes a brown colour with traces of ammonia, even with a few hundredths of a milligram in c.c. of liquid. with larger quantities of ammonia the reagent gives a precipitate. this reagent is a strongly alkaline solution of potassic mercuric iodide; and is thus made:-- _nessler's solution_: dissolve grams of mercuric chloride in c.c. of water; and add the solution to one of grams of potassium iodide in c.c. of water until a permanent precipitate is produced. both solutions must be cold. then make up to a litre by adding a per cent. solution of potash. add more of the mercuric chloride (a little at a time) until a permanent precipitate is again formed. allow to settle, decant, and use the clear liquor. four or five c.c. are used for each c.c. of liquid to be tested. _a standard solution of ammonia_ is made by dissolving . gram of ammonic chloride in water, and diluting to c.c. ten c.c. of this are taken and diluted to litre. one c.c. contains . milligram of ammonia (nh_{ }). in working, the solution containing the ammonia is diluted to a definite volume, and to such an extent that c.c. of it shall not contain more than . or . milligram of ammonia. fifty c.c. of it are transferred to a nessler glass and mixed with c.c. of nessler's reagent. the colour is noted, and an estimate made as to the amount of ammonia it indicates. a measured quantity of the standard ammonia, judged to contain about as much ammonia as that in the assay, is then put into another nessler glass. it is diluted to c.c. with water, and mixed with c.c. of "nessler." after standing a minute or two, the colours in the two glasses are compared. if the tints are equal, the assay is finished; but if the standard is weaker or stronger than the assay, another standard, containing more or less ammonia, as the case may be, must be prepared and compared with the assay. two such experiments will generally be sufficient; but, if not, a third must be made. the addition of more standard ammonia to the solution to which the "nessler" has already been added does not give a satisfactory result. when the ammonia in c.c. has been determined, that in the whole solution is ascertained by a suitable multiplication. by , for example, if the bulk was c.c., or by if it was a litre. distilled water is used throughout. it must be free from ammonia; and is best prepared by distilling an ammonia-free spring water. footnotes: [ ] al_{ }cl_{ } + na_{ }s_{ }o_{ } + h_{ }o = al_{ }(ho)_{ } + nacl + s + so_{ } [ ] beo,al_{ }o_{ }, sio_{ } [ ] cac_{ }o_{ } = caco_{ }+co. [ ] resolved into two with a powerful spectroscope. [ ] ammonium compounds are frequently produced when dissolving metals in nitric acid; or when nitrates are heated in the presence of the metals. part iii--non-metals. chapter xv. oxygen and oxides.--the halogens. oxygen. oxygen occurs in nature in the free state, forming per cent. by weight, or per cent. by volume of the atmosphere; but, since it is a gas, its presence is easily overlooked and its importance underestimated. except in the examination of furnace-gases, &c., the assayer is not often called upon to determine its quantity, but it forms one of his most useful reagents, and there are many cases where he cannot afford to disregard its presence. it occurs not only in the air, but also dissolved in water; ordinary waters containing on an average . per cent. by weight, or . parts per , . chemically, it is characterised by its power of combining, especially at high temperatures, with the other elements, forming an important class of compounds called oxides. this combination, when rapid, is accompanied by the evolution of light and heat; hence oxygen is generally called the supporter of combustion. this property is taken advantage of in the operation of calcining, scorifying, cupelling, &c. the importance of a free access of air in all such work is seen when it is remembered that litre of air contains . gram of oxygen, and this quantity will only oxidise . gram of carbon, . gram of sulphur, or . grams of lead. oxidation takes place at the ordinary temperature with many substances. examples of such action are seen in the weathering of pyrites, rusting of iron, and (in the assay office) the weakening of solutions of many reducing agents. for methods of determining the percentage of oxygen in gases, for technical purposes, the student is referred to winkler & lunge's "technical gas analysis." oxides. oxides are abundant in nature, almost all the commonly occurring bodies being oxidised. water (h_{ }o) contains . per cent. of oxygen; silica, lime, alumina, magnesia, and the other earths are oxides, and the oxides of the heavier metals are in many cases important ores; as, for example, cassiterite (sno_{ }), hæmatite (fe_{ }o_{ }), magnetite (fe_{ }o_{ }), and pyrolusite (mno_{ }). in fact, the last-named mineral owes its value to the excess of oxygen it contains, and may be regarded as an ore of oxygen rather than of manganese. most of the metals, when heated to redness in contact with air, lose their metallic lustre and become coated with, or (if the heating be prolonged) altogether converted into, oxide. this oxide was formerly termed a "calx," and has long been known to weigh more than the metal from which it was obtained. for example, one part by weight of tin becomes, on calcining, . parts of oxide (putty powder). the student will do well to try the following experiments:--take grams of tin and heat them in a muffle on a scorifier, scraping back the dross as it forms, and continuing the operation until the whole of the metal is burnt to a white powder and ceases to increase in weight.[ ] take care to avoid loss, and, when cold, weigh the oxide formed. the oxide should weigh . grams, which increase in weight is due to the oxygen absorbed from the air and combined with the metal. it can be calculated from this experiment (if there has been no loss) that oxide of tin contains . per cent. of oxygen and . per cent. of tin. oxidation is performed with greater convenience by wet methods, using reagents, such as nitric acid, which contain a large proportion of oxygen loosely held. such reagents are termed oxidising agents. besides nitric acid, permanganate of potash, bichromate of potash, and peroxide of hydrogen are largely used for this purpose. one c.c. of nitric acid contains as much oxygen as . litres of air, and the greater part of this is available for oxidising purposes. try the following experiment:--take grams of tin and cover in a weighed berlin dish with c.c. of dilute nitric acid, heat till decomposed, evaporate to dryness, ignite, and weigh. the grams of tin should yield . grams of oxide. the increase in weight will be proportionally the same as in the previous experiment by calcination, and is due to oxygen, which in this case has been derived from the nitric acid. the percentage of oxygen in this oxide of tin (or in any of the oxides of the heavier metals) may be directly determined by heating such oxides in a current of hydrogen, and collecting and weighing the water formed. it is found by experiment that . parts by weight of oxygen, combining with . parts of hydrogen, form parts of water; so that from the weight of water formed it is easy to calculate the amount of oxygen the oxide contained. [illustration: fig. .] take gram of the dried and powdered oxide and place it in a warm dry combustion tube. place the tube in a furnace, and connect at one end with a hydrogen apparatus provided with a sulphuric acid bulb for drying the gas, and at the other with a weighed sulphuric acid tube for collecting the water formed. the apparatus required is shown in fig. . pass hydrogen through the apparatus, and, when the air has been cleared out, light the furnace. continue the heat and current of hydrogen for half an hour (or longer, if necessary). allow to cool. draw a current of dry air through the weighed tube. weigh. the increase in weight gives the amount of water formed, and this, multiplied by . , gives the weight of the oxygen. the percentage of oxygen thus determined should be compared with that got by the oxidation of the metal. it will be practically the same. the following results can be taken as examples:-- twenty grams of tin, calcined as described, gave . grams of oxide. two grams of tin, oxidised with nitric acid and ignited, gave . grams of oxide. one gram of the oxide of tin, on reduction in a current of hydrogen, gave . gram of water (equivalent to . gram of oxygen), and left . gram of metal. ten grams of ferrous sulphate gave, on strong ignition, . grams of ferric oxide (fe_{ }o_{ })[ ] instead of . . the student should similarly determine the percentage of oxygen in oxides of copper and iron. the former oxide may be prepared by dissolving grams of copper in c.c. of dilute nitric acid, evaporating to dryness, and strongly igniting the residue. the oxide of iron may be made by weighing up grams of powdered ferrous sulphate (= to . grams of iron) and heating, at first gently, to drive off the water, and then at a red heat, until completely decomposed. the weight of oxide, in each case, should be determined; and the percentage of oxygen calculated. compare the figures arrived at with those calculated from the formula of the oxides, cuo and fe_{ }o_{ }. it would be found in a more extended series of experiments that the same metal will, under certain conditions, form two or more oxides differing among themselves in the amount of oxygen they contain. these oxides are distinguished from one another by such names as "higher" and "lower oxides," "peroxides," "protoxides," "dioxides," &c. the oxides may be conveniently classified under three heads:-- ( ) _those that are reduced to metal by heat alone_, such as the oxides of mercury, silver, platinum, gold, &c.; ( ) _those which are reduced by hydrogen at a red heat_, which includes the oxides of the heavy metals; ( ) _those which are not reduced by these means_, good examples of which are silica, alumina, the alkalies, and the alkaline earths. another important classification is into acid, basic and neutral oxides. the oxides of the non-metallic elements, such as sulphur, carbon, phosphorus, &c., are, as a rule, acid; and the more oxygen they contain, the more distinctly acid they are. the oxides of the metals are nearly all basic; and, as a rule, the less oxygen they contain, the more distinctly basic they are. the basic oxides, which are soluble in acids, give rise to the formation of salts when dissolved therein. during the solution, water is formed, but no gas is evolved. the oxide dissolved in each case neutralizes an equivalent of the acid used for solution.[ ] the basic properties of many of these can be taken advantage of for their determination. this is done in the case of soda, potash, lime, &c., by finding the quantity of acid required to neutralize a given weight of the substance. there are some oxides which, under certain conditions, are acid to one substance (a stronger base) and basic to another (a stronger acid). for example, the oxides of lead and of tin, as also alumina, dissolve in caustic soda, acting as acids; whilst, on the other hand, they combine with sulphuric or hydrochloric acid, playing the part of bases. the oxides known as "earths," when ignited, are many of them insoluble in acids, although easily dissolved before ignition. it is common in complete analyses of minerals to meet with cases in which the sum total of the elements found falls short of the amount of ore taken; and here oxygen must be looked for. for example, this occurs in the case of a mixture of pyrites with oxide of iron, or in a mixture of sulphides and sulphates. the state in which the elements are present, and the percentage (say of sulphides and sulphates) can in many cases be determined; but this is not always required. when the difference between the sum total and the elements found is small, it is reported as "oxygen and loss." when, however, it is considerable, the oxygen may be reported as such; and its amount be either determined directly in the way already described, or calculated from the best determination that can be made of the relative amounts of oxides, sulphides, sulphates, &c., present. such cases require a careful qualitative analysis to find out that the substance is present; and then the separation of each constituent is made as strictly as possible. these remarks apply especially to ores of the heavy metals. the separation of the constituents is effected with suitable solvents applied in proper order. the soluble sulphates, for example, are extracted with water; the oxides by the dilute acids or alkalies in which they are known to be soluble. the oxygen in the sulphates and oxides thus obtained is estimated by determining the sulphur and metals in the solutions, and calculating the amount of oxygen with which they combine. the metals of the earths and alkalies are almost invariably present as oxides, and are reported as such; except it is known that they are present in some other form, such as fluoride or chloride. thus, silica, alumina, lime, water, &c., appear in an analysis; even in those cases where "oxygen and loss" is also mentioned. as an example of such a report, take the following analysis of spanish pyrites:-- sulphur . iron . copper . arsenic . lead . zinc . lime . silica, &c. . water . oxygen and loss . ----- . the following example will illustrate the mode of calculating and reporting. a mineral, occurring as blue crystals soluble in water, and found on testing to be a mixed sulphate of iron and copper, gave on analysis the following results:-- water . per cent. sulphuric oxide . " copper . " ferrous iron . " ferric iron . " zinc . " ----- . there is here a deficiency of . per cent. due to oxygen. nothing else could be found, and it is known that in the sulphates the metals exist as oxides. by multiplying the weight of the copper by . , the weight of copper oxide (cuo) will be ascertained; in this case it equals . per cent. the ferrous iron multiplied by . will give the ferrous oxide (feo); in this case . per cent. the ferric iron multiplied by . will give the ferric oxide (fe_{ }o_{ }); in this case . per cent. the zinc multiplied by . will give the zinc oxide (zno); in this case it equals . per cent. the analysis will be reported as-- water . sulphuric oxide . copper oxide . equal to copper . % ferrous oxide . ferric oxide . zinc oxide . ----- . the following (a) is an analysis of a sample of south american copper ore, which will serve as a further illustration. the analysis showed the presence of . per cent. of ferrous oxide, and some oxide of copper. the analysis (b) is that of an ore from the same mine after an imperfect roasting. it will be seen that the carbonates have been converted into sulphates. if the total sulphur simply had been determined, and the sulphate overlooked, the "oxygen and loss" would have been . per cent., an amount which would obviously require an explanation. a. b. water . . organic matter . -- sulphur . . copper . . {copper . {copper oxide . iron . . {iron . {ferric oxide . lead . . zinc . . cobalt . . lime . . magnesia . . sulphuric oxide . . carbon dioxide . -- "insoluble silicates" . . oxygen and loss . . ----- potash . . soda . ----- . water. water occurs in minerals in two forms, free and combined. the term "moisture" ought, strictly, to be limited to the first, although, as has already been explained, it is more convenient in assaying to apply the term to all water which is driven off on drying at ° c. the combined water is really a part of the mineral itself, although it may be driven off at a high temperature, which varies with the base. in some cases a prolonged red heat is required; whilst with crystallised salts it is sometimes given off at the ordinary temperatures. this latter phenomenon, known as efflorescence, is mostly confined to artificial salts. the determination of the combined water may often be made by simply igniting the substance from which the moisture has been removed. the quantity of water may be determined, either indirectly by the loss, or directly by collecting it in a calcium chloride tube, and weighing. in some cases, in which the loss on ignition does not give simply the proportion of combined water, it can be seen from the analysis to what else the loss is due; and, after a proper deduction, the amount of water can be estimated. for example, gram of crystallised iron sulphate was found to contain on analysis . gram of sulphuric oxide; and on igniting another gram, . gram of ferric oxide was left. as the salt is known to be made up of ferrous oxide, sulphuric oxide, and combined water, the combined water can be thus calculated: . gram of ferric oxide is equal to . gram of ferrous oxide,[ ] and consequently, the loss on ignition has been diminished by . gram, which is the weight of oxygen absorbed by the ferrous oxide during calcining. the loss on ignition was . gram, to which must be added . gram; hence . gram is the weight of the combined sulphuric oxide and water present. deducting the weight of sulphuric oxide found, . gram, there is left for combined water . gram. the composition of gram of the dry salt is then:-- water . sulphuric oxide . ferrous oxide . ------ . the following is another example:--a sample of malachite lost on ignition . per cent., leaving a residue which was found on analysis to be made up of oxide of copper (equal to . per cent. on the mineral), and silica and oxide of iron (equal to . per cent.). carbon dioxide and water (but nothing else) was found to be present, and the carbon dioxide amounted to . per cent.; deducting this from the loss on ignition, we have . as the percentage of water present. the analysis was then reported as follows:-- cupric oxide . equal to . % copper. silica and ferric oxide . carbon dioxide . water . ----- . [illustration: fig. .] ~direct determination of combined water.~--transfer about grams of the substance to a piece of combustion tube ( or inches long), attached (as in fig. ) at one end to a ~u~-tube containing sulphuric acid, and at the other end to a calcium chloride tube. the last is weighed previous to the determination. the tube should be warmed to ensure complete dryness, and must be free from a misty appearance. aspirate a current of air through the apparatus, heat the mineral by means of a bunsen burner, cautiously at first, and afterwards to redness (if necessary). the water is driven off and condenses in the calcium chloride tube, which is afterwards cooled and weighed. the increase in weight is due to the water. if the substance gives off acid products on heating, it is previously mixed with some dry oxide of lead or pure calcined magnesia. examination of waters. the assayer is occasionally called on to test water for the purpose of ascertaining the nature and quantity of the salts contained in it, and whether it is or is not fit for technical and drinking purposes. in mineral districts the water is generally of exceptional character, being more or less charged, not only with earthy salts, but also frequently with those of the metals. distilled water is only used by assayers in certain exceptional cases, so that by many it would be classed among the rarer oxides. water of ordinary purity will do for most purposes, but the nature and quantity of the impurities must be known. the following determinations are of chief importance:-- ~total solids at ° c.~--where simply the amount is required, take c.c. and evaporate on the water-bath in a weighed dish; then dry in the water-oven, and weigh. ~total solids ignited.~--the above residue is very gently ignited (keeping the heat well below redness), and again weighed. a larger loss than or parts per , on the water requires an explanation. ~chlorine.~--take c.c. of the water in a porcelain dish, add c.c. of a per cent. solution of neutral potassic chromate, and titrate with a neutral standard solution of nitrate of silver, made by dissolving . grams of crystallised silver nitrate in distilled water, and diluting to litre. the addition of the nitrate of silver is continued until the yellow of the solution assumes a reddish tint. the reaction is very sharp. each c.c. of nitrate of silver used is equal to part by weight of chlorine in , of water. at inland places this rarely amounts to more than in , ; but near the sea it may amount to or . more than this requires explanation, and generally indicates sewage pollution. ~nitric pentoxide (n_{ }o_{ }).~--it is more generally reported under the heading, "nitrogen as nitrates." take c.c. of the water and evaporate to or c.c.; acidulate with a few drops of dilute sulphuric acid, and transfer to a nitrometer (using strong sulphuric acid to wash in the last traces). the sulphuric acid must be added to at least twice the bulk of the liquid. shake up with mercury. the mercury rapidly flours, and nitric oxide is given off (if any nitrate is present). the volume of the nitric oxide (corrected to normal temperature and pressure), multiplied by . , gives the parts of nitrogen per , ; or, multiplied by . , will give the nitric pentoxide in parts per , . in well and spring waters the nitrogen may amount to . or . parts per , ; or in richly cultivated districts . or . parts per , . an excess of nitrates is a suspicious feature, and is generally due to previous contamination. ~ammonia.~--take c.c. of the water and place them in a retort connected with a liebig's condenser. add a drop or two of a solution of carbonate of soda and distil over c.c.; collect another c.c. separately. determine the ammonia in the distillate colorimetrically (with nessler's solution, as described under _ammonia_) and compare with a standard solution of ammonic chloride containing . gram of ammonic chloride in litre of water. one c.c. contains . milligram of ammonia. the second distillate will show little, if any, ammonia in ordinary cases. the amounts found in both distillates are added together, and expressed in parts per , . waters (other than rain and tank waters) which contain more than . per , are suspicious. ~organic matter.~--the organic matter cannot be determined directly; but for ordinary purposes it may be measured by the amount of permanganate of potassium which it reduces, or by the amount of ammonia which it evolves on boiling with an alkaline permanganate of potassium solution. a. _albuminoid ammonia._--to the residue left after distilling the ammonia add c.c. of a solution made by dissolving grams of potash and grams of potassium permanganate in c.c. of water, and rapidly boiling till the volume is reduced to litre (this should be kept in a well stoppered bottle, and be occasionally tested to see that it is free from ammonia). continue the distillation, collecting c.c. at a time, until the distillate is free from ammonia. three or four fractions are generally sufficient. determine the ammonia colorimetrically as before. if the total albuminoid ammonia does not exceed . in , , the water may be regarded as clean as regards organic matter; if it amounts to more than . , it is dirty. b. _oxygen consumed._--a standard solution of permanganate of potash is made by dissolving . gram of the salt in water and diluting to litre. each c.c. equals . milligram of available oxygen. the following are also required:-- . a solution of sodium hyposulphite containing gram of the salt (na_{ }s_{ }o_{ }. h_{ }o) in litre of water. . dilute sulphuric acid, made by adding one part of the acid to three of water, and titrating with the permanganate solution till a faint pink persists after warming for several hours. . starch paste. . potassium iodide solution. take c.c. of the water in a stoppered bottle, add c.c. of sulphuric acid and c.c. of the permanganate, and allow to stand in a warm place for four hours. then add a few drops of the solution of potassium iodide, and titrate the liberated iodine with "hypo," using starch paste towards the end as an indicator. to standardise the hyposulphite, take c.c. of water and c.c. of sulphuric acid, and a few drops of potassium iodide; then run in c.c. of the "permanganate" solution, and again titrate; about c.c. of the "hypo" will be used. the difference in the two titrations, divided by the last and multiplied by , will give the c.c. of permanganate solution used in oxidising the organic matter in the c.c. of water. each c.c. represents . parts of oxygen in , . ~metals.~--these may for the most part be estimated colorimetrically. ~lead.~--take c.c. of the water in a nessler tube, and add c.c. of sulphuretted hydrogen water, and compare the tint, if any, against a standard lead solution, as described under _colorimetric lead_. report in parts per , . ~copper.~--proceed as with the last-mentioned metal; but, if lead is also present, boil down c.c. to about c.c., then add ammonia, filter, and estimate the copper in the blue solution, as described under _colorimetric copper_. ~iron.~--take c.c., or a smaller quantity (if necessary), dilute up to the mark with distilled water, and determine with potassium sulphocyanate, as described under _colorimetric iron_. ~zinc.~--zinc is the only other metal likely to be present; and, since it cannot be determined colorimetrically, it must be separately estimated during the examination of the "total solids." ~examination of "total solids."~--evaporate c.c. to dryness with a drop or two of hydrochloric acid. take up with hydrochloric acid, filter, ignite, and weigh the residue as "silica." to the filtrate add a little ammonic chloride and ammonia, boil and filter, ignite, and weigh the precipitate as "oxide of iron and alumina." collect the filtrate in a small flask, add a few drops of ammonium sulphide or pass sulphuretted hydrogen, cork the flask, and allow to stand overnight; filter, wash, and determine the zinc gravimetrically as oxide of zinc. if copper or lead were present, they should have been previously removed with sulphuretted hydrogen in the acid solution. to the filtrate add ammonic oxalate and ammonia, boil for some time, allow to stand, filter, wash, ignite, and weigh as "lime." evaporate the filtrate with nitric acid, and ignite. take up with a few drops of dilute hydrochloric acid, add baric hydrate in excess, evaporate, and extract with water. the residue contains the magnesia; boil with dilute sulphuric acid, filter, precipitate it with phosphate of soda and ammonia, and weigh as pyrophosphate. the aqueous extract contains the alkalies with the excess of barium. add sulphuric acid in slight excess, filter, evaporate, and ignite strongly. the residue consists of the sulphates of the alkalies (which are separately determined, as described under _potash_). ~sulphuric oxide (so_{ }).~--take c.c. and boil to a small bulk with a little hydrochloric acid, filter (if necessary), add baric chloride solution in slight excess to the hot solution, filter, ignite, and weigh as baric sulphate. ~carbon dioxide (free).~--carbon dioxide exists in waters in two forms, free and combined. the latter generally occurs as bicarbonate, although on analysis it is more convenient to consider it as carbonate, and to count the excess of carbon dioxide with the free. the method is as follows:--to determine the free carbon dioxide, take c.c. of the water, place them in a flask with c.c. of a strong solution of calcium chloride and c.c. of a solution of ammonic chloride, next add c.c. of lime-water. the strength of the lime-water must be known. make up to c.c. with distilled water, stop the flask, and allow the precipitate to settle. take out c.c. of the clear solution with a pipette, and titrate with the standard solution of acid.[ ] the number of c.c. required, multiplied by two, and deducted from that required for the c.c. of lime-water, and then multiplied by . , will give the carbon dioxide present other than as normal carbonates. ~carbon dioxide combined~ as normal carbonate.-- c.c. of the water are tinted with phenacetolin or lacmoid; then heated to near boiling, and titrated with standard acid. the number of c.c. used, multiplied by . , will give the weight in grams of the combined carbon dioxide. ~free acid.~--in some waters (especially those from mining districts) there will be no carbonates. on the contrary, there may be free mineral acid or acid salts. in these cases it is necessary to determine the amount of acid (other than carbon dioxide) present in excess of that required to form normal salts. this is done in the following way:--make an ammoniacal copper solution by taking grams of copper sulphate (cuso_{ }. h_{ }o), dissolving in water, adding solution of ammonia until the precipitate first formed has nearly dissolved, and diluting to litre. allow to settle, and decant off the clear liquid. the strength of this solution is determined by titrating against or c.c. of the standard solution of sulphuric acid ( c.c. = gram h_{ }so_{ }). the finishing point is reached as soon as the solution becomes turbid from precipitated cupric hydrate. at first, as each drop falls into the acid solution, the ammonia and cupric hydrate combine with the free acid to form ammonic and cupric sulphates; but as soon as the free acid is used up, the ammonia in the next drop not only precipitates an equivalent of cupric hydrate from the solution, but also throws down that carried by itself. this method is applicable in the presence of metallic sulphates _other than ferric_. the standardising and titration should be made under the same conditions. since sulphuric acid and sulphates are predominant in waters of this kind, it is most convenient to report the acidity of the water as equivalent to so much sulphuric acid. ~dissolved oxygen.~--for the gasometric method of analysing for dissolved oxygen, and for the schützenberger's volumetric method, the student is referred to sutton's "volumetric analysis." the following is an easy method of estimating the free oxygen in a water:--take c.c. of a stannous chloride solution (about grams of the salt with c.c. of hydrochloric acid to the litre); add c.c. of hydrochloric acid, and titrate in an atmosphere of carbon dioxide with standard permanganate of potassium solution (made by dissolving . gram of the salt in litre of water: c.c. equals . milligram of oxygen). a similar titration is made with the addition of c.c. of the water to be tested. less permanganate will be required in the second titration, according to the amount of oxygen in the water; and the difference, multiplied by . , will give the weight of the oxygen in milligrams. small quantities of nitrates do not interfere. in reporting the results of the analysis, it is customary to combine the acids and bases found on some such principle as the following:--the sulphuric oxide is calculated as combined with the potash, and reported as potassic sulphate (k_{ }so_{ }); the balance of the sulphuric oxide is then apportioned to the soda, and reported as sulphate of soda (na_{ }so_{ }); if any is still left, it is reported as calcium sulphate (caso_{ }), and after that as magnesic sulphate (mgso_{ }). when the sulphuric oxide has been satisfied, the chlorine is distributed, taking the bases in the same order, then the nitric pentoxide, and lastly the carbon dioxide. but any method for thus combining the bases and acids must be arbitrary and inaccurate. it is extremely improbable that any simple statement can represent the manner in which the bases and acids are distributed whilst in solution; and, since different chemists are not agreed as to any one system, it is better to give up the attempt, and simply state the results of the analysis. this has only one inconvenience. the bases are represented as oxides; and, since some of them are present as chlorides, the sum total of the analysis will be in excess of the actual amount present by the weight of the oxygen equivalent to the chlorine present as chloride. the following is an example of such a statement:-- parts per , . total solids, dried at ° c. . chlorine . nitrogen as nitrate . ammonia . albuminoid ammonia . "oxygen consumed" in hours . the solids were made up as under:-- per , of the water. potash . soda . magnesia . lime . ferric oxide . silica . sulphuric oxide . nitrogen pentoxide . carbon dioxide . chlorine . volatile and organic matter . ----- . less oxygen equivalent to chlorine found . ----- . for the preparation of distilled water, the apparatus shown in fig. is convenient for laboratory use. it consists of a copper retort heated by a ring gas-burner, and connected with a worm-condenser. [illustration: fig. ] practical exercise. a mineral, on analysis, gave the following results:--water, . per cent.; sulphuric oxide, . per cent.; ferrous iron, . per cent.; ferric iron, . per cent.; copper, . per cent. the mineral was soluble in water, and showed nothing else on testing. how would you report the analysis? calculate the formula for the salt. the halogens. there is a group of closely allied elements to which the name halogen (salt-producer) has been given. it comprises chlorine, bromine, iodine, and fluorine. these elements combine directly with metals, forming as many series of salts (chlorides, bromides, iodides, and fluorides), corresponding to the respective oxides, but differing in their formulæ by having two atoms of the halogen in the place of one atom of oxygen. for example, ferrous oxide is feo and ferrous chloride is fecl_{ }, and, again, ferric oxide is fe_{ }o_{ }, whilst ferric chloride is fe_{ }cl_{ }. these salts differ from the carbonates, nitrates, &c., in containing no oxygen. consequently, it is incorrect to speak of such compounds as chloride of potash, fluoride of lime, &c., since potash and lime are oxides. it is important to bear this in mind in reporting analyses in which determinations have been made, say, of chlorine, magnesia, and potash, or of fluorine, silica, and alumina. it is necessary in all such cases to deduct from the total an amount of oxygen equivalent to the halogen found, except, of course, where the base has been determined and recorded as metal. compounds containing oxides and fluorides, &c., do not lend themselves to the method of determining the halogen by difference. for example, topaz, which, according to dana, has the formula al_{ }sio_{ }f_{ }, would yield in the ordinary course of analysis-- alumina . % silica . fluorine . ----- . the oxygen equivalent to . per cent. fluorine may be found by multiplying the percentage of fluorine by . ; it is . per cent., and must be deducted. the analysis would then be reported thus:-- alumina . % silica . fluorine . ----- . less oxygen equivalent to fluorine . ----- . take as an illustration the following actual analysis by f.w. clarke and j.s. diller:-- alumina . % silica . fluorine . potash . soda . water . ------ . deduct oxygen equivalent . ------ . in calculating the factor for the "oxygen equivalent," divide the weight of one atom of oxygen ( ) by the weight of two atoms of the halogen; for example, with chlorine it would be / or . ; with bromine, / or . ; with iodine, / or . ; and with fluorine, / or . . chlorine and chlorides. chlorine occurs in nature chiefly combined with sodium, as halite or rock salt (nacl). with potassium it forms sylvine (kcl), and, together with magnesium, carnallite (kcl.mgcl_{ }. h_{ }o). of the metalliferous minerals containing chlorine, kerargyrite, or horn silver (agcl), and atacamite, an oxychloride of copper (cucl_{ }. cu(ho)_{ }.) are the most important. apatite (phosphate of lime) and pyromorphite (phosphate of lead) contain a considerable amount of it. chlorine is a gas of a greenish colour, possessing a characteristic odour, and moderately soluble in water. it does not occur native, and is generally prepared by the action of an oxidising agent on hydrochloric acid. it combines directly with metals at the ordinary temperature (even with platinum and gold), forming chlorides, which (except in the case of silver) are soluble. it is important in metallurgy, because of the extensive use of it in extracting gold by "chloridising" processes. it is also used in refining gold. ~detection.~--compounds containing the oxides of chlorine are not found in nature, because of the readiness with which they lose oxygen. by reduction they yield a chloride; the form in which chlorine is met with in minerals. in testing, the compound supposed to contain a chloride is boiled with water, or, in some cases, dilute nitric acid. to the clear solution containing nitric acid a few drops of nitrate of silver solution are added. if, on shaking, a white curdy precipitate, soluble in ammonia, separates out, it is sufficiently satisfactory evidence of the presence of chlorides. ~solution and separation.~--the chlorides are generally soluble in water, and are got into solution by extracting with warm dilute nitric acid. or, if insoluble, the substance is fused with carbonate of soda, extracted with water, and the filtrate acidified with nitric acid. for the determination, it is not necessary to obtain the solution of the chloride free from other acids or metals. if tin, antimony, mercury, or platinum is present, it is best to separate by means of sulphuretted hydrogen. the chloride is determined in the solution after removal of the excess of the gas. where traces of chlorides are being looked for, a blank experiment is made to determine the quantity introduced with the reagents. one hundred c.c. of ordinary water contains from to milligrams of chlorine. on the addition of nitrate of silver to the nitric acid solution, chloride of silver separates out. this is free from other substances, except, perhaps, bromide and iodide. gravimetric determination. freely mix the solution containing the chloride with dilute nitric acid, filter (if necessary), and treat with nitrate of silver. heat nearly to boiling, and, when the precipitate has settled, filter, and wash with hot distilled water. dry, and transfer to a weighed berlin crucible. burn the filter-paper separately, and convert any reduced silver into chloride by alternate treatment with drops of nitric and of hydrochloric acid. add the main portion to this, and heat cautiously till the edges of the mass show signs of fusing (about °). cool in the desiccator and weigh. the substance is chloride of silver (agcl), and contains . per cent. of chlorine. the precipitated chloride is filtered and washed as soon as possible after settling, since on exposure to light it becomes purple, and loses a small amount of chlorine. volumetric method. there are several volumetric methods; but that based on the precipitation of silver chloride in neutral solution, by means of a standard solution of silver nitrate (using potassium chromate as indicator), is preferred. silver chromate is a red-coloured salt; and, when silver nitrate is added to a solution containing both chloride and chromate, the development of the red colour marks off sharply the point at which the chloride is used up. silver chromate is decomposed and consequently decolorised by solution of any chloride. the solution for this method must be neutral, since free acid prevents the formation of the red silver chromate. if not already neutral, it is neutralised by titrating cautiously with a solution of soda. in a neutral solution, other substances (such as phosphates and arsenates) also yield a precipitate with a solution of nitrate of silver; and will count as chloride if they are not removed. _the standard solution of nitrate of silver_ is made by dissolving . grams of the salt (agno_{ }) in distilled water, and diluting to litre; c.c. are equal to . gram of chlorine. the _indicator_ is made by adding silver nitrate to a strong neutral solution of yellow chromate of potash (k_{ }cro_{ }), till a permanent red precipitate is formed. the solution is allowed to settle, and the clear liquid decanted into a stoppered bottle labelled "chromate indicator for chlorine." standardise the silver nitrate by weighing up . gram of pure sodium chloride (or potassium chloride). transfer to a flask and dissolve in distilled water; dilute to c.c. fill an ordinary burette with the standard silver solution, and (after adjusting) run into the flask a quantity sufficient to throw down the greater part of the chlorine. add a few drops of the chromate indicator and continue the addition of the silver nitrate until the yellow colour of the solution becomes permanently tinted red, after shaking. this shows that the chlorine is all precipitated, and that the chromate is beginning to come down. the further addition of a couple of drops of the silver solution will cause a marked difference in the tint. read off the quantity run in, and calculate the standard. one gram of sodium chloride contains . gram of chlorine; and gram of potassium chloride contains . gram. for the determination of small quantities of chloride (a few milligrams), the same method is used; but the standard solution is diluted so that each c.c. is equal to milligram of chlorine; and the chromate indicator is added before titrating. the standard solution is made by measuring off c.c. of the solution described above, and diluting with distilled water to litre. bromine and bromides. bromine closely resembles chlorine in the nature of its compounds. it does not occur free in nature, but is occasionally found in combination with silver as bromargyrite (agbr) and, together with chloride, in embolite. it mainly occurs as alkaline bromides in certain natural waters. nearly all the bromine of commerce is derived from the mother liquors of salt-works--_i.e._, the liquors from which the common salt has been crystallised out. bromine combines directly with the metals, forming a series of salts--the bromides. in ordinary work they are separated with, and (except when specially tested for) counted as, chlorides. they are detected by adding chlorine water to the suspected solution and shaking up with carbon bisulphide. bromine colours the latter brown. iodine and iodides. iodine does not occur in nature in the free state; and iodides are rare, iodargyrite or iodide of silver (agi) being the only one which ranks as a mineral species. iodates are found associated with chili saltpetre, which is an important source of the element. iodine and iodides are largely used in the laboratory, and have already been frequently referred to. it is used as an oxidising agent in a similar manner as permanganate and bichromate of potash, especially in the determinations of copper, arsenic, antimony, and manganese. iodine is not readily soluble in water; but dissolves easily in a concentrated solution of potassium iodide. its solutions are strongly coloured; a drop of a dilute solution colours a large volume of water decidedly yellow; on the addition of starch paste, this becomes blue. the delicacy of this reaction is taken advantage of in titrations to determine when free iodine is present. the blue colour may be alternately developed and removed by the addition of iodine (or an oxidising agent) and hyposulphite of soda (or some other reducing agent). in decolorising, the solution changes from blue or black to colourless or pale yellow according to circumstances. sometimes the solution, instead of remaining colourless, gradually develops a blue which recurs in spite of the further addition of the reducing agent. in these cases the conditions of the assay have been departed from, or (and this is more often the case) there is some substance present capable of liberating iodine. iodine forms a series of salts--the iodides--resembling in many respects the chlorides. these can be obtained by direct combination of the metals with iodine. ~detection.~--free iodine is best recognised by the violet vapours evolved from the solution on heating, and by the blue or black colour which it strikes on the addition of starch paste. iodides are detected by boiling with strong solutions of ferric sulphate or chloride. iodine is liberated, distilled over, and collected. chlorine also liberates iodine from iodides; and this reaction is frequently made use of in assaying. a process based on this is described under _manganese_. all substances which liberate chlorine on boiling with hydrochloric acid (dioxides, bichromates, permanganates, &c.) are determined in a similar way. ~solution and separation.~--most iodides are soluble in water or dilute acids. the separation is effected by distilling the substance with solution of ferric sulphate, and collecting the vapour in a dilute solution of sulphurous acid or arsenite of soda. on the completion of the distillation, the iodine will be in the distillate as iodide; and the gravimetric determination is made on this. gravimetric determination. to the solution containing the iodine, as iodide, and which is free from chlorides (and bromides), add a little dilute nitric acid and nitrate of silver till no further precipitate is produced. filter off, wash with hot water, and dry. clean the filter-paper as much as possible, and burn it. collect the ash in a weighed porcelain crucible, add the main portion, and heat to incipient fusion; cool, and weigh. the substance is silver iodide, and contains . per cent. of iodine. volumetric method. this is for the titration of free iodine, and is practically that which is described under _manganese_. the substance to be determined is distilled with ferric sulphate, and the iodine is collected in a solution of potassium iodide, in which it readily dissolves. if flaky crystals separate out in the receiver, more potassium iodide crystals are added. when the distillation is finished, the receiver is disconnected, and its contents washed out into a beaker and titrated with "hypo." the standard solution of "hypo" is made by dissolving . grams of hyposulphite of soda (na_{ }s_{ }o_{ }. h_{ }o) in water and diluting to litre; c.c. are equal to gram of iodine. to standardise the solution, weigh up . gram of pure iodine in a small beaker. add or crystals of potassium iodide; cover with water; and, when dissolved, dilute to or c.c. titrate, and calculate the standard. fluorine and fluorides. fluorine is frequently met with as calcium fluoride or fluor-spar (caf_{ }). it occurs less abundantly as cryolite (na_{ }alf_{ }), a fluoride of aluminium and sodium, which is used in glass-making. certain other rarer fluorides are occasionally met with. fluorine is also found in apatite, and in some silicates, such as topaz, tourmaline, micas, &c. hydrofluoric acid is used for etching glass and opening up silicates. it attacks silica, forming fluoride of silicon (sif_{ }), which is volatile. silica is by this means eliminated from other oxides, which, in the presence of sulphuric acid, are fixed. the commercial acid is seldom pure, and generally weak; and the acid itself is dangerously obnoxious. the use of ammonium fluoride (or sodium fluoride) and a mineral acid is more convenient. determinations of this kind are made in platinum dishes enclosed in lead or copper vessels in a well-ventilated place. fluor-spar is useful as a flux in dry assaying; it renders slags, which would otherwise be pasty, quite fluid. fluorides generally are fusible, and impart fusibility to substances with which they form weak compounds. their fluxing action does not depend on the removal of silicon as fluoride. ~detection.~--fluorides in small quantity are easily overlooked unless specially sought for. in larger amounts they are recognised by the property hydrofluoric acid has of etching glass. a watch-glass is warmed, and a layer of wax is melted over the convex side. when cold, some lines are engraved on the waxed surface with any sharp-pointed instrument. the substance to be tested is powdered; and moistened, in a platinum dish, with sulphuric acid. the watch-glass is filled with cold water and supported over the dish. the dish is then carefully warmed, but not sufficiently to melt the wax. after a minute or two, the glass is taken off, and the wax removed. if the substance contained fluorine, the characters will be found permanently etched on the glass. an equally good, but more rapid, test is to mix the powdered substance with some silica, and to heat the mixture in a test tube with sulphuric acid. silicon fluoride is evolved, and, if a moistened glass rod is held in the tube, it becomes coated with a white deposit of silica, formed by the decomposition of the silicon fluoride by the water. this is also used as a test for silica; but in this case the substance is mixed with a fluoride, and the experiment must obviously be carried out in a platinum vessel. ~separation and determination.~--the determination of fluorine is difficult. in the case of fluorides free from silicates (such as fluor-spar), it is determined indirectly by decomposing a weighed portion with sulphuric acid, evaporating, igniting, and weighing the residual sulphate. the increase in weight multiplied by . gives the weight of fluorine. in the presence of silica this method does not answer, because of the volatilisation of silicon fluoride. in these cases wöhler adopted the following plan, which resembles that for the indirect determination of carbon dioxide. mix the weighed substance in a small flask with powdered silica and sulphuric acid. the mouth of the flask is closed with a cork carrying a tube which is filled, the first half with calcium chloride and the second half with pumice coated with dried copper sulphate. the apparatus is weighed quickly, and then warmed till decomposition is complete. a current of dry air is aspirated for a minute or two; and the apparatus again weighed. the loss in weight gives that of the silicon fluoride (sif_{ }), which, multiplied by . , gives the weight of fluorine. fresenius uses the same reaction; but collects and weighs the silicon fluoride. the finely powdered and dried substance is mixed with ten or fifteen times its weight of ignited and powdered silica. the mixture is introduced into a small dry flask connected on one side with a series of drying-tubes, and on the other with an empty tube (to condense any sulphuric acid). to this last is joined a drying-tube containing chloride of calcium and anhydrous copper sulphate. this is directly connected with a series of three weighed tubes in which the fluoride of silicon is collected. the last of these is joined to another drying-tube. the first weighed tube contains pumice and cotton wool, moistened with water; the second tube contains soda-lime as well as (in the upper half of the second limb) fused calcium chloride between plugs of wool; the third tube is filled half with soda-lime and half with fused calcium chloride. the distilling-flask containing the substance mixed with silica is charged with or c.c. of sulphuric acid, and placed on the hot plate. alongside it is placed a similar dry flask containing a thermometer, and the temperature in this is kept at ° or ° c. a current of air is sent through the tubes during the operation, which takes from one to three hours for from . to gram of the substance. a correction is made by deducting . gram for every hour the dried air has been passed through. the increase in weight of the three tubes gives the weight of the silicon fluoride. penfield uses a similar arrangement, but passes his silicon fluoride into an alcoholic solution of potassium chloride. silica and potassium silico-fluoride are precipitated, and hydrochloric acid is set free.[ ] the acid thus liberated is titrated, with a standard solution of alkali, in the alcoholic solution, and from the amount of free acid found the fluorine is calculated. the weight of hydrochloric acid (hcl) found, multiplied by . , gives the weight of the fluorine. with this method of working, fewer ~u~-tubes are required. the exit tube from the flask is bent so as to form a small ~v~, which is kept cool in water; this is directly connected with the ~u~-tube containing the alcoholic solution of potassium chloride. the flask with the assay is heated for about two hours, and a current of dry air is aspirated throughout the determination. fluoride of silicon is a gas not easily condensed to a liquid: but is immediately decomposed by water or moist air. footnotes: [ ] this will require two or three hours to thoroughly complete. it is best to powder the oxide first produced, and recalcine. [ ] no magnetic oxide was formed. [ ] for example:-- cao + hcl = cacl_{ } + h_{ }o. pbo + h_{ }so_{ } = pbso_{ } + h_{ }o. mgo + hno_{ } = mg(no_{ })_{ } + h_{ }o. al_{ }o_{ } + hcl = al_{ }cl_{ } + h_{ }o. fe_{ }o_{ } + h_{ }so_{ } = fe_{ }(so_{ })_{ } + h_{ }o. [ ] fe_{ }o_{ }: feo:: . : . . [ ] c.c. contain gram of sulphuric acid. [ ] sif_{ } + kcl + h_{ }o = k_{ }sif_{ } + sio_{ } + hcl. chapter xvi. sulphur and sulphates. sulphur occurs native in volcanic districts, and is mined in sicily, italy, and california in considerable quantities. combined with metals (sulphides), it is common in all mineral districts. iron pyrites (fes_{ }) is the most abundant source of this element. sulphates, such as gypsum, are fairly common, but have no value so far as the sulphur in them is concerned. in coal it exists as an impurity, occurring partly as a constituent of organic compounds. sulphur, whether free or combined with metals, forms, on burning, sulphurous oxide (so_{ }), which by the action of oxidising agents and water is converted into sulphuric acid. it forms two oxides, sulphurous (so_{ }) and sulphuric (so_{ }), which combine with bases to form sulphites and sulphates. sulphites are of little importance to the assayer, and are converted into sulphates by the action of nitric acid and other oxidising agents. the native sulphides, when acted on with hydrochloric acid, give off sulphuretted hydrogen; with nitric acid or aqua regia, sulphates are formed, and more or less sulphur separated. sulphur is detected in sulphides by the irritating odour of sulphurous oxide given off on roasting, by the evolution of sulphuretted hydrogen when treated with hydrochloric acid, or by a white precipitate of barium sulphate formed when barium chloride is added to the aqua regia solution. ~dry assay.~--there is no method of general application. free or native sulphur may be volatilised, condensed, and weighed, but pyrites only gives up a portion of its sulphur when heated in a closed vessel, while most sulphides, and all sulphates, give up none at all. in the determination of sulphur in brimstone, grams of the substance are taken, placed in a small porcelain dish, heated over a bunsen burner in a well-ventilated place, and ignited. when the sulphur has been completely burnt off, the residue (which consists chiefly of sand) is collected and weighed. in a separate portion the moisture and arsenic are determined; the amounts of these are deducted from the loss in the first experiment. the difference, multiplied by , gives the percentage of sulphur. wet methods. ~solution.~--all sulphates, excepting those of lead, barium, strontium, and lime, are soluble in water or dilute acid. all sulphides, except cinnabar, are converted into sulphates by the action of nitric acid at a gentle heat; or, better, by the action of a mixture of three volumes of nitric acid and one volume of hydrochloric acid. this last attacks cinnabar as well. with most substances it is difficult to convert the whole of the sulphur into sulphuric acid. the sulphur separates out at first as a dark spongy mass, which (on continued treatment) changes to light-coloured flakes. when the solution becomes concentrated and the temperature rises sufficiently, the sulphur fuses into one or more honey-coloured globules which, owing to the small surface they oppose to the acid, are very slowly oxidised. it is not desirable to assist the formation of these globules; therefore, the temperature is kept as low as possible, and strong nitric acid is used. when such globules form, it is best to allow the solution to cool, when the globules will solidify. they can then be filtered off and picked out from the insoluble residue, dried, weighed, ignited, and again weighed, the loss being counted as sulphur. with iron pyrites this difficulty seldom occurs. metallic sulphides when fused with an excess of nitre are completely oxidised. if the ore is rich in sulphur, some inert body (such as sodium chloride, or, better, sodium carbonate) is added to dilute the action. with pure sulphur, the action is so energetic as to cause an explosion, so that care should be taken. with burnt ores (incompletely calcined pyrites), there is sufficient oxide of iron present to prevent too rapid action. these fusions with nitre are best conducted in a platinum dish covered with a piece of platinum foil. the ore is ground with the nitre to ensure complete mixing. the heat need not be excessive, so that a single bunsen burner placed beneath the dish will suffice; if the bottom of the dish is seen to be red-hot, it is sufficient. on cooling and extracting with water, the sulphur will pass into solution as potassium sulphate, which is then filtered off from the insoluble oxides of iron, copper, &c. the filtrate, after having been treated with a large excess of hydrochloric acid, evaporated to dryness, and re-dissolved in water, is ready for the determination. lead sulphate may be dissolved by boiling with ammonium acetate. the insoluble sulphates of barium, strontium, and lime, are decomposed by fusing with or times their weight of "fusion mixture." the alkaline sulphates are then dissolved out with water, and filtered off from the insoluble residue. the filtrate is rendered acid with hydrochloric acid. ~separation.~--the determination of the sulphuric acid in these solutions by precipitation with barium chloride also serves as a separation; but in hot acid solutions containing copper, and more especially iron salts, the baric sulphate has a strong tendency to carry down amounts of those bodies, varying, no doubt, with the conditions of the precipitation. boiling hydrochloric acid fails to completely extract them. moreover, the use of hot concentrated hydrochloric acid causes a loss by dissolving barium sulphate. nitric acid and nitrates must be decomposed by prolonged boiling and evaporation with hydrochloric acid. the iron may be removed by adding a slight excess of ammonia to the faintly acid solution, filtering off, and washing the precipitated ferric hydrate with hot water. by slightly acidulating the filtrate with hydrochloric acid, it will be rendered ready for the determination. gravimetric method. this assay is one of those which strikingly shows the necessity of getting the assay solution under proper conditions, in order to obtain satisfactory results. the method has been repeatedly investigated, and the conclusion arrived at, "that it can be correct only by accident." yet there are many chemists who get good results, and place considerable faith in its accuracy. this can only be due to differences in the manner of working. it is generally understood that nitric acid or nitrates must be absent; and our experience fully confirms this. precipitations in nitrate solutions are worthless, as the following experiments show. in each experiment the bulk of the solution was c.c. the solutions contained grams of nitre, were freely acid with hydrochloric acid, and were precipitated (while boiling) with slight excess of baric chloride. sulphuric acid taken . gram . gram . gram " found . " . " . " " taken . " . " . " " found . " . " . " all the precipitates were boiled with hydrochloric acid, and thoroughly washed before weighing. the results of some other experiments on this subject are given under "sulphur" in the "examination of commercial copper," page . the solution having been obtained free from nitrates and chlorates (and containing but little free hydrochloric acid), is largely diluted, heated to boiling, and precipitated with a moderate excess of a solution of chloride of barium ( parts of the crystallized barium chloride are sufficient for of sulphur). it is allowed to settle for half-an-hour, and then decanted through a filter. the precipitate is shaken up with boiling water, rendered slightly acid, filtered, washed, dried, ignited, and weighed. the ignited precipitate, when pure, is white, and is not decomposed at a red heat; it is barium sulphate (baso_{ }), and contains . per cent. of sulphur, or . per cent. of sulphuric oxide (so_{ }). ~determination of sulphur in pyrites.~--weigh up half a gram of the dried and powdered sample, and treat with c.c. of a mixture of volumes of nitric acid and volume of hydrochloric acid, occasionally heating. evaporate to dryness, treat with c.c. of hydrochloric acid, and again evaporate; take up with c.c. of hydrochloric acid and c.c. of hot water, filter through a small filter, and wash. the residue may contain sulphates of lead, barium, or lime; it must be separately examined, if the total sulphur is wanted. the filtrate is heated, and rendered slightly alkaline with ammonia. filter off the precipitated ferric hydrate through a quick filter, and wash with hot water. if necessary, evaporate the bulk to about c.c., render faintly acid with hydrochloric acid, and add c.c. of solution of barium chloride; allow to stand for half-an-hour, and decant through a filter. wash with hot water, dry, ignite, and weigh. pure pyrites contains . per cent. of sulphur. volumetric method. this is based upon the easy conversion of all sulphur compounds into sulphates by fusion with nitre or by oxidation with nitric acid; and on the determination of the sulphate formed by titration in an acetic acid solution with baric chloride.[ ] the finishing point is determined by filtering off portions of the assay solution, and testing with sulphuric acid. a slight excess of baric chloride will cause a precipitate. the process may be divided into--( ) the preparation of the solution, and ( ) the titration. ~preparation of the solution.~--weigh up from to grams of the dried and powdered substance, and mix intimately with grams of powdered nitre; clean out the mortar with another gram of nitre, and add this as a cover. heat in a platinum crucible for fifteen minutes at a low temperature; cool, and extract with water in an evaporating-dish about inches across, and holding or c.c. add grams of sodium acetate and c.c. of acetic acid, and dilute to half a litre. boil. the solution is ready for titrating. substances which lose sulphur on heating (such as pyrites) are thus treated:--weigh up gram, and evaporate nearly to dryness with c.c. each of nitric and hydrochloric acids. take up with c.c. of hydrochloric acid, and again boil down to a small bulk; dilute and transfer to a -inch evaporating-dish; add grams of sodium acetate and c.c. of acetic acid, dilute to half a litre, and boil. the solution is ready for titrating. sulphates may be dissolved up in the dish itself with the help of a c.c. or so of hydrochloric acid; sodium acetate and acetic acid are then added; and, after dilution and boiling, the solutions are at once titrated. the solution before titration must contain no free mineral acid, but or c.c. of acetic acid should be present. it must contain grams of sodium acetate, or sufficient to convert any free mineral acid into its corresponding sodic salt; or, if chlorides, nitrates or sulphates of the metals are present, sufficient to decompose them. if a precipitation occurs, as is the case with ferric salts, &c., the solution is titrated with the precipitate in it. ~the titration.~--_the standard solution of barium chloride_ is made by dissolving . grams of the crystallized salt (bacl_{ }. h_{ }o) in distilled water, and diluting to litre. c.c. will equal gram of sulphur. as indicator, use dilute sulphuric acid. the strength of the solution may be checked by the titration of grams of ferrous sulphate (oxidized with permanganate of potassium or a few drops of nitric acid), which should require . c.c. of the barium chloride solution; or any pure sulphate of known composition can be used; anhydrous salts should be preferred. [illustration: fig. .] fill an ordinary c.c. burette with the solution of barium chloride. the evaporating dish containing the assay solution is placed on a round burner (as shown in fig. ), and the solution is kept steadily boiling. an ordinary bunsen-burner flame will cause bumping, and should not be used. run in the standard solution in quantity known to be insufficient; then withdraw a portion of about c.c., with a pipette, and filter through a fine filter-paper into a test tube. run in another . c.c. of the standard solution, and withdraw and filter into a test tube another portion of c.c.; and continue this operation until half-a-dozen or more portions have been drawn off. the test tubes should be arranged in order in a stand resting on a piece of paper, so that each test tube representing . c.c. of the standard baric chloride may have its value recorded beneath it (fig. ). add to each test tube drops of dilute sulphuric acid; that which shows the first appearance of a precipitate marks the point at which the titration is complete. suppose, for example, that the test tube marked . c.c. shows no precipitate, while that at . c.c. shows one, it is evident that the finishing point lies between these readings. with a little practice, one can judge from the appearance of the precipitate in the c.c. tube, whether / c.c. should be deducted or not. [illustration: fig. .] it is better to add dilute sulphuric acid, and to watch for the appearance of a precipitate in the test tube, than to add baric chloride and to look for its non-appearance; besides, baric chloride is much less likely to be present in a test tube as impurity than sulphates are. in this way the chance of error from what are termed "accidental causes" is diminished. the following experiments show the effect of variation in the conditions of titration:-- make _a standard solution of sulphuric acid_ by diluting . grams of sulphuric acid (sp. g. . ) to litre: c.c. will contain gram of sulphur. an equivalent solution may be made by dissolving . grams of sodium sulphate crystals (na_{ }so_{ }. h_{ }o), or . grams of ferrous sulphate (feso_{ }. h_{ }o), in water (oxidising the latter), and diluting to litre. the order in which these experiments are given is that in which they were made in an investigation into the conditions under which the titration could most accurately be effected. ~effect of hydrochloric and nitric acids.~--the titrations were performed in the manner already described, but sodic acetate and acetic acid were absent. twenty c.c. of the standard solution of sulphuric acid were used. hydrochloric acid present . c.c. . c.c. . c.c. . c.c. "baric chloride" required . " . " . " . " nitric acid present . c.c. . c.c. . c.c. . c.c. "baric chloride" required . " . " . " . " these show clearly the interference of free mineral acids, although very dilute hydrochloric acid ( c.c. in of water) has no effect. ~effect of acetic and citric acids.~--a similar series of experiments with these acids gave the following results:-- acetic acid present . c.c. . c.c. . c.c. . c.c. "baric chloride" required . " . " . " . " citric acid present gram gram grams "baric chloride" required . c.c. . c.c. . c.c. these acids do not interfere. ~effect of sodic acetate and acetic acid.~--in each of these experiments c.c. of acetic acid was present. sodium acetate added gram gram grams grams "baric chloride" required . c.c. . c.c. . c.c. . c.c. as sodic acetate and acetic acid did not interfere, it became desirable to make some experiments on the _finishing point_. the first object sought for was the smallest amount of the standard baric chloride in c.c. of water, required to give an indication when tested in the manner already described. baric chloride conditions of assay solution. required. water only . c.c. with grams of sodium acetate and c.c. of acetic acid . " the same with grams of nitre . " like the last, but with grams of salt instead of nitre . " these show that as small an amount of baric chloride solution as is equal to only . gram of sulphur in the c.c. of solution tested yields a decided precipitate on the addition of drops of sulphuric acid. to determine whether the same finishing point is obtained on testing the filtered portions in the test tubes with baric chloride as is obtained on testing with sulphuric acid, a titration was made with c.c. of standard solution of sulphuric acid, together with the usual quantities of sodic acetate and acetic acid; and two lots of c.c. each were filtered into two sets of test tubes after each addition of the standard baric chloride. to one series drops of baric chloride solution were added, and to the other drops of sulphuric acid. the results were-- with dilute with baric "baric chloride" added. sulphuric acid. chloride solution. . c.c. clear cloudy . " clear cloudy . " finished finished . " cloudy clear . " cloudy clear the two methods of testing give the same result. but this balance is disturbed in the presence of much nitre, the indications with baric chloride being disturbed by an opalescence for some c.c. beyond the finishing point. in solutions containing free hydrochloric or nitric acid, a precipitate is obtained with either baric chloride or sulphuric acid. ~effect of varying sulphur.~--in these and the subsequent experiments the titrations were performed in the presence of grams of sodic acetate and c.c. of acetic acid in the manner already described. standard sulphuric acid used . c.c. . c.c. . c.c. . c.c. . c.c. "baric chloride" required . " . " . " . " . " ~effect of varying temperature.~--with c.c. of standard sulphuric acid titrated at ° c., c.c. of baric chloride were required; but with larger quantities the results were altogether unsatisfactory when titrated cold. ~effect of varying bulk.~-- bulk . c.c. . c.c. . c.c. . c.c. "baric chloride" required . " . " . " . " considerable variation in bulk has no effect, but c.c. is the most convenient volume to work with. it is well to occasionally replace the water boiled off during titration. ~effect of foreign salts.~--in all these experiments c.c. of "sulphuric acid" were used, and the titration was performed in the ordinary way. _sodic chloride_ added gram grams grams "baric chloride" required . c.c. . c.c. . c.c. _ammonic chloride_ added gram grams grams "baric chloride" required . c.c. . c.c. . c.c. _calcic chloride_ added gram gram grams grams "baric chloride" required . c.c. . c.c. . c.c. . c.c. _zinc chloride_ added gram gram grams grams "baric chloride" required . c.c. . c.c. . c.c. . c.c. _ferrous chloride_ added gram gram grams grams "baric chloride" required . c.c. . c.c. . c.c. . c.c. _ferric chloride_ added gram gram grams grams "baric chloride" required . c.c. . c.c. . c.c. . c.c. _copper chloride_ added gram gram grams grams "baric chloride" required . c.c. . c.c. . c.c. . c.c. _potassic nitrate_ added gram gram grams grams "baric chloride" required . c.c. . c.c. . c.c. . c.c. _potassic nitrite_ added gram gram grams "baric chloride" required . c.c. . c.c. . c.c. _sodic phosphate_ added gram gram "baric chloride" required . c.c. . c.c. _sodic arsenate_ added gram gram "baric chloride" required . c.c. . c.c. in the absence of ferric salts, phosphates and arsenates count as sulphur. in two series of experiments for determining the effect of varying amounts of sulphur in the form of ferrous sulphate, we obtained the following results:--in the first series the assay solution was prepared in the manner we have described for _pyrites_; and in the second series, by fusion with nitre. sulphur added . gram . gram . gram "baric chloride" required ( ) . c.c. . c.c. . c.c. " " ( ) . " . " . " sulphur added . gram . gram "baric chloride" required ( ) . c.c. . c.c. " " ( ) . " . " more than grams of nitre must not be used in an assay; and, since the requisite amount of nitre considerably exceeds that sufficient to oxidise the sulphur, not more than . gram of unoxidised sulphur should be present in the portion of the sample weighed up for determination. when the amount of sulphur present is not known within reasonable limits, the test portions may be tried with a drop of baric chloride solution instead of sulphuric acid, so that the diminishing quantity of precipitate may give warning of an approach to the finishing point. ~determination of sulphur in blende.~--weigh up gram of dried and powdered blende, and mix and fuse with grams of nitre in the manner described. place the dish and its contents in the titrating-dish, extract with water, add grams of sodium acetate and c.c. of acetic acid, remove and wash the platinum-dish, and dilute to c.c.; boil and titrate. in the example, duplicate determinations required (a) . c.c., (b) . c.c., giving an average of . per cent. of sulphur. ~determination of sulphur in chalcopyrite~ (yellow copper ore).--take gram of the finely-powdered sample, and grams of nitre. sprinkle a little of the nitre in a small wedgwood mortar, place the ore on it, and cover with or grams more of the nitre. rub up together, and transfer to a small porcelain dish; clean out the mortar with the rest of the nitre, and add to the contents of the dish. cover with a piece of platinum foil, and heat gently with a bunsen burner till the nitre melts and the stuff shows signs of deflagrating; remove the heat, and allow the action to go on by itself for a minute or so, then heat over the bunsen burner for minutes. cool; transfer the whole to the titrating-dish; boil with c.c. of water; remove the small dish and foil; add sodic acetate and acetic acid, and titrate. for example, gram required . c.c. of "barium chloride" (standard = . gram s), which is equivalent to . per cent. sulphur. the theoretical percentage is . . ~determination of sulphur in chalcocite~ (grey copper ore).--proceed as in the last experiment but, since the action with nitre is more moderate, no special precautions need be taken on heating. a platinum dish may be used. an example which was heated for minutes required . c.c. of the barium chloride solution. this is equivalent to . per cent. of sulphur. the theoretical yield is . per cent. ~determination of sulphur in pyrites.~--take gram of the finely-powdered sample, cover with c.c. of nitric acid, and, when action has ceased, evaporate to a small bulk. add or c.c. of hydrochloric acid, and again evaporate to a paste. take up with or c.c. of dilute hydrochloric acid, dilute with water, transfer to a titrating-dish, add grams of sodic acetate and c.c. of acetic acid, and dilute with water to c.c. boil and titrate. an example with gram of a pure crystallized pyrites required . c.c. of the barium chloride solution, which is equivalent to . per cent. of sulphur. theory requires . per cent. of sulphur. ~determination of sulphur in mispickel.~--take gram of the powdered ore and evaporate with c.c. of nitric acid, and take up with or c.c. of hydrochloric acid. if any globules of sulphur remain, again evaporate with nitric acid. dilute, and transfer to the titrating-dish. add grams of sodic acetate, dilute with water, boil, and titrate. the mispickel carries (according to theory) exactly sufficient iron to precipitate the arsenic as ferric arsenate in an acetic acid solution, so no more iron need be added. the ferric arsenate will separate out as a yellowish-white flocculent precipitate. an example required, in duplicate experiment, . c.c. and . c.c. of barium chloride, equivalent to . per cent. of sulphur. the formula, fes_{ }.feas_{ }, requires . percent., but the sulphur generally varies considerably from this amount. ~determination of sulphur in burnt ores.~--take grams of the dried and powdered ore, and rub up with grams of nitre; transfer to the platinum-dish; clean out the mortar with another gram of nitre, and add this as a cover. heat, and extract with water as before; add the sodium acetate and acetic acid; and titrate. burnt ores carry from . to per cent. of sulphur. a series of four determinations gave:-- "baric chloride" required. percentage of sulphur. gravimetric results. . c.c. . % . % . " . " . " . " . " . " . " . " . " for ores carrying less than per cent. of sulphur, take grams for the assay. ~determination of sulphuric oxide (so_{ }) in sulphates.~--when the sulphur exists in the sample received by the assayer in an oxidised state as sulphate, it is usual to report it in terms of sulphuric oxide (so_{ }). in this case, the metal must also be reported as oxide. for example, an analysis of copper sulphate would be thus reported:-- oxide of copper (cuo) . % sulphuric oxide (so_{ }) . " water . " ----- . the percentage of sulphur multiplied by . gives the percentage of sulphuric oxide. thus a sample of copper sulphate containing . per cent. of sulphur will contain . × . or . per cent. of sulphuric oxide. in minerals and metallurgical products, it is common to find the sulphur in both conditions--_i.e._, as sulphate and sulphide. generally in these the percentage of sulphur only is wanted; but this will depend entirely on commercial requirements, and not on the fancy of the assayer. soluble sulphates are determined separately by extracting with small quantities of cold water, so as to avoid the separation of basic sulphates, or, if the sulphides present are not at the same time attacked, by dilute hydrochloric acid. lead sulphate may be extracted by boiling with ammonic acetate; whilst barium, strontium, and, perhaps, calcium sulphate, will be mainly found in the residue insoluble in acids. weigh up from to grams of the material according to the amount of sulphur judged to be present, and dissolve them in the titrating-dish with c.c. of hydrochloric acid and c.c. of water. add grams of sodic acetate, and c.c. of acetic acid; dilute, boil, and titrate. in the case of ferric salts, half the quantity of acetic acid will be better, as then the ferric iron will be precipitated, and a colourless solution will be left, in which the end reaction is more readily distinguished. determined in this way, gram samples of the following salts gave the results indicated below:-- "barium chloride" salt. required. sulphuric oxide. copper sulphate . c.c. . % magnesium sulphate . " . " zinc sulphate . " . " ferrous sulphate . " . " sodium sulphate . " . " ~determination of sulphuric oxide in barytes~ (heavy spar).--fuse grams of the powdered mineral with grams of "fusion mixture" for five minutes; and, when cold, extract with water. filter, acidulate the filtrate with an excess of c.c. of acetic acid, dilute, boil, and titrate. for example, a transparent crystallised sample required . c.c. of barium chloride, which is equivalent to . per cent. of sulphur, or . per cent. of sulphuric oxide. theory requires . per cent. of the latter. since both carbonate of soda and potash are liable to contain sulphates, a blank determination should be made on grams of the "fusion mixture," and the amount found be deducted from that got in the assay. practical exercises. . the price of sulphur in an ore being - / d. per unit in the northern markets, what would be the price of a ton of ore containing per cent. of sulphur? what would be the effect on the price of an error of . per cent. in the assay? . pyrites carries per cent. of sulphur, and on calcining yields per cent. of its weight of burnt ore. supposing the burnt ore carries . per cent. of sulphur, what proportion of the sulphur will have been removed in the calcining? . how would blende compare with pyrites as a source of sulphur for sulphuric acid making? . how would you determine the percentage of sulphuric oxide in a sample of gypsum? what is sulphuric oxide, and what relation does it bear to sulphur? . a mineral contains . per cent. of water, . per cent. of lime, and . per cent. of sulphur. what is its probable composition? what experiment would you try to determine the accuracy of your conclusion? selenium occurs in nature combined with copper, mercury, and lead, in certain rare minerals. in small quantities it is found in many ores. it is detected in solution by the red precipitate produced on boiling the acid solution with sodium sulphite. this reaction is used for its determination. ~solution.~--the solution is effected by boiling with nitric acid or aqua regia, or by fusing with nitre. to separate the selenium, the solution is evaporated with an excess of hydrochloric acid and a little sodium or potassium chloride. this destroys any nitric acid that may be present, and reduces selenic acid (h_{ }seo_{ }) to selenious (h_{ }seo_{ }). the solution is diluted with water, and treated with a solution of sulphite of soda. it is warmed, and at last boiled. the selenium separates as a red precipitate, which (on boiling) becomes denser and black. it is collected on a weighed filter, washed with hot water, dried at ° c., and weighed as pure selenium. selenium can be precipitated with sulphuretted hydrogen as a sulphide, which is readily soluble in ammonium sulphide. this sulphide may be oxidised with hydrochloric acid and chlorate of potash; and the selenium separated in the manner described. tellurium. tellurium occurs in nature, native, and in combination with gold, silver, bismuth and lead. it is sometimes met with in assaying gold ores. it may be detected by the purple colour it imparts to strong sulphuric acid when dissolved in the cold, and by the black precipitate of metallic tellurium which its solutions yield on treatment with a reducing agent. telluric acid is reduced to tellurous (with evolution of chlorine) on boiling with hydrochloric acid. ~solution~ is effected by boiling with aqua regia, or by fusing with nitre and sodium carbonate. ~separation.~--tellurium closely resembles selenium in its reactions. it is separated and determined in the same way. like it, it forms a sulphide soluble in ammonium sulphide. it is distinguished from selenium by the insolubility, in a solution of cyanide of potassium, of the metal precipitated by sodium sulphite; whereas selenium dissolves, forming a soluble potassic seleno-cyanide.[ ] for the determination, solution is effected by fusing with nitre and sodium carbonate, dissolving out the tellurate of potash with water, and boiling with hydrochloric acid. tellurous compounds are formed, with evolution of chlorine; and the solution, on treating with a reducing agent (such as sulphurous acid or stannous chloride), yields metallic tellurium; which is washed, dried at ° c., and weighed. footnotes: [ ] bacl_{ } + na_{ }so_{ } = baso_{ } + nacl. [ ] se + kcy = kcyse. chapter xvii. arsenic, phosphorus, nitrogen. arsenic. the chief source of the arsenic of commerce is arsenical pyrites, or mispickel, which contains about per cent. of arsenic (as). arsenic also occurs as a constituent of several comparatively rare minerals; and, as an impurity, it is very widely distributed. white arsenic is an oxide of arsenic, and is obtained by roasting arsenical ores, and refining the material (crude arsenic), which condenses in the flues. arsenic itself is volatile, and many of its compounds have the same property. it forms two well-defined series of salts, corresponding to the oxides: arsenious oxide (as_{ }o_{ }), and arsenic oxide (as_{ }o_{ }). these combine with bases to form arsenites and arsenates respectively. boiling with nitric acid converts the lower into the higher oxide; and powerful reducing-agents, such as cuprous chloride, have the opposite effect. arsenic may be detected by dissolving the substance in hydrochloric acid, or in aqua regia (avoiding an excess of nitric acid), and adding a little of this solution to the contents of a small flask in which hydrogen is being made by the action of zinc and hydrochloric acid. the ignited jet of hydrogen assumes a blue colour if arsenic is present, and a cold porcelain dish held in the flame (fig. ) becomes coated with a dark deposit of metallic arsenic. antimony produces a similar effect, but is distinguished by the insolubility of its deposit in a cold solution of bleaching-powder. [illustration fig. .] arsenites are distinguished by the volatility of the chloride; by decolorising a solution of permanganate of potassium, and by immediately giving a yellow precipitate with sulphuretted hydrogen. arsenates are distinguished (after converting into soda salts by boiling with carbonate of soda and neutralising) by giving with nitrate of silver a red precipitate, and with "magnesia mixture" a white crystalline one. ~dry assay.~--there is no dry assay which is trustworthy. the following method is sometimes used to find the proportion of arsenious oxide in "crude arsenic":--weigh up grams of the dried sample, and place them in a clean dry test-tube about inches long. tie a small filter-paper over the mouth of the tube, so as to prevent air-currents. heat the tube cautiously so as to sublime off the white arsenic into the upper part of the tube. cut off the bottom of the test-tube by wetting whilst hot. scrape out the arsenic and weigh it. the weight gives an approximate idea of the quantity, and the colour of the quality, of the white arsenic obtainable from the sample. some workers (sellers) weigh the residue, and determine the white arsenic by difference. in determining the percentage of moisture in these samples, the substance is dried on a water-bath or in a water-oven. wet methods. ~solution.~--where, as in crude arsenic, the substance is arsenious oxide (as_{ }o_{ }) mixed with impurities, the arsenic is best got into solution by warming with caustic soda, and neutralising the excess with hydrochloric acid; it will be present as sodium arsenite. metals and alloys are acted on by means of nitric acid; or the arsenic may be at the same time dissolved and separated by distilling with a strongly-acid solution of ferric chloride, in the way described under _volumetric methods_. with minerals, mattes, &c., solution is thus effected:--the finely-powdered substance is mixed (in a large platinum or porcelain crucible) with from six to ten times its weight of a mixture of equal parts of carbonate of soda and nitre. the mass is then heated gradually to fusion, and kept for a few minutes in that state. when cold, it is extracted with warm water, and filtered from the insoluble residue. the solution, acidified with nitric acid and boiled, contains the arsenic as sodium arsenate. with mispickel, and those substances which easily give off arsenic on heating, the substance is first treated with nitric acid, evaporated to dryness, and then the residue is treated in the way just described. when the arsenic is present as arsenite or arsenide, distillation with an acid solution of ferric chloride will give the whole of the arsenic in the distillate free from any metal except, perhaps, tin as stannic chloride. with arsenates, dissolve the substance in acid and then add an excess of soda. pass sulphuretted hydrogen into the solution; warm, and filter. acidulate the filtrate, and pass sulphuretted hydrogen. decant off the liquid through a filter, and digest the precipitate with ammonic carbonate; filter, and re-precipitate with hydrochloric acid and sulphuretted hydrogen. allow to stand in a warm place, and filter off the yellow sulphide of arsenic. wash it into a beaker, clean the filter-paper (if necessary) with a drop or two of dilute ammonia; evaporate with c.c. of dilute nitric acid to a small bulk; dilute; and filter off the globules of sulphur. the filtrate contains the arsenic as arsenic acid. gravimetric method. having got the arsenic into solution as arsenic acid, and in a volume not much exceeding c.c., add about c.c. of dilute ammonia and c.c. of "magnesia mixture." stir with a glass rod, and allow to settle overnight. filter, and wash with dilute ammonia, avoiding the use of large quantities of wash water. dry, transfer the precipitate to a berlin crucible, and clean the filter-paper thoroughly. burn this paper carefully and completely; and add the ash to the contents of the crucible, together with or drops of nitric acid. evaporate with a bunsen burner, and slowly ignite, finishing off with the blow-pipe or muffle. cool, and weigh. the ignited precipitate is pyrarsenate of magnesia (mg_{ }as_{ }o_{ }), and contains . per cent. of arsenic (as). instead of igniting the precipitate with nitric acid, it may be collected on a weighed filter-paper, dried at ° c., and weighed as ammonic-magnesic arsenate ( ammgaso_{ }.h_{ }o), which contains . per cent. of arsenic. the results in this case are likely to be a little higher. the drying is very tedious, and is likely to leave behind more water than is allowed for in the formula. in a series of determinations in which the arsenic was weighed in both forms, the results were:-- ammonic-magnesic arsenic magnesium pyrarsenate arsenic arsenate in grams. in grams. in grams. in grams. . . . . . . . . . . . . . . . . . . . . . . . . volumetric methods. there are two methods: one for determining the arsenic in the lower, and the other in the higher state of oxidation. in the first-mentioned method this is done by titrating with a standard solution of iodine; and in the latter with a solution of uranium acetate. where the arsenic already exists as arsenious oxide, or where it is most conveniently separated by distillation as arsenious chloride, the iodine method should be used; but when the arsenic is separated as ammonic-magnesic arsenate or as sulphide, the uranium acetate titration should be adopted. iodine process. this is based on the fact that sodium arsenite in a solution containing an excess of bicarbonate of soda is indirectly oxidised by iodine to sodium arsenate,[ ] and that an excess of iodine may be recognised by the blue colour it strikes with starch. the process is divided into two parts--( ) the preparation of the solution, and ( ) the titration. ~preparation of the solution.~--for substances like crude arsenic, in which the arsenic is present as arsenious oxide, the method is as follows:--take a portion which shall contain from . to . gram of the oxide, place in a beaker, and cover with c.c. of sodic hydrate solution; warm till dissolved, put a small piece of litmus paper in the solution, and render acid with dilute hydrochloric acid. add grams of bicarbonate of soda in solution, filter (if necessary), and dilute to c.c. the solution is now ready for titrating. [illustration: fig. .] where the arsenic has to be separated as arsenious chloride, the process is as follows:[ ]--weigh up gram of the finely-powdered ore (metals should be hammered out into a thin foil or be used as filings), and place in a -ounce flask provided with a well-fitting cork, and connected with a ~u~-tube, as shown in the drawing (fig. ). the ~u~-tube should contain or c.c. of water, and is cooled by being placed in a jar or large beaker of cold water. the water used for cooling should be renewed for each assay. pour on the assay in the flask c.c. of a "ferric chloride mixture," made by dissolving grams of calcium chloride and grams of ferric chloride in c.c. of hydrochloric acid, and making up to litre with water. firmly cork up the apparatus, and boil over a small bunsen-burner flame for fifteen or twenty minutes, but avoid evaporating to dryness. disconnect the flask, and pour away its contents at once to prevent breakage of the flask by their solidification. the arsenic will be condensed in the ~u~-tube, together with the greater part of the hydrochloric acid; transfer the distillate to a beaker washing out the tube two or three times with water; add a small piece of litmus paper; neutralise with ammonia; render faintly _acid_ with dilute hydrochloric acid; add grams of bicarbonate of soda in solution; and dilute to c.c. the solution is now ready for titrating. the arsenic comes over in the early part of the distillation, as will be seen from the following experiment, made on gram of copper precipitate; in which experiment the distillate was collected in separate portions at equal intervals, and the arsenic in each portion determined:-- time iodine equivalent to arsenic distilling. required. in the distillate. minutes . c.c. . gram " . " . " " . " " . " to dryness . " the volume of each distillate was about c.c. in this operation the metals are converted into chlorides by the action of ferric chloride, which gives up a part of its chlorine, and becomes reduced to the ferrous salt. the calcium chloride does not enter into the chemical reaction, but raises the temperature at which the solution boils, and is essential for the completion of the distillation.[ ] two experiments with material containing . per cent. of arsenic gave--( ) with ferric chloride alone, . per cent.; and ( ) with the addition of calcium chloride, . per cent. it is always necessary to make a blank determination with gram of electrotype copper, to find out the amount of arsenic in the ferric chloride mixture.[ ] unfortunately, a correction is always required. this amounts to about . per cent. of arsenic on each assay, even when the mixture has been purified; and this constitutes the weakness of the method, since, in some cases, the correction is as much as, or even greater than, the percentage to be determined. the acid distillate containing the arsenious chloride may be left for an hour or so without much fear of oxidation; but it is safer to neutralise and then to add the bicarbonate of soda, as the following experiments show. several portions of a solution, each having a bulk of c.c., were exposed for varying lengths of time, and the arsenic in each determined. _____________________________________________________________________ | | | | | | acid solutions. | neutralised solutions. | | time exposed. | "iodine" arsenic found. |"iodine" arsenic found. | | | required. | required | |_______________|___________________________|_________________________| | | | | | -- | . c.c. = . gram | . c.c. = . gram | | hour | . " = . " | . " = . " | | hours | . " = . " | . " = . " | | " | . " = . " | . " = . " | | " | . " = . " | . " = . " | |_______________|___________________________|_________________________| ~the titration.~--make a _standard solution of iodine_ by weighing up in a beaker . grams of iodine and grams of potassium iodide in crystals; add a few c.c. of water, and, when dissolved, dilute to litre: c.c. will equal . gram of arsenic. a solution of starch similar to that used in the iodide-copper assay will be required. use c.c. for each assay. variations in the quantity of starch used do not interfere; but the solution must be freshly prepared, as after seven or eight days it becomes useless. to standardise the iodine solution, weigh up . gram of white arsenic; dissolve in caustic soda; neutralise; after acidulating, add grams of bicarbonate of soda and c.c. of the starch solution, and dilute to c.c. with cold water. fill a burette having a glass stop-cock with the iodine solution, and run it into the solution of arsenic, rapidly at first, and then more cautiously, till a final drop produces a blue colour throughout the solution. calculate the standard in the usual way. white arsenic contains . per cent. of arsenic. the following experiments show the effect of variation in the conditions of the titration:-- make a solution of arsenic by dissolving . grams of white arsenic in c.c. of sodic hydrate solution; render slightly acid with hydrochloric acid; add grains of bicarbonate of soda, and dilute to litre: c.c. will contain . gram of arsenic. ~effect of varying temperature.~--the reaction goes on very quickly in the cold, and, since there is no occasion for heating, all titrations should therefore be carried out cold. ~effect of varying bulk.~--in these experiments, c.c. of arsenic solution were taken, grams of bicarbonate of soda and c.c. of starch solution added, and water supplied to the required bulk. the results were:-- bulk . c.c. . c.c. . c.c. . c.c. "iodine" required . " . " . " . " considerable variation in bulk does not interfere. ~effect of varying bicarbonate of soda.~--this salt must be present in each titration in considerable excess, to prevent the interference of free acid. the bicarbonate must be dissolved without heating, as neutral carbonates should be avoided. bicarbonate added gram grams grams grams "iodine" required . c.c. . c.c. . c.c. . c.c. these results show that large variation in the quantity of bicarbonate has no effect. ~effect of free acid.~--in these experiments, the arsenic taken, the starch, and the bulk were as before, but no bicarbonate was added. in one case the solution was rendered acid with c.c. of acetic acid, and in the other with c.c. of hydrochloric acid; in both cases the interference was strongly marked, and no satisfactory finishing point could be obtained. this was much more marked with the hydrochloric acid. ~effect of foreign salts.~--the process for getting the arsenic into solution will exclude all metals except tin, but the solution will be charged with sodium or ammonium salts in the process of neutralising, so that it is only necessary to see if these cause any interference. the alkaline hydrates, including ammonia, are plainly inadmissible, since no free iodine can exist in their presence. monocarbonates similarly interfere, but to a much less extent; hence the necessity for rendering the assay distinctly acid before adding the bicarbonate of soda. with c.c. of arsenic solution; and with bulk, soda, and starch as before, the results obtained were:-- "iodine" required. with grams of ammonic chloride . c.c. " grams of sodium chloride . " " grams of sodium acetate . " " . gram of tin, as stannic chloride . " without any addition . " the interference of the stannic salt is probably mechanical, the precipitate carrying down some arsenious acid. ~effect of varying arsenic.~--with bulk, starch, and soda as before, but with varying arsenic, the results were:-- arsenic added . c.c. . c.c. . c.c. . c.c. . c.c. "iodine" required . " . " . " . " . " ~determination of arsenic in metallic copper.~--put gram of the copper filings, freed from particles of the file with a magnet, into a -oz.-flask; and distil with the ferric chloride mixture, as above described. neutralise the distillate; acidify; add bicarbonate of soda and starch; dilute; and titrate with the standard solution of iodine.[ ] make a blank determination with gram of electrotype copper, proceeding exactly as with the assay; and deduct the amount of arsenic found in this experiment from that previously obtained. working in this way on a copper containing . per cent. of arsenic and . per cent. of antimony, . per cent. of arsenic was found. ~determination of white arsenic in crude arsenic.~--weigh out gram of the dried and powdered substance (or . gram if rich), and digest with c.c. of a per cent. solution of soda; dilute to about c.c., and filter. render faintly acid with hydrochloric acid, and filter (if necessary); add or grams of bicarbonate of soda in solution, then c.c. of starch, and titrate the cold solution with the standard solution of iodine. the following is an example:-- gram of crude arsenic required . c.c. "iodine;" c.c. "iodine" = . gram white arsenic; : . :: . : . , or . per cent. with the test-tube method of dry assaying, this same sample gave results varying from to per cent. of white arsenic, which (judging from its appearance) was impure. uranic acetate process. this may be looked upon as an alternative to the gravimetric method. it is applicable in all cases where the arsenic exists in solution as arsenic acid or as arsenate of soda. the process may be considered in two parts: ( ) the preparation of the solution, and ( ) the titration. ~preparation of the solution.~--if the arsenic has been separated as sulphide, it is sufficient to attack it with or c.c. of nitric acid, and to heat gently till dissolved, avoiding too high a temperature at first. afterwards continue the heat till the separated sulphur runs into globules, and the bulk of the acid has been reduced to or c.c. dilute with or c.c. of water; put in a piece of litmus paper; and add dilute ammonia until just alkaline. then add c.c. of the sodium acetate and acetic acid solution (which should make the solution distinctly acid); dilute to c.c., and heat to boiling. the solution is ready for titrating. when the arsenic exists in a nitric acid solution mixed with much copper, it is separated in the way described under _examination of commercial copper_ (arsenic and phosphorus), pages , . if the arsenic has been separated as ammonium-magnesium arsenate, and phosphates are known to be absent; dissolve the precipitate (after filtering, but without washing) in dilute hydrochloric acid. add dilute ammonia till a slight precipitate is formed, and then c.c. of the sodium acetate and acetic acid solution; dilute to c.c., and heat to boiling. titrate. if phosphates are present (which will always be the case if they were present in the original substance, and no separation with sulphuretted hydrogen has been made), the phosphorus will count in the subsequent titration as arsenic (one part of phosphorus counting as . parts of arsenic). it will be necessary to dissolve the mixed arsenate and phosphate of magnesia in hydrochloric acid. add about four or five times as much iron (as ferric chloride) as the combined phosphorus and arsenic present will unite with, and separate by the "basic acetate" process as described under phosphorus in the _examination of commercial copper_, page . obviously, when phosphates are present, it is easier to separate the arsenic as sulphide than to precipitate it with the "magnesia mixture." ~the titration.~--the _standard solution of uranium acetate_ is made by dissolving . grams of the salt (with the help of c.c. of acetic acid) in water; and diluting to litre. the water and acid are added a little at a time, and warmed till solution is effected; then cooled, and diluted to the required volume: c.c. will equal . gram of arsenic. the _sodic acetate and acetic acid solution_ is made by dissolving grams of sodic acetate in c.c. of acetic acid, and diluting with water to litre. five c.c. are used for each assay. the solution of potassic ferrocyanide used as _indicator_ is made by dissolving grams of the salt in c.c. of water. to standardise the solution of uranium acetate, weigh up a quantity of white arsenic (as_{ }o_{ }) which shall be about equivalent to the arsenic contained in the assay ( . or . gram); transfer to a flask, and dissolve in c.c. of nitric acid with the aid of heat. evaporate to a small bulk (taking care to avoid the presence of hydrochloric acid); dilute with water; add a small piece of litmus paper; render faintly alkaline with ammonia; then add c.c. of the sodic acetate mixture; dilute to c.c.; and heat to boiling. fill an ordinary burette with the uranium acetate solution, and run into the assay a quantity known to be insufficient. again heat for a minute or two. arrange a series of drops of the solution of ferrocyanide of potassium on a porcelain slab, and, with the help of a glass rod, bring a drop of the assay solution in contact with one of these. if no colour is produced, run in the uranium acetate, c.c. at a time, testing after each addition, till a brown colour is developed. it is best to overdo the assay, and to count back. it is not necessary to filter off a portion of the assay before testing with the "ferrocyanide," since the precipitate (uranic arsenate) has no effect. the following experiments show the effect of variation in the conditions of titration. make a solution of arsenic acid by dissolving . grams of arsenious acid (as_{ }o_{ }) in a covered beaker with c.c. of nitric acid; evaporate down to or c.c.; and dilute with water to litre: c.c. will contain . gram of arsenic. use c.c. for each experiment. ~effect of varying temperature.~--it is generally recommended to titrate the boiling solution, since it is possible that the precipitation is only complete on boiling. low results are obtained in a cold solution, the apparent excess of uranium acetate striking a colour at once; on boiling, however, it ceases to do so; consequently, the solution should always be boiled directly before testing. in four experiments made in the way described, but with c.c. of a solution of arsenic acid stronger than that given ( c.c. = . gram as), the results at varying temperatures were:-- temperature ° c. ° c. ° c. ° c. "uranium" required . c.c. . c.c. . c.c. . c.c. ~effect of varying bulk.~--these experiments were like those last mentioned, but were titrated boiling, and the volume was varied:-- bulk . c.c. . c.c. . c.c. . c.c. "uranium" required . " . " . " . " considerable variations in bulk are to be avoided. ~effect of varying sodium acetate.~--these experiments were carried out like those last noticed, but the bulk was c.c., and varying amounts of sodic acetate were added in excess of the quantity used in the experiments previously described:-- sodic acetate added gram gram grams grams "uranium" required . c.c. . c.c. . c.c. . c.c. it is evidently important that the quantity of this salt present in each titration be measured out, so as to avoid variation. ~effect of varying the sodium acetate and acetic acid solution.~--acetic acid also affects the results, but in the opposite direction, by preventing the precipitation of uranium arsenate. with varying volumes of the solution now under notice, the results were:-- solution added . c.c. . c.c. . c.c. . c.c. "uranium" required . " . " . " . " solution added . " . " . " . " "uranium" required . " . " . " . " these show that the quantity ordered ( c.c.) must be adhered to. ~effect of foreign salts.~--in these experiments, grams of the salt (the effect of which it was desired to determine) were added to a solution in other respects resembling those previously used:-- salt added {ammonic ammonic ammonic magnesium {sulphate nitrate chloride sulphate "uranium" required . c.c. . c.c. . c.c. . c.c. without any addition, . c.c. were required; and in another experiment, in which grams of ammonic salts were present, . c.c. of uranium solution were required. such variations in the amount of ammonic salts as occur in ordinary working are unimportant. phosphates, of course, interfere. in fact, the uranium acetate solution can be standardised by titrating with a known weight of phosphate, and calculating its equivalent of arsenic. thus, in an experiment with . gram of hydric sodic phosphate (na_{ }hpo_{ }. h_{ }o), equivalent to . gram of phosphorus, or . gram of arsenic, . c.c. of a solution of uranium acetate were required. the same solution standardised with white arsenic gave a standard of which c.c. = . gram arsenic. on this standard the . gram of sodic phosphate should have required . c.c. experiments in which . gram of bismuth and . gram of antimony were present with . gram of arsenic, showed no interference on the titration. ferric or aluminic salts would remove their equivalent of arsenic, and, consequently, must be removed before titrating. ~effect of varying arsenic.~--varying amounts of metallic arsenic were weighed up and dissolved in nitric acid, &c., and titrated:-- arsenic taken . gram . gram . gram . gram arsenic found . " . " . " . " these experiments show that the method yields good results within these limits. ~determination of arsenic in mispickel.~--weigh up gram of the dried and powdered ore, and evaporate to near dryness with c.c. of dilute nitric acid. make up to c.c. with water, and pass sulphuretted hydrogen to reduce the ferric iron to the ferrous state, then add c.c. of dilute ammonia, and again pass sulphuretted hydrogen. warm, filter, and evaporate the filtrate to drive off the excess of ammonia; then add c.c. of nitric acid, and boil down till the sulphide of arsenic at first precipitated is dissolved; neutralise; add c.c. of sodium acetate and acetic acid solution; transfer to a pint flask, boil, and titrate. for example, an impure sample of ore required, in duplicate assay of half a gram each, when treated in the above-mentioned way, . and . c.c. of the uranium acetate solution ( c.c. = . gram of arsenic), equivalent to . gram of arsenic, or . per cent. an alternative method is as follows. powder the ore very finely and weigh up . gram. place in a - / inch berlin dish and add strong nitric acid, one drop at a time until the action ceases; with care there need be no very violent reaction. dry over a water bath. cover with grams of nitre and over this spread grams of a mixture of equal parts of nitre and carbonate of soda. fuse in a muffle or over a large gentle blow-pipe flame for or minutes. this will spoil the dish. allow to cool and boil out in a larger dish with c.c. of water. filter and wash into an oz. flask. acidify the liquor with nitric and boil down to about c.c. the acid should not be in too large excess, but an excess is needed to destroy nitrites. neutralise with soda or ammonia. add c.c. of the mixture of sodium acetate and acetic acid. titrate with uranium acetate. ~determination of arsenic (as) in crude arsenic.~--the method given under the iodine titration simply determines that portion of the arsenic which is present in the substance as arsenious oxide or white arsenic. the following method will give the total arsenic in the sample. it would be incorrect to report this as so much per cent. of arsenious oxide, although it may be reported as so much per cent. of arsenic equivalent to so much per cent. of white arsenic, thus:-- arsenic . per cent. equivalent to white arsenic . " the equivalent of white arsenic is calculated by multiplying the percentage of arsenic by . . the method of determining the percentage of arsenic is as follows:---boil gram of the sample with c.c. of nitric acid. when the bulk of the solution has been reduced to one-half, and red fumes are no longer evolved, dilute with a little water, and filter into a flask. neutralise the filtrate, add c.c. of sodic acetate solution, boil and filter. the precipitate (ferric arsenate) is transferred to a small beaker, treated with c.c. of dilute ammonia, and sulphuretted hydrogen passed through it. the iron sulphide is filtered off, and the filtrate evaporated with an excess of nitric acid. when the solution is clear, it is neutralised, and or c.c. of sodic acetate solution having been added, is then mixed with the first filtrate. the solution is boiled and titrated. a sample treated in this way required . c.c. of the uranium acetate solution ( c.c. = . gram of arsenic), equivalent to . per cent. ~determination of arsenic in brimstone.~--take grams of the substance, and powder in a mortar; rub up with c.c. of dilute ammonia and a little water; rinse into a pint flask; pass a current of sulphuretted hydrogen; and warm on a hot plate for a few minutes. filter, acidulate the filtrate with sulphuric acid; filter off the precipitate; attack it with c.c. of nitric acid; and proceed as in the other determinations. practical exercises. . mispickel contains . per cent. of arsenic, to how much white arsenic will this be equivalent? . how would you make a standard solution of iodine so that c.c. shall be equivalent to gram of white arsenic? . what weight of arsenic is contained in gram of pyrarsenate of magnesia, and what weight of ammonic-magnesic arsenate would it be equivalent to? . the residue, after heating grams of crude arsenic, weighed . gram. what information does this give as to the composition of the substance? if another grams of the substance, heated on a water-bath, lost . gram, what conclusions would you draw, and how would you report your results? . if a sample of copper contained . per cent. of arsenic, and gram of it were taken for an assay, how much standard uranium acetate solution would be required in the titration? phosphorus and phosphates. phosphorus rarely occurs among minerals except in its highest oxidized state, phosphoric oxide (p_{ }o_{ }), in which it occurs abundantly as "rock phosphate," a variety of apatite which is mainly phosphate of lime. phosphates of most of the metallic oxides are found. phosphoric oxide in small quantities is widely diffused, and is a constituent of most rocks. its presence in varying amounts in iron ores is a matter of importance, since it affects the quality of the iron obtainable from them. phosphorus occurs in alloys in the unoxidized state. it is directly combined with the metal, forming a phosphide. in this manner it occurs in meteoric iron. the alloy phosphor-bronze is made up of copper, tin, zinc, and phosphorus. phosphates are mined in large quantities for the use of manure manufacturers, and for making phosphorus. phosphorus and arsenic closely resemble each other in their chemical properties, more especially those which the assayer makes use of for their determination. phosphorus forms several series of salts; but the phosphates are the only ones which need be considered. pyrophosphate of magnesia, which is the form in which phosphoric oxide is generally weighed, differs from the ordinary phosphate in the proportion of base to acid. metaphosphates differ in the same way. if these are present, it must be remembered they act differently with some reagents from the ordinary phosphates, which are called orthophosphates. they are, however, all convertible into orthophosphates by some means which will remove their base, such as fusion with alkaline carbonates, boiling with strong acids, &c.[ ] phosphides are converted into phosphates by the action of nitric acid or other oxidizing agents. dilute acids, when they act on the substance, evolve phosphuretted hydrogen (ph_{ }). the student should be on his guard against losing phosphorus in this manner. there is no dry assay for phosphorus. all assays for it are made either gravimetrically or volumetrically. the separation of phosphoric oxide is made as follows:--the ore or metal is dissolved in acid and evaporated, to render the silica insoluble. it is taken up with hydrochloric acid, diluted with water, and treated with sulphuretted hydrogen. the filtrate is boiled, to get rid of the excess of gas, and treated with nitric acid, to peroxidize the iron present. if the iron is not present in more than sufficient quantity to form ferric phosphate with all the phosphorus present, some ferric chloride is added. the iron is then separated as basic acetate. the precipitate will contain the phosphorus, together with any arsenic acid not reduced by the sulphuretted hydrogen. the precipitate should have a decided brown colour. the precipitate is washed, transferred to a flask, and treated first with ammonia, and then with a current of sulphuretted hydrogen. the filtrate from this (acidulated with hydrochloric acid, and, if necessary, filtered) contains the phosphorus as phosphoric acid. this method is not applicable in the presence of alumina, chromium, titanium, or tin, if the solution is effected with nitric acid. the precipitate obtained by the action of nitric acid on tin retains any phosphoric or arsenic oxide that may be present. a method of separation more generally applicable and more convenient to work is based on the precipitation of a yellow phospho-molybdate of ammonia,[ ] by the action of an excess of ammonic molybdate upon a solution of a phosphate in nitric acid. dissolve the substance by treatment with acid, and evaporate to dryness. take up with c.c. of nitric acid, and add grams of ammonic nitrate, together with a little water. next put in the solution of ammonium molybdate solution in the proportion of about c.c. for each . gram of phosphoric oxide judged to be present. warm to about ° c., and allow to stand for an hour. filter, and wash with a per cent. solution of ammonic nitrate. it is not necessary that the whole of the precipitate be placed on the filter; but the beaker must be completely cleaned. dissolve the precipitate off the filter with dilute ammonia, and run the solution into the original beaker. run in from a burette, slowly and with stirring, "magnesia mixture," using about c.c. for each . gram of phosphoric oxide. allow to stand for one hour. the white crystalline precipitate contains the phosphorus as ammonium-magnesium phosphate. phosphate of lead is decomposed by sulphuric acid; the lead is converted into the insoluble lead sulphate, and the phosphoric acid is dissolved. phosphate of copper and phosphate of iron may be treated with sulphuretted hydrogen; the former in an acid, and the latter in an alkaline, solution. phosphate of alumina is generally weighed without separation of the alumina, since this requires a fusion. in all cases the aim is to get the phosphoric oxide either free, or combined with some metal whose phosphate is soluble in ammonia. joulie's method of separation is as follows:--one to ten grams of the sample are treated with hydrochloric acid, and evaporated to dryness with the addition (if any pyrites is present) of a little nitric acid. the residue is taken up with hydrochloric acid, cooled, transferred to a graduated flask, and diluted to the mark. it is then shaken up, filtered through a dry filter, and a measured portion (containing about . gram of phosphoric acid) transferred to a small beaker. ten c.c. of a citric-acid solution of magnesia[ ] is added, and then an excess of ammonia. if an immediate precipitate is formed, a fresh portion must be measured out and treated with c.c. of the citrate of magnesia solution and with ammonia as before. the beaker is put aside for from two to twelve hours. the precipitate is then filtered off and washed with weak ammonia; it contains the phosphorus as ammonium-magnesium phosphate. gravimetric determination. if the phosphate is not already in the form of ammonic-magnesic phosphate, it is converted into this by the addition to its solution of an excess of ammonia and "magnesia mixture." in order to get the precipitate pure, the "magnesia mixture" is run in gradually (by drops) from a burette, with constant stirring. a white crystalline precipitate at once falls, if much phosphorus is present; but, if there is only a small quantity, it may be an hour or two before it shows itself. the solution is best allowed to rest for twelve or fifteen hours (overnight) before filtering. the presence of tartaric acid should be avoided; and the appearance of the precipitate should be crystalline. the solution is decanted through a filter, and the precipitate washed with dilute ammonia, using as little as may be necessary. the precipitate is dried, transferred to a weighed berlin or platinum crucible; the filter-paper is carefully burnt, and its ash added to the precipitate, which is then ignited, at first gently over a bunsen burner, and then more strongly over the blowpipe or in the muffle. the residue is a white mass of magnesium pyrophosphate containing . per cent. of phosphorus, or . per cent. of phosphoric oxide. volumetric method. instead of separating and weighing this compound, the phosphoric oxide in it can be determined by titration. in many cases the ore may be dissolved and immediately titrated without previous separation. it is better, however, to carry the separation so far as to get phosphoric acid, an alkaline phosphate, or the magnesia precipitate. it may then be prepared for titration in the following way:--the precipitate in the last case (without much washing) is dissolved in a little hydrochloric acid, and the solution in any case rendered fairly acid. dilute ammonia is added till it is just alkaline, and then c.c. of the sodic acetate and acetic acid mixture (as described under the arsenic assay). this should yield a clear distinctly-acid solution. it is diluted to or c.c., heated to boiling, and titrated with the uranium acetate solution, using that of potassic ferrocyanide as indicator. the _standard solution_ required is made by dissolving grams of uranium acetate in water with the aid of c.c. of acetic acid, and diluting to litre. an _equivalent solution of phosphoric oxide_ is made by dissolving . grams of crystallised hydric disodic phosphate (hna_{ }po_{ }. h_{ }o) in water, and making up to litre. c.c. will contain . gram of phosphoric oxide (p_{ }o_{ }), or . gram of phosphorus. in making this solution, transparent crystals only must be used. the uranium acetate solution is only approximately equivalent to this, so that its exact standard must be determined. _sodic acetate and acetic acid solution._--it is the same as that described under _arsenic_.[ ] use c.c. for each assay. the following experiments show the effect of variation in the conditions of the titration:-- ~effect of varying temperature.~--the solution should be titrated while boiling. this is especially necessary for the last few c.c. in order to get a decided and fixed finishing point. temperature ° c. ° c. ° c. ° c. "uranium" required . c.c. . c.c. . c.c. . c.c. ~effect of varying bulk.~-- bulk . c.c. . c.c. . c.c. . c.c. "uranium" required . " . " . " . " variation in bulk affects the results; therefore, a constant bulk should be adhered to. ~effect of varying sodium acetate and acetic acid solution.~-- sodium acetate and acetic acid solution . c.c. . c.c. . c.c. . c.c. . c.c. "uranium" required . " . " . " . " . " as in the titration with arsenates, an excess is dangerous to the assay; a definite quantity ( c.c.) should, therefore, be used. ~effect of foreign salts.~--besides the sodium acetate, &c., added, the only salts likely to be present are those of ammonia and magnesia. in three experiments, in one of which no foreign salts were introduced, while in the other two grams of ammonic chloride and of magnesium sulphate respectively were added, there were required:-- with ammonic chloride . c.c. "uranium" solution with magnesium sulphate . " " without foreign salts . " " ~effect of varying phosphate.~-- "phosphate" solution added . c.c. . c.c. . c.c. . c.c. "uranium" required . " . " . " . " the quantity of phosphoric oxide in the assay solution for the conditions of titration should not be much less than . gram. for smaller quantities the uranium solution should be diluted to half its strength, and the assay solution concentrated by reducing its bulk to c.c. and using . c.c. of the sodium acetate and acetic acid solution. ~determination of phosphoric oxide in apatite.~--weigh up . gram of the dried and powdered sample, and dissolve it in c.c. of hydrochloric acid. evaporate to a paste, add c.c. of the sodic acetate and acetic acid solution, dilute to c.c. with water, boil, and titrate with uranium acetate solution. in an example, . gram of apatite required . c.c. of uranium acetate solution (standard equal to . gram of phosphoric oxide). the sample therefore contained . gram of p_{ }o_{ }, equal to . per cent. ~determination of phosphoric oxide in an iron ore.~--take grams, boil with c.c. of hydrochloric acid, and evaporate to a paste; take up with c.c. of dilute hydrochloric acid, and dilute with water to c.c. pass sulphuretted hydrogen for nearly a quarter of an hour; warm, and filter. boil off the excess of gas; cool, add ammonia till nearly neutral, and then a few drops of ferric chloride solution, and or grams of sodium acetate, with a drop or two of acetic acid. boil and filter. dissolve the precipitate in hot dilute hydrochloric acid, and add citro-magnesia mixture and ammonia; allow to stand overnight; filter, ignite, and weigh. in an example, grams of ore gave . milligrams of magnesic pyrophosphate, which is equivalent to . per cent. of phosphoric oxide. ~determination of phosphorus in iron.~--take from to grams (according to the amount of phosphorus present), and dissolve in aqua regia, keeping the nitric acid in excess; evaporate to dryness and take up with hydrochloric acid, boil, dilute, and filter. add c.c. of nitric acid, nearly neutralise with ammonia, render acid with or c.c. of nitric acid, and add or c.c. of ammonic molybdate solution. heat for some time, allow to settle, filter, and wash the precipitate with a solution of ammonic nitrate. dissolve the precipitate in dilute ammonia, nearly neutralise with dilute hydrochloric acid, and add first "magnesia mixture," and then ammonia; allow to stand overnight; filter, wash with dilute ammonia, dry, ignite, and weigh as magnesic pyrophosphate. calculate to phosphorus. practical exercises. . ten grams of an iron yielded milligrams of pyrophosphate of magnesia. what percentage of phosphorus did the metal contain? . ten grams of an iron ore gave milligrams of pyrophosphate. what percentage of phosphoric oxide did it contain? . what weight of apatite ca_{ }(po_{ })_{ }.caclf would require c.c. of standard uranium solution ( c.c. equal to . gram of p_{ }o_{ })? . you have reason to believe that a precipitate which has been weighed as magnetic pyrophosphate contains some arsenate. how would you determine the amount of phosphate really present? . twenty c.c. of a solution of sodic phosphate containing . gram of p_{ }o_{ } was found to require a solution containing . gram of hydrated uranium acetate in a titration. the precipitate contains . per cent. uranium oxide and . per cent. of phosphoric oxide. what percentage of uranium oxide was contained in the uranic acetate? nitrogen and nitrates. nitrogen occurs in nature in the free state, and forms about four-fifths of the atmosphere. in combination, as nitrate, it is found in nitre (kno_{ }), and chili saltpetre (nano_{ }), minerals which have a commercial importance. the latter occurs in beds, and is extensively worked for use as a manure and in the preparation of nitric acid. nitrogen is mainly characterised by negative properties, although many of its compounds are very energetic bodies. it is a gas, present everywhere, but so inactive that the assayer can always afford to ignore its presence, and, except in testing furnace gases, &c., he is never called on to determine its quantity. the nitrates are an important class of salts, and may be looked on as compounds of the bases with nitric pentoxide (n_{ }o_{ }). they are, with the exception of a few basic compounds, soluble in water, and are remarkable for the ease with which they give up their oxygen. the alkaline nitrates fuse readily, and lose oxygen with effervescence forming nitrites; while at a higher temperature they yield more oxygen and lose their nitrogen, either as a lower oxide or as nitrogen. the nitrates of the metals, on heating, leave the oxide of the metal. it is as yielders of oxygen that nitrates are so largely used in the manufacture of explosives. gunpowder contains from to per cent. of potassium nitrate (nitre). nitrates are best detected and determined by their yielding nitric oxide when treated with sulphuric acid and a suitable reducing agent, such as ferrous sulphate, mercury, or copper. nitric oxide is a colourless gas very slightly soluble in water. it combines at once with oxygen, on mixing with the air, to form brown "nitrous fumes," and dissolves in a solution of ferrous sulphate, producing a characteristic blackish-brown colour. it is this colour which affords the best and most easily-applied test for nitrates. the substance suspected to contain nitrates is dissolved in about c.c. of water, and treated with an equal volume of strong sulphuric acid. after cooling, a solution of ferrous sulphate is poured on its surface, so as to form a layer resting on it. on standing, a brown or black ring is developed where the liquids join, if any nitrate or nitrite is present. nitrites are distinguished from nitrates by effervescing and yielding brown fumes when treated with a little dilute sulphuric acid. the separation of nitrates is in many cases difficult. generally, on treating the substance with water, the nitrate will be in the solution, and is filtered off from any insoluble matter. in the exceptional cases it is got into solution by treating with a boiling solution of sodium carbonate; the nitrate will contain it as an alkaline nitrate. since, however, in their determination, nitrates are never separated and weighed as such, the difficulty of separating them has little importance. usually, the determination can be made on the original aqueous solution, and it is never necessary to do more than remove any special substance which has a bad effect; and this is easily done by the usual reagents. gravimetric determination. it follows from what has been said that there is no direct gravimetric determination. the percentage of nitrogen pentoxide (n_{ }o_{ }) in a comparatively pure nitrate is sometimes determined indirectly in the following way:--place in a platinum-crucible or grams of powdered and cleaned quartz. ignite, cool in a desiccator, and weigh with the cover. mix gram of the dried and powdered salt with the quartz in the crucible by stirring with a stout platinum-wire. cover the crucible, and heat in a bunsen-burner flame at scarcely visible redness for half-an-hour. cool and weigh. the loss in weight gives the amount of nitrogen pentoxide. sulphates and chlorides in moderate quantity do not interfere. the following is an example of the process:-- crucible and sand . grams nitre taken . " ------- . " weight after ignition . " ------- loss on ignition . " this is equal to . per cent. of nitrogen pentoxide. volumetric determination. this is based on the oxidising action of nitric acid, or of nitrates in acid solutions on ferrous salts. the pentoxide (n_{ }o_{ }) of the nitrate is reduced to nitric oxide (no), so that parts of iron peroxidised represent parts of nitric pentoxide as oxidising agent.[ ] the quantity of iron peroxidised is determined by taking a known quantity of ferrous salt, oxidizing with a weighed sample of nitrate, and then determining the residual ferrous iron by titration with bichromate or permanganate of potassium solution. the difference between the ferrous iron taken and that found, gives the amount oxidized by the nitrate. the speed with which nitric oxide takes up oxygen from the air, and thus becomes capable of oxidising more iron, renders some precautions necessary; ferrous chloride should, therefore, be used, since it is easier to expel nitric oxide (by boiling) from solutions of a chloride than it is from those of a sulphate. the process is as follows:--dissolve grams of thin soft iron wire in c.c. of hydrochloric acid in a flask provided with an arrangement for maintaining an atmosphere of carbon dioxide. when the iron has dissolved, allow the solution to cool, and add . gram of the nitrate. heat gently for a few minutes, and then boil until the nitric oxide is expelled. an atmosphere of carbon dioxide must be kept up. dilute with water, and titrate the residual iron with standard solution of bichromate of potassium. the standard "bichromate" is made by dissolving . grams of the salt (k_{ }cr_{ }o_{ }) in water, and diluting to litre: c.c. equal grams of iron. deduct the weight of iron found from the grams originally taken, and multiply by . . this gives the weight of the pentoxide in the sample. in an example, . gram of nitre was taken, and . c.c. of the "bichromate" solution were required. the . c.c. thus used are equivalent to . gram of iron. this leaves . gram as the quantity oxidised by the nitre, which, multiplied by . , gives . gram for the nitrogen pentoxide, or . per cent. gasometric method. this is based upon the measurement of the nitric oxide evolved on shaking up a weighed quantity of the nitrate with sulphuric acid over mercury in a nitrometer. each c.c. of nitric oxide obtained, when reduced to normal temperature and pressure, is equivalent to:-- . milligram of nitrogen. . " of nitric oxide. . " of nitric pentoxide. . " of nitric acid. . " of sodium nitrate. . " of potassium nitrate. in working on substances not rich in nitrates, an ordinary nitrometer (fig. ) is used; but in the assay of sodium nitrate, nitroglycerine, &c., an instrument provided with a bulb having a capacity of c.c. is employed. [illustration: fig. .] the plan of working is as follows:--the "measuring tube" is filled with mercury until it reaches up into the tap, and the levelling-tube is placed so that it contains an inch or two of mercury. if the nitrate is in solution, or c.c. of the liquid (dilute liquids are brought to this bulk by evaporation) are measured into the cup. the levelling-tube is lowered a little, and the tap cautiously opened until all but the last drop of the liquid has run in. the cup is then rinsed with or c.c. of sulphuric acid, which is run in in the same way, and the operation is repeated with another lot of acid. the measuring-tube is now taken from the clamp, and shaken for two or three minutes, until no more gas is given off. it is replaced, and the mercury-level in the two tubes adjusted. then it is allowed to stand until the froth has subsided, and the gas has cooled to the temperature of the room. the volume of the gas is then read off. in adjusting the level, account must be taken of the sulphuric acid in the measuring-tube; this is allowed for by having the mercury higher in the other tube by, say, mm. for each . mm. of sulphuric acid, or it is counterpoised by an equal height of sulphuric acid in the levelling-tube, in which case the two mercury-levels are made to correspond. on opening the tap after reading off the volume, there should be no change in the level of the mercury. if it should rise or fall a little, a slight increase or decrease (say . c.c.) is made to the volume previously read off. in working with nitrate of soda, &c., in the bulb nitrometer, it is necessary to take a quantity of the substance which will yield more than and less than c.c. of the gas. footnotes: [ ] na_{ }aso_{ } + h_{ }o + i = na_{ }aso_{ } + hi. the acid is at once neutralised. [ ] mr. thomas gibb is the originator of this ingenious process. [ ] by taking hold of the water present, it may prevent the dissociation of arsenious chloride. [ ] it is difficult to get ferric chloride free from arsenic; but the following treatment will remove or per cent. of the arsenic contained in the commercial material:--dissolve or lbs. of ferric chloride with the smallest amount of water that will effect solution with the addition of c.c. of hydrochloric acid; add a solution of sulphurous acid in quantity sufficient to reduce or per cent. of the iron to the ferrous state; allow to stand a week; and then boil, to remove the hydrochloric acid added. nitric acid, which is prejudicial, is also removed by this treatment. [ ] when the amount of arsenic to be estimated is small (as in refined coppers), it is better to use a weaker solution of iodine. this is made by diluting c.c. of the standard solution with water to litre. each c.c. will equal . per cent., if gram of the metal has been taken for the assay. [ ] the constitution of these phosphates may be thus illustrated-- magnesic meta-phosphate mgo.p_{ }o_{ }. magnesic pyro-phosphate mgo.p_{ }o_{ }. magnesic ortho-phosphate mgo.p_{ }o_{ }. [ ] the composition of which is-- moo_{ } . , p_{ }o_{ } . , (nh_{ })_{ }o . , h_{ }o . = . . [ ] this is made by adding grams of magnesium carbonate (a little at a time) to a solution of grams of citric acid in c.c. of warm water; and, when dissolved, adding c.c. of dilute ammonia, and making up the bulk to litre; c.c. of the solution is sufficient for . gram of p_{ }o_{ }, although more will be required if much iron or alumina is present. [ ] for the details of the titration, the student is referred to the same place. [ ] n_{ }o_{ } + feo = fe_{ }o_{ } + no. chapter xviii. silicon, carbon, boron. silicon and silicates. in assaying, more especially products direct from the mine, there is always found, when the rock is siliceous, a quantity of white sandy-looking substance, insoluble in acids, which is sometimes accompanied by a light gelatinous material very difficult to filter. this is variously described as "insoluble," "sand," "insoluble silicates," "gangue," or "rocky matter." it may be pure quartz; but oftener it is mixed with silicates from the rock containing the mineral. some silicates, but not many, are completely decomposed by boiling with hydrochloric acid or aqua regia; and others are partly so, they yield a gelatinous precipitate of silica which greatly interferes with the filtering. it is a common practice with assayers to carry the first attack of the sample with acids to dryness, and to take up with a fresh portion of acid. by this means the separated silica becomes granular and insoluble, and capable of being filtered off and washed with comparative ease. this residue may be ignited and weighed; and be reported as so much per cent. of "silica and silicates insoluble in acids." unless specially wanted, a determination of its constituents need not be made. when required, the analysis is best made on the ignited residue, and separately reported as "analysis of the insoluble portion." silicon only occurs in nature in the oxidised state; but the oxide generally known as silica (sio_{ }) is common, being represented by the abundant minerals--quartz, flint, &c. silica, combined with alumina, lime, oxide of iron, magnesia and the alkalies, forms a large number of rock-forming minerals. most rock masses, other than limestones, contain over per cent. of silica. the following are analyses of some of the commoner silicates; but it must be noted that these minerals often show great variation in composition. this is more especially true of chlorite, schorl, hornblende and augite. [table has been split into two because of its width--transcriber] ------------------+--------+------------+------------+-------+---------------- | | | ferric |ferrous| | silica | alumina | oxide, | oxide,| fluorine, |sio_{ }.|al_{ }o_{ }.|fe_{ }o_{ }.| feo. | water &c. ------------------+--------+------------+------------+-------+---------------- potash-felspar | . | . | . | -- | soda-felspar | . | . | -- | . | lime-felspar | . | . | -- | . | potash-mica | . | . | . | -- |f ( . ) | | | | | h_{ }o ( . ) magnesia-mica | . | . | . | -- |f ( . ) hornblende | . | . | . | . | augite | . | . | . | . |mno ( . ) almandine (garnet)| . | . | -- | . |mno ( . ) chlorite (peach) | . | . | -- | -- |h_{ }o ( . ) schorl | . | . | . | . |b_{ }o_{ } ( . ) | | | | | f ( . ) china-clay | . | . | -- | -- |h_{ }o ( . ) talc | . | -- | -- | . |h_{ }o ( . ) serpentine | . | -- | -- | . |h_{ }o ( . ) olivine | . | -- | -- | . | ------------------+--------+------------+------------+-------+---------------- ------------------+-----+--------+-------+--------+------------------------ | | | | | |lime,|magnesia|potash | soda, | fluorine, |cao. | mgo. |k_{ }o.|na_{ }o.| water, &c. ------------------+-----+--------+-------+--------+------------------------ potash-felspar | -- | -- | . | . | soda-felspar | . | . | . | . | lime-felspar | . | . | . | . | potash-mica | -- | . | . | . |f ( . ) h_{ }o ( . ) | | | | | magnesia-mica | -- | . | . | . |f ( . ) hornblende | . | . | . | . | augite | . | . | -- | -- |mno ( . ) almandine (garnet)| -- | -- | -- | -- |mno ( . ) chlorite (peach) | -- | . | -- | -- |h_{ }o ( . ) schorl | . | . | . | . |b_{ }o_{ } ( . ) f ( . ) | | | | | china-clay | -- | -- | -- | -- |h_{ }o ( . ) talc | -- | . | -- | -- |h_{ }o ( . ) serpentine | -- | . | -- | -- |h_{ }o ( . ) olivine | -- | . | -- | -- | ------------------+-----+--------+-------+--------+------------------------ silicon, from a chemical point of view, is an interesting body. it combines with iron to form a silicide; and is present in this condition in cast iron. only in the case of the analysis of this and similar substances is the assayer called on to report the percentage of _silicon_. silicon is readily converted into silica by the action of oxidizing agents. silica forms only one series of salts--the silicates--which have in many cases a complex constitution; thus there are a large number of double silicates, which vary among themselves, not only in the relation of base to acid (which is the essential difference), but also in the ratio of the bases between themselves (which varies with almost every specimen). silica is detected by heating the substance with a fluoride and sulphuric acid in a platinum-crucible. on holding a rod, moistened with a drop of water, over the escaping fumes, the white crust of silica formed on the drop of water shows its presence. the insolubility of a fragment of the mineral in a bead of microcosmic salt, is also a very good test; the fragment, on prolonged heating, does not lose its angular form. there is no dry assay for this substance, nor volumetric method; when the determination is required, it is carried out gravimetrically and, generally, by the following plan. if the sample contains oxides, sulphides, &c., in any quantity, these are first dissolved out by treatment with acid, evaporated to dryness, taken up with hydrochloric acid, and filtered. the dried residue is treated in the same way as the silicates. some silicates are completely decomposed by such treatment; but it saves time (unless one is sure that no undecomposable silicate is present) to treat these in the same way as the others. on the other hand, there are some silicates which are only attacked with difficulty even by fusion with alkaline carbonates; consequently, it is always well to have the substance reduced to the finest state of division by careful powdering, as this greatly assists the subsequent action. with very hard silicates, the grinding away of the mortar in this operation will be perceptible; the foreign matter thus introduced must not be ignored. previously igniting the substance sometimes assists the powdering; but it is best to use a steel mortar. the particles of steel can be removed by a magnet, or, where the nature of the substance will allow it, by boiling with a little dilute hydrochloric acid. the dried and powdered material is intimately mixed with four times its weight of "fusion mixture" in a platinum-crucible or dish. it is then moderately heated over a bunsen burner, and afterwards more strongly fused over a blast, or enclosed in a clay crucible in the wind-furnace. the action is continued until the fused mass is perfectly tranquil. with very refractory substances, the action must be long continued at a high temperature. when sufficiently cold, the crucible is examined to see that no particles of foreign matter are adhering to its outer surface. it is then transferred to a five- or six-inch evaporating-dish, where its contents are acted upon with warm water for some time. the "melt" will slowly dissolve, but the solution should be hastened by keeping the liquid moderately acid with hydrochloric acid. when the "melt" has dissolved, clean and remove the platinum-dish, and evaporate the solution to a paste. continue the evaporation to dryness on a water-bath (not on the hot plate), and whilst drying stir with a glass rod, feeling at the bottom of the dish for any unfused particles, which, if present, can be detected by their grittiness. if there is much grit, it will be necessary to repeat the assay; but with a small quantity it will only be necessary to refuse the grit and silica after ignition. during solution of the "melt" and evaporation (which may be carried on together), a clear solution will not be obtained, a flocculent silica will separate out, and towards the end of the evaporation the mass will get gelatinous. the drying of the jelly must be finished on the water-bath; first, because at this temperature the silica is rendered insoluble in hydrochloric acid, whilst the solubility of the alumina, iron, &c., is unaffected, which would not be the case at a much higher temperature; and second, because the gelatinous residue requires very cautious drying to prevent loss from spirting. when dry, the substance is moistened, and heated with strong hydrochloric acid, and the sides of the dish are washed down with water. the silica is washed by decantation two or three times with hydrochloric acid and hot water, before being thrown on to the filter. the filtrate is again evaporated to dryness, taken up with a little hydrochloric acid and water and again filtered. the residue on the filter is silica. the two lots of silica are washed free from chlorides with hot water, dried on an air-bath, transferred to a platinum-crucible, ignited gently at first, at last strongly over the blast or in a muffle, cooled in a desiccator, and weighed. the white powdery precipitate is silica (sio_{ }), and its weight, multiplied by , and divided by the weight of ore taken, gives the percentage of silica in the sample. where the percentage of silicon is wanted, which is very rarely the case, it is got by multiplying this result by . . it is always necessary to examine the purity of the body weighed as silica. this is done by re-fusing the material weighed, and re-determining the silica in it; or, better, by mixing a weighed portion in a platinum-dish with a little strong sulphuric acid, covering with hydrofluoric acid, and evaporating. in the latter case, the silica will be converted into fluoride, which will be driven off, and the impurities will be left behind as sulphates of barium, phosphate and oxide of tin, titanium, &c. this must be weighed and deducted from the weight of the silica. in a complete examination of a silicate it should be treated with the precipitate containing alumina, ferric oxide, &c. examination of silicates. the student interested in the analysis of rocks and rock-forming minerals is advised to consult a valuable paper by dr. w.f. hillebrand in the _bulletin of the united states geological survey_, _no._ , to which i am very largely indebted in the revision of the following pages. ~moisture.~--five grams of the powdered sample is dried between watch-glasses in the water-oven for two hours, or till its weight is constant; and the loss is reported as water lost at ° c. the rest of the determinations are made on this dried mineral. ~combined water, &c.~--weigh up gram of the substance, and ignite over the blowpipe for some time in a platinum-crucible, cool in a desiccator, and weigh. record the loss as "loss on ignition," not as "combined water." ~silica.~--the ignition should have been performed in an oxidising atmosphere in a muffle or over a slanting blowpipe flame; this will ensure the oxidation of any pyrites or other sulphide present, which if unoxidised would injure the crucible in the next operation. the ignited residue is mixed with or grams of anhydrous sodium carbonate. this reagent should be the purest obtainable, but its purity should be checked, or rather its impurities should be determined by running a "check" or "blank" assay with grams of it through the stages of the analysis; the impurities will be chiefly silica, alumina and lime, and altogether they ought not to exceed milligram. the crucible with the mixture is heated at first gently over a bunsen and afterwards more strongly in an oxidising atmosphere in a muffle or over the blowpipe. the fused mass is allowed to cool in the crucible, and is then dissolved out in a basin with water and a small excess of hydrochloric acid. after the removal and cleaning of the crucible, the liquor is evaporated almost to dryness. dr. hillebrand advises stopping short of complete dryness. the residue is taken up with a little hydrochloric acid and water and filtered and washed. the liquor, including the washings, is again evaporated and taken up with water and a little acid. usually about per cent. of silica will be thus recovered. it is to be filtered off and washed and added to the main silica. the filtrate is reserved. the silica, thoroughly washed, is dried and ignited at a high temperature for twenty or thirty minutes. it is then weighed in a platinum crucible. after weighing it is treated with hydrofluoric acid and a little sulphuric, carefully evaporated and ignited strongly. the residue, which in extreme cases may amount to or per cent. of the rock, is weighed and deducted from the weight of the impure silica. it is retained in the crucible. ~alumina, &c.~--the filtrate from silica is treated by the basic acetate method. that is, it is first treated by a cautious addition of a solution of soda, almost to the point of producing a precipitate, in order to neutralise the excess of acid; or grams of sodium acetate are added, and the whole boiled for a minute or so. the precipitate is filtered off and washed only slightly. save the filtrate. the precipitate is dissolved in hydrochloric, or, perhaps better, in nitric acid; and is reprecipitated by adding an excess of ammonia and boiling. the precipitate is filtered and washed with water containing per cent. of ammonium nitrate. both filtrates are evaporated separately to a small bulk, a drop or two of ammonia being added to the second towards the finish. they are next filtered into a or -ounce flask through a small filter, the second filtrate coming after, and serving in a manner as wash water for the first[ ]. the two washed alumina precipitates are dried and placed in the platinum crucible containing the residue from silica after treatment with hydrofluoric acid. they are then ignited in an oxidising atmosphere at a high temperature for about minutes. the weight, including that of the residue from the silica, is noted as that of "alumina, &c." the weighed oxides are next fused with bisulphate of potash for some hours. the bisulphate should have been first fused, apart, until the effervescence from the escape of steam has stopped. the melt is dissolved out with cold water and dilute sulphuric acid, and any insoluble residue is filtered off, washed, ignited and weighed. the filtrate is reserved for determinations of iron and titanium. the residue, after weighing, may be treated with hydrofluoric and sulphuric acids for any silica,[ ] which would be determined by loss. it may be tested for barium sulphate by treatment with hot strong sulphuric acid; in which this salt dissolves, but is again insoluble (and so comes out as a white precipitate) on diluting with cold water; the acid also must be cold before adding the water. the filtrate containing the iron is reduced with sulphuretted hydrogen, boiled till free from that gas, filtered and titrated with a standard solution of permanganate of potassium. the iron found is calculated to ferric oxide by dividing by . . the iron solution after titration serves for the determination of titanium oxide (tio_{ }). this is done colorimetrically, by adding peroxide of hydrogen free from hydrofluoric acid, and comparing the brown colour produced with that produced by the addition of a standard solution of titanium to an equal volume of water containing sulphuric acid.[ ] the alumina is determined by difference. from the weight of the combined precipitate which has been recorded as "alumina, &c.," deduct ( ) the residue, insoluble, after fusion with bisulphate; ( ) the ferric oxide; ( ) the titanium oxide; and ( ) the phosphoric oxide (p_{ }o_{ }), the amount of which is subsequently determined in a separate portion. this gives the alumina. ~manganous oxide, &c.~--the filtrate from the "alumina, &c." contained in a or -ounce flask, which it nearly fills, is made slightly alkaline with ammonia and treated with a small excess of ammonium sulphide; the flask is then corked and placed on one side for some time (a day or so) so that the manganese sulphide may separate. the precipitate is filtered off and washed with water containing ammonium chloride and a few drops of ammonium sulphide. the filtrate is reserved for lime, &c. the precipitate is digested with sulphuretted hydrogen water, to which one-fifth of its volume of strong hydrochloric acid has been added; this dissolves the sulphides of zinc and manganese; any black residue should be tested for copper and perhaps nickel. the solution is evaporated to dryness, taken up with a little water and treated with a small excess of solution of carbonate of soda. it is boiled and again evaporated, washed out with hot water and filtered on to a small filter, dried, ignited, and weighed as mn_{ }o_{ }. it is calculated to mno. it may contain, and should be tested for oxide of zinc, which, if present, must be deducted. if the dish becomes stained during evaporation, take up with a few drops of hydrochloric and sulphurous acids, evaporate, and then treat with carbonate of soda. ~lime, &c.~--the filtrate from the manganese sulphide is boiled, and without cooling, treated with ammonium oxalate in solution, which also should be heated to boiling. the liquid is filtered off and reserved for magnesia. the precipitate is dissolved in very little hydrochloric acid and reprecipitated by adding ammonium oxalate and ammonia to the boiling solution. the filtrate and washings from this are reserved for magnesia. the precipitate is either dissolved in dilute sulphuric and titrated with permanganate of potash as described under lime (p. ); or it is ignited and weighed as oxide. in this last case it may be examined for barium and strontium, the former of which will rarely be present. ~magnesia.~--the filtrate from the first lime precipitate is treated with sodium phosphate and ammonia, and allowed to stand overnight. it is then filtered. the precipitate is dissolved in hydrochloric acid; the solution is filtered into the beaker containing the solution from the second lime precipitate. ammonia and sodium phosphate are again added, and the precipitate, after standing, is filtered off, washed with water containing ammonia; it is then dried, ignited and weighed as magnesium pyrophosphate. this is calculated into magnesia. ~potash and soda.~--weigh out . gram of the dried ore, and mix with an equal quantity of ammonic chloride; and to the mixture add gradually grams of calcium carbonate ("precipitated"). introduce into a platinum-crucible and cover loosely. heat, at first, gently; and then at a red heat for from forty to sixty minutes. transfer to a porcelain dish, and digest with or c.c. of water; warm and filter: to the filtrate add ammonic carbonate and ammonia, and filter; evaporate the filtrate to dryness, adding a few drops more of ammonic carbonate towards the end; when dry, heat gently, and then raise the temperature to a little below redness. dissolve in a small quantity of water, add a drop of ammonic carbonate, and filter through a small filter into a weighed platinum dish. evaporate, ignite gently, and weigh. the residue contains the soda and potash of the mineral as chlorides. to determine the proportion of potassium, dissolve this residue in a little water, add platinum chloride in excess, evaporate to a paste, extract with alcohol, decant through a small weighed filter, wash with alcohol, and dry at ° c. weigh. the substance is potassium platinic chloride ( kcl.ptcl_{ }). its weight, multiplied by . , will give the weight of potash (k_{ }o). to find the proportion of soda, multiply the weight of the potassium platinic chloride by . ; this gives the weight of potassium chloride. deduct this from the weight of the mixed chlorides first got; the difference will be the sodium chloride, which weight, multiplied by . , will give the weight of soda (na_{ }o). ~ferrous oxide.~--when a qualitative test shows both ferric and ferrous oxide to be present, the proportion of the ferrous oxide must be separately determined. the finely ground mineral mixed with dilute sulphuric acid is treated on a water bath with hydrofluoric acid. solution is best effected in an atmosphere of carbonic acid. in about an hour the decomposition is complete, and the solution is diluted with cold water, and titrated with the solution of bichromate or of permanganate of potassium. the iron found is multiplied by . , and reported as ferrous oxide. to find the proportion of ferric oxide, the ferrous iron found is multiplied by . , and this is deducted from the weight of ferric oxide obtained by precipitation with ammonia. the ammonia precipitate contains the whole of the iron as ferric oxide; hence the necessity for calculating the ferrous oxide as ferric, and deducting it. ~phosphoric oxide (p_{ }o_{ }).~--weigh up grams of the finely-divided and dry sample, and digest with or c.c. of nitric acid; evaporate to dryness on the water-bath; take up with a little dilute nitric acid; dilute with water; and filter. add a few grams of ammonic nitrate and c.c. of ammonium molybdate solution, heat nearly to boiling, and allow to settle; filter off, and wash the yellow precipitate. dissolve with dilute ammonia, add "magnesia mixture," and allow to stand overnight. filter, wash with dilute ammonia, dry, ignite, and weigh as pyrophosphate of magnesia. the weight, multiplied by . , gives the weight of phosphoric oxide. ~soluble silica.~--some silicates are acted on by hydrochloric acid, and leave on evaporation a residue; which, when the soluble salts have been washed out, consists generally of the separated silica with perhaps quartz and unattacked silicates. it should be ignited, weighed and boiled with a solution containing less than per cent. of caustic soda: this dissolves the separated silica. the liquor is diluted, rendered faintly acid, and filtered. the residue is washed, ignited and weighed. the loss gives the soluble silica. ~estimation of silica in slags~ (ferrous silicates).--take gram of the powdered slag, treat with aqua regia, evaporate to dryness, extract with hydrochloric acid, filter, dry, ignite, and fuse the ignited residue with "fusion mixture," then separate and weigh the silica in the usual way. slags are for the most part decomposed by boiling with aqua regia, but it will be found more convenient and accurate to first extract with acids and then to treat the residue as an insoluble silicate. ~estimation of "silica and insoluble silicates" in an ore.~--take grams of the powdered mineral, evaporate with nitric acid (if sulphides are present), treat the dried residue (or the original substance if sulphides are absent) with or c.c. of hydrochloric acid; again evaporate to dryness, take up with dilute hydrochloric acid, filter, wash, ignite, and weigh. ~estimation of silicon in iron.~--place grams of the metal (borings or filings) in a four-inch evaporating dish, and dissolve (with aid of heat) in c.c. of dilute nitric acid. evaporate to complete dryness, take up with c.c. of hydrochloric acid, and allow to digest for one hour. boil down to a small bulk, dilute with a per cent. solution of hydrochloric acid, boil, and filter. wash with acid and water, dry, ignite in a platinum crucible, and weigh the sio_{ }. this, multiplied by . , gives the weight of the silicon. the percentage is calculated in the usual way. practical exercises. . a certain rock is a mixture of per cent. of quartz, per cent. of potash-felspar, and per cent. of potash-mica. what per cent. of silica will it contain? . two grams of a mixture of silica and cassiterite left, after reduction in hydrogen, . grams. assuming all the oxide of tin to have been reduced, what will be the percentage of silica? . the formula of a compound is feo.sio_{ }. what percentage of silica will it contain? . two grams of a sample of cast-iron gave . gram of silica. find the percentage of silicon in the metal. . what weights of quartz and marble (caco_{ }) would you take to make grams of a slag having the formula cao.sio_{ }? carbon and carbonates. carbon compounds enter so largely into the structure of organised bodies that their chemistry is generally considered apart from that of the other elements under the head of _organic chemistry_. carbon occurs, however, among minerals not only in the oxidised state (as carbonates), but also in the elementary form (as in diamond and graphite), and combined with hydrogen, oxygen, &c. (as in petroleums, bitumens, lignites, shales, and coals). in small quantities "organic matter" is widely diffused in minerals and rocks. in shales and clays it may amount to as much as or per cent. (mainly as bituminous and coaly matters). the assayer has only to take account of the organic matter when it is of commercial importance, so that in assays it is generally included under "loss on ignition." in coals, shales, lignites, &c., the carbon compounds are, on heating, split up into oils and similar compounds. the products of distillation may be classified as water, gas, tars, coke, and ash. the assay of these bodies generally resolves itself into a distillation, and, in the case of the shales, an examination of the distillates for the useful oils, paraffin, creosote, &c., contained in them. elementary carbon is found in nature in three different forms, but these all re-act chemically in the same way. they combine with oxygen to form the dioxide.[ ] the weight of oxygen required to burn a given weight of any form of carbon is the same, and the resulting product from all three has the same characteristic properties. carbon dioxide is the common oxide of carbon. a lower oxide exists, but on burning it is converted into the dioxide. wherever the oxidation of carbon takes place, if there is sufficient oxygen, carbon dioxide (carbonic acid) is formed; this re-action is the one used for the determination of carbon in bodies generally. the dioxide has acid properties, and combines with lime and other bases forming a series of salts called carbonates. the carbon-compounds (other than carbonates, which will be subsequently considered) occurring in minerals are generally characterised by their sparing solubility in acids. the diamond is distinguished from other crystals by its hardness, lustre, and specific gravity. it may be subjected to a red heat without being apparently affected, but at a higher temperature it slowly burns away. graphite, also, burns slowly, but at a lower temperature. the other bodies (coals, shales, &c.) differ considerably among themselves in the temperature at which they commence to burn. some, such as anthracite, burn with little or no flame, but most give off gases, which burn with a luminous flame. they deflagrate when sprinkled on fused nitre, forming carbonate of potash. in making this test the student must remember that sulphur and, in fact, all oxidisable bodies similarly deflagrate, but it is only in the case of carbon compounds that carbonate of potash is formed. carbon unites with iron and some of the metals to form carbides; combined carbon of this kind is detected by the odour of the carburetted hydrogen evolved when the metal is treated with hydrochloric acid; for example, on dissolving steel in acid. the natural carbon compounds, although, speaking generally, insoluble in hydrochloric or nitric acids, are more or less attacked by aqua regia. the assayer seldom requires these compounds to be in solution. the presence of "organic matter"[ ] interferes with most of the reactions which are used for the determination of the metals. consequently, in such cases, it should be removed by calcination unless it is known that its presence will not interfere. when calcination is not admissible it may be destroyed by heating with strong sulphuric acid and bichromate or permanganate of potash or by fusion with nitre. carbon may be separated from other substances by conversion into carbon dioxide by burning. in most cases substances soluble in acids are first removed, and the insoluble residue dried, weighed, and then calcined or burned in a current of air. the quantity of "organic matter" may be determined indirectly by the loss the substance undergoes, but it is better to determine the "organic carbon" by confining the calcination in a tube, and collecting and weighing the carbon dioxide formed. each gram of carbon dioxide is equivalent to . gram of carbon. [illustration: fig. .] [illustration: fig. .] instead of a current of oxygen or air, oxide of copper may be more conveniently used. the operation is as follows:--take a clean and dry piece of combustion tube drawn out and closed at one end, as shown in the figure (fig. ), and about eighteen inches long. fit it with a perforated cork connected with a ~u~-tube (containing freshly-fused calcium chloride in coarse grains) and a set of potash bulbs (fig. ) (containing a strong solution of potash), the exit of which last is provided with a small tube containing calcium chloride or a stick of potash. both the ~u~-tube and bulbs should have a loop of fine wire, by which they may be suspended on the hook of the balance for convenience in weighing. they must both be weighed before the combustion is commenced; to prevent absorption of moisture during weighing, &c., the ends are plugged with pieces of tube and glass rod. fill the combustion tube to a depth of about eight inches with some copper oxide, which has been recently ignited and cooled in a close vessel. put in the weighed portion for assay and a little fresh copper oxide, and mix in the tube by means of an iron wire shaped at the end after the manner of a corkscrew. put in some more oxide of copper, and clean the stirrer in it. close loosely with a plug of recently ignited asbestos, place in the furnace, and connect the ~u~-tube and bulbs in the way shown in the sketch (fig. ). [illustration: fig. .] see that the joints are tight, and then commence the combustion by lighting the burners nearest the ~u~-tube; make the first three or four inches red hot, and gradually extend the heat backwards the length of the tube, but avoid too rapid a disengagement of gas. when gas ceases to come off, open the pointed end of the tube and draw a current of dried air through the apparatus. the carbon dioxide is absorbed in the potash bulbs, and their increase in weight multiplied . gives the amount of carbon in the substance taken. the increase in weight in the calcium chloride tube will be due to the water formed by the oxidation of the combined hydrogen. if this last is required the increase in weight multiplied by . gives its amount. coals. the determination of the actual carbon in coals and shales is seldom called for; if required, it would be performed in the way just described.[ ] the ordinary assay of a sample of coal involves the following determinations--moisture, volatile matter, fixed carbon, ash, and sulphur. these are thus carried out:-- ~determination of moisture.~--take grams of the powdered sample and dry in a water-bath for an hour or so. the loss is reported as moisture. coals carry from to per cent. if the drying is carried too far, coals gain a little in weight owing to oxidation, so that it is not advisable to extend it over more than one or two hours. ~determination of volatile matter.~--this determination is an approximate one, and it is only when working under the same conditions with regard to time, amount of coal taken, and degree of heat used, that concordant results can be arrived at. it is a matter of importance whether the coal has been previously dried before heating or not, since a difference of per cent. may be got by working on the dried or undried sample. take grams of the powdered, but undried, sample of coal, place in a weighed platinum crucible, and support this over a good bunsen burner by means of a thin platinum-wire triangle. the heat is continued until no further quantity of gas comes off and burns at the mouth. this takes only a few minutes. the cover is tightly fitted on, and when cold the crucible is weighed. the loss in weight, after deducting the moisture, gives the "volatile matter," and the residue consists of "fixed carbon" and "ash." ~determination of ash.~--the coke produced in the last operation is turned out into a porcelain dish and ignited over a bunsen burner till the residue is free from particles of carbon. calcination is hastened by stirring with a platinum wire. the operation may be done in a muffle, but this gives results a few tenths of a per cent. too low. the dish is cooled in a dessicator, and weighed. the increase in weight gives the amount of "ash," and the difference between this and the weight of the coke gives the "fixed carbon." the assay is reported as follows:-- moisture at ° c. ---- per cent. volatile matter ---- " fixed carbon ---- " ash ---- " contains sulphur ---- per cent. ~determination of sulphur.~--the sulphur exists in the coal partly in organic combination, partly as metallic sulphide (iron pyrites, marcasite, &c.), and, perhaps, as sulphate. so that the sulphur determination must be separately reported, since a portion will go off with the volatile matter, and the remainder would be retained and weighed with the coke. the sulphur is thus determined:--take gram of the coal and mix with . gram of a mixture of parts of calcined magnesia and part of carbonate of soda, and heat in a platinum crucible for one hour or until oxidation is complete. turn out the mass and extract it with water and bromine, filter, acidulate with hydrochloric acid, boil off the bromine, and precipitate with baric chloride (estimating gravimetrically as given under _sulphur_). another method is as follows:--take gram of the coal and drop it gradually from a sheet of note paper on to grams of fused nitre contained in a platinum dish. extract with water, acidify with acetic acid, and estimate volumetrically as described under _sulphur_. [illustration: fig. .] ~calorific effect of coals.~--the heat-giving value of a coal is best expressed in the number of pounds of water, previously heated to the boiling point, which it will convert into steam. this is generally termed its evaporative-power. it may be determined by means of the calorimeter (fig. ). this consists of a glass cylinder marked to hold . grains of water. the instrument consists of a perforated copper stand, provided with a socket and three springs. the socket holds a copper cylinder which is charged with grains of the dried coal mixed with grains of a mixture of parts of potassium chlorate and part of nitre. the charge is well packed in the cylinder and provided with a small fuse of cotton saturated with nitre. fill the glass cylinder to its mark with water and take the temperature with a thermometer marked in degrees fahrenheit. ignite the fuse and immediately cover with the outer copper cylinder (extinguisher-fashion), which will be held in its place by the springs. the stop-cock should be closed before this is done. place the apparatus quickly in the cylinder of water. when the action is over open the stop-cock and agitate the water by raising and lowering the instrument a few times. again take the temperature. the rise in temperature, plus per cent. for the heat used in warming the apparatus and lost by radiation, gives the evaporative-power. the following is an example:-- temperature before experiment . ° f. temperature after " . ° " -------- rise . ° " + / th . ° " -------- gives . ° " one pound of the coal will evaporate . pounds of water. shales, etc. the assay of these is carried out in the same way as that of coals, but the volatile matters are separately examined, and, in consequence, a larger quantity of material must be used. for the moisture, volatile matter, fixed carbon and ash, the determinations are the same, but a special distillation must be made to obtain a sufficient quantity of the volatile products for subsequent examination. take or grams of the well-sampled and powdered shale, and introduce into a cast-iron retort as shown in fig. . lute the joint with fire-clay, place the cover on, and bolt it down. the bolts should have a covering of fire-clay to protect them from the action of the fire. place the retort in a wind furnace, supporting it on a brick, and pack well around with coke. build up the furnace around and over the retort with loose fire-bricks, and heat gradually. [illustration: fig. .] as soon as water begins to drip, the tube of the retort is cooled by wrapping a wet cloth around it, and keeping wet with water. the water is kept from running into the receiver by a ring of damp fire-clay. a quantity of gas first comes over and will be lost, afterwards water and oily matters. the retort must be red hot at the close of the distillation, and when nothing more distils off, which occurs in about two or three hours, the wet cloth is removed, and the tube heated with a bunsen burner to drive forward the matter condensed in it into the receiver, and thus to clean the tube. it can be seen when the tube is clean by looking up through it into the red-hot retort. the receiver is then removed, and the retort, taken from the furnace, is allowed to cool. when cold it is opened, and the fixed carbon and ash weighed, as a check on the smaller assay. the distillate of water and oil is warmed, and will separate into two layers, the upper one of which is oil, and the lower water. these are measured, and if the specific gravity of the oil is taken, its weight may be calculated. if the two liquids do not separate well, the water may be filtered off, after cooling, through a damped filter. the separation is, however, best effected in a separator (fig. ). the liquids are poured into this, allowed to settle, and the lower layer drained off. the volume of the water is measured and its weight calculated in per cents. on the amount of shale taken. [illustration: fig. .] ~examination of the oil.~--a sufficient quantity of the oil must be got, so that if one distillation does not yield enough, the requisite quantity must be obtained by making two or more distillations. the oils are mixed, and the mixture, after having had its volume and specific gravity ascertained, is placed in a copper retort, and re-distilled with the aid of a current of steam. the residue in the retort is coke. the distillate is separated from the water by means of the separator, and shaken for ten minutes with one-twentieth of its bulk of sulphuric acid (sp. g. . ). the temperature should not be allowed to rise above °. allow to stand, and run off the "acid tar." the oil is now shaken up with from c.c. to c.c. of sodic hydrate solution (sp. g. . ), allowed to stand, warmed for half-an-hour, and the "soda-tar" run off. on mixing this soda-tar with dilute acid, the "crude shale oil creosote" separates, and is measured off. the purified oil is next re-distilled in fractions, which come over in the following order:--"naphtha," "light oil," "heavy oil," and "still bottoms." for the first product, which is only got from certain shales, the receiver is changed when the distillate has a specific gravity of . . for the second product the process is continued till a drop of the distillate, caught as it falls from the neck of the retort on a cold spatula, shows signs of solidifying. this is "crude light oil." the receiver is changed, and the "heavy oil" comes over; towards the end a thick brown or yellow viscid product is got. the receiver is again changed, and the distillation carried to dryness. the "crude light oil" is washed cold with per cent. of sulphuric acid (concentrated), and afterwards with excess of soda. thus purified it is again distilled to dryness, three fractions being collected as before. naphtha, which is added to the main portion, and measured; "light oil," which is also measured; and "heavy oil," which is added to that got in the first distillation. this last is poured into a flat-bottom capsule, and allowed to cool slowly. the temperature may with advantage be carried below freezing-point. the cooled cake is pressed between folds of linen, and the paraffin scale detached and weighed. the results may be reported thus:-- naphtha, sp. g. ---- light oil, sp. g. ---- heavy oil, sp. g. ---- paraffin scale ---- coke, &c. ---- the results are calculated in per cents. on the oil taken. some workers take their fractions at each rise of ° c. the composition of average shale, as given by mills, is as follows:--specific gravity, . ; moisture, . . gas } volatile matter, water, ammonia } . oil } fixed carbon . ash . _____ . the ash is made up of silica, . ; ferric oxide, . ; alumina, . ; lime, . ; sulphur, . ; soluble salts (containing . per cent. sulphuric oxide), . . total sulphur in shale . per cent. " " in ash . " for further information on these assays, and for the assay of petroleums, bitumens, &c., the student is referred to allen's "commercial organic analysis," vol. ii. ~determination of organic carbon in a limestone.~--take or grams and dissolve with a very slight excess of dilute hydrochloric acid, evaporate to dryness, and determine the carbon in the residue by combustion with copper oxide. ~estimation of carbon in a sample of graphite (black-lead).~--weigh up or grams in a dish and calcine in the muffle till the carbon is burnt off. weigh the residue, and calculate the carbon by difference. [illustration: fig. .] [illustration: fig. .] [illustration: fig. .] ~determination of carbon in iron.~--the carbon exists in two states--free (graphite) and combined. the following process estimates the total carbon:--the carbon existing as graphite may be separately estimated in another portion by the same process, but using hydrochloric acid to dissolve the iron instead of the copper solution:--weigh up grams of the iron (or a larger quantity if very poor in carbon), and attack it with grams of ammonic-cupric chloride[ ] dissolved in c.c. of water. let the reaction proceed for a quarter-of-an-hour, and then warm until the copper is dissolved. allow to settle, and filter through a filtering-tube. this is a piece of combustion tube drawn out and narrowed at one end, as shown in fig. . the narrow part is blocked with a pea of baked clay, and on this is placed half-an-inch of silica sand (previously calcined to remove organic matter), then a small plug of asbestos, and then a quarter-of-an-inch of sand. the tube is connected with a pump working at a gentle pressure, and the solution is filtered through the tube with the aid of a small funnel (fig. ). the residue is washed, first with dilute hydrochloric acid, and then with distilled water. the tube is dried by aspirating air through it, and gently warming with a bunsen burner. the tube is then placed in a small combustion-furnace, and connected with calcium chloride and potash bulbs, as shown in fig. . the potash bulb to the right of the figure must be weighed. a slow stream of air is drawn through the apparatus, and the heat gradually raised; in from thirty minutes to one hour the combustion will be complete. the potash bulbs are then disconnected and weighed, and the increase multiplied by . gives the weight of carbon. carbonates. carbon dioxide, which is formed by the complete oxidation of carbon, is a gas with a sweetish odour and taste, having a strong affinity for alkalies, and forming a series of compounds termed carbonates. the gas itself occurs in nature, and is sometimes met with in quantity in mining. the carbonates occur largely in nature, forming mountain masses of limestone, &c. carbonates of many of the metals, such as carbonate of lead (cerussite), carbonate of iron (chalybite), carbonates of copper (malachite and chessylite), and carbonate of magnesia (magnesite), are common. all the carbonates (those of the alkalies and alkaline earths excepted) are completely decomposed on ignition into the oxide of the metal and carbon dioxide; but the temperature required for this decomposition varies with the nature of the base. all carbonates are soluble with effervescence in dilute acids; some, such as chalybite and magnesite, require the aid of heat. the alkaline carbonates are soluble in water; the rest, with the exception of the bicarbonates, are insoluble therein. carbonates are recognised by their effervescence with acids--a stream of bubbles of gas are given off which collect in the tube, and possess the property of extinguishing a lighted match. the most characteristic test for the gas is a white precipitate, which is produced by passing it into lime or baryta-water, or into a solution of subacetate of lead. the expulsion of carbon dioxide by the stronger acids serves for the separation of this body from the other acids and bases. ~dry assay.~--there is no dry assay in use. any method which may be adopted will necessarily be applicable only to special compounds. wet methods. there are several methods in use which leave little to be desired either in speed or accuracy. we will give ( ) a gravimetric method in which the estimation may be made directly by weighing the carbonic acid, or, indirectly, by estimating the carbon dioxide from the loss; ( ) a volumetric one, by which an indirect determination is made of the gas; and ( ) a gasometric method, in which the volume of carbon dioxide given off is measured, and its weight deducted. [illustration: fig. .] [illustration: fig. .] ~direct gravimetric method.~--fit up the apparatus shown in the diagram (fig. ). the various tubes are supported by a fixed rod with nails and wire loops, and connected by short lengths of rubber-tubing. the first tube contains soda-lime. the small flask is fitted with a rubber-stopper perforated with two holes, through one of which passes the tube of a pipette holding or c.c. this pipette is to contain the acid. the substance to be determined is weighed out into the flask. the second tube contains strong sulphuric acid; the third, pumice stone, saturated with copper sulphate solution, and dried until nearly white (at ° c.); the fourth contains recently fused calcium chloride; and the fifth, which is the weighed tube in which the carbonic acid is absorbed, contains calcium chloride and soda-lime,[ ] as shown in fig. . the sixth also contains calcium chloride and soda-lime; its object is to prevent the access of moisture and carbonic acid to the weighed tube from this direction; it is connected with an aspirator. having weighed the ~u~-tube and got the apparatus in order, weigh up , , or grams of the substance and place in the flask. fill the pipette with dilute acid, close the clamp, and cork the flask. then see that the apparatus is tight. open the clamp and allow from to c.c. of the acid to run on to the assay. carbonic acid will be evolved and will be driven through the tubes. the gas should bubble through the sulphuric acid in a moderate and regular stream. when the effervescence slackens the clamp is opened and the greater part of the remaining acid run in. when the effervescence has ceased the clamp is opened to its full extent and a current of air drawn through with an aspirator. a gentle heat is applied to the flask; but it should not be prolonged or carried to boiling. after the removal of the heat a gentle current of air is drawn through the apparatus for or minutes. the weighed ~u~-tube, which in the early part of the operation will have become warm if much carbonic acid was present, will by this time be cold. it is disconnected, plugged, and weighed. the increase in weight is due to the carbon dioxide of the sample. _example._--ore taken gram. weight of tube, before . grams " " after . " ------- increase equals co_{ } . " [illustration: fig. .] ~indirect gravimetric, or determination by loss.~--take a geissler's carbonic-acid apparatus (fig. ) and place in the double bulb some strong sulphuric acid. put into the other bulb, the stopcock being closed, or c.c. of nitric acid diluted with water. leave the apparatus in the balance-box for a few minutes and weigh. introduce into the flask (through a) about gram of the powdered substance and again weigh to find the exact amount added. allow the acid to run gradually on to the carbonate, and when solution is complete, heat and aspirate. cool and again weigh; the loss in weight is the carbonic acid. for _example_:-- weight of apparatus and acids . grams " " marble . " ------ equal to marble taken . " weight of apparatus and marble . grams " " minus carbonic acid . " ------- equal to carbonic acid . " . : :: . : _x_ _x_ = . per cent. the substance contains . per cent. of carbonic acid; a duplicate experiment gave . per cent. this method is quicker, but less exact, than the direct gravimetric determination. volumetric method. this, which is of somewhat limited application, is based upon the determination of the quantity of acid required to decompose the carbonate. it consists in adding to a weighed quantity of the mineral a known amount of standard solution of acid which is in excess of that required to effect the decomposition. the quantity of residual acid is then determined by titrating with standard solution of alkali. this method has been described under _lime_. gasometric method. this method is the quickest of all, and the least troublesome after the apparatus has been once prepared. it yields fairly accurate results when worked in the manner described below; but if greater precautions are taken the results are exact. it depends on the measurement of the volume of gas given off on treating the weighed sample with acid. the apparatus described, page , is used. weigh out a portion of the mineral which shall contain not more than . gram of carbonic acid (or . gram of carbonate of lime) and put it in the bottle. put in the inner tube c.c. of dilute hydrochloric acid ( -- ), cork tightly, and read off the level of the liquid in the burette after adjusting the pressure. turn the acid over on to the mineral. run out the water so as to keep the level in the two burettes the same. when effervescence has ceased, rotate the contents of the bottle; finally, adjust the level in the burettes and read off the volume. the increase in volume is due to the evolved carbon dioxide. at the same time read off the "volume corrector." some of the carbon dioxide remains dissolved in the acid in the generating bottle, and the quantity thus dissolved will depend on the amount of carbonate as well as on the amount of acid present. consequently, a measured quantity of acid should be used in each assay and a comparative experiment made with a known weight of pure carbonate of lime which will yield about the same volume of gas. the number of c.c. of gas got in the assay multiplied by . will give the number of milligrams of pure carbonate of lime that must be taken for the standard. with ordinary work the error rarely exceeds half a c.c. the following example will illustrate the calculations:-- one gram of a mineral was taken, and yielded . c.c. of gas. the "volume corrector" reading was . c.c. . gram of pure carbonate of lime was then taken, and treated in the same way; . c.c. of gas were got. the volume corrector still read . c.c. . gram of carbonate of lime is equivalent to . gram of carbon dioxide; then, . : . :: . : _x_ _x_ = . per cent. ~estimation of carbonic acid in the air of mines.~--according to a series of analyses by angus smith, the proportion of carbonic acid in the air of underground workings varied from . to . per cent. by volume. in places where men are working the proportion ought not to reach . per cent. a simple method of determining whether a sample of air reaches this limit ( . per cent.) is described by dr. c. le neve foster in the "proceedings of the mining association and institute of cornwall" for . the apparatus used is an ordinary corked -ounce medicine bottle. this is filled with the air to be examined by sucking out its contents with a piece of rubber-tube. half-an-ounce of dilute lime-water[ ] (tinted with phenolphthalein) is poured in. if, on corking the bottle and shaking, the colour is not discharged, the air contains less than . per cent. of carbon dioxide. "if the colour fades slowly, and does not finally vanish till after a great deal of shaking, it may be assumed that the percentage of carbon dioxide does not greatly exceed one quarter; whereas, if the disappearance is rapid after a very few shakes, the contrary, of course, is the case." the dilute lime-water is measured out and carried in ordinary half-ounce phials. this method does not pretend to great accuracy, but as a method of distinguishing between good and bad air it is very convenient, and will be found useful. for determining the actual proportion in the air the following plan is adopted:--take a bottle which will hold about ounces, and measure its capacity; fill the bottle with the air to be examined, pour in c.c. of lime-water, and shake up for some time; add phenolphthalein, and titrate the remaining calcium hydrate with standard solution of oxalic acid. the solution of oxalic acid is made by dissolving . grams of re-crystallised oxalic acid (h_{ }c_{ }o_{ }. h_{ }o) in water and diluting to litre. one c.c. = . gram of lime (cao), or . gram of carbon dioxide. take c.c. of the same lime-water, to which add the same amount of phenolphthalein as before. titrate. the difference between the two readings gives the amount of "acid" equivalent to the lime-water neutralised by the carbon dioxide. the number of c.c. thus used up, when multiplied by . , gives the number of c.c. of carbon dioxide (at ° c. and mm.) in the volume of air taken. this volume, which is that of the bottle less c.c., must in accurate work be reduced to the normal temperature and pressure.[ ] the percentage by volume can then be calculated. practical exercises. . in a gasometric determination . c.c. of gas were obtained from . gram of mineral. the "volume corrector" reading was . c.c. . gram of pure carbonate of lime gave . c.c. the "volume corrector" reading was . . what is the percentage of carbon dioxide in the substance? . what volume of dry gas at ° c. and m.m. pressure should be obtained from . gram of carbonate of lime? c.c. of co_{ } under these conditions weighs . milligrams. . a sample of coal is reported on as follows:-- specific gravity . moisture . volatile matter . fixed carbon . ash . ------- . what is there about this requiring explanation? . calculate the percentage of carbonic acid in a mineral from the following data:-- weight of apparatus and acids . grams " " " plus mineral . " " " " after loss of carbonic acid . " . a sample of pig iron contains . per cent. of "combined" and . per cent. of "free" carbon. taking grams of it for each determination, what weight of co_{ } will be got on burning the residue from solution in ammonium cupric chloride, and what from the residue after solution in hydrochloric acid? boron and borates. boron occurs in nature as boric acid or sassoline (h_{ }bo_{ }); borax or tincal (na_{ }b_{ }o_{ }. h_{ }o); ulexite or boronatrocalcite ( cab_{ }o_{ }.na_{ }b_{ }o_{ }); borocalcite (cab_{ }o_{ }. h_{ }o); boracite, mg_{ }b_{ }o_{ }.mgcl_{ }, and some other minerals. boric acid is also a constituent of certain silicates, such as tourmaline, axinite, and datholite. the natural borates are used in the preparation of borax, which is largely employed as a preservative agent, for fluxing, and for other purposes. there is only one series of boron compounds which have any importance. these are the borates in which the trioxide (b_{ }o_{ }) acts the part of a weak acid. the addition of any acid liberates boric acid, which separates out in cold solutions as a crystalline precipitate. boric acid is soluble in alcohol and in hot water. on evaporating these solutions it is volatilised, although the anhydrous oxide is "fixed" at a red heat. the borates are mostly fusible compounds, and are soluble in acids and in solutions of ammonic salts. ~detection.~--boron in small quantities will escape detection unless specially looked for, but there is no difficulty in detecting its presence. heated in the bunsen-burner flame with "turner's test," it gives an evanescent yellowish-green colour, due to fluoride of boron (bf_{ }). "turner's test" is a mixture of parts of bisulphate of potash and part of fluor spar. boric acid itself imparts a characteristic green colour to the flame, which gives a spectrum made up of four well-marked and equidistant lines, three in the green and one in the blue. solutions of boric acid give with "turmeric paper," which has been dipped into it and dried, a characteristic red tint. this is a very delicate test, but in trying it a blank experiment should be carried out alongside with a solution made up of the same re-agents which have been used in liberating the boric acid in the sample. ~solution and separation.~--the solution presents no difficulty, but the separation is troublesome. the best method is that of gooch; who, if necessary, first fuses with carbonate of soda, and after the removal of chlorides and fluorides (by nitrate of silver or a lime salt), evaporates the aqueous extract with nitric or acetic acid to dryness in a retort and, subsequently, with repeated doses of c.c. each of methyl alcohol. the distillate contains the boron as boric acid. half a gram of the trioxide (b_{ }o_{ }) is completely carried over by two evaporations, each with c.c. of the alcohol; but if water or foreign salts are present, more than this is required. in ordinary cases six such evaporations are sufficient for . gram of the oxide.[ ] gravimetric determination. before the introduction of gooch's process it was usual to determine the boron trioxide "by difference." if the alcoholic distillate containing the boric acid is digested with about gram (a known weight) of lime for ten or fifteen minutes, the alcohol can be evaporated off without danger of loss. either calcium nitrate or acetate (which will be formed at the same time) yields lime upon subsequent ignition. consequently, the increase in weight, after ignition, upon that of the lime taken gives the amount of boron trioxide present. the trioxide contains . per cent. of boron (b). since magnesia does not form a soluble hydrate it cannot satisfactorily be used instead of lime. [illustration: fig. .] the apparatus required is shown in fig. . it consists of a small retort or evaporating vessel made out of a pipette of c.c. capacity. this is heated by means of a paraffin-bath at ° or ° c. it is connected with an upright condenser, at the lower end of which is a small flask which serves as a receiver. the quantity of the borate taken should contain not more than . gram of the trioxide. insoluble compounds are "dissolved in nitric acid at once, or, if necessary, first fused with sodium carbonate." with soluble and alkaline borates sufficient nitric acid is added to render it faintly acid. the solution is then introduced into the retort. "the lime, to retain the boric acid in the distillate, is ignited in the crucible in which the evaporation of the distillate is to be made subsequently." it is then cooled in the desiccator for ten minutes, and weighed. the lime is transferred to the receiving flask and slaked with a little water. the retort is lowered into the bath so that "only the rear dips below the surface." the evaporation is carried to dryness, the retort being lowered further into the bath as the evaporation proceeds. ten c.c. of methyl alcohol are introduced upon the residue, and the evaporation again started. six such portions of alcohol are thus distilled and c.c. of water are introduced and evaporated between the second and third, as also between the fourth and fifth distillations. if acetic acid is used instead of nitric in the first instance this addition of water is unnecessary. the distillate is evaporated in the crucible ignited over the blowpipe, cooled in the desiccator for ten minutes and weighed. the increase in weight gives the boron trioxide. the results tend to be from to milligrams too high. volumetric method. this method is applicable to the indirect determination of boric acid in borax and similar compounds. it is based on the measurement of the quantity of normal solution of acid required to replace the boric acid, and, consequently, is rather a measure of the soda present. the process is an alkalimetric one, and is carried out as follows:--weigh up grams of the sample and dissolve in water. tint with methyl orange, and run in from an ordinary burette normal solution of sulphuric acid until a pink tint is got. c.c. of the normal solution of acid are equal to . grams of boron trioxide (b_{ }o_{ }), or . grams of anhydrous borax (na_{ }b_{ }o_{ }). ~examination of borax.~--in addition to the determination just given, the following determinations are also required:-- ~water.~--take about grams and heat to tranquil fusion in a platinum crucible. count the loss in weight as water. ~sulphuric oxide.~--take grams, dissolve in water, acidify with hydrochloric acid, filter, and precipitate with barium chloride. wash the precipitate, ignite, and weigh as barium sulphate (see _sulphur_). ~chlorine.~--take grams, dissolve in water, acidify with nitric acid, filter, and add silver nitrate. collect, wash, and weigh the precipitate as silver chloride. ~alumina.~--take or grams, dissolve in water, boil, add ammonia in slight excess, and filter off the precipitate when it has settled. wash with hot water, ignite, and weigh as alumina (al_{ }o_{ }). footnotes: [ ] if the dishes show a manganese stain, wash them out with a few drops of hydrochloric and sulphurous acids. pass the acid liquor through the same small filter but collect the liquor apart. make ammoniacal and again pass through the filter, this time collecting the liquid with the main filtrate. [ ] this rarely amounts to more than milligram. [ ] to make this, dissolve gram of titanium oxide by fusing for some time with an excess of bisulphate of potash and dissolve out with cold water and sulphuric acid. dilute to litre, having previously added not less than c.c. of strong sulphuric acid: c.c. will contain . gram of tio_{ }. for the assay take c.c. of this, add c.c. of peroxide of hydrogen and dilute to c.c. run this from a burette into the flask until the colour equals that of the assay. each c.c. equals milligram of tio_{ }. fluorides must be absent. [ ] c + o_{ } = co_{ } [ ] for example, soluble organic acids formed by partial oxidation with nitric acid. [ ] for coals, and other bodies containing sulphur, chromate of lead should be used instead of oxide of copper; and the temperature should be limited to dull redness. [ ] this may be prepared by dissolving grams of ammonium chloride and grams of crystallized cupric chloride (cucl_{ }. h_{ }o) in hot water and crystallizing. [ ] soda-lime is made by dissolving grams of "soda" in water, and carefully slaking grams of lime with it. evaporate to dryness in an iron dish and ignite at a low red heat in a crucible. use the small lumps. [ ] made by diluting part by measure of saturated lime-water up to with recently boiled distilled water. [ ] see under _gasometric assays_. [ ] see "a method for the separation and estimation of boric acid," by f.a. gooch, _chemical news_, january , . appendix a. table of atomic weights and other constants. ---------+------------+----------+----------+--------- | | | | symbols.| names. | atomic | specific | melting | | weights. | gravity. | points. ---------+------------+----------+----------+--------- | | | | c. ag | silver | . | . | ° al | aluminium | . | . | ° as | arsenic | . | . | au | gold | . | . | ° b | boron | . | . | ba | barium | . | . | be | beryllium | . | . | bi | bismuth | . | . | ° br | bromine | . | . | - ° c | carbon | . | | ca | calcium | . | . | cd | cadmium | . | . | ° ce | cerium | . | . | cl | chlorine | . | | co | cobalt | . | . | cr | chromium | . | . | cs | caesium | . | . | ° cu | copper | . | . | ° di | didymium | . | . | er | erbium | . | | f | fluorine | . | | fe | iron | . | . | ga | gallium | . | . | ° ge | germanium | . | | h | hydrogen | . | | hg | mercury | . | . | - ° i | iodine | . | . | ° in | indium | . | . | ° ir | iridium | . | . | k | potassium | . | . | . ° la | lanthanum | . | . | li | lithium | . | . | ° mg | magnesium | . | . | mn | manganese | . | . | mo | molybdenum | . | . | n | nitrogen | . | | na | sodium | . | . | . ° nb | niobium | . | . | ni | nickel | . | . | o | oxygen | . | | os | osmium | . | . | p | phosphorus | . | . | ° pb | lead | . | . | ° pd | palladium | . | . | ° pt | platinum | . | . | ° rb | rubidium | . | . | . ° rh | rhodium | . | . | ru | ruthenium | . | . | s | sulphur | . | . | ° sb | antimony | . | . | ° se | selenium | . | . | ° si | silicon | . | . | sn | tin | . | . | ° sr | strontium | . | . | ta | tantalum | . | | te | tellurium | . | . | ° th | thorium | . | . | ti | titanium | . | . | tl | thallium | . | . | ° u | uranium | . | . | v | vanadium | . | . | w | tungsten | . | . | y | yttrium | . | | yb | ytterbium | . | | zn | zinc | . | . | ° zr | zirconium | . | . | _________|____________|__________|__________|_________ the atomic weights in this table are in accord with the numbers given by f.w. clarke (dec. , ), chief chemist of the united states geological survey. [illustration: _table for converting degrees of the centigrade thermometer into degrees of fahrenheit's scale._] nitric acid. _table showing the percentage, by weight, of real acid_ (hno_{ }) _in aqueous solutions of nitric acid of different specific gravities. temperature_, ° c. -------+-------++-------+-------++-------+------- . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || | || | -------+-------++-------+-------++-------+-------- hydrochloric acid. _table showing the percentage, by weight, of real acid_ (hcl) _in aqueous solutions of hydrochloric acid of different specific gravities. temperature_, ° c. -----------+---------++----------+---------++----------+--------- | . | . || . | . || . | . | | . | . || . | . || . | . | | . | . || . | . || . | . | | . | . || . | . || . | . | | . | . || . | . || . | . | | . | . || . | . || . | . | | . | . || . | . || . | . | | . | . || . | . || . | . | | . | . || . | . || . | . | | . | . || . | . || . | . | | . | . || . | . || . | . | | . | . || . | . || . | . | | . | . || . | . || . | . | | . | . || . | . || . | . | | . | . || . | . || . | . | | . | . || . | . || . | . | | . | . || . | . || . | . | | . | . || . | . || . | . | | . | . || . | . || . | . | | . | . || . | . || . | . | | . | . || . | . || . | . | | . | . || . | . || . | . | | . | . || . | . || . | . | | . | . || . | . || . | . | | . | . || . | . || . | . | | . | . || . | . || . | . | | . | . || . | . || . | . | | . | . || . | . || . | . | | . | . || . | . || . | . | | . | . || . | . || . | . | -----------+---------++----------+---------++----------+--------- ammonia. _table showing the percentage, by weight, of real ammonia_ (nh_{ }) _in aqueous solutions of ammonia of different specific gravities. temperature_, ° c. ----------+--------++----------+--------++----------+-------- . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || | || | ----------+--------++----------+--------++----------+-------- sulphuric acid. _table showing the percentage, by weight, of real acid_ (h_{ }so_{ }) _in aqueous solutions of sulphuric acid of varying specific gravity. temperature_, ° c. --------+--------++--------+--------++--------+-------- . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || . | . || . | . . | . || | || | --------+--------++--------+--------++--------+-------- appendix b. estimation of small quantities of gold.[ ] in the case of small buttons of gold the weight can be determined more easily and accurately by measuring with the help of a microscope than by the actual use of a balance. moreover, the method of measurement is applicable to the determination of quantities of gold too minute to affect even the most delicate balance. for quantities of gold of from . to . milligram a microscope with / inch objective and b eyepiece is suitable. the measurements are made with the help of a scale engraved (or, better, photographed) on a circular piece of glass which rests on the diaphragm of the eyepiece. this scale and the object upon the stage can be easily brought into focus at the same time. the button of gold obtained by cupelling is loosened from the cupel by gently touching with the moistened point of a knife; it generally adheres to the knife, and is then transferred to a glass slide. the slide is placed on the stage of the microscope, illuminated from below; and the button is brought into focus, and so placed that it apparently coincides with the scale. the diameters in two or three directions (avoiding the flattened surface) are then read off: the different directions being got by rotating the eyepiece. the mean diameter is taken. the weight of the button is arrived at by comparing with the mean diameter of a _standard prill_ of gold of known weight. the weights are in the proportion of the cubes of the diameters. for example, suppose a prill has been obtained which measures . divisions of the scale, and that a standard prill weighing . milligram measures . divisions. the weight will be calculated as follows: . ^{ } : . ^{ } :: . : _x_ . × . × . × . _x_ = -------------------- = . milligram. . × . × . the calculations are simplified by the use of a table of cubes. the standard prills used in the comparison should not differ much in size from the prills to be determined. they are prepared by alloying known weights of gold and lead, so as to get an alloy of known composition, say one per cent. gold. portions of the alloy containing the weight of gold required (say . milligram) are then weighed off and cupelled on small smooth cupels, made with the finest bone-ash. care must be taken to remove the cupels as soon as cupellation has finished. several standard prills of the same size should be made at the same time, and their mean diameter calculated. the lead for making the gold-lead alloy is prepared from litharge purified by reducing from it about per cent. of its lead by fusion with a suitable proportion of flour; the purified litharge is powdered, mixed with sufficient flour and reduced to metal. in determining the gold contained in small buttons of silver-gold alloy obtained in assaying (and in which the silver is almost sure to be in excess of that required for parting), transfer the button from the cupel to a small clean porcelain crucible; pour on it a drop or two of nitric acid (diluted with half its bulk of water), and heat gently and cautiously until action has ceased. if the residual gold is broken up, move the crucible so as to bring the particles together, so that they may cohere. wash three or four times with distilled water, about half filling the crucible each time and decanting off against the finger. dry the crucible in a warm place; and when dry, but whilst still black, take the gold up on a small piece of pure lead. half a grain of lead is sufficient, and it is best to hold it on the point of a blunt penknife, and press it on the gold in the crucible. the latter generally adheres. transfer to a small smooth cupel and place in the muffle. when the cupellation has finished, the button of gold is measured as already described. practical notes on the iodide process of copper assaying. for the following remarks and experiments we are indebted to mr. j.w. westmoreland, who has had considerable experience with the process. having dissolved the ore he converts the metals into sulphates by evaporating with sulphuric acid. the copper is then separated as subsulphide by means of hyposulphite of soda, and the precipitate is washed, dried, and calcined. the resulting oxide of copper is then dissolved in nitric acid; and to the concentrated solution, a saturated solution of carbonate of soda is added in sufficient quantity to throw down a considerable proportion of the copper. acetic acid is added to dissolve the precipitate, and when this is effected more of the acid is poured on so as to render the solution strongly acid. to this potassium iodide crystals are added in the proportion of ten parts of iodide to each one part of copper supposed to be present. the solution is then titrated with "hypo" as usual. for the examination of technical products experiments made in sulphuric acid solutions have no value, since arsenic acid, which is generally present to a greater or less extent, affects the end reaction. in such solutions bismuth may also interfere. the solution best suited for the assay is one containing acetate of soda and free acetic acid. the presence of acetate of soda counteracts the interference of arsenic and of bismuth. the return of the blue colour after titration is due to the excessive dilution of the assay, or to an insufficiency of potassium iodide, or to the presence of nitrous fumes. the interference of an excess of sodium acetate is avoided by adding more iodide crystals to the extent of doubling the usual amount. the interference of lead can be avoided by the addition of sulphuric acid or of phosphate of soda to the acid solution containing the copper, and before neutralising with carbonate of soda. the end reaction is, however, with care distinguishable without this addition. the following experiments, each containing . gram of lead, were made by him in illustration: ---------------+-------------------+---------------+--------------------- copper taken. | reagent added. | copper found. | end reaction. ---------------+-------------------+---------------+--------------------- . gram | -- | . gram | fairly satisfactory . " | -- | . " | " . " | sulphuric acid | . " | " . " | " | . " | " . " | phosphate of soda | . " | good, colourless . " | " | . " | rather yellow ---------------+-------------------+---------------+--------------------- _effect of sodium acetate._--each solution contained . gram of copper. a.b.c. d. e. f. g. grams. grams. grams. grams. grams. "acetate" added -- . . . . "iodide" added . . . . . copper found . . . . . in these experiments, except with the excessive quantities of acetate of soda and the insufficiency of potassium iodide in the cases of c and f, there was no difficulty with the after-blueing. method of separating cobalt and nickel. the following method of separating and estimating cobalt and nickel has been described by mr. james hope,[ ] with whom it has been in daily use for several years with completely satisfactory results. the quantity of ore taken should contain about . gram of the mixed metals. it is dissolved in hydrochloric acid or aqua regia, and the solution evaporated to dryness. the residue is taken up with dilute hydrochloric acid and hot water. the solution is filtered off from the silica, freed from second group metals by treatment with sulphuretted hydrogen and filtered, and after oxidation with nitric acid is separated from iron and alumina by the basic acetate method (page ). the precipitate is redissolved in a little hydrochloric acid, and again precipitated by sodium acetate. the two filtrates are mixed and treated with a little acetic acid, and the cobalt and nickel are then precipitated as sulphides by a current of sulphuretted hydrogen. the precipitate is filtered off, washed, dried, and calcined, and the resulting oxides are weighed to get an idea as to the quantity of the two metals present. the calcined precipitate is dissolved in a small covered beaker in aqua regia with the help of a few drops of bromine to remove any separated sulphur, and the solution evaporated to dryness with a few drops of sulphuric acid. the residue is dissolved in hot water, diluted to about c.c., and heated to boiling. about grams (four times the quantity of mixed metals present) of ammonium phosphate (amh_{ }po_{ }) are weighed off, dissolved in the smallest possible quantity of water, and boiled for a minute or two with a few c.c. of dilute sulphuric acid. this is added to the boiling-hot solution of cobalt and nickel, which is then treated cautiously with dilute ammonia until the precipitate partially dissolves. the addition of the ammonia is continued drop by drop with constant stirring, until the cobalt comes down as a pink precipitate of ammonium cobalt phosphate (amcopo_{ }). the beaker is placed on the top of a water bath with occasional stirring for five or ten minutes. the blue liquid containing the nickel is decanted through a small filter and the precipitate is dissolved with a few drops of dilute sulphuric acid. the resulting solution is treated with a small excess of ammonium phosphate and the cobalt again precipitated by the cautious addition of ammonia exactly as before. the precipitate containing the whole of the cobalt is filtered off and washed with small quantities of hot water. the filtrate is added to the previous one containing the greater part of the nickel. the ammonium cobalt phosphate is dried, transferred to a platinum crucible, and ignited over a bunsen flame for fifteen or twenty minutes. a purple coloured cobalt pyrophosphate (co_{ }p_{ }o_{ }) is thus formed, and is weighed. it contains . per cent. of cobalt. the mixed filtrates containing the nickel are placed in a tall beaker, and dilated if necessary to about c.c. ten c.c. of strong ammonia are added, and the solution, heated to ° c., is ready for electrolysis. a battery of two - / pint bunsen cells is used. this is found capable of depositing from . to . gram of nickel per hour, and from two to three hours is generally sufficient for the electrolysis. the electrode with the deposited nickel is washed with distilled water, afterwards with alcohol as described under copper, and is then dried and weighed. the following results obtained with this method by mr. hope illustrate the accuracy of the method. they were obtained by working on solutions containing known weights of the two metals: -------------------------+------------------------- taken. | found. ------------+------------+------------+------------ cobalt. | nickel. | cobalt. | nickel. ------------+------------+------------+------------ . gram | . gram | . gram | . gram . " | . " | . " | . " . " | . " | . " | . " . " | . " | . " | . " . " | . " | . " | . " . " | . " | . " | . " . " | . " | . " | . " ------------+------------+------------+------------ footnotes: [ ] for fuller information see a paper on "the estimation of minute quantities of gold," by dr. george tate; read before the liverpool polytechnic society, nov. . [ ] _journal of the society of chemical industry_, no , vol. ix. april , . appendix c. a lecture on the theory of sampling. the problem of the sampler is essentially the same as that of the student of statistics. one aims at getting a small parcel of ore, the other a number of data, but each hopes to obtain what shall represent a true average applicable to a much larger mass of material. ignoring the mechanical part of the problems, the sampling errors of the one and the deviations from the average of the other are the same thing. it may be doubted whether many not specially trained in the study of statistics could answer such a question as the following:--seven hundred thousand men being employed, there are, in a given year, one thousand deaths from accident. assuming the conditions to remain unaltered, within what limits could one foretell the number of deaths by accident in any other year? on the other hand, there is a widespread belief in the efficacy of what is called the law of averages. even the ordinary newspaper reader is accustomed to look on the national death-rate or birth-rate as a thing capable of being stated with accuracy to one or two places of decimals, and he knows that the annual number of suicides is practically constant. if a man played whist often and kept a record of the number of trumps n each hand, he would find fortune treated him quite fairly; in a year's play the average number would deviate very little from the theoretical average, _i.e._, one-quarter of thirteen. and a knowledge of this truth is useful, and that not merely in keeping ejaculations in due restraint. but every good player knows more than this: he has a sense of what variations in the number of trumps may reasonably be expected. for example, he will be prepared to risk something on neither of his opponents having more than five trumps, and will accept it as a practical certainty that no one has more than eight. much of what is known as good judgment is based on a proper estimate of deviations from the average. the question has an important bearing on sampling, as may be seen from the fact that shuffling and dealing at cards are but modifications of the well-known mixing and quartering of the sampler. because of this bearing on sampling and for other reasons, i became many years ago much interested in the question, and gave to its solution perhaps more labour than it was worth. in books on medical statistics the answer to the question is stated in a mathematical formula, called poisson's formula, which, in a modified form, i shall give further on. but this did not satisfy me, because i wanted to learn what a reasonably safe _limit of error_ actually meant, and this could be best learnt by experiment; so with the help of some friends i went in for a thorough course of penny-tossing. tossing a penny twenty times, an average result would be ten heads and ten tails. to find the deviations from this, we tossed two hundred twenties, _i.e._, four thousand times. of the two hundred, thirty-three gave the exact average, viz.:-- heads; sixty-four gave an error of one, viz.:-- or heads; forty-nine, an error of two; twenty-six, an error of three; twenty, an error of four; eight gave an error of five, and this limit was not exceeded. from these we may say that six is a reasonably safe limit of error. ninety-seven cases, say one-half, gave an error not exceeding one; and the mean error is . . in other words, in twenty tosses you will not get more than nor less than heads; you are as likely as not to get , , or heads; and lastly, if you lost in twenty throws all heads or tails over your average loss would be . penny, or say roughly d. on the twenty throws. it was necessary to compare these with another series containing a larger average, say that of heads in throws. i confess the labour of tossing pennies two hundred at a time was little to our taste. so from a bag of pennies borrowed from the bank, we weighed out samples containing two hundred, and for an evening we were busy counting heads and tails in these. the heads in sixty samples ranged from to . one hundred heads occurred seven times. the extent and frequency of the errors is shown in the table. ------+-------+------+-------+------+------- error.|no. of |error.|no. of |error.|no. of | times.| | times.| | times. ------+-------+------+-------+------+------- | | | | | | | | | | | | | | | | | | | | | | | | | -------------------------------------------- we may call the limit of error . twenty-nine results out of sixty, say one-half, had an error not exceeding ; and the mean error is . . in comparing these with the series in we must, working by rule, divide not by but by . , the square root of ; for if we multiply an average by any number[ ] the error is also multiplied but only by the square root of the number. the error varies as the square root of the number. now / . = . = limit of error for in . . / . = . = mean error " " " / . = . = probable error " " " it will be seen that these calculated results agree fairly well with those actually obtained. the rule by which these calculations are made is important and will bear further illustration. to calculate the number of heads in throws, we have to find the limit of error on a true average of in . this being times the average of in , the corresponding errors must be multiplied by . this gives × = = limit of error. . × = . = mean error. × = = probable error. the results i have actually obtained with these large numbers are hardly enough to base much on, but have a value by way of confirmation. expecting heads, the actual numbers were , , , , , , , . it will be seen that exactly half are within the probable error; but this, considering the small number of results, must be more or less of an accident; it is more to the point they are all well within the limits of error. i have a large number of other results which with a single exception are all in accord with those given; and this exception only just overstepped the limits. it was like a case of nine trumps, which though in a sense possible, is very unlikely to happen in any one's experience. but even now we are not quite in a position to answer the question with which we started. if you refer to it you will see that we are face to face with this problem: the limit of variation on the who died would be say ,[ ] ignoring decimals. but if we calculate on the number who did not die, viz.-- , ,[ ] we shall get a variation times as great as this. but it is evident the variation must be the same in each case. i submitted this kind of problem also to the test of experiment, the results of which gave me great faith in poisson's formula. imagine two hundred pennies in a bag all heads up. any shaking will spoil this arrangement and give a certain proportion of tails. and, further, the probable effect of shaking and turning will be to reduce the preponderance of heads or tails whichever may be in excess. this of course is the reason why we are so unlikely to get more than of them in either position. but if the two hundred pennies are increased to , by adding pennies which have tails on both sides, then the shaking or mixing would be less effective. we should still expect as an average result to get the heads but in , instead of . the variation will be or on the instead of . and this is a better limit in such cases. _taking as the limit of error on instances_ and proportionally increasing the others so that _the mean error becomes . and the probable error . _, we may now calculate the answer without gross mistake. the probable variation on the deaths by accident will be , the mean variation will be . , and the limits of variation . . one such table showing in five years a mean number of deaths of about per annum gives an annual deviation of about up or down of this. it will be seen at once that an improvement of or in any one year would be without meaning, but that an improvement of from to would indicate some change for the better in the circumstances of the industry. before applying these principles to the elucidation of some of the problems of sampling it will be well to give poisson's formula (in a modified form) and to illustrate its working. let _x_ equal the number of cases of one sort, _y_ the cases of the other sort, and _z_ the total. in the example, _z_ will be the , engaged in the industry; _x_ will be the killed by accidents, and _y_ will be the , who did not so die. the limit of deviation or error calculated by poisson's formula will be the square root of _xy_/_z_. replacing _x_, _y_ and _z_ by the figures of the example we get the square root of ( × × )/ , , which works out to the square root of . , or . . which means that we may reasonably expect the number of deaths not to vary from by more than , _i.e._, they will be between and . it will be seen that this number is in very satisfactory agreement with . given by the rougher calculation based on my own experiments. to come to the question of sampling. consider a powder of uniform fineness and fine enough to pass through an sieve. for purposes of calculation this may be assumed to be made up of particles of about one-eighth of a millimetre across (say roughly / of an inch); cubed, this gives the content as about / (strictly / ) of a cubic m.m. now one cubic m.m. of water weighs milligram; therefore such particles if they have the specific gravity of water weigh milligram, and otherwise weigh milligram multiplied by the sp. gr.: particles of ruby silver (pyrargyrite)[ ] will weigh . milligrams and will contain nearly . milligrams of silver. now suppose a portion of . grams ( / assay ton) of silver ore to contain such particles of ruby silver and no other material carrying silver: such an ore would contain ozs. of silver to the ton. but the limits of variation on particles would be [ ] multiplied by the square root of , or particles. thus the limit of sampling error would amount to just one-eighth of the silver present, or say to rather more than ozs. to the ton; the mean sampling error would be rather more than a quarter of this, or say about . ozs. to the ton. on the other hand, if one took for the assay a charge six times greater (say about grams), the number of particles would be and the limits of variation would be multiplied by the square root of , or particles, which is very closely / of the silver present, or say . ozs. to the ton, whilst the mean error would amount to about . ozs. to the ton. to work these examples by poisson's formula let us assume the gangue to have a mean sp. gr. of . then particles would weigh milligrams; and . [ ] grams would contain , particles. there would be then of ruby silver and , of gangue, together , , and the formula gives the square root of ( × × )/ , which works out to particles as against by the other method. a practical conclusion from this is of course that either the ore must be powdered more finely or a larger portion than grams must be taken for the assay. moreover, it is evident that on such an ore no small sample must be taken containing less than several million particles. consider now a copper ore of the same uniform fineness containing particles of copper pyrites (sp. gr. ) of which particles will weigh milligrams, mixed with gangue of which particles weigh milligrams. if one gram of such ore contain . gram of copper pyrites (= . gram copper) and . gram of gangue, these will contain , and say , particles respectively. altogether , particles. with poisson's formula this gives the limit of sampling error as the square root of ( × × )/ or particles. but a variation of on , is a variation of . per cent. the percentage of copper in the ore is . per cent., and . per cent. of this is . per cent. the limits of sampling error, therefore, are . per cent. and . per cent. again, it must be remembered that the mean sampling error would be a little over one-quarter of this, or say from . per cent. to . per cent. the practical conclusion is that a powder of this degree of fineness is not fine enough. in the last place let us consider a similar iron ore containing per cent. of hæmatite (sp. gr. ) and per cent. of gangue (sp. gr. ), gram of such ore will contain , particles of hæmatite weighing . gram and containing . gram of iron with say , particles of gangue weighing . gram. altogether , particles. poisson's formula then gives the limits of variation as the square root of ( × × )/ or particles. but on , is . on . , which is the percentage of iron present. the limits of sampling error then are . per cent. and . per cent. and the mean variation is from . per cent. to . per cent. these examples are worthy of careful consideration, and it must be remembered that the calculations are made on the assumption that the ore is made up of uniform particles of mineral of such fineness as would pass easily through an sieve, but which does not pretend to represent with great exactness the fineness of the powdered ore customary in practice. they show that having passed through such a sieve is no proof of sufficient powdering, not that all ores powdered and so sifted are unfit for assaying. this last would be an absurd and illogical conclusion. if an ore be powdered to a fairly fine sand and then be passed through a series of sieves, say a , , and , in such a state that little or none remains on the first, but the others retain a large proportion; then of that which comes through the sieve, perhaps two-thirds by weight may be even coarser than the powder i have used in the example. of the rest most may be of about half this diameter; the weight of the really fine powder may be quite inconsiderable. on the other hand, if the grinding be continued until, on sifting, little or nothing that is powderable remains on the sieves; then in the sifted product the proportions will be very different. this last, of course, is the only right way of powdering. also it is evident that so much depends on the manner of powdering that nothing precise can be stated as to the average coarseness of the powder. suppose, however, by good powdering a product is obtained which may be represented by a uniform powder with particles / th of a millimetre in diameter (say roughly / inch). compared with the previous powder, the diameter has been divided by . ; their number, therefore, in any given weight has been increased by the cube of . , which is . . but the value of a sample varies as the square root of the number of particles. hence the reduction in size and consequent increase in number has made the sample nearly four times better than before; and it will be seen that this brings the sampling error within tolerable limits. there are one or two words of warning which should be given. in the first place, using a sieve instead of an must not be too much relied on; the powder i took in the example would pass through it. it is a question of good powdering rather than of fine sifting. in the second place, a set of, say half-a-dozen, assays concordant within oz. where the theory gives ozs. as the limit of error does not upset the theory: the theory itself states this as likely. it is the error you _may_ get in one or two assays out of a hundred, not the error you are _likely_ to get in any one assay, which is considered under the heading "limit of error." accepting the result just arrived at that a portion of gram may be safely taken for an assay if the particles are - th of a millimetre in diameter, the further question remains as to what weight of the original sample must be reduced to this degree of fineness. this may be answered on the principle that the same degree of excellence should be aimed at in each of a series of samplings. this principle is illustrated in the table on page . a fine sand, such as would pass a sieve but be retained on a sieve, would be fairly represented by particles one-quarter of a millimetre in diameter. this being five times coarser, to contain the same number of particles must be times (the cube of ) as heavy; therefore grams of it can be taken with the same degree of safety as gram of the finer powder. of such a sand about this weight should be taken and reduced to the finer powder. if the ore were in coarse sand, say in particles millimetre in diameter, this would be four times as coarse as that last considered, and we should have to take times as much of it: times grams is kilos, or say roughly from to lbs. this should be crushed to the finer size and mixed; then from to grams should be taken and ground to the finest powder. there is, however, a reason why, on the coarser stuff, a smaller proportion may safely be used. this becomes more evident if we consider a still coarser sample. a heap of ore in stones about inches across would be times coarser than the sand, and an equivalent sample would need to be , times heavier; this would amount to about tons. experienced samplers would say that under such conditions so large a sample was hardly necessary. this is because i have assumed in the calculations that the grains of copper pyrites, for example, were all copper pyrites and the particles of gangue were free from copper. this would be true or nearly so for the very fine powder, but far from true in the case of the ore heap. in the heap probably few of the stones would be pure ore and still fewer would be free from copper. the stones would differ among themselves in their copper contents only within certain comparatively narrow limits. and it is evident that, if replacing one stone by another, instead of resulting in the gain or loss of all the copper one or other contained, merely affected the result to one-tenth of this amount, then a sample of - th of the weight (say tons) would be equally safe. it should be remembered, however, that while the man who samples on a large scale can safely and properly reduce the size of his samples on this account, yet the principle is one which counts less and less as the stuff becomes more finely divided, and ought to be ignored in the working down of the smaller samples which come to the assayer. footnotes: [ ] the in multiplied by = in . [ ] multiply the errors for by the square root of . [ ] multiply the errors for by the square root of . [ ] sp. gr. . . silver per cent. [ ] taking as the limit of variation on . [ ] the weight of the ore less the weight of ruby silver in it. index. acid measures, acidimetry, acidity of ores, acids, strength of, , , air of mines, carbonic acid in, alkalies, determination of, lawrence smith's method for, , separation of, alkalimetry, alkaline earths, alumina, determination of, in mineral phosphates, separation of, , amalgamation, ammonia, detection of, determination of, in natural waters, antimony, detection of, dry assay for, gravimetric assay, separation of, volumetric assay, arsenic, detection of, dry assay for, gravimetric assay, in brimstone, in crude arsenic, , in mispickel, , iodine, assay for, separation by distilling, uranium acetate, assay for, volhard's method applied to, assay book, note, results, tons, , assaying, methods, assays, check, preliminary, atomic weights, table of, barium, baryta, barytes, sulphur in, base bullion, sampling of, basic acetate separation, baumé's hydrometer, beryllia, bismuth, colorimetric assay, detection of, gravimetric determination of, in commercial copper, separation of, black tin, an analysis of, assay of, copper in, examination of, separation by vanning, blank assays, blende, sulphur in, zinc in, book, assay, laboratory, sample, boracic acid. _see boron_ borax, examination of, boron, direct determination of, brass, copper in, zinc in, bromine and bromides, bronze, copper in, tin in, burettes, burnt ore, silver in, , sulphur in, cadmium, gravimetric determination, separation of, caesium, calcination, , , , calcium, detection of, gravimetric determination, separation of, titration with normal acid, titration with permanganate, calculation of results, calculations from formulæ, calorific effect of coal, calorimeter, calx, carbon, gravimetric determination, in iron or steel, carbonates, carbonic acid in the air of mines, caustic potash = potassium hydroxide, caustic soda = sodium hydroxide, cerium, chalybite, iron in, charcoal, , check assays for gold, for silver, , chlorine and chlorides, chromium, gravimetric assay, in chrome iron ore, volumetric assay, clays, examination of, coals, cobalt, detection of, dry assay for, gravimetric determination, in hardhead, separation from nickel, , , coke, common salt, examination of, concentrates, assay for gold of, colorimetric assays, copper, copper, bismuth in, colorimetric assay for, , commercial, arsenic in, , commercial, copper in, commercial, examination of, cyanide assay for, dry assay of, dry assay, loss of, in, electrolytic assay for, , gold in, iodide assay for, iron in, , lead in, separation of, silver in, sulphur in, copper ores, solution of, valuation of, copper pyrites, copper in, , , , sulphur in, culm, cupel, , cupellation, loss, corrections for, loss in gold, loss in silver, of gold lead alloys, of silver lead alloys, , temperature of, cyanicides, cyanide assay for copper, for nickel, for tin, cyanides, alkalinity of, assay of, commercial, double, gold-dissolving power, prussic acid, volumetric determination of, , cyanide liquors, alkalinity of, assay of, , assay of, for gold, assay of, for zinc, &c., daniell cells, didymium, dollars to the ton, dry assays, drying, , earths, the alkaline, electrodes, electrolysis for copper, for nickel, equations, erbia, ferrous and ferric salts, filtration, finishing point, flasks, graduated, flatting, fluorine and fluorides, fluxes, , , , , formulæ, furnaces, galena, lead in, , gangue, iron in the, gas-measuring apparatus, gases, measurement of, gay-lussac's assay for silver, assay for silver modified, german silver, copper in, nickel in, , gold, amalgamation of, in cyanide liquor, loss of, in cupellation, loss of, in parting, preparation of, silver in, silver in, after parting, test for, gold-lead alloys, cupellation of, sampling of, gold ores assay with cyanide solutions, calcination of, concentrates, fluxing, , , sampling of, size of assay charges, tailings, gold-parting, platinum in, , , , gold-zinc slimes, graduated vessels, gravimetric methods, , halogens, hardhead, an analysis of, hot plate, hydrogen, preparation of, reduction by, hydrometer, ignition, in hydrogen, indicators, inquartation, iodine and iodides, iridium, iron, bichromate assay for, , , carbon in, colorimetric assay for, ferrous and ferric, gravimetric determination, permanganate assay for, , phosphorus in, reduction of ferric solutions, , separation of, stannous chloride assay for, volumetric assays for, iron ores, iron in, , phosphates in, laboratory books, lanthanum, lawrence smith's method for alkalies, , lead, colorimetric assay for, detection of, dry assay for, gravimetric determination of, in commercial copper, in commercial zinc, in galena, , separation of, , volumetric determination of, litharge, use of, in dry assays, , lithium, lime, milk of, volumetric assays for, limestone, examination of, lime in, limewater, loths, magnesia, magnesium, mixture, preparation of, manganese, colorimetric assay, detection of, gravimetric determination of, separation of, volumetric determination of, manganese peroxide, ferrous sulphate assay for, iodine assay for, = manganese dioxide, manganese ore, copper in, manganese in, peroxide in, matte, measuring, flasks, gases, , gold buttons, , , liquids, silver buttons, mechanical methods, mercury, dry assay, wet assay, metallic particles in ores, gold, particles in ores, silver, particles, tin, , micrometer, microscope, measuring with the, , mispickel, arsenic in, , sulphur in, moisture, , molybdate separation for phosphates, solution, preparation of, molybdenum, muffle, nessler's solution, nickel, dry assay for, electrolytic assay, gravimetric determination of, in german silver, , separation from cobalt, , , separation from iron, separation from manganese, separation of, volumetric assay, niobium, nitre, use of, in dry assays, nitrogen and nitrates, nitrometer, normal acid, normal solutions, ores, determining water in, , drying, powdering, , , , quantities of, for an assay, , , sampling, , , with metallic particles, , , osmiridium, osmium, ounces to the ton, long, to the ton, short, oxidation, oxides, determination of oxygen in, oxidising agents, , , effect of nitre, effect of nitric acid, oxygen, equivalent, in natural waters, , in ores, palladium, parting, acids, in flasks, in glazed crucibles, in special apparatus, in test tubes, phosphate, assay of apatite for, assay of iron ore for, phosphates, gravimetric assay, volumetric assay, phosphorus and phosphates, in iron, pipette, , platinum, in gold, , , potash, commercial examination of, potassium, gravimetric determination, potassium cyanide, , , commercial assay of, commercial, purity of, powdering, , , , precipitation, precipitates, drying, igniting, , washing, preliminary assays, , preparation of acids, of other reagents, prill, , , , produce, pyrarsenate of magnesia, pyrites, iron in, sulphur in, , pyrophosphate of magnesia, quantity to be taken for an assay, , , quartation, quartering, reagents, strength of, red lead for dry assays, , , reducing agents, , effects of charcoal, &c., effect of mineral sulphides, , , reduction by hydrogen, of ferric solutions, , , regulus, report form, results, calculation of, , , , , , , statement of, rhodium, roasting, , rolling, rubidium, ruthenium, sample book, sampling, effect of powdering on, errors, gold ores, metals, theory of, scorification of silver ores, scorifier, , selenium, separation, as sulphides, basic acetate, molybdate, shales, bituminous, silicon and silicates, in iron, silica in rocks, in slags, silicates, alkalies in, , beryllia in, examination of, titanium in, silver, correction for cupellation loss, detection of, gay-lussac's assay, gay-lussac's assay modified, gravimetric determination of, in bullion, in burnt ore, , in copper, , in galena, in lead, in oxide of lead, in silver precipitate, loss in cupellation, pure preparation of, volhard's assay, volumetric methods, , , silver lead alloys, cupellation of, sampling of, silver ore, crucible assay of, metallic particles in, scorification of, size of assay charges, , , slags, soda-lime, sodium, sodium cyanide, solution, solutions, normal, standard, specific gravity, , speise, standard, solutions, standardising, steel, carbon in, chromium in, manganese in, stoking, , strength of reagents, strontium, sulphates and sulphur, gravimetric determination, volumetric determination, sulphides, reducing action of, , sulphocyanate assay for silver, sulphur in blende, in burnt ore, in chalcocite, in coal, in copper, in copper pyrites, in mispickel, in pyrites, , sulphuretted hydrogen, preparation, surcharge, system in assaying, table, atomic weights, comparing thermometers, ounces to the long ton, ounces to the short ton, sp. g. ammonia, sp. g. hydrochloric acid, sp. g. minerals, sp. g. nitric acid, sp. g. sulphuric acid, sp. g. water, tantalum, tartar, , tellurium, improved test for, thallium, thorium, tin, _see also black tin_ assay for, by vanning, copper in, cornish assay, cyanide assay, detection of, gravimetric determination of, iron in, separation of, volumetric assay for, tin arsenide, tin phosphide, tin slag, an analysis of, tin in, titanium, detection of, in black tin, , in rocks, separation, &c., titration, indirect, , ton, assay, , , long, lbs. = , . oz., short, lbs = , . oz., tungsten, tungstic acid, gravimetric determination, in black tin, in wolfram, uranium, valuation, of copper ores, vanadium, vanning, volhard's assay applied to arsenic, silver assay, volume-corrector, volumetric assay, , water, , direct determination of, examination of, expansion of, solids in, weighing, small gold buttons, weights, wolfram, an analysis of, tungstic acid in, yttria, zinc, commercial, examination of, commercial, iron in, commercial, lead in, dry assay, gasometric assay, gravimetric determination, in blende, in cyanide liquors, in silver precipitate, separation of, volumetric assay, zirconia, printed by ballantyne, hanson & co. london & edinburgh. a selection from the scientific and technical works _published by_ ~charles griffin & company, limited.~ [illustration] messrs. charles griffin & company's publications may be obtained through any bookseller in the united kingdom, or will be sent post-free on receipt of a remittance to cover published price. to prevent delay, orders should be accompanied by a cheque or postal order crossed "union of london and smith's bank, chancery lane branch." *** _for index, see next page._ [transcriber's note: no index on next page.] [illustration] complete technical, medical, and general catalogues forwarded post-free on application. ~london:~ ~exeter street, strand.~ * * * * * third edition, _revised, with an additional chapter on foundations. numerous diagrams, examples, and tables. large vo. cloth. s._ ~the design of structures:~ ~a practical treatise on the building of bridges, roofs, &c.~ by s. anglin, c.e., master of engineering, royal university of ireland, late whitworth scholar, &c. 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[_shortly._ gas and oil engines: an introductory text-book on the theory, design, construction, and testing of internal combustion engines without boiler. for the use of students. by prof. w.h. watkinson, whit. sch., m. inst. mech. e., glasgow and west of scotland technical college. * * * * * second edition, revised. with numerous plates reduced from working drawings and illustrations in the text. s. _a manual of_ locomotive engineering: a practical text-book for the use of engine builders, designers and draughtsmen, railway engineers, and students. by william frank pettigrew, m. inst. c.e. with a section on american and continental engines. by albert f. ravenshear, b.sc., of his majesty's patent office. _contents_.--historical introduction, - .--modern locomotives: simple.--modern locomotives: compound.--primary consideration in locomotive design.--cylinders, steam chests, and stuffing boxes.--pistons, piston rods, crossheads, and slide bars.--connecting and coupling rods.--wheels and axles, axle boxes, hornblocks, and bearing springs.--balancing.--valve gear.--slide valves and valve gear details.--framing, bogies and axle trucks, radial axle boxes.--boilers.--smokebox, blast pipe, firebox fittings.--boiler mountings.--tenders.--railway brakes.--lubrication.--consumption of fuel, evaporation and engine efficiency.--american locomotives.--continental locomotives.--repairs, running, inspection, and renewals.--three appendices.--index. 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"concise explanations illustrated by very clear diagrams and drawings and folding-plates ... the book fulfils a valuable function."--_athenæum._ "mr. hurst's valves and valve-gearing will prove a very valuable aid, and tend to the production of engines of scientific design and economical working.... will be largely sought after by students and designers.--_marine engineer._ "useful and thoroughly practical. will undoubtedly be found of great value to all concerned with the design of valve-gearing."--_mechanical world._ "almost every type of valve and its gearing is clearly set forth, and illustrated in such a way as to be readily understood and practically applied by either the engineer, draughtsman, or student.... should prove both useful and valuable to all engineers seeking for reliable and clear information on the subject. its moderate price brings it within the reach of all"--_industries and iron._ "mr. hurst's work is admirably suited to the needs of the practical mechanic.... it is free from any elaborate theoretical discussions, and the explanations of the various types of valve-gear are accompanied by diagrams which render them easily understood."--_the scientific american._ * * * * * ~hints on steam engine design and construction.~ by charles hurst, "author of valves and valve gearing." in paper boards, vo., cloth back. illustrated. price s. d. net. contents.--i. steam pipes.--ii. valves.--iii. cylinders.--iv. air pumps and condensers.--v. motion work.--vi. crank shafts and pedestals.--vii. valve gear.--viii. lubrication.--ix. miscellaneous details--index. "a handy volume which every practical young engineer should possess."--_the model engineer._ * * * * * just out. strongly bound in super royal vo. cloth boards. ~bonus tables:~ for calculating wages on the bonus or premium systems. _for engineering, technical and allied trades._ by henry a. golding, a.m.inst.m.e., technical assistant to messrs. bryan donkin and clench, ltd., and assistant lecturer in mechanical engineering at the northampton institute, london, e.c. "the adoption of this system for the payment of workmen has created a demand for some handy table or series of tables, by means of which the wages may be easily found without the necessity of any calculations whatever. with the object of supplying this need, the author has compiled the following tables, which have been in practical use for some time past at a large engineering works in london, and have been found of inestimable value. not only are they of great value as a 'time saving appliance,' the computation of the bonus or premiums earned by a number of men taking only _one-tenth_ the time by the aid of these tables compared with ordinary calculations, but they possess the additional advantage of being less liable to error, as there is practically no possibility of a mistake occurring."--_extract from preface._ * * * * * large vo, handsome cloth. with illustrations, tables, &c. s. lubrication & lubricants: a treatise on the ~theory and practice of lubrication~ and on the ~nature, properties, and testing of lubricants.~ by leonard archbutt, f.i.c., f.c.s., chemist to the midland railway company, and r. mountford deeley, m.i.m.e., f.g.s., midland railway locomotive works' manager, derby. contents.--i. friction of solids.--ii. liquid friction or viscosity, and plastic friction.--iii. superficial tension.--iv. the theory of lubrication.--v. lubricants, their sources, preparation, and properties.--vi. physical properties and methods of examination of lubricants.--vii. chemical properties and methods of examination of lubricants.--viii. the systematic testing of lubricants by physical and chemical methods.--ix. the mechanical testing of lubricants.--x. the design and lubrication of bearings.--xi. the lubrication of machinery.--index. "destined to become a classic on the subject."--_industries and iron._ "contains practically all that is known on the subject. deserves the careful attention of all engineers."--_railway official guide._ * * * * * fourth edition. _very fully illustrated. cloth_, _ s. d._ steam-boilers: their defects, management, and construction. by r.d. munro, _chief engineer of the scottish boiler insurance and engine inspection company._ general contents.--i. explosions caused ( ) by overheating of plates--( ) by defective and overloaded safety valves--( ) by corrosion, internal or external--( ) by defective design and construction (unsupported flue tubes; unstrengthened manholes; defective staying; strength of rivetted joints; factor of safety)--ii. construction of vertical boilers: shells--crown plates and uptake tubes--man-holes, mud-holes, and fire-holes--fireboxes--mountings--management--cleaning--table of bursting pressures of steel boilers--table of rivetted joints--specifications and drawings of lancashire boiler for working pressures (a) lbs.; (b) lbs. per square inch respectively. "a valuable companion for workmen and engineers engaged about steam boilers, ought to be carefully studied, and always at hand."--_coll. guardian._ "the book is very useful, especially to steam users, artisans, and young engineers."--_engineer._ * * * * * by the same author. kitchen boiler explosions: why they occur, and how to prevent their occurrence. a practical handbook based on actual experiment. with diagram and coloured plate. price s. * * * * * just out. _in crown vo, handsome cloth. with numerous illustrations. s. net._ emery grinding machinery. ~_a text-book of workshop practice in general tool grinding, and the design, construction, and application of the machines employed._~ by r.b. hodgson, a.m. inst. mech. e., author of "machines and tools employed in the working of sheet metals." introduction.--tool grinding.--emery wheels.--mounting emery wheels.--emery rings and cylinders.--conditions to ensure efficient working.--leading types of machines.--concave and convex grinding.--cup and cone machines.--multiple grinding.--"guest" universal and cutter grinding machines.--ward universal cutter grinder.--press.--tool grinding.--lathe centre grinder.--polishing.--index. "deals practically with every phase of his subject."--_ironmonger._ * * * * * fifth edition. folio, strongly half-bound, /. traverse tables: ~computed to four places of decimals for every minute of angle up to of distance.~ ~for the use of surveyors and engineers.~ by richard lloyd gurden, authorised surveyor for the governments of new south wales and victoria. *** _published with the concurrence of the surveyors-general for new south wales and victoria._ "those who have experience in exact survey-work will best know how to appreciate the enormous amount of labour represented by this valuable book. the computations enable the user to ascertain the sines and cosines for a distance of twelve miles to within half an inch, and this by reference to but one table, in place of the usual fifteen minute computations required. this alone is evidence of the assistance which the tables ensure to every user, and as every surveyor in active practice has felt the want of such assistance few knowing of their publication will remain without them."--_engineer._ * * * * * works by andrew jamieson, m. inst. c.e., m.i.e.e., f.r.s.e., _formerly professor of electrical engineering, the glasgow and west of scotland technical college._ * * * * * professor jamieson's advanced text-books. _in large crown vo. fully illustrated._ ~steam and steam-engines (a text-book on).~ for the use of students preparing for competitive examinations. with pp., over illustrations, folding plates, and numerous examination papers. thirteenth edition, revised. / . "professor jamieson fascinates the reader by his clearness of conception and simplicity of expression. his treatment recalls the lecturing of faraday."--_athenæum._ "the best book yet published for the use of students."--_engineer._ ~magnetism and electricity (an advanced text-book on).~ for advanced and "honours" students. by prof. jamieson, assisted by david robertson, b.sc., professor of electrical engineering in the merchant venturers' technical college, bristol. [_shortly._ ~applied mechanics (an advanced text-book on).~ vol. i.--comprising part i.: the principle of work and its applications; part ii.: gearing. price s. d. third edition. "fully maintains the reputation of the author."--_pract. engineer._ vol. ii.--comprising parts iii. to vi.: motion and energy; graphic statics; strength of materials; hydraulics and hydraulic machinery. second edition. s. d. "well and lucidly written."--_the engineer._ *** _each of the above volumes is complete in itself, and sold separately._ * * * * * professor jamieson's introductory manuals. _crown vo. with illustrations and examination papers._ ~steam and the steam-engine (elementary manual of).~ for first-year students. ninth edition, revised. / . "should be in the hands of every engineering apprentice."--_practical engineer._ ~magnetism and electricity (elementary manual of).~ for first-year students. fifth edition.. / . "a capital text-book.... the diagrams are an important feature."--_schoolmaster._ "a thoroughly trustworthy text-book. practical and clear."--_nature._ ~applied mechanics (elementary manual of).~ specially arranged for first-year students. fifth edition, revised. / . "the work has very high qualities, which may be condensed into the one word 'clear.'"--_science and art._ * * * * * in preparation. _ pages. crown vo. profusely illustrated._ ~modern electric tramway traction: a text-book of present-day practice.~ _for the use of electrical engineering students and those interested in electric transmission of power._ by prof. andrew jamieson. * * * * * ~a pocket-book of electrical rules and tables.~ for the use of electricians and engineers. pocket size. leather, s. d. sixteenth edition. [see p. . * * * * * works by w.j. macquorn rankine, ll.d., f.r.s., _late regius professor of civil engineering in the university of glasgow._ thoroughly revised by w.j. millar, c.e., _late secretary to the institute of engineers and shipbuilders in scotland._ * * * * * ~a manual of applied mechanics:~ comprising the principles of statics and cinematics, and theory of structures, mechanism, and machines. with numerous diagrams. crown vo, cloth. sixteenth edition. s. d. * * * * * ~a manual of civil engineering:~ comprising engineering surveys, earthwork, foundations, masonry, carpentry, metal work, roads, railways, canals, rivers, waterworks, harbours, &c. with numerous tables and illustrations. crown vo. cloth. twenty-first edition. s. * * * * * ~a manual of machinery and millwork:~ comprising the geometry, motions, work, strength, construction, and objects of machines, &c. illustrated with nearly woodcuts, crown vo, cloth. seventh edition. s. d. * * * * * ~a manual of the steam-engine and other prime movers:~ with a section on gas, oil, and air engines, by bryan donkin, m.inst.c.e. with folding plates and numerous illustrations. crown vo, cloth. fifteenth edition. s. d. * * * * * ~useful rules and tables:~ for architects, builders, engineers, founders, mechanics, shipbuilders, surveyors, &c. with appendix for the use of electrical engineers. by professor jamieson, f.r.s.e. seventh edition. s. d. * * * * * ~a mechanical text-book:~ a practical and simple introduction to the study of mechanics. by professor rankine and e.f. bamber, c.e. with numerous illustrations. crown vo, cloth. fifth edition. s. *** _the_ "mechanical text-book" _was designed by_ professor rankine _as an_ introduction _to the above series of manuals._ * * * * * ~miscellaneous scientific papers.~ royal vo. cloth, s. d. part i. papers relating to temperature, elasticity, and expansion of vapours, liquids, and solids. part ii. papers on energy and its transformations. part iii. papers on wave-forms, propulsion of vessels, &c. with memoir by professor tait, m.a. edited by w.j. millar, c.e. with fine portrait on steel, plates, and diagrams. "no more enduring memorial of professor rankine could be devised than the publication of these papers in an accessible form.... the collection is most valuable on account of the nature of his discoveries, and the beauty and completeness of his analysis.... the volume exceeds in importance any work in the same department published in our time."--_architect._ * * * * * shelton-bey (w. vincent, foreman to the imperial ottoman gun factories, constantinople): ~the mechanic's guide:~ a hand-book for engineers and artizans. with copious tables and valuable recipes for practical use. illustrated. _second edition._ crown vo. cloth, / . * * * * * _second edition, revised and enlarged. in large vo, handsome cloth, s._ hydraulic power and hydraulic machinery. by henry robinson, m. inst. c.e., f.g.s., fellow of king's college, london; prof. of civil engineering, king's college, etc., etc. with numerous woodcuts, and sixty-nine plates. "a book of great professional usefulness."--_iron._ * * * * * _in large vo, handsome cloth. with frontispiece, several plates, and over illustrations. s._ the principles and construction of pumping machinery (steam and water pressure). with practical illustrations of engines and pumps applied to mining, town water supply, drainage of lands, &c., also economy and efficiency trials of pumping machinery. by henry davey, member of the institution of civil engineers, member of the institution of mechanical engineers, f.g.s., &c. contents--early history of pumping engines--steam pumping engines--pumps and pump valves--general principles of non-rotative pumping engines--the cornish engine, simple and compound--types of mining engines--pit work--shaft sinking--hydraulic transmission of power in mines--valve gears of pumping engines--water pressure pumping engines--water works engines--pumping engine economy and trials of pumping machinery--centrifugal and other low-lift pumps--hydraulic rams. pumping mains, &c.--index. "by the 'one' english engineer who probably knows more about pumping machinery than any other.' ... a volume recording the results of long experience and study."--_the engineer._ "undoubtedly the best and most practical treatise on pumping machinery that has yet been published."--_mining journal._ * * * * * _royal vo, handsome cloth. with numerous illustrations and tables. s._ the stability of ships. by sir edward j. reed, k.c.b., f.r.s., m.p., knight of the imperial orders of st. stanilaus of russia; francis joseph of austria; medjidie of turkey; and rising sun of japan; vice-president of the institution of naval architects. in order to render the work complete for the purposes of the shipbuilder, whether at home or abroad, the methods of calculation introduced by mr. f.k. barnes, mr. gray, m. reech, m. daymard, and mr. benjamin, are all given separately, illustrated by tables and worked-out examples. the book contains more than diagrams, and is illustrated by a large number of actual cases, derived from ships of all descriptions. "sir edward reed's 'stability of ships' is invaluable. the naval architect will find brought together and ready to his hand, a mass of information which he would otherwise have to seek in an almost endless variety of publications, and some of which he would possibly not be able to obtain at all elsewhere."--_steamship._ * * * * * ~the design and construction of ships.~ by john harvard biles, m.inst.n.a., professor of naval architecture in the university of glasgow. [_in preparation._ * * * * * second edition. illustrated with plates, numerous diagrams, and figures in the text. s. net. ~steel ships: their construction and maintenance.~ _a manual for shipbuilders, ship superintendents, students, and marine engineers._ by thomas walton, naval architect, author of "know your own ship." contents.--i. manufacture of cast iron, wrought iron, and steel.--composition of iron and steel, quality, strength, tests, &c. ii. classification of steel ships. iii. considerations in making choice of type of vessel.--framing of ships. iv. strains experienced by ships.--methods of computing and comparing strengths of ships. v. construction of ships.--alternative modes of construction.--types of vessels.--turret, self trimming, and trunk steamers, &c.--rivets and rivetting, workmanship. vi. pumping arrangements. vii. maintenance.--prevention of deterioration in the hulls of ships.--cement, paint, &c.--index. "so thorough and well written is every chapter in the book that it is difficult to select any of them as being worthy of exceptional praise. altogether, the work is excellent, and will prove of great value to those for whom it is intended."--_the engineer._ "mr. walton has written for the profession of which he is an ornament. his work will be read and appreciated, no doubt, by every m.i.n.a., and with great benefit by the majority of them."--_journal of commerce._ * * * * * second edition, cloth, s. d. leather, for the pocket, s. d. ~griffin's electrical price-book:~ for electrical, civil, marine, and borough engineers, local authorities, architects, railway contractors, &c., &c. edited by h.j. dowsing. "the electrical price-book removes all mystery about the cost of electrical power. by its aid the expense that will be entailed by utilising electricity on a large or small scale can be discovered."--_architect._ * * * * * griffin's nautical series, edited by edw. blackmore, master mariner, first class trinity house certificate, assoc. inst. n.a.; and written, mainly, by sailors for sailors. "this admirable series."--_fairplay_. "a very useful series."--_nature_. "the volumes of messrs. griffin's nautical series may well and profitably be read by all interested in our national maritime progress."--_marine engineer._ "every ship should have the whole series as a reference library. handsomely bound, clearly printed and illustrated."--_liverpool journ. of commerce._ ~the british mercantile marine:~ an historical sketch of its rise and development. by the editor, capt. blackmore. s. d. "captain blackmore's splendid book ... contains paragraphs on every point of interest to the merchant marine. the pages of this book are the most valuable to the sea captain that have ever been compiled."--_merchant service review._ ~elementary seamanship.~ by d. wilson-barker, master mariner, f.r.s.e., f.r.g.s. with numerous plates, two in colours, and frontispiece. third edition, thoroughly revised, enlarged, and re-set. with additional illustrations. s. "this admirable manual, by capt. wilson barker, of the 'worcester', seems to us perfectly designed. "--_athenæum._ ~know your own ship~: a simple explanation of the stability, construction, tonnage, and freeboard of ships. by thos. walton, naval architect. with numerous illustrations and additional chapters on buoyancy, trim, and calculations. sixth edition, revised. s. d. "mr. walton's book will be found very useful."--_the engineer._ ~navigation: theoretical and practical.~ by d. wilson-barker, master mariner, &c., and william allingham. second edition, revised. s. d. "precisely the kind of work required for the new certificates of competency. candidates will find it invaluable."--_dundee advertiser._ ~marine meteorology~: for officers of the merchant navy. by william allingham, first class honours, navigation, science and art department. with illustrations, maps, and diagrams, and _facsimile_ reproduction of log page. s. d. "quite the best publication on this subject."--_shipping gazette._ ~latitude and longitude: how to find them.~ by w.j. millar, c.e., late sec. to the inst. of engineers and shipbuilders in scotland. second edition, revised. s. "cannot but prove an acquisition to those studying navigation."--_marine engineer._ ~practical mechanics:~ applied to the requirements of the sailor. by thos. mackenzie, master mariner, f.r.a.s. second edition, revised. s. d. "well worth the money ... exceedingly helpful."--_shipping world._ ~trigonometry:~ for the young sailor, &c. by rich. c. buck, of the thames nautical training college, h.m.s. "worcester." second edition, revised. price s. d. "this eminently practical and reliable volume."--_schoolmaster_. ~practical algebra.~ by rich. c. buck. companion volume to the above, for sailors and others. price s. d. "it is just the book for the young sailor mindful of progress."--_nautical magazine._ ~the legal duties of shipmasters.~ by benedict wm. ginsburg, m.a., ll.d., of the inner temple and northern circuit; barrister-at-law. second edition, thoroughly revised and extended. price s. d. "invaluable to masters ... we can fully recommend it."--_shipping gazette._ ~a medical and surgical help for shipmasters.~ including first aid at sea. by wm. johnson smith, f.r.c.s., principal medical officer, seamen's hospital, greenwich. second edition, revised. s. "sound, judicious, really helpful."--_the lancet._ * * * * * _introductory volume. price s. d._ the ~british mercantile marine.~ by edward blackmore, master mariner; associate of the institution of naval architects; member of the institution of engineers and shipbuilders in scotland; editor of griffin's "nautical series." general contents.--historical: from early times to --progress under henry viii.--to death of mary--during elizabeth's reign--up to the reign of william iii.--the th and th centuries--institution of examinations--rise and progress of steam propulsion--development of free trade--shipping legislation, to --"locksley hall" case--shipmasters' societies--loading of ships--shipping legislation, to --statistics of shipping. the personnel: shipowners--officers--mariners--duties and present position. education: a seaman's education: what it should be--present means of education--hints. discipline and duty--postscript--the serious decrease in the number of british seamen, a matter demanding the attention of the nation. "interesting and instructive ... may be read with profit and enjoyment."--_glasgow herald._ "every branch of the subject is dealt with in a way which shows that the writer 'knows the ropes' familiarly."--_scotsman._ "this admirable book ... teems with useful information--should be in the hands of every sailor."--_western morning news._ * * * * * third edition, _thoroughly revised, enlarged, and re-set. with additional illustrations. price s._ ~a manual of elementary seamanship.~ by d. wilson-barker, master mariner; f.r.s.e., f.r.g.s., &c., &c.; younger brother of the trinity house. with frontispiece, numerous plates (two in colours), and illustrations in the text. general contents.--the building of a ship; parts of hull, masts, &c.--ropes, knots, splicing, &c.--gear, lead and log, &c.--rigging, anchors--sailmaking--the sails, &c.--handling of boats under sail--signals and signalling--rule of the road--keeping and relieving watch--points of etiquette--glossary of sea terms and phrases--index. *** the volume contains the new rules of the road. "this admirable manual, by capt. wilson-barker of the 'worcester,' seems to us perfectly designed, and holds its place excellently in griffin's nautical series.' ... although intended for those who are to become officers of the merchant navy, it will be found useful by all yachtsmen."--_athenæum._ *** for complete list of griffin's nautical series, see p. . * * * * * second edition, _revised and illustrated. price s. d._ ~navigation:~ ~practical and theoretical~ by david wilson-barker, r.n.r, f.r.s.e., &c., &c., and william allingham, first-class honors, navigation, science and art department. with numerous illustrations and examination questions. general contents.--definitions--latitude and longitude--instruments of navigation--correction of courses--plane sailing--traverse sailing--day's work--parallel sailing--middle latitude sailing--mercator's chart--mercator sailing--current sailing--position by bearings--great circle sailing--the tides--questions--appendix: compass error--numerous useful hints, &c.--index. "precisely the kind of work required for the new certificates of competency in grades from second mate to extra master.... candidates will find it invaluable."--_dundee advertiser._ "a capital little book ... specially adapted to the new examinations. the authors are capt. wilson-barker (captain-superintendent of the nautical college, h.m.s. 'worcester,' who has had great experience in the highest problems of navigation), and mr. allingham, a well-known writer on the science of navigation and nautical astronomy."--_shipping world._ * * * * * _handsome cloth. fully illustrated. price s. d._ ~marine meteorology, for officers of the merchant navy.~ by william allingham, joint author of "navigation, theoretical and practical." with numerous plates, maps, diagrams, and illustrations, and a facsimile reproduction of a page from an actual meteorological log-book. summary of contents. introductory.--instruments used at sea for meteorological purposes.--meteorological log-books.--atmospheric pressure.--air temperatures.--sea temperatures.--winds.--wind force scales.--history of the law of storms.--hurricanes, seasons, and storm tracks.--solution of the cyclone problem.--ocean currents.--icebergs.--synchronous charts.--dew, mists, fogs, and haze.--clouds.--rain, snow, and hail.--mirage, rainbows, coronas, halos, and meteors.--lightning, corposants, and auroras.--questions.--appendix.--index. "quite the best publication, and certainly the most interesting, on this subject ever presented to nautical men."--_shipping gazette._ *** for complete list of griffin's nautical series, see p. . * * * * * second edition, revised. with numerous illustrations. price ~ s. d.~ ~practical mechanics:~ applied to the requirements of the sailor. by thos. mackenzie, _master mariner, f.r.a.s._ general contents.--resolution and composition of forces--work done by machines and living agents--the mechanical powers: the lever; derricks as bent levers--the wheel and axle: windlass; ship's capstan; crab winch--tackles: the "old man"--the inclined plane; the screw--the centre of gravity of a ship and cargo--relative strength of rope: steel wire, manilla, hemp, coir--derricks and shears--calculation of the cross-breaking strain of fir spar--centre of effort of sails--hydrostatics: the diving-bell; stability of floating bodies; the ship's pump, &c. "this excellent book ... contains a large amount of information."--_nature._ "well worth the money ... will be found exceedingly helpful."--_shipping world._ "no ships' officers' bookcase will henceforth be complete without captain mackenzie's 'practical mechanics.' notwithstanding my many years' experience at sea, it has told me _how much more there is to acquire_."--(letter to the publishers from a master mariner). "i must express my thanks to you for the labour and care you have taken in 'practical mechanics.' ... it is a life's experience. ... what an amount we frequently see wasted by rigging purchases without reason and accidents to spars, &c., &c.! 'practical mechanics' would save all this."--(letter to the author from another master mariner). * * * * * ~works by richard c. buck,~ of the thames nautical training college, h.m.s. 'worcester.' ~a manual of trigonometry:~ _with diagrams, examples, and exercises. price s. d._ second edition, revised and corrected. *** mr. buck's text-book has been specially prepared with a view to the new examinations of the board of trade, in which trigonometry is an obligatory subject. "this eminently practical and reliable volume."--_schoolmaster._ * * * * * ~a manual of algebra.~ _designed to meet the requirements of sailors and others. price s. d._ *** these elementary works on algebra and trigonometry are written specially for those who will have little opportunity of consulting a teacher. they are books for "self-help." all but the simplest explanations have, therefore, been avoided, and answers to the exercises are given. any person may readily, by careful study, become master of their contents, and thus lay the foundation for a further mathematical course, if desired. it is hoped that to the younger officers of our mercantile marine they will be found decidedly serviceable. the examples and exercises are taken from the examination papers set for the cadets of the "worcester." "clearly arranged, and well got up.... a first-rate elementary algebra."--_nautical magazine._ * * * * * second edition, thoroughly revised and extended. in crown vo. handsome cloth. price s. d. ~the legal duties of shipmasters.~ by benedict wm. ginsburg, m.a., ll.d. (cantab.), of the inner temple and northern circuit; barrister-at-law. ~general contents.~--the qualification for the position of shipmaster--the contract with the shipowner--the master's duty in respect of the crew: engagement; apprentices; discipline; provisions, accommodation, and medical comforts; payment of wages and discharge--the master's duty in respect of the passengers--the master's financial responsibilities--the master's duty in respect of the cargo--the master's duty in case of casualty--the master's duty to certain public authorities--the master's duty in relation to pilots, signals, flags, and light dues--the master's duty upon arrival at the port of discharge--appendices relative to certain legal matters: board of trade certificates, dietary scales, stowage of grain cargoes, load line regulations, life-saving appliances, carriage of cattle at sea, &c., &c.--copious index. "no intelligent master should fail to add this to his list of necessary books. a few lines of it may save a lawyer's fee, besides endless worry."--_liverpool journal of commerce._ "sensible, plainly written, in clear and non-technical language, and will be found of much service by the shipmaster."--_british trade review._ * * * * * second edition, revised. with diagrams. price s. ~latitude and longitude: how to find them.~ by w.j. millar, c.e., _late secretary to the inst. of engineers and shipbuilders in scotland._ "concisely and clearly written ... cannot but prove an acquisition to those studying navigation."--_marine engineer._ "young seamen will find it handy and useful, simple and clear."--_the engineer._ * * * * * ~first aid at sea.~ second edition, revised. with coloured plates and numerous illustrations, and comprising the latest regulations respecting the carriage of medical stores on board ship. price s. ~a medical and surgical help for shipmasters and officers in the merchant navy.~ by wm. johnson smith, f.r.c.s., principal medical officer, seamen's hospital, greenwich. *** the attention of all interested in our merchant navy is requested to this exceedingly useful and valuable work. it is needless to say that it is the outcome of many years practical experience amongst seamen. "sound, judicious, really helpful."--_the lancet._ * * * * * sixth edition. _revised, with chapters on trim, buoyancy, and calculations. numerous illustrations. handsome cloth, crown vo. price s. d._ ~know your own ship.~ by thomas walton, naval architect. specially arranged to suit the requirements of ships' officers, shipowners, superintendents, draughtsmen, engineers, and others. this work explains, in a simple manner, such important subjects as:-- displacement, deadweight, tonnage, freeboard, moments, buoyancy, strain, structure, stability, rolling, ballasting, loading, shifting cargoes, admission of water, sail area, &c., &c. "the little book will be found exceedingly handy by most officers and officials connected with shipping.... mr. walton's work will obtain lasting success, because of its unique fitness for those for whom it has been written."--_shipping world._ "an excellent work, full of solid instruction and invaluable to every officer of the mercantile marine who has his profession at heart."--_shipping._ "not one of the pages could well be spared. it will admirably fulfil its purpose ... useful to ship owners, ship superintendents, ship draughtsmen, and all interested in shipping."--_liverpool journal of commerce._ "a mass of very useful information, accompanied by diagrams and illustrations, is given in a compact form."--_fairplay._ "we have found no one statement that we could have wished differently expressed. the matter has, so far as clearness allows, been admirably condensed, and is simple enough to be understood by every seaman."--_marine engineer._ * * * * * ~by the same author.~ ~steel ships: their construction and maintenance.~ (~see page .~) * * * * * fourteenth edition, revised. price s. _demy vo, cloth. with numerous illustrations, reduced from working drawings._ ~a manual of marine engineering:~ comprising the designing, construction, and working of marine machinery. by a.e. seaton, m. inst. c.e., m. inst. mech. e., m. inst. n.a. general contents.--part i.--principles of marine propulsion. part ii.--principles of steam engineering. part iii.--details of marine engines: design and calculations for cylinders, pistons, valves, expansion valves, &c. part iv.--propellers. part v.--boilers. part vi.--miscellaneous. *** this edition includes a chapter on water-tube boilers, with illustrations of the leading types and the revised rules of the _bureau veritas_. "in the three-fold capacity of enabling a student to learn how to design, construct, and work a marine steam-engine, mr. seaton's manual has no rival."--_times._ "by far the best manual in existence.... gives a complete account of the methods of solving, with the utmost possible economy, the problems before the marine engineer."--_athenæum._ "the student, draughtsman, and engineer will find this work the most valuable handbook of reference on the marine engine now in existence."--_marine engineer._ * * * * * seventh edition, thoroughly revised. pocket-size, leather. s. d. ~a pocket-book of marine engineering rules and tables, for the use of marine engineers, naval architects, designers, draughtsmen, superintendents and others.~ by a.e. seaton, m.i.c.e., m.i.mech.e., m.i.n.a., and h.m. rounthwaite, m.i.mech.e., m.i.n.a. "admirably fulfils its purpose."--_marine engineer._ * * * * * by b. cunningham. ~docks: their construction & maintenance.~ (see page .) * * * * * works by prof. robert h. smith, assoc. m.i.c.e., m.i.m.e., m.i.el.b., m.i. min. e., whit. sch., m. ord. meiji. * * * * * the calculus for engineers and physicists, applied to technical problems. with extensive classified reference list of integrals. by prof. robert h. smith. assisted by r.f. muirhead, m.a., b.sc., formerly clark fellow of glasgow university, and lecturer on mathematics at mason college. _in crown vo, extra, with diagrams and folding-plate._ s. d. "prof. r.h. smith's book will be serviceable in rendering a hard road as easy as practicable for the non-mathematical student and engineer."--_athenæum._ "interesting diagrams, with practical illustrations of actual occurrence, are to be found here in abundance. the very complete classified reference table will prove very useful in saving the time of those who want an integral in a hurry."--_the engineer._ * * * * * measurement conversions (english and french): graphic tables or diagrams. showing at a glance the mutual conversion of measurements in different units of lengths, areas, volumes, weights, stresses, densities, quantities of work, horse powers, temperatures, &c. _for the use of engineers, surveyors, architects, and contractors._ _in to, boards. s. d._ * * * * * *** prof. smith's conversion-tables form the most unique and comprehensive collection ever placed before the profession. by their use much time and labour will be saved, and the chances of error in calculation diminished. it is believed that henceforth no engineer's office will be considered complete without them. "the work is invaluable."--_colliery guardian._ "ought to be in every office where even occasional conversions are required.... prof. smith's tables form very excellent checks on results."--_electrical review._ "prof. smith deserves the hearty thanks, not only of the engineer, but of the commercial world, for having smoothed the way for the adoption of the metric system of measurement, a subject which is now assuming great importance as a factor in maintaining our hold upon foreign trade."--_the machinery market._ * * * * * in large vo. handsome cloth. s. d. chemistry for engineers. by bertram blount, f.i.c., f.c.s., a.i.c.e., consulting chemist to the crown agents for the colonies. and a.g. bloxam, f.i.c., f.c.s., consulting chemist, head of the chemistry department, goldsmiths' inst., new cross. general contents.--introduction--chemistry of the chief materials of construction--sources of energy--chemistry of steam-raising--chemistry of lubrication and lubricants--metallurgical processes used in the winning and manufacture of metals. "the authors have succeeded beyond all expectation, and have produced a work which should give fresh power to the engineer and manufacturer."--_the times._ "practical throughout ... an admirable text-book, useful not only to students, but to engineers and managers of works in preventing waste and improving processes."--_scotsman._ "a book worthy to take high rank ... treatment of the subject of gaseous fuel particularly good.... water gas and its production clearly worked out.... we warmly recommend the work."--_journal of gas lighting._ for companion volume by the same authors, see "chemistry for manufacturers," p. . * * * * * works by walter r. browne, m.a., m. inst. c.e., late fellow of trinity college, cambridge. ~the student's mechanics: an introduction to the study of force and motion.~ with diagrams. crown vo. cloth, s. d. "clear in style and practical in method, 'the student's mechanics' is cordially to be commended from all points of view."--_athenæum._ * * * * * foundations of mechanics. papers reprinted from the _engineer._ in crown vo, s. * * * * * demy vo, with numerous illustrations, s. fuel and water: a manual for users of steam and water. by prof. franz schwackhÖfer of vienna, and walter r. browne, m.a., c.e. general contents.--heat and combustion--fuel, varieties of--firing arrangements: furnace, flues, chimney--the boiler, choice of--varieties--feed-water heaters--steam pipes--water: composition, purification--prevention of scale, &c., &c. "the section on heat is one of the best and most lucid ever written."--_engineer._ "cannot fail to be valuable to thousands using steam power."--_railway engineer._ * * * * * griffins local government handbooks. works suitable for municipal and county engineers, analysts, and others. see also davies' _hygiene_, p. , and macleod's _public health_, p. . ~gas manufacture (the chemistry of).~ a handbook on the production, purification, and testing of illuminating gas, and the assay of bye-products. by w.j.a. butterfield, m.a., f.i.c., f.c.s. with illustrations. third edition, revised (in preparation). [see page . ~water supply:~ a practical treatise on the selection of sources and the distribution of water. by reginald e. middleton, m. inst. c.e., m. inst. mech. e., f.s.i. with four plates and numerous diagrams. crown vo. [see page . ~central electrical stations:~ their design, organisation, and management. by ~c.h. wordingham~, a.k.c., m. inst. c.e. price s. net. _for details see opposite page._ ~sewage disposal works:~ a guide to the construction of works for the prevention of the pollution by sewage of rivers and estuaries. by w. santo crimp, m. inst. c.e., f.g.s. second edition, revised and enlarged. large vo, handsome cloth. with plates. price s. [see page . ~trades' waste:~ its treatment and utilisation, with special reference to the prevention of rivers' pollution. by w. naylor, f.c.s., a.m. inst. c.e. with numerous plates, diagrams, and illustrations. s. net. [see page . ~calcareous cements:~ their nature, preparation, and uses. with some remarks upon cement testing. by gilbert redgrave, assoc. inst. c.e. with illustrations, analytical data, and appendices on costs, &c. s. d. [see page . ~road making and maintenance:~ a practical treatise for engineers, surveyors, and others. with an historical sketch of ancient and modern practice. by thomas aitken, assoc. m. inst. c.e., m. assoc. municipal and county engrs.; m. san. inst. with numerous plates, diagrams, and illustrations. s. [see page . ~light railways at home and abroad.~ by william henry cole, m. inst. c.e., late deputy manager, north-western railway, india. large vo, handsome cloth, plates and illustrations. s. [see page . ~practical sanitation:~ a handbook for sanitary inspectors and others interested in sanitation. by geo. reid, m.d., d.p.h., medical officer, staffordshire county council. with appendix on sanitary law, by herbert manley, m.a., m.b., d.p.h. tenth edition, revised. s. [see page . ~sanitary engineering~: a practical manual of town drainage and sewage and refuse disposal. by frank wood, a.m. inst. c.e., f.g.s., borough surveyor, fulham. fully illustrated. s. d. net. [see page . ~dairy chemistry:~ a practical handbook for dairy managers, chemists, and analysts. by ~h. droop richmond~, f.c.s., chemist to the aylesbury dairy company. with tables, illustrations, &c. handsome cloth, s. [see page . ~milk: its production and uses.~ with chapters on dairy farming, the diseases of cattle, and on the hygiene and control of supplies. by edward f. willoughby, m.d. (lond.), d.p.h. (lond. and camb.), inspector of farms and general scientific adviser to welford & sons, ltd. [see page . ~flesh foods:~ with methods for their chemical, microscopical, and bacteriological examination. a handbook for medical men, inspectors, analysts, and others. by c. ainsworth mitchell, b.a., f.i.c., mem. council soc. of public analysts. with numerous illustrations and a coloured plate. s. d. [see page . ~foods:~ their composition and analysis. by a. wynter blyth, m.r.c.s., f.c.s., public analyst for the county of devon. with tables, folding plate, and frontispiece. fifth edition, thoroughly revised. s. [see page . "an admirable digest of the most recent state of knowledge."--_chemical news._ * * * * * electrical engineering. _in large vo. handsome cloth. profusely illustrated with plates, diagrams, and figures. s. net._ central electrical stations: their design, organisation, and management. by chas. h. wordingham, a.k.c., m. inst. c.e., m. inst. mech. e., late memb. of council inst. e.e., and electrical engineer to the city of manchester. abridged contents. introductory.--central station work as a profession.--as an investment.--the establishment of a central station.--systems of supply.--site.--architecture.--plant.--boilers.--systems of draught and waste heat economy.--coal handling, weighing, and storing.--the transmission of steam.--generators.--condensing appliances.--switching gear, instruments, and connections.--distributing mains.--insulation, resistance, and cost.--distributing networks.--service mains and feeders.--testing mains.--meters and appliances.--standardising and testing laboratory.--secondary batteries.--street lighting.--cost.--general organisation.--mains department.--installation department.--standardising department.--drawing office.--clerical department.--the consumer.--routine and main laying.--index. "one of the most valuable contributions to central station literature we have had for some time."--_electricity._ * * * * * electricity control. a treatise on electricity switchgear and systems of transmission. by leonard andrews, m.i.e.e., ex-member of council of the incorporated municipal electrical association; consulting electrical engineer to the hastings corporation, &c., &c. general principles of switchgear design.--constructional details.--circuit breakers or arc interrupting devices.--automatically operated circuit breakers.--alternating reverse current devices.--arrangement of 'bus bars, and apparatus for parallel running.--general arrangement of controlling apparatus for high tension systems.--general arrangement of controlling apparatus for low tension systems.--examples of complete installations.--long distance transmission schemes. * * * * * sixteenth edition, thoroughly revised and enlarged. a pocket-book of electrical rules & tables _for the use of electricians and engineers._ by john munro, c.e., & prof. jamieson, m. inst. c.e., f.r.s.e. with numerous diagrams. pocket size. leather, s. d. ~general contents.~ units of measurement.--measures.--testing.--conductors.--dielectrics.-- submarine cables.--telegraphy.--electro-chemistry.--electro-metallurgy.-- batteries.--dynamos and motors.--transformers.--electric lighting.--miscellaneous.--logarithms.--appendices. "wonderfully perfect.... worthy of the highest commendation we can give it."--_electrician._ "the sterling value of messrs. munro and jamieson's pocket-book."--_electrical review._ * * * * * ~by professors j.h. poynting & j.j. thomson.~ in five volumes. large vo. sold separately. ~a text-book of physics.~ by j.h. poynting, sc.d., f.r.s., late fellow of trinity college, cambridge; professor of physics, birmingham university. and j.j. thomson, m.a., f.r.s. fellow of trinity college, cambridge; prof. of experimental physics in the university of cambridge. * * * * * introductory volume, fully illustrated. second edition, revised. price s. d. ~properties of matter.~ contents.--gravitation.--the acceleration of gravity.--elasticity.--stresses and strains.--torsion.--bending of rods.--spiral springs.--collision.--compressibility of liquids.--pressures and volumes of gases.--thermal effects accompanying strain.--capillarity.--surface tension.--laplace's theory of capillarity.--diffusion of liquids.--diffusion of gases.--viscosity of liquids.--index. * * * * * volume ii. second edition. fully illustrated. price s. d. ~sound.~ contents.--the nature of sound and its chief characteristics.--the velocity of sound in air and other media.--reflection and refraction of sound.--frequency and pitch of notes.--resonance and forced oscillations.--analysis of vibrations.--the transverse vibrations of stretched strings or wires.--pipes and other air cavities.--rods.--plates.--membranes.--vibrations maintained by heat.--sensitive flames and jets.--musical sand.--the superposition of waves.--index. "the work ... may be recommended to anyone desirous of possessing an easy up-to-date standard treatise on acoustics."--_literature._ "very clearly written.... the names of the authors are a guarantee of the scientific accuracy and up-to-date character of the work."--_educational times._ * * * * * volume iii. at press. fully illustrated. ~heat.~ remaining volumes in preparation-- ~light; magnetism and electricity.~ * * * * * ~the mean density of the earth:~ an essay to which the adams prize was adjudged in in the university of cambridge. by j.h. poynting, sc.d., f.r.s., late fellow of trinity college, cambridge; professor of physics, birmingham university. in large vo, with bibliography, illustrations in the text, and seven lithographed plates. s. d. "an account of this subject cannot fail to be of great and general interest to the scientific mind. especially is this the case when the account is given by one who has contributed so considerably as has prof. poynting to our present state of knowledge with respect to a very difficult subject.... remarkably has newton's estimate been verified by prof. poynting."--_athenæum._ * * * * * ~griffin's geological, prospecting, mining, and metallurgical publications.~ for works on chemistry and chemical industries see p. . page geology, stratigraphical, r. etheridge, f.r.s., " physical, prof. h.g. seeley, " practical aids, prof. grenville cole, " open air studies, " " griffin's "new land" series, ed. by prof. cole, prospecting for minerals, s. herbert cox, a.r.s.m., food supply, robt. bruce, new lands, h.r. mill, d.sc., f.r.s.e., building construction, prof. james lyon, ore and stone mining, prof. le neve foster, elementary mining, " " coal mining, h.w. hughes, f.g.s., practical coal mining, g.l. kerr, m.inst.m.e., elementary " " " electrical coal mining, d. burns, mine-surveying, bennett h. brough, a.r.s.m., blasting and explosives, o. guttmann, a.m.i.c.e., mine accounts, prof. j.g. lawn, mining engineers' pkt.-bk., e.r. field, m.inst.m.m., petroleum, redwood and holloway, a handbook on petroleum, j.h. thomson and dr. redwood, the petroleum lamp, " " metallurgical analysis, macleod and walker, metallurgy (general), phillips and bauerman, " (elementary), prof. humboldt sexton, getting gold, j.c.f. johnson, f.g.s., gold seeking in south africa, theo kassner, cyanide process, james park, f.g.s., cyaniding, smart and julian, electric smelting, borchers and mcmillan, electro-metallurgy, w.g. mcmillan, f.i.c., assaying, j.j. & c. beringer, metallurgical analysis, j.j. morgan, f.c.s, griffin's metallurgical series ed. by sir w. roberts-austen, introduction, sir w. roberts-austen, k.c.b., gold, metallurgy of, dr. kirke rose, a.r.s.m., lead and silver, " h.f. collins, a.r.s.m., iron, metallurgy of, thos. turner, a.r.s.m., steel, " f.w. harbord, metallurgical machinery, h.c. jenkins, a.r.s.m., goldsmith and jeweller's art, thos. b. wigley, precious stones, dr. max bauer, * * * * * _demy vo, handsome cloth, s._ physical geology and palæontology, _on the basis of phillips._ by harry govier seeley, f.r.s., professor of geography in king's college, london. with frontispiece in chromo-lithography, and illustrations. "it is impossible to praise too highly the research which professor seeley's 'physical geology' evidences. it is far more than a text-book--it is a directory to the student in prosecuting his researches."--_presidential address to the geological society, , by rev. prof. bonney, d.sc., ll.d., f.r.s._ "professor seeley maintains in his 'physical geology' the high reputation he already deservedly bears as a teacher."--_dr. henry woodward, f.r.s., in the "geological magazine."_ "professor seeley's work includes one of the most satisfactory treatises on lithology in the english language."--_american journal of engineering._ * * * * * _demy vo, handsome cloth, s._ stratigraphical geology & palæontology, _on the basis of phillips._ by robert etheridge, f.r.s., of the natural hist. department, british museum, late palÆontologist to the geological survey of great britain, past president of the geological society, etc. with map, numerous tables, and thirty-six plates. "no such compendium of geological knowledge has ever been brought together before."--_westminster review._ "if prof. seeley's volume was remarkable for its originality and the breadth of its views, mr. etheridge fully justifies the assertion made in his preface that his book differs in construction and detail from any known manual.... must take high rank among works of reference."--_athenæum._ * * * * * open-air studies in geology: an introduction to geology out-of-doors. by professor grenville cole, m.r.i.a., f.g.s. for details, see griffin's introductory science series, p. . * * * * * _crown vo. handsome cloth, s. d._ ~researches on the past and present history of the earth's atmosphere.~ _including the latest discoveries and their practical applications._ by dr. thomas lamb phipson. part i.--the earth's atmosphere in remote geological periods. part ii.--the atmosphere of our present period. appendices; index. *** dr. phipson's work presents, amidst much which is of interest to the scientist and the general reader alike, a short _résumé_ of his discovery of the origin of atmospheric oxygen, the existence of which he attributes wholly to the action of solar radiation upon vegetable life. the book will be found replete with much that is new, curious, and interesting, both in connection with weather lore, and with scientific meteorology.--_publisher's note._ "the book should prove of interest to general readers, as well as to meteorologists and other students of science."--_nature._ * * * * * by grenville a.j. cole, m.r.i.a., f.g.s., professor of geology in the royal college of science for ireland, and examiner in the university of london. _see also the two following pages ( , ), and page ._ * * * * * ~aids in practical geology:~ _with a section on palÆontology._ by professor grenville cole, m.r.i.a., f.g.s. fourth edition, thoroughly revised. with frontispiece and illustrations. cloth, s. d. general contents.-- part i.--sampling of the earth's crust. part ii.--examination of minerals. part iii.--examination of rocks. part iv.--examination of fossils. "prof. cole treats of the examination of minerals and rocks in a way that has never been attempted before ... deserving of the highest praise. here indeed are 'aids' innumerable and invaluable. all the directions are given, with the utmost clearness and precision."--_athenæum._ "that the work deserves its title, that it is full of 'aids,' and in the highest degree 'practical,' will be the verdict of all who use it."--_nature._ "this excellent manual ... will be a very great help.... the section on the examination of fossils is probably the best of its kind yet published.... full of well-digested information from the newest sources and from personal research."--_annals of nat. history._ * * * * * griffins "new land" series. * * * * * _practical hand-books for the use of prospectors, explorers, settlers, colonists, and all interested in the opening up and development of new lands._ edited by grenville a.j. cole, m.r.i.a., f.g.s., professor of geology in the royal college of science for ireland, and examiner in the university of london. * * * * * _in crown vo. handsome cloth. s._ _with numerous maps specially drawn and executed for this work._ new lands: their resources and prospective advantages. by hugh robert mill, d.sc., ll.d., f.r.s.e., librarian to the royal geographical society. introductory.--the development of new lands.--the dominion of canada.--canada, eastern provinces.--canada, western provinces and territories.--newfoundland.--the united states.--latin america, mexico.--latin america, temperate brazil and chili.--latin america, argentina.--the falkland islands.--victoria.--new south wales.--queensland.--south australia.--tasmania.--western australia.--new zealand.--the resources of south africa.--southern rhodesia.--index. "painstaking ... complete ... of great practical assistance."--_the field._ "a want admirably supplied.... has the advantage of being written by a professed geographer."--_geographical journal._ * * * * * _in preparation._ ~building construction in wood, stone, and concrete.~ by james lyon, m.a., professor of engineering in the royal college of science for ireland; sometime superintendent of the engineering department in the university of cambridge; and j. taylor, a.r.c.s.i. * * * * * *** other volumes, dealing with subjects of primary importance in the examination and utilisation of lands which have not as yet been fully developed, are in preparation. * * * * * third edition, _revised. with illustrations. handsome cloth, s._ prospecting for minerals. a practical handbook for prospectors, explorers, settlers, and all interested in the opening up and development of new lands. by s. herbert cox, assoc. r.s.m., m. inst. m.m., f.g.s., &c. general contents.--introduction and hints on geology--the determination of minerals: use of the blow-pipe, &c.--rock-forming minerals and non-metallic minerals of commercial value: rock salt, borax, marbles, lithographic stone, quartz and opal, &c., &c.--precious stones and gems--stratified deposits: coal and ores--mineral veins and lodes--irregular deposits--dynamics of lodes: faults, &c.--alluvial deposits--noble metals: gold, platinum, silver, &c.--lead--mercury--copper--tin--zinc--iron--nickel, &c.--sulphur, antimony, arsenic, &c.--combustible minerals--petroleum--general hints on prospecting--glossary--index. "this admirable little work ... written with scientific accuracy in a clear and lucid style.... an important addition to technical literature ... will be of value not only to the student, but to the experienced prospector.... if the succeeding volumes of the new land series are equal in merit to the first, we must congratulate the publishers on successfully filling up a gap in existing literature.--_mining journal._ "this excellent handbook will prove a perfect _vade-mecum_ to those engaged in the practical work of mining and metallurgy."--_times of africa._ * * * * * with many engravings and photographs. handsome cloth, s. d. food supply. by robert bruce, agricultural superintendent to the royal dublin society. with appendix on preserved foods by c.a. mitchell, b.a., f.l.c. general contents.--climate and soil--drainage and rotation of crops--seeds and crops--vegetables and fruits--cattle and cattle-breeding--sheep and sheep rearing--pigs--poultry--horses--the dairy--the farmer's implements--the settler's home. "bristles with information."--_farmers' gazette._ "the work is one which will appeal to those intending to become farmers at home or in the colonies, and who desire to obtain a general idea of the true principles of farming in all its branches."--_journal of the royal colonial inst._ "a most readable and valuable book, and merits an extensive sale."--_scottish farmer._ "will prove of service in any part of the world."--_nature._ * * * * * fourth edition, revised, and brought thoroughly up-to-date by l.h. cooke, instructor in mine surveying, royal college of science. with frontispiece and illustrations. price s. ore & stone mining. by c. le neve foster, d.sc., f.r.s., professor of mining, royal college of science; examiner in mining to the board of education. general contents. introduction. mode of occurrence of minerals.--prospecting.--boring.--breaking ground.--supporting excavations.--exploitation.--haulage or transport.--hoisting or winding.--drainage.--ventilation.--lighting.--descent and ascent.--dressing.--principles of employment of mining labour.--legislation affecting mines and quarries.--condition of the miner.--accidents.--index. "dr. foster's book was expected to be epoch-making, and it fully justifies such expectation.... a most admirable account of the mode of occurrence of practically all known minerals. probably stands unrivalled for completeness."--_the mining journal_. "this epoch-making work ... appeals to men of experience no less than to students."--_berg- und hüttenmännische zeitung_. "this splendid work."--_oesterr. ztschrft. für berg- und hüttenwesen_. * * * * * elementary mining and quarrying (an introductory text-book). by prof. c. le neve foster, f.r.s. with illustrations. [_at press._ * * * * * fourth edition, _revised and greatly enlarged. with numerous additional illustrations, mostly reduced from working drawings. price s. net._ a text-book of coal-mining: _for the use of colliery managers and others engaged in coal-mining._ by herbert william hughes, f.g.s., assoc. royal school of mines, general manager of sandwell park colliery. general contents. geology.--search for coal.--breaking ground.--sinking.--preliminary operations.--methods of working.--haulage.--winding.--pumping.-- ventilation.--lighting.--works at surface.--preparation of coal for market.--index. "quite the best book of its kind ... as practical in aim as a book can be ... the illustrations are excellent."--_athenæum_. "we cordially recommend the work."--_colliery guardian_. "will soon come to be regarded as the standard work of its kind."--_birmingham daily gazette._ * * * * * tenth edition, revised and enlarged. with numerous diagrams. cloth, s. d. ~a treatise on mine-surveying: for the use of managers of mines and collieries, students at the royal school of mines, &c.~ by bennett h. brough, f.g.s., assoc.r.s.m., formerly instructor of mine-surveying, royal school of mines. general contents.--general explanations.--measurement of distances.--miner's dial.--variation of the magnetic-needle.--surveying.--german dial.--theodolite.--traversing underground.--surface-surveys.--plotting the survey.--calculation of areas.--levelling.--measuring distances by telescope.--setting-out.--problems.--photographic surveying.--_appendices._ "its clearness of style, lucidity of description, and fulness of detail have long ago won for it a place unique in the literature of this branch of mining engineering, and the present edition fully maintains the high standard of its predecessors. to the student, and to the mining engineer alike, its value is inestimable. the illustrations are excellent."--_the mining journal._ * * * * * _in large vo._ second edition. _price s. d._ ~mine accounts and mining book-keeping.~ for students, managers, secretaries, and others. _with examples taken from actual practice of leading companies._ by james gunson lawn, assoc.r.s.m., assoc. mem. inst. c.e., f.g.s., professor of mining at the south african school of mines. edited by c. le neve foster, d.sc., f.r.s. general contents.--introduction.--part i. engagement and payment of workmen.--part ii. purchases and sales.--part iii. working summaries and analyses.--part iv. ledger, balance sheet, and company books.--part v. reports and statistics. "it seems impossible to suggest how mr. lawn's book could be made more complete or more valuable, careful, and exhaustive."--_accountants' magazine_. * * * * * _in large vo, with illustrations and folding-plates. s. d._ ~blasting~: and the use of explosives. a handbook for engineers and others engaged in mining, tunnelling, quarrying, &c. by oscar guttmann, assoc. m. inst. c.e. _member of the societies of civil engineers and architects of vienna and budapest, corresponding member of the imp. roy. geological institution of austria, &c._ "this admirable work."--_colliery guardian._ "should prove a _vade-mecum_ to mining engineers and all engaged in practical work."--_iron and coal trades review._ * * * * * _in crown vo. handsome cloth. with numerous illustrations. s. net._ ~electrical practice in collieries.~ by d. burns, m.e., m.inst.m.e., certificated colliery manager, and lecturer on mining and geology to the glasgow and west of scotland technical college. units of measurement, conductors, &c.--the theory of the dynamo.--the dynamo, details of construction and working.--motors.--lighting installations in collieries.--pumping by electricity.--electrical haulage.--coal cutting.--miscellaneous applications of electricity in mines.--index. "a clear and concise introduction to electrical practice in collieries."--_mining journal._ * * * * * second edition. large crown vo. handsome cloth. with over illustrations in the text. s. d. ~practical coal-mining:~ a manual for managers, under-managers, colliery engineers, and others. _with worked-out problems on haulage, pumping, ventilation, &c._ by george l. kerr, m.e., m.inst.m.e. "an essentially practical work, and can be confidently recommended. no department of coal-mining has been overlooked."--_engineers' gazette._ "this book just meets the wants of students preparing for the colliery managers' examinations. i have decided to use it for our classes here.... we have, i believe the largest atining class in great britain."--_the principal of a training college._ * * * * * elementary coal-mining: for the use of students, miners, and others preparing for examinations. by george l. kerr, m.e., m.inst.m.e., author of "practical coal-mining." in crown vo. handsome cloth. with illustrations. s. d. "an abundance of information conveyed in a popular and attractive form.... will be of great use to all who are in any way interested in coal mining."--_scottish critic._ * * * * * second edition. _with illustrations. cloth, s. d._ ~getting gold:~ a gold-mining handbook for practical men. by j.c.f. johnson, f.g.s., a.i.m.e., life member australasian mine-managers' association. general contents.--introductory: prospecting (alluvial and general)--lode or reef prospecting--genesiology of gold--auriferous lodes--drifts--gold extraction--lixiviation--calcination--motor power and its transmission--company formation--mining appliances and methods--australasian mining regulations. "practical from beginning to end ... deals thoroughly with the prospecting, sinking, crushing, and extraction of gold."--_brit. australasian._ * * * * * _with plates and illustrations. handsome cloth. at press._ ~the cyanide process of gold extraction.~ _a text-book for the use of metallurgists and students at schools of mines, &c._ by james park, f.g.s., m.inst.m.m., professor of mining and director of the otago university school of mines; late director thames school of mines, and geological surveyor and mining geologist to the government of new zealand. third english edition. thoroughly revised and greatly enlarged. with additional details concerning the siemens-halske and other recent processes. contents.--the macarthur process.--chemistry of the process.--laboratory experiments.--control testing and analysis of solutions.--appliances for cyanide extraction.--the actual extraction by cyanide.--application of the process.--leaching by agitation.--zinc precipitation of gold.--the siemens-halske process.--other cyanide processes.--antidotes for cyanide poisoning.--cyaniding in new zealand. "mr. park's book deserves to be ranked as amongst the best of existing treatises on this subject."--_mining journal._ * * * * * at press. _with numerous plates, maps, and illustrations._ ~cyaniding gold & silver ores.~ a practical treatise on the cyanide process; its application, methods of working, design and construction of plant, and costs. by h. forbes julian, mining and metallurgical engineer; specialist in gold: late technical adviser of the deutsche gold und silber scheide anstalt, frankfort-on-maine. and edgar smart, a.m.i.c.e., civil and metallurgical engineer. *** this book deals with the cyanide process from technical, commercial, and scientific points of view. it is adapted for the use of directors, managers, and superintendents of mines and metallurgical works, mining engineers, metallurgists, chemists, assayers, working cyaniders, and students. * * * * * _in crown. vo. illustrated. fancy cloth boards._ c. c. ~gold seeking in south africa:~ a handbook of hints for intending explorers, prospectors, and settlers. by theo kassner, mine manager, author of the geological sketch map of the de kaap gold fields. _with a chapter on the agricultural prospects of south africa._ abstract of contents--history.--geology.--prospecting.--the de kaap goldfields.--komati and swaziland.--cost of mining, native labour, &c.--lydenberg goldfields--zoutspanberg.--witwatersrand.--other goldfields.--general considerations--conclusions.--agricultural prospects, tables, index, &c. "as fascinating in its way as anything ever penned by jules verne. mr. kassner manages to impart his information in a way that enables him to be understanded even of the dullest."--_african commerce._ * * * * * at press. large vo. handsome cloth. with illustrations. metallurgical analysis & assaying: a three years' course for students of schools of mines. by w.a. macleod, b.a., b.sc., a.o.s.m. (n.z.), formerly assist.-director, thames school of mines (n.z.), and lecturer in chemistry, university of tasmania; director of queensland government school of mines, charters towers; and chas. walker, f.c.s., formerly assist.-demonstrator in chemistry, sydney university; lecturer in chemistry and metallurgy, charters towers school of mines part i.--qualitative analysis and preparation and properties of gases. part ii.--qualitative and quantitative analysis. part iii.--assaying, technical analysis (gas, water, fuels, oils, &c.). *** "the aim of this work is to provide the student with a graded course of work leading from simple quantitative analysis up to the technical quantitative methods. it has been specially prepared to meet the requirements of schools of mines, and more especially, of those in the colonies, the subject matter having been selected to cover a three years' laboratory course."--_extract from author's preface._ * * * * * third edition. with folding plates and many illustrations. s. elements of metallurgy. a practical treatise on the art of extracting metals from their ores. by j. arthur phillips, m. inst. c.e., f.c.s., f.g.s., &c., and h. bauerman, v.p.g.s. general contents.--refractory materials.--fire-clays.--fuels, &c.--aluminium.--copper.--tin.--antimony.--arsenic.--zinc.--mercury.-- bismuth.--lead.--iron.--cobalt.--nickel.--silver.--gold.--platinum. "of the third edition, we are still able to say that, as a text-book of metallurgy, it is the best with which we are acquainted."--_engineer._ "a work which is equally valuable to the student as a text-book, and to the practical smelter as a standard work of reference.... the illustrations are admirable examples of wood engraving."--_chemical news._ * * * * * ~the mining engineers' report book and directors'~ and shareholders' guide to mining reports. by edwin r. field, m.inst.m.m. with notes on the valuation of mining property and tabulating reports, useful tables, &c., and provided with detachable blank pages for ms. notes. "an admirably compiled book which mining engineers and managers will find extremely useful."--_mining journal._ * * * * * second edition. _in preparation. in two volumes, large vo. with numerous maps, plates, and illustrations in the text. price s._ ~petroleum _and its products:_ a practical treatise.~ by dr. boverton redwood, f.r.s.e., f.i.c., assoc.r.c.s., hon. corr. mem. of the imperial russian technical society; mem. of the american chemical society; adviser to the home office and to the corporation of london under the petroleum acts, &c., &c. assisted by geo. t. holloway, f.i.c., assoc. r.c.s., and numerous contributors. general contents.--i. historical.--ii. geological and geographical distribution of petroleum and natural gas.--iii. chemical and physical properties.--iv. origin--v. production.--vi. refining.--vii. the shale oil and allied industries.--viii. transport, storage, and distribution.--ix. testing.--x. application and uses.--xi. legislation at home and abroad.--xii. statistics.--index. "the most comprehensive and convenient account that has yet appeared of a gigantic industry which has made incalculable additions to the comfort of civilised man."--_the times._ "a splendid contribution to our technical literature."--_chemical news._ * * * * * _with plates (one coloured) and illustrations. price s. d. net._ ~a handbook on petroleum.~ _for inspectors under the petroleum acts,_ and for those engaged in the storage, transport, distribution, and industrial use of petroleum and its products, and of calcium carbide. with suggestions on the construction and use of mineral oil lamps. by captain j.h. thomson, h.m. chief inspector of explosives, and dr. boverton redwood, author of "petroleum and its products." contents.--i. introductory.--ii. sources of supply.--iii. production.--iv. chemical products, shale oil, and coal tar.--v. flash point and fire test.--vi. testings.--vii. existing legislation relating to petroleum.--viii.--ix.--precautions necessary.--x. petroleum oil lamps.--xi. carbide of calcium and acetylene.--appendices.--index. "a volume that will enrich the world's petroleum literature, and render a service to the british branch of the industry.... reliable, indispensable, a brilliant contribution."--_petroleum._ * * * * * ~the petroleum lamp: its choice and use.~ a guide to the safe employment of mineral oil in what is commonly termed the paraffin lamp. by capt. j.h. thomson and dr. boverton redwood. popular edition, illustrated. s. net. "the book contains a great deal of interesting reading, much of which is thoroughly practical and useful. it is a work which will meet every purpose for which it has been written."--_petroleum._ * * * * * griffin's metallurgical series. * * * * * _standard works of reference_ for metallurgists, mine-owners, assayers, manufacturers, and all interested in the development of the metallurgical industries. edited by sir w. roberts-austen, k.c.b., d.c.l, f.r.s. _in large vo, handsome cloth. with illustrations._ * * * * * ~introduction to the study of metallurgy.~ by the editor. fifth edition. s. (see p. .) ~gold (the metallurgy of).~ by thos. kirke rose, d.sc., assoc.r.s.m., f.i.c., chemist and assayer of the royal mint. fourth edition. s. (see p. .) ~lead and silver (the metallurgy of).~ by h.f. collins, assoc.r.s.m., m.inst.m.m. part i., lead, s; part ii., silver, s. (see p. .) ~iron (the metallurgy of).~ by t. turner, a.r.s.m., f.i.c., f.c.s. second edition, revised. s. (see p. .) ~steel (the metallurgy of).~ by f.w. harbord, assoc.r.s.m., f.i.c., with a section on mechanical treatment by j.w. hall, a.m.inst, c.e. (see p. .) [_ready shortly._ * * * * * _will be published at short intervals._ ~metallurgical machinery:~ the application of engineering to metallurgical problems. by henry charles jenkins, wh.sc., assoc.r.s.m., assoc.m.inst.c.e., of the royal college of science. (see p. ). ~alloys.~ by the editor. *** other volumes in preparation. * * * * * fifth edition, thoroughly revised and considerably enlarged. large vo, with numerous illustrations and micro-photographic plates of different varieties of steel. s. ~an introduction to the study of metallurgy.~ by sir w. roberts-austen, k.c.b., d.c.l., f.r.s., a.r.s.m., late chemist and assayer of the royal mint, and professor of metallurgy in the royal college of science. general contents.--the relation of metallurgy to chemistry.--physical properties of metals.--alloys.--the thermal treatment of metals.--fuel and thermal measurements.--materials and products of metallurgical processes.--furnaces.--means of supplying air to furnaces.--thermo-chemistry.--typical metallurgical processes.--the micro-structure of metals and alloys.--economic considerations. "no english text-book at all approaches this in the completeness with which the most modern views on the subject are dealt with. professor austen's volume will be invaluable, not only to the student, but also to those whose knowledge of the art is far advanced."--_chemical news._ * * * * * fourth edition, revised, considerably enlarged, and in part re-written. including the most recent improvements in the cyanide process. with frontispiece and numerous illustrations. s. ~the metallurgy of gold.~ by t. kirke rose, d.sc.lond., assoc.r.s.m., _chemist and assayer of the royal mint_. general contents.--the properties of gold and its alloys.--chemistry of gold.--mode of occurrence and distribution.--placer mining.--shallow deposits.--deep placer mining.--quartz crushing in the stamp battery.--amalgamation.--other forms of crushing and amalgamating.--concentration.--stamp battery practice.--chlorination: the preparation of ore.--the vat process.--the barrel process.--chlorination practice in particular mills.--the cyanide process.--chemistry of the process.--pyritic smelting.--the refining and parting of gold bullion--the assay of gold ores.--the assay of bullion--economic considerations.--bibliography. "a comprehensive practical treatise on this important subject."--_the times._ "the most complete description of the chlorination process which has yet been published."--_mining journal._ "adapted for all who are interested in the gold mining industry, being free from technicalities as far as possible, but is more particularly of value to those engaged in the industry."--_cape times._ * * * * * edited by sir w. roberts-austen, k.c.b., f.r.s., d.c.l. _in large vo. handsome cloth. with illustrations._ * * * * * in two volumes, each complete in itself and sold separately. ~the metallurgy of lead and silver.~ by h.f. collins, assoc.r.s.m., m.inst.m.m. ~part i.--lead:~ a complete and exhaustive treatise on the manufacture of lead, with sections on smelting and desilverisation, and chapters on the assay and analysis of the materials involved. price s. summary of contents.--sampling and assaying lead and silver.--properties and compounds of lead.--lead ores.--lead smelting.--reverberatories.--lead smelting in hearths.--the roasting of lead ores.--blast furnace smelting; principles, practice, and examples; products.--flue dust, its composition, collection and treatment.--costs and losses, purchase of ores.--treatment of zinc, lead sulphides, desilverisation, softening and refining.--the pattinson process.--the parkes process.--cupellation and refining, &c., &c. "a thoroughly sound and useful digest. may with every confidence be recommended."--_mining journal._ * * * * * ~part ii. silver.~ comprising details regarding the sources and treatment of silver ores, together with descriptions of plant, machinery, and processes of manufacture, refining of bullion, cost of working, &c. price s. summary of contents.--properties of silver and its principal compounds.--silver ores.--the patio process.--the kazo, fondon, kröhnke, and tina processes.--the pan process.--roast amalgamation.--treatment of tailings and concentration.--retorting, melting, and assaying.--chloridising-roasting.--the augustin, claudet, and ziervogel processes.--the hypo-sulphite leaching process.--refining.--matte smelting.--pyritic smelting.--matte smelting in reverberatories.--silver-copper smelting and refining.--index. "the author has focussed a large amount of valuable information into a convenient form.... the author has evidently considerable practical experience, and describes the various processes clearly and well."--_mining journal._ * * * * * ~_in preparation._~ ~metallurgical machinery: the application of engineering to metallurgical problems.~ by henry charles jenkins, _wh.sc., assoc.r.s.m., assoc.m.inst.c.e._ * * * * * ready shortly. with numerous illustrations. large vo. handsome cloth. ~the metallurgy of steel.~ by f.w. harbord, assoc.r.s.m., f.i.c., _consulting metallurgist and analytical chemist to the indian government, royal indian engineering college, coopers hill._ with over plates, illustrations (comprising nearly micro-sections of steel), diagrams of plant and machinery, reduced from working drawings, and a section on mill practice. by j.w. hall, a.m.inst.c.e. abridged contents.--the plant, machinery, methods and chemistry of the bessemer and of the open hearth processes (acid and basic).--the mechanical treatment of steel comprising mill practice, plant and machinery.--the influence of metalloids, heat treatment, special steels, microstructure, testing, and specifications. * * * * * second edition, revised. price s. ~the metallurgy of iron.~ by thomas turner, assoc.r.s.m., f.i.c., _professor of metallurgy in the university of birmingham._ in large vo, handsome cloth, with numerous illustrations (many from photographs). _general contents._--early history of iron.--modern history of iron.--the age of steel.--chief iron ores.--preparation of iron ores.--the blast furnace.--the air used in the blast furnace.--reactions of the blast furnace.--the fuel used in the blast furnace.--slags and fluxes of iron smelting.--properties of cast iron.--foundry practice.--wrought iron.--indirect production of wrought iron.--the puddling process.--further treatment of wrought iron.--corrosion of iron and steel. "a most valuable summary of knowledge relating to every method and stage in the manufacture of cast and wrought iron ... rich in chemical details.... exhaustive and thoroughly up-to-date."--_bulletin of the american iron and steel association._ "this is a delightful book, giving, as it does, reliable information on a subject becoming every day more elaborate."--_colliery guardian._ "a thoroughly useful book, which brings the subject up to date. of great value to those engaged in the iron industry."--_mining journal._ * * * * * *** for details of works on mining, see pages - . * * * * * ~a text-book of assaying:~ _for the use of students, mine managers, assayers, &c._ by j.j. beringer, f.i.c., f.c.s., public analyst for, and lecturer to the mining association of, cornwall. and c. beringer, f.c.s., late chief assayer to the rio tinto copper company, london. with numerous tables and illustrations. crown vo. cloth, s. d. eighth edition. general contents.--part i.--introductory; manipulation: sampling; drying; calculation of results--laboratory-books and reports. methods: dry gravimetric; wet gravimetric--volumetric assays: titrometric, colorimetric, gasometric--weighing and measuring--reagents--formulæ, equations, &c.--specific gravity. part ii.--metals: detection and assay of silver, gold, platinum, mercury, copper, lead, thallium, bismuth, antimony, iron, nickel, cobalt, zinc, cadmium, tin, tungsten, titanium, manganese, chromium, &c.--earths, alkalies. part iii.--non-metals: oxygen and oxides; the halogens--sulphur and sulphates--arsenic, phosphorus, nitrogen--silicon, carbon, boron--useful tables. "a really meritorious work, that may be safely depended upon either for systematic instruction or for reference."--_nature._ "this work is one of the best of its kind."--_engineer._ * * * * * third edition, _revised. handsome cloth. with numerous illustrations. s._ a text-book of ~elementary metallurgy.~ including the author's practical laboratory course. by a. humboldt sexton, f.i.c., f.c.s., professor of metallurgy in the glasgow and west of scotland technical college. general contents.--introduction.--properties of the metals.--combustion.--fuels.--refractory materials.--furnaces.--occurrence of the metals in nature.--preparation of the ore for the smelter.--metallurgical processes.--iron.--steel.---copper.--lead.--zinc and tin.--silver.--gold.--mercury.--alloys.--applications of electricity to metallurgy.--laboratory course. "just the kind of work for students commencing the study of metallurgy, or for engineering students."--_practical engineer._ "excellently got-up and well-arranged."--_chemical trade journal._ * * * * * in large vo. handsome cloth. price s. ~tables for quantitative metallurgical analysis.~ for laboratory use. _on the principle of "group" separations._ by j. james morgan, f.c.s., m.s.c.i. "the author may be congratulated on the way his work has been carried out."--_the engineer._ "will commend itself highly in laboratory practice. its clearness and precision mark the book out as a highly useful one."--_mining journal._ * * * * * second edition, revised, enlarged, and in part re-written. with additional sections on modern theories of electrolysis costs, &c. price s. d. a treatise on ~electro-metallurgy:~ embracing the application of electrolysis to the plating, depositing, smelting, and refining of various metals, and to the reproduction of printing surfaces and art-work, &c. by walter g. mcmillan, f.i.c., f.c.s., _secretary to the institution of electrical engineers; late lecturer in metallurgy at mason college, birmingham._ with numerous illustrations. large crown vo. cloth. "this excellent treatise, ... one of the best and most complete manuals hitherto published on electro-metallurgy."--_electrical review._ "this work will be a standard."--_jeweller._ "any metallurgical process which reduces the cost of production must of necessity prove of great commercial importance.... we recommend this manual to all who are interested in the practical application of electrolytic processes."--_nature._ * * * * * in large vo. with numerous illustrations and three folding-plates. price s. ~electric smelting & refining:~ a practical manual of the extraction and treatment of metals by electrical methods. being the "elektro-metallurgie" of dr. w. borchers. translated from the second edition by walter g. mcmillan, f.i.c., f.c.s * * * * * contents. part i.--alkalies and alkaline earth metals: magnesium, lithium, beryllium, sodium, potassium, calcium, strontium, barium, the carbides of the alkaline earth metals. part ii.--the earth metals: aluminium, cerium, lanthanum, didymium. part iii.--the heavy metals: copper, silver, gold, zinc and cadmium, mercury, tin, lead, bismuth, antimony, chromium, molybdenum, tungsten, uranium, manganese, iron, nickel, and cobalt, the platinum group. "comprehensive and authoritative ... not only full of valuable information, but gives evidence of a thorough insight into the technical value and possibilities of all the methods discussed."--_the electrician._ "dr. borchers' well-known work ... must of necessity be acquired by every one interested in the subject. excellently put into english with additional matter by mr. mcmillan."--_nature._ "will be of great service to the practical man and the student."--_electric smelting._ * * * * * _in large to, library style. beautifully illustrated with plates, many in colours, and figures in the text._ ~precious stones: their properties, occurrences, and uses.~ _a treatise for dealers, manufacturers, jewellers, and for all collectors and others interested in gems._ by dr. max bauer, professor in the university of marburg, translated by l.j. spencer, m.a. (cantab.), f.g.s. general contents.--general properties of gems: their natural characters, occurrence, application, and uses.--detailed description of particular gems: the diamond, rubies, sapphires; emeralds, tourmalines, and opals; felspars, amphiboles, malachite.--non-mineral gems: amber, &c.--optical features, transparency, translucency, opacity, refraction and dispersion, &c.--appendix: pearls; coral. * * * * * _in large crown vo. with numerous illustrations. s. d._ ~the art of the goldsmith and jeweller a manual on the manipulation of gold and the manufacture of personal ornaments.~ by thos. b. wigley, headmaster of the jewellers and silversmiths' association technical school, birmingham. assisted by j.h. stansbie, b.sc. (lond.), f.i.c., lecturer at the birmingham municipal technical school. * * * * * general contents.--introduction.--the ancient goldsmith's art.--metallurgy of gold.--prices, &c.--alloys.--melting, rolling, and slitting gold.--the workshop and tools.--wire drawing.--rings.--chains and insignia.--antique jewellery work.--precious stones.--cutting.--polishing and finishing.--chasing, and its revival.--etruscan embossing, and repoussé work.--colouring and finishing.--enamelling.--engraving.--moulding and casting ornaments, &c.--fluxes. &c.--recovery of the precious metals.--refining and assaying.--gilding and electro deposition.--hall-marking.--miscellaneous.--appendix. * * * * * ~griffin's chemical and technological publications.~ * * * * * _for metallurgy and electro-metallurgy, see previous section._ page ~inorganic chemistry~, profs. duprÉ and hake, ~quantitative analysis~, prof. humboldt sexton, ~qualitative "~ " " ~chemistry for engineers~, blount and bloxam, ~" " manufacturers~, " " ~foods, analysis of~, a. wynter blyth, ~poisons, detection of~, " " ~tables for chemists and manufacturers~, prof. castell-evans, ~agricultural chemistry~, prof. j.m.h. munro, ~dairy chemistry~, h. d. richmond, ~milk~, e.f. willoughby, ~flesh foods~, c.a. mitchell, ~practical sanitation~, dr. g. reid, ~sanitary engineering~, f. wood, ~technical mycology~, lafar and salter, ~ferments~, c. oppenheimer, ~brewing~, dr. w.j. sykes, ~sewage disposal~, santo crimp, ~trades' waste~, w. naylor, ~cements~, g.r. redgrave, ~water supply~, r.e. middleton, ~road making~, thos. aitken, ~gas manufacture~, w. atkinson butterfield, ~acetylene~, leeds and butterfield, ~fire risks~, dr. schwartz, ~petroleum~, redwood and holloway, ~---- (handbook)~, thomson and redwood, ~oils, soaps, candles~, dr. alder wright, ~lubrication and lubricants~, archbutt and deeley, ~india rubber~, dr. carl o. weber, ~painters' colours, oils, and varnishes~, g.h. hurst, ~painters' laboratory guide~, " " ~painting and decorating~, w.j. pearce, ~photography~, a. brothers, ~dyeing~, knecht and rawson, ~dictionary of dyes~, rawson, gardner, and laycock, ~textile printing~, seymour rothwell, ~textile fibres of commerce~, w.i. hannan, ~dyeing and cleaning~, g.h. hurst, ~bleaching and calico-printing~, geo. duerr, * * * * * ~a short manual of inorganic chemistry.~ by a. duprÉ, ph.d., f.r.s., and wilson hake, ph.d., f.i.c., f.c.s., of the westminster hospital medical school third edition, revised, enlarged, and re-issued. price s. net. "a well-written, clear and accurate elementary manual of inorganic chemistry.... we agree heartily with the system adopted by drs. dupré and hake. will make experimental work trebly interesting because intelligible."--_saturday review._ "there is no question that, given the perfect grounding of the student in his science, the remainder comes afterwards to him in a manner much more simple and easily acquired. the work is an example of the advantages of the systematic treatment of a science over the fragmentary style so generally followed. by a long way the best of the small manuals for students."--_analyst._ * * * * * ~laboratory handbooks by a. humboldt sexton,~ professor of metallurgy in the glasgow and west of scotland technical college. * * * * * ~outlines of quantitative analysis.~ _for the use of students._ with illustrations. fourth edition. crown vo, cloth, s. "a compact laboratory guide for beginners was wanted, and the want has been well supplied.... a good and useful book."--_lancet_. * * * * * ~outlines of qualitative analysis.~ _for the use of students._ with illustrations. fourth edition, revised. crown vo, cloth, s. d. "the work of a thoroughly practical chemist."--_british medical journal._ "compiled with great care, and will supply a want."--_journal of education._ * * * * * ~elementary metallurgy:~ including the author's practical laboratory course. with many illustrations. [see p. . third edition, revised. crown vo. cloth, s. "just the kind of work for students commencing the study of metallurgy."--_practical engineer._ * * * * * ~chemistry for engineers and manufacturers.~ a practical text-book. by bertram blount, f.i.c., f.c.s., assoc.inst.c.e., consulting chemist to the crown agents for the colonies. and a.g. bloxam, f.i.c., f.c.s., consulting chemist, head of the chemistry department, goldsmiths' inst., new cross. in two vols., large vo. with illustrations. sold separately. * * * * * "the authors have succeeded beyond all expectations, and have produced a work which should give fresh power to the engineer and manufacturer."--_the times_. * * * * * ~volume i. price s. d.~ chemistry of engineering, building, and metallurgy. _general content._--introduction--chemistry of the chief materials of construction--sources of energy--chemistry of steam-raising--chemistry of lubrication and lubricants--metallurgical processes used in the winning and manufacture of metals. "practical throughout ... an admirable text-book, useful not only to students, but to engineers and managers of works in preventing waste and improving processes."--_scotsman._ "eminently practical."--_glasgow herald._ "a book worthy of high rank ... its merit is great ... treatment of the subject of gaseous fuel particularly good.... water gas and the production clearly worked out.... altogether a most creditable production. we warmly recommend it, and look forward with keen interest to the appearance of vol. ii."--_journal of gas lighting._ ~volume ii. price s.~ the chemistry of manufacturing processes. _general contents._--sulphuric acid manufacture--manufacture of alkali, &c.--destructive distillation--artificial manure manufacture--petroleum--lime and cement--clay industries and glass--sugar and starch--brewing and distilling--oils, resins, and varnishes--soap and candles--textiles and bleaching--colouring matters, dyeing, and printing--paper and pasteboard--pigments and paints--leather, glue, and size--explosives and matches--minor chemical manufactures. "certainly a good and useful book, constituting a practical guide for students by affording a clear conception of the numerous processes as a whole."--_chemical trade journal._ "we confidently recommend this volume as a practical, and not overloaded, text-book, of great value to students."--_the builder._ * * * * * just out. fifth edition, thoroughly revised, greatly enlarged and re-written. with additional tables, plates, and illustrations. s. ~foods: their composition and analysis.~ by a. wynter blyth, m.r.c.s., f.i.c., f.c.s., barrister-at-law, public analyst for the county of devon, and medical officer of health for st. marylebone. and m. wynter blyth, b.a., b.sc., f.c.s. general contents.--history of adulteration.--legislation.--apparatus.--"ash."--sugar.--confectionery.-- honey.--treacle.--jams and preserved fruits.--starches.--wheaten-flour.-- bread.--oats.--barley.--rye.--rice.--maize.--millet.--potato.--peas.-- lentils.--beans.--milk.--cream.--butter.--oleo-margarine.--cheese.-- lard.--tea.--coffee.--cocoa and chocolate.--alcohol.--brandy.--rum.-- whisky.--gin.--arrack.--liqueurs.--absinthe.--yeast.---beer.--wine.-- vinegar.--lemon and lime juice.--mustard.--pepper.--sweet and bitter almonds.--annatto.--olive oil.--water analysis.--appendix: adulteration acts, &c. "simply indispensable in the analyst's laboratory."--_the lancet._ "a new edition of mr. wynter blyth's standard work, enriched with all the recent discoveries and improvements, will be accepted as a boon."--_chemical news._ * * * * * third edition. in large vo, cloth, with tables and illustrations. price s. ~poisons: their effects and detection.~ by a. wynter blyth, m.r.c.s., f.i.c., f.c.s., barrister-at-law, public analyst for the county of devon, and medical officer of health for st. marylebone. general contents. i.--historical introduction. ii.--classification--statistics--connection between toxic action and chemical composition--life tests--general method of procedure--the spectroscope--examination of blood and blood stains. iii.--poisonous gases. iv.--acids and alkalies. v.--more or less volatile poisonous substances. vi.--alkaloids and poisonous vegetable principles. vii.--poisons derived from living or dead animal substances. viii.--the oxalic acid group. ix.--inorganic poisons. appendix: treatment, by antidotes or otherwise, of cases of poisoning. "undoubtedly the most complete work on toxicology in our language."--_the analyst (on the third edition)._ "as a practical guide, we know no better work."--_the lancet (on the third edition)._ *** in the third edition, enlarged and partly re-written, new analytical methods have been introduced, and the cadaveric alkaloids, or ptomaines, bodies playing so great a part in food-poisoning and in the manifestations of disease, have received special attention. * * * * * with numerous tables, and illustrations. s. ~dairy chemistry for dairy managers, chemists, and analysts~ a practical handbook for dairy chemists and others having control of dairies. by h. droop richmond, f.c.s., chemist to the aylesbury dairy company. _contents._--i. introductory.--the constituents of milk. ii. the analysis of milk. iii. normal milk: its adulterations and and their detection. iv. the chemical control of the dairy. v. alterations, biological and sanitary matters. vi. butter. vii. other milk products. viii. the milk of mammals other than the cow.--appendices.--tables.--index. " ... in our opinion the book is the best contribution on the subject that has yet appeared in the english language."--_lancet._ * * * * * at press, fully illustrated. ~milk: its production & uses.~ _with chapters on dairy farming, the diseases of cattle, and on the hygiene and control of supplies._ by edward f. willoughby, m.d. (lond.), d.p.h. (lond. and camb.), inspector of farms and general scientific adviser to welford and sons, ltd. * * * * * crown vo, handsome cloth. fully illustrated. s. d. ~flesh foods: with methods for their chemical, microscopical, and bacteriological examination.~ _a practical handbook for medical men, analysts, inspectors and others._ by c. ainsworth mitchell, b.a.(oxon), fellow of the institute of chemistry; member of council, society of public analysts. _with numerous tables, illustrations, and a coloured plate._ contents.--structure and chemical composition of muscular fibre.--of connective tissue, and blood.--the flesh of different animals.--the examination of flesh.--methods of examining animal fat.--the preservation of flesh.--composition and analysis of sausages.--proteids of flesh.--meat extracts and flesh peptones.--the cooking of flesh.--poisonous flesh.--the animal parasites of flesh.--the bacteriological examination of flesh.--the extraction and separation of ptomaines.--index. *** this work is a complete compendium of the chemistry of animal tissues. it contains directions for the detection of morbid conditions, putrefactive changes, and poisonous or injurious constituents, together with an account of their causes and effects.--_publishers' note._ "a compilation which will be most useful for the class for whom it is intended."--_athenæum._ "a book which no one whose duties involve considerations of food supply can afford to be without."--_municipal journal._ * * * * * in large vo. handsome cloth. with numerous illustrations. _each volume complete in itself, and sold separately._ ~technical mycology:~ the utilisation of micro-organisms in the arts and manufactures. _a practical handbook on fermentation and fermentative processes for the use of brewers and distillers, analysts, technical and agricultural chemists, and all interested in the industries dependent on fermentation._ by dr. franz lafar, professor of fermentation-physiology and bacteriology in the technical high school, vienna. with an introduction by dr. emil chr. hansen, principal of the carlsberg laboratory, copenhagen. translated by charles t.c. salter. ~vol. i.--schizomycetic fermentation.~ s. _including the theory of fermentation, the principles of sterilization, and pure culture processes._ ~vol. ii., part i. eumycetic fermentation.~ s. d. _the morphology, chemistry, physiology, and fermentative processes of the eumycetes, zygomycetes, and saccharomycetes._ "the first work of the kind which can lay claim to completeness in the treatment of a fascinating subject. the plan is admirable, the classification simple, the style is good, and the tendency of the whole volume is to convey sure information to the reader."--_lancet_. *** the publishers trust that before long they will be able to present english readers with the whole of the second volume, arrangements having been concluded whereby, upon its appearance in germany, the english translation will be at once put in hand. this is now being done with part i., which will be issued shortly, and which will be followed by the two final parts. * * * * * in crown vo, handsome cloth. price s. d. net. ~_ferments_ and their actions.~ _a text-book on the chemistry and physics of fermentative changes._ by carl oppenheimer, ph.d., m.d., of the physiological institute at eilangen. translated from the german by c. ainsworth mitchell, b.a., f.i.c., f.c.s. abridged contents.--introduction.--definition.--chemical nature of ferments.--influence of external factors.--mode of action.--physiological action.--secretion.--importance of ferments to vital action.--proteolytic ferments.--trypsin.--bacteriolytic and hæmolytic ferments.--vegetable ferments.--coagulating ferments.--saccharifying ferments.--diastases.--polysaccharides.--enzymes.--ferments which decompose glucosides.--hydrolytic ferments.--lactic acid fermentation.--alcoholic fermentation.--biology of alcoholic fermentation.--oxydases.--oxidising fermentation.--bibliography.--index. ~the present translation embodies notes and additions to the work made by the author subsequent to its publication in germany.~ "such a veritable _multum in parvo_ has never yet appeared. the author has set himself the task of writing a work on ferments that should embrace human erudition on the subject"--_brewers' journal_. * * * * * second edition, revised. in large vo. handsome cloth. with plate and illustrations. price s. ~the principles and practice of brewing.~ for the use of students and practical men. by walter j. sykes, m.d., d.p.h., f.i.c., editor of "the analyst." abstract of contents. i. physical principles involved in brewing operations. chemistry with special reference to the materials used in brewing. ii. the microscope. vegetable biology. fermentation. iii. water. barley and malting. brewery plant. brewing. beer and its diseases. appendices. index. "a volume of brewing science, which has long been awaited.... we consider it one of the most complete in contents and novel in arrangement that has yet been published.... will command a large sale."--_the brewers' journal._ "the appearance of a work such as this serves to remind us of the enormously rapid advances made in our knowledge of the scientific principles underlying the brewing processes.... dr. sykes' work will undoubtedly be of the greatest assistance, not merely to brewers, but to all chemists and biologists interested in the problems which the fermentation industries present."--_the analyst._ "the publication of dr. sykes' masterly treatise on the art of brewing is quite an event in the brewing world.... deserves our warmest praise.... a better guide than dr. sykes could hardly be found."--_county brewers' gazette._ * * * * * in large vo. handsome cloth. ~agricultural chemistry and analysis:~ _a practical handbook for the use of agricultural students._ by j.m.h. munro, d.sc., f.i.c., f.c.s., professor of chemistry, downton college of agriculture. [_in preparation._ * * * * * second edition, revised and enlarged. with tables, illustrations in the text, and lithographic plates. medium vo. handsome cloth. s. ~sewage disposal works:~ a guide to the construction of works for the prevention of the pollution by sewage of rivers and estuaries. by w. santo crimp, m.inst.c.e., f.g.s., late assistant-engineer, london county council. part i.--introductory. part ii.--sewage disposal works in operation--their construction, maintenance, and cost. *** from the fact of the author's having, for some years, had charge of the main drainage works of the northern section of the metropolis, the chapter on london will be found to contain many important details which would not otherwise have been available. "all persons interested in sanitary science owe a debt of gratitude to mr. crimp.... his work will be especially useful to sanitary authorities and their advisers ... eminently practical and useful."--_lancet._ "probably the most complete and best treatise on the subject which has appeared in our language.... will prove of the greatest use to all who have the problem of sewage disposal to face."--_edinburgh medical journal._ * * * * * _beautifully illustrated, with numerous plates, diagrams, and figures in the text. s. net._ ~trades' waste: its treatment and utilisation.~ a handbook for borough engineers, surveyors, architects, and analysts. by w. naylor, f.c.s., a.m.inst.c.e., chief inspector of rivers, ribble joint committee. contents.--i. introduction.--ii. chemical engineering.--iii.--wool de-greasing and grease recovery.--iv. textile industries; calico bleaching and dyeing.--v. dyeing and calico-printing,--vi. tanning and fellmongery.--vii. brewery and distillery waste.--viii. paper mill refuse.--ix. general trades' waste.--index. "there is probably no person in england to-day better fitted to deal rationally with such a subject."--_british sanitarian._ "the work is thoroughly practical, and will serve as a handbook in the future for those who have to encounter the problems discussed."--_chemical trade journal._ * * * * * in crown vo, extra. with illustrations. s. d. ~calcareous cements: _their nature, preparation, and uses_.~ ~with some remarks upon cement testing.~ by gilbert r. redgrave, assoc. inst. c.e., assistant secretary for technology, board of education, south kensington. "invaluable to the student, architect, and engineer."--_building news._ "will be useful to all interested in the manufacture, use, and testing of cements."--_engineer._ * * * * * just out. with four folding plates and numerous illustrations. large vo. ~water supply:~ _a practical treatise on the selection of sources and the distribution of water._ by reginald e. middleton, m.inst.c.e., m.inst.mech.e., f.s.i. abridged contents.--introductory.--requirements as to quality.--requirements as to quantity.--storage reservoirs.--purification.--service reservoirs.--the flow of water through pipes.--distributing systems.--pumping machines.--special requirements. * * * * * third edition, revised. fully illustrated. _at press._ the chemistry of ~gas manufacture:~ _a hand-book on the production, purification, and testing of illuminating gas, and the assay of the bye-products of gas manufacture._ by w.j. atkinson butterfield, m.a., f.i.c., f.c.s., formerly head chemist, gas works, beckton, london, e. general contents.--i. raw materials for gas manufacture.--ii. coal gas.--iii. carburetted water gas.--iv. oil gas.--v. enriching by light oils.--vi. final details of manufacture.--vii. gas analysis.--viii. photometry.--ix. applications of gas.--x. bye-products.--xi. acetylene.--index. "the best work of its kind which we have ever had the pleasure of reviewing."--_journal of gas lighting_. * * * * * just out. with diagrams and illustrations. s. net. ~acetylene:~ the principles of its generation and use. by f.h. leeds, f.i.c., f.c.s., member of the society of public analysts and of the acetylene association; and w.j. atkinson butterfield, m.a., f.i.c., f.c.s., consulting chemist, author of "the chemistry of gas manufacture." general contents.--introductory.--advantages of acetylene and other illuminants.--chemistry and physics.--general principles of acetylene generation.--choice of a generator.--statutory regulations.--treatment of acetylene after generation.--general properties.--mains and service pipes.--subsidiary apparatus.--burners.--incandescent burners.--heating apparatus and motors.--carburetted, compressed, and dissolved acetylene.--mixtures with other gases.--sundry uses.--acetylene lamps.--valuation and analysis of carbide. * * * * * ready immediately. large vo. handsome cloth. price s. net. ~fire and explosion risks.~ _a handbook of the detection, investigation, and prevention of fires and explosion._ by dr. von schwartz. translated from the revised german edition by c.t.c. salter. abridged general contents.--fires and explosions of a general character.--dangers arising from sources of light and heat.--dangerous gases.--risks attending special industries.--materials employed.--agricultural products.--fats, oils, and resins.--mineral oils and tar.--alcohol, &c.--metals, oxides, acids, &c.--lightning, ignition appliances, fireworks. * * * * * tenth edition, revised. price s. ~practical sanitation: _a hand-book for sanitary inspectors and others interested in sanitation._~ by george reid, m.d., d.p.h., _fellow, mem. council, and examiner, sanitary institute of great britain, and medical officer to the staffordshire county council._ ~with an appendix on sanitary law.~ by herbert manley, m.a., m.b., d.p.h., _medical officer of health for the county borough of west bromwich._ general contents.--introduction--water supply: drinking water, pollution of water--ventilation and warming--principles of sewage removal--details of drainage; refuse removal and disposal--sanitary and insanitary work and appliances--details of plumbers' work--house construction--infection and disinfection--food, inspection of; characteristics of good meat; meat, milk, fish, &c., unfit for human food--appendix: sanitary law; model bye-laws, &c. "dr. reid's very useful manual ... abounds in practical detail."--_british medical journal_. "a very useful handbook, with a very useful appendix. we recommend it not only to sanitary inspectors, but to householders and all interested in sanitary matters."--_sanitary record_. * * * * * companion volume to reid's sanitation. in crown vo. handsome cloth. profusely illustrated. s. d. net. ~sanitary engineering:~ _a practical manual of town drainage and sewage and refuse disposal._ for sanitary authorities, engineers, inspectors, architects, contractors, and students. by francis wood, a.m.inst.c.e., f.g.s., borough engineer and surveyor, fulham; late borough engineer, bacup, lancs. general contents. introduction.--hydraulics.--velocity of water in pipes.--earth pressures and retaining walls.--powers.--house drainage.--land drainage.--sewers.--separate system.--sewage pumping.--sewer ventilation.--drainage areas.--sewers, manholes, &c.--trade refuse.--sewage disposal works.--bacteriolysis.--sludge disposal.--construction and cleansing of sewers.--refuse disposal.--chimneys and foundations. "the volume bristles with information which will be greedily read by those in need of assistance. the book is one that ought to be on the bookshelves of every practical engineer."--_sanitary journal_. "a veritable pocket compendium of sanitary engineering.... a work which may, in many respects, be considered as complete ... commendably cautious ... interesting ... suggestive."--_public health engineer_. * * * * * vol. i. now ready. in half morocco, s. _in two volumes, each complete in itself._ ~physico-chemical tables~ for the use of analysts, physicists, chemical manufacturers, and scientific chemists. volume i.--chemical engineering, physical chemistry. [_just out._ volume ii.--chemical physics, pure and analytical chemistry. by john castell-evans, f.i.c., f.c.s., superintendent of the chemical laboratories, and lecturer on inorganic chemistry and metallurgy at the finsbury technical college. the tables may almost claim to be exhaustive, and embody and collate all the most recent data established by experimentalists at home and abroad. the volumes will be found invaluable to all engaged in research and experimental investigation in chemistry and physics. the work comprehends as far as possible all rulles and tables required by the analyst, brewer, distiller, acid- and alkali-manufacturer, &c., &c.; and also the principal data in thermo-chemistry, electro-chemistry, and the various branches of chemical physics. every possible care has been taken to ensure perfect accuracy, and to include the results of the most recent investigations. * * * * * _in large vo. handsome cloth. beautifully illustrated. with plates and figures in the text._ s. ~road making and maintenance:~ a practical treatise for engineers, surveyors, and others. with an historical sketch of ancient and modern practice. by thos. aitken, assoc.m.inst.c.e., member of the association of municipal and county engineers; member of the sanitary inst.; surveyor to the county council of fife, cupar division. _with numerous plates, diagrams, and illustrations._ contents.--historical sketch.--resistance of traction.--laying out new roads.--earthworks, drainage, and retaining walls.--road materials, or metal.--quarrying.--stone breaking and haulage.--road-rolling and scarifying.--the construction of new, and the maintenance of existing roads.--carriage ways and foot ways. "the literary style is excellent ... a comprehensive and excellent modern book, an up-to-date work ... should be on the reference shelf of every municipal and county engineer or surveyor in the united kingdom, and of every colonial engineer."--_the surveyor_. * * * * * third edition, revised and enlarged. with illustrations, s. d. ~painters' colours, oils, & varnishes:~ ~a practical manual.~ by george h. hurst, f.c.s., member of the society of chemical industry; lecturer on the technology of painters' colours, oils, and varnishes, the municipal technical school, manchester. general contents.--introductory--the composition, manufacture, assay, and analysis of pigments, white, red, yellow and orange, green, blue, brown, and black--lakes--colour and paint machinery--paint vehicles (oils, turpentine, &c., &c.)--driers--varnishes. "a thoroughly practical book, ... the only english work that satisfactorily treats of the manufacture of oils, colours, and pigments."--_chemical trades' journal_. *** for mr. hurst's garment dyeing and cleaning, see p. . * * * * * in crown vo. handsome cloth. with illustrations. s. ~the painter's laboratory guide.~ a student's handbook of paints, colours, and varnishes. by george h. hurst, f.c.s., m.s.c.i. abstract of contents.--preparation of pigment colours.--chemical principles involved.--oils and varnishes.--properties of oils and varnishes.--tests and experiments.--plants, methods, and machinery of the paint and varnish manufactures. _this work has been designed by the author for the laboratory of the technical school, and of the paint and colour works, and for all interested or engaged in these industries._ * * * * * second edition, revised. in crown vo. extra. with numerous illustrations and plates (some in colours), including original designs. s. d. ~painting and decorating:~ _a complete practical manual for house painters and decorators._ by walter john pearce, lecturer at the manchester technical school for house-painting and decorating. general contents. introduction--workshop and stores--plant and appliances--brushes and tools--materials: pigments, driers, painters' oils--wall hangings--paper hanging--colour mixing--distempering--plain painting--staining--varnish and varnishing--imitative painting--graining--marbling--gilding--sign-writing and lettering--decoration: general principles--decoration in distemper--painted decoration--relievo decoration--colour--measuring and estimating--coach-painting--ship-painting. "a thoroughly useful book ... good, sound, practical information in a clear and concise form."--_plumber and decorator_. "a thoroughly good and reliable text-book.... so full and complete that it would be difficult to imagine how anything further could be added about the painter's craft."--_builders' journal_. * * * * * in large vo. handsome cloth. with plates and several illustrations. s. net. ~the chemistry of india rubber.~ a treatise on the nature of india rubber, its chemical and physical examination, and the determination and valuation of india rubber substitutes. _including the outlines of a theory on vulcanisation._ by carl otto weber, ph.d. abstract of contents.--introduction.--the chemistry of india rubber.--the examination and valuation of india rubber.--examination of india rubber substitutes.--inorganic filling materials.--vulcanisers and sulphur carriers.--india rubber solvents.--colouring matters and pigment colours.--constructive components of india rubber articles.--analysis of manufactured india rubber.--sanitary conditions in india rubber works.--index. "replete with scientific and also with technical interest.... the sub-section on the physical properties is a complete _résumé_ of every thing known to-day on the subject."--_india-rubber journal_. * * * * * new edition. in large vo. handsome cloth. with illustrations. ~oils, fats, butters & waxes:~ _their preparation and properties, and manufacture therefrom of candles, soaps, and other products._ by c.r. alder wright, d.sc., f.r.s., late lecturer on chemistry, st. mary's hospital medical school; examiner in "soap" to the city and guilds of london institute. thoroughly revised, enlarged, and in part rewritten by c. ainsworth mitchell, b.a., f.i.c. "dr. wright's work will be found absolutely indispensable by every chemist. teems with information valuable alike to the analyst and the technical chemist."--_the analyst_. "will rank as the standard english authority on oils and fats for many years to come."--_industries and iron_. * * * * * ~the textile industries.~ * * * * * _in two large volumes, pp., with a supplementary volume, containing specimens of dyed fabrics. s._ ~a manual of dyeing: _for the use of practical dyers, manufacturers, students, and all interested in the art of dyeing._~ by e. knecht, ph.d., f.i.c., head of the chemistry and dyeing department of the technical college, manchester; editor of "the journal of the society of dyers and colourists;" chr. rawson, f.i.c., f.c.s., late head of the chemistry and dyeing department of the technical college, bradford; member of council of the society of dyers and colourists; and richard loewenthal, ph.d. * * * * * general contents.--chemical technology of the textile fabrics--water--washing and bleaching--acids, alkalies, mordants--natural colouring matters--artificial organic colouring matters--mineral colours--machinery used in dyeing--tinctorial properties of colouring matters--analysis and valuation of materials used in dyeing, &c., &c. "the most valuable and useful work on dyeing that has yet appeared in the english language ... likely to be the standard work of reference for years to come."--_textile mercury_. "this authoritative and exhaustive work ... the most complete we have yet seen on the subject."--_textile manufacturer._ "the most exhaustive and complete work on the subject extant."--_textile recorder._ * * * * * _companion volume to knecht & rawson's "dyeing." in large vo. handsome cloth, library style. s. net._ ~a dictionary of dyes, mordants, & other compounds used in dyeing and calico printing.~ _with formulæ, properties, and applications of the various substances described, and concise directions for their commercial valuation. and for the detection of adulterants._ by christopher rawson, f.i.c., f.c.s., consulting chemist to the behar indigo planters' association: co-author of "a manual of dyeing;" walter m. gardner, f.c.s., head of the department of chemistry and dyeing, bradford municipal technical college; editor of the "journ. soc. dyers and colourists;" and w.f. laycock, ph.d., f.c.s., analytical and consulting chemist. "turn to the book as one may on any subject, or any substance in connection with the trade, and a reference is sure to be found. the authors have apparently left nothing out. considering the immense amount of information, the book is a cheap one, and we trust it will be widely appreciated,"--_textile mercury._ * * * * * _in large vo, handsome cloth, with numerous illustrations. s. net._ ~textile fibres of commerce.~ a handbook of the occurrence, distribution, preparation, and industrial uses of the animal, vegetable, and mineral products used in spinning and weaving. by william i. hannan, lecturer on botany at the ashton municipal technical school, lecturer on cotton spinning at the chorley science and art school, &c. with numerous photo engravings from nature. *** the subjects discussed in this volume are, in order to facilitate reference, arranged in alphabetical order under their respective heads. the work may thus be regarded as a dictionary of textile fibres. a feature of the work is the wealth of botanical description which accompanies the section dealing with vegetable fibres.--_publishers' note._ "useful information.... admirable illustrations.... the information is not easily attainable, and in its present convenient form will be valuable."--_textile recorder._ * * * * * ~textile printing: a practical manual.~ including the processes used in the printing of cotton, woollen, silk, and half-silk fabrics. by c.f. seymour rothwell, f.c.s., _mem. soc. of chemical industries; late lecturer at the municipal technical school, manchester_. in large vo, with illustrations and printed patterns. price s. general contents.--introduction.--the machinery used in textile printing.--thickeners and mordants.--the printing of cotton goods.--the steam style.--colours produced directly on the fibre.--dyed styles.--padding style.--resist and discharge styles.--the printing of compound colourings, &c.--the printing of woollen goods.--the printing of silk goods.--practical recipes for printing.--appendix.--useful tables.--patterns. "by far the best and most practical book on textile printing which has yet been brought out, and will long remain the standard work on the subject. it is essentially practical in character."--_textile mercury._ "the most practical manual of textile printing which has yet appeared. we have no hesitation in recommending it."--_the textile manufacturer._ * * * * * large vo. handsome cloth. s. d. ~bleaching & calico-printing.~ a short manual for students and practical men. by george duerr, director of the bleaching, dyeing, and printing department at the accrington and bacup technical schools; chemist and colourist at the irwell print works. assisted by william turnbull (of turnbull & stockdale, limited). with illustrations and upwards of one hundred dyed and printed patterns designed specially to show various stages of the processes described. general contents.--cotton, composition of; bleaching, new processes; printing, hand-block; flat-press work; machine printing--mordants--styles of calico-printing: the dyed or madder style, resist padded style, discharge and extract style, chromed or raised colours, insoluble colours, &c.--thickeners--natural organic colouring matters--tannin matters--oils, soaps, solvents--organic acids--salts--mineral colours--coal tar colours--dyeing--water, softening of--theory of colours--weights and measures, &c. "when a ready way out of a difficulty is wanted, it is in books like this that it is found."--_textile recorder._ "mr. duerr's work will be found most useful.... the information given is of great value.... the recipes are thoroughly practical."--_textile manufacturer._ * * * * * second edition. revised and enlarged. with numerous illustrations. s. d. ~garment dyeing and cleaning.~ a practical book for practical men. by george h. hurst, f.c.s., member of the society of chemical industry. general contents.--technology of the textile fibres--garment cleaning--dyeing of textile fabrics--bleaching--finishing of dyed and cleaned fabrics--scouring and dyeing of skin rugs and mats--cleaning and dyeing of feathers--glove cleaning and dyeing--straw bleaching and dyeing--glossary of drugs and chemicals--useful tables. 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(to subscribers, s.)._ the official year-book of the scientific and learned societies of great britain and ireland. compiled from official sources. _comprising (together with other official information) lists of the papers read during the session - before all the leading societies throughout the kingdom engaged in the following departments of research_:-- § . science generally: _i.e._, societies occupying themselves with several branches of science, or with science and literature jointly. § . mathematics and physics. § . chemistry and photography. § . geology, geography, and mineralogy. § . biology, including microscopy and anthropology. § . economic science and statistics. § . mechanical science, engineering, and architecture. § . naval and military science. § . agriculture and horticulture. § . law. § . literature. § . psychology. § . archæology. § . medicine. "fills a very real want."--_engineering._ "indispensable to any one who may wish to keep himself abreast of the scientific work of the day."--_edinburgh medical journal._ "the year-book of societies is a record which ought to be of the _greatest use for the progress of science_."--_lord playfair, f.r.s., k.c.b., m.p., past-president of the british association._ "it goes almost without saying that a handbook of this subject will be in time _one of the most generally useful works for the library or the desk_."--_the times._ "british societies are now _well represented_ in the 'year-book of the scientific and learned societies of great britain and ireland'"--(art. "societies" in new edition of "encyclopædia britannica," vol. xxii.) * * * * * copies of the first issue, giving an account of the history, organization, and conditions of membership of the various societies, and forming the groundwork of the series, may still be had, price / . _also copies of the issues following._ the _year-book of societies_ forms a complete _index to the scientific work_ of the sessional year in the various departments. it is used as a handbook in all our great scientific centres, museums, and libraries throughout the kingdom, and has become an _indispensable book of reference_ to every one engaged in scientific work. _ready in october each year._ ~griffin's metallurgical series.~ edited by sir w. roberts-austen, k.c.b., f.r.s., d.c.l. * * * * * _fifth edition, thoroughly revised and considerably enlarged._ s. ~introduction to the study of metallurgy.~ by sir w.c. roberts-austen. with additional illustrations and micro-photographic plates of different varieties of steel. _fourth edition, thoroughly revised and enlarged._ s. ~the metallurgy of gold.~ by t. kirke rose, d.sc., assayer of the royal mint. including the most recent improvements in the cyanide process. with new frontispiece and additional illustrations. _in two volumes, each complete in itself._ ~the metallurgy of lead and silver.~ by h.f. collins, assoc. r.s.m., m.inst.m.m. ~part i.--lead.~ with sections on smelting and desilverisation, and the assay and analysis of the materials involved. s. ~part ii.--silver.~ sources and treatment of ores, with descriptions of plant, machinery, &c. s. _second edition, revised. with numerous illustrations._ s. ~the metallurgy of iron.~ by thomas turner, f.i.c., assoc. r.s.m. professor of metallurgy at the university of birmingham. _large vo. profusely illustrated with plates and diagrams._ ~the metallurgy of steel.~ by f.w. harbord. with a section on the mechanical treatment of steel. by j.w. hall. s. net. * * * * * ~assaying.~ by j.j. beringer, f.i.c., f.c.s., and c. beringer, f.c.s. ninth edition, revised. with diagrams, s. d. ~getting gold.~ a practical treatise for prospectors and miners. by j.c.f. johnson, a.i.m.e.. f.g.s., life member australian mine managers' association. numerous illustrations. second edition. s. d. ~gold seeking in south africa.~ a handbook of hints for intending explorers, prospectors, and settlers. by theo. kassner. with a chapter on agriculture. crown vo, fancy cloth boards. illustrated. s. d. net. ~the cyanide process of gold extraction.~ by james park, f.g.s., m.inst.m.m., late geological surveyor and mining geologist to the new zealand government. new edition, revised and enlarged from the last new zealand edition. with frontispiece, plates and illustrations. s. net. ~prospecting for minerals.~ a practical handbook. by s. herbert cox, assoc. r.s.m., m.inst.m.m., f.g.s., &c. with illustrations. second edition, revised. cloth, s.; leather, s. d. ~tables for quantitative metallurgical analysis for laboratory use.~ by j. james morgan, f.c.s. large vo, strongly bound, cloth, s. ~electric smelting and refining.~ by dr. w. borchers. translated by walter g. mcmillan, f.i.c., f.c.s., from the second german edition. with numerous illustrations and three folding plates. s. ~mine accounts and mining bookkeeping.~ from the actual practice of leading mining companies. by james g. lawn, assoc. r.s.m., a.m.inst.c.e.f.g.s. edited by sir le neve foster, d.sc., f.r.s. large vo. third edition. s. d. * * * * * _large vo. handsome cloth. illustrated, s. d. net._ ~metallurgical analysis and assaying:~ a three years' course for students. by w.a. macleod, b.a., b.sc., a.o.s.m. (n.z.), and chas. walker, f.c.s. ~part i.--qualitative analysis, and preparation and properties of cases.~ ~part ii.--qualitative and quantitative analysis.~ ~part iii.--assaying, technical analysis (gas, water, fuels, oils, &c.).~ * * * * * london: charles griffin & co., ltd., exeter street, strand. generously made available by the internet archive/american libraries.) hittel on gold mines and mining. quebec: printed by g. & g. e. desbarats. . hittel on gold mines and mining. _chief industry._--mining is the chief industry of california. it employs more men and pays larger average wages than any other branch of physical labor. although it has been gradually decreasing in the amount of its production, in the profits to the individuals engaged in it, and in its relative importance in the business of the state, it is yet and will long continue to be the largest source of our wealth, and the basis to support the other kinds of occupation. _metals obtained._--our mines now wrought are of gold, silver, quicksilver, copper and coal. ores of tin, lead, and antimony in large veins, beds of sulphur, alum and asphaltum; lakes of borax and springs of sulphate of magnesia, are also found in the state, but they are not wrought at the present time, though they will probably all become valuable in a few years. platinum, iridium, and osmium are obtained with the gold in some of the placer mines, but are never found alone, nor are they ever the main object sought by the miner. the annual yield of our gold mines is about forty millions of dollars, of our quicksilver two millions of dollars. our silver, copper and coal mines have been opened within a year, and their value is yet unknown. all our other mining is of little importance as compared with the gold. _gold mines._--our gold mines are divided into placer and quartz. in the former, the metal is found imbedded in layers of earthy matter, such as clay, sand and gravel; in the latter it is incased in veins of rock. the methods of mining must be adapted to the size of the particles of gold, and the nature of the material in which they are found. in placer mining, the earthy matter containing the gold, called the "pay-dirt," is washed in water, which dissolves the clay and carries it off in solution, and the current sweeps away the sand, gravel and stones, while the gold, by reason of the higher specific gravity, remains in the channel or is caught with quicksilver. in quartz mining the auriferous rock is ground to a very fine powder, the gold in which is caught in quicksilver, or on the rough surface of a blanket, over which the fine material is borne by a stream of water. about two-thirds of our gold is obtained from the placers, and one-third from the quartz. a mine is defined and generally understood to mean "a subterraneous work or excavation for obtaining metals, metallic ores or mineral substances;" but this definition does not apply to our placer mines, which are places where gold is taken from diluvial or alluvial deposits. most of the work is not subterraneous; it is done in the full light of day. in some of the claims the pay-dirt lies within two feet of the surface; in others it lies much deeper, but all the superincumbent matter is swept away. water is the great agent of the placer miner; it is the element of his power; its amount is the measure of his work, and its cost is the measure of his profit. with an abundance of water he can wash every thing; without water he can do little or nothing. placer mining is almost entirely mechanical, and of such a kind that no accuracy of workmanship or scientific or literary education is necessary to mastery in it. amalgamation is a chemical process it is true, but it is so simple that after a few days' experience, the rudest laborer will manage it as well as the most thorough chemist. it is impossible to ascertain the amount of gold which has been taken from the mines of california. records have been kept of the sums manifested at the san francisco custom house, for exportation, and deposited for coinage in the mints of the united states; and there is also some knowledge of the amounts sent in bars and dust to england; but we have no account of the sums carried by passengers to foreign countries and coined elsewhere than at london, or used as jewelry, or of the amount now in circulation in this state. according to the books of the custom house of san francisco, the sums manifested for export were as follows: in , $ , , ; in , $ , , ; in , $ , , ; in , $ , , ; in , $ , , ; in , $ , , ; in , $ , , ; in , $ , , ; in , $ , , ; in , $ , , ; in , $ , , ; in , $ , , ; in , $ , , ; a total of $ , , in twelve years. the exportation of gold commenced in , but we have no record of the sums sent away in that year. previous to very large sums were carried away by passengers, who gave no statement at the custom house; since that year, the manifests show the exportation correctly within a few millions. i am entirely satisfied that the total gold yield of california has been not less than seven hundred millions of dollars; but i have not room here to state the reasons for this opinion. my estimate is considerably less than that of most business men of the state, and less than that made by hunt's _merchants' magazine_. there was undoubtedly a regular increase in the annual yield of the mines from to the end of ; and there has been a gradual decrease since the beginning of --a decrease perhaps not very regular but still certain. since considerable sums exported from san francisco, and included in our tables, came from mines beyond the limits of california, such as the mines in southern oregon, in the eastern part of washington territory, in british columbia, and in nevada territory; and while the california gold yield has been decreasing, these extraneous supplies have been increasing. several millions must be deducted from the annual shipments since , for foreign gold. the gold yield will undoubtedly continue to fall, but to what point and at what rate no one can know. i believe that in , the yield will not exceed thirty millions of dollars. _placer mines._--placer mines are divided into many classifications. the first and most important is into deep and shallow. in the former the pay-dirt is found deep, twenty feet or more beneath the surface; in the latter, near the surface. the shallow or surface diggings are chiefly found in the beds of ravines and gullies, in the bars of rivers, and in shallow flats; the deep diggings are in hills and deep flats. the pay-dirt is usually covered by layers of barren dirt, which is sometimes washed, and sometimes left undisturbed, while the pay-dirt is taken out from beneath it through tunnels or shafts. so far as our present information goes, we have reason to believe that no gold country ever possessed so large an extent of paying placer mines, with the pay-dirt so near the surface, and with so many facilities for working them as california. in australia the diggings are very deep and spotted, that is, the gold is unevenly distributed, and the supply of water for mining is scanty. in siberia the winter is terribly cold during six months of the year. in brazil the diggings were not so extensive nor so rich as in this state. here we have numerous large streams coming down through the mining districts, very large bodies of pay-dirt, and a mild climate. after dividing placers into deep and shallow, the next classification will be according to their topographical position, as into hill, flat, bench, bar, river-bed, ancient river-bed, and gulch mines. hill diggings are those where the pay-dirt is in or under a hill. flat diggings are in a flat. bench diggings are in a "bench" or narrow table on the side of a hill above a river. benches of this kind are not uncommon in california, and they often indicate the place where the stream ran in some very remote age. bars are low collections of sand and gravel at the side of a river and above its surface at low water. river-bed claims are those beneath the surface of the river at low water, and access is obtained to them only by removing the water from the bed by flumes or ditches. ancient river-bed claims are those of which the gold was deposited by streams in places where no streams now exist. gulch claims are those in gullies which have no water, save during a small part of the year. a "claim" is the mining land owned or held by one man or a company. the placer mines are again classified according to the manner in which, or the instruments with which they are wrought. there are sluice claims, hydraulic claims, tunnel claims, dry washing, dry digging, and knife claims. in and , the main classification of the placers was into wet diggings and dry diggings, the former meaning mines in the bars and beds of rivers, and dry diggings were those in gullies and flats where water could be obtained only part of the year or not at all. that classification was made while nearly all the mining was done near the surface, before the great deposits of pay-dirt in the hills had been discovered, and before ditches, sluices, and the hydraulic process had been introduced. the class of mines then known as the "dry diggings," and which for several years furnished nearly half of the gold yield of the state, are now, with a few unimportant exceptions, exhausted, or left to the attention of the chinamen. the purpose of all placer miners is not to catch all the gold in the dirt which they wash, but to catch the greatest possible quantity within a given time. it is not supposed that any process used in gold mining catches all the metal. part of it is lost; in some processes a considerable proportion. the general estimate in california is, that one-twentieth of the gold in the dirt which is washed is lost. many of the particles are so very small as to be invisible to the naked eye, and so light that their specific gravity does not avail to prevent them from being carried away by the water like sand. the larger pieces will sink to the bottom and resist the force of the water; the smaller the particles, the greater the danger that it will be borne away. many devices have been tried to catch all the gold, but none have succeeded perfectly, and some which have caught a portion of what escaped from the ordinary modes of mining, have been found to cost more than their yield. the miner does not grieve about that which he cannot catch. he is not careful to catch all that he could. his purpose is to draw the largest possible revenue per day from his claim. he does not intend to spend many years in mining, or if he does, he has become thriftless and improvident. in either case, he wishes to derive the utmost immediate profit from his mine. if his claim contain a dollar to the ton, and he can save five dollars by slowly washing only six tons in a day, while he might make ten dollars by rapidly washing fifteen tons in a day, he will prefer the latter result, though he will loose twice as much of the precious metal by the fast as by the slow mode of working. the object of the miner is the practical dispatch of work, and his success will depend to a great extent upon the amount of dirt which he can wash within a given space of time. he regrets that any of the gold should be wasted, but his regret is because it escapes from his sluice and his pocket, rather than because it is lost to industry and commerce. _the sluice._--the board-sluice is a long wooden trough, through which a constant stream of water runs, and into which the auriferous dirt is thrown. the water carries away the clay, sand, gravel and stones, and leaves the gold in the bottom of the sluice, where it is caught by its gravity and by quicksilver. the board-sluice is the great washing machine, and the most important instrument used in the placer mining of california. it washes nearly all the dirt and catches nearly all the placer gold of the country. it was invented here, although it had previously been used elsewhere; it has been more extensively employed here than in any other country, and it can be used here to more advantage than elsewhere. it is not less than fifty feet long, nor less than a foot wide, made of boards. the width is usually sixteen or eighteen inches; and never exceeds five feet. the length is ordinarily several hundred and sometimes several thousand feet. it is made in sections or "boxes" twelve or fourteen feet long. the boards are an inch and a half thick, and are sawn for that special purpose, the bottom boards being four inches wider at one end than the other. the narrow end of one box therefore fits in the wide end of another, and in that way the sluice is put together, a long succession of boxes, the lower end of each resting in the upper end of another, and not fastened together otherwise. these boxes stand upon trestles, with a descent varying from eight to eighteen inches in twelve feet. it is therefore an easy matter to put up or take down a sluice after the boxes are made, and it is not uncommon for the miners to haul their boxes from one claim to another. the descent of a sluice is usually the same throughout its length, and is called its "grade." if there be a fall of eight inches in twelve feet, the sluice has an "eight-inch grade," and if the fall be twice as great, it is a "sixteen-inch grade." the grade depends upon the character of the pay-dirt, the length of the sluice, and its position. the steeper the descent, the more rapidly the dirt is dissolved, but the greater the danger also that the fine particles of gold will be carried away by the water. the tougher the dirt, that is, the greater its resistance to the dissolving power of the water, the steeper, other things being equal, should be the sluice. a slow current does not dissolve tough clay, and that is the greater part of the pay-dirt, so rapidly as a swift one. the shorter the sluice, other things being equal, the smaller the grade should be. there is more danger that the fine particles of gold will be lost by a short sluice than by a longer one, and to diminish this danger, the rapidity of the current must be reduced by a small grade. the greater the amount of dirt to be washed, other things being equal, the steeper should be the grade; for a swift current will wash more dirt than a slow one. in many claims the pay-dirt is full of large stones and boulders, weighing from one hundred to five hundred pounds each, all of which must be carried away through the sluice. some are sent down whole, and others are broken into pieces with sledge hammers before they are thrown into the box. these require a swift current and a large body of water. the larger the supply of water, the steeper the sluice is made, other things being equal. of course economy and convenience of working require that the sluice should be near the level of the ground, and as that may be steep or level below the claim, the grade of the sluice must to some extent conform to it. there are thus a multitude of points to be taken into consideration in fixing the grade of a sluice; but a fall of less than eight or more than twenty inches, in a box of twelve feet, would be considered as unsuitable for the board-sluice. sometimes the upper part of the sluice is made steeper so as to dissolve the dirt, and the lower part has a small grade to catch the gold. the clayey matter of ordinary pay-dirt is fully dissolved in a sluice two hundred feet long with a low grade, so the use of the boxes beyond that length is merely to catch the gold. there are claims however in which the clay is so extremely tough that it will roll in large balls more than a quarter of a mile through a steep sluice with a large head of water, and come out at the lower end scarcely diminished in size. the gold is caught in the sluice-boxes by false bottoms of various kinds. it would not do to leave the smooth boards, for the water would sweep all the gold away, and the boards themselves would soon be worn through. the most common false bottom is the longitudinal riffle-bar, which is from two to four inches thick, from three to seven inches wide, and six feet long. two sets of these riffle-bars go into each sluice-box, the box being twice as long as the bar. a set of riffle-bars is as many as fill one half of a box. they are wedged in, from an inch to two inches apart; the wedging being used, because the bars can more readily be fastened in their places, and more easily taken up, than if nails were used. before the work of sluicing commences, all the boxes are fitted with riffle-bars, and the bottom of the sluice is therefore full of holes from one to two inches wide, from three to seven inches deep, and six feet long. these are the places in which the gold, quicksilver, and amalgam are caught. quicksilver is used now in nearly all the sluices, and is the more necessary the smaller the particles of gold. the large pieces of the metal would all be caught by their specific gravity without the aid of amalgamation. the sluice-boxes having been made, and set up with the proper grade, the water is turned in. the boxes are made of the rough boards as they come from the saw, and the joints are not waterproof, but the leaks are soon stopped by the swelling of the wood, or by the dirt. the stream of water in the sluice is at least two inches deep over the bottom. the height of the sides of the boxes is from eight inches to two feet. the sluice usually runs through the claim, and the auriferous dirt is thrown in with shovels, of which from four to twenty are constantly at work. a man will throw in from two to five cubic yards of dirt in one day. the water rushing over the dirt as it lies in the box, rapidly dissolves the clay and loam, and then sweeps the sand, gravel and stones down. the first dirt in the box goes to fill the spaces between the riffle-bars. after the sluicing has been in progress a couple of hours, some quicksilver is put in at the head of the sluice, and it gradually finds its way downward, most of it stopping, however, near where it is put in. _amalgamation._--there are a few metals, including gold, silver, copper and tin, which, with quicksilver, form a peculiar chemical union called amalgamation, a process of great importance to the gold miner. when a piece of gold or silver is placed in mercury, the latter metal gradually penetrates through it, destroys the coherence of its particles, and form with it a mass like dough. a lump of gold as large as a bean will be soaked through in three or four days; with silver and copper the process is slower, but they are affected in the same manner. amalgamation, though a union of a solid with a liquid, differs much from a solution. in the latter the union is mechanical; in the former it is chemical. in the latter the solid is reduced to particles of impalpable fineness; in the former it is not. an ounce of salt will be dissolved in, and nearly equally diffused through, a pint of water; but if an ounce of gold be thrown into a pint of quicksilver, it will, after forming an amalgam with the quicksilver, remain at the bottom. we have no texture so fine that it will strain salt out of water; but the particles of gold are so coarse in amalgam that they can easily be strained out by means of buckskin or tight cloths. however, a little gold will remain in the quicksilver--about the fiftieth part of an ounce of gold in every pound of quicksilver; and the only method of obtaining this gold is by retorting. quicksilver is used in gold mining for catching the small particles of metal; the large ones are caught by their weight. but many of the particles are so small that they are almost invisible to the naked eye, and when in moving water they float. miners frequently show visitors the fineness of their gold by putting some of the dust in a vial with water, and upon shaking, the particles of metal can be seen floating about in the clear water. riffles, and all the devices to get the benefit of specific gravity, are of little use to arrest this "float-gold," so amalgamation is employed. if a bit of quicksilver is put in the way of the fine gold, the two metals unite at once and make a larger bulk, which can be caught. there is no such attraction between gold and quicksilver as there is between the magnet and iron; but when the two former metals once touch, an amalgam is immediately formed, and if the proportions of the metals be about even, they in time make a hard mass. some gold does not amalgamate readily; in various diggings of siskiyou county, the gold has a reddish coating, which prevents amalgamation. grease or resin in the water used for washing, is also unfavorable. so is cold. heat is favorable, and therefore less gold is lost in summer than in winter. quicksilver that has been once used is considered better than that fresh from the flask. no tinned iron or copper vessel should be used for holding or panning out amalgam, or dirt containing amalgam; since quicksilver forms an amalgam with tin and copper, and will stick to the sides of a tinned or copper pan. in most sluices, the quicksilver is put in above the riffle-bars at various places along in the boxes, with a confidence that the great specific gravity of the metal will prevent it from being lost. the greater the quantity and proportion of fine gold, the greater the importance of the quicksilver. the best method of catching very fine gold by amalgamation is to cover a large copper plate with mercury, and let the dirt and water, in a thickness of not more than a quarter of an inch, pass over it slowly. there are various methods of covering copper plates with quicksilver. the first thing, in every case, is to wash the copper with diluted nitric acid, so as to remove all dirt and grease. the quicksilver may then be rubbed on with a rag; or, still better, it may be dissolved in nitric acid, and the liquid nitrate of quicksilver may be applied with a rag. the nitric acid will attack the copper, and leave the quicksilver as an amalgam on the surface of the copper. this is the most common process, but the nitrate of copper continues for a long time to come up through the quicksilver and interfere with the catching of the gold. when the nitrate of copper appears--it is a green slime--it should be scraped off and the place rubbed over with quicksilver. when a plate is once covered with mercury, the operation need never be repeated; but more mercury must be sprinkled on as the gold collects and forms a solid amalgam. the plate is usually three feet wide and six feet long, and is set nearly level. in very large sluices the stream should be divided so as to run over different plates. the slowness of the current and the shallowness of the water are important, for with a swift current or deep water many of the particles of float-gold may escape without touching the quicksilver. wherever a speck of gold has fixed itself on the plate, there others will collect about, evidently preferring to fix themselves in a neighborhood rather than in a waste place. the more gold there is on a plate, the better it is considered to be. the seasons for cleaning up are usually determined by the danger of theft. miners do not like to leave their gold out in quantities so large as to attract thieves. the amalgam is sometimes half an inch thick, and is usually, at cleaning-up time, a hard mass, which must be loosened by heat. the plate is put on a fire, and when it gets so warm that the hand can scarcely bear it, the amalgam is softened and loosened, so that it can be scraped off readily. the plate is then sprinkled anew with quicksilver, and is ready for use again. mercury does not amalgamate with copper so readily as with gold or silver. a copper plate, the sixteenth of an inch thick, may be used for at least five years, and perhaps for ten; whereas a gold plate of equal thickness would, if exposed to the action of quicksilver in the same manner, fall to pieces in a few weeks. after a time the quicksilver pervades the copper, and gives it a silvery whiteness all through on the under side. it is said that a solution of cyanuret or prussiate of potash, is used instead of nitric acid in applying mercury to copper plates, and that it is still better, there being then no trouble with the green spots of nitrate of copper. a good amalgamated copper plate is considered as serviceable as a bed of quicksilver of equal size, and it is very much cheaper and more convenient to manage. the dirt and water should be admitted to the copper plate, by falling first through a sheet-iron plate, pierced with holes half an inch long and a sixteenth of an inch wide. some miners place this sheet-iron plate immediately over the copper. very soon after the water and dirt commence to run in the sluice, all the spaces between the riffle-bars are filled with sand, gravel and dirt; which, however, present many little inequalities of surface, sufficient to catch all the particles of gold larger than a pin-head. the largest gold is caught near the head of the sluice; and the farther down the sluice, the finer the gold. in some sluices, where the pay-dirt contains much coarse gold, the quicksilver is introduced from thirty to sixty yards below the head, so as to catch only the fine particles of metal. _cleaning up._--the separation of the gold, amalgam, and quicksilver, from the dirt in the bottom of the sluice, is called "cleaning up;" and the period between one "cleaning up" and another is called a "run." a run in a common board-sluice usually lasts from six to ten days. ordinarily the sluice runs only during daylight, but in some claims the work continues night and day. cleaning up occupies from half a day to a day, and therefore must not be repeated too often, because it consumes too much time. in some sluices the cleaning up does not occur until the riffle-bars have been worn out or much bruised by the wear of the stones and gravel. cleaning up is considered light and pleasant work as compared with other sluicing, and is often reserved for sunday. at the time fixed, the throwing in of dirt ceases, and the water runs until it becomes clear. five or six sets of riffle-bars, a distance of thirty or thirty-five feet, are taken up at the head of the sluice, and the dirt between the bars is washed down, while the gold and amalgam lodge above the first remaining set of riffle-bars, whence it is taken out with a scoop or large spoon, and put into a pan. five or six more sets of bars are taken up, and so on down. sometimes all the riffle-bars are taken up at once, save one set in every thirty-six feet, and then the work of cleaning up is dispatched much more rapidly. the quicksilver and amalgam taken from the sluice are put into a buckskin or cloth, and pressed, so that the liquid metal passes through, and the amalgam is retained. the amalgam is then heated, to drive off the mercury. this may be done either in an open pan or in a close retort. in the former, the quicksilver is lost; in the latter, it is saved. the pan is generally preferred. often a shovel or plate of iron is used. three pounds of amalgam, from which the liquid metal has been carefully pressed out, will yield one pound of gold. the gold remaining after the quicksilver has been driven off by heat from the amalgam, is a porous mass, somewhat resembling sponge-cake in appearance. _riffle-bars._--the riffle-bars are usually sawn longitudinally with the grain of the wood, but "block riffle-bars" are considered preferable; the latter are cut across the tree, and the grain stands upright in the sluice-box. the block riffle-bars are three times more durable than the longitudinal; and as the latter kind are worn out in a week in some large sluices, there is a considerable saving in using the former. the block riffle-bars are only two or three feet long. in some small sluices the riffle-bars are not placed in the boxes longitudinally, nor in sets; but one bar near the head runs downward at an angle of forty-five degrees to the course of the box, not touching its lower end to the side of the box, but leaving an open space of an inch there. just below this open space another bar starts from the side of the box and runs downward at right angles to the course of the first bar, and an open space is again left at the end of this bar; and so on down to near the lower end of the sluice, where there are longitudinal riffle-bars in sets as described in the preceding paragraphs. the consequence of using this kind of riffle-bar is, that though much of the water and light dirt runs straight over the bars, the heavier material runs down from side to side in a zigzag course. near the head of the sluice is a vessel, from which quicksilver falls by drops into the box; and it follows the course of riffle-bars, overtaking the gold which takes the same route. these zigzag riffle-bars are nailed down. in all sluices, men must keep watch to see that the boxes do not choke; that is, that the dirt and stones do not collect in one place, so as to make a dam, and cause the water to run over the sides, and thus waste the gold. there are small sluices, from which all stones as large as a doubled fist are thrown out. for this purpose the miner uses a sluice-fork, which is like a large manure-fork or garden-fork, but has tines which are blunt and of equal width all the way down; the bluntness being intended to prevent the tines from catching in the wood, and the equality of width to prevent the stones from getting fast in the fork. in some sluices, the "block riffle-bars"--that is, bars cut across the grain of the tree--are set transversely in the boxes, and about two inches apart. another device is, to fill the pores of such riffle-bars with quicksilver. this is done by driving an iron cylinder with a sharp edge into the surface of the bar, then putting mercury into the cylinder, and pressing it into the wood. the quicksilver, thus fastened in the wood, catches particles of gold, which must be scraped off when the time for "cleaning up" comes. _double sluices._--sluices are sometimes made double--that is, with a longitudinal division through the middle, so that there are two distinct sluice-boxes side by side. two companies may be working side by side, so that it will be cheaper for them to build their sluices jointly. in some places the amount of water varies greatly; so that in the winter there is enough to run two sluices, and in the summer only one. and there are companies which wish to continue washing without interruption; so they wash first on one side and then on the other, and clean up without any interruption to the process of washing. another device for saving gold in sluices is the "under-current box." there is a grating of iron bars in the bottom of a box, near the lower end of a sluice; and under this grating is another sluice, with an additional supply of clean water, and with a lower grade. the grating allows only the fine material to fall through; and the current of water being moderate, many particles of gold, that would otherwise be lost, are saved. sometimes the matter from the under-current box is led back to the main sluice. _rock-sluices._--large sluices are frequently paved with stone, which makes a more durable false bottom than wood, and catches fine gold better than riffle-bars. the stone bottoms have another advantage--that it is not so easy for thieves to come and clean up at night, as is often done in riffle-bar sluices. but, on the other hand, cleaning up is more difficult and tedious in a rock-sluice, and so is the putting down of the false bottom after cleaning up. the stones used are cobbles, six or eight inches through at the greatest diameter, and usually flattish. a good workman will pave eight hundred square feet of sluice-box with them in a day; and after the water and dirt have run over them for an hour, they are fastened very tightly by the sand collected between them. in large sluices, wooden riffle-bars are worn away very rapidly--the expense amounting sometimes, in very large and long sluices, to twenty or thirty dollars a day; and in this point there is an important saving by using the stone bottoms. they are used only in large sluices, and they generally have a grade of twelve or fourteen inches to the box of twelve feet. _hydraulic mining._--after the board-sluice, with its various adjuncts of riffle-bars, stone bottoms, copper plates, and so forth, the next instrument of importance in the gold-mining of california, is the hydraulic hose, used to let water down from a considerable height, and throw it under the pressure of its own weight against the pay-dirt, which is thus torn down, broken up, dissolved and carried into the sluice below. the sluice is a necessary part of hydraulic mining. the hose is used, not to wash the dirt, but to save digging with shovels, and to carry it to the sluice. the hydraulic process is applied only in claims where the dirt is deep and where the water is abundant. if the dirt were shallow in the claim and its vicinity, the necessary head of water could not be obtained. hydraulic claims are usually in hills. the water is led along on the hill at a height varying from fifty to two hundred feet above the bed-rock, to the claim at the end or side of the hill, where the water, playing against the dirt, soon cuts a large hole, with perpendicular or at least steep banks. at the top of the bank is a little reservoir, containing perhaps not more than a hundred gallons, into which the water runs constantly, and from which the hose extends down to the bottom of the claim. the hose is of heavy duck, sometimes double, sewn by machine. this hose when full is from four to ten inches in diameter, and will bear a perpendicular column of water fifty feet high; but a greater height will burst it. now, as the force of the stream increases with the height of the water, it is a matter of great importance to have the hose as strong as possible; and for this purpose, in some claims, it is surrounded by iron bands, which are about two inches wide, and are connected by four ropes which run perpendicularly down. the rings are about three inches apart. the "crinoline hose," thus made, is very flexible, and will support a column of water one hundred and fifty or two hundred feet high. the pipe at the end of the hose is like the pipe of a fire-engine hose, though usually larger. sometimes the pipe will be eight inches in diameter where it connects with the hose, and not more than two inches at the mouth; and the force with which the stream rushes from it is so great, that it will kill a man instantaneously, and tear down a hill more rapidly than could a hundred men with shovels. one or two men are required to hold the pipe. they usually turn the stream upon the bank near its bottom until a large mass of dirt tumbles down, and then they wash this all away into the sluice; when they commence at the bottom of the bank again, and so on. if the bank is one hundred and fifty feet high, the mass of earth that tumbles down is of course immense, and the pipemen must stand far off, for fear that they will be caught in the avalanche. such accidents are of daily occurrence, and the deaths from this cause probably are not less than threescore every year in the state. often legs are broken; still more frequently the pipemen have warning, and escape in time. when men are buried in the falling dirt, the water is used to wash them out. in some claims, the pipe will tear down more dirt than the sluice can wash; in other claims, the sluice always demands more dirt than the pipe can bring down. in the latter case, blasting may be used to loosen the dirt, or the miners may undermine the bank, leaving a few columns of dirt for support; and then these being washed away by the pipe, the whole bank comes tumbling down. in hydraulic claims, all the dirt is washed; in all other kinds of claims, such dirt as contains no gold is thrown to one side, or "stripped off." "hydraulic mining" is the highest branch of placer mining; it washes more dirt, and requires more water, and a larger sluice, than any other kind of mining. the number of men employed in a hydraulic claim, however, is usually small, from three to six, the water doing nearly all the work. in some claims a man is constantly employed with a heavy sledge-hammer in breaking up large stones, so that the pieces may be sent down the sluice. one man attends to the sluice, and sees that the dirt does not choke up in the sluice, or in the claim above it. the quantity of dirt that can be washed with a hydraulic pipe depends upon various circumstances--such as the supply of water, the height of its fall, the toughness of the dirt, and the amount of moisture in it. more can be washed in winter than in summer, because the dirt is then moister, and requires less water to loosen and dissolve it. the quantity of water used in a hydraulic claim is from forty to two hundred inches. with one hundred inches, at least thirty cubic yards can be washed in ten hours, on an average; and three men can do all the work. if there were a cent's worth of gold in each cubic foot, the thirty cubic yards would yield eight dollars and ten cents per day, or two dollars and seventy cents to the man, exclusive of the cost of water. but, as a matter of fact, nearly all the hydraulic claims pay more than that, and they will average at least three cents to the cubic foot, and many of them yield five cents. the water usually costs twenty cents an inch per day, so that one hundred inches would cost twenty dollars. allowing for the water at that rate, a claim in which thirty cubic yards could be washed in a day with one hundred inches of water, and in which the dirt contained five cents to the cubic foot, would leave a net pay of six dollars and sixty-six cents to each man per day. one hydraulic company, of whose labors i have a note, washed two hundred and twenty-four thousand cubic feet of dirt in six days, using two hundred inches of water, and employing ten men. the wages of the men amounted, at four dollars per day each, to two hundred and forty dollars; the water cost three hundred dollars; and the waste of quicksilver, and wear of sluice, perhaps one hundred dollars more, making a total expenditure of six hundred and forty dollars: and the gold obtained was three thousand dollars, leaving a clear profit of twenty-three hundred and fifty dollars. the dirt contained one cent and a fifth of gold in a cubic foot. the greater the amount of water used, the greater the proportionate amount of dirt that can be washed, and the greater the proportionate profits. it is far more profitable to have a large sluice than a little one, if the water and dirt can be obtained in abundance. usually, in a hydraulic claim, the dirt is washed down to the bed-rock; but in some places the washing stops far above the bed-rock, because there is no outlet for the water. _blasting._--in some hydraulic claims, the dirt, in dry seasons, is blasted, so as to loosen it. a drift or hole is cut into the bottom of a hill, one or two hundred feet high, and a number of kegs of powder (from twenty to two hundred) are introduced, and they are fired with a slow match. the explosion makes an earthquake in the vicinity; and the ground is loosened to such an extent that there is a great saving of labor. the breaking up of the dirt and the exposure to the air are supposed to facilitate the washing greatly. more water is required for piping down banks than for washing the dirt; and often the sluice is almost idle for want of dirt, while the water, after being thrown against the hillside, runs away without doing any service at washing. blasting, therefore, by loosening the earth, enables the hydraulic miner to have an abundant and regular supply of dirt in his sluice, at an expense much less than the cost of manual labor to dig the bank down with pick and shovel. _tail-sluice._--the tail-sluice is a large sluice made for rewashing the tailings or dirt which has previously passed through other sluices. it is placed ordinarily in the bed of a ravine or creek through which tailings run, and it receives no attention for weeks or months at a time, save to keep it from choking. the sluices emptying into it furnish both dirt and water, and in the dirt there is always a large amount of fine gold, as is plainly proved by the fact that some of the tail-sluices have paid large profits to their owners. tail-sluices are always large, long and paved with stones; and sometimes they are double, so that one side may be cleaned up while the other continues washing. in a branch of the yuba there is, or was not long since, a tail-sluice twenty feet wide. _tunnel-sluice._--a tunnel-sluice is a sluice in a tunnel. it sometimes happens that a considerable body of water runs out through a tunnel; and in such case, a sluice at the bottom of the tunnel offers the easiest method of getting out and washing the dirt. the tunnels are never cut level, but with a slightly ascending grade, so that the water will always run out. the grade is so low, that transverse riffle-bars must be used; for with longitudinal riffle-bars or stones, there would be too much danger of choking. these tunnel-sluices, because of their low grades, require much more attention than any other kind of sluices. _ground sluice._--all the sluices hitherto mentioned and described have wooden boxes, but the ground-sluice has no box: the water runs on the ground. the place selected for the ground-sluice is some spot where there is a considerable supply of water, a steep descent for it, and much poor dirt. the stream is turned through a little ditch, which the miners labor to deepen and enlarge, and when it is deep they prize off the high banks so that the dirt may fall down into the ditch. this is a very cheap and expeditious way of washing, but it is not applied extensively. it is used to the most advantage for washing where the water is abundant for only a few weeks after heavy rains, and where it would not pay to erect large sluices. a few cobble-stones should be left or thrown at intervals in the bed of the ground-sluice to arrest the gold, for if the bed were smooth clay, the precious metal might all be carried off. quicksilver is not used in the ground-sluice. after the dirt has all been put through the ground-sluice, it is cleaned up in a short board-sluice, or a tom. _long tom._--the tom or long tom, an instrument extensively used in the californian mines in and , but now rarely seen, is a wooden trough about twelve feet long, eighteen inches wide at the upper end, and widening at the lower to thirty inches, with sides eight inches high. it is used like a board-sluice, but has no riffle-bars, and at the lower end its bottom is of sheet-iron, perforated with holes half an inch in diameter. this sheet-iron is turned up at the lower end, so that the water never runs over there, but always drops down through the perforated sheet-iron or riddle, into a little riffle-box, containing transverse riffle-bars. a stream of water of about ten inches makes a "tom-head"--or the amount considered necessary for a tom--through the tom, which has a grade similar to that of a board-sluice. the dirt is thrown in at the head of the tom, and a man is constantly employed in moving the dirt with a shovel, throwing back such pieces of clay as are not dissolved, to the head of the tom, and throwing out stones. from two to four men can work with a tom; but the amount of dirt that can be washed is not half that of a sluice. the tom may be used to advantage in diggings where the amount of pay-dirt is small and the gold coarse. the riffle-box contains quicksilver, and as the dirt in it is kept loose by the water falling down on it from the riddle above, a large part of the gold is caught; but where the particles are fine, much must be lost. _cradle._--the rocker or cradle is still less than the tom and inferior in capacity. it bears some resemblance in shape and size to a child's cradle, and rests upon similar rockers. the cradle-box is about forty inches long, twenty wide, and four high, and it stands with the upper end about two feet higher than the lower end, which is open so that the tailings can run out. on the upper end of the cradle-box stands a hopper or riddle-box twenty inches square, with sides four inches high. the bottom of this riddle box is of sheet-iron, perforated with holes half an inch in diameter. the riddle-box is not nailed to the cradle-box, but can be lifted off without difficulty. under the riddle is an "apron" of wood or cloth, fastened to the sides of the cradle-box and sloping down to the upper end of it. across the bottom of the cradle-box are two riffle-bars about an inch square, one in the middle, the other at the end of the box. the dirt is shovelled into the hopper, the "cradler" sits down beside his machine, and while with one hand with a ladle he pours water from a pool at his side upon the dirt, with the other he rocks the cradle. with the water and the motion the dirt is dissolved, and carried down through the riddle, falling upon the apron which carries it to the head of the cradle-box, whence it runs downward and out, leaving its gold, black sand, and heavier particles of sand and gravel behind the riffle-bars. the man who rocks a cradle learns to appreciate the fact, that the "golden sands" of california are not pure sand, but are often extremely tough clay, a hopperful of which must be shaken about for ten minutes before it will dissolve under a constant pouring of water. many large stones are found in the pay-dirt. such as give an unpleasant shock to the cradle, as they roll from side to side of the riddle-box, are pitched out by hand, and after a glance to see that no gold sticks to their sides, are thrown away; but the smaller ones are left until the hopperful has been washed, so that nothing but clean stones remain in the riddle, and then the cradler rises from his seat, lifts up his hopper, and with a jerk throws all the stones out. the water and the rocking are both necessary. without the water, the dirt could not be washed; and without the rocking, the dirt would dissolve very slowly, and the gold would most of it be lost. the rocking keeps the dirt in the bottom of the cradle more or less loose, so that the particles of gold can sink down in it, whereas if the cradle stood still, the sand there would almost immediately pack down into a hard floor, over which the gold would run almost as readily as over a board. the whole business of washing with a cradle, is a repetition of the process already described--some dirt, about one-third or one-fourth of what the hopper would hold, if full, is put into the hopper, and while the cradle is rocked with one hand, the other pours in the water. the cradle is cleaned up two or four times in a day. the cleaning up is done by lifting the hopper, taking out the apron, scraping up all the dirt in the bottom of the cradle with an iron spoon, putting it into a pan and washing out the dirt, so that only the gold will be left. this last process is called panning out, and will be described in the next section. most of the gold collects above the upper riffle-bar, including all the larger lumps. if the apron be of rough woollen cloth, some of the fine gold will be caught there. in diggings where the gold is very fine, the hopper is sometimes placed over the lower end of the cradle, and the apron is made twice as long, and with a lower inclination than in the more common form of the rocker. the water for the cradle should be supplied by a little ditch, with a reservoir at the head of the cradle, to contain five or six gallons. the dipper should be of tin, shaped like a basin, hold about a gallon when full, and have a handle an inch and a half in diameter, and eight inches long. the difference of height between the upper and lower ends of the cradle should not be more than two inches: a steeper inclination will make the current running through it too strong, and the gold will be carried off; and, on the other hand, if the cradle be nearer a level it will be hard to rock, and the dirt in the bottom will pack more rapidly. the amount of dirt that can be washed in a day with a cradle, varies from one to three cubic yards. the dirt is usually shovelled into a pan or bucket, from which it is thrown into the hopper. the miners usually measure the amount of dirt washed by the number of "pans." one man working alone with a cradle ought to wash from seventy-five to one hundred and fifty pans in a day, and two men will wash twice as much. a pan may contain one-third or one-half of a cubic foot. two men can work more conveniently with the rocker than one. there is enough work to give constant employment to a cradler and a shoveller. the latter has a couple of buckets or pans, which he fills alternately, always keeping one full and near the cradler, so that without moving his feet he can pick it up and empty it into the riddle-box. if the rocker have only one man, he must stop rocking after washing every pan and get more dirt. this delay is injurious to the process of washing, because it allows the dirt in the bottom of the cradle to harden and pack, and some gold is always lost as a consequence. if the dirt and water be convenient, not more than two men can work to a profit with a rocker. but sometimes it happens that water cannot be led to the claim, and in such case the dirt must be carried to the water, a greater weight of which is used than of dirt. at least three times as much water as dirt is required for washing. if the distance from the hole to the water be not over ten or twenty feet, the miners will usually carry the dirt in buckets; if farther they will use wheelbarrows; and sometimes for greater distances pack-mules or waggons. the greater the distance, the more the men required for carrying the dirt. sometimes, too, it happens that the claim is troubled by water, and then one man may be constantly employed in bailing. it is of great importance in mining with the cradle, to have the cradle placed within four or five feet of the hole from which the pay-dirt is obtained, and to have a good supply of water at the head of the cradle, and then to have a good descent below the cradle, so that the tailings may all be carried away by the water, so as not to accumulate. the rocker washes about one-half the amount of dirt that can be washed by an equal number of men with the tom, one-fourth of what can be washed with the sluice, and one-hundredth of the amount that can be washed with the hydraulic process; but it is peculiarly fitted for some kinds of diggings. many little gullies, containing coarse gold in their beds, cannot obtain water for washing except during rains, and then only for a few days at a time. in these gullies the cradle can be used to the best advantage, for it can easily be transported, and it is very good for saving coarse gold. while dirt that would pay from ten to twenty-five cents, was abundant at the surface of the earth in the californian mines, the cradle was extensively used, but now it has been abandoned by the whites, and is left to the chinamen, who think themselves doing well if they make seventy-five cents or one dollar per day. the great difficulty in mining with the cradle is, that the sand will "pack," or make a hard mass on a level with the top of the riffle-bars, and the gold then is lost. so long as the cradle is in motion the dirt does not pack, but when the rocking ceases, the mass hardens in a few minutes. if the miner leaves his cradle standing for fifteen minutes, he stirs up the dirt with his spoon before commencing again to wash. one device to prevent packing is to put a little block under each end of the rockers, so that at the end of every motion the cradle receives a shock. quicksilver is sometimes used in cradles, but not usually. _pan._--the pan is used in all branches of gold mining, either as an instrument for washing, or as a receptacle for gold, amalgam, or rich dirt. it is made of stiff tin or sheet-iron, with a flat bottom about a foot across, and with sides six inches high, rising at an angle of forty-five degrees. a little variation in the size or shape of the pan will not injure its value for washing. sheet-iron is preferable to tin, because it is usually stronger and does not amalgamate with mercury. the pan is the simplest of all instruments used for washing auriferous dirt. some dirt, not enough to fill it full, is put in, and the pan is then put under water. the water ought to be not more than a foot deep, so that the pan may rest on the bottom, while the miner inserts his fingers in and under the dirt and lifts it up a little, so that the whole mass is wet. if the water be deep, the pan may be held in one hand while the other is used to stir up the dirt, but it is more convenient to take both. the dirt having been filled with water, the miner catches the pan at the sides, raises that part toward his body, and lowers the outer edge a little, and commences to shake the pan from side to side, holding it so that all the dirt is under water, and so that a little of the dirt can escape over the outer edge. the earthy part of the dirt is rapidly dissolved by the water, assisted by the shaking of the pan and the rolling of the gravel from side to side, and forms a mud which runs out while clean water runs in. the light sand flows out with the thin mud, while the lumps of tough clay and the large stones remain. the stones collect on the top of the clay, and they are scraped together with the fingers and thrown out. this process continues, the pan being gradually raised in the water, and its outer edge depressed, until all the earthy matter has been dissolved, and that as well as the stones swept away by the water, while the gold remains at the bottom. panning is not difficult, but it requires practice to learn the degree of shaking, which dissolves the dirt and throws out the stones most rapidly without losing the gold. if the shaking be too mild and slow, the process consumes too much time; whereas if it be too rapid and violent, the gold is carried off with the stones. sometimes the pan is shaken so that the dirt receives a rotary motion. this is the most rapid method of washing dirt, but also the most dangerous. the pan must always be used in cleaning up the dirt which collects in the cradle, in prospecting, and frequently in washing small quantities of dirt collected in other kinds of placer mining. amalgam can be separated from dirt by washing, almost as well as gold. in panning out, it frequently happens that considerable amounts of black sand containing fine particles of gold are obtained, and this sand is so heavy that it cannot be separated from the gold by washing, while it is easily separated by that process from gravel, stones and common dirt. the black sand is dried, and a small quantity of it is placed in a "blower," a shallow tin dish open at one end. the miner then holding the pan with the open end from him, blows out the sand, leaving the particles of gold. he must blow gently, just strong enough to blow out the sand, and no stronger. from time to time he must shake the blower so as to change the position of the particles, and bring all the sand in the range of his breath. the gold cannot be cleaned perfectly in this manner, but the sand contains iron, and the little of it remaining is easily removed by a magnet. the blower should be very smooth, and made of either tin, brass or copper. _dry washing._--dry washing is a method of winnowing gold from dirt. in many parts of the mining districts of california, water cannot be obtained during the summer for mining purposes. the miner therefore manages to wash his dirt without water. he takes only rich dirt, and putting it on a raw hide, he pulverizes all the lumps and picks out the large stones. he then with a large flat basin throws the dirt up into the air, catches it as it comes down, throws it up again, and repeats this operation until nothing but the gold remains. of course a pleasant breeze, that will carry away the dust, is a great assistance to the operation. sometimes two men have a hide or a blanket, with which they throw up the dirt. the process is very similar to the ancient method of separating grain from chaff. the miner who devotes himself to dry washing must be very particular to take only rich dirt, so he scrapes the bed-rock carefully. he never digs very deep--not more than twenty feet; and when he goes beyond seven or eight feet he "coyotes," or burrows after the pay-dirt. he may coyote into the side of a hill, or sink a shaft and coyote in all directions from it. this style of mining is named from the resemblance of the holes to the burrows of the coyote, or californian wolf. coyoting is not confined to the dry washing, but is used also by miners washing with the pan and cradle. one of the congressmen elected some years ago to represent california at washington, was a miner at the time of his nomination, and was so fond of coyoting, that he was generally known as "coyote joe." _dry digging._--dry digging is that mining where the miner, after using the shovel to strip off the barren dirt, scrapes the pay-dirt over with a knife, picking out the particles of gold as he comes to them, and throwing away the earthy matter. this is a slow process, but in rich placers may be profitable. the miner is, of course, particular to examine all the crevices in the bed-rock; and if the material be slate, he digs up part of it, to see whether the gold has not found its way into cracks scarcely perceptible on the surface. "dry digging," as a mode of mining, must not be confounded with "dry diggings," a kind of mining ground which has been described near the beginning of this chapter. knife-mining differs a little from dry digging. in the latter, a shovel is used to strip off the barren dirt; whereas the knife-mining is practised in those places where the gold is deposited in crevices in rocks along the banks of streams, without any covering of barren dirt, so that the knife alone is used in scraping out the dirt; and afterward the dirt, being placed in a pan, may be washed in water, which is never used in dry digging. _puddling-box._--the puddling-box is a rough wooden box, about a foot deep and six feet square, and is used for dissolving very tough clay. the clay is thrown into the box, with water, and a miner stirs the stuff with a hoe until the clay is all thoroughly dissolved, when he takes a plug from an auger-hole about four inches from the bottom, and lets the thin solution of the clay run off, while the heavier material, including the gold, remains at the bottom. he then puts in the plug again, fills up the box with water, throws in more clay, and repeats the process again and again until night, when he cleans up with a cradle or pan. the puddling-box is used only in small mining operations, and never with the sluice, or in hydraulic claims. _quicksilver-machine._--the quicksilver-machine, or burke rocker, is a cradle about seven feet long, two feet wide, and two feet high. in the bottom are a number of compartments, all containing quicksilver. one man rocks the machine without cessation. a constant stream of water pours into the machine at its head. the riddle extends the whole length of the machine; and the stones, after being washed clean, fall off the riddle at the lower end. one man is employed constantly working with a shovel to keep the dirt on the riddle under the stream of water, and in throwing off the big stones. if the pay-dirt is very convenient, two men can shovel enough to keep the machine in operation. the burke rocker was extensively used in california eight and ten years ago, but now it is a great rarity. _tunnel-mining._--a tunnel, in california mining, is an adit or drift entering a hill-side, or running out from a shaft. mining-tunnels are usually nearly horizontal--those entering hill-sides having a slight ascent, for the double purpose of draining the mine, and to facilitate the removal of the pay-dirt. in a few hills the tunnels run downward at an angle of twenty degrees or more, to avoid veins or ledges of rock, which would have to be blasted through if the tunnel were cut horizontally; but this can only be done with safety in hills which are drained by older horizontal tunnels. the mining-tunnel does not run through a hill, but only into it. the length of tunnels varies greatly; the longest are about a mile. the usual height is seven feet, the width five feet. ordinarily the top must be supported by timbers, to prevent it from falling in, and not unfrequently the sides must also be protected by boards. the cost of cutting a tunnel varies from two to forty dollars a longitudinal foot, according to the nature of the ground, the cost of getting timbers, &c. tunnels are usually made by companies of eight or ten men, of whom one-half may be merchants, lawyers, physicians or office-holders, and the remainder laboring miners. the latter class do the work; the former furnish provisions and tools, and a certain amount of cash weekly until the pay-dirt is reached. two or three men work at a time cutting a tunnel; one or two to dig the earth, and one or two to haul it out. the dirt of the first fifty yards is hauled out in a wheelbarrow; beyond that distance a little tram-way or railroad is laid down, and the dirt is hauled out in cars, pushed by the miners. it is not customary to use horses. it is common to have two relays of laborers--one set working from noon to midnight, the other from midnight to noon. work in a tunnel is as pleasant at night as in the daytime. when a company is rich, or has many laborers, it may have three relays, each to work eight hours in the twenty-four. it is not uncommon for two companies, owning adjacent claims in a hill, to unite and cut a tunnel on joint account along the dividing line. they go in until they reach the pay-dirt, and then a surveyor is employed to run the line between their claims, and the tunnel is continued through the pay-dirt. the dirt from the tunnel is washed for the joint account of the two companies. after the dividing line has been established, each company keeps on its own side, and each has its time to use the tram-way. they may also have a joint-stock sluice at the mouth of the tunnel--one company having the privilege of using the sluice one week, and the other the next. all the dirt brought out in a week can readily be washed in a day. the work of taking out the pay-dirt after the main tunnel has been cut, is called "drifting;" and the holes made by the men engaged in it are termed "drifts." the drifts are usually not so high as the tunnels. the large stones and barren dirt obtained in the drifts are piled up here and there to sustain the earth overhead. sometimes wooden posts are likewise necessary. _shafts._--shafts are used in prospecting, and also in mining, where the claims are deep and cannot be reached by either the hydraulic process or the tunnel. the prospecting shaft is sometimes sunk into hills supposed to be auriferous, where the shaft is far less expensive than the tunnel. after the shaft demonstrates that the dirt is rich, and precisely the altitude at which it lies, a tunnel is cut to strike it. the shaft may be the cheaper for prospecting, but the tunnel is usually the cheaper if any large amount of dirt is to be taken out. the shaft is dug by one man in the hole, and one or two are employed at a windlass in hauling up the dirt. mining-shafts in placer diggings are rarely over one hundred feet deep; but one was dug in trinity county to the depth of six hundred feet, for the purpose of prospecting, but it found neither pay-dirt nor the bed-rock. _river-mining._--river-mining is mining for gold in the beds of rivers, below low-water mark. the only practicable method of doing this is by damming the stream, and taking the water out of its bed, in a ditch or flume. it has been proposed by persons who never saw the mines, to get the gold by dredging, or with a diving-bell; but such schemes are absurd in the eyes of miners. the rivers in which the gold is found are mountain-torrents, in which a canoe can scarcely float in summer, much less a dredging machine; and any large scoop working under water would miss the crevices and corners in the rocks, where most of the gold is found. as the water is very seldom more than a couple of feet deep, a diving-bell would be of little service. the flume, the ditch, and the wing-dam, are the chief tasks of the river-miner. the ditch is rarely used, because the banks of the mining-streams are usually so steep, high, rocky and crooked, that a flume is cheaper. the wing-dam is not often used, because the river-beds are in most places too narrow. the flume is almost universally employed. the work of river-mining can be done only during the summer and fall, while the water is low, and while the miner can have confidence that it will not rise. it may be as low in january as in august, but the winter is the season of rains; and when the flood comes, it sweeps dams, flumes and every thing before it. if the dam and flume be commenced too early in the season, they may be carried off before they are finished; and it frequently happens that they are destroyed in the fall just when the miners are commencing to reap the reward of their summer's labor. river-mining has many disadvantages, as compared with other branches of mining. the miner cannot work at it more than half the year; he cannot prospect the dirt which is hidden under water; he must erect expensive dams and flumes, which can be used for only a few months; and then he is exposed to floods which may come and destroy all his work before he has commenced to wash. these disadvantages, and the exhaustion of most of the river-diggings in the state, have almost put an end to river-mining in california. in a few cases, extensive fluming enterprises have proved profitable; but, as a general rule, river-mining in this state has cost more than it has produced. a river is seldom flumed for less than three hundred yards, and sometimes for a mile; and the lumber and labor required to make so long a flume, and one large enough to hold all the water of a river, are very expensive. the dam will always leak, and water will run into the bed from the adjacent hills and mountains, and this water must be lifted out by pumps driven by wheels placed in the flume. the river-beds are full of large rocks, weighing from one to ten tons, and these must be moved by machinery, to allow the dirt to be taken out. river-mining is now never undertaken by an individual, but always by large associations, generally called "fluming companies," sometimes composed of miners exclusively, sometimes of miners and all the principal business-men living near the place where the work is to be done. the lawyers, doctors and office-holders, pay their assessments in cash; the merchants furnish provisions, the lumbermen supply lumber, and the miners make the dam, and help the carpenters build the flume. _beach-mining._--beach-mining is the business of washing the sands of the ocean-beach. between point mendocino, in california, and the mouth of the umpqua river, in oregon, the beach-sand contains gold, and in some places it is very rich. the beach is narrow, and lies at the foot of a bluff bank of auriferous sand. in times of storm, the waves wash against this bank, undermine it, sweep away the pieces which tumble down, leaving the gold on the beach. the gold is in very fine particles, and it moves with the heavier sand, which alters its position frequently under the influence of the waves and surf. one day, the beach will have six feet depth of sand; the next, there will be nothing save bare rocks. the sand differs greatly in richness at various times: one day, it will be full of golden specks; a few days later, at the same place it will be barren. the sand in the mean time has been moved by the waves, and replaced by other sand. it is a very difficult matter to know where the sand is rich and where it is not. the companies employed in mining on the beach number about ten men; and there is a foreman who rides out early every morning, following the beach about two miles to the northward and two miles to the southward of the camp, for the purpose of finding where the sand is the best. so changeable is the sand, that a new examination is made every day; and only three or four men are supposed to be good judges of the quality of sand, from its appearance. when the foreman has selected a place, he orders all the men to it, and they go with twenty pack-mules, which carry the sand in _alforjas_, or raw hide sacks, to the place of washing, which is up on the bluff, probably a mile or more distant from the spot where the sand is obtained. it happens occasionally that the foreman rides long distances on the beach, and sometimes he will order the sand to be obtained ten miles from the washing-place. the sand must, of course, be very rich, to pay for such transportation, but the beach-sand at times in the sunlight is said to be actually dazzling yellow with gold. the purpose of going upon the bluff to wash it, is to get fresh water for washing; for the sea-water is not so good, nor can it be obtained conveniently. the richest dirt is that the farthest down on the beach, so still weather and low tide are the best times for getting it. when a rich place is discovered low down on the beach, great exertions are made to get as much of the sand as possible before the tide rises. when high tide and storm come together, little can be done. the sand, having been separated from all clay and soluble matter by the action of the sea, is very easily washed, and all collected in a month can be washed in two days in a sluice. _mining-ditches._--the placer-mines of california would yield very little gold, were it not for the numerous ditches which supply them with water for washing. the auriferous districts are very dry in summer, and in some places there is not a spring nor a brook within many miles. the artificial ditch supplies the want. the ditches are made by large companies, which sell the water by the "inch." an inch of water is as much as will run out of an orifice an inch square, with the water standing six or seven inches deep in the flume over the orifice. the depth of water over the orifice is called the "head." the orifice is usually two inches high, and as long as necessary to give the amount of water desired. nobody wants less than ten or twelve inches for mining: a "sluice-head" is about eighteen inches; a "hydraulic-head" is from forty to two hundred inches. the water, however, is not measured accurately. of course the amount which runs through the orifice will depend to a considerable extent upon the "head," which is usually greater in the morning than at night. at sunrise there may be fifteen inches head, and at sunset only three. the water collects during the night, and is exhausted during the day. the price of water is in no place less than ten cents an inch per day; in some places it is forty cents; the average is about twenty cents. many of these ditches are extensive enterprises, and have cost hundreds of thousands of dollars. when they cross ravines and valleys, large flumes--wonders of carpentry--must be built. some of these are two hundred feet high and a mile long, and so large that a horse and waggon can be driven through them. in all, save length and durability, they are as wonderful as the great roman aqueducts, whose tall ruins still stand in the campagna, near the eternal city. in some cases iron tubes have been used, and although they are very expensive, yet they may pay for themselves, by preventing evaporation, leaking and soaking, which take away much of the water from flumes and ditches. _prospecting._--"prospecting" is the search for gold. the instruments used by the prospector for placer-mines are usually the pan, pick and shovel. he should be familiar with the general laws of the distribution of gold, and then try the dirt in the most favorable places. if there is any gold in a district, he can scarcely fail to find specks of it by washing dirt from the bed-rock in the ravines, and in bars. the existence of gold in a district having been established, close observation will suggest to the prospector where he may reasonably expect to find the best diggings. it is usually found that placer-gold is collected in those places where, if he had been familiar with the ancient topography of the country, he should have had reason to suppose that it would be. _quartz mining._--quartz mining differs much from placer mining. for the former, more capital, more experience, more complicated machinery and richer material are required than for the latter. the placer miner throws the dirt into the water, which then does the work; whereas the pulverizing of rock is a nice operation, requiring constant attention. quartz requires a mill and water-power; placer dirt is washed in a simple sluice. dirt containing ten cents in the cubic yard may pay the hydraulic miner, but the quartz miner must have a hundred times as much in a cubic yard of vein stone, or he cannot work. the placer gold, when freed from the baser material surrounding it, is much of it in coarse particles, which are easily caught by their specific gravity; the quartz gold must be reduced to a fine powder before it be set free from its gangue, and with the fineness of the particles increases the difficulty of catching them. auriferous quartz lodes are often found by accident. not unfrequently it happens that a rich streak of pay-dirt in a placer claim is followed up to the quartz vein from which it came. while miners are out walking or hunting, they occasionally will come upon lodes in which the gold is seen sparkling. some good leads have been found by men employed in making roads and cutting ditches. the quartz might be covered with soil, but the pick and shovel revealed its position and wealth. in tuolumne county in , a hunter shot a grizzly bear on the side of a steep _canon_, and the animal tumbling down, was caught by a projecting point of rock. the hunter followed his game, and while skinning the animal, discovered that the point of rock was auriferous quartz. in mariposa county, in , a robber attacked a miner, and the latter saw the rock behind his assailant sparkle in the sunlight, at a spot where a bullet struck a wall of rock. he killed the robber, and found that the rock was gold-bearing quartz. in nevada county, several years ago, a couple of unfortunate miners who had prepared to leave california, and were out on a drunken frolic, started a large boulder down a steep hill. on its way down, it struck a brown rock and broke a portion of it off--exposing a vein of white quartz which proved to be auriferous, induced the disappointed miners to remain some months longer in the state, and paid them well for remaining. science and experience do not appear to give much assistance in prospecting for quartz lodes. chemists, geologists, mineralogists and old miners, have not done better than ignorant men and new-comers. most of the best veins have been discovered by poor and ignorant men. not one has been found by a man of high education as a miner or geologist. no doubt geological knowledge is valuable to a miner, and it should assist him in prospecting; but it has never yet enabled any body to find a valuable claim. _distribution of gold in quartz._--the rich quartz-veins of california extend from kern river to the siskiyou, are found on hills, in _canons_ and in vales. they are at least two thousand feet above the level of the sea, and not more than ten thousand feet above it. their course is generally from north-north-west to south-south-east, and they dip steeply to the eastward, sometimes being nearly perpendicular. they differ in thickness from a line to sixty feet. quartz veins are very numerous in most of the mining districts, so the task is not to find the veins, but rather to find those which are gold-bearing. it is supposed that nearly all large veins come to the surface of the bed-rock or "country;" but many of them are covered with soil and thus are hidden. hidden veins are called "blind;" those plainly visible on the surface are called "croppings veins," because their position is shown by the out-croppings. experience has not ascertained whether large or small veins are more likely to contain gold. it is found in both. the porous quartz, or that containing many cavities, is more frequently found auriferous and richly auriferous, than the very compact quartz. the best gold-bearing veins are usually yellowish or brownish in tinge, near the surface at least; but very rich specimens are found in white and bluish-white rock. most quartz veins in california contain a little gold; the metal seems to have been distributed most lavishly, but unfortunately in nine-tenths of the veins, the proportion of metal is too small to pay. most of the large veins are supposed to run for miles upon miles, though they can rarely be traced clearly on the surface for more than a furlong. the auriferous veins vary much in richness. no vein is wrought for more than a few hundred feet. beyond that, it is either too poor to pay, or the vein is hidden. some persons have supposed that there is one great gold-bearing quartz vein running along the side of the sierra nevada, from mariposa to plumas county, and that many of the richest claims are really in this one vein; but this a supposition which cannot be proved now. sometimes a vein seems to spread out and divide into a number of smaller veins, all of which afterward unite again. these points of junction, and the narrower places in the vein, are usually richer than other parts of it. when two veins cross each other, one may be auriferous on one side of the intersection and not on the other; but in this case the other vein will be auriferous on both sides. it is as though they were streams, one rich, the other barren, and that after meeting, the wealth of the one was divided between them. it is a general rule that metalliferous veins running parallel with the strata of the bed-rock or country are not extensive. in fact they are rather deposits than veins, and though often extremely rich are soon exhausted, while the lodes which run across the stratification, run far and deep, and have a regular and straight course and dip. lodes lying between two different kinds of rock, are usually richer than those which have the same kind of rock on both sides. thus it is said that the richest veins of auriferous quartz in california, have been discovered at the intersection of trap and serpentine, and the richest places in veins are where they cross from one kind of bed-rock into another. the richest part of a lode of auriferous quartz is almost invariably on the lower side of the vein, near the foot-wall. all these are facts to be remembered by the prospector as a guide, and an assistance to him in his search for a rich gold-bearing vein. if the lode is covered with earthy matter, he may sometimes trace its course by the difference in the color of the dirt and stones over it from that elsewhere. when the prospector finds dirt and stones on a vein, evidently disintegrated portions of it, he should wash some of the dirt in a pan, and if he finds no gold, there is a strong presumption that the vein is barren. _prospecting quartz rock._--after finding a gold-bearing vein, the question arises whether it will pay. great sums are lost in gold-mining countries by injudicious investments in mills and machinery to work the auriferous rock, and persons going into the business should be particularly careful not to commit this great error. the business of quartz mining has great profits, but also great pecuniary dangers connected with it. it is rarely that all the rock of a vein will pay for working. in some lodes, the vein-stone will average one hundred dollars to the ton, for all the stone found in a certain part of the lode, but beyond that the rock may be poor or worthless. picked specimens may be worth several thousand dollars to the ton, but perhaps not more than a ton of such specimens has been obtained in the best lode ever opened in the state. the most profitable lodes are those which have a large supply of rock, easily to be obtained, and all of it yielding something above the cost of working. the common method of ascertaining whether rock will pay, is to pulverize a little of it and wash it in a horn spoon. in taking out the quartz rock in large lodes, it is important to take out only that which will pay, and to determine this, the superintendent of the quarry-men must occasionally test the vein-stone. he takes several little pieces of it, average specimens, places them on a hard, smooth, flat stone, about a foot square, on which he crushes them with a stone muller four inches square, and then by rubbing with the muller he reduces them to a fine powder. he has a horn spoon, made of a large ox-horn, with a bowl about three inches wide, and eight inches long, being merely one-half of the horn in its natural shape. with this spoon he washes out the powder in water, and if he does not find a speck of gold or a "color," as it is called, in a pound of the rock, he infers that it will not pay. the three principal quartz mines in the state are those of fremont in mariposa county, of the allison company in nevada county, and of the sierra butte company in sierra county. the first has produced $ , in a month, the second $ , , and the third $ , , but the average is probably thirty per cent. less, and the expenses about thirty per cent. of the total product. the average yield of the fremont rock is fourteen dollars to the ton, of the sierra butte rock eighteen dollars, and that of the allison company, according to report, has for more than a year at a time been one hundred dollars per ton. the cost of working quartz rock, including quarrying, crushing and amalgamating, is in the best mills from five to ten dollars per ton. the width of the vein, the softness of the rock, the amount of work done, and the skill and industry of the workmen, all are items of great importance in estimating the cost of quartz-mining. it is a business which the owner of the mill ought to understand. the cost of quarrying common quartz rock is about two dollars per ton, that is, for mill-owners that understand the business and superintend the labor themselves. when given out by the job, it usually cost more. when quartz is crushed in a custom mill, that is, a mill built to crush for all applicants, the cost is rarely less than five dollars per ton, and in washoe, the price was at one time thirty dollars per ton; but in the large mills, where many tons are crushed every day, is about two dollars per ton. _the divining rod._--in prospecting for auriferous quartz, use is sometimes made of the divining rod, a practice not without credit with some good miners. the rod is a fork of a green hazel-bush, shaped like a v, with the arms about a foot long. the prospector holds the end of an arm in each hand, with the point of the v directed forward horizontally, and as he walks along, the point turns down whenever he comes over a metalliferous vein, metallic body or water. it is supposed that very few persons can use the divining rod effectually; for most men it refuses to turn. it is used in nearly every civilized country, especially by miners, and is generally considered superstitious, because it is employed by ignorant people, and because there has been no generally accepted scientific explanation of the manner in which a stick could be influenced by a metal hidden under ground. a scientific explanation of the principle of the divining rod has been offered to the world, by baron reichenbach, (see page sixty of his _odic-magnetic letters_, translated by john s. hittel). _quarrying quartz._--the quarrying of quartz rock differs little from the quarrying of other metalliferous vein-stones. the lode descends steeply, and the excavation must follow its course. sometimes the quartz is so soft that it may easily be loosened with the pick. the harder rock is blasted. soft quartz is that which is penetrated by numerous cavities, though the lumps between the cavities may be very hard. some quartz on exposure to the air crumbles into sand, though hard when first taken from the vein. in narrow lodes, some of the wall-rock must be cut away to get room for the workmen. in wide lodes, that part of the vein-stone which does not pay is left. sometimes the gold from the lode penetrates a little way into the foot-wall, and in that case the quarrying must extend beyond the vein stone. the quartz loosened in the vein, must either be hoisted perpendicularly in a bucket with a windlass, or be hauled out through a tunnel. the common method is to hoist the rock with a windlass. most of the veins are in such places that shafts are more easily dug than tunnels. after the excavation has extended twenty or thirty feet below the surface, it is usual to dig a perpendicular shaft, so as to strike the vein sixty or seventy feet below the surface, and from this point the miner or "drifter" works upward, and as he loosens the rock it falls to the bottom of the shaft, where it is put in the bucket to be hoisted to the surface. our quartz mines are generally in dry hills, so that they are not troubled much by water; but there are a few shafts where steam-pumps are constantly at work to carry off the water. occasionally the miners find small quantities of auriferous quartz which are so easily broken up, and the pieces of gold in which are so coarse, that after the rock has been pounded a little in a mortar, the metal can easily be picked out with the fingers. _arastra._--quartz is pulverized either in an arastra, or chilean mill, or by stamps. the arastra is the simplest instrument for grinding auriferous quartz. it is a circular bed of stone, from eight to twenty feet in diameter, on which the quartz is ground by a large stone dragged round and round by horse or mule-power. there are two kinds of arastras, the rude or improved. the rude arastra is made with a pavement of unhewn flat stones, which are usually laid down in clay. the pavement of the improved arastra is made of hewn stone, cut very accurately and laid down in cement. in the centre of the bed of the arastra is an upright post which turns on a pivot, and running through the post is a horizontal bar, projecting on each side to the outer edge of the pavement. on each arm of this bar is attached by a chain a large flat stone or muller, weighing from three hundred to five hundred pounds. it is so hung that the forward end is about an inch above the bed, and the hind end drags on the bed. a mule hitched to one arm will drag two such mullers. in some arastras there are four mullers and two mules. outside of the pavement is a wall of stone a foot high to keep the quartz within reach of the mullers. about four hundred pounds of quartz, previously broken into pieces about the size of a pigeon's egg, are called a "charge" for an arastra ten feet in diameter, and are put in at a time. the mule is started, and in four or five hours the quartz is pulverized. water is now poured in until the powder is thoroughly mixed with it, and the mass has the consistence of thick cream. care is taken that the mixture be not too thin, for the thickness of it is important to the amalgamation. the paste being all right, some quicksilver (an ounce and a quarter of it for every ounce of gold in the quartz, and the amount of gold is guessed at from the appearance of the rock) is scattered over the arastra. the grinding continues for about two hours more, during which time it is supposed the quicksilver is divided up into very fine globules and mixed all through the paste (which is so stiff that the metal does not sink in it to the bottom), and that all the particles of gold are caught and amalgamated. the amalgamation having been completed, some water is let in three or four inches deep over the paste, and the mule is made to move slowly. the paste is thus dissolved in the water, and the gold, quicksilver and amalgam have an opportunity to fall to the bottom. at the end of half an hour, or sooner, the thin mud of the arastra is allowed to run off, leaving the precious material at the bottom. another charge of broken quartz is now put in and the process is repeated, and so on. the length of a "run," or the period from one cleaning up to another, varies much in different places. in the rude arastra a run is seldom less than a week, and sometimes three or four. the amalgam having settled down between the paving stones, the bed must be dug up and all the dirt between them carefully washed. in the improved arastra the paving fits so closely together, that the quicksilver and amalgam do not get down between them, but remain on the surface, and can readily be brushed up into a little pan, and therefore cleaning up is much less troublesome and is more frequently repeated than in the rude arastras; besides there is a greater need of frequent cleaning up in the improved arastras, because the amount of work done within a given time is usually greater. the arastra is a slow instrument, but in some important respects it is superior to any other method of working auriferous quartz. it grinds the quartz well, is unsurpassable as an amalgamator, is very cheap and simple, requires no chemical knowledge or peculiar mechanical skill in the work, requires but little power, and very little water--all of them important considerations. in many places, the scarcity of water alone is enough to enable the arastra to pay a larger profit than any other method. again, if a miner finds a rich spot in a lode, he may be doubtful as to the amount of paying rock which he can obtain. such cases very frequently happen in california, and the arastra is just the thing for the case; for then if the amount of paying rock is small, nothing is lost, whereas the erection of a stamping-mill would cost much time and money, and before it could get into smooth operation the rich rock would be exhausted, and the mill perhaps become worthless. no other simple process of amalgamation is equal to that of the arastra; and it has on various occasions happened in california, that mexicans making from fifty to sixty dollars per ton from quartz, have sold out to americans who have erected large mills at great expense, with patent amalgamators, and have not been able to get more than ten or fifteen dollars from a ton. the arastra is sometimes used for amalgamating tailings which have passed through stamping-mills. _chilean mill._--the chilean mill has a circular bed like the arastra, but much smaller, and the quartz is crushed by two large stone wheels which roll round on their edges. in the centre of the bed is an upright post, the top of which serves as a pivot for the axle on which both of the stones revolve. a mule is usually hitched to the end of one of the axles. the methods of managing the rock and amalgamating with the chilean mill, are very similar to those of the arastra. the chilean mill, however, is rarely used in california; the arastra being considered far preferable. _stamps._--nine-tenths of the quartz crushed in california is pulverized by stamps, of which there are two kinds, the square and rotary. the square stamp has a perpendicular wooden shaft, six or eight feet long, and six or eight inches square, with an iron shoe, weighing from a hundred to a thousand pounds. the wooden shaft has a mortice in front near the top, and a cam on a revolving horizontal shaft enters this mortice at every revolution. when the cam slips out of the mortice, the stamp falls with all its weight upon the quartz in the "battery" or "stamping-box." the rotary stamp has a shaft of wrought iron about two inches in diameter, and just before falling this shaft receives a whirling motion, which is continued by the shoe as it strikes the quartz. the rotary stamp is considered superior to the square, its advantage being that it crushes more rock with the same power, that it crushes more within the same space, and that it wears away less of the shoe in proportion to the amount of rock crushed. there are usually half a dozen square stamps or more, standing side by side in a square-stamp mill, and these do not all fall at the same moment, but successively, running from the head to the foot of the "battery." the quartz is put in at the head of the battery, and is gradually driven to the foot. the rotary stamps sometimes stand side by side, and sometimes in a circle. the battery of both rotary and square stamps is surrounded by wire gauze, or a perforated iron plate, allowing the finely pulverized quartz to escape, and retaining the coarser particles. quartz is crushed wet and dry. in wet crushing a little stream of water runs into the battery on one side and escapes on the other, carrying all the fine quartz with it. _separation._--after pulverization comes the separation of the gold from the rocky portion of the powder. the means of separation are mechanical or chemical. the chemical process is amalgamation; the mechanical are those wherein the gold is caught on a rough surface with the aid of its specific gravity. the chief reliance is upon amalgamation, and in some large quartz-mills mechanical appliances are not used at all for catching the particles of gold, but only for catching amalgam. the mechanical appliances used in quartz-mills in separating the gold from the pulverized rock, are the blanket, the sluice, and the raw hide. the blanket is a coarse, rough, gray blanket, which is laid down in a trough sixteen inches wide and six feet long. the pulverized quartz is carried over this by a stream of water, and the particles of gold are caught in the wool. the blanket is taken up and washed, at intervals depending upon the amount of gold deposited. in some mills where a large amount of rock is crushed, and where the powder is taken over the blanket before trying any other process of separation, the washing takes place every half hour. in mills where the pulverized quartz is exposed to amalgamation first, the blanket may be washed three or four times a day. the washing is done in a vat, kept for that especial purpose. the sluice used in quartz-mills is similar to the placer board-sluice, but the amount of matter to be washed is less, and there is no dirt to be dissolved, and there are no larger stones, and therefore the sluice is not so large, so strong, or so steep in grade, as the placer-sluice, and the riffle-bars are not so deep. in some quartz-mill sluices there are transverse riffle-bars. if the quartz has much iron or copper pyrites, the sluice is used to collect this material and save it for separation at some future time. the pyrites ordinarily contains, or is accompanied by much gold, which it protects from amalgamation. this separation of the pyrites from the pulverized rock is called "concentrating the tailings," and the material collected is called "concentrated tailings." in the sluices of some quartz-mills cast iron riffle-bars are used; cast in sections about fifteen inches square, and about an inch deep. much study has been devoted to the subject of making these riffle-bars in such a manner that the dirt will not pack in them, but will always remain loose, and keep in constant motion under the influence of the water running over them; but the object has never been fully attained. quicksilver is used in nearly all quartz-mill sluices. the raw hide used in separating gold from the pulverized quartz is a common cow hide, laid down in a trough with the hairy side up, and the grain of the hair against the course of the water. the gold is then caught in the hair. sheep hides have been used in the same manner, recalling to mind the golden fleece. the hides, however, are inferior to the blankets for this purpose, and are never used in the best mills. the methods of amalgamating are numerous. among them are amalgamation in the battery, amalgamation with the copper plate, amalgamating bowls, and patent amalgamation of many kinds. in many mills quicksilver is placed in the battery, two ounces of quicksilver for one of gold; and about two-thirds of the gold is caught thus. the copper plate in quartz-mills is made in the same manner as in placer-sluices, under which head a description of the plate may be found. some amalgamating bowls or basins are little chilean mills and arastras, made of cast iron. one plan of amalgamation is to use a cast iron bowl about four feet in diameter and a foot deep. near the bottom are horizontal iron arms, which revolve and stir the quicksilver and pulverized quartz together. four or five of these bowls sit in a row but at different levels: the bottom of the first bowl being level with the top of the second, and so on. the pulverized quartz passes through them all. under each bowl a fire is kept up, because heat forms the action of amalgamation. if there be any pyrites in the quartz, some common salt is thrown in to assist in releasing the gold from the embraces of the sulphurates, and preparing it to be seized by the mercury. another amalgamating bowl revolves on an axis that stands at an angle of about seventy-five degrees to the horizon, so that the material in the bowl is continually moving; and the bottom is divided by little compartments, which make a constant riffle. in other bowls the pulverized quartz is forced with water through the mercury. the methods of amalgamation differ very much, and a book might be filled with a description and discussion of the processes used at different quartz-mills in california. _sulphurets._--many auriferous quartz veins contain considerable quantities of sulphurets or pyrites of iron, copper and lead, and their presence prevents amalgamation, and thus causes a great loss of gold. it is said that on some occasions in good mills, not more than twenty or thirty dollars have been obtained from a ton of vein-stone which had seven or eight hundred dollars of gold in every ton. the best method of treating the quartz containing pyrites, is to roast it, and thus drive off the sulphur, but this process is so expensive that it is seldom used; and the common practice is to crush and amalgamate the rock, and save the concentrated tailings for some future time, when there may be a sale for them, or when it will be cheaper to reduce them. the pulverized sulphurets are decomposed by exposure to the air, and after the tailings have been preserved for a time, they may pay better at the second amalgamation than at the first. a mixture of common salt assists the decomposition of the pyrites. _chief quartz-mills._--the most productive quartz-mill in the state is the benton mill, on fremont's ranch, in mariposa county. it is also the largest, having forty-eight stamps. there are four mills on the estate, with ninety-one stamps in all, and their average yield per month is sixty thousand dollars. a railroad four miles long, conveys the quartz from the lode to the mills. the allison quartz mine in nevada county, produces forty thousand dollars per month. the sierra buttes quartz-mill, twelve miles from downieville, yields about fifteen thousand dollars per month. these last mills run night and day, and crush and amalgamate ten thousand tons of rock a year, or twenty-eight tons per day. forty men are employed, twenty-five to quarry the rock, five in the mill to attend to the stamps and amalgamation, one to do carpentry, one for blacksmithing, and eight for getting out timber, transporting quartz, and so forth. the cost of quarrying, crushing and amalgamating a ton of rock, is six dollars. the wages of the men are from fifty to seventy dollars per month with boarding. the average wages is sixty dollars. about ten miles eastward of sonora, in tuolumne county, are some rich veins of auriferous quartz, the most prominent of which are the soulsby and blakeslee lodes. the soulsby mill produced forty thousand dollars in three weeks, when it commenced work in , but it has not been so profitable of late. _silver mining._--silver mining has not yet been established fairly as a business in california. the silver ores of washoe were discovered in , and mining has been fairly commenced there, but the mines of esmeralda and coso, within the limits of this state, were not found until the summer of , and up to the present time no mills have been established there. silver mining differs much from gold mining. gold is always found as a metal, never as an ore, and the separation from the accompanying vein-stone with which it is mixed mechanically, is much more simple and easy than the reduction of the argentiferous ores in which the silver is chemically combined with base substances, for which it has a strong affinity. chemical knowledge and chemical processes are more necessary in mining for silver than for gold; and while all auriferous quartz is of the same kind, and may be treated in the same manner, there are many different kinds of silver ores, each of which requires a peculiar treatment. the reduction of silver ore costs on an average, from three to five times as much as the reduction of auriferous quartz. the silver ore of esmeralda and coso is a sulphuret of silver, nearly all the veins having the same material, though the amount of it scattered through the vein-stone differs greatly in different lodes. in some veins there is much free gold, that is, little specks of metallic gold which can be separated from the other material in the same manner that gold is separated from auriferous quartz. the methods of reducing silver ore are so numerous and complex, and vary so much in different districts and under different circumstances, that it is impossible to know now what process will be used in esmeralda and coso, the resources of which places have been so little studied. besides it is said that new processes for reducing silver ore have been invented, far superior to all the old methods; and these processes are kept secret. it is therefore unnecessary that i should go into a long description of the various processes practised elsewhere. silver ore after pulverization is smelted by mixing with it fifty per cent. of lead in metal or ore, and ten per cent. of iron, and exposing the whole to a heat sufficient to melt the silver which runs off. the metal thus obtained is not pure but contains much lead, which is driven off by heat while the silver is kept in a molten condition for a period of four or six hours. the cost of smelting in california at present, is about one hundred and twenty-five dollars per ton. in most of the other methods of reducing silver ore, the ore is roasted to drive off the sulphur. in the barrel amalgamation, which has been used at washoe, and will probably be used at esmeralda also, half a ton of ore, after being pulverized and roasted, three hundred pounds of water, and one hundred pounds of wrought iron, in little fragments, are put into a barrel, which revolves on a perpendicular axis. at the end of two hours the mass has taken the consistence of thick cream, when five hundred pounds of quicksilver are put in, and after the barrel has revolved four hours more, the amalgamation is complete. more water is now poured in; the barrel revolves very slowly to let the amalgam all settle to the bottom, the mud runs off through a cock four inches above the bottom, and the mercury and amalgam are then drawn off through a little hole in the bottom of the barrel. _quicksilver mining._--the ore from which quicksilver is obtained is a sulphuret. the sulphur is driven off by heat, and the metal, which rises in fumes from the ore, is collected by condensation. the miners are cornishmen and mexicans. the ore is in large masses underground, not in a connected vein of regular thickness; and after one mass is exhausted, much labor is often vainly spent in search of another. there are, however, usually little seams of ore running from one large deposit to another, and it is the business of the mining captains to observe these veins closely, and trace them up when a "fault" occurs. there are no scientific rules for finding the ore; and the business of searching for the large deposits is never intrusted to educated mining engineers, but always to mining captains, who have themselves been laborers, and have learned by experience where to seek. the new almaden mine produces two hundred and twenty thousand pounds of metal in a month. the _hacienda_, or reducing establishment of the mining company, has fourteen brick furnaces, each fifty feet long, twelve feet high, and twelve feet wide. at one end of each furnace is the fire chamber, which may be nine cubic feet inside; next to that is the ore chamber of about the same size; and beyond that is the condensing chamber, in which there are a number of partitions alternately running up from the bottom and down from the top, with a space for the fumes to pass, their course being up and down, and up and down again, and so on, for a distance of thirty feet to the chimney, which is forty feet high. in the bottom of the condensing chamber is water. the walls between the fire chamber and the ore chamber, and between the latter and the condensing chamber, are built with open spaces, so that the heat, smoke and fumes can pass through. the ore is placed in the ore chamber in such a manner as to leave many open spaces. the heat drives off the sulphur and mercury of the ore in fumes, which in passing through the condensing chambers, deposit the mercury, and the smoke and sulphur escape through the chimney. in the enriqueta and guadalupe mines the quicksilver is condensed in a close iron retort, and the sulphur is absorbed by quicklime. copper ore is dug from several mines in california, but it is all exported to be smelted elsewhere. _platinum._--platinum, iridium and osmium, three white metals of about the same specific gravity with gold, are found with the latter metal in the placers in the basin of the klamath and trinity rivers. their particles are usually fine scales, very rarely reaching a quarter of an ounce in weight, and the largest piece of either ever found was less than an ounce and a half. they cannot be separated from the gold by washing, but they do not unite with quicksilver, and therefore they are separated from the more precious metal by amalgamation. they have no regular market in the state; miners never make them the chief object of search, and they have not been studied, so it is not known to what extent they might be obtained. _del norte and klamath._--del norte county in the north-western corner of the state, is about forty miles long from east to west by thirty from north to south. the mining population in it is small. most of the mining is done along the banks of the klamath river, which runs about twenty miles through the south-eastern portion of the county. there are some miners on the head-waters of althouse creek, which runs northward into oregon. the county assessor, in his report for , does not mention the existence of any quartz-mill or mining-ditch in the county. the mining districts are very mountainous and difficult of access. they obtain most of their supplies from crescent city. the mining is chiefly in shallow placers, in deep and narrow ravines, and on bars of the klamath river. klamath county lies immediately south of del norte, and is about the same size. it is almost exclusively a mining county, and has a population of about eighteen hundred. the diggings are placers in the bars and banks of the klamath river and its tributaries, the trinity and salmon rivers, and many small creeks. the principal mining places are orleans bar, gullion's bar, negro flat, cecilville, weitspeck and red cap. the whole county is very rugged and mountainous, and much of it is covered with heavy timber. the diggings are so difficult of access, and are so protected by mountains against ditches, that they will last for many years. there is probably no part of the state where the single miner, without capital, has a better chance to dig gold with a profit. nearly the whole beach of the county is auriferous. _siskiyou._--siskiyou county lies east of del norte and klamath, is forty miles wide from north to south, one hundred miles long from east to west, and reaches to the eastern boundary of the state. it has a population of , , the large majority of whom are engaged in mining. the mining district is all in the western end of the county, along the banks of the klamath river and its tributaries, the scott and shasta rivers. the klamath runs through a deep _canon_; the scott and shasta rivers, have pleasant open valleys, but the diggings along their banks are chiefly among the _canons_ near the klamath. hydraulic and tunnel claims are rare. there are six quartz-mills in the county, and fifteen mining ditches, of which last the principal is the yreka canal, forty miles long, bringing water from the head of shasta river to the town of yreka. in , there were four quartz-mills in the county, one of which was at mugginsville, one in scott's valley and two in quartz valley. i have no information about the situation of the two built since that time. the principal mining towns are yreka, scott's bar, hawkinsville, johnson's bar, deadwood and cottonwood. _trinity and shasta._--south of the western part of siskiyou and the eastern part of klamath, lies trinity county, ninety miles long from north to south, and about twenty miles wide on an average. the northern part of the county is the basin of the trinity river, and is auriferous. from the county assessor's report for , it is to be inferred that there is not a quartz-mill or a mining-ditch in the state. the county is very mountainous, and most of the mining is done in rugged _canons_ along the trinity river. the chief mining towns are weaverville, cox's bar, big bar, arkansas flat, mooney's flat and trinity centre. south of siskiyou and east of trinity lies shasta county, which is on an average forty miles wide from north to south and one hundred miles long, reaching to the eastern border of the state. there is a rich auriferous district about twenty miles square, in the vicinity of the town of shasta, in the south-western part of the county. the diggings are mostly in the basins of clear creek, cottonwood creek, rock creek and salt creek, all of which enter into the sacramento. there are four quartz-mills in the county, one at french gulch, one at middle creek, one at muletown, and one at old diggings. the county has twenty-seven mining ditches, with a joint length of one hundred and forty-one miles, an average of five miles each. the chief mining towns are shasta, horsetown, french gulch, muletown, briggsville, whiskey and middletown. _plumas and sierra._--south of the eastern part of shasta county lies plumas, which is about seventy miles square. about one third of the county, in the south-western part of it, comprising that portion drained by the head waters of feather river, is auriferous. it lies high above the level of the sea, and the work of mining is interrupted during a considerable portion of the winter, by cold, snow and ice. hydraulic and tunnel claims in deep hills, furnish a large portion of the gold yield of the county. there are five quartz-mills, one at elizabethtown, one at eureka lake, and three at jamison creek. the principal mining towns are quincy, jamison city, indian bar, nelson's point and poorman's creek. south of plumas is sierra county, which is fifty miles long from east to west, and twenty miles wide from north to south. the north fork of the yuba river runs through its centre, and the middle fork is its southern boundary. though small, it is one of the richest mining counties of the state, and in proportion to the extent of its mining ground, is much richer than any other county. all its territory is four thousand feet above the sea level, at the lowest. most of the mining is done in hydraulic and tunnel claims in deep hills. near the centre of the county is a mountain called the downieville butte, or the yuba butte, eight thousand eight hundred and forty-six feet high, on the sides of which are found some rich quartz leads. in there were eleven quartz-mills in sierra county, of which seven are at the butte, two at downieville, one at the mountain house, and one at sierra city. the principal mining towns are downieville, monte cristo, pine grove, st. louis, la porte, poker flat, eureka city, forest city, alleghany town, and cox's bar. one of the most remarkable features of the placers of the state, is the blue lead, which was first discovered in sierra county, and has been more thoroughly examined there than elsewhere. the "blue lead" is a stratum of blue clay very rich in gold. it is found deep under other strata. the general opinion is, that the blue lead occupies the bed of a large antediluvian river, which ran parallel with the sacramento and about sixty miles eastward of it. it has been traced twenty miles or more, passing near monte cristo, alleghany town, forest city, chip's flat and zion hill. mr. c. s. capp wrote thus to the san francisco _bulletin_: "this is not one of the many petty leads, an inch or two in breadth and thickness, which, after being traced a few hundred feet, end as suddenly and mysteriously as they commence; but it is evidently the bed of some ancient river. it is often hundreds of feet in width, and extends for miles and miles, a thousand feet below the summits of high mountains, and entirely through them. now it crops out where the deep channels of some of the rivers and ravines of the present day have cut it asunder; and then, hidden beneath the rocks and strata above it, it only emerges again miles and miles away. wherever its continuity has been destroyed, the river or gulch which has washed a portion of it away, was found to be immensely rich for some distance below, and the materials of which the lead is composed are found with the gold in the bed of the stream. it is evidently the bed of some ancient stream, because it is walled in by steep banks of hard bed-rock, precisely like the banks of rivers and ravines in which water now runs, and because it is composed of clay which is evidently a sedimentary deposit, and of pebbles of black and white quartz, which could only be rounded and polished as they are by the long continued action of swiftly running water. the bed-rock in the bottom of this lead is worn into long smooth channels, and also has its roughness and crevices like other river beds. the lighter and poorer qualities of gold are found nearest to its edges, while the heavier and finer portions have found their way to the deeper places near the centre. trees and pieces of wood, more or less petrified and changed in their nature, which once floated in its waters, are also every where encountered throughout this stratum. "the clay and fine gravel in which these pebbles and boulders are found to be tightly packed, is of a light-blue color, which gives the name to the lead. much of this clay is remarkably fine and free from coarse particles, and is smooth and unctuous to the touch. it is said to be strongly impregnated with arsenic, as was shown by chemical analysis, and contains large quantities of iron and sulphur in solution, for pyrites and sulphurets of iron are deposited in shining metallic crystals in every vacant crevice. fine gold is found among this clay, and the heavier particles beneath it, upon the bed-rock. this stratum varies in thickness from eighteen inches to eight or ten feet, while the whole lead varies in width from a hundred and fifty to five hundred feet. "the same lead has been found at sebastopol, four miles above monte christo, and also higher up among the mountains. it appears at monte christo, which is four miles above the high-lying downieville, and over three thousand feet above it, and at chapparal hill on the side of a deep ravine; then at the city of six, which is also on very high land, about four miles from downieville, across the north yuba. it is next found at forest city, on both sides of a creek, and is there traced directly through the mountain to alleghany town and smith's flat, on the opposite side. there it is again cut in twain by a deep ravine. it crops out on the other side at chip's flat, where it has been followed by tunnels passing completely through the mountain to centreville and minnesota on the other side. here it is obliterated by the middle fork of the yuba, but it is believed to be again found at snow point, on the opposite side of the river, and again at zion hill, several miles beyond. there is no reason for doubting that after thus reaching over twenty miles, it still extends further. hundreds of tunnels have been run in search of it. where the line it follows was adhered to, they have always found it, and have been well rewarded for their labor. millions of dollars have been taken from this lead, and its richness, even in portions longest worked, is yet undiminished. these tunnels have cost from $ , to $ , each, and interest in the claims they enter sell readily at from $ , to $ , , in proportion to the amount of ground within them remaining untouched, and the facilities which exist for working it. many of these claims will yet afford from five to ten or more years' profitable labor to their owners, before the lead itself within them is exhausted. as in some of them quartz veins and poorer paying gravel have been found, many of them may be valuable to work from the top down as hydraulic claims." this idea that the blue lead occupies the bed of an antediluvian river is however not universally accepted. mr. b. p. avery, who has written numerous newspaper articles upon the mineral deposits, asserts that the "blue lead," as it is called, is not a "lead" but an extensive stratum which is many miles wide, and is found all the way from the foot hills to the summit of the sierra nevada. in reply to this, it is said that while a bluish stratum of clay similar to that of the blue lead is found over a wide district, that it is evidently different in origin from the blue lead itself, which is confined to a narrow bed, and marked by the signs found in all the other ancient river beds of the state. the sierra butte quartz mining company has some of the best auriferous quartz lodes in the state. one lode called the cliff ledge, is twenty-five feet wide; and another called the aërial ledge, is about three feet wide. in the cliff ledge, the paying rock averages about six feet in thickness next the foot wall. the average yield is eighteen dollars per ton. the quartz is bluish white in color, and very hard when first taken from the lode, but on exposure to the air it slowly crumbles into sand. _yuba and butte._--west of sierra county, and drained by the same streams, is yuba, which reaches to the sacramento river, lying half in the mountains and half in the plains, the mining district being in the former half. the principal mining towns are camptonville, timbuctoo, foster's bar, texas bar and long's bar. in there were nine quartz-mills in the county, three at brown's valley, and one each at camptonville, dobbin's ranch, dry creek, honcut, indiana creek and robbin's creek. the assessor in reported only two quartz-mills in the county. there are twenty-two ditches in the county, with an aggregate length of nine hundred and fifty-two miles, an average of forty-three miles each. the most important ditch, called "bovyer's," supplies timbuctoo with five thousand inches of water in the winter, less in the summer. the diggings at timbuctoo are in a deep hill, which is washed away by the hydraulic process. west of yuba and plumas counties lies butte, which is drained by the feather river. the principal mining towns are oroville, bidwell's bar, forbestown, natchez and whiterock. in there were seventeen quartz-mills in the county, of which four were at oregon gulch, at columbiaville and hansonville, three each, two at yankee hill, and at evansville, gold run, long bar, nesbitt's flat and spring valley, one each. the assessor reports for , twenty-nine quartz-mills, worth fifty thousand dollars, and crushing in the aggregate one hundred and sixty-two and a half tons per day. there are sixty-four mining-ditches, with an aggregate length of five hundred and eighty-three miles. the bars and beds of feather river were once very rich, and some of the most extensive enterprises of river mining in the state have been undertaken within the limits of butte county. the greatest flume ever built in california was that of the cape claim company, near oroville, in . it was three quarters of a mile long and twenty feet wide, and furnished employment for two hundred and fifty men from may till november. the expenditures during that period were $ , , and the receipts $ , , showing a clear profit of $ , . the next year, after the water had fallen, the company commenced its labors again; spent $ , and received $ , , and thus lost $ , . north of oroville is a "table-mountain" with a top of basalt, covering a rich deposit of auriferous clay. _nevada and placer._--south of yuba and butte is nevada, the richest mining county of the state. within its limits the tom, sluice, under-current sluice, and crinoline hose were invented, and the ditch and hydraulic power were first applied to placer-mining; and quartz-mining was first undertaken extensively. in there were thirty-two quartz-mills in the county, and twenty-eight mining-ditches, with an aggregate length of three hundred and ninety-four miles. no part of the mineral region of the state is better supplied with water than nevada county. the richest quartz district is in the vicinity of nevada city, which has fifteen mills, and grass valley, five miles distant, has seventeen. the great allison mine, which has the richest lode in the state, is in grass valley. the quartz mines here are much troubled with water, and during the winter of - , many of the mills were compelled to stop for weeks until the shafts could be drained by steam engines, after having been filled by a long and heavy rain. the annual gold yield of grass valley has been estimated at four millions of dollars. north san juan has the finest hydraulic claims, and sweetland the largest tail-sluices. the eureka lake ditch company has more ditching and water than any other company in the state. their main ditch is seventy-five miles long, and there are one hundred and ninety miles of branches, making a total of two hundred and sixty-five miles, which have cost nine hundred thousand dollars. the daily sale of water is six thousand inches, with a weekly income of six thousand dollars. the principal mining towns are nevada, grass valley, north san juan, rough and ready, orleans flat, moore's flat and humbug city. index. pages. chief industry metals obtained gold mines placer mines the sluice amalgamation cleaning up riffle-bars double sluices rock-sluices hydraulic mining blasting tail-sluice tunnel-sluice ground sluice long tom cradle pan dry washing dry digging puddling-box quicksilver-machine tunnel-mining shafts river-mining beach-mining mining-ditches prospecting quartz-mining distribution of gold in quartz prospecting quartz rock the divining rod quarrying quartz arastra chilean mill stamps separation sulphurets chief quartz-mills silver mining quicksilver mining platinum del norte and klamath siskiyou trinity and shasta plumas and sierra yuba and butte nevada and placer none united states fuel administration bureau of conservation engineering bulletin no. boiler and furnace testing prepared by rufus t. strohm associate editor, power [illustration: maximum production minimum waste] washington government printing office ---------------------------------------------------------------------- maximum production. minimum waste. the united states fuel administration is making every effort, through the producers and transportation lines, to obtain an adequate supply of fuel for the industries of the country. twenty-five to fifty million tons of coal a year can be saved by the improved operation of steam-power plants without changing their present equipment and without abating their production the slightest. it is absolutely necessary that this saving be realized, if our overburdened railroads are to be relieved and our industries kept in full operation. the extent to which it will be realized depends upon the cooperation of the owners, engineers, and firemen of every power plant of the country. your firing line is at the furnace door. david moffat myers, _advisory engineer to united states fuel administration_. ---------------------------------------------------------------------- boiler and furnace testing. by rufus t. strohm. necessity for testing boilers. a boiler test is necessary in order to determine how well the boiler is doing the work expected of it; that is to say, we must find out whether we are wasting coal in making steam and how much this waste may be. such a test may be made to discover the efficiency of the boiler, or the quantity of water it is evaporating, or the cost of evaporating , pounds of water. the united states fuel administration recommends that every boiler plant have some means of daily checking the efficiency of the boiler and furnace. the simplest and best way of finding out how efficiently the boiler is working is to make an evaporation test, as described in this bulletin. all the necessary records can be made automatically with suitable instruments, although in many small plants the coal must be weighed on ordinary scales. the efficiency of the furnace can be found by making analyses of the flue gases. (see bulletin no. of the united states fuel administration.) too many engineers and firemen have the idea that they are not fitted to make boiler tests. this is altogether wrong. any man who can weigh water and coal and read steam gages and thermometers is able to do the work required in making a boiler test for evaporation or efficiency. such a test requires a knowledge of the following: . the total weight of coal used. . [ ]the total weight of water fed to and evaporated by the boiler. . the average temperature of the feed water. . the average steam pressure in the boiler. if these four items are known, a series of simple calculations will show how much water is being evaporated per pound of coal, and the efficiency of the boiler and furnace. to make a test, the following apparatus and instruments are necessary: . scales to weigh the coal. . apparatus to weigh or measure the feed water. . thermometers to take feed-water temperature. . gages to indicate steam pressure. a boiler test to be of value should extend over a period of at least eight hours. the longer the test the more accurate the results. [footnote : for the sake of simplicity, only the essential elements of boiler and furnace testing are treated in this bulletin. for rules covering the refinements for an exhaustive test, the reader is referred to the boiler test code of the american society of mechanical engineers. copies of this code can be obtained from the secretary, west thirty-ninth street, new york city.] weighing the coal. the weight of coal used during a test may easily be found by using an ordinary wheelbarrow and a platform scales, arranged as in figure . at each side of the scales build an incline with its top level with the top of the platform, but take care not to have either one touch the platform. set the empty wheelbarrow on the scales, run the movable weight or poise out until it exactly balances the weight of the barrow and lock it in position with the thumbscrew. next, put weights on the scale pan _a_ to correspond to a net weight of or pounds of coal. fill the barrow with coal, run it on the scales, and add coal or take off coal until the scales balance. this is easily done by having a small pile of coal _b_ beside the scales. if the weights on the scale pan represent, say, pounds, the net weight of coal in the barrow is exactly pounds. this coal is wheeled in front of the boiler and dumped on the clean floor, and the barrow is returned for another load. [illustration: _fig. ._ _set to balance tare of wheelbarrow_ _add to balance net weight of coal_] each time the barrow of coal is weighed on the scales and taken to the boiler being tested, a tally mark should be made on a board nailed to the wall beside the scales. each tally mark represents pounds of coal, since the amount of coal in the barrow is adjusted at each weighing, so that the scales just balance. at the end of the test, therefore, the number of tally marks is multiplied by , and the product is the weight of coal used, provided it has all been fired; but if any coal remains in front of the boiler at the close of the test, it must be gathered up and weighed, and its weight must be subtracted from the total weight indicated by the tally marks to get the number of pounds of coal actually fired. you should, of course, start the test with no coal in front of the boiler. care must be taken not to forget to make a tally mark each time a barrow of coal is run off the scales. by setting the scales so as to show any net weight, such as or pounds, and making each barrow load exactly this weight, much time is saved, as it is unnecessary to change any of the weights or the position of the rider on the scale beam. if the coal used in the test is to be analyzed, take a sample of from to pounds from each barrow and throw it into a box near the scales. do this _before_ the coal is weighed. these small amounts from the various barrow loads will then give a fair average sample of the coal used during the test. the condition of the furnace should be the same at the end of the test period as at the start. therefore, at the moment the test is begun, observe the thickness of the fuel bed and the condition of the fire. if the fire was cleaned, say, an hour before the test began, see that it is cleaned an hour before the time when the test is scheduled to end. if the coal was fired, say, eight minutes before the test started, the last coal used during the test should be fired eight minutes before the end of the test. the object of these precautions is to insure the same conditions at start and finish, as nearly as possible; otherwise, the coal weighed will not be the same as the coal consumed. measuring the feed water. the quantity of water fed to the boiler during the test may be found by metering or by weighing. a reliable water meter is recommended for this work. there are a number of good makes, of different types, such as: . venturi meter. . weir or v-notch meters. . diaphragm meters. . displacement meters. . water weighers. the best form of meter to use in any particular case depends on the local conditions in the plant; but _every plant should be provided with a permanently installed meter of some type_. the displacement form of meter should be used only with cold water, however. if there is no meter or water weigher in the plant, the feed water used during the test can be measured by the three-barrel arrangement illustrated in figure . obtain three water-tight barrels, and set two of them close together on a platform directly over the third, leaving about inches above barrel in which to fit the valves _v_ and the nipples in the bottoms of barrels and . near the top of each of the barrels and screw a -inch overflow pipe _o_. run a pipe _p_ from the city main or other source of supply above barrels and , and put a valve _a_ on the pipe leading to each barrel. from barrel run a suction pipe to the feed pump that is to pump water to the boiler to be tested. it is best to have a by-pass from the usual water supply direct to the feed pump, or to another pump connected to the boiler, so that in case of any trouble with the testing barrels, the regular operation of the boiler may be resumed without shutting down. the next step is to fill barrels and with water until they overflow at _o_. this water should be of practically the same average temperature as that which is to be used during the test. barrel should be high enough above the feed pump so that the pump will handle hot water. put barrel on a scales, before connecting it to the feed pump, and weigh it. then let the water from barrel run into barrel , and weigh again. the second weight minus the first weight is the net weight of water run in from barrel and is the weight of water contained in barrel when filled to the overflow. the weight of water in barrel when it is filled to the overflow can be found in like manner. mark these weights down. [illustration: _fig. ._] when the net weights are found and barrel is removed from the scales and connected to the feed pump, the apparatus is ready to begin the test. start with the level of the water about foot below the top of the barrel , and drive a nail into the barrel to mark this level. when the test is finished, the level should be brought to the same point, so that the water that has passed through barrels and will accurately represent the weight of water fed to the boiler during the test. when the test is to begin, stop the feed pump and tie a string around the gage glass on the boiler to mark the height of the water level in the boiler. then start the pump connected to barrel . fill barrels and up to the overflow before the test is started. then open the valve _v_ on barrel and let the water run into barrel as fast as the feed pump draws water from barrel . when barrel is emptied close its valve _v_ and open its valve _a_ so as to refill it. while barrel is filling empty barrel into barrel in the same way, and continue to fill and empty barrels and alternately. in this way barrel will be kept supplied with water that has been measured in barrels and , the net weights of which were found before the test began. keep a separate tally of the number of times each of the barrels and is emptied into barrel . at the end of the test the number of tallies for each barrel multiplied by the weight of the water that barrel will hold will be the weight of water measured in that barrel. the sum of these weights for barrels and will be the weight of water used in the test. with a three-barrel arrangement like this, water can be weighed rapidly enough to supply boiler horsepower. before starting a test make sure that there is no chance for water to leak into or out of the boiler. see that the blow-off is tight, that there is no drip from gage cocks, and that the feed-line connections are tight, so that all the water fed to the boiler will represent accurately the amount evaporated during the test. if a meter is used instead of the three-barrel method, make absolutely sure that the meter is correct, as the accuracy of the test depends on the accuracy with which the water measurements are made. _after a meter is installed, test it to see that it operates correctly under the plant conditions._ the water level in the boiler should be the same at the end of the test as at the beginning. as the time for stopping the test draws near, therefore, try to bring the conditions the same as at the start. do not, however, run the feed pump rapidly in the last few minutes for the test in order to obtain the same water level. if there is a slight difference in level, calculate the weight of water it represents and make the necessary correction to the total weight of water fed. temperature of feed water. every plant should have a thermometer on the feed line, so as to find the temperature of the feed water. preferably, this thermometer should be of the recording type. if such a form of thermometer is used during the test, it is unnecessary to take the feed temperature at stated intervals, as the record will show the varying temperatures, and so the average feed temperature during the test can easily be found. if there is no thermometer in the feed line, take the feed-water temperature by means of a thermometer hung in barrel (figure ) by a hook over the edge of the barrel. read this thermometer every half hour during the test if the feed-water temperature is fairly uniform; but if it varies considerably, read the thermometer every minutes. the object is to obtain the average feed-water temperature during the test period. therefore, mark down the temperatures as read at the stated intervals. at the close of the test add the readings and divide their sum by the number of readings and you will have the average temperature of the feed water. steam pressure. every boiler is fitted with a steam gage by which the pressure is indicated. it is important that the pressure gage be accurate. what is wanted in a test is the average pressure of the steam in the boiler, therefore, observe the pressure at regular intervals, just as with the feed-water temperature, and mark down these gage readings. the sum of the readings divided by the number of readings taken will be the average steam pressure during the test. a recording steam gage is best and makes its own readings. working up the test. after the boiler test has been made, so as to find the weight of coal burned, weight of feed water used, feed-water temperature and steam pressure, the efficiency, the horsepower, and the economy must be obtained by calculation from the test results. the process of figuring the desired results from the test data is called "working up the test." to illustrate the method used in finding the efficiency, etc., suppose that the data obtained from the test are as follows: length of test hours total weight of coal fired pounds , total weight of water evaporated do. , average temperature of feed water °f average steam pressure, gage pounds per square inch the efficiency of any process is always a comparison, or ratio, of the output to the input. in the case of a steam boiler the efficiency is the percentage of the heat supplied in the coal that is usefully employed in making steam. the output of the steam boiler is the heat represented by the quantity of water evaporated by a pound of coal, taking into account the feed temperature and the steam pressure, and input is the amount of heat contained in a pound of the coal used. the efficiency of the boiler is the output divided by the input. the heat contained in a pound of coal is called the "calorific value" or "heating value" of the coal. it can be found by taking a fair average sample of the coal used during the test, as explained in connection with weighing the coal, and sending the sample to a chemist, who will make a calorimeter test to determine its heating value. at the end of the test the sample fuel should be spread out on a clean floor and all lumps broken up, so that no pieces are larger than inches maximum diameter. then the gross sample should be very thoroughly mixed by shoveling, after which it should be spread out in the form of a square of uniform depth and quartered down until a final average sample is obtained for shipment to a competent chemist, experienced in fuel analysis. (see bureau of mines technical paper no. .) about quarts of the chemist's sample should be put in air-tight tins or jars for the determination of moisture; the balance of the sample (the total weight of which should be from to pounds, depending on the total weight of coal used in the test) may be packed in a wooden box lined with paper to prevent splinters from mingling with the sample. a duplicate coal sample should be kept at the plant to be used in case of loss of the sample sent to the chemist. the bureau of mines has published a bulletin or pamphlet giving the analyses and heating values of the various kinds and grades of coal from all parts of the united states. (bureau of mines bulletin no. .) this bulletin can be used to learn the approximate heating value of the coal. simply find out what district the coal used in the test came from, and its grade, and then refer to the bulletin to obtain the heating value of the coal. if a chemist can be obtained to make a heat test, however, it is better to use the heating value he determines. suppose that during the test the coal used was run-of-mine bituminous having a heating value of , b. t. u. every pound of coal fired, then, carried into the furnace , heat units, and this value therefore is the _input_ to be used in calculating the boiler efficiency. during the test , pounds of coal was fired and , pounds of water was fed and evaporated. this means that , ÷ , = pounds of water was evaporated per pound of coal burned. this is the "actual evaporation," and the heat required to evaporate this pounds of water is the output to be used in calculating the efficiency. every fireman knows that it takes more coal, and therefore more heat, to make steam with cold feed water than with hot feed water; also, that it is somewhat easier to make steam at a low pressure than at a high pressure. so it is plain that the heat required to evaporate pounds of water into steam depends on two things, namely, ( ) the temperature of the feed water and ( ) the pressure of the steam in the boiler. from the data of the test, both the average feed-water temperature and the average steam pressure are known, and so it is a simple matter to find out the amount of heat needed to evaporate pounds of water from the average temperature to steam at the average pressure. a pound of water at ° f. must have . b. t. u. added to it to become a pound of steam at ° f., or zero gage pressure. this value, . b. t. u., is called the latent heat of steam at atmospheric pressure, or the heat "from and at ° f." it is the heat required to change a pound of water _from_ ° f. to steam _at_ ° f., and is used by engineers as a standard by which to compare the evaporation of different boilers. in a boiler test the temperature of the feed water is usually something less than ° f., and the steam pressure is commonly higher than zero, gage. in the test outlined previously, the feed-water temperature was ° f. and the pressure was pounds per square inch, gage. it must be clear, then, that the amount of heat required to change a pound of water at ° to steam at pounds gage pressure is not the same as to make a pound of steam from and at ° f. to make allowance for the differences in temperature and pressure, the actual evaporation must be multiplied by a number called the "factor of evaporation." the factor of evaporation has a certain value corresponding to every feed-water temperature and boiler pressure, and the values of this factor are given in the accompanying table. along the top of the table are given the gage pressures of the steam. in the columns at the sides of the table are given the feed-water temperatures. to find the factor of evaporation for a given set of conditions, locate the gage pressure at the top of the table and follow down that column to the horizontal line on which the feed-water temperature is located. the value in this column and on the horizontal line thus found is the factor of evaporation required. if the feed water has a temperature greater than ° f., obtain the proper factor of evaporation from the marks and davis steam tables. take the data of the test, for example. the average steam pressure is pounds, gage. the average feed-water temperature is ° f. so, in the table locate the column headed and follow down this column to the line having at the ends, and the value where the column and the line cross is . , which is the factor of evaporation for a feed-water temperature of ° f. and a steam pressure of pounds, gage. this factor, . , indicates that to change a pound of water at ° f. to steam at pounds requires . times as much heat as to change a pound of water at ° f. to steam at atmospheric pressure. in other words, the heat used in producing an actual evaporation of pounds under the test conditions would have evaporated × . = . pounds from and at ° f. hence, . pounds is called the "equivalent evaporation from and at ° f." per pound of coal used. as already stated, it takes . b. t. u. to make a pound of steam from and at ° f. then to make . pounds there would be required . × . = , b. t. u. this is the amount of heat required to change . pounds of water at ° f. to steam at zero gage pressure, but it is also the heat required to change pounds of water at ° f. to steam at pounds gage pressure, because . pounds from and at ° f. is equivalent to pounds from ° f. to steam at pounds. therefore, the , b. t. u. is the amount of heat usefully employed in making steam per pound of coal fired, and so it is the _output_. accordingly, the efficiency of the boiler is-- output , ~ efficiency = ------ = ------ = . , nearly. input , in other words, the efficiency of the boiler is . , or per cent, which means that only a little more than half of the heat in the coal is usefully employed in making steam. the chart shown in figure is given to save the work of figuring the efficiency. if the equivalent evaporation per pound of coal is calculated and the heating value of the coal is known, the boiler efficiency may be found directly from the chart. at the left-hand side locate the point corresponding to the equivalent evaporation and at the bottom locate the point corresponding to the heating value of the coal. follow the horizontal and vertical lines from these two points until they cross, and note the diagonal line that is nearest to the crossing point. the figures marked on the diagonal line indicate the boiler efficiency. take the case just worked out, for example. the equivalent evaporation is . pounds and the heating value of the fuel is , b. t. u. at the left of the chart locate the point . midway between and and at the bottom locate the point , midway between , and , . then follow the horizontal and vertical lines from these two points until they cross, as indicated by the dotted lines. the crossing point lies on the diagonal corresponding to , and so the efficiency is per cent. boiler horsepower or capacity. the capacity of a boiler is usually stated in boiler horsepower. a boiler horsepower means the evaporation of . pounds of water per hour from and at ° f. therefore, to find the boiler horsepower developed during a test, calculate the evaporation from and at ° f. per hour and divide it by . . take the test previously mentioned, for example. the evaporation from and at ° f. or the equivalent evaporation, was . pounds of water per pound of coal. the weight of coal burned per hour was , ÷ = pounds. then the equivalent evaporation was . × = , pounds per hour. according to the foregoing definition of a boiler horsepower, then-- , boiler horsepower = ----- = . . the "rated horsepower" of a boiler, or the "builders' rating," is the number of square feet of heating surface in the boiler divided by a number. in the case of stationary boilers this number is or , but is very commonly taken as the amount of heating surface per horsepower. assuming this value and assuming further that the boiler tested had , square feet of heating surface, its rated horsepower would be , ÷ = boiler horsepower. it is often desirable to know what per cent of the rated capacity is developed in a test. this is found by dividing the horsepower developed during the test by the builders' rating. in the case of the boiler tested, horsepower was developed. the percentage of rated capacity developed, therefore, was ÷ = . , or per cent. heating surface. the heating surface of a boiler is the surface of metal exposed to the fire or hot gases on one side and to water on the other side. thus, the internal surface of the tubes of a fire-tube boiler is the heating surface of the tubes, but the outside surface of the tubes of a water-tube boiler is the heating surface of those tubes. in addition to the tubes, all other surfaces which have hot gases on one side and water on the other must be taken into account. for instance, in a fire-tube boiler from one-half to two-thirds of the shell (depending on how the boiler is set) acts as heating surface. in addition to this, the surface presented by both heads, below the water level, has to be computed. the heating surface of each head is equal to two-thirds its area minus the total area of the holes cut away to receive the tubes. cost of evaporation. the cost of evaporation is usually stated as the cost of fuel required to evaporate , pounds of water from and at ° f. to find it, multiply the price of coal per ton by , and divide the result by the product of the equivalent evaporation per pound of coal and the number of pounds in a ton. suppose that the cost of the coal used in the foregoing test was $ . per ton of , pounds. the equivalent evaporation per pound of coal was . pounds. therefore the cost of evaporating , pounds of water from ° f. to steam at -pound gage, is-- $ . × , ------------- = $ . , or cents. . × , table of test results. after the test has been made and properly worked up, as heretofore described, collect all the results of the test on one sheet, so that they can be kept in convenient form for reference and for comparison with later tests. a brief form of arranging the results is as follows: . date of test may , . duration of test hours . weight of coal used pounds , . weight of water fed and evaporated do. , . average steam pressure, gauge do. . average feed-water temperature °f. . factor of evaporation . . equivalent evaporation from and at ° f. pounds , efficiency. . efficiency of boiler and furnace per cent capacity. . boiler horsepower developed . builders' rated horsepower . percentage of rated horsepower developed per cent economic results. . actual evaporation per pound of coal pounds . equivalent evaporation from and at ° f. per pound of coal as fired, pounds . . cost of coal per ton ( , pounds) $ . . cost of coal to evaporate , pounds from and at ° f. $ . how to use the test results. the object of working up a test is to obtain a clear idea as to the efficiency of operation of the boiler or its operating cost. consequently, after the calculations have been made, they should be used as a basis for study with the idea of improving the boiler performance. take the matter of boiler efficiency, for example, as found from the test mentioned. its value was per cent. this is altogether too low and indicates wasteful operation. the efficiency of a hand-fired boiler ought not to be less than per cent, and it can be increased to per cent by careful management under good conditions. the chart in figure can be used to indicate the evaporation that should be obtained in order to reach a desired efficiency. suppose, for example, that it is desired to know how much water per pound of coal must be evaporated to produce a boiler efficiency of per cent with coal having a heating value of , b. t. u. per pound. locate , at the bottom of the chart, follow the vertical line until it meets the diagonal marked per cent, and then from this point follow the horizontal line to the left-hand edge, where the figure is found. this means that the equivalent evaporation from and by ° f. per pound of coal must be pounds of water. if the steam pressure is pounds gauge, and the feed-water temperature is ° f. the factor of evaporation is . , then the actual evaporation must be ÷ . = . pounds per pound of coal. in other words, to increase the efficiency from per cent to per cent under the same conditions of pressure and feed-water temperature, it would be necessary to increase the actual evaporation from pounds to . pounds. this would mean practically per cent more steam from the same weight of coal used. [illustration: _heating value of coal, in b. t. u. per pound_ fig. .] how to do this will require some study and experimenting on the part of the fireman or engineer. the three most common reasons for low-boiler efficiency are ( ) excess air, ( ) dirty heating surfaces, and ( ) loss of coal through the grates. _the first of these items is the most important of the three._ in most cases the greatest preventable waste of coal in a boiler plant is directly due to excess air. excess air simply means the amount of air which gets into the furnace and boiler which is not needed for completing the combustion of the coal. very often twice as much air is admitted to the boiler setting as is required. this extra or excess air is heated and carries heat out through the chimney instead of heating the water in the boiler to make steam. there are two ways in which this excess air gets into the furnace and boiler setting. first, by a combination of bad regulation of drafts and firing. the chances are your uptake damper is too wide open. try closing it a little. then, there may be holes in the fire. keep these covered. the second way excess air occurs is by leakage through the boiler setting, through cracks in the brickwork, leaks around the frames and edges of cleaning doors, and holes around the blow-off pipes. there are also other places where such air can leak in. take a torch or candle and go over the entire surface of your boiler setting--front, back, sides, and top. where the flame of the torch is drawn inward there is an air leak. plaster up all air leaks and repair the brickwork around door frames where necessary. you should go over your boiler for air leaks once a month. in regard to best methods of firing soft coal, see technical paper no. of the bureau of mines, which may be obtained from your state fuel administrator. dirty heating surfaces cause low efficiency because they prevent the heat in the hot gases from getting through into the water. therefore, keep the shell and tubes free of soot on one side and scale on the other. soot may be removed by the daily use of blowers, scrapers, and cleaners. the problem of scale and pure feed water is a big one and should be taken up with proper authorities on the subject. there are many things that may be done to increase the efficiency of the boiler and to save coal. for convenience a number of these points are grouped in the following list: what to do. | why. | . close up all leaks in the boiler | to prevent waste of heat due to setting. | excess air admitted. | . keep shell and tubes free from | to allow the heat to pass easily soot and scale. | into the water. | . use grates suited to the fuel | to prevent loss of unburnt coal to be burned. | through air spaces. | . fire often, and little at a | to obtain uniform conditions and time. | better combustion. | . cover all thin spots and keep | to prevent burning holes in bed fire bed level. | and admitting excess air. | . do not allow clinkers to form | because they reduce the effective on side or bridge walls. | area of the grate. | . keep the ash pit free from ashes | to prevent warping and burning out and hot clinkers. | of the grates. | . do not stir the fire except when | because stirring causes clinker necessary. | and is likely to waste coal. | . use damper and not ash-pit doors | because less excess air is to control draft. | admitted by so doing. | . see that steam pipes and valves | because steam leaks waste heat are tight. | and therefore coal. | . keep blow-off valves tight. | because leaks of hot water waste | coal. | . cover steam pipes and the tops | to prevent radiation and loss of of boilers. | heat. make a boiler test under the conditions of operation as they now exist in your plant. then make all possible improvements as suggested in this bulletin, make another test afterwards and note the increase in the equivalent evaporation per pound of coal used. remember that the _firing line_ in the boiler room can be just as patriotic and helpful as the _firing line_ at the front. _table of factors of evaporation._ ============================================================================ feed | steam pressure in pounds per square inch, gauge. temperature,|--------------------------------------------------------------- °f. | | | | | | | | ------------+-------+-------+-------+-------+-------+-------+-------+------- | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . ---------------------------------------------------------------------------- _table of factors of evaporation_--concluded. ============================================================================ feed | steam pressure in pounds per square inch, gauge. temperature,|--------------------------------------------------------------- °f. | | | | | | | | ------------+-------+-------+-------+-------+-------+-------+-------+------- | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . publications on the utilization of coal and lignite. a limited supply of the following publications of the bureau of mines has been printed and is available for free distribution until the edition is exhausted. requests for all publications can not be granted, and to insure equitable distribution applicants are requested to limit their selection to publications that may be of especial interest to them. requests for publications should be addressed to the director, bureau of mines. the bureau of mines issues a list showing all its publications available for free distribution, as well as those obtainable only from the superintendent of documents, government printing office, on payment of the price of printing. interested persons should apply to the director, bureau of mines, for a copy of the latest list. publications available for free distribution. bulletin . fuel briquetting investigations, july, , to july, , by c. a. wright. . pp., pls., figs. bulletin . united states coals available for export trade, by van. h. manning. . pp., pl. bulletin . analyses of mine and car samples of coal collected in the fiscal years to , by a. c. fieldner, h. i. smith, a. h. fay, and samuel sanford. . pp., figs. bulletin . economic methods of utilizing western lignites, by e. j. babcock. . pp., pls., figs. bulletin . analyses of coals purchased by the government during the fiscal years - , by g. s. pope. . pp. bulletin . combustion of coal and design of furnaces, by henry kreisinger, c. e. augustine, and f. k. ovitz. . pp., pl., figs. bulletin . deterioration in the heating value of coal during storage, by h. c. porter and f. k. ovitz. . pp., pls. bulletin . coking of illinois coals, by f. k. ovitz. . pp., pls. fig. technical paper . experiments with furnaces for a hand-fired return tubular boiler, by s. b. flagg, g. c. cook, and f. e. woodman. . pp., pl., figs. technical paper . metallurgical coke, by a. w. belden. . pp., pl., figs. technical paper . notes on the sampling and analysis of coal, by a. c. fieldner. . pp., figs. technical paper . hand-firing soft coal under power-plant boilers, by henry kreisinger. . pp., figs. technical paper . saving fuel in heating a house, by l. p. breckenridge and s. b. flagg. . pp., figs. technical paper . effect of low-temperature oxidation on the hydrogen in coal and the change of weight of coal in drying, by s. h. katz and h. c. porter. . pp., figs. technical paper . notes on the uses of low-grade fuel in europe, by r. h. fernald. . pp., pls., figs. technical paper . directions for sampling coal for shipment or delivery, by g. s. pope. . pp., pl. technical paper . combustion in the fuel bed of hand-fired furnaces, by henry kreisinger, f. k. ovitz, and c. e. augustine. . pp., pls., figs. cents. technical paper . the determination of moisture in coke, by a. c. fieldner and w. a. selvig. . pp. technical paper . the diffusion of oxygen through stored coal, by s. h. katz. . pp., pl., figs. technical paper . effects of moisture on the spontaneous heating of stored coal, by s. h. katz and h. c. porter. . pp., pl., figs. publications that may be obtained only through the superintendent of documents. bulletin . the flow of heat through furnace walls, by w. t. ray and henry kreisinger. . pp., figs. cents. bulletin . the purchase of coal by the government under specifications, with analyses of coal delivered for the fiscal year - , by g. s. pope. . pp. cents. bulletin . résumé of producer-gas investigations, october , , to june , , by r. h. fernald and c. d. smith. . pp., pls., figs. cents. bulletin . briquetting tests of lignite at pittsburgh, pa., - , with a chapter on sulphite-pitch binder, by c. l. wright. . pp., pls., figs. cents. bulletin . the transmission of heat into steam boilers, by henry kreisinger and w. t. ray. . pp., figs. cents. bulletin . the significance of drafts in steam-boiler practice, by w. t. ray and henry kreisinger. pp., figs. cents. bulletin . analyses of coals in the united states, with descriptions of mine and field samples collected between july , , and june , , by n. w. lord, with chapters by j. a. holmes, f. m. stanton, a. c. fieldner, and samuel sanford. . part i, analyses, pp. - ; part ii, descriptions of samples, pp. - . cents. bulletin . steaming tests of coals and related investigations, september , , to december , , by l. p. breckenridge, henry kreisinger, and w. t. ray. . pp., pls., figs. cents. bulletin . tests of coal and briquets as fuel for house-heating boilers, by d. t. randall. pp., pls., figs. cents. bulletin . comparative tests of run-of-mine and briquetted coal on locomotives, including torpedo-boat tests, and some foreign specifications for briquetted fuel, by w. f. m. goss. . pp., pls., figs. cents. bulletin . the smokeless combustion of coal in boiler furnaces, with a chapter on central heating plants, by d. t. randall and h. w. weeks. . pp., figs. cents. bulletin . government coal purchases under specifications, with analyses, for the fiscal year - by g. s. pope, with a chapter on the fuel-inspection laboratory of the bureau of mines, by j. d. davis. . pp., pls., figs. cents. bulletin . operating details of gas producers, by r. h. fernald. . pp. cents. bulletin . methods of sampling delivered coal, and specifications for the purchase of coal for the government, by g. s. pope. . pp., pls., figs. cents. technical paper . the slagging type of gas producer, with a brief report of preliminary tests, by c. d. smith. . pp., pl. cents. technical paper . factors governing the combustion of coal in boiler furnaces; a preliminary report, by j. k. clement, j. c. w. frazer, and c. e. augustine. . pp., figs. cents. technical paper . a study of the oxidation of coal, by h. c. porter. . pp., figs. cents. technical paper . heat transmission through boiler tubes, by henry kreisinger and f. k. ovitz. . pp., figs. cents. transcriber's notes: page : added period to the sentence: "if the coal used in the test is to be analyzed, take a sample of from to pounds from each barrow and throw it into a box near the scales.". page : changed typo "calcuate" to "calculate." page : changed typo " . " to " . ", see intersecting columns ° f and psi. page : changed typo "samuel sandford" to "samuel sanford." produced by core historical literature in agriculture (chla), cornell university) peat and its uses, as fertilizer and fuel. by samuel w. johnson, a. m., professor of analytical and agricultural chemistry, yale college. fully illustrated. new-york: orange judd & company. broadway. entered according to act of congress, in the year , by orange judd & co., at the clerk's office of the district court of the united states for the southern district of new-york. lovejoy & son, electrotypers and stereotypers vandewater street n. y. to my father, my earliest and best instructor in rural affairs, this volume is gratefully dedicated. s. w. j. contents. introduction vii part i.--origin, varieties, and chemical characters of peat. page . what is peat? . conditions of its formation . different kinds of peat swamp muck salt mud . chemical characters and composition of peat a. organic or combustible part ulmic and humic acids ulmin and humin--crenic and apocrenic acids ulmates and humates crenates and apocrenates gein and geic acid--elementary composition of peat ultimate composition of the constituents of peat b. mineral part--ashes . chemical changes that occur in the formation of peat part ii.--on the agricultural uses of peat and swamp muck. . characters that adapt peat for agricultural use a. physical or amending characters i. absorbent power for water, as liquid and vapor ii. " " for ammonia iii. influence in disintegrating the soil iv. influence on the temperature of soils b. fertilizing characters i. fertilizing effects of the organic matters, excluding nitrogen . organic matters as direct food to plants . organic matters as indirect food to plants . nitrogen, including ammonia and nitric acid ii. fertilizing effects of the ashes of peat iii. peculiarities in the decay of peat iv. comparison of peat with stable manure . characters of peat that are detrimental, or that need correction i. possible bad effects on heavy soils ii. noxious ingredients a. vitriol peats b. acidity--c. resinous matters . preparation of peat for agricultural use a. excavation b. exposure, or seasoning c. composting compost with stable manure " " night soil " " guano " " fish and other animal matters " " potash-lye & soda-ash; wood-ashes, shell-marl, lime " " salt and lime mixture " " carbonate of lime, mortar, etc . the author's experiments with peat composts . examination of peat with reference to its agricultural value . composition of connecticut peats method of analysis tables of composition - - part iii.--on peat as fuel . kinds of peat that make the best fuel . density of peat . heating power of peat as compared with wood and anthracite . modes of burning peat . burning of broken peat . hygroscopic water of peat-fuel . shrinkage . time of excavation and drying . drainage . cutting of peat for fuel--a. preparations for cutting b. cutting by hand; with common spade; german peat knife " with irish slane--system employed in east friesland c. machines for cutting peat; brosowsky's machine; lepreux's machine . dredging of peat . moulding of peat . preparation of peat-fuel by machinery, etc a. condensation by pressure a. of fresh peat mannhardt's method the neustadt method b. of air-dried peat--lithuanian process c. of hot-dried peat--gwynne's method; exter's method elsberg's process b. condensation without pressure a. of earthy peat challeton's method, at mennecy, france " " langenberg, prussia roberts' " pekin, n. y. siemens' " boeblingen, wirtemberg b. condensation of fibrous peat--weber's method; hot-drying gysser's method and machine c. condensation of peat of all kinds--schlickeysen's machine leavitt's peat mill, lexington, mass ashcroft & betteley's machine versmann's machine, great britain buckland's " " . artificial drying of peat . peat coal . metallurgical uses of peat . peat as a source of illuminating gas . examination of peat with regard to its value as fuel introduction. in the years and , the writer, in the capacity of chemist to the state agricultural society of connecticut, was commissioned to make investigations into the agricultural uses of the deposits of peat or swamp muck which are abundant in this state; and, in , he submitted a report to henry a. dyer, esq., corresponding secretary of the society, embodying his conclusions. in the present work the valuable portions of that report have been recast, and, with addition of much new matter, form parts i. and ii. the remainder of the book, relating to the preparation and employment of peat for fuel, &c., is now for the first time published, and is intended to give a faithful account of the results of the experience that has been acquired in europe, during the last twenty-five years, in regard to the important subject of which it treats. the employment of peat as an amendment and absorbent for agricultural purposes has proved to be of great advantage in new-england farming. it is not to be doubted, that, as fuel, it will be even more valuable than as a fertilizer. our peat-beds, while they do not occupy so much territory as to be an impediment and a reproach to our country, as they have been to ireland, are yet so abundant and so widely distributed--occurring from the atlantic to the missouri, along and above the th parallel, and appearing on our eastern coast at least as far south as north carolina[ ]--as to present, at numberless points, material, which, sooner or later, will serve us most usefully when other fuel has become scarce and costly. the high prices which coal and wood have commanded for several years back have directed attention to peat fuel; and, such is the adventurous character of american enterprise, it cannot be doubted that we shall rapidly develop and improve the machinery for producing it. as has always been the case, we shall waste a vast deal of time and money in contriving machines that violate every principle of mechanism and of economy; but the results of european invention furnish a safe basis from which to set out, and we have among us the genius and the patience that shall work out the perfect method. it may well be urged that a good degree of caution is advisable in entering upon the peat enterprise. in this country we have exhaustless mines of the best coal, which can be afforded at a very low rate, with which other fuel must compete. in germany, where the best methods of working peat have originated, fuel is more costly than here; and a universal and intense economy there prevails, of which we, as a people, have no conception. if, as the germans themselves admit, the peat question there is still a nice one as regards the test of dollars and cents, it is obvious, that, for a time, we must "hasten slowly." it is circumstances that make peat, and gold as well, remunerative or otherwise; and these must be well considered in each individual case. peat is the name for a material that varies extremely in its quality, and this quality should be investigated carefully before going to work upon general deductions. in my account of the various processes for working peat by machinery, such data as i have been able to find have been given as to cost of production. these data are however very imperfect, and not altogether trustworthy, in direct application to american conditions. the cheapness of labor in europe is an item to our disadvantage in interpreting foreign estimates. i incline to the belief that this is more than offset among us by the quality of our labor, by the energy of our administration, by the efficiency of our overseeing, and, especially, by our greater skill in the adaptation of mechanical appliances. while counselling caution, i also recommend enterprise in developing our resources in this important particular; knowing full well, however, that what i can say in its favor will scarcely add to the impulse already apparent among my countrymen. samuel w. johnson. _sheffield scientific school_,} _yale college, june, ._ } footnotes: [ ] the great dismal swamp is a grand peat bog, and doubtless other of the swamps of the coast, as far south as florida and the gulf, are of the same character. part i. the origin, varieties, and chemical characters of peat. . _what is peat?_ by the general term peat, we understand the organic matter or vegetable soil of bogs, swamps, beaver-meadows and salt-marshes. it consists of substances that have resulted from the decay of many generations of aquatic or marsh plants, as mosses, sedges, coarse grasses, and a great variety of shrubs, mixed with more or less mineral substances, derived from these plants, or in many cases blown or washed in from the surrounding lands. . _the conditions under which peat is formed._ in this country the production of peat from fallen and decaying plants, depends upon the presence of so much water as to cover or saturate the vegetable matters, and thereby hinder the full access of air. saturation with water also has the effect to maintain the decaying matters at a low temperature, and by these two causes in combination, the process of decay is made to proceed with great slowness, and the solid products of such slow decay, are compounds that themselves resist decay, and hence they accumulate. in the united states there appears to be nothing like the extensive _moors_ or _heaths_, that abound in ireland, scotland, the north of england, north germany, holland, and the elevated plains of bavaria, which are mostly level or gently sloping tracts of country, covered with peat or turf to a depth often of , and sometimes of , or more, feet. in this country it is only in low places, where streams become obstructed and form swamps, or in bays and inlets on salt water, where the flow of the tide furnishes the requisite moisture, that our peat-beds occur. if we go north-east as far as anticosti, labrador, or newfoundland, we find true moors. in these regions have been found a few localities of the _heather_ (_calluna vulgaris_), which is so conspicuous a plant on the moors of europe, but which is wanting in the peat-beds of the united states. in the countries above named, the weather is more uniform than here, the air is more moist, and the excessive heat of our summers is scarcely known. such is the greater humidity of the atmosphere that the bog-mosses,--the so-called _sphagnums_,--which have a wonderful avidity for moisture, (hence used for packing plants which require to be kept moist on journeys), are able to keep fresh and in growth during the entire summer. these mosses decay below, and throw out new vegetation above, and thus produce a bog, especially wherever the earth is springy. it is in this way that in those countries, moors and peat-bogs actually grow, increasing in depth and area, from year to year, and raise themselves above the level of the surrounding country. prof. marsh informs the writer that he has seen in ireland, near the north-west coast, a granite hill, capped with a peat-bed, several feet in thickness. in the bavarian highlands similar cases have been observed, in localities where the atmosphere and the ground are kept moist enough for the growth of moss by the extraordinary prevalence of fogs. many of the european moors rise more or less above the level of their borders towards the centre, often to a height of or and sometimes of feet. they are hence known in germany as _high_ moors (_hochmoore_) to distinguish from the level or dishing _meadow-moors_, (_wiesenmoore_). the peat-producing vegetation of the former is chiefly moss and heather, of the latter coarse grasses and sedges. in great britain the reclamation of a moor is usually an expensive operation, for which not only much draining, but actual cutting out and burning of the compact peat is necessary. the warmth of our summers and the dryness of our atmosphere prevent the accumulation of peat above the highest level of the standing water of our marshes, and so soon as the marshes are well drained, the peat ceases to form, and in most cases the swamp may be easily converted into good meadow land. springy hill-sides, which in cooler, moister climates would become moors, here dry up in summer to such an extent that no peat can be formed upon them. as already observed, our peat is found in low places. in many instances its accumulation began by the obstruction of a stream. to that remarkable creature, the beaver, we owe many of our peat-bogs. these animals, from time immemorial, have built their dams across rivers so as to flood the adjacent forest. in the rich leaf-mold at the water's verge, and in the cool shade of the standing trees, has begun the growth of the sphagnums, sedges, and various purely aquatic plants. these in their annual decay have shortly filled the shallow borders of the stagnating water, and by slow encroachments, going on through many years, they have occupied the deeper portions, aided by the trees, which, perishing, give their fallen branches and trunks, towards completing the work. the trees decay and fall, and become entirely converted into peat; or, as not unfrequently happens, especially in case of resinous woods, preserve their form, and to some extent their soundness. in a similar manner, ponds and lakes are encroached upon; or, if shallow, entirely filled up by peat deposits. in the great forest of northern new york, the voyager has abundant opportunity to observe the formation of peat-swamps, both as a result of beaver dams, and of the filling of shallow ponds, or the narrowing of level river courses. the formation of peat in water of some depth greatly depends upon the growth of aquatic plants, other than those already mentioned. in our eastern states the most conspicuous are the arrow-head, (_sagittaria_); the pickerel weed, (_pontederia_;) duck meat, (_lemna_;) pond weed, (_potamogeton_;) various _polygonums_, brothers of buckwheat and smart-weed; and especially the pond lilies, _(nymphoea_ and _nuphar_.) the latter grow in water four or five feet deep, their leaves and long stems are thick and fleshy, and their roots, which fill the oozy mud, are often several inches in diameter. their decaying leaves and stems, and their huge roots, living or dead, accumulate below and gradually raise the bed of the pond. their living foliage which often covers the water almost completely for acres, becomes a shelter or support for other more delicate aquatic plants and sphagnums, which, creeping out from the shore, may so develop as to form a floating carpet, whereon the leaves of the neighboring wood, and dust scattered by the wind collect, bearing down the mass, which again increases above, or is reproduced until the water is filled to its bottom with vegetable matter. it is not rare to find in our bogs, patches of moss of considerable area concealing deep water with a treacherous appearance of solidity, as the hunter and botanist have often found to their cost. in countries of more humid atmosphere, they are more common and attain greater dimensions. in zealand the surfaces of ponds are so frequently covered with floating beds of moss, often stout enough to bear a man, that they have there received a special name "_hangesak_." in the russian ural, there occur lakes whose floating covers of moss often extend five or six feet above the water, and are so firm that roads are made across them, and forests of large fir-trees find support. these immense accumulations are in fact floating moors, consisting entirely of peat, save the living vegetation at the surface. sometimes these floating peat-beds, bearing trees, are separated by winds from their connection with the shore, and become swimming peat islands. in a small lake near eisenach, in central germany, is a swimming island of this sort. its diameter is rods, and it consists of a felt-like mass of peat, three to five feet in depth, covered above by sphagnums and a great variety of aquatic plants. a few birches and dwarf firs grow in this peat, binding it together by their roots, and when the wind blows, they act as sails, so that the island is constantly moving about upon the lake. on the neusiedler lake, in hungary, is said to float a peat island having an area of six square miles, and on lakes of the high mexican plateau are similar islands which, long ago, were converted in fruitful gardens. . _the different kinds of peat._ very great differences in the characters of the deposits in our peat-beds are observable. these differences are partly of color, some peats being gray, others red, others again black; the majority, when dry, possess a dark brown-red or snuff color. they also vary remarkably in weight and consistency. some are compact, destitute of fibres or other traces of the vegetation from which they have been derived, and on drying, shrink greatly and yield tough dense masses which burn readily, and make an excellent fuel. others again are light and porous, and remain so on drying; these contain intermixed vegetable matter that is but little advanced in the peaty decomposition. some peats are almost entirely free from mineral matters, and on burning, leave but a few _per cent._ of ash, others contain considerable quantities of lime or iron, in chemical combination, or of sand and clay that have been washed in from the hills adjoining the swamps. as has been observed, the peat of some swamps is mostly derived from mosses, that of others originates largely from grasses; some contain much decayed wood and leaves, others again are free from these. in the same swamp we usually observe more or less of all these differences. we find the surface peat is light and full of partly decayed vegetation, while below, the deposits are more compact. we commonly can trace distinct strata or layers of peat, which are often very unlike each other in appearance and quality, and in some cases the light and compact layers alternate so that the former are found below the latter. the light and porous kinds of peat appear in general to be formed in shallow swamps or on the surface of bogs, where there is considerable access of air to the decaying matters, while the compacter, older, riper peats are found at a depth, and seem to have been formed beneath the low water mark, in more complete exclusion of the atmosphere, and under a considerable degree of pressure. the nature of the vegetation that flourishes in a bog, has much effect on the character of the peat. the peats chiefly derived from mosses that have grown in the full sunlight, have a yellowish-red color in their upper layers, which usually becomes darker as we go down, running through all shades of brown until at a considerable depth it is black. peats produced principally from grasses are grayish in appearance at the surface, being full of silvery fibres--the skeletons of the blades of grasses and sedges, while below they are commonly black. _moss peat_ is more often fibrous in structure, and when dried forms somewhat elastic masses. _grass peat_, when taken a little below the surface, is commonly destitute of fibres; when wet, is earthy in its look, and dries to dense hard lumps. where mosses and grasses have grown together simultaneously in the same swamp, the peat is modified in its characters accordingly. where, as may happen, grass succeeds moss, or moss succeeds grass, the different layers reveal their origin by their color and texture. at considerable depths, however, where the peat is very old, these differences nearly or entirely disappear. the geological character of a country is not without influence on the kind of peat. it is only in regions where the rocks are granitic or silicious, where, at least, the surface waters are free or nearly free from lime, that _mosses_ make the bulk of the peat. in limestone districts, peat is chiefly formed from _grasses_ and _sedges_. this is due to the fact that mosses (sphagnums) need little lime for their growth, while the grasses require much; aquatic grasses cannot, therefore, thrive in pure waters, and in waters containing the requisite proportion of lime, grasses and sedges choke out the moss. the accidental admixtures of soil often greatly affect the appearance and value of a peat, but on the whole it would appear that its quality is most influenced by the degree of decomposition it has been subjected to. in meadows and marshes, overflowed by the ocean tides, we have _salt-peat_, formed from sea-weeds (_algæ_,) salt-wort (_salicornia_,) and a great variety of marine or strand-plants. in its upper portions, salt-peat is coarsely fibrous from the grass roots, and dark-brown in color. at sufficient depth it is black and destitute of fibres. the fact that peat is fibrous in texture shows that it is of comparatively recent formation, or that the decomposition has been arrested before reaching its later stages. fibrous peat is found near the surface, and as we dig down into a very deep bed we find almost invariably that the fibrous structure becomes less and less evident until at a certain depth it entirely disappears. it is not depth simply, but age or advancement in decomposition, which determines these differences of texture. the "ripest," most perfectly formed peat, that in which the peaty decomposition has reached its last stage,--which, in germany, is termed _pitchy-peat_ or _fat peat_, (_pechtorf_, _specktorf_)--is dark-brown or black in color, and comparatively heavy and dense. when moist, it is firm, sticky and coherent almost like clay, may be cut and moulded to any shape. dried, it becomes hard, and on a cut or burnished surface takes a luster like wax or pitch. in holland, west friesland, holstein, denmark and pomerania, a so-called _mud-peat_ (_schlammtorf_, also _baggertorf_ and _streichtorf_,) is "fished up" from the bottoms of ponds, as a black mud or paste, which, on drying, becomes hard and dense like the pitchy-peat. the two varieties of peat last named are those which are most prized as fuel in europe. _vitriol peat_ is peat of any kind impregnated with sulphate of iron (_copperas_,) and sulphate of alumina, (the astringent ingredient of alum.) _swamp muck._--in new england, the vegetable remains occurring in swamps, etc., are commonly called _muck_. in proper english usage, muck is a general term for manure of any sort, and has no special application to the contents of bogs. with us, however, this meaning appears to be quite obsolete, though in our agricultural literature--formerly, more than now, it must be admitted,--the word as applied to the subject of our treatise, has been qualified as _swamp muck_. in germany, peat of whatever character, is designated by the single word _torf_; in france it is _tourbe_, and of the same origin is the word _turf_, applied to it in great britain. with us turf appears never to have had this signification. peat, no doubt, is a correct name for the substance which results from the decomposition of vegetable matters under or saturated with water, whatever its appearance or properties. there is, however, with us, an inclination to apply this word particularly to those purer and more compact sorts which are adapted for fuel, while to the lighter, less decomposed or more weathered kinds, and to those which are considerably intermixed with soil or silt, the term muck or swamp muck is given. these distinctions are not, indeed, always observed, and, in fact, so great is the range of variation in the quality of the substance, that it would be impossible to draw a line where muck leaves off and peat begins. notwithstanding, a rough distinction is better than none, and we shall therefore employ the two terms when any greater clearness of meaning can be thereby conveyed. it happens, that in new england, the number of small shallow swales, that contain unripe or impure peat, is much greater than that of large and deep bogs. their contents are therefore more of the "mucky" than of the "peaty" order, and this may partly account for new england usage in regard to these old english words. by the term muck, some farmers understand leaf-mold (decayed leaves), especially that which collects in low and wet places. when the deposit is deep and saturated with water, it may have all the essential characters of peat. ripe peat, from such a source is, however, so far as the writer is informed, unknown to any extent in this country. we might distinguish as _leaf-muck_ the leaves which have decomposed under or saturated with water, retaining the well established term leaf-mold to designate the dry or drier covering of the soil in a dense forest of deciduous trees. _salt-mud._--in the marshes, bays, and estuaries along the sea-shore, accumulate large quantities of fine silt, brought down by rivers or deposited from the sea-water, which are more or less mixed with finely divided peat or partly decomposed vegetable matters, derived largely from sea-weed, and in many cases also with animal remains (mussels and other shell-fish, crabs, and myriads of minute organisms.) this black mud has great value as a fertilizer. . _the chemical characters and composition of peat._ the process of burning, demonstrates that peat consists of two kinds of substance; one of which, the larger portion, is combustible, and is _organic_ or vegetable matter; the other, smaller portion, remaining indestructible by fire is _inorganic matter_ or _ash_. we shall consider these separately. a. _the organic or combustible part of peat_ varies considerably in its proximate composition. it is in fact an indefinite mixture of several or perhaps of many compound bodies, whose precise nature is little known. these bodies have received the collective names _humus_ and _geine_. we shall employ the term _humus_ to designate this mixture, whether occurring in peat, swamp-muck, salt-mud, in composts, or in the arable soil. its chemical characters are much the same, whatever its appearance or mode of occurrence; and this is to be expected since it is always formed from the same materials and under essentially similar conditions. _resinous_ and _bituminous matters_.--if dry pulverized peat be agitated and warmed for a short time with alcohol, there is usually extracted a small amount of _resinous_ and sometimes of _bituminous_ matters, which are of no account in the agricultural applications of peat, but have a bearing on its value as fuel. _ulmic_ and _humic acids_.--on boiling what remains from the treatment with alcohol, with a weak solution of carbonate of soda (sal-soda), we obtain a yellowish-brown or black liquid. this liquid contains certain acid ingredients of the peat which become soluble by entering into chemical combination with soda. on adding to the solution strong vinegar, or any other strong acid, there separates a bulky brown or black substance, which, after a time, subsides to the bottom of the vessel as a precipitate, to use a chemical term, leaving the liquid of a more or less yellow tinge. this deposit, if obtained from light brown peat, is _ulmic acid_; if from black peat, it is _humic acid_. these acids, when in the precipitated state, are insoluble in vinegar; but when this is washed away, they are considerably soluble in water. they are, in fact, modified by the action of the soda, so as to acquire much greater solubility in water than they otherwise possess. on drying the bulky bodies thus obtained, brown or black lustrous masses result, which have much the appearance of coal. _ulmin_ and _humin_.--after extracting the peat with solution of carbonate of soda, it still contains ulmin or humin. these bodies cannot be obtained in the pure state from peat, since they are mixed with more or less partially decomposed vegetable matters from which they cannot be separated without suffering chemical change. they have been procured, however, by the action of muriatic acid on sugar. they are indifferent in their chemical characters, are insoluble in water and in solution of carbonate of soda; but upon heating with solution of hydrate of soda they give dark-colored liquids, being in fact converted by this treatment into ulmic and humic acids, respectively, with which they are identical in composition. the terms ulmic and humic acids do not refer each to a single compound, but rather to a group of bodies of closely similar appearance and properties, which, however, do differ slightly in their characteristics, and differ also in composition by containing more or less of oxygen and hydrogen in equal equivalents. after complete extraction with hydrate of soda, there remains more or less undecomposed vegetable matter, together with sand and soil, were these contained in the peat. _crenic_ and _apocrenic acids_.--from the usually yellowish liquid out of which the ulmic and humic acids have been separated, may further be procured by appropriate chemical means, not needful to be detailed here, two other bodies which bear the names respectively of _crenic acid_ and _apocrenic acid_. these acids were discovered by berzelius, the great swedish chemist, in the water and sediment of the porla spring, in sweden. by the action upon peat of carbonate of ammonia, which is generated to some extent in the decay of vegetable matters and is also absorbed from the air, ulmic and humic acids are made soluble, and combine with the ammonia as well as with lime, oxide of iron, etc. in some cases the ulmates and humates thus produced may be extracted from the peat by water, and consequently occur dissolved in the water of the swamp from which the peat is taken, giving it a yellow or brown color. _ulmates_ and _humates_.--of considerable interest to us here, are the properties of the compounds of these acids, that may be formed in peat when it is used as an ingredient of composts. the ulmates and humates of the alkalies, viz.: _potash_, _soda_, and _ammonia_, dissolve readily in water. they are formed when the alkalies or their carbonates act on ulmin and humin, or upon ulmates or humates of lime, iron, etc. their dilute solutions are yellow, or brown. the ulmates and humates of _lime_, _magnesia_, oxide of _iron_, oxide of _manganese_ and _alumina_, are insoluble, or nearly so in water. in ordinary soils, the earths and oxides just named, predominate over the alkalies, and although they may contain considerable ulmic and humic acids, water is able to extract but very minute quantities of the latter, on account of the insolubility of the compounds they have formed. on the other hand, peat, highly manured garden soil, leaf-mold, rotted manure and composts, yield yellow or brown extracts with water, from the fact that alkalies are here present to form soluble compounds. an important fact established by mulder is, that when solutions of alkali-carbonates are put in contact with the insoluble ulmates and humates, the latter are decomposed; soluble alkali-ulmates and humates being formed, and _in these, a portion of the otherwise insoluble ulmates and humates dissolve_, so that thus, in a compost, lime, magnesia, oxide of iron, and even alumina may exist in soluble combinations, by the agency of these acids. _crenates_ and _apocrenates_.--the ulmic and humic acids when separated from their compounds, are nearly insoluble, and, so far as we know, comparatively inert bodies; by further change, (uniting with oxygen) they pass into or yield the crenic and apocrenic acids which, according to mulder, have an acid taste, being freely soluble in water, and in all respects, decided acids. the compounds of both these acids with the alkalies are soluble. the crenates of lime, magnesia, and protoxide of iron are soluble, crenates of peroxide of iron and of oxide of manganese are but very slightly soluble; crenate of alumina is insoluble. the apocrenates of iron and manganese are slightly soluble; those of lime, magnesia, and alumina are insoluble. all the insoluble crenates and apocrenates, are soluble in solutions of the corresponding salts of the alkalies. application of these facts will be given in subsequent paragraphs. it may be here remarked, that the crenate of protoxide of iron is not unfrequently formed in considerable quantity in peat-bogs, and dissolving in the water of springs gives them a chalybeate character. copious springs of this kind occur at the edge of a peat-bed at woodstock, conn., which are in no small repute for their medicinal qualities, having a tonic effect from the iron they contain. such waters, on exposure to the air, shortly absorb oxygen, and the substance is thereby converted into crenate and afterwards into apocrenate of peroxide of iron, which, being but slightly soluble, or insoluble, separates as a yellow or brown ochreous deposit along the course of the water. by further exposure to air the organic acid is oxidized to carbonic acid, and hydrated oxide of iron remains. bog-iron ore appears often to have originated in this way. _gein and geic acid._--mulder formerly believed another substance to exist in peat which he called _gein_, and from this by the action of alkalies he supposed geic acid to be formed. in his later writings, however, he expresses doubt as to the existence of such a substance, and we may omit further notice of it, especially since, if it really do occur, its properties are not distinct from those of humic acid. we should not neglect to remark, however, that the word gein has been employed by some writers in the sense in which we use humus, viz.: to denote the brown or black products of the decomposition of vegetable matters. it is scarcely to be doubted that other organic compounds exist in peat. as yet, however, we have no knowledge of any other ingredients, while it appears certain that those we have described are its chief constituents, and give it its peculiar properties. with regard to them it must nevertheless be admitted, that our chemical knowledge is not entirely satisfactory, and new investigations are urgently demanded to supply the deficiencies of the researches so ably made by mulder, more than twenty years ago. _elementary composition of peat._ after this brief notice of those organic _compounds_ that have been recognized in or produced from peat, we may give attention to the elementary composition of peat itself. like that of the vegetation from which it originates, the organic part of peat consists of carbon, hydrogen, oxygen and nitrogen. in the subjoined table are given the proportions of these elements as found in the combustible part of sphagnum, of several kinds of wood, and in that of a number of peats in various stages of ripeness. they are arranged in the order of their content of carbon. -----------------------------------+----------+-----+-------+-----+------- | |_car-|_hydro-|_oxy-|_nitro- |_analyst._|bon._| gen._ |gen._| gen._ -----------------------------------+----------+-----+-------+-----+------- --sphagnum } | websky | . | . | . | . --peach wood } undecomposed |chevandier| . | . | . | . --poplar " } | " | . | . | . | . --oak " } | " | . | . | . | . --peat, porous, light-brown, | | | | | sphagnous | websky | . | . | . | . -- " porous, red-brown. | jæckel | . | . | . -- " heavy, brown. | " | . | . | . -- " dark red-brown, | | | | | well decomposed | websky | . | . | . | . -- " black, very dense | | | | | and hard. | " | . | . | . | . -- " black, heavy, }best quality| " | . | . | . | . -- " brown, heavy, }for fuel. | " | . | . | . | . -----------------------------------+----------+-----+-------+-----+------- from this table it is seen that sphagnum, and the wood of our forest trees are very similar in composition, though not identical. further, it is seen from analyses and , that in the first stages of the conversion of sphagnum into peat--which are marked by a change of color, but in which the form of the sphagnum is to a considerable extent preserved--but little alteration occurs in ultimate composition; about one _per cent._ of carbon being gained, and one of hydrogen lost. we notice in running down the columns that as the peat becomes heavier and darker in color, it also becomes richer in carbon and poorer in oxygen. hydrogen varies but slightly. as a general statement we may say that the ripest and heaviest peat contains or _per cent._ more carbon and or _per cent._ less oxygen than the vegetable matter from which it is produced; while between the unaltered vegetation and the last stage of humification, the peat runs through an indefinite number of intermediate stages. nitrogen is variable, but, in general, the older peats contain the most. to this topic we shall shortly recur, and now pass on to notice-- _the ultimate composition of the compounds of which peat consists._ below are tabulated analyses of the organic acids of peat:-- _carbon._ _hydrogen._ _oxygen._ ulmic acid, artificial from sugar . . . humic acid, from frisian peat . . . crenic acid . . . apocrenic acid . . . it is seen that the amount of carbon diminishes from ulmic acid to apocrenic, that of oxygen increases in the same direction and to the same extent, viz.: about _per cent._, while the hydrogen remains nearly the same in all. b. _the mineral part of peat, which remains as ashes_ when the organic matters are burned away, is variable in quantity and composition. usually a portion of sand or soil is found in it, and this not unfrequently constitutes its larger portion. some peats leave on burning much carbonate of lime; others chiefly sulphate of lime; the ash of others again is mostly oxyd of iron; silicic, and phosphoric acids, magnesia, potash, soda, alumina and chlorine, also occur in small quantities in the ash of all peats. with one exception (alumina) all these bodies are important ingredients of agricultural plants. in some rare instances, peats are found, which are so impregnated with soluble sulphates of iron and alumina, as to yield these salts to water in large quantity; and sulphate of iron (green vitriol,) has actually been manufactured from such peats, which in consequence have been characterized as _vitriol peats_. those bases (lime, oxide of iron, etc.,) which are found as carbonates or simple oxides in the ashes, exist in the peat itself in combination with the humic and other organic acids. when these compounds are destroyed by burning, the bases remain united to carbonic acid. .--_chemical changes that occur in the formation of peat._ when a plant perishes, its conversion into humus usually begins at once. when exposed to the atmosphere, the oxygen of the air attacks it, uniting with its carbon producing carbonic acid gas, and with its hydrogen generating water. this action goes on, though slowly, even at some depth under water, because the latter dissolves oxygen from the air in small quantity,[ ] and constantly resupplies itself as rapidly as the gas is consumed. whether exposed to the air or not, the organic matter suffers internal decomposition, and portions of its elements assume the gaseous or liquid form. we have seen that ripe peat is to _per cent._ richer in carbon and equally poorer in oxygen, than the vegetable matters from which it originates. organic matters, in passing into peat, lose carbon and nitrogen; but they lose oxygen more rapidly than the other two elements, and hence the latter become relatively more abundant. the loss of hydrogen is such that its proportion to the other elements is but little altered. the bodies that separate from the decomposing vegetable matter are carbonic acid gas, carburetted hydrogen (marsh gas), nitrogen gas, and water. carbonic acid is the most abundant gaseous product of the peaty decomposition. since it contains nearly _per cent._ of oxygen and but _per cent._ of carbon, it is obvious that by its escape the proportion of carbon in the residual mass is increased. in the formation of water from the decaying matters, part of hydrogen carries off parts of oxygen, and this change increases the proportion of carbon and of hydrogen. marsh gas consists of one part of hydrogen to three of carbon, but it is evolved in comparatively small quantity, and hence has no effect in diminishing the _per cent._ of carbon. the gas that bubbles up through the water of a peat-bog, especially if the decomposing matters at the bottom be stirred, consists largely of marsh gas and nitrogen, often with but a small proportion of carbonic acid. thus websky found in gas from a peat-bed carbonic acid . marsh gas . nitrogen . ------ . carbonic acid, however, dissolves to a considerable extent in water, and is furthermore absorbed by the living vegetation, which is not true of marsh gas and nitrogen; hence the latter escape while the former does not. nitrogen escapes in the uncombined state, as it always (or usually) does in the decay of vegetable and animal matters that contain it. its loss is, in general, slower than that of the other elements, and it sometimes accumulates in the peat in considerable quantity. a small portion of nitrogen unites with hydrogen, forming ammonia, which remains combined with the humic and other acids. part ii. on the agricultural uses of peat and swamp muck. after the foregoing account of the composition of peat, we may proceed to notice: .--_the characters that adapt it for agricultural uses._ these characters are conveniently discussed under two heads, viz.: those which render it useful in improving the texture and physical characters of the soil, and indirectly contribute to the nourishment of crops,--characters which constitute it an _amendment_ to the soil (_a_); and those which make it a direct _fertilizer_ (_b_). a.--considered as an amendment, the value of peat depends upon _its remarkable power of absorbing and retaining water, both as a liquid and as a vapor_ (i): _its power of absorbing ammonia_ (ii): _its effect in promoting the disintegration and solution of mineral ingredients, that is the stony matters of the soil_ (iii): _and_ _its influence on the temperature of the soil_ (iv). the agricultural importance of these properties of peat is best illustrated by considering the faults of a certain class of soils. throughout the state of connecticut, for instance, are found abundant examples of light, leachy, hungry soils, which consist of coarse sand or fine gravel; are surface-dry in a few hours after the heaviest rains, and in the summer drouths, are as dry as an ash-heap to a depth of several or many feet. these soils are easy to work, are ready for the plow early in the spring, and if well manured give fair crops in wet seasons. in a dry summer, however, they yield poorly, or fail of crops entirely; and, at the best, they require constant and very heavy manuring to keep them in heart. crops fail on these soils from two causes, viz.; _want of moisture_ and _want of food_. cultivated plants demand as an indispensable condition of their growth and perfection, to be supplied with water in certain quantities, which differ with different crops. buckwheat will flourish best on dry soils, while cranberries and rice grow in swamps. our ordinary cereal, root, forage and garden crops require a medium degree of moisture, and with us it is in all cases desirable that the soil be equally protected from excess of water and from drouth. soils must be thus situated either naturally, or as the result of improvement, before any steadily good results can be obtained in their cultivation. the remedy for excess of water in too heavy soils, is thorough drainage. it is expensive, but effectual. it makes the earth more porous, opens and maintains channels, through which the surplus water speedily runs off, and permits the roots of crops to go down to a considerable depth. what, let us consider, is the means of obviating the defects of soils that are naturally too porous, from which the water runs off too readily, and whose crops "burn up" in dry seasons? in wet summers, these light soils, as we have remarked, are quite productive if well manured. it is then plain that if we could add anything to them which would retain the moisture of dews and rains in spite of the summer-heats, our crops would be uniformly fair, provided the supply of manure were kept up. but why is it that light soils, need more manure than loamy or heavy lands? we answer--because, in the first place the rains which quickly descend through the open soil, wash down out of the reach of vegetation the soluble fertilizing matters, especially the nitrates, for which the soil has no retentive power; and in the second place, from the porosity of the soil, the air has too great access, so that the vegetable and animal matters of manures decay too rapidly, their volatile portions, ammonia and carbonic acid, escape into the atmosphere, and are in measure lost to the crops. from these combined causes we find that a heavy dressing of well-rotted stable manure, almost if not entirely, disappears from such soils in one season, so that another year the field requires a renewed application; while on loamy soils the same amount of manure would have lasted several years, and produced each year a better effect. we want then to _amend_ light soils by incorporating with them something that prevents the rains from leaching through them too rapidly, and also that renders them less open to the air, or absorbs and retains for the use of crops the volatile products of the decay of manures. for these purposes, vegetable matter of some sort is the best and almost the only amendment that can be economically employed. in many cases a good peat or muck is the best form of this material, that lies at the farmer's command. i.--_its absorbent power for liquid water_ is well known to every farmer who has thrown it up in a pile to season for use. it holds the water like a sponge, and, according to its greater or less porosity, will retain from to or more _per cent._ of its weight of liquid, without dripping. nor can this water escape from it rapidly. it dries almost as slowly as clay, and a heap of it that has been exposed to sun and wind for a whole summer, though it has of course lost much water, is still distinctly wet to the eye and the feel a little below the surface. _its absorbent power for vapor of water_ is so great that more than once it has happened in germany, that barns or close sheds filled with partially dried peat, such as is used for fuel, have been burst by the swelling of the peat in damp weather, occasioned by the absorption of moisture from the air. this power is further shown by the fact that when peat has been kept all summer long in a warm room, thinly spread out to the air, and has become like dry snuff to the feel, it still contains from to _per cent._ (average _per cent._) of water. to dry a peat thoroughly, it requires to be exposed for some time to the temperature of boiling water. it is thus plain, as experience has repeatedly demonstrated, that no ordinary summer heats can dry up a soil which has had a good dressing of this material, for on the one hand, it soaks up and holds the rains that fall upon it, and on the other, it absorbs the vapor of water out of the atmosphere whenever it is moist, as at night and in cloudy weather. when peat has once become _air-dry_, it no longer manifests this avidity for water. in drying it shrinks, loses its porosity and requires long soaking to saturate it again. in the soil, however, it rarely becomes air-dry, unless indeed, this may happen during long drouth with a peaty soil, such as results from the draining of a bog. ii.--_absorbent power for ammonia._ all soils that deserve to be called fertile, have the property of absorbing and retaining ammonia and the volatile matters which escape from fermenting manures, but light and coarse soils may be deficient in this power. here again in respect to its absorptive power for ammonia, peat comes to our aid. it is easy to show by direct experiment that peat absorbs and combines with ammonia. in i took a weighed quantity of air-dry peat from the new haven beaver pond, (a specimen furnished me by chauncey goodyear, esq.,) and poured upon it a known quantity of dilute solution of ammonia, and agitated the two together occasionally during hours. i then distilled off at a boiling heat the unabsorbed ammonia and determined its quantity. this amount subtracted from that of the ammonia originally employed, gave the quantity of ammonia absorbed and retained by the peat at the temperature of boiling water. the peat retained ammonia to the amount of . of _one per cent._ i made another trial at the same time with carbonate of ammonia, adding excess of solution of this salt to a quantity of peat, and exposing it to the heat of boiling water, until no smell of ammonia was perceptible. the entire nitrogen in the peat was then determined, and it was found that the dry peat which originally contained nitrogen equivalent to . _per cent._ of ammonia, now yielded an amount corresponding to . _per cent._ the quantity of ammonia absorbed and retained at a temperature of °, was thus . _per cent._ this last experiment most nearly represents the true power of absorption; because, in fermenting manures, ammonia mostly occurs in the form of carbonate, and this is more largely retained than free ammonia, on account of its power of decomposing the humate of lime, forming with it carbonate of lime and humate of ammonia. the absorbent power of peat is well shown by the analyses of three specimens, sent me in , by edwin hoyt, esq., of new canaan, conn. the first of these was the swamp muck he employed. it contained in the air-dry state nitrogen equivalent to . _per cent._ of ammonia. the second sample was the same muck that had lain under the flooring of the horse stables, and had been, in this way, partially saturated with urine. it contained nitrogen equivalent to . _per cent._ of ammonia. the third sample was, finally, the same muck composted with white-fish. it contained nitrogen corresponding to . _per cent._ of ammonia.[ ] the quantities of ammonia thus absorbed, both in the laboratory and field experiments are small--from . to . _per cent._ the absorption is without doubt chiefly due to the organic matter of the peats, and in all the specimens on which these trials were made, the proportion of inorganic matter is large. the results therefore become a better expression of the power of _peat_, in general, to absorb ammonia, if we reckon them on the organic matter alone. calculated in this way, the organic matter of the beaver pond peat (which constitutes but _per cent._ of the dry peat) absorbs . _per cent._ of free ammonia, and . _per cent._ of ammonia out of the carbonate of ammonia. similar experiments, by anderson, on a scotch peat, showed it to possess, when wet, an absorptive power of _per cent._, and, after drying in the air, it still retained . _per cent._--[trans. highland and ag'l soc'y.] when we consider how small an ingredient of most manures nitrogen is, viz.: from one-half to three-quarters of one _per cent._ in case of stable manure, and how little of it, in the shape of guano for instance, is usually applied to crops--not more than to lbs. to the acre, (the usual dressings with guano are from to lbs. per acre, and nitrogen averages but _per cent._ of the guano), we at once perceive that an absorptive power of one or even one-half _per cent._ is greatly more than adequate for every agricultural purpose. iii.--_peat promotes the disintegration of the soil._ the soil is a storehouse of food for crops; the stores it contains are, however, only partly available for immediate use. in fact, by far the larger share is locked up, as it were, in insoluble combinations, and only by a slow and gradual change can it become accessible to the plant. this change is largely brought about by the united action of _water_ and _carbonic acid gas_. nearly all the rocks and minerals out of which fertile soils are formed,--which therefore contain those inorganic matters that are essential to vegetable growth,--though very slowly acted on by pure water, are decomposed and dissolved to a much greater extent by water, charged with carbonic acid gas. it is by these solvents that the formation of soil from broken rocks is to a great extent due. clay is invariably a result of their direct action upon rocks. the efficiency of the soil depends greatly upon their chemical influence. _the only abundant source of carbonic acid in the soil, is decaying vegetable matter._ hungry, leachy soils, from their deficiency of vegetable matter and of moisture, do not adequately yield their own native resources to the support of crops, because the conditions for converting their fixed into floating capital are wanting. such soils dressed with peat or green manured, at once acquire the power of retaining water, and keep that water ever charged with carbonic acid: thus not only the extraneous manures which the farmer applies are fully economized; but the soil becomes more productive from its own stores of fertility which now begin to be unlocked and available. dr. peters, of saxony, has made some instructive experiments that are here in point. he filled several large glass jars, ( - / feet high and - / inches wide) with a rather poor loamy sand, containing considerable humus, and planted in each one, june , , an equal number of seeds of oats and peas. jar no. had daily passed into it through a tube, adapted to the bottom, about - / pints of common air. no. received daily the same bulk of a mixture of air and carbonic acid gas, of which the latter amounted to one-fourth. no. remained without any treatment of this kind, _i. e._: in just the condition of the soil in an open field, having no air in its pores, save that penetrating it from the atmosphere. on october , the plants were removed from the soil, and after drying at the boiling point of water, were weighed. the crops from the pots into which air and carbonic acid were daily forced, were about _twice as heavy_ as no. , which remained in the ordinary condition. examination of the soil further demonstrated, that in the last two soils, a considerably greater quantity of mineral and organic matters had become soluble in water, than in the soil that was not artificially aërated. the actual results are given in the table below in grammes, and refer to grammes of soil in each case:-- action of carbonic acid on the soil. -----------------------------------+-----------+--------+------------ | _no. , | | | without |_no. , | _no. , _substances soluble in water, etc._| artificial| common | air and | supply of | air | carbonic | air._ | added._|acid added._ -----------------------------------+-----------+--------+------------ mineral matters | . | . | . potash | . | . | . soda | . | . | . organic matters | . | . | . | | | weight of crops | . | . | . -----------------------------------+-----------+--------+------------ it will be seen from the above that air alone exercised nearly as much solvent effect as the mixture of air with one-fourth its weight of carbonic acid; this is doubtless, in part due to the fact that the air, upon entering the soil rich in humus, caused the abundant formation of carbonic acid, as will be presently shown must have been the case. it is, however, probable that organic acids (crenic and apocrenic,) and nitric acid were also produced (by oxidation,) and shared with carbonic the work of solution. it is almost certain, that the acids of peat exert a powerful decomposing, and ultimately solvent effect on the minerals of the soil; but on this point we have no precise information, and must therefore be content merely to present the probability. this is sustained by the fact that the crenic, apocrenic and humic acids, though often partly uncombined, are never wholly so, but usually occur united in part to various bases, viz.: lime, magnesia, ammonia, potash, alumina and oxide of iron. the crenic and apocrenic acids (that are formed by the oxidation of ulmic and humic acids,) have such decided acid characters,--crenic acid especially, which has a strongly sour taste--that we cannot well doubt their dissolving action. iv.--_the influence of peat on the temperature_ of light soils dressed with it may often be of considerable practical importance. a light dry soil is subject to great variations of temperature, and rapidly follows the changes of the atmosphere from cold to hot, and from hot to cold. in the summer noon a sandy soil becomes so warm as to be hardly endurable to the feel, and again it is on such soils that the earliest frosts take effect. if a soil thus subject to extremes of temperature have a dressing of peat, it will on the one hand not become so warm in the hot day, and on the other hand it will not cool so rapidly, nor so much in the night; its temperature will be rendered more uniform, and on the whole, more conducive to the welfare of vegetation. this regulative effect on temperature is partly due to the stores of water held by peat. in a hot day this water is constantly evaporating, and this, as all know, is a cooling process. at night the peat absorbs vapor of water from the air, and condenses it within its pores, this condensation is again accompanied with the evolution of heat. it appears to be a general, though not invariable fact, that dark colored soils, other things being equal, are constantly the warmest, or at any rate maintain the temperature most favorable to vegetation. it has been repeatedly observed that on light-colored soils plants mature more rapidly, if the earth be thinly covered with a coating of some black substance. thus lampadius, professor in the school of mines at freiberg, a town situated in a mountainous part of saxony, found that he could ripen melons, even in the coolest summers, by strewing a coating of coal-dust an inch deep over the surface of the soil. in some of the vineyards of the rhine, the powder of a black slate is employed to hasten the ripening of the grape. girardin, an eminent french agriculturist, in a series of experiments on the cultivation of potatoes, found that the time of their ripening varied eight to fourteen days, according to the character of the soil. he found, on the th of august, in a very dark soil, made so by the presence of much humus or decaying vegetable matter, twenty-six varieties ripe; in sandy soil but twenty, in clay nineteen, and in a white lime soil only sixteen. it cannot be doubted then, that the effect of dressing a light sandy or gravelly soil with peat, or otherwise enriching it in vegetable matter, is to render it warmer, in the sense in which that word is usually applied to soils. the upward range of the thermometer is not, indeed, increased, but the uniform warmth so salutary to our most valued crops is thereby secured. in the light soils stable-manure wastes too rapidly because, for one reason, at the extremes of high temperature, oxidation and decay proceed with great rapidity, and the volatile portions of the fertilizer are used up faster than the plant can appropriate them, so that not only are they wasted during the early periods of growth, but they are wanting at a later period when their absence may prove the failure of a crop. b. the ingredients and qualities which make peat _a direct fertilizer_ next come under discussion. we shall notice: _the organic matters including nitrogen (ammonia and nitric acid)_ (i): _the inorganic or mineral ingredients_ (ii): _peculiarities in the decay of peat_ (iii), _and_ _institute a comparison between peat and stable manure_ (iv). i.--under this division we have to consider: . _the organic matters as direct food to plants._ thirty years ago, when chemistry and vegetable physiology began to be applied to agriculture, the opinion was firmly held among scientific men, that the organic parts of humus--by which we understand decayed vegetable matter, such as is found to a greater or less extent in all good soils, and _abounds_ in many fertile ones, such as constitutes the leaf-mold of forests, such as is produced in the fermenting of stable manure, and that forms the principal part of swamp-muck and peat,--are the true nourishment of vegetation, at any rate of the higher orders of plants, those which supply food to man and to domestic animals. in , liebig, in his celebrated treatise on the "applications of chemistry to agriculture and physiology," gave as his opinion that these organic bodies do not nourish vegetation except by the products of their decay. he asserted that they cannot enter the plant directly, but that the water, carbonic acid and ammonia resulting from their decay, are the substances actually imbibed by plants, and from these alone is built up the organic or combustible part of vegetation. to this day there is a division of opinion among scientific men on this subject, some adopting the views of liebig, others maintaining that certain soluble organic matters, viz., crenic and apocrenic acids are proper food of plants. on the one hand it has been abundantly demonstrated that these organic matters are not at all essential to the growth of agricultural plants, and can constitute but a small part of the actual food of vegetation taken in the aggregate. on the other hand, we are acquainted with no satisfactory evidence that the soluble organic matters of the soil and of peat, especially the crenates and apocrenates, are not actually appropriated by, and, so far as they go, are not directly serviceable as food to plants. be this as it may, practice has abundantly demonstrated the value of humus as an ingredient of the soil, and if not directly, yet indirectly, it furnishes the material out of which plants build up their parts. . _the organic matters of peat as indirect food to plants._ very nearly one-half, by weight, of our common crops, when perfectly dry, consists of _carbon_. the substance which supplies this element to plants is the gas, carbonic acid. plants derive this gas mostly from the atmosphere, absorbing it by means of their leaves. but the free atmosphere, at only a little space above the soil, contains on the average but / of its bulk of this gas, whereas plants flourish in air containing a larger quantity, and, in fact, their other wants being supplied, they grow better as the quantity is increased to / the bulk of the air. these considerations make sufficiently obvious how important it is that the soil have in itself a constant and abundant source of carbonic acid gas. as before said, _organic matter, in a state of decay_, is the single material which the farmer can incorporate with his soil in order to make the latter a supply of this most indispensable form of plant-food. when organic matters decay in the soil, their carbon ultimately assumes the form of carbonic acid. this gas, constantly exhaling from the soil, is taken up by the foliage of the crops, and to some extent is absorbed likewise by their roots. boussingault & lewy have examined the air inclosed in the interstices of various soils, and invariably found it much richer ( to times) than that of the atmosphere above. here follow some of their results: carbonic acid in soils. -------------------------------------------------------------------------- key: a - _volumes of carbonic acid in of air in pores of soil._ b - _cubic feet of air in acre to depth of inches._ c - _cubic feet of carbonic acid in acre to depth of inches._ d - _volumes of carbonic acid to of air above the soil._ e - _cubic feet of air over one acre to height of inches._ f - _cubic feet of carbonic acid over one acre to a height of inches._ --------------------------------------------------------+-----+------+---- _designation and condition of soil._ | a | b | c --------------------------------------------------------+-----+------+---- sandy subsoil of forest | . | , | loamy " " " | . | , | surface soil " " | . | , | clayey soil of artichoke field | . | , | soil of asparagus bed, unmanured for one year | . | , | " " " " newly manured | . | , | sandy soil, six days after manuring, and three | | | days of rain.| . | , | " " ten " " " " " | | | " " " | . | , | compost of vegetable mold | . | , | | | | _carbonic acid in atmosphere_ | d | e | f |-----+------+---- | . | , | --------------------------------------------------------+-----+------+---- from the above it is seen that in soils containing little decomposing organic matters--as the forest sub-soils--the quantity of carbonic acid is no greater than that contained in an equal bulk of the atmosphere. it is greater in loamy and clayey soils; but is still small. in the artichoke field (probably light soil not lately manured), and even in an asparagus bed unmanured for one year, the amount of carbonic acid is not greatly larger. in newly manured fields, and especially in a vegetable compost, the quantity is vastly greater. the organic matters which come from manures, or from the roots and other residues of crops, are the source of the carbonic acid of the soil. these matters continually waste in yielding this gas, and must be supplied anew. boussingault found that the rich soil of his kitchen garden (near strasburg) which had been heavily manured from the barn-yard for many years, lost one-third of its carbon by exposure to the air for three months (july, august and september,) being daily watered. it originally contained . _per cent._ at the conclusion of the experiment it contained but . _per cent._, having lost . _per cent._ peat and swamp-muck, when properly prepared, furnish carbonic acid in large quantities during their slow oxidation in the soil. . _the nitrogen of peat, including ammonia and nitric acid._ the sources of the nitrogen of plants, and the real cause of the value of nitrogenous fertilizers, are topics that have excited more discussion than any other points in agricultural chemistry. this is the result of two circumstances. one is the obscurity in which some parts of the subject have rested; the other is the immense practical and commercial importance of this element, as a characteristic and essential ingredient of the most precious fertilizers. it is a rule that the most valuable manures, _commercially considered_, are those containing the most nitrogen. peruvian guano, sulphate of ammonia, soda-saltpeter, fish and flesh manures, bones and urine, cost the farmer more money per ton than any other manures he buys or makes, superphosphate of lime excepted, and this does not find sale, for general purposes, unless it contains several _per cent._ of nitrogen. these are, in the highest sense, nitrogenous fertilizers, and, if deprived of their nitrogen, they would lose the greater share of their fertilizing power. the importance of the nitrogen of manures depends upon the fact that those forms (compounds) of nitrogen which are capable of supplying it to vegetation are comparatively scarce. it has long been known that peat contains a considerable quantity of nitrogen. the average amount in thirty specimens, analyzed under the author's direction, including peats and swamp mucks of all grades of quality, is equivalent to - / _per cent._ of the air-dried substance, or more than thrice as much as exists in ordinary stable or yard manure. in several peats the amount is as high as . _per cent._, and in one case . _per cent._ were found. of these thirty samples, one-half were largely mixed with soil, and contained from to _per cent._ of mineral matters. reducing them to an average of _per cent._ of water and _per cent._ of ash, they contain . _per cent._ of nitrogen, while the organic part, considered free from water and mineral substances, contains on the average . _per cent._ see table, page . the five peats, analyzed by websky and chevandier, as cited on page , considered free from water and ash, contain an average of . _per cent._ of nitrogen. we should not neglect to notice that peat is often comparatively poor in nitrogen. of the specimens, examined in the yale analytical laboratory, several contained but half a _per cent._ or less. so in the analyses of websky, one sample contained but . _per cent._ of the element in question. as concerns the state of combination in which nitrogen exists in peat, there is a difference of opinion. mulder regards it as chiefly occurring in the form of _ammonia_ (a compound of nitrogen and hydrogen), united to the organic acids from which it is very difficult to separate it. recent investigations indicate that in general, peat contains but a small proportion of ready-formed ammonia. the great part of the nitrogen of peat exists in an insoluble and inert form: but, by the action of the atmosphere upon it, especially when mixed with and divided by the soil, it gradually becomes available to vegetation to as great an extent as the nitrogen of ordinary fertilizers. it appears from late examinations that weathered peat may contain _nitric acid_ (compound of nitrogen with oxygen) in a proportion which, though small, is yet of great importance, agriculturally speaking. what analytical data we possess are subjoined. proportions of nitrogen, etc., in peat. ---------+-------------+------------+------------+---------+------------ | | | total |ammonia, | | | analyst. | nitrogen. |per cent.|nitric acid. ---------+-------------+------------+------------+---------+------------ --brown | | | | | peat|air dry (?) |boussingault| . | . | . --black | | | | | peat| " | " |undetermined| . |undetermined --peat |dried at °|reichardt[ ]| " | . | . --peat | " | " | " | . | . --peat | " | " | " | . | . --peat | " | " | " | . | . ---------+-------------+------------+------------+---------+------------ specimens , and , are swamp (or heath) mucks, and have been weathered for use in flower-culture. and are alike, save that has been weathered a year longer than . they contain respectively , and _per cent._ of organic matter. sample , containing _per cent._ of organic matter, is employed as a manure with great advantage, and probably was weathered before analysis. it contained _per cent._ of organic substance. more important to us than the circumstance that this peat contains but little or no ammonia or nitric acid, and the other contains such or such a fraction of one _per cent._ of these bodies, is the grand fact that all peats may yield a good share of their nitrogen to the support of crops, when properly treated and applied. under the influence of liebig's teachings, which were logically based upon the best data at the disposal of this distinguished philosopher when he wrote years ago, it has been believed that the nitrogen of a fertilizer, in order to be available, must be converted into ammonia and presented in that shape to the plant. it has been recently made clear that nitric acid, rather than ammonia, is the form of nitrogenous food which is most serviceable to vegetation, and the one which is most abundantly supplied by the air and soil. the value of ammonia is however positive, and not to be overlooked. when peat, properly prepared by weathering or composting, is suitably incorporated with a poor or light soil, it slowly suffers decomposition and wastes away. if it be wet, and air have access in limited quantity, especially if _lime_ be mixed with it, a portion of its nitrogen is gradually converted into ammonia. with full access of air _nitric acid_ is produced. in either case, it appears that a considerable share of the nitrogen escapes in the free state as gas, thereby becoming useless to vegetation until it shall have become converted again into ammonia or nitric acid. it happens in a cultivated soil that the oxygen of the air is in excess at the surface, and less abundant as we go down until we get below organic matters: it happens that one day it is saturated with water more or less, and another day it is dry, so that at one time we have the conditions for the formation of ammonia, and at another, those favorable to producing nitric acid. in this way, so far as our present knowledge warrants us to affirm, organic matters, decaying in the soil, continuously yield portions of their nitrogen in the forms of ammonia and nitric acid for the nourishment of plants. the farmer who skillfully employs as a fertilizer a peat containing a good proportion of nitrogen, may thus expect to get from it results similar to what would come from the corresponding quantity of nitrogen in guano or stable manure. but the capacity of peat for feeding crops with, nitrogen appears not to stop here. under certain conditions, _the free nitrogen of the air which cannot be directly appropriated by vegetation, is oxidized in the pores of the soil to nitric acid, and thus, free of expense to the farmer, his crops are daily dressed with the most precious of all fertilizers_. this gathering of useless nitrogen from the air, and making it over into plant-food cannot go on in a soil destitute of organic matter, requires in fact that vegetable remains or humified substances of some sort be present there. the evidence of this statement, whose truth was maintained years ago as a matter of opinion by many of the older chemists, has recently become nearly a matter of demonstration by the investigations of boussingault and knop, while the explanation of it is furnished by the researches of schoenbein and zabelin. to attempt any elucidation of it here would require more space than is at our disposal. it is plain from the contents of this paragraph that peat or swamp muck is, in general, an abundant source of nitrogen, and is often therefore an extremely cheap means of replacing the most rare and costly fertilizers. ii.--with regard to the _inorganic matters of peat_ considered as food to plants, it is obvious, that, leaving out of the account for the present, some exceptional cases, they are useful as far as they go. in the ashes of peats, we almost always find small quantities of sulphate of lime, magnesia and phosphoric acid. potash and soda too, are often present, though rarely to any considerable amount. carbonate and sulphate of lime are large ingredients of the ashes of about one-half, of the thirty-three peats and swamp mucks i have examined. the ashes of the other half are largely mixed with sand and soil, but in most cases also contain considerable sulphate of lime, and often carbonates of lime and magnesia. in one swamp-muck, from milford, conn., there was found but two _per cent._ of ash, at least one-half of which was sand, and the remainder sulphate of lime, (gypsum.) in other samples , , and even _per cent._ remained after burning off the organic matter. in these cases the ash is chiefly sand. the amount of ash found in those peats which were most free from sand, ranges from five to nine _per cent._ probably the average proportion of true ash, viz.: that derived from the organic matters themselves, not including sand and accidental ingredients, is not far from five _per cent._ in twenty-two specimens of european peat, examined by websky, jæckel, walz, wiegmann, einhof and berthier, eleven contained from . to . _per cent._ of ash. the other eleven yielded from . to _per cent._ the average of the former was . , that of the latter . _per cent._ most of these contained a considerable proportion of sand or soil. variation in the composition as well as in the quantity of ash is very great. three analyses of peat-ashes have been executed at the author's instance with the subjoined results: analyses of peat-ashes. ---------------------------+-----------+-----------+---------- | a. | b. | c. potash. | . | . | . soda. | . | | trace. lime. | . | . | . magnesia. | . | . | . oxide of iron and alumina. | . | . | . phosphoric acid. | . | . | . sulphuric acid. | . | . | . chlorine. | . | . | . soluble silica. | . | . } | carbonic acid. | . | . } | . sand. | . | . } | +-----------+-----------+---------- | . | . | . ---------------------------+-----------+-----------+---------- a was furnished by mr. daniel buck, jr., of poquonock, conn., and comes from a peat which he uses as fuel. b was sent by mr. j. h. stanwood, of colebrook, conn. c was sent from guilford, conn., by mr. andrew foote.[ ] a and b, after excluding sand, are seen to consist chiefly of carbonates and sulphates of lime and magnesia. iii. contains a very large proportion of sand and soluble silica, much iron and alumina, less lime and sulphuric acid. potash and phosphoric acid are three times more abundant in c than in the others. instead of citing in full the results of websky, jæckel and others, it will serve our object better to present the maximum, minimum and average proportions of the important ingredients in twenty-six recent analyses, (including these three,) that have come under the author's notice. variations and averages in composition of peat-ashes. _minimum._ _maximum._ _average._ potash . to . . per cent. soda none " . . " lime . " . . " magnesia none " . . " alumina . " . . " oxide of iron none " . . " sulphuric acid none " . . " chlorine " " . . " phosphoric acid " " . . " sand . " . . " it is seen from the above figures that the ash of peat varies in composition to an indefinite degree. lime is the only ingredient that is never quite wanting, and with the exception of sand, it is on the average the largest. of the other agriculturally valuable components, sulphuric acid has the highest average; then follows magnesia; then phosphoric acid, and lastly, potash and soda: all of these, however, may be nearly or quite lacking. websky, who has recently made a study of the composition of a number of german peats, believes himself warranted to conclude that peat is so modified in appearance by its mineral matters, that the quantity or character of the latter may be judged of in many cases by the eye. he remarks, (_journal fuer praktische chemie, bd. , s. _,) "that while for example the peats containing much sand and clay have a red-brown powdery appearance, and never assume a lustrous surface by pressure; those which are very rich in lime, are black, sticky when moist, hard and of a waxy luster on a pressed surface, when dry: a property which they share indeed with very dense peats that contain little ash. peats impregnated with iron are easily recognized. their peculiar odor, and their changed appearance distinguish them from all others." from my own investigations on thirty specimens of connecticut peats, i am forced to disagree with websky entirely, and to assert that except as regards sand, which may often be detected by the eye, there is no connection whatever between the quantity or character of the ash and the color, consistency, density or any other external quality of the peat. the causes of this variation in the ash-content of peat, deserve a moment's notice. the plants that produce peat contain considerable proportions of lime, magnesia, alkalies, sulphuric acid, chlorine and phosphoric acid, as seen from the following analysis by websky. composition of the ash of sphagnum. potash. . soda. . lime. . magnesia. . sulphuric acid. . chlorine. . phosphoric acid. . _per cent._ of ash, . . the mineral matters of the sphagnum do not all become ingredients of the peat; but, as rapidly as the moss decays below, its soluble matters are to a great degree absorbed by the vegetation, which is still living and growing above. again, when a stream flows through a peat-bed, soluble matters are carried away by the water, which is often dark-brown from the substances dissolved in it. finally the soil of the adjacent land is washed or blown upon the swamp, in greater or less quantities. iii.--_the decomposition of peat in the soil offers some peculiarities_ that are worthy of notice in this place. peat is more gradual and regular in decay than the vegetable matters of stable dung, or than that furnished by turning under sod or green crops. it is thus a more steady and lasting benefit, especially in light soils, out of which ordinary vegetable manures disappear too rapidly. the decay of peat appears to proceed through a regular series of steps. in the soil, especially in contact with soluble alkaline bodies, as ammonia and lime, there is a progressive conversion of the _insoluble_ or _less soluble_ into _soluble_ compounds. thus the inert matters that resist the immediate solvent power of alkalies, absorb oxygen from the air, and form the humic or ulmic acids soluble in alkalies; the humic acids undergo conversion into crenic acid, and this body, by oxidation, passes into apocrenic acid. the two latter are soluble in water, and, in the porous soil, they are rapidly brought to the end-results of decay, viz.: water, carbonic acid, ammonia and free nitrogen. great differences must be observed, however, in the rapidity with which these changes take place. doubtless they go on most slowly in case of the fibrous compact peats, and perhaps some of the lighter and more porous samples of swamp muck, would decay nearly as fast as rotted stable dung. it might appear from the above statement, that the effect of exposing peat to the air, as is done when it is incorporated with the soil, would be to increase relatively the amount of soluble organic matters; but the truth is, that they are often actually diminished. in fact, the oxidation and consequent removal of these soluble matters (crenic and apocrenic acids,) is likely to proceed more rapidly than they can be produced from the less soluble humic acid of the peat. iv.--_comparison of peat with stable manure._ the fertilizing value of peat is best understood by comparing it with some standard manure. stable manure is obviously that fertilizer whose effects are most universally observed and appreciated, and by setting analyses of the two side by side, we may see at a glance, what are the excellencies and what the deficiencies of peat. in order rightly to estimate the worth of those ingredients which occur in but small proportion in peat, we must remember that it, like stable manure, may be, and usually should be, applied in large doses, so that in fact the smallest ingredients come upon an acre in considerable quantity. in making our comparison, we will take the analysis of peat from the farm of mr. daniel buck, jr., of poquonock, conn., and the average of several analyses of rotted stable dung of _good quality_. no. _i_, is the analysis of peat; no. _ii_, that of well rotted stable manure:-- _i._ _ii._ water expelled at degrees. . . {soluble in dilute solution } org. { of carbonate of soda. . } matter. {insoluble in solution } . { of carbonate of soda. . } potash. . . soda. . lime. . . magnesia. . . phosphoric acid. . . sulphuric acid. . . nitrogen. . . matters, soluble in water. . . to make the comparison as just as possible, the peat is calculated with the same content of water, that stable dung usually has. we observe then, that the peat contains in a given quantity, _about one-third more organic matter, an equal amount of lime and nitrogen_; but is _deficient in potash, magnesia, phosphoric and sulphuric acids_. the deficiencies of this peat in the matter of composition may be corrected, as regards potash, by adding to lbs. of it lb. of potash of commerce, or lbs. of unleached wood-ashes; as regards phosphoric and sulphuric acids, by adding lb. of good superphosphate, or lb. each of bone dust and plaster of paris. in fact, the additions just named, will convert _any fresh peat_, containing not more than _per cent._ of water and not less than _per cent._ of organic matter, into a mixture having as much fertilizing matters as stable dung, with the possible exception of nitrogen. it is a fact, however, that two manures may reveal to the chemist the same composition, and yet be very unlike in their fertilizing effects, because their conditions are unlike, because they differ in their degrees of solubility or availability. as before insisted upon, it is true in general, that peat is more slow of decomposition than yard-manure, and this fact, which is an advantage in an amendment, is a disadvantage in a fertilizer. though there may be some peats, or rather swamp mucks, which are energetic and rapid in their action, it seems that they need to be applied in larger quantities than stable manure in order to produce corresponding fertilizing effects. in many cases peat requires some preparation by weathering, or by chemical action--"fermentation"--induced by decomposing animal matters or by alkalies. this topic will shortly be discussed. we adopt, as a general fact, the conclusion that peat is inferior in fertilizing power to stable manure. experience asserts, however, with regard to some individual kinds, that they are equal to common yard manure without any preparation whatever. mr. daniel buck, of poquonock, conn., says, of the 'muck,' over-lying the peat, whose composition has just been compared with stable manure, that it "has been applied fresh to meadow with good results; the grass is not as tall but thicker and finer, and of a darker green in the spring, than when barn-yard manure is spread on." a swamp muck, from mr. a. m. haling, rockville, conn., "has been used as a top-dressing, on grass, with excellent results. it is a good substitute for barn-yard manure." a peat, from mr. russell u. peck, of berlin, conn., "has been used fresh, on corn and meadow, with good effect." of the peat, from the 'beaver pond,' near new haven, mr. chauncey goodyear, says, "it has been largely used in a fresh state, and in this condition is as good as cow dung." mr. henry keeler, remarks, concerning a swamp muck occurring at south salem, n. y., that "it has been used in the fresh state, applied to corn and potatoes, and appears to be equal to good barn manure:" further:--"it has rarely been weathered more than two months, and then applied side by side with the best yard manure has given equally good results." a few words as to the apparent contradiction between chemistry, which says that peat is not equal to stable dung as a fertilizer, and practice, which in these cases affirms that it is equal to our standard manure. in the first place, the chemical conclusion is a general one, and does not apply to individual peats, which, in a few instances, may be superior to yard manure. the practical judgment also is, that, in general, yard manure is the best. to go to the individual cases; second: a peat in which nitrogen exists in as large a proportion as is found in stable or yard manure, being used in larger quantity, or being more durable in its action, may for a few seasons produce better results than the latter, merely on account of the presence of this one ingredient, it may in fact, for the soil and crop to which it is applied, be a better fertilizer than yard manure, because nitrogen is most needed in that soil, and yet for the generality of soils, or in the long run, it may prove to be an inferior fertilizer. again; third--the melioration of the physical qualities of a soil, the amendment of its dryness and excessive porosity, by means of peat, may be more effective for agricultural purposes, than the application of tenfold as much fertilizing, _i. e._ plant-feeding materials; in the same way that the mere draining of an over-moist soil often makes it more productive than the heaviest manuring. .--_on the characters of peat that are detrimental, or that may sometimes need correction before it is agriculturally useful._ i.--_bad effects on wet heavy soils._ we have laid much stress on the amending qualities of peat, when applied to dry and leachy soils, which by its use are rendered more retentive of moisture and manure. these properties, which it would seem, are just adapted to renovate very light land, under certain circumstances, may become disadvantageous on heavier soils. on clays no application is needed to retain moisture. they are already too wet as a general thing. peat, when put into the soil, lasts much longer than stubble, or green crops plowed in, or than long manure. if buried too deeply, or put into a heavy soil, especially if in large quantity, it does not decay, but remains wet, and tends to make a bog of the field itself. for soils that are rather heavy, it is therefore best to compost the peat with some rapidly fermenting manure. we thus get a compound which is quicker than muck, and slower than stable manure, etc., and is therefore better adapted to the wants of the soil than either of these would be alone. here it will be seen that much depends on the character of the peat itself. if light and spongy, and easily dried, it may be used alone with advantage on loamy soils, whereas if dense, and coherent, it would most likely be a poor amendment on a soil which has much tendency to become compact, and therefore does not readily free itself from excess of water. but even a clay soil, if _thorough-drained and deeply plowed_, may be wonderfully improved by even a heavy dressing of muck, as then, the water being let off, the muck can exert no detrimental action; but operates as effectually to loosen a too heavy soil, as in case of sand, it makes an over-porous soil compact or retentive. a clay may be made friable, if well drained, by incorporating with it any substance as lime, sand, long manure or muck, which interposing between the clayey particles, prevents their adhering together. ii.--_noxious ingredients._ a. _vitriol peat._ occasionally a peat is met with which is injurious if applied in the fresh state to crops, from its containing some substance which exerts a poisonous action on vegetation. the principal detrimental ingredients that occur in peat, appear to be sulphate of protoxide of iron,--the same body that is popularly known under the names copperas and green-vitriol,--and sulphate of alumina, the astringent component of alum. i have found these substances ready formed in large quantity in but one of the peats that i have examined, viz.: that sent me by mr. perrin scarborough; of brooklyn, conn. this peat dissolved in water to the extent of _per cent._, and the soluble portion, although containing some organic matter and sulphate of lime, consisted in great part of green-vitriol. portions of this muck, when thrown up to the air, become covered with "a white crust, having the taste of alum or saltpeter." the bed containing this peat, though drained, yields but a little poor bog hay, and the peat itself, even after weathering for a year, when applied, mixed with one-fifth of stable manure to corn in the hill, gave no encouraging results, though a fair crop was obtained. it is probable that the sample analyzed was much richer in salts of iron and alumina, than the average of the muck. green-vitriol in minute doses is not hurtful, but rather beneficial to vegetation; but in larger quantity it is fatally destructive. in a salt-marsh mud sent me by the rev. wm. clift, of stonington, conn., there was found sulphate of iron in considerable quantity. this noxious substance likewise occurred in small amount in swamp muck from e. hoyt, esq., new canaan, conn., and in hardly appreciable quantity in several others that i have examined. besides green-vitriol, it is possible that certain organic salts of iron, may be deleterious. the poisonous properties of vitriol-peats may be effectually corrected by composting with lime, or wood-ashes. by the action of these substances, sulphate of lime, (plaster of paris) is formed, while the iron separates as peroxide, which, being insoluble, is without deleterious effect on vegetation. where only soluble organic salts of iron (crenate of iron) are present, simple exposure to the air suffices to render them innocuous. b. _the acidity of peats._--many writers have asserted that peat and muck possess a hurtful "acidity" which must be corrected before they can be usefully employed. it is indeed a fact, that peat consists largely of acids, but, except perhaps in the vitriol-peats, (those containing copperas,) they are so insoluble, or if soluble, are so quickly modified by the absorption of oxygen, that they do not exhibit any "acidity" that can be deleterious to vegetation. it is advised to neutralize this supposed acidity by lime or an alkali before using peat as a fertilizer or amendment, and there is great use in such mixtures of peat with alkaline matters, as we shall presently notice under the head of composts. by the word acidity is conveyed the idea of something hurtful to plants. this something is, doubtless, in many cases, the salts of iron we have just noticed. in others, it is simply the inertness, "coldness" of the peat, which is not positively injurious, but is, for a time at least, of no benefit to the soil. c. _resinous matters_ are mentioned by various writers as injurious ingredients of peat, but i find no evidence that this notion is well-founded. the peat or muck formed from the decay of resinous wood and leaves does not appear to be injurious, and the amount of resin in peat is exceedingly small. .--_the preparation of peat for agricultural use._ a. _excavation._--as to the time and manner of getting out peat, the circumstances of each case must determine. i only venture here to offer a few hints on this subject, which belongs so exclusively to the farm. the month of august is generally the appropriate time for throwing up peat, as then the swamps are usually most free from water, and most accessible to men and teams; but peat is often dug to best advantage in the winter, not only on account of the cheapness of labor, and from there being less hurry with other matters on the farm at that season, but also, because the freezing and thawing of the peat that is thrown out, greatly aid to disintegrate it and prepare it for use. a correspondent of the _homestead_, signing himself "commentator," has given directions for getting out peat that are well worth the attention of farmers. he says:-- "the composting of muck and peat, with our stable and barn-yard manures, is surely destined to become one of the most important items in farm management throughout all the older states at least. one of the difficulties which lie in the way, is the first removal of the muck from its low and generally watery bed; to facilitate this, in many locations, it is less expensive to dry it before carting, by beginning an excavation at the border of the marsh in autumn, sufficiently wide for a cart path, throwing the muck out upon the surface on each side, and on a floor of boards or planks, to prevent it from absorbing moisture from the wet ground beneath; this broad ditch to be carried a sufficient length and depth to obtain the requisite quantity of muck. thus thrown out, the two piles are now in a convenient form to be covered with boards, and, if properly done, the muck kept covered till the succeeding autumn, will be found to be dry and light, and in some cases may be carted away on the surface, or it may be best to let it remain a few months longer until the bottom of the ditch has become sufficiently frozen to bear a team; it can then be more easily loaded upon a sled or sleigh, and drawn to the yards and barn. in other localities, and where large quantities are wanted, and it lies deep, a sort of wooden railroad and inclined plane can be constructed by means of a plank track for the wheels of the cart to run upon, the team walking between these planks, and if the vehicle is inclined to 'run off the track,' it may usually be prevented by scantlings, say four inches thick, nailed upon one of the tracks on each side of the place where the wheel should run. two or more teams and carts may now be employed, returning into the excavation outside of this track. as the work progresses, the track can be extended at both ends, and by continuing or increasing the inclination at the upper end, a large and high pile may be made, and if kept dry, will answer for years for composting, and can be easily drawn to the barn at any time." b. _exposure, weathering, or seasoning of peat._--in some cases, the chief or only use of exposing the thrown-up peat to the action of the air and weather during several months or a whole year, is to rid it of the great amount of water which adheres to it, and thus reduce its bulk and weight previous to cartage. the general effect of exposure as indicated by my analyses, is to reduce the amount of matter soluble in water, and cause peats to approach in this respect a fertile soil, so that instead of containing , , or _per cent._ of substances soluble in water, as at first, they are brought to contain but one-half these amounts, or even less. this change, however, goes on so rapidly after peat is mingled with the soil, that previous exposure on this account is rarely necessary, and most peats might be used perfectly fresh but for the difficulty often experienced, of reducing them to such a state of division as to admit of proper mixture with the soil. the coherent peats which may be cut out in tough blocks, must be weathered, in order that the fibres of moss or grass-roots, which give them their consistency, may be decomposed or broken to an extent admitting of easy pulverization by the instruments of tillage. the subjection of fresh and wet peat to frost, speedily destroys its coherence and reduces it to the proper state of pulverization. for this reason, fibrous peat should be exposed when wet to winter weather. another advantage of exposure is, to bring the peat into a state of more active chemical change. peat, of the deeper denser sorts, is generally too inert ("sour," cold) to be directly useful to the plant. by exposure to the air it appears gradually to acquire the properties of the humus of the soil, or of stable manure, which are vegetable matters, altered by the same exposure. it appears to become more readily oxidable, more active, chemically, and thus more capable of exciting or rather aiding vegetable growth, which, so far as the soil is concerned, is the result of chemical activities. account has been already given of certain peats, which, used fresh, are accounted equal or nearly equal to stable manure. others have come under the writer's notice, which have had little immediate effect when used before seasoning. mr. j. h. stanwood says of a peat, from colebrook, conn., that it "has been used to some extent as a top-dressing for grass and other crops with satisfactory results, _although no particular benefit was noticeable during the first year_. after that, the effects might be seen for a number of years." rev. wm. clift observes, concerning a salt peat, from stonington, conn.:--"it has not been used fresh; is too acid; even potatoes do not yield well _in it the first season_, without manure." the nature of the chemical changes induced by weathering, is to some extent understood so far as the nitrogen, the most important fertilizing element, is concerned. the nitrogen of peat, as we have seen, is mostly inert, a small portion of it only, existing in a soluble or available form. by weathering, portions of this nitrogen become converted into nitric acid. this action goes on at the surface of the heap, where it is most fully exposed to the air. below, where the peat is more moist, ammonia is formed, perhaps simply by the reduction of nitric acid--not unlikely also, by the transformation of inert nitrogen. on referring to the analyses given on page , it is seen, that the first two samples contain but little ammonia and no nitric acid. though it is not stated what was the condition of these peats, it is probable they had not been weathered. the other four samples were weathered, and the weathering had been the more effectual from the large admixture of sand with them. they yielded to the analyst very considerable quantities of ammonia and nitrates. when a peat contains sulphate of protoxide of iron, or soluble organic salts of iron, to an injurious extent, these may be converted into other insoluble and innocuous bodies, by a sufficient exposure to the air. sulphate of protoxide of iron is thus changed into sulphate of peroxide of iron, which is insoluble, and can therefore exert no hurtful effect on vegetation, while the soluble organic bodies of peat are oxydized and either converted into carbonic acid gas, carbonate of ammonia and water, or else made insoluble. it is not probable, however, that merely throwing up a well characterized vitriol-peat into heaps, and exposing it thus imperfectly to the atmosphere, is sufficient to correct its bad qualities. such peats need the addition of some alkaline body, as ammonia, lime, or potash, to render them salutary fertilizers. c. _this brings us to the subject of composting_, which appears to be the best means of taking full advantage of all the good qualities of peat, and of obviating or neutralizing the ill results that might follow the use of some raw peats, either from a peculiarity in their composition, (soluble organic compounds of iron, sulphate of protoxide of iron,) or from too great indestructibility. the chemical changes (oxidation of _iron_ and _organic acids_), which prepare the inert or even hurtful ingredients of peat to minister to the support of vegetation, take place most rapidly in presence of certain other substances. the substances which rapidly induce chemical change in peats, are of two kinds, viz.: .--animal or vegetable matters that are highly susceptible to alteration and decay, and .--alkalies, either _ammonia_ coming from the decomposition of animal matters, or _lime_, _potash_ and _soda_. a great variety of matters may of course be employed for making or mixing with peat composts; but there are comparatively few which allow of extensive and economical use, and our notice will be confined to these. first of all, the composting of peat with _animal manures_ deserves attention. its advantages may be summed up in two statements. .--it is an easy and perfect method of economizing all such manures, even those kinds most liable to loss by fermentation, as night soil and horse dung; and, .--it develops most fully and speedily the inert fertilizing qualities of the peat itself. without attempting any explanation of the changes undergone by a peat and manure compost, further than to say that the fermentation which begins in the manure extends to and involves the peat, reducing the whole nearly, if not exactly, to the condition of well-rotted dung, and that in this process the peat effectually prevents the loss of nitrogen as ammonia,--i may appropriately give the practical experience of farmers who have proved in the most conclusive manner how profitable it is to devote a share of time and labor to the manufacture of this kind of compost. _preparation of composts with stable manure._--the best plan of composting is to have a water tight trench, four inches deep and twenty inches wide, constructed in the stable floor, immediately behind the cattle, and every morning put a bushel-basketful of muck behind each animal. in this way the urine is perfectly absorbed by the muck, while the warmth of the freshly voided excrements so facilitates the fermentative process, that, according to mr. f. holbrook, brattleboro, vt., who has described this method, _much more muck can thus be well prepared for use_ in the spring, than by any of the ordinary modes of composting. when the dung and muck are removed from the stable, they should be well intermixed, and as fast as the compost is prepared, it should be put into a compact heap, and covered with a layer of muck several inches thick. it will then hardly require any shelter if used in the spring. if the peat be sufficiently dry and powdery, or free from tough lumps, it may usefully serve as bedding, or litter for horses and cattle, as it absorbs the urine, and is sufficiently mixed with the dung in the operation of cleaning the stable. it is especially good in the pig-pen, where the animals themselves work over the compost in the most thorough manner, especially if a few kernels of corn be occasionally scattered upon it. mr. edwin hoyt, of new canaan, conn., writes:--"our horse stables are constructed with a movable floor and pit beneath, which holds loads of muck of bushels per load. spring and fall, this pit is filled with fresh muck, which receives all the urine of the horses, and being occasionally worked over and mixed, furnishes us annually with loads of the most valuable manure." "our stables are sprinkled with muck every morning, at the rate of one bushel per stall, and the smell of ammonia, etc., so offensive in most stables, is never perceived in ours. not only are the stables kept sweet, but the ammonia is saved by this procedure." when it is preferred to make the compost out of doors, the plan generally followed is to lay down a bed of weathered peat, say eight to twelve inches thick; cover this with a layer of stable dung, of four to eight inches; put on another stratum of peat, and so, until a heap of three to four feet is built up. the heap may be six to eight feet wide, and indefinitely long. it should be finished with a thick coating of peat, and the manure should be covered as fast as brought out. the proportions of manure and peat should vary somewhat according to their quality and characters. strawy manure, or that from milch-cows, will "ferment" less peat than clear dung, especially when the latter is made by horses or highly fed animals. some kinds of peat heat much easier than others. there are peats which will ferment of themselves in warm moist weather--even in the bog, giving off ammonia in perceptible though small amount. experience is the only certain guide as to the relative quantities to be employed, various proportions from one to five of peat for one of manure, by bulk, being used. when the land is light and needs amending, as regards its retentive power, it is best to make the quantity of peat as large as can be thoroughly fermented by the manure. the making of a high heap, and the keeping it trim and in shape, is a matter requiring more labor than is generally necessary. mr. j. h. stanwood, of colebrook, conn., writes me:-- "my method of composting is as follows: i draw my muck to the barn-yard, placing the loads as near together as i can tip them from the cart. upon this i spread whatever manure i have at hand, and mix with the feet of the cattle, and heap up with a scraper." peat may be advantageously used to save from waste the droppings of the yard. mr. edwin hoyt, of new canaan, conn., says:--"we use muck largely in our barn-yards, and after it becomes thoroughly saturated and intermixed with the droppings of the stock, it is piled up to ferment, and the yard is covered again with fresh muck." mr. n. hart, jr., of west cornwall, conn., writes:--"in the use of muck we proceed as follows: soon after haying we throw up enough for a year's use, or several hundred loads. in the fall, the summer's accumulation in hog-pens and barn cellars is spread upon the mowing grounds, and a liberal supply of muck carted in and spread in the bottoms of the cellars, ready for the season for stabling cattle. when this is well saturated with the drippings of the stables, a new supply is added. the accumulation of the winter is usually applied to the land for the corn crop, except the finer portion, which is used to top-dress meadow land. a new supply is then drawn in for the swine to work up. this is added to from time to time, and as the swine are fed on whey, they will convert a large quantity into valuable manure for top-dressing mowing land." a difference of opinion exists as to the treatment of the compost. some hold it indifferent whether the peat and manure are mixed, or put in layers when the composting begins. others assert, that the fermentation proceeds better when the ingredients are stratified. some direct, that the compost should not be stirred. the general testimony is, that mixture, at the outset, is as effectual as putting up in layers; but, if the manure be strawy, it is, of course, difficult or impracticable to mix at first. opinion also preponderates in favor of stirring, during or after the fermentation. mr. hoyt remarks:--"we are convinced, that the oftener a compost pile of yard manure and muck is worked over after fermenting, the better. we work it over and add to it a little more muck and other material, and the air being thus allowed to penetrate it, a new fermentation or heating takes place, rendering it more decomposable and valuable." rev. wm. clift, writes:--"three or four loads of muck to one of stable manure, put together in the fall or winter in alternate layers, forked over twice before spreading and plowing in, may represent the method of composting." mr. adams white, of brooklyn, conn., proceeds in a different manner. he says:--"in composting, loads are drawn on to upland in september, and thrown up in a long pile. early in the spring loads of stable manure are laid along side, and covered with the muck. as soon as it has heated moderately, the whole is forked over and well mixed." those who have practiced making peat composts with their yard, stable, and pen manure, almost invariably find them highly satisfactory in use, especially upon light soils. a number of years ago, i saw a large pile of compost in the farm-yard of mr. pond, of milford, conn., and witnessed its effect as applied by that gentleman to a field of sixteen acres of fine gravelly or coarse sandy soil. the soil, from having a light color and excessive porosity, had become dark, unctuous, and retentive of moisture, so that during the drouth of , the crops on this field were good and continued to flourish, while on the contiguous land they were dried up and nearly ruined. this compost was made from a light muck, that contained but three _per cent._ of ash (more than half of which was sand), and but . _per cent._ of nitrogen, in the air-dry state--(twenty _per cent._ of water). three loads of this muck were used to one of stable manure. here follow some estimates of the value of this compost by practical men. they are given to show that older statements, to the same effect, cannot be regarded as exaggerated. mr. j. h. stanwood, of colebrook, conn., says:--"experiments made by myself, have confirmed me in the opinion that a compost of equal parts of muck and stable manure is equal to the same quantity of stable manure." mr. daniel buck, jr., of poquonock, conn., remarks:--" loads of muck and of manure in compost, when properly forked over, are equal to loads of barn-yard manure on sandy soil." rev. wm. clift, of stonington, conn., writes:--"i consider a compost made of one load of stable manure and three of muck, equal in value to four loads of yard manure." mr. n. hart, jr., of west cornwall, conn., observes of a peat sent by him for analysis:--"we formerly composted it in the yard with stable manure, but have remodeled our stables, and now use it as an absorbent and to increase the bulk of manure to double its original quantity. we consider the mixture more valuable than the same quantity of stable manure." again, "so successful has been the use of it, that we could hardly carry on our farming operations without it." mr. adams white, of brooklyn, conn., states:--"the compost of equal bulks of muck and stable manure, has been used for corn (with plaster in the hill,) on dry sandy soil to great advantage. i consider the compost worth more per cord than the barn-yard manure." _night soil_ is a substance which possesses, when fresh, the most valuable fertilizing qualities, in a very concentrated form. it is also one which is liable to rapid and almost complete deterioration, as i have demonstrated by analyses. the only methods of getting the full effect of this material are, either to use it fresh, as is done by the chinese and japanese on a most extensive and offensive scale; or to compost it before it can decompose. the former method, will, it is to be hoped, never find acceptance among us. the latter plan has nearly all the advantages of the former, without its unpleasant features. when the night soil falls into a vault, it may be composted, by simply sprinkling fine peat over its surface, once or twice weekly, as the case may require, _i. e._ as often as a bad odor prevails. the quantity thus added, may be from twice to ten times the bulk of the night soil,--the more within these limits, the better. when the vault is full, the mass should be removed, worked well over and after a few days standing, will be ready to use to manure corn, tobacco, etc., in the hill, or for any purpose to which guano or poudrette is applied. if it cannot be shortly used, it should be made into a compact heap, and covered with a thick stratum of peat. when signs of heating appear, it should be watched closely; and if the process attains too much violence, additional peat should be worked into it. drenching with water is one of the readiest means of checking too much heating, but acts only temporarily. dilution with peat to a proper point, which experience alone can teach, is the surest way of preventing loss. it should not be forgotten to put a thick layer of peat at the bottom of the vault to begin with. another excellent plan, when circumstances admit, is, to have the earth-floor where the night soil drops, level with the surface of the ground, or but slightly excavated, and a shed attached to the rear of the privy to shelter a good supply of peat as well as the compost itself. operations are begun by putting down a layer of peat to receive the droppings; enough should be used to absorb all the urine. when this is nearly saturated, more should be sprinkled on, and the process is repeated until the accumulations must be removed to make room for more. then, once a week or so, the whole is hauled out into the shed, well mixed, and formed into a compact heap, or placed as a layer upon a stratum of peat, some inches thick, and covered with the same. the quantity of first-class compost that may be made yearly upon any farm, if due care be taken, would astonish those who have not tried it. james smith, of deanston, scotland, who originated our present system of thorough drainage, asserted, that the excrements of one man for a year, are sufficient to manure half an acre of land. in belgium the manure from such a source has a commercial value of $ . gold. it is certain, that the skillful farmer may make considerably more than that sum from it in new england, _per annum_. mr. hoyt, of new canaan, conn., says:-- "our privies are deodorized by the use of muck, which is sprinkled over the surface of the pit once a week, and from them alone we thus prepare annually, enough "poudrette" to manure our corn in the hill." _peruvian guano_, so serviceable in its first applications to light soils, may be composted with muck to the greatest advantage. guano is an excellent material for bringing muck into good condition, and on the other hand the muck most effectually prevents any waste of the costly guano, and at the same time, by furnishing the soil with its own ingredients, to a greater or less degree prevents the exhaustion that often follows the use of guano alone. the quantity of muck should be pretty large compared to that of the guano,--a bushel of guano will compost six, eight, or ten of muck. both should be quite fine, and should be well mixed, the mixture should be moist and kept covered with a layer of muck of several inches of thickness. this sort of compost would probably be sufficiently fermented in a week or two of warm weather, and should be made and kept under cover. if no more than five or six parts of muck to one of guano are employed, the compost, according to the experience of simon brown, esq., of the boston _cultivator_, (patent office report for ), will prove injurious, if placed in the hill in contact with seed, but may be applied broadcast without danger. the _menhaden_ or "_white fish_", so abundantly caught along our sound coast during the summer months, or any variety of fish may be composted with muck, so as to make a powerful manure, with avoidance of the excessively disagreeable stench which is produced when these fish are put directly on the land. messrs. stephen hoyt & sons, of new canaan, conn., make this compost on a large scale. i cannot do better than to give entire mr. edwin hoyt's account of their operations, communicated to me several years ago. "during the present season, ( ,) we have composted about , white fish with about loads ( , bushels) of muck. we vary the proportions somewhat according to the crop the compost is intended for. for rye we apply to loads per acre of a compost made with , fish, (one load) and with this manuring, no matter how poor the soil, the rye will be as large as a man can cradle. much of ours we have to reap. for oats we use less fish, as this crop is apt to lodge. for corn, one part fish to ten or twelve muck is about right, while for grass or any top-dressing, the proportion of fish may be increased." "we find it is best to mix the fish in the summer and not use the compost until the next spring and summer. yet we are obliged to use in september for our winter rye a great deal of the compost made in july. we usually compost the first arrivals of fish in june for our winter grain; after this pile has stood three or four weeks, it is worked over thoroughly. in this space of time the fish become pretty well decomposed, though they still preserve their form and smell outrageously. as the pile is worked over, a sprinkling of muck or plaster is given to retain any escaping ammonia. at the time of use in september the fish have completely disappeared, bones and fins excepted." "the effect on the muck is to blacken it and make it more loose and crumbly. as to the results of the use of this compost, we find them in the highest degree satisfactory. we have raised to bushels of rye per acre on land that without it could have yielded or bushels at the utmost. this year we have corn that will give to bushels per acre, that otherwise would yield but to bushels. it makes large potatoes, excellent turnips and carrots." fish compost thus prepared, is a uniform mass of fishy but not putrefactive odor, not disagreeable to handle. it retains perfectly all the fertilizing power of the fish. lands, manured with this compost, will keep in heart and improve: while, as is well known to our coast farmers, the use of fish alone is ruinous in the end, on light soils. it is obvious that _any other easily decomposing animal matters, as slaughter-house offal, soap boiler's scraps, glue waste, horn shavings, shoddy, castor pummace, cotton seed-meal, etc., etc._, may be composted in a similar manner, and that several or all these substances may be made together into one compost. in case of the composts with yard manure, guano and other animal matters, the alkali, _ammonia_, formed in the fermentation, greatly promotes chemical change, and it would appear that this substance, on some accounts, excels all others in its efficacy. the other alkaline bodies, _potash_, _soda_ and _lime_, are however scarcely less active in this respect, and being at the same time, of themselves, useful fertilizers, they also may be employed in preparing muck composts. _potash-lye_ and _soda-ash_ have been recommended for composting with muck; but, although they are no doubt highly efficacious, they are too costly for extended use. the other alkaline materials that may be cheaply employed, and are recommended, are _wood-ashes_, leached and unleached, _ashes of peat_, _shell marl_, (consisting of carbonate of lime,) _quick lime_, _gas lime_, and what is called "_salt and lime mixture_." with regard to the proportions to be used, no very definite rules can be laid down; but we may safely follow those who have had experience in the matter. thus, to a cord of muck, which is about bushels, may be added, of unleached wood ashes twelve bushels, or of leached wood ashes twenty bushels, or of peat ashes twenty bushels, or of marl, or of gas lime twenty bushels. ten bushels of quick lime, slaked with water or salt-brine previous to use, is enough for a cord of muck. instead of using the above mentioned substances singly, any or all of them may be employed together. the muck should be as fine and free from lumps as possible, and must be intimately mixed with the other ingredients by shoveling over. the mass is then thrown up into a compact heap, which may be four feet high. when the heap is formed, it is well to pour on as much water as the mass will absorb, (this may be omitted if the muck is already quite moist,) and finally the whole is covered over with a few inches of pure muck, so as to retain moisture and heat. if the heap is put up in the spring, it may stand undisturbed for one or two months, when it is well to shovel it over and mix it thoroughly. it should then be built up again, covered with fresh muck, and allowed to stand as before until thoroughly decomposed. the time required for this purpose varies with the kind of muck, and the quality of the other material used. the weather and thoroughness of intermixture of the ingredients also materially affect the rapidity of decomposition. in all cases five or six months of summer weather is a sufficient time to fit these composts for application to the soil. mr. stanwood of colebrook, conn., says: "i have found a compost made of two bushels of unleached ashes to twenty-five of muck, superior to stable manure as a top-dressing for grass, on a warm, dry soil." n. hart, jr., of west cornwall, conn., states: "i have mixed bushels of ashes with the same number of loads of muck, and applied it to / of an acre. the result was far beyond that obtained by applying lbs. best guano to the same piece." the use of "_salt and lime mixture_" is so strongly recommended, that a few words may be devoted to its consideration. when quick-lime is slaked with a brine of common salt (chloride of sodium), there are formed by double decomposition, small portions of caustic soda and chloride of calcium, which dissolve in the liquid. if the solution stand awhile, carbonic acid is absorbed from the air, forming carbonate of soda: but carbonate of soda and chloride of calcium instantly exchange their ingredients, forming insoluble carbonate of lime and reproducing common salt. when the fresh mixture of quick-lime and salt is incorporated with _any porous body_, as soil or peat, then, as graham has shown, _unequal diffusion_ of the caustic soda and chloride of calcium occurs from the point where they are formed, through the moist porous mass, and the result is, that the small portion of caustic soda which diffuses most rapidly, or the carbonate of soda formed by its speedy union with carbonic acid, is removed from contact with the chloride of calcium. soda and carbonate of soda are more soluble in water and more strongly alkaline than lime. they, therefore, act on peat more energetically than the latter. it is on account of the formation of soda and carbonate of soda from the lime and salt mixture, that this mixture exerts a more powerful decomposing action than lime alone. where salt is cheap and wood ashes scarce, the mixture may be employed accordingly to advantage. of its usefulness we have the testimony of practical men. says mr. f. holbrook of vermont, (patent office report for , page .) "i had a heap of seventy-five half cords of muck mixed with lime in the proportion of a half cord of muck to a bushel of lime. the muck was drawn to the field when wanted in august. a bushel of salt to six bushels of lime was dissolved in water enough to slake the lime down to a fine dry powder, the lime being slaked no faster than wanted, and spread immediately while warm, over the layers of muck, which were about six inches thick; then a coating of lime and so on, until the heap reached the height of five feet, a convenient width, and length enough to embrace the whole quantity of the muck. in about three weeks a powerful decomposition was apparent, and the heap was nicely overhauled, nothing more being done to it till it was loaded the next spring for spreading. the compost was spread on the plowed surface of a dry sandy loam at the rate of about fifteen cords to the acre, and harrowed in. the land was planted with corn and the crop was more than sixty bushels to the acre." other writers assert that they "have decomposed with this mixture, spent tan, saw dust, corn stalks, swamp muck, leaves from the woods, indeed every variety of inert substance, and in _much shorter time than it could be done by any other means_." (working farmer, vol. iii. p. .) some experiments that have a bearing on the efficacy of this compost will be detailed presently. there is no doubt that the soluble and more active (caustic) forms of alkaline bodies exert a powerful decomposing and solvent action on peat. it is asserted too that the _nearly insoluble and less active matters of this kind_, also have an effect, though a less complete and rapid one. thus, _carbonate of lime_ in the various forms of chalk, shell marl,[ ] old mortar, leached ashes and peat ashes, (for in all these it is the chief and most "alkaline" ingredient,) is recommended to compost with peat. let us inquire whether carbonate of lime can really exert any noticeable influence in improving the fertilizing quality of peat. in the case of vitriol peats, carbonate of lime is the cheapest and most appropriate means of destroying the noxious sulphate of protoxide of iron, and correcting their deleterious quality. when carbonate of lime is brought in contact with sulphate of protoxide of iron, the two bodies mutually decompose, with formation of sulphate of lime (gypsum) and carbonate of protoxide of iron. the latter substance absorbs oxygen from the air with the utmost avidity, and passes into the peroxide of iron, which is entirely inert. the admixture of any earthy matter with peat, will facilitate its decomposition, and make it more active chemically, in so far as it promotes the separation of the particles of the peat from each other, and the consequent access of air. this benefit may well amount to something when we add to peat one-fifth of its bulk of marl or leached ashes, but the question comes up: do these insoluble mild alkalies exert any direct action? would not as much soil of any kind be equally efficacious, by promoting to an equal degree the contact of oxygen from the atmosphere? there are two ways in which carbonate of lime may exert a chemical action on the organic matters of peat. carbonate of lime, itself, in the forms we have mentioned, is commonly called insoluble in water. it is, however, soluble to a very slight extent; it dissolves, namely, in about , times its weight of pure water. it is nearly thirty times more soluble in water saturated with carbonic acid; and this solution has distinct alkaline characters. since the water contained in a heap of peat must be considerably impregnated with carbonic acid, it follows that when carbonate of lime is present, the latter must form a solution, very dilute indeed, but still capable of some direct effect on the organic matters of the peat, when it acts through a long space of time. again, it is possible that the solution of carbonate of lime in carbonic acid, may act to liberate some ammonia from the soluble portions of the peat, and this ammonia may react on the remainder of the peat to produce the same effects as it does in the case of a compost made with animal matters. whether the effects thus theoretically possible, amount to anything practically important, is a question of great interest. it often happens that opinions entertained by practical men, not only by farmers, but by mechanics and artisans as well, are founded on so untrustworthy a basis, are supported by trials so destitute of precision, that their accuracy may well be doubted, and from all the accounts i have met with, it does not seem to have been well established, practically, that composts made with carbonate of lime, are better than the peat and carbonate used separately. carbonate of lime (leached ashes, shell marl, etc.), is very well to use _in conjunction with_ peat, to furnish a substance or substances needful to the growth of plants, and supply the deficiencies of peat as regards composition. although in the agricultural papers, numerous accounts of the efficacy of such mixtures are given, we do not learn from them whether these bodies exert any such good effect upon the peat itself, as to warrant the trouble of making a _compost_. .--_experiments by the author on the effect of alkaline bodies in developing the fertilizing power of peat._ during the summer of , the author undertook a series of experiments with a view of ascertaining the effect of various composting materials upon peat. two bushels of peat were obtained from a heap that had been weathering for some time on the "beaver meadow," near new haven. this was thoroughly air-dried, then crushed by the hand, and finally rubbed through a moderately fine sieve. in this way, the peat was brought to a perfectly homogeneous condition. twelve-quart flower-pots, new from the warehouse, were filled as described below; the trials being made in duplicate:-- pots and contained each grammes of peat. pots and contained each grammes of peat, mixed-with grammes of ashes of young grass. pots and contained each grammes of peat, grammes of ashes, and grammes of carbonate of lime. pots and contained each grammes of peat, grammes of ashes, and grammes of slaked (hydrate of) lime. pots and contained each grammes of peat, grammes of ashes, and grammes of lime, slaked with strong solution of common salt. pots and contained each grammes of peat, grammes of ashes, and grammes of peruvian guano. in each case the materials were thoroughly mixed together, and so much water was cautiously added as served to wet them thoroughly. five kernels of dwarf (pop) corn were planted in each pot, the weight of each planting being carefully ascertained. the pots were disposed in a glazed case within a cold grapery,[ ] and were watered when needful with pure water. the seeds sprouted duly, and developed into healthy plants. the plants served thus as tests of the chemical effect of carbonate of lime, of slaked lime, and of salt and lime mixture, on the peat. the guano pots enabled making a comparison with a well-known fertilizer. the plants were allowed to grow until those best developed, enlarged above, not at the expense of the peat, etc., but of their own lower leaves, as shown by the withering of the latter. they were then cut, and, after drying in the air, were weighed with the subjoined results. vegetation experiments in peat composts. key a - _weight of crops in grammes._ b - _comparative weight of crops, the sum of . and . taken as unity._ c - _ratio of weight of crops to weight of seeds, the latter assumed as unity._ -------------------------------------------+---------------+----+------- _nos._ _medium of growth._ | a | b | c -------------------------------------------+---------------+----+------- } | . } | | } peat alone. | . } . | | - / | | | } | . } | | } peat, and ashes of grass, | . } . | | - / | | | } | . } | | } peat, ashes, and carbonate of lime, | . } . | | - / | | | } | . } | | } peat, ashes, and slaked lime, | . } . | | - / | | | } | . } | | } peat, ashes, slaked lime, and salt, | . } . | | - / | | | } | . } | | } peat, ashes, and peruvian guano, | . } . | | - / -------------------------------------------+---------------+----+------- let us now examine the above results. the experiments and , demonstrate that the peat itself is deficient in something needful to the plant. in both pots, but . grammes of crop were produced, a quantity two and a half times greater than that of the seeds, which weighed . grammes. the plants were pale in color, slender, and reached a height of but about six inches. nos. and make evident what are some of the deficiencies of the peat. a supply of mineral matters, such as are contained in all plants, being made by the addition of _ashes_, consisting chiefly of phosphates, carbonates and sulphates of lime, magnesia and potash, a crop is realized nearly eight times greater than in the previous cases; the yield being . grammes, or - / times the weight of the seed. the quantity of ashes added, viz.:-- grammes, was capable of supplying every mineral element, greatly in excess of the wants of any crop that could be grown in a quart of soil. the plants in pots and were much stouter than those in and , and had a healthy color. the experiments and appear to demonstrate that _carbonate of lime_ considerably aided in converting the peat itself into plant-food. the ashes alone contained enough carbonate of lime to supply the wants of the plant in respect to that substance. more carbonate of lime could only operate by acting on the organic matters of the peat. the amount of the crop is raised by the effect of carbonate of lime from . to . grammes, or from - / to - / times that of the seed. experiments and show, that _slaked lime_ has more effect than the carbonate, as we should anticipate. its influence does not, however, exceed that of the carbonate very greatly, the yield rising from . to . grammes, or from - / to - / times the weight of the seed. in fact, quick-lime can only act as such for a very short space of time, since it rapidly combines with the carbonic acid, which is supplied abundantly by the peat. in experiments and , a good share of the influence exerted must therefore be actually ascribed to the carbonate, rather than to the quick-lime itself. in experiments and , we have proof that the "_lime and salt mixture_" has a greater efficacy than lime alone, the crop being increased thereby from . , to . grammes, or from - / to - / times that of the seed. finally, we see from experiments and that in all the foregoing cases it was a limited supply of _nitrogen_ that limited the crop; for, on adding peruvian guano, which could only act by this element (its other ingredients, phosphates of lime and potash, being abundantly supplied in the ashes), the yield was carried up to . grammes, or - / times the weight of the seed, and times the weight of the crop obtained from the unmixed peat. .--_the examination of peat (muck and marsh-mud) with reference to its agricultural value._ since, as we are forced to conclude, the variations in the composition of peat stand in no recognizable relations to differences of appearance, it is only possible to ascertain the value of any given specimen by actual trial or by chemical investigation. the method _by practical trial_ is usually the cheaper and more satisfactory of the two, though a half year or more is needful to gain the desired information. it is sufficient to apply to small measured plots of ground, each say two rods square, known quantities of the fresh, the weathered, and the composted peat in order, by comparison of the growth and _weight_ of the crop, to decide the question of their value. peat and its composts are usually applied at rates ranging from to wagon or cart loads per acre. there being square rods in the acre, the quantity proper to a plot of two rods square (= four square rods,) would be one half to one load. the composts with stable manure and lime, or salt and lime mixture, are those which, in general, it would be best to experiment with. from the effects of the stable manure compost, could be inferred with safety the value of any compost, of which animal manure is an essential ingredient. one great advantage of the practical trial on the small scale is, that the adaptation of the peat or of the compost to the _peculiarities of the soil_, is decided beyond a question. it must be borne in mind, however, that the results of experiments can only be relied upon, when the plots are accurately measured, when the peat, etc., are applied in known quantities, and when the crops are separately harvested and carefully weighed. if experiments are made upon grass or clover, the gravest errors may arise by drawing conclusions from the appearance of the standing crop. experience has shown that two clover crops, gathered from contiguous plots differently manured, may strikingly differ in appearance, but yield the same amounts of hay. the _chemical examination_ of a peat may serve to inform us, without loss of time, upon a number of important points. to test a peat for _soluble iron salts_ which might render it deleterious, we soak and agitate a handful for some hours, with four or five times its bulk of warm soft water. from a _good fresh-water peat_ we obtain, by this treatment, a yellow liquid, more or less deep in tint, the taste of which is very slight and scarcely definable. from a _vitriol peat_ we get a dark-brown or black solution, which has a bitter, astringent, metallic or inky taste, like that of copperas. _salt peat_ will yield a solution having the taste of salt-brine, unless it contains iron, when the taste of the latter will prevail. on evaporating the water-solution to dryness and heating strongly in a china cup, a _vitriol peat_ gives off white choking fumes of sulphuric acid, and there remains, after burning, brown-red oxide of iron in the dish. the above testings are easily conducted by any one, with the ordinary conveniences of the kitchen. those that follow, require, for the most part, the chemical laboratory, and the skill of the practised chemist, for satisfactory execution. besides testing for soluble iron compounds, as already indicated, the points to be regarded in the chemical examination, are:-- st. _water or moisture._--this must be estimated, because it is so variable, and a knowledge of its quantity is needful, if we will compare together different samples. a weighed amount of the peat is dried for this purpose at ° f., as long as it suffers loss. d. the _proportions of organic matter and ash_ are ascertained by carefully burning a weighed sample of the peat. by this trial we distinguish between peat with to _per cent._ of ash and peaty soil, or mud, containing but a few _per cent._ of organic matter. this experiment may be made in a rough way, but with sufficient accuracy for common purposes, by burning a few lbs. or ozs. of peat upon a piece of sheet iron, or in a sauce pan, and noting the loss, which includes both _water_ and _organic matter_. d. as further regards the organic matters, we ascertain _the extent to which the peaty decomposition has taken place_ by boiling with dilute solution of carbonate of soda. this solvent separates the humic and ulmic acids from the undecomposed vegetable fibers. for practical purposes this treatment with carbonate of soda may be dispensed with, since the amount of undecomposed fiber is gathered with sufficient accuracy from careful inspection of the peat. special examination of the organic acids is of no consequence in the present state of our knowledge. th. the _proportion of nitrogen_ is of the first importance to be ascertained. in examinations of samples of peat, i have found the content of nitrogen to range from . to . _per cent._, the richest containing seven times as much as the poorest. it is practically a matter of great moment whether, for example, a peruvian guano contains _per cent._ of nitrogen as it should, or but one-seventh that amount, as it may when grossly adulterated. in the same sense, it is important before making a heavy outlay in excavating and composting peat, to know whether (as regards nitrogen) it belongs to the poorer or richer sorts. this can only be done by the complicated methods known to the chemist. th. the estimation of _ammonia_ (actual or ready-formed,) is a matter of scientific interest, but subordinate in a practical point of view. th. _nitric acid_ and _nitrates_ can scarcely exist in peat except where it is well exposed to the air, in a merely moist but not wet state. their estimation in composts is of great interest, though troublesome to execute. th. as regards the ash, its red color indicates _iron_. pouring hydrochloric acid upon it, causes effervescence in the presence of _carbonate of lime_. this compound, in most cases, has been formed in the burning, from humate and other organic salts of lime. _sand_, or _clay_, being insoluble in the acid, remains, and may be readily estimated. _phosphoric acid_ and alkalies, especially _potash_, are, next to lime, the important ingredients of the ash. _magnesia_ and _sulphuric acid_, rank next in value. their estimation requires a number of tedious operations, and can scarcely be required for practical purposes, until more ready methods of analyses shall have been discovered. th. the quantity of _matters soluble in water_ has considerable interest, but is not ordinarily requisite to be ascertained. .--_composition of connecticut peats_. in the years and , the author was charged by the connecticut state agricultural society[ ] with the chemical investigation of samples of peat and swamp muck, sent to him in compliance with official request. in the foregoing pages, the facts revealed by the laborious analyses executed on these samples, have been for the most part communicated, together with many valuable practical results derived from the experience of the gentlemen who sent in the specimens. the analytical data themselves appear to me to be worthy of printing again, for the information of those who may hereafter make investigations in the same direction.--see tables i, ii, and iii, p.p. , , and . the specimens came in all stages of dryness. some were freshly dug and wet, others had suffered long exposure, so that they were air-dry; some that were sent in the moist state, became dry before being subjected to examination; others were prepared for analysis while still moist. a sufficient quantity of each specimen was carefully pulverized, intermixed, and put into a stoppered bottle and thus preserved for experiment. the analyses were begun in the winter of by my assistant, edward h. twining, esq. the samples to of the subjoined tables were then analyzed. in the following year the work was continued on the remaining specimens -- by dr. robert a. fisher. the method of analysis was the same in both cases, except in two particulars. in the earlier analyses, to inclusive, the treatment with carbonate of soda was not carried far enough to dissolve the whole of the soluble organic acids. it was merely attempted to make _comparative_ determinations by treating all alike for the same time, and with the same quantity of alkali. i have little doubt that in some cases not more than one-half of the portion really soluble in carbonate of soda is given as such. in the later analyses, to , however, the treatment was continued until complete separation of the soluble organic acids was effected. by acting on a peat for a long time with a hot solution of carbonate of soda, there is taken up not merely a quantity of organic matter, but inorganic matters likewise enter solution. silica, oxyd of iron and alumina are thus dissolved. in this process too, sulphate of lime is converted into carbonate of lime. the total amount of these soluble inorganic matters has been determined with approximate accuracy in analyses to . in the analyses to the collective amount of matters soluble in water was determined. in the later analyses the proportions of organic and inorganic matters in the water-solution were separately estimated. the process of analysis as elaborated and employed by dr. fisher and the author, is as follows: i. to prepare a sample for analysis, half a pound, more or less, of the substance is pulverized and passed through a wire sieve of meshes to the inch. it is then thoroughly mixed and bottled. ii. grammes of the above are dried (in tared watch-glasses) at the temperature of degrees, until they no longer decrease in weight. the loss sustained represents the _amount of water_, (according to marsilly, annales des mines, , xii., , peat loses carbon if dried at a temperature higher than degrees.) iii. the capsule containing the residue from i. is slowly heated to incipient redness, and maintained at that temperature until the organic matter is entirely consumed. the loss gives the total amount of _organic_, the residue the total amount of _inorganic_ matter. note.--in peats containing sulphate of the protoxide of iron, the loss that occurs during ignition is partly due to the escape of sulphuric acid, which is set free by the decomposition of the above mentioned salt of iron. but the quantity is usually so small in comparison with the organic matter, that it may be disregarded. the same may be said of the combined water in the clay that is mixed with some mucks, which is only expelled at a high temperature. iv. grammes of the sample are digested for half an hour, with cubic centimeters ( . times their weight,) of boiling water, then removed from the sand bath, and at the end of twenty-four hours, the clear liquid is decanted. this operation is twice repeated upon the residue; the three solutions are mixed, filtered, concentrated, and finally evaporated to dryness (in a tared platinum capsule,) over a water bath. the residue, which must be dried at degrees, until it ceases to lose weight, gives the _total amount soluble in water_. the dried residue is then heated to low redness, and maintained at that temperature until the organic matter is burned off. the loss represents the amount of _organic matter soluble in water_, the ash gives the quantity of _soluble inorganic matter_. v. gramme is digested for two hours, at a temperature just below the boiling point, with cubic centimeters of a solution containing _per cent._ of crystallized carbonate of soda. it is then removed from the sand bath and allowed to settle. when the supernatant liquid has become perfectly transparent, it is carefully decanted. this operation is repeated until all the organic matter soluble in this menstruum is removed; which is accomplished as soon as the carbonate of soda solution comes off colorless. the residue, which is to be washed with boiling water until the washings no longer affect test papers, is thrown upon a tared filter, and dried at degrees. it is the _total amount of organic and inorganic matter insoluble in carbonate of soda_. the loss that it suffers upon ignition, indicates the amount of _organic matter_, the ash gives the _inorganic_ matter. note.--the time required to insure perfect settling after digesting with carbonate of soda solution, varies, with different peats, from hours to several days. with proper care, the results obtained are very satisfactory. two analyses of no. , executed at different times, gave _total insoluble in carbonate of soda_-- st analysis . _per cent._; d analysis . _per cent._ these residues yielded respectively . and . _per cent._ of ash. vi. the quantity of _organic matter insoluble in water but soluble in solution of carbonate of soda_, is ascertained by deducting the joint weight of the amounts soluble in water, and insoluble in carbonate of soda, from the total amount of organic matter present. the _inorganic matter insoluble in water, but soluble in carbonate of soda_, is determined by deducting the joint weight of the amounts of inorganic matter soluble in water, and insoluble in carbonate of soda, from the total inorganic matter. vii. the amount of nitrogen is estimated by the combustion of gramme with soda-lime in an iron tube, collection of the ammonia in a standard solution of sulphuric acid, and determination of the residual free acid by an equivalent solution of caustic potash and a few drops of tincture of cochineal as an indicator. the results of the analyses are given in the following tables. table i. gives the direct results of analysis. in table ii. the analyses are calculated on dry matter, and the nitrogen upon the organic matters. table iii. gives a condensed statement of the external characters and agricultural value[ ] of the samples in their different localities, and the names of the parties supplying them. table i.-composition of connecticut peats and mucks. key: a - _soluble in water._ b - _insol. in water, but soluble in carbonate of soda._ c - _insol. in water and carbonate of soda._ d - _total._ e - _water._ f - _nitrogen._ g - _total matters soluble in water._ -------------------------+-----------------------+ | organic matter. | _from whom and |-----+-----+-----+-----+ whence received_ | a | b | c | d | -------------------------+~~~~~v~~~~~+-----+-----+ . lewis m. norton. | | | | goshen conn. | . | . | . | . " " " | . | . | . | . " " " | . | . | . | . messrs. pond & miles.| | | | " milford conn. | . | . | . | . " " " | . | . | . | . samuel camp. | | | | plainville conn. | . | . | . | . russell u. peck. | | | | berlin conn. | . | . | . | . rev. b. f. northrop. | | | | griswold conn. | . | . | . | . j. h. stanwood. | | | | colebrook conn. | . | . | . | . n. hart, jr. | | | | west cornwall conn.| . | . | . | . a. l. loveland. | | | | north granby " | . | . | . | . daniel buck, jr. | | | | poquonock " | . | . | . | . " " " | . | . | . | . philip scarborough | | | | brooklyn conn. | . | . | . | . adams white. | | | | brooklyn " | . | . | . | . paris dyer. | | | | brooklyn " | . | . | . | . perrin scarborough. | | | | brooklyn conn. | . | . | . | . geo. k. virgin. | | | | collinsville conn.| . | . | . | . | . " " " | . | . | . | . | . " " " | . | . | . | . | . s. mead. | | | | | new haven conn. | . | . | . | . | . edwin hoyt. | | | | | new canaan " | . | . | . | . | . " " " | . | . | . | . | . " " " | . | . | . | . | . a. m. haling. | | | | | rockville " | . | . | . | . | . " " " | . | . | . | . | . " " " | . | . | . | . | . albert day. | | | | | brooklyn " | . | . | . | . | . c. goodyear. | | | | | new haven " | . | . | . | . | . rev. wm. clift | | | | | stonington " | . | . | . | . | . henry keeler. | | | | | south salem n. y. | . | . | . | . | . john adams. | | | | | salisbury conn. | . | . | . | . | . rev. wm. clift. | | | | | stonington " | . | . | . | . | | | |-----| | average | | | . | | -------------------------+-----------------------+-----+-----+----- | inorganic matter. | | | _from whom and |-----+-----+-----+-----| | | whence received_ | a | b | c | d | e | f | g -------------------------+-----+-----+-----+-----+-----+-----+----- . lewis m. norton. | | | | | | | goshen conn. | | | | . | . | . | . . " " " | | | | . | . | . | . " " " | | | | . | . | . | . . messrs. pond & miles.| | | | | | | " milford conn. | | | | . | . | . | . . " " " | | | | . | . | . | . . samuel camp. |~~~~~v~~~~~| | | | | plainville conn. | . | . | . | . | . | . . russell u. peck. | | | | | | | berlin conn. | | | | . | . | . | . . rev. b. f. northrop. | | | | | | | griswold conn. | | | | . | . | . | . . j. h. stanwood. | | | | | | | colebrook conn. | | | | . | . | . | . . n. hart, jr. | | | | | | | west cornwall conn.| | | | . | . | . | . . a. l. loveland. | | | | | | | north granby " | | | | . | . | . | . . daniel buck, jr. | | | | | | | poquonock " | | | | . | . | . | . . " " " | | | | . | . | . | . . philip scarborough. | | | | | | | brooklyn conn. | | | | . | . | . | . . adams white. | | | | | | | brooklyn " | | | | . | . | . | . . paris dyer. | | | | | | | brooklyn " | | | | . | . | . | . . perrin scarborough. | | | | | | | brooklyn conn. | | | | . | . | . | . . geo. k. virgin. | | | | | | | collinsville conn.| . | . | . | . | . | . | . . " " " | . | . | . | . | . | . | . . " " " | . | . | . | . | . | . | . . s. mead. | | | | | | | new haven conn. | . | . | . | . | . | . | . . edwin hoyt. | | | | | | | new canaan " | . | . | . | . | . | . | . . " " " | . | . | . | . | . | . | . . " " " | . | . | . | . | . | . | . . a. m. haling. | | | | | | | rockville " | . | . | . | . | . | . | . . " " " | . | | . | . | . | . | . . " " " | . | . | . | . | . | . | . . albert day. | | | | | | | brooklyn " | . | . | . | . | . | . | . . c. goodyear. | | | | | | | new haven " | . | . | . | . | . | . | . . rev. wm. clift | | | | | | | stonington " | . | | . | . | . | . | . . henry keeler. | | | | | | | south salem n. y. | . | . | . | . | . | . | . . john adams. | | | | | | | salisbury conn. | . | . | . | . | . | . | . . rev. wm. clift. | | | | | | | stonington " | . | . | . | . | . | . | . | | |-----| | |-----|----- average | | | . | | | . | . table ii.-composition of connecticut peats and mucks. _calculated in the dry state: the percentage of nitrogen calculated also on organic matters._ key: a - _in this table the matters soluble in water and the nitrogen are calculated to two places of decimals; the other ingredients are expressed in round numbers._ b - _soluble in water._ c - _insol. in water, but soluble in carbonate of soda._ d - _insol. in water and carbonate of soda._ e - _total._ f - _total matters soluble in water._ g - _nitrogen._ h - _nitrogen in per cent. of the organic matter._ -------------------------+-----------------------+ | organic matter. | |-----+-----+-----+-----+ a | b | c | d | e | -------------------------+~~~~~v~~~~~+-----+-----+ . lewis m. norton. | | | | goshen conn. | | | | . " " " | | | | . " " " | | | | . messrs. pond & miles.| | | | " milford conn. | | | | . " " " | | | | . samuel camp. | | | | plainville conn. | | | | . russell u. peck. | | | | berlin conn. | | | | . rev. b. f. northrop. | | | | griswold conn. | | | | . j. h. stanwood. | | | | colebrook conn. | | | | . n. hart, jr. | | | | west cornwall conn.| | | | . a. l. loveland. | | | | north granby " | | | | . daniel buck, jr. | | | | poquonock " | | | | . " " " | | | | . philip scarborough. | | | | brooklyn conn. | | | | . adams white. | | | | brooklyn " | | | | . paris dyer. | | | | brooklyn " | | | | . perrin scarborough. | | | | brooklyn conn. | | | | . geo. k. virgin. | | | | collinsville conn.| . | | | | . " " " | . | | | | . " " " | . | | | | . solomon mead. | | | | | new haven conn. | . | | | | . edwin hoyt. | | | | | new canaan " | . | | | | . " " " | . | | | | . " " " | . | | | | . a. m. haling. | | | | | rockville " | . | | | | . " " " | . | | | | . " " " | . | | | | . albert day. | | | | | brooklyn " | . | | | | . c. goodyear. | | | | | new haven " | . | | | | . rev. wm. clift | | | | | stonington " | . | | | | . henry keeler. | | | | | south salem n. y. | . | | | | . john adams. | | | | | salisbury conn. | . | | | | . rev. wm. clift. | | | | | stonington " | . | | | | -------------------------+-----+-----+-----+-----+ -------------------------+-----------------------+-----+-----+----- | inorganic matter. | | | |-----+-----+-----+-----| | | a | b | c | d | e | f | g | h -------------------------+-----+-----+-----+-----+-----+-----+----- . lewis m. norton. | | | | | | | goshen conn. | | | | | . | . | . . " " " | | | | | | . | . . " " " | | | | | . | . | . . messrs. pond & miles.| | | | | | | " milford conn. | | | | | . | . | . . " " " |~~~~~v~~~~~| | | . | . | . . samuel camp. | | | | | | plainville conn. | | | | | . | . | . . russell u. peck. | | | | | | | berlin conn. | | | | | . | . | . . rev. b. f. northrop. | | | | | | | griswold conn. | | | | | . | . | . . j. h. stanwood. | | | | | | | colebrook conn. | | | | | . | . | . . n. hart, jr. | | | | | | | west cornwall conn.| | | | | . | . | . . a. l. loveland. | | | | | | | north granby " | | | | | . | . | . . daniel buck, jr. | | | | | | | poquonock " | | | | | . | . | . . " " " | | | | | . | . | . . philip scarborough. | | | | | | | brooklyn conn. | | | | | . | . | . . adams white. | | | | | | | brooklyn " | | | | | . | . | . . paris dyer. | | | | | | | brooklyn " | | | | | . | . | . . perrin scarborough. | | | | | | | brooklyn conn. | | | | | . | . | . . geo. k. virgin. | | | | | | | collinsville conn.| . | | | | . | . | . . " " " | . | | | | . | . | . . " " " | . | | | | . | . | . . solomon mead. | | | | | | | new haven conn. | . | | | | . | . | . . edwin hoyt. | | | | | | | new canaan " | . | | | | . | . | . . " " " | . | | | | . | . | . . " " " | . | | | | . | . | . . a. m. haling. | | | | | | | rockville " | . | | | | . | . | . . " " " | . | | | | . | . | . . " " " | . | | | | . | . | . . albert day. | | | | | | | brooklyn " | . | | | | . | . | . . c. goodyear. | | | | | | | new haven " | . | | | | . | . | . . rev. wm. clift | | | | | | | stonington " | . | | | | . | . | . . henry keeler. | | | | | | | south salem n. y. | . | | | | . | . | . . john adams. | | | | | | | salisbury conn. | . | | | | . | . | . . rev. wm. clift. | | | | | | | stonington " | . | | | | . | . | . -------------------------+-----+-----+-----+-----+-----+-----+----- table iii.--description, etc., of peats and mucks. _no._ _color._ . lewis m. norton |chocolate-brown,| | |. . " " | " " | | | . " " |light-brown, | | | . messrs. pond & miles|chocolate-brown,| | | | | . " " |brownish-red, | | | . samuel camp |black, | | | . russell u. peck |chocolate-brown,| | | . rev. b. f. northrop |grayish-brown, | | | | | . j. h. stanwood |chocolate-brown,| | | . n. hart, jr |brownish-black, | . a. l. loveland |black, | | | . daniel buck, jr |chocolate-brown,| | | . " " | " " | . philip scarborough | | | | . adams white |chocolate-brown,| | | . paris dyer |grayish-black, | | | . perrin scarborough |chocolate-brown,| | | | | . geo. k. virgin |light | | brownish-gray | | | . " " |chocolate-brown,| | | . " " |black, | . solomon mead |grayish-brown, | | | | | . edwin hoyt |brownish-gray, | | | . " " | " | | | . " " | " | | | . a. m. haling |chocolate-brown,| . " " | " " | . " " | " " | | | . albert day |dark-brown, | | | | | . c. goodyear |black, | | | . rev. wm. clift |chocolate-brown,| | | | | . henry keeler |light-brown, | | | . john adams | " | | | . rev. wm. clift |dark ash-gray, | | | _condition at time of analysis, _no._ reputed value, etc._ . lewis m. norton |air-dry, tough, compact, heavy; from bottom; | to feet deep; very good in compost. . " " | " tough, compact, heavier than , from | near surface; very good in compost. . " " | " coherent but light, from between and | , very good in compost. . messrs. pond & miles| " coherent but light, surface peat, | considered better than no. ; good in | compost. . " " | " very light and loose in texture, from | depth of feet, good in compost. . samuel camp | " hard lumps, half as good as yard manure, | in compost equal to yard manure. . russell u. peck | " is good fresh, long exposed, half as | good as barn-yard manure. . rev. b. f. northrop | " light, easily crushed masses containing | sand, has not been used alone, good in | compost. . j. h. stanwood |moist, hard lumps, used fresh good after first | year; excellent in compost. . n. hart, jr |air-dry, hard lumps, excellent in compost. . a. l. loveland | " hard lumps, contains grains of coarse | sand. . daniel buck, jr | " coherent cakes, good as top dressing on | grass when fresh; excellent in compost. . " " | " light surface layers of no. . . philip scarborough | " after exposure over winter, has | one-third value of yard-manure. . adams white | " hard lumps, good in compost, causes | great growth of straw. . paris dyer | " easily crushed lumps, largely admixed | with soil. . perrin scarborough | " well-characterized "vitriol peat;" in | compost, after year's exposure, gives | indifferent results. . geo. k. virgin | " light, coherent surface peat; sample | long exposed; astonishing results on | sandy soil. . " " |moist, crumbly, contains much sand, four feet | from surface. . " " |wet. . solomon mead |air-dry, light, porous, coherent from grass | roots; long weathered, good; fresh, | better in compost. . edwin hoyt | " loose, light, much mixed with soil, | good in compost. . " " | " no. saturated with horse urine, | darker than no. . . " " | " no. composted with white fish, | darker than no. ; fish-bones evident. . a. m. haling |moist, fresh dug. . " " |air-dry, no. after two year's weathering. . " " |moist, fresh dug, good substitute for yard | manure as top-dressing on grass. . albert day | " coherent and hard; fresh dug, but from | surface where weathered; injurious to | crops; vitriol peat. (?) . c. goodyear |air-dry, very hard tough cakes; when fresh dug, | "as good as cow dung." . rev. wm. clift |moist, from an originally fresh water bog, | broken into years ago by tide, now | salt marsh; good after weathering. . henry keeler |air-dry, leaf-muck, friable; when fresh, appears | equal to good yard manure. . john adams |moist, overlies shell marl, fresh or weathered | does not compare with ordinary manure. . rev. wm. clift |air-dry, from bottom of salt ditch, where tide | flows daily; contains sulphate of iron. footnotes: [ ] the oxygen thus absorbed by water, serves for the respiration of fish and aquatic animals. [ ] this sample contained also fish-bones, hence the larger content of nitrogen was not entirely due to absorbed ammonia. [ ] reichardt's analyses are probably inaccurate, and give too much ammonia and nitric acid. [ ] these analyses were executed--a by professor g. f. barker; b by mr. o. c. sparrow; c by mr. peter collier. [ ] _shell marl_, consisting of fragments and powder of fresh-water shells, is frequently met with, underlying peat beds. such a deposit occurs on the farm of mr. john adams, in salisbury, conn. it is eight to ten feet thick. an air-dry sample, analyzed under the writer's direction, gave results as follows: "water . {soluble in water . } organic matter { } . {insoluble in water . } carbonate of lime . sand . oxide of iron and alumina, with traces of potash, magnesia, sulphuric and phosphoric acid . ------- . another specimen from near milwaukee, wis., said to occur there in immense quantities underlying peat, contained, by the author's analysis-- water . carbonate of lime . carbonate of magnesia . peroxide of iron with a trace of phosphoric acid . sand . ------ . [ ] to the kindness of joseph sheffield, esq., of new haven, the author is indebted for facilities in carrying on these experiments. [ ] at the instigation of henry a. dyer, esq., at that time the society's corresponding secretary. [ ] derived from the communications published in the author's report. trans. conn. state ag. soc. p.p. - . part iii. on peat as fuel. .--_kinds of peat that make the best fuel._ the value of peat for fuel varies greatly, like its other qualities. only those kinds which can be cut out in the shape of coherent blocks, or which admit of being artificially formed into firm masses, are of use in ordinary stoves and furnaces. the powdery or friable surface peat, which has been disintegrated by frost and exposure, is ordinarily useless as fuel, unless it be rendered coherent by some mode of preparation. unripe peat which contains much undecomposed moss or grass roots, which is therefore very light and porous, is in general too bulky to make an effective heating material before subjection to mechanical treatment. the best peat for burning, is that which is most free from visible fiber or undecomposed vegetable matters, which has therefore a homogeneous brown or black aspect, and which is likewise free from admixture of earthy substances in the form of sand or clay. such peat is unctuous when moist, shrinks greatly on drying, and forms hard and heavy masses when dry. it is usually found at a considerable depth, where it has been subjected to pressure, and then has such consistence as to admit of cutting out in blocks; or it may exist as a black mud or paste at the bottom of bogs and sluices. the value of peat as fuel stands in direct ratio to its content of carbon. we have seen that this ranges from to _per cent. of the organic matter_, and the increase of carbon is related to its ripeness and density. the poorest, youngest peat, has the same proportion of carbon as exists in wood. it does not, however, follow that its heating power is the same. the various kinds of wood have essentially the same proportion of carbon, but their heating power is very different. the close textured woods--those which weigh the most per cord--make the best fuel for most purposes. we know, that a cord of hickory will produce twice as much heat as a cord of bass-wood. peat, though having the same or a greater proportion of carbon, is generally inferior to wood on account of its occupying a greater bulk for a given weight, a necessary result of its porosity. the best qualities of peat, or poor kinds artificially condensed, may, on the other hand, equal or exceed wood in heating power, bulk for bulk. one reason that peat is, in general, inferior to wood in heating effect, lies in its greater content of incombustible ash. wood has but . to . _per cent._ of mineral matters, while peat contains usually to _per cent._, and often more. the oldest, ripest peats are those which contain the most carbon, and have at the same time the greatest compactness. from these two circumstances they make the best fuel. it thus appears that peat which is light, loose in structure, and much mixed with clay or sand, is a poor or very poor article for producing heat: while a dense pure peat is very good. a great drawback to the usefulness of most kinds of peat-fuel, lies in their great friability. this property renders them unable to endure transportation. the blocks of peat which are commonly used in most parts of germany as fuel, break and crumble in handling, so that they cannot be carried far without great waste. besides, when put into a stove, there can only go on a slow smouldering combustion as would happen in cut tobacco or saw-dust. a free-burning fuel must exist in compact lumps or blocks, which so retain their form and solidity, as to admit of a rapid draught of air through the burning mass. the bulkiness of ordinary peat fuel, as compared with hard wood, and especially with coal, likewise renders transportation costly, especially by water, where freights are charged by bulk and not by weight, and renders storage an item of great expense. the chief value of that peat fuel, which is simply cut from the bog, and dried without artificial condensation, must be for the domestic use of the farmer or villager who owns a supply of it not far from his dwelling, and can employ his own time in getting it out. though worth perhaps much less cord for cord when dry than hard wood, it may be cheaper for home consumption than fuel brought from a distance. various processes have been devised for preparing peat, with a view to bringing it into a condition of density and toughness, sufficient to obviate its usual faults, and make it compare with wood or even with coal in heating power. the efforts in this direction have met with abundant success as regards producing a good fuel. in many cases, however, the cost of preparation has been too great to warrant the general adoption of these processes. we shall recur to this subject on a subsequent page, and give an account of the methods that have been proposed or employed for the manufacture of condensed peat fuel. .--_density of peat._ the apparent[ ] specific gravity of peat in the air-dry state, ranges from . to . . in other words, a full cubic foot weighs from one-tenth as much as, to slightly more than a cubic foot of water, = - / lbs. peat, which has a specific gravity of but . , may be and is employed as fuel. a full cubic foot of it will weigh about lbs. in germany, the cubic foot of "good ordinary peat" in blocks,[ ] ranges from to lbs. in weight, and is employed for domestic purposes. the heavier peat, weighing or more lbs. per cubic foot in blocks, is used for manufacturing and metallurgical purposes, and for firing locomotives. karmarsch has carefully investigated more than peats belonging to the kingdom of hanover, with reference to their heating effect. he classifies them as follows:-- a. _turfy peat_, (_rasentorf_,) consisting of slightly decomposed mosses and other peat-producing plants, having a yellow or yellowish-brown color, very soft, spongy and elastic, sp. gr. . to . , the full english cubic foot weighing from to lbs. b. _fibrous peat_, unripe peat, which is brown or black in color, less elastic than turfy peat, the fibres either of moss, grass, roots, leaves, or wood, distinguishable by the eye, but brittle, and easily broken; sp. gr. . to . , the weight of a full cubic foot being from to lbs. c. _earthy peat._--nearly or altogether destitute of fibrous structure, drying to earth-like masses which break with more or less difficulty, giving lustreless surfaces of fracture; sp. gr. . to . , the full cubic foot weighing, accordingly, from to lbs. d. _pitchy peat_, (_pechtorf_,) dense; when dry, hard; often resisting the blows of a hammer, breaking with a smooth, sometimes lustrous fracture, into sharp-angled pieces. sp. gr. . to . , the full cubic foot weighing from to lbs. in kane and sullivan's examination of kinds of irish peat, the specific gravities ranged from . to . . .--_heating power of peat as compared with wood and anthracite._ karmarsch found that in absolute heating effect lbs. of turfy, air-dry peat, on the average = lbs. of pine wood. " fibrous " " " = " " " earthy " " " = " " " pitchy " " " = " " the comparison of heating power by bulk, instead of weight, is as follows:-- cubic ft. of turfy peat, on the average[ ] = cubic ft. of pine wood, in sticks. " " fibrous " " = cubic ft. of pine wood, in sticks. " " earthy " " = cubic ft. of pine wood, in sticks. " " pitchy " " = cubic ft. of pine wood, in sticks. according to brix, the weight per english cord and relative heating effect of several air-dry peats--the heating power of an equal bulk of oak wood being taken at as a standard--are as follows, _bulk for bulk_:[ ] _weight per _heating cord._ effect._ oak wood lbs. peat from linum, st quality, dense and pitchy " " " d " fibrous " " " d " turfy " peat from buechsenfeld, st quality, pitchy, very hard and heavy lbs. peat from buechsenfeld, d quality " these statements agree in showing, that, while weight for weight, the ordinary qualities of peat do not differ much from wood in heating power; the heating effect of _equal bulks_ of this fuel, as found in commerce, may vary extremely, ranging from one-half to three quarters that of oak wood. condensed peat may be prepared by machinery, which will weigh more than hard wood, bulk for bulk, and whose heating power will therefore exceed that of wood. gysser gives the following comparisons of a good peat with various german woods and charcoals, equal weights being employed, and split beech wood, air-dry, assumed as the standard.[ ] beech wood, split, air dry . peat, condensed by weber's & gysser's method,[ ] air-dried, with _per cent._ moisture. . peat, condensed by weber's & gysser's method, hot-dried, with _per cent._ moisture. . peat-charcoal, from condensed peat. . the same peat, simply cut and air-dried. . beech-charcoal. . summer-oak wood. . birch wood. . white pine wood. . alder. . linden. . red pine. . poplar. . some experiments have been made in this country on the value of peat as fuel. one was tried on the n. y. central railroad, jan. , . a locomotive with empty freight cars attached, was propelled from syracuse westward--the day being cold and the wind ahead--at the rate of miles the hour. the engineer reported that "the peat gave us as much steam as wood, and burnt a beautiful fire." the peat, we infer, was cut and prepared near syracuse, n. y. in one of the pumping houses of the nassau water department of the city of brooklyn, an experiment has been made for the purpose of comparing peat with anthracite, for the results of which i am indebted to the courtesy of moses lane, esq., chief engineer of the department. fire was started under a steam boiler with wood. when steam was up, the peat was burned--its quantity being lbs., or barrels--and after it was consumed, the firing was continued with coal. the pressure of steam was kept as nearly uniform as possible throughout the trial, and it was found that with lbs. of peat the engine made revolutions, while with lbs. of coal it made revolutions. in other words, lbs. of coal produced - / revolutions, and lbs. of peat produced - / revolutions. one pound of coal therefore equalled - / lbs. of peat in heating effect. the peat burned well and generated steam freely. mr. lane could not designate the quality of the peat, not having been able to witness the experiment. these trials have not, indeed, all the precision needful to fix with accuracy the comparative heating effect of the fuels employed; for a furnace, that is adapted for wood, is not necessarily suited to peat, and a coal grate must have a construction unlike that which is proper for a peat fire; nevertheless they exhibit the relative merits of wood, peat, and anthracite, with sufficient closeness for most practical purposes. two considerations would prevent the use of ordinary cut peat in large works, even could two and one-fourth tons of it be afforded at the same price as one ton of coal. the nassau water department consumes , tons of coal yearly, the handling of which is a large expense, six firemen being employed to feed the furnaces. to generate the same amount of steam with peat of the quality experimented with, would require the force of firemen to be considerably increased. again, it would be necessary to lay in, under cover, a large stock of fuel during the summer, for use in winter, when peat cannot be raised. since a barrel of this peat weighed less than lbs., the short ton would occupy the volume of barrels; as is well known, a ton of anthracite can be put into barrels. a given weight of peat therefore requires - / times as much storage room, as the same weight of coal. as - / tons of peat, in the case we are considering, are equivalent to but one ton of coal in heating effect, the winter's supply of peat fuel would occupy - / times the bulk of the same supply in coal, admitting that the unoccupied or air-space in a pile of peat is the same as in a heap of coal. in fact, the calculation would really turn out still more to the disadvantage of peat, because the air-space in a bin of peat is greater than in one of coal, and coal can be excavated for at least two months more of the year than peat. it is asserted by some, that, because peat can be condensed so as to approach anthracite in specific gravity, it must, in the same ratio, approach the latter in heating power. its effective heating power is, indeed, considerably augmented by condensation, but no mechanical treatment can increase its percentage of carbon or otherwise alter its chemical composition; hence it must forever remain inferior to anthracite. the composition and density of the best condensed peat is compared with that of hard wood and anthracite in the following statement:-- _in _carbon._ _hydrogen._ _oxygen and _ash._ _water._ _specific parts._ nitrogen._ gravity._ wood, . . . . . . condensed peat . . . . . . anthracite . . . . . in combustion in ordinary fires, the _water_ of the fuel is a source of waste, since it consumes heat in acquiring the state of vapor. this is well seen in the comparison of the same kind of peat in different states of dryness. thus, in the table of gysser, (page ) weber's condensed peat, containing _per cent._ of moisture, surpasses in heating effect that containing _per cent._ of moisture, by nearly one-half. the _oxygen_ is a source of waste, for heat as developed from fuel, is chiefly a result of the chemical union of atmospheric or free oxygen, with the carbon and hydrogen of the combustible. the oxygen of the fuel, being already combined with carbon and hydrogen, not only cannot itself contribute to the generation of heat, but neutralizes the heating effect of those portions of the carbon and hydrogen of the fuel with which it remains in combination. the quantity of heating effect thus destroyed, cannot, however, be calculated with certainty, because physical changes, viz: the conversion of solids into gases, not to speak of secondary chemical transformations, whose influence cannot be estimated, enter into the computation. _nitrogen_ and ash are practically indifferent in the burning process, and simply impair the heating value of fuel in as far as they occupy space in it and make a portion of its weight, to the exclusion of combustible matter. again, as regards density, peat is, in general, considerably inferior to anthracite. the best uncondensed peat has a specific gravity of . . condensed peat usually does not exceed . . sometimes it is made of sp. gr. . . assertions to the effect of its acquiring a density of . , can hardly be credited of pure peat, though a considerable admixture of sand or clay might give such a result. the comparative heating power of fuels is ascertained by burning them in an apparatus, so constructed, that the heat generated shall expend itself in evaporating or raising the temperature of a known quantity of water. _the amount of heat that will raise the temperature of one gramme of water, one degree of the centigrade thermometer, is agreed upon as the unit of heat._[ ] in the complete combustion of carbon in the form of charcoal or gas-coal, there are developed units of heat. in the combustion of one gramme of hydrogen gas, , units of heat are generated. the heating effect of hydrogen is therefore . times greater than that of carbon. it was long supposed that the heating effect of compound combustibles could be calculated from their elementary composition. this view is proved to be erroneous, and direct experiment is the only satisfactory means of getting at the truth in this respect. the data of karmarsch, brix, and gysser, already given, were obtained by the experimental method. they were, however, made mostly on a small scale, and, in some cases, without due regard to the peculiar requirements of the different kinds of fuel, as regards fire space, draught, etc. they can only be regarded as approximations to the truth, and have simply a comparative value, which is, however, sufficient for ordinary purposes. the general results of the investigations hitherto made on all the common kinds of fuel, are given in the subjoined statement. the comparison is made in units of heat, and refers to equal weights of the materials experimented with. heating power of different kinds of fuel. air-dry wood " peat perfectly dry wood " " peat air-dry lignite or brown coal perfectly dry lignite or brown coal bituminous coal anthracite wood charcoal coke .--_modes of burning peat._ in the employment of peat fuel, regard must be had to its shape and bulk. commonly, peat is cut or moulded into blocks or sods like bricks, which have a length of to inches; a breadth of to inches, and a thickness of - / to inches. machine peat is sometimes formed into circular disks of to inches diameter, and to inches thickness and thereabouts. it is made also in the shape of balls of to inches diameter. another form is that of thick-walled pipes, to inches in diameter, a foot or more long, and with a bore of one-half inch. flat blocks are apt to lie closely together in the fire, and obstruct the draft. a fire-place, constructed properly for burning them, should be shallow, not admitting of more than two or three layers being superposed. according to the bulkiness of the peat, the fire-place should be roomy, as regards length and breadth. fibrous and easily crumbling peat is usually burned upon a hearth, _i. e._ without a grate, either in stoves or open fire-places. dense peat burns best upon a grate, the bars of which should be thin and near together, so that the air have access to every part of the fuel. the denser and tougher the peat, and the more its shape corresponds with that usual to coal, the better is it adapted for use in our ordinary coal stoves and furnaces. .--_burning of broken peat._ [illustration: fig. --stair grate.] broken peat--the fragments and waste of the cut or moulded blocks, and peat as obtained by plowing and harrowing the surface of drained peat-beds--may be used to advantage in the _stair grate_, fig. , which was introduced some years ago in austria, and is adapted exclusively for burning finely divided fuel. it consists of a series of thin iron bars to inches wide, _a_, _a_, _a_, ... which are arranged above each other like steps, as shown in the figure. they are usually half as long as the grate is wide, and are supported at each end by two side pieces or walls, _l._ below, the grate is closed by a heavy iron plate. the fuel is placed in the hopper _a_, which is kept filled, and from which it falls down the incline as rapidly as it is consumed. the air enters from the space _g_, and is regulated by doors, not shown in the cut, which open into it. the masonry is supported at _u_, by a hollow iron beam. below, a lateral opening serves for clearing out the ashes. the effect of the fire depends upon the width of the throat of the hopper at _u_, which regulates the supply of fuel to the grate, and upon the inclination of the latter. the throat is usually from to inches wide, according to the nature of the fuel. the inclination of the grate is to ° and, in general, should be that which is assumed by the sides of a pile of the fuel to be burned, when it is thrown up into a heap. this grate ensures complete combustion of fuel that would fall through ordinary grates, and that would merely smoulder upon a hearth. the fire admits of easy regulation, the ashes may be removed and the fuel may be supplied without _checking the fire_. not only broken peat, but coal dust, saw dust, wood turnings and the like may be burned on this grate. the figure represents it as adapted to a steam boiler. .--_hygroscopic water of peat fuel._ the quantity of water retained by air-dried peat appears to be the same as exists in air-dried wood, viz., about _per cent._ the proportion will vary however according to the time of seasoning. in thoroughly seasoned wood or peat, it may be but _per cent._; while in the poorly dried material it may amount to or more _per cent._ when _hot-dried_, the proportion of water may be reduced to _per cent._, or less. when peat is still moist, it gathers water rapidly from damp air, and in this condition has been known to burst the sheds in which it was stored, but after becoming dry to the eye and feel, it is but little affected by dampness, no more so, it appears, than seasoned wood. .--_shrinkage._ in estimating the value and cost of peat fuel, it must be remembered that peat shrinks greatly in drying, so that three to five cords of fresh peat yield but one cord of dry peat. when the fiber of the peat is broken by the hand, or by machinery, the shrinkage is often much greater, and may sometimes amount to seven-eighths of the original volume.--_dingler's journal, oct. _, _s._ . the difference in weight between fresh and dry peat is even greater. fibrous peat, fresh from the bog, may contain ninety _per cent._ of water, of which seventy _per cent._ must evaporate before it can be called dry. the proportion of water in earthy or pitchy peat is indeed less; but the quantity is always large, so that from five to nine hundred weight of fresh peat must be lifted in order to make one hundred weight of dry fuel. .--_time of excavation, and drying._ peat which is intended to be used after simply drying, must be excavated so early in the season that it shall become dry before frosty weather arrives: because, if frozen when wet, its coherence is destroyed, and on thawing it falls to a powder useless for fuel. peat must be dried with certain precautions. if a block of fresh peat be exposed to hot sunshine, it dries and shrinks on the surface much more rapidly than within: as a consequence it cracks, loses its coherence, and the block is easily broken, or of itself falls to pieces. in europe, it is indeed customary to dry peat without shelter, the loss by too rapid drying not being greater than the expense of building and maintaining drying sheds. there however the sun is not as intense, nor the air nearly so dry, as it is here. even there, the occurrence of an unusually hot summer, causes great loss. in our climate, some shelter would be commonly essential unless the peat be dug early in the spring, so as to lose the larger share of its water before the hot weather; or, as would be best of all, in the autumn late enough to escape the heat, but early enough to ensure such dryness as would prevent damage by frost. the peculiarities of climate must decide the time of excavating and the question of shelter. the point in drying peat is to make it lose its water gradually and regularly, so that the inside of each block shall dry nearly as fast as the outside. some of the methods of hot-drying peat, will be subsequently noticed. summer or fall digging would be always advantageous on account of the swamps being then most free from water. in bavaria, peat is dug mostly in july and the first half of august. .--_drainage._ when it is intended to raise peat fuel _in the form of blocks_, the bog should be drained no more rapidly than it is excavated. peat, which is to be worth cutting in the spring, must be covered with water during the winter, else it is pulverized by the frost. so, too, it must be protected against drying away and losing its coherency in summer, by being kept sufficiently impregnated with water. in case an extensive bog is to be drained to facilitate the cutting out of the peat for use as fuel, the canals that carry off the water from the parts which are excavating, should be so constructed, that on the approach of cold weather, the remaining peat may be flooded again to the usual height. in most of the smaller swamps, systematic draining is unnecessary, the water drying away in summer enough to admit of easy working. in some methods of preparing or condensing peat by machinery, it is best or even needful to drain and air-dry the peat, preliminary to working. by draining, the peat settles, especially on the borders of the ditches, several inches, or even feet, according to its nature and depth. it thus becomes capable of bearing teams and machinery, and its density is very considerably augmented. .--_the cutting of peat._--a. _preparations._ in preparing to raise peat fuel from the bog, the surface material, which from the action of frost and sun has been pulverized to "muck," or which otherwise is full of roots and undecomposed matters, must be removed usually to the depth of to inches. it is only those portions of the peat which have never frozen nor become dry, and are free from coarse fibers of recent vegetation, that can be cut for fuel. peat fuel must be brought into the form of blocks or masses of such size and shape as to adapt them to use in our common stoves and furnaces. commonly, the peat is of such consistence in its native bed, that it may be cut out with a spade or appropriate tool into blocks having more or less coherence. sometimes it is needful to take away the surplus water from the bog, and allow the peat to settle and drain a while before it can be cut to advantage. when a bog is to be opened, a deep ditch is run from an outlet or lowest point a short distance into the peat bed, and the working goes on from the banks of this ditch. it is important that system be followed in raising the peat, or there will be great waste of fuel and of labor. if, as often happens, the peat is so soft in the wet season as to break on the vertical walls of a ditch and fill it, at the same time dislocating the mass and spoiling it for cutting, it is best to carry down the ditch in terraces, making it wide above and narrow at the bottom. b. _cutting by hand._ the simplest mode of procedure, consists in laying off a "field" or plot of, say feet square, and making vertical cuts with a sharp spade three or four inches deep from end to end in parallel lines, as far apart as it is proposed to make the breadth of the peats or sods, usually four to five inches. then, the field is cut in a similar manner in lines at right angles to the first, and at a distance that shall be the length of the peats, say to inches. finally, the workman lifts the peats by horizontal thrusts of his spade, made at a depth of three inches. the sods as lifted, are placed on a light barrow or upon a board or rack, and are carried off to a drying ground, near at hand, where they are laid down flatwise to drain and dry. in ireland, it is the custom, after the peats have lain thus for a fortnight or so, to "foot" them, i. e. to place them on end close together; after further drying the "footing" is succeeded by "clamping," which is building the sods up into stacks of about twelve to fifteen feet long, four feet wide at bottom, narrowing to one foot at top, with a height of four to five feet. the outer turfs are inclined so as to shed the rain. the peat often remains in these clamps on the bog until wanted for use, though in rainy seasons the loss by crumbling is considerable. [illustration: fig. .--german peat-knife.] other modes of lifting peat, require tools of particular construction.... in germany it is common to excavate by _vertical_ thrusts of the tool, the cutting part of which is represented above, fig. . this tool is pressed down into the peat to a depth corresponding to the thickness of the required block: its three edges cut as many sides of the block, and the bottom is then broken or torn out by a prying motion. in other cases, this or a similar tool is forced down by help of the foot as deeply into the peat as possible by a workman standing above, while a second man in the ditch cuts out the blocks of proper thickness by means of a sharp spade thrust horizontally. when the peats are taken out to the depth of the first vertical cutting, the knife is used again from above, and the process is thus continued as before, until the bottom of the peat or the desired depth is reached. in ireland, is employed the "slane," a common form of which is shown in fig. , it being a long, narrow and sharp spade, inches by six, with a wing at right angles to the blade. [illustration: fig. .--irish slane.] the peats are cut by one thrust of this instrument which is worked by the arms alone. after a vertical cut is made by a spade, in a line at right angles to a bank of peat, the slane cuts the bottom and other side of the block; while at the end the latter is simply lifted or broken away. peat is most easily cut in a vertical direction, but when, as often happens, it is made up of layers, the sods are likely to break apart where these join. horizontal cutting is therefore best for stratified peat. _system employed in east friesland._--in raising peat, great waste both of labor and of fuel may easily occur as the result of random and unsystematic methods of working. for this reason, the mode of cutting peat, followed in the extensive moors of east friesland, is worthy of particular description. there, the business is pursued systematically on a plan, which, it is claimed, long experience[ ] has developed to such perfection that the utmost economy of time and labor is attained. the cost of producing marketable peat in east friesland in , was one silver groschen=about - / cents, per hundred weight; while at that time, in bavaria, the hundred weight cost three times as much when fit for market; and this, notwithstanding living and labor are much cheaper in the latter country. the method to be described, presupposes that the workmen are not hindered by water, which, in most cases, can be easily removed from the high-moors of the region. the peat is worked in long stretches of feet in width, and to paces in length: each stretch or plot is excavated at once to a considerable depth and to its full width. each successive year the excavation is widened by feet, its length remaining the same. sometimes, unusual demand leads to more rapid working; but the width of feet is adhered to for each cutting, and, on account of the labor of carrying the peats, it is preferred to extend the length rather than the width. assuming that the peat bed has been opened by a previous cutting, to the depth of - / feet, and the surface muck and light peat, - / feet thick, have been thrown into the excavation of the year before--a new plot is worked by five men as follows. one man, the "bunker," removes from the surface, about two inches of peat, disintegrated by the winter's frost, throwing it into last year's ditch. following him, come two "diggers," of whom one stands on the surface of the peat, and with a heavy, long handled tool, cuts out the sides and end of the blocks, which are about seventeen by five inches; while the other stands in the ditch, and by horizontal thrusts of a light, sharp spade, removes the sods, each of five and a half inches thickness, and places them on a small board near by. each block of peat has the dimensions of one fourth of a cubic foot, and weighs about pounds. two good workmen will raise such peats, or - / cubic feet, per minute. a fourth man, the "loader," puts the sods upon a wheel-barrow, always two rows of six each, one upon the other, and-- a fifth, the "wheeler," removes the load to the drying ground, and with some help from the bunker, disposes them flatwise in rows of sods wide, which run at right angles to the ditch, and, beginning at a little more than feet from the latter, extend feet. the space of feet between the plot that is excavating, and the drying ground, is, at the same time, cleared of the useless surface muck by the bunker, in preparation for the next year's work. with moderate activity, the five men will lift and lay out , sods ( cubic feet,) daily, and it is not uncommon that five first-rate hands get out , peats ( cubic feet,) in this time. a gang of five men, working as described, suffices for cutting out a bed of four feet of solid peat. when the excavation is to be made deeper, a sixth man, the "hanker," is needful for economical work; and with his help the cutting may be extended down to nine and a half feet; i. e. through eight feet of solid peat. the cutting is carried down at first, four feet as before, but the peats are carried feet further, in order to leave room for those to be subsequently lifted. the "hanker" aids here, with a second wheel-barrow. in taking out the lower peat, the "hanker" stands on the bottom of the first excavation, receives the blocks from the diggers, on a broad wooden shovel, and hands them up to the loader; while the wheeler, having only the usual distance to carry them, lays them out in the drying rows without difficulty. after a little drying in the rows, the peats are gradually built up into narrow piles, like a brick wall of one and a half bricks thickness. these piles are usually raised by women. they are made in the spaces between the rows, and are laid up one course at a time, so that each block may dry considerably, before it is covered by another. a woman can lay up , peats daily--the number lifted by men--and as it requires about a month of good weather to give each course time (two days) to dry, she is able to pile for gangs of workmen. if the weather be very favorable, the peats may be stacked or put into sheds, in a few days after the piling is finished. stacking is usually practised. the stacks are carefully laid up in cylindrical form, and contain to cubic feet. when the stacks are properly built, the peat suffers but little from the weather. according to schroeder, from whose account (dingler's polytechnisches journal, bd. , s. ) the above statements are derived, the peats excavated under his direction, in drying thoroughly, shrank to about one-fourth of their original bulk (became inches x inches x inches,) and to one-seventh or one-eighth of their original weight. c. _machines for cutting peat._ in north prussia, the peat cutting machine of brosowsky, see fig. , is extensively employed. it consists of a cutter, made like the four sides of a box, but with oblique edges, _a_, which by its own weight, and by means of a crank and rack-work, operated by men, is forced down into the peat to a depth that may reach feet. it can cut only at the edge of a ditch or excavation, and when it has penetrated sufficiently, a spade like blade, _d_, is driven under the cutter by means of levers _c_, and thus a mass is loosened, having a vertical length of feet or more, and whose other dimensions are about Ã� inches. this is lifted by reversing the crank motion, and is then cut up by the spade into blocks of inches Ã� inches Ã� inches. each parallelopipedon of peat, cut to a depth of feet, makes sods, and this number can be cut in less than minutes. four hands will cut and lay out to dry, , to , peats daily, or cubic feet. one great advantage of this machine consists in the circumstance that it can be used to raise peat from below the surface of water, rendering drainage in many cases unnecessary. independently of this, it appears to be highly labor saving, since machines were put to use in mecklenburg and pomerania in about years from its introduction. the mecklenburg moors are now traversed by canals, cut by this machine, which are used for the transportation of the peat to market.[ ] [illustration: fig. .--brosowsky's peat cutter.] lepreux in paris, has invented a similar but more complicated machine, which is said to be very effective in its operation. according to hervé mangon, this machine, when worked by two men, raises and cuts , peats daily, of which seven make one cubic foot, equal to cubic feet. the saving in expense by using this machine[ ] is said to be _per cent._, when the peat to be raised is under water. .--_the dredging of peat._ when peat exists, not as a coherent more or less fibrous mass, but as a paste or mud, saturated with water, it cannot be raised and formed by the methods above described. in such cases the peat is dredged from the bottom of the bog by means of an iron scoop, like a pail with sharp upper edges, which is fastened to a long handle. the bottom is made of coarse sacking, so that the water may run off. sometimes, a stout ring of iron with a bag attached, is employed in the same way. the fine peat is emptied from the dredge upon the ground, where it remains, until the water has been absorbed or has evaporated, so far as to leave the mass somewhat firm and plastic. in the mean time, a drying bed is prepared by smoothing, and, if needful, stamping a sufficient space of ground, and enclosing it in boards inches wide, set on edge. into this bed the partially dried peat is thrown, and, as it cracks on the surface by drying, it is compressed by blows with a heavy mallet or flail, or by treading it with flat boards, attached to the feet, somewhat like snow shoes. by this treatment the mass is reduced to a continuous sheet of less than one-half its first thickness, and becomes so firm, that a man's step gives little impression in it. the boards are now removed, and it is cut into blocks by means of a very thin, sharp spade. every other block being lifted out and placed crosswise upon those remaining, air is admitted to the whole and the drying goes on rapidly. this kind of peat is usually of excellent quality. in north germany it is called "baggertorf," i. e. mud-peat. peat is sometimes dredged by machinery, as will be noticed hereafter. .--_the moulding of peat._ when black, earthy or pitchy peat cannot be cut, and is not so saturated with water as to make a mud; it is, after raking or picking out roots, etc., often worked into a paste by the hands or feet, with addition of water, until it can be formed into blocks which, by slow drying, acquire great firmness. in ireland this product is termed "hand-peat." in germany it is called "formtorf," _i. e._ moulded peat, or "backtorf," _i. e._ baked peat. the shaping is sometimes accomplished by plastering the soft mass into wooden moulds, as in making bricks. .--_preparation of peat fuel by machinery, etc._ within the last years, numerous inventions have been made with a view to improving the quality of peat fuel, as well as to expedite its production. these inventions are directed to the following points, viz.: . _condensation_ of the peat, so as bring more fuel into a given space, thus making it capable of giving out an intenser heat; at the same time increasing its hardness and toughness, and rendering it easier and more economical of transportation. . _drying_ by artificial heat or reducing the amount of water from or _per cent._ to half that quantity or less. this exalts the heating power in no inconsiderable degree. . _charring._ peat-charcoal is as much better than peat, for use where intense heat is required, as wood charcoal is better than wood. . _purifying from useless matters._ separation of earthy admixtures which are incombustible and hinder draught. a.--_condensation by pressure._ _pressing wet peat._--the condensation of peat was first attempted by subjecting the fresh, wet material, to severe pressure. as long ago as the year , pernitzsch, in saxony, prepared peat by this method, and shortly afterwards lord willoughby d'eresby, in scotland, and others, adopted the same principle. simple pressure will, indeed, bring fresh peat at once into much smaller bulk; but, if the peat be fibrous and light, and for this reason require condensation, it is also elastic, and, when the pressure is relieved, it acquires again much of its original volume. furthermore, although pressure will squeeze out much water from a saturated well-ripened peat, the complete drying of the pressed blocks usually requires as much or more time than that of the unpressed material, on account of the closeness of texture of the surface produced by the pressure. the advantages of subjecting fresh peat to pressure in the ordinary presses, it is found, are more than offset by the expense of the operation, and it is therefore unnecessary to give the subject further attention. fresh peat appears however to have been advantageously pressed by other mechanical means. two methods require notice. _mannhardt's method_, invented about the year , has been practically applied on the large scale at _schleissheim_, bavaria. mannhardt's machine consists of two colossal iron rolls, each of feet diameter, and - / feet length, geared into each other so as to revolve horizontally in opposite directions and with equal velocity. these rolls are hollow, their circumference consists of stout iron plate perforated with numerous small holes, and is supported by iron bars which connect the ends of the roll, having intervals between them of about one inch. each roll is covered by an endless band of hair cloth, stretched over and kept in place by rollers. the rolls are operated by a steam engine of horse power. the fresh peat is thrown into a hopper, and passing between the rolls, loses a considerable share of its water, issuing as a broad continuous sheet, which is divided into blocks by an arrangement presently to be described. the cloth, covering the rolls, must have great strength, sufficient porosity to allow water to pass it freely, and such closeness of texture as to retain the fine particles of peat. many trials have led to the use of a fabric, specially made for the purpose, of goat's hair. the cloth for each pair of rolls, costs $ . the peat at schleissheim is about feet in depth, and consists of a dark-brown mud or paste, free from stones and sticks, and penetrated only by fine fibers. the peat is thrown up on the edge of a ditch, and after draining, is moved on a tram-way to the machine. it is there thrown upon a chain of buckets, which deliver it at the hopper above the rolls. the rolls revolve once in - / minutes and at each revolution turn out a sheet of peat, which cuts into blocks. each block has, when moist, a length of about inches, by inches of width and - / inches of thickness, and weighs on the average - / lbs. the water that is pressed out of the peat, falls within the rolls and is conducted away; it is but slightly turbid from suspended particles. the band of pressed peat is divided in one direction as it is formed, by narrow slats which are secured horizontally to the press-cloth, at about inches distance from each other. the further division of the peat is accomplished by a series of six circular saws, under which the peat is carried as it is released from the rolls, by a system of endless cords strung over rollers. these cords run parallel until the peat passes the saws; thenceforth they radiate, so that the peat-blocks are separated somewhat from each other. they are carried on until they reach a roll, over which they are delivered upon drying lattices. the latter move regularly under the roll; the peats arrange themselves upon them edgewise, one leaning against the other, so as to admit of free circulation of air. the lattices are loaded upon cars, and moved on a tram-way to the drying ground, where they are set up in frames. the peat-cake separates well from the press-cloths; but the pores of the latter become somewhat choked by fine particles that penetrate them. they are therefore washed at each revolution by passing before a pipe from which issue, against them, a number of jets of water under high pressure. the blocks, after leaving the machine, are soft, and require or days to become air-dry. when dry they are dense and of good quality, but not better than the same raw material yields by simple moulding. the capacity of the rolls, which easily turn out , peats in hours, greatly exceeds at present that of the drying arrangements, and for this reason the works are not, as yet, remunerative. the rolls are, in reality, a simple forming machine. the pressure they exert on the peat, is but inconsiderable, owing to its soft pasty character; and since the pair of rolls costs $ and can only be worked to months, this method must be regarded rather as an ingenious and instructive essay in the art of making peat-fuel, than as a practical success. the persevering efforts of the inventor may yet overcome all difficulties and prove the complete efficacy of the method. it is especially important, that blocks of greater thickness should be produced, since those now made, pack together too closely in the fire. _neustadt method._--at neustadt, in hanover, a loose-textured fibrous peat was prepared for metallurgical use in , by passing through iron rolls of ordinary construction. the peat was thereby reduced two-thirds in bulk, burned more regularly, gave a coherent coal, and withstood carriage better. the peat was, however, first cut into sods of regular size, and these were fed into the rollers by boys. b. _pressing air-dried peat._ some kinds of peat, when in the air-dry and pulverized state, yield by great pressure very firm, excellent, and economical fuel. _lithuanian process._--in lithuania, according to leo,[ ] the following method is extensively adopted. the bog is drained, the surface moss or grass-turf and roots are removed, and then the peat is broken up by a simple spade-plow, in furrows inches wide and or inches deep. the broken peat is repeatedly traversed with wooden harrows, and is thus pulverized and dried. when suitably dry, it is carried to a magazine, where it is rammed into moulds by a simple stamp of two hundred pounds weight. the broken peat is reduced to two-fifths its first bulk, and the blocks thus formed are so hard, as to admit of cutting with a saw or ax without fracture. they require no further drying, are of a deep-brown color, with lustrous surfaces, and their preparation may go on in winter with the stock of broken peat, which is accumulated in the favorable weather of summer. in this manufacture there is no waste of material. the peat is dry enough for pressing when, after forming in the hands to a ball, it will not firmly retain this shape, but on being let fall to the ground, breaks to powder. the entire cost of preparing peats for use, or market, was thalers, or $ . . thirty peats, or "stones" as they are called from their hardness, have the bulk of two cubic feet, and weigh lbs. the cost of preparing a hundred weight, was therefore, (in ,) four silver-groschen, or about cents. the stamp is of simple construction, somewhat like a pile driver, the mould and face of the ram being made of cast iron. the above process is not applicable to _fibrous peat_. c. _pressing hot-dried peat._ the two methods to be next described, are similar to the last mentioned, save that the peat is _hot-pressed_. _gwynne's method._--in , gwynne of london, patented machinery and a method for condensing peat for fuel. his process consisted, first, in rapidly drying and pulverizing the fresh peat by a centrifugal machine, or by passing between rollers, and subsequent exposure to heat in revolving cylinders; and, second, in compressing the dry peat-powder in a powerful press at a high temperature, about ° f. by this heat it is claimed, that the peat is not only thoroughly dried, but is likewise partially decomposed; _bituminous matters being developed, which cement the particles to a hard dense mass_. gwynne's machinery was expensive and complicated, and although an excellent fuel was produced, the process appears not to have been carried put on the large scale with pecuniary success. a specimen of so-called "peat coal" in the author's possession, made in massachusetts some years ago, under gwynne's patent, appears to consist of pulverized peat, prepared as above described; but contains an admixture of rosin. it must have been an excellent fuel, but could not at that time compete with coal in this country. _exter's method._[ ] [illustration: fig. .--exter's drying oven.] [illustration: fig. .--exter's drying oven.] in , exter, of bavaria, carried into operation on an extensive scale, a plan of preparing peat-fuel in some respects not unlike the last mentioned method. exter's works, belonging to the bavarian government, are on the haspelmoor, situated between augsburg and munich. according to ruehlmann, who examined them at the command of the hanoverian government in , the method is as follows:-- . the bog is laid dry by drains and the surface is cleared of bushes, roots, and grass-turf, down to good peat. . the peat is broken up superficially to the depth of about one inch, by a gang of three plows, propelled by a portable steam engine. . the peat is further pulverized by a harrow, drawn by a yoke of oxen. . in two or three days after harrowing, the peat is turned by an implement like our cultivator, this process being repeated at suitable intervals. . the fine and air-dry peat is gathered together by scrapers, and loaded into wagons; then drawn by rope connected with the engine, to the press or magazine. . if needful, the peat, thus collected, is further pulverized by passing it through toothed rollers. . the fine peat is now introduced into a complicated drying oven, see figures and . it falls through the opening _t_, and is moved by means of the spirals along the horizontal floors _o_, _o_, falling from one to another until it emerges at _q_. the floors, _o_, _o_, are made by wide and thin iron chambers, through which passes waste steam from an engine. the oven is heated further by hot air, which circulates through the canals _k_, _k_. the peat occupies about one hour in its passage through the oven and falls from _q_, into the press, having a temperature of from ° to °fahrenheit. the press employed at staltach is essentially the same as that now used at the kolbermoor, and figured on p. . it is a powerful eccentric of simple construction, and turns out continuously finished peats per minute. these occupy about one-fourth the space of the peat before pressing, the cubic foot weighing about lbs. the peats are inches long, inches wide, and one half to three quarters of an inch thick, each weighing three quarters of a pound. three presses furnish annually , cwt. of condensed peat, which is used exclusively for firing locomotives. its specific gravity is . , and its quality as fuel is excellent. ruehlmann estimated its cost, at haspelmoor in , at - / kreuzers, or a little more than cents per cwt., and calculated that by adopting certain obvious improvements, and substituting steam power for the labor of men and cattle, the cost might be reduced to - / kreuzers, or a little more than cents per cwt. exter's method has been adopted with some modifications at kolbermoor, near munich, in bavaria, at miskolz, in hungary, and also at the neustadt smelting works, in hanover. at the latter place, however, it appears to have been abandoned for the reasons that it could be applied only to the better kinds of peat; and the expense was there so great, that the finished article could not compete with other fuel in the hanoverian markets. details of the mechanical arrangements at present employed on the kolbermoor, are as follows: after the bog is drained, and the surface cleared of dwarf pines, etc., and suitably leveled, the peat is plowed by steam. this is accomplished in a way which the annexed cut serves to illustrate. the plot to be plowed, is traversed through the middle by the railway _x_, _y_. a locomotive _a_, sets in motion an endless wire-rope, which moves upon large horizontal pulleys _o_, _o_, stationed at either border of the land. four gang plows _b_, _b_, are attached to the rope, and as the latter is set in motion, they break up the strip of peat they pass over, completely. the locomotive and the pulleys are then moved back, and the process is repeated until the whole field has been plowed. the plows are square frames, carrying six to eight shares and as many coulters. [illustration: fig. .] the press employed at kolbermoor, is shown in figs. and . the hot peat falls into the hopper, _b_, _c_. the plunger _d_, worked in the cavity _e_, by an eccentric, allows the latter to fill with peat as it is withdrawn, and by its advance compresses it into a block. the blocks _m_, once formed, by their friction in the channel _e_, oppose enough resistance to the peat to effect its compression. in order to regulate this resistance according to the varying quality of the peat, the piece of metal _g_, which hangs on a pivot at _o_, is depressed or raised, by the screw _i_, so as to contract or enlarge the channel. at each stroke of the plunger a block is formed, and when the channel _e_ is once filled, the peats fall continuously from its extremity. their dimensions are inches long, - / wide, and - / thick. [illustration: fig. .--exter's peat press.] several presses are worked by the same engine at the kolbermoor, each of which turns out daily to cwt. of peats, which, in , were sold at kreuzers ( cents), per cwt. [illustration: fig. .--exter's peat press.] c. hodgson has patented in great britain a compressing-ram similar to exter's, and works were put up at derrylea, in ireland, some years ago, in which exter's process of manufacturing peat fuel appears to have been adopted. _elsberg's process._ dr. louis elsberg, of new york city, has invented a modification of exter's method, which appears to be of great importance. his experimental machine, which is in operation near belleville, n. j., consists of a cylindrical pug-mill, in which the peat, air-dried as in exter's method, is further broken, and at the same time is subjected to a current of steam admitted through a pipe and jacket surrounding the cylinder. the steamed peat is then condensed by a pair of presses similar to that just described, which are fed directly from the mill. in this way the complicated drying oven of exter is dispensed with. elsberg & co. are still engaged in perfecting their arrangements. some samples of their making are of very excellent quality, having a density of . to . . the pressing of air-dry peat only succeeds when it is made warm, and is, at the same time, moist. in exter's original process the peat is considerably dried in the ovens, but on leaving them, is so moist as to bedew the hand that is immersed in it. it is, in fact, steamed by the vaporization of its own water. in elsberg's process, the air-dry peat is not further desiccated, but is made moist and warm by the admission of hot steam. the latter method is the more ready and doubtless the more economical of the two. whether the former gives a dryer product or not, the author cannot decide. elsberg's peat occurs in cylindrical cakes inches broad, and one inch in thickness. the cakes are somewhat cracked upon the edges, as if by contraction, in drying. when wet, the surface of the cakes swells up, and exfoliates as far as the water has penetrated. in the fire, a similar breaking away of the surface takes place, and when coked, the coal is but moderately coherent. the reasons why steamed peat admits of solidification by pressure, are simply that the air, ordinarily adhering to the fibres and particles, is removed, and the fibres themselves become softened and more plastic, so that pressure brings them into intimate contact. the idea that the heat develops bituminous matters, or fuses the resins which exist in peat, and that these cement the particles, does not harmonize with the fact that the peat, thus condensed, flakes to pieces by a short immersion in water. the great advantage of exter's and elsberg's method consists in avoiding what most of the others require, viz.: the expensive transportation and handling of fresh peat, which contains to _per cent._ of water, and the rapid removal of this excess of water before the manufacture. in the other methods the surplus water must be slowly removed during or after condensation. again, enough peat may be air-dried and stored during summer weather, to supply a machine with work during the whole year. its disadvantages are, that it requires a large outlay of capital and great expenditure of mechanical force. its product is, moreover, not adapted for coking. b.--_condensation without pressure._ the methods of condensing peat, that remain to be described, are based upon radically different principles from those already noticed. in these, little or no pressure is employed in the operations; but advantage is taken of the important fact that when wet or moist peat is ground, cut or in any way reduced to a pulpy or pasty consistence, with destruction of the elastic fibres, it will, on drying, shrink together to a coherent mass, that may acquire a density and toughness much greater than it is possible to obtain by any amount of mere pressure. the various processes that remain to notice are essentially reducible to two types, of which the french method, invented by challeton, and the german, invented it appears by weber, are the original representatives. the former method is only applicable to earthy, well-decomposed peat, containing little fibre. the latter was originally applied to fibrous moss-peat, but has since been adapted to all kinds. other inventors, english, german, and american, have modified these methods in their details, or in the construction of the requisite machinery, rendering them more perfect in their execution and perhaps more profitable in their results; but, as regards the essential principles of production, or the quality of product, no advance appears to have been made beyond the original inventors. a. _condensation of earthy peat._ _challeton's method_ consists essentially in destroying the fibres, and reducing the peat by cutting and grinding with water to a pulp; then slowly removing the liquid, until the peat dries away to a hard coherent mass. it provides also for the purification of the peat from earthy matters. it is, in many respects, an imitation of the old dutch and irish mode of making "hand peat" (_baggertorf_), and is very like the paper manufacture in its operations. challeton's works, situated near paris, at mennecy, near montanges, were visited in by a commission of the agricultural society of holstein, consisting of drs. meyn and luetkens, and also by dr. ruehlmann, in the interest of the hanoverian government. from their account[ ] the following statements are derived. the peat at mennecy comes from the decay of grasses, is black, well decomposed, and occasionally intermingled with shells and sand. the moor is traversed by canals, which serve for the transport of the excavated peat in boats. the peat, when brought to the manufactory, is emptied into a cistern, which, by communicating with the adjacent canal, maintains a constant level of water. from this cistern the peat is carried up by a chain of buckets and emptied into a hopper, where it is caught by toothed cylinders in rapid revolution, and cut or torn to pieces. thence it passes into a chamber where the fine parts are separated from unbroken roots and fibres by revolving brushes, which force the former through small holes in the walls of the chamber, while the latter are swept out through a larger passage. the pulverized peat finally falls into a cistern, in which it is agitated by revolving arms. a stream of water constantly enters this vessel from beneath, while a chain of buckets as rapidly carries off the peat pulp. all sand, shells, and other heavy matters, remain at the bottom of this cistern. the peat pulp, thus purified, flows through wooden troughs into a series of basins, in which the peat is formed and dried. these basins are made upon the ground by putting up a square frame (of boards on edge,) about one foot deep, and placing at the bottom old matting or a layer of flags or reeds. each basin is about a rod square, and of them are employed. they are filled with the peat pulp to the top. in a few days the water either filters away into the ground, or evaporates, so that a soft stratum of peat, about inches in thickness, remains. before it begins to crack from drying, it is divided into blocks, by pressing into it a light trellis-like framework, having thin partitions that serve to indent the peat in lines corresponding to the intended divisions. on further drying, the mass separates into blocks at the lines thus impressed, and in a few days, they are ready to remove and arrange for further desiccation. the finished peats from challeton's works, as well as those made by the same method near neuchatel, switzerland, by the messrs. roy, were of excellent quality, and in the opinion of the commission from holstein, the method is admirably adapted for the purification and concentration of the heavy kinds of peat. in holstein, a french company constructed, and in worked successfully a portable machine for preparing peat on this plan, but were shortly restrained by legal proceedings. of their later operations we have no information. no data are at hand regarding the cost of producing fuel by challeton's machinery. it is believed, however, that his own works were unremunerative, and several manufactories on his pattern, erected in germany, have likewise proved unprofitable. the principle is, however, a good one, though his machinery is only applicable to earthy or pitchy, and not to very fibrous peat. it has been elsewhere applied with satisfactory results. _simplified machinery_ for applying challeton's method is in operation at langenberg, near stettin, in prussia.[ ] the moss-meadows along the river oder, near which langenberg is situated, are but a foot or so higher at the surface than the medium level of this river, and are subject to frequent and sudden inundations, so that draining and partial drying of the peat are out of the question. the character of the peat is unadapted to cutting by hand, since portions of it are pitchy and crumble too easily to form good sods; and others, usually the lower layers, at a depth of seven feet or more, are made up to a considerable extent of quite firm reeds and flags, having the consistence of half decayed straw. the earthy peat is manufactured after challeton's method. it is raised with a steam dredger of horse power, and emptied into flat boats, seven in number, which are drawn to the works by an endless rope operated by horse power. the works themselves are situated on a small sand hill in the middle of the moor, and communicate by canal with the dredger and with the drying ground. a chain of buckets, working in a frame feet long, attached by a horizontal hinge to the top of the machine house, reaches over the dock where the boats haul up, into the rear end of the latter; and, as the buckets begin to raise the peat, the boat itself is moved under the frame towards the house, until, with a man's assistance, its entire load is taken up. the contents of one boat are six square yards, with a depth of one foot, and a boat is emptied in minutes time. forty to forty-four boatloads are thus passed into the pulverizing machine daily, by two chains of buckets. the peat-mud falls from the buckets into a large wooden trough, which branches into two channels, conducting to two large tubs standing side by side. these tubs are feet in diameter and feet deep, and are made of -inch plank. within each tub is placed concentrically a cylindrical sieve, or colander, feet in diameter and feet high, made of / round iron, and it is within this that the peat is emptied. the peat is stirred and forced through the meshes of the sieve by four arms of a shaft that revolves times per minute, the arms carrying at their extremities stiff vertical brooms, which rub the inside of the sieve. in these four tubs the peat is pulverized under addition of water; the fine parts pass the sieves, while the latter retain the coarse fibres, roots, etc. the peat-mud flows from the tubs into mills, made like a flour mill, but the "stones" constructed of hard wood. the "stones" have a diameter of feet inches; the lower is inches; the upper inches thick. the pressure of the upper "stone" is regulated by adjusting the level of the discharging channel, so that the "stone" may be more or less buoyed, or even fully floated by the water with which it is surrounded. the peat-substance, which is thus finely ground, gathers from the four mills into a common reservoir whence it is lifted by a centrifugal pump into a trough, which distributes it over the drying ground. the drying ground consists of the surface formed by grading the sand hill, on which the works are built, and includes about english acres. this is divided into small plots, each of which is enclosed on three sides with a wall of earth, and on the fourth side by boards set on edge. each plot is surrounded by a ditch to carry off water, and by means of portable troughs, the peat is let on from the main channel. the peat-slime is run into these beds to the depth of to inches, an acre being covered daily. after to days, according to the weather, the peat has lost so much water, which, rapidly soaks off through the sand, that its surface begins to crack. it is then thoroughly trodden by men, shod with boards inches by inches, and after to days more, it is cut with sharp spades into sods. the peats are dried in the usual manner. the works at langenberg yielded, in , as the result of the operations of days of hours each, , cwt. of marketable peat. it is chiefly employed for metallurgical purposes, and sells at - / silver-groschen, or nearly cents per cwt. the specific gravity of the peat ranges from . to . . _roberts' process._ in this country attempts have been made to apply challeton's method. in , mr. s. roberts, of pekin, n. y., erected machinery at that place, which was described in the "buffalo express," of nov. , , as follows:-- "in outward form, the machine was like a small frame house on wheels, supposing the smoke-stack to be a chimney. the engine and boiler are of locomotive style; the engine being of thirteen horse power. the principal features of the machine are a revolving elevator and a conveyer. the elevator is seventy-five feet long, and runs from the top of the machine to the ground, where the peat is dug up, placed on the elevator, carried to the top of the machine, and dropped into a revolving wheel that cuts it up; separates from it all the coarse particles, bits of sticks, stones, etc.; and throws them to one side. the peat is next dropped into a box below, where water is passed in, sufficient to bring it to the consistency of mortar. by means of a slide under the control of the engineer, it is next sent to the rear of the machine, where the conveyer, one hundred feet long, takes it, and carries it within two rods of the end; at which point the peat begins to drop through to the ground to the depth of about four or five inches. when sufficient has passed through to cover the ground to the end of the conveyer,--two rods,--the conveyer is swung around about two feet, and the same process gone through, as fast as the ground under the elevator, for the distance of two rods in length and two feet in width gets covered, the elevator being moved. at each swing of the elevator, the peat just spread is cut into blocks (soft ones, however) by knives attached to the elevator. it generally takes from three to four weeks before it is ready for use. it has to lie a week before it is touched, after the knives pass through it; when it is turned over, and allowed to lie another week. it has then to be taken up, and put in a shed, and within a week or ten days can be used, although it is better to let it remain a little longer time. the machine can spread the peat over eighteen square rods of ground--taking out one square rod of peat--without being moved. after the eighteen rods are covered, the machine is moved two rods ahead, enabling it to again spread a semicircular space of some thirty-two feet in width by eighteen rods in length. the same power, which drives the engine, moves the machine. it is estimated by mr. roberts, that, by the use of this machine, from twenty to thirty tons of peat can be turned out in a day." mr. roberts informs us that he is making (april ,) some modifications of his machinery. he employs a revolving digger to take up the peat from the bed, and carry it to the machine. at the time of going to press, we do not learn whether he regards his experiments as leading to a satisfactory conclusion, or otherwise. _siemens' method._ siemens, professor of technology, in the agricultural academy, at hohenheim, successfully applied the following mode of preparing peat for the beet sugar manufactory at boeblingen, near hohenheim, in the year . much of the peat there is simply cut and dried in the usual manner. there is great waste, however, in this process, owing to the frequent occurrence of shells and clay, which destroy the coherence of the peat. besides, a large quantity of material accumulates in the colder months, from the ditches which are then dug, that cannot be worked in the usual manner at that time of the year. it was to economize this otherwise useless material that the following process was devised, after a failure to employ challeton's method with profit. in the first place, the peat was dumped into a boarded cistern, where it was soaked and worked with water, until it could be raised by a chain of buckets into the pulverizer. the pulverization of the peat was next effected by passing it through a machine invented by siemens, for pulping potatoes and beets. this machine, (the same we suppose as that described and figured in otto's landwirthschaftliche gewerbe), perfectly breaks up and grates the peat to a fine pulp, delivers it in the consistency of mortar into the moulds, made of wooden frames, with divisions to form the peats. the peat-paste is plastered by hand into these moulds, which are immediately emptied to fill again, while the blocks are carried away to the drying ground where they are cured in the ordinary style without cover. in this simple manner men were able to make , peats daily, which, on drying, were considerably denser and harder than the cut peat. the peat thus prepared, cost about one-third more than the cut peat. siemens reckoned, this greater cost would be covered by its better heating effect, and its ability to withstand transportation without waste by crumbling. b. _condensation of fibrous peat._ _weber's method._ at staltach, in southern bavaria, weber has established an extensive peat works, of which vogel has given a circumstantial account.[ ] the peat at staltach is very light and fibrous, but remarkably free from mineral matters, containing less than _per cent._ of ash in the perfectly dry substance. the moor is large, ( acres), and the peat is from to feet in depth. the preparation consists in converting the fresh peat into pulp or paste, forming it into moulds and drying it; at first by exposure to the air at ordinary temperature, and finally, by artificial heat, in a drying house constructed for the purpose. the peat is cut out by a gang of men, in large masses, cleared of coarse roots and sticks, and pushed on tram wagons to the works, which, are situated lower than the surface of the bog. arrived at the works, the peat is carried upon an inclined endless apron, up to a platform feet high, where a workman pushes it into the pulverizing mill, the construction of which is seen from the accompanying cut. the vertical shaft _b_ is armed with sickle-shaped knives, _d_, which revolve between and cut contrary to similar knives _c_, fixed to the interior of the vessel. the latter is made of iron, is - / feet high, feet across at top and - / feet wide at the bottom. from the base of the machine at _g_, the perfectly pulverized or minced peat issues as a stiff paste. if the peat is dry, a little water is added. vogel found the fresh peat to contain _per cent._, of water, the pulp _per cent._ weber's machine, operated by an engine of horse power, working usually to half its capacity only, reduced cubic feet of peat per hour, to the proper consistency for moulding. [illustration: fig. .--weber's peat mill.] three modes of forming the paste into blocks have been practiced. one was in imitation of that employed with mud-peat. the paste was carried by railway to sheds, where it was filled by hand into moulds inches by - / by - / inches, and put upon frames to dry. these sheds occupied together , square feet, and contained at once , peats. the peats remained here to days or more, according to the weather, when they were either removed to the drying house, or piled in large stacks to dry slowly out-of-doors. the sheds could be filled and emptied at least times each season, and since they protected from light frosts, the season began in april and lasted until november. the second mode of forming the peat was to run off the pulp into large and deep pits, excavated in the ground, and provided with drains for carrying off water. the water soaked away into the soil, and in a few weeks of good weather, the peat was stiff enough to cut out into blocks by the spade, having lost to _per cent._ of its water, and _per cent._ of its bulk. the blocks were removed to the drying sheds, and set upon edge in the spaces left by the shrinking of the peats made by the other method. the working of the peat for the pits could go on, except in the coldest weather, as a slight covering usually sufficed to protect them from frost. both of these methods have been given up as too expensive, and are replaced, at present, by the following: in the third method the peat-mass falls from the mill into a hopper, which directs it between the rolls _a b_ of fig. , (see next page). the roll _a_ has a series of boxes on its periphery _m m_, with movable bottoms which serve as moulds. the peat is carried into these boxes by the rolls _c c_. the iron projections _n n_ of the large roll _b_, which work cog-like into the boxes, compress the peat gently and, at last, the eccentric p acting upon the pin _z_, forces up the movable bottom of the box and throws out the peat-block upon an endless band of cloth, which carries it to the drying place. the peats which are dried at first under cover and therefore slowly, shrink more evenly and to a greater extent than those which are allowed to dry rapidly. the latter become cracked upon the surface and have cavities internally, which the former do not. this fact is of great importance for the density of the peat, for its usefulness in producing intense heat, and its power to withstand carriage. [illustration: fig. --weber's peat moulding machine.] the _complete drying_ is, on the other hand, by this method, a much slower process, since the dense, fissureless exterior of the peats hinders the escape of water from within. it requires, in fact, several months of ordinary drying for the removal of the greater share of the water, and at the expiration of this time they are still often moist in the interior. artificial drying is therefore employed to produce the most compact, driest, and best fuel. weber's _drying house_ is feet long and feet wide. four large flues traverse the whole length of it, and are heated with the pine roots and stumps which abound in the moor. these flues are enclosed in brick-work, leaving a narrow space for the passage of air from without, which is heated by the flues, and is discharged at various openings in the brick-work into the house itself, where the peat is arranged on frames. the warm air being light, ascends through the peat, charges itself with moisture, thereby becomes heavier and falls to the floor, whence it is drawn off by flues of sheet zinc that pass up through the roof. this house holds at once , peats, which are heated to ° to ° f., and require to days for drying. the effect of the hot air upon the peat is, in the first place, to soften and cause it to swell; it, however, shortly begins to shrink again and dries away to masses of great solidity. it becomes almost horny in its character, can be broken only by a heavy blow, and endures the roughest handling without detriment. its quality as fuel is correspondingly excellent. the effects of the mechanical treatment and drying on the staltach peat, are seen from the subjoined figures: _lbs. _specific per cubic _per cent of gravity._ foot._ water._ peat, raised and dried in usual way, . to machine-worked and hot-dried . vogel estimates the cost of peat made by weber's method at kreuzers per (bavarian) hundred weight, while that of ordinary peat is - / kreuzers. schroeder, in his comparison of machine-wrought and ordinary peat, demonstrates that the latter can be produced much cheaper than was customary in bavaria, in , by a better system of labor. weber's method was adopted with some improvements in an extensive works built in , by the government of baden, at willaringen, for the purpose of raising as much fuel as possible, during the course of a lease that expired with the year . [illustration: fig. .--geysser's peat machine.] _gysser's method._[ ]--rudolph gysser, of freiburg, who was charged with the erection of the works at willaringen just alluded to, invented a portable hand-machine on the general plan of weber, but with important improvements; and likewise omitted and varied some details of the manufacture, bringing it within the reach of parties of small means. in the accompanying cuts, (figs. , , and ), are given an elevation of gysser's machine, together with a bird's-eye view and vertical section of the interior mechanism. [illustration: fig. .] [illustration: fig. .] it consists of a cast iron funnel _c d i_ of the elevation, (fig. ), having above a sheet iron hopper _a b_ to receive the peat, and within a series of six knives fastened in a spiral, and curving outwards and downwards, (figs. and ); another series of three similar knives is affixed to a vertical shaft, which is geared to a crank and turned by a man standing on the platform _j k_; these revolving knives curve upwards and cut between and in a direction contrary to the fixed knives; below the knives, and affixed to the shaft a spiral plate of iron and a scraper _m_, (fig. ), serve to force the peat, which has been at once minced and carried downwards by the knives, as a somewhat compressed mass through the lateral opening at the bottom of the funnel, whence it issues as a continuous hollow cylinder like drain-tile, having a diameter of four inches. the iron cone _i_, held in the axis of the opening by the thin and sharp-edged support _g h_, forms the bore of the tube of peat as it issues. two men operate the machine; one turning the crank, which, by suitable gearing, works the shaft, and the other digging and throwing in the peat. the mass, as it issues from the machine, is received by two boys alternately, who hold below the opening a semi-cylindrical tin-plate shovel, (fig. ), of the width and length of the required peats, and break or rather wipe them off, when they reach the length of inches. [illustration: fig. .] [illustration: fig. .] the formed peats are dried in light, cheap and portable houses, fig. , each of which consists of six rectangular frames supported one above another, and covered by a light roof. the frames, fig. , have square posts at each corner like a bedstead, and are made by nailing light strips to these posts. the tops of these posts are obtusely beveled to an edge, and at the bottom they are notched to correspond. the direction of the edges and of the notches in two diagonally opposite posts, is at right angles to that of the other two. by this construction the frames, being of the same size, when placed above each other, fit together by the edges and notches of their posts into a structure that cannot be readily overturned. the upper frame has a light shingled roof, which completes the house. each frame has transverse slats, cast in plaster of paris, in number, which support the peats. the latter being tubular, dry more readily, uniformly, and to a denser consistence than they could otherwise. the machine being readily set up where the peat is excavated, the labor of transporting the fresh and water-soaked material is greatly reduced. the drying-frames are built up into houses as fast as they are filled from the machine. they can be set up anywhere without difficulty, require no leveling of the ground, and, once filled, no labor in turning or stacking the peats is necessary; while the latter are insured against damage from rain. these advantages, gysser claims, more than cover their cost. [illustration: fig. .] the daily production of a machine operated by two men with the assistance of one or two boys, is to peats, which, on drying, have - / to inches of length, and - / in diameter, and weigh, on the average, one pound each. c.--_condensation of peat of all kinds._--_weber's method with modified machinery._ [illustration: fig. .--schlickeysen's peat mill.] _schlickeysen's machine._[ ]--this machine has been in use in germany since , in the preparation of peat. it appears to have been originally constructed for the working and moulding of clay for making bricks. the principle of its operation is identical with that of weber's process. the peat is finely pulverized, worked into a homogenous mass, and moulded into suitable forms. like gysser's machine, it forces the peat under some pressure through a nozzle, or, in the larger kinds through several nozzles, whence it issues in a continuous block or pipe that is cut off in proper lengths, either by hand or by mechanism it consists of a vertical cylinder, through the axis of which revolves a shaft, whereon are fastened the blades, whose edges cut and whose winding figure forces down the peat. the blades are arranged nearly, but not exactly, in a true spiral; the effect is therefore that they act unequally upon the mass, and thus mix and divide it more perfectly. no blades or projections are affixed to the interior of the cylinder. above, where the peat enters into a flaring hopper, is a scraper, that prevents adhesion to the sides and gives downward propulsion to the peat. the blades are, by this construction, very strong, and not liable to injury from small stones or roots, and effectually reduce the toughest and most compact peat. furthermore, addition of water is not only unnecessary in any case, but the peat may be advantageously air-dried to a considerable extent before it enters the machine. wet peat is, indeed, worked with less expenditure of power; but the moulded peats are then so soft as to require much care in the handling, and must be spread out in single courses, as they will not bear to be placed one upon another. peat, that is somewhat dry, though requiring more power to work, leaves the machine in blocks that can be piled up on edge and upon each other, six or eight high, without difficulty, and require, of course, less time for curing. the cut, (fig. ), represents one of schlickeysen's portable peat-mills, with elevator for feeding, from which an idea of the pulverizing arrangements may be gathered. in livonia, near pernan, according to leo, two of schlickeysen's machines, no. , were put in operation upon a purely fibrous peat. they were driven by an engine of horse-power. the peat was plowed, once harrowed, then carted directly to the hopper of the machine. these two machines, with men and horses, produced daily , peats = cubic feet. cubic feet of these peats were equal in heating effect to cubic feet of fir-wood, and cost but two-thirds as much. the peats were extremely hard, and dried in a few days sufficiently for use. in , five large schlickeysen machines were in operation at one establishment at st. miskolz, in hungary. the smaller sizes of schlickeysen's machine are easily-portable, and adapted for horse or hand-power. _leavitt's peat-condensing and moulding mill._[ ]--in this country, mr. t. h. leavitt, of boston, has patented machinery, which is in operation at east lexington, mass., at the works of the boston peat company. the process is essentially identical with that of weber, the hot-drying omitted. the fresh peat is pulverized or cut fine, moulded into blocks, and dried on light frames in the open air. the results claimed by mr. leavitt, indicate, that his machine is very efficacious. it consists, principally, of a strong box or cistern, three feet in diameter, and six feet high, the exterior of which, with its gearing, is shown in figure . the mill is adapted to be driven by a four horse-power engine. "the upper portion of the box is divided by a series of horizontal partitions, the upper ones being open latticework, and the lower ones perforated with numerous holes. the upright shaft, which rotates in the centre of the box, carries a series of arms or blades, extending alternately on opposite sides, and as these revolve, they cut the peat, and force it through the openings in the diaphragms. the lower portion of the box, in place of complete partitions, has a series of corrugated shelves extending alternately from opposite sides, and the peat is pressed and scraped from these by a series of arms adapted to the work. by this series of severe operations the air-bubbles are expelled from the peat, and it is reduced to a homogeneous paste. when it arrives at the bottom of the box, it is still further compressed by the converging sides of the hopper, and it is received in light moulds which are carried on an endless belt." mr. leavitt has patented the use of powdered peat for the purpose of preventing the prepared peat from adhering to the moulds. [illustration: fig. .--leavitt's peat mill.] this mill, it is asserted, will condense tons of crude peat daily, which, at lexington, is estimated to yield to tons of dry merchantable fuel. the cost of producing the latter is asserted to be less than $ . per ton; while its present value, in boston, is $ per ton. it requires seven men, three boys, and two horses to dig, cart, mill, and spread the peat. the machine costs $ , the needful buildings, engine, etc., from $ to $ . the samples of peat, manufactured by this machine, are of excellent quality. the drying in the open air is said to proceed with great rapidity, eight or ten days being ordinarily sufficient in the summer season. the dry peat, at lexington, occupies one-fourth the bulk, and has one-fourth to one-third the weight of the raw material; the latter, as we gather, being by no means saturated with water, but well drained, and considerably dry, before milling. _ashcroft & betteley's machinery._ the american peat company, of boston, are the owners of five patents, taken out by messrs. ashcroft & betteley, for peat machinery. they claim to "make fuel equal to the best english cannel coal," and really do make a very good peat, though with a rather complicated apparatus. the following statement is derived from the circular issued by the company. the machinery consists of the following parts:-- _first._--triturating machine-- inches diameter, feet inches high, with arms both on the inside of this cylinder and on the upright revolving shaft. in the bottom of the cylinder or tub a large slide gate is fitted to work with a lever, so that the peat may be discharged, at pleasure, into the combing machine, which is placed directly under this triturator. _second._--combing machine--semi-circular vessel feet long and feet inches in diameter. inside, a shaft is placed, which is provided with fingers, placed one inch apart; the fingers to be inches long, so as to reach within inches of the bottom and sides of this vessel. another shaft, of the same size and dimensions, is placed at an angle of °, inches from the first shaft, with arms of the same dimensions placed upon this shaft, with the same spaces, and so placed that this set of arms pass between the first set, both shafts revolving in the same direction; the second shaft mentioned being driven at double the speed of the first. at the bottom of this combing machine is to be fixed a gate, to be operated by a lever, to deliver, at pleasure, the cleansed peat into the manipulator or kneading machine. _third._--manipulator.--a tube of iron feet long and inches diameter, fitted with a shaft, with flanges upon it, to gain inches in each revolution. _fourth._--conveyor.--this conveyor, to be made with two endless chains and buckets of iron, with a driving shaft. the hopper, to receive the peat when first taken from the bog, to be placed below the surface of the ground, so that the top edge of the hopper may be level with the surface, that the peat may be dumped from the car by which it is taken from the bog, and carried to the hopper without hand labor; and this conveyor to be so arranged that the peat will be delivered into the triturator without hand labor. _fifth._--conveyor.--another conveyor, precisely like the one above described, is to be placed so as to convey the peat from the manipulator into the tank without hand labor. _sixth._--tank.--a tank feet high and feet in diameter; the bottom of this tank is made sloping towards the sides, at an angle of °, and is covered with sole tile or drain tile, and the entire inside of this tank is also ribbed with these tile; the ends of these pipes of tile being left open, so that the water which percolates through the pores of the tile, by the pressure of the column of peat, will pass out at the bottom, through the false floor of the tank into the drain, and the solid peat is retained in the tank. a worm is fixed in the bottom of this tank, which is driven by machinery, which forces out the peat in the form of brick, which are cut to any length, and stacked up in sheds, for fuel, after it is fully dried by the air. [illustration: fig. .--versmann's peat pulverizer.] _versmann's machine_[ ]--this machine, see fig. , was invented by a german engineer, in london, and was patented there in sept., . it consists of a funnel or hollow cone _b_, of boiler-plate, from one to two feet in diameter at top, and perforated with to small holes per square foot of surface, within which rapidly revolves an iron cone _a_, carrying on its circumference two spiral knives. the peat thrown in at the top of the funnel is carried down by the knives, and at once cut or broken and forced in a state of fine division through the holes of the funnel, as through a colander. the fine peat collects on the inclined bottom of the chamber _d_, whence it is carried by means of archimedean screws to a moulding machine. the coarse stuff that escapes pulverization falls through _e_ into the cavity _c_. it may be employed as fuel for the engine, or again put through the machine. this machine effects a more perfect pulverization of the peat, than any other hitherto described. this extreme division is, however, unnecessary to the perfection of the product, and is secured at great expense of power. through the opening at the bottom of the funnel, much unpulverized peat finds its way, which must be continually returned to the machine. again, stones, entering the funnel, are likely to break or damage the spiral knives, which bear close to the walls of the funnel. the pulverized peat must be moulded by hand, or by a separate instrument. _buckland's machine_[ ] is identical in principle with versmann's, and in construction differs simply in the fact of the interior cone having spiral grooves instead of spiral knives. this gives greater simplicity and durability to the machine. it appears, however, to require too much power to work it, and can hardly equal other machines in the quantity of product it will deliver for a given expenditure. the ground peat yielded by it, must be moulded by hand, or by other machinery. this machine, we understand, has been tried near boston, and abandoned as uneconomical. the machines we have described are by no means all that have been proposed and patented. they include, however, so the author believes, all that have been put into actual operation, at the date of this writing, or that present important peculiarities of construction. the account that has been given of them will serve to illustrate what mechanism has accomplished hitherto in the manufacture of peat-fuel, and may save the talent of the american inventor from wasting itself on what is already in use, or having been tried, has been found wanting. at present, very considerable attention is devoted to the subject. scarcely a week passes without placing one or more peat-mill patents on record. in this treatise our business is with what has been before the public in a more or less practical way, and it would, therefore, be useless to copy the specifications of new, and for the most part untried patents, which can be found in the files of our mechanical journals. . _artificial drying of peat._ as we have seen, air-dry peat contains to and may easily contain _per cent._ of water, and the best hot-made machine peat contains _per cent._ when peat is used as fuel in ordinary furnaces, this water must be evaporated, and in this process a large amount of heat is consumed, as is well understood. it is calculated, that the temperature which can be produced in perfectly burning full-dried peat, compares with that developed in the combustion of peat containing water, as follows:-- pyrometric effect of perfectly dry peat ° f. " " peat with _per cent._ of water ° " " " " " " ° " but, furthermore, moist or air-dried peat does not burn in ordinary furnaces, except with considerable waste, as is evident from the smokiness of its flame. when air-dried peat is distilled in a retort, a heavy yellow vapor escapes for some time after the distillation begins, which, obviously, contains much inflammable matter, but which is so mixed and diluted with steam that it will not burn at all, or but imperfectly. it is obvious then, that when a high temperature is to be attained, anhydrous or full-dried peat is vastly superior to that which has simply been cured in the open air. notice has already been made of weber's drying-house, the use of which is an essential part of his system of producing peat-fuel. various other arrangements have been proposed from time to time, for accomplishing the same object. it appears, however, that in most cases the anticipations regarding their economy have not been fully realized. it is hardly probable, that artificially dried peat can be employed to advantage except where waste heat is utilized in the operation. a point of the utmost importance in reference to the question of drying peat by artificial warmth is this, viz.: although the drying may be carried so far as to remove the whole of the water, and produce an absolutely dry fuel, the peat absorbs moisture from the air again on exposure; so that drying to less than _per cent._ of water is of no advantage, unless the peat is to be used immediately, or within a few days. the employment of highly dried peat is consequently practicable only for smelting-works, locomotives, and manufacturing establishments, where it may be consumed as fast as it is produced. a fact likewise to be regarded is, that artificial drying is usually inapplicable to fresh peat. the precautions needful in curing peat have already been detailed. above all, slow drying is necessary, in order that the blocks shrink uniformly, without cracking and warping in such a way as to seriously injure their solidity and usefulness. in general, peat must be air-dried to a considerable extent before it can be kiln-dried to advantage. if exposed to dry artificial heat, when comparatively moist, a hard crust is formed externally, which greatly hinders subsequent desiccation. at the same time this crust, contracting around the moist interior, becomes so rifted and broken, that the ultimate shrinkage and condensation of the mass is considerably less than it would have been had the drying proceeded more slowly. besides weber's drying oven, the fuel for firing which is derived without cost from the stumps and roots of trees that are abundant on the moor, at staltach, and which are thus conveniently disposed of, we have briefly to notice several other drying kilns with regard to all of which, however, it must be remarked, that they can only be employed with profit, by the use of waste heat, or, as at staltach, of fuel that is comparatively worthless for other purposes. [illustration: fig. .--carinthian peat drying-kiln.] the _peat kilns_ employed at lippitzbach, in carinthia, and at neustadt, in hanover, are of the kind shown in fig. . the peat with which the main chamber is filled, is heated directly by the hot gases that arise from a fire made in the fire-place at the left. these gases first enter a vault, where they intermingle and cool down somewhat; thence they ascend through the openings of the brick grating, and through the mass of peat to the top of the chamber. on their way they become charged with vapor, and falling, pass off through the chimney, as is indicated by the arrows. the draught is regulated by the damper on the top of the chimney. to manage the fire, so that on the one hand the chimney is sufficiently heated to create a draught, and on the other waste of fuel, or even ignition of the peat itself is prevented, requires some care. in _welkner's peat kiln_[ ] (fig. ) the peat, previously air-dried, is exposed to a stream of hot air, until it is completely desiccated, and the arrangement is such, that air-dried peat may be thrown in at the top, and the hot-dried fuel be removed at the bottom, continuously. in the cut, _a_ represents the section of a wooden cylinder about feet wide and - / feet deep, which surmounts a funnel of iron plate _a'_. the mouth of the funnel is closed by a door _n_; about inches above the door the pipe _b_, which conducts hot air, terminates in the ring _a a_, through the holes in which, _e e_, it is distributed into the funnel filled with peat. the air is driven in by a blower, and is heated by circulating through a system of pipes, which are disposed in the chimney of a steam boiler. from time to time a quantity of dried peat is drawn off into the wagon _d_, which runs on rails, and a similar amount of undried peat is thrown in above. according to welkner, a kiln of the dimensions stated, which cost, about $ gold, is capable of desiccating daily ten tons of peat with _per cent._ of water, using thereby cubic feet of air of a temperature of ° f. when the air is heated by a fire kept up exclusively for that purpose, _per cent._ of the dried peat, or its equivalent, is consumed in the operation. at the alexis smelting works, near lingen, in hanover, this peat kiln furnishes about half the fuel for a high furnace, in which bog iron ore is smelted. the drying costs but little, since half the requisite heat is obtained from the waste heat of the furnace itself. [illustration: fig. .--welkner's peat drying kiln.] the advantages of this drying kiln are, that it is cheap in construction and working; dries gradually and uniformly; occupies little ground, and runs without intermission. other drying ovens are described in knapp's _lehrbuch_ der _chemischen technologie_, . aufl. bd. , theil , pp. - ; _jahrbuch der bergakademien schemnitz_ und _leoben_, , p. , , p. ; wagner's _jahresbericht der chemischen technologie_, , p. ; zerrenner's _metallurgische gasfeuerung in oesterreich_; tunner's _stabeisen- und stahlbereitung_, . auflage, bd. i, pp. - . . _peat coal, or coke._ when peat is charred, it yields a coal or coke which, being richer in carbon, is capable of giving an intenser heat than peat itself, in the same way that charcoal emits an intenser heat in its combustion than the wood from which it is made. peat coal has been and is employed to some extent in metallurgical processes, as a substitute for charcoal, and when properly prepared from good peat, is in no way inferior to the latter; is, in fact, better. it is only, however, from peat which naturally dries to a hard and dense consistency, or which has been solidified on the principles of challeton's and weber's methods, that a coal can be made possessing the firmness necessary for furnace use. fibrous peat, or that condensed by pressure, as in exter's, elsberg's, and the lithuanian process, yields by coking or charring, a friable coal comparatively unsuited for heating purposes. a peat which is dense as the result of proper mechanical treatment and slow drying, yields a very homogeneous and compact coal, superior to any wood charcoal, the best qualities weighing nearly twice as much per bushel. peat is either charred in pits and heaps, or in kilns. from the regularity of the rectangular blocks into which peat is usually formed, it may be charred more easily in pits than wood, since the blocks admit of closer packing in the heap, and because the peat coal is less inflammable than wood coal. the heaps may likewise be made much smaller than is needful in case of wood, viz.: six to eight feet in diameter, and four feet high. the pit is arranged as follows: the ground is selected and prepared as for charcoal burning, and should be elevated, dry and compact. three stout poles are firmly driven into the ground, so as to stand vertically and equi-distant from each other, leaving within them a space of six or eight inches. around these poles the peats are placed endwise, in concentric rows to the required width and height, leaving at the bottom a number of air-channels of the width of one peat, radiating from the centre outwards. the upper layers of peat are narrowed in so as to round off the heap, which is first covered with dry leaves, sods, or moss, over which a layer of soil is thrown. dry, light wood being placed at the bottom of the central shaft, it is kindled from one of the canals at the bottom, and the charring is conducted as is usual in making wood coal. the yield of coal ranges from to _per cent._ of the peat by weight, and from to _per cent._ by volume. gysser recommends to mould the peat for charring in the form of cylinders of to feet long, which, when dry, may be built up into a heap like wood. a great variety of ovens or kilns have been constructed for coking peat. at the gun factory of oberndorf, in wirtemberg, peat is charred in the kiln represented in the accompanying figure. the chamber is feet high, and - / feet in diameter. the oven proper, _b b_, is surrounded by a mantle of brick _a a_, and the space between, _c c_, is filled with sand. each wall, as well as the space, is inches in thickness, and the walls are connected by stones _d d_, at intervals of three feet. above the sole of the kiln, are three series of air holes, made by imbedding old gun barrels in the walls. the door, which serves to empty the kiln, is a plate of cast iron, the sides of its frame are wider than the thickness of the wall, and by means of a board _e_, a box _m_ can be made in front of the door, which is filled with sand to prevent access of air. the peat is filled in through _i_, a channel being arranged across the bottom of the kiln, from the door _f_, for kindling. when the firing begins, the lowest air-holes and _i_ are open. when, through the lower gun barrels, the peat is seen to be ignited, these are corked, and those above are opened. when the smoke ceases to escape above, all the openings are closed, _m_, is filled with sand, _i_ is covered over with it, and the whole is left to cool. it requires about to days to finish the charring of a charge. several kilns are kept in operation, so that the work proceeds uninterruptedly. [illustration: fig. .--oberndorfer peat charring kiln.] [illustration: fig. .--weber's charring furnace.--transverse section.] [illustration: fig. .--weber's charring furnace.--longitudinal section.] at staltach, weber prepares peat coal in a cylinder of sheet iron, which is surrounded by masonry. below, it rests on a grating of stout wire. above, it has a cover, that may be raised by a pulley and on one side is attached a small furnace, figure , the draught of which is kept up by means of a blower, or an exhauster, and the flame and hot gases from it, _which contain no excess of oxygen_, play upon the peat and decompose it, expelling its volatile portions without burning or wasting it in the slightest degree. the construction of the furnace, see fig. , is such, that the sticks of wood, which are employed for fuel, are supported at their ends on shoulders in the brick-work, and the draught enters the fire above instead of below. the wood is hereby completely consumed, and by regulating the supply of air at _a_ (fig. ) by a sliding cover, and at _b_ by a register, the flame and current of air which enters the cylinder containing the peat, is intensely hot and accomplishes a rapid carbonization of the peat, but as before stated, does not burn it. in this furnace the wood, which is cut of uniform length, is itself the grate, since iron would melt or rapidly burn out; and the coals that fall are consumed by the air admitted through c. the hot gases which enter the cylinder filled with peat near its top, are distributed by pipes, and, passing off through the grating at the bottom, enter the surrounding brick mantle. before reaching the exhaustor, however, they pass through a cooler in which a quantity of tar and pyroligneous acid is collected. weber's oven is feet in diameter, and - / feet high; cubic feet of peat may be coked in it in the space of hours. the wood furnace is feet in section, and consumes for the above amount of peat - / cwt. of wood. so perfectly are the contents of the iron cylinder protected from contact of oxygen, that a rabbit placed within it, has been converted into coal without the singeing of a hair; and a bouquet of flowers has been carbonized, perfectly retaining its shape. the yield of coal in weber's oven is nearly _per cent._ of the peat by weight. whenever possible, charring of peat should be carried on, or aided by waste heat, or the heat necessary to coking should be itself economized. in manufacturing and metallurgical establishments, a considerable economy in both the drying and coking may often be effected in this manner. on the bog of allen, in ireland, we have an example of this kind. peat is placed in iron ovens in the form of truncated pyramids, the bottoms of which consist of movable and perforated iron plates. the ovens are mounted on wheels, and run on a rail track. five ovens filled with peat are run into a pit in a drying house, in which blocks of fresh peat are arranged for drying. each oven is connected with a flue, and fire is applied. the peat burns below, and the heat generated in the coking, warms the air of the drying house. when the escaping smoke becomes transparent, the pit in which the ovens stand is filled with water slightly above their lower edges, whereby access of air to the burning peat is at once cut off. when cool, the ovens are run out and replaced by others filled with peat. each oven holds about lbs. of peat, and the yield of coal is _per cent._ by weight. the small yield compared with that obtained by weber's method, is due to the burning of the peat and the coal itself, in the draught of air that passes through the ovens. the author has carbonized, in an iron retort, specimens of peat prepared by elsberg's, leavitt's, and aschcroft and betteley's processes. elsberg's gave , the others _per cent._ of coal. the coal from elsberg's peat was greatly fissured, and could be crushed in the fingers to small fragments. that from the other peats was more firm, and required considerable exertion to break it. all had a decided metallic brilliancy of surface. .--_metallurgical uses of peat._ in austria, more than any other country, peat has been employed in the manufacture of iron. in bavaria, prussia, wirtemberg, hanover, and sweden, and latterly in great britain, peat has been put to the same use. the general results of experience, are as follows:-- peat can only be employed to advantage, when wood and mineral coal are expensive, or of poor quality. peat can be used in furnaces adapted for charcoal, but not in those built for mineral coal. good air-dry peat, containing to _per cent._ of water, in some cases may replace a share of charcoal in the high furnace. at pillersee, in austria, spathic iron ore has been reduced by a mixture of fir-wood charcoal, and air-dry peat in the proportions of three parts by bulk of the former to one of the latter. the use of peat was found to effect a considerable saving in the outlay for fuel, and enabled the production to be somewhat increased, while the excellence of the iron was in no way impaired. the peat was of the best quality, and was worked and moulded by hand. when the ore is refractory and contains impurities that must be fluxed and worked off in slag, a large proportion of air-dry peat cannot be used to advantage, because the evaporation of the water in it consumes so much heat, that the requisite temperature is not easily attained. at achthal, in bavaria, air-dry peat was employed in , to replace a portion of the fir wood charcoal, which had been used for smelting an impure clay-iron-stone: the latter fuel having become so dear, that peat was resorted to as a make shift. instead of one "sack," or cubic feet of charcoal, cubic feet of charcoal and cubic feet of peat were employed in each charge, and the quantity of ore had to be diminished thereby, so that the yield of pig was reduced, on the average, by about _per cent._ in this case the quality of the iron, when worked into bar, was injured by the use of peat, obviously from an increase of its content of phosphorus. the exclusive use of air-dry peat as fuel in the high furnace, appears to be out of the question. at ransko, in bohemia, _kiln-dried peat_, nearly altogether free from water, has been employed in a high furnace, mixed with but one-third its bulk of charcoal, and in cupola furnaces for re-melting pig, full-dried peat has been used alone, answering the purpose perfectly. the most important metallurgical application of peat is in the refining of iron. dried peat is extensively used in puddling furnaces, especially in the so-called gas puddling furnaces, in carinthia, steyermark, silesia, bavaria, wirtemberg, sweden, and other parts of europe. in steyermark, peat has been thus employed for years. air-dry peat is, indeed, also employed, but is not so well adapted for puddling, as its water burns away a notable quantity of iron. it is one of the best known facts in chemistry, that ignited iron is rapidly oxidized in a stream of water-vapor, free hydrogen being at the same time evolved. in the high furnace, _peat-coal_, when compact and firm (not crumbly) may replace charcoal perfectly, but its cost is usually too great. when peat or peat-coal is employed in smelting, it must be as free as possible from ash, because the ash usually consists largely of silica, and this must be worked off by flux. if the ash be carbonate of lime, it will, in most cases, serve itself usefully as flux. in hearth puddling, it is important not only that the peat or peat-coal contain little ash, but especially that the ash be as free as possible from sulphates and phosphates, which act so deleteriously on the metal. the notion that, in general, peat and peat charcoal are peculiarly adapted for the iron manufacture, because they are free from sulphur and phosphorus, is extremely erroneous. not infrequently they contain these bodies in such quantity, as to forbid their use in smelting. in the gas-puddling furnace, or in the ordinary reverberatory, impure peat may, however, be employed, since the ashes do not come in contact with the metal. the only disadvantage in the use of peat in these furnaces is, that the grates require cleaning more frequently, which interrupts the fire, and, according to tunner, increases the consumption of fuel to _per cent._, and diminishes the amount of metal that can be turned out in a given time by the same quantity. notwithstanding the interruption of work, it has been found, at rothburga, in austria, that by substitution of machine-made and kiln-dried peat for wood in the gas-puddling furnace, a saving of _per cent._ in the cost of bar iron was effected, in . what is to the point, in estimating the economy of peat, is the fact that while . cubic feet of dry fir-wood were required to produce lbs. of crude bar, this quantity of iron could be puddled with . cubic feet of peat. in the gas furnace, a second blast of air is thrown into the flame, effecting its complete combustion; dellvik asserts, that at lesjoeforss, in sweden, lbs. of kiln-dried peat are equal to lbs. of kiln-dried wood in heavy forging. in an ordinary fire, the peat would be less effective from the escape of unburned carbon in the smoke. in other metallurgical and manufacturing operations where flame is required, as well as in those which are not inconvenienced by the ingredients of its ash, it is obvious that peat can be employed when circumstances conspire to render its use economical. .--_peat as a source of illuminating gas._ prof pettenkofer, of munich, was the first to succeed in making illuminating gas from wood; and peat, when operated according to his method, furnishes also a gas of good quality, though somewhat inferior to wood-gas in illuminating power. it is essential, that well-dried peat be employed, and the waste heat from the retorts may serve in part, at least, for the drying. the retorts must be of a good conducting material; therefore cast iron is better than clay. they are made of the [symbol: d] form, and must be relatively larger than those used for coal. a retort of two feet width, one foot depth, and to feet length, must receive but lbs. of peat at a charge. the quantity of gas yielded in a given time, is much greater than from bituminous coal. from retorts of the size just named, to cubic feet of gas are delivered in hours. the exit pipes must, therefore, be large, not less than to inches, and the coolers must be much more effective than is needful for coal gas, in order to separate from it the tarry matters. the number of retorts requisite to furnish a given volume of gas, is much less than in the manufacture from coal. on the other hand, the dimensions of the furnace are considerably greater, because the consumption of fuel must be more rapid, in order to supply the heat, which is carried off by the copious formation of gas. gas may be made from peat at a comparatively low temperature, but its illuminating power is then trifling. at a red heat alone can we procure a gas of good quality. the chief impurity of peat-gas is carbonic acid: this amounts to to _per cent._ of the gas before purification, and if the peat be insufficiently dried, it is considerably more. the quantity of slaked lime that is consumed in purifying, is therefore much greater than is needed for coal-gas, and is an expensive item in the making of peat-gas. while wood-gas is practically free from sulphur compounds and ammonia, peat-gas may contain them both, especially the latter, in quantity that depends upon the composition of the peat, which, as regards sulphur and nitrogen, is very variable. peat-gas is denser than coal-gas, and therefore cannot be burned to advantage except from considerably wider orifices than answer for the latter, and under slight pressure. the above statements show the absurdity of judging of the value of peat as a source of gas, by the results of trials made in gas works arranged for bituminous coal. as to the yield of gas we have the following data, weights and measures being english:-- lbs. of peat of medium quality from munich, gave reissig cub. ft. " air-dry peat from biermoos, salzburg, gave riedinger " " very light fibrous peat, gave reissig to " " exter's machine-peat, from haspelmoor, gave " thenius states, that, to produce english cubic feet of purified peat-gas, in the works at kempten, bavaria, there are required in the retorts lbs of peat. to distil this, - / lbs. of peat are consumed in the fire; and to purify the gas from carbonic acid, - / lbs. of lime are used. in the retorts remain lbs. of peat coal, and nearly lbs. of tar are collected in the operation, besides smaller quantities of acetic acid and ammonia. according to stammer, cwt. of dry peat are required for cubic feet of purified gas. the quality of the gas is somewhat better than that made from bituminous coal. .--_the examination of peat as to its value for fuel_, begins with and refers to the air-dry substance, in which: .--water is estimated, by drying the pulverized peat, at °, as long as any diminution of weight occurs. well-dried peat-fuel should not contain more than _per cent._ of water. on the other hand it cannot contain less than _per cent._, except it has been artificially dried at a high temperature, or kept for a long time in a heated apartment. .--_ash_ is estimated by carefully burning the dry residue in . in first-rate fuel, it should amount to less than _per cent._ if more than _per cent._, the peat is thereby rendered of inferior quality, though peat is employed which contains considerably more. .--_sulphur_ and _phosphorus_ are estimated by processes, which it would be useless to describe here. only in case of vitriol peats is so much sulphur present, that it is recognizable by the suffocating fumes of sulphuric acid or of sulphurous acid, which escape in the burning. when peat is to be employed for iron manufacture, or under steam boilers, its phosphorus, and especially its sulphur, should be estimated, as they injure the quality of iron when their quantity exceeds a certain small amount, and have a destructive effect on grate-bars and boilers. for common uses it is unnecessary to regard these substances. .--the quantity of _coal_ or _coke_ yielded by peat, is determined by heating a weighed quantity of the peat to redness in an iron retort, or in a large platinum crucible, until gases cease to escape. the neck of the retort is corked, and when the vessel is cool, the coal is removed and weighed. in case a platinum crucible is employed, it should have a tight-fitting cover, and when gases cease to escape, the crucible is quickly cooled by placing it in cold water. coal, or coke, includes of course the ash of the peat. this, being variable, should be deducted, and the _ash-free coal_ be considered in comparing fuels. .--the _density_ of peat-fuel may be ascertained by cutting out a block that will admit of accurate measurement, calculating its cubic contents, and comparing its weight with that of an equal bulk of water. to avoid calculation, the block may be made accurately one or several cubic inches in dimensions and weighed. the cubic inch of water at ° f., weighs - / grains. footnotes: [ ] the apparent specific gravity here means the weight of the mass,--the air-filled cavities and pores included--as compared with an equal bulk of water. the real specific gravity of the _peat itself_ is always greater than that of water, and all kinds of peat will sink in water when they soak long enough, or are otherwise treated so that all air is removed. [ ] the "full" cubic foot implies a cubic foot having no cavities or waste space, such as exist in a pile, made up of numerous blocks. if a number of peat blocks be put into a box and shaken together, the empty space between the more or less irregular blocks, may amount to _per cent._ of the whole; and when closely packed, the cavities amount to _per cent._, according to the observations of _wasserzieher_. (_dingler's journal_, oct., , p. .) some confusion exists in the statements of writers in regard to this matter, and want of attention to it, has led to grave errors in estimating the weight of fuel. [ ] the _waste space_ in peat and wood as commonly piled, is probably included here in the statement, and is usually about the same in both; viz.: not far from _per cent._ [ ] see note on the preceding page. [ ] _der torf, etc._, s. . [ ] see page . [ ] on account of the great convenience of the decimal weights and measures, and their nearly universal recognition by scientific men, we have adopted them here. the gramme = grains; degrees centigrade = degrees fahrenheit. [ ] pliny, hist. nat. (lib. xvi, ) expresses his pity for the "miserable people" living in east friesland and vicinity in his day, who "dug out with the hands a moor earth, which, dried more by wind than sun, they used for preparing their food and warming their bodies:" _captum manibus lutum ventis magis quam sole siccantis, terra cibos et rigentia septembrione viscera sua urunt_. as regards the "_misera gens_," it should be said that rich grain fields and numerous flourishing villages have occupied for several centuries large portions of the duevel moor near bremen. [ ] for further account and plans of this machine see dingler's polytechnisches journal, bd. , s. . [ ] described and figured in bulletin de la societe d'encouragement, august , p. ; also dingler's polytechnisches journal, bd. , s. . [ ] berg- und huettenmænnische zeitung, , nr. . [ ] henneberg's journal fuer landwirthschaft, , s. . [ ] henneberg's journal fuer landwirthschaft, , p.p. and . [ ] dingler's journal, oct., . [ ] dingler's polytechnisches journal, bd. , s. . see also, knapp, lehrbuch der chemischen technologie, te auflage, ., . [ ] der torf; seine bildung und bereitungsweise, von rudolph gysser, weimar, . [ ] dingler's journal, bd. , s. .; und bd. , s, . [ ] scientific american, feb. , ; also, facts about peat as fuel, by t. h. leavitt, d ed., boston, p. . [ ] dingler's journal, bd. , s. , und bd. , s. . [ ] described in journal of the society of arts, , p. . [ ] bernemann & kerl's berg und huettenmænnische zeitung, , . +-------------------------------------------+ | transcriber's note: | | | | typographical errors corrected in text: | | | | page robert's changed to roberts' | | page jaeckel changed to jæckel | | page poquonnock changed to poquonock | | page connexion changed to connection | | page poquonnock changed to poquonock | | page poquonnock changed to poquonock | | page russel changed to russell | | page subtances changed to substances | | page poquonnock changed to poquonock | | page changed to | | page poquonnock changed to poquonock | | page poquonnock changed to poquonock | | page poquonnock changed to poquonock | | page artifical changed to artificial | | page developes changed to develops | | page kneeding changed to kneading | | page the symbol looks like a d | | lying on its back. | | | +-------------------------------------------+